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>
14 #include <linux/blktrace_api.h>
19 /* max queue in one round of service */
20 static const int cfq_quantum = 4;
21 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
22 /* maximum backwards seek, in KiB */
23 static const int cfq_back_max = 16 * 1024;
24 /* penalty of a backwards seek */
25 static const int cfq_back_penalty = 2;
26 static const int cfq_slice_sync = HZ / 10;
27 static int cfq_slice_async = HZ / 25;
28 static const int cfq_slice_async_rq = 2;
29 static int cfq_slice_idle = HZ / 125;
30 static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
31 static const int cfq_hist_divisor = 4;
34 * offset from end of service tree
36 #define CFQ_IDLE_DELAY (HZ / 5)
39 * below this threshold, we consider thinktime immediate
41 #define CFQ_MIN_TT (2)
44 * Allow merged cfqqs to perform this amount of seeky I/O before
45 * deciding to break the queues up again.
47 #define CFQQ_COOP_TOUT (HZ)
49 #define CFQ_SLICE_SCALE (5)
50 #define CFQ_HW_QUEUE_MIN (5)
53 ((struct cfq_io_context *) (rq)->elevator_private)
54 #define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2)
56 static struct kmem_cache *cfq_pool;
57 static struct kmem_cache *cfq_ioc_pool;
59 static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
60 static struct completion *ioc_gone;
61 static DEFINE_SPINLOCK(ioc_gone_lock);
63 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
64 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
65 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
67 #define sample_valid(samples) ((samples) > 80)
70 * Most of our rbtree usage is for sorting with min extraction, so
71 * if we cache the leftmost node we don't have to walk down the tree
72 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
73 * move this into the elevator for the rq sorting as well.
80 #define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, 0, }
83 * Per process-grouping structure
88 /* various state flags, see below */
91 struct cfq_data *cfqd;
92 /* service_tree member */
93 struct rb_node rb_node;
94 /* service_tree key */
96 /* prio tree member */
97 struct rb_node p_node;
98 /* prio tree root we belong to, if any */
99 struct rb_root *p_root;
100 /* sorted list of pending requests */
101 struct rb_root sort_list;
102 /* if fifo isn't expired, next request to serve */
103 struct request *next_rq;
104 /* requests queued in sort_list */
106 /* currently allocated requests */
108 /* fifo list of requests in sort_list */
109 struct list_head fifo;
111 unsigned long slice_end;
113 unsigned int slice_dispatch;
115 /* pending metadata requests */
117 /* number of requests that are on the dispatch list or inside driver */
120 /* io prio of this group */
121 unsigned short ioprio, org_ioprio;
122 unsigned short ioprio_class, org_ioprio_class;
124 unsigned int seek_samples;
127 sector_t last_request_pos;
128 unsigned long seeky_start;
132 struct cfq_rb_root *service_tree;
133 struct cfq_queue *new_cfqq;
137 * First index in the service_trees.
138 * IDLE is handled separately, so it has negative index
147 * Second index in the service_trees.
151 SYNC_NOIDLE_WORKLOAD = 1,
157 * Per block device queue structure
160 struct request_queue *queue;
163 * rr lists of queues with requests, onle rr for each priority class.
164 * Counts are embedded in the cfq_rb_root
166 struct cfq_rb_root service_trees[2][3];
167 struct cfq_rb_root service_tree_idle;
169 * The priority currently being served
171 enum wl_prio_t serving_prio;
172 enum wl_type_t serving_type;
173 unsigned long workload_expires;
176 * Each priority tree is sorted by next_request position. These
177 * trees are used when determining if two or more queues are
178 * interleaving requests (see cfq_close_cooperator).
180 struct rb_root prio_trees[CFQ_PRIO_LISTS];
182 unsigned int busy_queues;
183 unsigned int busy_queues_avg[2];
189 * queue-depth detection
194 int rq_in_driver_peak;
197 * idle window management
199 struct timer_list idle_slice_timer;
200 struct work_struct unplug_work;
202 struct cfq_queue *active_queue;
203 struct cfq_io_context *active_cic;
206 * async queue for each priority case
208 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
209 struct cfq_queue *async_idle_cfqq;
211 sector_t last_position;
214 * tunables, see top of file
216 unsigned int cfq_quantum;
217 unsigned int cfq_fifo_expire[2];
218 unsigned int cfq_back_penalty;
219 unsigned int cfq_back_max;
220 unsigned int cfq_slice[2];
221 unsigned int cfq_slice_async_rq;
222 unsigned int cfq_slice_idle;
223 unsigned int cfq_latency;
225 struct list_head cic_list;
228 * Fallback dummy cfqq for extreme OOM conditions
230 struct cfq_queue oom_cfqq;
232 unsigned long last_end_sync_rq;
235 static struct cfq_rb_root *service_tree_for(enum wl_prio_t prio,
237 struct cfq_data *cfqd)
239 if (prio == IDLE_WORKLOAD)
240 return &cfqd->service_tree_idle;
242 return &cfqd->service_trees[prio][type];
245 enum cfqq_state_flags {
246 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
247 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
248 CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */
249 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
250 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
251 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */
252 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
253 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
254 CFQ_CFQQ_FLAG_sync, /* synchronous queue */
255 CFQ_CFQQ_FLAG_coop, /* cfqq is shared */
258 #define CFQ_CFQQ_FNS(name) \
259 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
261 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
263 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
265 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
267 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
269 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
273 CFQ_CFQQ_FNS(wait_request);
274 CFQ_CFQQ_FNS(must_dispatch);
275 CFQ_CFQQ_FNS(must_alloc_slice);
276 CFQ_CFQQ_FNS(fifo_expire);
277 CFQ_CFQQ_FNS(idle_window);
278 CFQ_CFQQ_FNS(prio_changed);
279 CFQ_CFQQ_FNS(slice_new);
284 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
285 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
286 #define cfq_log(cfqd, fmt, args...) \
287 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
289 static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
291 if (cfq_class_idle(cfqq))
292 return IDLE_WORKLOAD;
293 if (cfq_class_rt(cfqq))
299 static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
301 if (!cfq_cfqq_sync(cfqq))
302 return ASYNC_WORKLOAD;
303 if (!cfq_cfqq_idle_window(cfqq))
304 return SYNC_NOIDLE_WORKLOAD;
305 return SYNC_WORKLOAD;
308 static inline int cfq_busy_queues_wl(enum wl_prio_t wl, struct cfq_data *cfqd)
310 if (wl == IDLE_WORKLOAD)
311 return cfqd->service_tree_idle.count;
313 return cfqd->service_trees[wl][ASYNC_WORKLOAD].count
314 + cfqd->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
315 + cfqd->service_trees[wl][SYNC_WORKLOAD].count;
318 static void cfq_dispatch_insert(struct request_queue *, struct request *);
319 static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
320 struct io_context *, gfp_t);
321 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
322 struct io_context *);
324 static inline int rq_in_driver(struct cfq_data *cfqd)
326 return cfqd->rq_in_driver[0] + cfqd->rq_in_driver[1];
329 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
332 return cic->cfqq[is_sync];
335 static inline void cic_set_cfqq(struct cfq_io_context *cic,
336 struct cfq_queue *cfqq, bool is_sync)
338 cic->cfqq[is_sync] = cfqq;
342 * We regard a request as SYNC, if it's either a read or has the SYNC bit
343 * set (in which case it could also be direct WRITE).
345 static inline bool cfq_bio_sync(struct bio *bio)
347 return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO);
351 * scheduler run of queue, if there are requests pending and no one in the
352 * driver that will restart queueing
354 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
356 if (cfqd->busy_queues) {
357 cfq_log(cfqd, "schedule dispatch");
358 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
362 static int cfq_queue_empty(struct request_queue *q)
364 struct cfq_data *cfqd = q->elevator->elevator_data;
366 return !cfqd->busy_queues;
370 * Scale schedule slice based on io priority. Use the sync time slice only
371 * if a queue is marked sync and has sync io queued. A sync queue with async
372 * io only, should not get full sync slice length.
374 static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
377 const int base_slice = cfqd->cfq_slice[sync];
379 WARN_ON(prio >= IOPRIO_BE_NR);
381 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
385 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
387 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
391 * get averaged number of queues of RT/BE priority.
392 * average is updated, with a formula that gives more weight to higher numbers,
393 * to quickly follows sudden increases and decrease slowly
396 static inline unsigned cfq_get_avg_queues(struct cfq_data *cfqd, bool rt)
398 unsigned min_q, max_q;
399 unsigned mult = cfq_hist_divisor - 1;
400 unsigned round = cfq_hist_divisor / 2;
401 unsigned busy = cfq_busy_queues_wl(rt, cfqd);
403 min_q = min(cfqd->busy_queues_avg[rt], busy);
404 max_q = max(cfqd->busy_queues_avg[rt], busy);
405 cfqd->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
407 return cfqd->busy_queues_avg[rt];
411 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
413 unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
414 if (cfqd->cfq_latency) {
415 /* interested queues (we consider only the ones with the same
417 unsigned iq = cfq_get_avg_queues(cfqd, cfq_class_rt(cfqq));
418 unsigned sync_slice = cfqd->cfq_slice[1];
419 unsigned expect_latency = sync_slice * iq;
420 if (expect_latency > cfq_target_latency) {
421 unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
422 /* scale low_slice according to IO priority
423 * and sync vs async */
425 min(slice, base_low_slice * slice / sync_slice);
426 /* the adapted slice value is scaled to fit all iqs
427 * into the target latency */
428 slice = max(slice * cfq_target_latency / expect_latency,
432 cfqq->slice_end = jiffies + slice;
433 cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
437 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
438 * isn't valid until the first request from the dispatch is activated
439 * and the slice time set.
441 static inline bool cfq_slice_used(struct cfq_queue *cfqq)
443 if (cfq_cfqq_slice_new(cfqq))
445 if (time_before(jiffies, cfqq->slice_end))
452 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
453 * We choose the request that is closest to the head right now. Distance
454 * behind the head is penalized and only allowed to a certain extent.
456 static struct request *
457 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
459 sector_t s1, s2, d1 = 0, d2 = 0;
460 unsigned long back_max;
461 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
462 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
463 unsigned wrap = 0; /* bit mask: requests behind the disk head? */
465 if (rq1 == NULL || rq1 == rq2)
470 if (rq_is_sync(rq1) && !rq_is_sync(rq2))
472 else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
474 if (rq_is_meta(rq1) && !rq_is_meta(rq2))
476 else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
479 s1 = blk_rq_pos(rq1);
480 s2 = blk_rq_pos(rq2);
483 * by definition, 1KiB is 2 sectors
485 back_max = cfqd->cfq_back_max * 2;
488 * Strict one way elevator _except_ in the case where we allow
489 * short backward seeks which are biased as twice the cost of a
490 * similar forward seek.
494 else if (s1 + back_max >= last)
495 d1 = (last - s1) * cfqd->cfq_back_penalty;
497 wrap |= CFQ_RQ1_WRAP;
501 else if (s2 + back_max >= last)
502 d2 = (last - s2) * cfqd->cfq_back_penalty;
504 wrap |= CFQ_RQ2_WRAP;
506 /* Found required data */
509 * By doing switch() on the bit mask "wrap" we avoid having to
510 * check two variables for all permutations: --> faster!
513 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
529 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
532 * Since both rqs are wrapped,
533 * start with the one that's further behind head
534 * (--> only *one* back seek required),
535 * since back seek takes more time than forward.
545 * The below is leftmost cache rbtree addon
547 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
550 root->left = rb_first(&root->rb);
553 return rb_entry(root->left, struct cfq_queue, rb_node);
558 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
564 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
568 rb_erase_init(n, &root->rb);
573 * would be nice to take fifo expire time into account as well
575 static struct request *
576 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
577 struct request *last)
579 struct rb_node *rbnext = rb_next(&last->rb_node);
580 struct rb_node *rbprev = rb_prev(&last->rb_node);
581 struct request *next = NULL, *prev = NULL;
583 BUG_ON(RB_EMPTY_NODE(&last->rb_node));
586 prev = rb_entry_rq(rbprev);
589 next = rb_entry_rq(rbnext);
591 rbnext = rb_first(&cfqq->sort_list);
592 if (rbnext && rbnext != &last->rb_node)
593 next = rb_entry_rq(rbnext);
596 return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
599 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
600 struct cfq_queue *cfqq)
603 * just an approximation, should be ok.
605 return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) -
606 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
610 * The cfqd->service_trees holds all pending cfq_queue's that have
611 * requests waiting to be processed. It is sorted in the order that
612 * we will service the queues.
614 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
617 struct rb_node **p, *parent;
618 struct cfq_queue *__cfqq;
619 unsigned long rb_key;
620 struct cfq_rb_root *service_tree;
623 service_tree = service_tree_for(cfqq_prio(cfqq), cfqq_type(cfqq), cfqd);
624 if (cfq_class_idle(cfqq)) {
625 rb_key = CFQ_IDLE_DELAY;
626 parent = rb_last(&service_tree->rb);
627 if (parent && parent != &cfqq->rb_node) {
628 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
629 rb_key += __cfqq->rb_key;
632 } else if (!add_front) {
634 * Get our rb key offset. Subtract any residual slice
635 * value carried from last service. A negative resid
636 * count indicates slice overrun, and this should position
637 * the next service time further away in the tree.
639 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
640 rb_key -= cfqq->slice_resid;
641 cfqq->slice_resid = 0;
644 __cfqq = cfq_rb_first(service_tree);
645 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
648 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
650 * same position, nothing more to do
652 if (rb_key == cfqq->rb_key &&
653 cfqq->service_tree == service_tree)
656 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
657 cfqq->service_tree = NULL;
662 cfqq->service_tree = service_tree;
663 p = &service_tree->rb.rb_node;
668 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
671 * sort by key, that represents service time.
673 if (time_before(rb_key, __cfqq->rb_key))
684 service_tree->left = &cfqq->rb_node;
686 cfqq->rb_key = rb_key;
687 rb_link_node(&cfqq->rb_node, parent, p);
688 rb_insert_color(&cfqq->rb_node, &service_tree->rb);
689 service_tree->count++;
692 static struct cfq_queue *
693 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
694 sector_t sector, struct rb_node **ret_parent,
695 struct rb_node ***rb_link)
697 struct rb_node **p, *parent;
698 struct cfq_queue *cfqq = NULL;
706 cfqq = rb_entry(parent, struct cfq_queue, p_node);
709 * Sort strictly based on sector. Smallest to the left,
710 * largest to the right.
712 if (sector > blk_rq_pos(cfqq->next_rq))
714 else if (sector < blk_rq_pos(cfqq->next_rq))
722 *ret_parent = parent;
728 static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
730 struct rb_node **p, *parent;
731 struct cfq_queue *__cfqq;
734 rb_erase(&cfqq->p_node, cfqq->p_root);
738 if (cfq_class_idle(cfqq))
743 cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
744 __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
745 blk_rq_pos(cfqq->next_rq), &parent, &p);
747 rb_link_node(&cfqq->p_node, parent, p);
748 rb_insert_color(&cfqq->p_node, cfqq->p_root);
754 * Update cfqq's position in the service tree.
756 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
759 * Resorting requires the cfqq to be on the RR list already.
761 if (cfq_cfqq_on_rr(cfqq)) {
762 cfq_service_tree_add(cfqd, cfqq, 0);
763 cfq_prio_tree_add(cfqd, cfqq);
768 * add to busy list of queues for service, trying to be fair in ordering
769 * the pending list according to last request service
771 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
773 cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
774 BUG_ON(cfq_cfqq_on_rr(cfqq));
775 cfq_mark_cfqq_on_rr(cfqq);
778 cfq_resort_rr_list(cfqd, cfqq);
782 * Called when the cfqq no longer has requests pending, remove it from
785 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
787 cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
788 BUG_ON(!cfq_cfqq_on_rr(cfqq));
789 cfq_clear_cfqq_on_rr(cfqq);
791 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
792 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
793 cfqq->service_tree = NULL;
796 rb_erase(&cfqq->p_node, cfqq->p_root);
800 BUG_ON(!cfqd->busy_queues);
805 * rb tree support functions
807 static void cfq_del_rq_rb(struct request *rq)
809 struct cfq_queue *cfqq = RQ_CFQQ(rq);
810 struct cfq_data *cfqd = cfqq->cfqd;
811 const int sync = rq_is_sync(rq);
813 BUG_ON(!cfqq->queued[sync]);
814 cfqq->queued[sync]--;
816 elv_rb_del(&cfqq->sort_list, rq);
818 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
819 cfq_del_cfqq_rr(cfqd, cfqq);
822 static void cfq_add_rq_rb(struct request *rq)
824 struct cfq_queue *cfqq = RQ_CFQQ(rq);
825 struct cfq_data *cfqd = cfqq->cfqd;
826 struct request *__alias, *prev;
828 cfqq->queued[rq_is_sync(rq)]++;
831 * looks a little odd, but the first insert might return an alias.
832 * if that happens, put the alias on the dispatch list
834 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
835 cfq_dispatch_insert(cfqd->queue, __alias);
837 if (!cfq_cfqq_on_rr(cfqq))
838 cfq_add_cfqq_rr(cfqd, cfqq);
841 * check if this request is a better next-serve candidate
843 prev = cfqq->next_rq;
844 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
847 * adjust priority tree position, if ->next_rq changes
849 if (prev != cfqq->next_rq)
850 cfq_prio_tree_add(cfqd, cfqq);
852 BUG_ON(!cfqq->next_rq);
855 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
857 elv_rb_del(&cfqq->sort_list, rq);
858 cfqq->queued[rq_is_sync(rq)]--;
862 static struct request *
863 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
865 struct task_struct *tsk = current;
866 struct cfq_io_context *cic;
867 struct cfq_queue *cfqq;
869 cic = cfq_cic_lookup(cfqd, tsk->io_context);
873 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
875 sector_t sector = bio->bi_sector + bio_sectors(bio);
877 return elv_rb_find(&cfqq->sort_list, sector);
883 static void cfq_activate_request(struct request_queue *q, struct request *rq)
885 struct cfq_data *cfqd = q->elevator->elevator_data;
887 cfqd->rq_in_driver[rq_is_sync(rq)]++;
888 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
891 cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
894 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
896 struct cfq_data *cfqd = q->elevator->elevator_data;
897 const int sync = rq_is_sync(rq);
899 WARN_ON(!cfqd->rq_in_driver[sync]);
900 cfqd->rq_in_driver[sync]--;
901 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
905 static void cfq_remove_request(struct request *rq)
907 struct cfq_queue *cfqq = RQ_CFQQ(rq);
909 if (cfqq->next_rq == rq)
910 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
912 list_del_init(&rq->queuelist);
915 cfqq->cfqd->rq_queued--;
916 if (rq_is_meta(rq)) {
917 WARN_ON(!cfqq->meta_pending);
918 cfqq->meta_pending--;
922 static int cfq_merge(struct request_queue *q, struct request **req,
925 struct cfq_data *cfqd = q->elevator->elevator_data;
926 struct request *__rq;
928 __rq = cfq_find_rq_fmerge(cfqd, bio);
929 if (__rq && elv_rq_merge_ok(__rq, bio)) {
931 return ELEVATOR_FRONT_MERGE;
934 return ELEVATOR_NO_MERGE;
937 static void cfq_merged_request(struct request_queue *q, struct request *req,
940 if (type == ELEVATOR_FRONT_MERGE) {
941 struct cfq_queue *cfqq = RQ_CFQQ(req);
943 cfq_reposition_rq_rb(cfqq, req);
948 cfq_merged_requests(struct request_queue *q, struct request *rq,
949 struct request *next)
951 struct cfq_queue *cfqq = RQ_CFQQ(rq);
953 * reposition in fifo if next is older than rq
955 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
956 time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
957 list_move(&rq->queuelist, &next->queuelist);
958 rq_set_fifo_time(rq, rq_fifo_time(next));
961 if (cfqq->next_rq == next)
963 cfq_remove_request(next);
966 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
969 struct cfq_data *cfqd = q->elevator->elevator_data;
970 struct cfq_io_context *cic;
971 struct cfq_queue *cfqq;
974 * Disallow merge of a sync bio into an async request.
976 if (cfq_bio_sync(bio) && !rq_is_sync(rq))
980 * Lookup the cfqq that this bio will be queued with. Allow
981 * merge only if rq is queued there.
983 cic = cfq_cic_lookup(cfqd, current->io_context);
987 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
988 return cfqq == RQ_CFQQ(rq);
991 static void __cfq_set_active_queue(struct cfq_data *cfqd,
992 struct cfq_queue *cfqq)
995 cfq_log_cfqq(cfqd, cfqq, "set_active");
997 cfqq->slice_dispatch = 0;
999 cfq_clear_cfqq_wait_request(cfqq);
1000 cfq_clear_cfqq_must_dispatch(cfqq);
1001 cfq_clear_cfqq_must_alloc_slice(cfqq);
1002 cfq_clear_cfqq_fifo_expire(cfqq);
1003 cfq_mark_cfqq_slice_new(cfqq);
1005 del_timer(&cfqd->idle_slice_timer);
1008 cfqd->active_queue = cfqq;
1012 * current cfqq expired its slice (or was too idle), select new one
1015 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1018 cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
1020 if (cfq_cfqq_wait_request(cfqq))
1021 del_timer(&cfqd->idle_slice_timer);
1023 cfq_clear_cfqq_wait_request(cfqq);
1026 * store what was left of this slice, if the queue idled/timed out
1028 if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
1029 cfqq->slice_resid = cfqq->slice_end - jiffies;
1030 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
1033 cfq_resort_rr_list(cfqd, cfqq);
1035 if (cfqq == cfqd->active_queue)
1036 cfqd->active_queue = NULL;
1038 if (cfqd->active_cic) {
1039 put_io_context(cfqd->active_cic->ioc);
1040 cfqd->active_cic = NULL;
1044 static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
1046 struct cfq_queue *cfqq = cfqd->active_queue;
1049 __cfq_slice_expired(cfqd, cfqq, timed_out);
1053 * Get next queue for service. Unless we have a queue preemption,
1054 * we'll simply select the first cfqq in the service tree.
1056 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
1058 struct cfq_rb_root *service_tree =
1059 service_tree_for(cfqd->serving_prio, cfqd->serving_type, cfqd);
1061 if (RB_EMPTY_ROOT(&service_tree->rb))
1063 return cfq_rb_first(service_tree);
1067 * Get and set a new active queue for service.
1069 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
1070 struct cfq_queue *cfqq)
1073 cfqq = cfq_get_next_queue(cfqd);
1075 __cfq_set_active_queue(cfqd, cfqq);
1079 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
1082 if (blk_rq_pos(rq) >= cfqd->last_position)
1083 return blk_rq_pos(rq) - cfqd->last_position;
1085 return cfqd->last_position - blk_rq_pos(rq);
1088 #define CFQQ_SEEK_THR 8 * 1024
1089 #define CFQQ_SEEKY(cfqq) ((cfqq)->seek_mean > CFQQ_SEEK_THR)
1091 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1094 sector_t sdist = cfqq->seek_mean;
1096 if (!sample_valid(cfqq->seek_samples))
1097 sdist = CFQQ_SEEK_THR;
1099 return cfq_dist_from_last(cfqd, rq) <= sdist;
1102 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
1103 struct cfq_queue *cur_cfqq)
1105 struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
1106 struct rb_node *parent, *node;
1107 struct cfq_queue *__cfqq;
1108 sector_t sector = cfqd->last_position;
1110 if (RB_EMPTY_ROOT(root))
1114 * First, if we find a request starting at the end of the last
1115 * request, choose it.
1117 __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
1122 * If the exact sector wasn't found, the parent of the NULL leaf
1123 * will contain the closest sector.
1125 __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1126 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1129 if (blk_rq_pos(__cfqq->next_rq) < sector)
1130 node = rb_next(&__cfqq->p_node);
1132 node = rb_prev(&__cfqq->p_node);
1136 __cfqq = rb_entry(node, struct cfq_queue, p_node);
1137 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1145 * cur_cfqq - passed in so that we don't decide that the current queue is
1146 * closely cooperating with itself.
1148 * So, basically we're assuming that that cur_cfqq has dispatched at least
1149 * one request, and that cfqd->last_position reflects a position on the disk
1150 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
1153 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1154 struct cfq_queue *cur_cfqq)
1156 struct cfq_queue *cfqq;
1158 if (!cfq_cfqq_sync(cur_cfqq))
1160 if (CFQQ_SEEKY(cur_cfqq))
1164 * We should notice if some of the queues are cooperating, eg
1165 * working closely on the same area of the disk. In that case,
1166 * we can group them together and don't waste time idling.
1168 cfqq = cfqq_close(cfqd, cur_cfqq);
1173 * It only makes sense to merge sync queues.
1175 if (!cfq_cfqq_sync(cfqq))
1177 if (CFQQ_SEEKY(cfqq))
1181 * Do not merge queues of different priority classes
1183 if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
1190 * Determine whether we should enforce idle window for this queue.
1193 static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1195 enum wl_prio_t prio = cfqq_prio(cfqq);
1196 struct cfq_rb_root *service_tree = cfqq->service_tree;
1198 /* We never do for idle class queues. */
1199 if (prio == IDLE_WORKLOAD)
1202 /* We do for queues that were marked with idle window flag. */
1203 if (cfq_cfqq_idle_window(cfqq))
1207 * Otherwise, we do only if they are the last ones
1208 * in their service tree.
1211 service_tree = service_tree_for(prio, cfqq_type(cfqq), cfqd);
1213 if (service_tree->count == 0)
1216 return (service_tree->count == 1 && cfq_rb_first(service_tree) == cfqq);
1219 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
1221 struct cfq_queue *cfqq = cfqd->active_queue;
1222 struct cfq_io_context *cic;
1226 * SSD device without seek penalty, disable idling. But only do so
1227 * for devices that support queuing, otherwise we still have a problem
1228 * with sync vs async workloads.
1230 if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
1233 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
1234 WARN_ON(cfq_cfqq_slice_new(cfqq));
1237 * idle is disabled, either manually or by past process history
1239 if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq))
1243 * still requests with the driver, don't idle
1245 if (rq_in_driver(cfqd))
1249 * task has exited, don't wait
1251 cic = cfqd->active_cic;
1252 if (!cic || !atomic_read(&cic->ioc->nr_tasks))
1256 * If our average think time is larger than the remaining time
1257 * slice, then don't idle. This avoids overrunning the allotted
1260 if (sample_valid(cic->ttime_samples) &&
1261 (cfqq->slice_end - jiffies < cic->ttime_mean))
1264 cfq_mark_cfqq_wait_request(cfqq);
1266 sl = cfqd->cfq_slice_idle;
1267 /* are we servicing noidle tree, and there are more queues?
1268 * non-rotational or NCQ: no idle
1269 * non-NCQ rotational : very small idle, to allow
1270 * fair distribution of slice time for a process doing back-to-back
1273 if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
1274 service_tree_for(cfqd->serving_prio, SYNC_NOIDLE_WORKLOAD, cfqd)
1276 if (blk_queue_nonrot(cfqd->queue) || cfqd->hw_tag)
1278 sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT));
1281 mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
1282 cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
1286 * Move request from internal lists to the request queue dispatch list.
1288 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
1290 struct cfq_data *cfqd = q->elevator->elevator_data;
1291 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1293 cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
1295 cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
1296 cfq_remove_request(rq);
1298 elv_dispatch_sort(q, rq);
1300 if (cfq_cfqq_sync(cfqq))
1301 cfqd->sync_flight++;
1305 * return expired entry, or NULL to just start from scratch in rbtree
1307 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
1309 struct request *rq = NULL;
1311 if (cfq_cfqq_fifo_expire(cfqq))
1314 cfq_mark_cfqq_fifo_expire(cfqq);
1316 if (list_empty(&cfqq->fifo))
1319 rq = rq_entry_fifo(cfqq->fifo.next);
1320 if (time_before(jiffies, rq_fifo_time(rq)))
1323 cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
1328 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1330 const int base_rq = cfqd->cfq_slice_async_rq;
1332 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1334 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1338 * Must be called with the queue_lock held.
1340 static int cfqq_process_refs(struct cfq_queue *cfqq)
1342 int process_refs, io_refs;
1344 io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
1345 process_refs = atomic_read(&cfqq->ref) - io_refs;
1346 BUG_ON(process_refs < 0);
1347 return process_refs;
1350 static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
1352 int process_refs, new_process_refs;
1353 struct cfq_queue *__cfqq;
1355 /* Avoid a circular list and skip interim queue merges */
1356 while ((__cfqq = new_cfqq->new_cfqq)) {
1362 process_refs = cfqq_process_refs(cfqq);
1364 * If the process for the cfqq has gone away, there is no
1365 * sense in merging the queues.
1367 if (process_refs == 0)
1371 * Merge in the direction of the lesser amount of work.
1373 new_process_refs = cfqq_process_refs(new_cfqq);
1374 if (new_process_refs >= process_refs) {
1375 cfqq->new_cfqq = new_cfqq;
1376 atomic_add(process_refs, &new_cfqq->ref);
1378 new_cfqq->new_cfqq = cfqq;
1379 atomic_add(new_process_refs, &cfqq->ref);
1383 static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd, enum wl_prio_t prio,
1386 struct cfq_queue *queue;
1388 bool key_valid = false;
1389 unsigned long lowest_key = 0;
1390 enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
1394 * When priorities switched, we prefer starting
1395 * from SYNC_NOIDLE (first choice), or just SYNC
1398 if (service_tree_for(prio, cur_best, cfqd)->count)
1400 cur_best = SYNC_WORKLOAD;
1401 if (service_tree_for(prio, cur_best, cfqd)->count)
1404 return ASYNC_WORKLOAD;
1407 for (i = 0; i < 3; ++i) {
1408 /* otherwise, select the one with lowest rb_key */
1409 queue = cfq_rb_first(service_tree_for(prio, i, cfqd));
1411 (!key_valid || time_before(queue->rb_key, lowest_key))) {
1412 lowest_key = queue->rb_key;
1421 static void choose_service_tree(struct cfq_data *cfqd)
1423 enum wl_prio_t previous_prio = cfqd->serving_prio;
1428 /* Choose next priority. RT > BE > IDLE */
1429 if (cfq_busy_queues_wl(RT_WORKLOAD, cfqd))
1430 cfqd->serving_prio = RT_WORKLOAD;
1431 else if (cfq_busy_queues_wl(BE_WORKLOAD, cfqd))
1432 cfqd->serving_prio = BE_WORKLOAD;
1434 cfqd->serving_prio = IDLE_WORKLOAD;
1435 cfqd->workload_expires = jiffies + 1;
1440 * For RT and BE, we have to choose also the type
1441 * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
1444 prio_changed = (cfqd->serving_prio != previous_prio);
1445 count = service_tree_for(cfqd->serving_prio, cfqd->serving_type, cfqd)
1449 * If priority didn't change, check workload expiration,
1450 * and that we still have other queues ready
1452 if (!prio_changed && count &&
1453 !time_after(jiffies, cfqd->workload_expires))
1456 /* otherwise select new workload type */
1457 cfqd->serving_type =
1458 cfq_choose_wl(cfqd, cfqd->serving_prio, prio_changed);
1459 count = service_tree_for(cfqd->serving_prio, cfqd->serving_type, cfqd)
1463 * the workload slice is computed as a fraction of target latency
1464 * proportional to the number of queues in that workload, over
1465 * all the queues in the same priority class
1467 slice = cfq_target_latency * count /
1468 max_t(unsigned, cfqd->busy_queues_avg[cfqd->serving_prio],
1469 cfq_busy_queues_wl(cfqd->serving_prio, cfqd));
1471 if (cfqd->serving_type == ASYNC_WORKLOAD)
1472 /* async workload slice is scaled down according to
1473 * the sync/async slice ratio. */
1474 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
1476 /* sync workload slice is at least 2 * cfq_slice_idle */
1477 slice = max(slice, 2 * cfqd->cfq_slice_idle);
1479 slice = max_t(unsigned, slice, CFQ_MIN_TT);
1480 cfqd->workload_expires = jiffies + slice;
1484 * Select a queue for service. If we have a current active queue,
1485 * check whether to continue servicing it, or retrieve and set a new one.
1487 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
1489 struct cfq_queue *cfqq, *new_cfqq = NULL;
1491 cfqq = cfqd->active_queue;
1496 * The active queue has run out of time, expire it and select new.
1498 if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq))
1502 * The active queue has requests and isn't expired, allow it to
1505 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
1509 * If another queue has a request waiting within our mean seek
1510 * distance, let it run. The expire code will check for close
1511 * cooperators and put the close queue at the front of the service
1512 * tree. If possible, merge the expiring queue with the new cfqq.
1514 new_cfqq = cfq_close_cooperator(cfqd, cfqq);
1516 if (!cfqq->new_cfqq)
1517 cfq_setup_merge(cfqq, new_cfqq);
1522 * No requests pending. If the active queue still has requests in
1523 * flight or is idling for a new request, allow either of these
1524 * conditions to happen (or time out) before selecting a new queue.
1526 if (timer_pending(&cfqd->idle_slice_timer) ||
1527 (cfqq->dispatched && cfq_should_idle(cfqd, cfqq))) {
1533 cfq_slice_expired(cfqd, 0);
1536 * Current queue expired. Check if we have to switch to a new
1540 choose_service_tree(cfqd);
1542 cfqq = cfq_set_active_queue(cfqd, new_cfqq);
1547 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
1551 while (cfqq->next_rq) {
1552 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
1556 BUG_ON(!list_empty(&cfqq->fifo));
1561 * Drain our current requests. Used for barriers and when switching
1562 * io schedulers on-the-fly.
1564 static int cfq_forced_dispatch(struct cfq_data *cfqd)
1566 struct cfq_queue *cfqq;
1569 for (i = 0; i < 2; ++i)
1570 for (j = 0; j < 3; ++j)
1571 while ((cfqq = cfq_rb_first(&cfqd->service_trees[i][j]))
1573 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
1575 while ((cfqq = cfq_rb_first(&cfqd->service_tree_idle)) != NULL)
1576 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
1578 cfq_slice_expired(cfqd, 0);
1580 BUG_ON(cfqd->busy_queues);
1582 cfq_log(cfqd, "forced_dispatch=%d", dispatched);
1586 static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1588 unsigned int max_dispatch;
1591 * Drain async requests before we start sync IO
1593 if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
1597 * If this is an async queue and we have sync IO in flight, let it wait
1599 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
1602 max_dispatch = cfqd->cfq_quantum;
1603 if (cfq_class_idle(cfqq))
1607 * Does this cfqq already have too much IO in flight?
1609 if (cfqq->dispatched >= max_dispatch) {
1611 * idle queue must always only have a single IO in flight
1613 if (cfq_class_idle(cfqq))
1617 * We have other queues, don't allow more IO from this one
1619 if (cfqd->busy_queues > 1)
1623 * Sole queue user, allow bigger slice
1629 * Async queues must wait a bit before being allowed dispatch.
1630 * We also ramp up the dispatch depth gradually for async IO,
1631 * based on the last sync IO we serviced
1633 if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
1634 unsigned long last_sync = jiffies - cfqd->last_end_sync_rq;
1637 depth = last_sync / cfqd->cfq_slice[1];
1638 if (!depth && !cfqq->dispatched)
1640 if (depth < max_dispatch)
1641 max_dispatch = depth;
1645 * If we're below the current max, allow a dispatch
1647 return cfqq->dispatched < max_dispatch;
1651 * Dispatch a request from cfqq, moving them to the request queue
1654 static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1658 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
1660 if (!cfq_may_dispatch(cfqd, cfqq))
1664 * follow expired path, else get first next available
1666 rq = cfq_check_fifo(cfqq);
1671 * insert request into driver dispatch list
1673 cfq_dispatch_insert(cfqd->queue, rq);
1675 if (!cfqd->active_cic) {
1676 struct cfq_io_context *cic = RQ_CIC(rq);
1678 atomic_long_inc(&cic->ioc->refcount);
1679 cfqd->active_cic = cic;
1686 * Find the cfqq that we need to service and move a request from that to the
1689 static int cfq_dispatch_requests(struct request_queue *q, int force)
1691 struct cfq_data *cfqd = q->elevator->elevator_data;
1692 struct cfq_queue *cfqq;
1694 if (!cfqd->busy_queues)
1697 if (unlikely(force))
1698 return cfq_forced_dispatch(cfqd);
1700 cfqq = cfq_select_queue(cfqd);
1705 * Dispatch a request from this cfqq, if it is allowed
1707 if (!cfq_dispatch_request(cfqd, cfqq))
1710 cfqq->slice_dispatch++;
1711 cfq_clear_cfqq_must_dispatch(cfqq);
1714 * expire an async queue immediately if it has used up its slice. idle
1715 * queue always expire after 1 dispatch round.
1717 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
1718 cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1719 cfq_class_idle(cfqq))) {
1720 cfqq->slice_end = jiffies + 1;
1721 cfq_slice_expired(cfqd, 0);
1724 cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
1729 * task holds one reference to the queue, dropped when task exits. each rq
1730 * in-flight on this queue also holds a reference, dropped when rq is freed.
1732 * queue lock must be held here.
1734 static void cfq_put_queue(struct cfq_queue *cfqq)
1736 struct cfq_data *cfqd = cfqq->cfqd;
1738 BUG_ON(atomic_read(&cfqq->ref) <= 0);
1740 if (!atomic_dec_and_test(&cfqq->ref))
1743 cfq_log_cfqq(cfqd, cfqq, "put_queue");
1744 BUG_ON(rb_first(&cfqq->sort_list));
1745 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1746 BUG_ON(cfq_cfqq_on_rr(cfqq));
1748 if (unlikely(cfqd->active_queue == cfqq)) {
1749 __cfq_slice_expired(cfqd, cfqq, 0);
1750 cfq_schedule_dispatch(cfqd);
1753 kmem_cache_free(cfq_pool, cfqq);
1757 * Must always be called with the rcu_read_lock() held
1760 __call_for_each_cic(struct io_context *ioc,
1761 void (*func)(struct io_context *, struct cfq_io_context *))
1763 struct cfq_io_context *cic;
1764 struct hlist_node *n;
1766 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
1771 * Call func for each cic attached to this ioc.
1774 call_for_each_cic(struct io_context *ioc,
1775 void (*func)(struct io_context *, struct cfq_io_context *))
1778 __call_for_each_cic(ioc, func);
1782 static void cfq_cic_free_rcu(struct rcu_head *head)
1784 struct cfq_io_context *cic;
1786 cic = container_of(head, struct cfq_io_context, rcu_head);
1788 kmem_cache_free(cfq_ioc_pool, cic);
1789 elv_ioc_count_dec(cfq_ioc_count);
1793 * CFQ scheduler is exiting, grab exit lock and check
1794 * the pending io context count. If it hits zero,
1795 * complete ioc_gone and set it back to NULL
1797 spin_lock(&ioc_gone_lock);
1798 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
1802 spin_unlock(&ioc_gone_lock);
1806 static void cfq_cic_free(struct cfq_io_context *cic)
1808 call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
1811 static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
1813 unsigned long flags;
1815 BUG_ON(!cic->dead_key);
1817 spin_lock_irqsave(&ioc->lock, flags);
1818 radix_tree_delete(&ioc->radix_root, cic->dead_key);
1819 hlist_del_rcu(&cic->cic_list);
1820 spin_unlock_irqrestore(&ioc->lock, flags);
1826 * Must be called with rcu_read_lock() held or preemption otherwise disabled.
1827 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
1828 * and ->trim() which is called with the task lock held
1830 static void cfq_free_io_context(struct io_context *ioc)
1833 * ioc->refcount is zero here, or we are called from elv_unregister(),
1834 * so no more cic's are allowed to be linked into this ioc. So it
1835 * should be ok to iterate over the known list, we will see all cic's
1836 * since no new ones are added.
1838 __call_for_each_cic(ioc, cic_free_func);
1841 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1843 struct cfq_queue *__cfqq, *next;
1845 if (unlikely(cfqq == cfqd->active_queue)) {
1846 __cfq_slice_expired(cfqd, cfqq, 0);
1847 cfq_schedule_dispatch(cfqd);
1851 * If this queue was scheduled to merge with another queue, be
1852 * sure to drop the reference taken on that queue (and others in
1853 * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs.
1855 __cfqq = cfqq->new_cfqq;
1857 if (__cfqq == cfqq) {
1858 WARN(1, "cfqq->new_cfqq loop detected\n");
1861 next = __cfqq->new_cfqq;
1862 cfq_put_queue(__cfqq);
1866 cfq_put_queue(cfqq);
1869 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
1870 struct cfq_io_context *cic)
1872 struct io_context *ioc = cic->ioc;
1874 list_del_init(&cic->queue_list);
1877 * Make sure key == NULL is seen for dead queues
1880 cic->dead_key = (unsigned long) cic->key;
1883 if (ioc->ioc_data == cic)
1884 rcu_assign_pointer(ioc->ioc_data, NULL);
1886 if (cic->cfqq[BLK_RW_ASYNC]) {
1887 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
1888 cic->cfqq[BLK_RW_ASYNC] = NULL;
1891 if (cic->cfqq[BLK_RW_SYNC]) {
1892 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
1893 cic->cfqq[BLK_RW_SYNC] = NULL;
1897 static void cfq_exit_single_io_context(struct io_context *ioc,
1898 struct cfq_io_context *cic)
1900 struct cfq_data *cfqd = cic->key;
1903 struct request_queue *q = cfqd->queue;
1904 unsigned long flags;
1906 spin_lock_irqsave(q->queue_lock, flags);
1909 * Ensure we get a fresh copy of the ->key to prevent
1910 * race between exiting task and queue
1912 smp_read_barrier_depends();
1914 __cfq_exit_single_io_context(cfqd, cic);
1916 spin_unlock_irqrestore(q->queue_lock, flags);
1921 * The process that ioc belongs to has exited, we need to clean up
1922 * and put the internal structures we have that belongs to that process.
1924 static void cfq_exit_io_context(struct io_context *ioc)
1926 call_for_each_cic(ioc, cfq_exit_single_io_context);
1929 static struct cfq_io_context *
1930 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1932 struct cfq_io_context *cic;
1934 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
1937 cic->last_end_request = jiffies;
1938 INIT_LIST_HEAD(&cic->queue_list);
1939 INIT_HLIST_NODE(&cic->cic_list);
1940 cic->dtor = cfq_free_io_context;
1941 cic->exit = cfq_exit_io_context;
1942 elv_ioc_count_inc(cfq_ioc_count);
1948 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
1950 struct task_struct *tsk = current;
1953 if (!cfq_cfqq_prio_changed(cfqq))
1956 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
1957 switch (ioprio_class) {
1959 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1960 case IOPRIO_CLASS_NONE:
1962 * no prio set, inherit CPU scheduling settings
1964 cfqq->ioprio = task_nice_ioprio(tsk);
1965 cfqq->ioprio_class = task_nice_ioclass(tsk);
1967 case IOPRIO_CLASS_RT:
1968 cfqq->ioprio = task_ioprio(ioc);
1969 cfqq->ioprio_class = IOPRIO_CLASS_RT;
1971 case IOPRIO_CLASS_BE:
1972 cfqq->ioprio = task_ioprio(ioc);
1973 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1975 case IOPRIO_CLASS_IDLE:
1976 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1978 cfq_clear_cfqq_idle_window(cfqq);
1983 * keep track of original prio settings in case we have to temporarily
1984 * elevate the priority of this queue
1986 cfqq->org_ioprio = cfqq->ioprio;
1987 cfqq->org_ioprio_class = cfqq->ioprio_class;
1988 cfq_clear_cfqq_prio_changed(cfqq);
1991 static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
1993 struct cfq_data *cfqd = cic->key;
1994 struct cfq_queue *cfqq;
1995 unsigned long flags;
1997 if (unlikely(!cfqd))
2000 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2002 cfqq = cic->cfqq[BLK_RW_ASYNC];
2004 struct cfq_queue *new_cfqq;
2005 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
2008 cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
2009 cfq_put_queue(cfqq);
2013 cfqq = cic->cfqq[BLK_RW_SYNC];
2015 cfq_mark_cfqq_prio_changed(cfqq);
2017 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2020 static void cfq_ioc_set_ioprio(struct io_context *ioc)
2022 call_for_each_cic(ioc, changed_ioprio);
2023 ioc->ioprio_changed = 0;
2026 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2027 pid_t pid, bool is_sync)
2029 RB_CLEAR_NODE(&cfqq->rb_node);
2030 RB_CLEAR_NODE(&cfqq->p_node);
2031 INIT_LIST_HEAD(&cfqq->fifo);
2033 atomic_set(&cfqq->ref, 0);
2036 cfq_mark_cfqq_prio_changed(cfqq);
2039 if (!cfq_class_idle(cfqq))
2040 cfq_mark_cfqq_idle_window(cfqq);
2041 cfq_mark_cfqq_sync(cfqq);
2046 static struct cfq_queue *
2047 cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
2048 struct io_context *ioc, gfp_t gfp_mask)
2050 struct cfq_queue *cfqq, *new_cfqq = NULL;
2051 struct cfq_io_context *cic;
2054 cic = cfq_cic_lookup(cfqd, ioc);
2055 /* cic always exists here */
2056 cfqq = cic_to_cfqq(cic, is_sync);
2059 * Always try a new alloc if we fell back to the OOM cfqq
2060 * originally, since it should just be a temporary situation.
2062 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2067 } else if (gfp_mask & __GFP_WAIT) {
2068 spin_unlock_irq(cfqd->queue->queue_lock);
2069 new_cfqq = kmem_cache_alloc_node(cfq_pool,
2070 gfp_mask | __GFP_ZERO,
2072 spin_lock_irq(cfqd->queue->queue_lock);
2076 cfqq = kmem_cache_alloc_node(cfq_pool,
2077 gfp_mask | __GFP_ZERO,
2082 cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
2083 cfq_init_prio_data(cfqq, ioc);
2084 cfq_log_cfqq(cfqd, cfqq, "alloced");
2086 cfqq = &cfqd->oom_cfqq;
2090 kmem_cache_free(cfq_pool, new_cfqq);
2095 static struct cfq_queue **
2096 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
2098 switch (ioprio_class) {
2099 case IOPRIO_CLASS_RT:
2100 return &cfqd->async_cfqq[0][ioprio];
2101 case IOPRIO_CLASS_BE:
2102 return &cfqd->async_cfqq[1][ioprio];
2103 case IOPRIO_CLASS_IDLE:
2104 return &cfqd->async_idle_cfqq;
2110 static struct cfq_queue *
2111 cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
2114 const int ioprio = task_ioprio(ioc);
2115 const int ioprio_class = task_ioprio_class(ioc);
2116 struct cfq_queue **async_cfqq = NULL;
2117 struct cfq_queue *cfqq = NULL;
2120 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
2125 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
2128 * pin the queue now that it's allocated, scheduler exit will prune it
2130 if (!is_sync && !(*async_cfqq)) {
2131 atomic_inc(&cfqq->ref);
2135 atomic_inc(&cfqq->ref);
2140 * We drop cfq io contexts lazily, so we may find a dead one.
2143 cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
2144 struct cfq_io_context *cic)
2146 unsigned long flags;
2148 WARN_ON(!list_empty(&cic->queue_list));
2150 spin_lock_irqsave(&ioc->lock, flags);
2152 BUG_ON(ioc->ioc_data == cic);
2154 radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
2155 hlist_del_rcu(&cic->cic_list);
2156 spin_unlock_irqrestore(&ioc->lock, flags);
2161 static struct cfq_io_context *
2162 cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
2164 struct cfq_io_context *cic;
2165 unsigned long flags;
2174 * we maintain a last-hit cache, to avoid browsing over the tree
2176 cic = rcu_dereference(ioc->ioc_data);
2177 if (cic && cic->key == cfqd) {
2183 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
2187 /* ->key must be copied to avoid race with cfq_exit_queue() */
2190 cfq_drop_dead_cic(cfqd, ioc, cic);
2195 spin_lock_irqsave(&ioc->lock, flags);
2196 rcu_assign_pointer(ioc->ioc_data, cic);
2197 spin_unlock_irqrestore(&ioc->lock, flags);
2205 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2206 * the process specific cfq io context when entered from the block layer.
2207 * Also adds the cic to a per-cfqd list, used when this queue is removed.
2209 static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
2210 struct cfq_io_context *cic, gfp_t gfp_mask)
2212 unsigned long flags;
2215 ret = radix_tree_preload(gfp_mask);
2220 spin_lock_irqsave(&ioc->lock, flags);
2221 ret = radix_tree_insert(&ioc->radix_root,
2222 (unsigned long) cfqd, cic);
2224 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
2225 spin_unlock_irqrestore(&ioc->lock, flags);
2227 radix_tree_preload_end();
2230 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2231 list_add(&cic->queue_list, &cfqd->cic_list);
2232 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2237 printk(KERN_ERR "cfq: cic link failed!\n");
2243 * Setup general io context and cfq io context. There can be several cfq
2244 * io contexts per general io context, if this process is doing io to more
2245 * than one device managed by cfq.
2247 static struct cfq_io_context *
2248 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2250 struct io_context *ioc = NULL;
2251 struct cfq_io_context *cic;
2253 might_sleep_if(gfp_mask & __GFP_WAIT);
2255 ioc = get_io_context(gfp_mask, cfqd->queue->node);
2259 cic = cfq_cic_lookup(cfqd, ioc);
2263 cic = cfq_alloc_io_context(cfqd, gfp_mask);
2267 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
2271 smp_read_barrier_depends();
2272 if (unlikely(ioc->ioprio_changed))
2273 cfq_ioc_set_ioprio(ioc);
2279 put_io_context(ioc);
2284 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
2286 unsigned long elapsed = jiffies - cic->last_end_request;
2287 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
2289 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
2290 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
2291 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
2295 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2301 if (!cfqq->last_request_pos)
2303 else if (cfqq->last_request_pos < blk_rq_pos(rq))
2304 sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
2306 sdist = cfqq->last_request_pos - blk_rq_pos(rq);
2309 * Don't allow the seek distance to get too large from the
2310 * odd fragment, pagein, etc
2312 if (cfqq->seek_samples <= 60) /* second&third seek */
2313 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*1024);
2315 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*64);
2317 cfqq->seek_samples = (7*cfqq->seek_samples + 256) / 8;
2318 cfqq->seek_total = (7*cfqq->seek_total + (u64)256*sdist) / 8;
2319 total = cfqq->seek_total + (cfqq->seek_samples/2);
2320 do_div(total, cfqq->seek_samples);
2321 cfqq->seek_mean = (sector_t)total;
2324 * If this cfqq is shared between multiple processes, check to
2325 * make sure that those processes are still issuing I/Os within
2326 * the mean seek distance. If not, it may be time to break the
2327 * queues apart again.
2329 if (cfq_cfqq_coop(cfqq)) {
2330 if (CFQQ_SEEKY(cfqq) && !cfqq->seeky_start)
2331 cfqq->seeky_start = jiffies;
2332 else if (!CFQQ_SEEKY(cfqq))
2333 cfqq->seeky_start = 0;
2338 * Disable idle window if the process thinks too long or seeks so much that
2342 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2343 struct cfq_io_context *cic)
2345 int old_idle, enable_idle;
2348 * Don't idle for async or idle io prio class
2350 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
2353 enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
2355 if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
2356 (sample_valid(cfqq->seek_samples) && CFQQ_SEEKY(cfqq)))
2358 else if (sample_valid(cic->ttime_samples)) {
2359 if (cic->ttime_mean > cfqd->cfq_slice_idle)
2365 if (old_idle != enable_idle) {
2366 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
2368 cfq_mark_cfqq_idle_window(cfqq);
2370 cfq_clear_cfqq_idle_window(cfqq);
2375 * Check if new_cfqq should preempt the currently active queue. Return 0 for
2376 * no or if we aren't sure, a 1 will cause a preempt.
2379 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
2382 struct cfq_queue *cfqq;
2384 cfqq = cfqd->active_queue;
2388 if (cfq_slice_used(cfqq))
2391 if (cfq_class_idle(new_cfqq))
2394 if (cfq_class_idle(cfqq))
2397 if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD
2398 && new_cfqq->service_tree == cfqq->service_tree)
2402 * if the new request is sync, but the currently running queue is
2403 * not, let the sync request have priority.
2405 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
2409 * So both queues are sync. Let the new request get disk time if
2410 * it's a metadata request and the current queue is doing regular IO.
2412 if (rq_is_meta(rq) && !cfqq->meta_pending)
2416 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
2418 if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
2421 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
2425 * if this request is as-good as one we would expect from the
2426 * current cfqq, let it preempt
2428 if (cfq_rq_close(cfqd, cfqq, rq))
2435 * cfqq preempts the active queue. if we allowed preempt with no slice left,
2436 * let it have half of its nominal slice.
2438 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2440 cfq_log_cfqq(cfqd, cfqq, "preempt");
2441 cfq_slice_expired(cfqd, 1);
2444 * Put the new queue at the front of the of the current list,
2445 * so we know that it will be selected next.
2447 BUG_ON(!cfq_cfqq_on_rr(cfqq));
2449 cfq_service_tree_add(cfqd, cfqq, 1);
2451 cfqq->slice_end = 0;
2452 cfq_mark_cfqq_slice_new(cfqq);
2456 * Called when a new fs request (rq) is added (to cfqq). Check if there's
2457 * something we should do about it
2460 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2463 struct cfq_io_context *cic = RQ_CIC(rq);
2467 cfqq->meta_pending++;
2469 cfq_update_io_thinktime(cfqd, cic);
2470 cfq_update_io_seektime(cfqd, cfqq, rq);
2471 cfq_update_idle_window(cfqd, cfqq, cic);
2473 cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
2475 if (cfqq == cfqd->active_queue) {
2477 * Remember that we saw a request from this process, but
2478 * don't start queuing just yet. Otherwise we risk seeing lots
2479 * of tiny requests, because we disrupt the normal plugging
2480 * and merging. If the request is already larger than a single
2481 * page, let it rip immediately. For that case we assume that
2482 * merging is already done. Ditto for a busy system that
2483 * has other work pending, don't risk delaying until the
2484 * idle timer unplug to continue working.
2486 if (cfq_cfqq_wait_request(cfqq)) {
2487 if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
2488 cfqd->busy_queues > 1) {
2489 del_timer(&cfqd->idle_slice_timer);
2490 __blk_run_queue(cfqd->queue);
2492 cfq_mark_cfqq_must_dispatch(cfqq);
2494 } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
2496 * not the active queue - expire current slice if it is
2497 * idle and has expired it's mean thinktime or this new queue
2498 * has some old slice time left and is of higher priority or
2499 * this new queue is RT and the current one is BE
2501 cfq_preempt_queue(cfqd, cfqq);
2502 __blk_run_queue(cfqd->queue);
2506 static void cfq_insert_request(struct request_queue *q, struct request *rq)
2508 struct cfq_data *cfqd = q->elevator->elevator_data;
2509 struct cfq_queue *cfqq = RQ_CFQQ(rq);
2511 cfq_log_cfqq(cfqd, cfqq, "insert_request");
2512 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
2514 rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
2515 list_add_tail(&rq->queuelist, &cfqq->fifo);
2518 cfq_rq_enqueued(cfqd, cfqq, rq);
2522 * Update hw_tag based on peak queue depth over 50 samples under
2525 static void cfq_update_hw_tag(struct cfq_data *cfqd)
2527 struct cfq_queue *cfqq = cfqd->active_queue;
2529 if (rq_in_driver(cfqd) > cfqd->rq_in_driver_peak)
2530 cfqd->rq_in_driver_peak = rq_in_driver(cfqd);
2532 if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
2533 rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN)
2537 * If active queue hasn't enough requests and can idle, cfq might not
2538 * dispatch sufficient requests to hardware. Don't zero hw_tag in this
2541 if (cfqq && cfq_cfqq_idle_window(cfqq) &&
2542 cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
2543 CFQ_HW_QUEUE_MIN && rq_in_driver(cfqd) < CFQ_HW_QUEUE_MIN)
2546 if (cfqd->hw_tag_samples++ < 50)
2549 if (cfqd->rq_in_driver_peak >= CFQ_HW_QUEUE_MIN)
2554 cfqd->hw_tag_samples = 0;
2555 cfqd->rq_in_driver_peak = 0;
2558 static void cfq_completed_request(struct request_queue *q, struct request *rq)
2560 struct cfq_queue *cfqq = RQ_CFQQ(rq);
2561 struct cfq_data *cfqd = cfqq->cfqd;
2562 const int sync = rq_is_sync(rq);
2566 cfq_log_cfqq(cfqd, cfqq, "complete");
2568 cfq_update_hw_tag(cfqd);
2570 WARN_ON(!cfqd->rq_in_driver[sync]);
2571 WARN_ON(!cfqq->dispatched);
2572 cfqd->rq_in_driver[sync]--;
2575 if (cfq_cfqq_sync(cfqq))
2576 cfqd->sync_flight--;
2579 RQ_CIC(rq)->last_end_request = now;
2580 cfqd->last_end_sync_rq = now;
2584 * If this is the active queue, check if it needs to be expired,
2585 * or if we want to idle in case it has no pending requests.
2587 if (cfqd->active_queue == cfqq) {
2588 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
2590 if (cfq_cfqq_slice_new(cfqq)) {
2591 cfq_set_prio_slice(cfqd, cfqq);
2592 cfq_clear_cfqq_slice_new(cfqq);
2595 * If there are no requests waiting in this queue, and
2596 * there are other queues ready to issue requests, AND
2597 * those other queues are issuing requests within our
2598 * mean seek distance, give them a chance to run instead
2601 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
2602 cfq_slice_expired(cfqd, 1);
2603 else if (cfqq_empty && !cfq_close_cooperator(cfqd, cfqq) &&
2604 sync && !rq_noidle(rq))
2605 cfq_arm_slice_timer(cfqd);
2608 if (!rq_in_driver(cfqd))
2609 cfq_schedule_dispatch(cfqd);
2613 * we temporarily boost lower priority queues if they are holding fs exclusive
2614 * resources. they are boosted to normal prio (CLASS_BE/4)
2616 static void cfq_prio_boost(struct cfq_queue *cfqq)
2618 if (has_fs_excl()) {
2620 * boost idle prio on transactions that would lock out other
2621 * users of the filesystem
2623 if (cfq_class_idle(cfqq))
2624 cfqq->ioprio_class = IOPRIO_CLASS_BE;
2625 if (cfqq->ioprio > IOPRIO_NORM)
2626 cfqq->ioprio = IOPRIO_NORM;
2629 * unboost the queue (if needed)
2631 cfqq->ioprio_class = cfqq->org_ioprio_class;
2632 cfqq->ioprio = cfqq->org_ioprio;
2636 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
2638 if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
2639 cfq_mark_cfqq_must_alloc_slice(cfqq);
2640 return ELV_MQUEUE_MUST;
2643 return ELV_MQUEUE_MAY;
2646 static int cfq_may_queue(struct request_queue *q, int rw)
2648 struct cfq_data *cfqd = q->elevator->elevator_data;
2649 struct task_struct *tsk = current;
2650 struct cfq_io_context *cic;
2651 struct cfq_queue *cfqq;
2654 * don't force setup of a queue from here, as a call to may_queue
2655 * does not necessarily imply that a request actually will be queued.
2656 * so just lookup a possibly existing queue, or return 'may queue'
2659 cic = cfq_cic_lookup(cfqd, tsk->io_context);
2661 return ELV_MQUEUE_MAY;
2663 cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
2665 cfq_init_prio_data(cfqq, cic->ioc);
2666 cfq_prio_boost(cfqq);
2668 return __cfq_may_queue(cfqq);
2671 return ELV_MQUEUE_MAY;
2675 * queue lock held here
2677 static void cfq_put_request(struct request *rq)
2679 struct cfq_queue *cfqq = RQ_CFQQ(rq);
2682 const int rw = rq_data_dir(rq);
2684 BUG_ON(!cfqq->allocated[rw]);
2685 cfqq->allocated[rw]--;
2687 put_io_context(RQ_CIC(rq)->ioc);
2689 rq->elevator_private = NULL;
2690 rq->elevator_private2 = NULL;
2692 cfq_put_queue(cfqq);
2696 static struct cfq_queue *
2697 cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
2698 struct cfq_queue *cfqq)
2700 cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
2701 cic_set_cfqq(cic, cfqq->new_cfqq, 1);
2702 cfq_mark_cfqq_coop(cfqq->new_cfqq);
2703 cfq_put_queue(cfqq);
2704 return cic_to_cfqq(cic, 1);
2707 static int should_split_cfqq(struct cfq_queue *cfqq)
2709 if (cfqq->seeky_start &&
2710 time_after(jiffies, cfqq->seeky_start + CFQQ_COOP_TOUT))
2716 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
2717 * was the last process referring to said cfqq.
2719 static struct cfq_queue *
2720 split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
2722 if (cfqq_process_refs(cfqq) == 1) {
2723 cfqq->seeky_start = 0;
2724 cfqq->pid = current->pid;
2725 cfq_clear_cfqq_coop(cfqq);
2729 cic_set_cfqq(cic, NULL, 1);
2730 cfq_put_queue(cfqq);
2734 * Allocate cfq data structures associated with this request.
2737 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
2739 struct cfq_data *cfqd = q->elevator->elevator_data;
2740 struct cfq_io_context *cic;
2741 const int rw = rq_data_dir(rq);
2742 const bool is_sync = rq_is_sync(rq);
2743 struct cfq_queue *cfqq;
2744 unsigned long flags;
2746 might_sleep_if(gfp_mask & __GFP_WAIT);
2748 cic = cfq_get_io_context(cfqd, gfp_mask);
2750 spin_lock_irqsave(q->queue_lock, flags);
2756 cfqq = cic_to_cfqq(cic, is_sync);
2757 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2758 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
2759 cic_set_cfqq(cic, cfqq, is_sync);
2762 * If the queue was seeky for too long, break it apart.
2764 if (cfq_cfqq_coop(cfqq) && should_split_cfqq(cfqq)) {
2765 cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
2766 cfqq = split_cfqq(cic, cfqq);
2772 * Check to see if this queue is scheduled to merge with
2773 * another, closely cooperating queue. The merging of
2774 * queues happens here as it must be done in process context.
2775 * The reference on new_cfqq was taken in merge_cfqqs.
2778 cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
2781 cfqq->allocated[rw]++;
2782 atomic_inc(&cfqq->ref);
2784 spin_unlock_irqrestore(q->queue_lock, flags);
2786 rq->elevator_private = cic;
2787 rq->elevator_private2 = cfqq;
2792 put_io_context(cic->ioc);
2794 cfq_schedule_dispatch(cfqd);
2795 spin_unlock_irqrestore(q->queue_lock, flags);
2796 cfq_log(cfqd, "set_request fail");
2800 static void cfq_kick_queue(struct work_struct *work)
2802 struct cfq_data *cfqd =
2803 container_of(work, struct cfq_data, unplug_work);
2804 struct request_queue *q = cfqd->queue;
2806 spin_lock_irq(q->queue_lock);
2807 __blk_run_queue(cfqd->queue);
2808 spin_unlock_irq(q->queue_lock);
2812 * Timer running if the active_queue is currently idling inside its time slice
2814 static void cfq_idle_slice_timer(unsigned long data)
2816 struct cfq_data *cfqd = (struct cfq_data *) data;
2817 struct cfq_queue *cfqq;
2818 unsigned long flags;
2821 cfq_log(cfqd, "idle timer fired");
2823 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2825 cfqq = cfqd->active_queue;
2830 * We saw a request before the queue expired, let it through
2832 if (cfq_cfqq_must_dispatch(cfqq))
2838 if (cfq_slice_used(cfqq))
2842 * only expire and reinvoke request handler, if there are
2843 * other queues with pending requests
2845 if (!cfqd->busy_queues)
2849 * not expired and it has a request pending, let it dispatch
2851 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
2855 cfq_slice_expired(cfqd, timed_out);
2857 cfq_schedule_dispatch(cfqd);
2859 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2862 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
2864 del_timer_sync(&cfqd->idle_slice_timer);
2865 cancel_work_sync(&cfqd->unplug_work);
2868 static void cfq_put_async_queues(struct cfq_data *cfqd)
2872 for (i = 0; i < IOPRIO_BE_NR; i++) {
2873 if (cfqd->async_cfqq[0][i])
2874 cfq_put_queue(cfqd->async_cfqq[0][i]);
2875 if (cfqd->async_cfqq[1][i])
2876 cfq_put_queue(cfqd->async_cfqq[1][i]);
2879 if (cfqd->async_idle_cfqq)
2880 cfq_put_queue(cfqd->async_idle_cfqq);
2883 static void cfq_exit_queue(struct elevator_queue *e)
2885 struct cfq_data *cfqd = e->elevator_data;
2886 struct request_queue *q = cfqd->queue;
2888 cfq_shutdown_timer_wq(cfqd);
2890 spin_lock_irq(q->queue_lock);
2892 if (cfqd->active_queue)
2893 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
2895 while (!list_empty(&cfqd->cic_list)) {
2896 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2897 struct cfq_io_context,
2900 __cfq_exit_single_io_context(cfqd, cic);
2903 cfq_put_async_queues(cfqd);
2905 spin_unlock_irq(q->queue_lock);
2907 cfq_shutdown_timer_wq(cfqd);
2912 static void *cfq_init_queue(struct request_queue *q)
2914 struct cfq_data *cfqd;
2917 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
2921 for (i = 0; i < 2; ++i)
2922 for (j = 0; j < 3; ++j)
2923 cfqd->service_trees[i][j] = CFQ_RB_ROOT;
2924 cfqd->service_tree_idle = CFQ_RB_ROOT;
2927 * Not strictly needed (since RB_ROOT just clears the node and we
2928 * zeroed cfqd on alloc), but better be safe in case someone decides
2929 * to add magic to the rb code
2931 for (i = 0; i < CFQ_PRIO_LISTS; i++)
2932 cfqd->prio_trees[i] = RB_ROOT;
2935 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
2936 * Grab a permanent reference to it, so that the normal code flow
2937 * will not attempt to free it.
2939 cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
2940 atomic_inc(&cfqd->oom_cfqq.ref);
2942 INIT_LIST_HEAD(&cfqd->cic_list);
2946 init_timer(&cfqd->idle_slice_timer);
2947 cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2948 cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2950 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
2952 cfqd->cfq_quantum = cfq_quantum;
2953 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2954 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2955 cfqd->cfq_back_max = cfq_back_max;
2956 cfqd->cfq_back_penalty = cfq_back_penalty;
2957 cfqd->cfq_slice[0] = cfq_slice_async;
2958 cfqd->cfq_slice[1] = cfq_slice_sync;
2959 cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2960 cfqd->cfq_slice_idle = cfq_slice_idle;
2961 cfqd->cfq_latency = 1;
2963 cfqd->last_end_sync_rq = jiffies;
2967 static void cfq_slab_kill(void)
2970 * Caller already ensured that pending RCU callbacks are completed,
2971 * so we should have no busy allocations at this point.
2974 kmem_cache_destroy(cfq_pool);
2976 kmem_cache_destroy(cfq_ioc_pool);
2979 static int __init cfq_slab_setup(void)
2981 cfq_pool = KMEM_CACHE(cfq_queue, 0);
2985 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
2996 * sysfs parts below -->
2999 cfq_var_show(unsigned int var, char *page)
3001 return sprintf(page, "%d\n", var);
3005 cfq_var_store(unsigned int *var, const char *page, size_t count)
3007 char *p = (char *) page;
3009 *var = simple_strtoul(p, &p, 10);
3013 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
3014 static ssize_t __FUNC(struct elevator_queue *e, char *page) \
3016 struct cfq_data *cfqd = e->elevator_data; \
3017 unsigned int __data = __VAR; \
3019 __data = jiffies_to_msecs(__data); \
3020 return cfq_var_show(__data, (page)); \
3022 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
3023 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
3024 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
3025 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
3026 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
3027 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
3028 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
3029 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
3030 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
3031 SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
3032 #undef SHOW_FUNCTION
3034 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
3035 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3037 struct cfq_data *cfqd = e->elevator_data; \
3038 unsigned int __data; \
3039 int ret = cfq_var_store(&__data, (page), count); \
3040 if (__data < (MIN)) \
3042 else if (__data > (MAX)) \
3045 *(__PTR) = msecs_to_jiffies(__data); \
3047 *(__PTR) = __data; \
3050 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
3051 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
3053 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
3055 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
3056 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
3058 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
3059 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
3060 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
3061 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
3063 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
3064 #undef STORE_FUNCTION
3066 #define CFQ_ATTR(name) \
3067 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3069 static struct elv_fs_entry cfq_attrs[] = {
3071 CFQ_ATTR(fifo_expire_sync),
3072 CFQ_ATTR(fifo_expire_async),
3073 CFQ_ATTR(back_seek_max),
3074 CFQ_ATTR(back_seek_penalty),
3075 CFQ_ATTR(slice_sync),
3076 CFQ_ATTR(slice_async),
3077 CFQ_ATTR(slice_async_rq),
3078 CFQ_ATTR(slice_idle),
3079 CFQ_ATTR(low_latency),
3083 static struct elevator_type iosched_cfq = {
3085 .elevator_merge_fn = cfq_merge,
3086 .elevator_merged_fn = cfq_merged_request,
3087 .elevator_merge_req_fn = cfq_merged_requests,
3088 .elevator_allow_merge_fn = cfq_allow_merge,
3089 .elevator_dispatch_fn = cfq_dispatch_requests,
3090 .elevator_add_req_fn = cfq_insert_request,
3091 .elevator_activate_req_fn = cfq_activate_request,
3092 .elevator_deactivate_req_fn = cfq_deactivate_request,
3093 .elevator_queue_empty_fn = cfq_queue_empty,
3094 .elevator_completed_req_fn = cfq_completed_request,
3095 .elevator_former_req_fn = elv_rb_former_request,
3096 .elevator_latter_req_fn = elv_rb_latter_request,
3097 .elevator_set_req_fn = cfq_set_request,
3098 .elevator_put_req_fn = cfq_put_request,
3099 .elevator_may_queue_fn = cfq_may_queue,
3100 .elevator_init_fn = cfq_init_queue,
3101 .elevator_exit_fn = cfq_exit_queue,
3102 .trim = cfq_free_io_context,
3104 .elevator_attrs = cfq_attrs,
3105 .elevator_name = "cfq",
3106 .elevator_owner = THIS_MODULE,
3109 static int __init cfq_init(void)
3112 * could be 0 on HZ < 1000 setups
3114 if (!cfq_slice_async)
3115 cfq_slice_async = 1;
3116 if (!cfq_slice_idle)
3119 if (cfq_slab_setup())
3122 elv_register(&iosched_cfq);
3127 static void __exit cfq_exit(void)
3129 DECLARE_COMPLETION_ONSTACK(all_gone);
3130 elv_unregister(&iosched_cfq);
3131 ioc_gone = &all_gone;
3132 /* ioc_gone's update must be visible before reading ioc_count */
3136 * this also protects us from entering cfq_slab_kill() with
3137 * pending RCU callbacks
3139 if (elv_ioc_count_read(cfq_ioc_count))
3140 wait_for_completion(&all_gone);
3144 module_init(cfq_init);
3145 module_exit(cfq_exit);
3147 MODULE_AUTHOR("Jens Axboe");
3148 MODULE_LICENSE("GPL");
3149 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");