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aee69d78 PV |
1 | /* |
2 | * Budget Fair Queueing (BFQ) I/O scheduler. | |
3 | * | |
4 | * Based on ideas and code from CFQ: | |
5 | * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk> | |
6 | * | |
7 | * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it> | |
8 | * Paolo Valente <paolo.valente@unimore.it> | |
9 | * | |
10 | * Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it> | |
11 | * Arianna Avanzini <avanzini@google.com> | |
12 | * | |
13 | * Copyright (C) 2017 Paolo Valente <paolo.valente@linaro.org> | |
14 | * | |
15 | * This program is free software; you can redistribute it and/or | |
16 | * modify it under the terms of the GNU General Public License as | |
17 | * published by the Free Software Foundation; either version 2 of the | |
18 | * License, or (at your option) any later version. | |
19 | * | |
20 | * This program is distributed in the hope that it will be useful, | |
21 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
22 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
23 | * General Public License for more details. | |
24 | * | |
25 | * BFQ is a proportional-share I/O scheduler, with some extra | |
26 | * low-latency capabilities. BFQ also supports full hierarchical | |
27 | * scheduling through cgroups. Next paragraphs provide an introduction | |
28 | * on BFQ inner workings. Details on BFQ benefits, usage and | |
29 | * limitations can be found in Documentation/block/bfq-iosched.txt. | |
30 | * | |
31 | * BFQ is a proportional-share storage-I/O scheduling algorithm based | |
32 | * on the slice-by-slice service scheme of CFQ. But BFQ assigns | |
33 | * budgets, measured in number of sectors, to processes instead of | |
34 | * time slices. The device is not granted to the in-service process | |
35 | * for a given time slice, but until it has exhausted its assigned | |
36 | * budget. This change from the time to the service domain enables BFQ | |
37 | * to distribute the device throughput among processes as desired, | |
38 | * without any distortion due to throughput fluctuations, or to device | |
39 | * internal queueing. BFQ uses an ad hoc internal scheduler, called | |
40 | * B-WF2Q+, to schedule processes according to their budgets. More | |
41 | * precisely, BFQ schedules queues associated with processes. Each | |
42 | * process/queue is assigned a user-configurable weight, and B-WF2Q+ | |
43 | * guarantees that each queue receives a fraction of the throughput | |
44 | * proportional to its weight. Thanks to the accurate policy of | |
45 | * B-WF2Q+, BFQ can afford to assign high budgets to I/O-bound | |
46 | * processes issuing sequential requests (to boost the throughput), | |
47 | * and yet guarantee a low latency to interactive and soft real-time | |
48 | * applications. | |
49 | * | |
50 | * In particular, to provide these low-latency guarantees, BFQ | |
51 | * explicitly privileges the I/O of two classes of time-sensitive | |
52 | * applications: interactive and soft real-time. This feature enables | |
53 | * BFQ to provide applications in these classes with a very low | |
54 | * latency. Finally, BFQ also features additional heuristics for | |
55 | * preserving both a low latency and a high throughput on NCQ-capable, | |
56 | * rotational or flash-based devices, and to get the job done quickly | |
57 | * for applications consisting in many I/O-bound processes. | |
58 | * | |
43c1b3d6 PV |
59 | * NOTE: if the main or only goal, with a given device, is to achieve |
60 | * the maximum-possible throughput at all times, then do switch off | |
61 | * all low-latency heuristics for that device, by setting low_latency | |
62 | * to 0. | |
63 | * | |
aee69d78 PV |
64 | * BFQ is described in [1], where also a reference to the initial, more |
65 | * theoretical paper on BFQ can be found. The interested reader can find | |
66 | * in the latter paper full details on the main algorithm, as well as | |
67 | * formulas of the guarantees and formal proofs of all the properties. | |
68 | * With respect to the version of BFQ presented in these papers, this | |
69 | * implementation adds a few more heuristics, such as the one that | |
70 | * guarantees a low latency to soft real-time applications, and a | |
71 | * hierarchical extension based on H-WF2Q+. | |
72 | * | |
73 | * B-WF2Q+ is based on WF2Q+, which is described in [2], together with | |
74 | * H-WF2Q+, while the augmented tree used here to implement B-WF2Q+ | |
75 | * with O(log N) complexity derives from the one introduced with EEVDF | |
76 | * in [3]. | |
77 | * | |
78 | * [1] P. Valente, A. Avanzini, "Evolution of the BFQ Storage I/O | |
79 | * Scheduler", Proceedings of the First Workshop on Mobile System | |
80 | * Technologies (MST-2015), May 2015. | |
81 | * http://algogroup.unimore.it/people/paolo/disk_sched/mst-2015.pdf | |
82 | * | |
83 | * [2] Jon C.R. Bennett and H. Zhang, "Hierarchical Packet Fair Queueing | |
84 | * Algorithms", IEEE/ACM Transactions on Networking, 5(5):675-689, | |
85 | * Oct 1997. | |
86 | * | |
87 | * http://www.cs.cmu.edu/~hzhang/papers/TON-97-Oct.ps.gz | |
88 | * | |
89 | * [3] I. Stoica and H. Abdel-Wahab, "Earliest Eligible Virtual Deadline | |
90 | * First: A Flexible and Accurate Mechanism for Proportional Share | |
91 | * Resource Allocation", technical report. | |
92 | * | |
93 | * http://www.cs.berkeley.edu/~istoica/papers/eevdf-tr-95.pdf | |
94 | */ | |
95 | #include <linux/module.h> | |
96 | #include <linux/slab.h> | |
97 | #include <linux/blkdev.h> | |
e21b7a0b | 98 | #include <linux/cgroup.h> |
aee69d78 PV |
99 | #include <linux/elevator.h> |
100 | #include <linux/ktime.h> | |
101 | #include <linux/rbtree.h> | |
102 | #include <linux/ioprio.h> | |
103 | #include <linux/sbitmap.h> | |
104 | #include <linux/delay.h> | |
105 | ||
106 | #include "blk.h" | |
107 | #include "blk-mq.h" | |
108 | #include "blk-mq-tag.h" | |
109 | #include "blk-mq-sched.h" | |
ea25da48 | 110 | #include "bfq-iosched.h" |
b5dc5d4d | 111 | #include "blk-wbt.h" |
aee69d78 | 112 | |
ea25da48 PV |
113 | #define BFQ_BFQQ_FNS(name) \ |
114 | void bfq_mark_bfqq_##name(struct bfq_queue *bfqq) \ | |
115 | { \ | |
116 | __set_bit(BFQQF_##name, &(bfqq)->flags); \ | |
117 | } \ | |
118 | void bfq_clear_bfqq_##name(struct bfq_queue *bfqq) \ | |
119 | { \ | |
120 | __clear_bit(BFQQF_##name, &(bfqq)->flags); \ | |
121 | } \ | |
122 | int bfq_bfqq_##name(const struct bfq_queue *bfqq) \ | |
123 | { \ | |
124 | return test_bit(BFQQF_##name, &(bfqq)->flags); \ | |
44e44a1b PV |
125 | } |
126 | ||
ea25da48 PV |
127 | BFQ_BFQQ_FNS(just_created); |
128 | BFQ_BFQQ_FNS(busy); | |
129 | BFQ_BFQQ_FNS(wait_request); | |
130 | BFQ_BFQQ_FNS(non_blocking_wait_rq); | |
131 | BFQ_BFQQ_FNS(fifo_expire); | |
d5be3fef | 132 | BFQ_BFQQ_FNS(has_short_ttime); |
ea25da48 PV |
133 | BFQ_BFQQ_FNS(sync); |
134 | BFQ_BFQQ_FNS(IO_bound); | |
135 | BFQ_BFQQ_FNS(in_large_burst); | |
136 | BFQ_BFQQ_FNS(coop); | |
137 | BFQ_BFQQ_FNS(split_coop); | |
138 | BFQ_BFQQ_FNS(softrt_update); | |
139 | #undef BFQ_BFQQ_FNS \ | |
aee69d78 | 140 | |
ea25da48 PV |
141 | /* Expiration time of sync (0) and async (1) requests, in ns. */ |
142 | static const u64 bfq_fifo_expire[2] = { NSEC_PER_SEC / 4, NSEC_PER_SEC / 8 }; | |
aee69d78 | 143 | |
ea25da48 PV |
144 | /* Maximum backwards seek (magic number lifted from CFQ), in KiB. */ |
145 | static const int bfq_back_max = 16 * 1024; | |
aee69d78 | 146 | |
ea25da48 PV |
147 | /* Penalty of a backwards seek, in number of sectors. */ |
148 | static const int bfq_back_penalty = 2; | |
e21b7a0b | 149 | |
ea25da48 PV |
150 | /* Idling period duration, in ns. */ |
151 | static u64 bfq_slice_idle = NSEC_PER_SEC / 125; | |
aee69d78 | 152 | |
ea25da48 PV |
153 | /* Minimum number of assigned budgets for which stats are safe to compute. */ |
154 | static const int bfq_stats_min_budgets = 194; | |
aee69d78 | 155 | |
ea25da48 PV |
156 | /* Default maximum budget values, in sectors and number of requests. */ |
157 | static const int bfq_default_max_budget = 16 * 1024; | |
e21b7a0b | 158 | |
ea25da48 PV |
159 | /* |
160 | * Async to sync throughput distribution is controlled as follows: | |
161 | * when an async request is served, the entity is charged the number | |
162 | * of sectors of the request, multiplied by the factor below | |
163 | */ | |
164 | static const int bfq_async_charge_factor = 10; | |
aee69d78 | 165 | |
ea25da48 PV |
166 | /* Default timeout values, in jiffies, approximating CFQ defaults. */ |
167 | const int bfq_timeout = HZ / 8; | |
aee69d78 | 168 | |
ea25da48 | 169 | static struct kmem_cache *bfq_pool; |
e21b7a0b | 170 | |
ea25da48 PV |
171 | /* Below this threshold (in ns), we consider thinktime immediate. */ |
172 | #define BFQ_MIN_TT (2 * NSEC_PER_MSEC) | |
e21b7a0b | 173 | |
ea25da48 PV |
174 | /* hw_tag detection: parallel requests threshold and min samples needed. */ |
175 | #define BFQ_HW_QUEUE_THRESHOLD 4 | |
176 | #define BFQ_HW_QUEUE_SAMPLES 32 | |
aee69d78 | 177 | |
ea25da48 PV |
178 | #define BFQQ_SEEK_THR (sector_t)(8 * 100) |
179 | #define BFQQ_SECT_THR_NONROT (sector_t)(2 * 32) | |
180 | #define BFQQ_CLOSE_THR (sector_t)(8 * 1024) | |
181 | #define BFQQ_SEEKY(bfqq) (hweight32(bfqq->seek_history) > 32/8) | |
aee69d78 | 182 | |
ea25da48 PV |
183 | /* Min number of samples required to perform peak-rate update */ |
184 | #define BFQ_RATE_MIN_SAMPLES 32 | |
185 | /* Min observation time interval required to perform a peak-rate update (ns) */ | |
186 | #define BFQ_RATE_MIN_INTERVAL (300*NSEC_PER_MSEC) | |
187 | /* Target observation time interval for a peak-rate update (ns) */ | |
188 | #define BFQ_RATE_REF_INTERVAL NSEC_PER_SEC | |
aee69d78 | 189 | |
ea25da48 PV |
190 | /* Shift used for peak rate fixed precision calculations. */ |
191 | #define BFQ_RATE_SHIFT 16 | |
aee69d78 | 192 | |
ea25da48 PV |
193 | /* |
194 | * By default, BFQ computes the duration of the weight raising for | |
195 | * interactive applications automatically, using the following formula: | |
196 | * duration = (R / r) * T, where r is the peak rate of the device, and | |
197 | * R and T are two reference parameters. | |
198 | * In particular, R is the peak rate of the reference device (see below), | |
199 | * and T is a reference time: given the systems that are likely to be | |
200 | * installed on the reference device according to its speed class, T is | |
201 | * about the maximum time needed, under BFQ and while reading two files in | |
202 | * parallel, to load typical large applications on these systems. | |
203 | * In practice, the slower/faster the device at hand is, the more/less it | |
204 | * takes to load applications with respect to the reference device. | |
205 | * Accordingly, the longer/shorter BFQ grants weight raising to interactive | |
206 | * applications. | |
207 | * | |
208 | * BFQ uses four different reference pairs (R, T), depending on: | |
209 | * . whether the device is rotational or non-rotational; | |
210 | * . whether the device is slow, such as old or portable HDDs, as well as | |
211 | * SD cards, or fast, such as newer HDDs and SSDs. | |
212 | * | |
213 | * The device's speed class is dynamically (re)detected in | |
214 | * bfq_update_peak_rate() every time the estimated peak rate is updated. | |
215 | * | |
216 | * In the following definitions, R_slow[0]/R_fast[0] and | |
217 | * T_slow[0]/T_fast[0] are the reference values for a slow/fast | |
218 | * rotational device, whereas R_slow[1]/R_fast[1] and | |
219 | * T_slow[1]/T_fast[1] are the reference values for a slow/fast | |
220 | * non-rotational device. Finally, device_speed_thresh are the | |
221 | * thresholds used to switch between speed classes. The reference | |
222 | * rates are not the actual peak rates of the devices used as a | |
223 | * reference, but slightly lower values. The reason for using these | |
224 | * slightly lower values is that the peak-rate estimator tends to | |
225 | * yield slightly lower values than the actual peak rate (it can yield | |
226 | * the actual peak rate only if there is only one process doing I/O, | |
227 | * and the process does sequential I/O). | |
228 | * | |
229 | * Both the reference peak rates and the thresholds are measured in | |
230 | * sectors/usec, left-shifted by BFQ_RATE_SHIFT. | |
231 | */ | |
232 | static int R_slow[2] = {1000, 10700}; | |
233 | static int R_fast[2] = {14000, 33000}; | |
234 | /* | |
235 | * To improve readability, a conversion function is used to initialize the | |
236 | * following arrays, which entails that they can be initialized only in a | |
237 | * function. | |
238 | */ | |
239 | static int T_slow[2]; | |
240 | static int T_fast[2]; | |
241 | static int device_speed_thresh[2]; | |
aee69d78 | 242 | |
12cd3a2f | 243 | #define RQ_BIC(rq) icq_to_bic((rq)->elv.priv[0]) |
ea25da48 | 244 | #define RQ_BFQQ(rq) ((rq)->elv.priv[1]) |
aee69d78 | 245 | |
ea25da48 | 246 | struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, bool is_sync) |
e21b7a0b | 247 | { |
ea25da48 | 248 | return bic->bfqq[is_sync]; |
aee69d78 PV |
249 | } |
250 | ||
ea25da48 | 251 | void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq, bool is_sync) |
aee69d78 | 252 | { |
ea25da48 | 253 | bic->bfqq[is_sync] = bfqq; |
aee69d78 PV |
254 | } |
255 | ||
ea25da48 | 256 | struct bfq_data *bic_to_bfqd(struct bfq_io_cq *bic) |
aee69d78 | 257 | { |
ea25da48 | 258 | return bic->icq.q->elevator->elevator_data; |
e21b7a0b | 259 | } |
aee69d78 | 260 | |
ea25da48 PV |
261 | /** |
262 | * icq_to_bic - convert iocontext queue structure to bfq_io_cq. | |
263 | * @icq: the iocontext queue. | |
264 | */ | |
265 | static struct bfq_io_cq *icq_to_bic(struct io_cq *icq) | |
e21b7a0b | 266 | { |
ea25da48 PV |
267 | /* bic->icq is the first member, %NULL will convert to %NULL */ |
268 | return container_of(icq, struct bfq_io_cq, icq); | |
e21b7a0b | 269 | } |
aee69d78 | 270 | |
ea25da48 PV |
271 | /** |
272 | * bfq_bic_lookup - search into @ioc a bic associated to @bfqd. | |
273 | * @bfqd: the lookup key. | |
274 | * @ioc: the io_context of the process doing I/O. | |
275 | * @q: the request queue. | |
276 | */ | |
277 | static struct bfq_io_cq *bfq_bic_lookup(struct bfq_data *bfqd, | |
278 | struct io_context *ioc, | |
279 | struct request_queue *q) | |
e21b7a0b | 280 | { |
ea25da48 PV |
281 | if (ioc) { |
282 | unsigned long flags; | |
283 | struct bfq_io_cq *icq; | |
aee69d78 | 284 | |
ea25da48 PV |
285 | spin_lock_irqsave(q->queue_lock, flags); |
286 | icq = icq_to_bic(ioc_lookup_icq(ioc, q)); | |
287 | spin_unlock_irqrestore(q->queue_lock, flags); | |
aee69d78 | 288 | |
ea25da48 | 289 | return icq; |
e21b7a0b | 290 | } |
e21b7a0b | 291 | |
ea25da48 | 292 | return NULL; |
aee69d78 PV |
293 | } |
294 | ||
ea25da48 PV |
295 | /* |
296 | * Scheduler run of queue, if there are requests pending and no one in the | |
297 | * driver that will restart queueing. | |
298 | */ | |
299 | void bfq_schedule_dispatch(struct bfq_data *bfqd) | |
aee69d78 | 300 | { |
ea25da48 PV |
301 | if (bfqd->queued != 0) { |
302 | bfq_log(bfqd, "schedule dispatch"); | |
303 | blk_mq_run_hw_queues(bfqd->queue, true); | |
e21b7a0b | 304 | } |
aee69d78 PV |
305 | } |
306 | ||
307 | #define bfq_class_idle(bfqq) ((bfqq)->ioprio_class == IOPRIO_CLASS_IDLE) | |
308 | #define bfq_class_rt(bfqq) ((bfqq)->ioprio_class == IOPRIO_CLASS_RT) | |
309 | ||
310 | #define bfq_sample_valid(samples) ((samples) > 80) | |
311 | ||
aee69d78 PV |
312 | /* |
313 | * Lifted from AS - choose which of rq1 and rq2 that is best served now. | |
314 | * We choose the request that is closesr to the head right now. Distance | |
315 | * behind the head is penalized and only allowed to a certain extent. | |
316 | */ | |
317 | static struct request *bfq_choose_req(struct bfq_data *bfqd, | |
318 | struct request *rq1, | |
319 | struct request *rq2, | |
320 | sector_t last) | |
321 | { | |
322 | sector_t s1, s2, d1 = 0, d2 = 0; | |
323 | unsigned long back_max; | |
324 | #define BFQ_RQ1_WRAP 0x01 /* request 1 wraps */ | |
325 | #define BFQ_RQ2_WRAP 0x02 /* request 2 wraps */ | |
326 | unsigned int wrap = 0; /* bit mask: requests behind the disk head? */ | |
327 | ||
328 | if (!rq1 || rq1 == rq2) | |
329 | return rq2; | |
330 | if (!rq2) | |
331 | return rq1; | |
332 | ||
333 | if (rq_is_sync(rq1) && !rq_is_sync(rq2)) | |
334 | return rq1; | |
335 | else if (rq_is_sync(rq2) && !rq_is_sync(rq1)) | |
336 | return rq2; | |
337 | if ((rq1->cmd_flags & REQ_META) && !(rq2->cmd_flags & REQ_META)) | |
338 | return rq1; | |
339 | else if ((rq2->cmd_flags & REQ_META) && !(rq1->cmd_flags & REQ_META)) | |
340 | return rq2; | |
341 | ||
342 | s1 = blk_rq_pos(rq1); | |
343 | s2 = blk_rq_pos(rq2); | |
344 | ||
345 | /* | |
346 | * By definition, 1KiB is 2 sectors. | |
347 | */ | |
348 | back_max = bfqd->bfq_back_max * 2; | |
349 | ||
350 | /* | |
351 | * Strict one way elevator _except_ in the case where we allow | |
352 | * short backward seeks which are biased as twice the cost of a | |
353 | * similar forward seek. | |
354 | */ | |
355 | if (s1 >= last) | |
356 | d1 = s1 - last; | |
357 | else if (s1 + back_max >= last) | |
358 | d1 = (last - s1) * bfqd->bfq_back_penalty; | |
359 | else | |
360 | wrap |= BFQ_RQ1_WRAP; | |
361 | ||
362 | if (s2 >= last) | |
363 | d2 = s2 - last; | |
364 | else if (s2 + back_max >= last) | |
365 | d2 = (last - s2) * bfqd->bfq_back_penalty; | |
366 | else | |
367 | wrap |= BFQ_RQ2_WRAP; | |
368 | ||
369 | /* Found required data */ | |
370 | ||
371 | /* | |
372 | * By doing switch() on the bit mask "wrap" we avoid having to | |
373 | * check two variables for all permutations: --> faster! | |
374 | */ | |
375 | switch (wrap) { | |
376 | case 0: /* common case for CFQ: rq1 and rq2 not wrapped */ | |
377 | if (d1 < d2) | |
378 | return rq1; | |
379 | else if (d2 < d1) | |
380 | return rq2; | |
381 | ||
382 | if (s1 >= s2) | |
383 | return rq1; | |
384 | else | |
385 | return rq2; | |
386 | ||
387 | case BFQ_RQ2_WRAP: | |
388 | return rq1; | |
389 | case BFQ_RQ1_WRAP: | |
390 | return rq2; | |
391 | case BFQ_RQ1_WRAP|BFQ_RQ2_WRAP: /* both rqs wrapped */ | |
392 | default: | |
393 | /* | |
394 | * Since both rqs are wrapped, | |
395 | * start with the one that's further behind head | |
396 | * (--> only *one* back seek required), | |
397 | * since back seek takes more time than forward. | |
398 | */ | |
399 | if (s1 <= s2) | |
400 | return rq1; | |
401 | else | |
402 | return rq2; | |
403 | } | |
404 | } | |
405 | ||
36eca894 AA |
406 | static struct bfq_queue * |
407 | bfq_rq_pos_tree_lookup(struct bfq_data *bfqd, struct rb_root *root, | |
408 | sector_t sector, struct rb_node **ret_parent, | |
409 | struct rb_node ***rb_link) | |
410 | { | |
411 | struct rb_node **p, *parent; | |
412 | struct bfq_queue *bfqq = NULL; | |
413 | ||
414 | parent = NULL; | |
415 | p = &root->rb_node; | |
416 | while (*p) { | |
417 | struct rb_node **n; | |
418 | ||
419 | parent = *p; | |
420 | bfqq = rb_entry(parent, struct bfq_queue, pos_node); | |
421 | ||
422 | /* | |
423 | * Sort strictly based on sector. Smallest to the left, | |
424 | * largest to the right. | |
425 | */ | |
426 | if (sector > blk_rq_pos(bfqq->next_rq)) | |
427 | n = &(*p)->rb_right; | |
428 | else if (sector < blk_rq_pos(bfqq->next_rq)) | |
429 | n = &(*p)->rb_left; | |
430 | else | |
431 | break; | |
432 | p = n; | |
433 | bfqq = NULL; | |
434 | } | |
435 | ||
436 | *ret_parent = parent; | |
437 | if (rb_link) | |
438 | *rb_link = p; | |
439 | ||
440 | bfq_log(bfqd, "rq_pos_tree_lookup %llu: returning %d", | |
441 | (unsigned long long)sector, | |
442 | bfqq ? bfqq->pid : 0); | |
443 | ||
444 | return bfqq; | |
445 | } | |
446 | ||
ea25da48 | 447 | void bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq) |
36eca894 AA |
448 | { |
449 | struct rb_node **p, *parent; | |
450 | struct bfq_queue *__bfqq; | |
451 | ||
452 | if (bfqq->pos_root) { | |
453 | rb_erase(&bfqq->pos_node, bfqq->pos_root); | |
454 | bfqq->pos_root = NULL; | |
455 | } | |
456 | ||
457 | if (bfq_class_idle(bfqq)) | |
458 | return; | |
459 | if (!bfqq->next_rq) | |
460 | return; | |
461 | ||
462 | bfqq->pos_root = &bfq_bfqq_to_bfqg(bfqq)->rq_pos_tree; | |
463 | __bfqq = bfq_rq_pos_tree_lookup(bfqd, bfqq->pos_root, | |
464 | blk_rq_pos(bfqq->next_rq), &parent, &p); | |
465 | if (!__bfqq) { | |
466 | rb_link_node(&bfqq->pos_node, parent, p); | |
467 | rb_insert_color(&bfqq->pos_node, bfqq->pos_root); | |
468 | } else | |
469 | bfqq->pos_root = NULL; | |
470 | } | |
471 | ||
1de0c4cd AA |
472 | /* |
473 | * Tell whether there are active queues or groups with differentiated weights. | |
474 | */ | |
475 | static bool bfq_differentiated_weights(struct bfq_data *bfqd) | |
476 | { | |
477 | /* | |
478 | * For weights to differ, at least one of the trees must contain | |
479 | * at least two nodes. | |
480 | */ | |
481 | return (!RB_EMPTY_ROOT(&bfqd->queue_weights_tree) && | |
482 | (bfqd->queue_weights_tree.rb_node->rb_left || | |
483 | bfqd->queue_weights_tree.rb_node->rb_right) | |
484 | #ifdef CONFIG_BFQ_GROUP_IOSCHED | |
485 | ) || | |
486 | (!RB_EMPTY_ROOT(&bfqd->group_weights_tree) && | |
487 | (bfqd->group_weights_tree.rb_node->rb_left || | |
488 | bfqd->group_weights_tree.rb_node->rb_right) | |
489 | #endif | |
490 | ); | |
491 | } | |
492 | ||
493 | /* | |
494 | * The following function returns true if every queue must receive the | |
495 | * same share of the throughput (this condition is used when deciding | |
496 | * whether idling may be disabled, see the comments in the function | |
497 | * bfq_bfqq_may_idle()). | |
498 | * | |
499 | * Such a scenario occurs when: | |
500 | * 1) all active queues have the same weight, | |
501 | * 2) all active groups at the same level in the groups tree have the same | |
502 | * weight, | |
503 | * 3) all active groups at the same level in the groups tree have the same | |
504 | * number of children. | |
505 | * | |
506 | * Unfortunately, keeping the necessary state for evaluating exactly the | |
507 | * above symmetry conditions would be quite complex and time-consuming. | |
508 | * Therefore this function evaluates, instead, the following stronger | |
509 | * sub-conditions, for which it is much easier to maintain the needed | |
510 | * state: | |
511 | * 1) all active queues have the same weight, | |
512 | * 2) all active groups have the same weight, | |
513 | * 3) all active groups have at most one active child each. | |
514 | * In particular, the last two conditions are always true if hierarchical | |
515 | * support and the cgroups interface are not enabled, thus no state needs | |
516 | * to be maintained in this case. | |
517 | */ | |
518 | static bool bfq_symmetric_scenario(struct bfq_data *bfqd) | |
519 | { | |
520 | return !bfq_differentiated_weights(bfqd); | |
521 | } | |
522 | ||
523 | /* | |
524 | * If the weight-counter tree passed as input contains no counter for | |
525 | * the weight of the input entity, then add that counter; otherwise just | |
526 | * increment the existing counter. | |
527 | * | |
528 | * Note that weight-counter trees contain few nodes in mostly symmetric | |
529 | * scenarios. For example, if all queues have the same weight, then the | |
530 | * weight-counter tree for the queues may contain at most one node. | |
531 | * This holds even if low_latency is on, because weight-raised queues | |
532 | * are not inserted in the tree. | |
533 | * In most scenarios, the rate at which nodes are created/destroyed | |
534 | * should be low too. | |
535 | */ | |
ea25da48 PV |
536 | void bfq_weights_tree_add(struct bfq_data *bfqd, struct bfq_entity *entity, |
537 | struct rb_root *root) | |
1de0c4cd AA |
538 | { |
539 | struct rb_node **new = &(root->rb_node), *parent = NULL; | |
540 | ||
541 | /* | |
542 | * Do not insert if the entity is already associated with a | |
543 | * counter, which happens if: | |
544 | * 1) the entity is associated with a queue, | |
545 | * 2) a request arrival has caused the queue to become both | |
546 | * non-weight-raised, and hence change its weight, and | |
547 | * backlogged; in this respect, each of the two events | |
548 | * causes an invocation of this function, | |
549 | * 3) this is the invocation of this function caused by the | |
550 | * second event. This second invocation is actually useless, | |
551 | * and we handle this fact by exiting immediately. More | |
552 | * efficient or clearer solutions might possibly be adopted. | |
553 | */ | |
554 | if (entity->weight_counter) | |
555 | return; | |
556 | ||
557 | while (*new) { | |
558 | struct bfq_weight_counter *__counter = container_of(*new, | |
559 | struct bfq_weight_counter, | |
560 | weights_node); | |
561 | parent = *new; | |
562 | ||
563 | if (entity->weight == __counter->weight) { | |
564 | entity->weight_counter = __counter; | |
565 | goto inc_counter; | |
566 | } | |
567 | if (entity->weight < __counter->weight) | |
568 | new = &((*new)->rb_left); | |
569 | else | |
570 | new = &((*new)->rb_right); | |
571 | } | |
572 | ||
573 | entity->weight_counter = kzalloc(sizeof(struct bfq_weight_counter), | |
574 | GFP_ATOMIC); | |
575 | ||
576 | /* | |
577 | * In the unlucky event of an allocation failure, we just | |
578 | * exit. This will cause the weight of entity to not be | |
579 | * considered in bfq_differentiated_weights, which, in its | |
580 | * turn, causes the scenario to be deemed wrongly symmetric in | |
581 | * case entity's weight would have been the only weight making | |
582 | * the scenario asymmetric. On the bright side, no unbalance | |
583 | * will however occur when entity becomes inactive again (the | |
584 | * invocation of this function is triggered by an activation | |
585 | * of entity). In fact, bfq_weights_tree_remove does nothing | |
586 | * if !entity->weight_counter. | |
587 | */ | |
588 | if (unlikely(!entity->weight_counter)) | |
589 | return; | |
590 | ||
591 | entity->weight_counter->weight = entity->weight; | |
592 | rb_link_node(&entity->weight_counter->weights_node, parent, new); | |
593 | rb_insert_color(&entity->weight_counter->weights_node, root); | |
594 | ||
595 | inc_counter: | |
596 | entity->weight_counter->num_active++; | |
597 | } | |
598 | ||
599 | /* | |
600 | * Decrement the weight counter associated with the entity, and, if the | |
601 | * counter reaches 0, remove the counter from the tree. | |
602 | * See the comments to the function bfq_weights_tree_add() for considerations | |
603 | * about overhead. | |
604 | */ | |
ea25da48 PV |
605 | void bfq_weights_tree_remove(struct bfq_data *bfqd, struct bfq_entity *entity, |
606 | struct rb_root *root) | |
1de0c4cd AA |
607 | { |
608 | if (!entity->weight_counter) | |
609 | return; | |
610 | ||
611 | entity->weight_counter->num_active--; | |
612 | if (entity->weight_counter->num_active > 0) | |
613 | goto reset_entity_pointer; | |
614 | ||
615 | rb_erase(&entity->weight_counter->weights_node, root); | |
616 | kfree(entity->weight_counter); | |
617 | ||
618 | reset_entity_pointer: | |
619 | entity->weight_counter = NULL; | |
620 | } | |
621 | ||
aee69d78 PV |
622 | /* |
623 | * Return expired entry, or NULL to just start from scratch in rbtree. | |
624 | */ | |
625 | static struct request *bfq_check_fifo(struct bfq_queue *bfqq, | |
626 | struct request *last) | |
627 | { | |
628 | struct request *rq; | |
629 | ||
630 | if (bfq_bfqq_fifo_expire(bfqq)) | |
631 | return NULL; | |
632 | ||
633 | bfq_mark_bfqq_fifo_expire(bfqq); | |
634 | ||
635 | rq = rq_entry_fifo(bfqq->fifo.next); | |
636 | ||
637 | if (rq == last || ktime_get_ns() < rq->fifo_time) | |
638 | return NULL; | |
639 | ||
640 | bfq_log_bfqq(bfqq->bfqd, bfqq, "check_fifo: returned %p", rq); | |
641 | return rq; | |
642 | } | |
643 | ||
644 | static struct request *bfq_find_next_rq(struct bfq_data *bfqd, | |
645 | struct bfq_queue *bfqq, | |
646 | struct request *last) | |
647 | { | |
648 | struct rb_node *rbnext = rb_next(&last->rb_node); | |
649 | struct rb_node *rbprev = rb_prev(&last->rb_node); | |
650 | struct request *next, *prev = NULL; | |
651 | ||
652 | /* Follow expired path, else get first next available. */ | |
653 | next = bfq_check_fifo(bfqq, last); | |
654 | if (next) | |
655 | return next; | |
656 | ||
657 | if (rbprev) | |
658 | prev = rb_entry_rq(rbprev); | |
659 | ||
660 | if (rbnext) | |
661 | next = rb_entry_rq(rbnext); | |
662 | else { | |
663 | rbnext = rb_first(&bfqq->sort_list); | |
664 | if (rbnext && rbnext != &last->rb_node) | |
665 | next = rb_entry_rq(rbnext); | |
666 | } | |
667 | ||
668 | return bfq_choose_req(bfqd, next, prev, blk_rq_pos(last)); | |
669 | } | |
670 | ||
c074170e | 671 | /* see the definition of bfq_async_charge_factor for details */ |
aee69d78 PV |
672 | static unsigned long bfq_serv_to_charge(struct request *rq, |
673 | struct bfq_queue *bfqq) | |
674 | { | |
44e44a1b | 675 | if (bfq_bfqq_sync(bfqq) || bfqq->wr_coeff > 1) |
c074170e PV |
676 | return blk_rq_sectors(rq); |
677 | ||
cfd69712 PV |
678 | /* |
679 | * If there are no weight-raised queues, then amplify service | |
680 | * by just the async charge factor; otherwise amplify service | |
681 | * by twice the async charge factor, to further reduce latency | |
682 | * for weight-raised queues. | |
683 | */ | |
684 | if (bfqq->bfqd->wr_busy_queues == 0) | |
685 | return blk_rq_sectors(rq) * bfq_async_charge_factor; | |
686 | ||
687 | return blk_rq_sectors(rq) * 2 * bfq_async_charge_factor; | |
aee69d78 PV |
688 | } |
689 | ||
690 | /** | |
691 | * bfq_updated_next_req - update the queue after a new next_rq selection. | |
692 | * @bfqd: the device data the queue belongs to. | |
693 | * @bfqq: the queue to update. | |
694 | * | |
695 | * If the first request of a queue changes we make sure that the queue | |
696 | * has enough budget to serve at least its first request (if the | |
697 | * request has grown). We do this because if the queue has not enough | |
698 | * budget for its first request, it has to go through two dispatch | |
699 | * rounds to actually get it dispatched. | |
700 | */ | |
701 | static void bfq_updated_next_req(struct bfq_data *bfqd, | |
702 | struct bfq_queue *bfqq) | |
703 | { | |
704 | struct bfq_entity *entity = &bfqq->entity; | |
705 | struct request *next_rq = bfqq->next_rq; | |
706 | unsigned long new_budget; | |
707 | ||
708 | if (!next_rq) | |
709 | return; | |
710 | ||
711 | if (bfqq == bfqd->in_service_queue) | |
712 | /* | |
713 | * In order not to break guarantees, budgets cannot be | |
714 | * changed after an entity has been selected. | |
715 | */ | |
716 | return; | |
717 | ||
718 | new_budget = max_t(unsigned long, bfqq->max_budget, | |
719 | bfq_serv_to_charge(next_rq, bfqq)); | |
720 | if (entity->budget != new_budget) { | |
721 | entity->budget = new_budget; | |
722 | bfq_log_bfqq(bfqd, bfqq, "updated next rq: new budget %lu", | |
723 | new_budget); | |
80294c3b | 724 | bfq_requeue_bfqq(bfqd, bfqq, false); |
aee69d78 PV |
725 | } |
726 | } | |
727 | ||
3e2bdd6d PV |
728 | static unsigned int bfq_wr_duration(struct bfq_data *bfqd) |
729 | { | |
730 | u64 dur; | |
731 | ||
732 | if (bfqd->bfq_wr_max_time > 0) | |
733 | return bfqd->bfq_wr_max_time; | |
734 | ||
735 | dur = bfqd->RT_prod; | |
736 | do_div(dur, bfqd->peak_rate); | |
737 | ||
738 | /* | |
739 | * Limit duration between 3 and 13 seconds. Tests show that | |
740 | * higher values than 13 seconds often yield the opposite of | |
741 | * the desired result, i.e., worsen responsiveness by letting | |
742 | * non-interactive and non-soft-real-time applications | |
743 | * preserve weight raising for a too long time interval. | |
744 | * | |
745 | * On the other end, lower values than 3 seconds make it | |
746 | * difficult for most interactive tasks to complete their jobs | |
747 | * before weight-raising finishes. | |
748 | */ | |
749 | if (dur > msecs_to_jiffies(13000)) | |
750 | dur = msecs_to_jiffies(13000); | |
751 | else if (dur < msecs_to_jiffies(3000)) | |
752 | dur = msecs_to_jiffies(3000); | |
753 | ||
754 | return dur; | |
755 | } | |
756 | ||
757 | /* switch back from soft real-time to interactive weight raising */ | |
758 | static void switch_back_to_interactive_wr(struct bfq_queue *bfqq, | |
759 | struct bfq_data *bfqd) | |
760 | { | |
761 | bfqq->wr_coeff = bfqd->bfq_wr_coeff; | |
762 | bfqq->wr_cur_max_time = bfq_wr_duration(bfqd); | |
763 | bfqq->last_wr_start_finish = bfqq->wr_start_at_switch_to_srt; | |
764 | } | |
765 | ||
36eca894 | 766 | static void |
13c931bd PV |
767 | bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_data *bfqd, |
768 | struct bfq_io_cq *bic, bool bfq_already_existing) | |
36eca894 | 769 | { |
13c931bd PV |
770 | unsigned int old_wr_coeff = bfqq->wr_coeff; |
771 | bool busy = bfq_already_existing && bfq_bfqq_busy(bfqq); | |
772 | ||
d5be3fef PV |
773 | if (bic->saved_has_short_ttime) |
774 | bfq_mark_bfqq_has_short_ttime(bfqq); | |
36eca894 | 775 | else |
d5be3fef | 776 | bfq_clear_bfqq_has_short_ttime(bfqq); |
36eca894 AA |
777 | |
778 | if (bic->saved_IO_bound) | |
779 | bfq_mark_bfqq_IO_bound(bfqq); | |
780 | else | |
781 | bfq_clear_bfqq_IO_bound(bfqq); | |
782 | ||
783 | bfqq->ttime = bic->saved_ttime; | |
784 | bfqq->wr_coeff = bic->saved_wr_coeff; | |
785 | bfqq->wr_start_at_switch_to_srt = bic->saved_wr_start_at_switch_to_srt; | |
786 | bfqq->last_wr_start_finish = bic->saved_last_wr_start_finish; | |
787 | bfqq->wr_cur_max_time = bic->saved_wr_cur_max_time; | |
788 | ||
e1b2324d | 789 | if (bfqq->wr_coeff > 1 && (bfq_bfqq_in_large_burst(bfqq) || |
36eca894 | 790 | time_is_before_jiffies(bfqq->last_wr_start_finish + |
e1b2324d | 791 | bfqq->wr_cur_max_time))) { |
3e2bdd6d PV |
792 | if (bfqq->wr_cur_max_time == bfqd->bfq_wr_rt_max_time && |
793 | !bfq_bfqq_in_large_burst(bfqq) && | |
794 | time_is_after_eq_jiffies(bfqq->wr_start_at_switch_to_srt + | |
795 | bfq_wr_duration(bfqd))) { | |
796 | switch_back_to_interactive_wr(bfqq, bfqd); | |
797 | } else { | |
798 | bfqq->wr_coeff = 1; | |
799 | bfq_log_bfqq(bfqq->bfqd, bfqq, | |
800 | "resume state: switching off wr"); | |
801 | } | |
36eca894 AA |
802 | } |
803 | ||
804 | /* make sure weight will be updated, however we got here */ | |
805 | bfqq->entity.prio_changed = 1; | |
13c931bd PV |
806 | |
807 | if (likely(!busy)) | |
808 | return; | |
809 | ||
810 | if (old_wr_coeff == 1 && bfqq->wr_coeff > 1) | |
811 | bfqd->wr_busy_queues++; | |
812 | else if (old_wr_coeff > 1 && bfqq->wr_coeff == 1) | |
813 | bfqd->wr_busy_queues--; | |
36eca894 AA |
814 | } |
815 | ||
816 | static int bfqq_process_refs(struct bfq_queue *bfqq) | |
817 | { | |
818 | return bfqq->ref - bfqq->allocated - bfqq->entity.on_st; | |
819 | } | |
820 | ||
e1b2324d AA |
821 | /* Empty burst list and add just bfqq (see comments on bfq_handle_burst) */ |
822 | static void bfq_reset_burst_list(struct bfq_data *bfqd, struct bfq_queue *bfqq) | |
823 | { | |
824 | struct bfq_queue *item; | |
825 | struct hlist_node *n; | |
826 | ||
827 | hlist_for_each_entry_safe(item, n, &bfqd->burst_list, burst_list_node) | |
828 | hlist_del_init(&item->burst_list_node); | |
829 | hlist_add_head(&bfqq->burst_list_node, &bfqd->burst_list); | |
830 | bfqd->burst_size = 1; | |
831 | bfqd->burst_parent_entity = bfqq->entity.parent; | |
832 | } | |
833 | ||
834 | /* Add bfqq to the list of queues in current burst (see bfq_handle_burst) */ | |
835 | static void bfq_add_to_burst(struct bfq_data *bfqd, struct bfq_queue *bfqq) | |
836 | { | |
837 | /* Increment burst size to take into account also bfqq */ | |
838 | bfqd->burst_size++; | |
839 | ||
840 | if (bfqd->burst_size == bfqd->bfq_large_burst_thresh) { | |
841 | struct bfq_queue *pos, *bfqq_item; | |
842 | struct hlist_node *n; | |
843 | ||
844 | /* | |
845 | * Enough queues have been activated shortly after each | |
846 | * other to consider this burst as large. | |
847 | */ | |
848 | bfqd->large_burst = true; | |
849 | ||
850 | /* | |
851 | * We can now mark all queues in the burst list as | |
852 | * belonging to a large burst. | |
853 | */ | |
854 | hlist_for_each_entry(bfqq_item, &bfqd->burst_list, | |
855 | burst_list_node) | |
856 | bfq_mark_bfqq_in_large_burst(bfqq_item); | |
857 | bfq_mark_bfqq_in_large_burst(bfqq); | |
858 | ||
859 | /* | |
860 | * From now on, and until the current burst finishes, any | |
861 | * new queue being activated shortly after the last queue | |
862 | * was inserted in the burst can be immediately marked as | |
863 | * belonging to a large burst. So the burst list is not | |
864 | * needed any more. Remove it. | |
865 | */ | |
866 | hlist_for_each_entry_safe(pos, n, &bfqd->burst_list, | |
867 | burst_list_node) | |
868 | hlist_del_init(&pos->burst_list_node); | |
869 | } else /* | |
870 | * Burst not yet large: add bfqq to the burst list. Do | |
871 | * not increment the ref counter for bfqq, because bfqq | |
872 | * is removed from the burst list before freeing bfqq | |
873 | * in put_queue. | |
874 | */ | |
875 | hlist_add_head(&bfqq->burst_list_node, &bfqd->burst_list); | |
876 | } | |
877 | ||
878 | /* | |
879 | * If many queues belonging to the same group happen to be created | |
880 | * shortly after each other, then the processes associated with these | |
881 | * queues have typically a common goal. In particular, bursts of queue | |
882 | * creations are usually caused by services or applications that spawn | |
883 | * many parallel threads/processes. Examples are systemd during boot, | |
884 | * or git grep. To help these processes get their job done as soon as | |
885 | * possible, it is usually better to not grant either weight-raising | |
886 | * or device idling to their queues. | |
887 | * | |
888 | * In this comment we describe, firstly, the reasons why this fact | |
889 | * holds, and, secondly, the next function, which implements the main | |
890 | * steps needed to properly mark these queues so that they can then be | |
891 | * treated in a different way. | |
892 | * | |
893 | * The above services or applications benefit mostly from a high | |
894 | * throughput: the quicker the requests of the activated queues are | |
895 | * cumulatively served, the sooner the target job of these queues gets | |
896 | * completed. As a consequence, weight-raising any of these queues, | |
897 | * which also implies idling the device for it, is almost always | |
898 | * counterproductive. In most cases it just lowers throughput. | |
899 | * | |
900 | * On the other hand, a burst of queue creations may be caused also by | |
901 | * the start of an application that does not consist of a lot of | |
902 | * parallel I/O-bound threads. In fact, with a complex application, | |
903 | * several short processes may need to be executed to start-up the | |
904 | * application. In this respect, to start an application as quickly as | |
905 | * possible, the best thing to do is in any case to privilege the I/O | |
906 | * related to the application with respect to all other | |
907 | * I/O. Therefore, the best strategy to start as quickly as possible | |
908 | * an application that causes a burst of queue creations is to | |
909 | * weight-raise all the queues created during the burst. This is the | |
910 | * exact opposite of the best strategy for the other type of bursts. | |
911 | * | |
912 | * In the end, to take the best action for each of the two cases, the | |
913 | * two types of bursts need to be distinguished. Fortunately, this | |
914 | * seems relatively easy, by looking at the sizes of the bursts. In | |
915 | * particular, we found a threshold such that only bursts with a | |
916 | * larger size than that threshold are apparently caused by | |
917 | * services or commands such as systemd or git grep. For brevity, | |
918 | * hereafter we call just 'large' these bursts. BFQ *does not* | |
919 | * weight-raise queues whose creation occurs in a large burst. In | |
920 | * addition, for each of these queues BFQ performs or does not perform | |
921 | * idling depending on which choice boosts the throughput more. The | |
922 | * exact choice depends on the device and request pattern at | |
923 | * hand. | |
924 | * | |
925 | * Unfortunately, false positives may occur while an interactive task | |
926 | * is starting (e.g., an application is being started). The | |
927 | * consequence is that the queues associated with the task do not | |
928 | * enjoy weight raising as expected. Fortunately these false positives | |
929 | * are very rare. They typically occur if some service happens to | |
930 | * start doing I/O exactly when the interactive task starts. | |
931 | * | |
932 | * Turning back to the next function, it implements all the steps | |
933 | * needed to detect the occurrence of a large burst and to properly | |
934 | * mark all the queues belonging to it (so that they can then be | |
935 | * treated in a different way). This goal is achieved by maintaining a | |
936 | * "burst list" that holds, temporarily, the queues that belong to the | |
937 | * burst in progress. The list is then used to mark these queues as | |
938 | * belonging to a large burst if the burst does become large. The main | |
939 | * steps are the following. | |
940 | * | |
941 | * . when the very first queue is created, the queue is inserted into the | |
942 | * list (as it could be the first queue in a possible burst) | |
943 | * | |
944 | * . if the current burst has not yet become large, and a queue Q that does | |
945 | * not yet belong to the burst is activated shortly after the last time | |
946 | * at which a new queue entered the burst list, then the function appends | |
947 | * Q to the burst list | |
948 | * | |
949 | * . if, as a consequence of the previous step, the burst size reaches | |
950 | * the large-burst threshold, then | |
951 | * | |
952 | * . all the queues in the burst list are marked as belonging to a | |
953 | * large burst | |
954 | * | |
955 | * . the burst list is deleted; in fact, the burst list already served | |
956 | * its purpose (keeping temporarily track of the queues in a burst, | |
957 | * so as to be able to mark them as belonging to a large burst in the | |
958 | * previous sub-step), and now is not needed any more | |
959 | * | |
960 | * . the device enters a large-burst mode | |
961 | * | |
962 | * . if a queue Q that does not belong to the burst is created while | |
963 | * the device is in large-burst mode and shortly after the last time | |
964 | * at which a queue either entered the burst list or was marked as | |
965 | * belonging to the current large burst, then Q is immediately marked | |
966 | * as belonging to a large burst. | |
967 | * | |
968 | * . if a queue Q that does not belong to the burst is created a while | |
969 | * later, i.e., not shortly after, than the last time at which a queue | |
970 | * either entered the burst list or was marked as belonging to the | |
971 | * current large burst, then the current burst is deemed as finished and: | |
972 | * | |
973 | * . the large-burst mode is reset if set | |
974 | * | |
975 | * . the burst list is emptied | |
976 | * | |
977 | * . Q is inserted in the burst list, as Q may be the first queue | |
978 | * in a possible new burst (then the burst list contains just Q | |
979 | * after this step). | |
980 | */ | |
981 | static void bfq_handle_burst(struct bfq_data *bfqd, struct bfq_queue *bfqq) | |
982 | { | |
983 | /* | |
984 | * If bfqq is already in the burst list or is part of a large | |
985 | * burst, or finally has just been split, then there is | |
986 | * nothing else to do. | |
987 | */ | |
988 | if (!hlist_unhashed(&bfqq->burst_list_node) || | |
989 | bfq_bfqq_in_large_burst(bfqq) || | |
990 | time_is_after_eq_jiffies(bfqq->split_time + | |
991 | msecs_to_jiffies(10))) | |
992 | return; | |
993 | ||
994 | /* | |
995 | * If bfqq's creation happens late enough, or bfqq belongs to | |
996 | * a different group than the burst group, then the current | |
997 | * burst is finished, and related data structures must be | |
998 | * reset. | |
999 | * | |
1000 | * In this respect, consider the special case where bfqq is | |
1001 | * the very first queue created after BFQ is selected for this | |
1002 | * device. In this case, last_ins_in_burst and | |
1003 | * burst_parent_entity are not yet significant when we get | |
1004 | * here. But it is easy to verify that, whether or not the | |
1005 | * following condition is true, bfqq will end up being | |
1006 | * inserted into the burst list. In particular the list will | |
1007 | * happen to contain only bfqq. And this is exactly what has | |
1008 | * to happen, as bfqq may be the first queue of the first | |
1009 | * burst. | |
1010 | */ | |
1011 | if (time_is_before_jiffies(bfqd->last_ins_in_burst + | |
1012 | bfqd->bfq_burst_interval) || | |
1013 | bfqq->entity.parent != bfqd->burst_parent_entity) { | |
1014 | bfqd->large_burst = false; | |
1015 | bfq_reset_burst_list(bfqd, bfqq); | |
1016 | goto end; | |
1017 | } | |
1018 | ||
1019 | /* | |
1020 | * If we get here, then bfqq is being activated shortly after the | |
1021 | * last queue. So, if the current burst is also large, we can mark | |
1022 | * bfqq as belonging to this large burst immediately. | |
1023 | */ | |
1024 | if (bfqd->large_burst) { | |
1025 | bfq_mark_bfqq_in_large_burst(bfqq); | |
1026 | goto end; | |
1027 | } | |
1028 | ||
1029 | /* | |
1030 | * If we get here, then a large-burst state has not yet been | |
1031 | * reached, but bfqq is being activated shortly after the last | |
1032 | * queue. Then we add bfqq to the burst. | |
1033 | */ | |
1034 | bfq_add_to_burst(bfqd, bfqq); | |
1035 | end: | |
1036 | /* | |
1037 | * At this point, bfqq either has been added to the current | |
1038 | * burst or has caused the current burst to terminate and a | |
1039 | * possible new burst to start. In particular, in the second | |
1040 | * case, bfqq has become the first queue in the possible new | |
1041 | * burst. In both cases last_ins_in_burst needs to be moved | |
1042 | * forward. | |
1043 | */ | |
1044 | bfqd->last_ins_in_burst = jiffies; | |
1045 | } | |
1046 | ||
aee69d78 PV |
1047 | static int bfq_bfqq_budget_left(struct bfq_queue *bfqq) |
1048 | { | |
1049 | struct bfq_entity *entity = &bfqq->entity; | |
1050 | ||
1051 | return entity->budget - entity->service; | |
1052 | } | |
1053 | ||
1054 | /* | |
1055 | * If enough samples have been computed, return the current max budget | |
1056 | * stored in bfqd, which is dynamically updated according to the | |
1057 | * estimated disk peak rate; otherwise return the default max budget | |
1058 | */ | |
1059 | static int bfq_max_budget(struct bfq_data *bfqd) | |
1060 | { | |
1061 | if (bfqd->budgets_assigned < bfq_stats_min_budgets) | |
1062 | return bfq_default_max_budget; | |
1063 | else | |
1064 | return bfqd->bfq_max_budget; | |
1065 | } | |
1066 | ||
1067 | /* | |
1068 | * Return min budget, which is a fraction of the current or default | |
1069 | * max budget (trying with 1/32) | |
1070 | */ | |
1071 | static int bfq_min_budget(struct bfq_data *bfqd) | |
1072 | { | |
1073 | if (bfqd->budgets_assigned < bfq_stats_min_budgets) | |
1074 | return bfq_default_max_budget / 32; | |
1075 | else | |
1076 | return bfqd->bfq_max_budget / 32; | |
1077 | } | |
1078 | ||
aee69d78 PV |
1079 | /* |
1080 | * The next function, invoked after the input queue bfqq switches from | |
1081 | * idle to busy, updates the budget of bfqq. The function also tells | |
1082 | * whether the in-service queue should be expired, by returning | |
1083 | * true. The purpose of expiring the in-service queue is to give bfqq | |
1084 | * the chance to possibly preempt the in-service queue, and the reason | |
44e44a1b PV |
1085 | * for preempting the in-service queue is to achieve one of the two |
1086 | * goals below. | |
aee69d78 | 1087 | * |
44e44a1b PV |
1088 | * 1. Guarantee to bfqq its reserved bandwidth even if bfqq has |
1089 | * expired because it has remained idle. In particular, bfqq may have | |
1090 | * expired for one of the following two reasons: | |
aee69d78 PV |
1091 | * |
1092 | * - BFQQE_NO_MORE_REQUESTS bfqq did not enjoy any device idling | |
1093 | * and did not make it to issue a new request before its last | |
1094 | * request was served; | |
1095 | * | |
1096 | * - BFQQE_TOO_IDLE bfqq did enjoy device idling, but did not issue | |
1097 | * a new request before the expiration of the idling-time. | |
1098 | * | |
1099 | * Even if bfqq has expired for one of the above reasons, the process | |
1100 | * associated with the queue may be however issuing requests greedily, | |
1101 | * and thus be sensitive to the bandwidth it receives (bfqq may have | |
1102 | * remained idle for other reasons: CPU high load, bfqq not enjoying | |
1103 | * idling, I/O throttling somewhere in the path from the process to | |
1104 | * the I/O scheduler, ...). But if, after every expiration for one of | |
1105 | * the above two reasons, bfqq has to wait for the service of at least | |
1106 | * one full budget of another queue before being served again, then | |
1107 | * bfqq is likely to get a much lower bandwidth or resource time than | |
1108 | * its reserved ones. To address this issue, two countermeasures need | |
1109 | * to be taken. | |
1110 | * | |
1111 | * First, the budget and the timestamps of bfqq need to be updated in | |
1112 | * a special way on bfqq reactivation: they need to be updated as if | |
1113 | * bfqq did not remain idle and did not expire. In fact, if they are | |
1114 | * computed as if bfqq expired and remained idle until reactivation, | |
1115 | * then the process associated with bfqq is treated as if, instead of | |
1116 | * being greedy, it stopped issuing requests when bfqq remained idle, | |
1117 | * and restarts issuing requests only on this reactivation. In other | |
1118 | * words, the scheduler does not help the process recover the "service | |
1119 | * hole" between bfqq expiration and reactivation. As a consequence, | |
1120 | * the process receives a lower bandwidth than its reserved one. In | |
1121 | * contrast, to recover this hole, the budget must be updated as if | |
1122 | * bfqq was not expired at all before this reactivation, i.e., it must | |
1123 | * be set to the value of the remaining budget when bfqq was | |
1124 | * expired. Along the same line, timestamps need to be assigned the | |
1125 | * value they had the last time bfqq was selected for service, i.e., | |
1126 | * before last expiration. Thus timestamps need to be back-shifted | |
1127 | * with respect to their normal computation (see [1] for more details | |
1128 | * on this tricky aspect). | |
1129 | * | |
1130 | * Secondly, to allow the process to recover the hole, the in-service | |
1131 | * queue must be expired too, to give bfqq the chance to preempt it | |
1132 | * immediately. In fact, if bfqq has to wait for a full budget of the | |
1133 | * in-service queue to be completed, then it may become impossible to | |
1134 | * let the process recover the hole, even if the back-shifted | |
1135 | * timestamps of bfqq are lower than those of the in-service queue. If | |
1136 | * this happens for most or all of the holes, then the process may not | |
1137 | * receive its reserved bandwidth. In this respect, it is worth noting | |
1138 | * that, being the service of outstanding requests unpreemptible, a | |
1139 | * little fraction of the holes may however be unrecoverable, thereby | |
1140 | * causing a little loss of bandwidth. | |
1141 | * | |
1142 | * The last important point is detecting whether bfqq does need this | |
1143 | * bandwidth recovery. In this respect, the next function deems the | |
1144 | * process associated with bfqq greedy, and thus allows it to recover | |
1145 | * the hole, if: 1) the process is waiting for the arrival of a new | |
1146 | * request (which implies that bfqq expired for one of the above two | |
1147 | * reasons), and 2) such a request has arrived soon. The first | |
1148 | * condition is controlled through the flag non_blocking_wait_rq, | |
1149 | * while the second through the flag arrived_in_time. If both | |
1150 | * conditions hold, then the function computes the budget in the | |
1151 | * above-described special way, and signals that the in-service queue | |
1152 | * should be expired. Timestamp back-shifting is done later in | |
1153 | * __bfq_activate_entity. | |
44e44a1b PV |
1154 | * |
1155 | * 2. Reduce latency. Even if timestamps are not backshifted to let | |
1156 | * the process associated with bfqq recover a service hole, bfqq may | |
1157 | * however happen to have, after being (re)activated, a lower finish | |
1158 | * timestamp than the in-service queue. That is, the next budget of | |
1159 | * bfqq may have to be completed before the one of the in-service | |
1160 | * queue. If this is the case, then preempting the in-service queue | |
1161 | * allows this goal to be achieved, apart from the unpreemptible, | |
1162 | * outstanding requests mentioned above. | |
1163 | * | |
1164 | * Unfortunately, regardless of which of the above two goals one wants | |
1165 | * to achieve, service trees need first to be updated to know whether | |
1166 | * the in-service queue must be preempted. To have service trees | |
1167 | * correctly updated, the in-service queue must be expired and | |
1168 | * rescheduled, and bfqq must be scheduled too. This is one of the | |
1169 | * most costly operations (in future versions, the scheduling | |
1170 | * mechanism may be re-designed in such a way to make it possible to | |
1171 | * know whether preemption is needed without needing to update service | |
1172 | * trees). In addition, queue preemptions almost always cause random | |
1173 | * I/O, and thus loss of throughput. Because of these facts, the next | |
1174 | * function adopts the following simple scheme to avoid both costly | |
1175 | * operations and too frequent preemptions: it requests the expiration | |
1176 | * of the in-service queue (unconditionally) only for queues that need | |
1177 | * to recover a hole, or that either are weight-raised or deserve to | |
1178 | * be weight-raised. | |
aee69d78 PV |
1179 | */ |
1180 | static bool bfq_bfqq_update_budg_for_activation(struct bfq_data *bfqd, | |
1181 | struct bfq_queue *bfqq, | |
44e44a1b PV |
1182 | bool arrived_in_time, |
1183 | bool wr_or_deserves_wr) | |
aee69d78 PV |
1184 | { |
1185 | struct bfq_entity *entity = &bfqq->entity; | |
1186 | ||
1187 | if (bfq_bfqq_non_blocking_wait_rq(bfqq) && arrived_in_time) { | |
1188 | /* | |
1189 | * We do not clear the flag non_blocking_wait_rq here, as | |
1190 | * the latter is used in bfq_activate_bfqq to signal | |
1191 | * that timestamps need to be back-shifted (and is | |
1192 | * cleared right after). | |
1193 | */ | |
1194 | ||
1195 | /* | |
1196 | * In next assignment we rely on that either | |
1197 | * entity->service or entity->budget are not updated | |
1198 | * on expiration if bfqq is empty (see | |
1199 | * __bfq_bfqq_recalc_budget). Thus both quantities | |
1200 | * remain unchanged after such an expiration, and the | |
1201 | * following statement therefore assigns to | |
1202 | * entity->budget the remaining budget on such an | |
1203 | * expiration. For clarity, entity->service is not | |
1204 | * updated on expiration in any case, and, in normal | |
1205 | * operation, is reset only when bfqq is selected for | |
1206 | * service (see bfq_get_next_queue). | |
1207 | */ | |
1208 | entity->budget = min_t(unsigned long, | |
1209 | bfq_bfqq_budget_left(bfqq), | |
1210 | bfqq->max_budget); | |
1211 | ||
1212 | return true; | |
1213 | } | |
1214 | ||
1215 | entity->budget = max_t(unsigned long, bfqq->max_budget, | |
1216 | bfq_serv_to_charge(bfqq->next_rq, bfqq)); | |
1217 | bfq_clear_bfqq_non_blocking_wait_rq(bfqq); | |
44e44a1b PV |
1218 | return wr_or_deserves_wr; |
1219 | } | |
1220 | ||
4baa8bb1 PV |
1221 | /* |
1222 | * Return the farthest future time instant according to jiffies | |
1223 | * macros. | |
1224 | */ | |
1225 | static unsigned long bfq_greatest_from_now(void) | |
1226 | { | |
1227 | return jiffies + MAX_JIFFY_OFFSET; | |
1228 | } | |
1229 | ||
1230 | /* | |
1231 | * Return the farthest past time instant according to jiffies | |
1232 | * macros. | |
1233 | */ | |
1234 | static unsigned long bfq_smallest_from_now(void) | |
1235 | { | |
1236 | return jiffies - MAX_JIFFY_OFFSET; | |
1237 | } | |
1238 | ||
44e44a1b PV |
1239 | static void bfq_update_bfqq_wr_on_rq_arrival(struct bfq_data *bfqd, |
1240 | struct bfq_queue *bfqq, | |
1241 | unsigned int old_wr_coeff, | |
1242 | bool wr_or_deserves_wr, | |
77b7dcea | 1243 | bool interactive, |
e1b2324d | 1244 | bool in_burst, |
77b7dcea | 1245 | bool soft_rt) |
44e44a1b PV |
1246 | { |
1247 | if (old_wr_coeff == 1 && wr_or_deserves_wr) { | |
1248 | /* start a weight-raising period */ | |
77b7dcea PV |
1249 | if (interactive) { |
1250 | bfqq->wr_coeff = bfqd->bfq_wr_coeff; | |
1251 | bfqq->wr_cur_max_time = bfq_wr_duration(bfqd); | |
1252 | } else { | |
4baa8bb1 PV |
1253 | /* |
1254 | * No interactive weight raising in progress | |
1255 | * here: assign minus infinity to | |
1256 | * wr_start_at_switch_to_srt, to make sure | |
1257 | * that, at the end of the soft-real-time | |
1258 | * weight raising periods that is starting | |
1259 | * now, no interactive weight-raising period | |
1260 | * may be wrongly considered as still in | |
1261 | * progress (and thus actually started by | |
1262 | * mistake). | |
1263 | */ | |
1264 | bfqq->wr_start_at_switch_to_srt = | |
1265 | bfq_smallest_from_now(); | |
77b7dcea PV |
1266 | bfqq->wr_coeff = bfqd->bfq_wr_coeff * |
1267 | BFQ_SOFTRT_WEIGHT_FACTOR; | |
1268 | bfqq->wr_cur_max_time = | |
1269 | bfqd->bfq_wr_rt_max_time; | |
1270 | } | |
44e44a1b PV |
1271 | |
1272 | /* | |
1273 | * If needed, further reduce budget to make sure it is | |
1274 | * close to bfqq's backlog, so as to reduce the | |
1275 | * scheduling-error component due to a too large | |
1276 | * budget. Do not care about throughput consequences, | |
1277 | * but only about latency. Finally, do not assign a | |
1278 | * too small budget either, to avoid increasing | |
1279 | * latency by causing too frequent expirations. | |
1280 | */ | |
1281 | bfqq->entity.budget = min_t(unsigned long, | |
1282 | bfqq->entity.budget, | |
1283 | 2 * bfq_min_budget(bfqd)); | |
1284 | } else if (old_wr_coeff > 1) { | |
77b7dcea PV |
1285 | if (interactive) { /* update wr coeff and duration */ |
1286 | bfqq->wr_coeff = bfqd->bfq_wr_coeff; | |
1287 | bfqq->wr_cur_max_time = bfq_wr_duration(bfqd); | |
e1b2324d AA |
1288 | } else if (in_burst) |
1289 | bfqq->wr_coeff = 1; | |
1290 | else if (soft_rt) { | |
77b7dcea PV |
1291 | /* |
1292 | * The application is now or still meeting the | |
1293 | * requirements for being deemed soft rt. We | |
1294 | * can then correctly and safely (re)charge | |
1295 | * the weight-raising duration for the | |
1296 | * application with the weight-raising | |
1297 | * duration for soft rt applications. | |
1298 | * | |
1299 | * In particular, doing this recharge now, i.e., | |
1300 | * before the weight-raising period for the | |
1301 | * application finishes, reduces the probability | |
1302 | * of the following negative scenario: | |
1303 | * 1) the weight of a soft rt application is | |
1304 | * raised at startup (as for any newly | |
1305 | * created application), | |
1306 | * 2) since the application is not interactive, | |
1307 | * at a certain time weight-raising is | |
1308 | * stopped for the application, | |
1309 | * 3) at that time the application happens to | |
1310 | * still have pending requests, and hence | |
1311 | * is destined to not have a chance to be | |
1312 | * deemed soft rt before these requests are | |
1313 | * completed (see the comments to the | |
1314 | * function bfq_bfqq_softrt_next_start() | |
1315 | * for details on soft rt detection), | |
1316 | * 4) these pending requests experience a high | |
1317 | * latency because the application is not | |
1318 | * weight-raised while they are pending. | |
1319 | */ | |
1320 | if (bfqq->wr_cur_max_time != | |
1321 | bfqd->bfq_wr_rt_max_time) { | |
1322 | bfqq->wr_start_at_switch_to_srt = | |
1323 | bfqq->last_wr_start_finish; | |
1324 | ||
1325 | bfqq->wr_cur_max_time = | |
1326 | bfqd->bfq_wr_rt_max_time; | |
1327 | bfqq->wr_coeff = bfqd->bfq_wr_coeff * | |
1328 | BFQ_SOFTRT_WEIGHT_FACTOR; | |
1329 | } | |
1330 | bfqq->last_wr_start_finish = jiffies; | |
1331 | } | |
44e44a1b PV |
1332 | } |
1333 | } | |
1334 | ||
1335 | static bool bfq_bfqq_idle_for_long_time(struct bfq_data *bfqd, | |
1336 | struct bfq_queue *bfqq) | |
1337 | { | |
1338 | return bfqq->dispatched == 0 && | |
1339 | time_is_before_jiffies( | |
1340 | bfqq->budget_timeout + | |
1341 | bfqd->bfq_wr_min_idle_time); | |
aee69d78 PV |
1342 | } |
1343 | ||
1344 | static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, | |
1345 | struct bfq_queue *bfqq, | |
44e44a1b PV |
1346 | int old_wr_coeff, |
1347 | struct request *rq, | |
1348 | bool *interactive) | |
aee69d78 | 1349 | { |
e1b2324d AA |
1350 | bool soft_rt, in_burst, wr_or_deserves_wr, |
1351 | bfqq_wants_to_preempt, | |
44e44a1b | 1352 | idle_for_long_time = bfq_bfqq_idle_for_long_time(bfqd, bfqq), |
aee69d78 PV |
1353 | /* |
1354 | * See the comments on | |
1355 | * bfq_bfqq_update_budg_for_activation for | |
1356 | * details on the usage of the next variable. | |
1357 | */ | |
1358 | arrived_in_time = ktime_get_ns() <= | |
1359 | bfqq->ttime.last_end_request + | |
1360 | bfqd->bfq_slice_idle * 3; | |
1361 | ||
e21b7a0b | 1362 | |
aee69d78 | 1363 | /* |
44e44a1b PV |
1364 | * bfqq deserves to be weight-raised if: |
1365 | * - it is sync, | |
e1b2324d | 1366 | * - it does not belong to a large burst, |
36eca894 AA |
1367 | * - it has been idle for enough time or is soft real-time, |
1368 | * - is linked to a bfq_io_cq (it is not shared in any sense). | |
44e44a1b | 1369 | */ |
e1b2324d | 1370 | in_burst = bfq_bfqq_in_large_burst(bfqq); |
77b7dcea | 1371 | soft_rt = bfqd->bfq_wr_max_softrt_rate > 0 && |
e1b2324d | 1372 | !in_burst && |
77b7dcea | 1373 | time_is_before_jiffies(bfqq->soft_rt_next_start); |
e1b2324d | 1374 | *interactive = !in_burst && idle_for_long_time; |
44e44a1b PV |
1375 | wr_or_deserves_wr = bfqd->low_latency && |
1376 | (bfqq->wr_coeff > 1 || | |
36eca894 AA |
1377 | (bfq_bfqq_sync(bfqq) && |
1378 | bfqq->bic && (*interactive || soft_rt))); | |
44e44a1b PV |
1379 | |
1380 | /* | |
1381 | * Using the last flag, update budget and check whether bfqq | |
1382 | * may want to preempt the in-service queue. | |
aee69d78 PV |
1383 | */ |
1384 | bfqq_wants_to_preempt = | |
1385 | bfq_bfqq_update_budg_for_activation(bfqd, bfqq, | |
44e44a1b PV |
1386 | arrived_in_time, |
1387 | wr_or_deserves_wr); | |
aee69d78 | 1388 | |
e1b2324d AA |
1389 | /* |
1390 | * If bfqq happened to be activated in a burst, but has been | |
1391 | * idle for much more than an interactive queue, then we | |
1392 | * assume that, in the overall I/O initiated in the burst, the | |
1393 | * I/O associated with bfqq is finished. So bfqq does not need | |
1394 | * to be treated as a queue belonging to a burst | |
1395 | * anymore. Accordingly, we reset bfqq's in_large_burst flag | |
1396 | * if set, and remove bfqq from the burst list if it's | |
1397 | * there. We do not decrement burst_size, because the fact | |
1398 | * that bfqq does not need to belong to the burst list any | |
1399 | * more does not invalidate the fact that bfqq was created in | |
1400 | * a burst. | |
1401 | */ | |
1402 | if (likely(!bfq_bfqq_just_created(bfqq)) && | |
1403 | idle_for_long_time && | |
1404 | time_is_before_jiffies( | |
1405 | bfqq->budget_timeout + | |
1406 | msecs_to_jiffies(10000))) { | |
1407 | hlist_del_init(&bfqq->burst_list_node); | |
1408 | bfq_clear_bfqq_in_large_burst(bfqq); | |
1409 | } | |
1410 | ||
1411 | bfq_clear_bfqq_just_created(bfqq); | |
1412 | ||
1413 | ||
aee69d78 PV |
1414 | if (!bfq_bfqq_IO_bound(bfqq)) { |
1415 | if (arrived_in_time) { | |
1416 | bfqq->requests_within_timer++; | |
1417 | if (bfqq->requests_within_timer >= | |
1418 | bfqd->bfq_requests_within_timer) | |
1419 | bfq_mark_bfqq_IO_bound(bfqq); | |
1420 | } else | |
1421 | bfqq->requests_within_timer = 0; | |
1422 | } | |
1423 | ||
44e44a1b | 1424 | if (bfqd->low_latency) { |
36eca894 AA |
1425 | if (unlikely(time_is_after_jiffies(bfqq->split_time))) |
1426 | /* wraparound */ | |
1427 | bfqq->split_time = | |
1428 | jiffies - bfqd->bfq_wr_min_idle_time - 1; | |
1429 | ||
1430 | if (time_is_before_jiffies(bfqq->split_time + | |
1431 | bfqd->bfq_wr_min_idle_time)) { | |
1432 | bfq_update_bfqq_wr_on_rq_arrival(bfqd, bfqq, | |
1433 | old_wr_coeff, | |
1434 | wr_or_deserves_wr, | |
1435 | *interactive, | |
e1b2324d | 1436 | in_burst, |
36eca894 AA |
1437 | soft_rt); |
1438 | ||
1439 | if (old_wr_coeff != bfqq->wr_coeff) | |
1440 | bfqq->entity.prio_changed = 1; | |
1441 | } | |
44e44a1b PV |
1442 | } |
1443 | ||
77b7dcea PV |
1444 | bfqq->last_idle_bklogged = jiffies; |
1445 | bfqq->service_from_backlogged = 0; | |
1446 | bfq_clear_bfqq_softrt_update(bfqq); | |
1447 | ||
aee69d78 PV |
1448 | bfq_add_bfqq_busy(bfqd, bfqq); |
1449 | ||
1450 | /* | |
1451 | * Expire in-service queue only if preemption may be needed | |
1452 | * for guarantees. In this respect, the function | |
1453 | * next_queue_may_preempt just checks a simple, necessary | |
1454 | * condition, and not a sufficient condition based on | |
1455 | * timestamps. In fact, for the latter condition to be | |
1456 | * evaluated, timestamps would need first to be updated, and | |
1457 | * this operation is quite costly (see the comments on the | |
1458 | * function bfq_bfqq_update_budg_for_activation). | |
1459 | */ | |
1460 | if (bfqd->in_service_queue && bfqq_wants_to_preempt && | |
77b7dcea | 1461 | bfqd->in_service_queue->wr_coeff < bfqq->wr_coeff && |
aee69d78 PV |
1462 | next_queue_may_preempt(bfqd)) |
1463 | bfq_bfqq_expire(bfqd, bfqd->in_service_queue, | |
1464 | false, BFQQE_PREEMPTED); | |
1465 | } | |
1466 | ||
1467 | static void bfq_add_request(struct request *rq) | |
1468 | { | |
1469 | struct bfq_queue *bfqq = RQ_BFQQ(rq); | |
1470 | struct bfq_data *bfqd = bfqq->bfqd; | |
1471 | struct request *next_rq, *prev; | |
44e44a1b PV |
1472 | unsigned int old_wr_coeff = bfqq->wr_coeff; |
1473 | bool interactive = false; | |
aee69d78 PV |
1474 | |
1475 | bfq_log_bfqq(bfqd, bfqq, "add_request %d", rq_is_sync(rq)); | |
1476 | bfqq->queued[rq_is_sync(rq)]++; | |
1477 | bfqd->queued++; | |
1478 | ||
1479 | elv_rb_add(&bfqq->sort_list, rq); | |
1480 | ||
1481 | /* | |
1482 | * Check if this request is a better next-serve candidate. | |
1483 | */ | |
1484 | prev = bfqq->next_rq; | |
1485 | next_rq = bfq_choose_req(bfqd, bfqq->next_rq, rq, bfqd->last_position); | |
1486 | bfqq->next_rq = next_rq; | |
1487 | ||
36eca894 AA |
1488 | /* |
1489 | * Adjust priority tree position, if next_rq changes. | |
1490 | */ | |
1491 | if (prev != bfqq->next_rq) | |
1492 | bfq_pos_tree_add_move(bfqd, bfqq); | |
1493 | ||
aee69d78 | 1494 | if (!bfq_bfqq_busy(bfqq)) /* switching to busy ... */ |
44e44a1b PV |
1495 | bfq_bfqq_handle_idle_busy_switch(bfqd, bfqq, old_wr_coeff, |
1496 | rq, &interactive); | |
1497 | else { | |
1498 | if (bfqd->low_latency && old_wr_coeff == 1 && !rq_is_sync(rq) && | |
1499 | time_is_before_jiffies( | |
1500 | bfqq->last_wr_start_finish + | |
1501 | bfqd->bfq_wr_min_inter_arr_async)) { | |
1502 | bfqq->wr_coeff = bfqd->bfq_wr_coeff; | |
1503 | bfqq->wr_cur_max_time = bfq_wr_duration(bfqd); | |
1504 | ||
cfd69712 | 1505 | bfqd->wr_busy_queues++; |
44e44a1b PV |
1506 | bfqq->entity.prio_changed = 1; |
1507 | } | |
1508 | if (prev != bfqq->next_rq) | |
1509 | bfq_updated_next_req(bfqd, bfqq); | |
1510 | } | |
1511 | ||
1512 | /* | |
1513 | * Assign jiffies to last_wr_start_finish in the following | |
1514 | * cases: | |
1515 | * | |
1516 | * . if bfqq is not going to be weight-raised, because, for | |
1517 | * non weight-raised queues, last_wr_start_finish stores the | |
1518 | * arrival time of the last request; as of now, this piece | |
1519 | * of information is used only for deciding whether to | |
1520 | * weight-raise async queues | |
1521 | * | |
1522 | * . if bfqq is not weight-raised, because, if bfqq is now | |
1523 | * switching to weight-raised, then last_wr_start_finish | |
1524 | * stores the time when weight-raising starts | |
1525 | * | |
1526 | * . if bfqq is interactive, because, regardless of whether | |
1527 | * bfqq is currently weight-raised, the weight-raising | |
1528 | * period must start or restart (this case is considered | |
1529 | * separately because it is not detected by the above | |
1530 | * conditions, if bfqq is already weight-raised) | |
77b7dcea PV |
1531 | * |
1532 | * last_wr_start_finish has to be updated also if bfqq is soft | |
1533 | * real-time, because the weight-raising period is constantly | |
1534 | * restarted on idle-to-busy transitions for these queues, but | |
1535 | * this is already done in bfq_bfqq_handle_idle_busy_switch if | |
1536 | * needed. | |
44e44a1b PV |
1537 | */ |
1538 | if (bfqd->low_latency && | |
1539 | (old_wr_coeff == 1 || bfqq->wr_coeff == 1 || interactive)) | |
1540 | bfqq->last_wr_start_finish = jiffies; | |
aee69d78 PV |
1541 | } |
1542 | ||
1543 | static struct request *bfq_find_rq_fmerge(struct bfq_data *bfqd, | |
1544 | struct bio *bio, | |
1545 | struct request_queue *q) | |
1546 | { | |
1547 | struct bfq_queue *bfqq = bfqd->bio_bfqq; | |
1548 | ||
1549 | ||
1550 | if (bfqq) | |
1551 | return elv_rb_find(&bfqq->sort_list, bio_end_sector(bio)); | |
1552 | ||
1553 | return NULL; | |
1554 | } | |
1555 | ||
ab0e43e9 PV |
1556 | static sector_t get_sdist(sector_t last_pos, struct request *rq) |
1557 | { | |
1558 | if (last_pos) | |
1559 | return abs(blk_rq_pos(rq) - last_pos); | |
1560 | ||
1561 | return 0; | |
1562 | } | |
1563 | ||
aee69d78 PV |
1564 | #if 0 /* Still not clear if we can do without next two functions */ |
1565 | static void bfq_activate_request(struct request_queue *q, struct request *rq) | |
1566 | { | |
1567 | struct bfq_data *bfqd = q->elevator->elevator_data; | |
1568 | ||
1569 | bfqd->rq_in_driver++; | |
aee69d78 PV |
1570 | } |
1571 | ||
1572 | static void bfq_deactivate_request(struct request_queue *q, struct request *rq) | |
1573 | { | |
1574 | struct bfq_data *bfqd = q->elevator->elevator_data; | |
1575 | ||
1576 | bfqd->rq_in_driver--; | |
1577 | } | |
1578 | #endif | |
1579 | ||
1580 | static void bfq_remove_request(struct request_queue *q, | |
1581 | struct request *rq) | |
1582 | { | |
1583 | struct bfq_queue *bfqq = RQ_BFQQ(rq); | |
1584 | struct bfq_data *bfqd = bfqq->bfqd; | |
1585 | const int sync = rq_is_sync(rq); | |
1586 | ||
1587 | if (bfqq->next_rq == rq) { | |
1588 | bfqq->next_rq = bfq_find_next_rq(bfqd, bfqq, rq); | |
1589 | bfq_updated_next_req(bfqd, bfqq); | |
1590 | } | |
1591 | ||
1592 | if (rq->queuelist.prev != &rq->queuelist) | |
1593 | list_del_init(&rq->queuelist); | |
1594 | bfqq->queued[sync]--; | |
1595 | bfqd->queued--; | |
1596 | elv_rb_del(&bfqq->sort_list, rq); | |
1597 | ||
1598 | elv_rqhash_del(q, rq); | |
1599 | if (q->last_merge == rq) | |
1600 | q->last_merge = NULL; | |
1601 | ||
1602 | if (RB_EMPTY_ROOT(&bfqq->sort_list)) { | |
1603 | bfqq->next_rq = NULL; | |
1604 | ||
1605 | if (bfq_bfqq_busy(bfqq) && bfqq != bfqd->in_service_queue) { | |
e21b7a0b | 1606 | bfq_del_bfqq_busy(bfqd, bfqq, false); |
aee69d78 PV |
1607 | /* |
1608 | * bfqq emptied. In normal operation, when | |
1609 | * bfqq is empty, bfqq->entity.service and | |
1610 | * bfqq->entity.budget must contain, | |
1611 | * respectively, the service received and the | |
1612 | * budget used last time bfqq emptied. These | |
1613 | * facts do not hold in this case, as at least | |
1614 | * this last removal occurred while bfqq is | |
1615 | * not in service. To avoid inconsistencies, | |
1616 | * reset both bfqq->entity.service and | |
1617 | * bfqq->entity.budget, if bfqq has still a | |
1618 | * process that may issue I/O requests to it. | |
1619 | */ | |
1620 | bfqq->entity.budget = bfqq->entity.service = 0; | |
1621 | } | |
36eca894 AA |
1622 | |
1623 | /* | |
1624 | * Remove queue from request-position tree as it is empty. | |
1625 | */ | |
1626 | if (bfqq->pos_root) { | |
1627 | rb_erase(&bfqq->pos_node, bfqq->pos_root); | |
1628 | bfqq->pos_root = NULL; | |
1629 | } | |
aee69d78 PV |
1630 | } |
1631 | ||
1632 | if (rq->cmd_flags & REQ_META) | |
1633 | bfqq->meta_pending--; | |
e21b7a0b | 1634 | |
aee69d78 PV |
1635 | } |
1636 | ||
1637 | static bool bfq_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio) | |
1638 | { | |
1639 | struct request_queue *q = hctx->queue; | |
1640 | struct bfq_data *bfqd = q->elevator->elevator_data; | |
1641 | struct request *free = NULL; | |
1642 | /* | |
1643 | * bfq_bic_lookup grabs the queue_lock: invoke it now and | |
1644 | * store its return value for later use, to avoid nesting | |
1645 | * queue_lock inside the bfqd->lock. We assume that the bic | |
1646 | * returned by bfq_bic_lookup does not go away before | |
1647 | * bfqd->lock is taken. | |
1648 | */ | |
1649 | struct bfq_io_cq *bic = bfq_bic_lookup(bfqd, current->io_context, q); | |
1650 | bool ret; | |
1651 | ||
1652 | spin_lock_irq(&bfqd->lock); | |
1653 | ||
1654 | if (bic) | |
1655 | bfqd->bio_bfqq = bic_to_bfqq(bic, op_is_sync(bio->bi_opf)); | |
1656 | else | |
1657 | bfqd->bio_bfqq = NULL; | |
1658 | bfqd->bio_bic = bic; | |
1659 | ||
1660 | ret = blk_mq_sched_try_merge(q, bio, &free); | |
1661 | ||
1662 | if (free) | |
1663 | blk_mq_free_request(free); | |
1664 | spin_unlock_irq(&bfqd->lock); | |
1665 | ||
1666 | return ret; | |
1667 | } | |
1668 | ||
1669 | static int bfq_request_merge(struct request_queue *q, struct request **req, | |
1670 | struct bio *bio) | |
1671 | { | |
1672 | struct bfq_data *bfqd = q->elevator->elevator_data; | |
1673 | struct request *__rq; | |
1674 | ||
1675 | __rq = bfq_find_rq_fmerge(bfqd, bio, q); | |
1676 | if (__rq && elv_bio_merge_ok(__rq, bio)) { | |
1677 | *req = __rq; | |
1678 | return ELEVATOR_FRONT_MERGE; | |
1679 | } | |
1680 | ||
1681 | return ELEVATOR_NO_MERGE; | |
1682 | } | |
1683 | ||
1684 | static void bfq_request_merged(struct request_queue *q, struct request *req, | |
1685 | enum elv_merge type) | |
1686 | { | |
1687 | if (type == ELEVATOR_FRONT_MERGE && | |
1688 | rb_prev(&req->rb_node) && | |
1689 | blk_rq_pos(req) < | |
1690 | blk_rq_pos(container_of(rb_prev(&req->rb_node), | |
1691 | struct request, rb_node))) { | |
1692 | struct bfq_queue *bfqq = RQ_BFQQ(req); | |
1693 | struct bfq_data *bfqd = bfqq->bfqd; | |
1694 | struct request *prev, *next_rq; | |
1695 | ||
1696 | /* Reposition request in its sort_list */ | |
1697 | elv_rb_del(&bfqq->sort_list, req); | |
1698 | elv_rb_add(&bfqq->sort_list, req); | |
1699 | ||
1700 | /* Choose next request to be served for bfqq */ | |
1701 | prev = bfqq->next_rq; | |
1702 | next_rq = bfq_choose_req(bfqd, bfqq->next_rq, req, | |
1703 | bfqd->last_position); | |
1704 | bfqq->next_rq = next_rq; | |
1705 | /* | |
36eca894 AA |
1706 | * If next_rq changes, update both the queue's budget to |
1707 | * fit the new request and the queue's position in its | |
1708 | * rq_pos_tree. | |
aee69d78 | 1709 | */ |
36eca894 | 1710 | if (prev != bfqq->next_rq) { |
aee69d78 | 1711 | bfq_updated_next_req(bfqd, bfqq); |
36eca894 AA |
1712 | bfq_pos_tree_add_move(bfqd, bfqq); |
1713 | } | |
aee69d78 PV |
1714 | } |
1715 | } | |
1716 | ||
1717 | static void bfq_requests_merged(struct request_queue *q, struct request *rq, | |
1718 | struct request *next) | |
1719 | { | |
1720 | struct bfq_queue *bfqq = RQ_BFQQ(rq), *next_bfqq = RQ_BFQQ(next); | |
1721 | ||
1722 | if (!RB_EMPTY_NODE(&rq->rb_node)) | |
e21b7a0b | 1723 | goto end; |
aee69d78 PV |
1724 | spin_lock_irq(&bfqq->bfqd->lock); |
1725 | ||
1726 | /* | |
1727 | * If next and rq belong to the same bfq_queue and next is older | |
1728 | * than rq, then reposition rq in the fifo (by substituting next | |
1729 | * with rq). Otherwise, if next and rq belong to different | |
1730 | * bfq_queues, never reposition rq: in fact, we would have to | |
1731 | * reposition it with respect to next's position in its own fifo, | |
1732 | * which would most certainly be too expensive with respect to | |
1733 | * the benefits. | |
1734 | */ | |
1735 | if (bfqq == next_bfqq && | |
1736 | !list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && | |
1737 | next->fifo_time < rq->fifo_time) { | |
1738 | list_del_init(&rq->queuelist); | |
1739 | list_replace_init(&next->queuelist, &rq->queuelist); | |
1740 | rq->fifo_time = next->fifo_time; | |
1741 | } | |
1742 | ||
1743 | if (bfqq->next_rq == next) | |
1744 | bfqq->next_rq = rq; | |
1745 | ||
1746 | bfq_remove_request(q, next); | |
614822f8 | 1747 | bfqg_stats_update_io_remove(bfqq_group(bfqq), next->cmd_flags); |
aee69d78 PV |
1748 | |
1749 | spin_unlock_irq(&bfqq->bfqd->lock); | |
e21b7a0b AA |
1750 | end: |
1751 | bfqg_stats_update_io_merged(bfqq_group(bfqq), next->cmd_flags); | |
aee69d78 PV |
1752 | } |
1753 | ||
44e44a1b PV |
1754 | /* Must be called with bfqq != NULL */ |
1755 | static void bfq_bfqq_end_wr(struct bfq_queue *bfqq) | |
1756 | { | |
cfd69712 PV |
1757 | if (bfq_bfqq_busy(bfqq)) |
1758 | bfqq->bfqd->wr_busy_queues--; | |
44e44a1b PV |
1759 | bfqq->wr_coeff = 1; |
1760 | bfqq->wr_cur_max_time = 0; | |
77b7dcea | 1761 | bfqq->last_wr_start_finish = jiffies; |
44e44a1b PV |
1762 | /* |
1763 | * Trigger a weight change on the next invocation of | |
1764 | * __bfq_entity_update_weight_prio. | |
1765 | */ | |
1766 | bfqq->entity.prio_changed = 1; | |
1767 | } | |
1768 | ||
ea25da48 PV |
1769 | void bfq_end_wr_async_queues(struct bfq_data *bfqd, |
1770 | struct bfq_group *bfqg) | |
44e44a1b PV |
1771 | { |
1772 | int i, j; | |
1773 | ||
1774 | for (i = 0; i < 2; i++) | |
1775 | for (j = 0; j < IOPRIO_BE_NR; j++) | |
1776 | if (bfqg->async_bfqq[i][j]) | |
1777 | bfq_bfqq_end_wr(bfqg->async_bfqq[i][j]); | |
1778 | if (bfqg->async_idle_bfqq) | |
1779 | bfq_bfqq_end_wr(bfqg->async_idle_bfqq); | |
1780 | } | |
1781 | ||
1782 | static void bfq_end_wr(struct bfq_data *bfqd) | |
1783 | { | |
1784 | struct bfq_queue *bfqq; | |
1785 | ||
1786 | spin_lock_irq(&bfqd->lock); | |
1787 | ||
1788 | list_for_each_entry(bfqq, &bfqd->active_list, bfqq_list) | |
1789 | bfq_bfqq_end_wr(bfqq); | |
1790 | list_for_each_entry(bfqq, &bfqd->idle_list, bfqq_list) | |
1791 | bfq_bfqq_end_wr(bfqq); | |
1792 | bfq_end_wr_async(bfqd); | |
1793 | ||
1794 | spin_unlock_irq(&bfqd->lock); | |
1795 | } | |
1796 | ||
36eca894 AA |
1797 | static sector_t bfq_io_struct_pos(void *io_struct, bool request) |
1798 | { | |
1799 | if (request) | |
1800 | return blk_rq_pos(io_struct); | |
1801 | else | |
1802 | return ((struct bio *)io_struct)->bi_iter.bi_sector; | |
1803 | } | |
1804 | ||
1805 | static int bfq_rq_close_to_sector(void *io_struct, bool request, | |
1806 | sector_t sector) | |
1807 | { | |
1808 | return abs(bfq_io_struct_pos(io_struct, request) - sector) <= | |
1809 | BFQQ_CLOSE_THR; | |
1810 | } | |
1811 | ||
1812 | static struct bfq_queue *bfqq_find_close(struct bfq_data *bfqd, | |
1813 | struct bfq_queue *bfqq, | |
1814 | sector_t sector) | |
1815 | { | |
1816 | struct rb_root *root = &bfq_bfqq_to_bfqg(bfqq)->rq_pos_tree; | |
1817 | struct rb_node *parent, *node; | |
1818 | struct bfq_queue *__bfqq; | |
1819 | ||
1820 | if (RB_EMPTY_ROOT(root)) | |
1821 | return NULL; | |
1822 | ||
1823 | /* | |
1824 | * First, if we find a request starting at the end of the last | |
1825 | * request, choose it. | |
1826 | */ | |
1827 | __bfqq = bfq_rq_pos_tree_lookup(bfqd, root, sector, &parent, NULL); | |
1828 | if (__bfqq) | |
1829 | return __bfqq; | |
1830 | ||
1831 | /* | |
1832 | * If the exact sector wasn't found, the parent of the NULL leaf | |
1833 | * will contain the closest sector (rq_pos_tree sorted by | |
1834 | * next_request position). | |
1835 | */ | |
1836 | __bfqq = rb_entry(parent, struct bfq_queue, pos_node); | |
1837 | if (bfq_rq_close_to_sector(__bfqq->next_rq, true, sector)) | |
1838 | return __bfqq; | |
1839 | ||
1840 | if (blk_rq_pos(__bfqq->next_rq) < sector) | |
1841 | node = rb_next(&__bfqq->pos_node); | |
1842 | else | |
1843 | node = rb_prev(&__bfqq->pos_node); | |
1844 | if (!node) | |
1845 | return NULL; | |
1846 | ||
1847 | __bfqq = rb_entry(node, struct bfq_queue, pos_node); | |
1848 | if (bfq_rq_close_to_sector(__bfqq->next_rq, true, sector)) | |
1849 | return __bfqq; | |
1850 | ||
1851 | return NULL; | |
1852 | } | |
1853 | ||
1854 | static struct bfq_queue *bfq_find_close_cooperator(struct bfq_data *bfqd, | |
1855 | struct bfq_queue *cur_bfqq, | |
1856 | sector_t sector) | |
1857 | { | |
1858 | struct bfq_queue *bfqq; | |
1859 | ||
1860 | /* | |
1861 | * We shall notice if some of the queues are cooperating, | |
1862 | * e.g., working closely on the same area of the device. In | |
1863 | * that case, we can group them together and: 1) don't waste | |
1864 | * time idling, and 2) serve the union of their requests in | |
1865 | * the best possible order for throughput. | |
1866 | */ | |
1867 | bfqq = bfqq_find_close(bfqd, cur_bfqq, sector); | |
1868 | if (!bfqq || bfqq == cur_bfqq) | |
1869 | return NULL; | |
1870 | ||
1871 | return bfqq; | |
1872 | } | |
1873 | ||
1874 | static struct bfq_queue * | |
1875 | bfq_setup_merge(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq) | |
1876 | { | |
1877 | int process_refs, new_process_refs; | |
1878 | struct bfq_queue *__bfqq; | |
1879 | ||
1880 | /* | |
1881 | * If there are no process references on the new_bfqq, then it is | |
1882 | * unsafe to follow the ->new_bfqq chain as other bfqq's in the chain | |
1883 | * may have dropped their last reference (not just their last process | |
1884 | * reference). | |
1885 | */ | |
1886 | if (!bfqq_process_refs(new_bfqq)) | |
1887 | return NULL; | |
1888 | ||
1889 | /* Avoid a circular list and skip interim queue merges. */ | |
1890 | while ((__bfqq = new_bfqq->new_bfqq)) { | |
1891 | if (__bfqq == bfqq) | |
1892 | return NULL; | |
1893 | new_bfqq = __bfqq; | |
1894 | } | |
1895 | ||
1896 | process_refs = bfqq_process_refs(bfqq); | |
1897 | new_process_refs = bfqq_process_refs(new_bfqq); | |
1898 | /* | |
1899 | * If the process for the bfqq has gone away, there is no | |
1900 | * sense in merging the queues. | |
1901 | */ | |
1902 | if (process_refs == 0 || new_process_refs == 0) | |
1903 | return NULL; | |
1904 | ||
1905 | bfq_log_bfqq(bfqq->bfqd, bfqq, "scheduling merge with queue %d", | |
1906 | new_bfqq->pid); | |
1907 | ||
1908 | /* | |
1909 | * Merging is just a redirection: the requests of the process | |
1910 | * owning one of the two queues are redirected to the other queue. | |
1911 | * The latter queue, in its turn, is set as shared if this is the | |
1912 | * first time that the requests of some process are redirected to | |
1913 | * it. | |
1914 | * | |
6fa3e8d3 PV |
1915 | * We redirect bfqq to new_bfqq and not the opposite, because |
1916 | * we are in the context of the process owning bfqq, thus we | |
1917 | * have the io_cq of this process. So we can immediately | |
1918 | * configure this io_cq to redirect the requests of the | |
1919 | * process to new_bfqq. In contrast, the io_cq of new_bfqq is | |
1920 | * not available any more (new_bfqq->bic == NULL). | |
36eca894 | 1921 | * |
6fa3e8d3 PV |
1922 | * Anyway, even in case new_bfqq coincides with the in-service |
1923 | * queue, redirecting requests the in-service queue is the | |
1924 | * best option, as we feed the in-service queue with new | |
1925 | * requests close to the last request served and, by doing so, | |
1926 | * are likely to increase the throughput. | |
36eca894 AA |
1927 | */ |
1928 | bfqq->new_bfqq = new_bfqq; | |
1929 | new_bfqq->ref += process_refs; | |
1930 | return new_bfqq; | |
1931 | } | |
1932 | ||
1933 | static bool bfq_may_be_close_cooperator(struct bfq_queue *bfqq, | |
1934 | struct bfq_queue *new_bfqq) | |
1935 | { | |
1936 | if (bfq_class_idle(bfqq) || bfq_class_idle(new_bfqq) || | |
1937 | (bfqq->ioprio_class != new_bfqq->ioprio_class)) | |
1938 | return false; | |
1939 | ||
1940 | /* | |
1941 | * If either of the queues has already been detected as seeky, | |
1942 | * then merging it with the other queue is unlikely to lead to | |
1943 | * sequential I/O. | |
1944 | */ | |
1945 | if (BFQQ_SEEKY(bfqq) || BFQQ_SEEKY(new_bfqq)) | |
1946 | return false; | |
1947 | ||
1948 | /* | |
1949 | * Interleaved I/O is known to be done by (some) applications | |
1950 | * only for reads, so it does not make sense to merge async | |
1951 | * queues. | |
1952 | */ | |
1953 | if (!bfq_bfqq_sync(bfqq) || !bfq_bfqq_sync(new_bfqq)) | |
1954 | return false; | |
1955 | ||
1956 | return true; | |
1957 | } | |
1958 | ||
1959 | /* | |
1960 | * If this function returns true, then bfqq cannot be merged. The idea | |
1961 | * is that true cooperation happens very early after processes start | |
1962 | * to do I/O. Usually, late cooperations are just accidental false | |
1963 | * positives. In case bfqq is weight-raised, such false positives | |
1964 | * would evidently degrade latency guarantees for bfqq. | |
1965 | */ | |
1966 | static bool wr_from_too_long(struct bfq_queue *bfqq) | |
1967 | { | |
1968 | return bfqq->wr_coeff > 1 && | |
1969 | time_is_before_jiffies(bfqq->last_wr_start_finish + | |
1970 | msecs_to_jiffies(100)); | |
1971 | } | |
1972 | ||
1973 | /* | |
1974 | * Attempt to schedule a merge of bfqq with the currently in-service | |
1975 | * queue or with a close queue among the scheduled queues. Return | |
1976 | * NULL if no merge was scheduled, a pointer to the shared bfq_queue | |
1977 | * structure otherwise. | |
1978 | * | |
1979 | * The OOM queue is not allowed to participate to cooperation: in fact, since | |
1980 | * the requests temporarily redirected to the OOM queue could be redirected | |
1981 | * again to dedicated queues at any time, the state needed to correctly | |
1982 | * handle merging with the OOM queue would be quite complex and expensive | |
1983 | * to maintain. Besides, in such a critical condition as an out of memory, | |
1984 | * the benefits of queue merging may be little relevant, or even negligible. | |
1985 | * | |
1986 | * Weight-raised queues can be merged only if their weight-raising | |
1987 | * period has just started. In fact cooperating processes are usually | |
1988 | * started together. Thus, with this filter we avoid false positives | |
1989 | * that would jeopardize low-latency guarantees. | |
1990 | * | |
1991 | * WARNING: queue merging may impair fairness among non-weight raised | |
1992 | * queues, for at least two reasons: 1) the original weight of a | |
1993 | * merged queue may change during the merged state, 2) even being the | |
1994 | * weight the same, a merged queue may be bloated with many more | |
1995 | * requests than the ones produced by its originally-associated | |
1996 | * process. | |
1997 | */ | |
1998 | static struct bfq_queue * | |
1999 | bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq, | |
2000 | void *io_struct, bool request) | |
2001 | { | |
2002 | struct bfq_queue *in_service_bfqq, *new_bfqq; | |
2003 | ||
2004 | if (bfqq->new_bfqq) | |
2005 | return bfqq->new_bfqq; | |
2006 | ||
2007 | if (!io_struct || | |
2008 | wr_from_too_long(bfqq) || | |
2009 | unlikely(bfqq == &bfqd->oom_bfqq)) | |
2010 | return NULL; | |
2011 | ||
2012 | /* If there is only one backlogged queue, don't search. */ | |
2013 | if (bfqd->busy_queues == 1) | |
2014 | return NULL; | |
2015 | ||
2016 | in_service_bfqq = bfqd->in_service_queue; | |
2017 | ||
6fa3e8d3 PV |
2018 | if (!in_service_bfqq || in_service_bfqq == bfqq |
2019 | || wr_from_too_long(in_service_bfqq) || | |
36eca894 AA |
2020 | unlikely(in_service_bfqq == &bfqd->oom_bfqq)) |
2021 | goto check_scheduled; | |
2022 | ||
2023 | if (bfq_rq_close_to_sector(io_struct, request, bfqd->last_position) && | |
2024 | bfqq->entity.parent == in_service_bfqq->entity.parent && | |
2025 | bfq_may_be_close_cooperator(bfqq, in_service_bfqq)) { | |
2026 | new_bfqq = bfq_setup_merge(bfqq, in_service_bfqq); | |
2027 | if (new_bfqq) | |
2028 | return new_bfqq; | |
2029 | } | |
2030 | /* | |
2031 | * Check whether there is a cooperator among currently scheduled | |
2032 | * queues. The only thing we need is that the bio/request is not | |
2033 | * NULL, as we need it to establish whether a cooperator exists. | |
2034 | */ | |
2035 | check_scheduled: | |
2036 | new_bfqq = bfq_find_close_cooperator(bfqd, bfqq, | |
2037 | bfq_io_struct_pos(io_struct, request)); | |
2038 | ||
2039 | if (new_bfqq && !wr_from_too_long(new_bfqq) && | |
2040 | likely(new_bfqq != &bfqd->oom_bfqq) && | |
2041 | bfq_may_be_close_cooperator(bfqq, new_bfqq)) | |
2042 | return bfq_setup_merge(bfqq, new_bfqq); | |
2043 | ||
2044 | return NULL; | |
2045 | } | |
2046 | ||
2047 | static void bfq_bfqq_save_state(struct bfq_queue *bfqq) | |
2048 | { | |
2049 | struct bfq_io_cq *bic = bfqq->bic; | |
2050 | ||
2051 | /* | |
2052 | * If !bfqq->bic, the queue is already shared or its requests | |
2053 | * have already been redirected to a shared queue; both idle window | |
2054 | * and weight raising state have already been saved. Do nothing. | |
2055 | */ | |
2056 | if (!bic) | |
2057 | return; | |
2058 | ||
2059 | bic->saved_ttime = bfqq->ttime; | |
d5be3fef | 2060 | bic->saved_has_short_ttime = bfq_bfqq_has_short_ttime(bfqq); |
36eca894 | 2061 | bic->saved_IO_bound = bfq_bfqq_IO_bound(bfqq); |
e1b2324d AA |
2062 | bic->saved_in_large_burst = bfq_bfqq_in_large_burst(bfqq); |
2063 | bic->was_in_burst_list = !hlist_unhashed(&bfqq->burst_list_node); | |
894df937 PV |
2064 | if (unlikely(bfq_bfqq_just_created(bfqq) && |
2065 | !bfq_bfqq_in_large_burst(bfqq))) { | |
2066 | /* | |
2067 | * bfqq being merged right after being created: bfqq | |
2068 | * would have deserved interactive weight raising, but | |
2069 | * did not make it to be set in a weight-raised state, | |
2070 | * because of this early merge. Store directly the | |
2071 | * weight-raising state that would have been assigned | |
2072 | * to bfqq, so that to avoid that bfqq unjustly fails | |
2073 | * to enjoy weight raising if split soon. | |
2074 | */ | |
2075 | bic->saved_wr_coeff = bfqq->bfqd->bfq_wr_coeff; | |
2076 | bic->saved_wr_cur_max_time = bfq_wr_duration(bfqq->bfqd); | |
2077 | bic->saved_last_wr_start_finish = jiffies; | |
2078 | } else { | |
2079 | bic->saved_wr_coeff = bfqq->wr_coeff; | |
2080 | bic->saved_wr_start_at_switch_to_srt = | |
2081 | bfqq->wr_start_at_switch_to_srt; | |
2082 | bic->saved_last_wr_start_finish = bfqq->last_wr_start_finish; | |
2083 | bic->saved_wr_cur_max_time = bfqq->wr_cur_max_time; | |
2084 | } | |
36eca894 AA |
2085 | } |
2086 | ||
36eca894 AA |
2087 | static void |
2088 | bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic, | |
2089 | struct bfq_queue *bfqq, struct bfq_queue *new_bfqq) | |
2090 | { | |
2091 | bfq_log_bfqq(bfqd, bfqq, "merging with queue %lu", | |
2092 | (unsigned long)new_bfqq->pid); | |
2093 | /* Save weight raising and idle window of the merged queues */ | |
2094 | bfq_bfqq_save_state(bfqq); | |
2095 | bfq_bfqq_save_state(new_bfqq); | |
2096 | if (bfq_bfqq_IO_bound(bfqq)) | |
2097 | bfq_mark_bfqq_IO_bound(new_bfqq); | |
2098 | bfq_clear_bfqq_IO_bound(bfqq); | |
2099 | ||
2100 | /* | |
2101 | * If bfqq is weight-raised, then let new_bfqq inherit | |
2102 | * weight-raising. To reduce false positives, neglect the case | |
2103 | * where bfqq has just been created, but has not yet made it | |
2104 | * to be weight-raised (which may happen because EQM may merge | |
2105 | * bfqq even before bfq_add_request is executed for the first | |
e1b2324d AA |
2106 | * time for bfqq). Handling this case would however be very |
2107 | * easy, thanks to the flag just_created. | |
36eca894 AA |
2108 | */ |
2109 | if (new_bfqq->wr_coeff == 1 && bfqq->wr_coeff > 1) { | |
2110 | new_bfqq->wr_coeff = bfqq->wr_coeff; | |
2111 | new_bfqq->wr_cur_max_time = bfqq->wr_cur_max_time; | |
2112 | new_bfqq->last_wr_start_finish = bfqq->last_wr_start_finish; | |
2113 | new_bfqq->wr_start_at_switch_to_srt = | |
2114 | bfqq->wr_start_at_switch_to_srt; | |
2115 | if (bfq_bfqq_busy(new_bfqq)) | |
2116 | bfqd->wr_busy_queues++; | |
2117 | new_bfqq->entity.prio_changed = 1; | |
2118 | } | |
2119 | ||
2120 | if (bfqq->wr_coeff > 1) { /* bfqq has given its wr to new_bfqq */ | |
2121 | bfqq->wr_coeff = 1; | |
2122 | bfqq->entity.prio_changed = 1; | |
2123 | if (bfq_bfqq_busy(bfqq)) | |
2124 | bfqd->wr_busy_queues--; | |
2125 | } | |
2126 | ||
2127 | bfq_log_bfqq(bfqd, new_bfqq, "merge_bfqqs: wr_busy %d", | |
2128 | bfqd->wr_busy_queues); | |
2129 | ||
36eca894 AA |
2130 | /* |
2131 | * Merge queues (that is, let bic redirect its requests to new_bfqq) | |
2132 | */ | |
2133 | bic_set_bfqq(bic, new_bfqq, 1); | |
2134 | bfq_mark_bfqq_coop(new_bfqq); | |
2135 | /* | |
2136 | * new_bfqq now belongs to at least two bics (it is a shared queue): | |
2137 | * set new_bfqq->bic to NULL. bfqq either: | |
2138 | * - does not belong to any bic any more, and hence bfqq->bic must | |
2139 | * be set to NULL, or | |
2140 | * - is a queue whose owning bics have already been redirected to a | |
2141 | * different queue, hence the queue is destined to not belong to | |
2142 | * any bic soon and bfqq->bic is already NULL (therefore the next | |
2143 | * assignment causes no harm). | |
2144 | */ | |
2145 | new_bfqq->bic = NULL; | |
2146 | bfqq->bic = NULL; | |
2147 | /* release process reference to bfqq */ | |
2148 | bfq_put_queue(bfqq); | |
2149 | } | |
2150 | ||
aee69d78 PV |
2151 | static bool bfq_allow_bio_merge(struct request_queue *q, struct request *rq, |
2152 | struct bio *bio) | |
2153 | { | |
2154 | struct bfq_data *bfqd = q->elevator->elevator_data; | |
2155 | bool is_sync = op_is_sync(bio->bi_opf); | |
36eca894 | 2156 | struct bfq_queue *bfqq = bfqd->bio_bfqq, *new_bfqq; |
aee69d78 PV |
2157 | |
2158 | /* | |
2159 | * Disallow merge of a sync bio into an async request. | |
2160 | */ | |
2161 | if (is_sync && !rq_is_sync(rq)) | |
2162 | return false; | |
2163 | ||
2164 | /* | |
2165 | * Lookup the bfqq that this bio will be queued with. Allow | |
2166 | * merge only if rq is queued there. | |
2167 | */ | |
2168 | if (!bfqq) | |
2169 | return false; | |
2170 | ||
36eca894 AA |
2171 | /* |
2172 | * We take advantage of this function to perform an early merge | |
2173 | * of the queues of possible cooperating processes. | |
2174 | */ | |
2175 | new_bfqq = bfq_setup_cooperator(bfqd, bfqq, bio, false); | |
2176 | if (new_bfqq) { | |
2177 | /* | |
2178 | * bic still points to bfqq, then it has not yet been | |
2179 | * redirected to some other bfq_queue, and a queue | |
2180 | * merge beween bfqq and new_bfqq can be safely | |
2181 | * fulfillled, i.e., bic can be redirected to new_bfqq | |
2182 | * and bfqq can be put. | |
2183 | */ | |
2184 | bfq_merge_bfqqs(bfqd, bfqd->bio_bic, bfqq, | |
2185 | new_bfqq); | |
2186 | /* | |
2187 | * If we get here, bio will be queued into new_queue, | |
2188 | * so use new_bfqq to decide whether bio and rq can be | |
2189 | * merged. | |
2190 | */ | |
2191 | bfqq = new_bfqq; | |
2192 | ||
2193 | /* | |
2194 | * Change also bqfd->bio_bfqq, as | |
2195 | * bfqd->bio_bic now points to new_bfqq, and | |
2196 | * this function may be invoked again (and then may | |
2197 | * use again bqfd->bio_bfqq). | |
2198 | */ | |
2199 | bfqd->bio_bfqq = bfqq; | |
2200 | } | |
2201 | ||
aee69d78 PV |
2202 | return bfqq == RQ_BFQQ(rq); |
2203 | } | |
2204 | ||
44e44a1b PV |
2205 | /* |
2206 | * Set the maximum time for the in-service queue to consume its | |
2207 | * budget. This prevents seeky processes from lowering the throughput. | |
2208 | * In practice, a time-slice service scheme is used with seeky | |
2209 | * processes. | |
2210 | */ | |
2211 | static void bfq_set_budget_timeout(struct bfq_data *bfqd, | |
2212 | struct bfq_queue *bfqq) | |
2213 | { | |
77b7dcea PV |
2214 | unsigned int timeout_coeff; |
2215 | ||
2216 | if (bfqq->wr_cur_max_time == bfqd->bfq_wr_rt_max_time) | |
2217 | timeout_coeff = 1; | |
2218 | else | |
2219 | timeout_coeff = bfqq->entity.weight / bfqq->entity.orig_weight; | |
2220 | ||
44e44a1b PV |
2221 | bfqd->last_budget_start = ktime_get(); |
2222 | ||
2223 | bfqq->budget_timeout = jiffies + | |
77b7dcea | 2224 | bfqd->bfq_timeout * timeout_coeff; |
44e44a1b PV |
2225 | } |
2226 | ||
aee69d78 PV |
2227 | static void __bfq_set_in_service_queue(struct bfq_data *bfqd, |
2228 | struct bfq_queue *bfqq) | |
2229 | { | |
2230 | if (bfqq) { | |
aee69d78 PV |
2231 | bfq_clear_bfqq_fifo_expire(bfqq); |
2232 | ||
2233 | bfqd->budgets_assigned = (bfqd->budgets_assigned * 7 + 256) / 8; | |
2234 | ||
77b7dcea PV |
2235 | if (time_is_before_jiffies(bfqq->last_wr_start_finish) && |
2236 | bfqq->wr_coeff > 1 && | |
2237 | bfqq->wr_cur_max_time == bfqd->bfq_wr_rt_max_time && | |
2238 | time_is_before_jiffies(bfqq->budget_timeout)) { | |
2239 | /* | |
2240 | * For soft real-time queues, move the start | |
2241 | * of the weight-raising period forward by the | |
2242 | * time the queue has not received any | |
2243 | * service. Otherwise, a relatively long | |
2244 | * service delay is likely to cause the | |
2245 | * weight-raising period of the queue to end, | |
2246 | * because of the short duration of the | |
2247 | * weight-raising period of a soft real-time | |
2248 | * queue. It is worth noting that this move | |
2249 | * is not so dangerous for the other queues, | |
2250 | * because soft real-time queues are not | |
2251 | * greedy. | |
2252 | * | |
2253 | * To not add a further variable, we use the | |
2254 | * overloaded field budget_timeout to | |
2255 | * determine for how long the queue has not | |
2256 | * received service, i.e., how much time has | |
2257 | * elapsed since the queue expired. However, | |
2258 | * this is a little imprecise, because | |
2259 | * budget_timeout is set to jiffies if bfqq | |
2260 | * not only expires, but also remains with no | |
2261 | * request. | |
2262 | */ | |
2263 | if (time_after(bfqq->budget_timeout, | |
2264 | bfqq->last_wr_start_finish)) | |
2265 | bfqq->last_wr_start_finish += | |
2266 | jiffies - bfqq->budget_timeout; | |
2267 | else | |
2268 | bfqq->last_wr_start_finish = jiffies; | |
2269 | } | |
2270 | ||
44e44a1b | 2271 | bfq_set_budget_timeout(bfqd, bfqq); |
aee69d78 PV |
2272 | bfq_log_bfqq(bfqd, bfqq, |
2273 | "set_in_service_queue, cur-budget = %d", | |
2274 | bfqq->entity.budget); | |
2275 | } | |
2276 | ||
2277 | bfqd->in_service_queue = bfqq; | |
2278 | } | |
2279 | ||
2280 | /* | |
2281 | * Get and set a new queue for service. | |
2282 | */ | |
2283 | static struct bfq_queue *bfq_set_in_service_queue(struct bfq_data *bfqd) | |
2284 | { | |
2285 | struct bfq_queue *bfqq = bfq_get_next_queue(bfqd); | |
2286 | ||
2287 | __bfq_set_in_service_queue(bfqd, bfqq); | |
2288 | return bfqq; | |
2289 | } | |
2290 | ||
aee69d78 PV |
2291 | static void bfq_arm_slice_timer(struct bfq_data *bfqd) |
2292 | { | |
2293 | struct bfq_queue *bfqq = bfqd->in_service_queue; | |
aee69d78 PV |
2294 | u32 sl; |
2295 | ||
aee69d78 PV |
2296 | bfq_mark_bfqq_wait_request(bfqq); |
2297 | ||
2298 | /* | |
2299 | * We don't want to idle for seeks, but we do want to allow | |
2300 | * fair distribution of slice time for a process doing back-to-back | |
2301 | * seeks. So allow a little bit of time for him to submit a new rq. | |
2302 | */ | |
2303 | sl = bfqd->bfq_slice_idle; | |
2304 | /* | |
1de0c4cd AA |
2305 | * Unless the queue is being weight-raised or the scenario is |
2306 | * asymmetric, grant only minimum idle time if the queue | |
2307 | * is seeky. A long idling is preserved for a weight-raised | |
2308 | * queue, or, more in general, in an asymmetric scenario, | |
2309 | * because a long idling is needed for guaranteeing to a queue | |
2310 | * its reserved share of the throughput (in particular, it is | |
2311 | * needed if the queue has a higher weight than some other | |
2312 | * queue). | |
aee69d78 | 2313 | */ |
1de0c4cd AA |
2314 | if (BFQQ_SEEKY(bfqq) && bfqq->wr_coeff == 1 && |
2315 | bfq_symmetric_scenario(bfqd)) | |
aee69d78 PV |
2316 | sl = min_t(u64, sl, BFQ_MIN_TT); |
2317 | ||
2318 | bfqd->last_idling_start = ktime_get(); | |
2319 | hrtimer_start(&bfqd->idle_slice_timer, ns_to_ktime(sl), | |
2320 | HRTIMER_MODE_REL); | |
e21b7a0b | 2321 | bfqg_stats_set_start_idle_time(bfqq_group(bfqq)); |
aee69d78 PV |
2322 | } |
2323 | ||
ab0e43e9 PV |
2324 | /* |
2325 | * In autotuning mode, max_budget is dynamically recomputed as the | |
2326 | * amount of sectors transferred in timeout at the estimated peak | |
2327 | * rate. This enables BFQ to utilize a full timeslice with a full | |
2328 | * budget, even if the in-service queue is served at peak rate. And | |
2329 | * this maximises throughput with sequential workloads. | |
2330 | */ | |
2331 | static unsigned long bfq_calc_max_budget(struct bfq_data *bfqd) | |
2332 | { | |
2333 | return (u64)bfqd->peak_rate * USEC_PER_MSEC * | |
2334 | jiffies_to_msecs(bfqd->bfq_timeout)>>BFQ_RATE_SHIFT; | |
2335 | } | |
2336 | ||
44e44a1b PV |
2337 | /* |
2338 | * Update parameters related to throughput and responsiveness, as a | |
2339 | * function of the estimated peak rate. See comments on | |
2340 | * bfq_calc_max_budget(), and on T_slow and T_fast arrays. | |
2341 | */ | |
2342 | static void update_thr_responsiveness_params(struct bfq_data *bfqd) | |
2343 | { | |
2344 | int dev_type = blk_queue_nonrot(bfqd->queue); | |
2345 | ||
2346 | if (bfqd->bfq_user_max_budget == 0) | |
2347 | bfqd->bfq_max_budget = | |
2348 | bfq_calc_max_budget(bfqd); | |
2349 | ||
2350 | if (bfqd->device_speed == BFQ_BFQD_FAST && | |
2351 | bfqd->peak_rate < device_speed_thresh[dev_type]) { | |
2352 | bfqd->device_speed = BFQ_BFQD_SLOW; | |
2353 | bfqd->RT_prod = R_slow[dev_type] * | |
2354 | T_slow[dev_type]; | |
2355 | } else if (bfqd->device_speed == BFQ_BFQD_SLOW && | |
2356 | bfqd->peak_rate > device_speed_thresh[dev_type]) { | |
2357 | bfqd->device_speed = BFQ_BFQD_FAST; | |
2358 | bfqd->RT_prod = R_fast[dev_type] * | |
2359 | T_fast[dev_type]; | |
2360 | } | |
2361 | ||
2362 | bfq_log(bfqd, | |
2363 | "dev_type %s dev_speed_class = %s (%llu sects/sec), thresh %llu setcs/sec", | |
2364 | dev_type == 0 ? "ROT" : "NONROT", | |
2365 | bfqd->device_speed == BFQ_BFQD_FAST ? "FAST" : "SLOW", | |
2366 | bfqd->device_speed == BFQ_BFQD_FAST ? | |
2367 | (USEC_PER_SEC*(u64)R_fast[dev_type])>>BFQ_RATE_SHIFT : | |
2368 | (USEC_PER_SEC*(u64)R_slow[dev_type])>>BFQ_RATE_SHIFT, | |
2369 | (USEC_PER_SEC*(u64)device_speed_thresh[dev_type])>> | |
2370 | BFQ_RATE_SHIFT); | |
2371 | } | |
2372 | ||
ab0e43e9 PV |
2373 | static void bfq_reset_rate_computation(struct bfq_data *bfqd, |
2374 | struct request *rq) | |
2375 | { | |
2376 | if (rq != NULL) { /* new rq dispatch now, reset accordingly */ | |
2377 | bfqd->last_dispatch = bfqd->first_dispatch = ktime_get_ns(); | |
2378 | bfqd->peak_rate_samples = 1; | |
2379 | bfqd->sequential_samples = 0; | |
2380 | bfqd->tot_sectors_dispatched = bfqd->last_rq_max_size = | |
2381 | blk_rq_sectors(rq); | |
2382 | } else /* no new rq dispatched, just reset the number of samples */ | |
2383 | bfqd->peak_rate_samples = 0; /* full re-init on next disp. */ | |
2384 | ||
2385 | bfq_log(bfqd, | |
2386 | "reset_rate_computation at end, sample %u/%u tot_sects %llu", | |
2387 | bfqd->peak_rate_samples, bfqd->sequential_samples, | |
2388 | bfqd->tot_sectors_dispatched); | |
2389 | } | |
2390 | ||
2391 | static void bfq_update_rate_reset(struct bfq_data *bfqd, struct request *rq) | |
2392 | { | |
2393 | u32 rate, weight, divisor; | |
2394 | ||
2395 | /* | |
2396 | * For the convergence property to hold (see comments on | |
2397 | * bfq_update_peak_rate()) and for the assessment to be | |
2398 | * reliable, a minimum number of samples must be present, and | |
2399 | * a minimum amount of time must have elapsed. If not so, do | |
2400 | * not compute new rate. Just reset parameters, to get ready | |
2401 | * for a new evaluation attempt. | |
2402 | */ | |
2403 | if (bfqd->peak_rate_samples < BFQ_RATE_MIN_SAMPLES || | |
2404 | bfqd->delta_from_first < BFQ_RATE_MIN_INTERVAL) | |
2405 | goto reset_computation; | |
2406 | ||
2407 | /* | |
2408 | * If a new request completion has occurred after last | |
2409 | * dispatch, then, to approximate the rate at which requests | |
2410 | * have been served by the device, it is more precise to | |
2411 | * extend the observation interval to the last completion. | |
2412 | */ | |
2413 | bfqd->delta_from_first = | |
2414 | max_t(u64, bfqd->delta_from_first, | |
2415 | bfqd->last_completion - bfqd->first_dispatch); | |
2416 | ||
2417 | /* | |
2418 | * Rate computed in sects/usec, and not sects/nsec, for | |
2419 | * precision issues. | |
2420 | */ | |
2421 | rate = div64_ul(bfqd->tot_sectors_dispatched<<BFQ_RATE_SHIFT, | |
2422 | div_u64(bfqd->delta_from_first, NSEC_PER_USEC)); | |
2423 | ||
2424 | /* | |
2425 | * Peak rate not updated if: | |
2426 | * - the percentage of sequential dispatches is below 3/4 of the | |
2427 | * total, and rate is below the current estimated peak rate | |
2428 | * - rate is unreasonably high (> 20M sectors/sec) | |
2429 | */ | |
2430 | if ((bfqd->sequential_samples < (3 * bfqd->peak_rate_samples)>>2 && | |
2431 | rate <= bfqd->peak_rate) || | |
2432 | rate > 20<<BFQ_RATE_SHIFT) | |
2433 | goto reset_computation; | |
2434 | ||
2435 | /* | |
2436 | * We have to update the peak rate, at last! To this purpose, | |
2437 | * we use a low-pass filter. We compute the smoothing constant | |
2438 | * of the filter as a function of the 'weight' of the new | |
2439 | * measured rate. | |
2440 | * | |
2441 | * As can be seen in next formulas, we define this weight as a | |
2442 | * quantity proportional to how sequential the workload is, | |
2443 | * and to how long the observation time interval is. | |
2444 | * | |
2445 | * The weight runs from 0 to 8. The maximum value of the | |
2446 | * weight, 8, yields the minimum value for the smoothing | |
2447 | * constant. At this minimum value for the smoothing constant, | |
2448 | * the measured rate contributes for half of the next value of | |
2449 | * the estimated peak rate. | |
2450 | * | |
2451 | * So, the first step is to compute the weight as a function | |
2452 | * of how sequential the workload is. Note that the weight | |
2453 | * cannot reach 9, because bfqd->sequential_samples cannot | |
2454 | * become equal to bfqd->peak_rate_samples, which, in its | |
2455 | * turn, holds true because bfqd->sequential_samples is not | |
2456 | * incremented for the first sample. | |
2457 | */ | |
2458 | weight = (9 * bfqd->sequential_samples) / bfqd->peak_rate_samples; | |
2459 | ||
2460 | /* | |
2461 | * Second step: further refine the weight as a function of the | |
2462 | * duration of the observation interval. | |
2463 | */ | |
2464 | weight = min_t(u32, 8, | |
2465 | div_u64(weight * bfqd->delta_from_first, | |
2466 | BFQ_RATE_REF_INTERVAL)); | |
2467 | ||
2468 | /* | |
2469 | * Divisor ranging from 10, for minimum weight, to 2, for | |
2470 | * maximum weight. | |
2471 | */ | |
2472 | divisor = 10 - weight; | |
2473 | ||
2474 | /* | |
2475 | * Finally, update peak rate: | |
2476 | * | |
2477 | * peak_rate = peak_rate * (divisor-1) / divisor + rate / divisor | |
2478 | */ | |
2479 | bfqd->peak_rate *= divisor-1; | |
2480 | bfqd->peak_rate /= divisor; | |
2481 | rate /= divisor; /* smoothing constant alpha = 1/divisor */ | |
2482 | ||
2483 | bfqd->peak_rate += rate; | |
44e44a1b | 2484 | update_thr_responsiveness_params(bfqd); |
ab0e43e9 PV |
2485 | |
2486 | reset_computation: | |
2487 | bfq_reset_rate_computation(bfqd, rq); | |
2488 | } | |
2489 | ||
2490 | /* | |
2491 | * Update the read/write peak rate (the main quantity used for | |
2492 | * auto-tuning, see update_thr_responsiveness_params()). | |
2493 | * | |
2494 | * It is not trivial to estimate the peak rate (correctly): because of | |
2495 | * the presence of sw and hw queues between the scheduler and the | |
2496 | * device components that finally serve I/O requests, it is hard to | |
2497 | * say exactly when a given dispatched request is served inside the | |
2498 | * device, and for how long. As a consequence, it is hard to know | |
2499 | * precisely at what rate a given set of requests is actually served | |
2500 | * by the device. | |
2501 | * | |
2502 | * On the opposite end, the dispatch time of any request is trivially | |
2503 | * available, and, from this piece of information, the "dispatch rate" | |
2504 | * of requests can be immediately computed. So, the idea in the next | |
2505 | * function is to use what is known, namely request dispatch times | |
2506 | * (plus, when useful, request completion times), to estimate what is | |
2507 | * unknown, namely in-device request service rate. | |
2508 | * | |
2509 | * The main issue is that, because of the above facts, the rate at | |
2510 | * which a certain set of requests is dispatched over a certain time | |
2511 | * interval can vary greatly with respect to the rate at which the | |
2512 | * same requests are then served. But, since the size of any | |
2513 | * intermediate queue is limited, and the service scheme is lossless | |
2514 | * (no request is silently dropped), the following obvious convergence | |
2515 | * property holds: the number of requests dispatched MUST become | |
2516 | * closer and closer to the number of requests completed as the | |
2517 | * observation interval grows. This is the key property used in | |
2518 | * the next function to estimate the peak service rate as a function | |
2519 | * of the observed dispatch rate. The function assumes to be invoked | |
2520 | * on every request dispatch. | |
2521 | */ | |
2522 | static void bfq_update_peak_rate(struct bfq_data *bfqd, struct request *rq) | |
2523 | { | |
2524 | u64 now_ns = ktime_get_ns(); | |
2525 | ||
2526 | if (bfqd->peak_rate_samples == 0) { /* first dispatch */ | |
2527 | bfq_log(bfqd, "update_peak_rate: goto reset, samples %d", | |
2528 | bfqd->peak_rate_samples); | |
2529 | bfq_reset_rate_computation(bfqd, rq); | |
2530 | goto update_last_values; /* will add one sample */ | |
2531 | } | |
2532 | ||
2533 | /* | |
2534 | * Device idle for very long: the observation interval lasting | |
2535 | * up to this dispatch cannot be a valid observation interval | |
2536 | * for computing a new peak rate (similarly to the late- | |
2537 | * completion event in bfq_completed_request()). Go to | |
2538 | * update_rate_and_reset to have the following three steps | |
2539 | * taken: | |
2540 | * - close the observation interval at the last (previous) | |
2541 | * request dispatch or completion | |
2542 | * - compute rate, if possible, for that observation interval | |
2543 | * - start a new observation interval with this dispatch | |
2544 | */ | |
2545 | if (now_ns - bfqd->last_dispatch > 100*NSEC_PER_MSEC && | |
2546 | bfqd->rq_in_driver == 0) | |
2547 | goto update_rate_and_reset; | |
2548 | ||
2549 | /* Update sampling information */ | |
2550 | bfqd->peak_rate_samples++; | |
2551 | ||
2552 | if ((bfqd->rq_in_driver > 0 || | |
2553 | now_ns - bfqd->last_completion < BFQ_MIN_TT) | |
2554 | && get_sdist(bfqd->last_position, rq) < BFQQ_SEEK_THR) | |
2555 | bfqd->sequential_samples++; | |
2556 | ||
2557 | bfqd->tot_sectors_dispatched += blk_rq_sectors(rq); | |
2558 | ||
2559 | /* Reset max observed rq size every 32 dispatches */ | |
2560 | if (likely(bfqd->peak_rate_samples % 32)) | |
2561 | bfqd->last_rq_max_size = | |
2562 | max_t(u32, blk_rq_sectors(rq), bfqd->last_rq_max_size); | |
2563 | else | |
2564 | bfqd->last_rq_max_size = blk_rq_sectors(rq); | |
2565 | ||
2566 | bfqd->delta_from_first = now_ns - bfqd->first_dispatch; | |
2567 | ||
2568 | /* Target observation interval not yet reached, go on sampling */ | |
2569 | if (bfqd->delta_from_first < BFQ_RATE_REF_INTERVAL) | |
2570 | goto update_last_values; | |
2571 | ||
2572 | update_rate_and_reset: | |
2573 | bfq_update_rate_reset(bfqd, rq); | |
2574 | update_last_values: | |
2575 | bfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq); | |
2576 | bfqd->last_dispatch = now_ns; | |
2577 | } | |
2578 | ||
aee69d78 PV |
2579 | /* |
2580 | * Remove request from internal lists. | |
2581 | */ | |
2582 | static void bfq_dispatch_remove(struct request_queue *q, struct request *rq) | |
2583 | { | |
2584 | struct bfq_queue *bfqq = RQ_BFQQ(rq); | |
2585 | ||
2586 | /* | |
2587 | * For consistency, the next instruction should have been | |
2588 | * executed after removing the request from the queue and | |
2589 | * dispatching it. We execute instead this instruction before | |
2590 | * bfq_remove_request() (and hence introduce a temporary | |
2591 | * inconsistency), for efficiency. In fact, should this | |
2592 | * dispatch occur for a non in-service bfqq, this anticipated | |
2593 | * increment prevents two counters related to bfqq->dispatched | |
2594 | * from risking to be, first, uselessly decremented, and then | |
2595 | * incremented again when the (new) value of bfqq->dispatched | |
2596 | * happens to be taken into account. | |
2597 | */ | |
2598 | bfqq->dispatched++; | |
ab0e43e9 | 2599 | bfq_update_peak_rate(q->elevator->elevator_data, rq); |
aee69d78 PV |
2600 | |
2601 | bfq_remove_request(q, rq); | |
2602 | } | |
2603 | ||
2604 | static void __bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq) | |
2605 | { | |
36eca894 AA |
2606 | /* |
2607 | * If this bfqq is shared between multiple processes, check | |
2608 | * to make sure that those processes are still issuing I/Os | |
2609 | * within the mean seek distance. If not, it may be time to | |
2610 | * break the queues apart again. | |
2611 | */ | |
2612 | if (bfq_bfqq_coop(bfqq) && BFQQ_SEEKY(bfqq)) | |
2613 | bfq_mark_bfqq_split_coop(bfqq); | |
2614 | ||
44e44a1b PV |
2615 | if (RB_EMPTY_ROOT(&bfqq->sort_list)) { |
2616 | if (bfqq->dispatched == 0) | |
2617 | /* | |
2618 | * Overloading budget_timeout field to store | |
2619 | * the time at which the queue remains with no | |
2620 | * backlog and no outstanding request; used by | |
2621 | * the weight-raising mechanism. | |
2622 | */ | |
2623 | bfqq->budget_timeout = jiffies; | |
2624 | ||
e21b7a0b | 2625 | bfq_del_bfqq_busy(bfqd, bfqq, true); |
36eca894 | 2626 | } else { |
80294c3b | 2627 | bfq_requeue_bfqq(bfqd, bfqq, true); |
36eca894 AA |
2628 | /* |
2629 | * Resort priority tree of potential close cooperators. | |
2630 | */ | |
2631 | bfq_pos_tree_add_move(bfqd, bfqq); | |
2632 | } | |
e21b7a0b AA |
2633 | |
2634 | /* | |
2635 | * All in-service entities must have been properly deactivated | |
2636 | * or requeued before executing the next function, which | |
2637 | * resets all in-service entites as no more in service. | |
2638 | */ | |
2639 | __bfq_bfqd_reset_in_service(bfqd); | |
aee69d78 PV |
2640 | } |
2641 | ||
2642 | /** | |
2643 | * __bfq_bfqq_recalc_budget - try to adapt the budget to the @bfqq behavior. | |
2644 | * @bfqd: device data. | |
2645 | * @bfqq: queue to update. | |
2646 | * @reason: reason for expiration. | |
2647 | * | |
2648 | * Handle the feedback on @bfqq budget at queue expiration. | |
2649 | * See the body for detailed comments. | |
2650 | */ | |
2651 | static void __bfq_bfqq_recalc_budget(struct bfq_data *bfqd, | |
2652 | struct bfq_queue *bfqq, | |
2653 | enum bfqq_expiration reason) | |
2654 | { | |
2655 | struct request *next_rq; | |
2656 | int budget, min_budget; | |
2657 | ||
aee69d78 PV |
2658 | min_budget = bfq_min_budget(bfqd); |
2659 | ||
44e44a1b PV |
2660 | if (bfqq->wr_coeff == 1) |
2661 | budget = bfqq->max_budget; | |
2662 | else /* | |
2663 | * Use a constant, low budget for weight-raised queues, | |
2664 | * to help achieve a low latency. Keep it slightly higher | |
2665 | * than the minimum possible budget, to cause a little | |
2666 | * bit fewer expirations. | |
2667 | */ | |
2668 | budget = 2 * min_budget; | |
2669 | ||
aee69d78 PV |
2670 | bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last budg %d, budg left %d", |
2671 | bfqq->entity.budget, bfq_bfqq_budget_left(bfqq)); | |
2672 | bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last max_budg %d, min budg %d", | |
2673 | budget, bfq_min_budget(bfqd)); | |
2674 | bfq_log_bfqq(bfqd, bfqq, "recalc_budg: sync %d, seeky %d", | |
2675 | bfq_bfqq_sync(bfqq), BFQQ_SEEKY(bfqd->in_service_queue)); | |
2676 | ||
44e44a1b | 2677 | if (bfq_bfqq_sync(bfqq) && bfqq->wr_coeff == 1) { |
aee69d78 PV |
2678 | switch (reason) { |
2679 | /* | |
2680 | * Caveat: in all the following cases we trade latency | |
2681 | * for throughput. | |
2682 | */ | |
2683 | case BFQQE_TOO_IDLE: | |
54b60456 PV |
2684 | /* |
2685 | * This is the only case where we may reduce | |
2686 | * the budget: if there is no request of the | |
2687 | * process still waiting for completion, then | |
2688 | * we assume (tentatively) that the timer has | |
2689 | * expired because the batch of requests of | |
2690 | * the process could have been served with a | |
2691 | * smaller budget. Hence, betting that | |
2692 | * process will behave in the same way when it | |
2693 | * becomes backlogged again, we reduce its | |
2694 | * next budget. As long as we guess right, | |
2695 | * this budget cut reduces the latency | |
2696 | * experienced by the process. | |
2697 | * | |
2698 | * However, if there are still outstanding | |
2699 | * requests, then the process may have not yet | |
2700 | * issued its next request just because it is | |
2701 | * still waiting for the completion of some of | |
2702 | * the still outstanding ones. So in this | |
2703 | * subcase we do not reduce its budget, on the | |
2704 | * contrary we increase it to possibly boost | |
2705 | * the throughput, as discussed in the | |
2706 | * comments to the BUDGET_TIMEOUT case. | |
2707 | */ | |
2708 | if (bfqq->dispatched > 0) /* still outstanding reqs */ | |
2709 | budget = min(budget * 2, bfqd->bfq_max_budget); | |
2710 | else { | |
2711 | if (budget > 5 * min_budget) | |
2712 | budget -= 4 * min_budget; | |
2713 | else | |
2714 | budget = min_budget; | |
2715 | } | |
aee69d78 PV |
2716 | break; |
2717 | case BFQQE_BUDGET_TIMEOUT: | |
54b60456 PV |
2718 | /* |
2719 | * We double the budget here because it gives | |
2720 | * the chance to boost the throughput if this | |
2721 | * is not a seeky process (and has bumped into | |
2722 | * this timeout because of, e.g., ZBR). | |
2723 | */ | |
2724 | budget = min(budget * 2, bfqd->bfq_max_budget); | |
aee69d78 PV |
2725 | break; |
2726 | case BFQQE_BUDGET_EXHAUSTED: | |
2727 | /* | |
2728 | * The process still has backlog, and did not | |
2729 | * let either the budget timeout or the disk | |
2730 | * idling timeout expire. Hence it is not | |
2731 | * seeky, has a short thinktime and may be | |
2732 | * happy with a higher budget too. So | |
2733 | * definitely increase the budget of this good | |
2734 | * candidate to boost the disk throughput. | |
2735 | */ | |
54b60456 | 2736 | budget = min(budget * 4, bfqd->bfq_max_budget); |
aee69d78 PV |
2737 | break; |
2738 | case BFQQE_NO_MORE_REQUESTS: | |
2739 | /* | |
2740 | * For queues that expire for this reason, it | |
2741 | * is particularly important to keep the | |
2742 | * budget close to the actual service they | |
2743 | * need. Doing so reduces the timestamp | |
2744 | * misalignment problem described in the | |
2745 | * comments in the body of | |
2746 | * __bfq_activate_entity. In fact, suppose | |
2747 | * that a queue systematically expires for | |
2748 | * BFQQE_NO_MORE_REQUESTS and presents a | |
2749 | * new request in time to enjoy timestamp | |
2750 | * back-shifting. The larger the budget of the | |
2751 | * queue is with respect to the service the | |
2752 | * queue actually requests in each service | |
2753 | * slot, the more times the queue can be | |
2754 | * reactivated with the same virtual finish | |
2755 | * time. It follows that, even if this finish | |
2756 | * time is pushed to the system virtual time | |
2757 | * to reduce the consequent timestamp | |
2758 | * misalignment, the queue unjustly enjoys for | |
2759 | * many re-activations a lower finish time | |
2760 | * than all newly activated queues. | |
2761 | * | |
2762 | * The service needed by bfqq is measured | |
2763 | * quite precisely by bfqq->entity.service. | |
2764 | * Since bfqq does not enjoy device idling, | |
2765 | * bfqq->entity.service is equal to the number | |
2766 | * of sectors that the process associated with | |
2767 | * bfqq requested to read/write before waiting | |
2768 | * for request completions, or blocking for | |
2769 | * other reasons. | |
2770 | */ | |
2771 | budget = max_t(int, bfqq->entity.service, min_budget); | |
2772 | break; | |
2773 | default: | |
2774 | return; | |
2775 | } | |
44e44a1b | 2776 | } else if (!bfq_bfqq_sync(bfqq)) { |
aee69d78 PV |
2777 | /* |
2778 | * Async queues get always the maximum possible | |
2779 | * budget, as for them we do not care about latency | |
2780 | * (in addition, their ability to dispatch is limited | |
2781 | * by the charging factor). | |
2782 | */ | |
2783 | budget = bfqd->bfq_max_budget; | |
2784 | } | |
2785 | ||
2786 | bfqq->max_budget = budget; | |
2787 | ||
2788 | if (bfqd->budgets_assigned >= bfq_stats_min_budgets && | |
2789 | !bfqd->bfq_user_max_budget) | |
2790 | bfqq->max_budget = min(bfqq->max_budget, bfqd->bfq_max_budget); | |
2791 | ||
2792 | /* | |
2793 | * If there is still backlog, then assign a new budget, making | |
2794 | * sure that it is large enough for the next request. Since | |
2795 | * the finish time of bfqq must be kept in sync with the | |
2796 | * budget, be sure to call __bfq_bfqq_expire() *after* this | |
2797 | * update. | |
2798 | * | |
2799 | * If there is no backlog, then no need to update the budget; | |
2800 | * it will be updated on the arrival of a new request. | |
2801 | */ | |
2802 | next_rq = bfqq->next_rq; | |
2803 | if (next_rq) | |
2804 | bfqq->entity.budget = max_t(unsigned long, bfqq->max_budget, | |
2805 | bfq_serv_to_charge(next_rq, bfqq)); | |
2806 | ||
2807 | bfq_log_bfqq(bfqd, bfqq, "head sect: %u, new budget %d", | |
2808 | next_rq ? blk_rq_sectors(next_rq) : 0, | |
2809 | bfqq->entity.budget); | |
2810 | } | |
2811 | ||
aee69d78 | 2812 | /* |
ab0e43e9 PV |
2813 | * Return true if the process associated with bfqq is "slow". The slow |
2814 | * flag is used, in addition to the budget timeout, to reduce the | |
2815 | * amount of service provided to seeky processes, and thus reduce | |
2816 | * their chances to lower the throughput. More details in the comments | |
2817 | * on the function bfq_bfqq_expire(). | |
2818 | * | |
2819 | * An important observation is in order: as discussed in the comments | |
2820 | * on the function bfq_update_peak_rate(), with devices with internal | |
2821 | * queues, it is hard if ever possible to know when and for how long | |
2822 | * an I/O request is processed by the device (apart from the trivial | |
2823 | * I/O pattern where a new request is dispatched only after the | |
2824 | * previous one has been completed). This makes it hard to evaluate | |
2825 | * the real rate at which the I/O requests of each bfq_queue are | |
2826 | * served. In fact, for an I/O scheduler like BFQ, serving a | |
2827 | * bfq_queue means just dispatching its requests during its service | |
2828 | * slot (i.e., until the budget of the queue is exhausted, or the | |
2829 | * queue remains idle, or, finally, a timeout fires). But, during the | |
2830 | * service slot of a bfq_queue, around 100 ms at most, the device may | |
2831 | * be even still processing requests of bfq_queues served in previous | |
2832 | * service slots. On the opposite end, the requests of the in-service | |
2833 | * bfq_queue may be completed after the service slot of the queue | |
2834 | * finishes. | |
2835 | * | |
2836 | * Anyway, unless more sophisticated solutions are used | |
2837 | * (where possible), the sum of the sizes of the requests dispatched | |
2838 | * during the service slot of a bfq_queue is probably the only | |
2839 | * approximation available for the service received by the bfq_queue | |
2840 | * during its service slot. And this sum is the quantity used in this | |
2841 | * function to evaluate the I/O speed of a process. | |
aee69d78 | 2842 | */ |
ab0e43e9 PV |
2843 | static bool bfq_bfqq_is_slow(struct bfq_data *bfqd, struct bfq_queue *bfqq, |
2844 | bool compensate, enum bfqq_expiration reason, | |
2845 | unsigned long *delta_ms) | |
aee69d78 | 2846 | { |
ab0e43e9 PV |
2847 | ktime_t delta_ktime; |
2848 | u32 delta_usecs; | |
2849 | bool slow = BFQQ_SEEKY(bfqq); /* if delta too short, use seekyness */ | |
aee69d78 | 2850 | |
ab0e43e9 | 2851 | if (!bfq_bfqq_sync(bfqq)) |
aee69d78 PV |
2852 | return false; |
2853 | ||
2854 | if (compensate) | |
ab0e43e9 | 2855 | delta_ktime = bfqd->last_idling_start; |
aee69d78 | 2856 | else |
ab0e43e9 PV |
2857 | delta_ktime = ktime_get(); |
2858 | delta_ktime = ktime_sub(delta_ktime, bfqd->last_budget_start); | |
2859 | delta_usecs = ktime_to_us(delta_ktime); | |
aee69d78 PV |
2860 | |
2861 | /* don't use too short time intervals */ | |
ab0e43e9 PV |
2862 | if (delta_usecs < 1000) { |
2863 | if (blk_queue_nonrot(bfqd->queue)) | |
2864 | /* | |
2865 | * give same worst-case guarantees as idling | |
2866 | * for seeky | |
2867 | */ | |
2868 | *delta_ms = BFQ_MIN_TT / NSEC_PER_MSEC; | |
2869 | else /* charge at least one seek */ | |
2870 | *delta_ms = bfq_slice_idle / NSEC_PER_MSEC; | |
2871 | ||
2872 | return slow; | |
2873 | } | |
aee69d78 | 2874 | |
ab0e43e9 | 2875 | *delta_ms = delta_usecs / USEC_PER_MSEC; |
aee69d78 PV |
2876 | |
2877 | /* | |
ab0e43e9 PV |
2878 | * Use only long (> 20ms) intervals to filter out excessive |
2879 | * spikes in service rate estimation. | |
aee69d78 | 2880 | */ |
ab0e43e9 PV |
2881 | if (delta_usecs > 20000) { |
2882 | /* | |
2883 | * Caveat for rotational devices: processes doing I/O | |
2884 | * in the slower disk zones tend to be slow(er) even | |
2885 | * if not seeky. In this respect, the estimated peak | |
2886 | * rate is likely to be an average over the disk | |
2887 | * surface. Accordingly, to not be too harsh with | |
2888 | * unlucky processes, a process is deemed slow only if | |
2889 | * its rate has been lower than half of the estimated | |
2890 | * peak rate. | |
2891 | */ | |
2892 | slow = bfqq->entity.service < bfqd->bfq_max_budget / 2; | |
aee69d78 PV |
2893 | } |
2894 | ||
ab0e43e9 | 2895 | bfq_log_bfqq(bfqd, bfqq, "bfq_bfqq_is_slow: slow %d", slow); |
aee69d78 | 2896 | |
ab0e43e9 | 2897 | return slow; |
aee69d78 PV |
2898 | } |
2899 | ||
77b7dcea PV |
2900 | /* |
2901 | * To be deemed as soft real-time, an application must meet two | |
2902 | * requirements. First, the application must not require an average | |
2903 | * bandwidth higher than the approximate bandwidth required to playback or | |
2904 | * record a compressed high-definition video. | |
2905 | * The next function is invoked on the completion of the last request of a | |
2906 | * batch, to compute the next-start time instant, soft_rt_next_start, such | |
2907 | * that, if the next request of the application does not arrive before | |
2908 | * soft_rt_next_start, then the above requirement on the bandwidth is met. | |
2909 | * | |
2910 | * The second requirement is that the request pattern of the application is | |
2911 | * isochronous, i.e., that, after issuing a request or a batch of requests, | |
2912 | * the application stops issuing new requests until all its pending requests | |
2913 | * have been completed. After that, the application may issue a new batch, | |
2914 | * and so on. | |
2915 | * For this reason the next function is invoked to compute | |
2916 | * soft_rt_next_start only for applications that meet this requirement, | |
2917 | * whereas soft_rt_next_start is set to infinity for applications that do | |
2918 | * not. | |
2919 | * | |
2920 | * Unfortunately, even a greedy application may happen to behave in an | |
2921 | * isochronous way if the CPU load is high. In fact, the application may | |
2922 | * stop issuing requests while the CPUs are busy serving other processes, | |
2923 | * then restart, then stop again for a while, and so on. In addition, if | |
2924 | * the disk achieves a low enough throughput with the request pattern | |
2925 | * issued by the application (e.g., because the request pattern is random | |
2926 | * and/or the device is slow), then the application may meet the above | |
2927 | * bandwidth requirement too. To prevent such a greedy application to be | |
2928 | * deemed as soft real-time, a further rule is used in the computation of | |
2929 | * soft_rt_next_start: soft_rt_next_start must be higher than the current | |
2930 | * time plus the maximum time for which the arrival of a request is waited | |
2931 | * for when a sync queue becomes idle, namely bfqd->bfq_slice_idle. | |
2932 | * This filters out greedy applications, as the latter issue instead their | |
2933 | * next request as soon as possible after the last one has been completed | |
2934 | * (in contrast, when a batch of requests is completed, a soft real-time | |
2935 | * application spends some time processing data). | |
2936 | * | |
2937 | * Unfortunately, the last filter may easily generate false positives if | |
2938 | * only bfqd->bfq_slice_idle is used as a reference time interval and one | |
2939 | * or both the following cases occur: | |
2940 | * 1) HZ is so low that the duration of a jiffy is comparable to or higher | |
2941 | * than bfqd->bfq_slice_idle. This happens, e.g., on slow devices with | |
2942 | * HZ=100. | |
2943 | * 2) jiffies, instead of increasing at a constant rate, may stop increasing | |
2944 | * for a while, then suddenly 'jump' by several units to recover the lost | |
2945 | * increments. This seems to happen, e.g., inside virtual machines. | |
2946 | * To address this issue, we do not use as a reference time interval just | |
2947 | * bfqd->bfq_slice_idle, but bfqd->bfq_slice_idle plus a few jiffies. In | |
2948 | * particular we add the minimum number of jiffies for which the filter | |
2949 | * seems to be quite precise also in embedded systems and KVM/QEMU virtual | |
2950 | * machines. | |
2951 | */ | |
2952 | static unsigned long bfq_bfqq_softrt_next_start(struct bfq_data *bfqd, | |
2953 | struct bfq_queue *bfqq) | |
2954 | { | |
2955 | return max(bfqq->last_idle_bklogged + | |
2956 | HZ * bfqq->service_from_backlogged / | |
2957 | bfqd->bfq_wr_max_softrt_rate, | |
2958 | jiffies + nsecs_to_jiffies(bfqq->bfqd->bfq_slice_idle) + 4); | |
2959 | } | |
2960 | ||
aee69d78 PV |
2961 | /** |
2962 | * bfq_bfqq_expire - expire a queue. | |
2963 | * @bfqd: device owning the queue. | |
2964 | * @bfqq: the queue to expire. | |
2965 | * @compensate: if true, compensate for the time spent idling. | |
2966 | * @reason: the reason causing the expiration. | |
2967 | * | |
c074170e PV |
2968 | * If the process associated with bfqq does slow I/O (e.g., because it |
2969 | * issues random requests), we charge bfqq with the time it has been | |
2970 | * in service instead of the service it has received (see | |
2971 | * bfq_bfqq_charge_time for details on how this goal is achieved). As | |
2972 | * a consequence, bfqq will typically get higher timestamps upon | |
2973 | * reactivation, and hence it will be rescheduled as if it had | |
2974 | * received more service than what it has actually received. In the | |
2975 | * end, bfqq receives less service in proportion to how slowly its | |
2976 | * associated process consumes its budgets (and hence how seriously it | |
2977 | * tends to lower the throughput). In addition, this time-charging | |
2978 | * strategy guarantees time fairness among slow processes. In | |
2979 | * contrast, if the process associated with bfqq is not slow, we | |
2980 | * charge bfqq exactly with the service it has received. | |
aee69d78 | 2981 | * |
c074170e PV |
2982 | * Charging time to the first type of queues and the exact service to |
2983 | * the other has the effect of using the WF2Q+ policy to schedule the | |
2984 | * former on a timeslice basis, without violating service domain | |
2985 | * guarantees among the latter. | |
aee69d78 | 2986 | */ |
ea25da48 PV |
2987 | void bfq_bfqq_expire(struct bfq_data *bfqd, |
2988 | struct bfq_queue *bfqq, | |
2989 | bool compensate, | |
2990 | enum bfqq_expiration reason) | |
aee69d78 PV |
2991 | { |
2992 | bool slow; | |
ab0e43e9 PV |
2993 | unsigned long delta = 0; |
2994 | struct bfq_entity *entity = &bfqq->entity; | |
aee69d78 PV |
2995 | int ref; |
2996 | ||
2997 | /* | |
ab0e43e9 | 2998 | * Check whether the process is slow (see bfq_bfqq_is_slow). |
aee69d78 | 2999 | */ |
ab0e43e9 | 3000 | slow = bfq_bfqq_is_slow(bfqd, bfqq, compensate, reason, &delta); |
aee69d78 | 3001 | |
77b7dcea PV |
3002 | /* |
3003 | * Increase service_from_backlogged before next statement, | |
3004 | * because the possible next invocation of | |
3005 | * bfq_bfqq_charge_time would likely inflate | |
3006 | * entity->service. In contrast, service_from_backlogged must | |
3007 | * contain real service, to enable the soft real-time | |
3008 | * heuristic to correctly compute the bandwidth consumed by | |
3009 | * bfqq. | |
3010 | */ | |
3011 | bfqq->service_from_backlogged += entity->service; | |
3012 | ||
aee69d78 | 3013 | /* |
c074170e PV |
3014 | * As above explained, charge slow (typically seeky) and |
3015 | * timed-out queues with the time and not the service | |
3016 | * received, to favor sequential workloads. | |
3017 | * | |
3018 | * Processes doing I/O in the slower disk zones will tend to | |
3019 | * be slow(er) even if not seeky. Therefore, since the | |
3020 | * estimated peak rate is actually an average over the disk | |
3021 | * surface, these processes may timeout just for bad luck. To | |
3022 | * avoid punishing them, do not charge time to processes that | |
3023 | * succeeded in consuming at least 2/3 of their budget. This | |
3024 | * allows BFQ to preserve enough elasticity to still perform | |
3025 | * bandwidth, and not time, distribution with little unlucky | |
3026 | * or quasi-sequential processes. | |
aee69d78 | 3027 | */ |
44e44a1b PV |
3028 | if (bfqq->wr_coeff == 1 && |
3029 | (slow || | |
3030 | (reason == BFQQE_BUDGET_TIMEOUT && | |
3031 | bfq_bfqq_budget_left(bfqq) >= entity->budget / 3))) | |
c074170e | 3032 | bfq_bfqq_charge_time(bfqd, bfqq, delta); |
aee69d78 PV |
3033 | |
3034 | if (reason == BFQQE_TOO_IDLE && | |
ab0e43e9 | 3035 | entity->service <= 2 * entity->budget / 10) |
aee69d78 PV |
3036 | bfq_clear_bfqq_IO_bound(bfqq); |
3037 | ||
44e44a1b PV |
3038 | if (bfqd->low_latency && bfqq->wr_coeff == 1) |
3039 | bfqq->last_wr_start_finish = jiffies; | |
3040 | ||
77b7dcea PV |
3041 | if (bfqd->low_latency && bfqd->bfq_wr_max_softrt_rate > 0 && |
3042 | RB_EMPTY_ROOT(&bfqq->sort_list)) { | |
3043 | /* | |
3044 | * If we get here, and there are no outstanding | |
3045 | * requests, then the request pattern is isochronous | |
3046 | * (see the comments on the function | |
3047 | * bfq_bfqq_softrt_next_start()). Thus we can compute | |
3048 | * soft_rt_next_start. If, instead, the queue still | |
3049 | * has outstanding requests, then we have to wait for | |
3050 | * the completion of all the outstanding requests to | |
3051 | * discover whether the request pattern is actually | |
3052 | * isochronous. | |
3053 | */ | |
3054 | if (bfqq->dispatched == 0) | |
3055 | bfqq->soft_rt_next_start = | |
3056 | bfq_bfqq_softrt_next_start(bfqd, bfqq); | |
3057 | else { | |
3058 | /* | |
3059 | * The application is still waiting for the | |
3060 | * completion of one or more requests: | |
3061 | * prevent it from possibly being incorrectly | |
3062 | * deemed as soft real-time by setting its | |
3063 | * soft_rt_next_start to infinity. In fact, | |
3064 | * without this assignment, the application | |
3065 | * would be incorrectly deemed as soft | |
3066 | * real-time if: | |
3067 | * 1) it issued a new request before the | |
3068 | * completion of all its in-flight | |
3069 | * requests, and | |
3070 | * 2) at that time, its soft_rt_next_start | |
3071 | * happened to be in the past. | |
3072 | */ | |
3073 | bfqq->soft_rt_next_start = | |
3074 | bfq_greatest_from_now(); | |
3075 | /* | |
3076 | * Schedule an update of soft_rt_next_start to when | |
3077 | * the task may be discovered to be isochronous. | |
3078 | */ | |
3079 | bfq_mark_bfqq_softrt_update(bfqq); | |
3080 | } | |
3081 | } | |
3082 | ||
aee69d78 | 3083 | bfq_log_bfqq(bfqd, bfqq, |
d5be3fef PV |
3084 | "expire (%d, slow %d, num_disp %d, short_ttime %d)", reason, |
3085 | slow, bfqq->dispatched, bfq_bfqq_has_short_ttime(bfqq)); | |
aee69d78 PV |
3086 | |
3087 | /* | |
3088 | * Increase, decrease or leave budget unchanged according to | |
3089 | * reason. | |
3090 | */ | |
3091 | __bfq_bfqq_recalc_budget(bfqd, bfqq, reason); | |
3092 | ref = bfqq->ref; | |
3093 | __bfq_bfqq_expire(bfqd, bfqq); | |
3094 | ||
3095 | /* mark bfqq as waiting a request only if a bic still points to it */ | |
3096 | if (ref > 1 && !bfq_bfqq_busy(bfqq) && | |
3097 | reason != BFQQE_BUDGET_TIMEOUT && | |
3098 | reason != BFQQE_BUDGET_EXHAUSTED) | |
3099 | bfq_mark_bfqq_non_blocking_wait_rq(bfqq); | |
3100 | } | |
3101 | ||
3102 | /* | |
3103 | * Budget timeout is not implemented through a dedicated timer, but | |
3104 | * just checked on request arrivals and completions, as well as on | |
3105 | * idle timer expirations. | |
3106 | */ | |
3107 | static bool bfq_bfqq_budget_timeout(struct bfq_queue *bfqq) | |
3108 | { | |
44e44a1b | 3109 | return time_is_before_eq_jiffies(bfqq->budget_timeout); |
aee69d78 PV |
3110 | } |
3111 | ||
3112 | /* | |
3113 | * If we expire a queue that is actively waiting (i.e., with the | |
3114 | * device idled) for the arrival of a new request, then we may incur | |
3115 | * the timestamp misalignment problem described in the body of the | |
3116 | * function __bfq_activate_entity. Hence we return true only if this | |
3117 | * condition does not hold, or if the queue is slow enough to deserve | |
3118 | * only to be kicked off for preserving a high throughput. | |
3119 | */ | |
3120 | static bool bfq_may_expire_for_budg_timeout(struct bfq_queue *bfqq) | |
3121 | { | |
3122 | bfq_log_bfqq(bfqq->bfqd, bfqq, | |
3123 | "may_budget_timeout: wait_request %d left %d timeout %d", | |
3124 | bfq_bfqq_wait_request(bfqq), | |
3125 | bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3, | |
3126 | bfq_bfqq_budget_timeout(bfqq)); | |
3127 | ||
3128 | return (!bfq_bfqq_wait_request(bfqq) || | |
3129 | bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3) | |
3130 | && | |
3131 | bfq_bfqq_budget_timeout(bfqq); | |
3132 | } | |
3133 | ||
3134 | /* | |
3135 | * For a queue that becomes empty, device idling is allowed only if | |
44e44a1b PV |
3136 | * this function returns true for the queue. As a consequence, since |
3137 | * device idling plays a critical role in both throughput boosting and | |
3138 | * service guarantees, the return value of this function plays a | |
3139 | * critical role in both these aspects as well. | |
3140 | * | |
3141 | * In a nutshell, this function returns true only if idling is | |
3142 | * beneficial for throughput or, even if detrimental for throughput, | |
3143 | * idling is however necessary to preserve service guarantees (low | |
3144 | * latency, desired throughput distribution, ...). In particular, on | |
3145 | * NCQ-capable devices, this function tries to return false, so as to | |
3146 | * help keep the drives' internal queues full, whenever this helps the | |
3147 | * device boost the throughput without causing any service-guarantee | |
3148 | * issue. | |
3149 | * | |
3150 | * In more detail, the return value of this function is obtained by, | |
3151 | * first, computing a number of boolean variables that take into | |
3152 | * account throughput and service-guarantee issues, and, then, | |
3153 | * combining these variables in a logical expression. Most of the | |
3154 | * issues taken into account are not trivial. We discuss these issues | |
3155 | * individually while introducing the variables. | |
aee69d78 PV |
3156 | */ |
3157 | static bool bfq_bfqq_may_idle(struct bfq_queue *bfqq) | |
3158 | { | |
3159 | struct bfq_data *bfqd = bfqq->bfqd; | |
edaf9428 PV |
3160 | bool rot_without_queueing = |
3161 | !blk_queue_nonrot(bfqd->queue) && !bfqd->hw_tag, | |
3162 | bfqq_sequential_and_IO_bound, | |
3163 | idling_boosts_thr, idling_boosts_thr_without_issues, | |
e1b2324d | 3164 | idling_needed_for_service_guarantees, |
cfd69712 | 3165 | asymmetric_scenario; |
aee69d78 PV |
3166 | |
3167 | if (bfqd->strict_guarantees) | |
3168 | return true; | |
3169 | ||
d5be3fef PV |
3170 | /* |
3171 | * Idling is performed only if slice_idle > 0. In addition, we | |
3172 | * do not idle if | |
3173 | * (a) bfqq is async | |
3174 | * (b) bfqq is in the idle io prio class: in this case we do | |
3175 | * not idle because we want to minimize the bandwidth that | |
3176 | * queues in this class can steal to higher-priority queues | |
3177 | */ | |
3178 | if (bfqd->bfq_slice_idle == 0 || !bfq_bfqq_sync(bfqq) || | |
3179 | bfq_class_idle(bfqq)) | |
3180 | return false; | |
3181 | ||
edaf9428 PV |
3182 | bfqq_sequential_and_IO_bound = !BFQQ_SEEKY(bfqq) && |
3183 | bfq_bfqq_IO_bound(bfqq) && bfq_bfqq_has_short_ttime(bfqq); | |
3184 | ||
aee69d78 | 3185 | /* |
44e44a1b PV |
3186 | * The next variable takes into account the cases where idling |
3187 | * boosts the throughput. | |
3188 | * | |
e01eff01 PV |
3189 | * The value of the variable is computed considering, first, that |
3190 | * idling is virtually always beneficial for the throughput if: | |
edaf9428 PV |
3191 | * (a) the device is not NCQ-capable and rotational, or |
3192 | * (b) regardless of the presence of NCQ, the device is rotational and | |
3193 | * the request pattern for bfqq is I/O-bound and sequential, or | |
3194 | * (c) regardless of whether it is rotational, the device is | |
3195 | * not NCQ-capable and the request pattern for bfqq is | |
3196 | * I/O-bound and sequential. | |
bf2b79e7 PV |
3197 | * |
3198 | * Secondly, and in contrast to the above item (b), idling an | |
3199 | * NCQ-capable flash-based device would not boost the | |
e01eff01 | 3200 | * throughput even with sequential I/O; rather it would lower |
bf2b79e7 PV |
3201 | * the throughput in proportion to how fast the device |
3202 | * is. Accordingly, the next variable is true if any of the | |
edaf9428 PV |
3203 | * above conditions (a), (b) or (c) is true, and, in |
3204 | * particular, happens to be false if bfqd is an NCQ-capable | |
3205 | * flash-based device. | |
aee69d78 | 3206 | */ |
edaf9428 PV |
3207 | idling_boosts_thr = rot_without_queueing || |
3208 | ((!blk_queue_nonrot(bfqd->queue) || !bfqd->hw_tag) && | |
3209 | bfqq_sequential_and_IO_bound); | |
aee69d78 | 3210 | |
cfd69712 PV |
3211 | /* |
3212 | * The value of the next variable, | |
3213 | * idling_boosts_thr_without_issues, is equal to that of | |
3214 | * idling_boosts_thr, unless a special case holds. In this | |
3215 | * special case, described below, idling may cause problems to | |
3216 | * weight-raised queues. | |
3217 | * | |
3218 | * When the request pool is saturated (e.g., in the presence | |
3219 | * of write hogs), if the processes associated with | |
3220 | * non-weight-raised queues ask for requests at a lower rate, | |
3221 | * then processes associated with weight-raised queues have a | |
3222 | * higher probability to get a request from the pool | |
3223 | * immediately (or at least soon) when they need one. Thus | |
3224 | * they have a higher probability to actually get a fraction | |
3225 | * of the device throughput proportional to their high | |
3226 | * weight. This is especially true with NCQ-capable drives, | |
3227 | * which enqueue several requests in advance, and further | |
3228 | * reorder internally-queued requests. | |
3229 | * | |
3230 | * For this reason, we force to false the value of | |
3231 | * idling_boosts_thr_without_issues if there are weight-raised | |
3232 | * busy queues. In this case, and if bfqq is not weight-raised, | |
3233 | * this guarantees that the device is not idled for bfqq (if, | |
3234 | * instead, bfqq is weight-raised, then idling will be | |
3235 | * guaranteed by another variable, see below). Combined with | |
3236 | * the timestamping rules of BFQ (see [1] for details), this | |
3237 | * behavior causes bfqq, and hence any sync non-weight-raised | |
3238 | * queue, to get a lower number of requests served, and thus | |
3239 | * to ask for a lower number of requests from the request | |
3240 | * pool, before the busy weight-raised queues get served | |
3241 | * again. This often mitigates starvation problems in the | |
3242 | * presence of heavy write workloads and NCQ, thereby | |
3243 | * guaranteeing a higher application and system responsiveness | |
3244 | * in these hostile scenarios. | |
3245 | */ | |
3246 | idling_boosts_thr_without_issues = idling_boosts_thr && | |
3247 | bfqd->wr_busy_queues == 0; | |
3248 | ||
aee69d78 | 3249 | /* |
bf2b79e7 PV |
3250 | * There is then a case where idling must be performed not |
3251 | * for throughput concerns, but to preserve service | |
3252 | * guarantees. | |
3253 | * | |
3254 | * To introduce this case, we can note that allowing the drive | |
3255 | * to enqueue more than one request at a time, and hence | |
44e44a1b | 3256 | * delegating de facto final scheduling decisions to the |
bf2b79e7 | 3257 | * drive's internal scheduler, entails loss of control on the |
44e44a1b | 3258 | * actual request service order. In particular, the critical |
bf2b79e7 | 3259 | * situation is when requests from different processes happen |
44e44a1b PV |
3260 | * to be present, at the same time, in the internal queue(s) |
3261 | * of the drive. In such a situation, the drive, by deciding | |
3262 | * the service order of the internally-queued requests, does | |
3263 | * determine also the actual throughput distribution among | |
3264 | * these processes. But the drive typically has no notion or | |
3265 | * concern about per-process throughput distribution, and | |
3266 | * makes its decisions only on a per-request basis. Therefore, | |
3267 | * the service distribution enforced by the drive's internal | |
3268 | * scheduler is likely to coincide with the desired | |
3269 | * device-throughput distribution only in a completely | |
bf2b79e7 PV |
3270 | * symmetric scenario where: |
3271 | * (i) each of these processes must get the same throughput as | |
3272 | * the others; | |
3273 | * (ii) all these processes have the same I/O pattern | |
3274 | (either sequential or random). | |
3275 | * In fact, in such a scenario, the drive will tend to treat | |
3276 | * the requests of each of these processes in about the same | |
3277 | * way as the requests of the others, and thus to provide | |
3278 | * each of these processes with about the same throughput | |
3279 | * (which is exactly the desired throughput distribution). In | |
3280 | * contrast, in any asymmetric scenario, device idling is | |
3281 | * certainly needed to guarantee that bfqq receives its | |
3282 | * assigned fraction of the device throughput (see [1] for | |
3283 | * details). | |
3284 | * | |
3285 | * We address this issue by controlling, actually, only the | |
3286 | * symmetry sub-condition (i), i.e., provided that | |
3287 | * sub-condition (i) holds, idling is not performed, | |
3288 | * regardless of whether sub-condition (ii) holds. In other | |
3289 | * words, only if sub-condition (i) holds, then idling is | |
3290 | * allowed, and the device tends to be prevented from queueing | |
3291 | * many requests, possibly of several processes. The reason | |
3292 | * for not controlling also sub-condition (ii) is that we | |
3293 | * exploit preemption to preserve guarantees in case of | |
3294 | * symmetric scenarios, even if (ii) does not hold, as | |
3295 | * explained in the next two paragraphs. | |
3296 | * | |
3297 | * Even if a queue, say Q, is expired when it remains idle, Q | |
3298 | * can still preempt the new in-service queue if the next | |
3299 | * request of Q arrives soon (see the comments on | |
3300 | * bfq_bfqq_update_budg_for_activation). If all queues and | |
3301 | * groups have the same weight, this form of preemption, | |
3302 | * combined with the hole-recovery heuristic described in the | |
3303 | * comments on function bfq_bfqq_update_budg_for_activation, | |
3304 | * are enough to preserve a correct bandwidth distribution in | |
3305 | * the mid term, even without idling. In fact, even if not | |
3306 | * idling allows the internal queues of the device to contain | |
3307 | * many requests, and thus to reorder requests, we can rather | |
3308 | * safely assume that the internal scheduler still preserves a | |
3309 | * minimum of mid-term fairness. The motivation for using | |
3310 | * preemption instead of idling is that, by not idling, | |
3311 | * service guarantees are preserved without minimally | |
3312 | * sacrificing throughput. In other words, both a high | |
3313 | * throughput and its desired distribution are obtained. | |
3314 | * | |
3315 | * More precisely, this preemption-based, idleless approach | |
3316 | * provides fairness in terms of IOPS, and not sectors per | |
3317 | * second. This can be seen with a simple example. Suppose | |
3318 | * that there are two queues with the same weight, but that | |
3319 | * the first queue receives requests of 8 sectors, while the | |
3320 | * second queue receives requests of 1024 sectors. In | |
3321 | * addition, suppose that each of the two queues contains at | |
3322 | * most one request at a time, which implies that each queue | |
3323 | * always remains idle after it is served. Finally, after | |
3324 | * remaining idle, each queue receives very quickly a new | |
3325 | * request. It follows that the two queues are served | |
3326 | * alternatively, preempting each other if needed. This | |
3327 | * implies that, although both queues have the same weight, | |
3328 | * the queue with large requests receives a service that is | |
3329 | * 1024/8 times as high as the service received by the other | |
3330 | * queue. | |
44e44a1b | 3331 | * |
bf2b79e7 PV |
3332 | * On the other hand, device idling is performed, and thus |
3333 | * pure sector-domain guarantees are provided, for the | |
3334 | * following queues, which are likely to need stronger | |
3335 | * throughput guarantees: weight-raised queues, and queues | |
3336 | * with a higher weight than other queues. When such queues | |
3337 | * are active, sub-condition (i) is false, which triggers | |
3338 | * device idling. | |
44e44a1b | 3339 | * |
bf2b79e7 PV |
3340 | * According to the above considerations, the next variable is |
3341 | * true (only) if sub-condition (i) holds. To compute the | |
3342 | * value of this variable, we not only use the return value of | |
3343 | * the function bfq_symmetric_scenario(), but also check | |
3344 | * whether bfqq is being weight-raised, because | |
3345 | * bfq_symmetric_scenario() does not take into account also | |
3346 | * weight-raised queues (see comments on | |
3347 | * bfq_weights_tree_add()). | |
44e44a1b PV |
3348 | * |
3349 | * As a side note, it is worth considering that the above | |
3350 | * device-idling countermeasures may however fail in the | |
3351 | * following unlucky scenario: if idling is (correctly) | |
bf2b79e7 PV |
3352 | * disabled in a time period during which all symmetry |
3353 | * sub-conditions hold, and hence the device is allowed to | |
44e44a1b PV |
3354 | * enqueue many requests, but at some later point in time some |
3355 | * sub-condition stops to hold, then it may become impossible | |
3356 | * to let requests be served in the desired order until all | |
3357 | * the requests already queued in the device have been served. | |
3358 | */ | |
bf2b79e7 PV |
3359 | asymmetric_scenario = bfqq->wr_coeff > 1 || |
3360 | !bfq_symmetric_scenario(bfqd); | |
44e44a1b | 3361 | |
e1b2324d AA |
3362 | /* |
3363 | * Finally, there is a case where maximizing throughput is the | |
3364 | * best choice even if it may cause unfairness toward | |
3365 | * bfqq. Such a case is when bfqq became active in a burst of | |
3366 | * queue activations. Queues that became active during a large | |
3367 | * burst benefit only from throughput, as discussed in the | |
3368 | * comments on bfq_handle_burst. Thus, if bfqq became active | |
3369 | * in a burst and not idling the device maximizes throughput, | |
3370 | * then the device must no be idled, because not idling the | |
3371 | * device provides bfqq and all other queues in the burst with | |
3372 | * maximum benefit. Combining this and the above case, we can | |
3373 | * now establish when idling is actually needed to preserve | |
3374 | * service guarantees. | |
3375 | */ | |
3376 | idling_needed_for_service_guarantees = | |
3377 | asymmetric_scenario && !bfq_bfqq_in_large_burst(bfqq); | |
3378 | ||
44e44a1b | 3379 | /* |
d5be3fef PV |
3380 | * We have now all the components we need to compute the |
3381 | * return value of the function, which is true only if idling | |
3382 | * either boosts the throughput (without issues), or is | |
3383 | * necessary to preserve service guarantees. | |
aee69d78 | 3384 | */ |
d5be3fef PV |
3385 | return idling_boosts_thr_without_issues || |
3386 | idling_needed_for_service_guarantees; | |
aee69d78 PV |
3387 | } |
3388 | ||
3389 | /* | |
3390 | * If the in-service queue is empty but the function bfq_bfqq_may_idle | |
3391 | * returns true, then: | |
3392 | * 1) the queue must remain in service and cannot be expired, and | |
3393 | * 2) the device must be idled to wait for the possible arrival of a new | |
3394 | * request for the queue. | |
3395 | * See the comments on the function bfq_bfqq_may_idle for the reasons | |
3396 | * why performing device idling is the best choice to boost the throughput | |
3397 | * and preserve service guarantees when bfq_bfqq_may_idle itself | |
3398 | * returns true. | |
3399 | */ | |
3400 | static bool bfq_bfqq_must_idle(struct bfq_queue *bfqq) | |
3401 | { | |
d5be3fef | 3402 | return RB_EMPTY_ROOT(&bfqq->sort_list) && bfq_bfqq_may_idle(bfqq); |
aee69d78 PV |
3403 | } |
3404 | ||
3405 | /* | |
3406 | * Select a queue for service. If we have a current queue in service, | |
3407 | * check whether to continue servicing it, or retrieve and set a new one. | |
3408 | */ | |
3409 | static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd) | |
3410 | { | |
3411 | struct bfq_queue *bfqq; | |
3412 | struct request *next_rq; | |
3413 | enum bfqq_expiration reason = BFQQE_BUDGET_TIMEOUT; | |
3414 | ||
3415 | bfqq = bfqd->in_service_queue; | |
3416 | if (!bfqq) | |
3417 | goto new_queue; | |
3418 | ||
3419 | bfq_log_bfqq(bfqd, bfqq, "select_queue: already in-service queue"); | |
3420 | ||
3421 | if (bfq_may_expire_for_budg_timeout(bfqq) && | |
3422 | !bfq_bfqq_wait_request(bfqq) && | |
3423 | !bfq_bfqq_must_idle(bfqq)) | |
3424 | goto expire; | |
3425 | ||
3426 | check_queue: | |
3427 | /* | |
3428 | * This loop is rarely executed more than once. Even when it | |
3429 | * happens, it is much more convenient to re-execute this loop | |
3430 | * than to return NULL and trigger a new dispatch to get a | |
3431 | * request served. | |
3432 | */ | |
3433 | next_rq = bfqq->next_rq; | |
3434 | /* | |
3435 | * If bfqq has requests queued and it has enough budget left to | |
3436 | * serve them, keep the queue, otherwise expire it. | |
3437 | */ | |
3438 | if (next_rq) { | |
3439 | if (bfq_serv_to_charge(next_rq, bfqq) > | |
3440 | bfq_bfqq_budget_left(bfqq)) { | |
3441 | /* | |
3442 | * Expire the queue for budget exhaustion, | |
3443 | * which makes sure that the next budget is | |
3444 | * enough to serve the next request, even if | |
3445 | * it comes from the fifo expired path. | |
3446 | */ | |
3447 | reason = BFQQE_BUDGET_EXHAUSTED; | |
3448 | goto expire; | |
3449 | } else { | |
3450 | /* | |
3451 | * The idle timer may be pending because we may | |
3452 | * not disable disk idling even when a new request | |
3453 | * arrives. | |
3454 | */ | |
3455 | if (bfq_bfqq_wait_request(bfqq)) { | |
3456 | /* | |
3457 | * If we get here: 1) at least a new request | |
3458 | * has arrived but we have not disabled the | |
3459 | * timer because the request was too small, | |
3460 | * 2) then the block layer has unplugged | |
3461 | * the device, causing the dispatch to be | |
3462 | * invoked. | |
3463 | * | |
3464 | * Since the device is unplugged, now the | |
3465 | * requests are probably large enough to | |
3466 | * provide a reasonable throughput. | |
3467 | * So we disable idling. | |
3468 | */ | |
3469 | bfq_clear_bfqq_wait_request(bfqq); | |
3470 | hrtimer_try_to_cancel(&bfqd->idle_slice_timer); | |
3471 | } | |
3472 | goto keep_queue; | |
3473 | } | |
3474 | } | |
3475 | ||
3476 | /* | |
3477 | * No requests pending. However, if the in-service queue is idling | |
3478 | * for a new request, or has requests waiting for a completion and | |
3479 | * may idle after their completion, then keep it anyway. | |
3480 | */ | |
3481 | if (bfq_bfqq_wait_request(bfqq) || | |
3482 | (bfqq->dispatched != 0 && bfq_bfqq_may_idle(bfqq))) { | |
3483 | bfqq = NULL; | |
3484 | goto keep_queue; | |
3485 | } | |
3486 | ||
3487 | reason = BFQQE_NO_MORE_REQUESTS; | |
3488 | expire: | |
3489 | bfq_bfqq_expire(bfqd, bfqq, false, reason); | |
3490 | new_queue: | |
3491 | bfqq = bfq_set_in_service_queue(bfqd); | |
3492 | if (bfqq) { | |
3493 | bfq_log_bfqq(bfqd, bfqq, "select_queue: checking new queue"); | |
3494 | goto check_queue; | |
3495 | } | |
3496 | keep_queue: | |
3497 | if (bfqq) | |
3498 | bfq_log_bfqq(bfqd, bfqq, "select_queue: returned this queue"); | |
3499 | else | |
3500 | bfq_log(bfqd, "select_queue: no queue returned"); | |
3501 | ||
3502 | return bfqq; | |
3503 | } | |
3504 | ||
44e44a1b PV |
3505 | static void bfq_update_wr_data(struct bfq_data *bfqd, struct bfq_queue *bfqq) |
3506 | { | |
3507 | struct bfq_entity *entity = &bfqq->entity; | |
3508 | ||
3509 | if (bfqq->wr_coeff > 1) { /* queue is being weight-raised */ | |
3510 | bfq_log_bfqq(bfqd, bfqq, | |
3511 | "raising period dur %u/%u msec, old coeff %u, w %d(%d)", | |
3512 | jiffies_to_msecs(jiffies - bfqq->last_wr_start_finish), | |
3513 | jiffies_to_msecs(bfqq->wr_cur_max_time), | |
3514 | bfqq->wr_coeff, | |
3515 | bfqq->entity.weight, bfqq->entity.orig_weight); | |
3516 | ||
3517 | if (entity->prio_changed) | |
3518 | bfq_log_bfqq(bfqd, bfqq, "WARN: pending prio change"); | |
3519 | ||
3520 | /* | |
e1b2324d AA |
3521 | * If the queue was activated in a burst, or too much |
3522 | * time has elapsed from the beginning of this | |
3523 | * weight-raising period, then end weight raising. | |
44e44a1b | 3524 | */ |
e1b2324d AA |
3525 | if (bfq_bfqq_in_large_burst(bfqq)) |
3526 | bfq_bfqq_end_wr(bfqq); | |
3527 | else if (time_is_before_jiffies(bfqq->last_wr_start_finish + | |
3528 | bfqq->wr_cur_max_time)) { | |
77b7dcea PV |
3529 | if (bfqq->wr_cur_max_time != bfqd->bfq_wr_rt_max_time || |
3530 | time_is_before_jiffies(bfqq->wr_start_at_switch_to_srt + | |
e1b2324d | 3531 | bfq_wr_duration(bfqd))) |
77b7dcea PV |
3532 | bfq_bfqq_end_wr(bfqq); |
3533 | else { | |
3e2bdd6d | 3534 | switch_back_to_interactive_wr(bfqq, bfqd); |
77b7dcea PV |
3535 | bfqq->entity.prio_changed = 1; |
3536 | } | |
44e44a1b PV |
3537 | } |
3538 | } | |
431b17f9 PV |
3539 | /* |
3540 | * To improve latency (for this or other queues), immediately | |
3541 | * update weight both if it must be raised and if it must be | |
3542 | * lowered. Since, entity may be on some active tree here, and | |
3543 | * might have a pending change of its ioprio class, invoke | |
3544 | * next function with the last parameter unset (see the | |
3545 | * comments on the function). | |
3546 | */ | |
44e44a1b | 3547 | if ((entity->weight > entity->orig_weight) != (bfqq->wr_coeff > 1)) |
431b17f9 PV |
3548 | __bfq_entity_update_weight_prio(bfq_entity_service_tree(entity), |
3549 | entity, false); | |
44e44a1b PV |
3550 | } |
3551 | ||
aee69d78 PV |
3552 | /* |
3553 | * Dispatch next request from bfqq. | |
3554 | */ | |
3555 | static struct request *bfq_dispatch_rq_from_bfqq(struct bfq_data *bfqd, | |
3556 | struct bfq_queue *bfqq) | |
3557 | { | |
3558 | struct request *rq = bfqq->next_rq; | |
3559 | unsigned long service_to_charge; | |
3560 | ||
3561 | service_to_charge = bfq_serv_to_charge(rq, bfqq); | |
3562 | ||
3563 | bfq_bfqq_served(bfqq, service_to_charge); | |
3564 | ||
3565 | bfq_dispatch_remove(bfqd->queue, rq); | |
3566 | ||
44e44a1b PV |
3567 | /* |
3568 | * If weight raising has to terminate for bfqq, then next | |
3569 | * function causes an immediate update of bfqq's weight, | |
3570 | * without waiting for next activation. As a consequence, on | |
3571 | * expiration, bfqq will be timestamped as if has never been | |
3572 | * weight-raised during this service slot, even if it has | |
3573 | * received part or even most of the service as a | |
3574 | * weight-raised queue. This inflates bfqq's timestamps, which | |
3575 | * is beneficial, as bfqq is then more willing to leave the | |
3576 | * device immediately to possible other weight-raised queues. | |
3577 | */ | |
3578 | bfq_update_wr_data(bfqd, bfqq); | |
3579 | ||
aee69d78 PV |
3580 | /* |
3581 | * Expire bfqq, pretending that its budget expired, if bfqq | |
3582 | * belongs to CLASS_IDLE and other queues are waiting for | |
3583 | * service. | |
3584 | */ | |
3585 | if (bfqd->busy_queues > 1 && bfq_class_idle(bfqq)) | |
3586 | goto expire; | |
3587 | ||
3588 | return rq; | |
3589 | ||
3590 | expire: | |
3591 | bfq_bfqq_expire(bfqd, bfqq, false, BFQQE_BUDGET_EXHAUSTED); | |
3592 | return rq; | |
3593 | } | |
3594 | ||
3595 | static bool bfq_has_work(struct blk_mq_hw_ctx *hctx) | |
3596 | { | |
3597 | struct bfq_data *bfqd = hctx->queue->elevator->elevator_data; | |
3598 | ||
3599 | /* | |
3600 | * Avoiding lock: a race on bfqd->busy_queues should cause at | |
3601 | * most a call to dispatch for nothing | |
3602 | */ | |
3603 | return !list_empty_careful(&bfqd->dispatch) || | |
3604 | bfqd->busy_queues > 0; | |
3605 | } | |
3606 | ||
3607 | static struct request *__bfq_dispatch_request(struct blk_mq_hw_ctx *hctx) | |
3608 | { | |
3609 | struct bfq_data *bfqd = hctx->queue->elevator->elevator_data; | |
3610 | struct request *rq = NULL; | |
3611 | struct bfq_queue *bfqq = NULL; | |
3612 | ||
3613 | if (!list_empty(&bfqd->dispatch)) { | |
3614 | rq = list_first_entry(&bfqd->dispatch, struct request, | |
3615 | queuelist); | |
3616 | list_del_init(&rq->queuelist); | |
3617 | ||
3618 | bfqq = RQ_BFQQ(rq); | |
3619 | ||
3620 | if (bfqq) { | |
3621 | /* | |
3622 | * Increment counters here, because this | |
3623 | * dispatch does not follow the standard | |
3624 | * dispatch flow (where counters are | |
3625 | * incremented) | |
3626 | */ | |
3627 | bfqq->dispatched++; | |
3628 | ||
3629 | goto inc_in_driver_start_rq; | |
3630 | } | |
3631 | ||
3632 | /* | |
3633 | * We exploit the put_rq_private hook to decrement | |
3634 | * rq_in_driver, but put_rq_private will not be | |
3635 | * invoked on this request. So, to avoid unbalance, | |
3636 | * just start this request, without incrementing | |
3637 | * rq_in_driver. As a negative consequence, | |
3638 | * rq_in_driver is deceptively lower than it should be | |
3639 | * while this request is in service. This may cause | |
3640 | * bfq_schedule_dispatch to be invoked uselessly. | |
3641 | * | |
3642 | * As for implementing an exact solution, the | |
3643 | * put_request hook, if defined, is probably invoked | |
3644 | * also on this request. So, by exploiting this hook, | |
3645 | * we could 1) increment rq_in_driver here, and 2) | |
3646 | * decrement it in put_request. Such a solution would | |
3647 | * let the value of the counter be always accurate, | |
3648 | * but it would entail using an extra interface | |
3649 | * function. This cost seems higher than the benefit, | |
3650 | * being the frequency of non-elevator-private | |
3651 | * requests very low. | |
3652 | */ | |
3653 | goto start_rq; | |
3654 | } | |
3655 | ||
3656 | bfq_log(bfqd, "dispatch requests: %d busy queues", bfqd->busy_queues); | |
3657 | ||
3658 | if (bfqd->busy_queues == 0) | |
3659 | goto exit; | |
3660 | ||
3661 | /* | |
3662 | * Force device to serve one request at a time if | |
3663 | * strict_guarantees is true. Forcing this service scheme is | |
3664 | * currently the ONLY way to guarantee that the request | |
3665 | * service order enforced by the scheduler is respected by a | |
3666 | * queueing device. Otherwise the device is free even to make | |
3667 | * some unlucky request wait for as long as the device | |
3668 | * wishes. | |
3669 | * | |
3670 | * Of course, serving one request at at time may cause loss of | |
3671 | * throughput. | |
3672 | */ | |
3673 | if (bfqd->strict_guarantees && bfqd->rq_in_driver > 0) | |
3674 | goto exit; | |
3675 | ||
3676 | bfqq = bfq_select_queue(bfqd); | |
3677 | if (!bfqq) | |
3678 | goto exit; | |
3679 | ||
3680 | rq = bfq_dispatch_rq_from_bfqq(bfqd, bfqq); | |
3681 | ||
3682 | if (rq) { | |
3683 | inc_in_driver_start_rq: | |
3684 | bfqd->rq_in_driver++; | |
3685 | start_rq: | |
3686 | rq->rq_flags |= RQF_STARTED; | |
3687 | } | |
3688 | exit: | |
3689 | return rq; | |
3690 | } | |
3691 | ||
3692 | static struct request *bfq_dispatch_request(struct blk_mq_hw_ctx *hctx) | |
3693 | { | |
3694 | struct bfq_data *bfqd = hctx->queue->elevator->elevator_data; | |
3695 | struct request *rq; | |
a33801e8 | 3696 | #if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP) |
24bfd19b PV |
3697 | struct bfq_queue *in_serv_queue, *bfqq; |
3698 | bool waiting_rq, idle_timer_disabled; | |
3699 | #endif | |
aee69d78 PV |
3700 | |
3701 | spin_lock_irq(&bfqd->lock); | |
36eca894 | 3702 | |
a33801e8 | 3703 | #if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP) |
24bfd19b PV |
3704 | in_serv_queue = bfqd->in_service_queue; |
3705 | waiting_rq = in_serv_queue && bfq_bfqq_wait_request(in_serv_queue); | |
3706 | ||
aee69d78 | 3707 | rq = __bfq_dispatch_request(hctx); |
24bfd19b PV |
3708 | |
3709 | idle_timer_disabled = | |
3710 | waiting_rq && !bfq_bfqq_wait_request(in_serv_queue); | |
3711 | ||
3712 | #else | |
3713 | rq = __bfq_dispatch_request(hctx); | |
3714 | #endif | |
6fa3e8d3 | 3715 | spin_unlock_irq(&bfqd->lock); |
aee69d78 | 3716 | |
a33801e8 | 3717 | #if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP) |
24bfd19b PV |
3718 | bfqq = rq ? RQ_BFQQ(rq) : NULL; |
3719 | if (!idle_timer_disabled && !bfqq) | |
3720 | return rq; | |
3721 | ||
3722 | /* | |
3723 | * rq and bfqq are guaranteed to exist until this function | |
3724 | * ends, for the following reasons. First, rq can be | |
3725 | * dispatched to the device, and then can be completed and | |
3726 | * freed, only after this function ends. Second, rq cannot be | |
3727 | * merged (and thus freed because of a merge) any longer, | |
3728 | * because it has already started. Thus rq cannot be freed | |
3729 | * before this function ends, and, since rq has a reference to | |
3730 | * bfqq, the same guarantee holds for bfqq too. | |
3731 | * | |
3732 | * In addition, the following queue lock guarantees that | |
3733 | * bfqq_group(bfqq) exists as well. | |
3734 | */ | |
3735 | spin_lock_irq(hctx->queue->queue_lock); | |
3736 | if (idle_timer_disabled) | |
3737 | /* | |
3738 | * Since the idle timer has been disabled, | |
3739 | * in_serv_queue contained some request when | |
3740 | * __bfq_dispatch_request was invoked above, which | |
3741 | * implies that rq was picked exactly from | |
3742 | * in_serv_queue. Thus in_serv_queue == bfqq, and is | |
3743 | * therefore guaranteed to exist because of the above | |
3744 | * arguments. | |
3745 | */ | |
3746 | bfqg_stats_update_idle_time(bfqq_group(in_serv_queue)); | |
3747 | if (bfqq) { | |
3748 | struct bfq_group *bfqg = bfqq_group(bfqq); | |
3749 | ||
3750 | bfqg_stats_update_avg_queue_size(bfqg); | |
3751 | bfqg_stats_set_start_empty_time(bfqg); | |
3752 | bfqg_stats_update_io_remove(bfqg, rq->cmd_flags); | |
3753 | } | |
3754 | spin_unlock_irq(hctx->queue->queue_lock); | |
3755 | #endif | |
3756 | ||
aee69d78 PV |
3757 | return rq; |
3758 | } | |
3759 | ||
3760 | /* | |
3761 | * Task holds one reference to the queue, dropped when task exits. Each rq | |
3762 | * in-flight on this queue also holds a reference, dropped when rq is freed. | |
3763 | * | |
3764 | * Scheduler lock must be held here. Recall not to use bfqq after calling | |
3765 | * this function on it. | |
3766 | */ | |
ea25da48 | 3767 | void bfq_put_queue(struct bfq_queue *bfqq) |
aee69d78 | 3768 | { |
e21b7a0b AA |
3769 | #ifdef CONFIG_BFQ_GROUP_IOSCHED |
3770 | struct bfq_group *bfqg = bfqq_group(bfqq); | |
3771 | #endif | |
3772 | ||
aee69d78 PV |
3773 | if (bfqq->bfqd) |
3774 | bfq_log_bfqq(bfqq->bfqd, bfqq, "put_queue: %p %d", | |
3775 | bfqq, bfqq->ref); | |
3776 | ||
3777 | bfqq->ref--; | |
3778 | if (bfqq->ref) | |
3779 | return; | |
3780 | ||
99fead8d | 3781 | if (!hlist_unhashed(&bfqq->burst_list_node)) { |
e1b2324d | 3782 | hlist_del_init(&bfqq->burst_list_node); |
99fead8d PV |
3783 | /* |
3784 | * Decrement also burst size after the removal, if the | |
3785 | * process associated with bfqq is exiting, and thus | |
3786 | * does not contribute to the burst any longer. This | |
3787 | * decrement helps filter out false positives of large | |
3788 | * bursts, when some short-lived process (often due to | |
3789 | * the execution of commands by some service) happens | |
3790 | * to start and exit while a complex application is | |
3791 | * starting, and thus spawning several processes that | |
3792 | * do I/O (and that *must not* be treated as a large | |
3793 | * burst, see comments on bfq_handle_burst). | |
3794 | * | |
3795 | * In particular, the decrement is performed only if: | |
3796 | * 1) bfqq is not a merged queue, because, if it is, | |
3797 | * then this free of bfqq is not triggered by the exit | |
3798 | * of the process bfqq is associated with, but exactly | |
3799 | * by the fact that bfqq has just been merged. | |
3800 | * 2) burst_size is greater than 0, to handle | |
3801 | * unbalanced decrements. Unbalanced decrements may | |
3802 | * happen in te following case: bfqq is inserted into | |
3803 | * the current burst list--without incrementing | |
3804 | * bust_size--because of a split, but the current | |
3805 | * burst list is not the burst list bfqq belonged to | |
3806 | * (see comments on the case of a split in | |
3807 | * bfq_set_request). | |
3808 | */ | |
3809 | if (bfqq->bic && bfqq->bfqd->burst_size > 0) | |
3810 | bfqq->bfqd->burst_size--; | |
7cb04004 | 3811 | } |
e21b7a0b | 3812 | |
aee69d78 | 3813 | kmem_cache_free(bfq_pool, bfqq); |
e21b7a0b | 3814 | #ifdef CONFIG_BFQ_GROUP_IOSCHED |
8f9bebc3 | 3815 | bfqg_and_blkg_put(bfqg); |
e21b7a0b | 3816 | #endif |
aee69d78 PV |
3817 | } |
3818 | ||
36eca894 AA |
3819 | static void bfq_put_cooperator(struct bfq_queue *bfqq) |
3820 | { | |
3821 | struct bfq_queue *__bfqq, *next; | |
3822 | ||
3823 | /* | |
3824 | * If this queue was scheduled to merge with another queue, be | |
3825 | * sure to drop the reference taken on that queue (and others in | |
3826 | * the merge chain). See bfq_setup_merge and bfq_merge_bfqqs. | |
3827 | */ | |
3828 | __bfqq = bfqq->new_bfqq; | |
3829 | while (__bfqq) { | |
3830 | if (__bfqq == bfqq) | |
3831 | break; | |
3832 | next = __bfqq->new_bfqq; | |
3833 | bfq_put_queue(__bfqq); | |
3834 | __bfqq = next; | |
3835 | } | |
3836 | } | |
3837 | ||
aee69d78 PV |
3838 | static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq) |
3839 | { | |
3840 | if (bfqq == bfqd->in_service_queue) { | |
3841 | __bfq_bfqq_expire(bfqd, bfqq); | |
3842 | bfq_schedule_dispatch(bfqd); | |
3843 | } | |
3844 | ||
3845 | bfq_log_bfqq(bfqd, bfqq, "exit_bfqq: %p, %d", bfqq, bfqq->ref); | |
3846 | ||
36eca894 AA |
3847 | bfq_put_cooperator(bfqq); |
3848 | ||
aee69d78 PV |
3849 | bfq_put_queue(bfqq); /* release process reference */ |
3850 | } | |
3851 | ||
3852 | static void bfq_exit_icq_bfqq(struct bfq_io_cq *bic, bool is_sync) | |
3853 | { | |
3854 | struct bfq_queue *bfqq = bic_to_bfqq(bic, is_sync); | |
3855 | struct bfq_data *bfqd; | |
3856 | ||
3857 | if (bfqq) | |
3858 | bfqd = bfqq->bfqd; /* NULL if scheduler already exited */ | |
3859 | ||
3860 | if (bfqq && bfqd) { | |
3861 | unsigned long flags; | |
3862 | ||
3863 | spin_lock_irqsave(&bfqd->lock, flags); | |
3864 | bfq_exit_bfqq(bfqd, bfqq); | |
3865 | bic_set_bfqq(bic, NULL, is_sync); | |
6fa3e8d3 | 3866 | spin_unlock_irqrestore(&bfqd->lock, flags); |
aee69d78 PV |
3867 | } |
3868 | } | |
3869 | ||
3870 | static void bfq_exit_icq(struct io_cq *icq) | |
3871 | { | |
3872 | struct bfq_io_cq *bic = icq_to_bic(icq); | |
3873 | ||
3874 | bfq_exit_icq_bfqq(bic, true); | |
3875 | bfq_exit_icq_bfqq(bic, false); | |
3876 | } | |
3877 | ||
3878 | /* | |
3879 | * Update the entity prio values; note that the new values will not | |
3880 | * be used until the next (re)activation. | |
3881 | */ | |
3882 | static void | |
3883 | bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic) | |
3884 | { | |
3885 | struct task_struct *tsk = current; | |
3886 | int ioprio_class; | |
3887 | struct bfq_data *bfqd = bfqq->bfqd; | |
3888 | ||
3889 | if (!bfqd) | |
3890 | return; | |
3891 | ||
3892 | ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio); | |
3893 | switch (ioprio_class) { | |
3894 | default: | |
3895 | dev_err(bfqq->bfqd->queue->backing_dev_info->dev, | |
3896 | "bfq: bad prio class %d\n", ioprio_class); | |
fa393d1b | 3897 | /* fall through */ |
aee69d78 PV |
3898 | case IOPRIO_CLASS_NONE: |
3899 | /* | |
3900 | * No prio set, inherit CPU scheduling settings. | |
3901 | */ | |
3902 | bfqq->new_ioprio = task_nice_ioprio(tsk); | |
3903 | bfqq->new_ioprio_class = task_nice_ioclass(tsk); | |
3904 | break; | |
3905 | case IOPRIO_CLASS_RT: | |
3906 | bfqq->new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio); | |
3907 | bfqq->new_ioprio_class = IOPRIO_CLASS_RT; | |
3908 | break; | |
3909 | case IOPRIO_CLASS_BE: | |
3910 | bfqq->new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio); | |
3911 | bfqq->new_ioprio_class = IOPRIO_CLASS_BE; | |
3912 | break; | |
3913 | case IOPRIO_CLASS_IDLE: | |
3914 | bfqq->new_ioprio_class = IOPRIO_CLASS_IDLE; | |
3915 | bfqq->new_ioprio = 7; | |
aee69d78 PV |
3916 | break; |
3917 | } | |
3918 | ||
3919 | if (bfqq->new_ioprio >= IOPRIO_BE_NR) { | |
3920 | pr_crit("bfq_set_next_ioprio_data: new_ioprio %d\n", | |
3921 | bfqq->new_ioprio); | |
3922 | bfqq->new_ioprio = IOPRIO_BE_NR; | |
3923 | } | |
3924 | ||
3925 | bfqq->entity.new_weight = bfq_ioprio_to_weight(bfqq->new_ioprio); | |
3926 | bfqq->entity.prio_changed = 1; | |
3927 | } | |
3928 | ||
ea25da48 PV |
3929 | static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd, |
3930 | struct bio *bio, bool is_sync, | |
3931 | struct bfq_io_cq *bic); | |
3932 | ||
aee69d78 PV |
3933 | static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio) |
3934 | { | |
3935 | struct bfq_data *bfqd = bic_to_bfqd(bic); | |
3936 | struct bfq_queue *bfqq; | |
3937 | int ioprio = bic->icq.ioc->ioprio; | |
3938 | ||
3939 | /* | |
3940 | * This condition may trigger on a newly created bic, be sure to | |
3941 | * drop the lock before returning. | |
3942 | */ | |
3943 | if (unlikely(!bfqd) || likely(bic->ioprio == ioprio)) | |
3944 | return; | |
3945 | ||
3946 | bic->ioprio = ioprio; | |
3947 | ||
3948 | bfqq = bic_to_bfqq(bic, false); | |
3949 | if (bfqq) { | |
3950 | /* release process reference on this queue */ | |
3951 | bfq_put_queue(bfqq); | |
3952 | bfqq = bfq_get_queue(bfqd, bio, BLK_RW_ASYNC, bic); | |
3953 | bic_set_bfqq(bic, bfqq, false); | |
3954 | } | |
3955 | ||
3956 | bfqq = bic_to_bfqq(bic, true); | |
3957 | if (bfqq) | |
3958 | bfq_set_next_ioprio_data(bfqq, bic); | |
3959 | } | |
3960 | ||
3961 | static void bfq_init_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, | |
3962 | struct bfq_io_cq *bic, pid_t pid, int is_sync) | |
3963 | { | |
3964 | RB_CLEAR_NODE(&bfqq->entity.rb_node); | |
3965 | INIT_LIST_HEAD(&bfqq->fifo); | |
e1b2324d | 3966 | INIT_HLIST_NODE(&bfqq->burst_list_node); |
aee69d78 PV |
3967 | |
3968 | bfqq->ref = 0; | |
3969 | bfqq->bfqd = bfqd; | |
3970 | ||
3971 | if (bic) | |
3972 | bfq_set_next_ioprio_data(bfqq, bic); | |
3973 | ||
3974 | if (is_sync) { | |
d5be3fef PV |
3975 | /* |
3976 | * No need to mark as has_short_ttime if in | |
3977 | * idle_class, because no device idling is performed | |
3978 | * for queues in idle class | |
3979 | */ | |
aee69d78 | 3980 | if (!bfq_class_idle(bfqq)) |
d5be3fef PV |
3981 | /* tentatively mark as has_short_ttime */ |
3982 | bfq_mark_bfqq_has_short_ttime(bfqq); | |
aee69d78 | 3983 | bfq_mark_bfqq_sync(bfqq); |
e1b2324d | 3984 | bfq_mark_bfqq_just_created(bfqq); |
aee69d78 PV |
3985 | } else |
3986 | bfq_clear_bfqq_sync(bfqq); | |
3987 | ||
3988 | /* set end request to minus infinity from now */ | |
3989 | bfqq->ttime.last_end_request = ktime_get_ns() + 1; | |
3990 | ||
3991 | bfq_mark_bfqq_IO_bound(bfqq); | |
3992 | ||
3993 | bfqq->pid = pid; | |
3994 | ||
3995 | /* Tentative initial value to trade off between thr and lat */ | |
54b60456 | 3996 | bfqq->max_budget = (2 * bfq_max_budget(bfqd)) / 3; |
aee69d78 | 3997 | bfqq->budget_timeout = bfq_smallest_from_now(); |
aee69d78 | 3998 | |
44e44a1b | 3999 | bfqq->wr_coeff = 1; |
36eca894 | 4000 | bfqq->last_wr_start_finish = jiffies; |
77b7dcea | 4001 | bfqq->wr_start_at_switch_to_srt = bfq_smallest_from_now(); |
36eca894 | 4002 | bfqq->split_time = bfq_smallest_from_now(); |
77b7dcea PV |
4003 | |
4004 | /* | |
4005 | * Set to the value for which bfqq will not be deemed as | |
4006 | * soft rt when it becomes backlogged. | |
4007 | */ | |
4008 | bfqq->soft_rt_next_start = bfq_greatest_from_now(); | |
44e44a1b | 4009 | |
aee69d78 PV |
4010 | /* first request is almost certainly seeky */ |
4011 | bfqq->seek_history = 1; | |
4012 | } | |
4013 | ||
4014 | static struct bfq_queue **bfq_async_queue_prio(struct bfq_data *bfqd, | |
e21b7a0b | 4015 | struct bfq_group *bfqg, |
aee69d78 PV |
4016 | int ioprio_class, int ioprio) |
4017 | { | |
4018 | switch (ioprio_class) { | |
4019 | case IOPRIO_CLASS_RT: | |
e21b7a0b | 4020 | return &bfqg->async_bfqq[0][ioprio]; |
aee69d78 PV |
4021 | case IOPRIO_CLASS_NONE: |
4022 | ioprio = IOPRIO_NORM; | |
4023 | /* fall through */ | |
4024 | case IOPRIO_CLASS_BE: | |
e21b7a0b | 4025 | return &bfqg->async_bfqq[1][ioprio]; |
aee69d78 | 4026 | case IOPRIO_CLASS_IDLE: |
e21b7a0b | 4027 | return &bfqg->async_idle_bfqq; |
aee69d78 PV |
4028 | default: |
4029 | return NULL; | |
4030 | } | |
4031 | } | |
4032 | ||
4033 | static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd, | |
4034 | struct bio *bio, bool is_sync, | |
4035 | struct bfq_io_cq *bic) | |
4036 | { | |
4037 | const int ioprio = IOPRIO_PRIO_DATA(bic->ioprio); | |
4038 | const int ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio); | |
4039 | struct bfq_queue **async_bfqq = NULL; | |
4040 | struct bfq_queue *bfqq; | |
e21b7a0b | 4041 | struct bfq_group *bfqg; |
aee69d78 PV |
4042 | |
4043 | rcu_read_lock(); | |
4044 | ||
e21b7a0b AA |
4045 | bfqg = bfq_find_set_group(bfqd, bio_blkcg(bio)); |
4046 | if (!bfqg) { | |
4047 | bfqq = &bfqd->oom_bfqq; | |
4048 | goto out; | |
4049 | } | |
4050 | ||
aee69d78 | 4051 | if (!is_sync) { |
e21b7a0b | 4052 | async_bfqq = bfq_async_queue_prio(bfqd, bfqg, ioprio_class, |
aee69d78 PV |
4053 | ioprio); |
4054 | bfqq = *async_bfqq; | |
4055 | if (bfqq) | |
4056 | goto out; | |
4057 | } | |
4058 | ||
4059 | bfqq = kmem_cache_alloc_node(bfq_pool, | |
4060 | GFP_NOWAIT | __GFP_ZERO | __GFP_NOWARN, | |
4061 | bfqd->queue->node); | |
4062 | ||
4063 | if (bfqq) { | |
4064 | bfq_init_bfqq(bfqd, bfqq, bic, current->pid, | |
4065 | is_sync); | |
e21b7a0b | 4066 | bfq_init_entity(&bfqq->entity, bfqg); |
aee69d78 PV |
4067 | bfq_log_bfqq(bfqd, bfqq, "allocated"); |
4068 | } else { | |
4069 | bfqq = &bfqd->oom_bfqq; | |
4070 | bfq_log_bfqq(bfqd, bfqq, "using oom bfqq"); | |
4071 | goto out; | |
4072 | } | |
4073 | ||
4074 | /* | |
4075 | * Pin the queue now that it's allocated, scheduler exit will | |
4076 | * prune it. | |
4077 | */ | |
4078 | if (async_bfqq) { | |
e21b7a0b AA |
4079 | bfqq->ref++; /* |
4080 | * Extra group reference, w.r.t. sync | |
4081 | * queue. This extra reference is removed | |
4082 | * only if bfqq->bfqg disappears, to | |
4083 | * guarantee that this queue is not freed | |
4084 | * until its group goes away. | |
4085 | */ | |
4086 | bfq_log_bfqq(bfqd, bfqq, "get_queue, bfqq not in async: %p, %d", | |
aee69d78 PV |
4087 | bfqq, bfqq->ref); |
4088 | *async_bfqq = bfqq; | |
4089 | } | |
4090 | ||
4091 | out: | |
4092 | bfqq->ref++; /* get a process reference to this queue */ | |
4093 | bfq_log_bfqq(bfqd, bfqq, "get_queue, at end: %p, %d", bfqq, bfqq->ref); | |
4094 | rcu_read_unlock(); | |
4095 | return bfqq; | |
4096 | } | |
4097 | ||
4098 | static void bfq_update_io_thinktime(struct bfq_data *bfqd, | |
4099 | struct bfq_queue *bfqq) | |
4100 | { | |
4101 | struct bfq_ttime *ttime = &bfqq->ttime; | |
4102 | u64 elapsed = ktime_get_ns() - bfqq->ttime.last_end_request; | |
4103 | ||
4104 | elapsed = min_t(u64, elapsed, 2ULL * bfqd->bfq_slice_idle); | |
4105 | ||
4106 | ttime->ttime_samples = (7*bfqq->ttime.ttime_samples + 256) / 8; | |
4107 | ttime->ttime_total = div_u64(7*ttime->ttime_total + 256*elapsed, 8); | |
4108 | ttime->ttime_mean = div64_ul(ttime->ttime_total + 128, | |
4109 | ttime->ttime_samples); | |
4110 | } | |
4111 | ||
4112 | static void | |
4113 | bfq_update_io_seektime(struct bfq_data *bfqd, struct bfq_queue *bfqq, | |
4114 | struct request *rq) | |
4115 | { | |
aee69d78 | 4116 | bfqq->seek_history <<= 1; |
ab0e43e9 PV |
4117 | bfqq->seek_history |= |
4118 | get_sdist(bfqq->last_request_pos, rq) > BFQQ_SEEK_THR && | |
aee69d78 PV |
4119 | (!blk_queue_nonrot(bfqd->queue) || |
4120 | blk_rq_sectors(rq) < BFQQ_SECT_THR_NONROT); | |
4121 | } | |
4122 | ||
d5be3fef PV |
4123 | static void bfq_update_has_short_ttime(struct bfq_data *bfqd, |
4124 | struct bfq_queue *bfqq, | |
4125 | struct bfq_io_cq *bic) | |
aee69d78 | 4126 | { |
d5be3fef | 4127 | bool has_short_ttime = true; |
aee69d78 | 4128 | |
d5be3fef PV |
4129 | /* |
4130 | * No need to update has_short_ttime if bfqq is async or in | |
4131 | * idle io prio class, or if bfq_slice_idle is zero, because | |
4132 | * no device idling is performed for bfqq in this case. | |
4133 | */ | |
4134 | if (!bfq_bfqq_sync(bfqq) || bfq_class_idle(bfqq) || | |
4135 | bfqd->bfq_slice_idle == 0) | |
aee69d78 PV |
4136 | return; |
4137 | ||
36eca894 AA |
4138 | /* Idle window just restored, statistics are meaningless. */ |
4139 | if (time_is_after_eq_jiffies(bfqq->split_time + | |
4140 | bfqd->bfq_wr_min_idle_time)) | |
4141 | return; | |
4142 | ||
d5be3fef PV |
4143 | /* Think time is infinite if no process is linked to |
4144 | * bfqq. Otherwise check average think time to | |
4145 | * decide whether to mark as has_short_ttime | |
4146 | */ | |
aee69d78 | 4147 | if (atomic_read(&bic->icq.ioc->active_ref) == 0 || |
d5be3fef PV |
4148 | (bfq_sample_valid(bfqq->ttime.ttime_samples) && |
4149 | bfqq->ttime.ttime_mean > bfqd->bfq_slice_idle)) | |
4150 | has_short_ttime = false; | |
4151 | ||
4152 | bfq_log_bfqq(bfqd, bfqq, "update_has_short_ttime: has_short_ttime %d", | |
4153 | has_short_ttime); | |
aee69d78 | 4154 | |
d5be3fef PV |
4155 | if (has_short_ttime) |
4156 | bfq_mark_bfqq_has_short_ttime(bfqq); | |
aee69d78 | 4157 | else |
d5be3fef | 4158 | bfq_clear_bfqq_has_short_ttime(bfqq); |
aee69d78 PV |
4159 | } |
4160 | ||
4161 | /* | |
4162 | * Called when a new fs request (rq) is added to bfqq. Check if there's | |
4163 | * something we should do about it. | |
4164 | */ | |
4165 | static void bfq_rq_enqueued(struct bfq_data *bfqd, struct bfq_queue *bfqq, | |
4166 | struct request *rq) | |
4167 | { | |
4168 | struct bfq_io_cq *bic = RQ_BIC(rq); | |
4169 | ||
4170 | if (rq->cmd_flags & REQ_META) | |
4171 | bfqq->meta_pending++; | |
4172 | ||
4173 | bfq_update_io_thinktime(bfqd, bfqq); | |
d5be3fef | 4174 | bfq_update_has_short_ttime(bfqd, bfqq, bic); |
aee69d78 | 4175 | bfq_update_io_seektime(bfqd, bfqq, rq); |
aee69d78 PV |
4176 | |
4177 | bfq_log_bfqq(bfqd, bfqq, | |
d5be3fef PV |
4178 | "rq_enqueued: has_short_ttime=%d (seeky %d)", |
4179 | bfq_bfqq_has_short_ttime(bfqq), BFQQ_SEEKY(bfqq)); | |
aee69d78 PV |
4180 | |
4181 | bfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq); | |
4182 | ||
4183 | if (bfqq == bfqd->in_service_queue && bfq_bfqq_wait_request(bfqq)) { | |
4184 | bool small_req = bfqq->queued[rq_is_sync(rq)] == 1 && | |
4185 | blk_rq_sectors(rq) < 32; | |
4186 | bool budget_timeout = bfq_bfqq_budget_timeout(bfqq); | |
4187 | ||
4188 | /* | |
4189 | * There is just this request queued: if the request | |
4190 | * is small and the queue is not to be expired, then | |
4191 | * just exit. | |
4192 | * | |
4193 | * In this way, if the device is being idled to wait | |
4194 | * for a new request from the in-service queue, we | |
4195 | * avoid unplugging the device and committing the | |
4196 | * device to serve just a small request. On the | |
4197 | * contrary, we wait for the block layer to decide | |
4198 | * when to unplug the device: hopefully, new requests | |
4199 | * will be merged to this one quickly, then the device | |
4200 | * will be unplugged and larger requests will be | |
4201 | * dispatched. | |
4202 | */ | |
4203 | if (small_req && !budget_timeout) | |
4204 | return; | |
4205 | ||
4206 | /* | |
4207 | * A large enough request arrived, or the queue is to | |
4208 | * be expired: in both cases disk idling is to be | |
4209 | * stopped, so clear wait_request flag and reset | |
4210 | * timer. | |
4211 | */ | |
4212 | bfq_clear_bfqq_wait_request(bfqq); | |
4213 | hrtimer_try_to_cancel(&bfqd->idle_slice_timer); | |
4214 | ||
4215 | /* | |
4216 | * The queue is not empty, because a new request just | |
4217 | * arrived. Hence we can safely expire the queue, in | |
4218 | * case of budget timeout, without risking that the | |
4219 | * timestamps of the queue are not updated correctly. | |
4220 | * See [1] for more details. | |
4221 | */ | |
4222 | if (budget_timeout) | |
4223 | bfq_bfqq_expire(bfqd, bfqq, false, | |
4224 | BFQQE_BUDGET_TIMEOUT); | |
4225 | } | |
4226 | } | |
4227 | ||
24bfd19b PV |
4228 | /* returns true if it causes the idle timer to be disabled */ |
4229 | static bool __bfq_insert_request(struct bfq_data *bfqd, struct request *rq) | |
aee69d78 | 4230 | { |
36eca894 AA |
4231 | struct bfq_queue *bfqq = RQ_BFQQ(rq), |
4232 | *new_bfqq = bfq_setup_cooperator(bfqd, bfqq, rq, true); | |
24bfd19b | 4233 | bool waiting, idle_timer_disabled = false; |
36eca894 AA |
4234 | |
4235 | if (new_bfqq) { | |
4236 | if (bic_to_bfqq(RQ_BIC(rq), 1) != bfqq) | |
4237 | new_bfqq = bic_to_bfqq(RQ_BIC(rq), 1); | |
4238 | /* | |
4239 | * Release the request's reference to the old bfqq | |
4240 | * and make sure one is taken to the shared queue. | |
4241 | */ | |
4242 | new_bfqq->allocated++; | |
4243 | bfqq->allocated--; | |
4244 | new_bfqq->ref++; | |
4245 | /* | |
4246 | * If the bic associated with the process | |
4247 | * issuing this request still points to bfqq | |
4248 | * (and thus has not been already redirected | |
4249 | * to new_bfqq or even some other bfq_queue), | |
4250 | * then complete the merge and redirect it to | |
4251 | * new_bfqq. | |
4252 | */ | |
4253 | if (bic_to_bfqq(RQ_BIC(rq), 1) == bfqq) | |
4254 | bfq_merge_bfqqs(bfqd, RQ_BIC(rq), | |
4255 | bfqq, new_bfqq); | |
894df937 PV |
4256 | |
4257 | bfq_clear_bfqq_just_created(bfqq); | |
36eca894 AA |
4258 | /* |
4259 | * rq is about to be enqueued into new_bfqq, | |
4260 | * release rq reference on bfqq | |
4261 | */ | |
4262 | bfq_put_queue(bfqq); | |
4263 | rq->elv.priv[1] = new_bfqq; | |
4264 | bfqq = new_bfqq; | |
4265 | } | |
aee69d78 | 4266 | |
24bfd19b | 4267 | waiting = bfqq && bfq_bfqq_wait_request(bfqq); |
aee69d78 | 4268 | bfq_add_request(rq); |
24bfd19b | 4269 | idle_timer_disabled = waiting && !bfq_bfqq_wait_request(bfqq); |
aee69d78 PV |
4270 | |
4271 | rq->fifo_time = ktime_get_ns() + bfqd->bfq_fifo_expire[rq_is_sync(rq)]; | |
4272 | list_add_tail(&rq->queuelist, &bfqq->fifo); | |
4273 | ||
4274 | bfq_rq_enqueued(bfqd, bfqq, rq); | |
24bfd19b PV |
4275 | |
4276 | return idle_timer_disabled; | |
aee69d78 PV |
4277 | } |
4278 | ||
4279 | static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, | |
4280 | bool at_head) | |
4281 | { | |
4282 | struct request_queue *q = hctx->queue; | |
4283 | struct bfq_data *bfqd = q->elevator->elevator_data; | |
a33801e8 | 4284 | #if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP) |
614822f8 | 4285 | struct bfq_queue *bfqq = RQ_BFQQ(rq); |
24bfd19b PV |
4286 | bool idle_timer_disabled = false; |
4287 | unsigned int cmd_flags; | |
4288 | #endif | |
aee69d78 PV |
4289 | |
4290 | spin_lock_irq(&bfqd->lock); | |
4291 | if (blk_mq_sched_try_insert_merge(q, rq)) { | |
4292 | spin_unlock_irq(&bfqd->lock); | |
4293 | return; | |
4294 | } | |
4295 | ||
4296 | spin_unlock_irq(&bfqd->lock); | |
4297 | ||
4298 | blk_mq_sched_request_inserted(rq); | |
4299 | ||
4300 | spin_lock_irq(&bfqd->lock); | |
4301 | if (at_head || blk_rq_is_passthrough(rq)) { | |
4302 | if (at_head) | |
4303 | list_add(&rq->queuelist, &bfqd->dispatch); | |
4304 | else | |
4305 | list_add_tail(&rq->queuelist, &bfqd->dispatch); | |
4306 | } else { | |
a33801e8 | 4307 | #if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP) |
24bfd19b | 4308 | idle_timer_disabled = __bfq_insert_request(bfqd, rq); |
614822f8 LM |
4309 | /* |
4310 | * Update bfqq, because, if a queue merge has occurred | |
4311 | * in __bfq_insert_request, then rq has been | |
4312 | * redirected into a new queue. | |
4313 | */ | |
4314 | bfqq = RQ_BFQQ(rq); | |
24bfd19b PV |
4315 | #else |
4316 | __bfq_insert_request(bfqd, rq); | |
4317 | #endif | |
aee69d78 PV |
4318 | |
4319 | if (rq_mergeable(rq)) { | |
4320 | elv_rqhash_add(q, rq); | |
4321 | if (!q->last_merge) | |
4322 | q->last_merge = rq; | |
4323 | } | |
4324 | } | |
4325 | ||
a33801e8 | 4326 | #if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP) |
24bfd19b PV |
4327 | /* |
4328 | * Cache cmd_flags before releasing scheduler lock, because rq | |
4329 | * may disappear afterwards (for example, because of a request | |
4330 | * merge). | |
4331 | */ | |
4332 | cmd_flags = rq->cmd_flags; | |
4333 | #endif | |
6fa3e8d3 | 4334 | spin_unlock_irq(&bfqd->lock); |
24bfd19b | 4335 | |
a33801e8 | 4336 | #if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP) |
24bfd19b PV |
4337 | if (!bfqq) |
4338 | return; | |
4339 | /* | |
4340 | * bfqq still exists, because it can disappear only after | |
4341 | * either it is merged with another queue, or the process it | |
4342 | * is associated with exits. But both actions must be taken by | |
4343 | * the same process currently executing this flow of | |
4344 | * instruction. | |
4345 | * | |
4346 | * In addition, the following queue lock guarantees that | |
4347 | * bfqq_group(bfqq) exists as well. | |
4348 | */ | |
4349 | spin_lock_irq(q->queue_lock); | |
4350 | bfqg_stats_update_io_add(bfqq_group(bfqq), bfqq, cmd_flags); | |
4351 | if (idle_timer_disabled) | |
4352 | bfqg_stats_update_idle_time(bfqq_group(bfqq)); | |
4353 | spin_unlock_irq(q->queue_lock); | |
4354 | #endif | |
aee69d78 PV |
4355 | } |
4356 | ||
4357 | static void bfq_insert_requests(struct blk_mq_hw_ctx *hctx, | |
4358 | struct list_head *list, bool at_head) | |
4359 | { | |
4360 | while (!list_empty(list)) { | |
4361 | struct request *rq; | |
4362 | ||
4363 | rq = list_first_entry(list, struct request, queuelist); | |
4364 | list_del_init(&rq->queuelist); | |
4365 | bfq_insert_request(hctx, rq, at_head); | |
4366 | } | |
4367 | } | |
4368 | ||
4369 | static void bfq_update_hw_tag(struct bfq_data *bfqd) | |
4370 | { | |
4371 | bfqd->max_rq_in_driver = max_t(int, bfqd->max_rq_in_driver, | |
4372 | bfqd->rq_in_driver); | |
4373 | ||
4374 | if (bfqd->hw_tag == 1) | |
4375 | return; | |
4376 | ||
4377 | /* | |
4378 | * This sample is valid if the number of outstanding requests | |
4379 | * is large enough to allow a queueing behavior. Note that the | |
4380 | * sum is not exact, as it's not taking into account deactivated | |
4381 | * requests. | |
4382 | */ | |
4383 | if (bfqd->rq_in_driver + bfqd->queued < BFQ_HW_QUEUE_THRESHOLD) | |
4384 | return; | |
4385 | ||
4386 | if (bfqd->hw_tag_samples++ < BFQ_HW_QUEUE_SAMPLES) | |
4387 | return; | |
4388 | ||
4389 | bfqd->hw_tag = bfqd->max_rq_in_driver > BFQ_HW_QUEUE_THRESHOLD; | |
4390 | bfqd->max_rq_in_driver = 0; | |
4391 | bfqd->hw_tag_samples = 0; | |
4392 | } | |
4393 | ||
4394 | static void bfq_completed_request(struct bfq_queue *bfqq, struct bfq_data *bfqd) | |
4395 | { | |
ab0e43e9 PV |
4396 | u64 now_ns; |
4397 | u32 delta_us; | |
4398 | ||
aee69d78 PV |
4399 | bfq_update_hw_tag(bfqd); |
4400 | ||
4401 | bfqd->rq_in_driver--; | |
4402 | bfqq->dispatched--; | |
4403 | ||
44e44a1b PV |
4404 | if (!bfqq->dispatched && !bfq_bfqq_busy(bfqq)) { |
4405 | /* | |
4406 | * Set budget_timeout (which we overload to store the | |
4407 | * time at which the queue remains with no backlog and | |
4408 | * no outstanding request; used by the weight-raising | |
4409 | * mechanism). | |
4410 | */ | |
4411 | bfqq->budget_timeout = jiffies; | |
1de0c4cd AA |
4412 | |
4413 | bfq_weights_tree_remove(bfqd, &bfqq->entity, | |
4414 | &bfqd->queue_weights_tree); | |
44e44a1b PV |
4415 | } |
4416 | ||
ab0e43e9 PV |
4417 | now_ns = ktime_get_ns(); |
4418 | ||
4419 | bfqq->ttime.last_end_request = now_ns; | |
4420 | ||
4421 | /* | |
4422 | * Using us instead of ns, to get a reasonable precision in | |
4423 | * computing rate in next check. | |
4424 | */ | |
4425 | delta_us = div_u64(now_ns - bfqd->last_completion, NSEC_PER_USEC); | |
4426 | ||
4427 | /* | |
4428 | * If the request took rather long to complete, and, according | |
4429 | * to the maximum request size recorded, this completion latency | |
4430 | * implies that the request was certainly served at a very low | |
4431 | * rate (less than 1M sectors/sec), then the whole observation | |
4432 | * interval that lasts up to this time instant cannot be a | |
4433 | * valid time interval for computing a new peak rate. Invoke | |
4434 | * bfq_update_rate_reset to have the following three steps | |
4435 | * taken: | |
4436 | * - close the observation interval at the last (previous) | |
4437 | * request dispatch or completion | |
4438 | * - compute rate, if possible, for that observation interval | |
4439 | * - reset to zero samples, which will trigger a proper | |
4440 | * re-initialization of the observation interval on next | |
4441 | * dispatch | |
4442 | */ | |
4443 | if (delta_us > BFQ_MIN_TT/NSEC_PER_USEC && | |
4444 | (bfqd->last_rq_max_size<<BFQ_RATE_SHIFT)/delta_us < | |
4445 | 1UL<<(BFQ_RATE_SHIFT - 10)) | |
4446 | bfq_update_rate_reset(bfqd, NULL); | |
4447 | bfqd->last_completion = now_ns; | |
aee69d78 | 4448 | |
77b7dcea PV |
4449 | /* |
4450 | * If we are waiting to discover whether the request pattern | |
4451 | * of the task associated with the queue is actually | |
4452 | * isochronous, and both requisites for this condition to hold | |
4453 | * are now satisfied, then compute soft_rt_next_start (see the | |
4454 | * comments on the function bfq_bfqq_softrt_next_start()). We | |
4455 | * schedule this delayed check when bfqq expires, if it still | |
4456 | * has in-flight requests. | |
4457 | */ | |
4458 | if (bfq_bfqq_softrt_update(bfqq) && bfqq->dispatched == 0 && | |
4459 | RB_EMPTY_ROOT(&bfqq->sort_list)) | |
4460 | bfqq->soft_rt_next_start = | |
4461 | bfq_bfqq_softrt_next_start(bfqd, bfqq); | |
4462 | ||
aee69d78 PV |
4463 | /* |
4464 | * If this is the in-service queue, check if it needs to be expired, | |
4465 | * or if we want to idle in case it has no pending requests. | |
4466 | */ | |
4467 | if (bfqd->in_service_queue == bfqq) { | |
44e44a1b | 4468 | if (bfqq->dispatched == 0 && bfq_bfqq_must_idle(bfqq)) { |
aee69d78 PV |
4469 | bfq_arm_slice_timer(bfqd); |
4470 | return; | |
4471 | } else if (bfq_may_expire_for_budg_timeout(bfqq)) | |
4472 | bfq_bfqq_expire(bfqd, bfqq, false, | |
4473 | BFQQE_BUDGET_TIMEOUT); | |
4474 | else if (RB_EMPTY_ROOT(&bfqq->sort_list) && | |
4475 | (bfqq->dispatched == 0 || | |
4476 | !bfq_bfqq_may_idle(bfqq))) | |
4477 | bfq_bfqq_expire(bfqd, bfqq, false, | |
4478 | BFQQE_NO_MORE_REQUESTS); | |
4479 | } | |
3f7cb4f4 HT |
4480 | |
4481 | if (!bfqd->rq_in_driver) | |
4482 | bfq_schedule_dispatch(bfqd); | |
aee69d78 PV |
4483 | } |
4484 | ||
4485 | static void bfq_put_rq_priv_body(struct bfq_queue *bfqq) | |
4486 | { | |
4487 | bfqq->allocated--; | |
4488 | ||
4489 | bfq_put_queue(bfqq); | |
4490 | } | |
4491 | ||
7b9e9361 | 4492 | static void bfq_finish_request(struct request *rq) |
aee69d78 | 4493 | { |
5bbf4e5a CH |
4494 | struct bfq_queue *bfqq; |
4495 | struct bfq_data *bfqd; | |
4496 | ||
4497 | if (!rq->elv.icq) | |
4498 | return; | |
4499 | ||
4500 | bfqq = RQ_BFQQ(rq); | |
4501 | bfqd = bfqq->bfqd; | |
aee69d78 | 4502 | |
e21b7a0b AA |
4503 | if (rq->rq_flags & RQF_STARTED) |
4504 | bfqg_stats_update_completion(bfqq_group(bfqq), | |
4505 | rq_start_time_ns(rq), | |
4506 | rq_io_start_time_ns(rq), | |
4507 | rq->cmd_flags); | |
aee69d78 PV |
4508 | |
4509 | if (likely(rq->rq_flags & RQF_STARTED)) { | |
4510 | unsigned long flags; | |
4511 | ||
4512 | spin_lock_irqsave(&bfqd->lock, flags); | |
4513 | ||
4514 | bfq_completed_request(bfqq, bfqd); | |
4515 | bfq_put_rq_priv_body(bfqq); | |
4516 | ||
6fa3e8d3 | 4517 | spin_unlock_irqrestore(&bfqd->lock, flags); |
aee69d78 PV |
4518 | } else { |
4519 | /* | |
4520 | * Request rq may be still/already in the scheduler, | |
4521 | * in which case we need to remove it. And we cannot | |
4522 | * defer such a check and removal, to avoid | |
4523 | * inconsistencies in the time interval from the end | |
4524 | * of this function to the start of the deferred work. | |
4525 | * This situation seems to occur only in process | |
4526 | * context, as a consequence of a merge. In the | |
4527 | * current version of the code, this implies that the | |
4528 | * lock is held. | |
4529 | */ | |
4530 | ||
614822f8 | 4531 | if (!RB_EMPTY_NODE(&rq->rb_node)) { |
7b9e9361 | 4532 | bfq_remove_request(rq->q, rq); |
614822f8 LM |
4533 | bfqg_stats_update_io_remove(bfqq_group(bfqq), |
4534 | rq->cmd_flags); | |
4535 | } | |
aee69d78 PV |
4536 | bfq_put_rq_priv_body(bfqq); |
4537 | } | |
4538 | ||
4539 | rq->elv.priv[0] = NULL; | |
4540 | rq->elv.priv[1] = NULL; | |
4541 | } | |
4542 | ||
36eca894 AA |
4543 | /* |
4544 | * Returns NULL if a new bfqq should be allocated, or the old bfqq if this | |
4545 | * was the last process referring to that bfqq. | |
4546 | */ | |
4547 | static struct bfq_queue * | |
4548 | bfq_split_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq) | |
4549 | { | |
4550 | bfq_log_bfqq(bfqq->bfqd, bfqq, "splitting queue"); | |
4551 | ||
4552 | if (bfqq_process_refs(bfqq) == 1) { | |
4553 | bfqq->pid = current->pid; | |
4554 | bfq_clear_bfqq_coop(bfqq); | |
4555 | bfq_clear_bfqq_split_coop(bfqq); | |
4556 | return bfqq; | |
4557 | } | |
4558 | ||
4559 | bic_set_bfqq(bic, NULL, 1); | |
4560 | ||
4561 | bfq_put_cooperator(bfqq); | |
4562 | ||
4563 | bfq_put_queue(bfqq); | |
4564 | return NULL; | |
4565 | } | |
4566 | ||
4567 | static struct bfq_queue *bfq_get_bfqq_handle_split(struct bfq_data *bfqd, | |
4568 | struct bfq_io_cq *bic, | |
4569 | struct bio *bio, | |
4570 | bool split, bool is_sync, | |
4571 | bool *new_queue) | |
4572 | { | |
4573 | struct bfq_queue *bfqq = bic_to_bfqq(bic, is_sync); | |
4574 | ||
4575 | if (likely(bfqq && bfqq != &bfqd->oom_bfqq)) | |
4576 | return bfqq; | |
4577 | ||
4578 | if (new_queue) | |
4579 | *new_queue = true; | |
4580 | ||
4581 | if (bfqq) | |
4582 | bfq_put_queue(bfqq); | |
4583 | bfqq = bfq_get_queue(bfqd, bio, is_sync, bic); | |
4584 | ||
4585 | bic_set_bfqq(bic, bfqq, is_sync); | |
e1b2324d AA |
4586 | if (split && is_sync) { |
4587 | if ((bic->was_in_burst_list && bfqd->large_burst) || | |
4588 | bic->saved_in_large_burst) | |
4589 | bfq_mark_bfqq_in_large_burst(bfqq); | |
4590 | else { | |
4591 | bfq_clear_bfqq_in_large_burst(bfqq); | |
4592 | if (bic->was_in_burst_list) | |
99fead8d PV |
4593 | /* |
4594 | * If bfqq was in the current | |
4595 | * burst list before being | |
4596 | * merged, then we have to add | |
4597 | * it back. And we do not need | |
4598 | * to increase burst_size, as | |
4599 | * we did not decrement | |
4600 | * burst_size when we removed | |
4601 | * bfqq from the burst list as | |
4602 | * a consequence of a merge | |
4603 | * (see comments in | |
4604 | * bfq_put_queue). In this | |
4605 | * respect, it would be rather | |
4606 | * costly to know whether the | |
4607 | * current burst list is still | |
4608 | * the same burst list from | |
4609 | * which bfqq was removed on | |
4610 | * the merge. To avoid this | |
4611 | * cost, if bfqq was in a | |
4612 | * burst list, then we add | |
4613 | * bfqq to the current burst | |
4614 | * list without any further | |
4615 | * check. This can cause | |
4616 | * inappropriate insertions, | |
4617 | * but rarely enough to not | |
4618 | * harm the detection of large | |
4619 | * bursts significantly. | |
4620 | */ | |
e1b2324d AA |
4621 | hlist_add_head(&bfqq->burst_list_node, |
4622 | &bfqd->burst_list); | |
4623 | } | |
36eca894 | 4624 | bfqq->split_time = jiffies; |
e1b2324d | 4625 | } |
36eca894 AA |
4626 | |
4627 | return bfqq; | |
4628 | } | |
4629 | ||
aee69d78 PV |
4630 | /* |
4631 | * Allocate bfq data structures associated with this request. | |
4632 | */ | |
5bbf4e5a | 4633 | static void bfq_prepare_request(struct request *rq, struct bio *bio) |
aee69d78 | 4634 | { |
5bbf4e5a | 4635 | struct request_queue *q = rq->q; |
aee69d78 | 4636 | struct bfq_data *bfqd = q->elevator->elevator_data; |
9f210738 | 4637 | struct bfq_io_cq *bic; |
aee69d78 PV |
4638 | const int is_sync = rq_is_sync(rq); |
4639 | struct bfq_queue *bfqq; | |
36eca894 | 4640 | bool new_queue = false; |
13c931bd | 4641 | bool bfqq_already_existing = false, split = false; |
aee69d78 | 4642 | |
9f210738 | 4643 | if (!rq->elv.icq) |
5bbf4e5a | 4644 | return; |
9f210738 | 4645 | bic = icq_to_bic(rq->elv.icq); |
aee69d78 | 4646 | |
9f210738 | 4647 | spin_lock_irq(&bfqd->lock); |
aee69d78 | 4648 | |
8c9ff1ad CIK |
4649 | bfq_check_ioprio_change(bic, bio); |
4650 | ||
e21b7a0b AA |
4651 | bfq_bic_update_cgroup(bic, bio); |
4652 | ||
36eca894 AA |
4653 | bfqq = bfq_get_bfqq_handle_split(bfqd, bic, bio, false, is_sync, |
4654 | &new_queue); | |
4655 | ||
4656 | if (likely(!new_queue)) { | |
4657 | /* If the queue was seeky for too long, break it apart. */ | |
4658 | if (bfq_bfqq_coop(bfqq) && bfq_bfqq_split_coop(bfqq)) { | |
4659 | bfq_log_bfqq(bfqd, bfqq, "breaking apart bfqq"); | |
e1b2324d AA |
4660 | |
4661 | /* Update bic before losing reference to bfqq */ | |
4662 | if (bfq_bfqq_in_large_burst(bfqq)) | |
4663 | bic->saved_in_large_burst = true; | |
4664 | ||
36eca894 | 4665 | bfqq = bfq_split_bfqq(bic, bfqq); |
6fa3e8d3 | 4666 | split = true; |
36eca894 AA |
4667 | |
4668 | if (!bfqq) | |
4669 | bfqq = bfq_get_bfqq_handle_split(bfqd, bic, bio, | |
4670 | true, is_sync, | |
4671 | NULL); | |
13c931bd PV |
4672 | else |
4673 | bfqq_already_existing = true; | |
36eca894 | 4674 | } |
aee69d78 PV |
4675 | } |
4676 | ||
4677 | bfqq->allocated++; | |
4678 | bfqq->ref++; | |
4679 | bfq_log_bfqq(bfqd, bfqq, "get_request %p: bfqq %p, %d", | |
4680 | rq, bfqq, bfqq->ref); | |
4681 | ||
4682 | rq->elv.priv[0] = bic; | |
4683 | rq->elv.priv[1] = bfqq; | |
4684 | ||
36eca894 AA |
4685 | /* |
4686 | * If a bfq_queue has only one process reference, it is owned | |
4687 | * by only this bic: we can then set bfqq->bic = bic. in | |
4688 | * addition, if the queue has also just been split, we have to | |
4689 | * resume its state. | |
4690 | */ | |
4691 | if (likely(bfqq != &bfqd->oom_bfqq) && bfqq_process_refs(bfqq) == 1) { | |
4692 | bfqq->bic = bic; | |
6fa3e8d3 | 4693 | if (split) { |
36eca894 AA |
4694 | /* |
4695 | * The queue has just been split from a shared | |
4696 | * queue: restore the idle window and the | |
4697 | * possible weight raising period. | |
4698 | */ | |
13c931bd PV |
4699 | bfq_bfqq_resume_state(bfqq, bfqd, bic, |
4700 | bfqq_already_existing); | |
36eca894 AA |
4701 | } |
4702 | } | |
4703 | ||
e1b2324d AA |
4704 | if (unlikely(bfq_bfqq_just_created(bfqq))) |
4705 | bfq_handle_burst(bfqd, bfqq); | |
4706 | ||
6fa3e8d3 | 4707 | spin_unlock_irq(&bfqd->lock); |
aee69d78 PV |
4708 | } |
4709 | ||
4710 | static void bfq_idle_slice_timer_body(struct bfq_queue *bfqq) | |
4711 | { | |
4712 | struct bfq_data *bfqd = bfqq->bfqd; | |
4713 | enum bfqq_expiration reason; | |
4714 | unsigned long flags; | |
4715 | ||
4716 | spin_lock_irqsave(&bfqd->lock, flags); | |
4717 | bfq_clear_bfqq_wait_request(bfqq); | |
4718 | ||
4719 | if (bfqq != bfqd->in_service_queue) { | |
4720 | spin_unlock_irqrestore(&bfqd->lock, flags); | |
4721 | return; | |
4722 | } | |
4723 | ||
4724 | if (bfq_bfqq_budget_timeout(bfqq)) | |
4725 | /* | |
4726 | * Also here the queue can be safely expired | |
4727 | * for budget timeout without wasting | |
4728 | * guarantees | |
4729 | */ | |
4730 | reason = BFQQE_BUDGET_TIMEOUT; | |
4731 | else if (bfqq->queued[0] == 0 && bfqq->queued[1] == 0) | |
4732 | /* | |
4733 | * The queue may not be empty upon timer expiration, | |
4734 | * because we may not disable the timer when the | |
4735 | * first request of the in-service queue arrives | |
4736 | * during disk idling. | |
4737 | */ | |
4738 | reason = BFQQE_TOO_IDLE; | |
4739 | else | |
4740 | goto schedule_dispatch; | |
4741 | ||
4742 | bfq_bfqq_expire(bfqd, bfqq, true, reason); | |
4743 | ||
4744 | schedule_dispatch: | |
6fa3e8d3 | 4745 | spin_unlock_irqrestore(&bfqd->lock, flags); |
aee69d78 PV |
4746 | bfq_schedule_dispatch(bfqd); |
4747 | } | |
4748 | ||
4749 | /* | |
4750 | * Handler of the expiration of the timer running if the in-service queue | |
4751 | * is idling inside its time slice. | |
4752 | */ | |
4753 | static enum hrtimer_restart bfq_idle_slice_timer(struct hrtimer *timer) | |
4754 | { | |
4755 | struct bfq_data *bfqd = container_of(timer, struct bfq_data, | |
4756 | idle_slice_timer); | |
4757 | struct bfq_queue *bfqq = bfqd->in_service_queue; | |
4758 | ||
4759 | /* | |
4760 | * Theoretical race here: the in-service queue can be NULL or | |
4761 | * different from the queue that was idling if a new request | |
4762 | * arrives for the current queue and there is a full dispatch | |
4763 | * cycle that changes the in-service queue. This can hardly | |
4764 | * happen, but in the worst case we just expire a queue too | |
4765 | * early. | |
4766 | */ | |
4767 | if (bfqq) | |
4768 | bfq_idle_slice_timer_body(bfqq); | |
4769 | ||
4770 | return HRTIMER_NORESTART; | |
4771 | } | |
4772 | ||
4773 | static void __bfq_put_async_bfqq(struct bfq_data *bfqd, | |
4774 | struct bfq_queue **bfqq_ptr) | |
4775 | { | |
4776 | struct bfq_queue *bfqq = *bfqq_ptr; | |
4777 | ||
4778 | bfq_log(bfqd, "put_async_bfqq: %p", bfqq); | |
4779 | if (bfqq) { | |
e21b7a0b AA |
4780 | bfq_bfqq_move(bfqd, bfqq, bfqd->root_group); |
4781 | ||
aee69d78 PV |
4782 | bfq_log_bfqq(bfqd, bfqq, "put_async_bfqq: putting %p, %d", |
4783 | bfqq, bfqq->ref); | |
4784 | bfq_put_queue(bfqq); | |
4785 | *bfqq_ptr = NULL; | |
4786 | } | |
4787 | } | |
4788 | ||
4789 | /* | |
e21b7a0b AA |
4790 | * Release all the bfqg references to its async queues. If we are |
4791 | * deallocating the group these queues may still contain requests, so | |
4792 | * we reparent them to the root cgroup (i.e., the only one that will | |
4793 | * exist for sure until all the requests on a device are gone). | |
aee69d78 | 4794 | */ |
ea25da48 | 4795 | void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg) |
aee69d78 PV |
4796 | { |
4797 | int i, j; | |
4798 | ||
4799 | for (i = 0; i < 2; i++) | |
4800 | for (j = 0; j < IOPRIO_BE_NR; j++) | |
e21b7a0b | 4801 | __bfq_put_async_bfqq(bfqd, &bfqg->async_bfqq[i][j]); |
aee69d78 | 4802 | |
e21b7a0b | 4803 | __bfq_put_async_bfqq(bfqd, &bfqg->async_idle_bfqq); |
aee69d78 PV |
4804 | } |
4805 | ||
4806 | static void bfq_exit_queue(struct elevator_queue *e) | |
4807 | { | |
4808 | struct bfq_data *bfqd = e->elevator_data; | |
4809 | struct bfq_queue *bfqq, *n; | |
4810 | ||
4811 | hrtimer_cancel(&bfqd->idle_slice_timer); | |
4812 | ||
4813 | spin_lock_irq(&bfqd->lock); | |
4814 | list_for_each_entry_safe(bfqq, n, &bfqd->idle_list, bfqq_list) | |
e21b7a0b | 4815 | bfq_deactivate_bfqq(bfqd, bfqq, false, false); |
aee69d78 PV |
4816 | spin_unlock_irq(&bfqd->lock); |
4817 | ||
4818 | hrtimer_cancel(&bfqd->idle_slice_timer); | |
4819 | ||
e21b7a0b AA |
4820 | #ifdef CONFIG_BFQ_GROUP_IOSCHED |
4821 | blkcg_deactivate_policy(bfqd->queue, &blkcg_policy_bfq); | |
4822 | #else | |
4823 | spin_lock_irq(&bfqd->lock); | |
4824 | bfq_put_async_queues(bfqd, bfqd->root_group); | |
4825 | kfree(bfqd->root_group); | |
4826 | spin_unlock_irq(&bfqd->lock); | |
4827 | #endif | |
4828 | ||
aee69d78 PV |
4829 | kfree(bfqd); |
4830 | } | |
4831 | ||
e21b7a0b AA |
4832 | static void bfq_init_root_group(struct bfq_group *root_group, |
4833 | struct bfq_data *bfqd) | |
4834 | { | |
4835 | int i; | |
4836 | ||
4837 | #ifdef CONFIG_BFQ_GROUP_IOSCHED | |
4838 | root_group->entity.parent = NULL; | |
4839 | root_group->my_entity = NULL; | |
4840 | root_group->bfqd = bfqd; | |
4841 | #endif | |
36eca894 | 4842 | root_group->rq_pos_tree = RB_ROOT; |
e21b7a0b AA |
4843 | for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) |
4844 | root_group->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT; | |
4845 | root_group->sched_data.bfq_class_idle_last_service = jiffies; | |
4846 | } | |
4847 | ||
aee69d78 PV |
4848 | static int bfq_init_queue(struct request_queue *q, struct elevator_type *e) |
4849 | { | |
4850 | struct bfq_data *bfqd; | |
4851 | struct elevator_queue *eq; | |
aee69d78 PV |
4852 | |
4853 | eq = elevator_alloc(q, e); | |
4854 | if (!eq) | |
4855 | return -ENOMEM; | |
4856 | ||
4857 | bfqd = kzalloc_node(sizeof(*bfqd), GFP_KERNEL, q->node); | |
4858 | if (!bfqd) { | |
4859 | kobject_put(&eq->kobj); | |
4860 | return -ENOMEM; | |
4861 | } | |
4862 | eq->elevator_data = bfqd; | |
4863 | ||
e21b7a0b AA |
4864 | spin_lock_irq(q->queue_lock); |
4865 | q->elevator = eq; | |
4866 | spin_unlock_irq(q->queue_lock); | |
4867 | ||
aee69d78 PV |
4868 | /* |
4869 | * Our fallback bfqq if bfq_find_alloc_queue() runs into OOM issues. | |
4870 | * Grab a permanent reference to it, so that the normal code flow | |
4871 | * will not attempt to free it. | |
4872 | */ | |
4873 | bfq_init_bfqq(bfqd, &bfqd->oom_bfqq, NULL, 1, 0); | |
4874 | bfqd->oom_bfqq.ref++; | |
4875 | bfqd->oom_bfqq.new_ioprio = BFQ_DEFAULT_QUEUE_IOPRIO; | |
4876 | bfqd->oom_bfqq.new_ioprio_class = IOPRIO_CLASS_BE; | |
4877 | bfqd->oom_bfqq.entity.new_weight = | |
4878 | bfq_ioprio_to_weight(bfqd->oom_bfqq.new_ioprio); | |
e1b2324d AA |
4879 | |
4880 | /* oom_bfqq does not participate to bursts */ | |
4881 | bfq_clear_bfqq_just_created(&bfqd->oom_bfqq); | |
4882 | ||
aee69d78 PV |
4883 | /* |
4884 | * Trigger weight initialization, according to ioprio, at the | |
4885 | * oom_bfqq's first activation. The oom_bfqq's ioprio and ioprio | |
4886 | * class won't be changed any more. | |
4887 | */ | |
4888 | bfqd->oom_bfqq.entity.prio_changed = 1; | |
4889 | ||
4890 | bfqd->queue = q; | |
4891 | ||
e21b7a0b | 4892 | INIT_LIST_HEAD(&bfqd->dispatch); |
aee69d78 PV |
4893 | |
4894 | hrtimer_init(&bfqd->idle_slice_timer, CLOCK_MONOTONIC, | |
4895 | HRTIMER_MODE_REL); | |
4896 | bfqd->idle_slice_timer.function = bfq_idle_slice_timer; | |
4897 | ||
1de0c4cd AA |
4898 | bfqd->queue_weights_tree = RB_ROOT; |
4899 | bfqd->group_weights_tree = RB_ROOT; | |
4900 | ||
aee69d78 PV |
4901 | INIT_LIST_HEAD(&bfqd->active_list); |
4902 | INIT_LIST_HEAD(&bfqd->idle_list); | |
e1b2324d | 4903 | INIT_HLIST_HEAD(&bfqd->burst_list); |
aee69d78 PV |
4904 | |
4905 | bfqd->hw_tag = -1; | |
4906 | ||
4907 | bfqd->bfq_max_budget = bfq_default_max_budget; | |
4908 | ||
4909 | bfqd->bfq_fifo_expire[0] = bfq_fifo_expire[0]; | |
4910 | bfqd->bfq_fifo_expire[1] = bfq_fifo_expire[1]; | |
4911 | bfqd->bfq_back_max = bfq_back_max; | |
4912 | bfqd->bfq_back_penalty = bfq_back_penalty; | |
4913 | bfqd->bfq_slice_idle = bfq_slice_idle; | |
aee69d78 PV |
4914 | bfqd->bfq_timeout = bfq_timeout; |
4915 | ||
4916 | bfqd->bfq_requests_within_timer = 120; | |
4917 | ||
e1b2324d AA |
4918 | bfqd->bfq_large_burst_thresh = 8; |
4919 | bfqd->bfq_burst_interval = msecs_to_jiffies(180); | |
4920 | ||
44e44a1b PV |
4921 | bfqd->low_latency = true; |
4922 | ||
4923 | /* | |
4924 | * Trade-off between responsiveness and fairness. | |
4925 | */ | |
4926 | bfqd->bfq_wr_coeff = 30; | |
77b7dcea | 4927 | bfqd->bfq_wr_rt_max_time = msecs_to_jiffies(300); |
44e44a1b PV |
4928 | bfqd->bfq_wr_max_time = 0; |
4929 | bfqd->bfq_wr_min_idle_time = msecs_to_jiffies(2000); | |
4930 | bfqd->bfq_wr_min_inter_arr_async = msecs_to_jiffies(500); | |
77b7dcea PV |
4931 | bfqd->bfq_wr_max_softrt_rate = 7000; /* |
4932 | * Approximate rate required | |
4933 | * to playback or record a | |
4934 | * high-definition compressed | |
4935 | * video. | |
4936 | */ | |
cfd69712 | 4937 | bfqd->wr_busy_queues = 0; |
44e44a1b PV |
4938 | |
4939 | /* | |
4940 | * Begin by assuming, optimistically, that the device is a | |
4941 | * high-speed one, and that its peak rate is equal to 2/3 of | |
4942 | * the highest reference rate. | |
4943 | */ | |
4944 | bfqd->RT_prod = R_fast[blk_queue_nonrot(bfqd->queue)] * | |
4945 | T_fast[blk_queue_nonrot(bfqd->queue)]; | |
4946 | bfqd->peak_rate = R_fast[blk_queue_nonrot(bfqd->queue)] * 2 / 3; | |
4947 | bfqd->device_speed = BFQ_BFQD_FAST; | |
4948 | ||
aee69d78 | 4949 | spin_lock_init(&bfqd->lock); |
aee69d78 | 4950 | |
e21b7a0b AA |
4951 | /* |
4952 | * The invocation of the next bfq_create_group_hierarchy | |
4953 | * function is the head of a chain of function calls | |
4954 | * (bfq_create_group_hierarchy->blkcg_activate_policy-> | |
4955 | * blk_mq_freeze_queue) that may lead to the invocation of the | |
4956 | * has_work hook function. For this reason, | |
4957 | * bfq_create_group_hierarchy is invoked only after all | |
4958 | * scheduler data has been initialized, apart from the fields | |
4959 | * that can be initialized only after invoking | |
4960 | * bfq_create_group_hierarchy. This, in particular, enables | |
4961 | * has_work to correctly return false. Of course, to avoid | |
4962 | * other inconsistencies, the blk-mq stack must then refrain | |
4963 | * from invoking further scheduler hooks before this init | |
4964 | * function is finished. | |
4965 | */ | |
4966 | bfqd->root_group = bfq_create_group_hierarchy(bfqd, q->node); | |
4967 | if (!bfqd->root_group) | |
4968 | goto out_free; | |
4969 | bfq_init_root_group(bfqd->root_group, bfqd); | |
4970 | bfq_init_entity(&bfqd->oom_bfqq.entity, bfqd->root_group); | |
4971 | ||
b5dc5d4d | 4972 | wbt_disable_default(q); |
aee69d78 | 4973 | return 0; |
e21b7a0b AA |
4974 | |
4975 | out_free: | |
4976 | kfree(bfqd); | |
4977 | kobject_put(&eq->kobj); | |
4978 | return -ENOMEM; | |
aee69d78 PV |
4979 | } |
4980 | ||
4981 | static void bfq_slab_kill(void) | |
4982 | { | |
4983 | kmem_cache_destroy(bfq_pool); | |
4984 | } | |
4985 | ||
4986 | static int __init bfq_slab_setup(void) | |
4987 | { | |
4988 | bfq_pool = KMEM_CACHE(bfq_queue, 0); | |
4989 | if (!bfq_pool) | |
4990 | return -ENOMEM; | |
4991 | return 0; | |
4992 | } | |
4993 | ||
4994 | static ssize_t bfq_var_show(unsigned int var, char *page) | |
4995 | { | |
4996 | return sprintf(page, "%u\n", var); | |
4997 | } | |
4998 | ||
2f79136b | 4999 | static int bfq_var_store(unsigned long *var, const char *page) |
aee69d78 PV |
5000 | { |
5001 | unsigned long new_val; | |
5002 | int ret = kstrtoul(page, 10, &new_val); | |
5003 | ||
2f79136b BVA |
5004 | if (ret) |
5005 | return ret; | |
5006 | *var = new_val; | |
5007 | return 0; | |
aee69d78 PV |
5008 | } |
5009 | ||
5010 | #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ | |
5011 | static ssize_t __FUNC(struct elevator_queue *e, char *page) \ | |
5012 | { \ | |
5013 | struct bfq_data *bfqd = e->elevator_data; \ | |
5014 | u64 __data = __VAR; \ | |
5015 | if (__CONV == 1) \ | |
5016 | __data = jiffies_to_msecs(__data); \ | |
5017 | else if (__CONV == 2) \ | |
5018 | __data = div_u64(__data, NSEC_PER_MSEC); \ | |
5019 | return bfq_var_show(__data, (page)); \ | |
5020 | } | |
5021 | SHOW_FUNCTION(bfq_fifo_expire_sync_show, bfqd->bfq_fifo_expire[1], 2); | |
5022 | SHOW_FUNCTION(bfq_fifo_expire_async_show, bfqd->bfq_fifo_expire[0], 2); | |
5023 | SHOW_FUNCTION(bfq_back_seek_max_show, bfqd->bfq_back_max, 0); | |
5024 | SHOW_FUNCTION(bfq_back_seek_penalty_show, bfqd->bfq_back_penalty, 0); | |
5025 | SHOW_FUNCTION(bfq_slice_idle_show, bfqd->bfq_slice_idle, 2); | |
5026 | SHOW_FUNCTION(bfq_max_budget_show, bfqd->bfq_user_max_budget, 0); | |
5027 | SHOW_FUNCTION(bfq_timeout_sync_show, bfqd->bfq_timeout, 1); | |
5028 | SHOW_FUNCTION(bfq_strict_guarantees_show, bfqd->strict_guarantees, 0); | |
44e44a1b | 5029 | SHOW_FUNCTION(bfq_low_latency_show, bfqd->low_latency, 0); |
aee69d78 PV |
5030 | #undef SHOW_FUNCTION |
5031 | ||
5032 | #define USEC_SHOW_FUNCTION(__FUNC, __VAR) \ | |
5033 | static ssize_t __FUNC(struct elevator_queue *e, char *page) \ | |
5034 | { \ | |
5035 | struct bfq_data *bfqd = e->elevator_data; \ | |
5036 | u64 __data = __VAR; \ | |
5037 | __data = div_u64(__data, NSEC_PER_USEC); \ | |
5038 | return bfq_var_show(__data, (page)); \ | |
5039 | } | |
5040 | USEC_SHOW_FUNCTION(bfq_slice_idle_us_show, bfqd->bfq_slice_idle); | |
5041 | #undef USEC_SHOW_FUNCTION | |
5042 | ||
5043 | #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ | |
5044 | static ssize_t \ | |
5045 | __FUNC(struct elevator_queue *e, const char *page, size_t count) \ | |
5046 | { \ | |
5047 | struct bfq_data *bfqd = e->elevator_data; \ | |
1530486c | 5048 | unsigned long __data, __min = (MIN), __max = (MAX); \ |
2f79136b BVA |
5049 | int ret; \ |
5050 | \ | |
5051 | ret = bfq_var_store(&__data, (page)); \ | |
5052 | if (ret) \ | |
5053 | return ret; \ | |
1530486c BVA |
5054 | if (__data < __min) \ |
5055 | __data = __min; \ | |
5056 | else if (__data > __max) \ | |
5057 | __data = __max; \ | |
aee69d78 PV |
5058 | if (__CONV == 1) \ |
5059 | *(__PTR) = msecs_to_jiffies(__data); \ | |
5060 | else if (__CONV == 2) \ | |
5061 | *(__PTR) = (u64)__data * NSEC_PER_MSEC; \ | |
5062 | else \ | |
5063 | *(__PTR) = __data; \ | |
235f8da1 | 5064 | return count; \ |
aee69d78 PV |
5065 | } |
5066 | STORE_FUNCTION(bfq_fifo_expire_sync_store, &bfqd->bfq_fifo_expire[1], 1, | |
5067 | INT_MAX, 2); | |
5068 | STORE_FUNCTION(bfq_fifo_expire_async_store, &bfqd->bfq_fifo_expire[0], 1, | |
5069 | INT_MAX, 2); | |
5070 | STORE_FUNCTION(bfq_back_seek_max_store, &bfqd->bfq_back_max, 0, INT_MAX, 0); | |
5071 | STORE_FUNCTION(bfq_back_seek_penalty_store, &bfqd->bfq_back_penalty, 1, | |
5072 | INT_MAX, 0); | |
5073 | STORE_FUNCTION(bfq_slice_idle_store, &bfqd->bfq_slice_idle, 0, INT_MAX, 2); | |
5074 | #undef STORE_FUNCTION | |
5075 | ||
5076 | #define USEC_STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \ | |
5077 | static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count)\ | |
5078 | { \ | |
5079 | struct bfq_data *bfqd = e->elevator_data; \ | |
1530486c | 5080 | unsigned long __data, __min = (MIN), __max = (MAX); \ |
2f79136b BVA |
5081 | int ret; \ |
5082 | \ | |
5083 | ret = bfq_var_store(&__data, (page)); \ | |
5084 | if (ret) \ | |
5085 | return ret; \ | |
1530486c BVA |
5086 | if (__data < __min) \ |
5087 | __data = __min; \ | |
5088 | else if (__data > __max) \ | |
5089 | __data = __max; \ | |
aee69d78 | 5090 | *(__PTR) = (u64)__data * NSEC_PER_USEC; \ |
235f8da1 | 5091 | return count; \ |
aee69d78 PV |
5092 | } |
5093 | USEC_STORE_FUNCTION(bfq_slice_idle_us_store, &bfqd->bfq_slice_idle, 0, | |
5094 | UINT_MAX); | |
5095 | #undef USEC_STORE_FUNCTION | |
5096 | ||
aee69d78 PV |
5097 | static ssize_t bfq_max_budget_store(struct elevator_queue *e, |
5098 | const char *page, size_t count) | |
5099 | { | |
5100 | struct bfq_data *bfqd = e->elevator_data; | |
2f79136b BVA |
5101 | unsigned long __data; |
5102 | int ret; | |
235f8da1 | 5103 | |
2f79136b BVA |
5104 | ret = bfq_var_store(&__data, (page)); |
5105 | if (ret) | |
5106 | return ret; | |
aee69d78 PV |
5107 | |
5108 | if (__data == 0) | |
ab0e43e9 | 5109 | bfqd->bfq_max_budget = bfq_calc_max_budget(bfqd); |
aee69d78 PV |
5110 | else { |
5111 | if (__data > INT_MAX) | |
5112 | __data = INT_MAX; | |
5113 | bfqd->bfq_max_budget = __data; | |
5114 | } | |
5115 | ||
5116 | bfqd->bfq_user_max_budget = __data; | |
5117 | ||
235f8da1 | 5118 | return count; |
aee69d78 PV |
5119 | } |
5120 | ||
5121 | /* | |
5122 | * Leaving this name to preserve name compatibility with cfq | |
5123 | * parameters, but this timeout is used for both sync and async. | |
5124 | */ | |
5125 | static ssize_t bfq_timeout_sync_store(struct elevator_queue *e, | |
5126 | const char *page, size_t count) | |
5127 | { | |
5128 | struct bfq_data *bfqd = e->elevator_data; | |
2f79136b BVA |
5129 | unsigned long __data; |
5130 | int ret; | |
235f8da1 | 5131 | |
2f79136b BVA |
5132 | ret = bfq_var_store(&__data, (page)); |
5133 | if (ret) | |
5134 | return ret; | |
aee69d78 PV |
5135 | |
5136 | if (__data < 1) | |
5137 | __data = 1; | |
5138 | else if (__data > INT_MAX) | |
5139 | __data = INT_MAX; | |
5140 | ||
5141 | bfqd->bfq_timeout = msecs_to_jiffies(__data); | |
5142 | if (bfqd->bfq_user_max_budget == 0) | |
ab0e43e9 | 5143 | bfqd->bfq_max_budget = bfq_calc_max_budget(bfqd); |
aee69d78 | 5144 | |
235f8da1 | 5145 | return count; |
aee69d78 PV |
5146 | } |
5147 | ||
5148 | static ssize_t bfq_strict_guarantees_store(struct elevator_queue *e, | |
5149 | const char *page, size_t count) | |
5150 | { | |
5151 | struct bfq_data *bfqd = e->elevator_data; | |
2f79136b BVA |
5152 | unsigned long __data; |
5153 | int ret; | |
235f8da1 | 5154 | |
2f79136b BVA |
5155 | ret = bfq_var_store(&__data, (page)); |
5156 | if (ret) | |
5157 | return ret; | |
aee69d78 PV |
5158 | |
5159 | if (__data > 1) | |
5160 | __data = 1; | |
5161 | if (!bfqd->strict_guarantees && __data == 1 | |
5162 | && bfqd->bfq_slice_idle < 8 * NSEC_PER_MSEC) | |
5163 | bfqd->bfq_slice_idle = 8 * NSEC_PER_MSEC; | |
5164 | ||
5165 | bfqd->strict_guarantees = __data; | |
5166 | ||
235f8da1 | 5167 | return count; |
aee69d78 PV |
5168 | } |
5169 | ||
44e44a1b PV |
5170 | static ssize_t bfq_low_latency_store(struct elevator_queue *e, |
5171 | const char *page, size_t count) | |
5172 | { | |
5173 | struct bfq_data *bfqd = e->elevator_data; | |
2f79136b BVA |
5174 | unsigned long __data; |
5175 | int ret; | |
235f8da1 | 5176 | |
2f79136b BVA |
5177 | ret = bfq_var_store(&__data, (page)); |
5178 | if (ret) | |
5179 | return ret; | |
44e44a1b PV |
5180 | |
5181 | if (__data > 1) | |
5182 | __data = 1; | |
5183 | if (__data == 0 && bfqd->low_latency != 0) | |
5184 | bfq_end_wr(bfqd); | |
5185 | bfqd->low_latency = __data; | |
5186 | ||
235f8da1 | 5187 | return count; |
44e44a1b PV |
5188 | } |
5189 | ||
aee69d78 PV |
5190 | #define BFQ_ATTR(name) \ |
5191 | __ATTR(name, 0644, bfq_##name##_show, bfq_##name##_store) | |
5192 | ||
5193 | static struct elv_fs_entry bfq_attrs[] = { | |
5194 | BFQ_ATTR(fifo_expire_sync), | |
5195 | BFQ_ATTR(fifo_expire_async), | |
5196 | BFQ_ATTR(back_seek_max), | |
5197 | BFQ_ATTR(back_seek_penalty), | |
5198 | BFQ_ATTR(slice_idle), | |
5199 | BFQ_ATTR(slice_idle_us), | |
5200 | BFQ_ATTR(max_budget), | |
5201 | BFQ_ATTR(timeout_sync), | |
5202 | BFQ_ATTR(strict_guarantees), | |
44e44a1b | 5203 | BFQ_ATTR(low_latency), |
aee69d78 PV |
5204 | __ATTR_NULL |
5205 | }; | |
5206 | ||
5207 | static struct elevator_type iosched_bfq_mq = { | |
5208 | .ops.mq = { | |
5bbf4e5a | 5209 | .prepare_request = bfq_prepare_request, |
7b9e9361 | 5210 | .finish_request = bfq_finish_request, |
aee69d78 PV |
5211 | .exit_icq = bfq_exit_icq, |
5212 | .insert_requests = bfq_insert_requests, | |
5213 | .dispatch_request = bfq_dispatch_request, | |
5214 | .next_request = elv_rb_latter_request, | |
5215 | .former_request = elv_rb_former_request, | |
5216 | .allow_merge = bfq_allow_bio_merge, | |
5217 | .bio_merge = bfq_bio_merge, | |
5218 | .request_merge = bfq_request_merge, | |
5219 | .requests_merged = bfq_requests_merged, | |
5220 | .request_merged = bfq_request_merged, | |
5221 | .has_work = bfq_has_work, | |
5222 | .init_sched = bfq_init_queue, | |
5223 | .exit_sched = bfq_exit_queue, | |
5224 | }, | |
5225 | ||
5226 | .uses_mq = true, | |
5227 | .icq_size = sizeof(struct bfq_io_cq), | |
5228 | .icq_align = __alignof__(struct bfq_io_cq), | |
5229 | .elevator_attrs = bfq_attrs, | |
5230 | .elevator_name = "bfq", | |
5231 | .elevator_owner = THIS_MODULE, | |
5232 | }; | |
26b4cf24 | 5233 | MODULE_ALIAS("bfq-iosched"); |
aee69d78 PV |
5234 | |
5235 | static int __init bfq_init(void) | |
5236 | { | |
5237 | int ret; | |
5238 | ||
e21b7a0b AA |
5239 | #ifdef CONFIG_BFQ_GROUP_IOSCHED |
5240 | ret = blkcg_policy_register(&blkcg_policy_bfq); | |
5241 | if (ret) | |
5242 | return ret; | |
5243 | #endif | |
5244 | ||
aee69d78 PV |
5245 | ret = -ENOMEM; |
5246 | if (bfq_slab_setup()) | |
5247 | goto err_pol_unreg; | |
5248 | ||
44e44a1b PV |
5249 | /* |
5250 | * Times to load large popular applications for the typical | |
5251 | * systems installed on the reference devices (see the | |
5252 | * comments before the definitions of the next two | |
5253 | * arrays). Actually, we use slightly slower values, as the | |
5254 | * estimated peak rate tends to be smaller than the actual | |
5255 | * peak rate. The reason for this last fact is that estimates | |
5256 | * are computed over much shorter time intervals than the long | |
5257 | * intervals typically used for benchmarking. Why? First, to | |
5258 | * adapt more quickly to variations. Second, because an I/O | |
5259 | * scheduler cannot rely on a peak-rate-evaluation workload to | |
5260 | * be run for a long time. | |
5261 | */ | |
5262 | T_slow[0] = msecs_to_jiffies(3500); /* actually 4 sec */ | |
5263 | T_slow[1] = msecs_to_jiffies(6000); /* actually 6.5 sec */ | |
5264 | T_fast[0] = msecs_to_jiffies(7000); /* actually 8 sec */ | |
5265 | T_fast[1] = msecs_to_jiffies(2500); /* actually 3 sec */ | |
5266 | ||
5267 | /* | |
5268 | * Thresholds that determine the switch between speed classes | |
5269 | * (see the comments before the definition of the array | |
5270 | * device_speed_thresh). These thresholds are biased towards | |
5271 | * transitions to the fast class. This is safer than the | |
5272 | * opposite bias. In fact, a wrong transition to the slow | |
5273 | * class results in short weight-raising periods, because the | |
5274 | * speed of the device then tends to be higher that the | |
5275 | * reference peak rate. On the opposite end, a wrong | |
5276 | * transition to the fast class tends to increase | |
5277 | * weight-raising periods, because of the opposite reason. | |
5278 | */ | |
5279 | device_speed_thresh[0] = (4 * R_slow[0]) / 3; | |
5280 | device_speed_thresh[1] = (4 * R_slow[1]) / 3; | |
5281 | ||
aee69d78 PV |
5282 | ret = elv_register(&iosched_bfq_mq); |
5283 | if (ret) | |
37dcd657 | 5284 | goto slab_kill; |
aee69d78 PV |
5285 | |
5286 | return 0; | |
5287 | ||
37dcd657 | 5288 | slab_kill: |
5289 | bfq_slab_kill(); | |
aee69d78 | 5290 | err_pol_unreg: |
e21b7a0b AA |
5291 | #ifdef CONFIG_BFQ_GROUP_IOSCHED |
5292 | blkcg_policy_unregister(&blkcg_policy_bfq); | |
5293 | #endif | |
aee69d78 PV |
5294 | return ret; |
5295 | } | |
5296 | ||
5297 | static void __exit bfq_exit(void) | |
5298 | { | |
5299 | elv_unregister(&iosched_bfq_mq); | |
e21b7a0b AA |
5300 | #ifdef CONFIG_BFQ_GROUP_IOSCHED |
5301 | blkcg_policy_unregister(&blkcg_policy_bfq); | |
5302 | #endif | |
aee69d78 PV |
5303 | bfq_slab_kill(); |
5304 | } | |
5305 | ||
5306 | module_init(bfq_init); | |
5307 | module_exit(bfq_exit); | |
5308 | ||
5309 | MODULE_AUTHOR("Paolo Valente"); | |
5310 | MODULE_LICENSE("GPL"); | |
5311 | MODULE_DESCRIPTION("MQ Budget Fair Queueing I/O Scheduler"); |