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/rbtree.h>
13 #include <linux/ioprio.h>
18 static const int cfq_quantum = 4; /* max queue in one round of service */
19 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
20 static const int cfq_back_max = 16 * 1024; /* maximum backwards seek, in KiB */
21 static const int cfq_back_penalty = 2; /* penalty of a backwards seek */
23 static const int cfq_slice_sync = HZ / 10;
24 static int cfq_slice_async = HZ / 25;
25 static const int cfq_slice_async_rq = 2;
26 static int cfq_slice_idle = HZ / 125;
29 * grace period before allowing idle class to get disk access
31 #define CFQ_IDLE_GRACE (HZ / 10)
34 * below this threshold, we consider thinktime immediate
36 #define CFQ_MIN_TT (2)
38 #define CFQ_SLICE_SCALE (5)
40 #define RQ_CIC(rq) ((struct cfq_io_context*)(rq)->elevator_private)
41 #define RQ_CFQQ(rq) ((rq)->elevator_private2)
43 static struct kmem_cache *cfq_pool;
44 static struct kmem_cache *cfq_ioc_pool;
46 static DEFINE_PER_CPU(unsigned long, ioc_count);
47 static struct completion *ioc_gone;
49 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
50 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
51 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
56 #define sample_valid(samples) ((samples) > 80)
59 * Most of our rbtree usage is for sorting with min extraction, so
60 * if we cache the leftmost node we don't have to walk down the tree
61 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
62 * move this into the elevator for the rq sorting as well.
68 #define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, }
71 * Per block device queue structure
74 struct request_queue *queue;
77 * rr list of queues with requests and the count of them
79 struct cfq_rb_root service_tree;
80 unsigned int busy_queues;
87 * idle window management
89 struct timer_list idle_slice_timer;
90 struct work_struct unplug_work;
92 struct cfq_queue *active_queue;
93 struct cfq_io_context *active_cic;
96 * async queue for each priority case
98 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
99 struct cfq_queue *async_idle_cfqq;
101 struct timer_list idle_class_timer;
103 sector_t last_position;
104 unsigned long last_end_request;
107 * tunables, see top of file
109 unsigned int cfq_quantum;
110 unsigned int cfq_fifo_expire[2];
111 unsigned int cfq_back_penalty;
112 unsigned int cfq_back_max;
113 unsigned int cfq_slice[2];
114 unsigned int cfq_slice_async_rq;
115 unsigned int cfq_slice_idle;
117 struct list_head cic_list;
121 * Per process-grouping structure
124 /* reference count */
126 /* parent cfq_data */
127 struct cfq_data *cfqd;
128 /* service_tree member */
129 struct rb_node rb_node;
130 /* service_tree key */
131 unsigned long rb_key;
132 /* sorted list of pending requests */
133 struct rb_root sort_list;
134 /* if fifo isn't expired, next request to serve */
135 struct request *next_rq;
136 /* requests queued in sort_list */
138 /* currently allocated requests */
140 /* pending metadata requests */
142 /* fifo list of requests in sort_list */
143 struct list_head fifo;
145 unsigned long slice_end;
148 /* number of requests that are on the dispatch list or inside driver */
151 /* io prio of this group */
152 unsigned short ioprio, org_ioprio;
153 unsigned short ioprio_class, org_ioprio_class;
155 /* various state flags, see below */
159 enum cfqq_state_flags {
160 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
161 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
162 CFQ_CFQQ_FLAG_must_alloc, /* must be allowed rq alloc */
163 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
164 CFQ_CFQQ_FLAG_must_dispatch, /* must dispatch, even if expired */
165 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
166 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */
167 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
168 CFQ_CFQQ_FLAG_queue_new, /* queue never been serviced */
169 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
170 CFQ_CFQQ_FLAG_sync, /* synchronous queue */
173 #define CFQ_CFQQ_FNS(name) \
174 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
176 cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
178 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
180 cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
182 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
184 return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
188 CFQ_CFQQ_FNS(wait_request);
189 CFQ_CFQQ_FNS(must_alloc);
190 CFQ_CFQQ_FNS(must_alloc_slice);
191 CFQ_CFQQ_FNS(must_dispatch);
192 CFQ_CFQQ_FNS(fifo_expire);
193 CFQ_CFQQ_FNS(idle_window);
194 CFQ_CFQQ_FNS(prio_changed);
195 CFQ_CFQQ_FNS(queue_new);
196 CFQ_CFQQ_FNS(slice_new);
200 static void cfq_dispatch_insert(struct request_queue *, struct request *);
201 static struct cfq_queue *cfq_get_queue(struct cfq_data *, int,
202 struct task_struct *, gfp_t);
203 static struct cfq_io_context *cfq_cic_rb_lookup(struct cfq_data *,
204 struct io_context *);
206 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
209 return cic->cfqq[!!is_sync];
212 static inline void cic_set_cfqq(struct cfq_io_context *cic,
213 struct cfq_queue *cfqq, int is_sync)
215 cic->cfqq[!!is_sync] = cfqq;
219 * We regard a request as SYNC, if it's either a read or has the SYNC bit
220 * set (in which case it could also be direct WRITE).
222 static inline int cfq_bio_sync(struct bio *bio)
224 if (bio_data_dir(bio) == READ || bio_sync(bio))
231 * scheduler run of queue, if there are requests pending and no one in the
232 * driver that will restart queueing
234 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
236 if (cfqd->busy_queues)
237 kblockd_schedule_work(&cfqd->unplug_work);
240 static int cfq_queue_empty(struct request_queue *q)
242 struct cfq_data *cfqd = q->elevator->elevator_data;
244 return !cfqd->busy_queues;
248 * Scale schedule slice based on io priority. Use the sync time slice only
249 * if a queue is marked sync and has sync io queued. A sync queue with async
250 * io only, should not get full sync slice length.
252 static inline int cfq_prio_slice(struct cfq_data *cfqd, int sync,
255 const int base_slice = cfqd->cfq_slice[sync];
257 WARN_ON(prio >= IOPRIO_BE_NR);
259 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
263 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
265 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
269 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
271 cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
275 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
276 * isn't valid until the first request from the dispatch is activated
277 * and the slice time set.
279 static inline int cfq_slice_used(struct cfq_queue *cfqq)
281 if (cfq_cfqq_slice_new(cfqq))
283 if (time_before(jiffies, cfqq->slice_end))
290 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
291 * We choose the request that is closest to the head right now. Distance
292 * behind the head is penalized and only allowed to a certain extent.
294 static struct request *
295 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2)
297 sector_t last, s1, s2, d1 = 0, d2 = 0;
298 unsigned long back_max;
299 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
300 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
301 unsigned wrap = 0; /* bit mask: requests behind the disk head? */
303 if (rq1 == NULL || rq1 == rq2)
308 if (rq_is_sync(rq1) && !rq_is_sync(rq2))
310 else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
312 if (rq_is_meta(rq1) && !rq_is_meta(rq2))
314 else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
320 last = cfqd->last_position;
323 * by definition, 1KiB is 2 sectors
325 back_max = cfqd->cfq_back_max * 2;
328 * Strict one way elevator _except_ in the case where we allow
329 * short backward seeks which are biased as twice the cost of a
330 * similar forward seek.
334 else if (s1 + back_max >= last)
335 d1 = (last - s1) * cfqd->cfq_back_penalty;
337 wrap |= CFQ_RQ1_WRAP;
341 else if (s2 + back_max >= last)
342 d2 = (last - s2) * cfqd->cfq_back_penalty;
344 wrap |= CFQ_RQ2_WRAP;
346 /* Found required data */
349 * By doing switch() on the bit mask "wrap" we avoid having to
350 * check two variables for all permutations: --> faster!
353 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
369 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
372 * Since both rqs are wrapped,
373 * start with the one that's further behind head
374 * (--> only *one* back seek required),
375 * since back seek takes more time than forward.
385 * The below is leftmost cache rbtree addon
387 static struct rb_node *cfq_rb_first(struct cfq_rb_root *root)
390 root->left = rb_first(&root->rb);
395 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
400 rb_erase(n, &root->rb);
405 * would be nice to take fifo expire time into account as well
407 static struct request *
408 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
409 struct request *last)
411 struct rb_node *rbnext = rb_next(&last->rb_node);
412 struct rb_node *rbprev = rb_prev(&last->rb_node);
413 struct request *next = NULL, *prev = NULL;
415 BUG_ON(RB_EMPTY_NODE(&last->rb_node));
418 prev = rb_entry_rq(rbprev);
421 next = rb_entry_rq(rbnext);
423 rbnext = rb_first(&cfqq->sort_list);
424 if (rbnext && rbnext != &last->rb_node)
425 next = rb_entry_rq(rbnext);
428 return cfq_choose_req(cfqd, next, prev);
431 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
432 struct cfq_queue *cfqq)
435 * just an approximation, should be ok.
437 return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) -
438 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
442 * The cfqd->service_tree holds all pending cfq_queue's that have
443 * requests waiting to be processed. It is sorted in the order that
444 * we will service the queues.
446 static void cfq_service_tree_add(struct cfq_data *cfqd,
447 struct cfq_queue *cfqq, int add_front)
449 struct rb_node **p = &cfqd->service_tree.rb.rb_node;
450 struct rb_node *parent = NULL;
451 unsigned long rb_key;
455 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
456 rb_key += cfqq->slice_resid;
457 cfqq->slice_resid = 0;
461 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
463 * same position, nothing more to do
465 if (rb_key == cfqq->rb_key)
468 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
473 struct cfq_queue *__cfqq;
477 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
480 * sort RT queues first, we always want to give
481 * preference to them. IDLE queues goes to the back.
482 * after that, sort on the next service time.
484 if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq))
486 else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq))
488 else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq))
490 else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq))
492 else if (rb_key < __cfqq->rb_key)
497 if (n == &(*p)->rb_right)
504 cfqd->service_tree.left = &cfqq->rb_node;
506 cfqq->rb_key = rb_key;
507 rb_link_node(&cfqq->rb_node, parent, p);
508 rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb);
512 * Update cfqq's position in the service tree.
514 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
517 * Resorting requires the cfqq to be on the RR list already.
519 if (cfq_cfqq_on_rr(cfqq))
520 cfq_service_tree_add(cfqd, cfqq, 0);
524 * add to busy list of queues for service, trying to be fair in ordering
525 * the pending list according to last request service
528 cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
530 BUG_ON(cfq_cfqq_on_rr(cfqq));
531 cfq_mark_cfqq_on_rr(cfqq);
534 cfq_resort_rr_list(cfqd, cfqq);
538 * Called when the cfqq no longer has requests pending, remove it from
542 cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
544 BUG_ON(!cfq_cfqq_on_rr(cfqq));
545 cfq_clear_cfqq_on_rr(cfqq);
547 if (!RB_EMPTY_NODE(&cfqq->rb_node))
548 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
550 BUG_ON(!cfqd->busy_queues);
555 * rb tree support functions
557 static inline void cfq_del_rq_rb(struct request *rq)
559 struct cfq_queue *cfqq = RQ_CFQQ(rq);
560 struct cfq_data *cfqd = cfqq->cfqd;
561 const int sync = rq_is_sync(rq);
563 BUG_ON(!cfqq->queued[sync]);
564 cfqq->queued[sync]--;
566 elv_rb_del(&cfqq->sort_list, rq);
568 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
569 cfq_del_cfqq_rr(cfqd, cfqq);
572 static void cfq_add_rq_rb(struct request *rq)
574 struct cfq_queue *cfqq = RQ_CFQQ(rq);
575 struct cfq_data *cfqd = cfqq->cfqd;
576 struct request *__alias;
578 cfqq->queued[rq_is_sync(rq)]++;
581 * looks a little odd, but the first insert might return an alias.
582 * if that happens, put the alias on the dispatch list
584 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
585 cfq_dispatch_insert(cfqd->queue, __alias);
587 if (!cfq_cfqq_on_rr(cfqq))
588 cfq_add_cfqq_rr(cfqd, cfqq);
591 * check if this request is a better next-serve candidate
593 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq);
594 BUG_ON(!cfqq->next_rq);
598 cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
600 elv_rb_del(&cfqq->sort_list, rq);
601 cfqq->queued[rq_is_sync(rq)]--;
605 static struct request *
606 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
608 struct task_struct *tsk = current;
609 struct cfq_io_context *cic;
610 struct cfq_queue *cfqq;
612 cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
616 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
618 sector_t sector = bio->bi_sector + bio_sectors(bio);
620 return elv_rb_find(&cfqq->sort_list, sector);
626 static void cfq_activate_request(struct request_queue *q, struct request *rq)
628 struct cfq_data *cfqd = q->elevator->elevator_data;
630 cfqd->rq_in_driver++;
633 * If the depth is larger 1, it really could be queueing. But lets
634 * make the mark a little higher - idling could still be good for
635 * low queueing, and a low queueing number could also just indicate
636 * a SCSI mid layer like behaviour where limit+1 is often seen.
638 if (!cfqd->hw_tag && cfqd->rq_in_driver > 4)
641 cfqd->last_position = rq->hard_sector + rq->hard_nr_sectors;
644 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
646 struct cfq_data *cfqd = q->elevator->elevator_data;
648 WARN_ON(!cfqd->rq_in_driver);
649 cfqd->rq_in_driver--;
652 static void cfq_remove_request(struct request *rq)
654 struct cfq_queue *cfqq = RQ_CFQQ(rq);
656 if (cfqq->next_rq == rq)
657 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
659 list_del_init(&rq->queuelist);
662 if (rq_is_meta(rq)) {
663 WARN_ON(!cfqq->meta_pending);
664 cfqq->meta_pending--;
668 static int cfq_merge(struct request_queue *q, struct request **req,
671 struct cfq_data *cfqd = q->elevator->elevator_data;
672 struct request *__rq;
674 __rq = cfq_find_rq_fmerge(cfqd, bio);
675 if (__rq && elv_rq_merge_ok(__rq, bio)) {
677 return ELEVATOR_FRONT_MERGE;
680 return ELEVATOR_NO_MERGE;
683 static void cfq_merged_request(struct request_queue *q, struct request *req,
686 if (type == ELEVATOR_FRONT_MERGE) {
687 struct cfq_queue *cfqq = RQ_CFQQ(req);
689 cfq_reposition_rq_rb(cfqq, req);
694 cfq_merged_requests(struct request_queue *q, struct request *rq,
695 struct request *next)
698 * reposition in fifo if next is older than rq
700 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
701 time_before(next->start_time, rq->start_time))
702 list_move(&rq->queuelist, &next->queuelist);
704 cfq_remove_request(next);
707 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
710 struct cfq_data *cfqd = q->elevator->elevator_data;
711 struct cfq_io_context *cic;
712 struct cfq_queue *cfqq;
715 * Disallow merge of a sync bio into an async request.
717 if (cfq_bio_sync(bio) && !rq_is_sync(rq))
721 * Lookup the cfqq that this bio will be queued with. Allow
722 * merge only if rq is queued there.
724 cic = cfq_cic_rb_lookup(cfqd, current->io_context);
728 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
729 if (cfqq == RQ_CFQQ(rq))
736 __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
740 * stop potential idle class queues waiting service
742 del_timer(&cfqd->idle_class_timer);
745 cfq_clear_cfqq_must_alloc_slice(cfqq);
746 cfq_clear_cfqq_fifo_expire(cfqq);
747 cfq_mark_cfqq_slice_new(cfqq);
748 cfq_clear_cfqq_queue_new(cfqq);
751 cfqd->active_queue = cfqq;
755 * current cfqq expired its slice (or was too idle), select new one
758 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
761 if (cfq_cfqq_wait_request(cfqq))
762 del_timer(&cfqd->idle_slice_timer);
764 cfq_clear_cfqq_must_dispatch(cfqq);
765 cfq_clear_cfqq_wait_request(cfqq);
768 * store what was left of this slice, if the queue idled/timed out
770 if (timed_out && !cfq_cfqq_slice_new(cfqq))
771 cfqq->slice_resid = cfqq->slice_end - jiffies;
773 cfq_resort_rr_list(cfqd, cfqq);
775 if (cfqq == cfqd->active_queue)
776 cfqd->active_queue = NULL;
778 if (cfqd->active_cic) {
779 put_io_context(cfqd->active_cic->ioc);
780 cfqd->active_cic = NULL;
784 static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out)
786 struct cfq_queue *cfqq = cfqd->active_queue;
789 __cfq_slice_expired(cfqd, cfqq, timed_out);
793 * Get next queue for service. Unless we have a queue preemption,
794 * we'll simply select the first cfqq in the service tree.
796 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
798 struct cfq_queue *cfqq;
801 if (RB_EMPTY_ROOT(&cfqd->service_tree.rb))
804 n = cfq_rb_first(&cfqd->service_tree);
805 cfqq = rb_entry(n, struct cfq_queue, rb_node);
807 if (cfq_class_idle(cfqq)) {
811 * if we have idle queues and no rt or be queues had
812 * pending requests, either allow immediate service if
813 * the grace period has passed or arm the idle grace
816 end = cfqd->last_end_request + CFQ_IDLE_GRACE;
817 if (time_before(jiffies, end)) {
818 mod_timer(&cfqd->idle_class_timer, end);
827 * Get and set a new active queue for service.
829 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
831 struct cfq_queue *cfqq;
833 cfqq = cfq_get_next_queue(cfqd);
834 __cfq_set_active_queue(cfqd, cfqq);
838 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
841 if (rq->sector >= cfqd->last_position)
842 return rq->sector - cfqd->last_position;
844 return cfqd->last_position - rq->sector;
847 static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq)
849 struct cfq_io_context *cic = cfqd->active_cic;
851 if (!sample_valid(cic->seek_samples))
854 return cfq_dist_from_last(cfqd, rq) <= cic->seek_mean;
857 static int cfq_close_cooperator(struct cfq_data *cfq_data,
858 struct cfq_queue *cfqq)
861 * We should notice if some of the queues are cooperating, eg
862 * working closely on the same area of the disk. In that case,
863 * we can group them together and don't waste time idling.
868 #define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024))
870 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
872 struct cfq_queue *cfqq = cfqd->active_queue;
873 struct cfq_io_context *cic;
876 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
877 WARN_ON(cfq_cfqq_slice_new(cfqq));
880 * idle is disabled, either manually or by past process history
882 if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq))
886 * task has exited, don't wait
888 cic = cfqd->active_cic;
889 if (!cic || !cic->ioc->task)
893 * See if this prio level has a good candidate
895 if (cfq_close_cooperator(cfqd, cfqq) &&
896 (sample_valid(cic->ttime_samples) && cic->ttime_mean > 2))
899 cfq_mark_cfqq_must_dispatch(cfqq);
900 cfq_mark_cfqq_wait_request(cfqq);
903 * we don't want to idle for seeks, but we do want to allow
904 * fair distribution of slice time for a process doing back-to-back
905 * seeks. so allow a little bit of time for him to submit a new rq
907 sl = cfqd->cfq_slice_idle;
908 if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
909 sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT));
911 mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
915 * Move request from internal lists to the request queue dispatch list.
917 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
919 struct cfq_data *cfqd = q->elevator->elevator_data;
920 struct cfq_queue *cfqq = RQ_CFQQ(rq);
922 cfq_remove_request(rq);
924 elv_dispatch_sort(q, rq);
926 if (cfq_cfqq_sync(cfqq))
931 * return expired entry, or NULL to just start from scratch in rbtree
933 static inline struct request *cfq_check_fifo(struct cfq_queue *cfqq)
935 struct cfq_data *cfqd = cfqq->cfqd;
939 if (cfq_cfqq_fifo_expire(cfqq))
942 cfq_mark_cfqq_fifo_expire(cfqq);
944 if (list_empty(&cfqq->fifo))
947 fifo = cfq_cfqq_sync(cfqq);
948 rq = rq_entry_fifo(cfqq->fifo.next);
950 if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo]))
957 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
959 const int base_rq = cfqd->cfq_slice_async_rq;
961 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
963 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
967 * Select a queue for service. If we have a current active queue,
968 * check whether to continue servicing it, or retrieve and set a new one.
970 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
972 struct cfq_queue *cfqq;
974 cfqq = cfqd->active_queue;
979 * The active queue has run out of time, expire it and select new.
981 if (cfq_slice_used(cfqq))
985 * The active queue has requests and isn't expired, allow it to
988 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
992 * No requests pending. If the active queue still has requests in
993 * flight or is idling for a new request, allow either of these
994 * conditions to happen (or time out) before selecting a new queue.
996 if (timer_pending(&cfqd->idle_slice_timer) ||
997 (cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) {
1003 cfq_slice_expired(cfqd, 0);
1005 cfqq = cfq_set_active_queue(cfqd);
1011 * Dispatch some requests from cfqq, moving them to the request queue
1015 __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1020 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
1026 * follow expired path, else get first next available
1028 if ((rq = cfq_check_fifo(cfqq)) == NULL)
1032 * finally, insert request into driver dispatch list
1034 cfq_dispatch_insert(cfqd->queue, rq);
1038 if (!cfqd->active_cic) {
1039 atomic_inc(&RQ_CIC(rq)->ioc->refcount);
1040 cfqd->active_cic = RQ_CIC(rq);
1043 if (RB_EMPTY_ROOT(&cfqq->sort_list))
1046 } while (dispatched < max_dispatch);
1049 * expire an async queue immediately if it has used up its slice. idle
1050 * queue always expire after 1 dispatch round.
1052 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
1053 dispatched >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1054 cfq_class_idle(cfqq))) {
1055 cfqq->slice_end = jiffies + 1;
1056 cfq_slice_expired(cfqd, 0);
1062 static inline int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
1066 while (cfqq->next_rq) {
1067 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
1071 BUG_ON(!list_empty(&cfqq->fifo));
1076 * Drain our current requests. Used for barriers and when switching
1077 * io schedulers on-the-fly.
1079 static int cfq_forced_dispatch(struct cfq_data *cfqd)
1084 while ((n = cfq_rb_first(&cfqd->service_tree)) != NULL) {
1085 struct cfq_queue *cfqq = rb_entry(n, struct cfq_queue, rb_node);
1087 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
1090 cfq_slice_expired(cfqd, 0);
1092 BUG_ON(cfqd->busy_queues);
1097 static int cfq_dispatch_requests(struct request_queue *q, int force)
1099 struct cfq_data *cfqd = q->elevator->elevator_data;
1100 struct cfq_queue *cfqq;
1103 if (!cfqd->busy_queues)
1106 if (unlikely(force))
1107 return cfq_forced_dispatch(cfqd);
1110 while ((cfqq = cfq_select_queue(cfqd)) != NULL) {
1113 max_dispatch = cfqd->cfq_quantum;
1114 if (cfq_class_idle(cfqq))
1117 if (cfqq->dispatched >= max_dispatch) {
1118 if (cfqd->busy_queues > 1)
1120 if (cfqq->dispatched >= 4 * max_dispatch)
1124 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
1127 cfq_clear_cfqq_must_dispatch(cfqq);
1128 cfq_clear_cfqq_wait_request(cfqq);
1129 del_timer(&cfqd->idle_slice_timer);
1131 dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
1138 * task holds one reference to the queue, dropped when task exits. each rq
1139 * in-flight on this queue also holds a reference, dropped when rq is freed.
1141 * queue lock must be held here.
1143 static void cfq_put_queue(struct cfq_queue *cfqq)
1145 struct cfq_data *cfqd = cfqq->cfqd;
1147 BUG_ON(atomic_read(&cfqq->ref) <= 0);
1149 if (!atomic_dec_and_test(&cfqq->ref))
1152 BUG_ON(rb_first(&cfqq->sort_list));
1153 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1154 BUG_ON(cfq_cfqq_on_rr(cfqq));
1156 if (unlikely(cfqd->active_queue == cfqq)) {
1157 __cfq_slice_expired(cfqd, cfqq, 0);
1158 cfq_schedule_dispatch(cfqd);
1161 kmem_cache_free(cfq_pool, cfqq);
1164 static void cfq_free_io_context(struct io_context *ioc)
1166 struct cfq_io_context *__cic;
1170 ioc->ioc_data = NULL;
1172 while ((n = rb_first(&ioc->cic_root)) != NULL) {
1173 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1174 rb_erase(&__cic->rb_node, &ioc->cic_root);
1175 kmem_cache_free(cfq_ioc_pool, __cic);
1179 elv_ioc_count_mod(ioc_count, -freed);
1181 if (ioc_gone && !elv_ioc_count_read(ioc_count))
1185 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1187 if (unlikely(cfqq == cfqd->active_queue)) {
1188 __cfq_slice_expired(cfqd, cfqq, 0);
1189 cfq_schedule_dispatch(cfqd);
1192 cfq_put_queue(cfqq);
1195 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
1196 struct cfq_io_context *cic)
1198 list_del_init(&cic->queue_list);
1202 if (cic->cfqq[ASYNC]) {
1203 cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]);
1204 cic->cfqq[ASYNC] = NULL;
1207 if (cic->cfqq[SYNC]) {
1208 cfq_exit_cfqq(cfqd, cic->cfqq[SYNC]);
1209 cic->cfqq[SYNC] = NULL;
1213 static void cfq_exit_single_io_context(struct cfq_io_context *cic)
1215 struct cfq_data *cfqd = cic->key;
1218 struct request_queue *q = cfqd->queue;
1220 spin_lock_irq(q->queue_lock);
1221 __cfq_exit_single_io_context(cfqd, cic);
1222 spin_unlock_irq(q->queue_lock);
1227 * The process that ioc belongs to has exited, we need to clean up
1228 * and put the internal structures we have that belongs to that process.
1230 static void cfq_exit_io_context(struct io_context *ioc)
1232 struct cfq_io_context *__cic;
1235 ioc->ioc_data = NULL;
1238 * put the reference this task is holding to the various queues
1240 n = rb_first(&ioc->cic_root);
1242 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1244 cfq_exit_single_io_context(__cic);
1249 static struct cfq_io_context *
1250 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1252 struct cfq_io_context *cic;
1254 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
1257 cic->last_end_request = jiffies;
1258 INIT_LIST_HEAD(&cic->queue_list);
1259 cic->dtor = cfq_free_io_context;
1260 cic->exit = cfq_exit_io_context;
1261 elv_ioc_count_inc(ioc_count);
1267 static void cfq_init_prio_data(struct cfq_queue *cfqq)
1269 struct task_struct *tsk = current;
1272 if (!cfq_cfqq_prio_changed(cfqq))
1275 ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
1276 switch (ioprio_class) {
1278 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1279 case IOPRIO_CLASS_NONE:
1281 * no prio set, place us in the middle of the BE classes
1283 cfqq->ioprio = task_nice_ioprio(tsk);
1284 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1286 case IOPRIO_CLASS_RT:
1287 cfqq->ioprio = task_ioprio(tsk);
1288 cfqq->ioprio_class = IOPRIO_CLASS_RT;
1290 case IOPRIO_CLASS_BE:
1291 cfqq->ioprio = task_ioprio(tsk);
1292 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1294 case IOPRIO_CLASS_IDLE:
1295 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1297 cfq_clear_cfqq_idle_window(cfqq);
1302 * keep track of original prio settings in case we have to temporarily
1303 * elevate the priority of this queue
1305 cfqq->org_ioprio = cfqq->ioprio;
1306 cfqq->org_ioprio_class = cfqq->ioprio_class;
1307 cfq_clear_cfqq_prio_changed(cfqq);
1310 static inline void changed_ioprio(struct cfq_io_context *cic)
1312 struct cfq_data *cfqd = cic->key;
1313 struct cfq_queue *cfqq;
1314 unsigned long flags;
1316 if (unlikely(!cfqd))
1319 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1321 cfqq = cic->cfqq[ASYNC];
1323 struct cfq_queue *new_cfqq;
1324 new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc->task,
1327 cic->cfqq[ASYNC] = new_cfqq;
1328 cfq_put_queue(cfqq);
1332 cfqq = cic->cfqq[SYNC];
1334 cfq_mark_cfqq_prio_changed(cfqq);
1336 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1339 static void cfq_ioc_set_ioprio(struct io_context *ioc)
1341 struct cfq_io_context *cic;
1344 ioc->ioprio_changed = 0;
1346 n = rb_first(&ioc->cic_root);
1348 cic = rb_entry(n, struct cfq_io_context, rb_node);
1350 changed_ioprio(cic);
1355 static struct cfq_queue *
1356 cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
1357 struct task_struct *tsk, gfp_t gfp_mask)
1359 struct cfq_queue *cfqq, *new_cfqq = NULL;
1360 struct cfq_io_context *cic;
1363 cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
1364 /* cic always exists here */
1365 cfqq = cic_to_cfqq(cic, is_sync);
1371 } else if (gfp_mask & __GFP_WAIT) {
1373 * Inform the allocator of the fact that we will
1374 * just repeat this allocation if it fails, to allow
1375 * the allocator to do whatever it needs to attempt to
1378 spin_unlock_irq(cfqd->queue->queue_lock);
1379 new_cfqq = kmem_cache_alloc_node(cfq_pool,
1380 gfp_mask | __GFP_NOFAIL | __GFP_ZERO,
1382 spin_lock_irq(cfqd->queue->queue_lock);
1385 cfqq = kmem_cache_alloc_node(cfq_pool,
1386 gfp_mask | __GFP_ZERO,
1392 RB_CLEAR_NODE(&cfqq->rb_node);
1393 INIT_LIST_HEAD(&cfqq->fifo);
1395 atomic_set(&cfqq->ref, 0);
1399 cfq_mark_cfqq_idle_window(cfqq);
1400 cfq_mark_cfqq_sync(cfqq);
1403 cfq_mark_cfqq_prio_changed(cfqq);
1404 cfq_mark_cfqq_queue_new(cfqq);
1406 cfq_init_prio_data(cfqq);
1410 kmem_cache_free(cfq_pool, new_cfqq);
1413 WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
1417 static struct cfq_queue **
1418 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
1420 switch(ioprio_class) {
1421 case IOPRIO_CLASS_RT:
1422 return &cfqd->async_cfqq[0][ioprio];
1423 case IOPRIO_CLASS_BE:
1424 return &cfqd->async_cfqq[1][ioprio];
1425 case IOPRIO_CLASS_IDLE:
1426 return &cfqd->async_idle_cfqq;
1432 static struct cfq_queue *
1433 cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,
1436 const int ioprio = task_ioprio(tsk);
1437 const int ioprio_class = task_ioprio_class(tsk);
1438 struct cfq_queue **async_cfqq = NULL;
1439 struct cfq_queue *cfqq = NULL;
1442 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
1447 cfqq = cfq_find_alloc_queue(cfqd, is_sync, tsk, gfp_mask);
1450 * pin the queue now that it's allocated, scheduler exit will prune it
1452 if (!is_sync && !(*async_cfqq)) {
1453 atomic_inc(&cfqq->ref);
1457 atomic_inc(&cfqq->ref);
1462 * We drop cfq io contexts lazily, so we may find a dead one.
1465 cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)
1467 WARN_ON(!list_empty(&cic->queue_list));
1469 if (ioc->ioc_data == cic)
1470 ioc->ioc_data = NULL;
1472 rb_erase(&cic->rb_node, &ioc->cic_root);
1473 kmem_cache_free(cfq_ioc_pool, cic);
1474 elv_ioc_count_dec(ioc_count);
1477 static struct cfq_io_context *
1478 cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)
1481 struct cfq_io_context *cic;
1482 void *k, *key = cfqd;
1488 * we maintain a last-hit cache, to avoid browsing over the tree
1490 cic = ioc->ioc_data;
1491 if (cic && cic->key == cfqd)
1495 n = ioc->cic_root.rb_node;
1497 cic = rb_entry(n, struct cfq_io_context, rb_node);
1498 /* ->key must be copied to avoid race with cfq_exit_queue() */
1501 cfq_drop_dead_cic(ioc, cic);
1510 ioc->ioc_data = cic;
1519 cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
1520 struct cfq_io_context *cic)
1523 struct rb_node *parent;
1524 struct cfq_io_context *__cic;
1525 unsigned long flags;
1533 p = &ioc->cic_root.rb_node;
1536 __cic = rb_entry(parent, struct cfq_io_context, rb_node);
1537 /* ->key must be copied to avoid race with cfq_exit_queue() */
1540 cfq_drop_dead_cic(ioc, __cic);
1546 else if (cic->key > k)
1547 p = &(*p)->rb_right;
1552 rb_link_node(&cic->rb_node, parent, p);
1553 rb_insert_color(&cic->rb_node, &ioc->cic_root);
1555 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1556 list_add(&cic->queue_list, &cfqd->cic_list);
1557 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1561 * Setup general io context and cfq io context. There can be several cfq
1562 * io contexts per general io context, if this process is doing io to more
1563 * than one device managed by cfq.
1565 static struct cfq_io_context *
1566 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1568 struct io_context *ioc = NULL;
1569 struct cfq_io_context *cic;
1571 might_sleep_if(gfp_mask & __GFP_WAIT);
1573 ioc = get_io_context(gfp_mask, cfqd->queue->node);
1577 cic = cfq_cic_rb_lookup(cfqd, ioc);
1581 cic = cfq_alloc_io_context(cfqd, gfp_mask);
1585 cfq_cic_link(cfqd, ioc, cic);
1587 smp_read_barrier_depends();
1588 if (unlikely(ioc->ioprio_changed))
1589 cfq_ioc_set_ioprio(ioc);
1593 put_io_context(ioc);
1598 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1600 unsigned long elapsed = jiffies - cic->last_end_request;
1601 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
1603 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1604 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1605 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1609 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
1615 if (cic->last_request_pos < rq->sector)
1616 sdist = rq->sector - cic->last_request_pos;
1618 sdist = cic->last_request_pos - rq->sector;
1621 * Don't allow the seek distance to get too large from the
1622 * odd fragment, pagein, etc
1624 if (cic->seek_samples <= 60) /* second&third seek */
1625 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024);
1627 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64);
1629 cic->seek_samples = (7*cic->seek_samples + 256) / 8;
1630 cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
1631 total = cic->seek_total + (cic->seek_samples/2);
1632 do_div(total, cic->seek_samples);
1633 cic->seek_mean = (sector_t)total;
1637 * Disable idle window if the process thinks too long or seeks so much that
1641 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1642 struct cfq_io_context *cic)
1646 if (!cfq_cfqq_sync(cfqq))
1649 enable_idle = cfq_cfqq_idle_window(cfqq);
1651 if (!cic->ioc->task || !cfqd->cfq_slice_idle ||
1652 (cfqd->hw_tag && CIC_SEEKY(cic)))
1654 else if (sample_valid(cic->ttime_samples)) {
1655 if (cic->ttime_mean > cfqd->cfq_slice_idle)
1662 cfq_mark_cfqq_idle_window(cfqq);
1664 cfq_clear_cfqq_idle_window(cfqq);
1668 * Check if new_cfqq should preempt the currently active queue. Return 0 for
1669 * no or if we aren't sure, a 1 will cause a preempt.
1672 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1675 struct cfq_queue *cfqq;
1677 cfqq = cfqd->active_queue;
1681 if (cfq_slice_used(cfqq))
1684 if (cfq_class_idle(new_cfqq))
1687 if (cfq_class_idle(cfqq))
1691 * if the new request is sync, but the currently running queue is
1692 * not, let the sync request have priority.
1694 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
1698 * So both queues are sync. Let the new request get disk time if
1699 * it's a metadata request and the current queue is doing regular IO.
1701 if (rq_is_meta(rq) && !cfqq->meta_pending)
1704 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
1708 * if this request is as-good as one we would expect from the
1709 * current cfqq, let it preempt
1711 if (cfq_rq_close(cfqd, rq))
1718 * cfqq preempts the active queue. if we allowed preempt with no slice left,
1719 * let it have half of its nominal slice.
1721 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1723 cfq_slice_expired(cfqd, 1);
1726 * Put the new queue at the front of the of the current list,
1727 * so we know that it will be selected next.
1729 BUG_ON(!cfq_cfqq_on_rr(cfqq));
1731 cfq_service_tree_add(cfqd, cfqq, 1);
1733 cfqq->slice_end = 0;
1734 cfq_mark_cfqq_slice_new(cfqq);
1738 * Called when a new fs request (rq) is added (to cfqq). Check if there's
1739 * something we should do about it
1742 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1745 struct cfq_io_context *cic = RQ_CIC(rq);
1748 cfqq->meta_pending++;
1750 cfq_update_io_thinktime(cfqd, cic);
1751 cfq_update_io_seektime(cfqd, cic, rq);
1752 cfq_update_idle_window(cfqd, cfqq, cic);
1754 cic->last_request_pos = rq->sector + rq->nr_sectors;
1756 if (cfqq == cfqd->active_queue) {
1758 * if we are waiting for a request for this queue, let it rip
1759 * immediately and flag that we must not expire this queue
1762 if (cfq_cfqq_wait_request(cfqq)) {
1763 cfq_mark_cfqq_must_dispatch(cfqq);
1764 del_timer(&cfqd->idle_slice_timer);
1765 blk_start_queueing(cfqd->queue);
1767 } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
1769 * not the active queue - expire current slice if it is
1770 * idle and has expired it's mean thinktime or this new queue
1771 * has some old slice time left and is of higher priority
1773 cfq_preempt_queue(cfqd, cfqq);
1774 cfq_mark_cfqq_must_dispatch(cfqq);
1775 blk_start_queueing(cfqd->queue);
1779 static void cfq_insert_request(struct request_queue *q, struct request *rq)
1781 struct cfq_data *cfqd = q->elevator->elevator_data;
1782 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1784 cfq_init_prio_data(cfqq);
1788 list_add_tail(&rq->queuelist, &cfqq->fifo);
1790 cfq_rq_enqueued(cfqd, cfqq, rq);
1793 static void cfq_completed_request(struct request_queue *q, struct request *rq)
1795 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1796 struct cfq_data *cfqd = cfqq->cfqd;
1797 const int sync = rq_is_sync(rq);
1802 WARN_ON(!cfqd->rq_in_driver);
1803 WARN_ON(!cfqq->dispatched);
1804 cfqd->rq_in_driver--;
1807 if (cfq_cfqq_sync(cfqq))
1808 cfqd->sync_flight--;
1810 if (!cfq_class_idle(cfqq))
1811 cfqd->last_end_request = now;
1814 RQ_CIC(rq)->last_end_request = now;
1817 * If this is the active queue, check if it needs to be expired,
1818 * or if we want to idle in case it has no pending requests.
1820 if (cfqd->active_queue == cfqq) {
1821 if (cfq_cfqq_slice_new(cfqq)) {
1822 cfq_set_prio_slice(cfqd, cfqq);
1823 cfq_clear_cfqq_slice_new(cfqq);
1825 if (cfq_slice_used(cfqq))
1826 cfq_slice_expired(cfqd, 1);
1827 else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list))
1828 cfq_arm_slice_timer(cfqd);
1831 if (!cfqd->rq_in_driver)
1832 cfq_schedule_dispatch(cfqd);
1836 * we temporarily boost lower priority queues if they are holding fs exclusive
1837 * resources. they are boosted to normal prio (CLASS_BE/4)
1839 static void cfq_prio_boost(struct cfq_queue *cfqq)
1841 if (has_fs_excl()) {
1843 * boost idle prio on transactions that would lock out other
1844 * users of the filesystem
1846 if (cfq_class_idle(cfqq))
1847 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1848 if (cfqq->ioprio > IOPRIO_NORM)
1849 cfqq->ioprio = IOPRIO_NORM;
1852 * check if we need to unboost the queue
1854 if (cfqq->ioprio_class != cfqq->org_ioprio_class)
1855 cfqq->ioprio_class = cfqq->org_ioprio_class;
1856 if (cfqq->ioprio != cfqq->org_ioprio)
1857 cfqq->ioprio = cfqq->org_ioprio;
1861 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
1863 if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
1864 !cfq_cfqq_must_alloc_slice(cfqq)) {
1865 cfq_mark_cfqq_must_alloc_slice(cfqq);
1866 return ELV_MQUEUE_MUST;
1869 return ELV_MQUEUE_MAY;
1872 static int cfq_may_queue(struct request_queue *q, int rw)
1874 struct cfq_data *cfqd = q->elevator->elevator_data;
1875 struct task_struct *tsk = current;
1876 struct cfq_io_context *cic;
1877 struct cfq_queue *cfqq;
1880 * don't force setup of a queue from here, as a call to may_queue
1881 * does not necessarily imply that a request actually will be queued.
1882 * so just lookup a possibly existing queue, or return 'may queue'
1885 cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
1887 return ELV_MQUEUE_MAY;
1889 cfqq = cic_to_cfqq(cic, rw & REQ_RW_SYNC);
1891 cfq_init_prio_data(cfqq);
1892 cfq_prio_boost(cfqq);
1894 return __cfq_may_queue(cfqq);
1897 return ELV_MQUEUE_MAY;
1901 * queue lock held here
1903 static void cfq_put_request(struct request *rq)
1905 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1908 const int rw = rq_data_dir(rq);
1910 BUG_ON(!cfqq->allocated[rw]);
1911 cfqq->allocated[rw]--;
1913 put_io_context(RQ_CIC(rq)->ioc);
1915 rq->elevator_private = NULL;
1916 rq->elevator_private2 = NULL;
1918 cfq_put_queue(cfqq);
1923 * Allocate cfq data structures associated with this request.
1926 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
1928 struct cfq_data *cfqd = q->elevator->elevator_data;
1929 struct task_struct *tsk = current;
1930 struct cfq_io_context *cic;
1931 const int rw = rq_data_dir(rq);
1932 const int is_sync = rq_is_sync(rq);
1933 struct cfq_queue *cfqq;
1934 unsigned long flags;
1936 might_sleep_if(gfp_mask & __GFP_WAIT);
1938 cic = cfq_get_io_context(cfqd, gfp_mask);
1940 spin_lock_irqsave(q->queue_lock, flags);
1945 cfqq = cic_to_cfqq(cic, is_sync);
1947 cfqq = cfq_get_queue(cfqd, is_sync, tsk, gfp_mask);
1952 cic_set_cfqq(cic, cfqq, is_sync);
1955 cfqq->allocated[rw]++;
1956 cfq_clear_cfqq_must_alloc(cfqq);
1957 atomic_inc(&cfqq->ref);
1959 spin_unlock_irqrestore(q->queue_lock, flags);
1961 rq->elevator_private = cic;
1962 rq->elevator_private2 = cfqq;
1967 put_io_context(cic->ioc);
1969 cfq_schedule_dispatch(cfqd);
1970 spin_unlock_irqrestore(q->queue_lock, flags);
1974 static void cfq_kick_queue(struct work_struct *work)
1976 struct cfq_data *cfqd =
1977 container_of(work, struct cfq_data, unplug_work);
1978 struct request_queue *q = cfqd->queue;
1979 unsigned long flags;
1981 spin_lock_irqsave(q->queue_lock, flags);
1982 blk_start_queueing(q);
1983 spin_unlock_irqrestore(q->queue_lock, flags);
1987 * Timer running if the active_queue is currently idling inside its time slice
1989 static void cfq_idle_slice_timer(unsigned long data)
1991 struct cfq_data *cfqd = (struct cfq_data *) data;
1992 struct cfq_queue *cfqq;
1993 unsigned long flags;
1996 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1998 if ((cfqq = cfqd->active_queue) != NULL) {
2004 if (cfq_slice_used(cfqq))
2008 * only expire and reinvoke request handler, if there are
2009 * other queues with pending requests
2011 if (!cfqd->busy_queues)
2015 * not expired and it has a request pending, let it dispatch
2017 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) {
2018 cfq_mark_cfqq_must_dispatch(cfqq);
2023 cfq_slice_expired(cfqd, timed_out);
2025 cfq_schedule_dispatch(cfqd);
2027 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2031 * Timer running if an idle class queue is waiting for service
2033 static void cfq_idle_class_timer(unsigned long data)
2035 struct cfq_data *cfqd = (struct cfq_data *) data;
2036 unsigned long flags, end;
2038 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2041 * race with a non-idle queue, reset timer
2043 end = cfqd->last_end_request + CFQ_IDLE_GRACE;
2044 if (!time_after_eq(jiffies, end))
2045 mod_timer(&cfqd->idle_class_timer, end);
2047 cfq_schedule_dispatch(cfqd);
2049 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2052 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
2054 del_timer_sync(&cfqd->idle_slice_timer);
2055 del_timer_sync(&cfqd->idle_class_timer);
2056 blk_sync_queue(cfqd->queue);
2059 static void cfq_put_async_queues(struct cfq_data *cfqd)
2063 for (i = 0; i < IOPRIO_BE_NR; i++) {
2064 if (cfqd->async_cfqq[0][i])
2065 cfq_put_queue(cfqd->async_cfqq[0][i]);
2066 if (cfqd->async_cfqq[1][i])
2067 cfq_put_queue(cfqd->async_cfqq[1][i]);
2068 if (cfqd->async_idle_cfqq)
2069 cfq_put_queue(cfqd->async_idle_cfqq);
2073 static void cfq_exit_queue(elevator_t *e)
2075 struct cfq_data *cfqd = e->elevator_data;
2076 struct request_queue *q = cfqd->queue;
2078 cfq_shutdown_timer_wq(cfqd);
2080 spin_lock_irq(q->queue_lock);
2082 if (cfqd->active_queue)
2083 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
2085 while (!list_empty(&cfqd->cic_list)) {
2086 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2087 struct cfq_io_context,
2090 __cfq_exit_single_io_context(cfqd, cic);
2093 cfq_put_async_queues(cfqd);
2095 spin_unlock_irq(q->queue_lock);
2097 cfq_shutdown_timer_wq(cfqd);
2102 static void *cfq_init_queue(struct request_queue *q)
2104 struct cfq_data *cfqd;
2106 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
2110 cfqd->service_tree = CFQ_RB_ROOT;
2111 INIT_LIST_HEAD(&cfqd->cic_list);
2115 init_timer(&cfqd->idle_slice_timer);
2116 cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2117 cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2119 init_timer(&cfqd->idle_class_timer);
2120 cfqd->idle_class_timer.function = cfq_idle_class_timer;
2121 cfqd->idle_class_timer.data = (unsigned long) cfqd;
2123 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
2125 cfqd->cfq_quantum = cfq_quantum;
2126 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2127 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2128 cfqd->cfq_back_max = cfq_back_max;
2129 cfqd->cfq_back_penalty = cfq_back_penalty;
2130 cfqd->cfq_slice[0] = cfq_slice_async;
2131 cfqd->cfq_slice[1] = cfq_slice_sync;
2132 cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2133 cfqd->cfq_slice_idle = cfq_slice_idle;
2138 static void cfq_slab_kill(void)
2141 kmem_cache_destroy(cfq_pool);
2143 kmem_cache_destroy(cfq_ioc_pool);
2146 static int __init cfq_slab_setup(void)
2148 cfq_pool = KMEM_CACHE(cfq_queue, 0);
2152 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
2163 * sysfs parts below -->
2166 cfq_var_show(unsigned int var, char *page)
2168 return sprintf(page, "%d\n", var);
2172 cfq_var_store(unsigned int *var, const char *page, size_t count)
2174 char *p = (char *) page;
2176 *var = simple_strtoul(p, &p, 10);
2180 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
2181 static ssize_t __FUNC(elevator_t *e, char *page) \
2183 struct cfq_data *cfqd = e->elevator_data; \
2184 unsigned int __data = __VAR; \
2186 __data = jiffies_to_msecs(__data); \
2187 return cfq_var_show(__data, (page)); \
2189 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
2190 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2191 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
2192 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
2193 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
2194 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2195 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2196 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2197 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
2198 #undef SHOW_FUNCTION
2200 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
2201 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
2203 struct cfq_data *cfqd = e->elevator_data; \
2204 unsigned int __data; \
2205 int ret = cfq_var_store(&__data, (page), count); \
2206 if (__data < (MIN)) \
2208 else if (__data > (MAX)) \
2211 *(__PTR) = msecs_to_jiffies(__data); \
2213 *(__PTR) = __data; \
2216 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
2217 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1);
2218 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1);
2219 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
2220 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0);
2221 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2222 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2223 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
2224 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0);
2225 #undef STORE_FUNCTION
2227 #define CFQ_ATTR(name) \
2228 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2230 static struct elv_fs_entry cfq_attrs[] = {
2232 CFQ_ATTR(fifo_expire_sync),
2233 CFQ_ATTR(fifo_expire_async),
2234 CFQ_ATTR(back_seek_max),
2235 CFQ_ATTR(back_seek_penalty),
2236 CFQ_ATTR(slice_sync),
2237 CFQ_ATTR(slice_async),
2238 CFQ_ATTR(slice_async_rq),
2239 CFQ_ATTR(slice_idle),
2243 static struct elevator_type iosched_cfq = {
2245 .elevator_merge_fn = cfq_merge,
2246 .elevator_merged_fn = cfq_merged_request,
2247 .elevator_merge_req_fn = cfq_merged_requests,
2248 .elevator_allow_merge_fn = cfq_allow_merge,
2249 .elevator_dispatch_fn = cfq_dispatch_requests,
2250 .elevator_add_req_fn = cfq_insert_request,
2251 .elevator_activate_req_fn = cfq_activate_request,
2252 .elevator_deactivate_req_fn = cfq_deactivate_request,
2253 .elevator_queue_empty_fn = cfq_queue_empty,
2254 .elevator_completed_req_fn = cfq_completed_request,
2255 .elevator_former_req_fn = elv_rb_former_request,
2256 .elevator_latter_req_fn = elv_rb_latter_request,
2257 .elevator_set_req_fn = cfq_set_request,
2258 .elevator_put_req_fn = cfq_put_request,
2259 .elevator_may_queue_fn = cfq_may_queue,
2260 .elevator_init_fn = cfq_init_queue,
2261 .elevator_exit_fn = cfq_exit_queue,
2262 .trim = cfq_free_io_context,
2264 .elevator_attrs = cfq_attrs,
2265 .elevator_name = "cfq",
2266 .elevator_owner = THIS_MODULE,
2269 static int __init cfq_init(void)
2274 * could be 0 on HZ < 1000 setups
2276 if (!cfq_slice_async)
2277 cfq_slice_async = 1;
2278 if (!cfq_slice_idle)
2281 if (cfq_slab_setup())
2284 ret = elv_register(&iosched_cfq);
2291 static void __exit cfq_exit(void)
2293 DECLARE_COMPLETION_ONSTACK(all_gone);
2294 elv_unregister(&iosched_cfq);
2295 ioc_gone = &all_gone;
2296 /* ioc_gone's update must be visible before reading ioc_count */
2298 if (elv_ioc_count_read(ioc_count))
2299 wait_for_completion(ioc_gone);
2304 module_init(cfq_init);
2305 module_exit(cfq_exit);
2307 MODULE_AUTHOR("Jens Axboe");
2308 MODULE_LICENSE("GPL");
2309 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");