2 * CFQ, or complete fairness queueing, disk scheduler.
4 * Based on ideas from a previously unfinished io
5 * scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
7 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
9 #include <linux/module.h>
10 #include <linux/blkdev.h>
11 #include <linux/elevator.h>
12 #include <linux/jiffies.h>
13 #include <linux/rbtree.h>
14 #include <linux/ioprio.h>
15 #include <linux/blktrace_api.h>
16 #include "blk-cgroup.h"
21 /* max queue in one round of service */
22 static const int cfq_quantum = 4;
23 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
24 /* maximum backwards seek, in KiB */
25 static const int cfq_back_max = 16 * 1024;
26 /* penalty of a backwards seek */
27 static const int cfq_back_penalty = 2;
28 static const int cfq_slice_sync = HZ / 10;
29 static int cfq_slice_async = HZ / 25;
30 static const int cfq_slice_async_rq = 2;
31 static int cfq_slice_idle = HZ / 125;
32 static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
33 static const int cfq_hist_divisor = 4;
36 * offset from end of service tree
38 #define CFQ_IDLE_DELAY (HZ / 5)
41 * below this threshold, we consider thinktime immediate
43 #define CFQ_MIN_TT (2)
46 * Allow merged cfqqs to perform this amount of seeky I/O before
47 * deciding to break the queues up again.
49 #define CFQQ_COOP_TOUT (HZ)
51 #define CFQ_SLICE_SCALE (5)
52 #define CFQ_HW_QUEUE_MIN (5)
53 #define CFQ_SERVICE_SHIFT 12
56 ((struct cfq_io_context *) (rq)->elevator_private)
57 #define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2)
59 static struct kmem_cache *cfq_pool;
60 static struct kmem_cache *cfq_ioc_pool;
62 static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
63 static struct completion *ioc_gone;
64 static DEFINE_SPINLOCK(ioc_gone_lock);
66 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
67 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
68 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
70 #define sample_valid(samples) ((samples) > 80)
71 #define rb_entry_cfqg(node) rb_entry((node), struct cfq_group, rb_node)
74 * Most of our rbtree usage is for sorting with min extraction, so
75 * if we cache the leftmost node we don't have to walk down the tree
76 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
77 * move this into the elevator for the rq sorting as well.
84 struct rb_node *active;
85 unsigned total_weight;
87 #define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, 0, 0, }
90 * Per process-grouping structure
95 /* various state flags, see below */
98 struct cfq_data *cfqd;
99 /* service_tree member */
100 struct rb_node rb_node;
101 /* service_tree key */
102 unsigned long rb_key;
103 /* prio tree member */
104 struct rb_node p_node;
105 /* prio tree root we belong to, if any */
106 struct rb_root *p_root;
107 /* sorted list of pending requests */
108 struct rb_root sort_list;
109 /* if fifo isn't expired, next request to serve */
110 struct request *next_rq;
111 /* requests queued in sort_list */
113 /* currently allocated requests */
115 /* fifo list of requests in sort_list */
116 struct list_head fifo;
118 /* time when queue got scheduled in to dispatch first request. */
119 unsigned long dispatch_start;
120 /* time when first request from queue completed and slice started. */
121 unsigned long slice_start;
122 unsigned long slice_end;
124 unsigned int slice_dispatch;
126 /* pending metadata requests */
128 /* number of requests that are on the dispatch list or inside driver */
131 /* io prio of this group */
132 unsigned short ioprio, org_ioprio;
133 unsigned short ioprio_class, org_ioprio_class;
135 unsigned int seek_samples;
138 sector_t last_request_pos;
139 unsigned long seeky_start;
143 struct cfq_rb_root *service_tree;
144 struct cfq_queue *new_cfqq;
145 struct cfq_group *cfqg;
146 /* Sectors dispatched in current dispatch round */
147 unsigned long nr_sectors;
151 * First index in the service_trees.
152 * IDLE is handled separately, so it has negative index
161 * Second index in the service_trees.
165 SYNC_NOIDLE_WORKLOAD = 1,
169 /* This is per cgroup per device grouping structure */
171 /* group service_tree member */
172 struct rb_node rb_node;
174 /* group service_tree key */
179 /* number of cfqq currently on this group */
182 /* Per group busy queus average. Useful for workload slice calc. */
183 unsigned int busy_queues_avg[2];
185 * rr lists of queues with requests, onle rr for each priority class.
186 * Counts are embedded in the cfq_rb_root
188 struct cfq_rb_root service_trees[2][3];
189 struct cfq_rb_root service_tree_idle;
191 unsigned long saved_workload_slice;
192 enum wl_type_t saved_workload;
193 enum wl_prio_t saved_serving_prio;
194 struct blkio_group blkg;
195 #ifdef CONFIG_CFQ_GROUP_IOSCHED
196 struct hlist_node cfqd_node;
202 * Per block device queue structure
205 struct request_queue *queue;
206 /* Root service tree for cfq_groups */
207 struct cfq_rb_root grp_service_tree;
208 struct cfq_group root_group;
209 /* Number of active cfq groups on group service tree */
213 * The priority currently being served
215 enum wl_prio_t serving_prio;
216 enum wl_type_t serving_type;
217 unsigned long workload_expires;
218 struct cfq_group *serving_group;
219 bool noidle_tree_requires_idle;
222 * Each priority tree is sorted by next_request position. These
223 * trees are used when determining if two or more queues are
224 * interleaving requests (see cfq_close_cooperator).
226 struct rb_root prio_trees[CFQ_PRIO_LISTS];
228 unsigned int busy_queues;
234 * queue-depth detection
240 * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
241 * 1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
244 int hw_tag_est_depth;
245 unsigned int hw_tag_samples;
248 * idle window management
250 struct timer_list idle_slice_timer;
251 struct work_struct unplug_work;
253 struct cfq_queue *active_queue;
254 struct cfq_io_context *active_cic;
257 * async queue for each priority case
259 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
260 struct cfq_queue *async_idle_cfqq;
262 sector_t last_position;
265 * tunables, see top of file
267 unsigned int cfq_quantum;
268 unsigned int cfq_fifo_expire[2];
269 unsigned int cfq_back_penalty;
270 unsigned int cfq_back_max;
271 unsigned int cfq_slice[2];
272 unsigned int cfq_slice_async_rq;
273 unsigned int cfq_slice_idle;
274 unsigned int cfq_latency;
276 struct list_head cic_list;
279 * Fallback dummy cfqq for extreme OOM conditions
281 struct cfq_queue oom_cfqq;
283 unsigned long last_end_sync_rq;
285 /* List of cfq groups being managed on this device*/
286 struct hlist_head cfqg_list;
289 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
291 static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
294 struct cfq_data *cfqd)
299 if (prio == IDLE_WORKLOAD)
300 return &cfqg->service_tree_idle;
302 return &cfqg->service_trees[prio][type];
305 enum cfqq_state_flags {
306 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
307 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
308 CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */
309 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
310 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
311 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */
312 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
313 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
314 CFQ_CFQQ_FLAG_sync, /* synchronous queue */
315 CFQ_CFQQ_FLAG_coop, /* cfqq is shared */
316 CFQ_CFQQ_FLAG_deep, /* sync cfqq experienced large depth */
319 #define CFQ_CFQQ_FNS(name) \
320 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
322 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
324 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
326 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
328 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
330 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
334 CFQ_CFQQ_FNS(wait_request);
335 CFQ_CFQQ_FNS(must_dispatch);
336 CFQ_CFQQ_FNS(must_alloc_slice);
337 CFQ_CFQQ_FNS(fifo_expire);
338 CFQ_CFQQ_FNS(idle_window);
339 CFQ_CFQQ_FNS(prio_changed);
340 CFQ_CFQQ_FNS(slice_new);
346 #ifdef CONFIG_DEBUG_CFQ_IOSCHED
347 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
348 blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
349 cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
350 blkg_path(&(cfqq)->cfqg->blkg), ##args);
352 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...) \
353 blk_add_trace_msg((cfqd)->queue, "%s " fmt, \
354 blkg_path(&(cfqg)->blkg), ##args); \
357 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
358 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
359 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...) do {} while (0);
361 #define cfq_log(cfqd, fmt, args...) \
362 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
364 /* Traverses through cfq group service trees */
365 #define for_each_cfqg_st(cfqg, i, j, st) \
366 for (i = 0; i <= IDLE_WORKLOAD; i++) \
367 for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
368 : &cfqg->service_tree_idle; \
369 (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
370 (i == IDLE_WORKLOAD && j == 0); \
371 j++, st = i < IDLE_WORKLOAD ? \
372 &cfqg->service_trees[i][j]: NULL) \
375 static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
377 if (cfq_class_idle(cfqq))
378 return IDLE_WORKLOAD;
379 if (cfq_class_rt(cfqq))
385 static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
387 if (!cfq_cfqq_sync(cfqq))
388 return ASYNC_WORKLOAD;
389 if (!cfq_cfqq_idle_window(cfqq))
390 return SYNC_NOIDLE_WORKLOAD;
391 return SYNC_WORKLOAD;
394 static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl,
395 struct cfq_data *cfqd,
396 struct cfq_group *cfqg)
398 if (wl == IDLE_WORKLOAD)
399 return cfqg->service_tree_idle.count;
401 return cfqg->service_trees[wl][ASYNC_WORKLOAD].count
402 + cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
403 + cfqg->service_trees[wl][SYNC_WORKLOAD].count;
406 static void cfq_dispatch_insert(struct request_queue *, struct request *);
407 static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
408 struct io_context *, gfp_t);
409 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
410 struct io_context *);
412 static inline int rq_in_driver(struct cfq_data *cfqd)
414 return cfqd->rq_in_driver[0] + cfqd->rq_in_driver[1];
417 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
420 return cic->cfqq[is_sync];
423 static inline void cic_set_cfqq(struct cfq_io_context *cic,
424 struct cfq_queue *cfqq, bool is_sync)
426 cic->cfqq[is_sync] = cfqq;
430 * We regard a request as SYNC, if it's either a read or has the SYNC bit
431 * set (in which case it could also be direct WRITE).
433 static inline bool cfq_bio_sync(struct bio *bio)
435 return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO);
439 * scheduler run of queue, if there are requests pending and no one in the
440 * driver that will restart queueing
442 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
444 if (cfqd->busy_queues) {
445 cfq_log(cfqd, "schedule dispatch");
446 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
450 static int cfq_queue_empty(struct request_queue *q)
452 struct cfq_data *cfqd = q->elevator->elevator_data;
454 return !cfqd->rq_queued;
458 * Scale schedule slice based on io priority. Use the sync time slice only
459 * if a queue is marked sync and has sync io queued. A sync queue with async
460 * io only, should not get full sync slice length.
462 static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
465 const int base_slice = cfqd->cfq_slice[sync];
467 WARN_ON(prio >= IOPRIO_BE_NR);
469 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
473 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
475 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
478 static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
480 u64 d = delta << CFQ_SERVICE_SHIFT;
482 d = d * BLKIO_WEIGHT_DEFAULT;
483 do_div(d, cfqg->weight);
487 static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
489 s64 delta = (s64)(vdisktime - min_vdisktime);
491 min_vdisktime = vdisktime;
493 return min_vdisktime;
496 static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
498 s64 delta = (s64)(vdisktime - min_vdisktime);
500 min_vdisktime = vdisktime;
502 return min_vdisktime;
505 static void update_min_vdisktime(struct cfq_rb_root *st)
507 u64 vdisktime = st->min_vdisktime;
508 struct cfq_group *cfqg;
511 cfqg = rb_entry_cfqg(st->active);
512 vdisktime = cfqg->vdisktime;
516 cfqg = rb_entry_cfqg(st->left);
517 vdisktime = min_vdisktime(vdisktime, cfqg->vdisktime);
520 st->min_vdisktime = max_vdisktime(st->min_vdisktime, vdisktime);
524 * get averaged number of queues of RT/BE priority.
525 * average is updated, with a formula that gives more weight to higher numbers,
526 * to quickly follows sudden increases and decrease slowly
529 static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
530 struct cfq_group *cfqg, bool rt)
532 unsigned min_q, max_q;
533 unsigned mult = cfq_hist_divisor - 1;
534 unsigned round = cfq_hist_divisor / 2;
535 unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
537 min_q = min(cfqg->busy_queues_avg[rt], busy);
538 max_q = max(cfqg->busy_queues_avg[rt], busy);
539 cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
541 return cfqg->busy_queues_avg[rt];
544 static inline unsigned
545 cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
547 struct cfq_rb_root *st = &cfqd->grp_service_tree;
549 return cfq_target_latency * cfqg->weight / st->total_weight;
553 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
555 unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
556 if (cfqd->cfq_latency) {
558 * interested queues (we consider only the ones with the same
559 * priority class in the cfq group)
561 unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
563 unsigned sync_slice = cfqd->cfq_slice[1];
564 unsigned expect_latency = sync_slice * iq;
565 unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
567 if (expect_latency > group_slice) {
568 unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
569 /* scale low_slice according to IO priority
570 * and sync vs async */
572 min(slice, base_low_slice * slice / sync_slice);
573 /* the adapted slice value is scaled to fit all iqs
574 * into the target latency */
575 slice = max(slice * group_slice / expect_latency,
579 cfqq->slice_start = jiffies;
580 cfqq->slice_end = jiffies + slice;
581 cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
585 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
586 * isn't valid until the first request from the dispatch is activated
587 * and the slice time set.
589 static inline bool cfq_slice_used(struct cfq_queue *cfqq)
591 if (cfq_cfqq_slice_new(cfqq))
593 if (time_before(jiffies, cfqq->slice_end))
600 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
601 * We choose the request that is closest to the head right now. Distance
602 * behind the head is penalized and only allowed to a certain extent.
604 static struct request *
605 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
607 sector_t s1, s2, d1 = 0, d2 = 0;
608 unsigned long back_max;
609 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
610 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
611 unsigned wrap = 0; /* bit mask: requests behind the disk head? */
613 if (rq1 == NULL || rq1 == rq2)
618 if (rq_is_sync(rq1) && !rq_is_sync(rq2))
620 else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
622 if (rq_is_meta(rq1) && !rq_is_meta(rq2))
624 else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
627 s1 = blk_rq_pos(rq1);
628 s2 = blk_rq_pos(rq2);
631 * by definition, 1KiB is 2 sectors
633 back_max = cfqd->cfq_back_max * 2;
636 * Strict one way elevator _except_ in the case where we allow
637 * short backward seeks which are biased as twice the cost of a
638 * similar forward seek.
642 else if (s1 + back_max >= last)
643 d1 = (last - s1) * cfqd->cfq_back_penalty;
645 wrap |= CFQ_RQ1_WRAP;
649 else if (s2 + back_max >= last)
650 d2 = (last - s2) * cfqd->cfq_back_penalty;
652 wrap |= CFQ_RQ2_WRAP;
654 /* Found required data */
657 * By doing switch() on the bit mask "wrap" we avoid having to
658 * check two variables for all permutations: --> faster!
661 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
677 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
680 * Since both rqs are wrapped,
681 * start with the one that's further behind head
682 * (--> only *one* back seek required),
683 * since back seek takes more time than forward.
693 * The below is leftmost cache rbtree addon
695 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
697 /* Service tree is empty */
702 root->left = rb_first(&root->rb);
705 return rb_entry(root->left, struct cfq_queue, rb_node);
710 static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
713 root->left = rb_first(&root->rb);
716 return rb_entry_cfqg(root->left);
721 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
727 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
731 rb_erase_init(n, &root->rb);
736 * would be nice to take fifo expire time into account as well
738 static struct request *
739 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
740 struct request *last)
742 struct rb_node *rbnext = rb_next(&last->rb_node);
743 struct rb_node *rbprev = rb_prev(&last->rb_node);
744 struct request *next = NULL, *prev = NULL;
746 BUG_ON(RB_EMPTY_NODE(&last->rb_node));
749 prev = rb_entry_rq(rbprev);
752 next = rb_entry_rq(rbnext);
754 rbnext = rb_first(&cfqq->sort_list);
755 if (rbnext && rbnext != &last->rb_node)
756 next = rb_entry_rq(rbnext);
759 return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
762 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
763 struct cfq_queue *cfqq)
766 * just an approximation, should be ok.
768 return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
769 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
773 cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
775 return cfqg->vdisktime - st->min_vdisktime;
779 __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
781 struct rb_node **node = &st->rb.rb_node;
782 struct rb_node *parent = NULL;
783 struct cfq_group *__cfqg;
784 s64 key = cfqg_key(st, cfqg);
787 while (*node != NULL) {
789 __cfqg = rb_entry_cfqg(parent);
791 if (key < cfqg_key(st, __cfqg))
792 node = &parent->rb_left;
794 node = &parent->rb_right;
800 st->left = &cfqg->rb_node;
802 rb_link_node(&cfqg->rb_node, parent, node);
803 rb_insert_color(&cfqg->rb_node, &st->rb);
807 cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
809 struct cfq_rb_root *st = &cfqd->grp_service_tree;
810 struct cfq_group *__cfqg;
818 * Currently put the group at the end. Later implement something
819 * so that groups get lesser vtime based on their weights, so that
820 * if group does not loose all if it was not continously backlogged.
822 n = rb_last(&st->rb);
824 __cfqg = rb_entry_cfqg(n);
825 cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
827 cfqg->vdisktime = st->min_vdisktime;
829 __cfq_group_service_tree_add(st, cfqg);
832 st->total_weight += cfqg->weight;
836 cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
838 struct cfq_rb_root *st = &cfqd->grp_service_tree;
840 if (st->active == &cfqg->rb_node)
843 BUG_ON(cfqg->nr_cfqq < 1);
846 /* If there are other cfq queues under this group, don't delete it */
850 cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
853 st->total_weight -= cfqg->weight;
854 if (!RB_EMPTY_NODE(&cfqg->rb_node))
855 cfq_rb_erase(&cfqg->rb_node, st);
856 cfqg->saved_workload_slice = 0;
857 blkiocg_update_blkio_group_dequeue_stats(&cfqg->blkg, 1);
860 static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
862 unsigned int slice_used, allocated_slice;
865 * Queue got expired before even a single request completed or
866 * got expired immediately after first request completion.
868 if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
870 * Also charge the seek time incurred to the group, otherwise
871 * if there are mutiple queues in the group, each can dispatch
872 * a single request on seeky media and cause lots of seek time
873 * and group will never know it.
875 slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
878 slice_used = jiffies - cfqq->slice_start;
879 allocated_slice = cfqq->slice_end - cfqq->slice_start;
880 if (slice_used > allocated_slice)
881 slice_used = allocated_slice;
884 cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u sect=%lu", slice_used,
889 static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
890 struct cfq_queue *cfqq)
892 struct cfq_rb_root *st = &cfqd->grp_service_tree;
893 unsigned int used_sl;
895 used_sl = cfq_cfqq_slice_usage(cfqq);
897 /* Can't update vdisktime while group is on service tree */
898 cfq_rb_erase(&cfqg->rb_node, st);
899 cfqg->vdisktime += cfq_scale_slice(used_sl, cfqg);
900 __cfq_group_service_tree_add(st, cfqg);
902 /* This group is being expired. Save the context */
903 if (time_after(cfqd->workload_expires, jiffies)) {
904 cfqg->saved_workload_slice = cfqd->workload_expires
906 cfqg->saved_workload = cfqd->serving_type;
907 cfqg->saved_serving_prio = cfqd->serving_prio;
909 cfqg->saved_workload_slice = 0;
911 cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
913 blkiocg_update_blkio_group_stats(&cfqg->blkg, used_sl,
917 #ifdef CONFIG_CFQ_GROUP_IOSCHED
918 static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
921 return container_of(blkg, struct cfq_group, blkg);
925 static struct cfq_group *
926 cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
928 struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
929 struct cfq_group *cfqg = NULL;
932 struct cfq_rb_root *st;
933 struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
934 unsigned int major, minor;
936 /* Do we need to take this reference */
937 if (!css_tryget(&blkcg->css))
940 cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
944 cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node);
948 cfqg->weight = blkcg->weight;
949 for_each_cfqg_st(cfqg, i, j, st)
951 RB_CLEAR_NODE(&cfqg->rb_node);
954 * Take the initial reference that will be released on destroy
955 * This can be thought of a joint reference by cgroup and
956 * elevator which will be dropped by either elevator exit
957 * or cgroup deletion path depending on who is exiting first.
959 atomic_set(&cfqg->ref, 1);
961 /* Add group onto cgroup list */
962 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
963 blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
964 MKDEV(major, minor));
966 /* Add group on cfqd list */
967 hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
970 css_put(&blkcg->css);
975 * Search for the cfq group current task belongs to. If create = 1, then also
976 * create the cfq group if it does not exist. request_queue lock must be held.
978 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
980 struct cgroup *cgroup;
981 struct cfq_group *cfqg = NULL;
984 cgroup = task_cgroup(current, blkio_subsys_id);
985 cfqg = cfq_find_alloc_cfqg(cfqd, cgroup, create);
987 cfqg = &cfqd->root_group;
992 static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
994 /* Currently, all async queues are mapped to root group */
995 if (!cfq_cfqq_sync(cfqq))
996 cfqg = &cfqq->cfqd->root_group;
999 /* cfqq reference on cfqg */
1000 atomic_inc(&cfqq->cfqg->ref);
1003 static void cfq_put_cfqg(struct cfq_group *cfqg)
1005 struct cfq_rb_root *st;
1008 BUG_ON(atomic_read(&cfqg->ref) <= 0);
1009 if (!atomic_dec_and_test(&cfqg->ref))
1011 for_each_cfqg_st(cfqg, i, j, st)
1012 BUG_ON(!RB_EMPTY_ROOT(&st->rb) || st->active != NULL);
1016 static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
1018 /* Something wrong if we are trying to remove same group twice */
1019 BUG_ON(hlist_unhashed(&cfqg->cfqd_node));
1021 hlist_del_init(&cfqg->cfqd_node);
1024 * Put the reference taken at the time of creation so that when all
1025 * queues are gone, group can be destroyed.
1030 static void cfq_release_cfq_groups(struct cfq_data *cfqd)
1032 struct hlist_node *pos, *n;
1033 struct cfq_group *cfqg;
1035 hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) {
1037 * If cgroup removal path got to blk_group first and removed
1038 * it from cgroup list, then it will take care of destroying
1041 if (!blkiocg_del_blkio_group(&cfqg->blkg))
1042 cfq_destroy_cfqg(cfqd, cfqg);
1047 * Blk cgroup controller notification saying that blkio_group object is being
1048 * delinked as associated cgroup object is going away. That also means that
1049 * no new IO will come in this group. So get rid of this group as soon as
1050 * any pending IO in the group is finished.
1052 * This function is called under rcu_read_lock(). key is the rcu protected
1053 * pointer. That means "key" is a valid cfq_data pointer as long as we are rcu
1056 * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
1057 * it should not be NULL as even if elevator was exiting, cgroup deltion
1058 * path got to it first.
1060 void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
1062 unsigned long flags;
1063 struct cfq_data *cfqd = key;
1065 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1066 cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg));
1067 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1070 #else /* GROUP_IOSCHED */
1071 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
1073 return &cfqd->root_group;
1076 cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
1080 static void cfq_release_cfq_groups(struct cfq_data *cfqd) {}
1081 static inline void cfq_put_cfqg(struct cfq_group *cfqg) {}
1083 #endif /* GROUP_IOSCHED */
1086 * The cfqd->service_trees holds all pending cfq_queue's that have
1087 * requests waiting to be processed. It is sorted in the order that
1088 * we will service the queues.
1090 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1093 struct rb_node **p, *parent;
1094 struct cfq_queue *__cfqq;
1095 unsigned long rb_key;
1096 struct cfq_rb_root *service_tree;
1100 service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
1101 cfqq_type(cfqq), cfqd);
1102 if (cfq_class_idle(cfqq)) {
1103 rb_key = CFQ_IDLE_DELAY;
1104 parent = rb_last(&service_tree->rb);
1105 if (parent && parent != &cfqq->rb_node) {
1106 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1107 rb_key += __cfqq->rb_key;
1110 } else if (!add_front) {
1112 * Get our rb key offset. Subtract any residual slice
1113 * value carried from last service. A negative resid
1114 * count indicates slice overrun, and this should position
1115 * the next service time further away in the tree.
1117 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
1118 rb_key -= cfqq->slice_resid;
1119 cfqq->slice_resid = 0;
1122 __cfqq = cfq_rb_first(service_tree);
1123 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
1126 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1129 * same position, nothing more to do
1131 if (rb_key == cfqq->rb_key &&
1132 cfqq->service_tree == service_tree)
1135 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1136 cfqq->service_tree = NULL;
1141 cfqq->service_tree = service_tree;
1142 p = &service_tree->rb.rb_node;
1147 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1150 * sort by key, that represents service time.
1152 if (time_before(rb_key, __cfqq->rb_key))
1155 n = &(*p)->rb_right;
1163 service_tree->left = &cfqq->rb_node;
1165 cfqq->rb_key = rb_key;
1166 rb_link_node(&cfqq->rb_node, parent, p);
1167 rb_insert_color(&cfqq->rb_node, &service_tree->rb);
1168 service_tree->count++;
1169 if (add_front || !new_cfqq)
1171 cfq_group_service_tree_add(cfqd, cfqq->cfqg);
1174 static struct cfq_queue *
1175 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
1176 sector_t sector, struct rb_node **ret_parent,
1177 struct rb_node ***rb_link)
1179 struct rb_node **p, *parent;
1180 struct cfq_queue *cfqq = NULL;
1188 cfqq = rb_entry(parent, struct cfq_queue, p_node);
1191 * Sort strictly based on sector. Smallest to the left,
1192 * largest to the right.
1194 if (sector > blk_rq_pos(cfqq->next_rq))
1195 n = &(*p)->rb_right;
1196 else if (sector < blk_rq_pos(cfqq->next_rq))
1204 *ret_parent = parent;
1210 static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1212 struct rb_node **p, *parent;
1213 struct cfq_queue *__cfqq;
1216 rb_erase(&cfqq->p_node, cfqq->p_root);
1217 cfqq->p_root = NULL;
1220 if (cfq_class_idle(cfqq))
1225 cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
1226 __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
1227 blk_rq_pos(cfqq->next_rq), &parent, &p);
1229 rb_link_node(&cfqq->p_node, parent, p);
1230 rb_insert_color(&cfqq->p_node, cfqq->p_root);
1232 cfqq->p_root = NULL;
1236 * Update cfqq's position in the service tree.
1238 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1241 * Resorting requires the cfqq to be on the RR list already.
1243 if (cfq_cfqq_on_rr(cfqq)) {
1244 cfq_service_tree_add(cfqd, cfqq, 0);
1245 cfq_prio_tree_add(cfqd, cfqq);
1250 * add to busy list of queues for service, trying to be fair in ordering
1251 * the pending list according to last request service
1253 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1255 cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
1256 BUG_ON(cfq_cfqq_on_rr(cfqq));
1257 cfq_mark_cfqq_on_rr(cfqq);
1258 cfqd->busy_queues++;
1260 cfq_resort_rr_list(cfqd, cfqq);
1264 * Called when the cfqq no longer has requests pending, remove it from
1267 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1269 cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
1270 BUG_ON(!cfq_cfqq_on_rr(cfqq));
1271 cfq_clear_cfqq_on_rr(cfqq);
1273 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1274 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1275 cfqq->service_tree = NULL;
1278 rb_erase(&cfqq->p_node, cfqq->p_root);
1279 cfqq->p_root = NULL;
1282 cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1283 BUG_ON(!cfqd->busy_queues);
1284 cfqd->busy_queues--;
1288 * rb tree support functions
1290 static void cfq_del_rq_rb(struct request *rq)
1292 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1293 const int sync = rq_is_sync(rq);
1295 BUG_ON(!cfqq->queued[sync]);
1296 cfqq->queued[sync]--;
1298 elv_rb_del(&cfqq->sort_list, rq);
1300 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
1302 * Queue will be deleted from service tree when we actually
1303 * expire it later. Right now just remove it from prio tree
1307 rb_erase(&cfqq->p_node, cfqq->p_root);
1308 cfqq->p_root = NULL;
1313 static void cfq_add_rq_rb(struct request *rq)
1315 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1316 struct cfq_data *cfqd = cfqq->cfqd;
1317 struct request *__alias, *prev;
1319 cfqq->queued[rq_is_sync(rq)]++;
1322 * looks a little odd, but the first insert might return an alias.
1323 * if that happens, put the alias on the dispatch list
1325 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
1326 cfq_dispatch_insert(cfqd->queue, __alias);
1328 if (!cfq_cfqq_on_rr(cfqq))
1329 cfq_add_cfqq_rr(cfqd, cfqq);
1332 * check if this request is a better next-serve candidate
1334 prev = cfqq->next_rq;
1335 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
1338 * adjust priority tree position, if ->next_rq changes
1340 if (prev != cfqq->next_rq)
1341 cfq_prio_tree_add(cfqd, cfqq);
1343 BUG_ON(!cfqq->next_rq);
1346 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
1348 elv_rb_del(&cfqq->sort_list, rq);
1349 cfqq->queued[rq_is_sync(rq)]--;
1353 static struct request *
1354 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
1356 struct task_struct *tsk = current;
1357 struct cfq_io_context *cic;
1358 struct cfq_queue *cfqq;
1360 cic = cfq_cic_lookup(cfqd, tsk->io_context);
1364 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1366 sector_t sector = bio->bi_sector + bio_sectors(bio);
1368 return elv_rb_find(&cfqq->sort_list, sector);
1374 static void cfq_activate_request(struct request_queue *q, struct request *rq)
1376 struct cfq_data *cfqd = q->elevator->elevator_data;
1378 cfqd->rq_in_driver[rq_is_sync(rq)]++;
1379 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
1380 rq_in_driver(cfqd));
1382 cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
1385 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
1387 struct cfq_data *cfqd = q->elevator->elevator_data;
1388 const int sync = rq_is_sync(rq);
1390 WARN_ON(!cfqd->rq_in_driver[sync]);
1391 cfqd->rq_in_driver[sync]--;
1392 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
1393 rq_in_driver(cfqd));
1396 static void cfq_remove_request(struct request *rq)
1398 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1400 if (cfqq->next_rq == rq)
1401 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
1403 list_del_init(&rq->queuelist);
1406 cfqq->cfqd->rq_queued--;
1407 if (rq_is_meta(rq)) {
1408 WARN_ON(!cfqq->meta_pending);
1409 cfqq->meta_pending--;
1413 static int cfq_merge(struct request_queue *q, struct request **req,
1416 struct cfq_data *cfqd = q->elevator->elevator_data;
1417 struct request *__rq;
1419 __rq = cfq_find_rq_fmerge(cfqd, bio);
1420 if (__rq && elv_rq_merge_ok(__rq, bio)) {
1422 return ELEVATOR_FRONT_MERGE;
1425 return ELEVATOR_NO_MERGE;
1428 static void cfq_merged_request(struct request_queue *q, struct request *req,
1431 if (type == ELEVATOR_FRONT_MERGE) {
1432 struct cfq_queue *cfqq = RQ_CFQQ(req);
1434 cfq_reposition_rq_rb(cfqq, req);
1439 cfq_merged_requests(struct request_queue *q, struct request *rq,
1440 struct request *next)
1442 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1444 * reposition in fifo if next is older than rq
1446 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
1447 time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
1448 list_move(&rq->queuelist, &next->queuelist);
1449 rq_set_fifo_time(rq, rq_fifo_time(next));
1452 if (cfqq->next_rq == next)
1454 cfq_remove_request(next);
1457 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
1460 struct cfq_data *cfqd = q->elevator->elevator_data;
1461 struct cfq_io_context *cic;
1462 struct cfq_queue *cfqq;
1464 /* Deny merge if bio and rq don't belong to same cfq group */
1465 if ((RQ_CFQQ(rq))->cfqg != cfq_get_cfqg(cfqd, 0))
1468 * Disallow merge of a sync bio into an async request.
1470 if (cfq_bio_sync(bio) && !rq_is_sync(rq))
1474 * Lookup the cfqq that this bio will be queued with. Allow
1475 * merge only if rq is queued there.
1477 cic = cfq_cic_lookup(cfqd, current->io_context);
1481 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1482 return cfqq == RQ_CFQQ(rq);
1485 static void __cfq_set_active_queue(struct cfq_data *cfqd,
1486 struct cfq_queue *cfqq)
1489 cfq_log_cfqq(cfqd, cfqq, "set_active");
1490 cfqq->slice_start = 0;
1491 cfqq->dispatch_start = jiffies;
1492 cfqq->slice_end = 0;
1493 cfqq->slice_dispatch = 0;
1494 cfqq->nr_sectors = 0;
1496 cfq_clear_cfqq_wait_request(cfqq);
1497 cfq_clear_cfqq_must_dispatch(cfqq);
1498 cfq_clear_cfqq_must_alloc_slice(cfqq);
1499 cfq_clear_cfqq_fifo_expire(cfqq);
1500 cfq_mark_cfqq_slice_new(cfqq);
1502 del_timer(&cfqd->idle_slice_timer);
1505 cfqd->active_queue = cfqq;
1509 * current cfqq expired its slice (or was too idle), select new one
1512 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1515 cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
1517 if (cfq_cfqq_wait_request(cfqq))
1518 del_timer(&cfqd->idle_slice_timer);
1520 cfq_clear_cfqq_wait_request(cfqq);
1523 * store what was left of this slice, if the queue idled/timed out
1525 if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
1526 cfqq->slice_resid = cfqq->slice_end - jiffies;
1527 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
1530 cfq_group_served(cfqd, cfqq->cfqg, cfqq);
1532 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
1533 cfq_del_cfqq_rr(cfqd, cfqq);
1535 cfq_resort_rr_list(cfqd, cfqq);
1537 if (cfqq == cfqd->active_queue)
1538 cfqd->active_queue = NULL;
1540 if (&cfqq->cfqg->rb_node == cfqd->grp_service_tree.active)
1541 cfqd->grp_service_tree.active = NULL;
1543 if (cfqd->active_cic) {
1544 put_io_context(cfqd->active_cic->ioc);
1545 cfqd->active_cic = NULL;
1549 static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
1551 struct cfq_queue *cfqq = cfqd->active_queue;
1554 __cfq_slice_expired(cfqd, cfqq, timed_out);
1558 * Get next queue for service. Unless we have a queue preemption,
1559 * we'll simply select the first cfqq in the service tree.
1561 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
1563 struct cfq_rb_root *service_tree =
1564 service_tree_for(cfqd->serving_group, cfqd->serving_prio,
1565 cfqd->serving_type, cfqd);
1567 if (!cfqd->rq_queued)
1570 /* There is nothing to dispatch */
1573 if (RB_EMPTY_ROOT(&service_tree->rb))
1575 return cfq_rb_first(service_tree);
1578 static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
1580 struct cfq_group *cfqg;
1581 struct cfq_queue *cfqq;
1583 struct cfq_rb_root *st;
1585 if (!cfqd->rq_queued)
1588 cfqg = cfq_get_next_cfqg(cfqd);
1592 for_each_cfqg_st(cfqg, i, j, st)
1593 if ((cfqq = cfq_rb_first(st)) != NULL)
1599 * Get and set a new active queue for service.
1601 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
1602 struct cfq_queue *cfqq)
1605 cfqq = cfq_get_next_queue(cfqd);
1607 __cfq_set_active_queue(cfqd, cfqq);
1611 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
1614 if (blk_rq_pos(rq) >= cfqd->last_position)
1615 return blk_rq_pos(rq) - cfqd->last_position;
1617 return cfqd->last_position - blk_rq_pos(rq);
1620 #define CFQQ_SEEK_THR 8 * 1024
1621 #define CFQQ_SEEKY(cfqq) ((cfqq)->seek_mean > CFQQ_SEEK_THR)
1623 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1626 sector_t sdist = cfqq->seek_mean;
1628 if (!sample_valid(cfqq->seek_samples))
1629 sdist = CFQQ_SEEK_THR;
1631 return cfq_dist_from_last(cfqd, rq) <= sdist;
1634 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
1635 struct cfq_queue *cur_cfqq)
1637 struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
1638 struct rb_node *parent, *node;
1639 struct cfq_queue *__cfqq;
1640 sector_t sector = cfqd->last_position;
1642 if (RB_EMPTY_ROOT(root))
1646 * First, if we find a request starting at the end of the last
1647 * request, choose it.
1649 __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
1654 * If the exact sector wasn't found, the parent of the NULL leaf
1655 * will contain the closest sector.
1657 __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1658 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1661 if (blk_rq_pos(__cfqq->next_rq) < sector)
1662 node = rb_next(&__cfqq->p_node);
1664 node = rb_prev(&__cfqq->p_node);
1668 __cfqq = rb_entry(node, struct cfq_queue, p_node);
1669 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1677 * cur_cfqq - passed in so that we don't decide that the current queue is
1678 * closely cooperating with itself.
1680 * So, basically we're assuming that that cur_cfqq has dispatched at least
1681 * one request, and that cfqd->last_position reflects a position on the disk
1682 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
1685 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1686 struct cfq_queue *cur_cfqq)
1688 struct cfq_queue *cfqq;
1690 if (!cfq_cfqq_sync(cur_cfqq))
1692 if (CFQQ_SEEKY(cur_cfqq))
1696 * We should notice if some of the queues are cooperating, eg
1697 * working closely on the same area of the disk. In that case,
1698 * we can group them together and don't waste time idling.
1700 cfqq = cfqq_close(cfqd, cur_cfqq);
1704 /* If new queue belongs to different cfq_group, don't choose it */
1705 if (cur_cfqq->cfqg != cfqq->cfqg)
1709 * It only makes sense to merge sync queues.
1711 if (!cfq_cfqq_sync(cfqq))
1713 if (CFQQ_SEEKY(cfqq))
1717 * Do not merge queues of different priority classes
1719 if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
1726 * Determine whether we should enforce idle window for this queue.
1729 static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1731 enum wl_prio_t prio = cfqq_prio(cfqq);
1732 struct cfq_rb_root *service_tree = cfqq->service_tree;
1734 BUG_ON(!service_tree);
1735 BUG_ON(!service_tree->count);
1737 /* We never do for idle class queues. */
1738 if (prio == IDLE_WORKLOAD)
1741 /* We do for queues that were marked with idle window flag. */
1742 if (cfq_cfqq_idle_window(cfqq))
1746 * Otherwise, we do only if they are the last ones
1747 * in their service tree.
1749 return service_tree->count == 1;
1752 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
1754 struct cfq_queue *cfqq = cfqd->active_queue;
1755 struct cfq_io_context *cic;
1759 * SSD device without seek penalty, disable idling. But only do so
1760 * for devices that support queuing, otherwise we still have a problem
1761 * with sync vs async workloads.
1763 if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
1766 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
1767 WARN_ON(cfq_cfqq_slice_new(cfqq));
1770 * idle is disabled, either manually or by past process history
1772 if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq))
1776 * still active requests from this queue, don't idle
1778 if (cfqq->dispatched)
1782 * task has exited, don't wait
1784 cic = cfqd->active_cic;
1785 if (!cic || !atomic_read(&cic->ioc->nr_tasks))
1789 * If our average think time is larger than the remaining time
1790 * slice, then don't idle. This avoids overrunning the allotted
1793 if (sample_valid(cic->ttime_samples) &&
1794 (cfqq->slice_end - jiffies < cic->ttime_mean))
1797 cfq_mark_cfqq_wait_request(cfqq);
1799 sl = cfqd->cfq_slice_idle;
1801 mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
1802 cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
1806 * Move request from internal lists to the request queue dispatch list.
1808 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
1810 struct cfq_data *cfqd = q->elevator->elevator_data;
1811 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1813 cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
1815 cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
1816 cfq_remove_request(rq);
1818 elv_dispatch_sort(q, rq);
1820 if (cfq_cfqq_sync(cfqq))
1821 cfqd->sync_flight++;
1822 cfqq->nr_sectors += blk_rq_sectors(rq);
1826 * return expired entry, or NULL to just start from scratch in rbtree
1828 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
1830 struct request *rq = NULL;
1832 if (cfq_cfqq_fifo_expire(cfqq))
1835 cfq_mark_cfqq_fifo_expire(cfqq);
1837 if (list_empty(&cfqq->fifo))
1840 rq = rq_entry_fifo(cfqq->fifo.next);
1841 if (time_before(jiffies, rq_fifo_time(rq)))
1844 cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
1849 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1851 const int base_rq = cfqd->cfq_slice_async_rq;
1853 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1855 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1859 * Must be called with the queue_lock held.
1861 static int cfqq_process_refs(struct cfq_queue *cfqq)
1863 int process_refs, io_refs;
1865 io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
1866 process_refs = atomic_read(&cfqq->ref) - io_refs;
1867 BUG_ON(process_refs < 0);
1868 return process_refs;
1871 static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
1873 int process_refs, new_process_refs;
1874 struct cfq_queue *__cfqq;
1876 /* Avoid a circular list and skip interim queue merges */
1877 while ((__cfqq = new_cfqq->new_cfqq)) {
1883 process_refs = cfqq_process_refs(cfqq);
1885 * If the process for the cfqq has gone away, there is no
1886 * sense in merging the queues.
1888 if (process_refs == 0)
1892 * Merge in the direction of the lesser amount of work.
1894 new_process_refs = cfqq_process_refs(new_cfqq);
1895 if (new_process_refs >= process_refs) {
1896 cfqq->new_cfqq = new_cfqq;
1897 atomic_add(process_refs, &new_cfqq->ref);
1899 new_cfqq->new_cfqq = cfqq;
1900 atomic_add(new_process_refs, &cfqq->ref);
1904 static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
1905 struct cfq_group *cfqg, enum wl_prio_t prio,
1908 struct cfq_queue *queue;
1910 bool key_valid = false;
1911 unsigned long lowest_key = 0;
1912 enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
1916 * When priorities switched, we prefer starting
1917 * from SYNC_NOIDLE (first choice), or just SYNC
1920 if (service_tree_for(cfqg, prio, cur_best, cfqd)->count)
1922 cur_best = SYNC_WORKLOAD;
1923 if (service_tree_for(cfqg, prio, cur_best, cfqd)->count)
1926 return ASYNC_WORKLOAD;
1929 for (i = 0; i < 3; ++i) {
1930 /* otherwise, select the one with lowest rb_key */
1931 queue = cfq_rb_first(service_tree_for(cfqg, prio, i, cfqd));
1933 (!key_valid || time_before(queue->rb_key, lowest_key))) {
1934 lowest_key = queue->rb_key;
1943 static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
1945 enum wl_prio_t previous_prio = cfqd->serving_prio;
1949 struct cfq_rb_root *st;
1950 unsigned group_slice;
1953 cfqd->serving_prio = IDLE_WORKLOAD;
1954 cfqd->workload_expires = jiffies + 1;
1958 /* Choose next priority. RT > BE > IDLE */
1959 if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
1960 cfqd->serving_prio = RT_WORKLOAD;
1961 else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
1962 cfqd->serving_prio = BE_WORKLOAD;
1964 cfqd->serving_prio = IDLE_WORKLOAD;
1965 cfqd->workload_expires = jiffies + 1;
1970 * For RT and BE, we have to choose also the type
1971 * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
1974 prio_changed = (cfqd->serving_prio != previous_prio);
1975 st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type,
1980 * If priority didn't change, check workload expiration,
1981 * and that we still have other queues ready
1983 if (!prio_changed && count &&
1984 !time_after(jiffies, cfqd->workload_expires))
1987 /* otherwise select new workload type */
1988 cfqd->serving_type =
1989 cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio, prio_changed);
1990 st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type,
1995 * the workload slice is computed as a fraction of target latency
1996 * proportional to the number of queues in that workload, over
1997 * all the queues in the same priority class
1999 group_slice = cfq_group_slice(cfqd, cfqg);
2001 slice = group_slice * count /
2002 max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio],
2003 cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg));
2005 if (cfqd->serving_type == ASYNC_WORKLOAD)
2006 /* async workload slice is scaled down according to
2007 * the sync/async slice ratio. */
2008 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
2010 /* sync workload slice is at least 2 * cfq_slice_idle */
2011 slice = max(slice, 2 * cfqd->cfq_slice_idle);
2013 slice = max_t(unsigned, slice, CFQ_MIN_TT);
2014 cfqd->workload_expires = jiffies + slice;
2015 cfqd->noidle_tree_requires_idle = false;
2018 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
2020 struct cfq_rb_root *st = &cfqd->grp_service_tree;
2021 struct cfq_group *cfqg;
2023 if (RB_EMPTY_ROOT(&st->rb))
2025 cfqg = cfq_rb_first_group(st);
2026 st->active = &cfqg->rb_node;
2027 update_min_vdisktime(st);
2031 static void cfq_choose_cfqg(struct cfq_data *cfqd)
2033 struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
2035 cfqd->serving_group = cfqg;
2037 /* Restore the workload type data */
2038 if (cfqg->saved_workload_slice) {
2039 cfqd->workload_expires = jiffies + cfqg->saved_workload_slice;
2040 cfqd->serving_type = cfqg->saved_workload;
2041 cfqd->serving_prio = cfqg->saved_serving_prio;
2043 choose_service_tree(cfqd, cfqg);
2047 * Select a queue for service. If we have a current active queue,
2048 * check whether to continue servicing it, or retrieve and set a new one.
2050 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
2052 struct cfq_queue *cfqq, *new_cfqq = NULL;
2054 cfqq = cfqd->active_queue;
2058 if (!cfqd->rq_queued)
2061 * The active queue has run out of time, expire it and select new.
2063 if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq))
2067 * The active queue has requests and isn't expired, allow it to
2070 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
2074 * If another queue has a request waiting within our mean seek
2075 * distance, let it run. The expire code will check for close
2076 * cooperators and put the close queue at the front of the service
2077 * tree. If possible, merge the expiring queue with the new cfqq.
2079 new_cfqq = cfq_close_cooperator(cfqd, cfqq);
2081 if (!cfqq->new_cfqq)
2082 cfq_setup_merge(cfqq, new_cfqq);
2087 * No requests pending. If the active queue still has requests in
2088 * flight or is idling for a new request, allow either of these
2089 * conditions to happen (or time out) before selecting a new queue.
2091 if (timer_pending(&cfqd->idle_slice_timer) ||
2092 (cfqq->dispatched && cfq_should_idle(cfqd, cfqq))) {
2098 cfq_slice_expired(cfqd, 0);
2101 * Current queue expired. Check if we have to switch to a new
2105 cfq_choose_cfqg(cfqd);
2107 cfqq = cfq_set_active_queue(cfqd, new_cfqq);
2112 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
2116 while (cfqq->next_rq) {
2117 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
2121 BUG_ON(!list_empty(&cfqq->fifo));
2123 /* By default cfqq is not expired if it is empty. Do it explicitly */
2124 __cfq_slice_expired(cfqq->cfqd, cfqq, 0);
2129 * Drain our current requests. Used for barriers and when switching
2130 * io schedulers on-the-fly.
2132 static int cfq_forced_dispatch(struct cfq_data *cfqd)
2134 struct cfq_queue *cfqq;
2137 while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL)
2138 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
2140 cfq_slice_expired(cfqd, 0);
2141 BUG_ON(cfqd->busy_queues);
2143 cfq_log(cfqd, "forced_dispatch=%d", dispatched);
2147 static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2149 unsigned int max_dispatch;
2152 * Drain async requests before we start sync IO
2154 if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
2158 * If this is an async queue and we have sync IO in flight, let it wait
2160 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
2163 max_dispatch = cfqd->cfq_quantum;
2164 if (cfq_class_idle(cfqq))
2168 * Does this cfqq already have too much IO in flight?
2170 if (cfqq->dispatched >= max_dispatch) {
2172 * idle queue must always only have a single IO in flight
2174 if (cfq_class_idle(cfqq))
2178 * We have other queues, don't allow more IO from this one
2180 if (cfqd->busy_queues > 1)
2184 * Sole queue user, no limit
2190 * Async queues must wait a bit before being allowed dispatch.
2191 * We also ramp up the dispatch depth gradually for async IO,
2192 * based on the last sync IO we serviced
2194 if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
2195 unsigned long last_sync = jiffies - cfqd->last_end_sync_rq;
2198 depth = last_sync / cfqd->cfq_slice[1];
2199 if (!depth && !cfqq->dispatched)
2201 if (depth < max_dispatch)
2202 max_dispatch = depth;
2206 * If we're below the current max, allow a dispatch
2208 return cfqq->dispatched < max_dispatch;
2212 * Dispatch a request from cfqq, moving them to the request queue
2215 static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2219 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
2221 if (!cfq_may_dispatch(cfqd, cfqq))
2225 * follow expired path, else get first next available
2227 rq = cfq_check_fifo(cfqq);
2232 * insert request into driver dispatch list
2234 cfq_dispatch_insert(cfqd->queue, rq);
2236 if (!cfqd->active_cic) {
2237 struct cfq_io_context *cic = RQ_CIC(rq);
2239 atomic_long_inc(&cic->ioc->refcount);
2240 cfqd->active_cic = cic;
2247 * Find the cfqq that we need to service and move a request from that to the
2250 static int cfq_dispatch_requests(struct request_queue *q, int force)
2252 struct cfq_data *cfqd = q->elevator->elevator_data;
2253 struct cfq_queue *cfqq;
2255 if (!cfqd->busy_queues)
2258 if (unlikely(force))
2259 return cfq_forced_dispatch(cfqd);
2261 cfqq = cfq_select_queue(cfqd);
2266 * Dispatch a request from this cfqq, if it is allowed
2268 if (!cfq_dispatch_request(cfqd, cfqq))
2271 cfqq->slice_dispatch++;
2272 cfq_clear_cfqq_must_dispatch(cfqq);
2275 * expire an async queue immediately if it has used up its slice. idle
2276 * queue always expire after 1 dispatch round.
2278 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
2279 cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
2280 cfq_class_idle(cfqq))) {
2281 cfqq->slice_end = jiffies + 1;
2282 cfq_slice_expired(cfqd, 0);
2285 cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
2290 * task holds one reference to the queue, dropped when task exits. each rq
2291 * in-flight on this queue also holds a reference, dropped when rq is freed.
2293 * Each cfq queue took a reference on the parent group. Drop it now.
2294 * queue lock must be held here.
2296 static void cfq_put_queue(struct cfq_queue *cfqq)
2298 struct cfq_data *cfqd = cfqq->cfqd;
2299 struct cfq_group *cfqg;
2301 BUG_ON(atomic_read(&cfqq->ref) <= 0);
2303 if (!atomic_dec_and_test(&cfqq->ref))
2306 cfq_log_cfqq(cfqd, cfqq, "put_queue");
2307 BUG_ON(rb_first(&cfqq->sort_list));
2308 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
2311 if (unlikely(cfqd->active_queue == cfqq)) {
2312 __cfq_slice_expired(cfqd, cfqq, 0);
2313 cfq_schedule_dispatch(cfqd);
2316 BUG_ON(cfq_cfqq_on_rr(cfqq));
2317 kmem_cache_free(cfq_pool, cfqq);
2322 * Must always be called with the rcu_read_lock() held
2325 __call_for_each_cic(struct io_context *ioc,
2326 void (*func)(struct io_context *, struct cfq_io_context *))
2328 struct cfq_io_context *cic;
2329 struct hlist_node *n;
2331 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
2336 * Call func for each cic attached to this ioc.
2339 call_for_each_cic(struct io_context *ioc,
2340 void (*func)(struct io_context *, struct cfq_io_context *))
2343 __call_for_each_cic(ioc, func);
2347 static void cfq_cic_free_rcu(struct rcu_head *head)
2349 struct cfq_io_context *cic;
2351 cic = container_of(head, struct cfq_io_context, rcu_head);
2353 kmem_cache_free(cfq_ioc_pool, cic);
2354 elv_ioc_count_dec(cfq_ioc_count);
2358 * CFQ scheduler is exiting, grab exit lock and check
2359 * the pending io context count. If it hits zero,
2360 * complete ioc_gone and set it back to NULL
2362 spin_lock(&ioc_gone_lock);
2363 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
2367 spin_unlock(&ioc_gone_lock);
2371 static void cfq_cic_free(struct cfq_io_context *cic)
2373 call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
2376 static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
2378 unsigned long flags;
2380 BUG_ON(!cic->dead_key);
2382 spin_lock_irqsave(&ioc->lock, flags);
2383 radix_tree_delete(&ioc->radix_root, cic->dead_key);
2384 hlist_del_rcu(&cic->cic_list);
2385 spin_unlock_irqrestore(&ioc->lock, flags);
2391 * Must be called with rcu_read_lock() held or preemption otherwise disabled.
2392 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
2393 * and ->trim() which is called with the task lock held
2395 static void cfq_free_io_context(struct io_context *ioc)
2398 * ioc->refcount is zero here, or we are called from elv_unregister(),
2399 * so no more cic's are allowed to be linked into this ioc. So it
2400 * should be ok to iterate over the known list, we will see all cic's
2401 * since no new ones are added.
2403 __call_for_each_cic(ioc, cic_free_func);
2406 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2408 struct cfq_queue *__cfqq, *next;
2410 if (unlikely(cfqq == cfqd->active_queue)) {
2411 __cfq_slice_expired(cfqd, cfqq, 0);
2412 cfq_schedule_dispatch(cfqd);
2416 * If this queue was scheduled to merge with another queue, be
2417 * sure to drop the reference taken on that queue (and others in
2418 * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs.
2420 __cfqq = cfqq->new_cfqq;
2422 if (__cfqq == cfqq) {
2423 WARN(1, "cfqq->new_cfqq loop detected\n");
2426 next = __cfqq->new_cfqq;
2427 cfq_put_queue(__cfqq);
2431 cfq_put_queue(cfqq);
2434 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
2435 struct cfq_io_context *cic)
2437 struct io_context *ioc = cic->ioc;
2439 list_del_init(&cic->queue_list);
2442 * Make sure key == NULL is seen for dead queues
2445 cic->dead_key = (unsigned long) cic->key;
2448 if (ioc->ioc_data == cic)
2449 rcu_assign_pointer(ioc->ioc_data, NULL);
2451 if (cic->cfqq[BLK_RW_ASYNC]) {
2452 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
2453 cic->cfqq[BLK_RW_ASYNC] = NULL;
2456 if (cic->cfqq[BLK_RW_SYNC]) {
2457 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
2458 cic->cfqq[BLK_RW_SYNC] = NULL;
2462 static void cfq_exit_single_io_context(struct io_context *ioc,
2463 struct cfq_io_context *cic)
2465 struct cfq_data *cfqd = cic->key;
2468 struct request_queue *q = cfqd->queue;
2469 unsigned long flags;
2471 spin_lock_irqsave(q->queue_lock, flags);
2474 * Ensure we get a fresh copy of the ->key to prevent
2475 * race between exiting task and queue
2477 smp_read_barrier_depends();
2479 __cfq_exit_single_io_context(cfqd, cic);
2481 spin_unlock_irqrestore(q->queue_lock, flags);
2486 * The process that ioc belongs to has exited, we need to clean up
2487 * and put the internal structures we have that belongs to that process.
2489 static void cfq_exit_io_context(struct io_context *ioc)
2491 call_for_each_cic(ioc, cfq_exit_single_io_context);
2494 static struct cfq_io_context *
2495 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2497 struct cfq_io_context *cic;
2499 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
2502 cic->last_end_request = jiffies;
2503 INIT_LIST_HEAD(&cic->queue_list);
2504 INIT_HLIST_NODE(&cic->cic_list);
2505 cic->dtor = cfq_free_io_context;
2506 cic->exit = cfq_exit_io_context;
2507 elv_ioc_count_inc(cfq_ioc_count);
2513 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
2515 struct task_struct *tsk = current;
2518 if (!cfq_cfqq_prio_changed(cfqq))
2521 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
2522 switch (ioprio_class) {
2524 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
2525 case IOPRIO_CLASS_NONE:
2527 * no prio set, inherit CPU scheduling settings
2529 cfqq->ioprio = task_nice_ioprio(tsk);
2530 cfqq->ioprio_class = task_nice_ioclass(tsk);
2532 case IOPRIO_CLASS_RT:
2533 cfqq->ioprio = task_ioprio(ioc);
2534 cfqq->ioprio_class = IOPRIO_CLASS_RT;
2536 case IOPRIO_CLASS_BE:
2537 cfqq->ioprio = task_ioprio(ioc);
2538 cfqq->ioprio_class = IOPRIO_CLASS_BE;
2540 case IOPRIO_CLASS_IDLE:
2541 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
2543 cfq_clear_cfqq_idle_window(cfqq);
2548 * keep track of original prio settings in case we have to temporarily
2549 * elevate the priority of this queue
2551 cfqq->org_ioprio = cfqq->ioprio;
2552 cfqq->org_ioprio_class = cfqq->ioprio_class;
2553 cfq_clear_cfqq_prio_changed(cfqq);
2556 static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
2558 struct cfq_data *cfqd = cic->key;
2559 struct cfq_queue *cfqq;
2560 unsigned long flags;
2562 if (unlikely(!cfqd))
2565 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2567 cfqq = cic->cfqq[BLK_RW_ASYNC];
2569 struct cfq_queue *new_cfqq;
2570 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
2573 cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
2574 cfq_put_queue(cfqq);
2578 cfqq = cic->cfqq[BLK_RW_SYNC];
2580 cfq_mark_cfqq_prio_changed(cfqq);
2582 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2585 static void cfq_ioc_set_ioprio(struct io_context *ioc)
2587 call_for_each_cic(ioc, changed_ioprio);
2588 ioc->ioprio_changed = 0;
2591 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2592 pid_t pid, bool is_sync)
2594 RB_CLEAR_NODE(&cfqq->rb_node);
2595 RB_CLEAR_NODE(&cfqq->p_node);
2596 INIT_LIST_HEAD(&cfqq->fifo);
2598 atomic_set(&cfqq->ref, 0);
2601 cfq_mark_cfqq_prio_changed(cfqq);
2604 if (!cfq_class_idle(cfqq))
2605 cfq_mark_cfqq_idle_window(cfqq);
2606 cfq_mark_cfqq_sync(cfqq);
2611 #ifdef CONFIG_CFQ_GROUP_IOSCHED
2612 static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
2614 struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1);
2615 struct cfq_data *cfqd = cic->key;
2616 unsigned long flags;
2617 struct request_queue *q;
2619 if (unlikely(!cfqd))
2624 spin_lock_irqsave(q->queue_lock, flags);
2628 * Drop reference to sync queue. A new sync queue will be
2629 * assigned in new group upon arrival of a fresh request.
2631 cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
2632 cic_set_cfqq(cic, NULL, 1);
2633 cfq_put_queue(sync_cfqq);
2636 spin_unlock_irqrestore(q->queue_lock, flags);
2639 static void cfq_ioc_set_cgroup(struct io_context *ioc)
2641 call_for_each_cic(ioc, changed_cgroup);
2642 ioc->cgroup_changed = 0;
2644 #endif /* CONFIG_CFQ_GROUP_IOSCHED */
2646 static struct cfq_queue *
2647 cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
2648 struct io_context *ioc, gfp_t gfp_mask)
2650 struct cfq_queue *cfqq, *new_cfqq = NULL;
2651 struct cfq_io_context *cic;
2652 struct cfq_group *cfqg;
2655 cfqg = cfq_get_cfqg(cfqd, 1);
2656 cic = cfq_cic_lookup(cfqd, ioc);
2657 /* cic always exists here */
2658 cfqq = cic_to_cfqq(cic, is_sync);
2661 * Always try a new alloc if we fell back to the OOM cfqq
2662 * originally, since it should just be a temporary situation.
2664 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2669 } else if (gfp_mask & __GFP_WAIT) {
2670 spin_unlock_irq(cfqd->queue->queue_lock);
2671 new_cfqq = kmem_cache_alloc_node(cfq_pool,
2672 gfp_mask | __GFP_ZERO,
2674 spin_lock_irq(cfqd->queue->queue_lock);
2678 cfqq = kmem_cache_alloc_node(cfq_pool,
2679 gfp_mask | __GFP_ZERO,
2684 cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
2685 cfq_init_prio_data(cfqq, ioc);
2686 cfq_link_cfqq_cfqg(cfqq, cfqg);
2687 cfq_log_cfqq(cfqd, cfqq, "alloced");
2689 cfqq = &cfqd->oom_cfqq;
2693 kmem_cache_free(cfq_pool, new_cfqq);
2698 static struct cfq_queue **
2699 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
2701 switch (ioprio_class) {
2702 case IOPRIO_CLASS_RT:
2703 return &cfqd->async_cfqq[0][ioprio];
2704 case IOPRIO_CLASS_BE:
2705 return &cfqd->async_cfqq[1][ioprio];
2706 case IOPRIO_CLASS_IDLE:
2707 return &cfqd->async_idle_cfqq;
2713 static struct cfq_queue *
2714 cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
2717 const int ioprio = task_ioprio(ioc);
2718 const int ioprio_class = task_ioprio_class(ioc);
2719 struct cfq_queue **async_cfqq = NULL;
2720 struct cfq_queue *cfqq = NULL;
2723 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
2728 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
2731 * pin the queue now that it's allocated, scheduler exit will prune it
2733 if (!is_sync && !(*async_cfqq)) {
2734 atomic_inc(&cfqq->ref);
2738 atomic_inc(&cfqq->ref);
2743 * We drop cfq io contexts lazily, so we may find a dead one.
2746 cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
2747 struct cfq_io_context *cic)
2749 unsigned long flags;
2751 WARN_ON(!list_empty(&cic->queue_list));
2753 spin_lock_irqsave(&ioc->lock, flags);
2755 BUG_ON(ioc->ioc_data == cic);
2757 radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
2758 hlist_del_rcu(&cic->cic_list);
2759 spin_unlock_irqrestore(&ioc->lock, flags);
2764 static struct cfq_io_context *
2765 cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
2767 struct cfq_io_context *cic;
2768 unsigned long flags;
2777 * we maintain a last-hit cache, to avoid browsing over the tree
2779 cic = rcu_dereference(ioc->ioc_data);
2780 if (cic && cic->key == cfqd) {
2786 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
2790 /* ->key must be copied to avoid race with cfq_exit_queue() */
2793 cfq_drop_dead_cic(cfqd, ioc, cic);
2798 spin_lock_irqsave(&ioc->lock, flags);
2799 rcu_assign_pointer(ioc->ioc_data, cic);
2800 spin_unlock_irqrestore(&ioc->lock, flags);
2808 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2809 * the process specific cfq io context when entered from the block layer.
2810 * Also adds the cic to a per-cfqd list, used when this queue is removed.
2812 static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
2813 struct cfq_io_context *cic, gfp_t gfp_mask)
2815 unsigned long flags;
2818 ret = radix_tree_preload(gfp_mask);
2823 spin_lock_irqsave(&ioc->lock, flags);
2824 ret = radix_tree_insert(&ioc->radix_root,
2825 (unsigned long) cfqd, cic);
2827 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
2828 spin_unlock_irqrestore(&ioc->lock, flags);
2830 radix_tree_preload_end();
2833 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2834 list_add(&cic->queue_list, &cfqd->cic_list);
2835 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2840 printk(KERN_ERR "cfq: cic link failed!\n");
2846 * Setup general io context and cfq io context. There can be several cfq
2847 * io contexts per general io context, if this process is doing io to more
2848 * than one device managed by cfq.
2850 static struct cfq_io_context *
2851 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2853 struct io_context *ioc = NULL;
2854 struct cfq_io_context *cic;
2856 might_sleep_if(gfp_mask & __GFP_WAIT);
2858 ioc = get_io_context(gfp_mask, cfqd->queue->node);
2862 cic = cfq_cic_lookup(cfqd, ioc);
2866 cic = cfq_alloc_io_context(cfqd, gfp_mask);
2870 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
2874 smp_read_barrier_depends();
2875 if (unlikely(ioc->ioprio_changed))
2876 cfq_ioc_set_ioprio(ioc);
2878 #ifdef CONFIG_CFQ_GROUP_IOSCHED
2879 if (unlikely(ioc->cgroup_changed))
2880 cfq_ioc_set_cgroup(ioc);
2886 put_io_context(ioc);
2891 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
2893 unsigned long elapsed = jiffies - cic->last_end_request;
2894 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
2896 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
2897 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
2898 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
2902 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2908 if (!cfqq->last_request_pos)
2910 else if (cfqq->last_request_pos < blk_rq_pos(rq))
2911 sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
2913 sdist = cfqq->last_request_pos - blk_rq_pos(rq);
2916 * Don't allow the seek distance to get too large from the
2917 * odd fragment, pagein, etc
2919 if (cfqq->seek_samples <= 60) /* second&third seek */
2920 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*1024);
2922 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*64);
2924 cfqq->seek_samples = (7*cfqq->seek_samples + 256) / 8;
2925 cfqq->seek_total = (7*cfqq->seek_total + (u64)256*sdist) / 8;
2926 total = cfqq->seek_total + (cfqq->seek_samples/2);
2927 do_div(total, cfqq->seek_samples);
2928 cfqq->seek_mean = (sector_t)total;
2931 * If this cfqq is shared between multiple processes, check to
2932 * make sure that those processes are still issuing I/Os within
2933 * the mean seek distance. If not, it may be time to break the
2934 * queues apart again.
2936 if (cfq_cfqq_coop(cfqq)) {
2937 if (CFQQ_SEEKY(cfqq) && !cfqq->seeky_start)
2938 cfqq->seeky_start = jiffies;
2939 else if (!CFQQ_SEEKY(cfqq))
2940 cfqq->seeky_start = 0;
2945 * Disable idle window if the process thinks too long or seeks so much that
2949 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2950 struct cfq_io_context *cic)
2952 int old_idle, enable_idle;
2955 * Don't idle for async or idle io prio class
2957 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
2960 enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
2962 if (cfqq->queued[0] + cfqq->queued[1] >= 4)
2963 cfq_mark_cfqq_deep(cfqq);
2965 if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
2966 (!cfq_cfqq_deep(cfqq) && sample_valid(cfqq->seek_samples)
2967 && CFQQ_SEEKY(cfqq)))
2969 else if (sample_valid(cic->ttime_samples)) {
2970 if (cic->ttime_mean > cfqd->cfq_slice_idle)
2976 if (old_idle != enable_idle) {
2977 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
2979 cfq_mark_cfqq_idle_window(cfqq);
2981 cfq_clear_cfqq_idle_window(cfqq);
2986 * Check if new_cfqq should preempt the currently active queue. Return 0 for
2987 * no or if we aren't sure, a 1 will cause a preempt.
2990 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
2993 struct cfq_queue *cfqq;
2995 cfqq = cfqd->active_queue;
2999 if (cfq_class_idle(new_cfqq))
3002 if (cfq_class_idle(cfqq))
3006 * if the new request is sync, but the currently running queue is
3007 * not, let the sync request have priority.
3009 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
3012 if (new_cfqq->cfqg != cfqq->cfqg)
3015 if (cfq_slice_used(cfqq))
3018 /* Allow preemption only if we are idling on sync-noidle tree */
3019 if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
3020 cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
3021 new_cfqq->service_tree->count == 2 &&
3022 RB_EMPTY_ROOT(&cfqq->sort_list))
3026 * So both queues are sync. Let the new request get disk time if
3027 * it's a metadata request and the current queue is doing regular IO.
3029 if (rq_is_meta(rq) && !cfqq->meta_pending)
3033 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
3035 if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
3038 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
3042 * if this request is as-good as one we would expect from the
3043 * current cfqq, let it preempt
3045 if (cfq_rq_close(cfqd, cfqq, rq))
3052 * cfqq preempts the active queue. if we allowed preempt with no slice left,
3053 * let it have half of its nominal slice.
3055 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3057 cfq_log_cfqq(cfqd, cfqq, "preempt");
3058 cfq_slice_expired(cfqd, 1);
3061 * Put the new queue at the front of the of the current list,
3062 * so we know that it will be selected next.
3064 BUG_ON(!cfq_cfqq_on_rr(cfqq));
3066 cfq_service_tree_add(cfqd, cfqq, 1);
3068 cfqq->slice_end = 0;
3069 cfq_mark_cfqq_slice_new(cfqq);
3073 * Called when a new fs request (rq) is added (to cfqq). Check if there's
3074 * something we should do about it
3077 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3080 struct cfq_io_context *cic = RQ_CIC(rq);
3084 cfqq->meta_pending++;
3086 cfq_update_io_thinktime(cfqd, cic);
3087 cfq_update_io_seektime(cfqd, cfqq, rq);
3088 cfq_update_idle_window(cfqd, cfqq, cic);
3090 cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
3092 if (cfqq == cfqd->active_queue) {
3094 * Remember that we saw a request from this process, but
3095 * don't start queuing just yet. Otherwise we risk seeing lots
3096 * of tiny requests, because we disrupt the normal plugging
3097 * and merging. If the request is already larger than a single
3098 * page, let it rip immediately. For that case we assume that
3099 * merging is already done. Ditto for a busy system that
3100 * has other work pending, don't risk delaying until the
3101 * idle timer unplug to continue working.
3103 if (cfq_cfqq_wait_request(cfqq)) {
3104 if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
3105 cfqd->busy_queues > 1) {
3106 del_timer(&cfqd->idle_slice_timer);
3107 __blk_run_queue(cfqd->queue);
3109 cfq_mark_cfqq_must_dispatch(cfqq);
3111 } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
3113 * not the active queue - expire current slice if it is
3114 * idle and has expired it's mean thinktime or this new queue
3115 * has some old slice time left and is of higher priority or
3116 * this new queue is RT and the current one is BE
3118 cfq_preempt_queue(cfqd, cfqq);
3119 __blk_run_queue(cfqd->queue);
3123 static void cfq_insert_request(struct request_queue *q, struct request *rq)
3125 struct cfq_data *cfqd = q->elevator->elevator_data;
3126 struct cfq_queue *cfqq = RQ_CFQQ(rq);
3128 cfq_log_cfqq(cfqd, cfqq, "insert_request");
3129 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
3131 rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
3132 list_add_tail(&rq->queuelist, &cfqq->fifo);
3135 cfq_rq_enqueued(cfqd, cfqq, rq);
3139 * Update hw_tag based on peak queue depth over 50 samples under
3142 static void cfq_update_hw_tag(struct cfq_data *cfqd)
3144 struct cfq_queue *cfqq = cfqd->active_queue;
3146 if (rq_in_driver(cfqd) > cfqd->hw_tag_est_depth)
3147 cfqd->hw_tag_est_depth = rq_in_driver(cfqd);
3149 if (cfqd->hw_tag == 1)
3152 if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
3153 rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN)
3157 * If active queue hasn't enough requests and can idle, cfq might not
3158 * dispatch sufficient requests to hardware. Don't zero hw_tag in this
3161 if (cfqq && cfq_cfqq_idle_window(cfqq) &&
3162 cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
3163 CFQ_HW_QUEUE_MIN && rq_in_driver(cfqd) < CFQ_HW_QUEUE_MIN)
3166 if (cfqd->hw_tag_samples++ < 50)
3169 if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
3175 static void cfq_completed_request(struct request_queue *q, struct request *rq)
3177 struct cfq_queue *cfqq = RQ_CFQQ(rq);
3178 struct cfq_data *cfqd = cfqq->cfqd;
3179 const int sync = rq_is_sync(rq);
3183 cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d", !!rq_noidle(rq));
3185 cfq_update_hw_tag(cfqd);
3187 WARN_ON(!cfqd->rq_in_driver[sync]);
3188 WARN_ON(!cfqq->dispatched);
3189 cfqd->rq_in_driver[sync]--;
3192 if (cfq_cfqq_sync(cfqq))
3193 cfqd->sync_flight--;
3196 RQ_CIC(rq)->last_end_request = now;
3197 cfqd->last_end_sync_rq = now;
3201 * If this is the active queue, check if it needs to be expired,
3202 * or if we want to idle in case it has no pending requests.
3204 if (cfqd->active_queue == cfqq) {
3205 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
3207 if (cfq_cfqq_slice_new(cfqq)) {
3208 cfq_set_prio_slice(cfqd, cfqq);
3209 cfq_clear_cfqq_slice_new(cfqq);
3212 * Idling is not enabled on:
3214 * - idle-priority queues
3216 * - queues with still some requests queued
3217 * - when there is a close cooperator
3219 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
3220 cfq_slice_expired(cfqd, 1);
3221 else if (sync && cfqq_empty &&
3222 !cfq_close_cooperator(cfqd, cfqq)) {
3223 cfqd->noidle_tree_requires_idle |= !rq_noidle(rq);
3225 * Idling is enabled for SYNC_WORKLOAD.
3226 * SYNC_NOIDLE_WORKLOAD idles at the end of the tree
3227 * only if we processed at least one !rq_noidle request
3229 if (cfqd->serving_type == SYNC_WORKLOAD
3230 || cfqd->noidle_tree_requires_idle)
3231 cfq_arm_slice_timer(cfqd);
3235 if (!rq_in_driver(cfqd))
3236 cfq_schedule_dispatch(cfqd);
3240 * we temporarily boost lower priority queues if they are holding fs exclusive
3241 * resources. they are boosted to normal prio (CLASS_BE/4)
3243 static void cfq_prio_boost(struct cfq_queue *cfqq)
3245 if (has_fs_excl()) {
3247 * boost idle prio on transactions that would lock out other
3248 * users of the filesystem
3250 if (cfq_class_idle(cfqq))
3251 cfqq->ioprio_class = IOPRIO_CLASS_BE;
3252 if (cfqq->ioprio > IOPRIO_NORM)
3253 cfqq->ioprio = IOPRIO_NORM;
3256 * unboost the queue (if needed)
3258 cfqq->ioprio_class = cfqq->org_ioprio_class;
3259 cfqq->ioprio = cfqq->org_ioprio;
3263 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
3265 if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
3266 cfq_mark_cfqq_must_alloc_slice(cfqq);
3267 return ELV_MQUEUE_MUST;
3270 return ELV_MQUEUE_MAY;
3273 static int cfq_may_queue(struct request_queue *q, int rw)
3275 struct cfq_data *cfqd = q->elevator->elevator_data;
3276 struct task_struct *tsk = current;
3277 struct cfq_io_context *cic;
3278 struct cfq_queue *cfqq;
3281 * don't force setup of a queue from here, as a call to may_queue
3282 * does not necessarily imply that a request actually will be queued.
3283 * so just lookup a possibly existing queue, or return 'may queue'
3286 cic = cfq_cic_lookup(cfqd, tsk->io_context);
3288 return ELV_MQUEUE_MAY;
3290 cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
3292 cfq_init_prio_data(cfqq, cic->ioc);
3293 cfq_prio_boost(cfqq);
3295 return __cfq_may_queue(cfqq);
3298 return ELV_MQUEUE_MAY;
3302 * queue lock held here
3304 static void cfq_put_request(struct request *rq)
3306 struct cfq_queue *cfqq = RQ_CFQQ(rq);
3309 const int rw = rq_data_dir(rq);
3311 BUG_ON(!cfqq->allocated[rw]);
3312 cfqq->allocated[rw]--;
3314 put_io_context(RQ_CIC(rq)->ioc);
3316 rq->elevator_private = NULL;
3317 rq->elevator_private2 = NULL;
3319 cfq_put_queue(cfqq);
3323 static struct cfq_queue *
3324 cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
3325 struct cfq_queue *cfqq)
3327 cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
3328 cic_set_cfqq(cic, cfqq->new_cfqq, 1);
3329 cfq_mark_cfqq_coop(cfqq->new_cfqq);
3330 cfq_put_queue(cfqq);
3331 return cic_to_cfqq(cic, 1);
3334 static int should_split_cfqq(struct cfq_queue *cfqq)
3336 if (cfqq->seeky_start &&
3337 time_after(jiffies, cfqq->seeky_start + CFQQ_COOP_TOUT))
3343 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
3344 * was the last process referring to said cfqq.
3346 static struct cfq_queue *
3347 split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
3349 if (cfqq_process_refs(cfqq) == 1) {
3350 cfqq->seeky_start = 0;
3351 cfqq->pid = current->pid;
3352 cfq_clear_cfqq_coop(cfqq);
3356 cic_set_cfqq(cic, NULL, 1);
3357 cfq_put_queue(cfqq);
3361 * Allocate cfq data structures associated with this request.
3364 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
3366 struct cfq_data *cfqd = q->elevator->elevator_data;
3367 struct cfq_io_context *cic;
3368 const int rw = rq_data_dir(rq);
3369 const bool is_sync = rq_is_sync(rq);
3370 struct cfq_queue *cfqq;
3371 unsigned long flags;
3373 might_sleep_if(gfp_mask & __GFP_WAIT);
3375 cic = cfq_get_io_context(cfqd, gfp_mask);
3377 spin_lock_irqsave(q->queue_lock, flags);
3383 cfqq = cic_to_cfqq(cic, is_sync);
3384 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
3385 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
3386 cic_set_cfqq(cic, cfqq, is_sync);
3389 * If the queue was seeky for too long, break it apart.
3391 if (cfq_cfqq_coop(cfqq) && should_split_cfqq(cfqq)) {
3392 cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
3393 cfqq = split_cfqq(cic, cfqq);
3399 * Check to see if this queue is scheduled to merge with
3400 * another, closely cooperating queue. The merging of
3401 * queues happens here as it must be done in process context.
3402 * The reference on new_cfqq was taken in merge_cfqqs.
3405 cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
3408 cfqq->allocated[rw]++;
3409 atomic_inc(&cfqq->ref);
3411 spin_unlock_irqrestore(q->queue_lock, flags);
3413 rq->elevator_private = cic;
3414 rq->elevator_private2 = cfqq;
3419 put_io_context(cic->ioc);
3421 cfq_schedule_dispatch(cfqd);
3422 spin_unlock_irqrestore(q->queue_lock, flags);
3423 cfq_log(cfqd, "set_request fail");
3427 static void cfq_kick_queue(struct work_struct *work)
3429 struct cfq_data *cfqd =
3430 container_of(work, struct cfq_data, unplug_work);
3431 struct request_queue *q = cfqd->queue;
3433 spin_lock_irq(q->queue_lock);
3434 __blk_run_queue(cfqd->queue);
3435 spin_unlock_irq(q->queue_lock);
3439 * Timer running if the active_queue is currently idling inside its time slice
3441 static void cfq_idle_slice_timer(unsigned long data)
3443 struct cfq_data *cfqd = (struct cfq_data *) data;
3444 struct cfq_queue *cfqq;
3445 unsigned long flags;
3448 cfq_log(cfqd, "idle timer fired");
3450 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
3452 cfqq = cfqd->active_queue;
3457 * We saw a request before the queue expired, let it through
3459 if (cfq_cfqq_must_dispatch(cfqq))
3465 if (cfq_slice_used(cfqq))
3469 * only expire and reinvoke request handler, if there are
3470 * other queues with pending requests
3472 if (!cfqd->busy_queues)
3476 * not expired and it has a request pending, let it dispatch
3478 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3482 * Queue depth flag is reset only when the idle didn't succeed
3484 cfq_clear_cfqq_deep(cfqq);
3487 cfq_slice_expired(cfqd, timed_out);
3489 cfq_schedule_dispatch(cfqd);
3491 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
3494 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
3496 del_timer_sync(&cfqd->idle_slice_timer);
3497 cancel_work_sync(&cfqd->unplug_work);
3500 static void cfq_put_async_queues(struct cfq_data *cfqd)
3504 for (i = 0; i < IOPRIO_BE_NR; i++) {
3505 if (cfqd->async_cfqq[0][i])
3506 cfq_put_queue(cfqd->async_cfqq[0][i]);
3507 if (cfqd->async_cfqq[1][i])
3508 cfq_put_queue(cfqd->async_cfqq[1][i]);
3511 if (cfqd->async_idle_cfqq)
3512 cfq_put_queue(cfqd->async_idle_cfqq);
3515 static void cfq_exit_queue(struct elevator_queue *e)
3517 struct cfq_data *cfqd = e->elevator_data;
3518 struct request_queue *q = cfqd->queue;
3520 cfq_shutdown_timer_wq(cfqd);
3522 spin_lock_irq(q->queue_lock);
3524 if (cfqd->active_queue)
3525 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
3527 while (!list_empty(&cfqd->cic_list)) {
3528 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
3529 struct cfq_io_context,
3532 __cfq_exit_single_io_context(cfqd, cic);
3535 cfq_put_async_queues(cfqd);
3536 cfq_release_cfq_groups(cfqd);
3537 blkiocg_del_blkio_group(&cfqd->root_group.blkg);
3539 spin_unlock_irq(q->queue_lock);
3541 cfq_shutdown_timer_wq(cfqd);
3543 /* Wait for cfqg->blkg->key accessors to exit their grace periods. */
3548 static void *cfq_init_queue(struct request_queue *q)
3550 struct cfq_data *cfqd;
3552 struct cfq_group *cfqg;
3553 struct cfq_rb_root *st;
3555 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
3559 /* Init root service tree */
3560 cfqd->grp_service_tree = CFQ_RB_ROOT;
3562 /* Init root group */
3563 cfqg = &cfqd->root_group;
3564 for_each_cfqg_st(cfqg, i, j, st)
3566 RB_CLEAR_NODE(&cfqg->rb_node);
3568 /* Give preference to root group over other groups */
3569 cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;
3571 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3573 * Take a reference to root group which we never drop. This is just
3574 * to make sure that cfq_put_cfqg() does not try to kfree root group
3576 atomic_set(&cfqg->ref, 1);
3577 blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd,
3581 * Not strictly needed (since RB_ROOT just clears the node and we
3582 * zeroed cfqd on alloc), but better be safe in case someone decides
3583 * to add magic to the rb code
3585 for (i = 0; i < CFQ_PRIO_LISTS; i++)
3586 cfqd->prio_trees[i] = RB_ROOT;
3589 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
3590 * Grab a permanent reference to it, so that the normal code flow
3591 * will not attempt to free it.
3593 cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
3594 atomic_inc(&cfqd->oom_cfqq.ref);
3595 cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
3597 INIT_LIST_HEAD(&cfqd->cic_list);
3601 init_timer(&cfqd->idle_slice_timer);
3602 cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
3603 cfqd->idle_slice_timer.data = (unsigned long) cfqd;
3605 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
3607 cfqd->cfq_quantum = cfq_quantum;
3608 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
3609 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
3610 cfqd->cfq_back_max = cfq_back_max;
3611 cfqd->cfq_back_penalty = cfq_back_penalty;
3612 cfqd->cfq_slice[0] = cfq_slice_async;
3613 cfqd->cfq_slice[1] = cfq_slice_sync;
3614 cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
3615 cfqd->cfq_slice_idle = cfq_slice_idle;
3616 cfqd->cfq_latency = 1;
3618 cfqd->last_end_sync_rq = jiffies;
3622 static void cfq_slab_kill(void)
3625 * Caller already ensured that pending RCU callbacks are completed,
3626 * so we should have no busy allocations at this point.
3629 kmem_cache_destroy(cfq_pool);
3631 kmem_cache_destroy(cfq_ioc_pool);
3634 static int __init cfq_slab_setup(void)
3636 cfq_pool = KMEM_CACHE(cfq_queue, 0);
3640 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
3651 * sysfs parts below -->
3654 cfq_var_show(unsigned int var, char *page)
3656 return sprintf(page, "%d\n", var);
3660 cfq_var_store(unsigned int *var, const char *page, size_t count)
3662 char *p = (char *) page;
3664 *var = simple_strtoul(p, &p, 10);
3668 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
3669 static ssize_t __FUNC(struct elevator_queue *e, char *page) \
3671 struct cfq_data *cfqd = e->elevator_data; \
3672 unsigned int __data = __VAR; \
3674 __data = jiffies_to_msecs(__data); \
3675 return cfq_var_show(__data, (page)); \
3677 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
3678 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
3679 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
3680 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
3681 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
3682 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
3683 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
3684 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
3685 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
3686 SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
3687 #undef SHOW_FUNCTION
3689 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
3690 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3692 struct cfq_data *cfqd = e->elevator_data; \
3693 unsigned int __data; \
3694 int ret = cfq_var_store(&__data, (page), count); \
3695 if (__data < (MIN)) \
3697 else if (__data > (MAX)) \
3700 *(__PTR) = msecs_to_jiffies(__data); \
3702 *(__PTR) = __data; \
3705 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
3706 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
3708 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
3710 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
3711 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
3713 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
3714 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
3715 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
3716 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
3718 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
3719 #undef STORE_FUNCTION
3721 #define CFQ_ATTR(name) \
3722 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3724 static struct elv_fs_entry cfq_attrs[] = {
3726 CFQ_ATTR(fifo_expire_sync),
3727 CFQ_ATTR(fifo_expire_async),
3728 CFQ_ATTR(back_seek_max),
3729 CFQ_ATTR(back_seek_penalty),
3730 CFQ_ATTR(slice_sync),
3731 CFQ_ATTR(slice_async),
3732 CFQ_ATTR(slice_async_rq),
3733 CFQ_ATTR(slice_idle),
3734 CFQ_ATTR(low_latency),
3738 static struct elevator_type iosched_cfq = {
3740 .elevator_merge_fn = cfq_merge,
3741 .elevator_merged_fn = cfq_merged_request,
3742 .elevator_merge_req_fn = cfq_merged_requests,
3743 .elevator_allow_merge_fn = cfq_allow_merge,
3744 .elevator_dispatch_fn = cfq_dispatch_requests,
3745 .elevator_add_req_fn = cfq_insert_request,
3746 .elevator_activate_req_fn = cfq_activate_request,
3747 .elevator_deactivate_req_fn = cfq_deactivate_request,
3748 .elevator_queue_empty_fn = cfq_queue_empty,
3749 .elevator_completed_req_fn = cfq_completed_request,
3750 .elevator_former_req_fn = elv_rb_former_request,
3751 .elevator_latter_req_fn = elv_rb_latter_request,
3752 .elevator_set_req_fn = cfq_set_request,
3753 .elevator_put_req_fn = cfq_put_request,
3754 .elevator_may_queue_fn = cfq_may_queue,
3755 .elevator_init_fn = cfq_init_queue,
3756 .elevator_exit_fn = cfq_exit_queue,
3757 .trim = cfq_free_io_context,
3759 .elevator_attrs = cfq_attrs,
3760 .elevator_name = "cfq",
3761 .elevator_owner = THIS_MODULE,
3764 static int __init cfq_init(void)
3767 * could be 0 on HZ < 1000 setups
3769 if (!cfq_slice_async)
3770 cfq_slice_async = 1;
3771 if (!cfq_slice_idle)
3774 if (cfq_slab_setup())
3777 elv_register(&iosched_cfq);
3782 static void __exit cfq_exit(void)
3784 DECLARE_COMPLETION_ONSTACK(all_gone);
3785 elv_unregister(&iosched_cfq);
3786 ioc_gone = &all_gone;
3787 /* ioc_gone's update must be visible before reading ioc_count */
3791 * this also protects us from entering cfq_slab_kill() with
3792 * pending RCU callbacks
3794 if (elv_ioc_count_read(cfq_ioc_count))
3795 wait_for_completion(&all_gone);
3799 module_init(cfq_init);
3800 module_exit(cfq_exit);
3802 MODULE_AUTHOR("Jens Axboe");
3803 MODULE_LICENSE("GPL");
3804 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");