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/hash.h>
13 #include <linux/rbtree.h>
14 #include <linux/ioprio.h>
19 static const int cfq_quantum = 4; /* max queue in one round of service */
20 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
21 static const int cfq_back_max = 16 * 1024; /* maximum backwards seek, in KiB */
22 static const int cfq_back_penalty = 2; /* penalty of a backwards seek */
24 static const int cfq_slice_sync = HZ / 10;
25 static int cfq_slice_async = HZ / 25;
26 static const int cfq_slice_async_rq = 2;
27 static int cfq_slice_idle = HZ / 125;
29 #define CFQ_IDLE_GRACE (HZ / 10)
30 #define CFQ_SLICE_SCALE (5)
32 #define CFQ_KEY_ASYNC (0)
35 * for the hash of cfqq inside the cfqd
37 #define CFQ_QHASH_SHIFT 6
38 #define CFQ_QHASH_ENTRIES (1 << CFQ_QHASH_SHIFT)
39 #define list_entry_qhash(entry) hlist_entry((entry), struct cfq_queue, cfq_hash)
41 #define list_entry_cfqq(ptr) list_entry((ptr), struct cfq_queue, cfq_list)
43 #define RQ_CIC(rq) ((struct cfq_io_context*)(rq)->elevator_private)
44 #define RQ_CFQQ(rq) ((rq)->elevator_private2)
46 static struct kmem_cache *cfq_pool;
47 static struct kmem_cache *cfq_ioc_pool;
49 static DEFINE_PER_CPU(unsigned long, ioc_count);
50 static struct completion *ioc_gone;
52 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
53 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
54 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
59 #define cfq_cfqq_dispatched(cfqq) \
60 ((cfqq)->on_dispatch[ASYNC] + (cfqq)->on_dispatch[SYNC])
62 #define cfq_cfqq_class_sync(cfqq) ((cfqq)->key != CFQ_KEY_ASYNC)
64 #define cfq_cfqq_sync(cfqq) \
65 (cfq_cfqq_class_sync(cfqq) || (cfqq)->on_dispatch[SYNC])
67 #define sample_valid(samples) ((samples) > 80)
70 * Per block device queue structure
73 request_queue_t *queue;
76 * rr list of queues with requests and the count of them
78 struct list_head rr_list[CFQ_PRIO_LISTS];
79 struct list_head busy_rr;
80 struct list_head cur_rr;
81 struct list_head idle_rr;
82 unsigned int busy_queues;
87 struct hlist_head *cfq_hash;
93 * idle window management
95 struct timer_list idle_slice_timer;
96 struct work_struct unplug_work;
98 struct cfq_queue *active_queue;
99 struct cfq_io_context *active_cic;
100 int cur_prio, cur_end_prio;
101 unsigned int dispatch_slice;
103 struct timer_list idle_class_timer;
105 sector_t last_sector;
106 unsigned long last_end_request;
109 * tunables, see top of file
111 unsigned int cfq_quantum;
112 unsigned int cfq_fifo_expire[2];
113 unsigned int cfq_back_penalty;
114 unsigned int cfq_back_max;
115 unsigned int cfq_slice[2];
116 unsigned int cfq_slice_async_rq;
117 unsigned int cfq_slice_idle;
119 struct list_head cic_list;
123 * Per process-grouping structure
126 /* reference count */
128 /* parent cfq_data */
129 struct cfq_data *cfqd;
130 /* cfqq lookup hash */
131 struct hlist_node cfq_hash;
134 /* member of the rr/busy/cur/idle cfqd list */
135 struct list_head cfq_list;
136 /* sorted list of pending requests */
137 struct rb_root sort_list;
138 /* if fifo isn't expired, next request to serve */
139 struct request *next_rq;
140 /* requests queued in sort_list */
142 /* currently allocated requests */
144 /* pending metadata requests */
146 /* fifo list of requests in sort_list */
147 struct list_head fifo;
149 unsigned long slice_start;
150 unsigned long slice_end;
151 unsigned long slice_left;
153 /* number of requests that are on the dispatch list */
156 /* io prio of this group */
157 unsigned short ioprio, org_ioprio;
158 unsigned short ioprio_class, org_ioprio_class;
160 /* various state flags, see below */
164 enum cfqq_state_flags {
165 CFQ_CFQQ_FLAG_on_rr = 0,
166 CFQ_CFQQ_FLAG_wait_request,
167 CFQ_CFQQ_FLAG_must_alloc,
168 CFQ_CFQQ_FLAG_must_alloc_slice,
169 CFQ_CFQQ_FLAG_must_dispatch,
170 CFQ_CFQQ_FLAG_fifo_expire,
171 CFQ_CFQQ_FLAG_idle_window,
172 CFQ_CFQQ_FLAG_prio_changed,
173 CFQ_CFQQ_FLAG_queue_new,
176 #define CFQ_CFQQ_FNS(name) \
177 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
179 cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
181 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
183 cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
185 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
187 return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
191 CFQ_CFQQ_FNS(wait_request);
192 CFQ_CFQQ_FNS(must_alloc);
193 CFQ_CFQQ_FNS(must_alloc_slice);
194 CFQ_CFQQ_FNS(must_dispatch);
195 CFQ_CFQQ_FNS(fifo_expire);
196 CFQ_CFQQ_FNS(idle_window);
197 CFQ_CFQQ_FNS(prio_changed);
198 CFQ_CFQQ_FNS(queue_new);
201 static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsigned short);
202 static void cfq_dispatch_insert(request_queue_t *, struct request *);
203 static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask);
206 * scheduler run of queue, if there are requests pending and no one in the
207 * driver that will restart queueing
209 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
211 if (cfqd->busy_queues)
212 kblockd_schedule_work(&cfqd->unplug_work);
215 static int cfq_queue_empty(request_queue_t *q)
217 struct cfq_data *cfqd = q->elevator->elevator_data;
219 return !cfqd->busy_queues;
222 static inline pid_t cfq_queue_pid(struct task_struct *task, int rw, int is_sync)
225 return task->xid + (1 << 16);
227 * Use the per-process queue, for read requests and syncronous writes
229 if (!(rw & REQ_RW) || is_sync)
232 return CFQ_KEY_ASYNC;
236 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
237 * We choose the request that is closest to the head right now. Distance
238 * behind the head is penalized and only allowed to a certain extent.
240 static struct request *
241 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2)
243 sector_t last, s1, s2, d1 = 0, d2 = 0;
244 unsigned long back_max;
245 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
246 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
247 unsigned wrap = 0; /* bit mask: requests behind the disk head? */
249 if (rq1 == NULL || rq1 == rq2)
254 if (rq_is_sync(rq1) && !rq_is_sync(rq2))
256 else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
258 if (rq_is_meta(rq1) && !rq_is_meta(rq2))
260 else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
266 last = cfqd->last_sector;
269 * by definition, 1KiB is 2 sectors
271 back_max = cfqd->cfq_back_max * 2;
274 * Strict one way elevator _except_ in the case where we allow
275 * short backward seeks which are biased as twice the cost of a
276 * similar forward seek.
280 else if (s1 + back_max >= last)
281 d1 = (last - s1) * cfqd->cfq_back_penalty;
283 wrap |= CFQ_RQ1_WRAP;
287 else if (s2 + back_max >= last)
288 d2 = (last - s2) * cfqd->cfq_back_penalty;
290 wrap |= CFQ_RQ2_WRAP;
292 /* Found required data */
295 * By doing switch() on the bit mask "wrap" we avoid having to
296 * check two variables for all permutations: --> faster!
299 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
315 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
318 * Since both rqs are wrapped,
319 * start with the one that's further behind head
320 * (--> only *one* back seek required),
321 * since back seek takes more time than forward.
331 * would be nice to take fifo expire time into account as well
333 static struct request *
334 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
335 struct request *last)
337 struct rb_node *rbnext = rb_next(&last->rb_node);
338 struct rb_node *rbprev = rb_prev(&last->rb_node);
339 struct request *next = NULL, *prev = NULL;
341 BUG_ON(RB_EMPTY_NODE(&last->rb_node));
344 prev = rb_entry_rq(rbprev);
347 next = rb_entry_rq(rbnext);
349 rbnext = rb_first(&cfqq->sort_list);
350 if (rbnext && rbnext != &last->rb_node)
351 next = rb_entry_rq(rbnext);
354 return cfq_choose_req(cfqd, next, prev);
357 static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
359 struct cfq_data *cfqd = cfqq->cfqd;
360 struct list_head *list;
362 BUG_ON(!cfq_cfqq_on_rr(cfqq));
364 list_del(&cfqq->cfq_list);
366 if (cfq_class_rt(cfqq))
367 list = &cfqd->cur_rr;
368 else if (cfq_class_idle(cfqq))
369 list = &cfqd->idle_rr;
372 * if cfqq has requests in flight, don't allow it to be
373 * found in cfq_set_active_queue before it has finished them.
374 * this is done to increase fairness between a process that
375 * has lots of io pending vs one that only generates one
376 * sporadically or synchronously
378 if (cfq_cfqq_dispatched(cfqq))
379 list = &cfqd->busy_rr;
381 list = &cfqd->rr_list[cfqq->ioprio];
385 * If this queue was preempted or is new (never been serviced), let
386 * it be added first for fairness but beind other new queues.
387 * Otherwise, just add to the back of the list.
389 if (preempted || cfq_cfqq_queue_new(cfqq)) {
390 struct list_head *n = list;
391 struct cfq_queue *__cfqq;
393 while (n->next != list) {
394 __cfqq = list_entry_cfqq(n->next);
395 if (!cfq_cfqq_queue_new(__cfqq))
404 list_add_tail(&cfqq->cfq_list, list);
408 * add to busy list of queues for service, trying to be fair in ordering
409 * the pending list according to last request service
412 cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
414 BUG_ON(cfq_cfqq_on_rr(cfqq));
415 cfq_mark_cfqq_on_rr(cfqq);
418 cfq_resort_rr_list(cfqq, 0);
422 cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
424 BUG_ON(!cfq_cfqq_on_rr(cfqq));
425 cfq_clear_cfqq_on_rr(cfqq);
426 list_del_init(&cfqq->cfq_list);
428 BUG_ON(!cfqd->busy_queues);
433 * rb tree support functions
435 static inline void cfq_del_rq_rb(struct request *rq)
437 struct cfq_queue *cfqq = RQ_CFQQ(rq);
438 struct cfq_data *cfqd = cfqq->cfqd;
439 const int sync = rq_is_sync(rq);
441 BUG_ON(!cfqq->queued[sync]);
442 cfqq->queued[sync]--;
444 elv_rb_del(&cfqq->sort_list, rq);
446 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
447 cfq_del_cfqq_rr(cfqd, cfqq);
450 static void cfq_add_rq_rb(struct request *rq)
452 struct cfq_queue *cfqq = RQ_CFQQ(rq);
453 struct cfq_data *cfqd = cfqq->cfqd;
454 struct request *__alias;
456 cfqq->queued[rq_is_sync(rq)]++;
459 * looks a little odd, but the first insert might return an alias.
460 * if that happens, put the alias on the dispatch list
462 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
463 cfq_dispatch_insert(cfqd->queue, __alias);
465 if (!cfq_cfqq_on_rr(cfqq))
466 cfq_add_cfqq_rr(cfqd, cfqq);
469 * check if this request is a better next-serve candidate
471 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq);
472 BUG_ON(!cfqq->next_rq);
476 cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
478 elv_rb_del(&cfqq->sort_list, rq);
479 cfqq->queued[rq_is_sync(rq)]--;
483 static struct request *
484 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
486 struct task_struct *tsk = current;
487 pid_t key = cfq_queue_pid(tsk, bio_data_dir(bio), bio_sync(bio));
488 struct cfq_queue *cfqq;
490 cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
492 sector_t sector = bio->bi_sector + bio_sectors(bio);
494 return elv_rb_find(&cfqq->sort_list, sector);
500 static void cfq_activate_request(request_queue_t *q, struct request *rq)
502 struct cfq_data *cfqd = q->elevator->elevator_data;
504 cfqd->rq_in_driver++;
507 * If the depth is larger 1, it really could be queueing. But lets
508 * make the mark a little higher - idling could still be good for
509 * low queueing, and a low queueing number could also just indicate
510 * a SCSI mid layer like behaviour where limit+1 is often seen.
512 if (!cfqd->hw_tag && cfqd->rq_in_driver > 4)
516 static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
518 struct cfq_data *cfqd = q->elevator->elevator_data;
520 WARN_ON(!cfqd->rq_in_driver);
521 cfqd->rq_in_driver--;
524 static void cfq_remove_request(struct request *rq)
526 struct cfq_queue *cfqq = RQ_CFQQ(rq);
528 if (cfqq->next_rq == rq)
529 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
531 list_del_init(&rq->queuelist);
534 if (rq_is_meta(rq)) {
535 WARN_ON(!cfqq->meta_pending);
536 cfqq->meta_pending--;
541 cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
543 struct cfq_data *cfqd = q->elevator->elevator_data;
544 struct request *__rq;
546 __rq = cfq_find_rq_fmerge(cfqd, bio);
547 if (__rq && elv_rq_merge_ok(__rq, bio)) {
549 return ELEVATOR_FRONT_MERGE;
552 return ELEVATOR_NO_MERGE;
555 static void cfq_merged_request(request_queue_t *q, struct request *req,
558 if (type == ELEVATOR_FRONT_MERGE) {
559 struct cfq_queue *cfqq = RQ_CFQQ(req);
561 cfq_reposition_rq_rb(cfqq, req);
566 cfq_merged_requests(request_queue_t *q, struct request *rq,
567 struct request *next)
570 * reposition in fifo if next is older than rq
572 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
573 time_before(next->start_time, rq->start_time))
574 list_move(&rq->queuelist, &next->queuelist);
576 cfq_remove_request(next);
579 static int cfq_allow_merge(request_queue_t *q, struct request *rq,
582 struct cfq_data *cfqd = q->elevator->elevator_data;
583 const int rw = bio_data_dir(bio);
584 struct cfq_queue *cfqq;
588 * Disallow merge of a sync bio into an async request.
590 if ((bio_data_dir(bio) == READ || bio_sync(bio)) && !rq_is_sync(rq))
594 * Lookup the cfqq that this bio will be queued with. Allow
595 * merge only if rq is queued there.
597 key = cfq_queue_pid(current, rw, bio_sync(bio));
598 cfqq = cfq_find_cfq_hash(cfqd, key, current->ioprio);
600 if (cfqq == RQ_CFQQ(rq))
607 __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
611 * stop potential idle class queues waiting service
613 del_timer(&cfqd->idle_class_timer);
615 cfqq->slice_start = jiffies;
617 cfqq->slice_left = 0;
618 cfq_clear_cfqq_must_alloc_slice(cfqq);
619 cfq_clear_cfqq_fifo_expire(cfqq);
622 cfqd->active_queue = cfqq;
626 * current cfqq expired its slice (or was too idle), select new one
629 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
632 unsigned long now = jiffies;
634 if (cfq_cfqq_wait_request(cfqq))
635 del_timer(&cfqd->idle_slice_timer);
637 if (!preempted && !cfq_cfqq_dispatched(cfqq))
638 cfq_schedule_dispatch(cfqd);
640 cfq_clear_cfqq_must_dispatch(cfqq);
641 cfq_clear_cfqq_wait_request(cfqq);
642 cfq_clear_cfqq_queue_new(cfqq);
645 * store what was left of this slice, if the queue idled out
648 if (time_after(cfqq->slice_end, now))
649 cfqq->slice_left = cfqq->slice_end - now;
651 cfqq->slice_left = 0;
653 if (cfq_cfqq_on_rr(cfqq))
654 cfq_resort_rr_list(cfqq, preempted);
656 if (cfqq == cfqd->active_queue)
657 cfqd->active_queue = NULL;
659 if (cfqd->active_cic) {
660 put_io_context(cfqd->active_cic->ioc);
661 cfqd->active_cic = NULL;
664 cfqd->dispatch_slice = 0;
667 static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted)
669 struct cfq_queue *cfqq = cfqd->active_queue;
672 __cfq_slice_expired(cfqd, cfqq, preempted);
685 static int cfq_get_next_prio_level(struct cfq_data *cfqd)
694 for (p = cfqd->cur_prio; p <= cfqd->cur_end_prio; p++) {
695 if (!list_empty(&cfqd->rr_list[p])) {
704 if (++cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
705 cfqd->cur_end_prio = 0;
712 if (unlikely(prio == -1))
715 BUG_ON(prio >= CFQ_PRIO_LISTS);
717 list_splice_init(&cfqd->rr_list[prio], &cfqd->cur_rr);
719 cfqd->cur_prio = prio + 1;
720 if (cfqd->cur_prio > cfqd->cur_end_prio) {
721 cfqd->cur_end_prio = cfqd->cur_prio;
724 if (cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
726 cfqd->cur_end_prio = 0;
732 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
734 struct cfq_queue *cfqq = NULL;
736 if (!list_empty(&cfqd->cur_rr) || cfq_get_next_prio_level(cfqd) != -1) {
738 * if current list is non-empty, grab first entry. if it is
739 * empty, get next prio level and grab first entry then if any
742 cfqq = list_entry_cfqq(cfqd->cur_rr.next);
743 } else if (!list_empty(&cfqd->busy_rr)) {
745 * If no new queues are available, check if the busy list has
746 * some before falling back to idle io.
748 cfqq = list_entry_cfqq(cfqd->busy_rr.next);
749 } else if (!list_empty(&cfqd->idle_rr)) {
751 * if we have idle queues and no rt or be queues had pending
752 * requests, either allow immediate service if the grace period
753 * has passed or arm the idle grace timer
755 unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE;
757 if (time_after_eq(jiffies, end))
758 cfqq = list_entry_cfqq(cfqd->idle_rr.next);
760 mod_timer(&cfqd->idle_class_timer, end);
763 __cfq_set_active_queue(cfqd, cfqq);
767 #define CIC_SEEKY(cic) ((cic)->seek_mean > (128 * 1024))
769 static int cfq_arm_slice_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
772 struct cfq_io_context *cic;
775 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
776 WARN_ON(cfqq != cfqd->active_queue);
779 * idle is disabled, either manually or by past process history
781 if (!cfqd->cfq_slice_idle)
783 if (!cfq_cfqq_idle_window(cfqq))
786 * task has exited, don't wait
788 cic = cfqd->active_cic;
789 if (!cic || !cic->ioc->task)
792 cfq_mark_cfqq_must_dispatch(cfqq);
793 cfq_mark_cfqq_wait_request(cfqq);
795 sl = min(cfqq->slice_end - 1, (unsigned long) cfqd->cfq_slice_idle);
798 * we don't want to idle for seeks, but we do want to allow
799 * fair distribution of slice time for a process doing back-to-back
800 * seeks. so allow a little bit of time for him to submit a new rq
802 if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
803 sl = min(sl, msecs_to_jiffies(2));
805 mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
809 static void cfq_dispatch_insert(request_queue_t *q, struct request *rq)
811 struct cfq_data *cfqd = q->elevator->elevator_data;
812 struct cfq_queue *cfqq = RQ_CFQQ(rq);
814 cfq_remove_request(rq);
815 cfqq->on_dispatch[rq_is_sync(rq)]++;
816 elv_dispatch_sort(q, rq);
818 rq = list_entry(q->queue_head.prev, struct request, queuelist);
819 cfqd->last_sector = rq->sector + rq->nr_sectors;
823 * return expired entry, or NULL to just start from scratch in rbtree
825 static inline struct request *cfq_check_fifo(struct cfq_queue *cfqq)
827 struct cfq_data *cfqd = cfqq->cfqd;
831 if (cfq_cfqq_fifo_expire(cfqq))
833 if (list_empty(&cfqq->fifo))
836 fifo = cfq_cfqq_class_sync(cfqq);
837 rq = rq_entry_fifo(cfqq->fifo.next);
839 if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) {
840 cfq_mark_cfqq_fifo_expire(cfqq);
848 * Scale schedule slice based on io priority. Use the sync time slice only
849 * if a queue is marked sync and has sync io queued. A sync queue with async
850 * io only, should not get full sync slice length.
853 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
855 const int base_slice = cfqd->cfq_slice[cfq_cfqq_sync(cfqq)];
857 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
859 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - cfqq->ioprio));
863 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
865 cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
869 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
871 const int base_rq = cfqd->cfq_slice_async_rq;
873 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
875 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
879 * get next queue for service
881 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
883 unsigned long now = jiffies;
884 struct cfq_queue *cfqq;
886 cfqq = cfqd->active_queue;
893 if (!cfq_cfqq_must_dispatch(cfqq) && time_after(now, cfqq->slice_end))
897 * if queue has requests, dispatch one. if not, check if
898 * enough slice is left to wait for one
900 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
902 else if (cfq_cfqq_dispatched(cfqq)) {
905 } else if (cfq_cfqq_class_sync(cfqq)) {
906 if (cfq_arm_slice_timer(cfqd, cfqq))
911 cfq_slice_expired(cfqd, 0);
913 cfqq = cfq_set_active_queue(cfqd);
919 __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
924 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
930 * follow expired path, else get first next available
932 if ((rq = cfq_check_fifo(cfqq)) == NULL)
936 * finally, insert request into driver dispatch list
938 cfq_dispatch_insert(cfqd->queue, rq);
940 cfqd->dispatch_slice++;
943 if (!cfqd->active_cic) {
944 atomic_inc(&RQ_CIC(rq)->ioc->refcount);
945 cfqd->active_cic = RQ_CIC(rq);
948 if (RB_EMPTY_ROOT(&cfqq->sort_list))
951 } while (dispatched < max_dispatch);
954 * if slice end isn't set yet, set it.
956 if (!cfqq->slice_end)
957 cfq_set_prio_slice(cfqd, cfqq);
960 * expire an async queue immediately if it has used up its slice. idle
961 * queue always expire after 1 dispatch round.
963 if ((!cfq_cfqq_sync(cfqq) &&
964 cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
965 cfq_class_idle(cfqq) ||
966 !cfq_cfqq_idle_window(cfqq))
967 cfq_slice_expired(cfqd, 0);
973 cfq_forced_dispatch_cfqqs(struct list_head *list)
975 struct cfq_queue *cfqq, *next;
979 list_for_each_entry_safe(cfqq, next, list, cfq_list) {
980 while (cfqq->next_rq) {
981 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
984 BUG_ON(!list_empty(&cfqq->fifo));
991 cfq_forced_dispatch(struct cfq_data *cfqd)
993 int i, dispatched = 0;
995 for (i = 0; i < CFQ_PRIO_LISTS; i++)
996 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->rr_list[i]);
998 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->busy_rr);
999 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr);
1000 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->idle_rr);
1002 cfq_slice_expired(cfqd, 0);
1004 BUG_ON(cfqd->busy_queues);
1010 cfq_dispatch_requests(request_queue_t *q, int force)
1012 struct cfq_data *cfqd = q->elevator->elevator_data;
1013 struct cfq_queue *cfqq, *prev_cfqq;
1016 if (!cfqd->busy_queues)
1019 if (unlikely(force))
1020 return cfq_forced_dispatch(cfqd);
1024 while ((cfqq = cfq_select_queue(cfqd)) != NULL) {
1028 * Don't repeat dispatch from the previous queue.
1030 if (prev_cfqq == cfqq)
1033 cfq_clear_cfqq_must_dispatch(cfqq);
1034 cfq_clear_cfqq_wait_request(cfqq);
1035 del_timer(&cfqd->idle_slice_timer);
1037 max_dispatch = cfqd->cfq_quantum;
1038 if (cfq_class_idle(cfqq))
1041 dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
1044 * If the dispatch cfqq has idling enabled and is still
1045 * the active queue, break out.
1047 if (cfq_cfqq_idle_window(cfqq) && cfqd->active_queue)
1057 * task holds one reference to the queue, dropped when task exits. each rq
1058 * in-flight on this queue also holds a reference, dropped when rq is freed.
1060 * queue lock must be held here.
1062 static void cfq_put_queue(struct cfq_queue *cfqq)
1064 struct cfq_data *cfqd = cfqq->cfqd;
1066 BUG_ON(atomic_read(&cfqq->ref) <= 0);
1068 if (!atomic_dec_and_test(&cfqq->ref))
1071 BUG_ON(rb_first(&cfqq->sort_list));
1072 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1073 BUG_ON(cfq_cfqq_on_rr(cfqq));
1075 if (unlikely(cfqd->active_queue == cfqq))
1076 __cfq_slice_expired(cfqd, cfqq, 0);
1079 * it's on the empty list and still hashed
1081 list_del(&cfqq->cfq_list);
1082 hlist_del(&cfqq->cfq_hash);
1083 kmem_cache_free(cfq_pool, cfqq);
1086 static struct cfq_queue *
1087 __cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned int prio,
1090 struct hlist_head *hash_list = &cfqd->cfq_hash[hashval];
1091 struct hlist_node *entry;
1092 struct cfq_queue *__cfqq;
1094 hlist_for_each_entry(__cfqq, entry, hash_list, cfq_hash) {
1095 const unsigned short __p = IOPRIO_PRIO_VALUE(__cfqq->org_ioprio_class, __cfqq->org_ioprio);
1097 if (__cfqq->key == key && (__p == prio || !prio))
1104 static struct cfq_queue *
1105 cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned short prio)
1107 return __cfq_find_cfq_hash(cfqd, key, prio, hash_long(key, CFQ_QHASH_SHIFT));
1110 static void cfq_free_io_context(struct io_context *ioc)
1112 struct cfq_io_context *__cic;
1116 while ((n = rb_first(&ioc->cic_root)) != NULL) {
1117 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1118 rb_erase(&__cic->rb_node, &ioc->cic_root);
1119 kmem_cache_free(cfq_ioc_pool, __cic);
1123 elv_ioc_count_mod(ioc_count, -freed);
1125 if (ioc_gone && !elv_ioc_count_read(ioc_count))
1129 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1131 if (unlikely(cfqq == cfqd->active_queue))
1132 __cfq_slice_expired(cfqd, cfqq, 0);
1134 cfq_put_queue(cfqq);
1137 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
1138 struct cfq_io_context *cic)
1140 list_del_init(&cic->queue_list);
1144 if (cic->cfqq[ASYNC]) {
1145 cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]);
1146 cic->cfqq[ASYNC] = NULL;
1149 if (cic->cfqq[SYNC]) {
1150 cfq_exit_cfqq(cfqd, cic->cfqq[SYNC]);
1151 cic->cfqq[SYNC] = NULL;
1157 * Called with interrupts disabled
1159 static void cfq_exit_single_io_context(struct cfq_io_context *cic)
1161 struct cfq_data *cfqd = cic->key;
1164 request_queue_t *q = cfqd->queue;
1166 spin_lock_irq(q->queue_lock);
1167 __cfq_exit_single_io_context(cfqd, cic);
1168 spin_unlock_irq(q->queue_lock);
1172 static void cfq_exit_io_context(struct io_context *ioc)
1174 struct cfq_io_context *__cic;
1178 * put the reference this task is holding to the various queues
1181 n = rb_first(&ioc->cic_root);
1183 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1185 cfq_exit_single_io_context(__cic);
1190 static struct cfq_io_context *
1191 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1193 struct cfq_io_context *cic;
1195 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask, cfqd->queue->node);
1197 memset(cic, 0, sizeof(*cic));
1198 cic->last_end_request = jiffies;
1199 INIT_LIST_HEAD(&cic->queue_list);
1200 cic->dtor = cfq_free_io_context;
1201 cic->exit = cfq_exit_io_context;
1202 elv_ioc_count_inc(ioc_count);
1208 static void cfq_init_prio_data(struct cfq_queue *cfqq)
1210 struct task_struct *tsk = current;
1213 if (!cfq_cfqq_prio_changed(cfqq))
1216 ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
1217 switch (ioprio_class) {
1219 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1220 case IOPRIO_CLASS_NONE:
1222 * no prio set, place us in the middle of the BE classes
1224 cfqq->ioprio = task_nice_ioprio(tsk);
1225 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1227 case IOPRIO_CLASS_RT:
1228 cfqq->ioprio = task_ioprio(tsk);
1229 cfqq->ioprio_class = IOPRIO_CLASS_RT;
1231 case IOPRIO_CLASS_BE:
1232 cfqq->ioprio = task_ioprio(tsk);
1233 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1235 case IOPRIO_CLASS_IDLE:
1236 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1238 cfq_clear_cfqq_idle_window(cfqq);
1243 * keep track of original prio settings in case we have to temporarily
1244 * elevate the priority of this queue
1246 cfqq->org_ioprio = cfqq->ioprio;
1247 cfqq->org_ioprio_class = cfqq->ioprio_class;
1249 if (cfq_cfqq_on_rr(cfqq))
1250 cfq_resort_rr_list(cfqq, 0);
1252 cfq_clear_cfqq_prio_changed(cfqq);
1255 static inline void changed_ioprio(struct cfq_io_context *cic)
1257 struct cfq_data *cfqd = cic->key;
1258 struct cfq_queue *cfqq;
1259 unsigned long flags;
1261 if (unlikely(!cfqd))
1264 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1266 cfqq = cic->cfqq[ASYNC];
1268 struct cfq_queue *new_cfqq;
1269 new_cfqq = cfq_get_queue(cfqd, CFQ_KEY_ASYNC, cic->ioc->task,
1272 cic->cfqq[ASYNC] = new_cfqq;
1273 cfq_put_queue(cfqq);
1277 cfqq = cic->cfqq[SYNC];
1279 cfq_mark_cfqq_prio_changed(cfqq);
1281 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1284 static void cfq_ioc_set_ioprio(struct io_context *ioc)
1286 struct cfq_io_context *cic;
1289 ioc->ioprio_changed = 0;
1291 n = rb_first(&ioc->cic_root);
1293 cic = rb_entry(n, struct cfq_io_context, rb_node);
1295 changed_ioprio(cic);
1300 static struct cfq_queue *
1301 cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk,
1304 const int hashval = hash_long(key, CFQ_QHASH_SHIFT);
1305 struct cfq_queue *cfqq, *new_cfqq = NULL;
1306 unsigned short ioprio;
1309 ioprio = tsk->ioprio;
1310 cfqq = __cfq_find_cfq_hash(cfqd, key, ioprio, hashval);
1316 } else if (gfp_mask & __GFP_WAIT) {
1318 * Inform the allocator of the fact that we will
1319 * just repeat this allocation if it fails, to allow
1320 * the allocator to do whatever it needs to attempt to
1323 spin_unlock_irq(cfqd->queue->queue_lock);
1324 new_cfqq = kmem_cache_alloc_node(cfq_pool, gfp_mask|__GFP_NOFAIL, cfqd->queue->node);
1325 spin_lock_irq(cfqd->queue->queue_lock);
1328 cfqq = kmem_cache_alloc_node(cfq_pool, gfp_mask, cfqd->queue->node);
1333 memset(cfqq, 0, sizeof(*cfqq));
1335 INIT_HLIST_NODE(&cfqq->cfq_hash);
1336 INIT_LIST_HEAD(&cfqq->cfq_list);
1337 INIT_LIST_HEAD(&cfqq->fifo);
1340 hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
1341 atomic_set(&cfqq->ref, 0);
1344 * set ->slice_left to allow preemption for a new process
1346 cfqq->slice_left = 2 * cfqd->cfq_slice_idle;
1347 cfq_mark_cfqq_idle_window(cfqq);
1348 cfq_mark_cfqq_prio_changed(cfqq);
1349 cfq_mark_cfqq_queue_new(cfqq);
1350 cfq_init_prio_data(cfqq);
1354 kmem_cache_free(cfq_pool, new_cfqq);
1356 atomic_inc(&cfqq->ref);
1358 WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
1363 cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)
1365 WARN_ON(!list_empty(&cic->queue_list));
1366 rb_erase(&cic->rb_node, &ioc->cic_root);
1367 kmem_cache_free(cfq_ioc_pool, cic);
1368 elv_ioc_count_dec(ioc_count);
1371 static struct cfq_io_context *
1372 cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)
1375 struct cfq_io_context *cic;
1376 void *k, *key = cfqd;
1379 n = ioc->cic_root.rb_node;
1381 cic = rb_entry(n, struct cfq_io_context, rb_node);
1382 /* ->key must be copied to avoid race with cfq_exit_queue() */
1385 cfq_drop_dead_cic(ioc, cic);
1401 cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
1402 struct cfq_io_context *cic)
1405 struct rb_node *parent;
1406 struct cfq_io_context *__cic;
1407 unsigned long flags;
1415 p = &ioc->cic_root.rb_node;
1418 __cic = rb_entry(parent, struct cfq_io_context, rb_node);
1419 /* ->key must be copied to avoid race with cfq_exit_queue() */
1422 cfq_drop_dead_cic(ioc, __cic);
1428 else if (cic->key > k)
1429 p = &(*p)->rb_right;
1434 rb_link_node(&cic->rb_node, parent, p);
1435 rb_insert_color(&cic->rb_node, &ioc->cic_root);
1437 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1438 list_add(&cic->queue_list, &cfqd->cic_list);
1439 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1443 * Setup general io context and cfq io context. There can be several cfq
1444 * io contexts per general io context, if this process is doing io to more
1445 * than one device managed by cfq.
1447 static struct cfq_io_context *
1448 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1450 struct io_context *ioc = NULL;
1451 struct cfq_io_context *cic;
1453 might_sleep_if(gfp_mask & __GFP_WAIT);
1455 ioc = get_io_context(gfp_mask, cfqd->queue->node);
1459 cic = cfq_cic_rb_lookup(cfqd, ioc);
1463 cic = cfq_alloc_io_context(cfqd, gfp_mask);
1467 cfq_cic_link(cfqd, ioc, cic);
1469 smp_read_barrier_depends();
1470 if (unlikely(ioc->ioprio_changed))
1471 cfq_ioc_set_ioprio(ioc);
1475 put_io_context(ioc);
1480 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1482 unsigned long elapsed, ttime;
1485 * if this context already has stuff queued, thinktime is from
1486 * last queue not last end
1489 if (time_after(cic->last_end_request, cic->last_queue))
1490 elapsed = jiffies - cic->last_end_request;
1492 elapsed = jiffies - cic->last_queue;
1494 elapsed = jiffies - cic->last_end_request;
1497 ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
1499 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1500 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1501 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1505 cfq_update_io_seektime(struct cfq_io_context *cic, struct request *rq)
1510 if (cic->last_request_pos < rq->sector)
1511 sdist = rq->sector - cic->last_request_pos;
1513 sdist = cic->last_request_pos - rq->sector;
1516 * Don't allow the seek distance to get too large from the
1517 * odd fragment, pagein, etc
1519 if (cic->seek_samples <= 60) /* second&third seek */
1520 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024);
1522 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64);
1524 cic->seek_samples = (7*cic->seek_samples + 256) / 8;
1525 cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
1526 total = cic->seek_total + (cic->seek_samples/2);
1527 do_div(total, cic->seek_samples);
1528 cic->seek_mean = (sector_t)total;
1532 * Disable idle window if the process thinks too long or seeks so much that
1536 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1537 struct cfq_io_context *cic)
1539 int enable_idle = cfq_cfqq_idle_window(cfqq);
1541 if (!cic->ioc->task || !cfqd->cfq_slice_idle ||
1542 (cfqd->hw_tag && CIC_SEEKY(cic)))
1544 else if (sample_valid(cic->ttime_samples)) {
1545 if (cic->ttime_mean > cfqd->cfq_slice_idle)
1552 cfq_mark_cfqq_idle_window(cfqq);
1554 cfq_clear_cfqq_idle_window(cfqq);
1559 * Check if new_cfqq should preempt the currently active queue. Return 0 for
1560 * no or if we aren't sure, a 1 will cause a preempt.
1563 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1566 struct cfq_queue *cfqq = cfqd->active_queue;
1568 if (cfq_class_idle(new_cfqq))
1574 if (cfq_class_idle(cfqq))
1576 if (!cfq_cfqq_wait_request(new_cfqq))
1579 * if it doesn't have slice left, forget it
1581 if (new_cfqq->slice_left < cfqd->cfq_slice_idle)
1584 * if the new request is sync, but the currently running queue is
1585 * not, let the sync request have priority.
1587 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
1590 * So both queues are sync. Let the new request get disk time if
1591 * it's a metadata request and the current queue is doing regular IO.
1593 if (rq_is_meta(rq) && !cfqq->meta_pending)
1600 * cfqq preempts the active queue. if we allowed preempt with no slice left,
1601 * let it have half of its nominal slice.
1603 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1605 cfq_slice_expired(cfqd, 1);
1607 if (!cfqq->slice_left)
1608 cfqq->slice_left = cfq_prio_to_slice(cfqd, cfqq) / 2;
1611 * Put the new queue at the front of the of the current list,
1612 * so we know that it will be selected next.
1614 BUG_ON(!cfq_cfqq_on_rr(cfqq));
1615 list_move(&cfqq->cfq_list, &cfqd->cur_rr);
1617 cfqq->slice_end = cfqq->slice_left + jiffies;
1621 * Called when a new fs request (rq) is added (to cfqq). Check if there's
1622 * something we should do about it
1625 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1628 struct cfq_io_context *cic = RQ_CIC(rq);
1631 cfqq->meta_pending++;
1634 * we never wait for an async request and we don't allow preemption
1635 * of an async request. so just return early
1637 if (!rq_is_sync(rq)) {
1639 * sync process issued an async request, if it's waiting
1640 * then expire it and kick rq handling.
1642 if (cic == cfqd->active_cic &&
1643 del_timer(&cfqd->idle_slice_timer)) {
1644 cfq_slice_expired(cfqd, 0);
1645 blk_start_queueing(cfqd->queue);
1650 cfq_update_io_thinktime(cfqd, cic);
1651 cfq_update_io_seektime(cic, rq);
1652 cfq_update_idle_window(cfqd, cfqq, cic);
1654 cic->last_queue = jiffies;
1655 cic->last_request_pos = rq->sector + rq->nr_sectors;
1657 if (cfqq == cfqd->active_queue) {
1659 * if we are waiting for a request for this queue, let it rip
1660 * immediately and flag that we must not expire this queue
1663 if (cfq_cfqq_wait_request(cfqq)) {
1664 cfq_mark_cfqq_must_dispatch(cfqq);
1665 del_timer(&cfqd->idle_slice_timer);
1666 blk_start_queueing(cfqd->queue);
1668 } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
1670 * not the active queue - expire current slice if it is
1671 * idle and has expired it's mean thinktime or this new queue
1672 * has some old slice time left and is of higher priority
1674 cfq_preempt_queue(cfqd, cfqq);
1675 cfq_mark_cfqq_must_dispatch(cfqq);
1676 blk_start_queueing(cfqd->queue);
1680 static void cfq_insert_request(request_queue_t *q, struct request *rq)
1682 struct cfq_data *cfqd = q->elevator->elevator_data;
1683 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1685 cfq_init_prio_data(cfqq);
1689 list_add_tail(&rq->queuelist, &cfqq->fifo);
1691 cfq_rq_enqueued(cfqd, cfqq, rq);
1694 static void cfq_completed_request(request_queue_t *q, struct request *rq)
1696 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1697 struct cfq_data *cfqd = cfqq->cfqd;
1698 const int sync = rq_is_sync(rq);
1703 WARN_ON(!cfqd->rq_in_driver);
1704 WARN_ON(!cfqq->on_dispatch[sync]);
1705 cfqd->rq_in_driver--;
1706 cfqq->on_dispatch[sync]--;
1708 if (!cfq_class_idle(cfqq))
1709 cfqd->last_end_request = now;
1711 if (!cfq_cfqq_dispatched(cfqq) && cfq_cfqq_on_rr(cfqq))
1712 cfq_resort_rr_list(cfqq, 0);
1715 RQ_CIC(rq)->last_end_request = now;
1718 * If this is the active queue, check if it needs to be expired,
1719 * or if we want to idle in case it has no pending requests.
1721 if (cfqd->active_queue == cfqq) {
1722 if (time_after(now, cfqq->slice_end))
1723 cfq_slice_expired(cfqd, 0);
1724 else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list)) {
1725 if (!cfq_arm_slice_timer(cfqd, cfqq))
1726 cfq_schedule_dispatch(cfqd);
1732 * we temporarily boost lower priority queues if they are holding fs exclusive
1733 * resources. they are boosted to normal prio (CLASS_BE/4)
1735 static void cfq_prio_boost(struct cfq_queue *cfqq)
1737 const int ioprio_class = cfqq->ioprio_class;
1738 const int ioprio = cfqq->ioprio;
1740 if (has_fs_excl()) {
1742 * boost idle prio on transactions that would lock out other
1743 * users of the filesystem
1745 if (cfq_class_idle(cfqq))
1746 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1747 if (cfqq->ioprio > IOPRIO_NORM)
1748 cfqq->ioprio = IOPRIO_NORM;
1751 * check if we need to unboost the queue
1753 if (cfqq->ioprio_class != cfqq->org_ioprio_class)
1754 cfqq->ioprio_class = cfqq->org_ioprio_class;
1755 if (cfqq->ioprio != cfqq->org_ioprio)
1756 cfqq->ioprio = cfqq->org_ioprio;
1760 * refile between round-robin lists if we moved the priority class
1762 if ((ioprio_class != cfqq->ioprio_class || ioprio != cfqq->ioprio) &&
1763 cfq_cfqq_on_rr(cfqq))
1764 cfq_resort_rr_list(cfqq, 0);
1767 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
1769 if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
1770 !cfq_cfqq_must_alloc_slice(cfqq)) {
1771 cfq_mark_cfqq_must_alloc_slice(cfqq);
1772 return ELV_MQUEUE_MUST;
1775 return ELV_MQUEUE_MAY;
1778 static int cfq_may_queue(request_queue_t *q, int rw)
1780 struct cfq_data *cfqd = q->elevator->elevator_data;
1781 struct task_struct *tsk = current;
1782 struct cfq_queue *cfqq;
1785 key = cfq_queue_pid(tsk, rw, rw & REQ_RW_SYNC);
1788 * don't force setup of a queue from here, as a call to may_queue
1789 * does not necessarily imply that a request actually will be queued.
1790 * so just lookup a possibly existing queue, or return 'may queue'
1793 cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
1795 cfq_init_prio_data(cfqq);
1796 cfq_prio_boost(cfqq);
1798 return __cfq_may_queue(cfqq);
1801 return ELV_MQUEUE_MAY;
1805 * queue lock held here
1807 static void cfq_put_request(struct request *rq)
1809 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1812 const int rw = rq_data_dir(rq);
1814 BUG_ON(!cfqq->allocated[rw]);
1815 cfqq->allocated[rw]--;
1817 put_io_context(RQ_CIC(rq)->ioc);
1819 rq->elevator_private = NULL;
1820 rq->elevator_private2 = NULL;
1822 cfq_put_queue(cfqq);
1827 * Allocate cfq data structures associated with this request.
1830 cfq_set_request(request_queue_t *q, struct request *rq, gfp_t gfp_mask)
1832 struct cfq_data *cfqd = q->elevator->elevator_data;
1833 struct task_struct *tsk = current;
1834 struct cfq_io_context *cic;
1835 const int rw = rq_data_dir(rq);
1836 const int is_sync = rq_is_sync(rq);
1837 pid_t key = cfq_queue_pid(tsk, rw, is_sync);
1838 struct cfq_queue *cfqq;
1839 unsigned long flags;
1841 might_sleep_if(gfp_mask & __GFP_WAIT);
1843 cic = cfq_get_io_context(cfqd, gfp_mask);
1845 spin_lock_irqsave(q->queue_lock, flags);
1850 if (!cic->cfqq[is_sync]) {
1851 cfqq = cfq_get_queue(cfqd, key, tsk, gfp_mask);
1855 cic->cfqq[is_sync] = cfqq;
1857 cfqq = cic->cfqq[is_sync];
1859 cfqq->allocated[rw]++;
1860 cfq_clear_cfqq_must_alloc(cfqq);
1861 atomic_inc(&cfqq->ref);
1863 spin_unlock_irqrestore(q->queue_lock, flags);
1865 rq->elevator_private = cic;
1866 rq->elevator_private2 = cfqq;
1871 put_io_context(cic->ioc);
1873 cfq_schedule_dispatch(cfqd);
1874 spin_unlock_irqrestore(q->queue_lock, flags);
1878 static void cfq_kick_queue(struct work_struct *work)
1880 struct cfq_data *cfqd =
1881 container_of(work, struct cfq_data, unplug_work);
1882 request_queue_t *q = cfqd->queue;
1883 unsigned long flags;
1885 spin_lock_irqsave(q->queue_lock, flags);
1886 blk_start_queueing(q);
1887 spin_unlock_irqrestore(q->queue_lock, flags);
1891 * Timer running if the active_queue is currently idling inside its time slice
1893 static void cfq_idle_slice_timer(unsigned long data)
1895 struct cfq_data *cfqd = (struct cfq_data *) data;
1896 struct cfq_queue *cfqq;
1897 unsigned long flags;
1899 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1901 if ((cfqq = cfqd->active_queue) != NULL) {
1902 unsigned long now = jiffies;
1907 if (time_after(now, cfqq->slice_end))
1911 * only expire and reinvoke request handler, if there are
1912 * other queues with pending requests
1914 if (!cfqd->busy_queues)
1918 * not expired and it has a request pending, let it dispatch
1920 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) {
1921 cfq_mark_cfqq_must_dispatch(cfqq);
1926 cfq_slice_expired(cfqd, 0);
1928 cfq_schedule_dispatch(cfqd);
1930 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1934 * Timer running if an idle class queue is waiting for service
1936 static void cfq_idle_class_timer(unsigned long data)
1938 struct cfq_data *cfqd = (struct cfq_data *) data;
1939 unsigned long flags, end;
1941 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1944 * race with a non-idle queue, reset timer
1946 end = cfqd->last_end_request + CFQ_IDLE_GRACE;
1947 if (!time_after_eq(jiffies, end))
1948 mod_timer(&cfqd->idle_class_timer, end);
1950 cfq_schedule_dispatch(cfqd);
1952 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1955 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
1957 del_timer_sync(&cfqd->idle_slice_timer);
1958 del_timer_sync(&cfqd->idle_class_timer);
1959 blk_sync_queue(cfqd->queue);
1962 static void cfq_exit_queue(elevator_t *e)
1964 struct cfq_data *cfqd = e->elevator_data;
1965 request_queue_t *q = cfqd->queue;
1967 cfq_shutdown_timer_wq(cfqd);
1969 spin_lock_irq(q->queue_lock);
1971 if (cfqd->active_queue)
1972 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
1974 while (!list_empty(&cfqd->cic_list)) {
1975 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
1976 struct cfq_io_context,
1979 __cfq_exit_single_io_context(cfqd, cic);
1982 spin_unlock_irq(q->queue_lock);
1984 cfq_shutdown_timer_wq(cfqd);
1986 kfree(cfqd->cfq_hash);
1990 static void *cfq_init_queue(request_queue_t *q)
1992 struct cfq_data *cfqd;
1995 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL, q->node);
1999 memset(cfqd, 0, sizeof(*cfqd));
2001 for (i = 0; i < CFQ_PRIO_LISTS; i++)
2002 INIT_LIST_HEAD(&cfqd->rr_list[i]);
2004 INIT_LIST_HEAD(&cfqd->busy_rr);
2005 INIT_LIST_HEAD(&cfqd->cur_rr);
2006 INIT_LIST_HEAD(&cfqd->idle_rr);
2007 INIT_LIST_HEAD(&cfqd->cic_list);
2009 cfqd->cfq_hash = kmalloc_node(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL, q->node);
2010 if (!cfqd->cfq_hash)
2013 for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
2014 INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);
2018 init_timer(&cfqd->idle_slice_timer);
2019 cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2020 cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2022 init_timer(&cfqd->idle_class_timer);
2023 cfqd->idle_class_timer.function = cfq_idle_class_timer;
2024 cfqd->idle_class_timer.data = (unsigned long) cfqd;
2026 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
2028 cfqd->cfq_quantum = cfq_quantum;
2029 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2030 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2031 cfqd->cfq_back_max = cfq_back_max;
2032 cfqd->cfq_back_penalty = cfq_back_penalty;
2033 cfqd->cfq_slice[0] = cfq_slice_async;
2034 cfqd->cfq_slice[1] = cfq_slice_sync;
2035 cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2036 cfqd->cfq_slice_idle = cfq_slice_idle;
2044 static void cfq_slab_kill(void)
2047 kmem_cache_destroy(cfq_pool);
2049 kmem_cache_destroy(cfq_ioc_pool);
2052 static int __init cfq_slab_setup(void)
2054 cfq_pool = kmem_cache_create("cfq_pool", sizeof(struct cfq_queue), 0, 0,
2059 cfq_ioc_pool = kmem_cache_create("cfq_ioc_pool",
2060 sizeof(struct cfq_io_context), 0, 0, NULL, NULL);
2071 * sysfs parts below -->
2075 cfq_var_show(unsigned int var, char *page)
2077 return sprintf(page, "%d\n", var);
2081 cfq_var_store(unsigned int *var, const char *page, size_t count)
2083 char *p = (char *) page;
2085 *var = simple_strtoul(p, &p, 10);
2089 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
2090 static ssize_t __FUNC(elevator_t *e, char *page) \
2092 struct cfq_data *cfqd = e->elevator_data; \
2093 unsigned int __data = __VAR; \
2095 __data = jiffies_to_msecs(__data); \
2096 return cfq_var_show(__data, (page)); \
2098 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
2099 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2100 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
2101 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
2102 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
2103 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2104 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2105 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2106 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
2107 #undef SHOW_FUNCTION
2109 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
2110 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
2112 struct cfq_data *cfqd = e->elevator_data; \
2113 unsigned int __data; \
2114 int ret = cfq_var_store(&__data, (page), count); \
2115 if (__data < (MIN)) \
2117 else if (__data > (MAX)) \
2120 *(__PTR) = msecs_to_jiffies(__data); \
2122 *(__PTR) = __data; \
2125 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
2126 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1);
2127 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1);
2128 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
2129 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0);
2130 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2131 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2132 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
2133 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0);
2134 #undef STORE_FUNCTION
2136 #define CFQ_ATTR(name) \
2137 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2139 static struct elv_fs_entry cfq_attrs[] = {
2141 CFQ_ATTR(fifo_expire_sync),
2142 CFQ_ATTR(fifo_expire_async),
2143 CFQ_ATTR(back_seek_max),
2144 CFQ_ATTR(back_seek_penalty),
2145 CFQ_ATTR(slice_sync),
2146 CFQ_ATTR(slice_async),
2147 CFQ_ATTR(slice_async_rq),
2148 CFQ_ATTR(slice_idle),
2152 static struct elevator_type iosched_cfq = {
2154 .elevator_merge_fn = cfq_merge,
2155 .elevator_merged_fn = cfq_merged_request,
2156 .elevator_merge_req_fn = cfq_merged_requests,
2157 .elevator_allow_merge_fn = cfq_allow_merge,
2158 .elevator_dispatch_fn = cfq_dispatch_requests,
2159 .elevator_add_req_fn = cfq_insert_request,
2160 .elevator_activate_req_fn = cfq_activate_request,
2161 .elevator_deactivate_req_fn = cfq_deactivate_request,
2162 .elevator_queue_empty_fn = cfq_queue_empty,
2163 .elevator_completed_req_fn = cfq_completed_request,
2164 .elevator_former_req_fn = elv_rb_former_request,
2165 .elevator_latter_req_fn = elv_rb_latter_request,
2166 .elevator_set_req_fn = cfq_set_request,
2167 .elevator_put_req_fn = cfq_put_request,
2168 .elevator_may_queue_fn = cfq_may_queue,
2169 .elevator_init_fn = cfq_init_queue,
2170 .elevator_exit_fn = cfq_exit_queue,
2171 .trim = cfq_free_io_context,
2173 .elevator_attrs = cfq_attrs,
2174 .elevator_name = "cfq",
2175 .elevator_owner = THIS_MODULE,
2178 static int __init cfq_init(void)
2183 * could be 0 on HZ < 1000 setups
2185 if (!cfq_slice_async)
2186 cfq_slice_async = 1;
2187 if (!cfq_slice_idle)
2190 if (cfq_slab_setup())
2193 ret = elv_register(&iosched_cfq);
2200 static void __exit cfq_exit(void)
2202 DECLARE_COMPLETION_ONSTACK(all_gone);
2203 elv_unregister(&iosched_cfq);
2204 ioc_gone = &all_gone;
2205 /* ioc_gone's update must be visible before reading ioc_count */
2207 if (elv_ioc_count_read(ioc_count))
2208 wait_for_completion(ioc_gone);
2213 module_init(cfq_init);
2214 module_exit(cfq_exit);
2216 MODULE_AUTHOR("Jens Axboe");
2217 MODULE_LICENSE("GPL");
2218 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");