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 /* List of throtl groups on the request queue*/
45 struct hlist_node tg_node;
47 /* active throtl group service_tree member */
48 struct rb_node rb_node;
51 * Dispatch time in jiffies. This is the estimated time when group
52 * will unthrottle and is ready to dispatch more bio. It is used as
53 * key to sort active groups in service tree.
55 unsigned long disptime;
59 /* Two lists for READ and WRITE */
60 struct bio_list bio_lists[2];
62 /* Number of queued bios on READ and WRITE lists */
63 unsigned int nr_queued[2];
65 /* bytes per second rate limits */
71 /* Number of bytes disptached in current slice */
72 uint64_t bytes_disp[2];
73 /* Number of bio's dispatched in current slice */
74 unsigned int io_disp[2];
76 /* When did we start a new slice */
77 unsigned long slice_start[2];
78 unsigned long slice_end[2];
80 /* Some throttle limits got updated for the group */
86 /* List of throtl groups */
87 struct hlist_head tg_list;
89 /* service tree for active throtl groups */
90 struct throtl_rb_root tg_service_tree;
92 struct throtl_grp *root_tg;
93 struct request_queue *queue;
95 /* Total Number of queued bios on READ and WRITE lists */
96 unsigned int nr_queued[2];
99 * number of total undestroyed groups
101 unsigned int nr_undestroyed_grps;
103 /* Work for dispatching throttled bios */
104 struct delayed_work throtl_work;
109 static inline struct throtl_grp *blkg_to_tg(struct blkio_group *blkg)
111 return blkg_to_pdata(blkg, &blkio_policy_throtl);
114 static inline struct blkio_group *tg_to_blkg(struct throtl_grp *tg)
116 return pdata_to_blkg(tg, &blkio_policy_throtl);
119 enum tg_state_flags {
120 THROTL_TG_FLAG_on_rr = 0, /* on round-robin busy list */
123 #define THROTL_TG_FNS(name) \
124 static inline void throtl_mark_tg_##name(struct throtl_grp *tg) \
126 (tg)->flags |= (1 << THROTL_TG_FLAG_##name); \
128 static inline void throtl_clear_tg_##name(struct throtl_grp *tg) \
130 (tg)->flags &= ~(1 << THROTL_TG_FLAG_##name); \
132 static inline int throtl_tg_##name(const struct throtl_grp *tg) \
134 return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0; \
137 THROTL_TG_FNS(on_rr);
139 #define throtl_log_tg(td, tg, fmt, args...) \
140 blk_add_trace_msg((td)->queue, "throtl %s " fmt, \
141 blkg_path(tg_to_blkg(tg)), ##args); \
143 #define throtl_log(td, fmt, args...) \
144 blk_add_trace_msg((td)->queue, "throtl " fmt, ##args)
146 static inline unsigned int total_nr_queued(struct throtl_data *td)
148 return td->nr_queued[0] + td->nr_queued[1];
151 static void throtl_init_blkio_group(struct blkio_group *blkg)
153 struct throtl_grp *tg = blkg_to_tg(blkg);
155 INIT_HLIST_NODE(&tg->tg_node);
156 RB_CLEAR_NODE(&tg->rb_node);
157 bio_list_init(&tg->bio_lists[0]);
158 bio_list_init(&tg->bio_lists[1]);
159 tg->limits_changed = false;
164 tg->iops[WRITE] = -1;
167 static void throtl_link_blkio_group(struct request_queue *q,
168 struct blkio_group *blkg)
170 struct throtl_data *td = q->td;
171 struct throtl_grp *tg = blkg_to_tg(blkg);
173 hlist_add_head(&tg->tg_node, &td->tg_list);
174 td->nr_undestroyed_grps++;
178 throtl_grp *throtl_lookup_tg(struct throtl_data *td, struct blkio_cgroup *blkcg)
181 * This is the common case when there are no blkio cgroups.
182 * Avoid lookup in this case
184 if (blkcg == &blkio_root_cgroup)
187 return blkg_to_tg(blkg_lookup(blkcg, td->queue, BLKIO_POLICY_THROTL));
190 static struct throtl_grp *throtl_lookup_create_tg(struct throtl_data *td,
191 struct blkio_cgroup *blkcg)
193 struct request_queue *q = td->queue;
194 struct throtl_grp *tg = NULL;
197 * This is the common case when there are no blkio cgroups.
198 * Avoid lookup in this case
200 if (blkcg == &blkio_root_cgroup) {
203 struct blkio_group *blkg;
205 blkg = blkg_lookup_create(blkcg, q, BLKIO_POLICY_THROTL, false);
207 /* if %NULL and @q is alive, fall back to root_tg */
209 tg = blkg_to_tg(blkg);
210 else if (!blk_queue_dead(q))
217 static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root)
219 /* Service tree is empty */
224 root->left = rb_first(&root->rb);
227 return rb_entry_tg(root->left);
232 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
238 static void throtl_rb_erase(struct rb_node *n, struct throtl_rb_root *root)
242 rb_erase_init(n, &root->rb);
246 static void update_min_dispatch_time(struct throtl_rb_root *st)
248 struct throtl_grp *tg;
250 tg = throtl_rb_first(st);
254 st->min_disptime = tg->disptime;
258 tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg)
260 struct rb_node **node = &st->rb.rb_node;
261 struct rb_node *parent = NULL;
262 struct throtl_grp *__tg;
263 unsigned long key = tg->disptime;
266 while (*node != NULL) {
268 __tg = rb_entry_tg(parent);
270 if (time_before(key, __tg->disptime))
271 node = &parent->rb_left;
273 node = &parent->rb_right;
279 st->left = &tg->rb_node;
281 rb_link_node(&tg->rb_node, parent, node);
282 rb_insert_color(&tg->rb_node, &st->rb);
285 static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
287 struct throtl_rb_root *st = &td->tg_service_tree;
289 tg_service_tree_add(st, tg);
290 throtl_mark_tg_on_rr(tg);
294 static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
296 if (!throtl_tg_on_rr(tg))
297 __throtl_enqueue_tg(td, tg);
300 static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
302 throtl_rb_erase(&tg->rb_node, &td->tg_service_tree);
303 throtl_clear_tg_on_rr(tg);
306 static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
308 if (throtl_tg_on_rr(tg))
309 __throtl_dequeue_tg(td, tg);
312 static void throtl_schedule_next_dispatch(struct throtl_data *td)
314 struct throtl_rb_root *st = &td->tg_service_tree;
317 * If there are more bios pending, schedule more work.
319 if (!total_nr_queued(td))
324 update_min_dispatch_time(st);
326 if (time_before_eq(st->min_disptime, jiffies))
327 throtl_schedule_delayed_work(td, 0);
329 throtl_schedule_delayed_work(td, (st->min_disptime - jiffies));
333 throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
335 tg->bytes_disp[rw] = 0;
337 tg->slice_start[rw] = jiffies;
338 tg->slice_end[rw] = jiffies + throtl_slice;
339 throtl_log_tg(td, tg, "[%c] new slice start=%lu end=%lu jiffies=%lu",
340 rw == READ ? 'R' : 'W', tg->slice_start[rw],
341 tg->slice_end[rw], jiffies);
344 static inline void throtl_set_slice_end(struct throtl_data *td,
345 struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
347 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
350 static inline void throtl_extend_slice(struct throtl_data *td,
351 struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
353 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
354 throtl_log_tg(td, tg, "[%c] extend slice start=%lu end=%lu jiffies=%lu",
355 rw == READ ? 'R' : 'W', tg->slice_start[rw],
356 tg->slice_end[rw], jiffies);
359 /* Determine if previously allocated or extended slice is complete or not */
361 throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw)
363 if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
369 /* Trim the used slices and adjust slice start accordingly */
371 throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
373 unsigned long nr_slices, time_elapsed, io_trim;
376 BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
379 * If bps are unlimited (-1), then time slice don't get
380 * renewed. Don't try to trim the slice if slice is used. A new
381 * slice will start when appropriate.
383 if (throtl_slice_used(td, tg, rw))
387 * A bio has been dispatched. Also adjust slice_end. It might happen
388 * that initially cgroup limit was very low resulting in high
389 * slice_end, but later limit was bumped up and bio was dispached
390 * sooner, then we need to reduce slice_end. A high bogus slice_end
391 * is bad because it does not allow new slice to start.
394 throtl_set_slice_end(td, tg, rw, jiffies + throtl_slice);
396 time_elapsed = jiffies - tg->slice_start[rw];
398 nr_slices = time_elapsed / throtl_slice;
402 tmp = tg->bps[rw] * throtl_slice * nr_slices;
406 io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ;
408 if (!bytes_trim && !io_trim)
411 if (tg->bytes_disp[rw] >= bytes_trim)
412 tg->bytes_disp[rw] -= bytes_trim;
414 tg->bytes_disp[rw] = 0;
416 if (tg->io_disp[rw] >= io_trim)
417 tg->io_disp[rw] -= io_trim;
421 tg->slice_start[rw] += nr_slices * throtl_slice;
423 throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%llu io=%lu"
424 " start=%lu end=%lu jiffies=%lu",
425 rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
426 tg->slice_start[rw], tg->slice_end[rw], jiffies);
429 static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg,
430 struct bio *bio, unsigned long *wait)
432 bool rw = bio_data_dir(bio);
433 unsigned int io_allowed;
434 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
437 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
439 /* Slice has just started. Consider one slice interval */
441 jiffy_elapsed_rnd = throtl_slice;
443 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
446 * jiffy_elapsed_rnd should not be a big value as minimum iops can be
447 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
448 * will allow dispatch after 1 second and after that slice should
452 tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd;
456 io_allowed = UINT_MAX;
460 if (tg->io_disp[rw] + 1 <= io_allowed) {
466 /* Calc approx time to dispatch */
467 jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;
469 if (jiffy_wait > jiffy_elapsed)
470 jiffy_wait = jiffy_wait - jiffy_elapsed;
479 static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg,
480 struct bio *bio, unsigned long *wait)
482 bool rw = bio_data_dir(bio);
483 u64 bytes_allowed, extra_bytes, tmp;
484 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
486 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
488 /* Slice has just started. Consider one slice interval */
490 jiffy_elapsed_rnd = throtl_slice;
492 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
494 tmp = tg->bps[rw] * jiffy_elapsed_rnd;
498 if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) {
504 /* Calc approx time to dispatch */
505 extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed;
506 jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]);
512 * This wait time is without taking into consideration the rounding
513 * up we did. Add that time also.
515 jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
521 static bool tg_no_rule_group(struct throtl_grp *tg, bool rw) {
522 if (tg->bps[rw] == -1 && tg->iops[rw] == -1)
528 * Returns whether one can dispatch a bio or not. Also returns approx number
529 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
531 static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
532 struct bio *bio, unsigned long *wait)
534 bool rw = bio_data_dir(bio);
535 unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
538 * Currently whole state machine of group depends on first bio
539 * queued in the group bio list. So one should not be calling
540 * this function with a different bio if there are other bios
543 BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));
545 /* If tg->bps = -1, then BW is unlimited */
546 if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
553 * If previous slice expired, start a new one otherwise renew/extend
554 * existing slice to make sure it is at least throtl_slice interval
557 if (throtl_slice_used(td, tg, rw))
558 throtl_start_new_slice(td, tg, rw);
560 if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
561 throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);
564 if (tg_with_in_bps_limit(td, tg, bio, &bps_wait)
565 && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) {
571 max_wait = max(bps_wait, iops_wait);
576 if (time_before(tg->slice_end[rw], jiffies + max_wait))
577 throtl_extend_slice(td, tg, rw, jiffies + max_wait);
582 static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
584 bool rw = bio_data_dir(bio);
585 bool sync = rw_is_sync(bio->bi_rw);
587 /* Charge the bio to the group */
588 tg->bytes_disp[rw] += bio->bi_size;
591 blkiocg_update_dispatch_stats(tg_to_blkg(tg), bio->bi_size, rw, sync);
594 static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg,
597 bool rw = bio_data_dir(bio);
599 bio_list_add(&tg->bio_lists[rw], bio);
600 /* Take a bio reference on tg */
601 blkg_get(tg_to_blkg(tg));
604 throtl_enqueue_tg(td, tg);
607 static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg)
609 unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
612 if ((bio = bio_list_peek(&tg->bio_lists[READ])))
613 tg_may_dispatch(td, tg, bio, &read_wait);
615 if ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
616 tg_may_dispatch(td, tg, bio, &write_wait);
618 min_wait = min(read_wait, write_wait);
619 disptime = jiffies + min_wait;
621 /* Update dispatch time */
622 throtl_dequeue_tg(td, tg);
623 tg->disptime = disptime;
624 throtl_enqueue_tg(td, tg);
627 static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg,
628 bool rw, struct bio_list *bl)
632 bio = bio_list_pop(&tg->bio_lists[rw]);
634 /* Drop bio reference on blkg */
635 blkg_put(tg_to_blkg(tg));
637 BUG_ON(td->nr_queued[rw] <= 0);
640 throtl_charge_bio(tg, bio);
641 bio_list_add(bl, bio);
642 bio->bi_rw |= REQ_THROTTLED;
644 throtl_trim_slice(td, tg, rw);
647 static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg,
650 unsigned int nr_reads = 0, nr_writes = 0;
651 unsigned int max_nr_reads = throtl_grp_quantum*3/4;
652 unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
655 /* Try to dispatch 75% READS and 25% WRITES */
657 while ((bio = bio_list_peek(&tg->bio_lists[READ]))
658 && tg_may_dispatch(td, tg, bio, NULL)) {
660 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
663 if (nr_reads >= max_nr_reads)
667 while ((bio = bio_list_peek(&tg->bio_lists[WRITE]))
668 && tg_may_dispatch(td, tg, bio, NULL)) {
670 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
673 if (nr_writes >= max_nr_writes)
677 return nr_reads + nr_writes;
680 static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl)
682 unsigned int nr_disp = 0;
683 struct throtl_grp *tg;
684 struct throtl_rb_root *st = &td->tg_service_tree;
687 tg = throtl_rb_first(st);
692 if (time_before(jiffies, tg->disptime))
695 throtl_dequeue_tg(td, tg);
697 nr_disp += throtl_dispatch_tg(td, tg, bl);
699 if (tg->nr_queued[0] || tg->nr_queued[1]) {
700 tg_update_disptime(td, tg);
701 throtl_enqueue_tg(td, tg);
704 if (nr_disp >= throtl_quantum)
711 static void throtl_process_limit_change(struct throtl_data *td)
713 struct throtl_grp *tg;
714 struct hlist_node *pos, *n;
716 if (!td->limits_changed)
719 xchg(&td->limits_changed, false);
721 throtl_log(td, "limits changed");
723 hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) {
724 if (!tg->limits_changed)
727 if (!xchg(&tg->limits_changed, false))
730 throtl_log_tg(td, tg, "limit change rbps=%llu wbps=%llu"
731 " riops=%u wiops=%u", tg->bps[READ], tg->bps[WRITE],
732 tg->iops[READ], tg->iops[WRITE]);
735 * Restart the slices for both READ and WRITES. It
736 * might happen that a group's limit are dropped
737 * suddenly and we don't want to account recently
738 * dispatched IO with new low rate
740 throtl_start_new_slice(td, tg, 0);
741 throtl_start_new_slice(td, tg, 1);
743 if (throtl_tg_on_rr(tg))
744 tg_update_disptime(td, tg);
748 /* Dispatch throttled bios. Should be called without queue lock held. */
749 static int throtl_dispatch(struct request_queue *q)
751 struct throtl_data *td = q->td;
752 unsigned int nr_disp = 0;
753 struct bio_list bio_list_on_stack;
755 struct blk_plug plug;
757 spin_lock_irq(q->queue_lock);
759 throtl_process_limit_change(td);
761 if (!total_nr_queued(td))
764 bio_list_init(&bio_list_on_stack);
766 throtl_log(td, "dispatch nr_queued=%u read=%u write=%u",
767 total_nr_queued(td), td->nr_queued[READ],
768 td->nr_queued[WRITE]);
770 nr_disp = throtl_select_dispatch(td, &bio_list_on_stack);
773 throtl_log(td, "bios disp=%u", nr_disp);
775 throtl_schedule_next_dispatch(td);
777 spin_unlock_irq(q->queue_lock);
780 * If we dispatched some requests, unplug the queue to make sure
784 blk_start_plug(&plug);
785 while((bio = bio_list_pop(&bio_list_on_stack)))
786 generic_make_request(bio);
787 blk_finish_plug(&plug);
792 void blk_throtl_work(struct work_struct *work)
794 struct throtl_data *td = container_of(work, struct throtl_data,
796 struct request_queue *q = td->queue;
801 /* Call with queue lock held */
803 throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay)
806 struct delayed_work *dwork = &td->throtl_work;
808 /* schedule work if limits changed even if no bio is queued */
809 if (total_nr_queued(td) || td->limits_changed) {
811 * We might have a work scheduled to be executed in future.
812 * Cancel that and schedule a new one.
814 __cancel_delayed_work(dwork);
815 queue_delayed_work(kthrotld_workqueue, dwork, delay);
816 throtl_log(td, "schedule work. delay=%lu jiffies=%lu",
822 throtl_destroy_tg(struct throtl_data *td, struct throtl_grp *tg)
824 /* Something wrong if we are trying to remove same group twice */
825 BUG_ON(hlist_unhashed(&tg->tg_node));
827 hlist_del_init(&tg->tg_node);
830 * Put the reference taken at the time of creation so that when all
831 * queues are gone, group can be destroyed.
833 blkg_put(tg_to_blkg(tg));
834 td->nr_undestroyed_grps--;
837 static bool throtl_release_tgs(struct throtl_data *td, bool release_root)
839 struct hlist_node *pos, *n;
840 struct throtl_grp *tg;
843 hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) {
845 if (!release_root && tg == td->root_tg)
849 * If cgroup removal path got to blk_group first and removed
850 * it from cgroup list, then it will take care of destroying
853 if (!blkiocg_del_blkio_group(tg_to_blkg(tg)))
854 throtl_destroy_tg(td, tg);
862 * Blk cgroup controller notification saying that blkio_group object is being
863 * delinked as associated cgroup object is going away. That also means that
864 * no new IO will come in this group. So get rid of this group as soon as
865 * any pending IO in the group is finished.
867 * This function is called under rcu_read_lock(). @q is the rcu protected
868 * pointer. That means @q is a valid request_queue pointer as long as we
871 * @q was fetched from blkio_group under blkio_cgroup->lock. That means
872 * it should not be NULL as even if queue was going away, cgroup deltion
873 * path got to it first.
875 void throtl_unlink_blkio_group(struct request_queue *q,
876 struct blkio_group *blkg)
880 spin_lock_irqsave(q->queue_lock, flags);
881 throtl_destroy_tg(q->td, blkg_to_tg(blkg));
882 spin_unlock_irqrestore(q->queue_lock, flags);
885 static bool throtl_clear_queue(struct request_queue *q)
887 lockdep_assert_held(q->queue_lock);
890 * Clear tgs but leave the root one alone. This is necessary
891 * because root_tg is expected to be persistent and safe because
892 * blk-throtl can never be disabled while @q is alive. This is a
893 * kludge to prepare for unified blkg. This whole function will be
896 return throtl_release_tgs(q->td, false);
899 static void throtl_update_blkio_group_common(struct throtl_data *td,
900 struct throtl_grp *tg)
902 xchg(&tg->limits_changed, true);
903 xchg(&td->limits_changed, true);
904 /* Schedule a work now to process the limit change */
905 throtl_schedule_delayed_work(td, 0);
909 * For all update functions, @q should be a valid pointer because these
910 * update functions are called under blkcg_lock, that means, blkg is
911 * valid and in turn @q is valid. queue exit path can not race because
914 * Can not take queue lock in update functions as queue lock under blkcg_lock
915 * is not allowed. Under other paths we take blkcg_lock under queue_lock.
917 static void throtl_update_blkio_group_read_bps(struct request_queue *q,
918 struct blkio_group *blkg, u64 read_bps)
920 struct throtl_grp *tg = blkg_to_tg(blkg);
922 tg->bps[READ] = read_bps;
923 throtl_update_blkio_group_common(q->td, tg);
926 static void throtl_update_blkio_group_write_bps(struct request_queue *q,
927 struct blkio_group *blkg, u64 write_bps)
929 struct throtl_grp *tg = blkg_to_tg(blkg);
931 tg->bps[WRITE] = write_bps;
932 throtl_update_blkio_group_common(q->td, tg);
935 static void throtl_update_blkio_group_read_iops(struct request_queue *q,
936 struct blkio_group *blkg, unsigned int read_iops)
938 struct throtl_grp *tg = blkg_to_tg(blkg);
940 tg->iops[READ] = read_iops;
941 throtl_update_blkio_group_common(q->td, tg);
944 static void throtl_update_blkio_group_write_iops(struct request_queue *q,
945 struct blkio_group *blkg, unsigned int write_iops)
947 struct throtl_grp *tg = blkg_to_tg(blkg);
949 tg->iops[WRITE] = write_iops;
950 throtl_update_blkio_group_common(q->td, tg);
953 static void throtl_shutdown_wq(struct request_queue *q)
955 struct throtl_data *td = q->td;
957 cancel_delayed_work_sync(&td->throtl_work);
960 static struct blkio_policy_type blkio_policy_throtl = {
962 .blkio_init_group_fn = throtl_init_blkio_group,
963 .blkio_link_group_fn = throtl_link_blkio_group,
964 .blkio_unlink_group_fn = throtl_unlink_blkio_group,
965 .blkio_clear_queue_fn = throtl_clear_queue,
966 .blkio_update_group_read_bps_fn =
967 throtl_update_blkio_group_read_bps,
968 .blkio_update_group_write_bps_fn =
969 throtl_update_blkio_group_write_bps,
970 .blkio_update_group_read_iops_fn =
971 throtl_update_blkio_group_read_iops,
972 .blkio_update_group_write_iops_fn =
973 throtl_update_blkio_group_write_iops,
975 .plid = BLKIO_POLICY_THROTL,
976 .pdata_size = sizeof(struct throtl_grp),
979 bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
981 struct throtl_data *td = q->td;
982 struct throtl_grp *tg;
983 bool rw = bio_data_dir(bio), update_disptime = true;
984 struct blkio_cgroup *blkcg;
985 bool throttled = false;
987 if (bio->bi_rw & REQ_THROTTLED) {
988 bio->bi_rw &= ~REQ_THROTTLED;
993 * A throtl_grp pointer retrieved under rcu can be used to access
994 * basic fields like stats and io rates. If a group has no rules,
995 * just update the dispatch stats in lockless manner and return.
998 blkcg = task_blkio_cgroup(current);
999 tg = throtl_lookup_tg(td, blkcg);
1001 if (tg_no_rule_group(tg, rw)) {
1002 blkiocg_update_dispatch_stats(tg_to_blkg(tg),
1004 rw_is_sync(bio->bi_rw));
1005 goto out_unlock_rcu;
1010 * Either group has not been allocated yet or it is not an unlimited
1013 spin_lock_irq(q->queue_lock);
1014 tg = throtl_lookup_create_tg(td, blkcg);
1018 if (tg->nr_queued[rw]) {
1020 * There is already another bio queued in same dir. No
1021 * need to update dispatch time.
1023 update_disptime = false;
1028 /* Bio is with-in rate limit of group */
1029 if (tg_may_dispatch(td, tg, bio, NULL)) {
1030 throtl_charge_bio(tg, bio);
1033 * We need to trim slice even when bios are not being queued
1034 * otherwise it might happen that a bio is not queued for
1035 * a long time and slice keeps on extending and trim is not
1036 * called for a long time. Now if limits are reduced suddenly
1037 * we take into account all the IO dispatched so far at new
1038 * low rate and * newly queued IO gets a really long dispatch
1041 * So keep on trimming slice even if bio is not queued.
1043 throtl_trim_slice(td, tg, rw);
1048 throtl_log_tg(td, tg, "[%c] bio. bdisp=%llu sz=%u bps=%llu"
1049 " iodisp=%u iops=%u queued=%d/%d",
1050 rw == READ ? 'R' : 'W',
1051 tg->bytes_disp[rw], bio->bi_size, tg->bps[rw],
1052 tg->io_disp[rw], tg->iops[rw],
1053 tg->nr_queued[READ], tg->nr_queued[WRITE]);
1055 throtl_add_bio_tg(q->td, tg, bio);
1058 if (update_disptime) {
1059 tg_update_disptime(td, tg);
1060 throtl_schedule_next_dispatch(td);
1064 spin_unlock_irq(q->queue_lock);
1072 * blk_throtl_drain - drain throttled bios
1073 * @q: request_queue to drain throttled bios for
1075 * Dispatch all currently throttled bios on @q through ->make_request_fn().
1077 void blk_throtl_drain(struct request_queue *q)
1078 __releases(q->queue_lock) __acquires(q->queue_lock)
1080 struct throtl_data *td = q->td;
1081 struct throtl_rb_root *st = &td->tg_service_tree;
1082 struct throtl_grp *tg;
1086 WARN_ON_ONCE(!queue_is_locked(q));
1090 while ((tg = throtl_rb_first(st))) {
1091 throtl_dequeue_tg(td, tg);
1093 while ((bio = bio_list_peek(&tg->bio_lists[READ])))
1094 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), &bl);
1095 while ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
1096 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), &bl);
1098 spin_unlock_irq(q->queue_lock);
1100 while ((bio = bio_list_pop(&bl)))
1101 generic_make_request(bio);
1103 spin_lock_irq(q->queue_lock);
1106 int blk_throtl_init(struct request_queue *q)
1108 struct throtl_data *td;
1109 struct blkio_group *blkg;
1111 td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
1115 INIT_HLIST_HEAD(&td->tg_list);
1116 td->tg_service_tree = THROTL_RB_ROOT;
1117 td->limits_changed = false;
1118 INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work);
1123 /* alloc and init root group. */
1125 spin_lock_irq(q->queue_lock);
1127 blkg = blkg_lookup_create(&blkio_root_cgroup, q, BLKIO_POLICY_THROTL,
1130 td->root_tg = blkg_to_tg(blkg);
1132 spin_unlock_irq(q->queue_lock);
1142 void blk_throtl_exit(struct request_queue *q)
1144 struct throtl_data *td = q->td;
1149 throtl_shutdown_wq(q);
1151 spin_lock_irq(q->queue_lock);
1152 throtl_release_tgs(td, true);
1154 /* If there are other groups */
1155 if (td->nr_undestroyed_grps > 0)
1158 spin_unlock_irq(q->queue_lock);
1161 * Wait for tg_to_blkg(tg)->q accessors to exit their grace periods.
1162 * Do this wait only if there are other undestroyed groups out
1163 * there (other than root group). This can happen if cgroup deletion
1164 * path claimed the responsibility of cleaning up a group before
1165 * queue cleanup code get to the group.
1167 * Do not call synchronize_rcu() unconditionally as there are drivers
1168 * which create/delete request queue hundreds of times during scan/boot
1169 * and synchronize_rcu() can take significant time and slow down boot.
1175 * Just being safe to make sure after previous flush if some body did
1176 * update limits through cgroup and another work got queued, cancel
1179 throtl_shutdown_wq(q);
1184 static int __init throtl_init(void)
1186 kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
1187 if (!kthrotld_workqueue)
1188 panic("Failed to create kthrotld\n");
1190 blkio_policy_register(&blkio_policy_throtl);
1194 module_init(throtl_init);