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/jiffies.h>
13 #include <linux/rbtree.h>
14 #include <linux/ioprio.h>
15 #include <linux/blktrace_api.h>
20 /* max queue in one round of service */
21 static const int cfq_quantum = 4;
22 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
23 /* maximum backwards seek, in KiB */
24 static const int cfq_back_max = 16 * 1024;
25 /* penalty of a backwards seek */
26 static const int cfq_back_penalty = 2;
27 static const int cfq_slice_sync = HZ / 10;
28 static int cfq_slice_async = HZ / 25;
29 static const int cfq_slice_async_rq = 2;
30 static int cfq_slice_idle = HZ / 125;
31 static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
32 static const int cfq_hist_divisor = 4;
35 * offset from end of service tree
37 #define CFQ_IDLE_DELAY (HZ / 5)
40 * below this threshold, we consider thinktime immediate
42 #define CFQ_MIN_TT (2)
45 * Allow merged cfqqs to perform this amount of seeky I/O before
46 * deciding to break the queues up again.
48 #define CFQQ_COOP_TOUT (HZ)
50 #define CFQ_SLICE_SCALE (5)
51 #define CFQ_HW_QUEUE_MIN (5)
54 ((struct cfq_io_context *) (rq)->elevator_private)
55 #define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2)
57 static struct kmem_cache *cfq_pool;
58 static struct kmem_cache *cfq_ioc_pool;
60 static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
61 static struct completion *ioc_gone;
62 static DEFINE_SPINLOCK(ioc_gone_lock);
64 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
65 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
66 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
68 #define sample_valid(samples) ((samples) > 80)
71 * Most of our rbtree usage is for sorting with min extraction, so
72 * if we cache the leftmost node we don't have to walk down the tree
73 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
74 * move this into the elevator for the rq sorting as well.
81 #define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, 0, }
84 * Per process-grouping structure
89 /* various state flags, see below */
92 struct cfq_data *cfqd;
93 /* service_tree member */
94 struct rb_node rb_node;
95 /* service_tree key */
97 /* prio tree member */
98 struct rb_node p_node;
99 /* prio tree root we belong to, if any */
100 struct rb_root *p_root;
101 /* sorted list of pending requests */
102 struct rb_root sort_list;
103 /* if fifo isn't expired, next request to serve */
104 struct request *next_rq;
105 /* requests queued in sort_list */
107 /* currently allocated requests */
109 /* fifo list of requests in sort_list */
110 struct list_head fifo;
112 unsigned long slice_end;
114 unsigned int slice_dispatch;
116 /* pending metadata requests */
118 /* number of requests that are on the dispatch list or inside driver */
121 /* io prio of this group */
122 unsigned short ioprio, org_ioprio;
123 unsigned short ioprio_class, org_ioprio_class;
125 unsigned int seek_samples;
128 sector_t last_request_pos;
129 unsigned long seeky_start;
133 struct cfq_rb_root *service_tree;
134 struct cfq_queue *new_cfqq;
138 * First index in the service_trees.
139 * IDLE is handled separately, so it has negative index
148 * Second index in the service_trees.
152 SYNC_NOIDLE_WORKLOAD = 1,
158 * Per block device queue structure
161 struct request_queue *queue;
164 * rr lists of queues with requests, onle rr for each priority class.
165 * Counts are embedded in the cfq_rb_root
167 struct cfq_rb_root service_trees[2][3];
168 struct cfq_rb_root service_tree_idle;
170 * The priority currently being served
172 enum wl_prio_t serving_prio;
173 enum wl_type_t serving_type;
174 unsigned long workload_expires;
177 * Each priority tree is sorted by next_request position. These
178 * trees are used when determining if two or more queues are
179 * interleaving requests (see cfq_close_cooperator).
181 struct rb_root prio_trees[CFQ_PRIO_LISTS];
183 unsigned int busy_queues;
184 unsigned int busy_queues_avg[2];
190 * queue-depth detection
195 int rq_in_driver_peak;
198 * idle window management
200 struct timer_list idle_slice_timer;
201 struct work_struct unplug_work;
203 struct cfq_queue *active_queue;
204 struct cfq_io_context *active_cic;
207 * async queue for each priority case
209 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
210 struct cfq_queue *async_idle_cfqq;
212 sector_t last_position;
215 * tunables, see top of file
217 unsigned int cfq_quantum;
218 unsigned int cfq_fifo_expire[2];
219 unsigned int cfq_back_penalty;
220 unsigned int cfq_back_max;
221 unsigned int cfq_slice[2];
222 unsigned int cfq_slice_async_rq;
223 unsigned int cfq_slice_idle;
224 unsigned int cfq_latency;
226 struct list_head cic_list;
229 * Fallback dummy cfqq for extreme OOM conditions
231 struct cfq_queue oom_cfqq;
233 unsigned long last_end_sync_rq;
236 static struct cfq_rb_root *service_tree_for(enum wl_prio_t prio,
238 struct cfq_data *cfqd)
240 if (prio == IDLE_WORKLOAD)
241 return &cfqd->service_tree_idle;
243 return &cfqd->service_trees[prio][type];
246 enum cfqq_state_flags {
247 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
248 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
249 CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */
250 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
251 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
252 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */
253 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
254 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
255 CFQ_CFQQ_FLAG_sync, /* synchronous queue */
256 CFQ_CFQQ_FLAG_coop, /* cfqq is shared */
259 #define CFQ_CFQQ_FNS(name) \
260 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
262 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
264 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
266 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
268 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
270 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
274 CFQ_CFQQ_FNS(wait_request);
275 CFQ_CFQQ_FNS(must_dispatch);
276 CFQ_CFQQ_FNS(must_alloc_slice);
277 CFQ_CFQQ_FNS(fifo_expire);
278 CFQ_CFQQ_FNS(idle_window);
279 CFQ_CFQQ_FNS(prio_changed);
280 CFQ_CFQQ_FNS(slice_new);
285 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
286 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
287 #define cfq_log(cfqd, fmt, args...) \
288 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
290 static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
292 if (cfq_class_idle(cfqq))
293 return IDLE_WORKLOAD;
294 if (cfq_class_rt(cfqq))
300 static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
302 if (!cfq_cfqq_sync(cfqq))
303 return ASYNC_WORKLOAD;
304 if (!cfq_cfqq_idle_window(cfqq))
305 return SYNC_NOIDLE_WORKLOAD;
306 return SYNC_WORKLOAD;
309 static inline int cfq_busy_queues_wl(enum wl_prio_t wl, struct cfq_data *cfqd)
311 if (wl == IDLE_WORKLOAD)
312 return cfqd->service_tree_idle.count;
314 return cfqd->service_trees[wl][ASYNC_WORKLOAD].count
315 + cfqd->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
316 + cfqd->service_trees[wl][SYNC_WORKLOAD].count;
319 static void cfq_dispatch_insert(struct request_queue *, struct request *);
320 static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
321 struct io_context *, gfp_t);
322 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
323 struct io_context *);
325 static inline int rq_in_driver(struct cfq_data *cfqd)
327 return cfqd->rq_in_driver[0] + cfqd->rq_in_driver[1];
330 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
333 return cic->cfqq[is_sync];
336 static inline void cic_set_cfqq(struct cfq_io_context *cic,
337 struct cfq_queue *cfqq, bool is_sync)
339 cic->cfqq[is_sync] = cfqq;
343 * We regard a request as SYNC, if it's either a read or has the SYNC bit
344 * set (in which case it could also be direct WRITE).
346 static inline bool cfq_bio_sync(struct bio *bio)
348 return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO);
352 * scheduler run of queue, if there are requests pending and no one in the
353 * driver that will restart queueing
355 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
357 if (cfqd->busy_queues) {
358 cfq_log(cfqd, "schedule dispatch");
359 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
363 static int cfq_queue_empty(struct request_queue *q)
365 struct cfq_data *cfqd = q->elevator->elevator_data;
367 return !cfqd->busy_queues;
371 * Scale schedule slice based on io priority. Use the sync time slice only
372 * if a queue is marked sync and has sync io queued. A sync queue with async
373 * io only, should not get full sync slice length.
375 static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
378 const int base_slice = cfqd->cfq_slice[sync];
380 WARN_ON(prio >= IOPRIO_BE_NR);
382 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
386 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
388 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
392 * get averaged number of queues of RT/BE priority.
393 * average is updated, with a formula that gives more weight to higher numbers,
394 * to quickly follows sudden increases and decrease slowly
397 static inline unsigned cfq_get_avg_queues(struct cfq_data *cfqd, bool rt)
399 unsigned min_q, max_q;
400 unsigned mult = cfq_hist_divisor - 1;
401 unsigned round = cfq_hist_divisor / 2;
402 unsigned busy = cfq_busy_queues_wl(rt, cfqd);
404 min_q = min(cfqd->busy_queues_avg[rt], busy);
405 max_q = max(cfqd->busy_queues_avg[rt], busy);
406 cfqd->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
408 return cfqd->busy_queues_avg[rt];
412 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
414 unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
415 if (cfqd->cfq_latency) {
416 /* interested queues (we consider only the ones with the same
418 unsigned iq = cfq_get_avg_queues(cfqd, cfq_class_rt(cfqq));
419 unsigned sync_slice = cfqd->cfq_slice[1];
420 unsigned expect_latency = sync_slice * iq;
421 if (expect_latency > cfq_target_latency) {
422 unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
423 /* scale low_slice according to IO priority
424 * and sync vs async */
426 min(slice, base_low_slice * slice / sync_slice);
427 /* the adapted slice value is scaled to fit all iqs
428 * into the target latency */
429 slice = max(slice * cfq_target_latency / expect_latency,
433 cfqq->slice_end = jiffies + slice;
434 cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
438 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
439 * isn't valid until the first request from the dispatch is activated
440 * and the slice time set.
442 static inline bool cfq_slice_used(struct cfq_queue *cfqq)
444 if (cfq_cfqq_slice_new(cfqq))
446 if (time_before(jiffies, cfqq->slice_end))
453 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
454 * We choose the request that is closest to the head right now. Distance
455 * behind the head is penalized and only allowed to a certain extent.
457 static struct request *
458 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
460 sector_t s1, s2, d1 = 0, d2 = 0;
461 unsigned long back_max;
462 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
463 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
464 unsigned wrap = 0; /* bit mask: requests behind the disk head? */
466 if (rq1 == NULL || rq1 == rq2)
471 if (rq_is_sync(rq1) && !rq_is_sync(rq2))
473 else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
475 if (rq_is_meta(rq1) && !rq_is_meta(rq2))
477 else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
480 s1 = blk_rq_pos(rq1);
481 s2 = blk_rq_pos(rq2);
484 * by definition, 1KiB is 2 sectors
486 back_max = cfqd->cfq_back_max * 2;
489 * Strict one way elevator _except_ in the case where we allow
490 * short backward seeks which are biased as twice the cost of a
491 * similar forward seek.
495 else if (s1 + back_max >= last)
496 d1 = (last - s1) * cfqd->cfq_back_penalty;
498 wrap |= CFQ_RQ1_WRAP;
502 else if (s2 + back_max >= last)
503 d2 = (last - s2) * cfqd->cfq_back_penalty;
505 wrap |= CFQ_RQ2_WRAP;
507 /* Found required data */
510 * By doing switch() on the bit mask "wrap" we avoid having to
511 * check two variables for all permutations: --> faster!
514 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
530 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
533 * Since both rqs are wrapped,
534 * start with the one that's further behind head
535 * (--> only *one* back seek required),
536 * since back seek takes more time than forward.
546 * The below is leftmost cache rbtree addon
548 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
551 root->left = rb_first(&root->rb);
554 return rb_entry(root->left, struct cfq_queue, rb_node);
559 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
565 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
569 rb_erase_init(n, &root->rb);
574 * would be nice to take fifo expire time into account as well
576 static struct request *
577 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
578 struct request *last)
580 struct rb_node *rbnext = rb_next(&last->rb_node);
581 struct rb_node *rbprev = rb_prev(&last->rb_node);
582 struct request *next = NULL, *prev = NULL;
584 BUG_ON(RB_EMPTY_NODE(&last->rb_node));
587 prev = rb_entry_rq(rbprev);
590 next = rb_entry_rq(rbnext);
592 rbnext = rb_first(&cfqq->sort_list);
593 if (rbnext && rbnext != &last->rb_node)
594 next = rb_entry_rq(rbnext);
597 return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
600 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
601 struct cfq_queue *cfqq)
603 struct cfq_rb_root *service_tree;
605 service_tree = service_tree_for(cfqq_prio(cfqq), cfqq_type(cfqq), cfqd);
608 * just an approximation, should be ok.
610 return service_tree->count * (cfq_prio_slice(cfqd, 1, 0) -
611 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
615 * The cfqd->service_trees holds all pending cfq_queue's that have
616 * requests waiting to be processed. It is sorted in the order that
617 * we will service the queues.
619 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
622 struct rb_node **p, *parent;
623 struct cfq_queue *__cfqq;
624 unsigned long rb_key;
625 struct cfq_rb_root *service_tree;
628 service_tree = service_tree_for(cfqq_prio(cfqq), cfqq_type(cfqq), cfqd);
629 if (cfq_class_idle(cfqq)) {
630 rb_key = CFQ_IDLE_DELAY;
631 parent = rb_last(&service_tree->rb);
632 if (parent && parent != &cfqq->rb_node) {
633 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
634 rb_key += __cfqq->rb_key;
637 } else if (!add_front) {
639 * Get our rb key offset. Subtract any residual slice
640 * value carried from last service. A negative resid
641 * count indicates slice overrun, and this should position
642 * the next service time further away in the tree.
644 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
645 rb_key -= cfqq->slice_resid;
646 cfqq->slice_resid = 0;
649 __cfqq = cfq_rb_first(service_tree);
650 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
653 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
655 * same position, nothing more to do
657 if (rb_key == cfqq->rb_key &&
658 cfqq->service_tree == service_tree)
661 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
662 cfqq->service_tree = NULL;
667 cfqq->service_tree = service_tree;
668 p = &service_tree->rb.rb_node;
673 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
676 * sort by key, that represents service time.
678 if (time_before(rb_key, __cfqq->rb_key))
689 service_tree->left = &cfqq->rb_node;
691 cfqq->rb_key = rb_key;
692 rb_link_node(&cfqq->rb_node, parent, p);
693 rb_insert_color(&cfqq->rb_node, &service_tree->rb);
694 service_tree->count++;
697 static struct cfq_queue *
698 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
699 sector_t sector, struct rb_node **ret_parent,
700 struct rb_node ***rb_link)
702 struct rb_node **p, *parent;
703 struct cfq_queue *cfqq = NULL;
711 cfqq = rb_entry(parent, struct cfq_queue, p_node);
714 * Sort strictly based on sector. Smallest to the left,
715 * largest to the right.
717 if (sector > blk_rq_pos(cfqq->next_rq))
719 else if (sector < blk_rq_pos(cfqq->next_rq))
727 *ret_parent = parent;
733 static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
735 struct rb_node **p, *parent;
736 struct cfq_queue *__cfqq;
739 rb_erase(&cfqq->p_node, cfqq->p_root);
743 if (cfq_class_idle(cfqq))
748 cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
749 __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
750 blk_rq_pos(cfqq->next_rq), &parent, &p);
752 rb_link_node(&cfqq->p_node, parent, p);
753 rb_insert_color(&cfqq->p_node, cfqq->p_root);
759 * Update cfqq's position in the service tree.
761 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
764 * Resorting requires the cfqq to be on the RR list already.
766 if (cfq_cfqq_on_rr(cfqq)) {
767 cfq_service_tree_add(cfqd, cfqq, 0);
768 cfq_prio_tree_add(cfqd, cfqq);
773 * add to busy list of queues for service, trying to be fair in ordering
774 * the pending list according to last request service
776 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
778 cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
779 BUG_ON(cfq_cfqq_on_rr(cfqq));
780 cfq_mark_cfqq_on_rr(cfqq);
783 cfq_resort_rr_list(cfqd, cfqq);
787 * Called when the cfqq no longer has requests pending, remove it from
790 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
792 cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
793 BUG_ON(!cfq_cfqq_on_rr(cfqq));
794 cfq_clear_cfqq_on_rr(cfqq);
796 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
797 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
798 cfqq->service_tree = NULL;
801 rb_erase(&cfqq->p_node, cfqq->p_root);
805 BUG_ON(!cfqd->busy_queues);
810 * rb tree support functions
812 static void cfq_del_rq_rb(struct request *rq)
814 struct cfq_queue *cfqq = RQ_CFQQ(rq);
815 struct cfq_data *cfqd = cfqq->cfqd;
816 const int sync = rq_is_sync(rq);
818 BUG_ON(!cfqq->queued[sync]);
819 cfqq->queued[sync]--;
821 elv_rb_del(&cfqq->sort_list, rq);
823 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
824 cfq_del_cfqq_rr(cfqd, cfqq);
827 static void cfq_add_rq_rb(struct request *rq)
829 struct cfq_queue *cfqq = RQ_CFQQ(rq);
830 struct cfq_data *cfqd = cfqq->cfqd;
831 struct request *__alias, *prev;
833 cfqq->queued[rq_is_sync(rq)]++;
836 * looks a little odd, but the first insert might return an alias.
837 * if that happens, put the alias on the dispatch list
839 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
840 cfq_dispatch_insert(cfqd->queue, __alias);
842 if (!cfq_cfqq_on_rr(cfqq))
843 cfq_add_cfqq_rr(cfqd, cfqq);
846 * check if this request is a better next-serve candidate
848 prev = cfqq->next_rq;
849 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
852 * adjust priority tree position, if ->next_rq changes
854 if (prev != cfqq->next_rq)
855 cfq_prio_tree_add(cfqd, cfqq);
857 BUG_ON(!cfqq->next_rq);
860 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
862 elv_rb_del(&cfqq->sort_list, rq);
863 cfqq->queued[rq_is_sync(rq)]--;
867 static struct request *
868 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
870 struct task_struct *tsk = current;
871 struct cfq_io_context *cic;
872 struct cfq_queue *cfqq;
874 cic = cfq_cic_lookup(cfqd, tsk->io_context);
878 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
880 sector_t sector = bio->bi_sector + bio_sectors(bio);
882 return elv_rb_find(&cfqq->sort_list, sector);
888 static void cfq_activate_request(struct request_queue *q, struct request *rq)
890 struct cfq_data *cfqd = q->elevator->elevator_data;
892 cfqd->rq_in_driver[rq_is_sync(rq)]++;
893 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
896 cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
899 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
901 struct cfq_data *cfqd = q->elevator->elevator_data;
902 const int sync = rq_is_sync(rq);
904 WARN_ON(!cfqd->rq_in_driver[sync]);
905 cfqd->rq_in_driver[sync]--;
906 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
910 static void cfq_remove_request(struct request *rq)
912 struct cfq_queue *cfqq = RQ_CFQQ(rq);
914 if (cfqq->next_rq == rq)
915 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
917 list_del_init(&rq->queuelist);
920 cfqq->cfqd->rq_queued--;
921 if (rq_is_meta(rq)) {
922 WARN_ON(!cfqq->meta_pending);
923 cfqq->meta_pending--;
927 static int cfq_merge(struct request_queue *q, struct request **req,
930 struct cfq_data *cfqd = q->elevator->elevator_data;
931 struct request *__rq;
933 __rq = cfq_find_rq_fmerge(cfqd, bio);
934 if (__rq && elv_rq_merge_ok(__rq, bio)) {
936 return ELEVATOR_FRONT_MERGE;
939 return ELEVATOR_NO_MERGE;
942 static void cfq_merged_request(struct request_queue *q, struct request *req,
945 if (type == ELEVATOR_FRONT_MERGE) {
946 struct cfq_queue *cfqq = RQ_CFQQ(req);
948 cfq_reposition_rq_rb(cfqq, req);
953 cfq_merged_requests(struct request_queue *q, struct request *rq,
954 struct request *next)
956 struct cfq_queue *cfqq = RQ_CFQQ(rq);
958 * reposition in fifo if next is older than rq
960 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
961 time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
962 list_move(&rq->queuelist, &next->queuelist);
963 rq_set_fifo_time(rq, rq_fifo_time(next));
966 if (cfqq->next_rq == next)
968 cfq_remove_request(next);
971 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
974 struct cfq_data *cfqd = q->elevator->elevator_data;
975 struct cfq_io_context *cic;
976 struct cfq_queue *cfqq;
979 * Disallow merge of a sync bio into an async request.
981 if (cfq_bio_sync(bio) && !rq_is_sync(rq))
985 * Lookup the cfqq that this bio will be queued with. Allow
986 * merge only if rq is queued there.
988 cic = cfq_cic_lookup(cfqd, current->io_context);
992 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
993 return cfqq == RQ_CFQQ(rq);
996 static void __cfq_set_active_queue(struct cfq_data *cfqd,
997 struct cfq_queue *cfqq)
1000 cfq_log_cfqq(cfqd, cfqq, "set_active");
1001 cfqq->slice_end = 0;
1002 cfqq->slice_dispatch = 0;
1004 cfq_clear_cfqq_wait_request(cfqq);
1005 cfq_clear_cfqq_must_dispatch(cfqq);
1006 cfq_clear_cfqq_must_alloc_slice(cfqq);
1007 cfq_clear_cfqq_fifo_expire(cfqq);
1008 cfq_mark_cfqq_slice_new(cfqq);
1010 del_timer(&cfqd->idle_slice_timer);
1013 cfqd->active_queue = cfqq;
1017 * current cfqq expired its slice (or was too idle), select new one
1020 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1023 cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
1025 if (cfq_cfqq_wait_request(cfqq))
1026 del_timer(&cfqd->idle_slice_timer);
1028 cfq_clear_cfqq_wait_request(cfqq);
1031 * store what was left of this slice, if the queue idled/timed out
1033 if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
1034 cfqq->slice_resid = cfqq->slice_end - jiffies;
1035 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
1038 cfq_resort_rr_list(cfqd, cfqq);
1040 if (cfqq == cfqd->active_queue)
1041 cfqd->active_queue = NULL;
1043 if (cfqd->active_cic) {
1044 put_io_context(cfqd->active_cic->ioc);
1045 cfqd->active_cic = NULL;
1049 static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
1051 struct cfq_queue *cfqq = cfqd->active_queue;
1054 __cfq_slice_expired(cfqd, cfqq, timed_out);
1058 * Get next queue for service. Unless we have a queue preemption,
1059 * we'll simply select the first cfqq in the service tree.
1061 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
1063 struct cfq_rb_root *service_tree =
1064 service_tree_for(cfqd->serving_prio, cfqd->serving_type, cfqd);
1066 if (RB_EMPTY_ROOT(&service_tree->rb))
1068 return cfq_rb_first(service_tree);
1072 * Get and set a new active queue for service.
1074 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
1075 struct cfq_queue *cfqq)
1078 cfqq = cfq_get_next_queue(cfqd);
1080 __cfq_set_active_queue(cfqd, cfqq);
1084 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
1087 if (blk_rq_pos(rq) >= cfqd->last_position)
1088 return blk_rq_pos(rq) - cfqd->last_position;
1090 return cfqd->last_position - blk_rq_pos(rq);
1093 #define CFQQ_SEEK_THR 8 * 1024
1094 #define CFQQ_SEEKY(cfqq) ((cfqq)->seek_mean > CFQQ_SEEK_THR)
1096 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1099 sector_t sdist = cfqq->seek_mean;
1101 if (!sample_valid(cfqq->seek_samples))
1102 sdist = CFQQ_SEEK_THR;
1104 return cfq_dist_from_last(cfqd, rq) <= sdist;
1107 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
1108 struct cfq_queue *cur_cfqq)
1110 struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
1111 struct rb_node *parent, *node;
1112 struct cfq_queue *__cfqq;
1113 sector_t sector = cfqd->last_position;
1115 if (RB_EMPTY_ROOT(root))
1119 * First, if we find a request starting at the end of the last
1120 * request, choose it.
1122 __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
1127 * If the exact sector wasn't found, the parent of the NULL leaf
1128 * will contain the closest sector.
1130 __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1131 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1134 if (blk_rq_pos(__cfqq->next_rq) < sector)
1135 node = rb_next(&__cfqq->p_node);
1137 node = rb_prev(&__cfqq->p_node);
1141 __cfqq = rb_entry(node, struct cfq_queue, p_node);
1142 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1150 * cur_cfqq - passed in so that we don't decide that the current queue is
1151 * closely cooperating with itself.
1153 * So, basically we're assuming that that cur_cfqq has dispatched at least
1154 * one request, and that cfqd->last_position reflects a position on the disk
1155 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
1158 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1159 struct cfq_queue *cur_cfqq)
1161 struct cfq_queue *cfqq;
1163 if (!cfq_cfqq_sync(cur_cfqq))
1165 if (CFQQ_SEEKY(cur_cfqq))
1169 * We should notice if some of the queues are cooperating, eg
1170 * working closely on the same area of the disk. In that case,
1171 * we can group them together and don't waste time idling.
1173 cfqq = cfqq_close(cfqd, cur_cfqq);
1178 * It only makes sense to merge sync queues.
1180 if (!cfq_cfqq_sync(cfqq))
1182 if (CFQQ_SEEKY(cfqq))
1186 * Do not merge queues of different priority classes
1188 if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
1195 * Determine whether we should enforce idle window for this queue.
1198 static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1200 enum wl_prio_t prio = cfqq_prio(cfqq);
1201 struct cfq_rb_root *service_tree = cfqq->service_tree;
1203 /* We never do for idle class queues. */
1204 if (prio == IDLE_WORKLOAD)
1207 /* We do for queues that were marked with idle window flag. */
1208 if (cfq_cfqq_idle_window(cfqq))
1212 * Otherwise, we do only if they are the last ones
1213 * in their service tree.
1216 service_tree = service_tree_for(prio, cfqq_type(cfqq), cfqd);
1218 if (service_tree->count == 0)
1221 return (service_tree->count == 1 && cfq_rb_first(service_tree) == cfqq);
1224 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
1226 struct cfq_queue *cfqq = cfqd->active_queue;
1227 struct cfq_io_context *cic;
1231 * SSD device without seek penalty, disable idling. But only do so
1232 * for devices that support queuing, otherwise we still have a problem
1233 * with sync vs async workloads.
1235 if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
1238 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
1239 WARN_ON(cfq_cfqq_slice_new(cfqq));
1242 * idle is disabled, either manually or by past process history
1244 if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq))
1248 * still requests with the driver, don't idle
1250 if (rq_in_driver(cfqd))
1254 * task has exited, don't wait
1256 cic = cfqd->active_cic;
1257 if (!cic || !atomic_read(&cic->ioc->nr_tasks))
1261 * If our average think time is larger than the remaining time
1262 * slice, then don't idle. This avoids overrunning the allotted
1265 if (sample_valid(cic->ttime_samples) &&
1266 (cfqq->slice_end - jiffies < cic->ttime_mean))
1269 cfq_mark_cfqq_wait_request(cfqq);
1271 sl = cfqd->cfq_slice_idle;
1273 mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
1274 cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
1278 * Move request from internal lists to the request queue dispatch list.
1280 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
1282 struct cfq_data *cfqd = q->elevator->elevator_data;
1283 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1285 cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
1287 cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
1288 cfq_remove_request(rq);
1290 elv_dispatch_sort(q, rq);
1292 if (cfq_cfqq_sync(cfqq))
1293 cfqd->sync_flight++;
1297 * return expired entry, or NULL to just start from scratch in rbtree
1299 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
1301 struct request *rq = NULL;
1303 if (cfq_cfqq_fifo_expire(cfqq))
1306 cfq_mark_cfqq_fifo_expire(cfqq);
1308 if (list_empty(&cfqq->fifo))
1311 rq = rq_entry_fifo(cfqq->fifo.next);
1312 if (time_before(jiffies, rq_fifo_time(rq)))
1315 cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
1320 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1322 const int base_rq = cfqd->cfq_slice_async_rq;
1324 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1326 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1330 * Must be called with the queue_lock held.
1332 static int cfqq_process_refs(struct cfq_queue *cfqq)
1334 int process_refs, io_refs;
1336 io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
1337 process_refs = atomic_read(&cfqq->ref) - io_refs;
1338 BUG_ON(process_refs < 0);
1339 return process_refs;
1342 static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
1344 int process_refs, new_process_refs;
1345 struct cfq_queue *__cfqq;
1347 /* Avoid a circular list and skip interim queue merges */
1348 while ((__cfqq = new_cfqq->new_cfqq)) {
1354 process_refs = cfqq_process_refs(cfqq);
1356 * If the process for the cfqq has gone away, there is no
1357 * sense in merging the queues.
1359 if (process_refs == 0)
1363 * Merge in the direction of the lesser amount of work.
1365 new_process_refs = cfqq_process_refs(new_cfqq);
1366 if (new_process_refs >= process_refs) {
1367 cfqq->new_cfqq = new_cfqq;
1368 atomic_add(process_refs, &new_cfqq->ref);
1370 new_cfqq->new_cfqq = cfqq;
1371 atomic_add(new_process_refs, &cfqq->ref);
1375 static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd, enum wl_prio_t prio,
1378 struct cfq_queue *queue;
1380 bool key_valid = false;
1381 unsigned long lowest_key = 0;
1382 enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
1386 * When priorities switched, we prefer starting
1387 * from SYNC_NOIDLE (first choice), or just SYNC
1390 if (service_tree_for(prio, cur_best, cfqd)->count)
1392 cur_best = SYNC_WORKLOAD;
1393 if (service_tree_for(prio, cur_best, cfqd)->count)
1396 return ASYNC_WORKLOAD;
1399 for (i = 0; i < 3; ++i) {
1400 /* otherwise, select the one with lowest rb_key */
1401 queue = cfq_rb_first(service_tree_for(prio, i, cfqd));
1403 (!key_valid || time_before(queue->rb_key, lowest_key))) {
1404 lowest_key = queue->rb_key;
1413 static void choose_service_tree(struct cfq_data *cfqd)
1415 enum wl_prio_t previous_prio = cfqd->serving_prio;
1420 /* Choose next priority. RT > BE > IDLE */
1421 if (cfq_busy_queues_wl(RT_WORKLOAD, cfqd))
1422 cfqd->serving_prio = RT_WORKLOAD;
1423 else if (cfq_busy_queues_wl(BE_WORKLOAD, cfqd))
1424 cfqd->serving_prio = BE_WORKLOAD;
1426 cfqd->serving_prio = IDLE_WORKLOAD;
1427 cfqd->workload_expires = jiffies + 1;
1432 * For RT and BE, we have to choose also the type
1433 * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
1436 prio_changed = (cfqd->serving_prio != previous_prio);
1437 count = service_tree_for(cfqd->serving_prio, cfqd->serving_type, cfqd)
1441 * If priority didn't change, check workload expiration,
1442 * and that we still have other queues ready
1444 if (!prio_changed && count &&
1445 !time_after(jiffies, cfqd->workload_expires))
1448 /* otherwise select new workload type */
1449 cfqd->serving_type =
1450 cfq_choose_wl(cfqd, cfqd->serving_prio, prio_changed);
1451 count = service_tree_for(cfqd->serving_prio, cfqd->serving_type, cfqd)
1455 * the workload slice is computed as a fraction of target latency
1456 * proportional to the number of queues in that workload, over
1457 * all the queues in the same priority class
1459 slice = cfq_target_latency * count /
1460 max_t(unsigned, cfqd->busy_queues_avg[cfqd->serving_prio],
1461 cfq_busy_queues_wl(cfqd->serving_prio, cfqd));
1463 if (cfqd->serving_type == ASYNC_WORKLOAD)
1464 /* async workload slice is scaled down according to
1465 * the sync/async slice ratio. */
1466 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
1468 /* sync workload slice is at least 2 * cfq_slice_idle */
1469 slice = max(slice, 2 * cfqd->cfq_slice_idle);
1471 slice = max_t(unsigned, slice, CFQ_MIN_TT);
1472 cfqd->workload_expires = jiffies + slice;
1476 * Select a queue for service. If we have a current active queue,
1477 * check whether to continue servicing it, or retrieve and set a new one.
1479 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
1481 struct cfq_queue *cfqq, *new_cfqq = NULL;
1483 cfqq = cfqd->active_queue;
1488 * The active queue has run out of time, expire it and select new.
1490 if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq))
1494 * The active queue has requests and isn't expired, allow it to
1497 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
1501 * If another queue has a request waiting within our mean seek
1502 * distance, let it run. The expire code will check for close
1503 * cooperators and put the close queue at the front of the service
1504 * tree. If possible, merge the expiring queue with the new cfqq.
1506 new_cfqq = cfq_close_cooperator(cfqd, cfqq);
1508 if (!cfqq->new_cfqq)
1509 cfq_setup_merge(cfqq, new_cfqq);
1514 * No requests pending. If the active queue still has requests in
1515 * flight or is idling for a new request, allow either of these
1516 * conditions to happen (or time out) before selecting a new queue.
1518 if (timer_pending(&cfqd->idle_slice_timer) ||
1519 (cfqq->dispatched && cfq_should_idle(cfqd, cfqq))) {
1525 cfq_slice_expired(cfqd, 0);
1528 * Current queue expired. Check if we have to switch to a new
1532 choose_service_tree(cfqd);
1534 cfqq = cfq_set_active_queue(cfqd, new_cfqq);
1539 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
1543 while (cfqq->next_rq) {
1544 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
1548 BUG_ON(!list_empty(&cfqq->fifo));
1553 * Drain our current requests. Used for barriers and when switching
1554 * io schedulers on-the-fly.
1556 static int cfq_forced_dispatch(struct cfq_data *cfqd)
1558 struct cfq_queue *cfqq;
1561 for (i = 0; i < 2; ++i)
1562 for (j = 0; j < 3; ++j)
1563 while ((cfqq = cfq_rb_first(&cfqd->service_trees[i][j]))
1565 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
1567 while ((cfqq = cfq_rb_first(&cfqd->service_tree_idle)) != NULL)
1568 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
1570 cfq_slice_expired(cfqd, 0);
1572 BUG_ON(cfqd->busy_queues);
1574 cfq_log(cfqd, "forced_dispatch=%d", dispatched);
1578 static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1580 unsigned int max_dispatch;
1583 * Drain async requests before we start sync IO
1585 if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
1589 * If this is an async queue and we have sync IO in flight, let it wait
1591 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
1594 max_dispatch = cfqd->cfq_quantum;
1595 if (cfq_class_idle(cfqq))
1599 * Does this cfqq already have too much IO in flight?
1601 if (cfqq->dispatched >= max_dispatch) {
1603 * idle queue must always only have a single IO in flight
1605 if (cfq_class_idle(cfqq))
1609 * We have other queues, don't allow more IO from this one
1611 if (cfqd->busy_queues > 1)
1615 * Sole queue user, allow bigger slice
1621 * Async queues must wait a bit before being allowed dispatch.
1622 * We also ramp up the dispatch depth gradually for async IO,
1623 * based on the last sync IO we serviced
1625 if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
1626 unsigned long last_sync = jiffies - cfqd->last_end_sync_rq;
1629 depth = last_sync / cfqd->cfq_slice[1];
1630 if (!depth && !cfqq->dispatched)
1632 if (depth < max_dispatch)
1633 max_dispatch = depth;
1637 * If we're below the current max, allow a dispatch
1639 return cfqq->dispatched < max_dispatch;
1643 * Dispatch a request from cfqq, moving them to the request queue
1646 static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1650 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
1652 if (!cfq_may_dispatch(cfqd, cfqq))
1656 * follow expired path, else get first next available
1658 rq = cfq_check_fifo(cfqq);
1663 * insert request into driver dispatch list
1665 cfq_dispatch_insert(cfqd->queue, rq);
1667 if (!cfqd->active_cic) {
1668 struct cfq_io_context *cic = RQ_CIC(rq);
1670 atomic_long_inc(&cic->ioc->refcount);
1671 cfqd->active_cic = cic;
1678 * Find the cfqq that we need to service and move a request from that to the
1681 static int cfq_dispatch_requests(struct request_queue *q, int force)
1683 struct cfq_data *cfqd = q->elevator->elevator_data;
1684 struct cfq_queue *cfqq;
1686 if (!cfqd->busy_queues)
1689 if (unlikely(force))
1690 return cfq_forced_dispatch(cfqd);
1692 cfqq = cfq_select_queue(cfqd);
1697 * Dispatch a request from this cfqq, if it is allowed
1699 if (!cfq_dispatch_request(cfqd, cfqq))
1702 cfqq->slice_dispatch++;
1703 cfq_clear_cfqq_must_dispatch(cfqq);
1706 * expire an async queue immediately if it has used up its slice. idle
1707 * queue always expire after 1 dispatch round.
1709 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
1710 cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1711 cfq_class_idle(cfqq))) {
1712 cfqq->slice_end = jiffies + 1;
1713 cfq_slice_expired(cfqd, 0);
1716 cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
1721 * task holds one reference to the queue, dropped when task exits. each rq
1722 * in-flight on this queue also holds a reference, dropped when rq is freed.
1724 * queue lock must be held here.
1726 static void cfq_put_queue(struct cfq_queue *cfqq)
1728 struct cfq_data *cfqd = cfqq->cfqd;
1730 BUG_ON(atomic_read(&cfqq->ref) <= 0);
1732 if (!atomic_dec_and_test(&cfqq->ref))
1735 cfq_log_cfqq(cfqd, cfqq, "put_queue");
1736 BUG_ON(rb_first(&cfqq->sort_list));
1737 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1738 BUG_ON(cfq_cfqq_on_rr(cfqq));
1740 if (unlikely(cfqd->active_queue == cfqq)) {
1741 __cfq_slice_expired(cfqd, cfqq, 0);
1742 cfq_schedule_dispatch(cfqd);
1745 kmem_cache_free(cfq_pool, cfqq);
1749 * Must always be called with the rcu_read_lock() held
1752 __call_for_each_cic(struct io_context *ioc,
1753 void (*func)(struct io_context *, struct cfq_io_context *))
1755 struct cfq_io_context *cic;
1756 struct hlist_node *n;
1758 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
1763 * Call func for each cic attached to this ioc.
1766 call_for_each_cic(struct io_context *ioc,
1767 void (*func)(struct io_context *, struct cfq_io_context *))
1770 __call_for_each_cic(ioc, func);
1774 static void cfq_cic_free_rcu(struct rcu_head *head)
1776 struct cfq_io_context *cic;
1778 cic = container_of(head, struct cfq_io_context, rcu_head);
1780 kmem_cache_free(cfq_ioc_pool, cic);
1781 elv_ioc_count_dec(cfq_ioc_count);
1785 * CFQ scheduler is exiting, grab exit lock and check
1786 * the pending io context count. If it hits zero,
1787 * complete ioc_gone and set it back to NULL
1789 spin_lock(&ioc_gone_lock);
1790 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
1794 spin_unlock(&ioc_gone_lock);
1798 static void cfq_cic_free(struct cfq_io_context *cic)
1800 call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
1803 static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
1805 unsigned long flags;
1807 BUG_ON(!cic->dead_key);
1809 spin_lock_irqsave(&ioc->lock, flags);
1810 radix_tree_delete(&ioc->radix_root, cic->dead_key);
1811 hlist_del_rcu(&cic->cic_list);
1812 spin_unlock_irqrestore(&ioc->lock, flags);
1818 * Must be called with rcu_read_lock() held or preemption otherwise disabled.
1819 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
1820 * and ->trim() which is called with the task lock held
1822 static void cfq_free_io_context(struct io_context *ioc)
1825 * ioc->refcount is zero here, or we are called from elv_unregister(),
1826 * so no more cic's are allowed to be linked into this ioc. So it
1827 * should be ok to iterate over the known list, we will see all cic's
1828 * since no new ones are added.
1830 __call_for_each_cic(ioc, cic_free_func);
1833 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1835 struct cfq_queue *__cfqq, *next;
1837 if (unlikely(cfqq == cfqd->active_queue)) {
1838 __cfq_slice_expired(cfqd, cfqq, 0);
1839 cfq_schedule_dispatch(cfqd);
1843 * If this queue was scheduled to merge with another queue, be
1844 * sure to drop the reference taken on that queue (and others in
1845 * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs.
1847 __cfqq = cfqq->new_cfqq;
1849 if (__cfqq == cfqq) {
1850 WARN(1, "cfqq->new_cfqq loop detected\n");
1853 next = __cfqq->new_cfqq;
1854 cfq_put_queue(__cfqq);
1858 cfq_put_queue(cfqq);
1861 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
1862 struct cfq_io_context *cic)
1864 struct io_context *ioc = cic->ioc;
1866 list_del_init(&cic->queue_list);
1869 * Make sure key == NULL is seen for dead queues
1872 cic->dead_key = (unsigned long) cic->key;
1875 if (ioc->ioc_data == cic)
1876 rcu_assign_pointer(ioc->ioc_data, NULL);
1878 if (cic->cfqq[BLK_RW_ASYNC]) {
1879 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
1880 cic->cfqq[BLK_RW_ASYNC] = NULL;
1883 if (cic->cfqq[BLK_RW_SYNC]) {
1884 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
1885 cic->cfqq[BLK_RW_SYNC] = NULL;
1889 static void cfq_exit_single_io_context(struct io_context *ioc,
1890 struct cfq_io_context *cic)
1892 struct cfq_data *cfqd = cic->key;
1895 struct request_queue *q = cfqd->queue;
1896 unsigned long flags;
1898 spin_lock_irqsave(q->queue_lock, flags);
1901 * Ensure we get a fresh copy of the ->key to prevent
1902 * race between exiting task and queue
1904 smp_read_barrier_depends();
1906 __cfq_exit_single_io_context(cfqd, cic);
1908 spin_unlock_irqrestore(q->queue_lock, flags);
1913 * The process that ioc belongs to has exited, we need to clean up
1914 * and put the internal structures we have that belongs to that process.
1916 static void cfq_exit_io_context(struct io_context *ioc)
1918 call_for_each_cic(ioc, cfq_exit_single_io_context);
1921 static struct cfq_io_context *
1922 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1924 struct cfq_io_context *cic;
1926 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
1929 cic->last_end_request = jiffies;
1930 INIT_LIST_HEAD(&cic->queue_list);
1931 INIT_HLIST_NODE(&cic->cic_list);
1932 cic->dtor = cfq_free_io_context;
1933 cic->exit = cfq_exit_io_context;
1934 elv_ioc_count_inc(cfq_ioc_count);
1940 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
1942 struct task_struct *tsk = current;
1945 if (!cfq_cfqq_prio_changed(cfqq))
1948 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
1949 switch (ioprio_class) {
1951 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1952 case IOPRIO_CLASS_NONE:
1954 * no prio set, inherit CPU scheduling settings
1956 cfqq->ioprio = task_nice_ioprio(tsk);
1957 cfqq->ioprio_class = task_nice_ioclass(tsk);
1959 case IOPRIO_CLASS_RT:
1960 cfqq->ioprio = task_ioprio(ioc);
1961 cfqq->ioprio_class = IOPRIO_CLASS_RT;
1963 case IOPRIO_CLASS_BE:
1964 cfqq->ioprio = task_ioprio(ioc);
1965 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1967 case IOPRIO_CLASS_IDLE:
1968 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1970 cfq_clear_cfqq_idle_window(cfqq);
1975 * keep track of original prio settings in case we have to temporarily
1976 * elevate the priority of this queue
1978 cfqq->org_ioprio = cfqq->ioprio;
1979 cfqq->org_ioprio_class = cfqq->ioprio_class;
1980 cfq_clear_cfqq_prio_changed(cfqq);
1983 static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
1985 struct cfq_data *cfqd = cic->key;
1986 struct cfq_queue *cfqq;
1987 unsigned long flags;
1989 if (unlikely(!cfqd))
1992 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1994 cfqq = cic->cfqq[BLK_RW_ASYNC];
1996 struct cfq_queue *new_cfqq;
1997 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
2000 cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
2001 cfq_put_queue(cfqq);
2005 cfqq = cic->cfqq[BLK_RW_SYNC];
2007 cfq_mark_cfqq_prio_changed(cfqq);
2009 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2012 static void cfq_ioc_set_ioprio(struct io_context *ioc)
2014 call_for_each_cic(ioc, changed_ioprio);
2015 ioc->ioprio_changed = 0;
2018 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2019 pid_t pid, bool is_sync)
2021 RB_CLEAR_NODE(&cfqq->rb_node);
2022 RB_CLEAR_NODE(&cfqq->p_node);
2023 INIT_LIST_HEAD(&cfqq->fifo);
2025 atomic_set(&cfqq->ref, 0);
2028 cfq_mark_cfqq_prio_changed(cfqq);
2031 if (!cfq_class_idle(cfqq))
2032 cfq_mark_cfqq_idle_window(cfqq);
2033 cfq_mark_cfqq_sync(cfqq);
2038 static struct cfq_queue *
2039 cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
2040 struct io_context *ioc, gfp_t gfp_mask)
2042 struct cfq_queue *cfqq, *new_cfqq = NULL;
2043 struct cfq_io_context *cic;
2046 cic = cfq_cic_lookup(cfqd, ioc);
2047 /* cic always exists here */
2048 cfqq = cic_to_cfqq(cic, is_sync);
2051 * Always try a new alloc if we fell back to the OOM cfqq
2052 * originally, since it should just be a temporary situation.
2054 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2059 } else if (gfp_mask & __GFP_WAIT) {
2060 spin_unlock_irq(cfqd->queue->queue_lock);
2061 new_cfqq = kmem_cache_alloc_node(cfq_pool,
2062 gfp_mask | __GFP_ZERO,
2064 spin_lock_irq(cfqd->queue->queue_lock);
2068 cfqq = kmem_cache_alloc_node(cfq_pool,
2069 gfp_mask | __GFP_ZERO,
2074 cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
2075 cfq_init_prio_data(cfqq, ioc);
2076 cfq_log_cfqq(cfqd, cfqq, "alloced");
2078 cfqq = &cfqd->oom_cfqq;
2082 kmem_cache_free(cfq_pool, new_cfqq);
2087 static struct cfq_queue **
2088 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
2090 switch (ioprio_class) {
2091 case IOPRIO_CLASS_RT:
2092 return &cfqd->async_cfqq[0][ioprio];
2093 case IOPRIO_CLASS_BE:
2094 return &cfqd->async_cfqq[1][ioprio];
2095 case IOPRIO_CLASS_IDLE:
2096 return &cfqd->async_idle_cfqq;
2102 static struct cfq_queue *
2103 cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
2106 const int ioprio = task_ioprio(ioc);
2107 const int ioprio_class = task_ioprio_class(ioc);
2108 struct cfq_queue **async_cfqq = NULL;
2109 struct cfq_queue *cfqq = NULL;
2112 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
2117 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
2120 * pin the queue now that it's allocated, scheduler exit will prune it
2122 if (!is_sync && !(*async_cfqq)) {
2123 atomic_inc(&cfqq->ref);
2127 atomic_inc(&cfqq->ref);
2132 * We drop cfq io contexts lazily, so we may find a dead one.
2135 cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
2136 struct cfq_io_context *cic)
2138 unsigned long flags;
2140 WARN_ON(!list_empty(&cic->queue_list));
2142 spin_lock_irqsave(&ioc->lock, flags);
2144 BUG_ON(ioc->ioc_data == cic);
2146 radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
2147 hlist_del_rcu(&cic->cic_list);
2148 spin_unlock_irqrestore(&ioc->lock, flags);
2153 static struct cfq_io_context *
2154 cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
2156 struct cfq_io_context *cic;
2157 unsigned long flags;
2166 * we maintain a last-hit cache, to avoid browsing over the tree
2168 cic = rcu_dereference(ioc->ioc_data);
2169 if (cic && cic->key == cfqd) {
2175 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
2179 /* ->key must be copied to avoid race with cfq_exit_queue() */
2182 cfq_drop_dead_cic(cfqd, ioc, cic);
2187 spin_lock_irqsave(&ioc->lock, flags);
2188 rcu_assign_pointer(ioc->ioc_data, cic);
2189 spin_unlock_irqrestore(&ioc->lock, flags);
2197 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2198 * the process specific cfq io context when entered from the block layer.
2199 * Also adds the cic to a per-cfqd list, used when this queue is removed.
2201 static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
2202 struct cfq_io_context *cic, gfp_t gfp_mask)
2204 unsigned long flags;
2207 ret = radix_tree_preload(gfp_mask);
2212 spin_lock_irqsave(&ioc->lock, flags);
2213 ret = radix_tree_insert(&ioc->radix_root,
2214 (unsigned long) cfqd, cic);
2216 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
2217 spin_unlock_irqrestore(&ioc->lock, flags);
2219 radix_tree_preload_end();
2222 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2223 list_add(&cic->queue_list, &cfqd->cic_list);
2224 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2229 printk(KERN_ERR "cfq: cic link failed!\n");
2235 * Setup general io context and cfq io context. There can be several cfq
2236 * io contexts per general io context, if this process is doing io to more
2237 * than one device managed by cfq.
2239 static struct cfq_io_context *
2240 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2242 struct io_context *ioc = NULL;
2243 struct cfq_io_context *cic;
2245 might_sleep_if(gfp_mask & __GFP_WAIT);
2247 ioc = get_io_context(gfp_mask, cfqd->queue->node);
2251 cic = cfq_cic_lookup(cfqd, ioc);
2255 cic = cfq_alloc_io_context(cfqd, gfp_mask);
2259 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
2263 smp_read_barrier_depends();
2264 if (unlikely(ioc->ioprio_changed))
2265 cfq_ioc_set_ioprio(ioc);
2271 put_io_context(ioc);
2276 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
2278 unsigned long elapsed = jiffies - cic->last_end_request;
2279 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
2281 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
2282 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
2283 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
2287 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2293 if (!cfqq->last_request_pos)
2295 else if (cfqq->last_request_pos < blk_rq_pos(rq))
2296 sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
2298 sdist = cfqq->last_request_pos - blk_rq_pos(rq);
2301 * Don't allow the seek distance to get too large from the
2302 * odd fragment, pagein, etc
2304 if (cfqq->seek_samples <= 60) /* second&third seek */
2305 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*1024);
2307 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*64);
2309 cfqq->seek_samples = (7*cfqq->seek_samples + 256) / 8;
2310 cfqq->seek_total = (7*cfqq->seek_total + (u64)256*sdist) / 8;
2311 total = cfqq->seek_total + (cfqq->seek_samples/2);
2312 do_div(total, cfqq->seek_samples);
2313 cfqq->seek_mean = (sector_t)total;
2316 * If this cfqq is shared between multiple processes, check to
2317 * make sure that those processes are still issuing I/Os within
2318 * the mean seek distance. If not, it may be time to break the
2319 * queues apart again.
2321 if (cfq_cfqq_coop(cfqq)) {
2322 if (CFQQ_SEEKY(cfqq) && !cfqq->seeky_start)
2323 cfqq->seeky_start = jiffies;
2324 else if (!CFQQ_SEEKY(cfqq))
2325 cfqq->seeky_start = 0;
2330 * Disable idle window if the process thinks too long or seeks so much that
2334 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2335 struct cfq_io_context *cic)
2337 int old_idle, enable_idle;
2340 * Don't idle for async or idle io prio class
2342 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
2345 enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
2347 if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
2348 (sample_valid(cfqq->seek_samples) && CFQQ_SEEKY(cfqq)))
2350 else if (sample_valid(cic->ttime_samples)) {
2351 if (cic->ttime_mean > cfqd->cfq_slice_idle)
2357 if (old_idle != enable_idle) {
2358 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
2360 cfq_mark_cfqq_idle_window(cfqq);
2362 cfq_clear_cfqq_idle_window(cfqq);
2367 * Check if new_cfqq should preempt the currently active queue. Return 0 for
2368 * no or if we aren't sure, a 1 will cause a preempt.
2371 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
2374 struct cfq_queue *cfqq;
2376 cfqq = cfqd->active_queue;
2380 if (cfq_slice_used(cfqq))
2383 if (cfq_class_idle(new_cfqq))
2386 if (cfq_class_idle(cfqq))
2389 if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD
2390 && new_cfqq->service_tree == cfqq->service_tree)
2394 * if the new request is sync, but the currently running queue is
2395 * not, let the sync request have priority.
2397 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
2401 * So both queues are sync. Let the new request get disk time if
2402 * it's a metadata request and the current queue is doing regular IO.
2404 if (rq_is_meta(rq) && !cfqq->meta_pending)
2408 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
2410 if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
2413 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
2417 * if this request is as-good as one we would expect from the
2418 * current cfqq, let it preempt
2420 if (cfq_rq_close(cfqd, cfqq, rq))
2427 * cfqq preempts the active queue. if we allowed preempt with no slice left,
2428 * let it have half of its nominal slice.
2430 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2432 cfq_log_cfqq(cfqd, cfqq, "preempt");
2433 cfq_slice_expired(cfqd, 1);
2436 * Put the new queue at the front of the of the current list,
2437 * so we know that it will be selected next.
2439 BUG_ON(!cfq_cfqq_on_rr(cfqq));
2441 cfq_service_tree_add(cfqd, cfqq, 1);
2443 cfqq->slice_end = 0;
2444 cfq_mark_cfqq_slice_new(cfqq);
2448 * Called when a new fs request (rq) is added (to cfqq). Check if there's
2449 * something we should do about it
2452 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2455 struct cfq_io_context *cic = RQ_CIC(rq);
2459 cfqq->meta_pending++;
2461 cfq_update_io_thinktime(cfqd, cic);
2462 cfq_update_io_seektime(cfqd, cfqq, rq);
2463 cfq_update_idle_window(cfqd, cfqq, cic);
2465 cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
2467 if (cfqq == cfqd->active_queue) {
2469 * Remember that we saw a request from this process, but
2470 * don't start queuing just yet. Otherwise we risk seeing lots
2471 * of tiny requests, because we disrupt the normal plugging
2472 * and merging. If the request is already larger than a single
2473 * page, let it rip immediately. For that case we assume that
2474 * merging is already done. Ditto for a busy system that
2475 * has other work pending, don't risk delaying until the
2476 * idle timer unplug to continue working.
2478 if (cfq_cfqq_wait_request(cfqq)) {
2479 if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
2480 cfqd->busy_queues > 1) {
2481 del_timer(&cfqd->idle_slice_timer);
2482 __blk_run_queue(cfqd->queue);
2484 cfq_mark_cfqq_must_dispatch(cfqq);
2486 } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
2488 * not the active queue - expire current slice if it is
2489 * idle and has expired it's mean thinktime or this new queue
2490 * has some old slice time left and is of higher priority or
2491 * this new queue is RT and the current one is BE
2493 cfq_preempt_queue(cfqd, cfqq);
2494 __blk_run_queue(cfqd->queue);
2498 static void cfq_insert_request(struct request_queue *q, struct request *rq)
2500 struct cfq_data *cfqd = q->elevator->elevator_data;
2501 struct cfq_queue *cfqq = RQ_CFQQ(rq);
2503 cfq_log_cfqq(cfqd, cfqq, "insert_request");
2504 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
2506 rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
2507 list_add_tail(&rq->queuelist, &cfqq->fifo);
2510 cfq_rq_enqueued(cfqd, cfqq, rq);
2514 * Update hw_tag based on peak queue depth over 50 samples under
2517 static void cfq_update_hw_tag(struct cfq_data *cfqd)
2519 struct cfq_queue *cfqq = cfqd->active_queue;
2521 if (rq_in_driver(cfqd) > cfqd->rq_in_driver_peak)
2522 cfqd->rq_in_driver_peak = rq_in_driver(cfqd);
2524 if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
2525 rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN)
2529 * If active queue hasn't enough requests and can idle, cfq might not
2530 * dispatch sufficient requests to hardware. Don't zero hw_tag in this
2533 if (cfqq && cfq_cfqq_idle_window(cfqq) &&
2534 cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
2535 CFQ_HW_QUEUE_MIN && rq_in_driver(cfqd) < CFQ_HW_QUEUE_MIN)
2538 if (cfqd->hw_tag_samples++ < 50)
2541 if (cfqd->rq_in_driver_peak >= CFQ_HW_QUEUE_MIN)
2546 cfqd->hw_tag_samples = 0;
2547 cfqd->rq_in_driver_peak = 0;
2550 static void cfq_completed_request(struct request_queue *q, struct request *rq)
2552 struct cfq_queue *cfqq = RQ_CFQQ(rq);
2553 struct cfq_data *cfqd = cfqq->cfqd;
2554 const int sync = rq_is_sync(rq);
2558 cfq_log_cfqq(cfqd, cfqq, "complete");
2560 cfq_update_hw_tag(cfqd);
2562 WARN_ON(!cfqd->rq_in_driver[sync]);
2563 WARN_ON(!cfqq->dispatched);
2564 cfqd->rq_in_driver[sync]--;
2567 if (cfq_cfqq_sync(cfqq))
2568 cfqd->sync_flight--;
2571 RQ_CIC(rq)->last_end_request = now;
2572 cfqd->last_end_sync_rq = now;
2576 * If this is the active queue, check if it needs to be expired,
2577 * or if we want to idle in case it has no pending requests.
2579 if (cfqd->active_queue == cfqq) {
2580 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
2582 if (cfq_cfqq_slice_new(cfqq)) {
2583 cfq_set_prio_slice(cfqd, cfqq);
2584 cfq_clear_cfqq_slice_new(cfqq);
2587 * If there are no requests waiting in this queue, and
2588 * there are other queues ready to issue requests, AND
2589 * those other queues are issuing requests within our
2590 * mean seek distance, give them a chance to run instead
2593 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
2594 cfq_slice_expired(cfqd, 1);
2595 else if (cfqq_empty && !cfq_close_cooperator(cfqd, cfqq) &&
2596 sync && !rq_noidle(rq))
2597 cfq_arm_slice_timer(cfqd);
2600 if (!rq_in_driver(cfqd))
2601 cfq_schedule_dispatch(cfqd);
2605 * we temporarily boost lower priority queues if they are holding fs exclusive
2606 * resources. they are boosted to normal prio (CLASS_BE/4)
2608 static void cfq_prio_boost(struct cfq_queue *cfqq)
2610 if (has_fs_excl()) {
2612 * boost idle prio on transactions that would lock out other
2613 * users of the filesystem
2615 if (cfq_class_idle(cfqq))
2616 cfqq->ioprio_class = IOPRIO_CLASS_BE;
2617 if (cfqq->ioprio > IOPRIO_NORM)
2618 cfqq->ioprio = IOPRIO_NORM;
2621 * unboost the queue (if needed)
2623 cfqq->ioprio_class = cfqq->org_ioprio_class;
2624 cfqq->ioprio = cfqq->org_ioprio;
2628 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
2630 if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
2631 cfq_mark_cfqq_must_alloc_slice(cfqq);
2632 return ELV_MQUEUE_MUST;
2635 return ELV_MQUEUE_MAY;
2638 static int cfq_may_queue(struct request_queue *q, int rw)
2640 struct cfq_data *cfqd = q->elevator->elevator_data;
2641 struct task_struct *tsk = current;
2642 struct cfq_io_context *cic;
2643 struct cfq_queue *cfqq;
2646 * don't force setup of a queue from here, as a call to may_queue
2647 * does not necessarily imply that a request actually will be queued.
2648 * so just lookup a possibly existing queue, or return 'may queue'
2651 cic = cfq_cic_lookup(cfqd, tsk->io_context);
2653 return ELV_MQUEUE_MAY;
2655 cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
2657 cfq_init_prio_data(cfqq, cic->ioc);
2658 cfq_prio_boost(cfqq);
2660 return __cfq_may_queue(cfqq);
2663 return ELV_MQUEUE_MAY;
2667 * queue lock held here
2669 static void cfq_put_request(struct request *rq)
2671 struct cfq_queue *cfqq = RQ_CFQQ(rq);
2674 const int rw = rq_data_dir(rq);
2676 BUG_ON(!cfqq->allocated[rw]);
2677 cfqq->allocated[rw]--;
2679 put_io_context(RQ_CIC(rq)->ioc);
2681 rq->elevator_private = NULL;
2682 rq->elevator_private2 = NULL;
2684 cfq_put_queue(cfqq);
2688 static struct cfq_queue *
2689 cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
2690 struct cfq_queue *cfqq)
2692 cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
2693 cic_set_cfqq(cic, cfqq->new_cfqq, 1);
2694 cfq_mark_cfqq_coop(cfqq->new_cfqq);
2695 cfq_put_queue(cfqq);
2696 return cic_to_cfqq(cic, 1);
2699 static int should_split_cfqq(struct cfq_queue *cfqq)
2701 if (cfqq->seeky_start &&
2702 time_after(jiffies, cfqq->seeky_start + CFQQ_COOP_TOUT))
2708 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
2709 * was the last process referring to said cfqq.
2711 static struct cfq_queue *
2712 split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
2714 if (cfqq_process_refs(cfqq) == 1) {
2715 cfqq->seeky_start = 0;
2716 cfqq->pid = current->pid;
2717 cfq_clear_cfqq_coop(cfqq);
2721 cic_set_cfqq(cic, NULL, 1);
2722 cfq_put_queue(cfqq);
2726 * Allocate cfq data structures associated with this request.
2729 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
2731 struct cfq_data *cfqd = q->elevator->elevator_data;
2732 struct cfq_io_context *cic;
2733 const int rw = rq_data_dir(rq);
2734 const bool is_sync = rq_is_sync(rq);
2735 struct cfq_queue *cfqq;
2736 unsigned long flags;
2738 might_sleep_if(gfp_mask & __GFP_WAIT);
2740 cic = cfq_get_io_context(cfqd, gfp_mask);
2742 spin_lock_irqsave(q->queue_lock, flags);
2748 cfqq = cic_to_cfqq(cic, is_sync);
2749 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2750 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
2751 cic_set_cfqq(cic, cfqq, is_sync);
2754 * If the queue was seeky for too long, break it apart.
2756 if (cfq_cfqq_coop(cfqq) && should_split_cfqq(cfqq)) {
2757 cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
2758 cfqq = split_cfqq(cic, cfqq);
2764 * Check to see if this queue is scheduled to merge with
2765 * another, closely cooperating queue. The merging of
2766 * queues happens here as it must be done in process context.
2767 * The reference on new_cfqq was taken in merge_cfqqs.
2770 cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
2773 cfqq->allocated[rw]++;
2774 atomic_inc(&cfqq->ref);
2776 spin_unlock_irqrestore(q->queue_lock, flags);
2778 rq->elevator_private = cic;
2779 rq->elevator_private2 = cfqq;
2784 put_io_context(cic->ioc);
2786 cfq_schedule_dispatch(cfqd);
2787 spin_unlock_irqrestore(q->queue_lock, flags);
2788 cfq_log(cfqd, "set_request fail");
2792 static void cfq_kick_queue(struct work_struct *work)
2794 struct cfq_data *cfqd =
2795 container_of(work, struct cfq_data, unplug_work);
2796 struct request_queue *q = cfqd->queue;
2798 spin_lock_irq(q->queue_lock);
2799 __blk_run_queue(cfqd->queue);
2800 spin_unlock_irq(q->queue_lock);
2804 * Timer running if the active_queue is currently idling inside its time slice
2806 static void cfq_idle_slice_timer(unsigned long data)
2808 struct cfq_data *cfqd = (struct cfq_data *) data;
2809 struct cfq_queue *cfqq;
2810 unsigned long flags;
2813 cfq_log(cfqd, "idle timer fired");
2815 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2817 cfqq = cfqd->active_queue;
2822 * We saw a request before the queue expired, let it through
2824 if (cfq_cfqq_must_dispatch(cfqq))
2830 if (cfq_slice_used(cfqq))
2834 * only expire and reinvoke request handler, if there are
2835 * other queues with pending requests
2837 if (!cfqd->busy_queues)
2841 * not expired and it has a request pending, let it dispatch
2843 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
2847 cfq_slice_expired(cfqd, timed_out);
2849 cfq_schedule_dispatch(cfqd);
2851 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2854 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
2856 del_timer_sync(&cfqd->idle_slice_timer);
2857 cancel_work_sync(&cfqd->unplug_work);
2860 static void cfq_put_async_queues(struct cfq_data *cfqd)
2864 for (i = 0; i < IOPRIO_BE_NR; i++) {
2865 if (cfqd->async_cfqq[0][i])
2866 cfq_put_queue(cfqd->async_cfqq[0][i]);
2867 if (cfqd->async_cfqq[1][i])
2868 cfq_put_queue(cfqd->async_cfqq[1][i]);
2871 if (cfqd->async_idle_cfqq)
2872 cfq_put_queue(cfqd->async_idle_cfqq);
2875 static void cfq_exit_queue(struct elevator_queue *e)
2877 struct cfq_data *cfqd = e->elevator_data;
2878 struct request_queue *q = cfqd->queue;
2880 cfq_shutdown_timer_wq(cfqd);
2882 spin_lock_irq(q->queue_lock);
2884 if (cfqd->active_queue)
2885 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
2887 while (!list_empty(&cfqd->cic_list)) {
2888 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2889 struct cfq_io_context,
2892 __cfq_exit_single_io_context(cfqd, cic);
2895 cfq_put_async_queues(cfqd);
2897 spin_unlock_irq(q->queue_lock);
2899 cfq_shutdown_timer_wq(cfqd);
2904 static void *cfq_init_queue(struct request_queue *q)
2906 struct cfq_data *cfqd;
2909 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
2913 for (i = 0; i < 2; ++i)
2914 for (j = 0; j < 3; ++j)
2915 cfqd->service_trees[i][j] = CFQ_RB_ROOT;
2916 cfqd->service_tree_idle = CFQ_RB_ROOT;
2919 * Not strictly needed (since RB_ROOT just clears the node and we
2920 * zeroed cfqd on alloc), but better be safe in case someone decides
2921 * to add magic to the rb code
2923 for (i = 0; i < CFQ_PRIO_LISTS; i++)
2924 cfqd->prio_trees[i] = RB_ROOT;
2927 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
2928 * Grab a permanent reference to it, so that the normal code flow
2929 * will not attempt to free it.
2931 cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
2932 atomic_inc(&cfqd->oom_cfqq.ref);
2934 INIT_LIST_HEAD(&cfqd->cic_list);
2938 init_timer(&cfqd->idle_slice_timer);
2939 cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2940 cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2942 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
2944 cfqd->cfq_quantum = cfq_quantum;
2945 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2946 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2947 cfqd->cfq_back_max = cfq_back_max;
2948 cfqd->cfq_back_penalty = cfq_back_penalty;
2949 cfqd->cfq_slice[0] = cfq_slice_async;
2950 cfqd->cfq_slice[1] = cfq_slice_sync;
2951 cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2952 cfqd->cfq_slice_idle = cfq_slice_idle;
2953 cfqd->cfq_latency = 1;
2955 cfqd->last_end_sync_rq = jiffies;
2959 static void cfq_slab_kill(void)
2962 * Caller already ensured that pending RCU callbacks are completed,
2963 * so we should have no busy allocations at this point.
2966 kmem_cache_destroy(cfq_pool);
2968 kmem_cache_destroy(cfq_ioc_pool);
2971 static int __init cfq_slab_setup(void)
2973 cfq_pool = KMEM_CACHE(cfq_queue, 0);
2977 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
2988 * sysfs parts below -->
2991 cfq_var_show(unsigned int var, char *page)
2993 return sprintf(page, "%d\n", var);
2997 cfq_var_store(unsigned int *var, const char *page, size_t count)
2999 char *p = (char *) page;
3001 *var = simple_strtoul(p, &p, 10);
3005 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
3006 static ssize_t __FUNC(struct elevator_queue *e, char *page) \
3008 struct cfq_data *cfqd = e->elevator_data; \
3009 unsigned int __data = __VAR; \
3011 __data = jiffies_to_msecs(__data); \
3012 return cfq_var_show(__data, (page)); \
3014 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
3015 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
3016 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
3017 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
3018 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
3019 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
3020 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
3021 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
3022 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
3023 SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
3024 #undef SHOW_FUNCTION
3026 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
3027 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3029 struct cfq_data *cfqd = e->elevator_data; \
3030 unsigned int __data; \
3031 int ret = cfq_var_store(&__data, (page), count); \
3032 if (__data < (MIN)) \
3034 else if (__data > (MAX)) \
3037 *(__PTR) = msecs_to_jiffies(__data); \
3039 *(__PTR) = __data; \
3042 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
3043 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
3045 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
3047 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
3048 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
3050 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
3051 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
3052 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
3053 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
3055 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
3056 #undef STORE_FUNCTION
3058 #define CFQ_ATTR(name) \
3059 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3061 static struct elv_fs_entry cfq_attrs[] = {
3063 CFQ_ATTR(fifo_expire_sync),
3064 CFQ_ATTR(fifo_expire_async),
3065 CFQ_ATTR(back_seek_max),
3066 CFQ_ATTR(back_seek_penalty),
3067 CFQ_ATTR(slice_sync),
3068 CFQ_ATTR(slice_async),
3069 CFQ_ATTR(slice_async_rq),
3070 CFQ_ATTR(slice_idle),
3071 CFQ_ATTR(low_latency),
3075 static struct elevator_type iosched_cfq = {
3077 .elevator_merge_fn = cfq_merge,
3078 .elevator_merged_fn = cfq_merged_request,
3079 .elevator_merge_req_fn = cfq_merged_requests,
3080 .elevator_allow_merge_fn = cfq_allow_merge,
3081 .elevator_dispatch_fn = cfq_dispatch_requests,
3082 .elevator_add_req_fn = cfq_insert_request,
3083 .elevator_activate_req_fn = cfq_activate_request,
3084 .elevator_deactivate_req_fn = cfq_deactivate_request,
3085 .elevator_queue_empty_fn = cfq_queue_empty,
3086 .elevator_completed_req_fn = cfq_completed_request,
3087 .elevator_former_req_fn = elv_rb_former_request,
3088 .elevator_latter_req_fn = elv_rb_latter_request,
3089 .elevator_set_req_fn = cfq_set_request,
3090 .elevator_put_req_fn = cfq_put_request,
3091 .elevator_may_queue_fn = cfq_may_queue,
3092 .elevator_init_fn = cfq_init_queue,
3093 .elevator_exit_fn = cfq_exit_queue,
3094 .trim = cfq_free_io_context,
3096 .elevator_attrs = cfq_attrs,
3097 .elevator_name = "cfq",
3098 .elevator_owner = THIS_MODULE,
3101 static int __init cfq_init(void)
3104 * could be 0 on HZ < 1000 setups
3106 if (!cfq_slice_async)
3107 cfq_slice_async = 1;
3108 if (!cfq_slice_idle)
3111 if (cfq_slab_setup())
3114 elv_register(&iosched_cfq);
3119 static void __exit cfq_exit(void)
3121 DECLARE_COMPLETION_ONSTACK(all_gone);
3122 elv_unregister(&iosched_cfq);
3123 ioc_gone = &all_gone;
3124 /* ioc_gone's update must be visible before reading ioc_count */
3128 * this also protects us from entering cfq_slab_kill() with
3129 * pending RCU callbacks
3131 if (elv_ioc_count_read(cfq_ioc_count))
3132 wait_for_completion(&all_gone);
3136 module_init(cfq_init);
3137 module_exit(cfq_exit);
3139 MODULE_AUTHOR("Jens Axboe");
3140 MODULE_LICENSE("GPL");
3141 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");