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>
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 int cfq_group_idle = HZ / 125;
34 static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
35 static const int cfq_hist_divisor = 4;
38 * offset from end of service tree
40 #define CFQ_IDLE_DELAY (HZ / 5)
43 * below this threshold, we consider thinktime immediate
45 #define CFQ_MIN_TT (2)
47 #define CFQ_SLICE_SCALE (5)
48 #define CFQ_HW_QUEUE_MIN (5)
49 #define CFQ_SERVICE_SHIFT 12
51 #define CFQQ_SEEK_THR (sector_t)(8 * 100)
52 #define CFQQ_CLOSE_THR (sector_t)(8 * 1024)
53 #define CFQQ_SECT_THR_NONROT (sector_t)(2 * 32)
54 #define CFQQ_SEEKY(cfqq) (hweight32(cfqq->seek_history) > 32/8)
57 ((struct cfq_io_context *) (rq)->elevator_private[0])
58 #define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private[1])
59 #define RQ_CFQG(rq) (struct cfq_group *) ((rq)->elevator_private[2])
61 static struct kmem_cache *cfq_pool;
62 static struct kmem_cache *cfq_ioc_pool;
64 static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
65 static struct completion *ioc_gone;
66 static DEFINE_SPINLOCK(ioc_gone_lock);
68 static DEFINE_SPINLOCK(cic_index_lock);
69 static DEFINE_IDA(cic_index_ida);
71 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
72 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
73 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
75 #define sample_valid(samples) ((samples) > 80)
76 #define rb_entry_cfqg(node) rb_entry((node), struct cfq_group, rb_node)
79 * Most of our rbtree usage is for sorting with min extraction, so
80 * if we cache the leftmost node we don't have to walk down the tree
81 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
82 * move this into the elevator for the rq sorting as well.
88 unsigned total_weight;
90 struct cfq_ttime ttime;
92 #define CFQ_RB_ROOT (struct cfq_rb_root) { .rb = RB_ROOT, \
93 .ttime = {.last_end_request = jiffies,},}
96 * Per process-grouping structure
101 /* various state flags, see below */
103 /* parent cfq_data */
104 struct cfq_data *cfqd;
105 /* service_tree member */
106 struct rb_node rb_node;
107 /* service_tree key */
108 unsigned long rb_key;
109 /* prio tree member */
110 struct rb_node p_node;
111 /* prio tree root we belong to, if any */
112 struct rb_root *p_root;
113 /* sorted list of pending requests */
114 struct rb_root sort_list;
115 /* if fifo isn't expired, next request to serve */
116 struct request *next_rq;
117 /* requests queued in sort_list */
119 /* currently allocated requests */
121 /* fifo list of requests in sort_list */
122 struct list_head fifo;
124 /* time when queue got scheduled in to dispatch first request. */
125 unsigned long dispatch_start;
126 unsigned int allocated_slice;
127 unsigned int slice_dispatch;
128 /* time when first request from queue completed and slice started. */
129 unsigned long slice_start;
130 unsigned long slice_end;
133 /* number of requests that are on the dispatch list or inside driver */
136 /* io prio of this group */
137 unsigned short ioprio, org_ioprio;
138 unsigned short ioprio_class;
143 sector_t last_request_pos;
145 struct cfq_rb_root *service_tree;
146 struct cfq_queue *new_cfqq;
147 struct cfq_group *cfqg;
148 /* Number of sectors dispatched from queue in single dispatch round */
149 unsigned long nr_sectors;
153 * First index in the service_trees.
154 * IDLE is handled separately, so it has negative index
164 * Second index in the service_trees.
168 SYNC_NOIDLE_WORKLOAD = 1,
172 /* This is per cgroup per device grouping structure */
174 /* group service_tree member */
175 struct rb_node rb_node;
177 /* group service_tree key */
180 unsigned int new_weight;
183 /* number of cfqq currently on this group */
187 * Per group busy queues average. Useful for workload slice calc. We
188 * create the array for each prio class but at run time it is used
189 * only for RT and BE class and slot for IDLE class remains unused.
190 * This is primarily done to avoid confusion and a gcc warning.
192 unsigned int busy_queues_avg[CFQ_PRIO_NR];
194 * rr lists of queues with requests. We maintain service trees for
195 * RT and BE classes. These trees are subdivided in subclasses
196 * of SYNC, SYNC_NOIDLE and ASYNC based on workload type. For IDLE
197 * class there is no subclassification and all the cfq queues go on
198 * a single tree service_tree_idle.
199 * Counts are embedded in the cfq_rb_root
201 struct cfq_rb_root service_trees[2][3];
202 struct cfq_rb_root service_tree_idle;
204 unsigned long saved_workload_slice;
205 enum wl_type_t saved_workload;
206 enum wl_prio_t saved_serving_prio;
207 struct blkio_group blkg;
208 #ifdef CONFIG_CFQ_GROUP_IOSCHED
209 struct hlist_node cfqd_node;
212 /* number of requests that are on the dispatch list or inside driver */
214 struct cfq_ttime ttime;
218 * Per block device queue structure
221 struct request_queue *queue;
222 /* Root service tree for cfq_groups */
223 struct cfq_rb_root grp_service_tree;
224 struct cfq_group root_group;
227 * The priority currently being served
229 enum wl_prio_t serving_prio;
230 enum wl_type_t serving_type;
231 unsigned long workload_expires;
232 struct cfq_group *serving_group;
235 * Each priority tree is sorted by next_request position. These
236 * trees are used when determining if two or more queues are
237 * interleaving requests (see cfq_close_cooperator).
239 struct rb_root prio_trees[CFQ_PRIO_LISTS];
241 unsigned int busy_queues;
242 unsigned int busy_sync_queues;
248 * queue-depth detection
254 * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
255 * 1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
258 int hw_tag_est_depth;
259 unsigned int hw_tag_samples;
262 * idle window management
264 struct timer_list idle_slice_timer;
265 struct work_struct unplug_work;
267 struct cfq_queue *active_queue;
268 struct cfq_io_context *active_cic;
271 * async queue for each priority case
273 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
274 struct cfq_queue *async_idle_cfqq;
276 sector_t last_position;
279 * tunables, see top of file
281 unsigned int cfq_quantum;
282 unsigned int cfq_fifo_expire[2];
283 unsigned int cfq_back_penalty;
284 unsigned int cfq_back_max;
285 unsigned int cfq_slice[2];
286 unsigned int cfq_slice_async_rq;
287 unsigned int cfq_slice_idle;
288 unsigned int cfq_group_idle;
289 unsigned int cfq_latency;
291 unsigned int cic_index;
292 struct list_head cic_list;
295 * Fallback dummy cfqq for extreme OOM conditions
297 struct cfq_queue oom_cfqq;
299 unsigned long last_delayed_sync;
301 /* List of cfq groups being managed on this device*/
302 struct hlist_head cfqg_list;
304 /* Number of groups which are on blkcg->blkg_list */
305 unsigned int nr_blkcg_linked_grps;
308 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
310 static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
317 if (prio == IDLE_WORKLOAD)
318 return &cfqg->service_tree_idle;
320 return &cfqg->service_trees[prio][type];
323 enum cfqq_state_flags {
324 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
325 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
326 CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */
327 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
328 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
329 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */
330 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
331 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
332 CFQ_CFQQ_FLAG_sync, /* synchronous queue */
333 CFQ_CFQQ_FLAG_coop, /* cfqq is shared */
334 CFQ_CFQQ_FLAG_split_coop, /* shared cfqq will be splitted */
335 CFQ_CFQQ_FLAG_deep, /* sync cfqq experienced large depth */
336 CFQ_CFQQ_FLAG_wait_busy, /* Waiting for next request */
339 #define CFQ_CFQQ_FNS(name) \
340 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
342 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
344 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
346 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
348 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
350 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
354 CFQ_CFQQ_FNS(wait_request);
355 CFQ_CFQQ_FNS(must_dispatch);
356 CFQ_CFQQ_FNS(must_alloc_slice);
357 CFQ_CFQQ_FNS(fifo_expire);
358 CFQ_CFQQ_FNS(idle_window);
359 CFQ_CFQQ_FNS(prio_changed);
360 CFQ_CFQQ_FNS(slice_new);
363 CFQ_CFQQ_FNS(split_coop);
365 CFQ_CFQQ_FNS(wait_busy);
368 #ifdef CONFIG_CFQ_GROUP_IOSCHED
369 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
370 blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
371 cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
372 blkg_path(&(cfqq)->cfqg->blkg), ##args)
374 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...) \
375 blk_add_trace_msg((cfqd)->queue, "%s " fmt, \
376 blkg_path(&(cfqg)->blkg), ##args) \
379 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
380 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
381 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...) do {} while (0)
383 #define cfq_log(cfqd, fmt, args...) \
384 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
386 /* Traverses through cfq group service trees */
387 #define for_each_cfqg_st(cfqg, i, j, st) \
388 for (i = 0; i <= IDLE_WORKLOAD; i++) \
389 for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
390 : &cfqg->service_tree_idle; \
391 (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
392 (i == IDLE_WORKLOAD && j == 0); \
393 j++, st = i < IDLE_WORKLOAD ? \
394 &cfqg->service_trees[i][j]: NULL) \
396 static inline bool cfq_io_thinktime_big(struct cfq_data *cfqd,
397 struct cfq_ttime *ttime, bool group_idle)
400 if (!sample_valid(ttime->ttime_samples))
403 slice = cfqd->cfq_group_idle;
405 slice = cfqd->cfq_slice_idle;
406 return ttime->ttime_mean > slice;
409 static inline bool iops_mode(struct cfq_data *cfqd)
412 * If we are not idling on queues and it is a NCQ drive, parallel
413 * execution of requests is on and measuring time is not possible
414 * in most of the cases until and unless we drive shallower queue
415 * depths and that becomes a performance bottleneck. In such cases
416 * switch to start providing fairness in terms of number of IOs.
418 if (!cfqd->cfq_slice_idle && cfqd->hw_tag)
424 static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
426 if (cfq_class_idle(cfqq))
427 return IDLE_WORKLOAD;
428 if (cfq_class_rt(cfqq))
434 static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
436 if (!cfq_cfqq_sync(cfqq))
437 return ASYNC_WORKLOAD;
438 if (!cfq_cfqq_idle_window(cfqq))
439 return SYNC_NOIDLE_WORKLOAD;
440 return SYNC_WORKLOAD;
443 static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl,
444 struct cfq_data *cfqd,
445 struct cfq_group *cfqg)
447 if (wl == IDLE_WORKLOAD)
448 return cfqg->service_tree_idle.count;
450 return cfqg->service_trees[wl][ASYNC_WORKLOAD].count
451 + cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
452 + cfqg->service_trees[wl][SYNC_WORKLOAD].count;
455 static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
456 struct cfq_group *cfqg)
458 return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count
459 + cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
462 static void cfq_dispatch_insert(struct request_queue *, struct request *);
463 static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
464 struct io_context *, gfp_t);
465 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
466 struct io_context *);
468 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
471 return cic->cfqq[is_sync];
474 static inline void cic_set_cfqq(struct cfq_io_context *cic,
475 struct cfq_queue *cfqq, bool is_sync)
477 cic->cfqq[is_sync] = cfqq;
480 #define CIC_DEAD_KEY 1ul
481 #define CIC_DEAD_INDEX_SHIFT 1
483 static inline void *cfqd_dead_key(struct cfq_data *cfqd)
485 return (void *)(cfqd->cic_index << CIC_DEAD_INDEX_SHIFT | CIC_DEAD_KEY);
488 static inline struct cfq_data *cic_to_cfqd(struct cfq_io_context *cic)
490 struct cfq_data *cfqd = cic->key;
492 if (unlikely((unsigned long) cfqd & CIC_DEAD_KEY))
499 * We regard a request as SYNC, if it's either a read or has the SYNC bit
500 * set (in which case it could also be direct WRITE).
502 static inline bool cfq_bio_sync(struct bio *bio)
504 return bio_data_dir(bio) == READ || (bio->bi_rw & REQ_SYNC);
508 * scheduler run of queue, if there are requests pending and no one in the
509 * driver that will restart queueing
511 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
513 if (cfqd->busy_queues) {
514 cfq_log(cfqd, "schedule dispatch");
515 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
520 * Scale schedule slice based on io priority. Use the sync time slice only
521 * if a queue is marked sync and has sync io queued. A sync queue with async
522 * io only, should not get full sync slice length.
524 static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
527 const int base_slice = cfqd->cfq_slice[sync];
529 WARN_ON(prio >= IOPRIO_BE_NR);
531 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
535 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
537 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
540 static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
542 u64 d = delta << CFQ_SERVICE_SHIFT;
544 d = d * BLKIO_WEIGHT_DEFAULT;
545 do_div(d, cfqg->weight);
549 static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
551 s64 delta = (s64)(vdisktime - min_vdisktime);
553 min_vdisktime = vdisktime;
555 return min_vdisktime;
558 static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
560 s64 delta = (s64)(vdisktime - min_vdisktime);
562 min_vdisktime = vdisktime;
564 return min_vdisktime;
567 static void update_min_vdisktime(struct cfq_rb_root *st)
569 struct cfq_group *cfqg;
572 cfqg = rb_entry_cfqg(st->left);
573 st->min_vdisktime = max_vdisktime(st->min_vdisktime,
579 * get averaged number of queues of RT/BE priority.
580 * average is updated, with a formula that gives more weight to higher numbers,
581 * to quickly follows sudden increases and decrease slowly
584 static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
585 struct cfq_group *cfqg, bool rt)
587 unsigned min_q, max_q;
588 unsigned mult = cfq_hist_divisor - 1;
589 unsigned round = cfq_hist_divisor / 2;
590 unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
592 min_q = min(cfqg->busy_queues_avg[rt], busy);
593 max_q = max(cfqg->busy_queues_avg[rt], busy);
594 cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
596 return cfqg->busy_queues_avg[rt];
599 static inline unsigned
600 cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
602 struct cfq_rb_root *st = &cfqd->grp_service_tree;
604 return cfq_target_latency * cfqg->weight / st->total_weight;
607 static inline unsigned
608 cfq_scaled_cfqq_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
610 unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
611 if (cfqd->cfq_latency) {
613 * interested queues (we consider only the ones with the same
614 * priority class in the cfq group)
616 unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
618 unsigned sync_slice = cfqd->cfq_slice[1];
619 unsigned expect_latency = sync_slice * iq;
620 unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
622 if (expect_latency > group_slice) {
623 unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
624 /* scale low_slice according to IO priority
625 * and sync vs async */
627 min(slice, base_low_slice * slice / sync_slice);
628 /* the adapted slice value is scaled to fit all iqs
629 * into the target latency */
630 slice = max(slice * group_slice / expect_latency,
638 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
640 unsigned slice = cfq_scaled_cfqq_slice(cfqd, cfqq);
642 cfqq->slice_start = jiffies;
643 cfqq->slice_end = jiffies + slice;
644 cfqq->allocated_slice = slice;
645 cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
649 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
650 * isn't valid until the first request from the dispatch is activated
651 * and the slice time set.
653 static inline bool cfq_slice_used(struct cfq_queue *cfqq)
655 if (cfq_cfqq_slice_new(cfqq))
657 if (time_before(jiffies, cfqq->slice_end))
664 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
665 * We choose the request that is closest to the head right now. Distance
666 * behind the head is penalized and only allowed to a certain extent.
668 static struct request *
669 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
671 sector_t s1, s2, d1 = 0, d2 = 0;
672 unsigned long back_max;
673 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
674 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
675 unsigned wrap = 0; /* bit mask: requests behind the disk head? */
677 if (rq1 == NULL || rq1 == rq2)
682 if (rq_is_sync(rq1) != rq_is_sync(rq2))
683 return rq_is_sync(rq1) ? rq1 : rq2;
685 s1 = blk_rq_pos(rq1);
686 s2 = blk_rq_pos(rq2);
689 * by definition, 1KiB is 2 sectors
691 back_max = cfqd->cfq_back_max * 2;
694 * Strict one way elevator _except_ in the case where we allow
695 * short backward seeks which are biased as twice the cost of a
696 * similar forward seek.
700 else if (s1 + back_max >= last)
701 d1 = (last - s1) * cfqd->cfq_back_penalty;
703 wrap |= CFQ_RQ1_WRAP;
707 else if (s2 + back_max >= last)
708 d2 = (last - s2) * cfqd->cfq_back_penalty;
710 wrap |= CFQ_RQ2_WRAP;
712 /* Found required data */
715 * By doing switch() on the bit mask "wrap" we avoid having to
716 * check two variables for all permutations: --> faster!
719 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
735 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
738 * Since both rqs are wrapped,
739 * start with the one that's further behind head
740 * (--> only *one* back seek required),
741 * since back seek takes more time than forward.
751 * The below is leftmost cache rbtree addon
753 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
755 /* Service tree is empty */
760 root->left = rb_first(&root->rb);
763 return rb_entry(root->left, struct cfq_queue, rb_node);
768 static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
771 root->left = rb_first(&root->rb);
774 return rb_entry_cfqg(root->left);
779 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
785 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
789 rb_erase_init(n, &root->rb);
794 * would be nice to take fifo expire time into account as well
796 static struct request *
797 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
798 struct request *last)
800 struct rb_node *rbnext = rb_next(&last->rb_node);
801 struct rb_node *rbprev = rb_prev(&last->rb_node);
802 struct request *next = NULL, *prev = NULL;
804 BUG_ON(RB_EMPTY_NODE(&last->rb_node));
807 prev = rb_entry_rq(rbprev);
810 next = rb_entry_rq(rbnext);
812 rbnext = rb_first(&cfqq->sort_list);
813 if (rbnext && rbnext != &last->rb_node)
814 next = rb_entry_rq(rbnext);
817 return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
820 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
821 struct cfq_queue *cfqq)
824 * just an approximation, should be ok.
826 return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
827 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
831 cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
833 return cfqg->vdisktime - st->min_vdisktime;
837 __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
839 struct rb_node **node = &st->rb.rb_node;
840 struct rb_node *parent = NULL;
841 struct cfq_group *__cfqg;
842 s64 key = cfqg_key(st, cfqg);
845 while (*node != NULL) {
847 __cfqg = rb_entry_cfqg(parent);
849 if (key < cfqg_key(st, __cfqg))
850 node = &parent->rb_left;
852 node = &parent->rb_right;
858 st->left = &cfqg->rb_node;
860 rb_link_node(&cfqg->rb_node, parent, node);
861 rb_insert_color(&cfqg->rb_node, &st->rb);
865 cfq_update_group_weight(struct cfq_group *cfqg)
867 BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
868 if (cfqg->needs_update) {
869 cfqg->weight = cfqg->new_weight;
870 cfqg->needs_update = false;
875 cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
877 BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
879 cfq_update_group_weight(cfqg);
880 __cfq_group_service_tree_add(st, cfqg);
881 st->total_weight += cfqg->weight;
885 cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
887 struct cfq_rb_root *st = &cfqd->grp_service_tree;
888 struct cfq_group *__cfqg;
892 if (!RB_EMPTY_NODE(&cfqg->rb_node))
896 * Currently put the group at the end. Later implement something
897 * so that groups get lesser vtime based on their weights, so that
898 * if group does not loose all if it was not continuously backlogged.
900 n = rb_last(&st->rb);
902 __cfqg = rb_entry_cfqg(n);
903 cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
905 cfqg->vdisktime = st->min_vdisktime;
906 cfq_group_service_tree_add(st, cfqg);
910 cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg)
912 st->total_weight -= cfqg->weight;
913 if (!RB_EMPTY_NODE(&cfqg->rb_node))
914 cfq_rb_erase(&cfqg->rb_node, st);
918 cfq_group_notify_queue_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
920 struct cfq_rb_root *st = &cfqd->grp_service_tree;
922 BUG_ON(cfqg->nr_cfqq < 1);
925 /* If there are other cfq queues under this group, don't delete it */
929 cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
930 cfq_group_service_tree_del(st, cfqg);
931 cfqg->saved_workload_slice = 0;
932 cfq_blkiocg_update_dequeue_stats(&cfqg->blkg, 1);
935 static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq,
936 unsigned int *unaccounted_time)
938 unsigned int slice_used;
941 * Queue got expired before even a single request completed or
942 * got expired immediately after first request completion.
944 if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
946 * Also charge the seek time incurred to the group, otherwise
947 * if there are mutiple queues in the group, each can dispatch
948 * a single request on seeky media and cause lots of seek time
949 * and group will never know it.
951 slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
954 slice_used = jiffies - cfqq->slice_start;
955 if (slice_used > cfqq->allocated_slice) {
956 *unaccounted_time = slice_used - cfqq->allocated_slice;
957 slice_used = cfqq->allocated_slice;
959 if (time_after(cfqq->slice_start, cfqq->dispatch_start))
960 *unaccounted_time += cfqq->slice_start -
961 cfqq->dispatch_start;
967 static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
968 struct cfq_queue *cfqq)
970 struct cfq_rb_root *st = &cfqd->grp_service_tree;
971 unsigned int used_sl, charge, unaccounted_sl = 0;
972 int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
973 - cfqg->service_tree_idle.count;
976 used_sl = charge = cfq_cfqq_slice_usage(cfqq, &unaccounted_sl);
979 charge = cfqq->slice_dispatch;
980 else if (!cfq_cfqq_sync(cfqq) && !nr_sync)
981 charge = cfqq->allocated_slice;
983 /* Can't update vdisktime while group is on service tree */
984 cfq_group_service_tree_del(st, cfqg);
985 cfqg->vdisktime += cfq_scale_slice(charge, cfqg);
986 /* If a new weight was requested, update now, off tree */
987 cfq_group_service_tree_add(st, cfqg);
989 /* This group is being expired. Save the context */
990 if (time_after(cfqd->workload_expires, jiffies)) {
991 cfqg->saved_workload_slice = cfqd->workload_expires
993 cfqg->saved_workload = cfqd->serving_type;
994 cfqg->saved_serving_prio = cfqd->serving_prio;
996 cfqg->saved_workload_slice = 0;
998 cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
1000 cfq_log_cfqq(cfqq->cfqd, cfqq,
1001 "sl_used=%u disp=%u charge=%u iops=%u sect=%lu",
1002 used_sl, cfqq->slice_dispatch, charge,
1003 iops_mode(cfqd), cfqq->nr_sectors);
1004 cfq_blkiocg_update_timeslice_used(&cfqg->blkg, used_sl,
1006 cfq_blkiocg_set_start_empty_time(&cfqg->blkg);
1009 #ifdef CONFIG_CFQ_GROUP_IOSCHED
1010 static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
1013 return container_of(blkg, struct cfq_group, blkg);
1017 static void cfq_update_blkio_group_weight(void *key, struct blkio_group *blkg,
1018 unsigned int weight)
1020 struct cfq_group *cfqg = cfqg_of_blkg(blkg);
1021 cfqg->new_weight = weight;
1022 cfqg->needs_update = true;
1025 static void cfq_init_add_cfqg_lists(struct cfq_data *cfqd,
1026 struct cfq_group *cfqg, struct blkio_cgroup *blkcg)
1028 struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
1029 unsigned int major, minor;
1032 * Add group onto cgroup list. It might happen that bdi->dev is
1033 * not initialized yet. Initialize this new group without major
1034 * and minor info and this info will be filled in once a new thread
1038 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
1039 cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg,
1040 (void *)cfqd, MKDEV(major, minor));
1042 cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg,
1045 cfqd->nr_blkcg_linked_grps++;
1046 cfqg->weight = blkcg_get_weight(blkcg, cfqg->blkg.dev);
1048 /* Add group on cfqd list */
1049 hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
1053 * Should be called from sleepable context. No request queue lock as per
1054 * cpu stats are allocated dynamically and alloc_percpu needs to be called
1055 * from sleepable context.
1057 static struct cfq_group * cfq_alloc_cfqg(struct cfq_data *cfqd)
1059 struct cfq_group *cfqg = NULL;
1061 struct cfq_rb_root *st;
1063 cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node);
1067 for_each_cfqg_st(cfqg, i, j, st)
1069 RB_CLEAR_NODE(&cfqg->rb_node);
1071 cfqg->ttime.last_end_request = jiffies;
1074 * Take the initial reference that will be released on destroy
1075 * This can be thought of a joint reference by cgroup and
1076 * elevator which will be dropped by either elevator exit
1077 * or cgroup deletion path depending on who is exiting first.
1081 ret = blkio_alloc_blkg_stats(&cfqg->blkg);
1090 static struct cfq_group *
1091 cfq_find_cfqg(struct cfq_data *cfqd, struct blkio_cgroup *blkcg)
1093 struct cfq_group *cfqg = NULL;
1095 struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
1096 unsigned int major, minor;
1099 * This is the common case when there are no blkio cgroups.
1100 * Avoid lookup in this case
1102 if (blkcg == &blkio_root_cgroup)
1103 cfqg = &cfqd->root_group;
1105 cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
1107 if (cfqg && !cfqg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {
1108 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
1109 cfqg->blkg.dev = MKDEV(major, minor);
1116 * Search for the cfq group current task belongs to. request_queue lock must
1119 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd)
1121 struct blkio_cgroup *blkcg;
1122 struct cfq_group *cfqg = NULL, *__cfqg = NULL;
1123 struct request_queue *q = cfqd->queue;
1126 blkcg = task_blkio_cgroup(current);
1127 cfqg = cfq_find_cfqg(cfqd, blkcg);
1134 * Need to allocate a group. Allocation of group also needs allocation
1135 * of per cpu stats which in-turn takes a mutex() and can block. Hence
1136 * we need to drop rcu lock and queue_lock before we call alloc.
1138 * Not taking any queue reference here and assuming that queue is
1139 * around by the time we return. CFQ queue allocation code does
1140 * the same. It might be racy though.
1144 spin_unlock_irq(q->queue_lock);
1146 cfqg = cfq_alloc_cfqg(cfqd);
1148 spin_lock_irq(q->queue_lock);
1151 blkcg = task_blkio_cgroup(current);
1154 * If some other thread already allocated the group while we were
1155 * not holding queue lock, free up the group
1157 __cfqg = cfq_find_cfqg(cfqd, blkcg);
1166 cfqg = &cfqd->root_group;
1168 cfq_init_add_cfqg_lists(cfqd, cfqg, blkcg);
1173 static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
1179 static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
1181 /* Currently, all async queues are mapped to root group */
1182 if (!cfq_cfqq_sync(cfqq))
1183 cfqg = &cfqq->cfqd->root_group;
1186 /* cfqq reference on cfqg */
1190 static void cfq_put_cfqg(struct cfq_group *cfqg)
1192 struct cfq_rb_root *st;
1195 BUG_ON(cfqg->ref <= 0);
1199 for_each_cfqg_st(cfqg, i, j, st)
1200 BUG_ON(!RB_EMPTY_ROOT(&st->rb));
1201 free_percpu(cfqg->blkg.stats_cpu);
1205 static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
1207 /* Something wrong if we are trying to remove same group twice */
1208 BUG_ON(hlist_unhashed(&cfqg->cfqd_node));
1210 hlist_del_init(&cfqg->cfqd_node);
1212 BUG_ON(cfqd->nr_blkcg_linked_grps <= 0);
1213 cfqd->nr_blkcg_linked_grps--;
1216 * Put the reference taken at the time of creation so that when all
1217 * queues are gone, group can be destroyed.
1222 static void cfq_release_cfq_groups(struct cfq_data *cfqd)
1224 struct hlist_node *pos, *n;
1225 struct cfq_group *cfqg;
1227 hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) {
1229 * If cgroup removal path got to blk_group first and removed
1230 * it from cgroup list, then it will take care of destroying
1233 if (!cfq_blkiocg_del_blkio_group(&cfqg->blkg))
1234 cfq_destroy_cfqg(cfqd, cfqg);
1239 * Blk cgroup controller notification saying that blkio_group object is being
1240 * delinked as associated cgroup object is going away. That also means that
1241 * no new IO will come in this group. So get rid of this group as soon as
1242 * any pending IO in the group is finished.
1244 * This function is called under rcu_read_lock(). key is the rcu protected
1245 * pointer. That means "key" is a valid cfq_data pointer as long as we are rcu
1248 * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
1249 * it should not be NULL as even if elevator was exiting, cgroup deltion
1250 * path got to it first.
1252 static void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
1254 unsigned long flags;
1255 struct cfq_data *cfqd = key;
1257 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1258 cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg));
1259 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1262 #else /* GROUP_IOSCHED */
1263 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd)
1265 return &cfqd->root_group;
1268 static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
1274 cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
1278 static void cfq_release_cfq_groups(struct cfq_data *cfqd) {}
1279 static inline void cfq_put_cfqg(struct cfq_group *cfqg) {}
1281 #endif /* GROUP_IOSCHED */
1284 * The cfqd->service_trees holds all pending cfq_queue's that have
1285 * requests waiting to be processed. It is sorted in the order that
1286 * we will service the queues.
1288 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1291 struct rb_node **p, *parent;
1292 struct cfq_queue *__cfqq;
1293 unsigned long rb_key;
1294 struct cfq_rb_root *service_tree;
1298 service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
1300 if (cfq_class_idle(cfqq)) {
1301 rb_key = CFQ_IDLE_DELAY;
1302 parent = rb_last(&service_tree->rb);
1303 if (parent && parent != &cfqq->rb_node) {
1304 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1305 rb_key += __cfqq->rb_key;
1308 } else if (!add_front) {
1310 * Get our rb key offset. Subtract any residual slice
1311 * value carried from last service. A negative resid
1312 * count indicates slice overrun, and this should position
1313 * the next service time further away in the tree.
1315 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
1316 rb_key -= cfqq->slice_resid;
1317 cfqq->slice_resid = 0;
1320 __cfqq = cfq_rb_first(service_tree);
1321 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
1324 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1327 * same position, nothing more to do
1329 if (rb_key == cfqq->rb_key &&
1330 cfqq->service_tree == service_tree)
1333 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1334 cfqq->service_tree = NULL;
1339 cfqq->service_tree = service_tree;
1340 p = &service_tree->rb.rb_node;
1345 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1348 * sort by key, that represents service time.
1350 if (time_before(rb_key, __cfqq->rb_key))
1353 n = &(*p)->rb_right;
1361 service_tree->left = &cfqq->rb_node;
1363 cfqq->rb_key = rb_key;
1364 rb_link_node(&cfqq->rb_node, parent, p);
1365 rb_insert_color(&cfqq->rb_node, &service_tree->rb);
1366 service_tree->count++;
1367 if (add_front || !new_cfqq)
1369 cfq_group_notify_queue_add(cfqd, cfqq->cfqg);
1372 static struct cfq_queue *
1373 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
1374 sector_t sector, struct rb_node **ret_parent,
1375 struct rb_node ***rb_link)
1377 struct rb_node **p, *parent;
1378 struct cfq_queue *cfqq = NULL;
1386 cfqq = rb_entry(parent, struct cfq_queue, p_node);
1389 * Sort strictly based on sector. Smallest to the left,
1390 * largest to the right.
1392 if (sector > blk_rq_pos(cfqq->next_rq))
1393 n = &(*p)->rb_right;
1394 else if (sector < blk_rq_pos(cfqq->next_rq))
1402 *ret_parent = parent;
1408 static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1410 struct rb_node **p, *parent;
1411 struct cfq_queue *__cfqq;
1414 rb_erase(&cfqq->p_node, cfqq->p_root);
1415 cfqq->p_root = NULL;
1418 if (cfq_class_idle(cfqq))
1423 cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
1424 __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
1425 blk_rq_pos(cfqq->next_rq), &parent, &p);
1427 rb_link_node(&cfqq->p_node, parent, p);
1428 rb_insert_color(&cfqq->p_node, cfqq->p_root);
1430 cfqq->p_root = NULL;
1434 * Update cfqq's position in the service tree.
1436 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1439 * Resorting requires the cfqq to be on the RR list already.
1441 if (cfq_cfqq_on_rr(cfqq)) {
1442 cfq_service_tree_add(cfqd, cfqq, 0);
1443 cfq_prio_tree_add(cfqd, cfqq);
1448 * add to busy list of queues for service, trying to be fair in ordering
1449 * the pending list according to last request service
1451 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1453 cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
1454 BUG_ON(cfq_cfqq_on_rr(cfqq));
1455 cfq_mark_cfqq_on_rr(cfqq);
1456 cfqd->busy_queues++;
1457 if (cfq_cfqq_sync(cfqq))
1458 cfqd->busy_sync_queues++;
1460 cfq_resort_rr_list(cfqd, cfqq);
1464 * Called when the cfqq no longer has requests pending, remove it from
1467 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1469 cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
1470 BUG_ON(!cfq_cfqq_on_rr(cfqq));
1471 cfq_clear_cfqq_on_rr(cfqq);
1473 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1474 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1475 cfqq->service_tree = NULL;
1478 rb_erase(&cfqq->p_node, cfqq->p_root);
1479 cfqq->p_root = NULL;
1482 cfq_group_notify_queue_del(cfqd, cfqq->cfqg);
1483 BUG_ON(!cfqd->busy_queues);
1484 cfqd->busy_queues--;
1485 if (cfq_cfqq_sync(cfqq))
1486 cfqd->busy_sync_queues--;
1490 * rb tree support functions
1492 static void cfq_del_rq_rb(struct request *rq)
1494 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1495 const int sync = rq_is_sync(rq);
1497 BUG_ON(!cfqq->queued[sync]);
1498 cfqq->queued[sync]--;
1500 elv_rb_del(&cfqq->sort_list, rq);
1502 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
1504 * Queue will be deleted from service tree when we actually
1505 * expire it later. Right now just remove it from prio tree
1509 rb_erase(&cfqq->p_node, cfqq->p_root);
1510 cfqq->p_root = NULL;
1515 static void cfq_add_rq_rb(struct request *rq)
1517 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1518 struct cfq_data *cfqd = cfqq->cfqd;
1519 struct request *prev;
1521 cfqq->queued[rq_is_sync(rq)]++;
1523 elv_rb_add(&cfqq->sort_list, rq);
1525 if (!cfq_cfqq_on_rr(cfqq))
1526 cfq_add_cfqq_rr(cfqd, cfqq);
1529 * check if this request is a better next-serve candidate
1531 prev = cfqq->next_rq;
1532 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
1535 * adjust priority tree position, if ->next_rq changes
1537 if (prev != cfqq->next_rq)
1538 cfq_prio_tree_add(cfqd, cfqq);
1540 BUG_ON(!cfqq->next_rq);
1543 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
1545 elv_rb_del(&cfqq->sort_list, rq);
1546 cfqq->queued[rq_is_sync(rq)]--;
1547 cfq_blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg,
1548 rq_data_dir(rq), rq_is_sync(rq));
1550 cfq_blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg,
1551 &cfqq->cfqd->serving_group->blkg, rq_data_dir(rq),
1555 static struct request *
1556 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
1558 struct task_struct *tsk = current;
1559 struct cfq_io_context *cic;
1560 struct cfq_queue *cfqq;
1562 cic = cfq_cic_lookup(cfqd, tsk->io_context);
1566 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1568 sector_t sector = bio->bi_sector + bio_sectors(bio);
1570 return elv_rb_find(&cfqq->sort_list, sector);
1576 static void cfq_activate_request(struct request_queue *q, struct request *rq)
1578 struct cfq_data *cfqd = q->elevator->elevator_data;
1580 cfqd->rq_in_driver++;
1581 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
1582 cfqd->rq_in_driver);
1584 cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
1587 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
1589 struct cfq_data *cfqd = q->elevator->elevator_data;
1591 WARN_ON(!cfqd->rq_in_driver);
1592 cfqd->rq_in_driver--;
1593 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
1594 cfqd->rq_in_driver);
1597 static void cfq_remove_request(struct request *rq)
1599 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1601 if (cfqq->next_rq == rq)
1602 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
1604 list_del_init(&rq->queuelist);
1607 cfqq->cfqd->rq_queued--;
1608 cfq_blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg,
1609 rq_data_dir(rq), rq_is_sync(rq));
1612 static int cfq_merge(struct request_queue *q, struct request **req,
1615 struct cfq_data *cfqd = q->elevator->elevator_data;
1616 struct request *__rq;
1618 __rq = cfq_find_rq_fmerge(cfqd, bio);
1619 if (__rq && elv_rq_merge_ok(__rq, bio)) {
1621 return ELEVATOR_FRONT_MERGE;
1624 return ELEVATOR_NO_MERGE;
1627 static void cfq_merged_request(struct request_queue *q, struct request *req,
1630 if (type == ELEVATOR_FRONT_MERGE) {
1631 struct cfq_queue *cfqq = RQ_CFQQ(req);
1633 cfq_reposition_rq_rb(cfqq, req);
1637 static void cfq_bio_merged(struct request_queue *q, struct request *req,
1640 cfq_blkiocg_update_io_merged_stats(&(RQ_CFQG(req))->blkg,
1641 bio_data_dir(bio), cfq_bio_sync(bio));
1645 cfq_merged_requests(struct request_queue *q, struct request *rq,
1646 struct request *next)
1648 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1650 * reposition in fifo if next is older than rq
1652 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
1653 time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
1654 list_move(&rq->queuelist, &next->queuelist);
1655 rq_set_fifo_time(rq, rq_fifo_time(next));
1658 if (cfqq->next_rq == next)
1660 cfq_remove_request(next);
1661 cfq_blkiocg_update_io_merged_stats(&(RQ_CFQG(rq))->blkg,
1662 rq_data_dir(next), rq_is_sync(next));
1665 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
1668 struct cfq_data *cfqd = q->elevator->elevator_data;
1669 struct cfq_io_context *cic;
1670 struct cfq_queue *cfqq;
1673 * Disallow merge of a sync bio into an async request.
1675 if (cfq_bio_sync(bio) && !rq_is_sync(rq))
1679 * Lookup the cfqq that this bio will be queued with. Allow
1680 * merge only if rq is queued there.
1682 cic = cfq_cic_lookup(cfqd, current->io_context);
1686 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1687 return cfqq == RQ_CFQQ(rq);
1690 static inline void cfq_del_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1692 del_timer(&cfqd->idle_slice_timer);
1693 cfq_blkiocg_update_idle_time_stats(&cfqq->cfqg->blkg);
1696 static void __cfq_set_active_queue(struct cfq_data *cfqd,
1697 struct cfq_queue *cfqq)
1700 cfq_log_cfqq(cfqd, cfqq, "set_active wl_prio:%d wl_type:%d",
1701 cfqd->serving_prio, cfqd->serving_type);
1702 cfq_blkiocg_update_avg_queue_size_stats(&cfqq->cfqg->blkg);
1703 cfqq->slice_start = 0;
1704 cfqq->dispatch_start = jiffies;
1705 cfqq->allocated_slice = 0;
1706 cfqq->slice_end = 0;
1707 cfqq->slice_dispatch = 0;
1708 cfqq->nr_sectors = 0;
1710 cfq_clear_cfqq_wait_request(cfqq);
1711 cfq_clear_cfqq_must_dispatch(cfqq);
1712 cfq_clear_cfqq_must_alloc_slice(cfqq);
1713 cfq_clear_cfqq_fifo_expire(cfqq);
1714 cfq_mark_cfqq_slice_new(cfqq);
1716 cfq_del_timer(cfqd, cfqq);
1719 cfqd->active_queue = cfqq;
1723 * current cfqq expired its slice (or was too idle), select new one
1726 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1729 cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
1731 if (cfq_cfqq_wait_request(cfqq))
1732 cfq_del_timer(cfqd, cfqq);
1734 cfq_clear_cfqq_wait_request(cfqq);
1735 cfq_clear_cfqq_wait_busy(cfqq);
1738 * If this cfqq is shared between multiple processes, check to
1739 * make sure that those processes are still issuing I/Os within
1740 * the mean seek distance. If not, it may be time to break the
1741 * queues apart again.
1743 if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq))
1744 cfq_mark_cfqq_split_coop(cfqq);
1747 * store what was left of this slice, if the queue idled/timed out
1750 if (cfq_cfqq_slice_new(cfqq))
1751 cfqq->slice_resid = cfq_scaled_cfqq_slice(cfqd, cfqq);
1753 cfqq->slice_resid = cfqq->slice_end - jiffies;
1754 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
1757 cfq_group_served(cfqd, cfqq->cfqg, cfqq);
1759 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
1760 cfq_del_cfqq_rr(cfqd, cfqq);
1762 cfq_resort_rr_list(cfqd, cfqq);
1764 if (cfqq == cfqd->active_queue)
1765 cfqd->active_queue = NULL;
1767 if (cfqd->active_cic) {
1768 put_io_context(cfqd->active_cic->ioc);
1769 cfqd->active_cic = NULL;
1773 static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
1775 struct cfq_queue *cfqq = cfqd->active_queue;
1778 __cfq_slice_expired(cfqd, cfqq, timed_out);
1782 * Get next queue for service. Unless we have a queue preemption,
1783 * we'll simply select the first cfqq in the service tree.
1785 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
1787 struct cfq_rb_root *service_tree =
1788 service_tree_for(cfqd->serving_group, cfqd->serving_prio,
1789 cfqd->serving_type);
1791 if (!cfqd->rq_queued)
1794 /* There is nothing to dispatch */
1797 if (RB_EMPTY_ROOT(&service_tree->rb))
1799 return cfq_rb_first(service_tree);
1802 static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
1804 struct cfq_group *cfqg;
1805 struct cfq_queue *cfqq;
1807 struct cfq_rb_root *st;
1809 if (!cfqd->rq_queued)
1812 cfqg = cfq_get_next_cfqg(cfqd);
1816 for_each_cfqg_st(cfqg, i, j, st)
1817 if ((cfqq = cfq_rb_first(st)) != NULL)
1823 * Get and set a new active queue for service.
1825 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
1826 struct cfq_queue *cfqq)
1829 cfqq = cfq_get_next_queue(cfqd);
1831 __cfq_set_active_queue(cfqd, cfqq);
1835 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
1838 if (blk_rq_pos(rq) >= cfqd->last_position)
1839 return blk_rq_pos(rq) - cfqd->last_position;
1841 return cfqd->last_position - blk_rq_pos(rq);
1844 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1847 return cfq_dist_from_last(cfqd, rq) <= CFQQ_CLOSE_THR;
1850 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
1851 struct cfq_queue *cur_cfqq)
1853 struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
1854 struct rb_node *parent, *node;
1855 struct cfq_queue *__cfqq;
1856 sector_t sector = cfqd->last_position;
1858 if (RB_EMPTY_ROOT(root))
1862 * First, if we find a request starting at the end of the last
1863 * request, choose it.
1865 __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
1870 * If the exact sector wasn't found, the parent of the NULL leaf
1871 * will contain the closest sector.
1873 __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1874 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1877 if (blk_rq_pos(__cfqq->next_rq) < sector)
1878 node = rb_next(&__cfqq->p_node);
1880 node = rb_prev(&__cfqq->p_node);
1884 __cfqq = rb_entry(node, struct cfq_queue, p_node);
1885 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1893 * cur_cfqq - passed in so that we don't decide that the current queue is
1894 * closely cooperating with itself.
1896 * So, basically we're assuming that that cur_cfqq has dispatched at least
1897 * one request, and that cfqd->last_position reflects a position on the disk
1898 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
1901 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1902 struct cfq_queue *cur_cfqq)
1904 struct cfq_queue *cfqq;
1906 if (cfq_class_idle(cur_cfqq))
1908 if (!cfq_cfqq_sync(cur_cfqq))
1910 if (CFQQ_SEEKY(cur_cfqq))
1914 * Don't search priority tree if it's the only queue in the group.
1916 if (cur_cfqq->cfqg->nr_cfqq == 1)
1920 * We should notice if some of the queues are cooperating, eg
1921 * working closely on the same area of the disk. In that case,
1922 * we can group them together and don't waste time idling.
1924 cfqq = cfqq_close(cfqd, cur_cfqq);
1928 /* If new queue belongs to different cfq_group, don't choose it */
1929 if (cur_cfqq->cfqg != cfqq->cfqg)
1933 * It only makes sense to merge sync queues.
1935 if (!cfq_cfqq_sync(cfqq))
1937 if (CFQQ_SEEKY(cfqq))
1941 * Do not merge queues of different priority classes
1943 if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
1950 * Determine whether we should enforce idle window for this queue.
1953 static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1955 enum wl_prio_t prio = cfqq_prio(cfqq);
1956 struct cfq_rb_root *service_tree = cfqq->service_tree;
1958 BUG_ON(!service_tree);
1959 BUG_ON(!service_tree->count);
1961 if (!cfqd->cfq_slice_idle)
1964 /* We never do for idle class queues. */
1965 if (prio == IDLE_WORKLOAD)
1968 /* We do for queues that were marked with idle window flag. */
1969 if (cfq_cfqq_idle_window(cfqq) &&
1970 !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag))
1974 * Otherwise, we do only if they are the last ones
1975 * in their service tree.
1977 if (service_tree->count == 1 && cfq_cfqq_sync(cfqq) &&
1978 !cfq_io_thinktime_big(cfqd, &service_tree->ttime, false))
1980 cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d",
1981 service_tree->count);
1985 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
1987 struct cfq_queue *cfqq = cfqd->active_queue;
1988 struct cfq_io_context *cic;
1989 unsigned long sl, group_idle = 0;
1992 * SSD device without seek penalty, disable idling. But only do so
1993 * for devices that support queuing, otherwise we still have a problem
1994 * with sync vs async workloads.
1996 if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
1999 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
2000 WARN_ON(cfq_cfqq_slice_new(cfqq));
2003 * idle is disabled, either manually or by past process history
2005 if (!cfq_should_idle(cfqd, cfqq)) {
2006 /* no queue idling. Check for group idling */
2007 if (cfqd->cfq_group_idle)
2008 group_idle = cfqd->cfq_group_idle;
2014 * still active requests from this queue, don't idle
2016 if (cfqq->dispatched)
2020 * task has exited, don't wait
2022 cic = cfqd->active_cic;
2023 if (!cic || !atomic_read(&cic->ioc->nr_tasks))
2027 * If our average think time is larger than the remaining time
2028 * slice, then don't idle. This avoids overrunning the allotted
2031 if (sample_valid(cic->ttime.ttime_samples) &&
2032 (cfqq->slice_end - jiffies < cic->ttime.ttime_mean)) {
2033 cfq_log_cfqq(cfqd, cfqq, "Not idling. think_time:%lu",
2034 cic->ttime.ttime_mean);
2038 /* There are other queues in the group, don't do group idle */
2039 if (group_idle && cfqq->cfqg->nr_cfqq > 1)
2042 cfq_mark_cfqq_wait_request(cfqq);
2045 sl = cfqd->cfq_group_idle;
2047 sl = cfqd->cfq_slice_idle;
2049 mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
2050 cfq_blkiocg_update_set_idle_time_stats(&cfqq->cfqg->blkg);
2051 cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu group_idle: %d", sl,
2052 group_idle ? 1 : 0);
2056 * Move request from internal lists to the request queue dispatch list.
2058 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
2060 struct cfq_data *cfqd = q->elevator->elevator_data;
2061 struct cfq_queue *cfqq = RQ_CFQQ(rq);
2063 cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
2065 cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
2066 cfq_remove_request(rq);
2068 (RQ_CFQG(rq))->dispatched++;
2069 elv_dispatch_sort(q, rq);
2071 cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
2072 cfqq->nr_sectors += blk_rq_sectors(rq);
2073 cfq_blkiocg_update_dispatch_stats(&cfqq->cfqg->blkg, blk_rq_bytes(rq),
2074 rq_data_dir(rq), rq_is_sync(rq));
2078 * return expired entry, or NULL to just start from scratch in rbtree
2080 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
2082 struct request *rq = NULL;
2084 if (cfq_cfqq_fifo_expire(cfqq))
2087 cfq_mark_cfqq_fifo_expire(cfqq);
2089 if (list_empty(&cfqq->fifo))
2092 rq = rq_entry_fifo(cfqq->fifo.next);
2093 if (time_before(jiffies, rq_fifo_time(rq)))
2096 cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
2101 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2103 const int base_rq = cfqd->cfq_slice_async_rq;
2105 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
2107 return 2 * base_rq * (IOPRIO_BE_NR - cfqq->ioprio);
2111 * Must be called with the queue_lock held.
2113 static int cfqq_process_refs(struct cfq_queue *cfqq)
2115 int process_refs, io_refs;
2117 io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
2118 process_refs = cfqq->ref - io_refs;
2119 BUG_ON(process_refs < 0);
2120 return process_refs;
2123 static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
2125 int process_refs, new_process_refs;
2126 struct cfq_queue *__cfqq;
2129 * If there are no process references on the new_cfqq, then it is
2130 * unsafe to follow the ->new_cfqq chain as other cfqq's in the
2131 * chain may have dropped their last reference (not just their
2132 * last process reference).
2134 if (!cfqq_process_refs(new_cfqq))
2137 /* Avoid a circular list and skip interim queue merges */
2138 while ((__cfqq = new_cfqq->new_cfqq)) {
2144 process_refs = cfqq_process_refs(cfqq);
2145 new_process_refs = cfqq_process_refs(new_cfqq);
2147 * If the process for the cfqq has gone away, there is no
2148 * sense in merging the queues.
2150 if (process_refs == 0 || new_process_refs == 0)
2154 * Merge in the direction of the lesser amount of work.
2156 if (new_process_refs >= process_refs) {
2157 cfqq->new_cfqq = new_cfqq;
2158 new_cfqq->ref += process_refs;
2160 new_cfqq->new_cfqq = cfqq;
2161 cfqq->ref += new_process_refs;
2165 static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
2166 struct cfq_group *cfqg, enum wl_prio_t prio)
2168 struct cfq_queue *queue;
2170 bool key_valid = false;
2171 unsigned long lowest_key = 0;
2172 enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
2174 for (i = 0; i <= SYNC_WORKLOAD; ++i) {
2175 /* select the one with lowest rb_key */
2176 queue = cfq_rb_first(service_tree_for(cfqg, prio, i));
2178 (!key_valid || time_before(queue->rb_key, lowest_key))) {
2179 lowest_key = queue->rb_key;
2188 static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
2192 struct cfq_rb_root *st;
2193 unsigned group_slice;
2194 enum wl_prio_t original_prio = cfqd->serving_prio;
2196 /* Choose next priority. RT > BE > IDLE */
2197 if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
2198 cfqd->serving_prio = RT_WORKLOAD;
2199 else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
2200 cfqd->serving_prio = BE_WORKLOAD;
2202 cfqd->serving_prio = IDLE_WORKLOAD;
2203 cfqd->workload_expires = jiffies + 1;
2207 if (original_prio != cfqd->serving_prio)
2211 * For RT and BE, we have to choose also the type
2212 * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
2215 st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
2219 * check workload expiration, and that we still have other queues ready
2221 if (count && !time_after(jiffies, cfqd->workload_expires))
2225 /* otherwise select new workload type */
2226 cfqd->serving_type =
2227 cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio);
2228 st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
2232 * the workload slice is computed as a fraction of target latency
2233 * proportional to the number of queues in that workload, over
2234 * all the queues in the same priority class
2236 group_slice = cfq_group_slice(cfqd, cfqg);
2238 slice = group_slice * count /
2239 max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio],
2240 cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg));
2242 if (cfqd->serving_type == ASYNC_WORKLOAD) {
2246 * Async queues are currently system wide. Just taking
2247 * proportion of queues with-in same group will lead to higher
2248 * async ratio system wide as generally root group is going
2249 * to have higher weight. A more accurate thing would be to
2250 * calculate system wide asnc/sync ratio.
2252 tmp = cfq_target_latency * cfqg_busy_async_queues(cfqd, cfqg);
2253 tmp = tmp/cfqd->busy_queues;
2254 slice = min_t(unsigned, slice, tmp);
2256 /* async workload slice is scaled down according to
2257 * the sync/async slice ratio. */
2258 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
2260 /* sync workload slice is at least 2 * cfq_slice_idle */
2261 slice = max(slice, 2 * cfqd->cfq_slice_idle);
2263 slice = max_t(unsigned, slice, CFQ_MIN_TT);
2264 cfq_log(cfqd, "workload slice:%d", slice);
2265 cfqd->workload_expires = jiffies + slice;
2268 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
2270 struct cfq_rb_root *st = &cfqd->grp_service_tree;
2271 struct cfq_group *cfqg;
2273 if (RB_EMPTY_ROOT(&st->rb))
2275 cfqg = cfq_rb_first_group(st);
2276 update_min_vdisktime(st);
2280 static void cfq_choose_cfqg(struct cfq_data *cfqd)
2282 struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
2284 cfqd->serving_group = cfqg;
2286 /* Restore the workload type data */
2287 if (cfqg->saved_workload_slice) {
2288 cfqd->workload_expires = jiffies + cfqg->saved_workload_slice;
2289 cfqd->serving_type = cfqg->saved_workload;
2290 cfqd->serving_prio = cfqg->saved_serving_prio;
2292 cfqd->workload_expires = jiffies - 1;
2294 choose_service_tree(cfqd, cfqg);
2298 * Select a queue for service. If we have a current active queue,
2299 * check whether to continue servicing it, or retrieve and set a new one.
2301 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
2303 struct cfq_queue *cfqq, *new_cfqq = NULL;
2305 cfqq = cfqd->active_queue;
2309 if (!cfqd->rq_queued)
2313 * We were waiting for group to get backlogged. Expire the queue
2315 if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list))
2319 * The active queue has run out of time, expire it and select new.
2321 if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) {
2323 * If slice had not expired at the completion of last request
2324 * we might not have turned on wait_busy flag. Don't expire
2325 * the queue yet. Allow the group to get backlogged.
2327 * The very fact that we have used the slice, that means we
2328 * have been idling all along on this queue and it should be
2329 * ok to wait for this request to complete.
2331 if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list)
2332 && cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
2336 goto check_group_idle;
2340 * The active queue has requests and isn't expired, allow it to
2343 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
2347 * If another queue has a request waiting within our mean seek
2348 * distance, let it run. The expire code will check for close
2349 * cooperators and put the close queue at the front of the service
2350 * tree. If possible, merge the expiring queue with the new cfqq.
2352 new_cfqq = cfq_close_cooperator(cfqd, cfqq);
2354 if (!cfqq->new_cfqq)
2355 cfq_setup_merge(cfqq, new_cfqq);
2360 * No requests pending. If the active queue still has requests in
2361 * flight or is idling for a new request, allow either of these
2362 * conditions to happen (or time out) before selecting a new queue.
2364 if (timer_pending(&cfqd->idle_slice_timer)) {
2370 * This is a deep seek queue, but the device is much faster than
2371 * the queue can deliver, don't idle
2373 if (CFQQ_SEEKY(cfqq) && cfq_cfqq_idle_window(cfqq) &&
2374 (cfq_cfqq_slice_new(cfqq) ||
2375 (cfqq->slice_end - jiffies > jiffies - cfqq->slice_start))) {
2376 cfq_clear_cfqq_deep(cfqq);
2377 cfq_clear_cfqq_idle_window(cfqq);
2380 if (cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
2386 * If group idle is enabled and there are requests dispatched from
2387 * this group, wait for requests to complete.
2390 if (cfqd->cfq_group_idle && cfqq->cfqg->nr_cfqq == 1 &&
2391 cfqq->cfqg->dispatched &&
2392 !cfq_io_thinktime_big(cfqd, &cfqq->cfqg->ttime, true)) {
2398 cfq_slice_expired(cfqd, 0);
2401 * Current queue expired. Check if we have to switch to a new
2405 cfq_choose_cfqg(cfqd);
2407 cfqq = cfq_set_active_queue(cfqd, new_cfqq);
2412 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
2416 while (cfqq->next_rq) {
2417 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
2421 BUG_ON(!list_empty(&cfqq->fifo));
2423 /* By default cfqq is not expired if it is empty. Do it explicitly */
2424 __cfq_slice_expired(cfqq->cfqd, cfqq, 0);
2429 * Drain our current requests. Used for barriers and when switching
2430 * io schedulers on-the-fly.
2432 static int cfq_forced_dispatch(struct cfq_data *cfqd)
2434 struct cfq_queue *cfqq;
2437 /* Expire the timeslice of the current active queue first */
2438 cfq_slice_expired(cfqd, 0);
2439 while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL) {
2440 __cfq_set_active_queue(cfqd, cfqq);
2441 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
2444 BUG_ON(cfqd->busy_queues);
2446 cfq_log(cfqd, "forced_dispatch=%d", dispatched);
2450 static inline bool cfq_slice_used_soon(struct cfq_data *cfqd,
2451 struct cfq_queue *cfqq)
2453 /* the queue hasn't finished any request, can't estimate */
2454 if (cfq_cfqq_slice_new(cfqq))
2456 if (time_after(jiffies + cfqd->cfq_slice_idle * cfqq->dispatched,
2463 static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2465 unsigned int max_dispatch;
2468 * Drain async requests before we start sync IO
2470 if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_flight[BLK_RW_ASYNC])
2474 * If this is an async queue and we have sync IO in flight, let it wait
2476 if (cfqd->rq_in_flight[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq))
2479 max_dispatch = max_t(unsigned int, cfqd->cfq_quantum / 2, 1);
2480 if (cfq_class_idle(cfqq))
2484 * Does this cfqq already have too much IO in flight?
2486 if (cfqq->dispatched >= max_dispatch) {
2487 bool promote_sync = false;
2489 * idle queue must always only have a single IO in flight
2491 if (cfq_class_idle(cfqq))
2495 * If there is only one sync queue
2496 * we can ignore async queue here and give the sync
2497 * queue no dispatch limit. The reason is a sync queue can
2498 * preempt async queue, limiting the sync queue doesn't make
2499 * sense. This is useful for aiostress test.
2501 if (cfq_cfqq_sync(cfqq) && cfqd->busy_sync_queues == 1)
2502 promote_sync = true;
2505 * We have other queues, don't allow more IO from this one
2507 if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq) &&
2512 * Sole queue user, no limit
2514 if (cfqd->busy_queues == 1 || promote_sync)
2518 * Normally we start throttling cfqq when cfq_quantum/2
2519 * requests have been dispatched. But we can drive
2520 * deeper queue depths at the beginning of slice
2521 * subjected to upper limit of cfq_quantum.
2523 max_dispatch = cfqd->cfq_quantum;
2527 * Async queues must wait a bit before being allowed dispatch.
2528 * We also ramp up the dispatch depth gradually for async IO,
2529 * based on the last sync IO we serviced
2531 if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
2532 unsigned long last_sync = jiffies - cfqd->last_delayed_sync;
2535 depth = last_sync / cfqd->cfq_slice[1];
2536 if (!depth && !cfqq->dispatched)
2538 if (depth < max_dispatch)
2539 max_dispatch = depth;
2543 * If we're below the current max, allow a dispatch
2545 return cfqq->dispatched < max_dispatch;
2549 * Dispatch a request from cfqq, moving them to the request queue
2552 static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2556 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
2558 if (!cfq_may_dispatch(cfqd, cfqq))
2562 * follow expired path, else get first next available
2564 rq = cfq_check_fifo(cfqq);
2569 * insert request into driver dispatch list
2571 cfq_dispatch_insert(cfqd->queue, rq);
2573 if (!cfqd->active_cic) {
2574 struct cfq_io_context *cic = RQ_CIC(rq);
2576 atomic_long_inc(&cic->ioc->refcount);
2577 cfqd->active_cic = cic;
2584 * Find the cfqq that we need to service and move a request from that to the
2587 static int cfq_dispatch_requests(struct request_queue *q, int force)
2589 struct cfq_data *cfqd = q->elevator->elevator_data;
2590 struct cfq_queue *cfqq;
2592 if (!cfqd->busy_queues)
2595 if (unlikely(force))
2596 return cfq_forced_dispatch(cfqd);
2598 cfqq = cfq_select_queue(cfqd);
2603 * Dispatch a request from this cfqq, if it is allowed
2605 if (!cfq_dispatch_request(cfqd, cfqq))
2608 cfqq->slice_dispatch++;
2609 cfq_clear_cfqq_must_dispatch(cfqq);
2612 * expire an async queue immediately if it has used up its slice. idle
2613 * queue always expire after 1 dispatch round.
2615 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
2616 cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
2617 cfq_class_idle(cfqq))) {
2618 cfqq->slice_end = jiffies + 1;
2619 cfq_slice_expired(cfqd, 0);
2622 cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
2627 * task holds one reference to the queue, dropped when task exits. each rq
2628 * in-flight on this queue also holds a reference, dropped when rq is freed.
2630 * Each cfq queue took a reference on the parent group. Drop it now.
2631 * queue lock must be held here.
2633 static void cfq_put_queue(struct cfq_queue *cfqq)
2635 struct cfq_data *cfqd = cfqq->cfqd;
2636 struct cfq_group *cfqg;
2638 BUG_ON(cfqq->ref <= 0);
2644 cfq_log_cfqq(cfqd, cfqq, "put_queue");
2645 BUG_ON(rb_first(&cfqq->sort_list));
2646 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
2649 if (unlikely(cfqd->active_queue == cfqq)) {
2650 __cfq_slice_expired(cfqd, cfqq, 0);
2651 cfq_schedule_dispatch(cfqd);
2654 BUG_ON(cfq_cfqq_on_rr(cfqq));
2655 kmem_cache_free(cfq_pool, cfqq);
2660 * Call func for each cic attached to this ioc.
2663 call_for_each_cic(struct io_context *ioc,
2664 void (*func)(struct io_context *, struct cfq_io_context *))
2666 struct cfq_io_context *cic;
2667 struct hlist_node *n;
2671 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
2677 static void cfq_cic_free_rcu(struct rcu_head *head)
2679 struct cfq_io_context *cic;
2681 cic = container_of(head, struct cfq_io_context, rcu_head);
2683 kmem_cache_free(cfq_ioc_pool, cic);
2684 elv_ioc_count_dec(cfq_ioc_count);
2688 * CFQ scheduler is exiting, grab exit lock and check
2689 * the pending io context count. If it hits zero,
2690 * complete ioc_gone and set it back to NULL
2692 spin_lock(&ioc_gone_lock);
2693 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
2697 spin_unlock(&ioc_gone_lock);
2701 static void cfq_cic_free(struct cfq_io_context *cic)
2703 call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
2706 static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
2708 unsigned long flags;
2709 unsigned long dead_key = (unsigned long) cic->key;
2711 BUG_ON(!(dead_key & CIC_DEAD_KEY));
2713 spin_lock_irqsave(&ioc->lock, flags);
2714 radix_tree_delete(&ioc->radix_root, dead_key >> CIC_DEAD_INDEX_SHIFT);
2715 hlist_del_rcu(&cic->cic_list);
2716 spin_unlock_irqrestore(&ioc->lock, flags);
2722 * Must be called with rcu_read_lock() held or preemption otherwise disabled.
2723 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
2724 * and ->trim() which is called with the task lock held
2726 static void cfq_free_io_context(struct io_context *ioc)
2729 * ioc->refcount is zero here, or we are called from elv_unregister(),
2730 * so no more cic's are allowed to be linked into this ioc. So it
2731 * should be ok to iterate over the known list, we will see all cic's
2732 * since no new ones are added.
2734 call_for_each_cic(ioc, cic_free_func);
2737 static void cfq_put_cooperator(struct cfq_queue *cfqq)
2739 struct cfq_queue *__cfqq, *next;
2742 * If this queue was scheduled to merge with another queue, be
2743 * sure to drop the reference taken on that queue (and others in
2744 * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs.
2746 __cfqq = cfqq->new_cfqq;
2748 if (__cfqq == cfqq) {
2749 WARN(1, "cfqq->new_cfqq loop detected\n");
2752 next = __cfqq->new_cfqq;
2753 cfq_put_queue(__cfqq);
2758 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2760 if (unlikely(cfqq == cfqd->active_queue)) {
2761 __cfq_slice_expired(cfqd, cfqq, 0);
2762 cfq_schedule_dispatch(cfqd);
2765 cfq_put_cooperator(cfqq);
2767 cfq_put_queue(cfqq);
2770 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
2771 struct cfq_io_context *cic)
2773 struct io_context *ioc = cic->ioc;
2775 list_del_init(&cic->queue_list);
2778 * Make sure dead mark is seen for dead queues
2781 cic->key = cfqd_dead_key(cfqd);
2784 if (rcu_dereference(ioc->ioc_data) == cic) {
2786 spin_lock(&ioc->lock);
2787 rcu_assign_pointer(ioc->ioc_data, NULL);
2788 spin_unlock(&ioc->lock);
2792 if (cic->cfqq[BLK_RW_ASYNC]) {
2793 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
2794 cic->cfqq[BLK_RW_ASYNC] = NULL;
2797 if (cic->cfqq[BLK_RW_SYNC]) {
2798 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
2799 cic->cfqq[BLK_RW_SYNC] = NULL;
2803 static void cfq_exit_single_io_context(struct io_context *ioc,
2804 struct cfq_io_context *cic)
2806 struct cfq_data *cfqd = cic_to_cfqd(cic);
2809 struct request_queue *q = cfqd->queue;
2810 unsigned long flags;
2812 spin_lock_irqsave(q->queue_lock, flags);
2815 * Ensure we get a fresh copy of the ->key to prevent
2816 * race between exiting task and queue
2818 smp_read_barrier_depends();
2819 if (cic->key == cfqd)
2820 __cfq_exit_single_io_context(cfqd, cic);
2822 spin_unlock_irqrestore(q->queue_lock, flags);
2827 * The process that ioc belongs to has exited, we need to clean up
2828 * and put the internal structures we have that belongs to that process.
2830 static void cfq_exit_io_context(struct io_context *ioc)
2832 call_for_each_cic(ioc, cfq_exit_single_io_context);
2835 static struct cfq_io_context *
2836 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2838 struct cfq_io_context *cic;
2840 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
2843 cic->ttime.last_end_request = jiffies;
2844 INIT_LIST_HEAD(&cic->queue_list);
2845 INIT_HLIST_NODE(&cic->cic_list);
2846 cic->dtor = cfq_free_io_context;
2847 cic->exit = cfq_exit_io_context;
2848 elv_ioc_count_inc(cfq_ioc_count);
2854 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
2856 struct task_struct *tsk = current;
2859 if (!cfq_cfqq_prio_changed(cfqq))
2862 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
2863 switch (ioprio_class) {
2865 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
2866 case IOPRIO_CLASS_NONE:
2868 * no prio set, inherit CPU scheduling settings
2870 cfqq->ioprio = task_nice_ioprio(tsk);
2871 cfqq->ioprio_class = task_nice_ioclass(tsk);
2873 case IOPRIO_CLASS_RT:
2874 cfqq->ioprio = task_ioprio(ioc);
2875 cfqq->ioprio_class = IOPRIO_CLASS_RT;
2877 case IOPRIO_CLASS_BE:
2878 cfqq->ioprio = task_ioprio(ioc);
2879 cfqq->ioprio_class = IOPRIO_CLASS_BE;
2881 case IOPRIO_CLASS_IDLE:
2882 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
2884 cfq_clear_cfqq_idle_window(cfqq);
2889 * keep track of original prio settings in case we have to temporarily
2890 * elevate the priority of this queue
2892 cfqq->org_ioprio = cfqq->ioprio;
2893 cfq_clear_cfqq_prio_changed(cfqq);
2896 static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
2898 struct cfq_data *cfqd = cic_to_cfqd(cic);
2899 struct cfq_queue *cfqq;
2900 unsigned long flags;
2902 if (unlikely(!cfqd))
2905 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2907 cfqq = cic->cfqq[BLK_RW_ASYNC];
2909 struct cfq_queue *new_cfqq;
2910 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
2913 cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
2914 cfq_put_queue(cfqq);
2918 cfqq = cic->cfqq[BLK_RW_SYNC];
2920 cfq_mark_cfqq_prio_changed(cfqq);
2922 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2925 static void cfq_ioc_set_ioprio(struct io_context *ioc)
2927 call_for_each_cic(ioc, changed_ioprio);
2928 ioc->ioprio_changed = 0;
2931 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2932 pid_t pid, bool is_sync)
2934 RB_CLEAR_NODE(&cfqq->rb_node);
2935 RB_CLEAR_NODE(&cfqq->p_node);
2936 INIT_LIST_HEAD(&cfqq->fifo);
2941 cfq_mark_cfqq_prio_changed(cfqq);
2944 if (!cfq_class_idle(cfqq))
2945 cfq_mark_cfqq_idle_window(cfqq);
2946 cfq_mark_cfqq_sync(cfqq);
2951 #ifdef CONFIG_CFQ_GROUP_IOSCHED
2952 static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
2954 struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1);
2955 struct cfq_data *cfqd = cic_to_cfqd(cic);
2956 unsigned long flags;
2957 struct request_queue *q;
2959 if (unlikely(!cfqd))
2964 spin_lock_irqsave(q->queue_lock, flags);
2968 * Drop reference to sync queue. A new sync queue will be
2969 * assigned in new group upon arrival of a fresh request.
2971 cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
2972 cic_set_cfqq(cic, NULL, 1);
2973 cfq_put_queue(sync_cfqq);
2976 spin_unlock_irqrestore(q->queue_lock, flags);
2979 static void cfq_ioc_set_cgroup(struct io_context *ioc)
2981 call_for_each_cic(ioc, changed_cgroup);
2982 ioc->cgroup_changed = 0;
2984 #endif /* CONFIG_CFQ_GROUP_IOSCHED */
2986 static struct cfq_queue *
2987 cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
2988 struct io_context *ioc, gfp_t gfp_mask)
2990 struct cfq_queue *cfqq, *new_cfqq = NULL;
2991 struct cfq_io_context *cic;
2992 struct cfq_group *cfqg;
2995 cfqg = cfq_get_cfqg(cfqd);
2996 cic = cfq_cic_lookup(cfqd, ioc);
2997 /* cic always exists here */
2998 cfqq = cic_to_cfqq(cic, is_sync);
3001 * Always try a new alloc if we fell back to the OOM cfqq
3002 * originally, since it should just be a temporary situation.
3004 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
3009 } else if (gfp_mask & __GFP_WAIT) {
3010 spin_unlock_irq(cfqd->queue->queue_lock);
3011 new_cfqq = kmem_cache_alloc_node(cfq_pool,
3012 gfp_mask | __GFP_ZERO,
3014 spin_lock_irq(cfqd->queue->queue_lock);
3018 cfqq = kmem_cache_alloc_node(cfq_pool,
3019 gfp_mask | __GFP_ZERO,
3024 cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
3025 cfq_init_prio_data(cfqq, ioc);
3026 cfq_link_cfqq_cfqg(cfqq, cfqg);
3027 cfq_log_cfqq(cfqd, cfqq, "alloced");
3029 cfqq = &cfqd->oom_cfqq;
3033 kmem_cache_free(cfq_pool, new_cfqq);
3038 static struct cfq_queue **
3039 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
3041 switch (ioprio_class) {
3042 case IOPRIO_CLASS_RT:
3043 return &cfqd->async_cfqq[0][ioprio];
3044 case IOPRIO_CLASS_BE:
3045 return &cfqd->async_cfqq[1][ioprio];
3046 case IOPRIO_CLASS_IDLE:
3047 return &cfqd->async_idle_cfqq;
3053 static struct cfq_queue *
3054 cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
3057 const int ioprio = task_ioprio(ioc);
3058 const int ioprio_class = task_ioprio_class(ioc);
3059 struct cfq_queue **async_cfqq = NULL;
3060 struct cfq_queue *cfqq = NULL;
3063 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
3068 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
3071 * pin the queue now that it's allocated, scheduler exit will prune it
3073 if (!is_sync && !(*async_cfqq)) {
3083 * We drop cfq io contexts lazily, so we may find a dead one.
3086 cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
3087 struct cfq_io_context *cic)
3089 unsigned long flags;
3091 WARN_ON(!list_empty(&cic->queue_list));
3092 BUG_ON(cic->key != cfqd_dead_key(cfqd));
3094 spin_lock_irqsave(&ioc->lock, flags);
3096 BUG_ON(rcu_dereference_check(ioc->ioc_data,
3097 lockdep_is_held(&ioc->lock)) == cic);
3099 radix_tree_delete(&ioc->radix_root, cfqd->cic_index);
3100 hlist_del_rcu(&cic->cic_list);
3101 spin_unlock_irqrestore(&ioc->lock, flags);
3106 static struct cfq_io_context *
3107 cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
3109 struct cfq_io_context *cic;
3110 unsigned long flags;
3118 * we maintain a last-hit cache, to avoid browsing over the tree
3120 cic = rcu_dereference(ioc->ioc_data);
3121 if (cic && cic->key == cfqd) {
3127 cic = radix_tree_lookup(&ioc->radix_root, cfqd->cic_index);
3131 if (unlikely(cic->key != cfqd)) {
3132 cfq_drop_dead_cic(cfqd, ioc, cic);
3137 spin_lock_irqsave(&ioc->lock, flags);
3138 rcu_assign_pointer(ioc->ioc_data, cic);
3139 spin_unlock_irqrestore(&ioc->lock, flags);
3147 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
3148 * the process specific cfq io context when entered from the block layer.
3149 * Also adds the cic to a per-cfqd list, used when this queue is removed.
3151 static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
3152 struct cfq_io_context *cic, gfp_t gfp_mask)
3154 unsigned long flags;
3157 ret = radix_tree_preload(gfp_mask);
3162 spin_lock_irqsave(&ioc->lock, flags);
3163 ret = radix_tree_insert(&ioc->radix_root,
3164 cfqd->cic_index, cic);
3166 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
3167 spin_unlock_irqrestore(&ioc->lock, flags);
3169 radix_tree_preload_end();
3172 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
3173 list_add(&cic->queue_list, &cfqd->cic_list);
3174 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
3179 printk(KERN_ERR "cfq: cic link failed!\n");
3185 * Setup general io context and cfq io context. There can be several cfq
3186 * io contexts per general io context, if this process is doing io to more
3187 * than one device managed by cfq.
3189 static struct cfq_io_context *
3190 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
3192 struct io_context *ioc = NULL;
3193 struct cfq_io_context *cic;
3195 might_sleep_if(gfp_mask & __GFP_WAIT);
3197 ioc = get_io_context(gfp_mask, cfqd->queue->node);
3201 cic = cfq_cic_lookup(cfqd, ioc);
3205 cic = cfq_alloc_io_context(cfqd, gfp_mask);
3209 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
3213 smp_read_barrier_depends();
3214 if (unlikely(ioc->ioprio_changed))
3215 cfq_ioc_set_ioprio(ioc);
3217 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3218 if (unlikely(ioc->cgroup_changed))
3219 cfq_ioc_set_cgroup(ioc);
3225 put_io_context(ioc);
3230 __cfq_update_io_thinktime(struct cfq_ttime *ttime, unsigned long slice_idle)
3232 unsigned long elapsed = jiffies - ttime->last_end_request;
3233 elapsed = min(elapsed, 2UL * slice_idle);
3235 ttime->ttime_samples = (7*ttime->ttime_samples + 256) / 8;
3236 ttime->ttime_total = (7*ttime->ttime_total + 256*elapsed) / 8;
3237 ttime->ttime_mean = (ttime->ttime_total + 128) / ttime->ttime_samples;
3241 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3242 struct cfq_io_context *cic)
3244 if (cfq_cfqq_sync(cfqq)) {
3245 __cfq_update_io_thinktime(&cic->ttime, cfqd->cfq_slice_idle);
3246 __cfq_update_io_thinktime(&cfqq->service_tree->ttime,
3247 cfqd->cfq_slice_idle);
3249 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3250 __cfq_update_io_thinktime(&cfqq->cfqg->ttime, cfqd->cfq_group_idle);
3255 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3259 sector_t n_sec = blk_rq_sectors(rq);
3260 if (cfqq->last_request_pos) {
3261 if (cfqq->last_request_pos < blk_rq_pos(rq))
3262 sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
3264 sdist = cfqq->last_request_pos - blk_rq_pos(rq);
3267 cfqq->seek_history <<= 1;
3268 if (blk_queue_nonrot(cfqd->queue))
3269 cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT);
3271 cfqq->seek_history |= (sdist > CFQQ_SEEK_THR);
3275 * Disable idle window if the process thinks too long or seeks so much that
3279 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3280 struct cfq_io_context *cic)
3282 int old_idle, enable_idle;
3285 * Don't idle for async or idle io prio class
3287 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
3290 enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
3292 if (cfqq->queued[0] + cfqq->queued[1] >= 4)
3293 cfq_mark_cfqq_deep(cfqq);
3295 if (cfqq->next_rq && (cfqq->next_rq->cmd_flags & REQ_NOIDLE))
3297 else if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
3298 (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))
3300 else if (sample_valid(cic->ttime.ttime_samples)) {
3301 if (cic->ttime.ttime_mean > cfqd->cfq_slice_idle)
3307 if (old_idle != enable_idle) {
3308 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
3310 cfq_mark_cfqq_idle_window(cfqq);
3312 cfq_clear_cfqq_idle_window(cfqq);
3317 * Check if new_cfqq should preempt the currently active queue. Return 0 for
3318 * no or if we aren't sure, a 1 will cause a preempt.
3321 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
3324 struct cfq_queue *cfqq;
3326 cfqq = cfqd->active_queue;
3330 if (cfq_class_idle(new_cfqq))
3333 if (cfq_class_idle(cfqq))
3337 * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice.
3339 if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq))
3343 * if the new request is sync, but the currently running queue is
3344 * not, let the sync request have priority.
3346 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
3349 if (new_cfqq->cfqg != cfqq->cfqg)
3352 if (cfq_slice_used(cfqq))
3355 /* Allow preemption only if we are idling on sync-noidle tree */
3356 if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
3357 cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
3358 new_cfqq->service_tree->count == 2 &&
3359 RB_EMPTY_ROOT(&cfqq->sort_list))
3363 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
3365 if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
3368 /* An idle queue should not be idle now for some reason */
3369 if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq))
3372 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
3376 * if this request is as-good as one we would expect from the
3377 * current cfqq, let it preempt
3379 if (cfq_rq_close(cfqd, cfqq, rq))
3386 * cfqq preempts the active queue. if we allowed preempt with no slice left,
3387 * let it have half of its nominal slice.
3389 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3391 struct cfq_queue *old_cfqq = cfqd->active_queue;
3393 cfq_log_cfqq(cfqd, cfqq, "preempt");
3394 cfq_slice_expired(cfqd, 1);
3397 * workload type is changed, don't save slice, otherwise preempt
3400 if (cfqq_type(old_cfqq) != cfqq_type(cfqq))
3401 cfqq->cfqg->saved_workload_slice = 0;
3404 * Put the new queue at the front of the of the current list,
3405 * so we know that it will be selected next.
3407 BUG_ON(!cfq_cfqq_on_rr(cfqq));
3409 cfq_service_tree_add(cfqd, cfqq, 1);
3411 cfqq->slice_end = 0;
3412 cfq_mark_cfqq_slice_new(cfqq);
3416 * Called when a new fs request (rq) is added (to cfqq). Check if there's
3417 * something we should do about it
3420 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3423 struct cfq_io_context *cic = RQ_CIC(rq);
3427 cfq_update_io_thinktime(cfqd, cfqq, cic);
3428 cfq_update_io_seektime(cfqd, cfqq, rq);
3429 cfq_update_idle_window(cfqd, cfqq, cic);
3431 cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
3433 if (cfqq == cfqd->active_queue) {
3435 * Remember that we saw a request from this process, but
3436 * don't start queuing just yet. Otherwise we risk seeing lots
3437 * of tiny requests, because we disrupt the normal plugging
3438 * and merging. If the request is already larger than a single
3439 * page, let it rip immediately. For that case we assume that
3440 * merging is already done. Ditto for a busy system that
3441 * has other work pending, don't risk delaying until the
3442 * idle timer unplug to continue working.
3444 if (cfq_cfqq_wait_request(cfqq)) {
3445 if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
3446 cfqd->busy_queues > 1) {
3447 cfq_del_timer(cfqd, cfqq);
3448 cfq_clear_cfqq_wait_request(cfqq);
3449 __blk_run_queue(cfqd->queue);
3451 cfq_blkiocg_update_idle_time_stats(
3453 cfq_mark_cfqq_must_dispatch(cfqq);
3456 } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
3458 * not the active queue - expire current slice if it is
3459 * idle and has expired it's mean thinktime or this new queue
3460 * has some old slice time left and is of higher priority or
3461 * this new queue is RT and the current one is BE
3463 cfq_preempt_queue(cfqd, cfqq);
3464 __blk_run_queue(cfqd->queue);
3468 static void cfq_insert_request(struct request_queue *q, struct request *rq)
3470 struct cfq_data *cfqd = q->elevator->elevator_data;
3471 struct cfq_queue *cfqq = RQ_CFQQ(rq);
3473 cfq_log_cfqq(cfqd, cfqq, "insert_request");
3474 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
3476 rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
3477 list_add_tail(&rq->queuelist, &cfqq->fifo);
3479 cfq_blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg,
3480 &cfqd->serving_group->blkg, rq_data_dir(rq),
3482 cfq_rq_enqueued(cfqd, cfqq, rq);
3486 * Update hw_tag based on peak queue depth over 50 samples under
3489 static void cfq_update_hw_tag(struct cfq_data *cfqd)
3491 struct cfq_queue *cfqq = cfqd->active_queue;
3493 if (cfqd->rq_in_driver > cfqd->hw_tag_est_depth)
3494 cfqd->hw_tag_est_depth = cfqd->rq_in_driver;
3496 if (cfqd->hw_tag == 1)
3499 if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
3500 cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
3504 * If active queue hasn't enough requests and can idle, cfq might not
3505 * dispatch sufficient requests to hardware. Don't zero hw_tag in this
3508 if (cfqq && cfq_cfqq_idle_window(cfqq) &&
3509 cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
3510 CFQ_HW_QUEUE_MIN && cfqd->rq_in_driver < CFQ_HW_QUEUE_MIN)
3513 if (cfqd->hw_tag_samples++ < 50)
3516 if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
3522 static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3524 struct cfq_io_context *cic = cfqd->active_cic;
3526 /* If the queue already has requests, don't wait */
3527 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3530 /* If there are other queues in the group, don't wait */
3531 if (cfqq->cfqg->nr_cfqq > 1)
3534 /* the only queue in the group, but think time is big */
3535 if (cfq_io_thinktime_big(cfqd, &cfqq->cfqg->ttime, true))
3538 if (cfq_slice_used(cfqq))
3541 /* if slice left is less than think time, wait busy */
3542 if (cic && sample_valid(cic->ttime.ttime_samples)
3543 && (cfqq->slice_end - jiffies < cic->ttime.ttime_mean))
3547 * If think times is less than a jiffy than ttime_mean=0 and above
3548 * will not be true. It might happen that slice has not expired yet
3549 * but will expire soon (4-5 ns) during select_queue(). To cover the
3550 * case where think time is less than a jiffy, mark the queue wait
3551 * busy if only 1 jiffy is left in the slice.
3553 if (cfqq->slice_end - jiffies == 1)
3559 static void cfq_completed_request(struct request_queue *q, struct request *rq)
3561 struct cfq_queue *cfqq = RQ_CFQQ(rq);
3562 struct cfq_data *cfqd = cfqq->cfqd;
3563 const int sync = rq_is_sync(rq);
3567 cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d",
3568 !!(rq->cmd_flags & REQ_NOIDLE));
3570 cfq_update_hw_tag(cfqd);
3572 WARN_ON(!cfqd->rq_in_driver);
3573 WARN_ON(!cfqq->dispatched);
3574 cfqd->rq_in_driver--;
3576 (RQ_CFQG(rq))->dispatched--;
3577 cfq_blkiocg_update_completion_stats(&cfqq->cfqg->blkg,
3578 rq_start_time_ns(rq), rq_io_start_time_ns(rq),
3579 rq_data_dir(rq), rq_is_sync(rq));
3581 cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
3584 struct cfq_rb_root *service_tree;
3586 RQ_CIC(rq)->ttime.last_end_request = now;
3588 if (cfq_cfqq_on_rr(cfqq))
3589 service_tree = cfqq->service_tree;
3591 service_tree = service_tree_for(cfqq->cfqg,
3592 cfqq_prio(cfqq), cfqq_type(cfqq));
3593 service_tree->ttime.last_end_request = now;
3594 if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
3595 cfqd->last_delayed_sync = now;
3598 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3599 cfqq->cfqg->ttime.last_end_request = now;
3603 * If this is the active queue, check if it needs to be expired,
3604 * or if we want to idle in case it has no pending requests.
3606 if (cfqd->active_queue == cfqq) {
3607 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
3609 if (cfq_cfqq_slice_new(cfqq)) {
3610 cfq_set_prio_slice(cfqd, cfqq);
3611 cfq_clear_cfqq_slice_new(cfqq);
3615 * Should we wait for next request to come in before we expire
3618 if (cfq_should_wait_busy(cfqd, cfqq)) {
3619 unsigned long extend_sl = cfqd->cfq_slice_idle;
3620 if (!cfqd->cfq_slice_idle)
3621 extend_sl = cfqd->cfq_group_idle;
3622 cfqq->slice_end = jiffies + extend_sl;
3623 cfq_mark_cfqq_wait_busy(cfqq);
3624 cfq_log_cfqq(cfqd, cfqq, "will busy wait");
3628 * Idling is not enabled on:
3630 * - idle-priority queues
3632 * - queues with still some requests queued
3633 * - when there is a close cooperator
3635 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
3636 cfq_slice_expired(cfqd, 1);
3637 else if (sync && cfqq_empty &&
3638 !cfq_close_cooperator(cfqd, cfqq)) {
3639 cfq_arm_slice_timer(cfqd);
3643 if (!cfqd->rq_in_driver)
3644 cfq_schedule_dispatch(cfqd);
3647 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
3649 if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
3650 cfq_mark_cfqq_must_alloc_slice(cfqq);
3651 return ELV_MQUEUE_MUST;
3654 return ELV_MQUEUE_MAY;
3657 static int cfq_may_queue(struct request_queue *q, int rw)
3659 struct cfq_data *cfqd = q->elevator->elevator_data;
3660 struct task_struct *tsk = current;
3661 struct cfq_io_context *cic;
3662 struct cfq_queue *cfqq;
3665 * don't force setup of a queue from here, as a call to may_queue
3666 * does not necessarily imply that a request actually will be queued.
3667 * so just lookup a possibly existing queue, or return 'may queue'
3670 cic = cfq_cic_lookup(cfqd, tsk->io_context);
3672 return ELV_MQUEUE_MAY;
3674 cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
3676 cfq_init_prio_data(cfqq, cic->ioc);
3678 return __cfq_may_queue(cfqq);
3681 return ELV_MQUEUE_MAY;
3685 * queue lock held here
3687 static void cfq_put_request(struct request *rq)
3689 struct cfq_queue *cfqq = RQ_CFQQ(rq);
3692 const int rw = rq_data_dir(rq);
3694 BUG_ON(!cfqq->allocated[rw]);
3695 cfqq->allocated[rw]--;
3697 put_io_context(RQ_CIC(rq)->ioc);
3699 rq->elevator_private[0] = NULL;
3700 rq->elevator_private[1] = NULL;
3702 /* Put down rq reference on cfqg */
3703 cfq_put_cfqg(RQ_CFQG(rq));
3704 rq->elevator_private[2] = NULL;
3706 cfq_put_queue(cfqq);
3710 static struct cfq_queue *
3711 cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
3712 struct cfq_queue *cfqq)
3714 cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
3715 cic_set_cfqq(cic, cfqq->new_cfqq, 1);
3716 cfq_mark_cfqq_coop(cfqq->new_cfqq);
3717 cfq_put_queue(cfqq);
3718 return cic_to_cfqq(cic, 1);
3722 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
3723 * was the last process referring to said cfqq.
3725 static struct cfq_queue *
3726 split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
3728 if (cfqq_process_refs(cfqq) == 1) {
3729 cfqq->pid = current->pid;
3730 cfq_clear_cfqq_coop(cfqq);
3731 cfq_clear_cfqq_split_coop(cfqq);
3735 cic_set_cfqq(cic, NULL, 1);
3737 cfq_put_cooperator(cfqq);
3739 cfq_put_queue(cfqq);
3743 * Allocate cfq data structures associated with this request.
3746 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
3748 struct cfq_data *cfqd = q->elevator->elevator_data;
3749 struct cfq_io_context *cic;
3750 const int rw = rq_data_dir(rq);
3751 const bool is_sync = rq_is_sync(rq);
3752 struct cfq_queue *cfqq;
3753 unsigned long flags;
3755 might_sleep_if(gfp_mask & __GFP_WAIT);
3757 cic = cfq_get_io_context(cfqd, gfp_mask);
3759 spin_lock_irqsave(q->queue_lock, flags);
3765 cfqq = cic_to_cfqq(cic, is_sync);
3766 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
3767 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
3768 cic_set_cfqq(cic, cfqq, is_sync);
3771 * If the queue was seeky for too long, break it apart.
3773 if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) {
3774 cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
3775 cfqq = split_cfqq(cic, cfqq);
3781 * Check to see if this queue is scheduled to merge with
3782 * another, closely cooperating queue. The merging of
3783 * queues happens here as it must be done in process context.
3784 * The reference on new_cfqq was taken in merge_cfqqs.
3787 cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
3790 cfqq->allocated[rw]++;
3793 rq->elevator_private[0] = cic;
3794 rq->elevator_private[1] = cfqq;
3795 rq->elevator_private[2] = cfq_ref_get_cfqg(cfqq->cfqg);
3796 spin_unlock_irqrestore(q->queue_lock, flags);
3800 cfq_schedule_dispatch(cfqd);
3801 spin_unlock_irqrestore(q->queue_lock, flags);
3802 cfq_log(cfqd, "set_request fail");
3806 static void cfq_kick_queue(struct work_struct *work)
3808 struct cfq_data *cfqd =
3809 container_of(work, struct cfq_data, unplug_work);
3810 struct request_queue *q = cfqd->queue;
3812 spin_lock_irq(q->queue_lock);
3813 __blk_run_queue(cfqd->queue);
3814 spin_unlock_irq(q->queue_lock);
3818 * Timer running if the active_queue is currently idling inside its time slice
3820 static void cfq_idle_slice_timer(unsigned long data)
3822 struct cfq_data *cfqd = (struct cfq_data *) data;
3823 struct cfq_queue *cfqq;
3824 unsigned long flags;
3827 cfq_log(cfqd, "idle timer fired");
3829 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
3831 cfqq = cfqd->active_queue;
3836 * We saw a request before the queue expired, let it through
3838 if (cfq_cfqq_must_dispatch(cfqq))
3844 if (cfq_slice_used(cfqq))
3848 * only expire and reinvoke request handler, if there are
3849 * other queues with pending requests
3851 if (!cfqd->busy_queues)
3855 * not expired and it has a request pending, let it dispatch
3857 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3861 * Queue depth flag is reset only when the idle didn't succeed
3863 cfq_clear_cfqq_deep(cfqq);
3866 cfq_slice_expired(cfqd, timed_out);
3868 cfq_schedule_dispatch(cfqd);
3870 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
3873 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
3875 del_timer_sync(&cfqd->idle_slice_timer);
3876 cancel_work_sync(&cfqd->unplug_work);
3879 static void cfq_put_async_queues(struct cfq_data *cfqd)
3883 for (i = 0; i < IOPRIO_BE_NR; i++) {
3884 if (cfqd->async_cfqq[0][i])
3885 cfq_put_queue(cfqd->async_cfqq[0][i]);
3886 if (cfqd->async_cfqq[1][i])
3887 cfq_put_queue(cfqd->async_cfqq[1][i]);
3890 if (cfqd->async_idle_cfqq)
3891 cfq_put_queue(cfqd->async_idle_cfqq);
3894 static void cfq_exit_queue(struct elevator_queue *e)
3896 struct cfq_data *cfqd = e->elevator_data;
3897 struct request_queue *q = cfqd->queue;
3900 cfq_shutdown_timer_wq(cfqd);
3902 spin_lock_irq(q->queue_lock);
3904 if (cfqd->active_queue)
3905 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
3907 while (!list_empty(&cfqd->cic_list)) {
3908 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
3909 struct cfq_io_context,
3912 __cfq_exit_single_io_context(cfqd, cic);
3915 cfq_put_async_queues(cfqd);
3916 cfq_release_cfq_groups(cfqd);
3919 * If there are groups which we could not unlink from blkcg list,
3920 * wait for a rcu period for them to be freed.
3922 if (cfqd->nr_blkcg_linked_grps)
3925 spin_unlock_irq(q->queue_lock);
3927 cfq_shutdown_timer_wq(cfqd);
3929 spin_lock(&cic_index_lock);
3930 ida_remove(&cic_index_ida, cfqd->cic_index);
3931 spin_unlock(&cic_index_lock);
3934 * Wait for cfqg->blkg->key accessors to exit their grace periods.
3935 * Do this wait only if there are other unlinked groups out
3936 * there. This can happen if cgroup deletion path claimed the
3937 * responsibility of cleaning up a group before queue cleanup code
3940 * Do not call synchronize_rcu() unconditionally as there are drivers
3941 * which create/delete request queue hundreds of times during scan/boot
3942 * and synchronize_rcu() can take significant time and slow down boot.
3947 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3948 /* Free up per cpu stats for root group */
3949 free_percpu(cfqd->root_group.blkg.stats_cpu);
3954 static int cfq_alloc_cic_index(void)
3959 if (!ida_pre_get(&cic_index_ida, GFP_KERNEL))
3962 spin_lock(&cic_index_lock);
3963 error = ida_get_new(&cic_index_ida, &index);
3964 spin_unlock(&cic_index_lock);
3965 if (error && error != -EAGAIN)
3972 static void *cfq_init_queue(struct request_queue *q)
3974 struct cfq_data *cfqd;
3976 struct cfq_group *cfqg;
3977 struct cfq_rb_root *st;
3979 i = cfq_alloc_cic_index();
3983 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
3985 spin_lock(&cic_index_lock);
3986 ida_remove(&cic_index_ida, i);
3987 spin_unlock(&cic_index_lock);
3992 * Don't need take queue_lock in the routine, since we are
3993 * initializing the ioscheduler, and nobody is using cfqd
3995 cfqd->cic_index = i;
3997 /* Init root service tree */
3998 cfqd->grp_service_tree = CFQ_RB_ROOT;
4000 /* Init root group */
4001 cfqg = &cfqd->root_group;
4002 for_each_cfqg_st(cfqg, i, j, st)
4004 RB_CLEAR_NODE(&cfqg->rb_node);
4006 /* Give preference to root group over other groups */
4007 cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;
4009 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4011 * Set root group reference to 2. One reference will be dropped when
4012 * all groups on cfqd->cfqg_list are being deleted during queue exit.
4013 * Other reference will remain there as we don't want to delete this
4014 * group as it is statically allocated and gets destroyed when
4015 * throtl_data goes away.
4019 if (blkio_alloc_blkg_stats(&cfqg->blkg)) {
4027 cfq_blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg,
4030 cfqd->nr_blkcg_linked_grps++;
4032 /* Add group on cfqd->cfqg_list */
4033 hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
4036 * Not strictly needed (since RB_ROOT just clears the node and we
4037 * zeroed cfqd on alloc), but better be safe in case someone decides
4038 * to add magic to the rb code
4040 for (i = 0; i < CFQ_PRIO_LISTS; i++)
4041 cfqd->prio_trees[i] = RB_ROOT;
4044 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
4045 * Grab a permanent reference to it, so that the normal code flow
4046 * will not attempt to free it.
4048 cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
4049 cfqd->oom_cfqq.ref++;
4050 cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
4052 INIT_LIST_HEAD(&cfqd->cic_list);
4056 init_timer(&cfqd->idle_slice_timer);
4057 cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
4058 cfqd->idle_slice_timer.data = (unsigned long) cfqd;
4060 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
4062 cfqd->cfq_quantum = cfq_quantum;
4063 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
4064 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
4065 cfqd->cfq_back_max = cfq_back_max;
4066 cfqd->cfq_back_penalty = cfq_back_penalty;
4067 cfqd->cfq_slice[0] = cfq_slice_async;
4068 cfqd->cfq_slice[1] = cfq_slice_sync;
4069 cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
4070 cfqd->cfq_slice_idle = cfq_slice_idle;
4071 cfqd->cfq_group_idle = cfq_group_idle;
4072 cfqd->cfq_latency = 1;
4075 * we optimistically start assuming sync ops weren't delayed in last
4076 * second, in order to have larger depth for async operations.
4078 cfqd->last_delayed_sync = jiffies - HZ;
4082 static void cfq_slab_kill(void)
4085 * Caller already ensured that pending RCU callbacks are completed,
4086 * so we should have no busy allocations at this point.
4089 kmem_cache_destroy(cfq_pool);
4091 kmem_cache_destroy(cfq_ioc_pool);
4094 static int __init cfq_slab_setup(void)
4096 cfq_pool = KMEM_CACHE(cfq_queue, 0);
4100 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
4111 * sysfs parts below -->
4114 cfq_var_show(unsigned int var, char *page)
4116 return sprintf(page, "%d\n", var);
4120 cfq_var_store(unsigned int *var, const char *page, size_t count)
4122 char *p = (char *) page;
4124 *var = simple_strtoul(p, &p, 10);
4128 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
4129 static ssize_t __FUNC(struct elevator_queue *e, char *page) \
4131 struct cfq_data *cfqd = e->elevator_data; \
4132 unsigned int __data = __VAR; \
4134 __data = jiffies_to_msecs(__data); \
4135 return cfq_var_show(__data, (page)); \
4137 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
4138 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
4139 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
4140 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
4141 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
4142 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
4143 SHOW_FUNCTION(cfq_group_idle_show, cfqd->cfq_group_idle, 1);
4144 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
4145 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
4146 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
4147 SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
4148 #undef SHOW_FUNCTION
4150 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
4151 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
4153 struct cfq_data *cfqd = e->elevator_data; \
4154 unsigned int __data; \
4155 int ret = cfq_var_store(&__data, (page), count); \
4156 if (__data < (MIN)) \
4158 else if (__data > (MAX)) \
4161 *(__PTR) = msecs_to_jiffies(__data); \
4163 *(__PTR) = __data; \
4166 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
4167 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
4169 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
4171 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
4172 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
4174 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
4175 STORE_FUNCTION(cfq_group_idle_store, &cfqd->cfq_group_idle, 0, UINT_MAX, 1);
4176 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
4177 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
4178 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
4180 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
4181 #undef STORE_FUNCTION
4183 #define CFQ_ATTR(name) \
4184 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
4186 static struct elv_fs_entry cfq_attrs[] = {
4188 CFQ_ATTR(fifo_expire_sync),
4189 CFQ_ATTR(fifo_expire_async),
4190 CFQ_ATTR(back_seek_max),
4191 CFQ_ATTR(back_seek_penalty),
4192 CFQ_ATTR(slice_sync),
4193 CFQ_ATTR(slice_async),
4194 CFQ_ATTR(slice_async_rq),
4195 CFQ_ATTR(slice_idle),
4196 CFQ_ATTR(group_idle),
4197 CFQ_ATTR(low_latency),
4201 static struct elevator_type iosched_cfq = {
4203 .elevator_merge_fn = cfq_merge,
4204 .elevator_merged_fn = cfq_merged_request,
4205 .elevator_merge_req_fn = cfq_merged_requests,
4206 .elevator_allow_merge_fn = cfq_allow_merge,
4207 .elevator_bio_merged_fn = cfq_bio_merged,
4208 .elevator_dispatch_fn = cfq_dispatch_requests,
4209 .elevator_add_req_fn = cfq_insert_request,
4210 .elevator_activate_req_fn = cfq_activate_request,
4211 .elevator_deactivate_req_fn = cfq_deactivate_request,
4212 .elevator_completed_req_fn = cfq_completed_request,
4213 .elevator_former_req_fn = elv_rb_former_request,
4214 .elevator_latter_req_fn = elv_rb_latter_request,
4215 .elevator_set_req_fn = cfq_set_request,
4216 .elevator_put_req_fn = cfq_put_request,
4217 .elevator_may_queue_fn = cfq_may_queue,
4218 .elevator_init_fn = cfq_init_queue,
4219 .elevator_exit_fn = cfq_exit_queue,
4220 .trim = cfq_free_io_context,
4222 .elevator_attrs = cfq_attrs,
4223 .elevator_name = "cfq",
4224 .elevator_owner = THIS_MODULE,
4227 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4228 static struct blkio_policy_type blkio_policy_cfq = {
4230 .blkio_unlink_group_fn = cfq_unlink_blkio_group,
4231 .blkio_update_group_weight_fn = cfq_update_blkio_group_weight,
4233 .plid = BLKIO_POLICY_PROP,
4236 static struct blkio_policy_type blkio_policy_cfq;
4239 static int __init cfq_init(void)
4242 * could be 0 on HZ < 1000 setups
4244 if (!cfq_slice_async)
4245 cfq_slice_async = 1;
4246 if (!cfq_slice_idle)
4249 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4250 if (!cfq_group_idle)
4255 if (cfq_slab_setup())
4258 elv_register(&iosched_cfq);
4259 blkio_policy_register(&blkio_policy_cfq);
4264 static void __exit cfq_exit(void)
4266 DECLARE_COMPLETION_ONSTACK(all_gone);
4267 blkio_policy_unregister(&blkio_policy_cfq);
4268 elv_unregister(&iosched_cfq);
4269 ioc_gone = &all_gone;
4270 /* ioc_gone's update must be visible before reading ioc_count */
4274 * this also protects us from entering cfq_slab_kill() with
4275 * pending RCU callbacks
4277 if (elv_ioc_count_read(cfq_ioc_count))
4278 wait_for_completion(&all_gone);
4279 ida_destroy(&cic_index_ida);
4283 module_init(cfq_init);
4284 module_exit(cfq_exit);
4286 MODULE_AUTHOR("Jens Axboe");
4287 MODULE_LICENSE("GPL");
4288 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");