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/slab.h>
11 #include <linux/blkdev.h>
12 #include <linux/elevator.h>
13 #include <linux/jiffies.h>
14 #include <linux/rbtree.h>
15 #include <linux/ioprio.h>
16 #include <linux/blktrace_api.h>
17 #include "blk-cgroup.h"
22 /* max queue in one round of service */
23 static const int cfq_quantum = 8;
24 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
25 /* maximum backwards seek, in KiB */
26 static const int cfq_back_max = 16 * 1024;
27 /* penalty of a backwards seek */
28 static const int cfq_back_penalty = 2;
29 static const int cfq_slice_sync = HZ / 10;
30 static int cfq_slice_async = HZ / 25;
31 static const int cfq_slice_async_rq = 2;
32 static int cfq_slice_idle = HZ / 125;
33 static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
34 static const int cfq_hist_divisor = 4;
37 * offset from end of service tree
39 #define CFQ_IDLE_DELAY (HZ / 5)
42 * below this threshold, we consider thinktime immediate
44 #define CFQ_MIN_TT (2)
46 #define CFQ_SLICE_SCALE (5)
47 #define CFQ_HW_QUEUE_MIN (5)
48 #define CFQ_SERVICE_SHIFT 12
50 #define CFQQ_SEEK_THR (sector_t)(8 * 100)
51 #define CFQQ_CLOSE_THR (sector_t)(8 * 1024)
52 #define CFQQ_SECT_THR_NONROT (sector_t)(2 * 32)
53 #define CFQQ_SEEKY(cfqq) (hweight32(cfqq->seek_history) > 32/8)
56 ((struct cfq_io_context *) (rq)->elevator_private)
57 #define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2)
59 static struct kmem_cache *cfq_pool;
60 static struct kmem_cache *cfq_ioc_pool;
62 static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
63 static struct completion *ioc_gone;
64 static DEFINE_SPINLOCK(ioc_gone_lock);
66 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
67 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
68 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
70 #define sample_valid(samples) ((samples) > 80)
71 #define rb_entry_cfqg(node) rb_entry((node), struct cfq_group, rb_node)
74 * Most of our rbtree usage is for sorting with min extraction, so
75 * if we cache the leftmost node we don't have to walk down the tree
76 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
77 * move this into the elevator for the rq sorting as well.
83 unsigned total_weight;
85 struct rb_node *active;
87 #define CFQ_RB_ROOT (struct cfq_rb_root) { .rb = RB_ROOT, .left = NULL, \
88 .count = 0, .min_vdisktime = 0, }
91 * Per process-grouping structure
96 /* various state flags, see below */
99 struct cfq_data *cfqd;
100 /* service_tree member */
101 struct rb_node rb_node;
102 /* service_tree key */
103 unsigned long rb_key;
104 /* prio tree member */
105 struct rb_node p_node;
106 /* prio tree root we belong to, if any */
107 struct rb_root *p_root;
108 /* sorted list of pending requests */
109 struct rb_root sort_list;
110 /* if fifo isn't expired, next request to serve */
111 struct request *next_rq;
112 /* requests queued in sort_list */
114 /* currently allocated requests */
116 /* fifo list of requests in sort_list */
117 struct list_head fifo;
119 /* time when queue got scheduled in to dispatch first request. */
120 unsigned long dispatch_start;
121 unsigned int allocated_slice;
122 unsigned int slice_dispatch;
123 /* time when first request from queue completed and slice started. */
124 unsigned long slice_start;
125 unsigned long slice_end;
128 /* pending metadata requests */
130 /* number of requests that are on the dispatch list or inside driver */
133 /* io prio of this group */
134 unsigned short ioprio, org_ioprio;
135 unsigned short ioprio_class, org_ioprio_class;
140 sector_t last_request_pos;
142 struct cfq_rb_root *service_tree;
143 struct cfq_queue *new_cfqq;
144 struct cfq_group *cfqg;
145 struct cfq_group *orig_cfqg;
149 * First index in the service_trees.
150 * IDLE is handled separately, so it has negative index
159 * Second index in the service_trees.
163 SYNC_NOIDLE_WORKLOAD = 1,
167 /* This is per cgroup per device grouping structure */
169 /* group service_tree member */
170 struct rb_node rb_node;
172 /* group service_tree key */
177 /* number of cfqq currently on this group */
180 /* Per group busy queus average. Useful for workload slice calc. */
181 unsigned int busy_queues_avg[2];
183 * rr lists of queues with requests, onle rr for each priority class.
184 * Counts are embedded in the cfq_rb_root
186 struct cfq_rb_root service_trees[2][3];
187 struct cfq_rb_root service_tree_idle;
189 unsigned long saved_workload_slice;
190 enum wl_type_t saved_workload;
191 enum wl_prio_t saved_serving_prio;
192 struct blkio_group blkg;
193 #ifdef CONFIG_CFQ_GROUP_IOSCHED
194 struct hlist_node cfqd_node;
200 * Per block device queue structure
203 struct request_queue *queue;
204 /* Root service tree for cfq_groups */
205 struct cfq_rb_root grp_service_tree;
206 struct cfq_group root_group;
209 * The priority currently being served
211 enum wl_prio_t serving_prio;
212 enum wl_type_t serving_type;
213 unsigned long workload_expires;
214 struct cfq_group *serving_group;
215 bool noidle_tree_requires_idle;
218 * Each priority tree is sorted by next_request position. These
219 * trees are used when determining if two or more queues are
220 * interleaving requests (see cfq_close_cooperator).
222 struct rb_root prio_trees[CFQ_PRIO_LISTS];
224 unsigned int busy_queues;
230 * queue-depth detection
236 * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
237 * 1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
240 int hw_tag_est_depth;
241 unsigned int hw_tag_samples;
244 * idle window management
246 struct timer_list idle_slice_timer;
247 struct work_struct unplug_work;
249 struct cfq_queue *active_queue;
250 struct cfq_io_context *active_cic;
253 * async queue for each priority case
255 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
256 struct cfq_queue *async_idle_cfqq;
258 sector_t last_position;
261 * tunables, see top of file
263 unsigned int cfq_quantum;
264 unsigned int cfq_fifo_expire[2];
265 unsigned int cfq_back_penalty;
266 unsigned int cfq_back_max;
267 unsigned int cfq_slice[2];
268 unsigned int cfq_slice_async_rq;
269 unsigned int cfq_slice_idle;
270 unsigned int cfq_latency;
271 unsigned int cfq_group_isolation;
273 struct list_head cic_list;
276 * Fallback dummy cfqq for extreme OOM conditions
278 struct cfq_queue oom_cfqq;
280 unsigned long last_delayed_sync;
282 /* List of cfq groups being managed on this device*/
283 struct hlist_head cfqg_list;
287 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
289 static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
296 if (prio == IDLE_WORKLOAD)
297 return &cfqg->service_tree_idle;
299 return &cfqg->service_trees[prio][type];
302 enum cfqq_state_flags {
303 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
304 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
305 CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */
306 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
307 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
308 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */
309 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
310 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
311 CFQ_CFQQ_FLAG_sync, /* synchronous queue */
312 CFQ_CFQQ_FLAG_coop, /* cfqq is shared */
313 CFQ_CFQQ_FLAG_split_coop, /* shared cfqq will be splitted */
314 CFQ_CFQQ_FLAG_deep, /* sync cfqq experienced large depth */
315 CFQ_CFQQ_FLAG_wait_busy, /* Waiting for next request */
318 #define CFQ_CFQQ_FNS(name) \
319 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
321 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
323 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
325 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
327 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
329 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
333 CFQ_CFQQ_FNS(wait_request);
334 CFQ_CFQQ_FNS(must_dispatch);
335 CFQ_CFQQ_FNS(must_alloc_slice);
336 CFQ_CFQQ_FNS(fifo_expire);
337 CFQ_CFQQ_FNS(idle_window);
338 CFQ_CFQQ_FNS(prio_changed);
339 CFQ_CFQQ_FNS(slice_new);
342 CFQ_CFQQ_FNS(split_coop);
344 CFQ_CFQQ_FNS(wait_busy);
347 #ifdef CONFIG_DEBUG_CFQ_IOSCHED
348 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
349 blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
350 cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
351 blkg_path(&(cfqq)->cfqg->blkg), ##args);
353 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...) \
354 blk_add_trace_msg((cfqd)->queue, "%s " fmt, \
355 blkg_path(&(cfqg)->blkg), ##args); \
358 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
359 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
360 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...) do {} while (0);
362 #define cfq_log(cfqd, fmt, args...) \
363 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
365 /* Traverses through cfq group service trees */
366 #define for_each_cfqg_st(cfqg, i, j, st) \
367 for (i = 0; i <= IDLE_WORKLOAD; i++) \
368 for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
369 : &cfqg->service_tree_idle; \
370 (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
371 (i == IDLE_WORKLOAD && j == 0); \
372 j++, st = i < IDLE_WORKLOAD ? \
373 &cfqg->service_trees[i][j]: NULL) \
376 static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
378 if (cfq_class_idle(cfqq))
379 return IDLE_WORKLOAD;
380 if (cfq_class_rt(cfqq))
386 static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
388 if (!cfq_cfqq_sync(cfqq))
389 return ASYNC_WORKLOAD;
390 if (!cfq_cfqq_idle_window(cfqq))
391 return SYNC_NOIDLE_WORKLOAD;
392 return SYNC_WORKLOAD;
395 static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl,
396 struct cfq_data *cfqd,
397 struct cfq_group *cfqg)
399 if (wl == IDLE_WORKLOAD)
400 return cfqg->service_tree_idle.count;
402 return cfqg->service_trees[wl][ASYNC_WORKLOAD].count
403 + cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
404 + cfqg->service_trees[wl][SYNC_WORKLOAD].count;
407 static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
408 struct cfq_group *cfqg)
410 return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count
411 + cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
414 static void cfq_dispatch_insert(struct request_queue *, struct request *);
415 static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
416 struct io_context *, gfp_t);
417 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
418 struct io_context *);
420 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
423 return cic->cfqq[is_sync];
426 static inline void cic_set_cfqq(struct cfq_io_context *cic,
427 struct cfq_queue *cfqq, bool is_sync)
429 cic->cfqq[is_sync] = cfqq;
433 * We regard a request as SYNC, if it's either a read or has the SYNC bit
434 * set (in which case it could also be direct WRITE).
436 static inline bool cfq_bio_sync(struct bio *bio)
438 return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO);
442 * scheduler run of queue, if there are requests pending and no one in the
443 * driver that will restart queueing
445 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
447 if (cfqd->busy_queues) {
448 cfq_log(cfqd, "schedule dispatch");
449 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
453 static int cfq_queue_empty(struct request_queue *q)
455 struct cfq_data *cfqd = q->elevator->elevator_data;
457 return !cfqd->rq_queued;
461 * Scale schedule slice based on io priority. Use the sync time slice only
462 * if a queue is marked sync and has sync io queued. A sync queue with async
463 * io only, should not get full sync slice length.
465 static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
468 const int base_slice = cfqd->cfq_slice[sync];
470 WARN_ON(prio >= IOPRIO_BE_NR);
472 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
476 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
478 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
481 static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
483 u64 d = delta << CFQ_SERVICE_SHIFT;
485 d = d * BLKIO_WEIGHT_DEFAULT;
486 do_div(d, cfqg->weight);
490 static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
492 s64 delta = (s64)(vdisktime - min_vdisktime);
494 min_vdisktime = vdisktime;
496 return min_vdisktime;
499 static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
501 s64 delta = (s64)(vdisktime - min_vdisktime);
503 min_vdisktime = vdisktime;
505 return min_vdisktime;
508 static void update_min_vdisktime(struct cfq_rb_root *st)
510 u64 vdisktime = st->min_vdisktime;
511 struct cfq_group *cfqg;
514 cfqg = rb_entry_cfqg(st->active);
515 vdisktime = cfqg->vdisktime;
519 cfqg = rb_entry_cfqg(st->left);
520 vdisktime = min_vdisktime(vdisktime, cfqg->vdisktime);
523 st->min_vdisktime = max_vdisktime(st->min_vdisktime, vdisktime);
527 * get averaged number of queues of RT/BE priority.
528 * average is updated, with a formula that gives more weight to higher numbers,
529 * to quickly follows sudden increases and decrease slowly
532 static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
533 struct cfq_group *cfqg, bool rt)
535 unsigned min_q, max_q;
536 unsigned mult = cfq_hist_divisor - 1;
537 unsigned round = cfq_hist_divisor / 2;
538 unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
540 min_q = min(cfqg->busy_queues_avg[rt], busy);
541 max_q = max(cfqg->busy_queues_avg[rt], busy);
542 cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
544 return cfqg->busy_queues_avg[rt];
547 static inline unsigned
548 cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
550 struct cfq_rb_root *st = &cfqd->grp_service_tree;
552 return cfq_target_latency * cfqg->weight / st->total_weight;
556 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
558 unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
559 if (cfqd->cfq_latency) {
561 * interested queues (we consider only the ones with the same
562 * priority class in the cfq group)
564 unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
566 unsigned sync_slice = cfqd->cfq_slice[1];
567 unsigned expect_latency = sync_slice * iq;
568 unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
570 if (expect_latency > group_slice) {
571 unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
572 /* scale low_slice according to IO priority
573 * and sync vs async */
575 min(slice, base_low_slice * slice / sync_slice);
576 /* the adapted slice value is scaled to fit all iqs
577 * into the target latency */
578 slice = max(slice * group_slice / expect_latency,
582 cfqq->slice_start = jiffies;
583 cfqq->slice_end = jiffies + slice;
584 cfqq->allocated_slice = slice;
585 cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
589 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
590 * isn't valid until the first request from the dispatch is activated
591 * and the slice time set.
593 static inline bool cfq_slice_used(struct cfq_queue *cfqq)
595 if (cfq_cfqq_slice_new(cfqq))
597 if (time_before(jiffies, cfqq->slice_end))
604 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
605 * We choose the request that is closest to the head right now. Distance
606 * behind the head is penalized and only allowed to a certain extent.
608 static struct request *
609 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
611 sector_t s1, s2, d1 = 0, d2 = 0;
612 unsigned long back_max;
613 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
614 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
615 unsigned wrap = 0; /* bit mask: requests behind the disk head? */
617 if (rq1 == NULL || rq1 == rq2)
622 if (rq_is_sync(rq1) && !rq_is_sync(rq2))
624 else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
626 if (rq_is_meta(rq1) && !rq_is_meta(rq2))
628 else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
631 s1 = blk_rq_pos(rq1);
632 s2 = blk_rq_pos(rq2);
635 * by definition, 1KiB is 2 sectors
637 back_max = cfqd->cfq_back_max * 2;
640 * Strict one way elevator _except_ in the case where we allow
641 * short backward seeks which are biased as twice the cost of a
642 * similar forward seek.
646 else if (s1 + back_max >= last)
647 d1 = (last - s1) * cfqd->cfq_back_penalty;
649 wrap |= CFQ_RQ1_WRAP;
653 else if (s2 + back_max >= last)
654 d2 = (last - s2) * cfqd->cfq_back_penalty;
656 wrap |= CFQ_RQ2_WRAP;
658 /* Found required data */
661 * By doing switch() on the bit mask "wrap" we avoid having to
662 * check two variables for all permutations: --> faster!
665 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
681 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
684 * Since both rqs are wrapped,
685 * start with the one that's further behind head
686 * (--> only *one* back seek required),
687 * since back seek takes more time than forward.
697 * The below is leftmost cache rbtree addon
699 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
701 /* Service tree is empty */
706 root->left = rb_first(&root->rb);
709 return rb_entry(root->left, struct cfq_queue, rb_node);
714 static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
717 root->left = rb_first(&root->rb);
720 return rb_entry_cfqg(root->left);
725 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
731 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
735 rb_erase_init(n, &root->rb);
740 * would be nice to take fifo expire time into account as well
742 static struct request *
743 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
744 struct request *last)
746 struct rb_node *rbnext = rb_next(&last->rb_node);
747 struct rb_node *rbprev = rb_prev(&last->rb_node);
748 struct request *next = NULL, *prev = NULL;
750 BUG_ON(RB_EMPTY_NODE(&last->rb_node));
753 prev = rb_entry_rq(rbprev);
756 next = rb_entry_rq(rbnext);
758 rbnext = rb_first(&cfqq->sort_list);
759 if (rbnext && rbnext != &last->rb_node)
760 next = rb_entry_rq(rbnext);
763 return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
766 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
767 struct cfq_queue *cfqq)
770 * just an approximation, should be ok.
772 return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
773 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
777 cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
779 return cfqg->vdisktime - st->min_vdisktime;
783 __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
785 struct rb_node **node = &st->rb.rb_node;
786 struct rb_node *parent = NULL;
787 struct cfq_group *__cfqg;
788 s64 key = cfqg_key(st, cfqg);
791 while (*node != NULL) {
793 __cfqg = rb_entry_cfqg(parent);
795 if (key < cfqg_key(st, __cfqg))
796 node = &parent->rb_left;
798 node = &parent->rb_right;
804 st->left = &cfqg->rb_node;
806 rb_link_node(&cfqg->rb_node, parent, node);
807 rb_insert_color(&cfqg->rb_node, &st->rb);
811 cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
813 struct cfq_rb_root *st = &cfqd->grp_service_tree;
814 struct cfq_group *__cfqg;
822 * Currently put the group at the end. Later implement something
823 * so that groups get lesser vtime based on their weights, so that
824 * if group does not loose all if it was not continously backlogged.
826 n = rb_last(&st->rb);
828 __cfqg = rb_entry_cfqg(n);
829 cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
831 cfqg->vdisktime = st->min_vdisktime;
833 __cfq_group_service_tree_add(st, cfqg);
835 st->total_weight += cfqg->weight;
839 cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
841 struct cfq_rb_root *st = &cfqd->grp_service_tree;
843 if (st->active == &cfqg->rb_node)
846 BUG_ON(cfqg->nr_cfqq < 1);
849 /* If there are other cfq queues under this group, don't delete it */
853 cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
855 st->total_weight -= cfqg->weight;
856 if (!RB_EMPTY_NODE(&cfqg->rb_node))
857 cfq_rb_erase(&cfqg->rb_node, st);
858 cfqg->saved_workload_slice = 0;
859 blkiocg_update_dequeue_stats(&cfqg->blkg, 1);
862 static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
864 unsigned int slice_used;
867 * Queue got expired before even a single request completed or
868 * got expired immediately after first request completion.
870 if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
872 * Also charge the seek time incurred to the group, otherwise
873 * if there are mutiple queues in the group, each can dispatch
874 * a single request on seeky media and cause lots of seek time
875 * and group will never know it.
877 slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
880 slice_used = jiffies - cfqq->slice_start;
881 if (slice_used > cfqq->allocated_slice)
882 slice_used = cfqq->allocated_slice;
885 cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u", slice_used);
889 static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
890 struct cfq_queue *cfqq, bool forced)
892 struct cfq_rb_root *st = &cfqd->grp_service_tree;
893 unsigned int used_sl, charge_sl;
894 int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
895 - cfqg->service_tree_idle.count;
898 used_sl = charge_sl = cfq_cfqq_slice_usage(cfqq);
900 if (!cfq_cfqq_sync(cfqq) && !nr_sync)
901 charge_sl = cfqq->allocated_slice;
903 /* Can't update vdisktime while group is on service tree */
904 cfq_rb_erase(&cfqg->rb_node, st);
905 cfqg->vdisktime += cfq_scale_slice(charge_sl, cfqg);
906 __cfq_group_service_tree_add(st, cfqg);
908 /* This group is being expired. Save the context */
909 if (time_after(cfqd->workload_expires, jiffies)) {
910 cfqg->saved_workload_slice = cfqd->workload_expires
912 cfqg->saved_workload = cfqd->serving_type;
913 cfqg->saved_serving_prio = cfqd->serving_prio;
915 cfqg->saved_workload_slice = 0;
917 cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
919 blkiocg_update_timeslice_used(&cfqg->blkg, used_sl);
920 blkiocg_set_start_empty_time(&cfqg->blkg, forced);
923 #ifdef CONFIG_CFQ_GROUP_IOSCHED
924 static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
927 return container_of(blkg, struct cfq_group, blkg);
932 cfq_update_blkio_group_weight(struct blkio_group *blkg, unsigned int weight)
934 cfqg_of_blkg(blkg)->weight = weight;
937 static struct cfq_group *
938 cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
940 struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
941 struct cfq_group *cfqg = NULL;
944 struct cfq_rb_root *st;
945 struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
946 unsigned int major, minor;
948 cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
949 if (cfqg && !cfqg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {
950 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
951 cfqg->blkg.dev = MKDEV(major, minor);
957 cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node);
961 for_each_cfqg_st(cfqg, i, j, st)
963 RB_CLEAR_NODE(&cfqg->rb_node);
966 * Take the initial reference that will be released on destroy
967 * This can be thought of a joint reference by cgroup and
968 * elevator which will be dropped by either elevator exit
969 * or cgroup deletion path depending on who is exiting first.
971 atomic_set(&cfqg->ref, 1);
973 /* Add group onto cgroup list */
974 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
975 blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
976 MKDEV(major, minor));
977 cfqg->weight = blkcg_get_weight(blkcg, cfqg->blkg.dev);
979 /* Add group on cfqd list */
980 hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
987 * Search for the cfq group current task belongs to. If create = 1, then also
988 * create the cfq group if it does not exist. request_queue lock must be held.
990 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
992 struct cgroup *cgroup;
993 struct cfq_group *cfqg = NULL;
996 cgroup = task_cgroup(current, blkio_subsys_id);
997 cfqg = cfq_find_alloc_cfqg(cfqd, cgroup, create);
999 cfqg = &cfqd->root_group;
1004 static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
1006 /* Currently, all async queues are mapped to root group */
1007 if (!cfq_cfqq_sync(cfqq))
1008 cfqg = &cfqq->cfqd->root_group;
1011 /* cfqq reference on cfqg */
1012 atomic_inc(&cfqq->cfqg->ref);
1015 static void cfq_put_cfqg(struct cfq_group *cfqg)
1017 struct cfq_rb_root *st;
1020 BUG_ON(atomic_read(&cfqg->ref) <= 0);
1021 if (!atomic_dec_and_test(&cfqg->ref))
1023 for_each_cfqg_st(cfqg, i, j, st)
1024 BUG_ON(!RB_EMPTY_ROOT(&st->rb) || st->active != NULL);
1028 static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
1030 /* Something wrong if we are trying to remove same group twice */
1031 BUG_ON(hlist_unhashed(&cfqg->cfqd_node));
1033 hlist_del_init(&cfqg->cfqd_node);
1036 * Put the reference taken at the time of creation so that when all
1037 * queues are gone, group can be destroyed.
1042 static void cfq_release_cfq_groups(struct cfq_data *cfqd)
1044 struct hlist_node *pos, *n;
1045 struct cfq_group *cfqg;
1047 hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) {
1049 * If cgroup removal path got to blk_group first and removed
1050 * it from cgroup list, then it will take care of destroying
1053 if (!blkiocg_del_blkio_group(&cfqg->blkg))
1054 cfq_destroy_cfqg(cfqd, cfqg);
1059 * Blk cgroup controller notification saying that blkio_group object is being
1060 * delinked as associated cgroup object is going away. That also means that
1061 * no new IO will come in this group. So get rid of this group as soon as
1062 * any pending IO in the group is finished.
1064 * This function is called under rcu_read_lock(). key is the rcu protected
1065 * pointer. That means "key" is a valid cfq_data pointer as long as we are rcu
1068 * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
1069 * it should not be NULL as even if elevator was exiting, cgroup deltion
1070 * path got to it first.
1072 void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
1074 unsigned long flags;
1075 struct cfq_data *cfqd = key;
1077 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1078 cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg));
1079 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1082 #else /* GROUP_IOSCHED */
1083 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
1085 return &cfqd->root_group;
1088 cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
1092 static void cfq_release_cfq_groups(struct cfq_data *cfqd) {}
1093 static inline void cfq_put_cfqg(struct cfq_group *cfqg) {}
1095 #endif /* GROUP_IOSCHED */
1098 * The cfqd->service_trees holds all pending cfq_queue's that have
1099 * requests waiting to be processed. It is sorted in the order that
1100 * we will service the queues.
1102 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1105 struct rb_node **p, *parent;
1106 struct cfq_queue *__cfqq;
1107 unsigned long rb_key;
1108 struct cfq_rb_root *service_tree;
1111 int group_changed = 0;
1113 #ifdef CONFIG_CFQ_GROUP_IOSCHED
1114 if (!cfqd->cfq_group_isolation
1115 && cfqq_type(cfqq) == SYNC_NOIDLE_WORKLOAD
1116 && cfqq->cfqg && cfqq->cfqg != &cfqd->root_group) {
1117 /* Move this cfq to root group */
1118 cfq_log_cfqq(cfqd, cfqq, "moving to root group");
1119 if (!RB_EMPTY_NODE(&cfqq->rb_node))
1120 cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1121 cfqq->orig_cfqg = cfqq->cfqg;
1122 cfqq->cfqg = &cfqd->root_group;
1123 atomic_inc(&cfqd->root_group.ref);
1125 } else if (!cfqd->cfq_group_isolation
1126 && cfqq_type(cfqq) == SYNC_WORKLOAD && cfqq->orig_cfqg) {
1127 /* cfqq is sequential now needs to go to its original group */
1128 BUG_ON(cfqq->cfqg != &cfqd->root_group);
1129 if (!RB_EMPTY_NODE(&cfqq->rb_node))
1130 cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1131 cfq_put_cfqg(cfqq->cfqg);
1132 cfqq->cfqg = cfqq->orig_cfqg;
1133 cfqq->orig_cfqg = NULL;
1135 cfq_log_cfqq(cfqd, cfqq, "moved to origin group");
1139 service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
1141 if (cfq_class_idle(cfqq)) {
1142 rb_key = CFQ_IDLE_DELAY;
1143 parent = rb_last(&service_tree->rb);
1144 if (parent && parent != &cfqq->rb_node) {
1145 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1146 rb_key += __cfqq->rb_key;
1149 } else if (!add_front) {
1151 * Get our rb key offset. Subtract any residual slice
1152 * value carried from last service. A negative resid
1153 * count indicates slice overrun, and this should position
1154 * the next service time further away in the tree.
1156 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
1157 rb_key -= cfqq->slice_resid;
1158 cfqq->slice_resid = 0;
1161 __cfqq = cfq_rb_first(service_tree);
1162 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
1165 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1168 * same position, nothing more to do
1170 if (rb_key == cfqq->rb_key &&
1171 cfqq->service_tree == service_tree)
1174 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1175 cfqq->service_tree = NULL;
1180 cfqq->service_tree = service_tree;
1181 p = &service_tree->rb.rb_node;
1186 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1189 * sort by key, that represents service time.
1191 if (time_before(rb_key, __cfqq->rb_key))
1194 n = &(*p)->rb_right;
1202 service_tree->left = &cfqq->rb_node;
1204 cfqq->rb_key = rb_key;
1205 rb_link_node(&cfqq->rb_node, parent, p);
1206 rb_insert_color(&cfqq->rb_node, &service_tree->rb);
1207 service_tree->count++;
1208 if ((add_front || !new_cfqq) && !group_changed)
1210 cfq_group_service_tree_add(cfqd, cfqq->cfqg);
1213 static struct cfq_queue *
1214 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
1215 sector_t sector, struct rb_node **ret_parent,
1216 struct rb_node ***rb_link)
1218 struct rb_node **p, *parent;
1219 struct cfq_queue *cfqq = NULL;
1227 cfqq = rb_entry(parent, struct cfq_queue, p_node);
1230 * Sort strictly based on sector. Smallest to the left,
1231 * largest to the right.
1233 if (sector > blk_rq_pos(cfqq->next_rq))
1234 n = &(*p)->rb_right;
1235 else if (sector < blk_rq_pos(cfqq->next_rq))
1243 *ret_parent = parent;
1249 static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1251 struct rb_node **p, *parent;
1252 struct cfq_queue *__cfqq;
1255 rb_erase(&cfqq->p_node, cfqq->p_root);
1256 cfqq->p_root = NULL;
1259 if (cfq_class_idle(cfqq))
1264 cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
1265 __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
1266 blk_rq_pos(cfqq->next_rq), &parent, &p);
1268 rb_link_node(&cfqq->p_node, parent, p);
1269 rb_insert_color(&cfqq->p_node, cfqq->p_root);
1271 cfqq->p_root = NULL;
1275 * Update cfqq's position in the service tree.
1277 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1280 * Resorting requires the cfqq to be on the RR list already.
1282 if (cfq_cfqq_on_rr(cfqq)) {
1283 cfq_service_tree_add(cfqd, cfqq, 0);
1284 cfq_prio_tree_add(cfqd, cfqq);
1289 * add to busy list of queues for service, trying to be fair in ordering
1290 * the pending list according to last request service
1292 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1294 cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
1295 BUG_ON(cfq_cfqq_on_rr(cfqq));
1296 cfq_mark_cfqq_on_rr(cfqq);
1297 cfqd->busy_queues++;
1299 cfq_resort_rr_list(cfqd, cfqq);
1303 * Called when the cfqq no longer has requests pending, remove it from
1306 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1308 cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
1309 BUG_ON(!cfq_cfqq_on_rr(cfqq));
1310 cfq_clear_cfqq_on_rr(cfqq);
1312 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1313 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1314 cfqq->service_tree = NULL;
1317 rb_erase(&cfqq->p_node, cfqq->p_root);
1318 cfqq->p_root = NULL;
1321 cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1322 BUG_ON(!cfqd->busy_queues);
1323 cfqd->busy_queues--;
1327 * rb tree support functions
1329 static void cfq_del_rq_rb(struct request *rq)
1331 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1332 const int sync = rq_is_sync(rq);
1334 BUG_ON(!cfqq->queued[sync]);
1335 cfqq->queued[sync]--;
1337 elv_rb_del(&cfqq->sort_list, rq);
1339 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
1341 * Queue will be deleted from service tree when we actually
1342 * expire it later. Right now just remove it from prio tree
1346 rb_erase(&cfqq->p_node, cfqq->p_root);
1347 cfqq->p_root = NULL;
1352 static void cfq_add_rq_rb(struct request *rq)
1354 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1355 struct cfq_data *cfqd = cfqq->cfqd;
1356 struct request *__alias, *prev;
1358 cfqq->queued[rq_is_sync(rq)]++;
1361 * looks a little odd, but the first insert might return an alias.
1362 * if that happens, put the alias on the dispatch list
1364 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
1365 cfq_dispatch_insert(cfqd->queue, __alias);
1367 if (!cfq_cfqq_on_rr(cfqq))
1368 cfq_add_cfqq_rr(cfqd, cfqq);
1371 * check if this request is a better next-serve candidate
1373 prev = cfqq->next_rq;
1374 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
1377 * adjust priority tree position, if ->next_rq changes
1379 if (prev != cfqq->next_rq)
1380 cfq_prio_tree_add(cfqd, cfqq);
1382 BUG_ON(!cfqq->next_rq);
1385 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
1387 elv_rb_del(&cfqq->sort_list, rq);
1388 cfqq->queued[rq_is_sync(rq)]--;
1389 blkiocg_update_io_remove_stats(&cfqq->cfqg->blkg, rq_data_dir(rq),
1392 blkiocg_update_io_add_stats(
1393 &cfqq->cfqg->blkg, &cfqq->cfqd->serving_group->blkg,
1394 rq_data_dir(rq), rq_is_sync(rq));
1397 static struct request *
1398 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
1400 struct task_struct *tsk = current;
1401 struct cfq_io_context *cic;
1402 struct cfq_queue *cfqq;
1404 cic = cfq_cic_lookup(cfqd, tsk->io_context);
1408 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1410 sector_t sector = bio->bi_sector + bio_sectors(bio);
1412 return elv_rb_find(&cfqq->sort_list, sector);
1418 static void cfq_activate_request(struct request_queue *q, struct request *rq)
1420 struct cfq_data *cfqd = q->elevator->elevator_data;
1422 cfqd->rq_in_driver++;
1423 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
1424 cfqd->rq_in_driver);
1426 cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
1429 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
1431 struct cfq_data *cfqd = q->elevator->elevator_data;
1433 WARN_ON(!cfqd->rq_in_driver);
1434 cfqd->rq_in_driver--;
1435 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
1436 cfqd->rq_in_driver);
1439 static void cfq_remove_request(struct request *rq)
1441 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1443 if (cfqq->next_rq == rq)
1444 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
1446 list_del_init(&rq->queuelist);
1449 cfqq->cfqd->rq_queued--;
1450 blkiocg_update_io_remove_stats(&cfqq->cfqg->blkg, rq_data_dir(rq),
1452 if (rq_is_meta(rq)) {
1453 WARN_ON(!cfqq->meta_pending);
1454 cfqq->meta_pending--;
1458 static int cfq_merge(struct request_queue *q, struct request **req,
1461 struct cfq_data *cfqd = q->elevator->elevator_data;
1462 struct request *__rq;
1464 __rq = cfq_find_rq_fmerge(cfqd, bio);
1465 if (__rq && elv_rq_merge_ok(__rq, bio)) {
1467 return ELEVATOR_FRONT_MERGE;
1470 return ELEVATOR_NO_MERGE;
1473 static void cfq_merged_request(struct request_queue *q, struct request *req,
1476 if (type == ELEVATOR_FRONT_MERGE) {
1477 struct cfq_queue *cfqq = RQ_CFQQ(req);
1479 cfq_reposition_rq_rb(cfqq, req);
1483 static void cfq_bio_merged(struct request_queue *q, struct request *req,
1486 struct cfq_queue *cfqq = RQ_CFQQ(req);
1487 blkiocg_update_io_merged_stats(&cfqq->cfqg->blkg, bio_data_dir(bio),
1492 cfq_merged_requests(struct request_queue *q, struct request *rq,
1493 struct request *next)
1495 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1497 * reposition in fifo if next is older than rq
1499 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
1500 time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
1501 list_move(&rq->queuelist, &next->queuelist);
1502 rq_set_fifo_time(rq, rq_fifo_time(next));
1505 if (cfqq->next_rq == next)
1507 cfq_remove_request(next);
1508 blkiocg_update_io_merged_stats(&cfqq->cfqg->blkg, rq_data_dir(next),
1512 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
1515 struct cfq_data *cfqd = q->elevator->elevator_data;
1516 struct cfq_io_context *cic;
1517 struct cfq_queue *cfqq;
1520 * Disallow merge of a sync bio into an async request.
1522 if (cfq_bio_sync(bio) && !rq_is_sync(rq))
1526 * Lookup the cfqq that this bio will be queued with. Allow
1527 * merge only if rq is queued there.
1529 cic = cfq_cic_lookup(cfqd, current->io_context);
1533 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1534 return cfqq == RQ_CFQQ(rq);
1537 static inline void cfq_del_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1539 del_timer(&cfqd->idle_slice_timer);
1540 blkiocg_update_idle_time_stats(&cfqq->cfqg->blkg);
1543 static void __cfq_set_active_queue(struct cfq_data *cfqd,
1544 struct cfq_queue *cfqq)
1547 cfq_log_cfqq(cfqd, cfqq, "set_active wl_prio:%d wl_type:%d",
1548 cfqd->serving_prio, cfqd->serving_type);
1549 blkiocg_update_avg_queue_size_stats(&cfqq->cfqg->blkg);
1550 cfqq->slice_start = 0;
1551 cfqq->dispatch_start = jiffies;
1552 cfqq->allocated_slice = 0;
1553 cfqq->slice_end = 0;
1554 cfqq->slice_dispatch = 0;
1556 cfq_clear_cfqq_wait_request(cfqq);
1557 cfq_clear_cfqq_must_dispatch(cfqq);
1558 cfq_clear_cfqq_must_alloc_slice(cfqq);
1559 cfq_clear_cfqq_fifo_expire(cfqq);
1560 cfq_mark_cfqq_slice_new(cfqq);
1562 cfq_del_timer(cfqd, cfqq);
1565 cfqd->active_queue = cfqq;
1569 * current cfqq expired its slice (or was too idle), select new one
1572 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1573 bool timed_out, bool forced)
1575 cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
1577 if (cfq_cfqq_wait_request(cfqq))
1578 cfq_del_timer(cfqd, cfqq);
1580 cfq_clear_cfqq_wait_request(cfqq);
1581 cfq_clear_cfqq_wait_busy(cfqq);
1584 * If this cfqq is shared between multiple processes, check to
1585 * make sure that those processes are still issuing I/Os within
1586 * the mean seek distance. If not, it may be time to break the
1587 * queues apart again.
1589 if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq))
1590 cfq_mark_cfqq_split_coop(cfqq);
1593 * store what was left of this slice, if the queue idled/timed out
1595 if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
1596 cfqq->slice_resid = cfqq->slice_end - jiffies;
1597 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
1600 cfq_group_served(cfqd, cfqq->cfqg, cfqq, forced);
1602 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
1603 cfq_del_cfqq_rr(cfqd, cfqq);
1605 cfq_resort_rr_list(cfqd, cfqq);
1607 if (cfqq == cfqd->active_queue)
1608 cfqd->active_queue = NULL;
1610 if (&cfqq->cfqg->rb_node == cfqd->grp_service_tree.active)
1611 cfqd->grp_service_tree.active = NULL;
1613 if (cfqd->active_cic) {
1614 put_io_context(cfqd->active_cic->ioc);
1615 cfqd->active_cic = NULL;
1619 static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out,
1622 struct cfq_queue *cfqq = cfqd->active_queue;
1625 __cfq_slice_expired(cfqd, cfqq, timed_out, forced);
1629 * Get next queue for service. Unless we have a queue preemption,
1630 * we'll simply select the first cfqq in the service tree.
1632 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
1634 struct cfq_rb_root *service_tree =
1635 service_tree_for(cfqd->serving_group, cfqd->serving_prio,
1636 cfqd->serving_type);
1638 if (!cfqd->rq_queued)
1641 /* There is nothing to dispatch */
1644 if (RB_EMPTY_ROOT(&service_tree->rb))
1646 return cfq_rb_first(service_tree);
1649 static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
1651 struct cfq_group *cfqg;
1652 struct cfq_queue *cfqq;
1654 struct cfq_rb_root *st;
1656 if (!cfqd->rq_queued)
1659 cfqg = cfq_get_next_cfqg(cfqd);
1663 for_each_cfqg_st(cfqg, i, j, st)
1664 if ((cfqq = cfq_rb_first(st)) != NULL)
1670 * Get and set a new active queue for service.
1672 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
1673 struct cfq_queue *cfqq)
1676 cfqq = cfq_get_next_queue(cfqd);
1678 __cfq_set_active_queue(cfqd, cfqq);
1682 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
1685 if (blk_rq_pos(rq) >= cfqd->last_position)
1686 return blk_rq_pos(rq) - cfqd->last_position;
1688 return cfqd->last_position - blk_rq_pos(rq);
1691 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1694 return cfq_dist_from_last(cfqd, rq) <= CFQQ_CLOSE_THR;
1697 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
1698 struct cfq_queue *cur_cfqq)
1700 struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
1701 struct rb_node *parent, *node;
1702 struct cfq_queue *__cfqq;
1703 sector_t sector = cfqd->last_position;
1705 if (RB_EMPTY_ROOT(root))
1709 * First, if we find a request starting at the end of the last
1710 * request, choose it.
1712 __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
1717 * If the exact sector wasn't found, the parent of the NULL leaf
1718 * will contain the closest sector.
1720 __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1721 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1724 if (blk_rq_pos(__cfqq->next_rq) < sector)
1725 node = rb_next(&__cfqq->p_node);
1727 node = rb_prev(&__cfqq->p_node);
1731 __cfqq = rb_entry(node, struct cfq_queue, p_node);
1732 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1740 * cur_cfqq - passed in so that we don't decide that the current queue is
1741 * closely cooperating with itself.
1743 * So, basically we're assuming that that cur_cfqq has dispatched at least
1744 * one request, and that cfqd->last_position reflects a position on the disk
1745 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
1748 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1749 struct cfq_queue *cur_cfqq)
1751 struct cfq_queue *cfqq;
1753 if (cfq_class_idle(cur_cfqq))
1755 if (!cfq_cfqq_sync(cur_cfqq))
1757 if (CFQQ_SEEKY(cur_cfqq))
1761 * Don't search priority tree if it's the only queue in the group.
1763 if (cur_cfqq->cfqg->nr_cfqq == 1)
1767 * We should notice if some of the queues are cooperating, eg
1768 * working closely on the same area of the disk. In that case,
1769 * we can group them together and don't waste time idling.
1771 cfqq = cfqq_close(cfqd, cur_cfqq);
1775 /* If new queue belongs to different cfq_group, don't choose it */
1776 if (cur_cfqq->cfqg != cfqq->cfqg)
1780 * It only makes sense to merge sync queues.
1782 if (!cfq_cfqq_sync(cfqq))
1784 if (CFQQ_SEEKY(cfqq))
1788 * Do not merge queues of different priority classes
1790 if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
1797 * Determine whether we should enforce idle window for this queue.
1800 static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1802 enum wl_prio_t prio = cfqq_prio(cfqq);
1803 struct cfq_rb_root *service_tree = cfqq->service_tree;
1805 BUG_ON(!service_tree);
1806 BUG_ON(!service_tree->count);
1808 /* We never do for idle class queues. */
1809 if (prio == IDLE_WORKLOAD)
1812 /* We do for queues that were marked with idle window flag. */
1813 if (cfq_cfqq_idle_window(cfqq) &&
1814 !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag))
1818 * Otherwise, we do only if they are the last ones
1819 * in their service tree.
1821 if (service_tree->count == 1 && cfq_cfqq_sync(cfqq))
1823 cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d",
1824 service_tree->count);
1828 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
1830 struct cfq_queue *cfqq = cfqd->active_queue;
1831 struct cfq_io_context *cic;
1835 * SSD device without seek penalty, disable idling. But only do so
1836 * for devices that support queuing, otherwise we still have a problem
1837 * with sync vs async workloads.
1839 if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
1842 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
1843 WARN_ON(cfq_cfqq_slice_new(cfqq));
1846 * idle is disabled, either manually or by past process history
1848 if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq))
1852 * still active requests from this queue, don't idle
1854 if (cfqq->dispatched)
1858 * task has exited, don't wait
1860 cic = cfqd->active_cic;
1861 if (!cic || !atomic_read(&cic->ioc->nr_tasks))
1865 * If our average think time is larger than the remaining time
1866 * slice, then don't idle. This avoids overrunning the allotted
1869 if (sample_valid(cic->ttime_samples) &&
1870 (cfqq->slice_end - jiffies < cic->ttime_mean)) {
1871 cfq_log_cfqq(cfqd, cfqq, "Not idling. think_time:%d",
1876 cfq_mark_cfqq_wait_request(cfqq);
1878 sl = cfqd->cfq_slice_idle;
1880 mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
1881 blkiocg_update_set_idle_time_stats(&cfqq->cfqg->blkg);
1882 cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
1886 * Move request from internal lists to the request queue dispatch list.
1888 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
1890 struct cfq_data *cfqd = q->elevator->elevator_data;
1891 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1893 cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
1895 cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
1896 cfq_remove_request(rq);
1898 elv_dispatch_sort(q, rq);
1900 cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
1901 blkiocg_update_dispatch_stats(&cfqq->cfqg->blkg, blk_rq_bytes(rq),
1902 rq_data_dir(rq), rq_is_sync(rq));
1906 * return expired entry, or NULL to just start from scratch in rbtree
1908 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
1910 struct request *rq = NULL;
1912 if (cfq_cfqq_fifo_expire(cfqq))
1915 cfq_mark_cfqq_fifo_expire(cfqq);
1917 if (list_empty(&cfqq->fifo))
1920 rq = rq_entry_fifo(cfqq->fifo.next);
1921 if (time_before(jiffies, rq_fifo_time(rq)))
1924 cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
1929 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1931 const int base_rq = cfqd->cfq_slice_async_rq;
1933 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1935 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1939 * Must be called with the queue_lock held.
1941 static int cfqq_process_refs(struct cfq_queue *cfqq)
1943 int process_refs, io_refs;
1945 io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
1946 process_refs = atomic_read(&cfqq->ref) - io_refs;
1947 BUG_ON(process_refs < 0);
1948 return process_refs;
1951 static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
1953 int process_refs, new_process_refs;
1954 struct cfq_queue *__cfqq;
1956 /* Avoid a circular list and skip interim queue merges */
1957 while ((__cfqq = new_cfqq->new_cfqq)) {
1963 process_refs = cfqq_process_refs(cfqq);
1965 * If the process for the cfqq has gone away, there is no
1966 * sense in merging the queues.
1968 if (process_refs == 0)
1972 * Merge in the direction of the lesser amount of work.
1974 new_process_refs = cfqq_process_refs(new_cfqq);
1975 if (new_process_refs >= process_refs) {
1976 cfqq->new_cfqq = new_cfqq;
1977 atomic_add(process_refs, &new_cfqq->ref);
1979 new_cfqq->new_cfqq = cfqq;
1980 atomic_add(new_process_refs, &cfqq->ref);
1984 static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
1985 struct cfq_group *cfqg, enum wl_prio_t prio)
1987 struct cfq_queue *queue;
1989 bool key_valid = false;
1990 unsigned long lowest_key = 0;
1991 enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
1993 for (i = 0; i <= SYNC_WORKLOAD; ++i) {
1994 /* select the one with lowest rb_key */
1995 queue = cfq_rb_first(service_tree_for(cfqg, prio, i));
1997 (!key_valid || time_before(queue->rb_key, lowest_key))) {
1998 lowest_key = queue->rb_key;
2007 static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
2011 struct cfq_rb_root *st;
2012 unsigned group_slice;
2015 cfqd->serving_prio = IDLE_WORKLOAD;
2016 cfqd->workload_expires = jiffies + 1;
2020 /* Choose next priority. RT > BE > IDLE */
2021 if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
2022 cfqd->serving_prio = RT_WORKLOAD;
2023 else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
2024 cfqd->serving_prio = BE_WORKLOAD;
2026 cfqd->serving_prio = IDLE_WORKLOAD;
2027 cfqd->workload_expires = jiffies + 1;
2032 * For RT and BE, we have to choose also the type
2033 * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
2036 st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
2040 * check workload expiration, and that we still have other queues ready
2042 if (count && !time_after(jiffies, cfqd->workload_expires))
2045 /* otherwise select new workload type */
2046 cfqd->serving_type =
2047 cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio);
2048 st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
2052 * the workload slice is computed as a fraction of target latency
2053 * proportional to the number of queues in that workload, over
2054 * all the queues in the same priority class
2056 group_slice = cfq_group_slice(cfqd, cfqg);
2058 slice = group_slice * count /
2059 max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio],
2060 cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg));
2062 if (cfqd->serving_type == ASYNC_WORKLOAD) {
2066 * Async queues are currently system wide. Just taking
2067 * proportion of queues with-in same group will lead to higher
2068 * async ratio system wide as generally root group is going
2069 * to have higher weight. A more accurate thing would be to
2070 * calculate system wide asnc/sync ratio.
2072 tmp = cfq_target_latency * cfqg_busy_async_queues(cfqd, cfqg);
2073 tmp = tmp/cfqd->busy_queues;
2074 slice = min_t(unsigned, slice, tmp);
2076 /* async workload slice is scaled down according to
2077 * the sync/async slice ratio. */
2078 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
2080 /* sync workload slice is at least 2 * cfq_slice_idle */
2081 slice = max(slice, 2 * cfqd->cfq_slice_idle);
2083 slice = max_t(unsigned, slice, CFQ_MIN_TT);
2084 cfq_log(cfqd, "workload slice:%d", slice);
2085 cfqd->workload_expires = jiffies + slice;
2086 cfqd->noidle_tree_requires_idle = false;
2089 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
2091 struct cfq_rb_root *st = &cfqd->grp_service_tree;
2092 struct cfq_group *cfqg;
2094 if (RB_EMPTY_ROOT(&st->rb))
2096 cfqg = cfq_rb_first_group(st);
2097 st->active = &cfqg->rb_node;
2098 update_min_vdisktime(st);
2102 static void cfq_choose_cfqg(struct cfq_data *cfqd)
2104 struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
2106 cfqd->serving_group = cfqg;
2108 /* Restore the workload type data */
2109 if (cfqg->saved_workload_slice) {
2110 cfqd->workload_expires = jiffies + cfqg->saved_workload_slice;
2111 cfqd->serving_type = cfqg->saved_workload;
2112 cfqd->serving_prio = cfqg->saved_serving_prio;
2114 cfqd->workload_expires = jiffies - 1;
2116 choose_service_tree(cfqd, cfqg);
2120 * Select a queue for service. If we have a current active queue,
2121 * check whether to continue servicing it, or retrieve and set a new one.
2123 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
2125 struct cfq_queue *cfqq, *new_cfqq = NULL;
2127 cfqq = cfqd->active_queue;
2131 if (!cfqd->rq_queued)
2135 * We were waiting for group to get backlogged. Expire the queue
2137 if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list))
2141 * The active queue has run out of time, expire it and select new.
2143 if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) {
2145 * If slice had not expired at the completion of last request
2146 * we might not have turned on wait_busy flag. Don't expire
2147 * the queue yet. Allow the group to get backlogged.
2149 * The very fact that we have used the slice, that means we
2150 * have been idling all along on this queue and it should be
2151 * ok to wait for this request to complete.
2153 if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list)
2154 && cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
2162 * The active queue has requests and isn't expired, allow it to
2165 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
2169 * If another queue has a request waiting within our mean seek
2170 * distance, let it run. The expire code will check for close
2171 * cooperators and put the close queue at the front of the service
2172 * tree. If possible, merge the expiring queue with the new cfqq.
2174 new_cfqq = cfq_close_cooperator(cfqd, cfqq);
2176 if (!cfqq->new_cfqq)
2177 cfq_setup_merge(cfqq, new_cfqq);
2182 * No requests pending. If the active queue still has requests in
2183 * flight or is idling for a new request, allow either of these
2184 * conditions to happen (or time out) before selecting a new queue.
2186 if (timer_pending(&cfqd->idle_slice_timer) ||
2187 (cfqq->dispatched && cfq_should_idle(cfqd, cfqq))) {
2193 cfq_slice_expired(cfqd, 0, false);
2196 * Current queue expired. Check if we have to switch to a new
2200 cfq_choose_cfqg(cfqd);
2202 cfqq = cfq_set_active_queue(cfqd, new_cfqq);
2207 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
2211 while (cfqq->next_rq) {
2212 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
2216 BUG_ON(!list_empty(&cfqq->fifo));
2218 /* By default cfqq is not expired if it is empty. Do it explicitly */
2219 __cfq_slice_expired(cfqq->cfqd, cfqq, 0, true);
2224 * Drain our current requests. Used for barriers and when switching
2225 * io schedulers on-the-fly.
2227 static int cfq_forced_dispatch(struct cfq_data *cfqd)
2229 struct cfq_queue *cfqq;
2232 /* Expire the timeslice of the current active queue first */
2233 cfq_slice_expired(cfqd, 0, true);
2234 while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL) {
2235 __cfq_set_active_queue(cfqd, cfqq);
2236 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
2239 BUG_ON(cfqd->busy_queues);
2241 cfq_log(cfqd, "forced_dispatch=%d", dispatched);
2245 static inline bool cfq_slice_used_soon(struct cfq_data *cfqd,
2246 struct cfq_queue *cfqq)
2248 /* the queue hasn't finished any request, can't estimate */
2249 if (cfq_cfqq_slice_new(cfqq))
2251 if (time_after(jiffies + cfqd->cfq_slice_idle * cfqq->dispatched,
2258 static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2260 unsigned int max_dispatch;
2263 * Drain async requests before we start sync IO
2265 if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_flight[BLK_RW_ASYNC])
2269 * If this is an async queue and we have sync IO in flight, let it wait
2271 if (cfqd->rq_in_flight[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq))
2274 max_dispatch = max_t(unsigned int, cfqd->cfq_quantum / 2, 1);
2275 if (cfq_class_idle(cfqq))
2279 * Does this cfqq already have too much IO in flight?
2281 if (cfqq->dispatched >= max_dispatch) {
2283 * idle queue must always only have a single IO in flight
2285 if (cfq_class_idle(cfqq))
2289 * We have other queues, don't allow more IO from this one
2291 if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq))
2295 * Sole queue user, no limit
2297 if (cfqd->busy_queues == 1)
2301 * Normally we start throttling cfqq when cfq_quantum/2
2302 * requests have been dispatched. But we can drive
2303 * deeper queue depths at the beginning of slice
2304 * subjected to upper limit of cfq_quantum.
2306 max_dispatch = cfqd->cfq_quantum;
2310 * Async queues must wait a bit before being allowed dispatch.
2311 * We also ramp up the dispatch depth gradually for async IO,
2312 * based on the last sync IO we serviced
2314 if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
2315 unsigned long last_sync = jiffies - cfqd->last_delayed_sync;
2318 depth = last_sync / cfqd->cfq_slice[1];
2319 if (!depth && !cfqq->dispatched)
2321 if (depth < max_dispatch)
2322 max_dispatch = depth;
2326 * If we're below the current max, allow a dispatch
2328 return cfqq->dispatched < max_dispatch;
2332 * Dispatch a request from cfqq, moving them to the request queue
2335 static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2339 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
2341 if (!cfq_may_dispatch(cfqd, cfqq))
2345 * follow expired path, else get first next available
2347 rq = cfq_check_fifo(cfqq);
2352 * insert request into driver dispatch list
2354 cfq_dispatch_insert(cfqd->queue, rq);
2356 if (!cfqd->active_cic) {
2357 struct cfq_io_context *cic = RQ_CIC(rq);
2359 atomic_long_inc(&cic->ioc->refcount);
2360 cfqd->active_cic = cic;
2367 * Find the cfqq that we need to service and move a request from that to the
2370 static int cfq_dispatch_requests(struct request_queue *q, int force)
2372 struct cfq_data *cfqd = q->elevator->elevator_data;
2373 struct cfq_queue *cfqq;
2375 if (!cfqd->busy_queues)
2378 if (unlikely(force))
2379 return cfq_forced_dispatch(cfqd);
2381 cfqq = cfq_select_queue(cfqd);
2386 * Dispatch a request from this cfqq, if it is allowed
2388 if (!cfq_dispatch_request(cfqd, cfqq))
2391 cfqq->slice_dispatch++;
2392 cfq_clear_cfqq_must_dispatch(cfqq);
2395 * expire an async queue immediately if it has used up its slice. idle
2396 * queue always expire after 1 dispatch round.
2398 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
2399 cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
2400 cfq_class_idle(cfqq))) {
2401 cfqq->slice_end = jiffies + 1;
2402 cfq_slice_expired(cfqd, 0, false);
2405 cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
2410 * task holds one reference to the queue, dropped when task exits. each rq
2411 * in-flight on this queue also holds a reference, dropped when rq is freed.
2413 * Each cfq queue took a reference on the parent group. Drop it now.
2414 * queue lock must be held here.
2416 static void cfq_put_queue(struct cfq_queue *cfqq)
2418 struct cfq_data *cfqd = cfqq->cfqd;
2419 struct cfq_group *cfqg, *orig_cfqg;
2421 BUG_ON(atomic_read(&cfqq->ref) <= 0);
2423 if (!atomic_dec_and_test(&cfqq->ref))
2426 cfq_log_cfqq(cfqd, cfqq, "put_queue");
2427 BUG_ON(rb_first(&cfqq->sort_list));
2428 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
2430 orig_cfqg = cfqq->orig_cfqg;
2432 if (unlikely(cfqd->active_queue == cfqq)) {
2433 __cfq_slice_expired(cfqd, cfqq, 0, false);
2434 cfq_schedule_dispatch(cfqd);
2437 BUG_ON(cfq_cfqq_on_rr(cfqq));
2438 kmem_cache_free(cfq_pool, cfqq);
2441 cfq_put_cfqg(orig_cfqg);
2445 * Must always be called with the rcu_read_lock() held
2448 __call_for_each_cic(struct io_context *ioc,
2449 void (*func)(struct io_context *, struct cfq_io_context *))
2451 struct cfq_io_context *cic;
2452 struct hlist_node *n;
2454 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
2459 * Call func for each cic attached to this ioc.
2462 call_for_each_cic(struct io_context *ioc,
2463 void (*func)(struct io_context *, struct cfq_io_context *))
2466 __call_for_each_cic(ioc, func);
2470 static void cfq_cic_free_rcu(struct rcu_head *head)
2472 struct cfq_io_context *cic;
2474 cic = container_of(head, struct cfq_io_context, rcu_head);
2476 kmem_cache_free(cfq_ioc_pool, cic);
2477 elv_ioc_count_dec(cfq_ioc_count);
2481 * CFQ scheduler is exiting, grab exit lock and check
2482 * the pending io context count. If it hits zero,
2483 * complete ioc_gone and set it back to NULL
2485 spin_lock(&ioc_gone_lock);
2486 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
2490 spin_unlock(&ioc_gone_lock);
2494 static void cfq_cic_free(struct cfq_io_context *cic)
2496 call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
2499 static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
2501 unsigned long flags;
2503 BUG_ON(!cic->dead_key);
2505 spin_lock_irqsave(&ioc->lock, flags);
2506 radix_tree_delete(&ioc->radix_root, cic->dead_key);
2507 hlist_del_rcu(&cic->cic_list);
2508 spin_unlock_irqrestore(&ioc->lock, flags);
2514 * Must be called with rcu_read_lock() held or preemption otherwise disabled.
2515 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
2516 * and ->trim() which is called with the task lock held
2518 static void cfq_free_io_context(struct io_context *ioc)
2521 * ioc->refcount is zero here, or we are called from elv_unregister(),
2522 * so no more cic's are allowed to be linked into this ioc. So it
2523 * should be ok to iterate over the known list, we will see all cic's
2524 * since no new ones are added.
2526 __call_for_each_cic(ioc, cic_free_func);
2529 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2531 struct cfq_queue *__cfqq, *next;
2533 if (unlikely(cfqq == cfqd->active_queue)) {
2534 __cfq_slice_expired(cfqd, cfqq, 0, false);
2535 cfq_schedule_dispatch(cfqd);
2539 * If this queue was scheduled to merge with another queue, be
2540 * sure to drop the reference taken on that queue (and others in
2541 * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs.
2543 __cfqq = cfqq->new_cfqq;
2545 if (__cfqq == cfqq) {
2546 WARN(1, "cfqq->new_cfqq loop detected\n");
2549 next = __cfqq->new_cfqq;
2550 cfq_put_queue(__cfqq);
2554 cfq_put_queue(cfqq);
2557 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
2558 struct cfq_io_context *cic)
2560 struct io_context *ioc = cic->ioc;
2562 list_del_init(&cic->queue_list);
2565 * Make sure key == NULL is seen for dead queues
2568 cic->dead_key = (unsigned long) cic->key;
2571 if (ioc->ioc_data == cic)
2572 rcu_assign_pointer(ioc->ioc_data, NULL);
2574 if (cic->cfqq[BLK_RW_ASYNC]) {
2575 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
2576 cic->cfqq[BLK_RW_ASYNC] = NULL;
2579 if (cic->cfqq[BLK_RW_SYNC]) {
2580 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
2581 cic->cfqq[BLK_RW_SYNC] = NULL;
2585 static void cfq_exit_single_io_context(struct io_context *ioc,
2586 struct cfq_io_context *cic)
2588 struct cfq_data *cfqd = cic->key;
2591 struct request_queue *q = cfqd->queue;
2592 unsigned long flags;
2594 spin_lock_irqsave(q->queue_lock, flags);
2597 * Ensure we get a fresh copy of the ->key to prevent
2598 * race between exiting task and queue
2600 smp_read_barrier_depends();
2602 __cfq_exit_single_io_context(cfqd, cic);
2604 spin_unlock_irqrestore(q->queue_lock, flags);
2609 * The process that ioc belongs to has exited, we need to clean up
2610 * and put the internal structures we have that belongs to that process.
2612 static void cfq_exit_io_context(struct io_context *ioc)
2614 call_for_each_cic(ioc, cfq_exit_single_io_context);
2617 static struct cfq_io_context *
2618 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2620 struct cfq_io_context *cic;
2622 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
2625 cic->last_end_request = jiffies;
2626 INIT_LIST_HEAD(&cic->queue_list);
2627 INIT_HLIST_NODE(&cic->cic_list);
2628 cic->dtor = cfq_free_io_context;
2629 cic->exit = cfq_exit_io_context;
2630 elv_ioc_count_inc(cfq_ioc_count);
2636 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
2638 struct task_struct *tsk = current;
2641 if (!cfq_cfqq_prio_changed(cfqq))
2644 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
2645 switch (ioprio_class) {
2647 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
2648 case IOPRIO_CLASS_NONE:
2650 * no prio set, inherit CPU scheduling settings
2652 cfqq->ioprio = task_nice_ioprio(tsk);
2653 cfqq->ioprio_class = task_nice_ioclass(tsk);
2655 case IOPRIO_CLASS_RT:
2656 cfqq->ioprio = task_ioprio(ioc);
2657 cfqq->ioprio_class = IOPRIO_CLASS_RT;
2659 case IOPRIO_CLASS_BE:
2660 cfqq->ioprio = task_ioprio(ioc);
2661 cfqq->ioprio_class = IOPRIO_CLASS_BE;
2663 case IOPRIO_CLASS_IDLE:
2664 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
2666 cfq_clear_cfqq_idle_window(cfqq);
2671 * keep track of original prio settings in case we have to temporarily
2672 * elevate the priority of this queue
2674 cfqq->org_ioprio = cfqq->ioprio;
2675 cfqq->org_ioprio_class = cfqq->ioprio_class;
2676 cfq_clear_cfqq_prio_changed(cfqq);
2679 static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
2681 struct cfq_data *cfqd = cic->key;
2682 struct cfq_queue *cfqq;
2683 unsigned long flags;
2685 if (unlikely(!cfqd))
2688 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2690 cfqq = cic->cfqq[BLK_RW_ASYNC];
2692 struct cfq_queue *new_cfqq;
2693 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
2696 cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
2697 cfq_put_queue(cfqq);
2701 cfqq = cic->cfqq[BLK_RW_SYNC];
2703 cfq_mark_cfqq_prio_changed(cfqq);
2705 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2708 static void cfq_ioc_set_ioprio(struct io_context *ioc)
2710 call_for_each_cic(ioc, changed_ioprio);
2711 ioc->ioprio_changed = 0;
2714 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2715 pid_t pid, bool is_sync)
2717 RB_CLEAR_NODE(&cfqq->rb_node);
2718 RB_CLEAR_NODE(&cfqq->p_node);
2719 INIT_LIST_HEAD(&cfqq->fifo);
2721 atomic_set(&cfqq->ref, 0);
2724 cfq_mark_cfqq_prio_changed(cfqq);
2727 if (!cfq_class_idle(cfqq))
2728 cfq_mark_cfqq_idle_window(cfqq);
2729 cfq_mark_cfqq_sync(cfqq);
2734 #ifdef CONFIG_CFQ_GROUP_IOSCHED
2735 static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
2737 struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1);
2738 struct cfq_data *cfqd = cic->key;
2739 unsigned long flags;
2740 struct request_queue *q;
2742 if (unlikely(!cfqd))
2747 spin_lock_irqsave(q->queue_lock, flags);
2751 * Drop reference to sync queue. A new sync queue will be
2752 * assigned in new group upon arrival of a fresh request.
2754 cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
2755 cic_set_cfqq(cic, NULL, 1);
2756 cfq_put_queue(sync_cfqq);
2759 spin_unlock_irqrestore(q->queue_lock, flags);
2762 static void cfq_ioc_set_cgroup(struct io_context *ioc)
2764 call_for_each_cic(ioc, changed_cgroup);
2765 ioc->cgroup_changed = 0;
2767 #endif /* CONFIG_CFQ_GROUP_IOSCHED */
2769 static struct cfq_queue *
2770 cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
2771 struct io_context *ioc, gfp_t gfp_mask)
2773 struct cfq_queue *cfqq, *new_cfqq = NULL;
2774 struct cfq_io_context *cic;
2775 struct cfq_group *cfqg;
2778 cfqg = cfq_get_cfqg(cfqd, 1);
2779 cic = cfq_cic_lookup(cfqd, ioc);
2780 /* cic always exists here */
2781 cfqq = cic_to_cfqq(cic, is_sync);
2784 * Always try a new alloc if we fell back to the OOM cfqq
2785 * originally, since it should just be a temporary situation.
2787 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2792 } else if (gfp_mask & __GFP_WAIT) {
2793 spin_unlock_irq(cfqd->queue->queue_lock);
2794 new_cfqq = kmem_cache_alloc_node(cfq_pool,
2795 gfp_mask | __GFP_ZERO,
2797 spin_lock_irq(cfqd->queue->queue_lock);
2801 cfqq = kmem_cache_alloc_node(cfq_pool,
2802 gfp_mask | __GFP_ZERO,
2807 cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
2808 cfq_init_prio_data(cfqq, ioc);
2809 cfq_link_cfqq_cfqg(cfqq, cfqg);
2810 cfq_log_cfqq(cfqd, cfqq, "alloced");
2812 cfqq = &cfqd->oom_cfqq;
2816 kmem_cache_free(cfq_pool, new_cfqq);
2821 static struct cfq_queue **
2822 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
2824 switch (ioprio_class) {
2825 case IOPRIO_CLASS_RT:
2826 return &cfqd->async_cfqq[0][ioprio];
2827 case IOPRIO_CLASS_BE:
2828 return &cfqd->async_cfqq[1][ioprio];
2829 case IOPRIO_CLASS_IDLE:
2830 return &cfqd->async_idle_cfqq;
2836 static struct cfq_queue *
2837 cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
2840 const int ioprio = task_ioprio(ioc);
2841 const int ioprio_class = task_ioprio_class(ioc);
2842 struct cfq_queue **async_cfqq = NULL;
2843 struct cfq_queue *cfqq = NULL;
2846 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
2851 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
2854 * pin the queue now that it's allocated, scheduler exit will prune it
2856 if (!is_sync && !(*async_cfqq)) {
2857 atomic_inc(&cfqq->ref);
2861 atomic_inc(&cfqq->ref);
2866 * We drop cfq io contexts lazily, so we may find a dead one.
2869 cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
2870 struct cfq_io_context *cic)
2872 unsigned long flags;
2874 WARN_ON(!list_empty(&cic->queue_list));
2876 spin_lock_irqsave(&ioc->lock, flags);
2878 BUG_ON(ioc->ioc_data == cic);
2880 radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
2881 hlist_del_rcu(&cic->cic_list);
2882 spin_unlock_irqrestore(&ioc->lock, flags);
2887 static struct cfq_io_context *
2888 cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
2890 struct cfq_io_context *cic;
2891 unsigned long flags;
2900 * we maintain a last-hit cache, to avoid browsing over the tree
2902 cic = rcu_dereference(ioc->ioc_data);
2903 if (cic && cic->key == cfqd) {
2909 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
2913 /* ->key must be copied to avoid race with cfq_exit_queue() */
2916 cfq_drop_dead_cic(cfqd, ioc, cic);
2921 spin_lock_irqsave(&ioc->lock, flags);
2922 rcu_assign_pointer(ioc->ioc_data, cic);
2923 spin_unlock_irqrestore(&ioc->lock, flags);
2931 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2932 * the process specific cfq io context when entered from the block layer.
2933 * Also adds the cic to a per-cfqd list, used when this queue is removed.
2935 static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
2936 struct cfq_io_context *cic, gfp_t gfp_mask)
2938 unsigned long flags;
2941 ret = radix_tree_preload(gfp_mask);
2946 spin_lock_irqsave(&ioc->lock, flags);
2947 ret = radix_tree_insert(&ioc->radix_root,
2948 (unsigned long) cfqd, cic);
2950 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
2951 spin_unlock_irqrestore(&ioc->lock, flags);
2953 radix_tree_preload_end();
2956 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2957 list_add(&cic->queue_list, &cfqd->cic_list);
2958 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2963 printk(KERN_ERR "cfq: cic link failed!\n");
2969 * Setup general io context and cfq io context. There can be several cfq
2970 * io contexts per general io context, if this process is doing io to more
2971 * than one device managed by cfq.
2973 static struct cfq_io_context *
2974 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2976 struct io_context *ioc = NULL;
2977 struct cfq_io_context *cic;
2979 might_sleep_if(gfp_mask & __GFP_WAIT);
2981 ioc = get_io_context(gfp_mask, cfqd->queue->node);
2985 cic = cfq_cic_lookup(cfqd, ioc);
2989 cic = cfq_alloc_io_context(cfqd, gfp_mask);
2993 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
2997 smp_read_barrier_depends();
2998 if (unlikely(ioc->ioprio_changed))
2999 cfq_ioc_set_ioprio(ioc);
3001 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3002 if (unlikely(ioc->cgroup_changed))
3003 cfq_ioc_set_cgroup(ioc);
3009 put_io_context(ioc);
3014 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
3016 unsigned long elapsed = jiffies - cic->last_end_request;
3017 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
3019 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
3020 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
3021 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
3025 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3029 sector_t n_sec = blk_rq_sectors(rq);
3030 if (cfqq->last_request_pos) {
3031 if (cfqq->last_request_pos < blk_rq_pos(rq))
3032 sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
3034 sdist = cfqq->last_request_pos - blk_rq_pos(rq);
3037 cfqq->seek_history <<= 1;
3038 if (blk_queue_nonrot(cfqd->queue))
3039 cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT);
3041 cfqq->seek_history |= (sdist > CFQQ_SEEK_THR);
3045 * Disable idle window if the process thinks too long or seeks so much that
3049 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3050 struct cfq_io_context *cic)
3052 int old_idle, enable_idle;
3055 * Don't idle for async or idle io prio class
3057 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
3060 enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
3062 if (cfqq->queued[0] + cfqq->queued[1] >= 4)
3063 cfq_mark_cfqq_deep(cfqq);
3065 if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
3066 (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))
3068 else if (sample_valid(cic->ttime_samples)) {
3069 if (cic->ttime_mean > cfqd->cfq_slice_idle)
3075 if (old_idle != enable_idle) {
3076 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
3078 cfq_mark_cfqq_idle_window(cfqq);
3080 cfq_clear_cfqq_idle_window(cfqq);
3085 * Check if new_cfqq should preempt the currently active queue. Return 0 for
3086 * no or if we aren't sure, a 1 will cause a preempt.
3089 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
3092 struct cfq_queue *cfqq;
3094 cfqq = cfqd->active_queue;
3098 if (cfq_class_idle(new_cfqq))
3101 if (cfq_class_idle(cfqq))
3105 * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice.
3107 if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq))
3111 * if the new request is sync, but the currently running queue is
3112 * not, let the sync request have priority.
3114 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
3117 if (new_cfqq->cfqg != cfqq->cfqg)
3120 if (cfq_slice_used(cfqq))
3123 /* Allow preemption only if we are idling on sync-noidle tree */
3124 if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
3125 cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
3126 new_cfqq->service_tree->count == 2 &&
3127 RB_EMPTY_ROOT(&cfqq->sort_list))
3131 * So both queues are sync. Let the new request get disk time if
3132 * it's a metadata request and the current queue is doing regular IO.
3134 if (rq_is_meta(rq) && !cfqq->meta_pending)
3138 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
3140 if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
3143 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
3147 * if this request is as-good as one we would expect from the
3148 * current cfqq, let it preempt
3150 if (cfq_rq_close(cfqd, cfqq, rq))
3157 * cfqq preempts the active queue. if we allowed preempt with no slice left,
3158 * let it have half of its nominal slice.
3160 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3162 cfq_log_cfqq(cfqd, cfqq, "preempt");
3163 cfq_slice_expired(cfqd, 1, false);
3166 * Put the new queue at the front of the of the current list,
3167 * so we know that it will be selected next.
3169 BUG_ON(!cfq_cfqq_on_rr(cfqq));
3171 cfq_service_tree_add(cfqd, cfqq, 1);
3173 cfqq->slice_end = 0;
3174 cfq_mark_cfqq_slice_new(cfqq);
3178 * Called when a new fs request (rq) is added (to cfqq). Check if there's
3179 * something we should do about it
3182 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3185 struct cfq_io_context *cic = RQ_CIC(rq);
3189 cfqq->meta_pending++;
3191 cfq_update_io_thinktime(cfqd, cic);
3192 cfq_update_io_seektime(cfqd, cfqq, rq);
3193 cfq_update_idle_window(cfqd, cfqq, cic);
3195 cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
3197 if (cfqq == cfqd->active_queue) {
3199 * Remember that we saw a request from this process, but
3200 * don't start queuing just yet. Otherwise we risk seeing lots
3201 * of tiny requests, because we disrupt the normal plugging
3202 * and merging. If the request is already larger than a single
3203 * page, let it rip immediately. For that case we assume that
3204 * merging is already done. Ditto for a busy system that
3205 * has other work pending, don't risk delaying until the
3206 * idle timer unplug to continue working.
3208 if (cfq_cfqq_wait_request(cfqq)) {
3209 if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
3210 cfqd->busy_queues > 1) {
3211 cfq_del_timer(cfqd, cfqq);
3212 cfq_clear_cfqq_wait_request(cfqq);
3213 __blk_run_queue(cfqd->queue);
3215 blkiocg_update_idle_time_stats(
3217 cfq_mark_cfqq_must_dispatch(cfqq);
3220 } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
3222 * not the active queue - expire current slice if it is
3223 * idle and has expired it's mean thinktime or this new queue
3224 * has some old slice time left and is of higher priority or
3225 * this new queue is RT and the current one is BE
3227 cfq_preempt_queue(cfqd, cfqq);
3228 __blk_run_queue(cfqd->queue);
3232 static void cfq_insert_request(struct request_queue *q, struct request *rq)
3234 struct cfq_data *cfqd = q->elevator->elevator_data;
3235 struct cfq_queue *cfqq = RQ_CFQQ(rq);
3237 cfq_log_cfqq(cfqd, cfqq, "insert_request");
3238 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
3240 rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
3241 list_add_tail(&rq->queuelist, &cfqq->fifo);
3244 blkiocg_update_io_add_stats(&cfqq->cfqg->blkg,
3245 &cfqd->serving_group->blkg, rq_data_dir(rq),
3247 cfq_rq_enqueued(cfqd, cfqq, rq);
3251 * Update hw_tag based on peak queue depth over 50 samples under
3254 static void cfq_update_hw_tag(struct cfq_data *cfqd)
3256 struct cfq_queue *cfqq = cfqd->active_queue;
3258 if (cfqd->rq_in_driver > cfqd->hw_tag_est_depth)
3259 cfqd->hw_tag_est_depth = cfqd->rq_in_driver;
3261 if (cfqd->hw_tag == 1)
3264 if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
3265 cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
3269 * If active queue hasn't enough requests and can idle, cfq might not
3270 * dispatch sufficient requests to hardware. Don't zero hw_tag in this
3273 if (cfqq && cfq_cfqq_idle_window(cfqq) &&
3274 cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
3275 CFQ_HW_QUEUE_MIN && cfqd->rq_in_driver < CFQ_HW_QUEUE_MIN)
3278 if (cfqd->hw_tag_samples++ < 50)
3281 if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
3287 static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3289 struct cfq_io_context *cic = cfqd->active_cic;
3291 /* If there are other queues in the group, don't wait */
3292 if (cfqq->cfqg->nr_cfqq > 1)
3295 if (cfq_slice_used(cfqq))
3298 /* if slice left is less than think time, wait busy */
3299 if (cic && sample_valid(cic->ttime_samples)
3300 && (cfqq->slice_end - jiffies < cic->ttime_mean))
3304 * If think times is less than a jiffy than ttime_mean=0 and above
3305 * will not be true. It might happen that slice has not expired yet
3306 * but will expire soon (4-5 ns) during select_queue(). To cover the
3307 * case where think time is less than a jiffy, mark the queue wait
3308 * busy if only 1 jiffy is left in the slice.
3310 if (cfqq->slice_end - jiffies == 1)
3316 static void cfq_completed_request(struct request_queue *q, struct request *rq)
3318 struct cfq_queue *cfqq = RQ_CFQQ(rq);
3319 struct cfq_data *cfqd = cfqq->cfqd;
3320 const int sync = rq_is_sync(rq);
3324 cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d", !!rq_noidle(rq));
3326 cfq_update_hw_tag(cfqd);
3328 WARN_ON(!cfqd->rq_in_driver);
3329 WARN_ON(!cfqq->dispatched);
3330 cfqd->rq_in_driver--;
3332 blkiocg_update_completion_stats(&cfqq->cfqg->blkg, rq_start_time_ns(rq),
3333 rq_io_start_time_ns(rq), rq_data_dir(rq),
3336 cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
3339 RQ_CIC(rq)->last_end_request = now;
3340 if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
3341 cfqd->last_delayed_sync = now;
3345 * If this is the active queue, check if it needs to be expired,
3346 * or if we want to idle in case it has no pending requests.
3348 if (cfqd->active_queue == cfqq) {
3349 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
3351 if (cfq_cfqq_slice_new(cfqq)) {
3352 cfq_set_prio_slice(cfqd, cfqq);
3353 cfq_clear_cfqq_slice_new(cfqq);
3357 * Should we wait for next request to come in before we expire
3360 if (cfq_should_wait_busy(cfqd, cfqq)) {
3361 cfqq->slice_end = jiffies + cfqd->cfq_slice_idle;
3362 cfq_mark_cfqq_wait_busy(cfqq);
3363 cfq_log_cfqq(cfqd, cfqq, "will busy wait");
3367 * Idling is not enabled on:
3369 * - idle-priority queues
3371 * - queues with still some requests queued
3372 * - when there is a close cooperator
3374 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
3375 cfq_slice_expired(cfqd, 1, false);
3376 else if (sync && cfqq_empty &&
3377 !cfq_close_cooperator(cfqd, cfqq)) {
3378 cfqd->noidle_tree_requires_idle |= !rq_noidle(rq);
3380 * Idling is enabled for SYNC_WORKLOAD.
3381 * SYNC_NOIDLE_WORKLOAD idles at the end of the tree
3382 * only if we processed at least one !rq_noidle request
3384 if (cfqd->serving_type == SYNC_WORKLOAD
3385 || cfqd->noidle_tree_requires_idle
3386 || cfqq->cfqg->nr_cfqq == 1)
3387 cfq_arm_slice_timer(cfqd);
3391 if (!cfqd->rq_in_driver)
3392 cfq_schedule_dispatch(cfqd);
3396 * we temporarily boost lower priority queues if they are holding fs exclusive
3397 * resources. they are boosted to normal prio (CLASS_BE/4)
3399 static void cfq_prio_boost(struct cfq_queue *cfqq)
3401 if (has_fs_excl()) {
3403 * boost idle prio on transactions that would lock out other
3404 * users of the filesystem
3406 if (cfq_class_idle(cfqq))
3407 cfqq->ioprio_class = IOPRIO_CLASS_BE;
3408 if (cfqq->ioprio > IOPRIO_NORM)
3409 cfqq->ioprio = IOPRIO_NORM;
3412 * unboost the queue (if needed)
3414 cfqq->ioprio_class = cfqq->org_ioprio_class;
3415 cfqq->ioprio = cfqq->org_ioprio;
3419 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
3421 if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
3422 cfq_mark_cfqq_must_alloc_slice(cfqq);
3423 return ELV_MQUEUE_MUST;
3426 return ELV_MQUEUE_MAY;
3429 static int cfq_may_queue(struct request_queue *q, int rw)
3431 struct cfq_data *cfqd = q->elevator->elevator_data;
3432 struct task_struct *tsk = current;
3433 struct cfq_io_context *cic;
3434 struct cfq_queue *cfqq;
3437 * don't force setup of a queue from here, as a call to may_queue
3438 * does not necessarily imply that a request actually will be queued.
3439 * so just lookup a possibly existing queue, or return 'may queue'
3442 cic = cfq_cic_lookup(cfqd, tsk->io_context);
3444 return ELV_MQUEUE_MAY;
3446 cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
3448 cfq_init_prio_data(cfqq, cic->ioc);
3449 cfq_prio_boost(cfqq);
3451 return __cfq_may_queue(cfqq);
3454 return ELV_MQUEUE_MAY;
3458 * queue lock held here
3460 static void cfq_put_request(struct request *rq)
3462 struct cfq_queue *cfqq = RQ_CFQQ(rq);
3465 const int rw = rq_data_dir(rq);
3467 BUG_ON(!cfqq->allocated[rw]);
3468 cfqq->allocated[rw]--;
3470 put_io_context(RQ_CIC(rq)->ioc);
3472 rq->elevator_private = NULL;
3473 rq->elevator_private2 = NULL;
3475 cfq_put_queue(cfqq);
3479 static struct cfq_queue *
3480 cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
3481 struct cfq_queue *cfqq)
3483 cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
3484 cic_set_cfqq(cic, cfqq->new_cfqq, 1);
3485 cfq_mark_cfqq_coop(cfqq->new_cfqq);
3486 cfq_put_queue(cfqq);
3487 return cic_to_cfqq(cic, 1);
3491 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
3492 * was the last process referring to said cfqq.
3494 static struct cfq_queue *
3495 split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
3497 if (cfqq_process_refs(cfqq) == 1) {
3498 cfqq->pid = current->pid;
3499 cfq_clear_cfqq_coop(cfqq);
3500 cfq_clear_cfqq_split_coop(cfqq);
3504 cic_set_cfqq(cic, NULL, 1);
3505 cfq_put_queue(cfqq);
3509 * Allocate cfq data structures associated with this request.
3512 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
3514 struct cfq_data *cfqd = q->elevator->elevator_data;
3515 struct cfq_io_context *cic;
3516 const int rw = rq_data_dir(rq);
3517 const bool is_sync = rq_is_sync(rq);
3518 struct cfq_queue *cfqq;
3519 unsigned long flags;
3521 might_sleep_if(gfp_mask & __GFP_WAIT);
3523 cic = cfq_get_io_context(cfqd, gfp_mask);
3525 spin_lock_irqsave(q->queue_lock, flags);
3531 cfqq = cic_to_cfqq(cic, is_sync);
3532 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
3533 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
3534 cic_set_cfqq(cic, cfqq, is_sync);
3537 * If the queue was seeky for too long, break it apart.
3539 if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) {
3540 cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
3541 cfqq = split_cfqq(cic, cfqq);
3547 * Check to see if this queue is scheduled to merge with
3548 * another, closely cooperating queue. The merging of
3549 * queues happens here as it must be done in process context.
3550 * The reference on new_cfqq was taken in merge_cfqqs.
3553 cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
3556 cfqq->allocated[rw]++;
3557 atomic_inc(&cfqq->ref);
3559 spin_unlock_irqrestore(q->queue_lock, flags);
3561 rq->elevator_private = cic;
3562 rq->elevator_private2 = cfqq;
3567 put_io_context(cic->ioc);
3569 cfq_schedule_dispatch(cfqd);
3570 spin_unlock_irqrestore(q->queue_lock, flags);
3571 cfq_log(cfqd, "set_request fail");
3575 static void cfq_kick_queue(struct work_struct *work)
3577 struct cfq_data *cfqd =
3578 container_of(work, struct cfq_data, unplug_work);
3579 struct request_queue *q = cfqd->queue;
3581 spin_lock_irq(q->queue_lock);
3582 __blk_run_queue(cfqd->queue);
3583 spin_unlock_irq(q->queue_lock);
3587 * Timer running if the active_queue is currently idling inside its time slice
3589 static void cfq_idle_slice_timer(unsigned long data)
3591 struct cfq_data *cfqd = (struct cfq_data *) data;
3592 struct cfq_queue *cfqq;
3593 unsigned long flags;
3596 cfq_log(cfqd, "idle timer fired");
3598 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
3600 cfqq = cfqd->active_queue;
3605 * We saw a request before the queue expired, let it through
3607 if (cfq_cfqq_must_dispatch(cfqq))
3613 if (cfq_slice_used(cfqq))
3617 * only expire and reinvoke request handler, if there are
3618 * other queues with pending requests
3620 if (!cfqd->busy_queues)
3624 * not expired and it has a request pending, let it dispatch
3626 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3630 * Queue depth flag is reset only when the idle didn't succeed
3632 cfq_clear_cfqq_deep(cfqq);
3635 cfq_slice_expired(cfqd, timed_out, false);
3637 cfq_schedule_dispatch(cfqd);
3639 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
3642 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
3644 del_timer_sync(&cfqd->idle_slice_timer);
3645 cancel_work_sync(&cfqd->unplug_work);
3648 static void cfq_put_async_queues(struct cfq_data *cfqd)
3652 for (i = 0; i < IOPRIO_BE_NR; i++) {
3653 if (cfqd->async_cfqq[0][i])
3654 cfq_put_queue(cfqd->async_cfqq[0][i]);
3655 if (cfqd->async_cfqq[1][i])
3656 cfq_put_queue(cfqd->async_cfqq[1][i]);
3659 if (cfqd->async_idle_cfqq)
3660 cfq_put_queue(cfqd->async_idle_cfqq);
3663 static void cfq_cfqd_free(struct rcu_head *head)
3665 kfree(container_of(head, struct cfq_data, rcu));
3668 static void cfq_exit_queue(struct elevator_queue *e)
3670 struct cfq_data *cfqd = e->elevator_data;
3671 struct request_queue *q = cfqd->queue;
3673 cfq_shutdown_timer_wq(cfqd);
3675 spin_lock_irq(q->queue_lock);
3677 if (cfqd->active_queue)
3678 __cfq_slice_expired(cfqd, cfqd->active_queue, 0, false);
3680 while (!list_empty(&cfqd->cic_list)) {
3681 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
3682 struct cfq_io_context,
3685 __cfq_exit_single_io_context(cfqd, cic);
3688 cfq_put_async_queues(cfqd);
3689 cfq_release_cfq_groups(cfqd);
3690 blkiocg_del_blkio_group(&cfqd->root_group.blkg);
3692 spin_unlock_irq(q->queue_lock);
3694 cfq_shutdown_timer_wq(cfqd);
3696 /* Wait for cfqg->blkg->key accessors to exit their grace periods. */
3697 call_rcu(&cfqd->rcu, cfq_cfqd_free);
3700 static void *cfq_init_queue(struct request_queue *q)
3702 struct cfq_data *cfqd;
3704 struct cfq_group *cfqg;
3705 struct cfq_rb_root *st;
3707 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
3711 /* Init root service tree */
3712 cfqd->grp_service_tree = CFQ_RB_ROOT;
3714 /* Init root group */
3715 cfqg = &cfqd->root_group;
3716 for_each_cfqg_st(cfqg, i, j, st)
3718 RB_CLEAR_NODE(&cfqg->rb_node);
3720 /* Give preference to root group over other groups */
3721 cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;
3723 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3725 * Take a reference to root group which we never drop. This is just
3726 * to make sure that cfq_put_cfqg() does not try to kfree root group
3728 atomic_set(&cfqg->ref, 1);
3729 blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd,
3733 * Not strictly needed (since RB_ROOT just clears the node and we
3734 * zeroed cfqd on alloc), but better be safe in case someone decides
3735 * to add magic to the rb code
3737 for (i = 0; i < CFQ_PRIO_LISTS; i++)
3738 cfqd->prio_trees[i] = RB_ROOT;
3741 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
3742 * Grab a permanent reference to it, so that the normal code flow
3743 * will not attempt to free it.
3745 cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
3746 atomic_inc(&cfqd->oom_cfqq.ref);
3747 cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
3749 INIT_LIST_HEAD(&cfqd->cic_list);
3753 init_timer(&cfqd->idle_slice_timer);
3754 cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
3755 cfqd->idle_slice_timer.data = (unsigned long) cfqd;
3757 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
3759 cfqd->cfq_quantum = cfq_quantum;
3760 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
3761 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
3762 cfqd->cfq_back_max = cfq_back_max;
3763 cfqd->cfq_back_penalty = cfq_back_penalty;
3764 cfqd->cfq_slice[0] = cfq_slice_async;
3765 cfqd->cfq_slice[1] = cfq_slice_sync;
3766 cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
3767 cfqd->cfq_slice_idle = cfq_slice_idle;
3768 cfqd->cfq_latency = 1;
3769 cfqd->cfq_group_isolation = 0;
3772 * we optimistically start assuming sync ops weren't delayed in last
3773 * second, in order to have larger depth for async operations.
3775 cfqd->last_delayed_sync = jiffies - HZ;
3776 INIT_RCU_HEAD(&cfqd->rcu);
3780 static void cfq_slab_kill(void)
3783 * Caller already ensured that pending RCU callbacks are completed,
3784 * so we should have no busy allocations at this point.
3787 kmem_cache_destroy(cfq_pool);
3789 kmem_cache_destroy(cfq_ioc_pool);
3792 static int __init cfq_slab_setup(void)
3794 cfq_pool = KMEM_CACHE(cfq_queue, 0);
3798 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
3809 * sysfs parts below -->
3812 cfq_var_show(unsigned int var, char *page)
3814 return sprintf(page, "%d\n", var);
3818 cfq_var_store(unsigned int *var, const char *page, size_t count)
3820 char *p = (char *) page;
3822 *var = simple_strtoul(p, &p, 10);
3826 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
3827 static ssize_t __FUNC(struct elevator_queue *e, char *page) \
3829 struct cfq_data *cfqd = e->elevator_data; \
3830 unsigned int __data = __VAR; \
3832 __data = jiffies_to_msecs(__data); \
3833 return cfq_var_show(__data, (page)); \
3835 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
3836 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
3837 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
3838 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
3839 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
3840 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
3841 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
3842 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
3843 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
3844 SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
3845 SHOW_FUNCTION(cfq_group_isolation_show, cfqd->cfq_group_isolation, 0);
3846 #undef SHOW_FUNCTION
3848 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
3849 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3851 struct cfq_data *cfqd = e->elevator_data; \
3852 unsigned int __data; \
3853 int ret = cfq_var_store(&__data, (page), count); \
3854 if (__data < (MIN)) \
3856 else if (__data > (MAX)) \
3859 *(__PTR) = msecs_to_jiffies(__data); \
3861 *(__PTR) = __data; \
3864 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
3865 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
3867 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
3869 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
3870 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
3872 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
3873 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
3874 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
3875 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
3877 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
3878 STORE_FUNCTION(cfq_group_isolation_store, &cfqd->cfq_group_isolation, 0, 1, 0);
3879 #undef STORE_FUNCTION
3881 #define CFQ_ATTR(name) \
3882 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3884 static struct elv_fs_entry cfq_attrs[] = {
3886 CFQ_ATTR(fifo_expire_sync),
3887 CFQ_ATTR(fifo_expire_async),
3888 CFQ_ATTR(back_seek_max),
3889 CFQ_ATTR(back_seek_penalty),
3890 CFQ_ATTR(slice_sync),
3891 CFQ_ATTR(slice_async),
3892 CFQ_ATTR(slice_async_rq),
3893 CFQ_ATTR(slice_idle),
3894 CFQ_ATTR(low_latency),
3895 CFQ_ATTR(group_isolation),
3899 static struct elevator_type iosched_cfq = {
3901 .elevator_merge_fn = cfq_merge,
3902 .elevator_merged_fn = cfq_merged_request,
3903 .elevator_merge_req_fn = cfq_merged_requests,
3904 .elevator_allow_merge_fn = cfq_allow_merge,
3905 .elevator_bio_merged_fn = cfq_bio_merged,
3906 .elevator_dispatch_fn = cfq_dispatch_requests,
3907 .elevator_add_req_fn = cfq_insert_request,
3908 .elevator_activate_req_fn = cfq_activate_request,
3909 .elevator_deactivate_req_fn = cfq_deactivate_request,
3910 .elevator_queue_empty_fn = cfq_queue_empty,
3911 .elevator_completed_req_fn = cfq_completed_request,
3912 .elevator_former_req_fn = elv_rb_former_request,
3913 .elevator_latter_req_fn = elv_rb_latter_request,
3914 .elevator_set_req_fn = cfq_set_request,
3915 .elevator_put_req_fn = cfq_put_request,
3916 .elevator_may_queue_fn = cfq_may_queue,
3917 .elevator_init_fn = cfq_init_queue,
3918 .elevator_exit_fn = cfq_exit_queue,
3919 .trim = cfq_free_io_context,
3921 .elevator_attrs = cfq_attrs,
3922 .elevator_name = "cfq",
3923 .elevator_owner = THIS_MODULE,
3926 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3927 static struct blkio_policy_type blkio_policy_cfq = {
3929 .blkio_unlink_group_fn = cfq_unlink_blkio_group,
3930 .blkio_update_group_weight_fn = cfq_update_blkio_group_weight,
3934 static struct blkio_policy_type blkio_policy_cfq;
3937 static int __init cfq_init(void)
3940 * could be 0 on HZ < 1000 setups
3942 if (!cfq_slice_async)
3943 cfq_slice_async = 1;
3944 if (!cfq_slice_idle)
3947 if (cfq_slab_setup())
3950 elv_register(&iosched_cfq);
3951 blkio_policy_register(&blkio_policy_cfq);
3956 static void __exit cfq_exit(void)
3958 DECLARE_COMPLETION_ONSTACK(all_gone);
3959 blkio_policy_unregister(&blkio_policy_cfq);
3960 elv_unregister(&iosched_cfq);
3961 ioc_gone = &all_gone;
3962 /* ioc_gone's update must be visible before reading ioc_count */
3966 * this also protects us from entering cfq_slab_kill() with
3967 * pending RCU callbacks
3969 if (elv_ioc_count_read(cfq_ioc_count))
3970 wait_for_completion(&all_gone);
3974 module_init(cfq_init);
3975 module_exit(cfq_exit);
3977 MODULE_AUTHOR("Jens Axboe");
3978 MODULE_LICENSE("GPL");
3979 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");