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"
15 /* Max dispatch from a group in 1 round */
16 static int throtl_grp_quantum = 8;
18 /* Total max dispatch from all groups in one round */
19 static int throtl_quantum = 32;
21 /* Throttling is performed over 100ms slice and after that slice is renewed */
22 static unsigned long throtl_slice = HZ/10; /* 100 ms */
24 static struct blkio_policy_type blkio_policy_throtl;
26 /* A workqueue to queue throttle related work */
27 static struct workqueue_struct *kthrotld_workqueue;
28 static void throtl_schedule_delayed_work(struct throtl_data *td,
31 struct throtl_rb_root {
35 unsigned long min_disptime;
38 #define THROTL_RB_ROOT (struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \
39 .count = 0, .min_disptime = 0}
41 #define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_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;
56 /* Two lists for READ and WRITE */
57 struct bio_list bio_lists[2];
59 /* Number of queued bios on READ and WRITE lists */
60 unsigned int nr_queued[2];
62 /* bytes per second rate limits */
68 /* Number of bytes disptached in current slice */
69 uint64_t bytes_disp[2];
70 /* Number of bio's dispatched in current slice */
71 unsigned int io_disp[2];
73 /* When did we start a new slice */
74 unsigned long slice_start[2];
75 unsigned long slice_end[2];
77 /* Some throttle limits got updated for the group */
83 /* service tree for active throtl groups */
84 struct throtl_rb_root tg_service_tree;
86 struct throtl_grp *root_tg;
87 struct request_queue *queue;
89 /* Total Number of queued bios on READ and WRITE lists */
90 unsigned int nr_queued[2];
93 * number of total undestroyed groups
95 unsigned int nr_undestroyed_grps;
97 /* Work for dispatching throttled bios */
98 struct delayed_work throtl_work;
103 static inline struct throtl_grp *blkg_to_tg(struct blkio_group *blkg)
105 return blkg_to_pdata(blkg, &blkio_policy_throtl);
108 static inline struct blkio_group *tg_to_blkg(struct throtl_grp *tg)
110 return pdata_to_blkg(tg, &blkio_policy_throtl);
113 enum tg_state_flags {
114 THROTL_TG_FLAG_on_rr = 0, /* on round-robin busy list */
117 #define THROTL_TG_FNS(name) \
118 static inline void throtl_mark_tg_##name(struct throtl_grp *tg) \
120 (tg)->flags |= (1 << THROTL_TG_FLAG_##name); \
122 static inline void throtl_clear_tg_##name(struct throtl_grp *tg) \
124 (tg)->flags &= ~(1 << THROTL_TG_FLAG_##name); \
126 static inline int throtl_tg_##name(const struct throtl_grp *tg) \
128 return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0; \
131 THROTL_TG_FNS(on_rr);
133 #define throtl_log_tg(td, tg, fmt, args...) \
134 blk_add_trace_msg((td)->queue, "throtl %s " fmt, \
135 blkg_path(tg_to_blkg(tg)), ##args); \
137 #define throtl_log(td, fmt, args...) \
138 blk_add_trace_msg((td)->queue, "throtl " fmt, ##args)
140 static inline unsigned int total_nr_queued(struct throtl_data *td)
142 return td->nr_queued[0] + td->nr_queued[1];
145 static void throtl_init_blkio_group(struct blkio_group *blkg)
147 struct throtl_grp *tg = blkg_to_tg(blkg);
149 RB_CLEAR_NODE(&tg->rb_node);
150 bio_list_init(&tg->bio_lists[0]);
151 bio_list_init(&tg->bio_lists[1]);
152 tg->limits_changed = false;
157 tg->iops[WRITE] = -1;
161 throtl_grp *throtl_lookup_tg(struct throtl_data *td, struct blkio_cgroup *blkcg)
164 * This is the common case when there are no blkio cgroups.
165 * Avoid lookup in this case
167 if (blkcg == &blkio_root_cgroup)
170 return blkg_to_tg(blkg_lookup(blkcg, td->queue));
173 static struct throtl_grp *throtl_lookup_create_tg(struct throtl_data *td,
174 struct blkio_cgroup *blkcg)
176 struct request_queue *q = td->queue;
177 struct throtl_grp *tg = NULL;
180 * This is the common case when there are no blkio cgroups.
181 * Avoid lookup in this case
183 if (blkcg == &blkio_root_cgroup) {
186 struct blkio_group *blkg;
188 blkg = blkg_lookup_create(blkcg, q, BLKIO_POLICY_THROTL, false);
190 /* if %NULL and @q is alive, fall back to root_tg */
192 tg = blkg_to_tg(blkg);
193 else if (!blk_queue_dead(q))
200 static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root)
202 /* Service tree is empty */
207 root->left = rb_first(&root->rb);
210 return rb_entry_tg(root->left);
215 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
221 static void throtl_rb_erase(struct rb_node *n, struct throtl_rb_root *root)
225 rb_erase_init(n, &root->rb);
229 static void update_min_dispatch_time(struct throtl_rb_root *st)
231 struct throtl_grp *tg;
233 tg = throtl_rb_first(st);
237 st->min_disptime = tg->disptime;
241 tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg)
243 struct rb_node **node = &st->rb.rb_node;
244 struct rb_node *parent = NULL;
245 struct throtl_grp *__tg;
246 unsigned long key = tg->disptime;
249 while (*node != NULL) {
251 __tg = rb_entry_tg(parent);
253 if (time_before(key, __tg->disptime))
254 node = &parent->rb_left;
256 node = &parent->rb_right;
262 st->left = &tg->rb_node;
264 rb_link_node(&tg->rb_node, parent, node);
265 rb_insert_color(&tg->rb_node, &st->rb);
268 static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
270 struct throtl_rb_root *st = &td->tg_service_tree;
272 tg_service_tree_add(st, tg);
273 throtl_mark_tg_on_rr(tg);
277 static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
279 if (!throtl_tg_on_rr(tg))
280 __throtl_enqueue_tg(td, tg);
283 static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
285 throtl_rb_erase(&tg->rb_node, &td->tg_service_tree);
286 throtl_clear_tg_on_rr(tg);
289 static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
291 if (throtl_tg_on_rr(tg))
292 __throtl_dequeue_tg(td, tg);
295 static void throtl_schedule_next_dispatch(struct throtl_data *td)
297 struct throtl_rb_root *st = &td->tg_service_tree;
300 * If there are more bios pending, schedule more work.
302 if (!total_nr_queued(td))
307 update_min_dispatch_time(st);
309 if (time_before_eq(st->min_disptime, jiffies))
310 throtl_schedule_delayed_work(td, 0);
312 throtl_schedule_delayed_work(td, (st->min_disptime - jiffies));
316 throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
318 tg->bytes_disp[rw] = 0;
320 tg->slice_start[rw] = jiffies;
321 tg->slice_end[rw] = jiffies + throtl_slice;
322 throtl_log_tg(td, tg, "[%c] new slice start=%lu end=%lu jiffies=%lu",
323 rw == READ ? 'R' : 'W', tg->slice_start[rw],
324 tg->slice_end[rw], jiffies);
327 static inline void throtl_set_slice_end(struct throtl_data *td,
328 struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
330 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
333 static inline void throtl_extend_slice(struct throtl_data *td,
334 struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
336 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
337 throtl_log_tg(td, tg, "[%c] extend slice start=%lu end=%lu jiffies=%lu",
338 rw == READ ? 'R' : 'W', tg->slice_start[rw],
339 tg->slice_end[rw], jiffies);
342 /* Determine if previously allocated or extended slice is complete or not */
344 throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw)
346 if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
352 /* Trim the used slices and adjust slice start accordingly */
354 throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
356 unsigned long nr_slices, time_elapsed, io_trim;
359 BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
362 * If bps are unlimited (-1), then time slice don't get
363 * renewed. Don't try to trim the slice if slice is used. A new
364 * slice will start when appropriate.
366 if (throtl_slice_used(td, tg, rw))
370 * A bio has been dispatched. Also adjust slice_end. It might happen
371 * that initially cgroup limit was very low resulting in high
372 * slice_end, but later limit was bumped up and bio was dispached
373 * sooner, then we need to reduce slice_end. A high bogus slice_end
374 * is bad because it does not allow new slice to start.
377 throtl_set_slice_end(td, tg, rw, jiffies + throtl_slice);
379 time_elapsed = jiffies - tg->slice_start[rw];
381 nr_slices = time_elapsed / throtl_slice;
385 tmp = tg->bps[rw] * throtl_slice * nr_slices;
389 io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ;
391 if (!bytes_trim && !io_trim)
394 if (tg->bytes_disp[rw] >= bytes_trim)
395 tg->bytes_disp[rw] -= bytes_trim;
397 tg->bytes_disp[rw] = 0;
399 if (tg->io_disp[rw] >= io_trim)
400 tg->io_disp[rw] -= io_trim;
404 tg->slice_start[rw] += nr_slices * throtl_slice;
406 throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%llu io=%lu"
407 " start=%lu end=%lu jiffies=%lu",
408 rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
409 tg->slice_start[rw], tg->slice_end[rw], jiffies);
412 static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg,
413 struct bio *bio, unsigned long *wait)
415 bool rw = bio_data_dir(bio);
416 unsigned int io_allowed;
417 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
420 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
422 /* Slice has just started. Consider one slice interval */
424 jiffy_elapsed_rnd = throtl_slice;
426 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
429 * jiffy_elapsed_rnd should not be a big value as minimum iops can be
430 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
431 * will allow dispatch after 1 second and after that slice should
435 tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd;
439 io_allowed = UINT_MAX;
443 if (tg->io_disp[rw] + 1 <= io_allowed) {
449 /* Calc approx time to dispatch */
450 jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;
452 if (jiffy_wait > jiffy_elapsed)
453 jiffy_wait = jiffy_wait - jiffy_elapsed;
462 static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg,
463 struct bio *bio, unsigned long *wait)
465 bool rw = bio_data_dir(bio);
466 u64 bytes_allowed, extra_bytes, tmp;
467 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
469 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
471 /* Slice has just started. Consider one slice interval */
473 jiffy_elapsed_rnd = throtl_slice;
475 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
477 tmp = tg->bps[rw] * jiffy_elapsed_rnd;
481 if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) {
487 /* Calc approx time to dispatch */
488 extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed;
489 jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]);
495 * This wait time is without taking into consideration the rounding
496 * up we did. Add that time also.
498 jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
504 static bool tg_no_rule_group(struct throtl_grp *tg, bool rw) {
505 if (tg->bps[rw] == -1 && tg->iops[rw] == -1)
511 * Returns whether one can dispatch a bio or not. Also returns approx number
512 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
514 static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
515 struct bio *bio, unsigned long *wait)
517 bool rw = bio_data_dir(bio);
518 unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
521 * Currently whole state machine of group depends on first bio
522 * queued in the group bio list. So one should not be calling
523 * this function with a different bio if there are other bios
526 BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));
528 /* If tg->bps = -1, then BW is unlimited */
529 if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
536 * If previous slice expired, start a new one otherwise renew/extend
537 * existing slice to make sure it is at least throtl_slice interval
540 if (throtl_slice_used(td, tg, rw))
541 throtl_start_new_slice(td, tg, rw);
543 if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
544 throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);
547 if (tg_with_in_bps_limit(td, tg, bio, &bps_wait)
548 && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) {
554 max_wait = max(bps_wait, iops_wait);
559 if (time_before(tg->slice_end[rw], jiffies + max_wait))
560 throtl_extend_slice(td, tg, rw, jiffies + max_wait);
565 static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
567 bool rw = bio_data_dir(bio);
568 bool sync = rw_is_sync(bio->bi_rw);
570 /* Charge the bio to the group */
571 tg->bytes_disp[rw] += bio->bi_size;
574 blkiocg_update_dispatch_stats(tg_to_blkg(tg), &blkio_policy_throtl,
575 bio->bi_size, rw, sync);
578 static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg,
581 bool rw = bio_data_dir(bio);
583 bio_list_add(&tg->bio_lists[rw], bio);
584 /* Take a bio reference on tg */
585 blkg_get(tg_to_blkg(tg));
588 throtl_enqueue_tg(td, tg);
591 static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg)
593 unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
596 if ((bio = bio_list_peek(&tg->bio_lists[READ])))
597 tg_may_dispatch(td, tg, bio, &read_wait);
599 if ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
600 tg_may_dispatch(td, tg, bio, &write_wait);
602 min_wait = min(read_wait, write_wait);
603 disptime = jiffies + min_wait;
605 /* Update dispatch time */
606 throtl_dequeue_tg(td, tg);
607 tg->disptime = disptime;
608 throtl_enqueue_tg(td, tg);
611 static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg,
612 bool rw, struct bio_list *bl)
616 bio = bio_list_pop(&tg->bio_lists[rw]);
618 /* Drop bio reference on blkg */
619 blkg_put(tg_to_blkg(tg));
621 BUG_ON(td->nr_queued[rw] <= 0);
624 throtl_charge_bio(tg, bio);
625 bio_list_add(bl, bio);
626 bio->bi_rw |= REQ_THROTTLED;
628 throtl_trim_slice(td, tg, rw);
631 static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg,
634 unsigned int nr_reads = 0, nr_writes = 0;
635 unsigned int max_nr_reads = throtl_grp_quantum*3/4;
636 unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
639 /* Try to dispatch 75% READS and 25% WRITES */
641 while ((bio = bio_list_peek(&tg->bio_lists[READ]))
642 && tg_may_dispatch(td, tg, bio, NULL)) {
644 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
647 if (nr_reads >= max_nr_reads)
651 while ((bio = bio_list_peek(&tg->bio_lists[WRITE]))
652 && tg_may_dispatch(td, tg, bio, NULL)) {
654 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
657 if (nr_writes >= max_nr_writes)
661 return nr_reads + nr_writes;
664 static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl)
666 unsigned int nr_disp = 0;
667 struct throtl_grp *tg;
668 struct throtl_rb_root *st = &td->tg_service_tree;
671 tg = throtl_rb_first(st);
676 if (time_before(jiffies, tg->disptime))
679 throtl_dequeue_tg(td, tg);
681 nr_disp += throtl_dispatch_tg(td, tg, bl);
683 if (tg->nr_queued[0] || tg->nr_queued[1]) {
684 tg_update_disptime(td, tg);
685 throtl_enqueue_tg(td, tg);
688 if (nr_disp >= throtl_quantum)
695 static void throtl_process_limit_change(struct throtl_data *td)
697 struct request_queue *q = td->queue;
698 struct blkio_group *blkg, *n;
700 if (!td->limits_changed)
703 xchg(&td->limits_changed, false);
705 throtl_log(td, "limits changed");
707 list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
708 struct throtl_grp *tg = blkg_to_tg(blkg);
710 if (!tg->limits_changed)
713 if (!xchg(&tg->limits_changed, false))
716 throtl_log_tg(td, tg, "limit change rbps=%llu wbps=%llu"
717 " riops=%u wiops=%u", tg->bps[READ], tg->bps[WRITE],
718 tg->iops[READ], tg->iops[WRITE]);
721 * Restart the slices for both READ and WRITES. It
722 * might happen that a group's limit are dropped
723 * suddenly and we don't want to account recently
724 * dispatched IO with new low rate
726 throtl_start_new_slice(td, tg, 0);
727 throtl_start_new_slice(td, tg, 1);
729 if (throtl_tg_on_rr(tg))
730 tg_update_disptime(td, tg);
734 /* Dispatch throttled bios. Should be called without queue lock held. */
735 static int throtl_dispatch(struct request_queue *q)
737 struct throtl_data *td = q->td;
738 unsigned int nr_disp = 0;
739 struct bio_list bio_list_on_stack;
741 struct blk_plug plug;
743 spin_lock_irq(q->queue_lock);
745 throtl_process_limit_change(td);
747 if (!total_nr_queued(td))
750 bio_list_init(&bio_list_on_stack);
752 throtl_log(td, "dispatch nr_queued=%u read=%u write=%u",
753 total_nr_queued(td), td->nr_queued[READ],
754 td->nr_queued[WRITE]);
756 nr_disp = throtl_select_dispatch(td, &bio_list_on_stack);
759 throtl_log(td, "bios disp=%u", nr_disp);
761 throtl_schedule_next_dispatch(td);
763 spin_unlock_irq(q->queue_lock);
766 * If we dispatched some requests, unplug the queue to make sure
770 blk_start_plug(&plug);
771 while((bio = bio_list_pop(&bio_list_on_stack)))
772 generic_make_request(bio);
773 blk_finish_plug(&plug);
778 void blk_throtl_work(struct work_struct *work)
780 struct throtl_data *td = container_of(work, struct throtl_data,
782 struct request_queue *q = td->queue;
787 /* Call with queue lock held */
789 throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay)
792 struct delayed_work *dwork = &td->throtl_work;
794 /* schedule work if limits changed even if no bio is queued */
795 if (total_nr_queued(td) || td->limits_changed) {
797 * We might have a work scheduled to be executed in future.
798 * Cancel that and schedule a new one.
800 __cancel_delayed_work(dwork);
801 queue_delayed_work(kthrotld_workqueue, dwork, delay);
802 throtl_log(td, "schedule work. delay=%lu jiffies=%lu",
807 static void throtl_update_blkio_group_common(struct throtl_data *td,
808 struct throtl_grp *tg)
810 xchg(&tg->limits_changed, true);
811 xchg(&td->limits_changed, true);
812 /* Schedule a work now to process the limit change */
813 throtl_schedule_delayed_work(td, 0);
817 * For all update functions, @q should be a valid pointer because these
818 * update functions are called under blkcg_lock, that means, blkg is
819 * valid and in turn @q is valid. queue exit path can not race because
822 * Can not take queue lock in update functions as queue lock under blkcg_lock
823 * is not allowed. Under other paths we take blkcg_lock under queue_lock.
825 static void throtl_update_blkio_group_read_bps(struct request_queue *q,
826 struct blkio_group *blkg, u64 read_bps)
828 struct throtl_grp *tg = blkg_to_tg(blkg);
830 tg->bps[READ] = read_bps;
831 throtl_update_blkio_group_common(q->td, tg);
834 static void throtl_update_blkio_group_write_bps(struct request_queue *q,
835 struct blkio_group *blkg, u64 write_bps)
837 struct throtl_grp *tg = blkg_to_tg(blkg);
839 tg->bps[WRITE] = write_bps;
840 throtl_update_blkio_group_common(q->td, tg);
843 static void throtl_update_blkio_group_read_iops(struct request_queue *q,
844 struct blkio_group *blkg, unsigned int read_iops)
846 struct throtl_grp *tg = blkg_to_tg(blkg);
848 tg->iops[READ] = read_iops;
849 throtl_update_blkio_group_common(q->td, tg);
852 static void throtl_update_blkio_group_write_iops(struct request_queue *q,
853 struct blkio_group *blkg, unsigned int write_iops)
855 struct throtl_grp *tg = blkg_to_tg(blkg);
857 tg->iops[WRITE] = write_iops;
858 throtl_update_blkio_group_common(q->td, tg);
861 static void throtl_shutdown_wq(struct request_queue *q)
863 struct throtl_data *td = q->td;
865 cancel_delayed_work_sync(&td->throtl_work);
868 static struct blkio_policy_type blkio_policy_throtl = {
870 .blkio_init_group_fn = throtl_init_blkio_group,
871 .blkio_update_group_read_bps_fn =
872 throtl_update_blkio_group_read_bps,
873 .blkio_update_group_write_bps_fn =
874 throtl_update_blkio_group_write_bps,
875 .blkio_update_group_read_iops_fn =
876 throtl_update_blkio_group_read_iops,
877 .blkio_update_group_write_iops_fn =
878 throtl_update_blkio_group_write_iops,
880 .plid = BLKIO_POLICY_THROTL,
881 .pdata_size = sizeof(struct throtl_grp),
884 bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
886 struct throtl_data *td = q->td;
887 struct throtl_grp *tg;
888 bool rw = bio_data_dir(bio), update_disptime = true;
889 struct blkio_cgroup *blkcg;
890 bool throttled = false;
892 if (bio->bi_rw & REQ_THROTTLED) {
893 bio->bi_rw &= ~REQ_THROTTLED;
897 /* bio_associate_current() needs ioc, try creating */
898 create_io_context(GFP_ATOMIC, q->node);
901 * A throtl_grp pointer retrieved under rcu can be used to access
902 * basic fields like stats and io rates. If a group has no rules,
903 * just update the dispatch stats in lockless manner and return.
906 blkcg = bio_blkio_cgroup(bio);
907 tg = throtl_lookup_tg(td, blkcg);
909 if (tg_no_rule_group(tg, rw)) {
910 blkiocg_update_dispatch_stats(tg_to_blkg(tg),
911 &blkio_policy_throtl,
913 rw_is_sync(bio->bi_rw));
919 * Either group has not been allocated yet or it is not an unlimited
922 spin_lock_irq(q->queue_lock);
923 tg = throtl_lookup_create_tg(td, blkcg);
927 if (tg->nr_queued[rw]) {
929 * There is already another bio queued in same dir. No
930 * need to update dispatch time.
932 update_disptime = false;
937 /* Bio is with-in rate limit of group */
938 if (tg_may_dispatch(td, tg, bio, NULL)) {
939 throtl_charge_bio(tg, bio);
942 * We need to trim slice even when bios are not being queued
943 * otherwise it might happen that a bio is not queued for
944 * a long time and slice keeps on extending and trim is not
945 * called for a long time. Now if limits are reduced suddenly
946 * we take into account all the IO dispatched so far at new
947 * low rate and * newly queued IO gets a really long dispatch
950 * So keep on trimming slice even if bio is not queued.
952 throtl_trim_slice(td, tg, rw);
957 throtl_log_tg(td, tg, "[%c] bio. bdisp=%llu sz=%u bps=%llu"
958 " iodisp=%u iops=%u queued=%d/%d",
959 rw == READ ? 'R' : 'W',
960 tg->bytes_disp[rw], bio->bi_size, tg->bps[rw],
961 tg->io_disp[rw], tg->iops[rw],
962 tg->nr_queued[READ], tg->nr_queued[WRITE]);
964 bio_associate_current(bio);
965 throtl_add_bio_tg(q->td, tg, bio);
968 if (update_disptime) {
969 tg_update_disptime(td, tg);
970 throtl_schedule_next_dispatch(td);
974 spin_unlock_irq(q->queue_lock);
982 * blk_throtl_drain - drain throttled bios
983 * @q: request_queue to drain throttled bios for
985 * Dispatch all currently throttled bios on @q through ->make_request_fn().
987 void blk_throtl_drain(struct request_queue *q)
988 __releases(q->queue_lock) __acquires(q->queue_lock)
990 struct throtl_data *td = q->td;
991 struct throtl_rb_root *st = &td->tg_service_tree;
992 struct throtl_grp *tg;
996 WARN_ON_ONCE(!queue_is_locked(q));
1000 while ((tg = throtl_rb_first(st))) {
1001 throtl_dequeue_tg(td, tg);
1003 while ((bio = bio_list_peek(&tg->bio_lists[READ])))
1004 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), &bl);
1005 while ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
1006 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), &bl);
1008 spin_unlock_irq(q->queue_lock);
1010 while ((bio = bio_list_pop(&bl)))
1011 generic_make_request(bio);
1013 spin_lock_irq(q->queue_lock);
1016 int blk_throtl_init(struct request_queue *q)
1018 struct throtl_data *td;
1019 struct blkio_group *blkg;
1021 td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
1025 td->tg_service_tree = THROTL_RB_ROOT;
1026 td->limits_changed = false;
1027 INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work);
1032 /* alloc and init root group. */
1034 spin_lock_irq(q->queue_lock);
1036 blkg = blkg_lookup_create(&blkio_root_cgroup, q, BLKIO_POLICY_THROTL,
1039 td->root_tg = blkg_to_tg(blkg);
1041 spin_unlock_irq(q->queue_lock);
1051 void blk_throtl_exit(struct request_queue *q)
1054 throtl_shutdown_wq(q);
1058 static int __init throtl_init(void)
1060 kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
1061 if (!kthrotld_workqueue)
1062 panic("Failed to create kthrotld\n");
1064 blkio_policy_register(&blkio_policy_throtl);
1068 module_init(throtl_init);