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 <linux/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 a slice and after that slice is renewed */
22 #define DFL_THROTL_SLICE_HD (HZ / 10)
23 #define DFL_THROTL_SLICE_SSD (HZ / 50)
24 #define MAX_THROTL_SLICE (HZ)
25 #define MAX_IDLE_TIME (5L * 1000 * 1000) /* 5 s */
26 #define MIN_THROTL_BPS (320 * 1024)
27 #define MIN_THROTL_IOPS (10)
28 #define DFL_LATENCY_TARGET (-1L)
29 #define DFL_IDLE_THRESHOLD (0)
30 #define DFL_HD_BASELINE_LATENCY (4000L) /* 4ms */
31 #define LATENCY_FILTERED_SSD (0)
33 * For HD, very small latency comes from sequential IO. Such IO is helpless to
34 * help determine if its IO is impacted by others, hence we ignore the IO
36 #define LATENCY_FILTERED_HD (1000L) /* 1ms */
38 #define SKIP_LATENCY (((u64)1) << BLK_STAT_RES_SHIFT)
40 static struct blkcg_policy blkcg_policy_throtl;
42 /* A workqueue to queue throttle related work */
43 static struct workqueue_struct *kthrotld_workqueue;
46 * To implement hierarchical throttling, throtl_grps form a tree and bios
47 * are dispatched upwards level by level until they reach the top and get
48 * issued. When dispatching bios from the children and local group at each
49 * level, if the bios are dispatched into a single bio_list, there's a risk
50 * of a local or child group which can queue many bios at once filling up
51 * the list starving others.
53 * To avoid such starvation, dispatched bios are queued separately
54 * according to where they came from. When they are again dispatched to
55 * the parent, they're popped in round-robin order so that no single source
56 * hogs the dispatch window.
58 * throtl_qnode is used to keep the queued bios separated by their sources.
59 * Bios are queued to throtl_qnode which in turn is queued to
60 * throtl_service_queue and then dispatched in round-robin order.
62 * It's also used to track the reference counts on blkg's. A qnode always
63 * belongs to a throtl_grp and gets queued on itself or the parent, so
64 * incrementing the reference of the associated throtl_grp when a qnode is
65 * queued and decrementing when dequeued is enough to keep the whole blkg
66 * tree pinned while bios are in flight.
69 struct list_head node; /* service_queue->queued[] */
70 struct bio_list bios; /* queued bios */
71 struct throtl_grp *tg; /* tg this qnode belongs to */
74 struct throtl_service_queue {
75 struct throtl_service_queue *parent_sq; /* the parent service_queue */
78 * Bios queued directly to this service_queue or dispatched from
79 * children throtl_grp's.
81 struct list_head queued[2]; /* throtl_qnode [READ/WRITE] */
82 unsigned int nr_queued[2]; /* number of queued bios */
85 * RB tree of active children throtl_grp's, which are sorted by
88 struct rb_root pending_tree; /* RB tree of active tgs */
89 struct rb_node *first_pending; /* first node in the tree */
90 unsigned int nr_pending; /* # queued in the tree */
91 unsigned long first_pending_disptime; /* disptime of the first tg */
92 struct timer_list pending_timer; /* fires on first_pending_disptime */
96 THROTL_TG_PENDING = 1 << 0, /* on parent's pending tree */
97 THROTL_TG_WAS_EMPTY = 1 << 1, /* bio_lists[] became non-empty */
100 #define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
109 /* must be the first member */
110 struct blkg_policy_data pd;
112 /* active throtl group service_queue member */
113 struct rb_node rb_node;
115 /* throtl_data this group belongs to */
116 struct throtl_data *td;
118 /* this group's service queue */
119 struct throtl_service_queue service_queue;
122 * qnode_on_self is used when bios are directly queued to this
123 * throtl_grp so that local bios compete fairly with bios
124 * dispatched from children. qnode_on_parent is used when bios are
125 * dispatched from this throtl_grp into its parent and will compete
126 * with the sibling qnode_on_parents and the parent's
129 struct throtl_qnode qnode_on_self[2];
130 struct throtl_qnode qnode_on_parent[2];
133 * Dispatch time in jiffies. This is the estimated time when group
134 * will unthrottle and is ready to dispatch more bio. It is used as
135 * key to sort active groups in service tree.
137 unsigned long disptime;
141 /* are there any throtl rules between this group and td? */
144 /* internally used bytes per second rate limits */
145 uint64_t bps[2][LIMIT_CNT];
146 /* user configured bps limits */
147 uint64_t bps_conf[2][LIMIT_CNT];
149 /* internally used IOPS limits */
150 unsigned int iops[2][LIMIT_CNT];
151 /* user configured IOPS limits */
152 unsigned int iops_conf[2][LIMIT_CNT];
154 /* Number of bytes disptached in current slice */
155 uint64_t bytes_disp[2];
156 /* Number of bio's dispatched in current slice */
157 unsigned int io_disp[2];
159 unsigned long last_low_overflow_time[2];
161 uint64_t last_bytes_disp[2];
162 unsigned int last_io_disp[2];
164 unsigned long last_check_time;
166 unsigned long latency_target; /* us */
167 unsigned long latency_target_conf; /* us */
168 /* When did we start a new slice */
169 unsigned long slice_start[2];
170 unsigned long slice_end[2];
172 unsigned long last_finish_time; /* ns / 1024 */
173 unsigned long checked_last_finish_time; /* ns / 1024 */
174 unsigned long avg_idletime; /* ns / 1024 */
175 unsigned long idletime_threshold; /* us */
176 unsigned long idletime_threshold_conf; /* us */
178 unsigned int bio_cnt; /* total bios */
179 unsigned int bad_bio_cnt; /* bios exceeding latency threshold */
180 unsigned long bio_cnt_reset_time;
183 /* We measure latency for request size from <= 4k to >= 1M */
184 #define LATENCY_BUCKET_SIZE 9
186 struct latency_bucket {
187 unsigned long total_latency; /* ns / 1024 */
191 struct avg_latency_bucket {
192 unsigned long latency; /* ns / 1024 */
198 /* service tree for active throtl groups */
199 struct throtl_service_queue service_queue;
201 struct request_queue *queue;
203 /* Total Number of queued bios on READ and WRITE lists */
204 unsigned int nr_queued[2];
206 unsigned int throtl_slice;
208 /* Work for dispatching throttled bios */
209 struct work_struct dispatch_work;
210 unsigned int limit_index;
211 bool limit_valid[LIMIT_CNT];
213 unsigned long low_upgrade_time;
214 unsigned long low_downgrade_time;
218 struct latency_bucket tmp_buckets[LATENCY_BUCKET_SIZE];
219 struct avg_latency_bucket avg_buckets[LATENCY_BUCKET_SIZE];
220 struct latency_bucket __percpu *latency_buckets;
221 unsigned long last_calculate_time;
222 unsigned long filtered_latency;
224 bool track_bio_latency;
227 static void throtl_pending_timer_fn(unsigned long arg);
229 static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
231 return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
234 static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
236 return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
239 static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
241 return pd_to_blkg(&tg->pd);
245 * sq_to_tg - return the throl_grp the specified service queue belongs to
246 * @sq: the throtl_service_queue of interest
248 * Return the throtl_grp @sq belongs to. If @sq is the top-level one
249 * embedded in throtl_data, %NULL is returned.
251 static struct throtl_grp *sq_to_tg(struct throtl_service_queue *sq)
253 if (sq && sq->parent_sq)
254 return container_of(sq, struct throtl_grp, service_queue);
260 * sq_to_td - return throtl_data the specified service queue belongs to
261 * @sq: the throtl_service_queue of interest
263 * A service_queue can be embedded in either a throtl_grp or throtl_data.
264 * Determine the associated throtl_data accordingly and return it.
266 static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
268 struct throtl_grp *tg = sq_to_tg(sq);
273 return container_of(sq, struct throtl_data, service_queue);
277 * cgroup's limit in LIMIT_MAX is scaled if low limit is set. This scale is to
278 * make the IO dispatch more smooth.
279 * Scale up: linearly scale up according to lapsed time since upgrade. For
280 * every throtl_slice, the limit scales up 1/2 .low limit till the
281 * limit hits .max limit
282 * Scale down: exponentially scale down if a cgroup doesn't hit its .low limit
284 static uint64_t throtl_adjusted_limit(uint64_t low, struct throtl_data *td)
286 /* arbitrary value to avoid too big scale */
287 if (td->scale < 4096 && time_after_eq(jiffies,
288 td->low_upgrade_time + td->scale * td->throtl_slice))
289 td->scale = (jiffies - td->low_upgrade_time) / td->throtl_slice;
291 return low + (low >> 1) * td->scale;
294 static uint64_t tg_bps_limit(struct throtl_grp *tg, int rw)
296 struct blkcg_gq *blkg = tg_to_blkg(tg);
297 struct throtl_data *td;
300 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
304 ret = tg->bps[rw][td->limit_index];
305 if (ret == 0 && td->limit_index == LIMIT_LOW) {
306 /* intermediate node or iops isn't 0 */
307 if (!list_empty(&blkg->blkcg->css.children) ||
308 tg->iops[rw][td->limit_index])
311 return MIN_THROTL_BPS;
314 if (td->limit_index == LIMIT_MAX && tg->bps[rw][LIMIT_LOW] &&
315 tg->bps[rw][LIMIT_LOW] != tg->bps[rw][LIMIT_MAX]) {
318 adjusted = throtl_adjusted_limit(tg->bps[rw][LIMIT_LOW], td);
319 ret = min(tg->bps[rw][LIMIT_MAX], adjusted);
324 static unsigned int tg_iops_limit(struct throtl_grp *tg, int rw)
326 struct blkcg_gq *blkg = tg_to_blkg(tg);
327 struct throtl_data *td;
330 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
334 ret = tg->iops[rw][td->limit_index];
335 if (ret == 0 && tg->td->limit_index == LIMIT_LOW) {
336 /* intermediate node or bps isn't 0 */
337 if (!list_empty(&blkg->blkcg->css.children) ||
338 tg->bps[rw][td->limit_index])
341 return MIN_THROTL_IOPS;
344 if (td->limit_index == LIMIT_MAX && tg->iops[rw][LIMIT_LOW] &&
345 tg->iops[rw][LIMIT_LOW] != tg->iops[rw][LIMIT_MAX]) {
348 adjusted = throtl_adjusted_limit(tg->iops[rw][LIMIT_LOW], td);
349 if (adjusted > UINT_MAX)
351 ret = min_t(unsigned int, tg->iops[rw][LIMIT_MAX], adjusted);
356 #define request_bucket_index(sectors) \
357 clamp_t(int, order_base_2(sectors) - 3, 0, LATENCY_BUCKET_SIZE - 1)
360 * throtl_log - log debug message via blktrace
361 * @sq: the service_queue being reported
362 * @fmt: printf format string
365 * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
366 * throtl_grp; otherwise, just "throtl".
368 #define throtl_log(sq, fmt, args...) do { \
369 struct throtl_grp *__tg = sq_to_tg((sq)); \
370 struct throtl_data *__td = sq_to_td((sq)); \
373 if (likely(!blk_trace_note_message_enabled(__td->queue))) \
378 blkg_path(tg_to_blkg(__tg), __pbuf, sizeof(__pbuf)); \
379 blk_add_trace_msg(__td->queue, "throtl %s " fmt, __pbuf, ##args); \
381 blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \
385 static inline unsigned int throtl_bio_data_size(struct bio *bio)
387 /* assume it's one sector */
388 if (unlikely(bio_op(bio) == REQ_OP_DISCARD))
390 return bio->bi_iter.bi_size;
393 static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg)
395 INIT_LIST_HEAD(&qn->node);
396 bio_list_init(&qn->bios);
401 * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it
402 * @bio: bio being added
403 * @qn: qnode to add bio to
404 * @queued: the service_queue->queued[] list @qn belongs to
406 * Add @bio to @qn and put @qn on @queued if it's not already on.
407 * @qn->tg's reference count is bumped when @qn is activated. See the
408 * comment on top of throtl_qnode definition for details.
410 static void throtl_qnode_add_bio(struct bio *bio, struct throtl_qnode *qn,
411 struct list_head *queued)
413 bio_list_add(&qn->bios, bio);
414 if (list_empty(&qn->node)) {
415 list_add_tail(&qn->node, queued);
416 blkg_get(tg_to_blkg(qn->tg));
421 * throtl_peek_queued - peek the first bio on a qnode list
422 * @queued: the qnode list to peek
424 static struct bio *throtl_peek_queued(struct list_head *queued)
426 struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node);
429 if (list_empty(queued))
432 bio = bio_list_peek(&qn->bios);
438 * throtl_pop_queued - pop the first bio form a qnode list
439 * @queued: the qnode list to pop a bio from
440 * @tg_to_put: optional out argument for throtl_grp to put
442 * Pop the first bio from the qnode list @queued. After popping, the first
443 * qnode is removed from @queued if empty or moved to the end of @queued so
444 * that the popping order is round-robin.
446 * When the first qnode is removed, its associated throtl_grp should be put
447 * too. If @tg_to_put is NULL, this function automatically puts it;
448 * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is
449 * responsible for putting it.
451 static struct bio *throtl_pop_queued(struct list_head *queued,
452 struct throtl_grp **tg_to_put)
454 struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node);
457 if (list_empty(queued))
460 bio = bio_list_pop(&qn->bios);
463 if (bio_list_empty(&qn->bios)) {
464 list_del_init(&qn->node);
468 blkg_put(tg_to_blkg(qn->tg));
470 list_move_tail(&qn->node, queued);
476 /* init a service_queue, assumes the caller zeroed it */
477 static void throtl_service_queue_init(struct throtl_service_queue *sq)
479 INIT_LIST_HEAD(&sq->queued[0]);
480 INIT_LIST_HEAD(&sq->queued[1]);
481 sq->pending_tree = RB_ROOT;
482 setup_timer(&sq->pending_timer, throtl_pending_timer_fn,
486 static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
488 struct throtl_grp *tg;
491 tg = kzalloc_node(sizeof(*tg), gfp, node);
495 throtl_service_queue_init(&tg->service_queue);
497 for (rw = READ; rw <= WRITE; rw++) {
498 throtl_qnode_init(&tg->qnode_on_self[rw], tg);
499 throtl_qnode_init(&tg->qnode_on_parent[rw], tg);
502 RB_CLEAR_NODE(&tg->rb_node);
503 tg->bps[READ][LIMIT_MAX] = U64_MAX;
504 tg->bps[WRITE][LIMIT_MAX] = U64_MAX;
505 tg->iops[READ][LIMIT_MAX] = UINT_MAX;
506 tg->iops[WRITE][LIMIT_MAX] = UINT_MAX;
507 tg->bps_conf[READ][LIMIT_MAX] = U64_MAX;
508 tg->bps_conf[WRITE][LIMIT_MAX] = U64_MAX;
509 tg->iops_conf[READ][LIMIT_MAX] = UINT_MAX;
510 tg->iops_conf[WRITE][LIMIT_MAX] = UINT_MAX;
511 /* LIMIT_LOW will have default value 0 */
513 tg->latency_target = DFL_LATENCY_TARGET;
514 tg->latency_target_conf = DFL_LATENCY_TARGET;
515 tg->idletime_threshold = DFL_IDLE_THRESHOLD;
516 tg->idletime_threshold_conf = DFL_IDLE_THRESHOLD;
521 static void throtl_pd_init(struct blkg_policy_data *pd)
523 struct throtl_grp *tg = pd_to_tg(pd);
524 struct blkcg_gq *blkg = tg_to_blkg(tg);
525 struct throtl_data *td = blkg->q->td;
526 struct throtl_service_queue *sq = &tg->service_queue;
529 * If on the default hierarchy, we switch to properly hierarchical
530 * behavior where limits on a given throtl_grp are applied to the
531 * whole subtree rather than just the group itself. e.g. If 16M
532 * read_bps limit is set on the root group, the whole system can't
533 * exceed 16M for the device.
535 * If not on the default hierarchy, the broken flat hierarchy
536 * behavior is retained where all throtl_grps are treated as if
537 * they're all separate root groups right below throtl_data.
538 * Limits of a group don't interact with limits of other groups
539 * regardless of the position of the group in the hierarchy.
541 sq->parent_sq = &td->service_queue;
542 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent)
543 sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
548 * Set has_rules[] if @tg or any of its parents have limits configured.
549 * This doesn't require walking up to the top of the hierarchy as the
550 * parent's has_rules[] is guaranteed to be correct.
552 static void tg_update_has_rules(struct throtl_grp *tg)
554 struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq);
555 struct throtl_data *td = tg->td;
558 for (rw = READ; rw <= WRITE; rw++)
559 tg->has_rules[rw] = (parent_tg && parent_tg->has_rules[rw]) ||
560 (td->limit_valid[td->limit_index] &&
561 (tg_bps_limit(tg, rw) != U64_MAX ||
562 tg_iops_limit(tg, rw) != UINT_MAX));
565 static void throtl_pd_online(struct blkg_policy_data *pd)
567 struct throtl_grp *tg = pd_to_tg(pd);
569 * We don't want new groups to escape the limits of its ancestors.
570 * Update has_rules[] after a new group is brought online.
572 tg_update_has_rules(tg);
575 static void blk_throtl_update_limit_valid(struct throtl_data *td)
577 struct cgroup_subsys_state *pos_css;
578 struct blkcg_gq *blkg;
579 bool low_valid = false;
582 blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
583 struct throtl_grp *tg = blkg_to_tg(blkg);
585 if (tg->bps[READ][LIMIT_LOW] || tg->bps[WRITE][LIMIT_LOW] ||
586 tg->iops[READ][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW])
591 td->limit_valid[LIMIT_LOW] = low_valid;
594 static void throtl_upgrade_state(struct throtl_data *td);
595 static void throtl_pd_offline(struct blkg_policy_data *pd)
597 struct throtl_grp *tg = pd_to_tg(pd);
599 tg->bps[READ][LIMIT_LOW] = 0;
600 tg->bps[WRITE][LIMIT_LOW] = 0;
601 tg->iops[READ][LIMIT_LOW] = 0;
602 tg->iops[WRITE][LIMIT_LOW] = 0;
604 blk_throtl_update_limit_valid(tg->td);
606 if (!tg->td->limit_valid[tg->td->limit_index])
607 throtl_upgrade_state(tg->td);
610 static void throtl_pd_free(struct blkg_policy_data *pd)
612 struct throtl_grp *tg = pd_to_tg(pd);
614 del_timer_sync(&tg->service_queue.pending_timer);
618 static struct throtl_grp *
619 throtl_rb_first(struct throtl_service_queue *parent_sq)
621 /* Service tree is empty */
622 if (!parent_sq->nr_pending)
625 if (!parent_sq->first_pending)
626 parent_sq->first_pending = rb_first(&parent_sq->pending_tree);
628 if (parent_sq->first_pending)
629 return rb_entry_tg(parent_sq->first_pending);
634 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
640 static void throtl_rb_erase(struct rb_node *n,
641 struct throtl_service_queue *parent_sq)
643 if (parent_sq->first_pending == n)
644 parent_sq->first_pending = NULL;
645 rb_erase_init(n, &parent_sq->pending_tree);
646 --parent_sq->nr_pending;
649 static void update_min_dispatch_time(struct throtl_service_queue *parent_sq)
651 struct throtl_grp *tg;
653 tg = throtl_rb_first(parent_sq);
657 parent_sq->first_pending_disptime = tg->disptime;
660 static void tg_service_queue_add(struct throtl_grp *tg)
662 struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq;
663 struct rb_node **node = &parent_sq->pending_tree.rb_node;
664 struct rb_node *parent = NULL;
665 struct throtl_grp *__tg;
666 unsigned long key = tg->disptime;
669 while (*node != NULL) {
671 __tg = rb_entry_tg(parent);
673 if (time_before(key, __tg->disptime))
674 node = &parent->rb_left;
676 node = &parent->rb_right;
682 parent_sq->first_pending = &tg->rb_node;
684 rb_link_node(&tg->rb_node, parent, node);
685 rb_insert_color(&tg->rb_node, &parent_sq->pending_tree);
688 static void __throtl_enqueue_tg(struct throtl_grp *tg)
690 tg_service_queue_add(tg);
691 tg->flags |= THROTL_TG_PENDING;
692 tg->service_queue.parent_sq->nr_pending++;
695 static void throtl_enqueue_tg(struct throtl_grp *tg)
697 if (!(tg->flags & THROTL_TG_PENDING))
698 __throtl_enqueue_tg(tg);
701 static void __throtl_dequeue_tg(struct throtl_grp *tg)
703 throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq);
704 tg->flags &= ~THROTL_TG_PENDING;
707 static void throtl_dequeue_tg(struct throtl_grp *tg)
709 if (tg->flags & THROTL_TG_PENDING)
710 __throtl_dequeue_tg(tg);
713 /* Call with queue lock held */
714 static void throtl_schedule_pending_timer(struct throtl_service_queue *sq,
715 unsigned long expires)
717 unsigned long max_expire = jiffies + 8 * sq_to_td(sq)->throtl_slice;
720 * Since we are adjusting the throttle limit dynamically, the sleep
721 * time calculated according to previous limit might be invalid. It's
722 * possible the cgroup sleep time is very long and no other cgroups
723 * have IO running so notify the limit changes. Make sure the cgroup
724 * doesn't sleep too long to avoid the missed notification.
726 if (time_after(expires, max_expire))
727 expires = max_expire;
728 mod_timer(&sq->pending_timer, expires);
729 throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu",
730 expires - jiffies, jiffies);
734 * throtl_schedule_next_dispatch - schedule the next dispatch cycle
735 * @sq: the service_queue to schedule dispatch for
736 * @force: force scheduling
738 * Arm @sq->pending_timer so that the next dispatch cycle starts on the
739 * dispatch time of the first pending child. Returns %true if either timer
740 * is armed or there's no pending child left. %false if the current
741 * dispatch window is still open and the caller should continue
744 * If @force is %true, the dispatch timer is always scheduled and this
745 * function is guaranteed to return %true. This is to be used when the
746 * caller can't dispatch itself and needs to invoke pending_timer
747 * unconditionally. Note that forced scheduling is likely to induce short
748 * delay before dispatch starts even if @sq->first_pending_disptime is not
749 * in the future and thus shouldn't be used in hot paths.
751 static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq,
754 /* any pending children left? */
758 update_min_dispatch_time(sq);
760 /* is the next dispatch time in the future? */
761 if (force || time_after(sq->first_pending_disptime, jiffies)) {
762 throtl_schedule_pending_timer(sq, sq->first_pending_disptime);
766 /* tell the caller to continue dispatching */
770 static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
771 bool rw, unsigned long start)
773 tg->bytes_disp[rw] = 0;
777 * Previous slice has expired. We must have trimmed it after last
778 * bio dispatch. That means since start of last slice, we never used
779 * that bandwidth. Do try to make use of that bandwidth while giving
782 if (time_after_eq(start, tg->slice_start[rw]))
783 tg->slice_start[rw] = start;
785 tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
786 throtl_log(&tg->service_queue,
787 "[%c] new slice with credit start=%lu end=%lu jiffies=%lu",
788 rw == READ ? 'R' : 'W', tg->slice_start[rw],
789 tg->slice_end[rw], jiffies);
792 static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw)
794 tg->bytes_disp[rw] = 0;
796 tg->slice_start[rw] = jiffies;
797 tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
798 throtl_log(&tg->service_queue,
799 "[%c] new slice start=%lu end=%lu jiffies=%lu",
800 rw == READ ? 'R' : 'W', tg->slice_start[rw],
801 tg->slice_end[rw], jiffies);
804 static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw,
805 unsigned long jiffy_end)
807 tg->slice_end[rw] = roundup(jiffy_end, tg->td->throtl_slice);
810 static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw,
811 unsigned long jiffy_end)
813 tg->slice_end[rw] = roundup(jiffy_end, tg->td->throtl_slice);
814 throtl_log(&tg->service_queue,
815 "[%c] extend slice start=%lu end=%lu jiffies=%lu",
816 rw == READ ? 'R' : 'W', tg->slice_start[rw],
817 tg->slice_end[rw], jiffies);
820 /* Determine if previously allocated or extended slice is complete or not */
821 static bool throtl_slice_used(struct throtl_grp *tg, bool rw)
823 if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
829 /* Trim the used slices and adjust slice start accordingly */
830 static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
832 unsigned long nr_slices, time_elapsed, io_trim;
835 BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
838 * If bps are unlimited (-1), then time slice don't get
839 * renewed. Don't try to trim the slice if slice is used. A new
840 * slice will start when appropriate.
842 if (throtl_slice_used(tg, rw))
846 * A bio has been dispatched. Also adjust slice_end. It might happen
847 * that initially cgroup limit was very low resulting in high
848 * slice_end, but later limit was bumped up and bio was dispached
849 * sooner, then we need to reduce slice_end. A high bogus slice_end
850 * is bad because it does not allow new slice to start.
853 throtl_set_slice_end(tg, rw, jiffies + tg->td->throtl_slice);
855 time_elapsed = jiffies - tg->slice_start[rw];
857 nr_slices = time_elapsed / tg->td->throtl_slice;
861 tmp = tg_bps_limit(tg, rw) * tg->td->throtl_slice * nr_slices;
865 io_trim = (tg_iops_limit(tg, rw) * tg->td->throtl_slice * nr_slices) /
868 if (!bytes_trim && !io_trim)
871 if (tg->bytes_disp[rw] >= bytes_trim)
872 tg->bytes_disp[rw] -= bytes_trim;
874 tg->bytes_disp[rw] = 0;
876 if (tg->io_disp[rw] >= io_trim)
877 tg->io_disp[rw] -= io_trim;
881 tg->slice_start[rw] += nr_slices * tg->td->throtl_slice;
883 throtl_log(&tg->service_queue,
884 "[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu",
885 rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
886 tg->slice_start[rw], tg->slice_end[rw], jiffies);
889 static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio,
892 bool rw = bio_data_dir(bio);
893 unsigned int io_allowed;
894 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
897 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
899 /* Slice has just started. Consider one slice interval */
901 jiffy_elapsed_rnd = tg->td->throtl_slice;
903 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);
906 * jiffy_elapsed_rnd should not be a big value as minimum iops can be
907 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
908 * will allow dispatch after 1 second and after that slice should
912 tmp = (u64)tg_iops_limit(tg, rw) * jiffy_elapsed_rnd;
916 io_allowed = UINT_MAX;
920 if (tg->io_disp[rw] + 1 <= io_allowed) {
926 /* Calc approx time to dispatch */
927 jiffy_wait = ((tg->io_disp[rw] + 1) * HZ) / tg_iops_limit(tg, rw) + 1;
929 if (jiffy_wait > jiffy_elapsed)
930 jiffy_wait = jiffy_wait - jiffy_elapsed;
939 static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio,
942 bool rw = bio_data_dir(bio);
943 u64 bytes_allowed, extra_bytes, tmp;
944 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
945 unsigned int bio_size = throtl_bio_data_size(bio);
947 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
949 /* Slice has just started. Consider one slice interval */
951 jiffy_elapsed_rnd = tg->td->throtl_slice;
953 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);
955 tmp = tg_bps_limit(tg, rw) * jiffy_elapsed_rnd;
959 if (tg->bytes_disp[rw] + bio_size <= bytes_allowed) {
965 /* Calc approx time to dispatch */
966 extra_bytes = tg->bytes_disp[rw] + bio_size - bytes_allowed;
967 jiffy_wait = div64_u64(extra_bytes * HZ, tg_bps_limit(tg, rw));
973 * This wait time is without taking into consideration the rounding
974 * up we did. Add that time also.
976 jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
983 * Returns whether one can dispatch a bio or not. Also returns approx number
984 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
986 static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
989 bool rw = bio_data_dir(bio);
990 unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
993 * Currently whole state machine of group depends on first bio
994 * queued in the group bio list. So one should not be calling
995 * this function with a different bio if there are other bios
998 BUG_ON(tg->service_queue.nr_queued[rw] &&
999 bio != throtl_peek_queued(&tg->service_queue.queued[rw]));
1001 /* If tg->bps = -1, then BW is unlimited */
1002 if (tg_bps_limit(tg, rw) == U64_MAX &&
1003 tg_iops_limit(tg, rw) == UINT_MAX) {
1010 * If previous slice expired, start a new one otherwise renew/extend
1011 * existing slice to make sure it is at least throtl_slice interval
1012 * long since now. New slice is started only for empty throttle group.
1013 * If there is queued bio, that means there should be an active
1014 * slice and it should be extended instead.
1016 if (throtl_slice_used(tg, rw) && !(tg->service_queue.nr_queued[rw]))
1017 throtl_start_new_slice(tg, rw);
1019 if (time_before(tg->slice_end[rw],
1020 jiffies + tg->td->throtl_slice))
1021 throtl_extend_slice(tg, rw,
1022 jiffies + tg->td->throtl_slice);
1025 if (tg_with_in_bps_limit(tg, bio, &bps_wait) &&
1026 tg_with_in_iops_limit(tg, bio, &iops_wait)) {
1032 max_wait = max(bps_wait, iops_wait);
1037 if (time_before(tg->slice_end[rw], jiffies + max_wait))
1038 throtl_extend_slice(tg, rw, jiffies + max_wait);
1043 static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
1045 bool rw = bio_data_dir(bio);
1046 unsigned int bio_size = throtl_bio_data_size(bio);
1048 /* Charge the bio to the group */
1049 tg->bytes_disp[rw] += bio_size;
1051 tg->last_bytes_disp[rw] += bio_size;
1052 tg->last_io_disp[rw]++;
1055 * BIO_THROTTLED is used to prevent the same bio to be throttled
1056 * more than once as a throttled bio will go through blk-throtl the
1057 * second time when it eventually gets issued. Set it when a bio
1058 * is being charged to a tg.
1060 if (!bio_flagged(bio, BIO_THROTTLED))
1061 bio_set_flag(bio, BIO_THROTTLED);
1065 * throtl_add_bio_tg - add a bio to the specified throtl_grp
1068 * @tg: the target throtl_grp
1070 * Add @bio to @tg's service_queue using @qn. If @qn is not specified,
1071 * tg->qnode_on_self[] is used.
1073 static void throtl_add_bio_tg(struct bio *bio, struct throtl_qnode *qn,
1074 struct throtl_grp *tg)
1076 struct throtl_service_queue *sq = &tg->service_queue;
1077 bool rw = bio_data_dir(bio);
1080 qn = &tg->qnode_on_self[rw];
1083 * If @tg doesn't currently have any bios queued in the same
1084 * direction, queueing @bio can change when @tg should be
1085 * dispatched. Mark that @tg was empty. This is automatically
1086 * cleaered on the next tg_update_disptime().
1088 if (!sq->nr_queued[rw])
1089 tg->flags |= THROTL_TG_WAS_EMPTY;
1091 throtl_qnode_add_bio(bio, qn, &sq->queued[rw]);
1093 sq->nr_queued[rw]++;
1094 throtl_enqueue_tg(tg);
1097 static void tg_update_disptime(struct throtl_grp *tg)
1099 struct throtl_service_queue *sq = &tg->service_queue;
1100 unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
1103 bio = throtl_peek_queued(&sq->queued[READ]);
1105 tg_may_dispatch(tg, bio, &read_wait);
1107 bio = throtl_peek_queued(&sq->queued[WRITE]);
1109 tg_may_dispatch(tg, bio, &write_wait);
1111 min_wait = min(read_wait, write_wait);
1112 disptime = jiffies + min_wait;
1114 /* Update dispatch time */
1115 throtl_dequeue_tg(tg);
1116 tg->disptime = disptime;
1117 throtl_enqueue_tg(tg);
1119 /* see throtl_add_bio_tg() */
1120 tg->flags &= ~THROTL_TG_WAS_EMPTY;
1123 static void start_parent_slice_with_credit(struct throtl_grp *child_tg,
1124 struct throtl_grp *parent_tg, bool rw)
1126 if (throtl_slice_used(parent_tg, rw)) {
1127 throtl_start_new_slice_with_credit(parent_tg, rw,
1128 child_tg->slice_start[rw]);
1133 static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)
1135 struct throtl_service_queue *sq = &tg->service_queue;
1136 struct throtl_service_queue *parent_sq = sq->parent_sq;
1137 struct throtl_grp *parent_tg = sq_to_tg(parent_sq);
1138 struct throtl_grp *tg_to_put = NULL;
1142 * @bio is being transferred from @tg to @parent_sq. Popping a bio
1143 * from @tg may put its reference and @parent_sq might end up
1144 * getting released prematurely. Remember the tg to put and put it
1145 * after @bio is transferred to @parent_sq.
1147 bio = throtl_pop_queued(&sq->queued[rw], &tg_to_put);
1148 sq->nr_queued[rw]--;
1150 throtl_charge_bio(tg, bio);
1153 * If our parent is another tg, we just need to transfer @bio to
1154 * the parent using throtl_add_bio_tg(). If our parent is
1155 * @td->service_queue, @bio is ready to be issued. Put it on its
1156 * bio_lists[] and decrease total number queued. The caller is
1157 * responsible for issuing these bios.
1160 throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg);
1161 start_parent_slice_with_credit(tg, parent_tg, rw);
1163 throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw],
1164 &parent_sq->queued[rw]);
1165 BUG_ON(tg->td->nr_queued[rw] <= 0);
1166 tg->td->nr_queued[rw]--;
1169 throtl_trim_slice(tg, rw);
1172 blkg_put(tg_to_blkg(tg_to_put));
1175 static int throtl_dispatch_tg(struct throtl_grp *tg)
1177 struct throtl_service_queue *sq = &tg->service_queue;
1178 unsigned int nr_reads = 0, nr_writes = 0;
1179 unsigned int max_nr_reads = throtl_grp_quantum*3/4;
1180 unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
1183 /* Try to dispatch 75% READS and 25% WRITES */
1185 while ((bio = throtl_peek_queued(&sq->queued[READ])) &&
1186 tg_may_dispatch(tg, bio, NULL)) {
1188 tg_dispatch_one_bio(tg, bio_data_dir(bio));
1191 if (nr_reads >= max_nr_reads)
1195 while ((bio = throtl_peek_queued(&sq->queued[WRITE])) &&
1196 tg_may_dispatch(tg, bio, NULL)) {
1198 tg_dispatch_one_bio(tg, bio_data_dir(bio));
1201 if (nr_writes >= max_nr_writes)
1205 return nr_reads + nr_writes;
1208 static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
1210 unsigned int nr_disp = 0;
1213 struct throtl_grp *tg = throtl_rb_first(parent_sq);
1214 struct throtl_service_queue *sq = &tg->service_queue;
1219 if (time_before(jiffies, tg->disptime))
1222 throtl_dequeue_tg(tg);
1224 nr_disp += throtl_dispatch_tg(tg);
1226 if (sq->nr_queued[0] || sq->nr_queued[1])
1227 tg_update_disptime(tg);
1229 if (nr_disp >= throtl_quantum)
1236 static bool throtl_can_upgrade(struct throtl_data *td,
1237 struct throtl_grp *this_tg);
1239 * throtl_pending_timer_fn - timer function for service_queue->pending_timer
1240 * @arg: the throtl_service_queue being serviced
1242 * This timer is armed when a child throtl_grp with active bio's become
1243 * pending and queued on the service_queue's pending_tree and expires when
1244 * the first child throtl_grp should be dispatched. This function
1245 * dispatches bio's from the children throtl_grps to the parent
1248 * If the parent's parent is another throtl_grp, dispatching is propagated
1249 * by either arming its pending_timer or repeating dispatch directly. If
1250 * the top-level service_tree is reached, throtl_data->dispatch_work is
1251 * kicked so that the ready bio's are issued.
1253 static void throtl_pending_timer_fn(unsigned long arg)
1255 struct throtl_service_queue *sq = (void *)arg;
1256 struct throtl_grp *tg = sq_to_tg(sq);
1257 struct throtl_data *td = sq_to_td(sq);
1258 struct request_queue *q = td->queue;
1259 struct throtl_service_queue *parent_sq;
1263 spin_lock_irq(q->queue_lock);
1264 if (throtl_can_upgrade(td, NULL))
1265 throtl_upgrade_state(td);
1268 parent_sq = sq->parent_sq;
1272 throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u",
1273 sq->nr_queued[READ] + sq->nr_queued[WRITE],
1274 sq->nr_queued[READ], sq->nr_queued[WRITE]);
1276 ret = throtl_select_dispatch(sq);
1278 throtl_log(sq, "bios disp=%u", ret);
1282 if (throtl_schedule_next_dispatch(sq, false))
1285 /* this dispatch windows is still open, relax and repeat */
1286 spin_unlock_irq(q->queue_lock);
1288 spin_lock_irq(q->queue_lock);
1295 /* @parent_sq is another throl_grp, propagate dispatch */
1296 if (tg->flags & THROTL_TG_WAS_EMPTY) {
1297 tg_update_disptime(tg);
1298 if (!throtl_schedule_next_dispatch(parent_sq, false)) {
1299 /* window is already open, repeat dispatching */
1306 /* reached the top-level, queue issueing */
1307 queue_work(kthrotld_workqueue, &td->dispatch_work);
1310 spin_unlock_irq(q->queue_lock);
1314 * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work
1315 * @work: work item being executed
1317 * This function is queued for execution when bio's reach the bio_lists[]
1318 * of throtl_data->service_queue. Those bio's are ready and issued by this
1321 static void blk_throtl_dispatch_work_fn(struct work_struct *work)
1323 struct throtl_data *td = container_of(work, struct throtl_data,
1325 struct throtl_service_queue *td_sq = &td->service_queue;
1326 struct request_queue *q = td->queue;
1327 struct bio_list bio_list_on_stack;
1329 struct blk_plug plug;
1332 bio_list_init(&bio_list_on_stack);
1334 spin_lock_irq(q->queue_lock);
1335 for (rw = READ; rw <= WRITE; rw++)
1336 while ((bio = throtl_pop_queued(&td_sq->queued[rw], NULL)))
1337 bio_list_add(&bio_list_on_stack, bio);
1338 spin_unlock_irq(q->queue_lock);
1340 if (!bio_list_empty(&bio_list_on_stack)) {
1341 blk_start_plug(&plug);
1342 while((bio = bio_list_pop(&bio_list_on_stack)))
1343 generic_make_request(bio);
1344 blk_finish_plug(&plug);
1348 static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
1351 struct throtl_grp *tg = pd_to_tg(pd);
1352 u64 v = *(u64 *)((void *)tg + off);
1356 return __blkg_prfill_u64(sf, pd, v);
1359 static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
1362 struct throtl_grp *tg = pd_to_tg(pd);
1363 unsigned int v = *(unsigned int *)((void *)tg + off);
1367 return __blkg_prfill_u64(sf, pd, v);
1370 static int tg_print_conf_u64(struct seq_file *sf, void *v)
1372 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_u64,
1373 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1377 static int tg_print_conf_uint(struct seq_file *sf, void *v)
1379 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_uint,
1380 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1384 static void tg_conf_updated(struct throtl_grp *tg, bool global)
1386 struct throtl_service_queue *sq = &tg->service_queue;
1387 struct cgroup_subsys_state *pos_css;
1388 struct blkcg_gq *blkg;
1390 throtl_log(&tg->service_queue,
1391 "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
1392 tg_bps_limit(tg, READ), tg_bps_limit(tg, WRITE),
1393 tg_iops_limit(tg, READ), tg_iops_limit(tg, WRITE));
1396 * Update has_rules[] flags for the updated tg's subtree. A tg is
1397 * considered to have rules if either the tg itself or any of its
1398 * ancestors has rules. This identifies groups without any
1399 * restrictions in the whole hierarchy and allows them to bypass
1402 blkg_for_each_descendant_pre(blkg, pos_css,
1403 global ? tg->td->queue->root_blkg : tg_to_blkg(tg)) {
1404 struct throtl_grp *this_tg = blkg_to_tg(blkg);
1405 struct throtl_grp *parent_tg;
1407 tg_update_has_rules(this_tg);
1408 /* ignore root/second level */
1409 if (!cgroup_subsys_on_dfl(io_cgrp_subsys) || !blkg->parent ||
1410 !blkg->parent->parent)
1412 parent_tg = blkg_to_tg(blkg->parent);
1414 * make sure all children has lower idle time threshold and
1415 * higher latency target
1417 this_tg->idletime_threshold = min(this_tg->idletime_threshold,
1418 parent_tg->idletime_threshold);
1419 this_tg->latency_target = max(this_tg->latency_target,
1420 parent_tg->latency_target);
1424 * We're already holding queue_lock and know @tg is valid. Let's
1425 * apply the new config directly.
1427 * Restart the slices for both READ and WRITES. It might happen
1428 * that a group's limit are dropped suddenly and we don't want to
1429 * account recently dispatched IO with new low rate.
1431 throtl_start_new_slice(tg, 0);
1432 throtl_start_new_slice(tg, 1);
1434 if (tg->flags & THROTL_TG_PENDING) {
1435 tg_update_disptime(tg);
1436 throtl_schedule_next_dispatch(sq->parent_sq, true);
1440 static ssize_t tg_set_conf(struct kernfs_open_file *of,
1441 char *buf, size_t nbytes, loff_t off, bool is_u64)
1443 struct blkcg *blkcg = css_to_blkcg(of_css(of));
1444 struct blkg_conf_ctx ctx;
1445 struct throtl_grp *tg;
1449 ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
1454 if (sscanf(ctx.body, "%llu", &v) != 1)
1459 tg = blkg_to_tg(ctx.blkg);
1462 *(u64 *)((void *)tg + of_cft(of)->private) = v;
1464 *(unsigned int *)((void *)tg + of_cft(of)->private) = v;
1466 tg_conf_updated(tg, false);
1469 blkg_conf_finish(&ctx);
1470 return ret ?: nbytes;
1473 static ssize_t tg_set_conf_u64(struct kernfs_open_file *of,
1474 char *buf, size_t nbytes, loff_t off)
1476 return tg_set_conf(of, buf, nbytes, off, true);
1479 static ssize_t tg_set_conf_uint(struct kernfs_open_file *of,
1480 char *buf, size_t nbytes, loff_t off)
1482 return tg_set_conf(of, buf, nbytes, off, false);
1485 static struct cftype throtl_legacy_files[] = {
1487 .name = "throttle.read_bps_device",
1488 .private = offsetof(struct throtl_grp, bps[READ][LIMIT_MAX]),
1489 .seq_show = tg_print_conf_u64,
1490 .write = tg_set_conf_u64,
1493 .name = "throttle.write_bps_device",
1494 .private = offsetof(struct throtl_grp, bps[WRITE][LIMIT_MAX]),
1495 .seq_show = tg_print_conf_u64,
1496 .write = tg_set_conf_u64,
1499 .name = "throttle.read_iops_device",
1500 .private = offsetof(struct throtl_grp, iops[READ][LIMIT_MAX]),
1501 .seq_show = tg_print_conf_uint,
1502 .write = tg_set_conf_uint,
1505 .name = "throttle.write_iops_device",
1506 .private = offsetof(struct throtl_grp, iops[WRITE][LIMIT_MAX]),
1507 .seq_show = tg_print_conf_uint,
1508 .write = tg_set_conf_uint,
1511 .name = "throttle.io_service_bytes",
1512 .private = (unsigned long)&blkcg_policy_throtl,
1513 .seq_show = blkg_print_stat_bytes,
1516 .name = "throttle.io_serviced",
1517 .private = (unsigned long)&blkcg_policy_throtl,
1518 .seq_show = blkg_print_stat_ios,
1523 static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
1526 struct throtl_grp *tg = pd_to_tg(pd);
1527 const char *dname = blkg_dev_name(pd->blkg);
1528 char bufs[4][21] = { "max", "max", "max", "max" };
1530 unsigned int iops_dft;
1531 char idle_time[26] = "";
1532 char latency_time[26] = "";
1537 if (off == LIMIT_LOW) {
1542 iops_dft = UINT_MAX;
1545 if (tg->bps_conf[READ][off] == bps_dft &&
1546 tg->bps_conf[WRITE][off] == bps_dft &&
1547 tg->iops_conf[READ][off] == iops_dft &&
1548 tg->iops_conf[WRITE][off] == iops_dft &&
1549 (off != LIMIT_LOW ||
1550 (tg->idletime_threshold_conf == DFL_IDLE_THRESHOLD &&
1551 tg->latency_target_conf == DFL_LATENCY_TARGET)))
1554 if (tg->bps_conf[READ][off] != U64_MAX)
1555 snprintf(bufs[0], sizeof(bufs[0]), "%llu",
1556 tg->bps_conf[READ][off]);
1557 if (tg->bps_conf[WRITE][off] != U64_MAX)
1558 snprintf(bufs[1], sizeof(bufs[1]), "%llu",
1559 tg->bps_conf[WRITE][off]);
1560 if (tg->iops_conf[READ][off] != UINT_MAX)
1561 snprintf(bufs[2], sizeof(bufs[2]), "%u",
1562 tg->iops_conf[READ][off]);
1563 if (tg->iops_conf[WRITE][off] != UINT_MAX)
1564 snprintf(bufs[3], sizeof(bufs[3]), "%u",
1565 tg->iops_conf[WRITE][off]);
1566 if (off == LIMIT_LOW) {
1567 if (tg->idletime_threshold_conf == ULONG_MAX)
1568 strcpy(idle_time, " idle=max");
1570 snprintf(idle_time, sizeof(idle_time), " idle=%lu",
1571 tg->idletime_threshold_conf);
1573 if (tg->latency_target_conf == ULONG_MAX)
1574 strcpy(latency_time, " latency=max");
1576 snprintf(latency_time, sizeof(latency_time),
1577 " latency=%lu", tg->latency_target_conf);
1580 seq_printf(sf, "%s rbps=%s wbps=%s riops=%s wiops=%s%s%s\n",
1581 dname, bufs[0], bufs[1], bufs[2], bufs[3], idle_time,
1586 static int tg_print_limit(struct seq_file *sf, void *v)
1588 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_limit,
1589 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1593 static ssize_t tg_set_limit(struct kernfs_open_file *of,
1594 char *buf, size_t nbytes, loff_t off)
1596 struct blkcg *blkcg = css_to_blkcg(of_css(of));
1597 struct blkg_conf_ctx ctx;
1598 struct throtl_grp *tg;
1600 unsigned long idle_time;
1601 unsigned long latency_time;
1603 int index = of_cft(of)->private;
1605 ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
1609 tg = blkg_to_tg(ctx.blkg);
1611 v[0] = tg->bps_conf[READ][index];
1612 v[1] = tg->bps_conf[WRITE][index];
1613 v[2] = tg->iops_conf[READ][index];
1614 v[3] = tg->iops_conf[WRITE][index];
1616 idle_time = tg->idletime_threshold_conf;
1617 latency_time = tg->latency_target_conf;
1619 char tok[27]; /* wiops=18446744073709551616 */
1624 if (sscanf(ctx.body, "%26s%n", tok, &len) != 1)
1633 if (!p || (sscanf(p, "%llu", &val) != 1 && strcmp(p, "max")))
1641 if (!strcmp(tok, "rbps"))
1643 else if (!strcmp(tok, "wbps"))
1645 else if (!strcmp(tok, "riops"))
1646 v[2] = min_t(u64, val, UINT_MAX);
1647 else if (!strcmp(tok, "wiops"))
1648 v[3] = min_t(u64, val, UINT_MAX);
1649 else if (off == LIMIT_LOW && !strcmp(tok, "idle"))
1651 else if (off == LIMIT_LOW && !strcmp(tok, "latency"))
1657 tg->bps_conf[READ][index] = v[0];
1658 tg->bps_conf[WRITE][index] = v[1];
1659 tg->iops_conf[READ][index] = v[2];
1660 tg->iops_conf[WRITE][index] = v[3];
1662 if (index == LIMIT_MAX) {
1663 tg->bps[READ][index] = v[0];
1664 tg->bps[WRITE][index] = v[1];
1665 tg->iops[READ][index] = v[2];
1666 tg->iops[WRITE][index] = v[3];
1668 tg->bps[READ][LIMIT_LOW] = min(tg->bps_conf[READ][LIMIT_LOW],
1669 tg->bps_conf[READ][LIMIT_MAX]);
1670 tg->bps[WRITE][LIMIT_LOW] = min(tg->bps_conf[WRITE][LIMIT_LOW],
1671 tg->bps_conf[WRITE][LIMIT_MAX]);
1672 tg->iops[READ][LIMIT_LOW] = min(tg->iops_conf[READ][LIMIT_LOW],
1673 tg->iops_conf[READ][LIMIT_MAX]);
1674 tg->iops[WRITE][LIMIT_LOW] = min(tg->iops_conf[WRITE][LIMIT_LOW],
1675 tg->iops_conf[WRITE][LIMIT_MAX]);
1676 tg->idletime_threshold_conf = idle_time;
1677 tg->latency_target_conf = latency_time;
1679 /* force user to configure all settings for low limit */
1680 if (!(tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW] ||
1681 tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW]) ||
1682 tg->idletime_threshold_conf == DFL_IDLE_THRESHOLD ||
1683 tg->latency_target_conf == DFL_LATENCY_TARGET) {
1684 tg->bps[READ][LIMIT_LOW] = 0;
1685 tg->bps[WRITE][LIMIT_LOW] = 0;
1686 tg->iops[READ][LIMIT_LOW] = 0;
1687 tg->iops[WRITE][LIMIT_LOW] = 0;
1688 tg->idletime_threshold = DFL_IDLE_THRESHOLD;
1689 tg->latency_target = DFL_LATENCY_TARGET;
1690 } else if (index == LIMIT_LOW) {
1691 tg->idletime_threshold = tg->idletime_threshold_conf;
1692 tg->latency_target = tg->latency_target_conf;
1695 blk_throtl_update_limit_valid(tg->td);
1696 if (tg->td->limit_valid[LIMIT_LOW]) {
1697 if (index == LIMIT_LOW)
1698 tg->td->limit_index = LIMIT_LOW;
1700 tg->td->limit_index = LIMIT_MAX;
1701 tg_conf_updated(tg, index == LIMIT_LOW &&
1702 tg->td->limit_valid[LIMIT_LOW]);
1705 blkg_conf_finish(&ctx);
1706 return ret ?: nbytes;
1709 static struct cftype throtl_files[] = {
1710 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
1713 .flags = CFTYPE_NOT_ON_ROOT,
1714 .seq_show = tg_print_limit,
1715 .write = tg_set_limit,
1716 .private = LIMIT_LOW,
1721 .flags = CFTYPE_NOT_ON_ROOT,
1722 .seq_show = tg_print_limit,
1723 .write = tg_set_limit,
1724 .private = LIMIT_MAX,
1729 static void throtl_shutdown_wq(struct request_queue *q)
1731 struct throtl_data *td = q->td;
1733 cancel_work_sync(&td->dispatch_work);
1736 static struct blkcg_policy blkcg_policy_throtl = {
1737 .dfl_cftypes = throtl_files,
1738 .legacy_cftypes = throtl_legacy_files,
1740 .pd_alloc_fn = throtl_pd_alloc,
1741 .pd_init_fn = throtl_pd_init,
1742 .pd_online_fn = throtl_pd_online,
1743 .pd_offline_fn = throtl_pd_offline,
1744 .pd_free_fn = throtl_pd_free,
1747 static unsigned long __tg_last_low_overflow_time(struct throtl_grp *tg)
1749 unsigned long rtime = jiffies, wtime = jiffies;
1751 if (tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW])
1752 rtime = tg->last_low_overflow_time[READ];
1753 if (tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW])
1754 wtime = tg->last_low_overflow_time[WRITE];
1755 return min(rtime, wtime);
1758 /* tg should not be an intermediate node */
1759 static unsigned long tg_last_low_overflow_time(struct throtl_grp *tg)
1761 struct throtl_service_queue *parent_sq;
1762 struct throtl_grp *parent = tg;
1763 unsigned long ret = __tg_last_low_overflow_time(tg);
1766 parent_sq = parent->service_queue.parent_sq;
1767 parent = sq_to_tg(parent_sq);
1772 * The parent doesn't have low limit, it always reaches low
1773 * limit. Its overflow time is useless for children
1775 if (!parent->bps[READ][LIMIT_LOW] &&
1776 !parent->iops[READ][LIMIT_LOW] &&
1777 !parent->bps[WRITE][LIMIT_LOW] &&
1778 !parent->iops[WRITE][LIMIT_LOW])
1780 if (time_after(__tg_last_low_overflow_time(parent), ret))
1781 ret = __tg_last_low_overflow_time(parent);
1786 static bool throtl_tg_is_idle(struct throtl_grp *tg)
1789 * cgroup is idle if:
1790 * - single idle is too long, longer than a fixed value (in case user
1791 * configure a too big threshold) or 4 times of idletime threshold
1792 * - average think time is more than threshold
1793 * - IO latency is largely below threshold
1798 time = min_t(unsigned long, MAX_IDLE_TIME, 4 * tg->idletime_threshold);
1799 ret = tg->latency_target == DFL_LATENCY_TARGET ||
1800 tg->idletime_threshold == DFL_IDLE_THRESHOLD ||
1801 (ktime_get_ns() >> 10) - tg->last_finish_time > time ||
1802 tg->avg_idletime > tg->idletime_threshold ||
1803 (tg->latency_target && tg->bio_cnt &&
1804 tg->bad_bio_cnt * 5 < tg->bio_cnt);
1805 throtl_log(&tg->service_queue,
1806 "avg_idle=%ld, idle_threshold=%ld, bad_bio=%d, total_bio=%d, is_idle=%d, scale=%d",
1807 tg->avg_idletime, tg->idletime_threshold, tg->bad_bio_cnt,
1808 tg->bio_cnt, ret, tg->td->scale);
1812 static bool throtl_tg_can_upgrade(struct throtl_grp *tg)
1814 struct throtl_service_queue *sq = &tg->service_queue;
1815 bool read_limit, write_limit;
1818 * if cgroup reaches low limit (if low limit is 0, the cgroup always
1819 * reaches), it's ok to upgrade to next limit
1821 read_limit = tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW];
1822 write_limit = tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW];
1823 if (!read_limit && !write_limit)
1825 if (read_limit && sq->nr_queued[READ] &&
1826 (!write_limit || sq->nr_queued[WRITE]))
1828 if (write_limit && sq->nr_queued[WRITE] &&
1829 (!read_limit || sq->nr_queued[READ]))
1832 if (time_after_eq(jiffies,
1833 tg_last_low_overflow_time(tg) + tg->td->throtl_slice) &&
1834 throtl_tg_is_idle(tg))
1839 static bool throtl_hierarchy_can_upgrade(struct throtl_grp *tg)
1842 if (throtl_tg_can_upgrade(tg))
1844 tg = sq_to_tg(tg->service_queue.parent_sq);
1845 if (!tg || !tg_to_blkg(tg)->parent)
1851 static bool throtl_can_upgrade(struct throtl_data *td,
1852 struct throtl_grp *this_tg)
1854 struct cgroup_subsys_state *pos_css;
1855 struct blkcg_gq *blkg;
1857 if (td->limit_index != LIMIT_LOW)
1860 if (time_before(jiffies, td->low_downgrade_time + td->throtl_slice))
1864 blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
1865 struct throtl_grp *tg = blkg_to_tg(blkg);
1869 if (!list_empty(&tg_to_blkg(tg)->blkcg->css.children))
1871 if (!throtl_hierarchy_can_upgrade(tg)) {
1880 static void throtl_upgrade_check(struct throtl_grp *tg)
1882 unsigned long now = jiffies;
1884 if (tg->td->limit_index != LIMIT_LOW)
1887 if (time_after(tg->last_check_time + tg->td->throtl_slice, now))
1890 tg->last_check_time = now;
1892 if (!time_after_eq(now,
1893 __tg_last_low_overflow_time(tg) + tg->td->throtl_slice))
1896 if (throtl_can_upgrade(tg->td, NULL))
1897 throtl_upgrade_state(tg->td);
1900 static void throtl_upgrade_state(struct throtl_data *td)
1902 struct cgroup_subsys_state *pos_css;
1903 struct blkcg_gq *blkg;
1905 throtl_log(&td->service_queue, "upgrade to max");
1906 td->limit_index = LIMIT_MAX;
1907 td->low_upgrade_time = jiffies;
1910 blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
1911 struct throtl_grp *tg = blkg_to_tg(blkg);
1912 struct throtl_service_queue *sq = &tg->service_queue;
1914 tg->disptime = jiffies - 1;
1915 throtl_select_dispatch(sq);
1916 throtl_schedule_next_dispatch(sq, false);
1919 throtl_select_dispatch(&td->service_queue);
1920 throtl_schedule_next_dispatch(&td->service_queue, false);
1921 queue_work(kthrotld_workqueue, &td->dispatch_work);
1924 static void throtl_downgrade_state(struct throtl_data *td, int new)
1928 throtl_log(&td->service_queue, "downgrade, scale %d", td->scale);
1930 td->low_upgrade_time = jiffies - td->scale * td->throtl_slice;
1934 td->limit_index = new;
1935 td->low_downgrade_time = jiffies;
1938 static bool throtl_tg_can_downgrade(struct throtl_grp *tg)
1940 struct throtl_data *td = tg->td;
1941 unsigned long now = jiffies;
1944 * If cgroup is below low limit, consider downgrade and throttle other
1947 if (time_after_eq(now, td->low_upgrade_time + td->throtl_slice) &&
1948 time_after_eq(now, tg_last_low_overflow_time(tg) +
1949 td->throtl_slice) &&
1950 (!throtl_tg_is_idle(tg) ||
1951 !list_empty(&tg_to_blkg(tg)->blkcg->css.children)))
1956 static bool throtl_hierarchy_can_downgrade(struct throtl_grp *tg)
1959 if (!throtl_tg_can_downgrade(tg))
1961 tg = sq_to_tg(tg->service_queue.parent_sq);
1962 if (!tg || !tg_to_blkg(tg)->parent)
1968 static void throtl_downgrade_check(struct throtl_grp *tg)
1972 unsigned long elapsed_time;
1973 unsigned long now = jiffies;
1975 if (tg->td->limit_index != LIMIT_MAX ||
1976 !tg->td->limit_valid[LIMIT_LOW])
1978 if (!list_empty(&tg_to_blkg(tg)->blkcg->css.children))
1980 if (time_after(tg->last_check_time + tg->td->throtl_slice, now))
1983 elapsed_time = now - tg->last_check_time;
1984 tg->last_check_time = now;
1986 if (time_before(now, tg_last_low_overflow_time(tg) +
1987 tg->td->throtl_slice))
1990 if (tg->bps[READ][LIMIT_LOW]) {
1991 bps = tg->last_bytes_disp[READ] * HZ;
1992 do_div(bps, elapsed_time);
1993 if (bps >= tg->bps[READ][LIMIT_LOW])
1994 tg->last_low_overflow_time[READ] = now;
1997 if (tg->bps[WRITE][LIMIT_LOW]) {
1998 bps = tg->last_bytes_disp[WRITE] * HZ;
1999 do_div(bps, elapsed_time);
2000 if (bps >= tg->bps[WRITE][LIMIT_LOW])
2001 tg->last_low_overflow_time[WRITE] = now;
2004 if (tg->iops[READ][LIMIT_LOW]) {
2005 iops = tg->last_io_disp[READ] * HZ / elapsed_time;
2006 if (iops >= tg->iops[READ][LIMIT_LOW])
2007 tg->last_low_overflow_time[READ] = now;
2010 if (tg->iops[WRITE][LIMIT_LOW]) {
2011 iops = tg->last_io_disp[WRITE] * HZ / elapsed_time;
2012 if (iops >= tg->iops[WRITE][LIMIT_LOW])
2013 tg->last_low_overflow_time[WRITE] = now;
2017 * If cgroup is below low limit, consider downgrade and throttle other
2020 if (throtl_hierarchy_can_downgrade(tg))
2021 throtl_downgrade_state(tg->td, LIMIT_LOW);
2023 tg->last_bytes_disp[READ] = 0;
2024 tg->last_bytes_disp[WRITE] = 0;
2025 tg->last_io_disp[READ] = 0;
2026 tg->last_io_disp[WRITE] = 0;
2029 static void blk_throtl_update_idletime(struct throtl_grp *tg)
2031 unsigned long now = ktime_get_ns() >> 10;
2032 unsigned long last_finish_time = tg->last_finish_time;
2034 if (now <= last_finish_time || last_finish_time == 0 ||
2035 last_finish_time == tg->checked_last_finish_time)
2038 tg->avg_idletime = (tg->avg_idletime * 7 + now - last_finish_time) >> 3;
2039 tg->checked_last_finish_time = last_finish_time;
2042 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2043 static void throtl_update_latency_buckets(struct throtl_data *td)
2045 struct avg_latency_bucket avg_latency[LATENCY_BUCKET_SIZE];
2047 unsigned long last_latency = 0;
2048 unsigned long latency;
2050 if (!blk_queue_nonrot(td->queue))
2052 if (time_before(jiffies, td->last_calculate_time + HZ))
2054 td->last_calculate_time = jiffies;
2056 memset(avg_latency, 0, sizeof(avg_latency));
2057 for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
2058 struct latency_bucket *tmp = &td->tmp_buckets[i];
2060 for_each_possible_cpu(cpu) {
2061 struct latency_bucket *bucket;
2063 /* this isn't race free, but ok in practice */
2064 bucket = per_cpu_ptr(td->latency_buckets, cpu);
2065 tmp->total_latency += bucket[i].total_latency;
2066 tmp->samples += bucket[i].samples;
2067 bucket[i].total_latency = 0;
2068 bucket[i].samples = 0;
2071 if (tmp->samples >= 32) {
2072 int samples = tmp->samples;
2074 latency = tmp->total_latency;
2076 tmp->total_latency = 0;
2081 avg_latency[i].latency = latency;
2085 for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
2086 if (!avg_latency[i].latency) {
2087 if (td->avg_buckets[i].latency < last_latency)
2088 td->avg_buckets[i].latency = last_latency;
2092 if (!td->avg_buckets[i].valid)
2093 latency = avg_latency[i].latency;
2095 latency = (td->avg_buckets[i].latency * 7 +
2096 avg_latency[i].latency) >> 3;
2098 td->avg_buckets[i].latency = max(latency, last_latency);
2099 td->avg_buckets[i].valid = true;
2100 last_latency = td->avg_buckets[i].latency;
2103 for (i = 0; i < LATENCY_BUCKET_SIZE; i++)
2104 throtl_log(&td->service_queue,
2105 "Latency bucket %d: latency=%ld, valid=%d", i,
2106 td->avg_buckets[i].latency, td->avg_buckets[i].valid);
2109 static inline void throtl_update_latency_buckets(struct throtl_data *td)
2114 static void blk_throtl_assoc_bio(struct throtl_grp *tg, struct bio *bio)
2116 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2119 ret = bio_associate_current(bio);
2120 if (ret == 0 || ret == -EBUSY)
2121 bio->bi_cg_private = tg;
2122 blk_stat_set_issue(&bio->bi_issue_stat, bio_sectors(bio));
2124 bio_associate_current(bio);
2128 bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
2131 struct throtl_qnode *qn = NULL;
2132 struct throtl_grp *tg = blkg_to_tg(blkg ?: q->root_blkg);
2133 struct throtl_service_queue *sq;
2134 bool rw = bio_data_dir(bio);
2135 bool throttled = false;
2136 struct throtl_data *td = tg->td;
2138 WARN_ON_ONCE(!rcu_read_lock_held());
2140 /* see throtl_charge_bio() */
2141 if (bio_flagged(bio, BIO_THROTTLED) || !tg->has_rules[rw])
2144 spin_lock_irq(q->queue_lock);
2146 throtl_update_latency_buckets(td);
2148 if (unlikely(blk_queue_bypass(q)))
2151 blk_throtl_assoc_bio(tg, bio);
2152 blk_throtl_update_idletime(tg);
2154 sq = &tg->service_queue;
2158 if (tg->last_low_overflow_time[rw] == 0)
2159 tg->last_low_overflow_time[rw] = jiffies;
2160 throtl_downgrade_check(tg);
2161 throtl_upgrade_check(tg);
2162 /* throtl is FIFO - if bios are already queued, should queue */
2163 if (sq->nr_queued[rw])
2166 /* if above limits, break to queue */
2167 if (!tg_may_dispatch(tg, bio, NULL)) {
2168 tg->last_low_overflow_time[rw] = jiffies;
2169 if (throtl_can_upgrade(td, tg)) {
2170 throtl_upgrade_state(td);
2176 /* within limits, let's charge and dispatch directly */
2177 throtl_charge_bio(tg, bio);
2180 * We need to trim slice even when bios are not being queued
2181 * otherwise it might happen that a bio is not queued for
2182 * a long time and slice keeps on extending and trim is not
2183 * called for a long time. Now if limits are reduced suddenly
2184 * we take into account all the IO dispatched so far at new
2185 * low rate and * newly queued IO gets a really long dispatch
2188 * So keep on trimming slice even if bio is not queued.
2190 throtl_trim_slice(tg, rw);
2193 * @bio passed through this layer without being throttled.
2194 * Climb up the ladder. If we''re already at the top, it
2195 * can be executed directly.
2197 qn = &tg->qnode_on_parent[rw];
2204 /* out-of-limit, queue to @tg */
2205 throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
2206 rw == READ ? 'R' : 'W',
2207 tg->bytes_disp[rw], bio->bi_iter.bi_size,
2208 tg_bps_limit(tg, rw),
2209 tg->io_disp[rw], tg_iops_limit(tg, rw),
2210 sq->nr_queued[READ], sq->nr_queued[WRITE]);
2212 tg->last_low_overflow_time[rw] = jiffies;
2214 td->nr_queued[rw]++;
2215 throtl_add_bio_tg(bio, qn, tg);
2219 * Update @tg's dispatch time and force schedule dispatch if @tg
2220 * was empty before @bio. The forced scheduling isn't likely to
2221 * cause undue delay as @bio is likely to be dispatched directly if
2222 * its @tg's disptime is not in the future.
2224 if (tg->flags & THROTL_TG_WAS_EMPTY) {
2225 tg_update_disptime(tg);
2226 throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true);
2230 spin_unlock_irq(q->queue_lock);
2233 * As multiple blk-throtls may stack in the same issue path, we
2234 * don't want bios to leave with the flag set. Clear the flag if
2238 bio_clear_flag(bio, BIO_THROTTLED);
2240 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2241 if (throttled || !td->track_bio_latency)
2242 bio->bi_issue_stat.stat |= SKIP_LATENCY;
2247 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2248 static void throtl_track_latency(struct throtl_data *td, sector_t size,
2249 int op, unsigned long time)
2251 struct latency_bucket *latency;
2254 if (!td || td->limit_index != LIMIT_LOW || op != REQ_OP_READ ||
2255 !blk_queue_nonrot(td->queue))
2258 index = request_bucket_index(size);
2260 latency = get_cpu_ptr(td->latency_buckets);
2261 latency[index].total_latency += time;
2262 latency[index].samples++;
2263 put_cpu_ptr(td->latency_buckets);
2266 void blk_throtl_stat_add(struct request *rq, u64 time_ns)
2268 struct request_queue *q = rq->q;
2269 struct throtl_data *td = q->td;
2271 throtl_track_latency(td, blk_stat_size(&rq->issue_stat),
2272 req_op(rq), time_ns >> 10);
2275 void blk_throtl_bio_endio(struct bio *bio)
2277 struct throtl_grp *tg;
2279 unsigned long finish_time;
2280 unsigned long start_time;
2283 tg = bio->bi_cg_private;
2286 bio->bi_cg_private = NULL;
2288 finish_time_ns = ktime_get_ns();
2289 tg->last_finish_time = finish_time_ns >> 10;
2291 start_time = blk_stat_time(&bio->bi_issue_stat) >> 10;
2292 finish_time = __blk_stat_time(finish_time_ns) >> 10;
2293 if (!start_time || finish_time <= start_time)
2296 lat = finish_time - start_time;
2297 /* this is only for bio based driver */
2298 if (!(bio->bi_issue_stat.stat & SKIP_LATENCY))
2299 throtl_track_latency(tg->td, blk_stat_size(&bio->bi_issue_stat),
2302 if (tg->latency_target && lat >= tg->td->filtered_latency) {
2304 unsigned int threshold;
2306 bucket = request_bucket_index(
2307 blk_stat_size(&bio->bi_issue_stat));
2308 threshold = tg->td->avg_buckets[bucket].latency +
2310 if (lat > threshold)
2313 * Not race free, could get wrong count, which means cgroups
2319 if (time_after(jiffies, tg->bio_cnt_reset_time) || tg->bio_cnt > 1024) {
2320 tg->bio_cnt_reset_time = tg->td->throtl_slice + jiffies;
2322 tg->bad_bio_cnt /= 2;
2328 * Dispatch all bios from all children tg's queued on @parent_sq. On
2329 * return, @parent_sq is guaranteed to not have any active children tg's
2330 * and all bios from previously active tg's are on @parent_sq->bio_lists[].
2332 static void tg_drain_bios(struct throtl_service_queue *parent_sq)
2334 struct throtl_grp *tg;
2336 while ((tg = throtl_rb_first(parent_sq))) {
2337 struct throtl_service_queue *sq = &tg->service_queue;
2340 throtl_dequeue_tg(tg);
2342 while ((bio = throtl_peek_queued(&sq->queued[READ])))
2343 tg_dispatch_one_bio(tg, bio_data_dir(bio));
2344 while ((bio = throtl_peek_queued(&sq->queued[WRITE])))
2345 tg_dispatch_one_bio(tg, bio_data_dir(bio));
2350 * blk_throtl_drain - drain throttled bios
2351 * @q: request_queue to drain throttled bios for
2353 * Dispatch all currently throttled bios on @q through ->make_request_fn().
2355 void blk_throtl_drain(struct request_queue *q)
2356 __releases(q->queue_lock) __acquires(q->queue_lock)
2358 struct throtl_data *td = q->td;
2359 struct blkcg_gq *blkg;
2360 struct cgroup_subsys_state *pos_css;
2364 queue_lockdep_assert_held(q);
2368 * Drain each tg while doing post-order walk on the blkg tree, so
2369 * that all bios are propagated to td->service_queue. It'd be
2370 * better to walk service_queue tree directly but blkg walk is
2373 blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg)
2374 tg_drain_bios(&blkg_to_tg(blkg)->service_queue);
2376 /* finally, transfer bios from top-level tg's into the td */
2377 tg_drain_bios(&td->service_queue);
2380 spin_unlock_irq(q->queue_lock);
2382 /* all bios now should be in td->service_queue, issue them */
2383 for (rw = READ; rw <= WRITE; rw++)
2384 while ((bio = throtl_pop_queued(&td->service_queue.queued[rw],
2386 generic_make_request(bio);
2388 spin_lock_irq(q->queue_lock);
2391 int blk_throtl_init(struct request_queue *q)
2393 struct throtl_data *td;
2396 td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
2399 td->latency_buckets = __alloc_percpu(sizeof(struct latency_bucket) *
2400 LATENCY_BUCKET_SIZE, __alignof__(u64));
2401 if (!td->latency_buckets) {
2406 INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
2407 throtl_service_queue_init(&td->service_queue);
2412 td->limit_valid[LIMIT_MAX] = true;
2413 td->limit_index = LIMIT_MAX;
2414 td->low_upgrade_time = jiffies;
2415 td->low_downgrade_time = jiffies;
2417 /* activate policy */
2418 ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
2420 free_percpu(td->latency_buckets);
2426 void blk_throtl_exit(struct request_queue *q)
2429 throtl_shutdown_wq(q);
2430 blkcg_deactivate_policy(q, &blkcg_policy_throtl);
2431 free_percpu(q->td->latency_buckets);
2435 void blk_throtl_register_queue(struct request_queue *q)
2437 struct throtl_data *td;
2443 if (blk_queue_nonrot(q)) {
2444 td->throtl_slice = DFL_THROTL_SLICE_SSD;
2445 td->filtered_latency = LATENCY_FILTERED_SSD;
2447 td->throtl_slice = DFL_THROTL_SLICE_HD;
2448 td->filtered_latency = LATENCY_FILTERED_HD;
2449 for (i = 0; i < LATENCY_BUCKET_SIZE; i++)
2450 td->avg_buckets[i].latency = DFL_HD_BASELINE_LATENCY;
2452 #ifndef CONFIG_BLK_DEV_THROTTLING_LOW
2453 /* if no low limit, use previous default */
2454 td->throtl_slice = DFL_THROTL_SLICE_HD;
2457 td->track_bio_latency = !q->mq_ops && !q->request_fn;
2458 if (!td->track_bio_latency)
2459 blk_stat_enable_accounting(q);
2462 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2463 ssize_t blk_throtl_sample_time_show(struct request_queue *q, char *page)
2467 return sprintf(page, "%u\n", jiffies_to_msecs(q->td->throtl_slice));
2470 ssize_t blk_throtl_sample_time_store(struct request_queue *q,
2471 const char *page, size_t count)
2478 if (kstrtoul(page, 10, &v))
2480 t = msecs_to_jiffies(v);
2481 if (t == 0 || t > MAX_THROTL_SLICE)
2483 q->td->throtl_slice = t;
2488 static int __init throtl_init(void)
2490 kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
2491 if (!kthrotld_workqueue)
2492 panic("Failed to create kthrotld\n");
2494 return blkcg_policy_register(&blkcg_policy_throtl);
2497 module_init(throtl_init);