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@suse.de>
9 #include <linux/config.h>
10 #include <linux/module.h>
11 #include <linux/blkdev.h>
12 #include <linux/elevator.h>
13 #include <linux/hash.h>
14 #include <linux/rbtree.h>
15 #include <linux/ioprio.h>
20 static const int cfq_quantum = 4; /* max queue in one round of service */
21 static const int cfq_queued = 8; /* minimum rq allocate limit per-queue*/
22 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
23 static const int cfq_back_max = 16 * 1024; /* maximum backwards seek, in KiB */
24 static const int cfq_back_penalty = 2; /* penalty of a backwards seek */
26 static const int cfq_slice_sync = HZ / 10;
27 static int cfq_slice_async = HZ / 25;
28 static const int cfq_slice_async_rq = 2;
29 static int cfq_slice_idle = HZ / 70;
31 #define CFQ_IDLE_GRACE (HZ / 10)
32 #define CFQ_SLICE_SCALE (5)
34 #define CFQ_KEY_ASYNC (0)
36 static DEFINE_SPINLOCK(cfq_exit_lock);
39 * for the hash of cfqq inside the cfqd
41 #define CFQ_QHASH_SHIFT 6
42 #define CFQ_QHASH_ENTRIES (1 << CFQ_QHASH_SHIFT)
43 #define list_entry_qhash(entry) hlist_entry((entry), struct cfq_queue, cfq_hash)
46 * for the hash of crq inside the cfqq
48 #define CFQ_MHASH_SHIFT 6
49 #define CFQ_MHASH_BLOCK(sec) ((sec) >> 3)
50 #define CFQ_MHASH_ENTRIES (1 << CFQ_MHASH_SHIFT)
51 #define CFQ_MHASH_FN(sec) hash_long(CFQ_MHASH_BLOCK(sec), CFQ_MHASH_SHIFT)
52 #define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors)
53 #define list_entry_hash(ptr) hlist_entry((ptr), struct cfq_rq, hash)
55 #define list_entry_cfqq(ptr) list_entry((ptr), struct cfq_queue, cfq_list)
56 #define list_entry_fifo(ptr) list_entry((ptr), struct request, queuelist)
58 #define RQ_DATA(rq) (rq)->elevator_private
64 #define RB_EMPTY(node) ((node)->rb_node == NULL)
65 #define RB_CLEAR_COLOR(node) (node)->rb_color = RB_NONE
66 #define RB_CLEAR(node) do { \
67 (node)->rb_parent = NULL; \
68 RB_CLEAR_COLOR((node)); \
69 (node)->rb_right = NULL; \
70 (node)->rb_left = NULL; \
72 #define RB_CLEAR_ROOT(root) ((root)->rb_node = NULL)
73 #define rb_entry_crq(node) rb_entry((node), struct cfq_rq, rb_node)
74 #define rq_rb_key(rq) (rq)->sector
76 static kmem_cache_t *crq_pool;
77 static kmem_cache_t *cfq_pool;
78 static kmem_cache_t *cfq_ioc_pool;
80 static atomic_t ioc_count = ATOMIC_INIT(0);
81 static struct completion *ioc_gone;
83 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
84 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
85 #define cfq_class_be(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_BE)
86 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
91 #define cfq_cfqq_dispatched(cfqq) \
92 ((cfqq)->on_dispatch[ASYNC] + (cfqq)->on_dispatch[SYNC])
94 #define cfq_cfqq_class_sync(cfqq) ((cfqq)->key != CFQ_KEY_ASYNC)
96 #define cfq_cfqq_sync(cfqq) \
97 (cfq_cfqq_class_sync(cfqq) || (cfqq)->on_dispatch[SYNC])
99 #define sample_valid(samples) ((samples) > 80)
102 * Per block device queue structure
105 request_queue_t *queue;
108 * rr list of queues with requests and the count of them
110 struct list_head rr_list[CFQ_PRIO_LISTS];
111 struct list_head busy_rr;
112 struct list_head cur_rr;
113 struct list_head idle_rr;
114 unsigned int busy_queues;
117 * non-ordered list of empty cfqq's
119 struct list_head empty_list;
124 struct hlist_head *cfq_hash;
127 * global crq hash for all queues
129 struct hlist_head *crq_hash;
131 unsigned int max_queued;
139 * schedule slice state info
142 * idle window management
144 struct timer_list idle_slice_timer;
145 struct work_struct unplug_work;
147 struct cfq_queue *active_queue;
148 struct cfq_io_context *active_cic;
149 int cur_prio, cur_end_prio;
150 unsigned int dispatch_slice;
152 struct timer_list idle_class_timer;
154 sector_t last_sector;
155 unsigned long last_end_request;
157 unsigned int rq_starved;
160 * tunables, see top of file
162 unsigned int cfq_quantum;
163 unsigned int cfq_queued;
164 unsigned int cfq_fifo_expire[2];
165 unsigned int cfq_back_penalty;
166 unsigned int cfq_back_max;
167 unsigned int cfq_slice[2];
168 unsigned int cfq_slice_async_rq;
169 unsigned int cfq_slice_idle;
171 struct list_head cic_list;
175 * Per process-grouping structure
178 /* reference count */
180 /* parent cfq_data */
181 struct cfq_data *cfqd;
182 /* cfqq lookup hash */
183 struct hlist_node cfq_hash;
186 /* on either rr or empty list of cfqd */
187 struct list_head cfq_list;
188 /* sorted list of pending requests */
189 struct rb_root sort_list;
190 /* if fifo isn't expired, next request to serve */
191 struct cfq_rq *next_crq;
192 /* requests queued in sort_list */
194 /* currently allocated requests */
196 /* fifo list of requests in sort_list */
197 struct list_head fifo;
199 unsigned long slice_start;
200 unsigned long slice_end;
201 unsigned long slice_left;
202 unsigned long service_last;
204 /* number of requests that are on the dispatch list */
207 /* io prio of this group */
208 unsigned short ioprio, org_ioprio;
209 unsigned short ioprio_class, org_ioprio_class;
211 /* various state flags, see below */
216 struct rb_node rb_node;
218 struct request *request;
219 struct hlist_node hash;
221 struct cfq_queue *cfq_queue;
222 struct cfq_io_context *io_context;
224 unsigned int crq_flags;
227 enum cfqq_state_flags {
228 CFQ_CFQQ_FLAG_on_rr = 0,
229 CFQ_CFQQ_FLAG_wait_request,
230 CFQ_CFQQ_FLAG_must_alloc,
231 CFQ_CFQQ_FLAG_must_alloc_slice,
232 CFQ_CFQQ_FLAG_must_dispatch,
233 CFQ_CFQQ_FLAG_fifo_expire,
234 CFQ_CFQQ_FLAG_idle_window,
235 CFQ_CFQQ_FLAG_prio_changed,
238 #define CFQ_CFQQ_FNS(name) \
239 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
241 cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
243 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
245 cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
247 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
249 return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
253 CFQ_CFQQ_FNS(wait_request);
254 CFQ_CFQQ_FNS(must_alloc);
255 CFQ_CFQQ_FNS(must_alloc_slice);
256 CFQ_CFQQ_FNS(must_dispatch);
257 CFQ_CFQQ_FNS(fifo_expire);
258 CFQ_CFQQ_FNS(idle_window);
259 CFQ_CFQQ_FNS(prio_changed);
262 enum cfq_rq_state_flags {
263 CFQ_CRQ_FLAG_is_sync = 0,
266 #define CFQ_CRQ_FNS(name) \
267 static inline void cfq_mark_crq_##name(struct cfq_rq *crq) \
269 crq->crq_flags |= (1 << CFQ_CRQ_FLAG_##name); \
271 static inline void cfq_clear_crq_##name(struct cfq_rq *crq) \
273 crq->crq_flags &= ~(1 << CFQ_CRQ_FLAG_##name); \
275 static inline int cfq_crq_##name(const struct cfq_rq *crq) \
277 return (crq->crq_flags & (1 << CFQ_CRQ_FLAG_##name)) != 0; \
280 CFQ_CRQ_FNS(is_sync);
283 static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsigned short);
284 static void cfq_dispatch_insert(request_queue_t *, struct cfq_rq *);
285 static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask);
287 #define process_sync(tsk) ((tsk)->flags & PF_SYNCWRITE)
290 * lots of deadline iosched dupes, can be abstracted later...
292 static inline void cfq_del_crq_hash(struct cfq_rq *crq)
294 hlist_del_init(&crq->hash);
297 static inline void cfq_add_crq_hash(struct cfq_data *cfqd, struct cfq_rq *crq)
299 const int hash_idx = CFQ_MHASH_FN(rq_hash_key(crq->request));
301 hlist_add_head(&crq->hash, &cfqd->crq_hash[hash_idx]);
304 static struct request *cfq_find_rq_hash(struct cfq_data *cfqd, sector_t offset)
306 struct hlist_head *hash_list = &cfqd->crq_hash[CFQ_MHASH_FN(offset)];
307 struct hlist_node *entry, *next;
309 hlist_for_each_safe(entry, next, hash_list) {
310 struct cfq_rq *crq = list_entry_hash(entry);
311 struct request *__rq = crq->request;
313 if (!rq_mergeable(__rq)) {
314 cfq_del_crq_hash(crq);
318 if (rq_hash_key(__rq) == offset)
326 * scheduler run of queue, if there are requests pending and no one in the
327 * driver that will restart queueing
329 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
331 if (cfqd->busy_queues)
332 kblockd_schedule_work(&cfqd->unplug_work);
335 static int cfq_queue_empty(request_queue_t *q)
337 struct cfq_data *cfqd = q->elevator->elevator_data;
339 return !cfqd->busy_queues;
342 static inline pid_t cfq_queue_pid(struct task_struct *task, int rw)
344 if (rw == READ || process_sync(task))
347 return CFQ_KEY_ASYNC;
351 * Lifted from AS - choose which of crq1 and crq2 that is best served now.
352 * We choose the request that is closest to the head right now. Distance
353 * behind the head is penalized and only allowed to a certain extent.
355 static struct cfq_rq *
356 cfq_choose_req(struct cfq_data *cfqd, struct cfq_rq *crq1, struct cfq_rq *crq2)
358 sector_t last, s1, s2, d1 = 0, d2 = 0;
359 unsigned long back_max;
360 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
361 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
362 unsigned wrap = 0; /* bit mask: requests behind the disk head? */
364 if (crq1 == NULL || crq1 == crq2)
369 if (cfq_crq_is_sync(crq1) && !cfq_crq_is_sync(crq2))
371 else if (cfq_crq_is_sync(crq2) && !cfq_crq_is_sync(crq1))
374 s1 = crq1->request->sector;
375 s2 = crq2->request->sector;
377 last = cfqd->last_sector;
380 * by definition, 1KiB is 2 sectors
382 back_max = cfqd->cfq_back_max * 2;
385 * Strict one way elevator _except_ in the case where we allow
386 * short backward seeks which are biased as twice the cost of a
387 * similar forward seek.
391 else if (s1 + back_max >= last)
392 d1 = (last - s1) * cfqd->cfq_back_penalty;
394 wrap |= CFQ_RQ1_WRAP;
398 else if (s2 + back_max >= last)
399 d2 = (last - s2) * cfqd->cfq_back_penalty;
401 wrap |= CFQ_RQ2_WRAP;
403 /* Found required data */
406 * By doing switch() on the bit mask "wrap" we avoid having to
407 * check two variables for all permutations: --> faster!
410 case 0: /* common case for CFQ: crq1 and crq2 not wrapped */
426 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both crqs wrapped */
429 * Since both rqs are wrapped,
430 * start with the one that's further behind head
431 * (--> only *one* back seek required),
432 * since back seek takes more time than forward.
442 * would be nice to take fifo expire time into account as well
444 static struct cfq_rq *
445 cfq_find_next_crq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
448 struct cfq_rq *crq_next = NULL, *crq_prev = NULL;
449 struct rb_node *rbnext, *rbprev;
451 if (!(rbnext = rb_next(&last->rb_node))) {
452 rbnext = rb_first(&cfqq->sort_list);
453 if (rbnext == &last->rb_node)
457 rbprev = rb_prev(&last->rb_node);
460 crq_prev = rb_entry_crq(rbprev);
462 crq_next = rb_entry_crq(rbnext);
464 return cfq_choose_req(cfqd, crq_next, crq_prev);
467 static void cfq_update_next_crq(struct cfq_rq *crq)
469 struct cfq_queue *cfqq = crq->cfq_queue;
471 if (cfqq->next_crq == crq)
472 cfqq->next_crq = cfq_find_next_crq(cfqq->cfqd, cfqq, crq);
475 static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
477 struct cfq_data *cfqd = cfqq->cfqd;
478 struct list_head *list, *entry;
480 BUG_ON(!cfq_cfqq_on_rr(cfqq));
482 list_del(&cfqq->cfq_list);
484 if (cfq_class_rt(cfqq))
485 list = &cfqd->cur_rr;
486 else if (cfq_class_idle(cfqq))
487 list = &cfqd->idle_rr;
490 * if cfqq has requests in flight, don't allow it to be
491 * found in cfq_set_active_queue before it has finished them.
492 * this is done to increase fairness between a process that
493 * has lots of io pending vs one that only generates one
494 * sporadically or synchronously
496 if (cfq_cfqq_dispatched(cfqq))
497 list = &cfqd->busy_rr;
499 list = &cfqd->rr_list[cfqq->ioprio];
503 * if queue was preempted, just add to front to be fair. busy_rr
506 if (preempted || list == &cfqd->busy_rr) {
507 list_add(&cfqq->cfq_list, list);
512 * sort by when queue was last serviced
515 while ((entry = entry->prev) != list) {
516 struct cfq_queue *__cfqq = list_entry_cfqq(entry);
518 if (!__cfqq->service_last)
520 if (time_before(__cfqq->service_last, cfqq->service_last))
524 list_add(&cfqq->cfq_list, entry);
528 * add to busy list of queues for service, trying to be fair in ordering
529 * the pending list according to last request service
532 cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
534 BUG_ON(cfq_cfqq_on_rr(cfqq));
535 cfq_mark_cfqq_on_rr(cfqq);
538 cfq_resort_rr_list(cfqq, 0);
542 cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
544 BUG_ON(!cfq_cfqq_on_rr(cfqq));
545 cfq_clear_cfqq_on_rr(cfqq);
546 list_move(&cfqq->cfq_list, &cfqd->empty_list);
548 BUG_ON(!cfqd->busy_queues);
553 * rb tree support functions
555 static inline void cfq_del_crq_rb(struct cfq_rq *crq)
557 struct cfq_queue *cfqq = crq->cfq_queue;
558 struct cfq_data *cfqd = cfqq->cfqd;
559 const int sync = cfq_crq_is_sync(crq);
561 BUG_ON(!cfqq->queued[sync]);
562 cfqq->queued[sync]--;
564 cfq_update_next_crq(crq);
566 rb_erase(&crq->rb_node, &cfqq->sort_list);
567 RB_CLEAR_COLOR(&crq->rb_node);
569 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY(&cfqq->sort_list))
570 cfq_del_cfqq_rr(cfqd, cfqq);
573 static struct cfq_rq *
574 __cfq_add_crq_rb(struct cfq_rq *crq)
576 struct rb_node **p = &crq->cfq_queue->sort_list.rb_node;
577 struct rb_node *parent = NULL;
578 struct cfq_rq *__crq;
582 __crq = rb_entry_crq(parent);
584 if (crq->rb_key < __crq->rb_key)
586 else if (crq->rb_key > __crq->rb_key)
592 rb_link_node(&crq->rb_node, parent, p);
596 static void cfq_add_crq_rb(struct cfq_rq *crq)
598 struct cfq_queue *cfqq = crq->cfq_queue;
599 struct cfq_data *cfqd = cfqq->cfqd;
600 struct request *rq = crq->request;
601 struct cfq_rq *__alias;
603 crq->rb_key = rq_rb_key(rq);
604 cfqq->queued[cfq_crq_is_sync(crq)]++;
607 * looks a little odd, but the first insert might return an alias.
608 * if that happens, put the alias on the dispatch list
610 while ((__alias = __cfq_add_crq_rb(crq)) != NULL)
611 cfq_dispatch_insert(cfqd->queue, __alias);
613 rb_insert_color(&crq->rb_node, &cfqq->sort_list);
615 if (!cfq_cfqq_on_rr(cfqq))
616 cfq_add_cfqq_rr(cfqd, cfqq);
619 * check if this request is a better next-serve candidate
621 cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
625 cfq_reposition_crq_rb(struct cfq_queue *cfqq, struct cfq_rq *crq)
627 rb_erase(&crq->rb_node, &cfqq->sort_list);
628 cfqq->queued[cfq_crq_is_sync(crq)]--;
633 static struct request *
634 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
636 struct task_struct *tsk = current;
637 pid_t key = cfq_queue_pid(tsk, bio_data_dir(bio));
638 struct cfq_queue *cfqq;
642 cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
646 sector = bio->bi_sector + bio_sectors(bio);
647 n = cfqq->sort_list.rb_node;
649 struct cfq_rq *crq = rb_entry_crq(n);
651 if (sector < crq->rb_key)
653 else if (sector > crq->rb_key)
663 static void cfq_activate_request(request_queue_t *q, struct request *rq)
665 struct cfq_data *cfqd = q->elevator->elevator_data;
667 cfqd->rq_in_driver++;
670 * If the depth is larger 1, it really could be queueing. But lets
671 * make the mark a little higher - idling could still be good for
672 * low queueing, and a low queueing number could also just indicate
673 * a SCSI mid layer like behaviour where limit+1 is often seen.
675 if (!cfqd->hw_tag && cfqd->rq_in_driver > 4)
679 static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
681 struct cfq_data *cfqd = q->elevator->elevator_data;
683 WARN_ON(!cfqd->rq_in_driver);
684 cfqd->rq_in_driver--;
687 static void cfq_remove_request(struct request *rq)
689 struct cfq_rq *crq = RQ_DATA(rq);
691 list_del_init(&rq->queuelist);
693 cfq_del_crq_hash(crq);
697 cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
699 struct cfq_data *cfqd = q->elevator->elevator_data;
700 struct request *__rq;
703 __rq = cfq_find_rq_hash(cfqd, bio->bi_sector);
704 if (__rq && elv_rq_merge_ok(__rq, bio)) {
705 ret = ELEVATOR_BACK_MERGE;
709 __rq = cfq_find_rq_fmerge(cfqd, bio);
710 if (__rq && elv_rq_merge_ok(__rq, bio)) {
711 ret = ELEVATOR_FRONT_MERGE;
715 return ELEVATOR_NO_MERGE;
721 static void cfq_merged_request(request_queue_t *q, struct request *req)
723 struct cfq_data *cfqd = q->elevator->elevator_data;
724 struct cfq_rq *crq = RQ_DATA(req);
726 cfq_del_crq_hash(crq);
727 cfq_add_crq_hash(cfqd, crq);
729 if (rq_rb_key(req) != crq->rb_key) {
730 struct cfq_queue *cfqq = crq->cfq_queue;
732 cfq_update_next_crq(crq);
733 cfq_reposition_crq_rb(cfqq, crq);
738 cfq_merged_requests(request_queue_t *q, struct request *rq,
739 struct request *next)
741 cfq_merged_request(q, rq);
744 * reposition in fifo if next is older than rq
746 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
747 time_before(next->start_time, rq->start_time))
748 list_move(&rq->queuelist, &next->queuelist);
750 cfq_remove_request(next);
754 __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
758 * stop potential idle class queues waiting service
760 del_timer(&cfqd->idle_class_timer);
762 cfqq->slice_start = jiffies;
764 cfqq->slice_left = 0;
765 cfq_clear_cfqq_must_alloc_slice(cfqq);
766 cfq_clear_cfqq_fifo_expire(cfqq);
769 cfqd->active_queue = cfqq;
773 * current cfqq expired its slice (or was too idle), select new one
776 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
779 unsigned long now = jiffies;
781 if (cfq_cfqq_wait_request(cfqq))
782 del_timer(&cfqd->idle_slice_timer);
784 if (!preempted && !cfq_cfqq_dispatched(cfqq)) {
785 cfqq->service_last = now;
786 cfq_schedule_dispatch(cfqd);
789 cfq_clear_cfqq_must_dispatch(cfqq);
790 cfq_clear_cfqq_wait_request(cfqq);
793 * store what was left of this slice, if the queue idled out
796 if (time_after(cfqq->slice_end, now))
797 cfqq->slice_left = cfqq->slice_end - now;
799 cfqq->slice_left = 0;
801 if (cfq_cfqq_on_rr(cfqq))
802 cfq_resort_rr_list(cfqq, preempted);
804 if (cfqq == cfqd->active_queue)
805 cfqd->active_queue = NULL;
807 if (cfqd->active_cic) {
808 put_io_context(cfqd->active_cic->ioc);
809 cfqd->active_cic = NULL;
812 cfqd->dispatch_slice = 0;
815 static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted)
817 struct cfq_queue *cfqq = cfqd->active_queue;
820 __cfq_slice_expired(cfqd, cfqq, preempted);
833 static int cfq_get_next_prio_level(struct cfq_data *cfqd)
842 for (p = cfqd->cur_prio; p <= cfqd->cur_end_prio; p++) {
843 if (!list_empty(&cfqd->rr_list[p])) {
852 if (++cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
853 cfqd->cur_end_prio = 0;
860 if (unlikely(prio == -1))
863 BUG_ON(prio >= CFQ_PRIO_LISTS);
865 list_splice_init(&cfqd->rr_list[prio], &cfqd->cur_rr);
867 cfqd->cur_prio = prio + 1;
868 if (cfqd->cur_prio > cfqd->cur_end_prio) {
869 cfqd->cur_end_prio = cfqd->cur_prio;
872 if (cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
874 cfqd->cur_end_prio = 0;
880 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
882 struct cfq_queue *cfqq = NULL;
885 * if current list is non-empty, grab first entry. if it is empty,
886 * get next prio level and grab first entry then if any are spliced
888 if (!list_empty(&cfqd->cur_rr) || cfq_get_next_prio_level(cfqd) != -1)
889 cfqq = list_entry_cfqq(cfqd->cur_rr.next);
892 * If no new queues are available, check if the busy list has some
893 * before falling back to idle io.
895 if (!cfqq && !list_empty(&cfqd->busy_rr))
896 cfqq = list_entry_cfqq(cfqd->busy_rr.next);
899 * if we have idle queues and no rt or be queues had pending
900 * requests, either allow immediate service if the grace period
901 * has passed or arm the idle grace timer
903 if (!cfqq && !list_empty(&cfqd->idle_rr)) {
904 unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE;
906 if (time_after_eq(jiffies, end))
907 cfqq = list_entry_cfqq(cfqd->idle_rr.next);
909 mod_timer(&cfqd->idle_class_timer, end);
912 __cfq_set_active_queue(cfqd, cfqq);
916 static int cfq_arm_slice_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
919 struct cfq_io_context *cic;
922 WARN_ON(!RB_EMPTY(&cfqq->sort_list));
923 WARN_ON(cfqq != cfqd->active_queue);
926 * idle is disabled, either manually or by past process history
928 if (!cfqd->cfq_slice_idle)
930 if (!cfq_cfqq_idle_window(cfqq))
933 * task has exited, don't wait
935 cic = cfqd->active_cic;
936 if (!cic || !cic->ioc->task)
939 cfq_mark_cfqq_must_dispatch(cfqq);
940 cfq_mark_cfqq_wait_request(cfqq);
942 sl = min(cfqq->slice_end - 1, (unsigned long) cfqd->cfq_slice_idle);
945 * we don't want to idle for seeks, but we do want to allow
946 * fair distribution of slice time for a process doing back-to-back
947 * seeks. so allow a little bit of time for him to submit a new rq
949 if (sample_valid(cic->seek_samples) && cic->seek_mean > 131072)
952 mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
956 static void cfq_dispatch_insert(request_queue_t *q, struct cfq_rq *crq)
958 struct cfq_data *cfqd = q->elevator->elevator_data;
959 struct cfq_queue *cfqq = crq->cfq_queue;
961 cfqq->next_crq = cfq_find_next_crq(cfqd, cfqq, crq);
962 cfq_remove_request(crq->request);
963 cfqq->on_dispatch[cfq_crq_is_sync(crq)]++;
964 elv_dispatch_sort(q, crq->request);
968 * return expired entry, or NULL to just start from scratch in rbtree
970 static inline struct cfq_rq *cfq_check_fifo(struct cfq_queue *cfqq)
972 struct cfq_data *cfqd = cfqq->cfqd;
976 if (cfq_cfqq_fifo_expire(cfqq))
979 if (!list_empty(&cfqq->fifo)) {
980 int fifo = cfq_cfqq_class_sync(cfqq);
982 crq = RQ_DATA(list_entry_fifo(cfqq->fifo.next));
984 if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) {
985 cfq_mark_cfqq_fifo_expire(cfqq);
994 * Scale schedule slice based on io priority. Use the sync time slice only
995 * if a queue is marked sync and has sync io queued. A sync queue with async
996 * io only, should not get full sync slice length.
999 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1001 const int base_slice = cfqd->cfq_slice[cfq_cfqq_sync(cfqq)];
1003 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1005 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - cfqq->ioprio));
1009 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1011 cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
1015 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1017 const int base_rq = cfqd->cfq_slice_async_rq;
1019 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1021 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1025 * get next queue for service
1027 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
1029 unsigned long now = jiffies;
1030 struct cfq_queue *cfqq;
1032 cfqq = cfqd->active_queue;
1039 if (!cfq_cfqq_must_dispatch(cfqq) && time_after(now, cfqq->slice_end))
1043 * if queue has requests, dispatch one. if not, check if
1044 * enough slice is left to wait for one
1046 if (!RB_EMPTY(&cfqq->sort_list))
1048 else if (cfq_cfqq_class_sync(cfqq) &&
1049 time_before(now, cfqq->slice_end)) {
1050 if (cfq_arm_slice_timer(cfqd, cfqq))
1055 cfq_slice_expired(cfqd, 0);
1057 cfqq = cfq_set_active_queue(cfqd);
1063 __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1068 BUG_ON(RB_EMPTY(&cfqq->sort_list));
1074 * follow expired path, else get first next available
1076 if ((crq = cfq_check_fifo(cfqq)) == NULL)
1077 crq = cfqq->next_crq;
1080 * finally, insert request into driver dispatch list
1082 cfq_dispatch_insert(cfqd->queue, crq);
1084 cfqd->dispatch_slice++;
1087 if (!cfqd->active_cic) {
1088 atomic_inc(&crq->io_context->ioc->refcount);
1089 cfqd->active_cic = crq->io_context;
1092 if (RB_EMPTY(&cfqq->sort_list))
1095 } while (dispatched < max_dispatch);
1098 * if slice end isn't set yet, set it. if at least one request was
1099 * sync, use the sync time slice value
1101 if (!cfqq->slice_end)
1102 cfq_set_prio_slice(cfqd, cfqq);
1105 * expire an async queue immediately if it has used up its slice. idle
1106 * queue always expire after 1 dispatch round.
1108 if ((!cfq_cfqq_sync(cfqq) &&
1109 cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1110 cfq_class_idle(cfqq))
1111 cfq_slice_expired(cfqd, 0);
1117 cfq_forced_dispatch_cfqqs(struct list_head *list)
1120 struct cfq_queue *cfqq, *next;
1123 list_for_each_entry_safe(cfqq, next, list, cfq_list) {
1124 while ((crq = cfqq->next_crq)) {
1125 cfq_dispatch_insert(cfqq->cfqd->queue, crq);
1128 BUG_ON(!list_empty(&cfqq->fifo));
1134 cfq_forced_dispatch(struct cfq_data *cfqd)
1136 int i, dispatched = 0;
1138 for (i = 0; i < CFQ_PRIO_LISTS; i++)
1139 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->rr_list[i]);
1141 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->busy_rr);
1142 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr);
1143 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->idle_rr);
1145 cfq_slice_expired(cfqd, 0);
1147 BUG_ON(cfqd->busy_queues);
1153 cfq_dispatch_requests(request_queue_t *q, int force)
1155 struct cfq_data *cfqd = q->elevator->elevator_data;
1156 struct cfq_queue *cfqq;
1158 if (!cfqd->busy_queues)
1161 if (unlikely(force))
1162 return cfq_forced_dispatch(cfqd);
1164 cfqq = cfq_select_queue(cfqd);
1168 cfq_clear_cfqq_must_dispatch(cfqq);
1169 cfq_clear_cfqq_wait_request(cfqq);
1170 del_timer(&cfqd->idle_slice_timer);
1172 max_dispatch = cfqd->cfq_quantum;
1173 if (cfq_class_idle(cfqq))
1176 return __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
1183 * task holds one reference to the queue, dropped when task exits. each crq
1184 * in-flight on this queue also holds a reference, dropped when crq is freed.
1186 * queue lock must be held here.
1188 static void cfq_put_queue(struct cfq_queue *cfqq)
1190 struct cfq_data *cfqd = cfqq->cfqd;
1192 BUG_ON(atomic_read(&cfqq->ref) <= 0);
1194 if (!atomic_dec_and_test(&cfqq->ref))
1197 BUG_ON(rb_first(&cfqq->sort_list));
1198 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1199 BUG_ON(cfq_cfqq_on_rr(cfqq));
1201 if (unlikely(cfqd->active_queue == cfqq))
1202 __cfq_slice_expired(cfqd, cfqq, 0);
1205 * it's on the empty list and still hashed
1207 list_del(&cfqq->cfq_list);
1208 hlist_del(&cfqq->cfq_hash);
1209 kmem_cache_free(cfq_pool, cfqq);
1212 static inline struct cfq_queue *
1213 __cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned int prio,
1216 struct hlist_head *hash_list = &cfqd->cfq_hash[hashval];
1217 struct hlist_node *entry;
1218 struct cfq_queue *__cfqq;
1220 hlist_for_each_entry(__cfqq, entry, hash_list, cfq_hash) {
1221 const unsigned short __p = IOPRIO_PRIO_VALUE(__cfqq->org_ioprio_class, __cfqq->org_ioprio);
1223 if (__cfqq->key == key && (__p == prio || !prio))
1230 static struct cfq_queue *
1231 cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned short prio)
1233 return __cfq_find_cfq_hash(cfqd, key, prio, hash_long(key, CFQ_QHASH_SHIFT));
1236 static void cfq_free_io_context(struct io_context *ioc)
1238 struct cfq_io_context *__cic;
1242 while ((n = rb_first(&ioc->cic_root)) != NULL) {
1243 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1244 rb_erase(&__cic->rb_node, &ioc->cic_root);
1245 kmem_cache_free(cfq_ioc_pool, __cic);
1249 if (atomic_sub_and_test(freed, &ioc_count) && ioc_gone)
1253 static void cfq_trim(struct io_context *ioc)
1255 ioc->set_ioprio = NULL;
1256 cfq_free_io_context(ioc);
1260 * Called with interrupts disabled
1262 static void cfq_exit_single_io_context(struct cfq_io_context *cic)
1264 struct cfq_data *cfqd = cic->key;
1272 WARN_ON(!irqs_disabled());
1274 spin_lock(q->queue_lock);
1276 if (cic->cfqq[ASYNC]) {
1277 if (unlikely(cic->cfqq[ASYNC] == cfqd->active_queue))
1278 __cfq_slice_expired(cfqd, cic->cfqq[ASYNC], 0);
1279 cfq_put_queue(cic->cfqq[ASYNC]);
1280 cic->cfqq[ASYNC] = NULL;
1283 if (cic->cfqq[SYNC]) {
1284 if (unlikely(cic->cfqq[SYNC] == cfqd->active_queue))
1285 __cfq_slice_expired(cfqd, cic->cfqq[SYNC], 0);
1286 cfq_put_queue(cic->cfqq[SYNC]);
1287 cic->cfqq[SYNC] = NULL;
1291 list_del_init(&cic->queue_list);
1292 spin_unlock(q->queue_lock);
1295 static void cfq_exit_io_context(struct io_context *ioc)
1297 struct cfq_io_context *__cic;
1298 unsigned long flags;
1302 * put the reference this task is holding to the various queues
1304 spin_lock_irqsave(&cfq_exit_lock, flags);
1306 n = rb_first(&ioc->cic_root);
1308 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1310 cfq_exit_single_io_context(__cic);
1314 spin_unlock_irqrestore(&cfq_exit_lock, flags);
1317 static struct cfq_io_context *
1318 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1320 struct cfq_io_context *cic = kmem_cache_alloc(cfq_ioc_pool, gfp_mask);
1323 RB_CLEAR(&cic->rb_node);
1325 cic->cfqq[ASYNC] = NULL;
1326 cic->cfqq[SYNC] = NULL;
1327 cic->last_end_request = jiffies;
1328 cic->ttime_total = 0;
1329 cic->ttime_samples = 0;
1330 cic->ttime_mean = 0;
1331 cic->dtor = cfq_free_io_context;
1332 cic->exit = cfq_exit_io_context;
1333 INIT_LIST_HEAD(&cic->queue_list);
1334 atomic_inc(&ioc_count);
1340 static void cfq_init_prio_data(struct cfq_queue *cfqq)
1342 struct task_struct *tsk = current;
1345 if (!cfq_cfqq_prio_changed(cfqq))
1348 ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
1349 switch (ioprio_class) {
1351 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1352 case IOPRIO_CLASS_NONE:
1354 * no prio set, place us in the middle of the BE classes
1356 cfqq->ioprio = task_nice_ioprio(tsk);
1357 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1359 case IOPRIO_CLASS_RT:
1360 cfqq->ioprio = task_ioprio(tsk);
1361 cfqq->ioprio_class = IOPRIO_CLASS_RT;
1363 case IOPRIO_CLASS_BE:
1364 cfqq->ioprio = task_ioprio(tsk);
1365 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1367 case IOPRIO_CLASS_IDLE:
1368 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1370 cfq_clear_cfqq_idle_window(cfqq);
1375 * keep track of original prio settings in case we have to temporarily
1376 * elevate the priority of this queue
1378 cfqq->org_ioprio = cfqq->ioprio;
1379 cfqq->org_ioprio_class = cfqq->ioprio_class;
1381 if (cfq_cfqq_on_rr(cfqq))
1382 cfq_resort_rr_list(cfqq, 0);
1384 cfq_clear_cfqq_prio_changed(cfqq);
1387 static inline void changed_ioprio(struct cfq_io_context *cic)
1389 struct cfq_data *cfqd = cic->key;
1390 struct cfq_queue *cfqq;
1392 spin_lock(cfqd->queue->queue_lock);
1393 cfqq = cic->cfqq[ASYNC];
1395 struct cfq_queue *new_cfqq;
1396 new_cfqq = cfq_get_queue(cfqd, CFQ_KEY_ASYNC,
1397 cic->ioc->task, GFP_ATOMIC);
1399 cic->cfqq[ASYNC] = new_cfqq;
1400 cfq_put_queue(cfqq);
1403 cfqq = cic->cfqq[SYNC];
1405 cfq_mark_cfqq_prio_changed(cfqq);
1406 cfq_init_prio_data(cfqq);
1408 spin_unlock(cfqd->queue->queue_lock);
1413 * callback from sys_ioprio_set, irqs are disabled
1415 static int cfq_ioc_set_ioprio(struct io_context *ioc, unsigned int ioprio)
1417 struct cfq_io_context *cic;
1420 spin_lock(&cfq_exit_lock);
1422 n = rb_first(&ioc->cic_root);
1424 cic = rb_entry(n, struct cfq_io_context, rb_node);
1426 changed_ioprio(cic);
1430 spin_unlock(&cfq_exit_lock);
1435 static struct cfq_queue *
1436 cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk,
1439 const int hashval = hash_long(key, CFQ_QHASH_SHIFT);
1440 struct cfq_queue *cfqq, *new_cfqq = NULL;
1441 unsigned short ioprio;
1444 ioprio = tsk->ioprio;
1445 cfqq = __cfq_find_cfq_hash(cfqd, key, ioprio, hashval);
1451 } else if (gfp_mask & __GFP_WAIT) {
1452 spin_unlock_irq(cfqd->queue->queue_lock);
1453 new_cfqq = kmem_cache_alloc(cfq_pool, gfp_mask);
1454 spin_lock_irq(cfqd->queue->queue_lock);
1457 cfqq = kmem_cache_alloc(cfq_pool, gfp_mask);
1462 memset(cfqq, 0, sizeof(*cfqq));
1464 INIT_HLIST_NODE(&cfqq->cfq_hash);
1465 INIT_LIST_HEAD(&cfqq->cfq_list);
1466 RB_CLEAR_ROOT(&cfqq->sort_list);
1467 INIT_LIST_HEAD(&cfqq->fifo);
1470 hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
1471 atomic_set(&cfqq->ref, 0);
1473 cfqq->service_last = 0;
1475 * set ->slice_left to allow preemption for a new process
1477 cfqq->slice_left = 2 * cfqd->cfq_slice_idle;
1479 cfq_mark_cfqq_idle_window(cfqq);
1480 cfq_mark_cfqq_prio_changed(cfqq);
1481 cfq_init_prio_data(cfqq);
1485 kmem_cache_free(cfq_pool, new_cfqq);
1487 atomic_inc(&cfqq->ref);
1489 WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
1494 cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)
1496 spin_lock(&cfq_exit_lock);
1497 rb_erase(&cic->rb_node, &ioc->cic_root);
1498 list_del_init(&cic->queue_list);
1499 spin_unlock(&cfq_exit_lock);
1500 kmem_cache_free(cfq_ioc_pool, cic);
1501 atomic_dec(&ioc_count);
1504 static struct cfq_io_context *
1505 cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)
1508 struct cfq_io_context *cic;
1509 void *k, *key = cfqd;
1512 n = ioc->cic_root.rb_node;
1514 cic = rb_entry(n, struct cfq_io_context, rb_node);
1515 /* ->key must be copied to avoid race with cfq_exit_queue() */
1518 cfq_drop_dead_cic(ioc, cic);
1534 cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
1535 struct cfq_io_context *cic)
1538 struct rb_node *parent;
1539 struct cfq_io_context *__cic;
1545 ioc->set_ioprio = cfq_ioc_set_ioprio;
1548 p = &ioc->cic_root.rb_node;
1551 __cic = rb_entry(parent, struct cfq_io_context, rb_node);
1552 /* ->key must be copied to avoid race with cfq_exit_queue() */
1555 cfq_drop_dead_cic(ioc, cic);
1561 else if (cic->key > k)
1562 p = &(*p)->rb_right;
1567 spin_lock(&cfq_exit_lock);
1568 rb_link_node(&cic->rb_node, parent, p);
1569 rb_insert_color(&cic->rb_node, &ioc->cic_root);
1570 list_add(&cic->queue_list, &cfqd->cic_list);
1571 spin_unlock(&cfq_exit_lock);
1575 * Setup general io context and cfq io context. There can be several cfq
1576 * io contexts per general io context, if this process is doing io to more
1577 * than one device managed by cfq.
1579 static struct cfq_io_context *
1580 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1582 struct io_context *ioc = NULL;
1583 struct cfq_io_context *cic;
1585 might_sleep_if(gfp_mask & __GFP_WAIT);
1587 ioc = get_io_context(gfp_mask);
1591 cic = cfq_cic_rb_lookup(cfqd, ioc);
1595 cic = cfq_alloc_io_context(cfqd, gfp_mask);
1599 cfq_cic_link(cfqd, ioc, cic);
1603 put_io_context(ioc);
1608 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1610 unsigned long elapsed, ttime;
1613 * if this context already has stuff queued, thinktime is from
1614 * last queue not last end
1617 if (time_after(cic->last_end_request, cic->last_queue))
1618 elapsed = jiffies - cic->last_end_request;
1620 elapsed = jiffies - cic->last_queue;
1622 elapsed = jiffies - cic->last_end_request;
1625 ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
1627 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1628 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1629 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1633 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
1639 if (cic->last_request_pos < crq->request->sector)
1640 sdist = crq->request->sector - cic->last_request_pos;
1642 sdist = cic->last_request_pos - crq->request->sector;
1645 * Don't allow the seek distance to get too large from the
1646 * odd fragment, pagein, etc
1648 if (cic->seek_samples <= 60) /* second&third seek */
1649 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024);
1651 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64);
1653 cic->seek_samples = (7*cic->seek_samples + 256) / 8;
1654 cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
1655 total = cic->seek_total + (cic->seek_samples/2);
1656 do_div(total, cic->seek_samples);
1657 cic->seek_mean = (sector_t)total;
1661 * Disable idle window if the process thinks too long or seeks so much that
1665 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1666 struct cfq_io_context *cic)
1668 int enable_idle = cfq_cfqq_idle_window(cfqq);
1670 if (!cic->ioc->task || !cfqd->cfq_slice_idle || cfqd->hw_tag)
1672 else if (sample_valid(cic->ttime_samples)) {
1673 if (cic->ttime_mean > cfqd->cfq_slice_idle)
1680 cfq_mark_cfqq_idle_window(cfqq);
1682 cfq_clear_cfqq_idle_window(cfqq);
1687 * Check if new_cfqq should preempt the currently active queue. Return 0 for
1688 * no or if we aren't sure, a 1 will cause a preempt.
1691 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1694 struct cfq_queue *cfqq = cfqd->active_queue;
1696 if (cfq_class_idle(new_cfqq))
1702 if (cfq_class_idle(cfqq))
1704 if (!cfq_cfqq_wait_request(new_cfqq))
1707 * if it doesn't have slice left, forget it
1709 if (new_cfqq->slice_left < cfqd->cfq_slice_idle)
1711 if (cfq_crq_is_sync(crq) && !cfq_cfqq_sync(cfqq))
1718 * cfqq preempts the active queue. if we allowed preempt with no slice left,
1719 * let it have half of its nominal slice.
1721 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1723 struct cfq_queue *__cfqq, *next;
1725 list_for_each_entry_safe(__cfqq, next, &cfqd->cur_rr, cfq_list)
1726 cfq_resort_rr_list(__cfqq, 1);
1728 if (!cfqq->slice_left)
1729 cfqq->slice_left = cfq_prio_to_slice(cfqd, cfqq) / 2;
1731 cfqq->slice_end = cfqq->slice_left + jiffies;
1732 __cfq_slice_expired(cfqd, cfqq, 1);
1733 __cfq_set_active_queue(cfqd, cfqq);
1737 * should really be a ll_rw_blk.c helper
1739 static void cfq_start_queueing(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1741 request_queue_t *q = cfqd->queue;
1743 if (!blk_queue_plugged(q))
1746 __generic_unplug_device(q);
1750 * Called when a new fs request (crq) is added (to cfqq). Check if there's
1751 * something we should do about it
1754 cfq_crq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1757 struct cfq_io_context *cic;
1759 cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
1761 cic = crq->io_context;
1764 * we never wait for an async request and we don't allow preemption
1765 * of an async request. so just return early
1767 if (!cfq_crq_is_sync(crq)) {
1769 * sync process issued an async request, if it's waiting
1770 * then expire it and kick rq handling.
1772 if (cic == cfqd->active_cic &&
1773 del_timer(&cfqd->idle_slice_timer)) {
1774 cfq_slice_expired(cfqd, 0);
1775 cfq_start_queueing(cfqd, cfqq);
1780 cfq_update_io_thinktime(cfqd, cic);
1781 cfq_update_io_seektime(cfqd, cic, crq);
1782 cfq_update_idle_window(cfqd, cfqq, cic);
1784 cic->last_queue = jiffies;
1785 cic->last_request_pos = crq->request->sector + crq->request->nr_sectors;
1787 if (cfqq == cfqd->active_queue) {
1789 * if we are waiting for a request for this queue, let it rip
1790 * immediately and flag that we must not expire this queue
1793 if (cfq_cfqq_wait_request(cfqq)) {
1794 cfq_mark_cfqq_must_dispatch(cfqq);
1795 del_timer(&cfqd->idle_slice_timer);
1796 cfq_start_queueing(cfqd, cfqq);
1798 } else if (cfq_should_preempt(cfqd, cfqq, crq)) {
1800 * not the active queue - expire current slice if it is
1801 * idle and has expired it's mean thinktime or this new queue
1802 * has some old slice time left and is of higher priority
1804 cfq_preempt_queue(cfqd, cfqq);
1805 cfq_mark_cfqq_must_dispatch(cfqq);
1806 cfq_start_queueing(cfqd, cfqq);
1810 static void cfq_insert_request(request_queue_t *q, struct request *rq)
1812 struct cfq_data *cfqd = q->elevator->elevator_data;
1813 struct cfq_rq *crq = RQ_DATA(rq);
1814 struct cfq_queue *cfqq = crq->cfq_queue;
1816 cfq_init_prio_data(cfqq);
1818 cfq_add_crq_rb(crq);
1820 list_add_tail(&rq->queuelist, &cfqq->fifo);
1822 if (rq_mergeable(rq))
1823 cfq_add_crq_hash(cfqd, crq);
1825 cfq_crq_enqueued(cfqd, cfqq, crq);
1828 static void cfq_completed_request(request_queue_t *q, struct request *rq)
1830 struct cfq_rq *crq = RQ_DATA(rq);
1831 struct cfq_queue *cfqq = crq->cfq_queue;
1832 struct cfq_data *cfqd = cfqq->cfqd;
1833 const int sync = cfq_crq_is_sync(crq);
1838 WARN_ON(!cfqd->rq_in_driver);
1839 WARN_ON(!cfqq->on_dispatch[sync]);
1840 cfqd->rq_in_driver--;
1841 cfqq->on_dispatch[sync]--;
1843 if (!cfq_class_idle(cfqq))
1844 cfqd->last_end_request = now;
1846 if (!cfq_cfqq_dispatched(cfqq)) {
1847 if (cfq_cfqq_on_rr(cfqq)) {
1848 cfqq->service_last = now;
1849 cfq_resort_rr_list(cfqq, 0);
1851 cfq_schedule_dispatch(cfqd);
1854 if (cfq_crq_is_sync(crq))
1855 crq->io_context->last_end_request = now;
1858 static struct request *
1859 cfq_former_request(request_queue_t *q, struct request *rq)
1861 struct cfq_rq *crq = RQ_DATA(rq);
1862 struct rb_node *rbprev = rb_prev(&crq->rb_node);
1865 return rb_entry_crq(rbprev)->request;
1870 static struct request *
1871 cfq_latter_request(request_queue_t *q, struct request *rq)
1873 struct cfq_rq *crq = RQ_DATA(rq);
1874 struct rb_node *rbnext = rb_next(&crq->rb_node);
1877 return rb_entry_crq(rbnext)->request;
1883 * we temporarily boost lower priority queues if they are holding fs exclusive
1884 * resources. they are boosted to normal prio (CLASS_BE/4)
1886 static void cfq_prio_boost(struct cfq_queue *cfqq)
1888 const int ioprio_class = cfqq->ioprio_class;
1889 const int ioprio = cfqq->ioprio;
1891 if (has_fs_excl()) {
1893 * boost idle prio on transactions that would lock out other
1894 * users of the filesystem
1896 if (cfq_class_idle(cfqq))
1897 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1898 if (cfqq->ioprio > IOPRIO_NORM)
1899 cfqq->ioprio = IOPRIO_NORM;
1902 * check if we need to unboost the queue
1904 if (cfqq->ioprio_class != cfqq->org_ioprio_class)
1905 cfqq->ioprio_class = cfqq->org_ioprio_class;
1906 if (cfqq->ioprio != cfqq->org_ioprio)
1907 cfqq->ioprio = cfqq->org_ioprio;
1911 * refile between round-robin lists if we moved the priority class
1913 if ((ioprio_class != cfqq->ioprio_class || ioprio != cfqq->ioprio) &&
1914 cfq_cfqq_on_rr(cfqq))
1915 cfq_resort_rr_list(cfqq, 0);
1919 __cfq_may_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1920 struct task_struct *task, int rw)
1923 if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
1924 !cfq_cfqq_must_alloc_slice(cfqq)) {
1925 cfq_mark_cfqq_must_alloc_slice(cfqq);
1926 return ELV_MQUEUE_MUST;
1929 return ELV_MQUEUE_MAY;
1931 if (!cfqq || task->flags & PF_MEMALLOC)
1932 return ELV_MQUEUE_MAY;
1933 if (!cfqq->allocated[rw] || cfq_cfqq_must_alloc(cfqq)) {
1934 if (cfq_cfqq_wait_request(cfqq))
1935 return ELV_MQUEUE_MUST;
1938 * only allow 1 ELV_MQUEUE_MUST per slice, otherwise we
1939 * can quickly flood the queue with writes from a single task
1941 if (rw == READ || !cfq_cfqq_must_alloc_slice(cfqq)) {
1942 cfq_mark_cfqq_must_alloc_slice(cfqq);
1943 return ELV_MQUEUE_MUST;
1946 return ELV_MQUEUE_MAY;
1948 if (cfq_class_idle(cfqq))
1949 return ELV_MQUEUE_NO;
1950 if (cfqq->allocated[rw] >= cfqd->max_queued) {
1951 struct io_context *ioc = get_io_context(GFP_ATOMIC);
1952 int ret = ELV_MQUEUE_NO;
1954 if (ioc && ioc->nr_batch_requests)
1955 ret = ELV_MQUEUE_MAY;
1957 put_io_context(ioc);
1961 return ELV_MQUEUE_MAY;
1965 static int cfq_may_queue(request_queue_t *q, int rw, struct bio *bio)
1967 struct cfq_data *cfqd = q->elevator->elevator_data;
1968 struct task_struct *tsk = current;
1969 struct cfq_queue *cfqq;
1972 * don't force setup of a queue from here, as a call to may_queue
1973 * does not necessarily imply that a request actually will be queued.
1974 * so just lookup a possibly existing queue, or return 'may queue'
1977 cfqq = cfq_find_cfq_hash(cfqd, cfq_queue_pid(tsk, rw), tsk->ioprio);
1979 cfq_init_prio_data(cfqq);
1980 cfq_prio_boost(cfqq);
1982 return __cfq_may_queue(cfqd, cfqq, tsk, rw);
1985 return ELV_MQUEUE_MAY;
1988 static void cfq_check_waiters(request_queue_t *q, struct cfq_queue *cfqq)
1990 struct cfq_data *cfqd = q->elevator->elevator_data;
1991 struct request_list *rl = &q->rq;
1993 if (cfqq->allocated[READ] <= cfqd->max_queued || cfqd->rq_starved) {
1995 if (waitqueue_active(&rl->wait[READ]))
1996 wake_up(&rl->wait[READ]);
1999 if (cfqq->allocated[WRITE] <= cfqd->max_queued || cfqd->rq_starved) {
2001 if (waitqueue_active(&rl->wait[WRITE]))
2002 wake_up(&rl->wait[WRITE]);
2007 * queue lock held here
2009 static void cfq_put_request(request_queue_t *q, struct request *rq)
2011 struct cfq_data *cfqd = q->elevator->elevator_data;
2012 struct cfq_rq *crq = RQ_DATA(rq);
2015 struct cfq_queue *cfqq = crq->cfq_queue;
2016 const int rw = rq_data_dir(rq);
2018 BUG_ON(!cfqq->allocated[rw]);
2019 cfqq->allocated[rw]--;
2021 put_io_context(crq->io_context->ioc);
2023 mempool_free(crq, cfqd->crq_pool);
2024 rq->elevator_private = NULL;
2026 cfq_check_waiters(q, cfqq);
2027 cfq_put_queue(cfqq);
2032 * Allocate cfq data structures associated with this request.
2035 cfq_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
2038 struct cfq_data *cfqd = q->elevator->elevator_data;
2039 struct task_struct *tsk = current;
2040 struct cfq_io_context *cic;
2041 const int rw = rq_data_dir(rq);
2042 pid_t key = cfq_queue_pid(tsk, rw);
2043 struct cfq_queue *cfqq;
2045 unsigned long flags;
2046 int is_sync = key != CFQ_KEY_ASYNC;
2048 might_sleep_if(gfp_mask & __GFP_WAIT);
2050 cic = cfq_get_io_context(cfqd, gfp_mask);
2052 spin_lock_irqsave(q->queue_lock, flags);
2057 if (!cic->cfqq[is_sync]) {
2058 cfqq = cfq_get_queue(cfqd, key, tsk, gfp_mask);
2062 cic->cfqq[is_sync] = cfqq;
2064 cfqq = cic->cfqq[is_sync];
2066 cfqq->allocated[rw]++;
2067 cfq_clear_cfqq_must_alloc(cfqq);
2068 cfqd->rq_starved = 0;
2069 atomic_inc(&cfqq->ref);
2070 spin_unlock_irqrestore(q->queue_lock, flags);
2072 crq = mempool_alloc(cfqd->crq_pool, gfp_mask);
2074 RB_CLEAR(&crq->rb_node);
2077 INIT_HLIST_NODE(&crq->hash);
2078 crq->cfq_queue = cfqq;
2079 crq->io_context = cic;
2082 cfq_mark_crq_is_sync(crq);
2084 cfq_clear_crq_is_sync(crq);
2086 rq->elevator_private = crq;
2090 spin_lock_irqsave(q->queue_lock, flags);
2091 cfqq->allocated[rw]--;
2092 if (!(cfqq->allocated[0] + cfqq->allocated[1]))
2093 cfq_mark_cfqq_must_alloc(cfqq);
2094 cfq_put_queue(cfqq);
2097 put_io_context(cic->ioc);
2099 * mark us rq allocation starved. we need to kickstart the process
2100 * ourselves if there are no pending requests that can do it for us.
2101 * that would be an extremely rare OOM situation
2103 cfqd->rq_starved = 1;
2104 cfq_schedule_dispatch(cfqd);
2105 spin_unlock_irqrestore(q->queue_lock, flags);
2109 static void cfq_kick_queue(void *data)
2111 request_queue_t *q = data;
2112 struct cfq_data *cfqd = q->elevator->elevator_data;
2113 unsigned long flags;
2115 spin_lock_irqsave(q->queue_lock, flags);
2117 if (cfqd->rq_starved) {
2118 struct request_list *rl = &q->rq;
2121 * we aren't guaranteed to get a request after this, but we
2122 * have to be opportunistic
2125 if (waitqueue_active(&rl->wait[READ]))
2126 wake_up(&rl->wait[READ]);
2127 if (waitqueue_active(&rl->wait[WRITE]))
2128 wake_up(&rl->wait[WRITE]);
2133 spin_unlock_irqrestore(q->queue_lock, flags);
2137 * Timer running if the active_queue is currently idling inside its time slice
2139 static void cfq_idle_slice_timer(unsigned long data)
2141 struct cfq_data *cfqd = (struct cfq_data *) data;
2142 struct cfq_queue *cfqq;
2143 unsigned long flags;
2145 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2147 if ((cfqq = cfqd->active_queue) != NULL) {
2148 unsigned long now = jiffies;
2153 if (time_after(now, cfqq->slice_end))
2157 * only expire and reinvoke request handler, if there are
2158 * other queues with pending requests
2160 if (!cfqd->busy_queues) {
2161 cfqd->idle_slice_timer.expires = min(now + cfqd->cfq_slice_idle, cfqq->slice_end);
2162 add_timer(&cfqd->idle_slice_timer);
2167 * not expired and it has a request pending, let it dispatch
2169 if (!RB_EMPTY(&cfqq->sort_list)) {
2170 cfq_mark_cfqq_must_dispatch(cfqq);
2175 cfq_slice_expired(cfqd, 0);
2177 cfq_schedule_dispatch(cfqd);
2179 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2183 * Timer running if an idle class queue is waiting for service
2185 static void cfq_idle_class_timer(unsigned long data)
2187 struct cfq_data *cfqd = (struct cfq_data *) data;
2188 unsigned long flags, end;
2190 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2193 * race with a non-idle queue, reset timer
2195 end = cfqd->last_end_request + CFQ_IDLE_GRACE;
2196 if (!time_after_eq(jiffies, end)) {
2197 cfqd->idle_class_timer.expires = end;
2198 add_timer(&cfqd->idle_class_timer);
2200 cfq_schedule_dispatch(cfqd);
2202 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2205 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
2207 del_timer_sync(&cfqd->idle_slice_timer);
2208 del_timer_sync(&cfqd->idle_class_timer);
2209 blk_sync_queue(cfqd->queue);
2212 static void cfq_exit_queue(elevator_t *e)
2214 struct cfq_data *cfqd = e->elevator_data;
2215 request_queue_t *q = cfqd->queue;
2217 cfq_shutdown_timer_wq(cfqd);
2219 spin_lock(&cfq_exit_lock);
2220 spin_lock_irq(q->queue_lock);
2222 if (cfqd->active_queue)
2223 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
2225 while (!list_empty(&cfqd->cic_list)) {
2226 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2227 struct cfq_io_context,
2229 if (cic->cfqq[ASYNC]) {
2230 cfq_put_queue(cic->cfqq[ASYNC]);
2231 cic->cfqq[ASYNC] = NULL;
2233 if (cic->cfqq[SYNC]) {
2234 cfq_put_queue(cic->cfqq[SYNC]);
2235 cic->cfqq[SYNC] = NULL;
2238 list_del_init(&cic->queue_list);
2241 spin_unlock_irq(q->queue_lock);
2242 spin_unlock(&cfq_exit_lock);
2244 cfq_shutdown_timer_wq(cfqd);
2246 mempool_destroy(cfqd->crq_pool);
2247 kfree(cfqd->crq_hash);
2248 kfree(cfqd->cfq_hash);
2252 static int cfq_init_queue(request_queue_t *q, elevator_t *e)
2254 struct cfq_data *cfqd;
2257 cfqd = kmalloc(sizeof(*cfqd), GFP_KERNEL);
2261 memset(cfqd, 0, sizeof(*cfqd));
2263 for (i = 0; i < CFQ_PRIO_LISTS; i++)
2264 INIT_LIST_HEAD(&cfqd->rr_list[i]);
2266 INIT_LIST_HEAD(&cfqd->busy_rr);
2267 INIT_LIST_HEAD(&cfqd->cur_rr);
2268 INIT_LIST_HEAD(&cfqd->idle_rr);
2269 INIT_LIST_HEAD(&cfqd->empty_list);
2270 INIT_LIST_HEAD(&cfqd->cic_list);
2272 cfqd->crq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_MHASH_ENTRIES, GFP_KERNEL);
2273 if (!cfqd->crq_hash)
2276 cfqd->cfq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL);
2277 if (!cfqd->cfq_hash)
2280 cfqd->crq_pool = mempool_create_slab_pool(BLKDEV_MIN_RQ, crq_pool);
2281 if (!cfqd->crq_pool)
2284 for (i = 0; i < CFQ_MHASH_ENTRIES; i++)
2285 INIT_HLIST_HEAD(&cfqd->crq_hash[i]);
2286 for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
2287 INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);
2289 e->elevator_data = cfqd;
2293 cfqd->max_queued = q->nr_requests / 4;
2294 q->nr_batching = cfq_queued;
2296 init_timer(&cfqd->idle_slice_timer);
2297 cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2298 cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2300 init_timer(&cfqd->idle_class_timer);
2301 cfqd->idle_class_timer.function = cfq_idle_class_timer;
2302 cfqd->idle_class_timer.data = (unsigned long) cfqd;
2304 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue, q);
2306 cfqd->cfq_queued = cfq_queued;
2307 cfqd->cfq_quantum = cfq_quantum;
2308 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2309 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2310 cfqd->cfq_back_max = cfq_back_max;
2311 cfqd->cfq_back_penalty = cfq_back_penalty;
2312 cfqd->cfq_slice[0] = cfq_slice_async;
2313 cfqd->cfq_slice[1] = cfq_slice_sync;
2314 cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2315 cfqd->cfq_slice_idle = cfq_slice_idle;
2319 kfree(cfqd->cfq_hash);
2321 kfree(cfqd->crq_hash);
2327 static void cfq_slab_kill(void)
2330 kmem_cache_destroy(crq_pool);
2332 kmem_cache_destroy(cfq_pool);
2334 kmem_cache_destroy(cfq_ioc_pool);
2337 static int __init cfq_slab_setup(void)
2339 crq_pool = kmem_cache_create("crq_pool", sizeof(struct cfq_rq), 0, 0,
2344 cfq_pool = kmem_cache_create("cfq_pool", sizeof(struct cfq_queue), 0, 0,
2349 cfq_ioc_pool = kmem_cache_create("cfq_ioc_pool",
2350 sizeof(struct cfq_io_context), 0, 0, NULL, NULL);
2361 * sysfs parts below -->
2365 cfq_var_show(unsigned int var, char *page)
2367 return sprintf(page, "%d\n", var);
2371 cfq_var_store(unsigned int *var, const char *page, size_t count)
2373 char *p = (char *) page;
2375 *var = simple_strtoul(p, &p, 10);
2379 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
2380 static ssize_t __FUNC(elevator_t *e, char *page) \
2382 struct cfq_data *cfqd = e->elevator_data; \
2383 unsigned int __data = __VAR; \
2385 __data = jiffies_to_msecs(__data); \
2386 return cfq_var_show(__data, (page)); \
2388 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
2389 SHOW_FUNCTION(cfq_queued_show, cfqd->cfq_queued, 0);
2390 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2391 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
2392 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
2393 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
2394 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2395 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2396 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2397 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
2398 #undef SHOW_FUNCTION
2400 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
2401 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
2403 struct cfq_data *cfqd = e->elevator_data; \
2404 unsigned int __data; \
2405 int ret = cfq_var_store(&__data, (page), count); \
2406 if (__data < (MIN)) \
2408 else if (__data > (MAX)) \
2411 *(__PTR) = msecs_to_jiffies(__data); \
2413 *(__PTR) = __data; \
2416 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
2417 STORE_FUNCTION(cfq_queued_store, &cfqd->cfq_queued, 1, UINT_MAX, 0);
2418 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1);
2419 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1);
2420 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
2421 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0);
2422 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2423 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2424 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
2425 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0);
2426 #undef STORE_FUNCTION
2428 #define CFQ_ATTR(name) \
2429 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2431 static struct elv_fs_entry cfq_attrs[] = {
2434 CFQ_ATTR(fifo_expire_sync),
2435 CFQ_ATTR(fifo_expire_async),
2436 CFQ_ATTR(back_seek_max),
2437 CFQ_ATTR(back_seek_penalty),
2438 CFQ_ATTR(slice_sync),
2439 CFQ_ATTR(slice_async),
2440 CFQ_ATTR(slice_async_rq),
2441 CFQ_ATTR(slice_idle),
2445 static struct elevator_type iosched_cfq = {
2447 .elevator_merge_fn = cfq_merge,
2448 .elevator_merged_fn = cfq_merged_request,
2449 .elevator_merge_req_fn = cfq_merged_requests,
2450 .elevator_dispatch_fn = cfq_dispatch_requests,
2451 .elevator_add_req_fn = cfq_insert_request,
2452 .elevator_activate_req_fn = cfq_activate_request,
2453 .elevator_deactivate_req_fn = cfq_deactivate_request,
2454 .elevator_queue_empty_fn = cfq_queue_empty,
2455 .elevator_completed_req_fn = cfq_completed_request,
2456 .elevator_former_req_fn = cfq_former_request,
2457 .elevator_latter_req_fn = cfq_latter_request,
2458 .elevator_set_req_fn = cfq_set_request,
2459 .elevator_put_req_fn = cfq_put_request,
2460 .elevator_may_queue_fn = cfq_may_queue,
2461 .elevator_init_fn = cfq_init_queue,
2462 .elevator_exit_fn = cfq_exit_queue,
2465 .elevator_attrs = cfq_attrs,
2466 .elevator_name = "cfq",
2467 .elevator_owner = THIS_MODULE,
2470 static int __init cfq_init(void)
2475 * could be 0 on HZ < 1000 setups
2477 if (!cfq_slice_async)
2478 cfq_slice_async = 1;
2479 if (!cfq_slice_idle)
2482 if (cfq_slab_setup())
2485 ret = elv_register(&iosched_cfq);
2492 static void __exit cfq_exit(void)
2494 DECLARE_COMPLETION(all_gone);
2495 elv_unregister(&iosched_cfq);
2496 ioc_gone = &all_gone;
2497 /* ioc_gone's update must be visible before reading ioc_count */
2499 if (atomic_read(&ioc_count))
2500 wait_for_completion(ioc_gone);
2505 module_init(cfq_init);
2506 module_exit(cfq_exit);
2508 MODULE_AUTHOR("Jens Axboe");
2509 MODULE_LICENSE("GPL");
2510 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");