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/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 kmem_cache_t *cfq_pool;
47 static kmem_cache_t *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 /* fifo list of requests in sort_list */
145 struct list_head fifo;
147 unsigned long slice_start;
148 unsigned long slice_end;
149 unsigned long slice_left;
151 /* number of requests that are on the dispatch list */
154 /* io prio of this group */
155 unsigned short ioprio, org_ioprio;
156 unsigned short ioprio_class, org_ioprio_class;
158 /* various state flags, see below */
162 enum cfqq_state_flags {
163 CFQ_CFQQ_FLAG_on_rr = 0,
164 CFQ_CFQQ_FLAG_wait_request,
165 CFQ_CFQQ_FLAG_must_alloc,
166 CFQ_CFQQ_FLAG_must_alloc_slice,
167 CFQ_CFQQ_FLAG_must_dispatch,
168 CFQ_CFQQ_FLAG_fifo_expire,
169 CFQ_CFQQ_FLAG_idle_window,
170 CFQ_CFQQ_FLAG_prio_changed,
171 CFQ_CFQQ_FLAG_queue_new,
174 #define CFQ_CFQQ_FNS(name) \
175 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
177 cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
179 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
181 cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
183 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
185 return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
189 CFQ_CFQQ_FNS(wait_request);
190 CFQ_CFQQ_FNS(must_alloc);
191 CFQ_CFQQ_FNS(must_alloc_slice);
192 CFQ_CFQQ_FNS(must_dispatch);
193 CFQ_CFQQ_FNS(fifo_expire);
194 CFQ_CFQQ_FNS(idle_window);
195 CFQ_CFQQ_FNS(prio_changed);
196 CFQ_CFQQ_FNS(queue_new);
199 static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsigned short);
200 static void cfq_dispatch_insert(request_queue_t *, struct request *);
201 static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask);
204 * scheduler run of queue, if there are requests pending and no one in the
205 * driver that will restart queueing
207 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
209 if (cfqd->busy_queues)
210 kblockd_schedule_work(&cfqd->unplug_work);
213 static int cfq_queue_empty(request_queue_t *q)
215 struct cfq_data *cfqd = q->elevator->elevator_data;
217 return !cfqd->busy_queues;
220 static inline pid_t cfq_queue_pid(struct task_struct *task, int rw)
222 if (rw == READ || rw == WRITE_SYNC)
225 return CFQ_KEY_ASYNC;
229 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
230 * We choose the request that is closest to the head right now. Distance
231 * behind the head is penalized and only allowed to a certain extent.
233 static struct request *
234 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2)
236 sector_t last, s1, s2, d1 = 0, d2 = 0;
237 unsigned long back_max;
238 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
239 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
240 unsigned wrap = 0; /* bit mask: requests behind the disk head? */
242 if (rq1 == NULL || rq1 == rq2)
247 if (rq_is_sync(rq1) && !rq_is_sync(rq2))
249 else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
255 last = cfqd->last_sector;
258 * by definition, 1KiB is 2 sectors
260 back_max = cfqd->cfq_back_max * 2;
263 * Strict one way elevator _except_ in the case where we allow
264 * short backward seeks which are biased as twice the cost of a
265 * similar forward seek.
269 else if (s1 + back_max >= last)
270 d1 = (last - s1) * cfqd->cfq_back_penalty;
272 wrap |= CFQ_RQ1_WRAP;
276 else if (s2 + back_max >= last)
277 d2 = (last - s2) * cfqd->cfq_back_penalty;
279 wrap |= CFQ_RQ2_WRAP;
281 /* Found required data */
284 * By doing switch() on the bit mask "wrap" we avoid having to
285 * check two variables for all permutations: --> faster!
288 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
304 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
307 * Since both rqs are wrapped,
308 * start with the one that's further behind head
309 * (--> only *one* back seek required),
310 * since back seek takes more time than forward.
320 * would be nice to take fifo expire time into account as well
322 static struct request *
323 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
324 struct request *last)
326 struct rb_node *rbnext = rb_next(&last->rb_node);
327 struct rb_node *rbprev = rb_prev(&last->rb_node);
328 struct request *next = NULL, *prev = NULL;
330 BUG_ON(RB_EMPTY_NODE(&last->rb_node));
333 prev = rb_entry_rq(rbprev);
336 next = rb_entry_rq(rbnext);
338 rbnext = rb_first(&cfqq->sort_list);
339 if (rbnext && rbnext != &last->rb_node)
340 next = rb_entry_rq(rbnext);
343 return cfq_choose_req(cfqd, next, prev);
346 static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
348 struct cfq_data *cfqd = cfqq->cfqd;
349 struct list_head *list;
351 BUG_ON(!cfq_cfqq_on_rr(cfqq));
353 list_del(&cfqq->cfq_list);
355 if (cfq_class_rt(cfqq))
356 list = &cfqd->cur_rr;
357 else if (cfq_class_idle(cfqq))
358 list = &cfqd->idle_rr;
361 * if cfqq has requests in flight, don't allow it to be
362 * found in cfq_set_active_queue before it has finished them.
363 * this is done to increase fairness between a process that
364 * has lots of io pending vs one that only generates one
365 * sporadically or synchronously
367 if (cfq_cfqq_dispatched(cfqq))
368 list = &cfqd->busy_rr;
370 list = &cfqd->rr_list[cfqq->ioprio];
374 * If this queue was preempted or is new (never been serviced), let
375 * it be added first for fairness but beind other new queues.
376 * Otherwise, just add to the back of the list.
378 if (preempted || cfq_cfqq_queue_new(cfqq)) {
379 struct list_head *n = list;
380 struct cfq_queue *__cfqq;
382 while (n->next != list) {
383 __cfqq = list_entry_cfqq(n->next);
384 if (!cfq_cfqq_queue_new(__cfqq))
393 list_add_tail(&cfqq->cfq_list, list);
397 * add to busy list of queues for service, trying to be fair in ordering
398 * the pending list according to last request service
401 cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
403 BUG_ON(cfq_cfqq_on_rr(cfqq));
404 cfq_mark_cfqq_on_rr(cfqq);
407 cfq_resort_rr_list(cfqq, 0);
411 cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
413 BUG_ON(!cfq_cfqq_on_rr(cfqq));
414 cfq_clear_cfqq_on_rr(cfqq);
415 list_del_init(&cfqq->cfq_list);
417 BUG_ON(!cfqd->busy_queues);
422 * rb tree support functions
424 static inline void cfq_del_rq_rb(struct request *rq)
426 struct cfq_queue *cfqq = RQ_CFQQ(rq);
427 struct cfq_data *cfqd = cfqq->cfqd;
428 const int sync = rq_is_sync(rq);
430 BUG_ON(!cfqq->queued[sync]);
431 cfqq->queued[sync]--;
433 elv_rb_del(&cfqq->sort_list, rq);
435 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
436 cfq_del_cfqq_rr(cfqd, cfqq);
439 static void cfq_add_rq_rb(struct request *rq)
441 struct cfq_queue *cfqq = RQ_CFQQ(rq);
442 struct cfq_data *cfqd = cfqq->cfqd;
443 struct request *__alias;
445 cfqq->queued[rq_is_sync(rq)]++;
448 * looks a little odd, but the first insert might return an alias.
449 * if that happens, put the alias on the dispatch list
451 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
452 cfq_dispatch_insert(cfqd->queue, __alias);
456 cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
458 elv_rb_del(&cfqq->sort_list, rq);
459 cfqq->queued[rq_is_sync(rq)]--;
463 static struct request *
464 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
466 struct task_struct *tsk = current;
467 pid_t key = cfq_queue_pid(tsk, bio_data_dir(bio));
468 struct cfq_queue *cfqq;
470 cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
472 sector_t sector = bio->bi_sector + bio_sectors(bio);
474 return elv_rb_find(&cfqq->sort_list, sector);
480 static void cfq_activate_request(request_queue_t *q, struct request *rq)
482 struct cfq_data *cfqd = q->elevator->elevator_data;
484 cfqd->rq_in_driver++;
487 * If the depth is larger 1, it really could be queueing. But lets
488 * make the mark a little higher - idling could still be good for
489 * low queueing, and a low queueing number could also just indicate
490 * a SCSI mid layer like behaviour where limit+1 is often seen.
492 if (!cfqd->hw_tag && cfqd->rq_in_driver > 4)
496 static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
498 struct cfq_data *cfqd = q->elevator->elevator_data;
500 WARN_ON(!cfqd->rq_in_driver);
501 cfqd->rq_in_driver--;
504 static void cfq_remove_request(struct request *rq)
506 struct cfq_queue *cfqq = RQ_CFQQ(rq);
508 if (cfqq->next_rq == rq)
509 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
511 list_del_init(&rq->queuelist);
516 cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
518 struct cfq_data *cfqd = q->elevator->elevator_data;
519 struct request *__rq;
521 __rq = cfq_find_rq_fmerge(cfqd, bio);
522 if (__rq && elv_rq_merge_ok(__rq, bio)) {
524 return ELEVATOR_FRONT_MERGE;
527 return ELEVATOR_NO_MERGE;
530 static void cfq_merged_request(request_queue_t *q, struct request *req,
533 if (type == ELEVATOR_FRONT_MERGE) {
534 struct cfq_queue *cfqq = RQ_CFQQ(req);
536 cfq_reposition_rq_rb(cfqq, req);
541 cfq_merged_requests(request_queue_t *q, struct request *rq,
542 struct request *next)
545 * reposition in fifo if next is older than rq
547 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
548 time_before(next->start_time, rq->start_time))
549 list_move(&rq->queuelist, &next->queuelist);
551 cfq_remove_request(next);
555 __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
559 * stop potential idle class queues waiting service
561 del_timer(&cfqd->idle_class_timer);
563 cfqq->slice_start = jiffies;
565 cfqq->slice_left = 0;
566 cfq_clear_cfqq_must_alloc_slice(cfqq);
567 cfq_clear_cfqq_fifo_expire(cfqq);
570 cfqd->active_queue = cfqq;
574 * current cfqq expired its slice (or was too idle), select new one
577 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
580 unsigned long now = jiffies;
582 if (cfq_cfqq_wait_request(cfqq))
583 del_timer(&cfqd->idle_slice_timer);
585 if (!preempted && !cfq_cfqq_dispatched(cfqq))
586 cfq_schedule_dispatch(cfqd);
588 cfq_clear_cfqq_must_dispatch(cfqq);
589 cfq_clear_cfqq_wait_request(cfqq);
590 cfq_clear_cfqq_queue_new(cfqq);
593 * store what was left of this slice, if the queue idled out
596 if (time_after(cfqq->slice_end, now))
597 cfqq->slice_left = cfqq->slice_end - now;
599 cfqq->slice_left = 0;
601 if (cfq_cfqq_on_rr(cfqq))
602 cfq_resort_rr_list(cfqq, preempted);
604 if (cfqq == cfqd->active_queue)
605 cfqd->active_queue = NULL;
607 if (cfqd->active_cic) {
608 put_io_context(cfqd->active_cic->ioc);
609 cfqd->active_cic = NULL;
612 cfqd->dispatch_slice = 0;
615 static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted)
617 struct cfq_queue *cfqq = cfqd->active_queue;
620 __cfq_slice_expired(cfqd, cfqq, preempted);
633 static int cfq_get_next_prio_level(struct cfq_data *cfqd)
642 for (p = cfqd->cur_prio; p <= cfqd->cur_end_prio; p++) {
643 if (!list_empty(&cfqd->rr_list[p])) {
652 if (++cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
653 cfqd->cur_end_prio = 0;
660 if (unlikely(prio == -1))
663 BUG_ON(prio >= CFQ_PRIO_LISTS);
665 list_splice_init(&cfqd->rr_list[prio], &cfqd->cur_rr);
667 cfqd->cur_prio = prio + 1;
668 if (cfqd->cur_prio > cfqd->cur_end_prio) {
669 cfqd->cur_end_prio = cfqd->cur_prio;
672 if (cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
674 cfqd->cur_end_prio = 0;
680 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
682 struct cfq_queue *cfqq = NULL;
684 if (!list_empty(&cfqd->cur_rr) || cfq_get_next_prio_level(cfqd) != -1) {
686 * if current list is non-empty, grab first entry. if it is
687 * empty, get next prio level and grab first entry then if any
690 cfqq = list_entry_cfqq(cfqd->cur_rr.next);
691 } else if (!list_empty(&cfqd->busy_rr)) {
693 * If no new queues are available, check if the busy list has
694 * some before falling back to idle io.
696 cfqq = list_entry_cfqq(cfqd->busy_rr.next);
697 } else if (!list_empty(&cfqd->idle_rr)) {
699 * if we have idle queues and no rt or be queues had pending
700 * requests, either allow immediate service if the grace period
701 * has passed or arm the idle grace timer
703 unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE;
705 if (time_after_eq(jiffies, end))
706 cfqq = list_entry_cfqq(cfqd->idle_rr.next);
708 mod_timer(&cfqd->idle_class_timer, end);
711 __cfq_set_active_queue(cfqd, cfqq);
715 #define CIC_SEEKY(cic) ((cic)->seek_mean > (128 * 1024))
717 static int cfq_arm_slice_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
720 struct cfq_io_context *cic;
723 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
724 WARN_ON(cfqq != cfqd->active_queue);
727 * idle is disabled, either manually or by past process history
729 if (!cfqd->cfq_slice_idle)
731 if (!cfq_cfqq_idle_window(cfqq))
734 * task has exited, don't wait
736 cic = cfqd->active_cic;
737 if (!cic || !cic->ioc->task)
740 cfq_mark_cfqq_must_dispatch(cfqq);
741 cfq_mark_cfqq_wait_request(cfqq);
743 sl = min(cfqq->slice_end - 1, (unsigned long) cfqd->cfq_slice_idle);
746 * we don't want to idle for seeks, but we do want to allow
747 * fair distribution of slice time for a process doing back-to-back
748 * seeks. so allow a little bit of time for him to submit a new rq
750 if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
751 sl = min(sl, msecs_to_jiffies(2));
753 mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
757 static void cfq_dispatch_insert(request_queue_t *q, struct request *rq)
759 struct cfq_data *cfqd = q->elevator->elevator_data;
760 struct cfq_queue *cfqq = RQ_CFQQ(rq);
762 cfq_remove_request(rq);
763 cfqq->on_dispatch[rq_is_sync(rq)]++;
764 elv_dispatch_sort(q, rq);
766 rq = list_entry(q->queue_head.prev, struct request, queuelist);
767 cfqd->last_sector = rq->sector + rq->nr_sectors;
771 * return expired entry, or NULL to just start from scratch in rbtree
773 static inline struct request *cfq_check_fifo(struct cfq_queue *cfqq)
775 struct cfq_data *cfqd = cfqq->cfqd;
779 if (cfq_cfqq_fifo_expire(cfqq))
781 if (list_empty(&cfqq->fifo))
784 fifo = cfq_cfqq_class_sync(cfqq);
785 rq = rq_entry_fifo(cfqq->fifo.next);
787 if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) {
788 cfq_mark_cfqq_fifo_expire(cfqq);
796 * Scale schedule slice based on io priority. Use the sync time slice only
797 * if a queue is marked sync and has sync io queued. A sync queue with async
798 * io only, should not get full sync slice length.
801 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
803 const int base_slice = cfqd->cfq_slice[cfq_cfqq_sync(cfqq)];
805 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
807 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - cfqq->ioprio));
811 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
813 cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
817 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
819 const int base_rq = cfqd->cfq_slice_async_rq;
821 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
823 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
827 * get next queue for service
829 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
831 unsigned long now = jiffies;
832 struct cfq_queue *cfqq;
834 cfqq = cfqd->active_queue;
841 if (!cfq_cfqq_must_dispatch(cfqq) && time_after(now, cfqq->slice_end))
845 * if queue has requests, dispatch one. if not, check if
846 * enough slice is left to wait for one
848 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
850 else if (cfq_cfqq_dispatched(cfqq)) {
853 } else if (cfq_cfqq_class_sync(cfqq)) {
854 if (cfq_arm_slice_timer(cfqd, cfqq))
859 cfq_slice_expired(cfqd, 0);
861 cfqq = cfq_set_active_queue(cfqd);
867 __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
872 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
878 * follow expired path, else get first next available
880 if ((rq = cfq_check_fifo(cfqq)) == NULL)
884 * finally, insert request into driver dispatch list
886 cfq_dispatch_insert(cfqd->queue, rq);
888 cfqd->dispatch_slice++;
891 if (!cfqd->active_cic) {
892 atomic_inc(&RQ_CIC(rq)->ioc->refcount);
893 cfqd->active_cic = RQ_CIC(rq);
896 if (RB_EMPTY_ROOT(&cfqq->sort_list))
899 } while (dispatched < max_dispatch);
902 * if slice end isn't set yet, set it.
904 if (!cfqq->slice_end)
905 cfq_set_prio_slice(cfqd, cfqq);
908 * expire an async queue immediately if it has used up its slice. idle
909 * queue always expire after 1 dispatch round.
911 if ((!cfq_cfqq_sync(cfqq) &&
912 cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
913 cfq_class_idle(cfqq) ||
914 !cfq_cfqq_idle_window(cfqq))
915 cfq_slice_expired(cfqd, 0);
921 cfq_forced_dispatch_cfqqs(struct list_head *list)
923 struct cfq_queue *cfqq, *next;
927 list_for_each_entry_safe(cfqq, next, list, cfq_list) {
928 while (cfqq->next_rq) {
929 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
932 BUG_ON(!list_empty(&cfqq->fifo));
939 cfq_forced_dispatch(struct cfq_data *cfqd)
941 int i, dispatched = 0;
943 for (i = 0; i < CFQ_PRIO_LISTS; i++)
944 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->rr_list[i]);
946 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->busy_rr);
947 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr);
948 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->idle_rr);
950 cfq_slice_expired(cfqd, 0);
952 BUG_ON(cfqd->busy_queues);
958 cfq_dispatch_requests(request_queue_t *q, int force)
960 struct cfq_data *cfqd = q->elevator->elevator_data;
961 struct cfq_queue *cfqq, *prev_cfqq;
964 if (!cfqd->busy_queues)
968 return cfq_forced_dispatch(cfqd);
972 while ((cfqq = cfq_select_queue(cfqd)) != NULL) {
976 * Don't repeat dispatch from the previous queue.
978 if (prev_cfqq == cfqq)
981 cfq_clear_cfqq_must_dispatch(cfqq);
982 cfq_clear_cfqq_wait_request(cfqq);
983 del_timer(&cfqd->idle_slice_timer);
985 max_dispatch = cfqd->cfq_quantum;
986 if (cfq_class_idle(cfqq))
989 dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
992 * If the dispatch cfqq has idling enabled and is still
993 * the active queue, break out.
995 if (cfq_cfqq_idle_window(cfqq) && cfqd->active_queue)
1005 * task holds one reference to the queue, dropped when task exits. each rq
1006 * in-flight on this queue also holds a reference, dropped when rq is freed.
1008 * queue lock must be held here.
1010 static void cfq_put_queue(struct cfq_queue *cfqq)
1012 struct cfq_data *cfqd = cfqq->cfqd;
1014 BUG_ON(atomic_read(&cfqq->ref) <= 0);
1016 if (!atomic_dec_and_test(&cfqq->ref))
1019 BUG_ON(rb_first(&cfqq->sort_list));
1020 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1021 BUG_ON(cfq_cfqq_on_rr(cfqq));
1023 if (unlikely(cfqd->active_queue == cfqq))
1024 __cfq_slice_expired(cfqd, cfqq, 0);
1027 * it's on the empty list and still hashed
1029 list_del(&cfqq->cfq_list);
1030 hlist_del(&cfqq->cfq_hash);
1031 kmem_cache_free(cfq_pool, cfqq);
1034 static struct cfq_queue *
1035 __cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned int prio,
1038 struct hlist_head *hash_list = &cfqd->cfq_hash[hashval];
1039 struct hlist_node *entry;
1040 struct cfq_queue *__cfqq;
1042 hlist_for_each_entry(__cfqq, entry, hash_list, cfq_hash) {
1043 const unsigned short __p = IOPRIO_PRIO_VALUE(__cfqq->org_ioprio_class, __cfqq->org_ioprio);
1045 if (__cfqq->key == key && (__p == prio || !prio))
1052 static struct cfq_queue *
1053 cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned short prio)
1055 return __cfq_find_cfq_hash(cfqd, key, prio, hash_long(key, CFQ_QHASH_SHIFT));
1058 static void cfq_free_io_context(struct io_context *ioc)
1060 struct cfq_io_context *__cic;
1064 while ((n = rb_first(&ioc->cic_root)) != NULL) {
1065 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1066 rb_erase(&__cic->rb_node, &ioc->cic_root);
1067 kmem_cache_free(cfq_ioc_pool, __cic);
1071 elv_ioc_count_mod(ioc_count, -freed);
1073 if (ioc_gone && !elv_ioc_count_read(ioc_count))
1077 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1079 if (unlikely(cfqq == cfqd->active_queue))
1080 __cfq_slice_expired(cfqd, cfqq, 0);
1082 cfq_put_queue(cfqq);
1085 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
1086 struct cfq_io_context *cic)
1088 list_del_init(&cic->queue_list);
1092 if (cic->cfqq[ASYNC]) {
1093 cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]);
1094 cic->cfqq[ASYNC] = NULL;
1097 if (cic->cfqq[SYNC]) {
1098 cfq_exit_cfqq(cfqd, cic->cfqq[SYNC]);
1099 cic->cfqq[SYNC] = NULL;
1105 * Called with interrupts disabled
1107 static void cfq_exit_single_io_context(struct cfq_io_context *cic)
1109 struct cfq_data *cfqd = cic->key;
1112 request_queue_t *q = cfqd->queue;
1114 spin_lock_irq(q->queue_lock);
1115 __cfq_exit_single_io_context(cfqd, cic);
1116 spin_unlock_irq(q->queue_lock);
1120 static void cfq_exit_io_context(struct io_context *ioc)
1122 struct cfq_io_context *__cic;
1126 * put the reference this task is holding to the various queues
1129 n = rb_first(&ioc->cic_root);
1131 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1133 cfq_exit_single_io_context(__cic);
1138 static struct cfq_io_context *
1139 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1141 struct cfq_io_context *cic;
1143 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask, cfqd->queue->node);
1145 memset(cic, 0, sizeof(*cic));
1146 cic->last_end_request = jiffies;
1147 INIT_LIST_HEAD(&cic->queue_list);
1148 cic->dtor = cfq_free_io_context;
1149 cic->exit = cfq_exit_io_context;
1150 elv_ioc_count_inc(ioc_count);
1156 static void cfq_init_prio_data(struct cfq_queue *cfqq)
1158 struct task_struct *tsk = current;
1161 if (!cfq_cfqq_prio_changed(cfqq))
1164 ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
1165 switch (ioprio_class) {
1167 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1168 case IOPRIO_CLASS_NONE:
1170 * no prio set, place us in the middle of the BE classes
1172 cfqq->ioprio = task_nice_ioprio(tsk);
1173 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1175 case IOPRIO_CLASS_RT:
1176 cfqq->ioprio = task_ioprio(tsk);
1177 cfqq->ioprio_class = IOPRIO_CLASS_RT;
1179 case IOPRIO_CLASS_BE:
1180 cfqq->ioprio = task_ioprio(tsk);
1181 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1183 case IOPRIO_CLASS_IDLE:
1184 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1186 cfq_clear_cfqq_idle_window(cfqq);
1191 * keep track of original prio settings in case we have to temporarily
1192 * elevate the priority of this queue
1194 cfqq->org_ioprio = cfqq->ioprio;
1195 cfqq->org_ioprio_class = cfqq->ioprio_class;
1197 if (cfq_cfqq_on_rr(cfqq))
1198 cfq_resort_rr_list(cfqq, 0);
1200 cfq_clear_cfqq_prio_changed(cfqq);
1203 static inline void changed_ioprio(struct cfq_io_context *cic)
1205 struct cfq_data *cfqd = cic->key;
1206 struct cfq_queue *cfqq;
1208 if (unlikely(!cfqd))
1211 spin_lock(cfqd->queue->queue_lock);
1213 cfqq = cic->cfqq[ASYNC];
1215 struct cfq_queue *new_cfqq;
1216 new_cfqq = cfq_get_queue(cfqd, CFQ_KEY_ASYNC, cic->ioc->task,
1219 cic->cfqq[ASYNC] = new_cfqq;
1220 cfq_put_queue(cfqq);
1224 cfqq = cic->cfqq[SYNC];
1226 cfq_mark_cfqq_prio_changed(cfqq);
1228 spin_unlock(cfqd->queue->queue_lock);
1231 static void cfq_ioc_set_ioprio(struct io_context *ioc)
1233 struct cfq_io_context *cic;
1236 ioc->ioprio_changed = 0;
1238 n = rb_first(&ioc->cic_root);
1240 cic = rb_entry(n, struct cfq_io_context, rb_node);
1242 changed_ioprio(cic);
1247 static struct cfq_queue *
1248 cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk,
1251 const int hashval = hash_long(key, CFQ_QHASH_SHIFT);
1252 struct cfq_queue *cfqq, *new_cfqq = NULL;
1253 unsigned short ioprio;
1256 ioprio = tsk->ioprio;
1257 cfqq = __cfq_find_cfq_hash(cfqd, key, ioprio, hashval);
1263 } else if (gfp_mask & __GFP_WAIT) {
1265 * Inform the allocator of the fact that we will
1266 * just repeat this allocation if it fails, to allow
1267 * the allocator to do whatever it needs to attempt to
1270 spin_unlock_irq(cfqd->queue->queue_lock);
1271 new_cfqq = kmem_cache_alloc_node(cfq_pool, gfp_mask|__GFP_NOFAIL, cfqd->queue->node);
1272 spin_lock_irq(cfqd->queue->queue_lock);
1275 cfqq = kmem_cache_alloc_node(cfq_pool, gfp_mask, cfqd->queue->node);
1280 memset(cfqq, 0, sizeof(*cfqq));
1282 INIT_HLIST_NODE(&cfqq->cfq_hash);
1283 INIT_LIST_HEAD(&cfqq->cfq_list);
1284 INIT_LIST_HEAD(&cfqq->fifo);
1287 hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
1288 atomic_set(&cfqq->ref, 0);
1291 * set ->slice_left to allow preemption for a new process
1293 cfqq->slice_left = 2 * cfqd->cfq_slice_idle;
1294 cfq_mark_cfqq_idle_window(cfqq);
1295 cfq_mark_cfqq_prio_changed(cfqq);
1296 cfq_mark_cfqq_queue_new(cfqq);
1297 cfq_init_prio_data(cfqq);
1301 kmem_cache_free(cfq_pool, new_cfqq);
1303 atomic_inc(&cfqq->ref);
1305 WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
1310 cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)
1312 WARN_ON(!list_empty(&cic->queue_list));
1313 rb_erase(&cic->rb_node, &ioc->cic_root);
1314 kmem_cache_free(cfq_ioc_pool, cic);
1315 elv_ioc_count_dec(ioc_count);
1318 static struct cfq_io_context *
1319 cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)
1322 struct cfq_io_context *cic;
1323 void *k, *key = cfqd;
1326 n = ioc->cic_root.rb_node;
1328 cic = rb_entry(n, struct cfq_io_context, rb_node);
1329 /* ->key must be copied to avoid race with cfq_exit_queue() */
1332 cfq_drop_dead_cic(ioc, cic);
1348 cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
1349 struct cfq_io_context *cic)
1352 struct rb_node *parent;
1353 struct cfq_io_context *__cic;
1361 p = &ioc->cic_root.rb_node;
1364 __cic = rb_entry(parent, struct cfq_io_context, rb_node);
1365 /* ->key must be copied to avoid race with cfq_exit_queue() */
1368 cfq_drop_dead_cic(ioc, __cic);
1374 else if (cic->key > k)
1375 p = &(*p)->rb_right;
1380 rb_link_node(&cic->rb_node, parent, p);
1381 rb_insert_color(&cic->rb_node, &ioc->cic_root);
1383 spin_lock_irq(cfqd->queue->queue_lock);
1384 list_add(&cic->queue_list, &cfqd->cic_list);
1385 spin_unlock_irq(cfqd->queue->queue_lock);
1389 * Setup general io context and cfq io context. There can be several cfq
1390 * io contexts per general io context, if this process is doing io to more
1391 * than one device managed by cfq.
1393 static struct cfq_io_context *
1394 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1396 struct io_context *ioc = NULL;
1397 struct cfq_io_context *cic;
1399 might_sleep_if(gfp_mask & __GFP_WAIT);
1401 ioc = get_io_context(gfp_mask, cfqd->queue->node);
1405 cic = cfq_cic_rb_lookup(cfqd, ioc);
1409 cic = cfq_alloc_io_context(cfqd, gfp_mask);
1413 cfq_cic_link(cfqd, ioc, cic);
1415 smp_read_barrier_depends();
1416 if (unlikely(ioc->ioprio_changed))
1417 cfq_ioc_set_ioprio(ioc);
1421 put_io_context(ioc);
1426 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1428 unsigned long elapsed, ttime;
1431 * if this context already has stuff queued, thinktime is from
1432 * last queue not last end
1435 if (time_after(cic->last_end_request, cic->last_queue))
1436 elapsed = jiffies - cic->last_end_request;
1438 elapsed = jiffies - cic->last_queue;
1440 elapsed = jiffies - cic->last_end_request;
1443 ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
1445 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1446 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1447 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1451 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
1457 if (cic->last_request_pos < rq->sector)
1458 sdist = rq->sector - cic->last_request_pos;
1460 sdist = cic->last_request_pos - rq->sector;
1463 * Don't allow the seek distance to get too large from the
1464 * odd fragment, pagein, etc
1466 if (cic->seek_samples <= 60) /* second&third seek */
1467 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024);
1469 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64);
1471 cic->seek_samples = (7*cic->seek_samples + 256) / 8;
1472 cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
1473 total = cic->seek_total + (cic->seek_samples/2);
1474 do_div(total, cic->seek_samples);
1475 cic->seek_mean = (sector_t)total;
1479 * Disable idle window if the process thinks too long or seeks so much that
1483 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1484 struct cfq_io_context *cic)
1486 int enable_idle = cfq_cfqq_idle_window(cfqq);
1488 if (!cic->ioc->task || !cfqd->cfq_slice_idle ||
1489 (cfqd->hw_tag && CIC_SEEKY(cic)))
1491 else if (sample_valid(cic->ttime_samples)) {
1492 if (cic->ttime_mean > cfqd->cfq_slice_idle)
1499 cfq_mark_cfqq_idle_window(cfqq);
1501 cfq_clear_cfqq_idle_window(cfqq);
1506 * Check if new_cfqq should preempt the currently active queue. Return 0 for
1507 * no or if we aren't sure, a 1 will cause a preempt.
1510 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1513 struct cfq_queue *cfqq = cfqd->active_queue;
1515 if (cfq_class_idle(new_cfqq))
1521 if (cfq_class_idle(cfqq))
1523 if (!cfq_cfqq_wait_request(new_cfqq))
1526 * if it doesn't have slice left, forget it
1528 if (new_cfqq->slice_left < cfqd->cfq_slice_idle)
1530 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
1537 * cfqq preempts the active queue. if we allowed preempt with no slice left,
1538 * let it have half of its nominal slice.
1540 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1542 cfq_slice_expired(cfqd, 1);
1544 if (!cfqq->slice_left)
1545 cfqq->slice_left = cfq_prio_to_slice(cfqd, cfqq) / 2;
1548 * Put the new queue at the front of the of the current list,
1549 * so we know that it will be selected next.
1551 BUG_ON(!cfq_cfqq_on_rr(cfqq));
1552 list_move(&cfqq->cfq_list, &cfqd->cur_rr);
1554 cfqq->slice_end = cfqq->slice_left + jiffies;
1558 * Called when a new fs request (rq) is added (to cfqq). Check if there's
1559 * something we should do about it
1562 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1565 struct cfq_io_context *cic = RQ_CIC(rq);
1568 * check if this request is a better next-serve candidate)) {
1570 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq);
1571 BUG_ON(!cfqq->next_rq);
1574 * we never wait for an async request and we don't allow preemption
1575 * of an async request. so just return early
1577 if (!rq_is_sync(rq)) {
1579 * sync process issued an async request, if it's waiting
1580 * then expire it and kick rq handling.
1582 if (cic == cfqd->active_cic &&
1583 del_timer(&cfqd->idle_slice_timer)) {
1584 cfq_slice_expired(cfqd, 0);
1585 blk_start_queueing(cfqd->queue);
1590 cfq_update_io_thinktime(cfqd, cic);
1591 cfq_update_io_seektime(cfqd, cic, rq);
1592 cfq_update_idle_window(cfqd, cfqq, cic);
1594 cic->last_queue = jiffies;
1595 cic->last_request_pos = rq->sector + rq->nr_sectors;
1597 if (cfqq == cfqd->active_queue) {
1599 * if we are waiting for a request for this queue, let it rip
1600 * immediately and flag that we must not expire this queue
1603 if (cfq_cfqq_wait_request(cfqq)) {
1604 cfq_mark_cfqq_must_dispatch(cfqq);
1605 del_timer(&cfqd->idle_slice_timer);
1606 blk_start_queueing(cfqd->queue);
1608 } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
1610 * not the active queue - expire current slice if it is
1611 * idle and has expired it's mean thinktime or this new queue
1612 * has some old slice time left and is of higher priority
1614 cfq_preempt_queue(cfqd, cfqq);
1615 cfq_mark_cfqq_must_dispatch(cfqq);
1616 blk_start_queueing(cfqd->queue);
1620 static void cfq_insert_request(request_queue_t *q, struct request *rq)
1622 struct cfq_data *cfqd = q->elevator->elevator_data;
1623 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1625 cfq_init_prio_data(cfqq);
1629 if (!cfq_cfqq_on_rr(cfqq))
1630 cfq_add_cfqq_rr(cfqd, cfqq);
1632 list_add_tail(&rq->queuelist, &cfqq->fifo);
1634 cfq_rq_enqueued(cfqd, cfqq, rq);
1637 static void cfq_completed_request(request_queue_t *q, struct request *rq)
1639 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1640 struct cfq_data *cfqd = cfqq->cfqd;
1641 const int sync = rq_is_sync(rq);
1646 WARN_ON(!cfqd->rq_in_driver);
1647 WARN_ON(!cfqq->on_dispatch[sync]);
1648 cfqd->rq_in_driver--;
1649 cfqq->on_dispatch[sync]--;
1651 if (!cfq_class_idle(cfqq))
1652 cfqd->last_end_request = now;
1654 if (!cfq_cfqq_dispatched(cfqq) && cfq_cfqq_on_rr(cfqq))
1655 cfq_resort_rr_list(cfqq, 0);
1658 RQ_CIC(rq)->last_end_request = now;
1661 * If this is the active queue, check if it needs to be expired,
1662 * or if we want to idle in case it has no pending requests.
1664 if (cfqd->active_queue == cfqq) {
1665 if (time_after(now, cfqq->slice_end))
1666 cfq_slice_expired(cfqd, 0);
1667 else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list)) {
1668 if (!cfq_arm_slice_timer(cfqd, cfqq))
1669 cfq_schedule_dispatch(cfqd);
1675 * we temporarily boost lower priority queues if they are holding fs exclusive
1676 * resources. they are boosted to normal prio (CLASS_BE/4)
1678 static void cfq_prio_boost(struct cfq_queue *cfqq)
1680 const int ioprio_class = cfqq->ioprio_class;
1681 const int ioprio = cfqq->ioprio;
1683 if (has_fs_excl()) {
1685 * boost idle prio on transactions that would lock out other
1686 * users of the filesystem
1688 if (cfq_class_idle(cfqq))
1689 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1690 if (cfqq->ioprio > IOPRIO_NORM)
1691 cfqq->ioprio = IOPRIO_NORM;
1694 * check if we need to unboost the queue
1696 if (cfqq->ioprio_class != cfqq->org_ioprio_class)
1697 cfqq->ioprio_class = cfqq->org_ioprio_class;
1698 if (cfqq->ioprio != cfqq->org_ioprio)
1699 cfqq->ioprio = cfqq->org_ioprio;
1703 * refile between round-robin lists if we moved the priority class
1705 if ((ioprio_class != cfqq->ioprio_class || ioprio != cfqq->ioprio) &&
1706 cfq_cfqq_on_rr(cfqq))
1707 cfq_resort_rr_list(cfqq, 0);
1710 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
1712 if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
1713 !cfq_cfqq_must_alloc_slice(cfqq)) {
1714 cfq_mark_cfqq_must_alloc_slice(cfqq);
1715 return ELV_MQUEUE_MUST;
1718 return ELV_MQUEUE_MAY;
1721 static int cfq_may_queue(request_queue_t *q, int rw)
1723 struct cfq_data *cfqd = q->elevator->elevator_data;
1724 struct task_struct *tsk = current;
1725 struct cfq_queue *cfqq;
1728 * don't force setup of a queue from here, as a call to may_queue
1729 * does not necessarily imply that a request actually will be queued.
1730 * so just lookup a possibly existing queue, or return 'may queue'
1733 cfqq = cfq_find_cfq_hash(cfqd, cfq_queue_pid(tsk, rw), tsk->ioprio);
1735 cfq_init_prio_data(cfqq);
1736 cfq_prio_boost(cfqq);
1738 return __cfq_may_queue(cfqq);
1741 return ELV_MQUEUE_MAY;
1745 * queue lock held here
1747 static void cfq_put_request(request_queue_t *q, struct request *rq)
1749 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1752 const int rw = rq_data_dir(rq);
1754 BUG_ON(!cfqq->allocated[rw]);
1755 cfqq->allocated[rw]--;
1757 put_io_context(RQ_CIC(rq)->ioc);
1759 rq->elevator_private = NULL;
1760 rq->elevator_private2 = NULL;
1762 cfq_put_queue(cfqq);
1767 * Allocate cfq data structures associated with this request.
1770 cfq_set_request(request_queue_t *q, struct request *rq, gfp_t gfp_mask)
1772 struct cfq_data *cfqd = q->elevator->elevator_data;
1773 struct task_struct *tsk = current;
1774 struct cfq_io_context *cic;
1775 const int rw = rq_data_dir(rq);
1776 pid_t key = cfq_queue_pid(tsk, rw);
1777 struct cfq_queue *cfqq;
1778 unsigned long flags;
1779 int is_sync = key != CFQ_KEY_ASYNC;
1781 might_sleep_if(gfp_mask & __GFP_WAIT);
1783 cic = cfq_get_io_context(cfqd, gfp_mask);
1785 spin_lock_irqsave(q->queue_lock, flags);
1790 if (!cic->cfqq[is_sync]) {
1791 cfqq = cfq_get_queue(cfqd, key, tsk, gfp_mask);
1795 cic->cfqq[is_sync] = cfqq;
1797 cfqq = cic->cfqq[is_sync];
1799 cfqq->allocated[rw]++;
1800 cfq_clear_cfqq_must_alloc(cfqq);
1801 atomic_inc(&cfqq->ref);
1803 spin_unlock_irqrestore(q->queue_lock, flags);
1805 rq->elevator_private = cic;
1806 rq->elevator_private2 = cfqq;
1811 put_io_context(cic->ioc);
1813 cfq_schedule_dispatch(cfqd);
1814 spin_unlock_irqrestore(q->queue_lock, flags);
1818 static void cfq_kick_queue(void *data)
1820 request_queue_t *q = data;
1821 unsigned long flags;
1823 spin_lock_irqsave(q->queue_lock, flags);
1824 blk_start_queueing(q);
1825 spin_unlock_irqrestore(q->queue_lock, flags);
1829 * Timer running if the active_queue is currently idling inside its time slice
1831 static void cfq_idle_slice_timer(unsigned long data)
1833 struct cfq_data *cfqd = (struct cfq_data *) data;
1834 struct cfq_queue *cfqq;
1835 unsigned long flags;
1837 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1839 if ((cfqq = cfqd->active_queue) != NULL) {
1840 unsigned long now = jiffies;
1845 if (time_after(now, cfqq->slice_end))
1849 * only expire and reinvoke request handler, if there are
1850 * other queues with pending requests
1852 if (!cfqd->busy_queues)
1856 * not expired and it has a request pending, let it dispatch
1858 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) {
1859 cfq_mark_cfqq_must_dispatch(cfqq);
1864 cfq_slice_expired(cfqd, 0);
1866 cfq_schedule_dispatch(cfqd);
1868 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1872 * Timer running if an idle class queue is waiting for service
1874 static void cfq_idle_class_timer(unsigned long data)
1876 struct cfq_data *cfqd = (struct cfq_data *) data;
1877 unsigned long flags, end;
1879 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1882 * race with a non-idle queue, reset timer
1884 end = cfqd->last_end_request + CFQ_IDLE_GRACE;
1885 if (!time_after_eq(jiffies, end))
1886 mod_timer(&cfqd->idle_class_timer, end);
1888 cfq_schedule_dispatch(cfqd);
1890 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1893 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
1895 del_timer_sync(&cfqd->idle_slice_timer);
1896 del_timer_sync(&cfqd->idle_class_timer);
1897 blk_sync_queue(cfqd->queue);
1900 static void cfq_exit_queue(elevator_t *e)
1902 struct cfq_data *cfqd = e->elevator_data;
1903 request_queue_t *q = cfqd->queue;
1905 cfq_shutdown_timer_wq(cfqd);
1907 spin_lock_irq(q->queue_lock);
1909 if (cfqd->active_queue)
1910 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
1912 while (!list_empty(&cfqd->cic_list)) {
1913 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
1914 struct cfq_io_context,
1917 __cfq_exit_single_io_context(cfqd, cic);
1920 spin_unlock_irq(q->queue_lock);
1922 cfq_shutdown_timer_wq(cfqd);
1924 kfree(cfqd->cfq_hash);
1928 static void *cfq_init_queue(request_queue_t *q, elevator_t *e)
1930 struct cfq_data *cfqd;
1933 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL, q->node);
1937 memset(cfqd, 0, sizeof(*cfqd));
1939 for (i = 0; i < CFQ_PRIO_LISTS; i++)
1940 INIT_LIST_HEAD(&cfqd->rr_list[i]);
1942 INIT_LIST_HEAD(&cfqd->busy_rr);
1943 INIT_LIST_HEAD(&cfqd->cur_rr);
1944 INIT_LIST_HEAD(&cfqd->idle_rr);
1945 INIT_LIST_HEAD(&cfqd->cic_list);
1947 cfqd->cfq_hash = kmalloc_node(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL, q->node);
1948 if (!cfqd->cfq_hash)
1951 for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
1952 INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);
1956 init_timer(&cfqd->idle_slice_timer);
1957 cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
1958 cfqd->idle_slice_timer.data = (unsigned long) cfqd;
1960 init_timer(&cfqd->idle_class_timer);
1961 cfqd->idle_class_timer.function = cfq_idle_class_timer;
1962 cfqd->idle_class_timer.data = (unsigned long) cfqd;
1964 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue, q);
1966 cfqd->cfq_quantum = cfq_quantum;
1967 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
1968 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
1969 cfqd->cfq_back_max = cfq_back_max;
1970 cfqd->cfq_back_penalty = cfq_back_penalty;
1971 cfqd->cfq_slice[0] = cfq_slice_async;
1972 cfqd->cfq_slice[1] = cfq_slice_sync;
1973 cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
1974 cfqd->cfq_slice_idle = cfq_slice_idle;
1982 static void cfq_slab_kill(void)
1985 kmem_cache_destroy(cfq_pool);
1987 kmem_cache_destroy(cfq_ioc_pool);
1990 static int __init cfq_slab_setup(void)
1992 cfq_pool = kmem_cache_create("cfq_pool", sizeof(struct cfq_queue), 0, 0,
1997 cfq_ioc_pool = kmem_cache_create("cfq_ioc_pool",
1998 sizeof(struct cfq_io_context), 0, 0, NULL, NULL);
2009 * sysfs parts below -->
2013 cfq_var_show(unsigned int var, char *page)
2015 return sprintf(page, "%d\n", var);
2019 cfq_var_store(unsigned int *var, const char *page, size_t count)
2021 char *p = (char *) page;
2023 *var = simple_strtoul(p, &p, 10);
2027 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
2028 static ssize_t __FUNC(elevator_t *e, char *page) \
2030 struct cfq_data *cfqd = e->elevator_data; \
2031 unsigned int __data = __VAR; \
2033 __data = jiffies_to_msecs(__data); \
2034 return cfq_var_show(__data, (page)); \
2036 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
2037 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2038 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
2039 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
2040 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
2041 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2042 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2043 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2044 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
2045 #undef SHOW_FUNCTION
2047 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
2048 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
2050 struct cfq_data *cfqd = e->elevator_data; \
2051 unsigned int __data; \
2052 int ret = cfq_var_store(&__data, (page), count); \
2053 if (__data < (MIN)) \
2055 else if (__data > (MAX)) \
2058 *(__PTR) = msecs_to_jiffies(__data); \
2060 *(__PTR) = __data; \
2063 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
2064 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1);
2065 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1);
2066 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
2067 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0);
2068 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2069 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2070 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
2071 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0);
2072 #undef STORE_FUNCTION
2074 #define CFQ_ATTR(name) \
2075 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2077 static struct elv_fs_entry cfq_attrs[] = {
2079 CFQ_ATTR(fifo_expire_sync),
2080 CFQ_ATTR(fifo_expire_async),
2081 CFQ_ATTR(back_seek_max),
2082 CFQ_ATTR(back_seek_penalty),
2083 CFQ_ATTR(slice_sync),
2084 CFQ_ATTR(slice_async),
2085 CFQ_ATTR(slice_async_rq),
2086 CFQ_ATTR(slice_idle),
2090 static struct elevator_type iosched_cfq = {
2092 .elevator_merge_fn = cfq_merge,
2093 .elevator_merged_fn = cfq_merged_request,
2094 .elevator_merge_req_fn = cfq_merged_requests,
2095 .elevator_dispatch_fn = cfq_dispatch_requests,
2096 .elevator_add_req_fn = cfq_insert_request,
2097 .elevator_activate_req_fn = cfq_activate_request,
2098 .elevator_deactivate_req_fn = cfq_deactivate_request,
2099 .elevator_queue_empty_fn = cfq_queue_empty,
2100 .elevator_completed_req_fn = cfq_completed_request,
2101 .elevator_former_req_fn = elv_rb_former_request,
2102 .elevator_latter_req_fn = elv_rb_latter_request,
2103 .elevator_set_req_fn = cfq_set_request,
2104 .elevator_put_req_fn = cfq_put_request,
2105 .elevator_may_queue_fn = cfq_may_queue,
2106 .elevator_init_fn = cfq_init_queue,
2107 .elevator_exit_fn = cfq_exit_queue,
2108 .trim = cfq_free_io_context,
2110 .elevator_attrs = cfq_attrs,
2111 .elevator_name = "cfq",
2112 .elevator_owner = THIS_MODULE,
2115 static int __init cfq_init(void)
2120 * could be 0 on HZ < 1000 setups
2122 if (!cfq_slice_async)
2123 cfq_slice_async = 1;
2124 if (!cfq_slice_idle)
2127 if (cfq_slab_setup())
2130 ret = elv_register(&iosched_cfq);
2137 static void __exit cfq_exit(void)
2139 DECLARE_COMPLETION(all_gone);
2140 elv_unregister(&iosched_cfq);
2141 ioc_gone = &all_gone;
2142 /* ioc_gone's update must be visible before reading ioc_count */
2144 if (elv_ioc_count_read(ioc_count))
2145 wait_for_completion(ioc_gone);
2150 module_init(cfq_init);
2151 module_exit(cfq_exit);
2153 MODULE_AUTHOR("Jens Axboe");
2154 MODULE_LICENSE("GPL");
2155 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");