2 * Interface for controlling IO bandwidth on a request queue
4 * Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com>
7 #include <linux/module.h>
8 #include <linux/slab.h>
9 #include <linux/blkdev.h>
10 #include <linux/bio.h>
11 #include <linux/blktrace_api.h>
12 #include "blk-cgroup.h"
14 /* Max dispatch from a group in 1 round */
15 static int throtl_grp_quantum = 8;
17 /* Total max dispatch from all groups in one round */
18 static int throtl_quantum = 32;
20 /* Throttling is performed over 100ms slice and after that slice is renewed */
21 static unsigned long throtl_slice = HZ/10; /* 100 ms */
23 /* A workqueue to queue throttle related work */
24 static struct workqueue_struct *kthrotld_workqueue;
25 static void throtl_schedule_delayed_work(struct throtl_data *td,
28 struct throtl_rb_root {
32 unsigned long min_disptime;
35 #define THROTL_RB_ROOT (struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \
36 .count = 0, .min_disptime = 0}
38 #define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
41 /* List of throtl groups on the request queue*/
42 struct hlist_node tg_node;
44 /* active throtl group service_tree member */
45 struct rb_node rb_node;
48 * Dispatch time in jiffies. This is the estimated time when group
49 * will unthrottle and is ready to dispatch more bio. It is used as
50 * key to sort active groups in service tree.
52 unsigned long disptime;
54 struct blkio_group blkg;
58 /* Two lists for READ and WRITE */
59 struct bio_list bio_lists[2];
61 /* Number of queued bios on READ and WRITE lists */
62 unsigned int nr_queued[2];
64 /* bytes per second rate limits */
70 /* Number of bytes disptached in current slice */
71 uint64_t bytes_disp[2];
72 /* Number of bio's dispatched in current slice */
73 unsigned int io_disp[2];
75 /* When did we start a new slice */
76 unsigned long slice_start[2];
77 unsigned long slice_end[2];
79 /* Some throttle limits got updated for the group */
85 /* List of throtl groups */
86 struct hlist_head tg_list;
88 /* service tree for active throtl groups */
89 struct throtl_rb_root tg_service_tree;
91 struct throtl_grp *root_tg;
92 struct request_queue *queue;
94 /* Total Number of queued bios on READ and WRITE lists */
95 unsigned int nr_queued[2];
98 * number of total undestroyed groups
100 unsigned int nr_undestroyed_grps;
102 /* Work for dispatching throttled bios */
103 struct delayed_work throtl_work;
108 enum tg_state_flags {
109 THROTL_TG_FLAG_on_rr = 0, /* on round-robin busy list */
112 #define THROTL_TG_FNS(name) \
113 static inline void throtl_mark_tg_##name(struct throtl_grp *tg) \
115 (tg)->flags |= (1 << THROTL_TG_FLAG_##name); \
117 static inline void throtl_clear_tg_##name(struct throtl_grp *tg) \
119 (tg)->flags &= ~(1 << THROTL_TG_FLAG_##name); \
121 static inline int throtl_tg_##name(const struct throtl_grp *tg) \
123 return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0; \
126 THROTL_TG_FNS(on_rr);
128 #define throtl_log_tg(td, tg, fmt, args...) \
129 blk_add_trace_msg((td)->queue, "throtl %s " fmt, \
130 blkg_path(&(tg)->blkg), ##args); \
132 #define throtl_log(td, fmt, args...) \
133 blk_add_trace_msg((td)->queue, "throtl " fmt, ##args)
135 static inline struct throtl_grp *tg_of_blkg(struct blkio_group *blkg)
138 return container_of(blkg, struct throtl_grp, blkg);
143 static inline int total_nr_queued(struct throtl_data *td)
145 return (td->nr_queued[0] + td->nr_queued[1]);
148 static inline struct throtl_grp *throtl_ref_get_tg(struct throtl_grp *tg)
150 atomic_inc(&tg->ref);
154 static void throtl_put_tg(struct throtl_grp *tg)
156 BUG_ON(atomic_read(&tg->ref) <= 0);
157 if (!atomic_dec_and_test(&tg->ref))
162 static void throtl_init_group(struct throtl_grp *tg)
164 INIT_HLIST_NODE(&tg->tg_node);
165 RB_CLEAR_NODE(&tg->rb_node);
166 bio_list_init(&tg->bio_lists[0]);
167 bio_list_init(&tg->bio_lists[1]);
168 tg->limits_changed = false;
170 /* Practically unlimited BW */
171 tg->bps[0] = tg->bps[1] = -1;
172 tg->iops[0] = tg->iops[1] = -1;
175 * Take the initial reference that will be released on destroy
176 * This can be thought of a joint reference by cgroup and
177 * request queue which will be dropped by either request queue
178 * exit or cgroup deletion path depending on who is exiting first.
180 atomic_set(&tg->ref, 1);
183 /* Should be called with rcu read lock held (needed for blkcg) */
185 throtl_add_group_to_td_list(struct throtl_data *td, struct throtl_grp *tg)
187 hlist_add_head(&tg->tg_node, &td->tg_list);
188 td->nr_undestroyed_grps++;
191 static void throtl_init_add_tg_lists(struct throtl_data *td,
192 struct throtl_grp *tg, struct blkio_cgroup *blkcg)
194 struct backing_dev_info *bdi = &td->queue->backing_dev_info;
195 unsigned int major, minor;
197 /* Add group onto cgroup list */
198 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
199 blkiocg_add_blkio_group(blkcg, &tg->blkg, (void *)td,
200 MKDEV(major, minor), BLKIO_POLICY_THROTL);
202 tg->bps[READ] = blkcg_get_read_bps(blkcg, tg->blkg.dev);
203 tg->bps[WRITE] = blkcg_get_write_bps(blkcg, tg->blkg.dev);
204 tg->iops[READ] = blkcg_get_read_iops(blkcg, tg->blkg.dev);
205 tg->iops[WRITE] = blkcg_get_write_iops(blkcg, tg->blkg.dev);
207 throtl_add_group_to_td_list(td, tg);
210 /* Should be called without queue lock and outside of rcu period */
211 static struct throtl_grp *throtl_alloc_tg(struct throtl_data *td)
213 struct throtl_grp *tg = NULL;
215 tg = kzalloc_node(sizeof(*tg), GFP_ATOMIC, td->queue->node);
219 throtl_init_group(tg);
224 throtl_grp *throtl_find_tg(struct throtl_data *td, struct blkio_cgroup *blkcg)
226 struct throtl_grp *tg = NULL;
228 struct backing_dev_info *bdi = &td->queue->backing_dev_info;
229 unsigned int major, minor;
232 * This is the common case when there are no blkio cgroups.
233 * Avoid lookup in this case
235 if (blkcg == &blkio_root_cgroup)
238 tg = tg_of_blkg(blkiocg_lookup_group(blkcg, key));
240 /* Fill in device details for root group */
241 if (tg && !tg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {
242 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
243 tg->blkg.dev = MKDEV(major, minor);
250 * This function returns with queue lock unlocked in case of error, like
251 * request queue is no more
253 static struct throtl_grp * throtl_get_tg(struct throtl_data *td)
255 struct throtl_grp *tg = NULL, *__tg = NULL;
256 struct blkio_cgroup *blkcg;
257 struct request_queue *q = td->queue;
260 blkcg = task_blkio_cgroup(current);
261 tg = throtl_find_tg(td, blkcg);
268 * Need to allocate a group. Allocation of group also needs allocation
269 * of per cpu stats which in-turn takes a mutex() and can block. Hence
270 * we need to drop rcu lock and queue_lock before we call alloc
272 * Take the request queue reference to make sure queue does not
273 * go away once we return from allocation.
277 spin_unlock_irq(q->queue_lock);
279 tg = throtl_alloc_tg(td);
281 * We might have slept in group allocation. Make sure queue is not
284 if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
289 return ERR_PTR(-ENODEV);
293 /* Group allocated and queue is still alive. take the lock */
294 spin_lock_irq(q->queue_lock);
297 * Initialize the new group. After sleeping, read the blkcg again.
300 blkcg = task_blkio_cgroup(current);
303 * If some other thread already allocated the group while we were
304 * not holding queue lock, free up the group
306 __tg = throtl_find_tg(td, blkcg);
314 /* Group allocation failed. Account the IO to root group */
320 throtl_init_add_tg_lists(td, tg, blkcg);
325 static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root)
327 /* Service tree is empty */
332 root->left = rb_first(&root->rb);
335 return rb_entry_tg(root->left);
340 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
346 static void throtl_rb_erase(struct rb_node *n, struct throtl_rb_root *root)
350 rb_erase_init(n, &root->rb);
354 static void update_min_dispatch_time(struct throtl_rb_root *st)
356 struct throtl_grp *tg;
358 tg = throtl_rb_first(st);
362 st->min_disptime = tg->disptime;
366 tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg)
368 struct rb_node **node = &st->rb.rb_node;
369 struct rb_node *parent = NULL;
370 struct throtl_grp *__tg;
371 unsigned long key = tg->disptime;
374 while (*node != NULL) {
376 __tg = rb_entry_tg(parent);
378 if (time_before(key, __tg->disptime))
379 node = &parent->rb_left;
381 node = &parent->rb_right;
387 st->left = &tg->rb_node;
389 rb_link_node(&tg->rb_node, parent, node);
390 rb_insert_color(&tg->rb_node, &st->rb);
393 static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
395 struct throtl_rb_root *st = &td->tg_service_tree;
397 tg_service_tree_add(st, tg);
398 throtl_mark_tg_on_rr(tg);
402 static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
404 if (!throtl_tg_on_rr(tg))
405 __throtl_enqueue_tg(td, tg);
408 static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
410 throtl_rb_erase(&tg->rb_node, &td->tg_service_tree);
411 throtl_clear_tg_on_rr(tg);
414 static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
416 if (throtl_tg_on_rr(tg))
417 __throtl_dequeue_tg(td, tg);
420 static void throtl_schedule_next_dispatch(struct throtl_data *td)
422 struct throtl_rb_root *st = &td->tg_service_tree;
425 * If there are more bios pending, schedule more work.
427 if (!total_nr_queued(td))
432 update_min_dispatch_time(st);
434 if (time_before_eq(st->min_disptime, jiffies))
435 throtl_schedule_delayed_work(td, 0);
437 throtl_schedule_delayed_work(td, (st->min_disptime - jiffies));
441 throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
443 tg->bytes_disp[rw] = 0;
445 tg->slice_start[rw] = jiffies;
446 tg->slice_end[rw] = jiffies + throtl_slice;
447 throtl_log_tg(td, tg, "[%c] new slice start=%lu end=%lu jiffies=%lu",
448 rw == READ ? 'R' : 'W', tg->slice_start[rw],
449 tg->slice_end[rw], jiffies);
452 static inline void throtl_set_slice_end(struct throtl_data *td,
453 struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
455 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
458 static inline void throtl_extend_slice(struct throtl_data *td,
459 struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
461 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
462 throtl_log_tg(td, tg, "[%c] extend slice start=%lu end=%lu jiffies=%lu",
463 rw == READ ? 'R' : 'W', tg->slice_start[rw],
464 tg->slice_end[rw], jiffies);
467 /* Determine if previously allocated or extended slice is complete or not */
469 throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw)
471 if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
477 /* Trim the used slices and adjust slice start accordingly */
479 throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
481 unsigned long nr_slices, time_elapsed, io_trim;
484 BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
487 * If bps are unlimited (-1), then time slice don't get
488 * renewed. Don't try to trim the slice if slice is used. A new
489 * slice will start when appropriate.
491 if (throtl_slice_used(td, tg, rw))
495 * A bio has been dispatched. Also adjust slice_end. It might happen
496 * that initially cgroup limit was very low resulting in high
497 * slice_end, but later limit was bumped up and bio was dispached
498 * sooner, then we need to reduce slice_end. A high bogus slice_end
499 * is bad because it does not allow new slice to start.
502 throtl_set_slice_end(td, tg, rw, jiffies + throtl_slice);
504 time_elapsed = jiffies - tg->slice_start[rw];
506 nr_slices = time_elapsed / throtl_slice;
510 tmp = tg->bps[rw] * throtl_slice * nr_slices;
514 io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ;
516 if (!bytes_trim && !io_trim)
519 if (tg->bytes_disp[rw] >= bytes_trim)
520 tg->bytes_disp[rw] -= bytes_trim;
522 tg->bytes_disp[rw] = 0;
524 if (tg->io_disp[rw] >= io_trim)
525 tg->io_disp[rw] -= io_trim;
529 tg->slice_start[rw] += nr_slices * throtl_slice;
531 throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%llu io=%lu"
532 " start=%lu end=%lu jiffies=%lu",
533 rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
534 tg->slice_start[rw], tg->slice_end[rw], jiffies);
537 static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg,
538 struct bio *bio, unsigned long *wait)
540 bool rw = bio_data_dir(bio);
541 unsigned int io_allowed;
542 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
545 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
547 /* Slice has just started. Consider one slice interval */
549 jiffy_elapsed_rnd = throtl_slice;
551 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
554 * jiffy_elapsed_rnd should not be a big value as minimum iops can be
555 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
556 * will allow dispatch after 1 second and after that slice should
560 tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd;
564 io_allowed = UINT_MAX;
568 if (tg->io_disp[rw] + 1 <= io_allowed) {
574 /* Calc approx time to dispatch */
575 jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;
577 if (jiffy_wait > jiffy_elapsed)
578 jiffy_wait = jiffy_wait - jiffy_elapsed;
587 static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg,
588 struct bio *bio, unsigned long *wait)
590 bool rw = bio_data_dir(bio);
591 u64 bytes_allowed, extra_bytes, tmp;
592 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
594 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
596 /* Slice has just started. Consider one slice interval */
598 jiffy_elapsed_rnd = throtl_slice;
600 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
602 tmp = tg->bps[rw] * jiffy_elapsed_rnd;
606 if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) {
612 /* Calc approx time to dispatch */
613 extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed;
614 jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]);
620 * This wait time is without taking into consideration the rounding
621 * up we did. Add that time also.
623 jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
630 * Returns whether one can dispatch a bio or not. Also returns approx number
631 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
633 static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
634 struct bio *bio, unsigned long *wait)
636 bool rw = bio_data_dir(bio);
637 unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
640 * Currently whole state machine of group depends on first bio
641 * queued in the group bio list. So one should not be calling
642 * this function with a different bio if there are other bios
645 BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));
647 /* If tg->bps = -1, then BW is unlimited */
648 if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
655 * If previous slice expired, start a new one otherwise renew/extend
656 * existing slice to make sure it is at least throtl_slice interval
659 if (throtl_slice_used(td, tg, rw))
660 throtl_start_new_slice(td, tg, rw);
662 if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
663 throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);
666 if (tg_with_in_bps_limit(td, tg, bio, &bps_wait)
667 && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) {
673 max_wait = max(bps_wait, iops_wait);
678 if (time_before(tg->slice_end[rw], jiffies + max_wait))
679 throtl_extend_slice(td, tg, rw, jiffies + max_wait);
684 static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
686 bool rw = bio_data_dir(bio);
687 bool sync = bio->bi_rw & REQ_SYNC;
689 /* Charge the bio to the group */
690 tg->bytes_disp[rw] += bio->bi_size;
694 * TODO: This will take blkg->stats_lock. Figure out a way
695 * to avoid this cost.
697 blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size, rw, sync);
700 static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg,
703 bool rw = bio_data_dir(bio);
705 bio_list_add(&tg->bio_lists[rw], bio);
706 /* Take a bio reference on tg */
707 throtl_ref_get_tg(tg);
710 throtl_enqueue_tg(td, tg);
713 static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg)
715 unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
718 if ((bio = bio_list_peek(&tg->bio_lists[READ])))
719 tg_may_dispatch(td, tg, bio, &read_wait);
721 if ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
722 tg_may_dispatch(td, tg, bio, &write_wait);
724 min_wait = min(read_wait, write_wait);
725 disptime = jiffies + min_wait;
727 /* Update dispatch time */
728 throtl_dequeue_tg(td, tg);
729 tg->disptime = disptime;
730 throtl_enqueue_tg(td, tg);
733 static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg,
734 bool rw, struct bio_list *bl)
738 bio = bio_list_pop(&tg->bio_lists[rw]);
740 /* Drop bio reference on tg */
743 BUG_ON(td->nr_queued[rw] <= 0);
746 throtl_charge_bio(tg, bio);
747 bio_list_add(bl, bio);
748 bio->bi_rw |= REQ_THROTTLED;
750 throtl_trim_slice(td, tg, rw);
753 static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg,
756 unsigned int nr_reads = 0, nr_writes = 0;
757 unsigned int max_nr_reads = throtl_grp_quantum*3/4;
758 unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
761 /* Try to dispatch 75% READS and 25% WRITES */
763 while ((bio = bio_list_peek(&tg->bio_lists[READ]))
764 && tg_may_dispatch(td, tg, bio, NULL)) {
766 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
769 if (nr_reads >= max_nr_reads)
773 while ((bio = bio_list_peek(&tg->bio_lists[WRITE]))
774 && tg_may_dispatch(td, tg, bio, NULL)) {
776 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
779 if (nr_writes >= max_nr_writes)
783 return nr_reads + nr_writes;
786 static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl)
788 unsigned int nr_disp = 0;
789 struct throtl_grp *tg;
790 struct throtl_rb_root *st = &td->tg_service_tree;
793 tg = throtl_rb_first(st);
798 if (time_before(jiffies, tg->disptime))
801 throtl_dequeue_tg(td, tg);
803 nr_disp += throtl_dispatch_tg(td, tg, bl);
805 if (tg->nr_queued[0] || tg->nr_queued[1]) {
806 tg_update_disptime(td, tg);
807 throtl_enqueue_tg(td, tg);
810 if (nr_disp >= throtl_quantum)
817 static void throtl_process_limit_change(struct throtl_data *td)
819 struct throtl_grp *tg;
820 struct hlist_node *pos, *n;
822 if (!td->limits_changed)
825 xchg(&td->limits_changed, false);
827 throtl_log(td, "limits changed");
829 hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) {
830 if (!tg->limits_changed)
833 if (!xchg(&tg->limits_changed, false))
836 throtl_log_tg(td, tg, "limit change rbps=%llu wbps=%llu"
837 " riops=%u wiops=%u", tg->bps[READ], tg->bps[WRITE],
838 tg->iops[READ], tg->iops[WRITE]);
841 * Restart the slices for both READ and WRITES. It
842 * might happen that a group's limit are dropped
843 * suddenly and we don't want to account recently
844 * dispatched IO with new low rate
846 throtl_start_new_slice(td, tg, 0);
847 throtl_start_new_slice(td, tg, 1);
849 if (throtl_tg_on_rr(tg))
850 tg_update_disptime(td, tg);
854 /* Dispatch throttled bios. Should be called without queue lock held. */
855 static int throtl_dispatch(struct request_queue *q)
857 struct throtl_data *td = q->td;
858 unsigned int nr_disp = 0;
859 struct bio_list bio_list_on_stack;
861 struct blk_plug plug;
863 spin_lock_irq(q->queue_lock);
865 throtl_process_limit_change(td);
867 if (!total_nr_queued(td))
870 bio_list_init(&bio_list_on_stack);
872 throtl_log(td, "dispatch nr_queued=%lu read=%u write=%u",
873 total_nr_queued(td), td->nr_queued[READ],
874 td->nr_queued[WRITE]);
876 nr_disp = throtl_select_dispatch(td, &bio_list_on_stack);
879 throtl_log(td, "bios disp=%u", nr_disp);
881 throtl_schedule_next_dispatch(td);
883 spin_unlock_irq(q->queue_lock);
886 * If we dispatched some requests, unplug the queue to make sure
890 blk_start_plug(&plug);
891 while((bio = bio_list_pop(&bio_list_on_stack)))
892 generic_make_request(bio);
893 blk_finish_plug(&plug);
898 void blk_throtl_work(struct work_struct *work)
900 struct throtl_data *td = container_of(work, struct throtl_data,
902 struct request_queue *q = td->queue;
907 /* Call with queue lock held */
909 throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay)
912 struct delayed_work *dwork = &td->throtl_work;
914 /* schedule work if limits changed even if no bio is queued */
915 if (total_nr_queued(td) > 0 || td->limits_changed) {
917 * We might have a work scheduled to be executed in future.
918 * Cancel that and schedule a new one.
920 __cancel_delayed_work(dwork);
921 queue_delayed_work(kthrotld_workqueue, dwork, delay);
922 throtl_log(td, "schedule work. delay=%lu jiffies=%lu",
928 throtl_destroy_tg(struct throtl_data *td, struct throtl_grp *tg)
930 /* Something wrong if we are trying to remove same group twice */
931 BUG_ON(hlist_unhashed(&tg->tg_node));
933 hlist_del_init(&tg->tg_node);
936 * Put the reference taken at the time of creation so that when all
937 * queues are gone, group can be destroyed.
940 td->nr_undestroyed_grps--;
943 static void throtl_release_tgs(struct throtl_data *td)
945 struct hlist_node *pos, *n;
946 struct throtl_grp *tg;
948 hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) {
950 * If cgroup removal path got to blk_group first and removed
951 * it from cgroup list, then it will take care of destroying
954 if (!blkiocg_del_blkio_group(&tg->blkg))
955 throtl_destroy_tg(td, tg);
959 static void throtl_td_free(struct throtl_data *td)
965 * Blk cgroup controller notification saying that blkio_group object is being
966 * delinked as associated cgroup object is going away. That also means that
967 * no new IO will come in this group. So get rid of this group as soon as
968 * any pending IO in the group is finished.
970 * This function is called under rcu_read_lock(). key is the rcu protected
971 * pointer. That means "key" is a valid throtl_data pointer as long as we are
974 * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
975 * it should not be NULL as even if queue was going away, cgroup deltion
976 * path got to it first.
978 void throtl_unlink_blkio_group(void *key, struct blkio_group *blkg)
981 struct throtl_data *td = key;
983 spin_lock_irqsave(td->queue->queue_lock, flags);
984 throtl_destroy_tg(td, tg_of_blkg(blkg));
985 spin_unlock_irqrestore(td->queue->queue_lock, flags);
988 static void throtl_update_blkio_group_common(struct throtl_data *td,
989 struct throtl_grp *tg)
991 xchg(&tg->limits_changed, true);
992 xchg(&td->limits_changed, true);
993 /* Schedule a work now to process the limit change */
994 throtl_schedule_delayed_work(td, 0);
998 * For all update functions, key should be a valid pointer because these
999 * update functions are called under blkcg_lock, that means, blkg is
1000 * valid and in turn key is valid. queue exit path can not race because
1003 * Can not take queue lock in update functions as queue lock under blkcg_lock
1004 * is not allowed. Under other paths we take blkcg_lock under queue_lock.
1006 static void throtl_update_blkio_group_read_bps(void *key,
1007 struct blkio_group *blkg, u64 read_bps)
1009 struct throtl_data *td = key;
1010 struct throtl_grp *tg = tg_of_blkg(blkg);
1012 tg->bps[READ] = read_bps;
1013 throtl_update_blkio_group_common(td, tg);
1016 static void throtl_update_blkio_group_write_bps(void *key,
1017 struct blkio_group *blkg, u64 write_bps)
1019 struct throtl_data *td = key;
1020 struct throtl_grp *tg = tg_of_blkg(blkg);
1022 tg->bps[WRITE] = write_bps;
1023 throtl_update_blkio_group_common(td, tg);
1026 static void throtl_update_blkio_group_read_iops(void *key,
1027 struct blkio_group *blkg, unsigned int read_iops)
1029 struct throtl_data *td = key;
1030 struct throtl_grp *tg = tg_of_blkg(blkg);
1032 tg->iops[READ] = read_iops;
1033 throtl_update_blkio_group_common(td, tg);
1036 static void throtl_update_blkio_group_write_iops(void *key,
1037 struct blkio_group *blkg, unsigned int write_iops)
1039 struct throtl_data *td = key;
1040 struct throtl_grp *tg = tg_of_blkg(blkg);
1042 tg->iops[WRITE] = write_iops;
1043 throtl_update_blkio_group_common(td, tg);
1046 static void throtl_shutdown_wq(struct request_queue *q)
1048 struct throtl_data *td = q->td;
1050 cancel_delayed_work_sync(&td->throtl_work);
1053 static struct blkio_policy_type blkio_policy_throtl = {
1055 .blkio_unlink_group_fn = throtl_unlink_blkio_group,
1056 .blkio_update_group_read_bps_fn =
1057 throtl_update_blkio_group_read_bps,
1058 .blkio_update_group_write_bps_fn =
1059 throtl_update_blkio_group_write_bps,
1060 .blkio_update_group_read_iops_fn =
1061 throtl_update_blkio_group_read_iops,
1062 .blkio_update_group_write_iops_fn =
1063 throtl_update_blkio_group_write_iops,
1065 .plid = BLKIO_POLICY_THROTL,
1068 int blk_throtl_bio(struct request_queue *q, struct bio **biop)
1070 struct throtl_data *td = q->td;
1071 struct throtl_grp *tg;
1072 struct bio *bio = *biop;
1073 bool rw = bio_data_dir(bio), update_disptime = true;
1075 if (bio->bi_rw & REQ_THROTTLED) {
1076 bio->bi_rw &= ~REQ_THROTTLED;
1080 spin_lock_irq(q->queue_lock);
1081 tg = throtl_get_tg(td);
1084 if (PTR_ERR(tg) == -ENODEV) {
1086 * Queue is gone. No queue lock held here.
1092 if (tg->nr_queued[rw]) {
1094 * There is already another bio queued in same dir. No
1095 * need to update dispatch time.
1097 update_disptime = false;
1102 /* Bio is with-in rate limit of group */
1103 if (tg_may_dispatch(td, tg, bio, NULL)) {
1104 throtl_charge_bio(tg, bio);
1107 * We need to trim slice even when bios are not being queued
1108 * otherwise it might happen that a bio is not queued for
1109 * a long time and slice keeps on extending and trim is not
1110 * called for a long time. Now if limits are reduced suddenly
1111 * we take into account all the IO dispatched so far at new
1112 * low rate and * newly queued IO gets a really long dispatch
1115 * So keep on trimming slice even if bio is not queued.
1117 throtl_trim_slice(td, tg, rw);
1122 throtl_log_tg(td, tg, "[%c] bio. bdisp=%u sz=%u bps=%llu"
1123 " iodisp=%u iops=%u queued=%d/%d",
1124 rw == READ ? 'R' : 'W',
1125 tg->bytes_disp[rw], bio->bi_size, tg->bps[rw],
1126 tg->io_disp[rw], tg->iops[rw],
1127 tg->nr_queued[READ], tg->nr_queued[WRITE]);
1129 throtl_add_bio_tg(q->td, tg, bio);
1132 if (update_disptime) {
1133 tg_update_disptime(td, tg);
1134 throtl_schedule_next_dispatch(td);
1138 spin_unlock_irq(q->queue_lock);
1142 int blk_throtl_init(struct request_queue *q)
1144 struct throtl_data *td;
1145 struct throtl_grp *tg;
1147 td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
1151 INIT_HLIST_HEAD(&td->tg_list);
1152 td->tg_service_tree = THROTL_RB_ROOT;
1153 td->limits_changed = false;
1154 INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work);
1156 /* alloc and Init root group. */
1158 tg = throtl_alloc_tg(td);
1168 blkiocg_add_blkio_group(&blkio_root_cgroup, &tg->blkg, (void *)td,
1169 0, BLKIO_POLICY_THROTL);
1171 throtl_add_group_to_td_list(td, tg);
1173 /* Attach throtl data to request queue */
1178 void blk_throtl_exit(struct request_queue *q)
1180 struct throtl_data *td = q->td;
1185 throtl_shutdown_wq(q);
1187 spin_lock_irq(q->queue_lock);
1188 throtl_release_tgs(td);
1190 /* If there are other groups */
1191 if (td->nr_undestroyed_grps > 0)
1194 spin_unlock_irq(q->queue_lock);
1197 * Wait for tg->blkg->key accessors to exit their grace periods.
1198 * Do this wait only if there are other undestroyed groups out
1199 * there (other than root group). This can happen if cgroup deletion
1200 * path claimed the responsibility of cleaning up a group before
1201 * queue cleanup code get to the group.
1203 * Do not call synchronize_rcu() unconditionally as there are drivers
1204 * which create/delete request queue hundreds of times during scan/boot
1205 * and synchronize_rcu() can take significant time and slow down boot.
1211 * Just being safe to make sure after previous flush if some body did
1212 * update limits through cgroup and another work got queued, cancel
1215 throtl_shutdown_wq(q);
1219 static int __init throtl_init(void)
1221 kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
1222 if (!kthrotld_workqueue)
1223 panic("Failed to create kthrotld\n");
1225 blkio_policy_register(&blkio_policy_throtl);
1229 module_init(throtl_init);