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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Interface for controlling IO bandwidth on a request queue
4 *
5 * Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com>
6 */
7
8#include <linux/module.h>
9#include <linux/slab.h>
10#include <linux/blkdev.h>
11#include <linux/bio.h>
12#include <linux/blktrace_api.h>
13#include "blk.h"
14#include "blk-cgroup-rwstat.h"
15#include "blk-stat.h"
16#include "blk-throttle.h"
17
18/* Max dispatch from a group in 1 round */
19#define THROTL_GRP_QUANTUM 8
20
21/* Total max dispatch from all groups in one round */
22#define THROTL_QUANTUM 32
23
24/* Throttling is performed over a slice and after that slice is renewed */
25#define DFL_THROTL_SLICE_HD (HZ / 10)
26#define DFL_THROTL_SLICE_SSD (HZ / 50)
27#define MAX_THROTL_SLICE (HZ)
28#define MAX_IDLE_TIME (5L * 1000 * 1000) /* 5 s */
29#define MIN_THROTL_BPS (320 * 1024)
30#define MIN_THROTL_IOPS (10)
31#define DFL_LATENCY_TARGET (-1L)
32#define DFL_IDLE_THRESHOLD (0)
33#define DFL_HD_BASELINE_LATENCY (4000L) /* 4ms */
34#define LATENCY_FILTERED_SSD (0)
35/*
36 * For HD, very small latency comes from sequential IO. Such IO is helpless to
37 * help determine if its IO is impacted by others, hence we ignore the IO
38 */
39#define LATENCY_FILTERED_HD (1000L) /* 1ms */
40
41/* A workqueue to queue throttle related work */
42static struct workqueue_struct *kthrotld_workqueue;
43
44#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
45
46/* We measure latency for request size from <= 4k to >= 1M */
47#define LATENCY_BUCKET_SIZE 9
48
49struct latency_bucket {
50 unsigned long total_latency; /* ns / 1024 */
51 int samples;
52};
53
54struct avg_latency_bucket {
55 unsigned long latency; /* ns / 1024 */
56 bool valid;
57};
58
59struct throtl_data
60{
61 /* service tree for active throtl groups */
62 struct throtl_service_queue service_queue;
63
64 struct request_queue *queue;
65
66 /* Total Number of queued bios on READ and WRITE lists */
67 unsigned int nr_queued[2];
68
69 unsigned int throtl_slice;
70
71 /* Work for dispatching throttled bios */
72 struct work_struct dispatch_work;
73 unsigned int limit_index;
74 bool limit_valid[LIMIT_CNT];
75
76 unsigned long low_upgrade_time;
77 unsigned long low_downgrade_time;
78
79 unsigned int scale;
80
81 struct latency_bucket tmp_buckets[2][LATENCY_BUCKET_SIZE];
82 struct avg_latency_bucket avg_buckets[2][LATENCY_BUCKET_SIZE];
83 struct latency_bucket __percpu *latency_buckets[2];
84 unsigned long last_calculate_time;
85 unsigned long filtered_latency;
86
87 bool track_bio_latency;
88};
89
90static void throtl_pending_timer_fn(struct timer_list *t);
91
92static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
93{
94 return pd_to_blkg(&tg->pd);
95}
96
97/**
98 * sq_to_tg - return the throl_grp the specified service queue belongs to
99 * @sq: the throtl_service_queue of interest
100 *
101 * Return the throtl_grp @sq belongs to. If @sq is the top-level one
102 * embedded in throtl_data, %NULL is returned.
103 */
104static struct throtl_grp *sq_to_tg(struct throtl_service_queue *sq)
105{
106 if (sq && sq->parent_sq)
107 return container_of(sq, struct throtl_grp, service_queue);
108 else
109 return NULL;
110}
111
112/**
113 * sq_to_td - return throtl_data the specified service queue belongs to
114 * @sq: the throtl_service_queue of interest
115 *
116 * A service_queue can be embedded in either a throtl_grp or throtl_data.
117 * Determine the associated throtl_data accordingly and return it.
118 */
119static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
120{
121 struct throtl_grp *tg = sq_to_tg(sq);
122
123 if (tg)
124 return tg->td;
125 else
126 return container_of(sq, struct throtl_data, service_queue);
127}
128
129/*
130 * cgroup's limit in LIMIT_MAX is scaled if low limit is set. This scale is to
131 * make the IO dispatch more smooth.
132 * Scale up: linearly scale up according to elapsed time since upgrade. For
133 * every throtl_slice, the limit scales up 1/2 .low limit till the
134 * limit hits .max limit
135 * Scale down: exponentially scale down if a cgroup doesn't hit its .low limit
136 */
137static uint64_t throtl_adjusted_limit(uint64_t low, struct throtl_data *td)
138{
139 /* arbitrary value to avoid too big scale */
140 if (td->scale < 4096 && time_after_eq(jiffies,
141 td->low_upgrade_time + td->scale * td->throtl_slice))
142 td->scale = (jiffies - td->low_upgrade_time) / td->throtl_slice;
143
144 return low + (low >> 1) * td->scale;
145}
146
147static uint64_t tg_bps_limit(struct throtl_grp *tg, int rw)
148{
149 struct blkcg_gq *blkg = tg_to_blkg(tg);
150 struct throtl_data *td;
151 uint64_t ret;
152
153 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
154 return U64_MAX;
155
156 td = tg->td;
157 ret = tg->bps[rw][td->limit_index];
158 if (ret == 0 && td->limit_index == LIMIT_LOW) {
159 /* intermediate node or iops isn't 0 */
160 if (!list_empty(&blkg->blkcg->css.children) ||
161 tg->iops[rw][td->limit_index])
162 return U64_MAX;
163 else
164 return MIN_THROTL_BPS;
165 }
166
167 if (td->limit_index == LIMIT_MAX && tg->bps[rw][LIMIT_LOW] &&
168 tg->bps[rw][LIMIT_LOW] != tg->bps[rw][LIMIT_MAX]) {
169 uint64_t adjusted;
170
171 adjusted = throtl_adjusted_limit(tg->bps[rw][LIMIT_LOW], td);
172 ret = min(tg->bps[rw][LIMIT_MAX], adjusted);
173 }
174 return ret;
175}
176
177static unsigned int tg_iops_limit(struct throtl_grp *tg, int rw)
178{
179 struct blkcg_gq *blkg = tg_to_blkg(tg);
180 struct throtl_data *td;
181 unsigned int ret;
182
183 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
184 return UINT_MAX;
185
186 td = tg->td;
187 ret = tg->iops[rw][td->limit_index];
188 if (ret == 0 && tg->td->limit_index == LIMIT_LOW) {
189 /* intermediate node or bps isn't 0 */
190 if (!list_empty(&blkg->blkcg->css.children) ||
191 tg->bps[rw][td->limit_index])
192 return UINT_MAX;
193 else
194 return MIN_THROTL_IOPS;
195 }
196
197 if (td->limit_index == LIMIT_MAX && tg->iops[rw][LIMIT_LOW] &&
198 tg->iops[rw][LIMIT_LOW] != tg->iops[rw][LIMIT_MAX]) {
199 uint64_t adjusted;
200
201 adjusted = throtl_adjusted_limit(tg->iops[rw][LIMIT_LOW], td);
202 if (adjusted > UINT_MAX)
203 adjusted = UINT_MAX;
204 ret = min_t(unsigned int, tg->iops[rw][LIMIT_MAX], adjusted);
205 }
206 return ret;
207}
208
209#define request_bucket_index(sectors) \
210 clamp_t(int, order_base_2(sectors) - 3, 0, LATENCY_BUCKET_SIZE - 1)
211
212/**
213 * throtl_log - log debug message via blktrace
214 * @sq: the service_queue being reported
215 * @fmt: printf format string
216 * @args: printf args
217 *
218 * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
219 * throtl_grp; otherwise, just "throtl".
220 */
221#define throtl_log(sq, fmt, args...) do { \
222 struct throtl_grp *__tg = sq_to_tg((sq)); \
223 struct throtl_data *__td = sq_to_td((sq)); \
224 \
225 (void)__td; \
226 if (likely(!blk_trace_note_message_enabled(__td->queue))) \
227 break; \
228 if ((__tg)) { \
229 blk_add_cgroup_trace_msg(__td->queue, \
230 &tg_to_blkg(__tg)->blkcg->css, "throtl " fmt, ##args);\
231 } else { \
232 blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \
233 } \
234} while (0)
235
236static inline unsigned int throtl_bio_data_size(struct bio *bio)
237{
238 /* assume it's one sector */
239 if (unlikely(bio_op(bio) == REQ_OP_DISCARD))
240 return 512;
241 return bio->bi_iter.bi_size;
242}
243
244static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg)
245{
246 INIT_LIST_HEAD(&qn->node);
247 bio_list_init(&qn->bios);
248 qn->tg = tg;
249}
250
251/**
252 * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it
253 * @bio: bio being added
254 * @qn: qnode to add bio to
255 * @queued: the service_queue->queued[] list @qn belongs to
256 *
257 * Add @bio to @qn and put @qn on @queued if it's not already on.
258 * @qn->tg's reference count is bumped when @qn is activated. See the
259 * comment on top of throtl_qnode definition for details.
260 */
261static void throtl_qnode_add_bio(struct bio *bio, struct throtl_qnode *qn,
262 struct list_head *queued)
263{
264 bio_list_add(&qn->bios, bio);
265 if (list_empty(&qn->node)) {
266 list_add_tail(&qn->node, queued);
267 blkg_get(tg_to_blkg(qn->tg));
268 }
269}
270
271/**
272 * throtl_peek_queued - peek the first bio on a qnode list
273 * @queued: the qnode list to peek
274 */
275static struct bio *throtl_peek_queued(struct list_head *queued)
276{
277 struct throtl_qnode *qn;
278 struct bio *bio;
279
280 if (list_empty(queued))
281 return NULL;
282
283 qn = list_first_entry(queued, struct throtl_qnode, node);
284 bio = bio_list_peek(&qn->bios);
285 WARN_ON_ONCE(!bio);
286 return bio;
287}
288
289/**
290 * throtl_pop_queued - pop the first bio form a qnode list
291 * @queued: the qnode list to pop a bio from
292 * @tg_to_put: optional out argument for throtl_grp to put
293 *
294 * Pop the first bio from the qnode list @queued. After popping, the first
295 * qnode is removed from @queued if empty or moved to the end of @queued so
296 * that the popping order is round-robin.
297 *
298 * When the first qnode is removed, its associated throtl_grp should be put
299 * too. If @tg_to_put is NULL, this function automatically puts it;
300 * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is
301 * responsible for putting it.
302 */
303static struct bio *throtl_pop_queued(struct list_head *queued,
304 struct throtl_grp **tg_to_put)
305{
306 struct throtl_qnode *qn;
307 struct bio *bio;
308
309 if (list_empty(queued))
310 return NULL;
311
312 qn = list_first_entry(queued, struct throtl_qnode, node);
313 bio = bio_list_pop(&qn->bios);
314 WARN_ON_ONCE(!bio);
315
316 if (bio_list_empty(&qn->bios)) {
317 list_del_init(&qn->node);
318 if (tg_to_put)
319 *tg_to_put = qn->tg;
320 else
321 blkg_put(tg_to_blkg(qn->tg));
322 } else {
323 list_move_tail(&qn->node, queued);
324 }
325
326 return bio;
327}
328
329/* init a service_queue, assumes the caller zeroed it */
330static void throtl_service_queue_init(struct throtl_service_queue *sq)
331{
332 INIT_LIST_HEAD(&sq->queued[READ]);
333 INIT_LIST_HEAD(&sq->queued[WRITE]);
334 sq->pending_tree = RB_ROOT_CACHED;
335 timer_setup(&sq->pending_timer, throtl_pending_timer_fn, 0);
336}
337
338static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp,
339 struct request_queue *q,
340 struct blkcg *blkcg)
341{
342 struct throtl_grp *tg;
343 int rw;
344
345 tg = kzalloc_node(sizeof(*tg), gfp, q->node);
346 if (!tg)
347 return NULL;
348
349 if (blkg_rwstat_init(&tg->stat_bytes, gfp))
350 goto err_free_tg;
351
352 if (blkg_rwstat_init(&tg->stat_ios, gfp))
353 goto err_exit_stat_bytes;
354
355 throtl_service_queue_init(&tg->service_queue);
356
357 for (rw = READ; rw <= WRITE; rw++) {
358 throtl_qnode_init(&tg->qnode_on_self[rw], tg);
359 throtl_qnode_init(&tg->qnode_on_parent[rw], tg);
360 }
361
362 RB_CLEAR_NODE(&tg->rb_node);
363 tg->bps[READ][LIMIT_MAX] = U64_MAX;
364 tg->bps[WRITE][LIMIT_MAX] = U64_MAX;
365 tg->iops[READ][LIMIT_MAX] = UINT_MAX;
366 tg->iops[WRITE][LIMIT_MAX] = UINT_MAX;
367 tg->bps_conf[READ][LIMIT_MAX] = U64_MAX;
368 tg->bps_conf[WRITE][LIMIT_MAX] = U64_MAX;
369 tg->iops_conf[READ][LIMIT_MAX] = UINT_MAX;
370 tg->iops_conf[WRITE][LIMIT_MAX] = UINT_MAX;
371 /* LIMIT_LOW will have default value 0 */
372
373 tg->latency_target = DFL_LATENCY_TARGET;
374 tg->latency_target_conf = DFL_LATENCY_TARGET;
375 tg->idletime_threshold = DFL_IDLE_THRESHOLD;
376 tg->idletime_threshold_conf = DFL_IDLE_THRESHOLD;
377
378 return &tg->pd;
379
380err_exit_stat_bytes:
381 blkg_rwstat_exit(&tg->stat_bytes);
382err_free_tg:
383 kfree(tg);
384 return NULL;
385}
386
387static void throtl_pd_init(struct blkg_policy_data *pd)
388{
389 struct throtl_grp *tg = pd_to_tg(pd);
390 struct blkcg_gq *blkg = tg_to_blkg(tg);
391 struct throtl_data *td = blkg->q->td;
392 struct throtl_service_queue *sq = &tg->service_queue;
393
394 /*
395 * If on the default hierarchy, we switch to properly hierarchical
396 * behavior where limits on a given throtl_grp are applied to the
397 * whole subtree rather than just the group itself. e.g. If 16M
398 * read_bps limit is set on a parent group, summary bps of
399 * parent group and its subtree groups can't exceed 16M for the
400 * device.
401 *
402 * If not on the default hierarchy, the broken flat hierarchy
403 * behavior is retained where all throtl_grps are treated as if
404 * they're all separate root groups right below throtl_data.
405 * Limits of a group don't interact with limits of other groups
406 * regardless of the position of the group in the hierarchy.
407 */
408 sq->parent_sq = &td->service_queue;
409 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent)
410 sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
411 tg->td = td;
412}
413
414/*
415 * Set has_rules[] if @tg or any of its parents have limits configured.
416 * This doesn't require walking up to the top of the hierarchy as the
417 * parent's has_rules[] is guaranteed to be correct.
418 */
419static void tg_update_has_rules(struct throtl_grp *tg)
420{
421 struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq);
422 struct throtl_data *td = tg->td;
423 int rw;
424
425 for (rw = READ; rw <= WRITE; rw++) {
426 tg->has_rules_iops[rw] =
427 (parent_tg && parent_tg->has_rules_iops[rw]) ||
428 (td->limit_valid[td->limit_index] &&
429 tg_iops_limit(tg, rw) != UINT_MAX);
430 tg->has_rules_bps[rw] =
431 (parent_tg && parent_tg->has_rules_bps[rw]) ||
432 (td->limit_valid[td->limit_index] &&
433 (tg_bps_limit(tg, rw) != U64_MAX));
434 }
435}
436
437static void throtl_pd_online(struct blkg_policy_data *pd)
438{
439 struct throtl_grp *tg = pd_to_tg(pd);
440 /*
441 * We don't want new groups to escape the limits of its ancestors.
442 * Update has_rules[] after a new group is brought online.
443 */
444 tg_update_has_rules(tg);
445}
446
447#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
448static void blk_throtl_update_limit_valid(struct throtl_data *td)
449{
450 struct cgroup_subsys_state *pos_css;
451 struct blkcg_gq *blkg;
452 bool low_valid = false;
453
454 rcu_read_lock();
455 blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
456 struct throtl_grp *tg = blkg_to_tg(blkg);
457
458 if (tg->bps[READ][LIMIT_LOW] || tg->bps[WRITE][LIMIT_LOW] ||
459 tg->iops[READ][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW]) {
460 low_valid = true;
461 break;
462 }
463 }
464 rcu_read_unlock();
465
466 td->limit_valid[LIMIT_LOW] = low_valid;
467}
468#else
469static inline void blk_throtl_update_limit_valid(struct throtl_data *td)
470{
471}
472#endif
473
474static void throtl_upgrade_state(struct throtl_data *td);
475static void throtl_pd_offline(struct blkg_policy_data *pd)
476{
477 struct throtl_grp *tg = pd_to_tg(pd);
478
479 tg->bps[READ][LIMIT_LOW] = 0;
480 tg->bps[WRITE][LIMIT_LOW] = 0;
481 tg->iops[READ][LIMIT_LOW] = 0;
482 tg->iops[WRITE][LIMIT_LOW] = 0;
483
484 blk_throtl_update_limit_valid(tg->td);
485
486 if (!tg->td->limit_valid[tg->td->limit_index])
487 throtl_upgrade_state(tg->td);
488}
489
490static void throtl_pd_free(struct blkg_policy_data *pd)
491{
492 struct throtl_grp *tg = pd_to_tg(pd);
493
494 del_timer_sync(&tg->service_queue.pending_timer);
495 blkg_rwstat_exit(&tg->stat_bytes);
496 blkg_rwstat_exit(&tg->stat_ios);
497 kfree(tg);
498}
499
500static struct throtl_grp *
501throtl_rb_first(struct throtl_service_queue *parent_sq)
502{
503 struct rb_node *n;
504
505 n = rb_first_cached(&parent_sq->pending_tree);
506 WARN_ON_ONCE(!n);
507 if (!n)
508 return NULL;
509 return rb_entry_tg(n);
510}
511
512static void throtl_rb_erase(struct rb_node *n,
513 struct throtl_service_queue *parent_sq)
514{
515 rb_erase_cached(n, &parent_sq->pending_tree);
516 RB_CLEAR_NODE(n);
517}
518
519static void update_min_dispatch_time(struct throtl_service_queue *parent_sq)
520{
521 struct throtl_grp *tg;
522
523 tg = throtl_rb_first(parent_sq);
524 if (!tg)
525 return;
526
527 parent_sq->first_pending_disptime = tg->disptime;
528}
529
530static void tg_service_queue_add(struct throtl_grp *tg)
531{
532 struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq;
533 struct rb_node **node = &parent_sq->pending_tree.rb_root.rb_node;
534 struct rb_node *parent = NULL;
535 struct throtl_grp *__tg;
536 unsigned long key = tg->disptime;
537 bool leftmost = true;
538
539 while (*node != NULL) {
540 parent = *node;
541 __tg = rb_entry_tg(parent);
542
543 if (time_before(key, __tg->disptime))
544 node = &parent->rb_left;
545 else {
546 node = &parent->rb_right;
547 leftmost = false;
548 }
549 }
550
551 rb_link_node(&tg->rb_node, parent, node);
552 rb_insert_color_cached(&tg->rb_node, &parent_sq->pending_tree,
553 leftmost);
554}
555
556static void throtl_enqueue_tg(struct throtl_grp *tg)
557{
558 if (!(tg->flags & THROTL_TG_PENDING)) {
559 tg_service_queue_add(tg);
560 tg->flags |= THROTL_TG_PENDING;
561 tg->service_queue.parent_sq->nr_pending++;
562 }
563}
564
565static void throtl_dequeue_tg(struct throtl_grp *tg)
566{
567 if (tg->flags & THROTL_TG_PENDING) {
568 struct throtl_service_queue *parent_sq =
569 tg->service_queue.parent_sq;
570
571 throtl_rb_erase(&tg->rb_node, parent_sq);
572 --parent_sq->nr_pending;
573 tg->flags &= ~THROTL_TG_PENDING;
574 }
575}
576
577/* Call with queue lock held */
578static void throtl_schedule_pending_timer(struct throtl_service_queue *sq,
579 unsigned long expires)
580{
581 unsigned long max_expire = jiffies + 8 * sq_to_td(sq)->throtl_slice;
582
583 /*
584 * Since we are adjusting the throttle limit dynamically, the sleep
585 * time calculated according to previous limit might be invalid. It's
586 * possible the cgroup sleep time is very long and no other cgroups
587 * have IO running so notify the limit changes. Make sure the cgroup
588 * doesn't sleep too long to avoid the missed notification.
589 */
590 if (time_after(expires, max_expire))
591 expires = max_expire;
592 mod_timer(&sq->pending_timer, expires);
593 throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu",
594 expires - jiffies, jiffies);
595}
596
597/**
598 * throtl_schedule_next_dispatch - schedule the next dispatch cycle
599 * @sq: the service_queue to schedule dispatch for
600 * @force: force scheduling
601 *
602 * Arm @sq->pending_timer so that the next dispatch cycle starts on the
603 * dispatch time of the first pending child. Returns %true if either timer
604 * is armed or there's no pending child left. %false if the current
605 * dispatch window is still open and the caller should continue
606 * dispatching.
607 *
608 * If @force is %true, the dispatch timer is always scheduled and this
609 * function is guaranteed to return %true. This is to be used when the
610 * caller can't dispatch itself and needs to invoke pending_timer
611 * unconditionally. Note that forced scheduling is likely to induce short
612 * delay before dispatch starts even if @sq->first_pending_disptime is not
613 * in the future and thus shouldn't be used in hot paths.
614 */
615static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq,
616 bool force)
617{
618 /* any pending children left? */
619 if (!sq->nr_pending)
620 return true;
621
622 update_min_dispatch_time(sq);
623
624 /* is the next dispatch time in the future? */
625 if (force || time_after(sq->first_pending_disptime, jiffies)) {
626 throtl_schedule_pending_timer(sq, sq->first_pending_disptime);
627 return true;
628 }
629
630 /* tell the caller to continue dispatching */
631 return false;
632}
633
634static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
635 bool rw, unsigned long start)
636{
637 tg->bytes_disp[rw] = 0;
638 tg->io_disp[rw] = 0;
639 tg->carryover_bytes[rw] = 0;
640 tg->carryover_ios[rw] = 0;
641
642 /*
643 * Previous slice has expired. We must have trimmed it after last
644 * bio dispatch. That means since start of last slice, we never used
645 * that bandwidth. Do try to make use of that bandwidth while giving
646 * credit.
647 */
648 if (time_after(start, tg->slice_start[rw]))
649 tg->slice_start[rw] = start;
650
651 tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
652 throtl_log(&tg->service_queue,
653 "[%c] new slice with credit start=%lu end=%lu jiffies=%lu",
654 rw == READ ? 'R' : 'W', tg->slice_start[rw],
655 tg->slice_end[rw], jiffies);
656}
657
658static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw,
659 bool clear_carryover)
660{
661 tg->bytes_disp[rw] = 0;
662 tg->io_disp[rw] = 0;
663 tg->slice_start[rw] = jiffies;
664 tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
665 if (clear_carryover) {
666 tg->carryover_bytes[rw] = 0;
667 tg->carryover_ios[rw] = 0;
668 }
669
670 throtl_log(&tg->service_queue,
671 "[%c] new slice start=%lu end=%lu jiffies=%lu",
672 rw == READ ? 'R' : 'W', tg->slice_start[rw],
673 tg->slice_end[rw], jiffies);
674}
675
676static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw,
677 unsigned long jiffy_end)
678{
679 tg->slice_end[rw] = roundup(jiffy_end, tg->td->throtl_slice);
680}
681
682static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw,
683 unsigned long jiffy_end)
684{
685 throtl_set_slice_end(tg, rw, jiffy_end);
686 throtl_log(&tg->service_queue,
687 "[%c] extend slice start=%lu end=%lu jiffies=%lu",
688 rw == READ ? 'R' : 'W', tg->slice_start[rw],
689 tg->slice_end[rw], jiffies);
690}
691
692/* Determine if previously allocated or extended slice is complete or not */
693static bool throtl_slice_used(struct throtl_grp *tg, bool rw)
694{
695 if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
696 return false;
697
698 return true;
699}
700
701/* Trim the used slices and adjust slice start accordingly */
702static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
703{
704 unsigned long nr_slices, time_elapsed, io_trim;
705 u64 bytes_trim, tmp;
706
707 BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
708
709 /*
710 * If bps are unlimited (-1), then time slice don't get
711 * renewed. Don't try to trim the slice if slice is used. A new
712 * slice will start when appropriate.
713 */
714 if (throtl_slice_used(tg, rw))
715 return;
716
717 /*
718 * A bio has been dispatched. Also adjust slice_end. It might happen
719 * that initially cgroup limit was very low resulting in high
720 * slice_end, but later limit was bumped up and bio was dispatched
721 * sooner, then we need to reduce slice_end. A high bogus slice_end
722 * is bad because it does not allow new slice to start.
723 */
724
725 throtl_set_slice_end(tg, rw, jiffies + tg->td->throtl_slice);
726
727 time_elapsed = jiffies - tg->slice_start[rw];
728
729 nr_slices = time_elapsed / tg->td->throtl_slice;
730
731 if (!nr_slices)
732 return;
733 tmp = tg_bps_limit(tg, rw) * tg->td->throtl_slice * nr_slices;
734 do_div(tmp, HZ);
735 bytes_trim = tmp;
736
737 io_trim = (tg_iops_limit(tg, rw) * tg->td->throtl_slice * nr_slices) /
738 HZ;
739
740 if (!bytes_trim && !io_trim)
741 return;
742
743 if (tg->bytes_disp[rw] >= bytes_trim)
744 tg->bytes_disp[rw] -= bytes_trim;
745 else
746 tg->bytes_disp[rw] = 0;
747
748 if (tg->io_disp[rw] >= io_trim)
749 tg->io_disp[rw] -= io_trim;
750 else
751 tg->io_disp[rw] = 0;
752
753 tg->slice_start[rw] += nr_slices * tg->td->throtl_slice;
754
755 throtl_log(&tg->service_queue,
756 "[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu",
757 rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
758 tg->slice_start[rw], tg->slice_end[rw], jiffies);
759}
760
761static unsigned int calculate_io_allowed(u32 iops_limit,
762 unsigned long jiffy_elapsed)
763{
764 unsigned int io_allowed;
765 u64 tmp;
766
767 /*
768 * jiffy_elapsed should not be a big value as minimum iops can be
769 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
770 * will allow dispatch after 1 second and after that slice should
771 * have been trimmed.
772 */
773
774 tmp = (u64)iops_limit * jiffy_elapsed;
775 do_div(tmp, HZ);
776
777 if (tmp > UINT_MAX)
778 io_allowed = UINT_MAX;
779 else
780 io_allowed = tmp;
781
782 return io_allowed;
783}
784
785static u64 calculate_bytes_allowed(u64 bps_limit, unsigned long jiffy_elapsed)
786{
787 return mul_u64_u64_div_u64(bps_limit, (u64)jiffy_elapsed, (u64)HZ);
788}
789
790static void __tg_update_carryover(struct throtl_grp *tg, bool rw)
791{
792 unsigned long jiffy_elapsed = jiffies - tg->slice_start[rw];
793 u64 bps_limit = tg_bps_limit(tg, rw);
794 u32 iops_limit = tg_iops_limit(tg, rw);
795
796 /*
797 * If config is updated while bios are still throttled, calculate and
798 * accumulate how many bytes/ios are waited across changes. And
799 * carryover_bytes/ios will be used to calculate new wait time under new
800 * configuration.
801 */
802 if (bps_limit != U64_MAX)
803 tg->carryover_bytes[rw] +=
804 calculate_bytes_allowed(bps_limit, jiffy_elapsed) -
805 tg->bytes_disp[rw];
806 if (iops_limit != UINT_MAX)
807 tg->carryover_ios[rw] +=
808 calculate_io_allowed(iops_limit, jiffy_elapsed) -
809 tg->io_disp[rw];
810}
811
812static void tg_update_carryover(struct throtl_grp *tg)
813{
814 if (tg->service_queue.nr_queued[READ])
815 __tg_update_carryover(tg, READ);
816 if (tg->service_queue.nr_queued[WRITE])
817 __tg_update_carryover(tg, WRITE);
818
819 /* see comments in struct throtl_grp for meaning of these fields. */
820 throtl_log(&tg->service_queue, "%s: %llu %llu %u %u\n", __func__,
821 tg->carryover_bytes[READ], tg->carryover_bytes[WRITE],
822 tg->carryover_ios[READ], tg->carryover_ios[WRITE]);
823}
824
825static unsigned long tg_within_iops_limit(struct throtl_grp *tg, struct bio *bio,
826 u32 iops_limit)
827{
828 bool rw = bio_data_dir(bio);
829 unsigned int io_allowed;
830 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
831
832 if (iops_limit == UINT_MAX) {
833 return 0;
834 }
835
836 jiffy_elapsed = jiffies - tg->slice_start[rw];
837
838 /* Round up to the next throttle slice, wait time must be nonzero */
839 jiffy_elapsed_rnd = roundup(jiffy_elapsed + 1, tg->td->throtl_slice);
840 io_allowed = calculate_io_allowed(iops_limit, jiffy_elapsed_rnd) +
841 tg->carryover_ios[rw];
842 if (tg->io_disp[rw] + 1 <= io_allowed) {
843 return 0;
844 }
845
846 /* Calc approx time to dispatch */
847 jiffy_wait = jiffy_elapsed_rnd - jiffy_elapsed;
848 return jiffy_wait;
849}
850
851static unsigned long tg_within_bps_limit(struct throtl_grp *tg, struct bio *bio,
852 u64 bps_limit)
853{
854 bool rw = bio_data_dir(bio);
855 u64 bytes_allowed, extra_bytes;
856 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
857 unsigned int bio_size = throtl_bio_data_size(bio);
858
859 /* no need to throttle if this bio's bytes have been accounted */
860 if (bps_limit == U64_MAX || bio_flagged(bio, BIO_BPS_THROTTLED)) {
861 return 0;
862 }
863
864 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
865
866 /* Slice has just started. Consider one slice interval */
867 if (!jiffy_elapsed)
868 jiffy_elapsed_rnd = tg->td->throtl_slice;
869
870 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);
871 bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd) +
872 tg->carryover_bytes[rw];
873 if (tg->bytes_disp[rw] + bio_size <= bytes_allowed) {
874 return 0;
875 }
876
877 /* Calc approx time to dispatch */
878 extra_bytes = tg->bytes_disp[rw] + bio_size - bytes_allowed;
879 jiffy_wait = div64_u64(extra_bytes * HZ, bps_limit);
880
881 if (!jiffy_wait)
882 jiffy_wait = 1;
883
884 /*
885 * This wait time is without taking into consideration the rounding
886 * up we did. Add that time also.
887 */
888 jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
889 return jiffy_wait;
890}
891
892/*
893 * Returns whether one can dispatch a bio or not. Also returns approx number
894 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
895 */
896static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
897 unsigned long *wait)
898{
899 bool rw = bio_data_dir(bio);
900 unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
901 u64 bps_limit = tg_bps_limit(tg, rw);
902 u32 iops_limit = tg_iops_limit(tg, rw);
903
904 /*
905 * Currently whole state machine of group depends on first bio
906 * queued in the group bio list. So one should not be calling
907 * this function with a different bio if there are other bios
908 * queued.
909 */
910 BUG_ON(tg->service_queue.nr_queued[rw] &&
911 bio != throtl_peek_queued(&tg->service_queue.queued[rw]));
912
913 /* If tg->bps = -1, then BW is unlimited */
914 if ((bps_limit == U64_MAX && iops_limit == UINT_MAX) ||
915 tg->flags & THROTL_TG_CANCELING) {
916 if (wait)
917 *wait = 0;
918 return true;
919 }
920
921 /*
922 * If previous slice expired, start a new one otherwise renew/extend
923 * existing slice to make sure it is at least throtl_slice interval
924 * long since now. New slice is started only for empty throttle group.
925 * If there is queued bio, that means there should be an active
926 * slice and it should be extended instead.
927 */
928 if (throtl_slice_used(tg, rw) && !(tg->service_queue.nr_queued[rw]))
929 throtl_start_new_slice(tg, rw, true);
930 else {
931 if (time_before(tg->slice_end[rw],
932 jiffies + tg->td->throtl_slice))
933 throtl_extend_slice(tg, rw,
934 jiffies + tg->td->throtl_slice);
935 }
936
937 bps_wait = tg_within_bps_limit(tg, bio, bps_limit);
938 iops_wait = tg_within_iops_limit(tg, bio, iops_limit);
939 if (bps_wait + iops_wait == 0) {
940 if (wait)
941 *wait = 0;
942 return true;
943 }
944
945 max_wait = max(bps_wait, iops_wait);
946
947 if (wait)
948 *wait = max_wait;
949
950 if (time_before(tg->slice_end[rw], jiffies + max_wait))
951 throtl_extend_slice(tg, rw, jiffies + max_wait);
952
953 return false;
954}
955
956static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
957{
958 bool rw = bio_data_dir(bio);
959 unsigned int bio_size = throtl_bio_data_size(bio);
960
961 /* Charge the bio to the group */
962 if (!bio_flagged(bio, BIO_BPS_THROTTLED)) {
963 tg->bytes_disp[rw] += bio_size;
964 tg->last_bytes_disp[rw] += bio_size;
965 }
966
967 tg->io_disp[rw]++;
968 tg->last_io_disp[rw]++;
969}
970
971/**
972 * throtl_add_bio_tg - add a bio to the specified throtl_grp
973 * @bio: bio to add
974 * @qn: qnode to use
975 * @tg: the target throtl_grp
976 *
977 * Add @bio to @tg's service_queue using @qn. If @qn is not specified,
978 * tg->qnode_on_self[] is used.
979 */
980static void throtl_add_bio_tg(struct bio *bio, struct throtl_qnode *qn,
981 struct throtl_grp *tg)
982{
983 struct throtl_service_queue *sq = &tg->service_queue;
984 bool rw = bio_data_dir(bio);
985
986 if (!qn)
987 qn = &tg->qnode_on_self[rw];
988
989 /*
990 * If @tg doesn't currently have any bios queued in the same
991 * direction, queueing @bio can change when @tg should be
992 * dispatched. Mark that @tg was empty. This is automatically
993 * cleared on the next tg_update_disptime().
994 */
995 if (!sq->nr_queued[rw])
996 tg->flags |= THROTL_TG_WAS_EMPTY;
997
998 throtl_qnode_add_bio(bio, qn, &sq->queued[rw]);
999
1000 sq->nr_queued[rw]++;
1001 throtl_enqueue_tg(tg);
1002}
1003
1004static void tg_update_disptime(struct throtl_grp *tg)
1005{
1006 struct throtl_service_queue *sq = &tg->service_queue;
1007 unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
1008 struct bio *bio;
1009
1010 bio = throtl_peek_queued(&sq->queued[READ]);
1011 if (bio)
1012 tg_may_dispatch(tg, bio, &read_wait);
1013
1014 bio = throtl_peek_queued(&sq->queued[WRITE]);
1015 if (bio)
1016 tg_may_dispatch(tg, bio, &write_wait);
1017
1018 min_wait = min(read_wait, write_wait);
1019 disptime = jiffies + min_wait;
1020
1021 /* Update dispatch time */
1022 throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq);
1023 tg->disptime = disptime;
1024 tg_service_queue_add(tg);
1025
1026 /* see throtl_add_bio_tg() */
1027 tg->flags &= ~THROTL_TG_WAS_EMPTY;
1028}
1029
1030static void start_parent_slice_with_credit(struct throtl_grp *child_tg,
1031 struct throtl_grp *parent_tg, bool rw)
1032{
1033 if (throtl_slice_used(parent_tg, rw)) {
1034 throtl_start_new_slice_with_credit(parent_tg, rw,
1035 child_tg->slice_start[rw]);
1036 }
1037
1038}
1039
1040static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)
1041{
1042 struct throtl_service_queue *sq = &tg->service_queue;
1043 struct throtl_service_queue *parent_sq = sq->parent_sq;
1044 struct throtl_grp *parent_tg = sq_to_tg(parent_sq);
1045 struct throtl_grp *tg_to_put = NULL;
1046 struct bio *bio;
1047
1048 /*
1049 * @bio is being transferred from @tg to @parent_sq. Popping a bio
1050 * from @tg may put its reference and @parent_sq might end up
1051 * getting released prematurely. Remember the tg to put and put it
1052 * after @bio is transferred to @parent_sq.
1053 */
1054 bio = throtl_pop_queued(&sq->queued[rw], &tg_to_put);
1055 sq->nr_queued[rw]--;
1056
1057 throtl_charge_bio(tg, bio);
1058
1059 /*
1060 * If our parent is another tg, we just need to transfer @bio to
1061 * the parent using throtl_add_bio_tg(). If our parent is
1062 * @td->service_queue, @bio is ready to be issued. Put it on its
1063 * bio_lists[] and decrease total number queued. The caller is
1064 * responsible for issuing these bios.
1065 */
1066 if (parent_tg) {
1067 throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg);
1068 start_parent_slice_with_credit(tg, parent_tg, rw);
1069 } else {
1070 bio_set_flag(bio, BIO_BPS_THROTTLED);
1071 throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw],
1072 &parent_sq->queued[rw]);
1073 BUG_ON(tg->td->nr_queued[rw] <= 0);
1074 tg->td->nr_queued[rw]--;
1075 }
1076
1077 throtl_trim_slice(tg, rw);
1078
1079 if (tg_to_put)
1080 blkg_put(tg_to_blkg(tg_to_put));
1081}
1082
1083static int throtl_dispatch_tg(struct throtl_grp *tg)
1084{
1085 struct throtl_service_queue *sq = &tg->service_queue;
1086 unsigned int nr_reads = 0, nr_writes = 0;
1087 unsigned int max_nr_reads = THROTL_GRP_QUANTUM * 3 / 4;
1088 unsigned int max_nr_writes = THROTL_GRP_QUANTUM - max_nr_reads;
1089 struct bio *bio;
1090
1091 /* Try to dispatch 75% READS and 25% WRITES */
1092
1093 while ((bio = throtl_peek_queued(&sq->queued[READ])) &&
1094 tg_may_dispatch(tg, bio, NULL)) {
1095
1096 tg_dispatch_one_bio(tg, bio_data_dir(bio));
1097 nr_reads++;
1098
1099 if (nr_reads >= max_nr_reads)
1100 break;
1101 }
1102
1103 while ((bio = throtl_peek_queued(&sq->queued[WRITE])) &&
1104 tg_may_dispatch(tg, bio, NULL)) {
1105
1106 tg_dispatch_one_bio(tg, bio_data_dir(bio));
1107 nr_writes++;
1108
1109 if (nr_writes >= max_nr_writes)
1110 break;
1111 }
1112
1113 return nr_reads + nr_writes;
1114}
1115
1116static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
1117{
1118 unsigned int nr_disp = 0;
1119
1120 while (1) {
1121 struct throtl_grp *tg;
1122 struct throtl_service_queue *sq;
1123
1124 if (!parent_sq->nr_pending)
1125 break;
1126
1127 tg = throtl_rb_first(parent_sq);
1128 if (!tg)
1129 break;
1130
1131 if (time_before(jiffies, tg->disptime))
1132 break;
1133
1134 nr_disp += throtl_dispatch_tg(tg);
1135
1136 sq = &tg->service_queue;
1137 if (sq->nr_queued[READ] || sq->nr_queued[WRITE])
1138 tg_update_disptime(tg);
1139 else
1140 throtl_dequeue_tg(tg);
1141
1142 if (nr_disp >= THROTL_QUANTUM)
1143 break;
1144 }
1145
1146 return nr_disp;
1147}
1148
1149static bool throtl_can_upgrade(struct throtl_data *td,
1150 struct throtl_grp *this_tg);
1151/**
1152 * throtl_pending_timer_fn - timer function for service_queue->pending_timer
1153 * @t: the pending_timer member of the throtl_service_queue being serviced
1154 *
1155 * This timer is armed when a child throtl_grp with active bio's become
1156 * pending and queued on the service_queue's pending_tree and expires when
1157 * the first child throtl_grp should be dispatched. This function
1158 * dispatches bio's from the children throtl_grps to the parent
1159 * service_queue.
1160 *
1161 * If the parent's parent is another throtl_grp, dispatching is propagated
1162 * by either arming its pending_timer or repeating dispatch directly. If
1163 * the top-level service_tree is reached, throtl_data->dispatch_work is
1164 * kicked so that the ready bio's are issued.
1165 */
1166static void throtl_pending_timer_fn(struct timer_list *t)
1167{
1168 struct throtl_service_queue *sq = from_timer(sq, t, pending_timer);
1169 struct throtl_grp *tg = sq_to_tg(sq);
1170 struct throtl_data *td = sq_to_td(sq);
1171 struct throtl_service_queue *parent_sq;
1172 struct request_queue *q;
1173 bool dispatched;
1174 int ret;
1175
1176 /* throtl_data may be gone, so figure out request queue by blkg */
1177 if (tg)
1178 q = tg->pd.blkg->q;
1179 else
1180 q = td->queue;
1181
1182 spin_lock_irq(&q->queue_lock);
1183
1184 if (!q->root_blkg)
1185 goto out_unlock;
1186
1187 if (throtl_can_upgrade(td, NULL))
1188 throtl_upgrade_state(td);
1189
1190again:
1191 parent_sq = sq->parent_sq;
1192 dispatched = false;
1193
1194 while (true) {
1195 throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u",
1196 sq->nr_queued[READ] + sq->nr_queued[WRITE],
1197 sq->nr_queued[READ], sq->nr_queued[WRITE]);
1198
1199 ret = throtl_select_dispatch(sq);
1200 if (ret) {
1201 throtl_log(sq, "bios disp=%u", ret);
1202 dispatched = true;
1203 }
1204
1205 if (throtl_schedule_next_dispatch(sq, false))
1206 break;
1207
1208 /* this dispatch windows is still open, relax and repeat */
1209 spin_unlock_irq(&q->queue_lock);
1210 cpu_relax();
1211 spin_lock_irq(&q->queue_lock);
1212 }
1213
1214 if (!dispatched)
1215 goto out_unlock;
1216
1217 if (parent_sq) {
1218 /* @parent_sq is another throl_grp, propagate dispatch */
1219 if (tg->flags & THROTL_TG_WAS_EMPTY) {
1220 tg_update_disptime(tg);
1221 if (!throtl_schedule_next_dispatch(parent_sq, false)) {
1222 /* window is already open, repeat dispatching */
1223 sq = parent_sq;
1224 tg = sq_to_tg(sq);
1225 goto again;
1226 }
1227 }
1228 } else {
1229 /* reached the top-level, queue issuing */
1230 queue_work(kthrotld_workqueue, &td->dispatch_work);
1231 }
1232out_unlock:
1233 spin_unlock_irq(&q->queue_lock);
1234}
1235
1236/**
1237 * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work
1238 * @work: work item being executed
1239 *
1240 * This function is queued for execution when bios reach the bio_lists[]
1241 * of throtl_data->service_queue. Those bios are ready and issued by this
1242 * function.
1243 */
1244static void blk_throtl_dispatch_work_fn(struct work_struct *work)
1245{
1246 struct throtl_data *td = container_of(work, struct throtl_data,
1247 dispatch_work);
1248 struct throtl_service_queue *td_sq = &td->service_queue;
1249 struct request_queue *q = td->queue;
1250 struct bio_list bio_list_on_stack;
1251 struct bio *bio;
1252 struct blk_plug plug;
1253 int rw;
1254
1255 bio_list_init(&bio_list_on_stack);
1256
1257 spin_lock_irq(&q->queue_lock);
1258 for (rw = READ; rw <= WRITE; rw++)
1259 while ((bio = throtl_pop_queued(&td_sq->queued[rw], NULL)))
1260 bio_list_add(&bio_list_on_stack, bio);
1261 spin_unlock_irq(&q->queue_lock);
1262
1263 if (!bio_list_empty(&bio_list_on_stack)) {
1264 blk_start_plug(&plug);
1265 while ((bio = bio_list_pop(&bio_list_on_stack)))
1266 submit_bio_noacct_nocheck(bio);
1267 blk_finish_plug(&plug);
1268 }
1269}
1270
1271static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
1272 int off)
1273{
1274 struct throtl_grp *tg = pd_to_tg(pd);
1275 u64 v = *(u64 *)((void *)tg + off);
1276
1277 if (v == U64_MAX)
1278 return 0;
1279 return __blkg_prfill_u64(sf, pd, v);
1280}
1281
1282static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
1283 int off)
1284{
1285 struct throtl_grp *tg = pd_to_tg(pd);
1286 unsigned int v = *(unsigned int *)((void *)tg + off);
1287
1288 if (v == UINT_MAX)
1289 return 0;
1290 return __blkg_prfill_u64(sf, pd, v);
1291}
1292
1293static int tg_print_conf_u64(struct seq_file *sf, void *v)
1294{
1295 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_u64,
1296 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1297 return 0;
1298}
1299
1300static int tg_print_conf_uint(struct seq_file *sf, void *v)
1301{
1302 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_uint,
1303 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1304 return 0;
1305}
1306
1307static void tg_conf_updated(struct throtl_grp *tg, bool global)
1308{
1309 struct throtl_service_queue *sq = &tg->service_queue;
1310 struct cgroup_subsys_state *pos_css;
1311 struct blkcg_gq *blkg;
1312
1313 throtl_log(&tg->service_queue,
1314 "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
1315 tg_bps_limit(tg, READ), tg_bps_limit(tg, WRITE),
1316 tg_iops_limit(tg, READ), tg_iops_limit(tg, WRITE));
1317
1318 /*
1319 * Update has_rules[] flags for the updated tg's subtree. A tg is
1320 * considered to have rules if either the tg itself or any of its
1321 * ancestors has rules. This identifies groups without any
1322 * restrictions in the whole hierarchy and allows them to bypass
1323 * blk-throttle.
1324 */
1325 blkg_for_each_descendant_pre(blkg, pos_css,
1326 global ? tg->td->queue->root_blkg : tg_to_blkg(tg)) {
1327 struct throtl_grp *this_tg = blkg_to_tg(blkg);
1328 struct throtl_grp *parent_tg;
1329
1330 tg_update_has_rules(this_tg);
1331 /* ignore root/second level */
1332 if (!cgroup_subsys_on_dfl(io_cgrp_subsys) || !blkg->parent ||
1333 !blkg->parent->parent)
1334 continue;
1335 parent_tg = blkg_to_tg(blkg->parent);
1336 /*
1337 * make sure all children has lower idle time threshold and
1338 * higher latency target
1339 */
1340 this_tg->idletime_threshold = min(this_tg->idletime_threshold,
1341 parent_tg->idletime_threshold);
1342 this_tg->latency_target = max(this_tg->latency_target,
1343 parent_tg->latency_target);
1344 }
1345
1346 /*
1347 * We're already holding queue_lock and know @tg is valid. Let's
1348 * apply the new config directly.
1349 *
1350 * Restart the slices for both READ and WRITES. It might happen
1351 * that a group's limit are dropped suddenly and we don't want to
1352 * account recently dispatched IO with new low rate.
1353 */
1354 throtl_start_new_slice(tg, READ, false);
1355 throtl_start_new_slice(tg, WRITE, false);
1356
1357 if (tg->flags & THROTL_TG_PENDING) {
1358 tg_update_disptime(tg);
1359 throtl_schedule_next_dispatch(sq->parent_sq, true);
1360 }
1361}
1362
1363static ssize_t tg_set_conf(struct kernfs_open_file *of,
1364 char *buf, size_t nbytes, loff_t off, bool is_u64)
1365{
1366 struct blkcg *blkcg = css_to_blkcg(of_css(of));
1367 struct blkg_conf_ctx ctx;
1368 struct throtl_grp *tg;
1369 int ret;
1370 u64 v;
1371
1372 ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
1373 if (ret)
1374 return ret;
1375
1376 ret = -EINVAL;
1377 if (sscanf(ctx.body, "%llu", &v) != 1)
1378 goto out_finish;
1379 if (!v)
1380 v = U64_MAX;
1381
1382 tg = blkg_to_tg(ctx.blkg);
1383 tg_update_carryover(tg);
1384
1385 if (is_u64)
1386 *(u64 *)((void *)tg + of_cft(of)->private) = v;
1387 else
1388 *(unsigned int *)((void *)tg + of_cft(of)->private) = v;
1389
1390 tg_conf_updated(tg, false);
1391 ret = 0;
1392out_finish:
1393 blkg_conf_finish(&ctx);
1394 return ret ?: nbytes;
1395}
1396
1397static ssize_t tg_set_conf_u64(struct kernfs_open_file *of,
1398 char *buf, size_t nbytes, loff_t off)
1399{
1400 return tg_set_conf(of, buf, nbytes, off, true);
1401}
1402
1403static ssize_t tg_set_conf_uint(struct kernfs_open_file *of,
1404 char *buf, size_t nbytes, loff_t off)
1405{
1406 return tg_set_conf(of, buf, nbytes, off, false);
1407}
1408
1409static int tg_print_rwstat(struct seq_file *sf, void *v)
1410{
1411 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1412 blkg_prfill_rwstat, &blkcg_policy_throtl,
1413 seq_cft(sf)->private, true);
1414 return 0;
1415}
1416
1417static u64 tg_prfill_rwstat_recursive(struct seq_file *sf,
1418 struct blkg_policy_data *pd, int off)
1419{
1420 struct blkg_rwstat_sample sum;
1421
1422 blkg_rwstat_recursive_sum(pd_to_blkg(pd), &blkcg_policy_throtl, off,
1423 &sum);
1424 return __blkg_prfill_rwstat(sf, pd, &sum);
1425}
1426
1427static int tg_print_rwstat_recursive(struct seq_file *sf, void *v)
1428{
1429 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1430 tg_prfill_rwstat_recursive, &blkcg_policy_throtl,
1431 seq_cft(sf)->private, true);
1432 return 0;
1433}
1434
1435static struct cftype throtl_legacy_files[] = {
1436 {
1437 .name = "throttle.read_bps_device",
1438 .private = offsetof(struct throtl_grp, bps[READ][LIMIT_MAX]),
1439 .seq_show = tg_print_conf_u64,
1440 .write = tg_set_conf_u64,
1441 },
1442 {
1443 .name = "throttle.write_bps_device",
1444 .private = offsetof(struct throtl_grp, bps[WRITE][LIMIT_MAX]),
1445 .seq_show = tg_print_conf_u64,
1446 .write = tg_set_conf_u64,
1447 },
1448 {
1449 .name = "throttle.read_iops_device",
1450 .private = offsetof(struct throtl_grp, iops[READ][LIMIT_MAX]),
1451 .seq_show = tg_print_conf_uint,
1452 .write = tg_set_conf_uint,
1453 },
1454 {
1455 .name = "throttle.write_iops_device",
1456 .private = offsetof(struct throtl_grp, iops[WRITE][LIMIT_MAX]),
1457 .seq_show = tg_print_conf_uint,
1458 .write = tg_set_conf_uint,
1459 },
1460 {
1461 .name = "throttle.io_service_bytes",
1462 .private = offsetof(struct throtl_grp, stat_bytes),
1463 .seq_show = tg_print_rwstat,
1464 },
1465 {
1466 .name = "throttle.io_service_bytes_recursive",
1467 .private = offsetof(struct throtl_grp, stat_bytes),
1468 .seq_show = tg_print_rwstat_recursive,
1469 },
1470 {
1471 .name = "throttle.io_serviced",
1472 .private = offsetof(struct throtl_grp, stat_ios),
1473 .seq_show = tg_print_rwstat,
1474 },
1475 {
1476 .name = "throttle.io_serviced_recursive",
1477 .private = offsetof(struct throtl_grp, stat_ios),
1478 .seq_show = tg_print_rwstat_recursive,
1479 },
1480 { } /* terminate */
1481};
1482
1483static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
1484 int off)
1485{
1486 struct throtl_grp *tg = pd_to_tg(pd);
1487 const char *dname = blkg_dev_name(pd->blkg);
1488 char bufs[4][21] = { "max", "max", "max", "max" };
1489 u64 bps_dft;
1490 unsigned int iops_dft;
1491 char idle_time[26] = "";
1492 char latency_time[26] = "";
1493
1494 if (!dname)
1495 return 0;
1496
1497 if (off == LIMIT_LOW) {
1498 bps_dft = 0;
1499 iops_dft = 0;
1500 } else {
1501 bps_dft = U64_MAX;
1502 iops_dft = UINT_MAX;
1503 }
1504
1505 if (tg->bps_conf[READ][off] == bps_dft &&
1506 tg->bps_conf[WRITE][off] == bps_dft &&
1507 tg->iops_conf[READ][off] == iops_dft &&
1508 tg->iops_conf[WRITE][off] == iops_dft &&
1509 (off != LIMIT_LOW ||
1510 (tg->idletime_threshold_conf == DFL_IDLE_THRESHOLD &&
1511 tg->latency_target_conf == DFL_LATENCY_TARGET)))
1512 return 0;
1513
1514 if (tg->bps_conf[READ][off] != U64_MAX)
1515 snprintf(bufs[0], sizeof(bufs[0]), "%llu",
1516 tg->bps_conf[READ][off]);
1517 if (tg->bps_conf[WRITE][off] != U64_MAX)
1518 snprintf(bufs[1], sizeof(bufs[1]), "%llu",
1519 tg->bps_conf[WRITE][off]);
1520 if (tg->iops_conf[READ][off] != UINT_MAX)
1521 snprintf(bufs[2], sizeof(bufs[2]), "%u",
1522 tg->iops_conf[READ][off]);
1523 if (tg->iops_conf[WRITE][off] != UINT_MAX)
1524 snprintf(bufs[3], sizeof(bufs[3]), "%u",
1525 tg->iops_conf[WRITE][off]);
1526 if (off == LIMIT_LOW) {
1527 if (tg->idletime_threshold_conf == ULONG_MAX)
1528 strcpy(idle_time, " idle=max");
1529 else
1530 snprintf(idle_time, sizeof(idle_time), " idle=%lu",
1531 tg->idletime_threshold_conf);
1532
1533 if (tg->latency_target_conf == ULONG_MAX)
1534 strcpy(latency_time, " latency=max");
1535 else
1536 snprintf(latency_time, sizeof(latency_time),
1537 " latency=%lu", tg->latency_target_conf);
1538 }
1539
1540 seq_printf(sf, "%s rbps=%s wbps=%s riops=%s wiops=%s%s%s\n",
1541 dname, bufs[0], bufs[1], bufs[2], bufs[3], idle_time,
1542 latency_time);
1543 return 0;
1544}
1545
1546static int tg_print_limit(struct seq_file *sf, void *v)
1547{
1548 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_limit,
1549 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1550 return 0;
1551}
1552
1553static ssize_t tg_set_limit(struct kernfs_open_file *of,
1554 char *buf, size_t nbytes, loff_t off)
1555{
1556 struct blkcg *blkcg = css_to_blkcg(of_css(of));
1557 struct blkg_conf_ctx ctx;
1558 struct throtl_grp *tg;
1559 u64 v[4];
1560 unsigned long idle_time;
1561 unsigned long latency_time;
1562 int ret;
1563 int index = of_cft(of)->private;
1564
1565 ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
1566 if (ret)
1567 return ret;
1568
1569 tg = blkg_to_tg(ctx.blkg);
1570 tg_update_carryover(tg);
1571
1572 v[0] = tg->bps_conf[READ][index];
1573 v[1] = tg->bps_conf[WRITE][index];
1574 v[2] = tg->iops_conf[READ][index];
1575 v[3] = tg->iops_conf[WRITE][index];
1576
1577 idle_time = tg->idletime_threshold_conf;
1578 latency_time = tg->latency_target_conf;
1579 while (true) {
1580 char tok[27]; /* wiops=18446744073709551616 */
1581 char *p;
1582 u64 val = U64_MAX;
1583 int len;
1584
1585 if (sscanf(ctx.body, "%26s%n", tok, &len) != 1)
1586 break;
1587 if (tok[0] == '\0')
1588 break;
1589 ctx.body += len;
1590
1591 ret = -EINVAL;
1592 p = tok;
1593 strsep(&p, "=");
1594 if (!p || (sscanf(p, "%llu", &val) != 1 && strcmp(p, "max")))
1595 goto out_finish;
1596
1597 ret = -ERANGE;
1598 if (!val)
1599 goto out_finish;
1600
1601 ret = -EINVAL;
1602 if (!strcmp(tok, "rbps") && val > 1)
1603 v[0] = val;
1604 else if (!strcmp(tok, "wbps") && val > 1)
1605 v[1] = val;
1606 else if (!strcmp(tok, "riops") && val > 1)
1607 v[2] = min_t(u64, val, UINT_MAX);
1608 else if (!strcmp(tok, "wiops") && val > 1)
1609 v[3] = min_t(u64, val, UINT_MAX);
1610 else if (off == LIMIT_LOW && !strcmp(tok, "idle"))
1611 idle_time = val;
1612 else if (off == LIMIT_LOW && !strcmp(tok, "latency"))
1613 latency_time = val;
1614 else
1615 goto out_finish;
1616 }
1617
1618 tg->bps_conf[READ][index] = v[0];
1619 tg->bps_conf[WRITE][index] = v[1];
1620 tg->iops_conf[READ][index] = v[2];
1621 tg->iops_conf[WRITE][index] = v[3];
1622
1623 if (index == LIMIT_MAX) {
1624 tg->bps[READ][index] = v[0];
1625 tg->bps[WRITE][index] = v[1];
1626 tg->iops[READ][index] = v[2];
1627 tg->iops[WRITE][index] = v[3];
1628 }
1629 tg->bps[READ][LIMIT_LOW] = min(tg->bps_conf[READ][LIMIT_LOW],
1630 tg->bps_conf[READ][LIMIT_MAX]);
1631 tg->bps[WRITE][LIMIT_LOW] = min(tg->bps_conf[WRITE][LIMIT_LOW],
1632 tg->bps_conf[WRITE][LIMIT_MAX]);
1633 tg->iops[READ][LIMIT_LOW] = min(tg->iops_conf[READ][LIMIT_LOW],
1634 tg->iops_conf[READ][LIMIT_MAX]);
1635 tg->iops[WRITE][LIMIT_LOW] = min(tg->iops_conf[WRITE][LIMIT_LOW],
1636 tg->iops_conf[WRITE][LIMIT_MAX]);
1637 tg->idletime_threshold_conf = idle_time;
1638 tg->latency_target_conf = latency_time;
1639
1640 /* force user to configure all settings for low limit */
1641 if (!(tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW] ||
1642 tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW]) ||
1643 tg->idletime_threshold_conf == DFL_IDLE_THRESHOLD ||
1644 tg->latency_target_conf == DFL_LATENCY_TARGET) {
1645 tg->bps[READ][LIMIT_LOW] = 0;
1646 tg->bps[WRITE][LIMIT_LOW] = 0;
1647 tg->iops[READ][LIMIT_LOW] = 0;
1648 tg->iops[WRITE][LIMIT_LOW] = 0;
1649 tg->idletime_threshold = DFL_IDLE_THRESHOLD;
1650 tg->latency_target = DFL_LATENCY_TARGET;
1651 } else if (index == LIMIT_LOW) {
1652 tg->idletime_threshold = tg->idletime_threshold_conf;
1653 tg->latency_target = tg->latency_target_conf;
1654 }
1655
1656 blk_throtl_update_limit_valid(tg->td);
1657 if (tg->td->limit_valid[LIMIT_LOW]) {
1658 if (index == LIMIT_LOW)
1659 tg->td->limit_index = LIMIT_LOW;
1660 } else
1661 tg->td->limit_index = LIMIT_MAX;
1662 tg_conf_updated(tg, index == LIMIT_LOW &&
1663 tg->td->limit_valid[LIMIT_LOW]);
1664 ret = 0;
1665out_finish:
1666 blkg_conf_finish(&ctx);
1667 return ret ?: nbytes;
1668}
1669
1670static struct cftype throtl_files[] = {
1671#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
1672 {
1673 .name = "low",
1674 .flags = CFTYPE_NOT_ON_ROOT,
1675 .seq_show = tg_print_limit,
1676 .write = tg_set_limit,
1677 .private = LIMIT_LOW,
1678 },
1679#endif
1680 {
1681 .name = "max",
1682 .flags = CFTYPE_NOT_ON_ROOT,
1683 .seq_show = tg_print_limit,
1684 .write = tg_set_limit,
1685 .private = LIMIT_MAX,
1686 },
1687 { } /* terminate */
1688};
1689
1690static void throtl_shutdown_wq(struct request_queue *q)
1691{
1692 struct throtl_data *td = q->td;
1693
1694 cancel_work_sync(&td->dispatch_work);
1695}
1696
1697struct blkcg_policy blkcg_policy_throtl = {
1698 .dfl_cftypes = throtl_files,
1699 .legacy_cftypes = throtl_legacy_files,
1700
1701 .pd_alloc_fn = throtl_pd_alloc,
1702 .pd_init_fn = throtl_pd_init,
1703 .pd_online_fn = throtl_pd_online,
1704 .pd_offline_fn = throtl_pd_offline,
1705 .pd_free_fn = throtl_pd_free,
1706};
1707
1708void blk_throtl_cancel_bios(struct gendisk *disk)
1709{
1710 struct request_queue *q = disk->queue;
1711 struct cgroup_subsys_state *pos_css;
1712 struct blkcg_gq *blkg;
1713
1714 spin_lock_irq(&q->queue_lock);
1715 /*
1716 * queue_lock is held, rcu lock is not needed here technically.
1717 * However, rcu lock is still held to emphasize that following
1718 * path need RCU protection and to prevent warning from lockdep.
1719 */
1720 rcu_read_lock();
1721 blkg_for_each_descendant_post(blkg, pos_css, q->root_blkg) {
1722 struct throtl_grp *tg = blkg_to_tg(blkg);
1723 struct throtl_service_queue *sq = &tg->service_queue;
1724
1725 /*
1726 * Set the flag to make sure throtl_pending_timer_fn() won't
1727 * stop until all throttled bios are dispatched.
1728 */
1729 tg->flags |= THROTL_TG_CANCELING;
1730
1731 /*
1732 * Do not dispatch cgroup without THROTL_TG_PENDING or cgroup
1733 * will be inserted to service queue without THROTL_TG_PENDING
1734 * set in tg_update_disptime below. Then IO dispatched from
1735 * child in tg_dispatch_one_bio will trigger double insertion
1736 * and corrupt the tree.
1737 */
1738 if (!(tg->flags & THROTL_TG_PENDING))
1739 continue;
1740
1741 /*
1742 * Update disptime after setting the above flag to make sure
1743 * throtl_select_dispatch() won't exit without dispatching.
1744 */
1745 tg_update_disptime(tg);
1746
1747 throtl_schedule_pending_timer(sq, jiffies + 1);
1748 }
1749 rcu_read_unlock();
1750 spin_unlock_irq(&q->queue_lock);
1751}
1752
1753#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
1754static unsigned long __tg_last_low_overflow_time(struct throtl_grp *tg)
1755{
1756 unsigned long rtime = jiffies, wtime = jiffies;
1757
1758 if (tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW])
1759 rtime = tg->last_low_overflow_time[READ];
1760 if (tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW])
1761 wtime = tg->last_low_overflow_time[WRITE];
1762 return min(rtime, wtime);
1763}
1764
1765static unsigned long tg_last_low_overflow_time(struct throtl_grp *tg)
1766{
1767 struct throtl_service_queue *parent_sq;
1768 struct throtl_grp *parent = tg;
1769 unsigned long ret = __tg_last_low_overflow_time(tg);
1770
1771 while (true) {
1772 parent_sq = parent->service_queue.parent_sq;
1773 parent = sq_to_tg(parent_sq);
1774 if (!parent)
1775 break;
1776
1777 /*
1778 * The parent doesn't have low limit, it always reaches low
1779 * limit. Its overflow time is useless for children
1780 */
1781 if (!parent->bps[READ][LIMIT_LOW] &&
1782 !parent->iops[READ][LIMIT_LOW] &&
1783 !parent->bps[WRITE][LIMIT_LOW] &&
1784 !parent->iops[WRITE][LIMIT_LOW])
1785 continue;
1786 if (time_after(__tg_last_low_overflow_time(parent), ret))
1787 ret = __tg_last_low_overflow_time(parent);
1788 }
1789 return ret;
1790}
1791
1792static bool throtl_tg_is_idle(struct throtl_grp *tg)
1793{
1794 /*
1795 * cgroup is idle if:
1796 * - single idle is too long, longer than a fixed value (in case user
1797 * configure a too big threshold) or 4 times of idletime threshold
1798 * - average think time is more than threshold
1799 * - IO latency is largely below threshold
1800 */
1801 unsigned long time;
1802 bool ret;
1803
1804 time = min_t(unsigned long, MAX_IDLE_TIME, 4 * tg->idletime_threshold);
1805 ret = tg->latency_target == DFL_LATENCY_TARGET ||
1806 tg->idletime_threshold == DFL_IDLE_THRESHOLD ||
1807 (ktime_get_ns() >> 10) - tg->last_finish_time > time ||
1808 tg->avg_idletime > tg->idletime_threshold ||
1809 (tg->latency_target && tg->bio_cnt &&
1810 tg->bad_bio_cnt * 5 < tg->bio_cnt);
1811 throtl_log(&tg->service_queue,
1812 "avg_idle=%ld, idle_threshold=%ld, bad_bio=%d, total_bio=%d, is_idle=%d, scale=%d",
1813 tg->avg_idletime, tg->idletime_threshold, tg->bad_bio_cnt,
1814 tg->bio_cnt, ret, tg->td->scale);
1815 return ret;
1816}
1817
1818static bool throtl_low_limit_reached(struct throtl_grp *tg, int rw)
1819{
1820 struct throtl_service_queue *sq = &tg->service_queue;
1821 bool limit = tg->bps[rw][LIMIT_LOW] || tg->iops[rw][LIMIT_LOW];
1822
1823 /*
1824 * if low limit is zero, low limit is always reached.
1825 * if low limit is non-zero, we can check if there is any request
1826 * is queued to determine if low limit is reached as we throttle
1827 * request according to limit.
1828 */
1829 return !limit || sq->nr_queued[rw];
1830}
1831
1832static bool throtl_tg_can_upgrade(struct throtl_grp *tg)
1833{
1834 /*
1835 * cgroup reaches low limit when low limit of READ and WRITE are
1836 * both reached, it's ok to upgrade to next limit if cgroup reaches
1837 * low limit
1838 */
1839 if (throtl_low_limit_reached(tg, READ) &&
1840 throtl_low_limit_reached(tg, WRITE))
1841 return true;
1842
1843 if (time_after_eq(jiffies,
1844 tg_last_low_overflow_time(tg) + tg->td->throtl_slice) &&
1845 throtl_tg_is_idle(tg))
1846 return true;
1847 return false;
1848}
1849
1850static bool throtl_hierarchy_can_upgrade(struct throtl_grp *tg)
1851{
1852 while (true) {
1853 if (throtl_tg_can_upgrade(tg))
1854 return true;
1855 tg = sq_to_tg(tg->service_queue.parent_sq);
1856 if (!tg || !tg_to_blkg(tg)->parent)
1857 return false;
1858 }
1859 return false;
1860}
1861
1862static bool throtl_can_upgrade(struct throtl_data *td,
1863 struct throtl_grp *this_tg)
1864{
1865 struct cgroup_subsys_state *pos_css;
1866 struct blkcg_gq *blkg;
1867
1868 if (td->limit_index != LIMIT_LOW)
1869 return false;
1870
1871 if (time_before(jiffies, td->low_downgrade_time + td->throtl_slice))
1872 return false;
1873
1874 rcu_read_lock();
1875 blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
1876 struct throtl_grp *tg = blkg_to_tg(blkg);
1877
1878 if (tg == this_tg)
1879 continue;
1880 if (!list_empty(&tg_to_blkg(tg)->blkcg->css.children))
1881 continue;
1882 if (!throtl_hierarchy_can_upgrade(tg)) {
1883 rcu_read_unlock();
1884 return false;
1885 }
1886 }
1887 rcu_read_unlock();
1888 return true;
1889}
1890
1891static void throtl_upgrade_check(struct throtl_grp *tg)
1892{
1893 unsigned long now = jiffies;
1894
1895 if (tg->td->limit_index != LIMIT_LOW)
1896 return;
1897
1898 if (time_after(tg->last_check_time + tg->td->throtl_slice, now))
1899 return;
1900
1901 tg->last_check_time = now;
1902
1903 if (!time_after_eq(now,
1904 __tg_last_low_overflow_time(tg) + tg->td->throtl_slice))
1905 return;
1906
1907 if (throtl_can_upgrade(tg->td, NULL))
1908 throtl_upgrade_state(tg->td);
1909}
1910
1911static void throtl_upgrade_state(struct throtl_data *td)
1912{
1913 struct cgroup_subsys_state *pos_css;
1914 struct blkcg_gq *blkg;
1915
1916 throtl_log(&td->service_queue, "upgrade to max");
1917 td->limit_index = LIMIT_MAX;
1918 td->low_upgrade_time = jiffies;
1919 td->scale = 0;
1920 rcu_read_lock();
1921 blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
1922 struct throtl_grp *tg = blkg_to_tg(blkg);
1923 struct throtl_service_queue *sq = &tg->service_queue;
1924
1925 tg->disptime = jiffies - 1;
1926 throtl_select_dispatch(sq);
1927 throtl_schedule_next_dispatch(sq, true);
1928 }
1929 rcu_read_unlock();
1930 throtl_select_dispatch(&td->service_queue);
1931 throtl_schedule_next_dispatch(&td->service_queue, true);
1932 queue_work(kthrotld_workqueue, &td->dispatch_work);
1933}
1934
1935static void throtl_downgrade_state(struct throtl_data *td)
1936{
1937 td->scale /= 2;
1938
1939 throtl_log(&td->service_queue, "downgrade, scale %d", td->scale);
1940 if (td->scale) {
1941 td->low_upgrade_time = jiffies - td->scale * td->throtl_slice;
1942 return;
1943 }
1944
1945 td->limit_index = LIMIT_LOW;
1946 td->low_downgrade_time = jiffies;
1947}
1948
1949static bool throtl_tg_can_downgrade(struct throtl_grp *tg)
1950{
1951 struct throtl_data *td = tg->td;
1952 unsigned long now = jiffies;
1953
1954 /*
1955 * If cgroup is below low limit, consider downgrade and throttle other
1956 * cgroups
1957 */
1958 if (time_after_eq(now, tg_last_low_overflow_time(tg) +
1959 td->throtl_slice) &&
1960 (!throtl_tg_is_idle(tg) ||
1961 !list_empty(&tg_to_blkg(tg)->blkcg->css.children)))
1962 return true;
1963 return false;
1964}
1965
1966static bool throtl_hierarchy_can_downgrade(struct throtl_grp *tg)
1967{
1968 struct throtl_data *td = tg->td;
1969
1970 if (time_before(jiffies, td->low_upgrade_time + td->throtl_slice))
1971 return false;
1972
1973 while (true) {
1974 if (!throtl_tg_can_downgrade(tg))
1975 return false;
1976 tg = sq_to_tg(tg->service_queue.parent_sq);
1977 if (!tg || !tg_to_blkg(tg)->parent)
1978 break;
1979 }
1980 return true;
1981}
1982
1983static void throtl_downgrade_check(struct throtl_grp *tg)
1984{
1985 uint64_t bps;
1986 unsigned int iops;
1987 unsigned long elapsed_time;
1988 unsigned long now = jiffies;
1989
1990 if (tg->td->limit_index != LIMIT_MAX ||
1991 !tg->td->limit_valid[LIMIT_LOW])
1992 return;
1993 if (!list_empty(&tg_to_blkg(tg)->blkcg->css.children))
1994 return;
1995 if (time_after(tg->last_check_time + tg->td->throtl_slice, now))
1996 return;
1997
1998 elapsed_time = now - tg->last_check_time;
1999 tg->last_check_time = now;
2000
2001 if (time_before(now, tg_last_low_overflow_time(tg) +
2002 tg->td->throtl_slice))
2003 return;
2004
2005 if (tg->bps[READ][LIMIT_LOW]) {
2006 bps = tg->last_bytes_disp[READ] * HZ;
2007 do_div(bps, elapsed_time);
2008 if (bps >= tg->bps[READ][LIMIT_LOW])
2009 tg->last_low_overflow_time[READ] = now;
2010 }
2011
2012 if (tg->bps[WRITE][LIMIT_LOW]) {
2013 bps = tg->last_bytes_disp[WRITE] * HZ;
2014 do_div(bps, elapsed_time);
2015 if (bps >= tg->bps[WRITE][LIMIT_LOW])
2016 tg->last_low_overflow_time[WRITE] = now;
2017 }
2018
2019 if (tg->iops[READ][LIMIT_LOW]) {
2020 iops = tg->last_io_disp[READ] * HZ / elapsed_time;
2021 if (iops >= tg->iops[READ][LIMIT_LOW])
2022 tg->last_low_overflow_time[READ] = now;
2023 }
2024
2025 if (tg->iops[WRITE][LIMIT_LOW]) {
2026 iops = tg->last_io_disp[WRITE] * HZ / elapsed_time;
2027 if (iops >= tg->iops[WRITE][LIMIT_LOW])
2028 tg->last_low_overflow_time[WRITE] = now;
2029 }
2030
2031 /*
2032 * If cgroup is below low limit, consider downgrade and throttle other
2033 * cgroups
2034 */
2035 if (throtl_hierarchy_can_downgrade(tg))
2036 throtl_downgrade_state(tg->td);
2037
2038 tg->last_bytes_disp[READ] = 0;
2039 tg->last_bytes_disp[WRITE] = 0;
2040 tg->last_io_disp[READ] = 0;
2041 tg->last_io_disp[WRITE] = 0;
2042}
2043
2044static void blk_throtl_update_idletime(struct throtl_grp *tg)
2045{
2046 unsigned long now;
2047 unsigned long last_finish_time = tg->last_finish_time;
2048
2049 if (last_finish_time == 0)
2050 return;
2051
2052 now = ktime_get_ns() >> 10;
2053 if (now <= last_finish_time ||
2054 last_finish_time == tg->checked_last_finish_time)
2055 return;
2056
2057 tg->avg_idletime = (tg->avg_idletime * 7 + now - last_finish_time) >> 3;
2058 tg->checked_last_finish_time = last_finish_time;
2059}
2060
2061static void throtl_update_latency_buckets(struct throtl_data *td)
2062{
2063 struct avg_latency_bucket avg_latency[2][LATENCY_BUCKET_SIZE];
2064 int i, cpu, rw;
2065 unsigned long last_latency[2] = { 0 };
2066 unsigned long latency[2];
2067
2068 if (!blk_queue_nonrot(td->queue) || !td->limit_valid[LIMIT_LOW])
2069 return;
2070 if (time_before(jiffies, td->last_calculate_time + HZ))
2071 return;
2072 td->last_calculate_time = jiffies;
2073
2074 memset(avg_latency, 0, sizeof(avg_latency));
2075 for (rw = READ; rw <= WRITE; rw++) {
2076 for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
2077 struct latency_bucket *tmp = &td->tmp_buckets[rw][i];
2078
2079 for_each_possible_cpu(cpu) {
2080 struct latency_bucket *bucket;
2081
2082 /* this isn't race free, but ok in practice */
2083 bucket = per_cpu_ptr(td->latency_buckets[rw],
2084 cpu);
2085 tmp->total_latency += bucket[i].total_latency;
2086 tmp->samples += bucket[i].samples;
2087 bucket[i].total_latency = 0;
2088 bucket[i].samples = 0;
2089 }
2090
2091 if (tmp->samples >= 32) {
2092 int samples = tmp->samples;
2093
2094 latency[rw] = tmp->total_latency;
2095
2096 tmp->total_latency = 0;
2097 tmp->samples = 0;
2098 latency[rw] /= samples;
2099 if (latency[rw] == 0)
2100 continue;
2101 avg_latency[rw][i].latency = latency[rw];
2102 }
2103 }
2104 }
2105
2106 for (rw = READ; rw <= WRITE; rw++) {
2107 for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
2108 if (!avg_latency[rw][i].latency) {
2109 if (td->avg_buckets[rw][i].latency < last_latency[rw])
2110 td->avg_buckets[rw][i].latency =
2111 last_latency[rw];
2112 continue;
2113 }
2114
2115 if (!td->avg_buckets[rw][i].valid)
2116 latency[rw] = avg_latency[rw][i].latency;
2117 else
2118 latency[rw] = (td->avg_buckets[rw][i].latency * 7 +
2119 avg_latency[rw][i].latency) >> 3;
2120
2121 td->avg_buckets[rw][i].latency = max(latency[rw],
2122 last_latency[rw]);
2123 td->avg_buckets[rw][i].valid = true;
2124 last_latency[rw] = td->avg_buckets[rw][i].latency;
2125 }
2126 }
2127
2128 for (i = 0; i < LATENCY_BUCKET_SIZE; i++)
2129 throtl_log(&td->service_queue,
2130 "Latency bucket %d: read latency=%ld, read valid=%d, "
2131 "write latency=%ld, write valid=%d", i,
2132 td->avg_buckets[READ][i].latency,
2133 td->avg_buckets[READ][i].valid,
2134 td->avg_buckets[WRITE][i].latency,
2135 td->avg_buckets[WRITE][i].valid);
2136}
2137#else
2138static inline void throtl_update_latency_buckets(struct throtl_data *td)
2139{
2140}
2141
2142static void blk_throtl_update_idletime(struct throtl_grp *tg)
2143{
2144}
2145
2146static void throtl_downgrade_check(struct throtl_grp *tg)
2147{
2148}
2149
2150static void throtl_upgrade_check(struct throtl_grp *tg)
2151{
2152}
2153
2154static bool throtl_can_upgrade(struct throtl_data *td,
2155 struct throtl_grp *this_tg)
2156{
2157 return false;
2158}
2159
2160static void throtl_upgrade_state(struct throtl_data *td)
2161{
2162}
2163#endif
2164
2165bool __blk_throtl_bio(struct bio *bio)
2166{
2167 struct request_queue *q = bdev_get_queue(bio->bi_bdev);
2168 struct blkcg_gq *blkg = bio->bi_blkg;
2169 struct throtl_qnode *qn = NULL;
2170 struct throtl_grp *tg = blkg_to_tg(blkg);
2171 struct throtl_service_queue *sq;
2172 bool rw = bio_data_dir(bio);
2173 bool throttled = false;
2174 struct throtl_data *td = tg->td;
2175
2176 rcu_read_lock();
2177
2178 if (!cgroup_subsys_on_dfl(io_cgrp_subsys)) {
2179 blkg_rwstat_add(&tg->stat_bytes, bio->bi_opf,
2180 bio->bi_iter.bi_size);
2181 blkg_rwstat_add(&tg->stat_ios, bio->bi_opf, 1);
2182 }
2183
2184 spin_lock_irq(&q->queue_lock);
2185
2186 throtl_update_latency_buckets(td);
2187
2188 blk_throtl_update_idletime(tg);
2189
2190 sq = &tg->service_queue;
2191
2192again:
2193 while (true) {
2194 if (tg->last_low_overflow_time[rw] == 0)
2195 tg->last_low_overflow_time[rw] = jiffies;
2196 throtl_downgrade_check(tg);
2197 throtl_upgrade_check(tg);
2198 /* throtl is FIFO - if bios are already queued, should queue */
2199 if (sq->nr_queued[rw])
2200 break;
2201
2202 /* if above limits, break to queue */
2203 if (!tg_may_dispatch(tg, bio, NULL)) {
2204 tg->last_low_overflow_time[rw] = jiffies;
2205 if (throtl_can_upgrade(td, tg)) {
2206 throtl_upgrade_state(td);
2207 goto again;
2208 }
2209 break;
2210 }
2211
2212 /* within limits, let's charge and dispatch directly */
2213 throtl_charge_bio(tg, bio);
2214
2215 /*
2216 * We need to trim slice even when bios are not being queued
2217 * otherwise it might happen that a bio is not queued for
2218 * a long time and slice keeps on extending and trim is not
2219 * called for a long time. Now if limits are reduced suddenly
2220 * we take into account all the IO dispatched so far at new
2221 * low rate and * newly queued IO gets a really long dispatch
2222 * time.
2223 *
2224 * So keep on trimming slice even if bio is not queued.
2225 */
2226 throtl_trim_slice(tg, rw);
2227
2228 /*
2229 * @bio passed through this layer without being throttled.
2230 * Climb up the ladder. If we're already at the top, it
2231 * can be executed directly.
2232 */
2233 qn = &tg->qnode_on_parent[rw];
2234 sq = sq->parent_sq;
2235 tg = sq_to_tg(sq);
2236 if (!tg) {
2237 bio_set_flag(bio, BIO_BPS_THROTTLED);
2238 goto out_unlock;
2239 }
2240 }
2241
2242 /* out-of-limit, queue to @tg */
2243 throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
2244 rw == READ ? 'R' : 'W',
2245 tg->bytes_disp[rw], bio->bi_iter.bi_size,
2246 tg_bps_limit(tg, rw),
2247 tg->io_disp[rw], tg_iops_limit(tg, rw),
2248 sq->nr_queued[READ], sq->nr_queued[WRITE]);
2249
2250 tg->last_low_overflow_time[rw] = jiffies;
2251
2252 td->nr_queued[rw]++;
2253 throtl_add_bio_tg(bio, qn, tg);
2254 throttled = true;
2255
2256 /*
2257 * Update @tg's dispatch time and force schedule dispatch if @tg
2258 * was empty before @bio. The forced scheduling isn't likely to
2259 * cause undue delay as @bio is likely to be dispatched directly if
2260 * its @tg's disptime is not in the future.
2261 */
2262 if (tg->flags & THROTL_TG_WAS_EMPTY) {
2263 tg_update_disptime(tg);
2264 throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true);
2265 }
2266
2267out_unlock:
2268#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2269 if (throttled || !td->track_bio_latency)
2270 bio->bi_issue.value |= BIO_ISSUE_THROTL_SKIP_LATENCY;
2271#endif
2272 spin_unlock_irq(&q->queue_lock);
2273
2274 rcu_read_unlock();
2275 return throttled;
2276}
2277
2278#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2279static void throtl_track_latency(struct throtl_data *td, sector_t size,
2280 enum req_op op, unsigned long time)
2281{
2282 const bool rw = op_is_write(op);
2283 struct latency_bucket *latency;
2284 int index;
2285
2286 if (!td || td->limit_index != LIMIT_LOW ||
2287 !(op == REQ_OP_READ || op == REQ_OP_WRITE) ||
2288 !blk_queue_nonrot(td->queue))
2289 return;
2290
2291 index = request_bucket_index(size);
2292
2293 latency = get_cpu_ptr(td->latency_buckets[rw]);
2294 latency[index].total_latency += time;
2295 latency[index].samples++;
2296 put_cpu_ptr(td->latency_buckets[rw]);
2297}
2298
2299void blk_throtl_stat_add(struct request *rq, u64 time_ns)
2300{
2301 struct request_queue *q = rq->q;
2302 struct throtl_data *td = q->td;
2303
2304 throtl_track_latency(td, blk_rq_stats_sectors(rq), req_op(rq),
2305 time_ns >> 10);
2306}
2307
2308void blk_throtl_bio_endio(struct bio *bio)
2309{
2310 struct blkcg_gq *blkg;
2311 struct throtl_grp *tg;
2312 u64 finish_time_ns;
2313 unsigned long finish_time;
2314 unsigned long start_time;
2315 unsigned long lat;
2316 int rw = bio_data_dir(bio);
2317
2318 blkg = bio->bi_blkg;
2319 if (!blkg)
2320 return;
2321 tg = blkg_to_tg(blkg);
2322 if (!tg->td->limit_valid[LIMIT_LOW])
2323 return;
2324
2325 finish_time_ns = ktime_get_ns();
2326 tg->last_finish_time = finish_time_ns >> 10;
2327
2328 start_time = bio_issue_time(&bio->bi_issue) >> 10;
2329 finish_time = __bio_issue_time(finish_time_ns) >> 10;
2330 if (!start_time || finish_time <= start_time)
2331 return;
2332
2333 lat = finish_time - start_time;
2334 /* this is only for bio based driver */
2335 if (!(bio->bi_issue.value & BIO_ISSUE_THROTL_SKIP_LATENCY))
2336 throtl_track_latency(tg->td, bio_issue_size(&bio->bi_issue),
2337 bio_op(bio), lat);
2338
2339 if (tg->latency_target && lat >= tg->td->filtered_latency) {
2340 int bucket;
2341 unsigned int threshold;
2342
2343 bucket = request_bucket_index(bio_issue_size(&bio->bi_issue));
2344 threshold = tg->td->avg_buckets[rw][bucket].latency +
2345 tg->latency_target;
2346 if (lat > threshold)
2347 tg->bad_bio_cnt++;
2348 /*
2349 * Not race free, could get wrong count, which means cgroups
2350 * will be throttled
2351 */
2352 tg->bio_cnt++;
2353 }
2354
2355 if (time_after(jiffies, tg->bio_cnt_reset_time) || tg->bio_cnt > 1024) {
2356 tg->bio_cnt_reset_time = tg->td->throtl_slice + jiffies;
2357 tg->bio_cnt /= 2;
2358 tg->bad_bio_cnt /= 2;
2359 }
2360}
2361#endif
2362
2363int blk_throtl_init(struct gendisk *disk)
2364{
2365 struct request_queue *q = disk->queue;
2366 struct throtl_data *td;
2367 int ret;
2368
2369 td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
2370 if (!td)
2371 return -ENOMEM;
2372 td->latency_buckets[READ] = __alloc_percpu(sizeof(struct latency_bucket) *
2373 LATENCY_BUCKET_SIZE, __alignof__(u64));
2374 if (!td->latency_buckets[READ]) {
2375 kfree(td);
2376 return -ENOMEM;
2377 }
2378 td->latency_buckets[WRITE] = __alloc_percpu(sizeof(struct latency_bucket) *
2379 LATENCY_BUCKET_SIZE, __alignof__(u64));
2380 if (!td->latency_buckets[WRITE]) {
2381 free_percpu(td->latency_buckets[READ]);
2382 kfree(td);
2383 return -ENOMEM;
2384 }
2385
2386 INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
2387 throtl_service_queue_init(&td->service_queue);
2388
2389 q->td = td;
2390 td->queue = q;
2391
2392 td->limit_valid[LIMIT_MAX] = true;
2393 td->limit_index = LIMIT_MAX;
2394 td->low_upgrade_time = jiffies;
2395 td->low_downgrade_time = jiffies;
2396
2397 /* activate policy */
2398 ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
2399 if (ret) {
2400 free_percpu(td->latency_buckets[READ]);
2401 free_percpu(td->latency_buckets[WRITE]);
2402 kfree(td);
2403 }
2404 return ret;
2405}
2406
2407void blk_throtl_exit(struct gendisk *disk)
2408{
2409 struct request_queue *q = disk->queue;
2410
2411 BUG_ON(!q->td);
2412 del_timer_sync(&q->td->service_queue.pending_timer);
2413 throtl_shutdown_wq(q);
2414 blkcg_deactivate_policy(q, &blkcg_policy_throtl);
2415 free_percpu(q->td->latency_buckets[READ]);
2416 free_percpu(q->td->latency_buckets[WRITE]);
2417 kfree(q->td);
2418}
2419
2420void blk_throtl_register(struct gendisk *disk)
2421{
2422 struct request_queue *q = disk->queue;
2423 struct throtl_data *td;
2424 int i;
2425
2426 td = q->td;
2427 BUG_ON(!td);
2428
2429 if (blk_queue_nonrot(q)) {
2430 td->throtl_slice = DFL_THROTL_SLICE_SSD;
2431 td->filtered_latency = LATENCY_FILTERED_SSD;
2432 } else {
2433 td->throtl_slice = DFL_THROTL_SLICE_HD;
2434 td->filtered_latency = LATENCY_FILTERED_HD;
2435 for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
2436 td->avg_buckets[READ][i].latency = DFL_HD_BASELINE_LATENCY;
2437 td->avg_buckets[WRITE][i].latency = DFL_HD_BASELINE_LATENCY;
2438 }
2439 }
2440#ifndef CONFIG_BLK_DEV_THROTTLING_LOW
2441 /* if no low limit, use previous default */
2442 td->throtl_slice = DFL_THROTL_SLICE_HD;
2443#endif
2444
2445 td->track_bio_latency = !queue_is_mq(q);
2446 if (!td->track_bio_latency)
2447 blk_stat_enable_accounting(q);
2448}
2449
2450#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2451ssize_t blk_throtl_sample_time_show(struct request_queue *q, char *page)
2452{
2453 if (!q->td)
2454 return -EINVAL;
2455 return sprintf(page, "%u\n", jiffies_to_msecs(q->td->throtl_slice));
2456}
2457
2458ssize_t blk_throtl_sample_time_store(struct request_queue *q,
2459 const char *page, size_t count)
2460{
2461 unsigned long v;
2462 unsigned long t;
2463
2464 if (!q->td)
2465 return -EINVAL;
2466 if (kstrtoul(page, 10, &v))
2467 return -EINVAL;
2468 t = msecs_to_jiffies(v);
2469 if (t == 0 || t > MAX_THROTL_SLICE)
2470 return -EINVAL;
2471 q->td->throtl_slice = t;
2472 return count;
2473}
2474#endif
2475
2476static int __init throtl_init(void)
2477{
2478 kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
2479 if (!kthrotld_workqueue)
2480 panic("Failed to create kthrotld\n");
2481
2482 return blkcg_policy_register(&blkcg_policy_throtl);
2483}
2484
2485module_init(throtl_init);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Interface for controlling IO bandwidth on a request queue
4 *
5 * Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com>
6 */
7
8#include <linux/module.h>
9#include <linux/slab.h>
10#include <linux/blkdev.h>
11#include <linux/bio.h>
12#include <linux/blktrace_api.h>
13#include <linux/blk-cgroup.h>
14#include "blk.h"
15#include "blk-cgroup-rwstat.h"
16
17/* Max dispatch from a group in 1 round */
18#define THROTL_GRP_QUANTUM 8
19
20/* Total max dispatch from all groups in one round */
21#define THROTL_QUANTUM 32
22
23/* Throttling is performed over a slice and after that slice is renewed */
24#define DFL_THROTL_SLICE_HD (HZ / 10)
25#define DFL_THROTL_SLICE_SSD (HZ / 50)
26#define MAX_THROTL_SLICE (HZ)
27#define MAX_IDLE_TIME (5L * 1000 * 1000) /* 5 s */
28#define MIN_THROTL_BPS (320 * 1024)
29#define MIN_THROTL_IOPS (10)
30#define DFL_LATENCY_TARGET (-1L)
31#define DFL_IDLE_THRESHOLD (0)
32#define DFL_HD_BASELINE_LATENCY (4000L) /* 4ms */
33#define LATENCY_FILTERED_SSD (0)
34/*
35 * For HD, very small latency comes from sequential IO. Such IO is helpless to
36 * help determine if its IO is impacted by others, hence we ignore the IO
37 */
38#define LATENCY_FILTERED_HD (1000L) /* 1ms */
39
40static struct blkcg_policy blkcg_policy_throtl;
41
42/* A workqueue to queue throttle related work */
43static struct workqueue_struct *kthrotld_workqueue;
44
45/*
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.
52 *
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.
57 *
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.
61 *
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.
67 */
68struct throtl_qnode {
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 */
72};
73
74struct throtl_service_queue {
75 struct throtl_service_queue *parent_sq; /* the parent service_queue */
76
77 /*
78 * Bios queued directly to this service_queue or dispatched from
79 * children throtl_grp's.
80 */
81 struct list_head queued[2]; /* throtl_qnode [READ/WRITE] */
82 unsigned int nr_queued[2]; /* number of queued bios */
83
84 /*
85 * RB tree of active children throtl_grp's, which are sorted by
86 * their ->disptime.
87 */
88 struct rb_root_cached pending_tree; /* RB tree of active tgs */
89 unsigned int nr_pending; /* # queued in the tree */
90 unsigned long first_pending_disptime; /* disptime of the first tg */
91 struct timer_list pending_timer; /* fires on first_pending_disptime */
92};
93
94enum tg_state_flags {
95 THROTL_TG_PENDING = 1 << 0, /* on parent's pending tree */
96 THROTL_TG_WAS_EMPTY = 1 << 1, /* bio_lists[] became non-empty */
97};
98
99#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
100
101enum {
102 LIMIT_LOW,
103 LIMIT_MAX,
104 LIMIT_CNT,
105};
106
107struct throtl_grp {
108 /* must be the first member */
109 struct blkg_policy_data pd;
110
111 /* active throtl group service_queue member */
112 struct rb_node rb_node;
113
114 /* throtl_data this group belongs to */
115 struct throtl_data *td;
116
117 /* this group's service queue */
118 struct throtl_service_queue service_queue;
119
120 /*
121 * qnode_on_self is used when bios are directly queued to this
122 * throtl_grp so that local bios compete fairly with bios
123 * dispatched from children. qnode_on_parent is used when bios are
124 * dispatched from this throtl_grp into its parent and will compete
125 * with the sibling qnode_on_parents and the parent's
126 * qnode_on_self.
127 */
128 struct throtl_qnode qnode_on_self[2];
129 struct throtl_qnode qnode_on_parent[2];
130
131 /*
132 * Dispatch time in jiffies. This is the estimated time when group
133 * will unthrottle and is ready to dispatch more bio. It is used as
134 * key to sort active groups in service tree.
135 */
136 unsigned long disptime;
137
138 unsigned int flags;
139
140 /* are there any throtl rules between this group and td? */
141 bool has_rules[2];
142
143 /* internally used bytes per second rate limits */
144 uint64_t bps[2][LIMIT_CNT];
145 /* user configured bps limits */
146 uint64_t bps_conf[2][LIMIT_CNT];
147
148 /* internally used IOPS limits */
149 unsigned int iops[2][LIMIT_CNT];
150 /* user configured IOPS limits */
151 unsigned int iops_conf[2][LIMIT_CNT];
152
153 /* Number of bytes dispatched in current slice */
154 uint64_t bytes_disp[2];
155 /* Number of bio's dispatched in current slice */
156 unsigned int io_disp[2];
157
158 unsigned long last_low_overflow_time[2];
159
160 uint64_t last_bytes_disp[2];
161 unsigned int last_io_disp[2];
162
163 unsigned long last_check_time;
164
165 unsigned long latency_target; /* us */
166 unsigned long latency_target_conf; /* us */
167 /* When did we start a new slice */
168 unsigned long slice_start[2];
169 unsigned long slice_end[2];
170
171 unsigned long last_finish_time; /* ns / 1024 */
172 unsigned long checked_last_finish_time; /* ns / 1024 */
173 unsigned long avg_idletime; /* ns / 1024 */
174 unsigned long idletime_threshold; /* us */
175 unsigned long idletime_threshold_conf; /* us */
176
177 unsigned int bio_cnt; /* total bios */
178 unsigned int bad_bio_cnt; /* bios exceeding latency threshold */
179 unsigned long bio_cnt_reset_time;
180
181 atomic_t io_split_cnt[2];
182 atomic_t last_io_split_cnt[2];
183
184 struct blkg_rwstat stat_bytes;
185 struct blkg_rwstat stat_ios;
186};
187
188/* We measure latency for request size from <= 4k to >= 1M */
189#define LATENCY_BUCKET_SIZE 9
190
191struct latency_bucket {
192 unsigned long total_latency; /* ns / 1024 */
193 int samples;
194};
195
196struct avg_latency_bucket {
197 unsigned long latency; /* ns / 1024 */
198 bool valid;
199};
200
201struct throtl_data
202{
203 /* service tree for active throtl groups */
204 struct throtl_service_queue service_queue;
205
206 struct request_queue *queue;
207
208 /* Total Number of queued bios on READ and WRITE lists */
209 unsigned int nr_queued[2];
210
211 unsigned int throtl_slice;
212
213 /* Work for dispatching throttled bios */
214 struct work_struct dispatch_work;
215 unsigned int limit_index;
216 bool limit_valid[LIMIT_CNT];
217
218 unsigned long low_upgrade_time;
219 unsigned long low_downgrade_time;
220
221 unsigned int scale;
222
223 struct latency_bucket tmp_buckets[2][LATENCY_BUCKET_SIZE];
224 struct avg_latency_bucket avg_buckets[2][LATENCY_BUCKET_SIZE];
225 struct latency_bucket __percpu *latency_buckets[2];
226 unsigned long last_calculate_time;
227 unsigned long filtered_latency;
228
229 bool track_bio_latency;
230};
231
232static void throtl_pending_timer_fn(struct timer_list *t);
233
234static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
235{
236 return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
237}
238
239static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
240{
241 return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
242}
243
244static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
245{
246 return pd_to_blkg(&tg->pd);
247}
248
249/**
250 * sq_to_tg - return the throl_grp the specified service queue belongs to
251 * @sq: the throtl_service_queue of interest
252 *
253 * Return the throtl_grp @sq belongs to. If @sq is the top-level one
254 * embedded in throtl_data, %NULL is returned.
255 */
256static struct throtl_grp *sq_to_tg(struct throtl_service_queue *sq)
257{
258 if (sq && sq->parent_sq)
259 return container_of(sq, struct throtl_grp, service_queue);
260 else
261 return NULL;
262}
263
264/**
265 * sq_to_td - return throtl_data the specified service queue belongs to
266 * @sq: the throtl_service_queue of interest
267 *
268 * A service_queue can be embedded in either a throtl_grp or throtl_data.
269 * Determine the associated throtl_data accordingly and return it.
270 */
271static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
272{
273 struct throtl_grp *tg = sq_to_tg(sq);
274
275 if (tg)
276 return tg->td;
277 else
278 return container_of(sq, struct throtl_data, service_queue);
279}
280
281/*
282 * cgroup's limit in LIMIT_MAX is scaled if low limit is set. This scale is to
283 * make the IO dispatch more smooth.
284 * Scale up: linearly scale up according to lapsed time since upgrade. For
285 * every throtl_slice, the limit scales up 1/2 .low limit till the
286 * limit hits .max limit
287 * Scale down: exponentially scale down if a cgroup doesn't hit its .low limit
288 */
289static uint64_t throtl_adjusted_limit(uint64_t low, struct throtl_data *td)
290{
291 /* arbitrary value to avoid too big scale */
292 if (td->scale < 4096 && time_after_eq(jiffies,
293 td->low_upgrade_time + td->scale * td->throtl_slice))
294 td->scale = (jiffies - td->low_upgrade_time) / td->throtl_slice;
295
296 return low + (low >> 1) * td->scale;
297}
298
299static uint64_t tg_bps_limit(struct throtl_grp *tg, int rw)
300{
301 struct blkcg_gq *blkg = tg_to_blkg(tg);
302 struct throtl_data *td;
303 uint64_t ret;
304
305 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
306 return U64_MAX;
307
308 td = tg->td;
309 ret = tg->bps[rw][td->limit_index];
310 if (ret == 0 && td->limit_index == LIMIT_LOW) {
311 /* intermediate node or iops isn't 0 */
312 if (!list_empty(&blkg->blkcg->css.children) ||
313 tg->iops[rw][td->limit_index])
314 return U64_MAX;
315 else
316 return MIN_THROTL_BPS;
317 }
318
319 if (td->limit_index == LIMIT_MAX && tg->bps[rw][LIMIT_LOW] &&
320 tg->bps[rw][LIMIT_LOW] != tg->bps[rw][LIMIT_MAX]) {
321 uint64_t adjusted;
322
323 adjusted = throtl_adjusted_limit(tg->bps[rw][LIMIT_LOW], td);
324 ret = min(tg->bps[rw][LIMIT_MAX], adjusted);
325 }
326 return ret;
327}
328
329static unsigned int tg_iops_limit(struct throtl_grp *tg, int rw)
330{
331 struct blkcg_gq *blkg = tg_to_blkg(tg);
332 struct throtl_data *td;
333 unsigned int ret;
334
335 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
336 return UINT_MAX;
337
338 td = tg->td;
339 ret = tg->iops[rw][td->limit_index];
340 if (ret == 0 && tg->td->limit_index == LIMIT_LOW) {
341 /* intermediate node or bps isn't 0 */
342 if (!list_empty(&blkg->blkcg->css.children) ||
343 tg->bps[rw][td->limit_index])
344 return UINT_MAX;
345 else
346 return MIN_THROTL_IOPS;
347 }
348
349 if (td->limit_index == LIMIT_MAX && tg->iops[rw][LIMIT_LOW] &&
350 tg->iops[rw][LIMIT_LOW] != tg->iops[rw][LIMIT_MAX]) {
351 uint64_t adjusted;
352
353 adjusted = throtl_adjusted_limit(tg->iops[rw][LIMIT_LOW], td);
354 if (adjusted > UINT_MAX)
355 adjusted = UINT_MAX;
356 ret = min_t(unsigned int, tg->iops[rw][LIMIT_MAX], adjusted);
357 }
358 return ret;
359}
360
361#define request_bucket_index(sectors) \
362 clamp_t(int, order_base_2(sectors) - 3, 0, LATENCY_BUCKET_SIZE - 1)
363
364/**
365 * throtl_log - log debug message via blktrace
366 * @sq: the service_queue being reported
367 * @fmt: printf format string
368 * @args: printf args
369 *
370 * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
371 * throtl_grp; otherwise, just "throtl".
372 */
373#define throtl_log(sq, fmt, args...) do { \
374 struct throtl_grp *__tg = sq_to_tg((sq)); \
375 struct throtl_data *__td = sq_to_td((sq)); \
376 \
377 (void)__td; \
378 if (likely(!blk_trace_note_message_enabled(__td->queue))) \
379 break; \
380 if ((__tg)) { \
381 blk_add_cgroup_trace_msg(__td->queue, \
382 tg_to_blkg(__tg)->blkcg, "throtl " fmt, ##args);\
383 } else { \
384 blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \
385 } \
386} while (0)
387
388static inline unsigned int throtl_bio_data_size(struct bio *bio)
389{
390 /* assume it's one sector */
391 if (unlikely(bio_op(bio) == REQ_OP_DISCARD))
392 return 512;
393 return bio->bi_iter.bi_size;
394}
395
396static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg)
397{
398 INIT_LIST_HEAD(&qn->node);
399 bio_list_init(&qn->bios);
400 qn->tg = tg;
401}
402
403/**
404 * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it
405 * @bio: bio being added
406 * @qn: qnode to add bio to
407 * @queued: the service_queue->queued[] list @qn belongs to
408 *
409 * Add @bio to @qn and put @qn on @queued if it's not already on.
410 * @qn->tg's reference count is bumped when @qn is activated. See the
411 * comment on top of throtl_qnode definition for details.
412 */
413static void throtl_qnode_add_bio(struct bio *bio, struct throtl_qnode *qn,
414 struct list_head *queued)
415{
416 bio_list_add(&qn->bios, bio);
417 if (list_empty(&qn->node)) {
418 list_add_tail(&qn->node, queued);
419 blkg_get(tg_to_blkg(qn->tg));
420 }
421}
422
423/**
424 * throtl_peek_queued - peek the first bio on a qnode list
425 * @queued: the qnode list to peek
426 */
427static struct bio *throtl_peek_queued(struct list_head *queued)
428{
429 struct throtl_qnode *qn;
430 struct bio *bio;
431
432 if (list_empty(queued))
433 return NULL;
434
435 qn = list_first_entry(queued, struct throtl_qnode, node);
436 bio = bio_list_peek(&qn->bios);
437 WARN_ON_ONCE(!bio);
438 return bio;
439}
440
441/**
442 * throtl_pop_queued - pop the first bio form a qnode list
443 * @queued: the qnode list to pop a bio from
444 * @tg_to_put: optional out argument for throtl_grp to put
445 *
446 * Pop the first bio from the qnode list @queued. After popping, the first
447 * qnode is removed from @queued if empty or moved to the end of @queued so
448 * that the popping order is round-robin.
449 *
450 * When the first qnode is removed, its associated throtl_grp should be put
451 * too. If @tg_to_put is NULL, this function automatically puts it;
452 * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is
453 * responsible for putting it.
454 */
455static struct bio *throtl_pop_queued(struct list_head *queued,
456 struct throtl_grp **tg_to_put)
457{
458 struct throtl_qnode *qn;
459 struct bio *bio;
460
461 if (list_empty(queued))
462 return NULL;
463
464 qn = list_first_entry(queued, struct throtl_qnode, node);
465 bio = bio_list_pop(&qn->bios);
466 WARN_ON_ONCE(!bio);
467
468 if (bio_list_empty(&qn->bios)) {
469 list_del_init(&qn->node);
470 if (tg_to_put)
471 *tg_to_put = qn->tg;
472 else
473 blkg_put(tg_to_blkg(qn->tg));
474 } else {
475 list_move_tail(&qn->node, queued);
476 }
477
478 return bio;
479}
480
481/* init a service_queue, assumes the caller zeroed it */
482static void throtl_service_queue_init(struct throtl_service_queue *sq)
483{
484 INIT_LIST_HEAD(&sq->queued[0]);
485 INIT_LIST_HEAD(&sq->queued[1]);
486 sq->pending_tree = RB_ROOT_CACHED;
487 timer_setup(&sq->pending_timer, throtl_pending_timer_fn, 0);
488}
489
490static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp,
491 struct request_queue *q,
492 struct blkcg *blkcg)
493{
494 struct throtl_grp *tg;
495 int rw;
496
497 tg = kzalloc_node(sizeof(*tg), gfp, q->node);
498 if (!tg)
499 return NULL;
500
501 if (blkg_rwstat_init(&tg->stat_bytes, gfp))
502 goto err_free_tg;
503
504 if (blkg_rwstat_init(&tg->stat_ios, gfp))
505 goto err_exit_stat_bytes;
506
507 throtl_service_queue_init(&tg->service_queue);
508
509 for (rw = READ; rw <= WRITE; rw++) {
510 throtl_qnode_init(&tg->qnode_on_self[rw], tg);
511 throtl_qnode_init(&tg->qnode_on_parent[rw], tg);
512 }
513
514 RB_CLEAR_NODE(&tg->rb_node);
515 tg->bps[READ][LIMIT_MAX] = U64_MAX;
516 tg->bps[WRITE][LIMIT_MAX] = U64_MAX;
517 tg->iops[READ][LIMIT_MAX] = UINT_MAX;
518 tg->iops[WRITE][LIMIT_MAX] = UINT_MAX;
519 tg->bps_conf[READ][LIMIT_MAX] = U64_MAX;
520 tg->bps_conf[WRITE][LIMIT_MAX] = U64_MAX;
521 tg->iops_conf[READ][LIMIT_MAX] = UINT_MAX;
522 tg->iops_conf[WRITE][LIMIT_MAX] = UINT_MAX;
523 /* LIMIT_LOW will have default value 0 */
524
525 tg->latency_target = DFL_LATENCY_TARGET;
526 tg->latency_target_conf = DFL_LATENCY_TARGET;
527 tg->idletime_threshold = DFL_IDLE_THRESHOLD;
528 tg->idletime_threshold_conf = DFL_IDLE_THRESHOLD;
529
530 return &tg->pd;
531
532err_exit_stat_bytes:
533 blkg_rwstat_exit(&tg->stat_bytes);
534err_free_tg:
535 kfree(tg);
536 return NULL;
537}
538
539static void throtl_pd_init(struct blkg_policy_data *pd)
540{
541 struct throtl_grp *tg = pd_to_tg(pd);
542 struct blkcg_gq *blkg = tg_to_blkg(tg);
543 struct throtl_data *td = blkg->q->td;
544 struct throtl_service_queue *sq = &tg->service_queue;
545
546 /*
547 * If on the default hierarchy, we switch to properly hierarchical
548 * behavior where limits on a given throtl_grp are applied to the
549 * whole subtree rather than just the group itself. e.g. If 16M
550 * read_bps limit is set on the root group, the whole system can't
551 * exceed 16M for the device.
552 *
553 * If not on the default hierarchy, the broken flat hierarchy
554 * behavior is retained where all throtl_grps are treated as if
555 * they're all separate root groups right below throtl_data.
556 * Limits of a group don't interact with limits of other groups
557 * regardless of the position of the group in the hierarchy.
558 */
559 sq->parent_sq = &td->service_queue;
560 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent)
561 sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
562 tg->td = td;
563}
564
565/*
566 * Set has_rules[] if @tg or any of its parents have limits configured.
567 * This doesn't require walking up to the top of the hierarchy as the
568 * parent's has_rules[] is guaranteed to be correct.
569 */
570static void tg_update_has_rules(struct throtl_grp *tg)
571{
572 struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq);
573 struct throtl_data *td = tg->td;
574 int rw;
575
576 for (rw = READ; rw <= WRITE; rw++)
577 tg->has_rules[rw] = (parent_tg && parent_tg->has_rules[rw]) ||
578 (td->limit_valid[td->limit_index] &&
579 (tg_bps_limit(tg, rw) != U64_MAX ||
580 tg_iops_limit(tg, rw) != UINT_MAX));
581}
582
583static void throtl_pd_online(struct blkg_policy_data *pd)
584{
585 struct throtl_grp *tg = pd_to_tg(pd);
586 /*
587 * We don't want new groups to escape the limits of its ancestors.
588 * Update has_rules[] after a new group is brought online.
589 */
590 tg_update_has_rules(tg);
591}
592
593#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
594static void blk_throtl_update_limit_valid(struct throtl_data *td)
595{
596 struct cgroup_subsys_state *pos_css;
597 struct blkcg_gq *blkg;
598 bool low_valid = false;
599
600 rcu_read_lock();
601 blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
602 struct throtl_grp *tg = blkg_to_tg(blkg);
603
604 if (tg->bps[READ][LIMIT_LOW] || tg->bps[WRITE][LIMIT_LOW] ||
605 tg->iops[READ][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW]) {
606 low_valid = true;
607 break;
608 }
609 }
610 rcu_read_unlock();
611
612 td->limit_valid[LIMIT_LOW] = low_valid;
613}
614#else
615static inline void blk_throtl_update_limit_valid(struct throtl_data *td)
616{
617}
618#endif
619
620static void throtl_upgrade_state(struct throtl_data *td);
621static void throtl_pd_offline(struct blkg_policy_data *pd)
622{
623 struct throtl_grp *tg = pd_to_tg(pd);
624
625 tg->bps[READ][LIMIT_LOW] = 0;
626 tg->bps[WRITE][LIMIT_LOW] = 0;
627 tg->iops[READ][LIMIT_LOW] = 0;
628 tg->iops[WRITE][LIMIT_LOW] = 0;
629
630 blk_throtl_update_limit_valid(tg->td);
631
632 if (!tg->td->limit_valid[tg->td->limit_index])
633 throtl_upgrade_state(tg->td);
634}
635
636static void throtl_pd_free(struct blkg_policy_data *pd)
637{
638 struct throtl_grp *tg = pd_to_tg(pd);
639
640 del_timer_sync(&tg->service_queue.pending_timer);
641 blkg_rwstat_exit(&tg->stat_bytes);
642 blkg_rwstat_exit(&tg->stat_ios);
643 kfree(tg);
644}
645
646static struct throtl_grp *
647throtl_rb_first(struct throtl_service_queue *parent_sq)
648{
649 struct rb_node *n;
650
651 n = rb_first_cached(&parent_sq->pending_tree);
652 WARN_ON_ONCE(!n);
653 if (!n)
654 return NULL;
655 return rb_entry_tg(n);
656}
657
658static void throtl_rb_erase(struct rb_node *n,
659 struct throtl_service_queue *parent_sq)
660{
661 rb_erase_cached(n, &parent_sq->pending_tree);
662 RB_CLEAR_NODE(n);
663 --parent_sq->nr_pending;
664}
665
666static void update_min_dispatch_time(struct throtl_service_queue *parent_sq)
667{
668 struct throtl_grp *tg;
669
670 tg = throtl_rb_first(parent_sq);
671 if (!tg)
672 return;
673
674 parent_sq->first_pending_disptime = tg->disptime;
675}
676
677static void tg_service_queue_add(struct throtl_grp *tg)
678{
679 struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq;
680 struct rb_node **node = &parent_sq->pending_tree.rb_root.rb_node;
681 struct rb_node *parent = NULL;
682 struct throtl_grp *__tg;
683 unsigned long key = tg->disptime;
684 bool leftmost = true;
685
686 while (*node != NULL) {
687 parent = *node;
688 __tg = rb_entry_tg(parent);
689
690 if (time_before(key, __tg->disptime))
691 node = &parent->rb_left;
692 else {
693 node = &parent->rb_right;
694 leftmost = false;
695 }
696 }
697
698 rb_link_node(&tg->rb_node, parent, node);
699 rb_insert_color_cached(&tg->rb_node, &parent_sq->pending_tree,
700 leftmost);
701}
702
703static void throtl_enqueue_tg(struct throtl_grp *tg)
704{
705 if (!(tg->flags & THROTL_TG_PENDING)) {
706 tg_service_queue_add(tg);
707 tg->flags |= THROTL_TG_PENDING;
708 tg->service_queue.parent_sq->nr_pending++;
709 }
710}
711
712static void throtl_dequeue_tg(struct throtl_grp *tg)
713{
714 if (tg->flags & THROTL_TG_PENDING) {
715 throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq);
716 tg->flags &= ~THROTL_TG_PENDING;
717 }
718}
719
720/* Call with queue lock held */
721static void throtl_schedule_pending_timer(struct throtl_service_queue *sq,
722 unsigned long expires)
723{
724 unsigned long max_expire = jiffies + 8 * sq_to_td(sq)->throtl_slice;
725
726 /*
727 * Since we are adjusting the throttle limit dynamically, the sleep
728 * time calculated according to previous limit might be invalid. It's
729 * possible the cgroup sleep time is very long and no other cgroups
730 * have IO running so notify the limit changes. Make sure the cgroup
731 * doesn't sleep too long to avoid the missed notification.
732 */
733 if (time_after(expires, max_expire))
734 expires = max_expire;
735 mod_timer(&sq->pending_timer, expires);
736 throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu",
737 expires - jiffies, jiffies);
738}
739
740/**
741 * throtl_schedule_next_dispatch - schedule the next dispatch cycle
742 * @sq: the service_queue to schedule dispatch for
743 * @force: force scheduling
744 *
745 * Arm @sq->pending_timer so that the next dispatch cycle starts on the
746 * dispatch time of the first pending child. Returns %true if either timer
747 * is armed or there's no pending child left. %false if the current
748 * dispatch window is still open and the caller should continue
749 * dispatching.
750 *
751 * If @force is %true, the dispatch timer is always scheduled and this
752 * function is guaranteed to return %true. This is to be used when the
753 * caller can't dispatch itself and needs to invoke pending_timer
754 * unconditionally. Note that forced scheduling is likely to induce short
755 * delay before dispatch starts even if @sq->first_pending_disptime is not
756 * in the future and thus shouldn't be used in hot paths.
757 */
758static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq,
759 bool force)
760{
761 /* any pending children left? */
762 if (!sq->nr_pending)
763 return true;
764
765 update_min_dispatch_time(sq);
766
767 /* is the next dispatch time in the future? */
768 if (force || time_after(sq->first_pending_disptime, jiffies)) {
769 throtl_schedule_pending_timer(sq, sq->first_pending_disptime);
770 return true;
771 }
772
773 /* tell the caller to continue dispatching */
774 return false;
775}
776
777static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
778 bool rw, unsigned long start)
779{
780 tg->bytes_disp[rw] = 0;
781 tg->io_disp[rw] = 0;
782
783 atomic_set(&tg->io_split_cnt[rw], 0);
784
785 /*
786 * Previous slice has expired. We must have trimmed it after last
787 * bio dispatch. That means since start of last slice, we never used
788 * that bandwidth. Do try to make use of that bandwidth while giving
789 * credit.
790 */
791 if (time_after_eq(start, tg->slice_start[rw]))
792 tg->slice_start[rw] = start;
793
794 tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
795 throtl_log(&tg->service_queue,
796 "[%c] new slice with credit start=%lu end=%lu jiffies=%lu",
797 rw == READ ? 'R' : 'W', tg->slice_start[rw],
798 tg->slice_end[rw], jiffies);
799}
800
801static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw)
802{
803 tg->bytes_disp[rw] = 0;
804 tg->io_disp[rw] = 0;
805 tg->slice_start[rw] = jiffies;
806 tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
807
808 atomic_set(&tg->io_split_cnt[rw], 0);
809
810 throtl_log(&tg->service_queue,
811 "[%c] new slice start=%lu end=%lu jiffies=%lu",
812 rw == READ ? 'R' : 'W', tg->slice_start[rw],
813 tg->slice_end[rw], jiffies);
814}
815
816static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw,
817 unsigned long jiffy_end)
818{
819 tg->slice_end[rw] = roundup(jiffy_end, tg->td->throtl_slice);
820}
821
822static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw,
823 unsigned long jiffy_end)
824{
825 throtl_set_slice_end(tg, rw, jiffy_end);
826 throtl_log(&tg->service_queue,
827 "[%c] extend slice start=%lu end=%lu jiffies=%lu",
828 rw == READ ? 'R' : 'W', tg->slice_start[rw],
829 tg->slice_end[rw], jiffies);
830}
831
832/* Determine if previously allocated or extended slice is complete or not */
833static bool throtl_slice_used(struct throtl_grp *tg, bool rw)
834{
835 if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
836 return false;
837
838 return true;
839}
840
841/* Trim the used slices and adjust slice start accordingly */
842static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
843{
844 unsigned long nr_slices, time_elapsed, io_trim;
845 u64 bytes_trim, tmp;
846
847 BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
848
849 /*
850 * If bps are unlimited (-1), then time slice don't get
851 * renewed. Don't try to trim the slice if slice is used. A new
852 * slice will start when appropriate.
853 */
854 if (throtl_slice_used(tg, rw))
855 return;
856
857 /*
858 * A bio has been dispatched. Also adjust slice_end. It might happen
859 * that initially cgroup limit was very low resulting in high
860 * slice_end, but later limit was bumped up and bio was dispatched
861 * sooner, then we need to reduce slice_end. A high bogus slice_end
862 * is bad because it does not allow new slice to start.
863 */
864
865 throtl_set_slice_end(tg, rw, jiffies + tg->td->throtl_slice);
866
867 time_elapsed = jiffies - tg->slice_start[rw];
868
869 nr_slices = time_elapsed / tg->td->throtl_slice;
870
871 if (!nr_slices)
872 return;
873 tmp = tg_bps_limit(tg, rw) * tg->td->throtl_slice * nr_slices;
874 do_div(tmp, HZ);
875 bytes_trim = tmp;
876
877 io_trim = (tg_iops_limit(tg, rw) * tg->td->throtl_slice * nr_slices) /
878 HZ;
879
880 if (!bytes_trim && !io_trim)
881 return;
882
883 if (tg->bytes_disp[rw] >= bytes_trim)
884 tg->bytes_disp[rw] -= bytes_trim;
885 else
886 tg->bytes_disp[rw] = 0;
887
888 if (tg->io_disp[rw] >= io_trim)
889 tg->io_disp[rw] -= io_trim;
890 else
891 tg->io_disp[rw] = 0;
892
893 tg->slice_start[rw] += nr_slices * tg->td->throtl_slice;
894
895 throtl_log(&tg->service_queue,
896 "[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu",
897 rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
898 tg->slice_start[rw], tg->slice_end[rw], jiffies);
899}
900
901static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio,
902 u32 iops_limit, unsigned long *wait)
903{
904 bool rw = bio_data_dir(bio);
905 unsigned int io_allowed;
906 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
907 u64 tmp;
908
909 if (iops_limit == UINT_MAX) {
910 if (wait)
911 *wait = 0;
912 return true;
913 }
914
915 jiffy_elapsed = jiffies - tg->slice_start[rw];
916
917 /* Round up to the next throttle slice, wait time must be nonzero */
918 jiffy_elapsed_rnd = roundup(jiffy_elapsed + 1, tg->td->throtl_slice);
919
920 /*
921 * jiffy_elapsed_rnd should not be a big value as minimum iops can be
922 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
923 * will allow dispatch after 1 second and after that slice should
924 * have been trimmed.
925 */
926
927 tmp = (u64)iops_limit * jiffy_elapsed_rnd;
928 do_div(tmp, HZ);
929
930 if (tmp > UINT_MAX)
931 io_allowed = UINT_MAX;
932 else
933 io_allowed = tmp;
934
935 if (tg->io_disp[rw] + 1 <= io_allowed) {
936 if (wait)
937 *wait = 0;
938 return true;
939 }
940
941 /* Calc approx time to dispatch */
942 jiffy_wait = jiffy_elapsed_rnd - jiffy_elapsed;
943
944 if (wait)
945 *wait = jiffy_wait;
946 return false;
947}
948
949static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio,
950 u64 bps_limit, unsigned long *wait)
951{
952 bool rw = bio_data_dir(bio);
953 u64 bytes_allowed, extra_bytes, tmp;
954 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
955 unsigned int bio_size = throtl_bio_data_size(bio);
956
957 if (bps_limit == U64_MAX) {
958 if (wait)
959 *wait = 0;
960 return true;
961 }
962
963 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
964
965 /* Slice has just started. Consider one slice interval */
966 if (!jiffy_elapsed)
967 jiffy_elapsed_rnd = tg->td->throtl_slice;
968
969 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);
970
971 tmp = bps_limit * jiffy_elapsed_rnd;
972 do_div(tmp, HZ);
973 bytes_allowed = tmp;
974
975 if (tg->bytes_disp[rw] + bio_size <= bytes_allowed) {
976 if (wait)
977 *wait = 0;
978 return true;
979 }
980
981 /* Calc approx time to dispatch */
982 extra_bytes = tg->bytes_disp[rw] + bio_size - bytes_allowed;
983 jiffy_wait = div64_u64(extra_bytes * HZ, bps_limit);
984
985 if (!jiffy_wait)
986 jiffy_wait = 1;
987
988 /*
989 * This wait time is without taking into consideration the rounding
990 * up we did. Add that time also.
991 */
992 jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
993 if (wait)
994 *wait = jiffy_wait;
995 return false;
996}
997
998/*
999 * Returns whether one can dispatch a bio or not. Also returns approx number
1000 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
1001 */
1002static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
1003 unsigned long *wait)
1004{
1005 bool rw = bio_data_dir(bio);
1006 unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
1007 u64 bps_limit = tg_bps_limit(tg, rw);
1008 u32 iops_limit = tg_iops_limit(tg, rw);
1009
1010 /*
1011 * Currently whole state machine of group depends on first bio
1012 * queued in the group bio list. So one should not be calling
1013 * this function with a different bio if there are other bios
1014 * queued.
1015 */
1016 BUG_ON(tg->service_queue.nr_queued[rw] &&
1017 bio != throtl_peek_queued(&tg->service_queue.queued[rw]));
1018
1019 /* If tg->bps = -1, then BW is unlimited */
1020 if (bps_limit == U64_MAX && iops_limit == UINT_MAX) {
1021 if (wait)
1022 *wait = 0;
1023 return true;
1024 }
1025
1026 /*
1027 * If previous slice expired, start a new one otherwise renew/extend
1028 * existing slice to make sure it is at least throtl_slice interval
1029 * long since now. New slice is started only for empty throttle group.
1030 * If there is queued bio, that means there should be an active
1031 * slice and it should be extended instead.
1032 */
1033 if (throtl_slice_used(tg, rw) && !(tg->service_queue.nr_queued[rw]))
1034 throtl_start_new_slice(tg, rw);
1035 else {
1036 if (time_before(tg->slice_end[rw],
1037 jiffies + tg->td->throtl_slice))
1038 throtl_extend_slice(tg, rw,
1039 jiffies + tg->td->throtl_slice);
1040 }
1041
1042 if (iops_limit != UINT_MAX)
1043 tg->io_disp[rw] += atomic_xchg(&tg->io_split_cnt[rw], 0);
1044
1045 if (tg_with_in_bps_limit(tg, bio, bps_limit, &bps_wait) &&
1046 tg_with_in_iops_limit(tg, bio, iops_limit, &iops_wait)) {
1047 if (wait)
1048 *wait = 0;
1049 return true;
1050 }
1051
1052 max_wait = max(bps_wait, iops_wait);
1053
1054 if (wait)
1055 *wait = max_wait;
1056
1057 if (time_before(tg->slice_end[rw], jiffies + max_wait))
1058 throtl_extend_slice(tg, rw, jiffies + max_wait);
1059
1060 return false;
1061}
1062
1063static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
1064{
1065 bool rw = bio_data_dir(bio);
1066 unsigned int bio_size = throtl_bio_data_size(bio);
1067
1068 /* Charge the bio to the group */
1069 tg->bytes_disp[rw] += bio_size;
1070 tg->io_disp[rw]++;
1071 tg->last_bytes_disp[rw] += bio_size;
1072 tg->last_io_disp[rw]++;
1073
1074 /*
1075 * BIO_THROTTLED is used to prevent the same bio to be throttled
1076 * more than once as a throttled bio will go through blk-throtl the
1077 * second time when it eventually gets issued. Set it when a bio
1078 * is being charged to a tg.
1079 */
1080 if (!bio_flagged(bio, BIO_THROTTLED))
1081 bio_set_flag(bio, BIO_THROTTLED);
1082}
1083
1084/**
1085 * throtl_add_bio_tg - add a bio to the specified throtl_grp
1086 * @bio: bio to add
1087 * @qn: qnode to use
1088 * @tg: the target throtl_grp
1089 *
1090 * Add @bio to @tg's service_queue using @qn. If @qn is not specified,
1091 * tg->qnode_on_self[] is used.
1092 */
1093static void throtl_add_bio_tg(struct bio *bio, struct throtl_qnode *qn,
1094 struct throtl_grp *tg)
1095{
1096 struct throtl_service_queue *sq = &tg->service_queue;
1097 bool rw = bio_data_dir(bio);
1098
1099 if (!qn)
1100 qn = &tg->qnode_on_self[rw];
1101
1102 /*
1103 * If @tg doesn't currently have any bios queued in the same
1104 * direction, queueing @bio can change when @tg should be
1105 * dispatched. Mark that @tg was empty. This is automatically
1106 * cleared on the next tg_update_disptime().
1107 */
1108 if (!sq->nr_queued[rw])
1109 tg->flags |= THROTL_TG_WAS_EMPTY;
1110
1111 throtl_qnode_add_bio(bio, qn, &sq->queued[rw]);
1112
1113 sq->nr_queued[rw]++;
1114 throtl_enqueue_tg(tg);
1115}
1116
1117static void tg_update_disptime(struct throtl_grp *tg)
1118{
1119 struct throtl_service_queue *sq = &tg->service_queue;
1120 unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
1121 struct bio *bio;
1122
1123 bio = throtl_peek_queued(&sq->queued[READ]);
1124 if (bio)
1125 tg_may_dispatch(tg, bio, &read_wait);
1126
1127 bio = throtl_peek_queued(&sq->queued[WRITE]);
1128 if (bio)
1129 tg_may_dispatch(tg, bio, &write_wait);
1130
1131 min_wait = min(read_wait, write_wait);
1132 disptime = jiffies + min_wait;
1133
1134 /* Update dispatch time */
1135 throtl_dequeue_tg(tg);
1136 tg->disptime = disptime;
1137 throtl_enqueue_tg(tg);
1138
1139 /* see throtl_add_bio_tg() */
1140 tg->flags &= ~THROTL_TG_WAS_EMPTY;
1141}
1142
1143static void start_parent_slice_with_credit(struct throtl_grp *child_tg,
1144 struct throtl_grp *parent_tg, bool rw)
1145{
1146 if (throtl_slice_used(parent_tg, rw)) {
1147 throtl_start_new_slice_with_credit(parent_tg, rw,
1148 child_tg->slice_start[rw]);
1149 }
1150
1151}
1152
1153static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)
1154{
1155 struct throtl_service_queue *sq = &tg->service_queue;
1156 struct throtl_service_queue *parent_sq = sq->parent_sq;
1157 struct throtl_grp *parent_tg = sq_to_tg(parent_sq);
1158 struct throtl_grp *tg_to_put = NULL;
1159 struct bio *bio;
1160
1161 /*
1162 * @bio is being transferred from @tg to @parent_sq. Popping a bio
1163 * from @tg may put its reference and @parent_sq might end up
1164 * getting released prematurely. Remember the tg to put and put it
1165 * after @bio is transferred to @parent_sq.
1166 */
1167 bio = throtl_pop_queued(&sq->queued[rw], &tg_to_put);
1168 sq->nr_queued[rw]--;
1169
1170 throtl_charge_bio(tg, bio);
1171
1172 /*
1173 * If our parent is another tg, we just need to transfer @bio to
1174 * the parent using throtl_add_bio_tg(). If our parent is
1175 * @td->service_queue, @bio is ready to be issued. Put it on its
1176 * bio_lists[] and decrease total number queued. The caller is
1177 * responsible for issuing these bios.
1178 */
1179 if (parent_tg) {
1180 throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg);
1181 start_parent_slice_with_credit(tg, parent_tg, rw);
1182 } else {
1183 throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw],
1184 &parent_sq->queued[rw]);
1185 BUG_ON(tg->td->nr_queued[rw] <= 0);
1186 tg->td->nr_queued[rw]--;
1187 }
1188
1189 throtl_trim_slice(tg, rw);
1190
1191 if (tg_to_put)
1192 blkg_put(tg_to_blkg(tg_to_put));
1193}
1194
1195static int throtl_dispatch_tg(struct throtl_grp *tg)
1196{
1197 struct throtl_service_queue *sq = &tg->service_queue;
1198 unsigned int nr_reads = 0, nr_writes = 0;
1199 unsigned int max_nr_reads = THROTL_GRP_QUANTUM * 3 / 4;
1200 unsigned int max_nr_writes = THROTL_GRP_QUANTUM - max_nr_reads;
1201 struct bio *bio;
1202
1203 /* Try to dispatch 75% READS and 25% WRITES */
1204
1205 while ((bio = throtl_peek_queued(&sq->queued[READ])) &&
1206 tg_may_dispatch(tg, bio, NULL)) {
1207
1208 tg_dispatch_one_bio(tg, bio_data_dir(bio));
1209 nr_reads++;
1210
1211 if (nr_reads >= max_nr_reads)
1212 break;
1213 }
1214
1215 while ((bio = throtl_peek_queued(&sq->queued[WRITE])) &&
1216 tg_may_dispatch(tg, bio, NULL)) {
1217
1218 tg_dispatch_one_bio(tg, bio_data_dir(bio));
1219 nr_writes++;
1220
1221 if (nr_writes >= max_nr_writes)
1222 break;
1223 }
1224
1225 return nr_reads + nr_writes;
1226}
1227
1228static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
1229{
1230 unsigned int nr_disp = 0;
1231
1232 while (1) {
1233 struct throtl_grp *tg;
1234 struct throtl_service_queue *sq;
1235
1236 if (!parent_sq->nr_pending)
1237 break;
1238
1239 tg = throtl_rb_first(parent_sq);
1240 if (!tg)
1241 break;
1242
1243 if (time_before(jiffies, tg->disptime))
1244 break;
1245
1246 throtl_dequeue_tg(tg);
1247
1248 nr_disp += throtl_dispatch_tg(tg);
1249
1250 sq = &tg->service_queue;
1251 if (sq->nr_queued[0] || sq->nr_queued[1])
1252 tg_update_disptime(tg);
1253
1254 if (nr_disp >= THROTL_QUANTUM)
1255 break;
1256 }
1257
1258 return nr_disp;
1259}
1260
1261static bool throtl_can_upgrade(struct throtl_data *td,
1262 struct throtl_grp *this_tg);
1263/**
1264 * throtl_pending_timer_fn - timer function for service_queue->pending_timer
1265 * @t: the pending_timer member of the throtl_service_queue being serviced
1266 *
1267 * This timer is armed when a child throtl_grp with active bio's become
1268 * pending and queued on the service_queue's pending_tree and expires when
1269 * the first child throtl_grp should be dispatched. This function
1270 * dispatches bio's from the children throtl_grps to the parent
1271 * service_queue.
1272 *
1273 * If the parent's parent is another throtl_grp, dispatching is propagated
1274 * by either arming its pending_timer or repeating dispatch directly. If
1275 * the top-level service_tree is reached, throtl_data->dispatch_work is
1276 * kicked so that the ready bio's are issued.
1277 */
1278static void throtl_pending_timer_fn(struct timer_list *t)
1279{
1280 struct throtl_service_queue *sq = from_timer(sq, t, pending_timer);
1281 struct throtl_grp *tg = sq_to_tg(sq);
1282 struct throtl_data *td = sq_to_td(sq);
1283 struct request_queue *q = td->queue;
1284 struct throtl_service_queue *parent_sq;
1285 bool dispatched;
1286 int ret;
1287
1288 spin_lock_irq(&q->queue_lock);
1289 if (throtl_can_upgrade(td, NULL))
1290 throtl_upgrade_state(td);
1291
1292again:
1293 parent_sq = sq->parent_sq;
1294 dispatched = false;
1295
1296 while (true) {
1297 throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u",
1298 sq->nr_queued[READ] + sq->nr_queued[WRITE],
1299 sq->nr_queued[READ], sq->nr_queued[WRITE]);
1300
1301 ret = throtl_select_dispatch(sq);
1302 if (ret) {
1303 throtl_log(sq, "bios disp=%u", ret);
1304 dispatched = true;
1305 }
1306
1307 if (throtl_schedule_next_dispatch(sq, false))
1308 break;
1309
1310 /* this dispatch windows is still open, relax and repeat */
1311 spin_unlock_irq(&q->queue_lock);
1312 cpu_relax();
1313 spin_lock_irq(&q->queue_lock);
1314 }
1315
1316 if (!dispatched)
1317 goto out_unlock;
1318
1319 if (parent_sq) {
1320 /* @parent_sq is another throl_grp, propagate dispatch */
1321 if (tg->flags & THROTL_TG_WAS_EMPTY) {
1322 tg_update_disptime(tg);
1323 if (!throtl_schedule_next_dispatch(parent_sq, false)) {
1324 /* window is already open, repeat dispatching */
1325 sq = parent_sq;
1326 tg = sq_to_tg(sq);
1327 goto again;
1328 }
1329 }
1330 } else {
1331 /* reached the top-level, queue issuing */
1332 queue_work(kthrotld_workqueue, &td->dispatch_work);
1333 }
1334out_unlock:
1335 spin_unlock_irq(&q->queue_lock);
1336}
1337
1338/**
1339 * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work
1340 * @work: work item being executed
1341 *
1342 * This function is queued for execution when bios reach the bio_lists[]
1343 * of throtl_data->service_queue. Those bios are ready and issued by this
1344 * function.
1345 */
1346static void blk_throtl_dispatch_work_fn(struct work_struct *work)
1347{
1348 struct throtl_data *td = container_of(work, struct throtl_data,
1349 dispatch_work);
1350 struct throtl_service_queue *td_sq = &td->service_queue;
1351 struct request_queue *q = td->queue;
1352 struct bio_list bio_list_on_stack;
1353 struct bio *bio;
1354 struct blk_plug plug;
1355 int rw;
1356
1357 bio_list_init(&bio_list_on_stack);
1358
1359 spin_lock_irq(&q->queue_lock);
1360 for (rw = READ; rw <= WRITE; rw++)
1361 while ((bio = throtl_pop_queued(&td_sq->queued[rw], NULL)))
1362 bio_list_add(&bio_list_on_stack, bio);
1363 spin_unlock_irq(&q->queue_lock);
1364
1365 if (!bio_list_empty(&bio_list_on_stack)) {
1366 blk_start_plug(&plug);
1367 while ((bio = bio_list_pop(&bio_list_on_stack)))
1368 submit_bio_noacct(bio);
1369 blk_finish_plug(&plug);
1370 }
1371}
1372
1373static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
1374 int off)
1375{
1376 struct throtl_grp *tg = pd_to_tg(pd);
1377 u64 v = *(u64 *)((void *)tg + off);
1378
1379 if (v == U64_MAX)
1380 return 0;
1381 return __blkg_prfill_u64(sf, pd, v);
1382}
1383
1384static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
1385 int off)
1386{
1387 struct throtl_grp *tg = pd_to_tg(pd);
1388 unsigned int v = *(unsigned int *)((void *)tg + off);
1389
1390 if (v == UINT_MAX)
1391 return 0;
1392 return __blkg_prfill_u64(sf, pd, v);
1393}
1394
1395static int tg_print_conf_u64(struct seq_file *sf, void *v)
1396{
1397 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_u64,
1398 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1399 return 0;
1400}
1401
1402static int tg_print_conf_uint(struct seq_file *sf, void *v)
1403{
1404 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_uint,
1405 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1406 return 0;
1407}
1408
1409static void tg_conf_updated(struct throtl_grp *tg, bool global)
1410{
1411 struct throtl_service_queue *sq = &tg->service_queue;
1412 struct cgroup_subsys_state *pos_css;
1413 struct blkcg_gq *blkg;
1414
1415 throtl_log(&tg->service_queue,
1416 "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
1417 tg_bps_limit(tg, READ), tg_bps_limit(tg, WRITE),
1418 tg_iops_limit(tg, READ), tg_iops_limit(tg, WRITE));
1419
1420 /*
1421 * Update has_rules[] flags for the updated tg's subtree. A tg is
1422 * considered to have rules if either the tg itself or any of its
1423 * ancestors has rules. This identifies groups without any
1424 * restrictions in the whole hierarchy and allows them to bypass
1425 * blk-throttle.
1426 */
1427 blkg_for_each_descendant_pre(blkg, pos_css,
1428 global ? tg->td->queue->root_blkg : tg_to_blkg(tg)) {
1429 struct throtl_grp *this_tg = blkg_to_tg(blkg);
1430 struct throtl_grp *parent_tg;
1431
1432 tg_update_has_rules(this_tg);
1433 /* ignore root/second level */
1434 if (!cgroup_subsys_on_dfl(io_cgrp_subsys) || !blkg->parent ||
1435 !blkg->parent->parent)
1436 continue;
1437 parent_tg = blkg_to_tg(blkg->parent);
1438 /*
1439 * make sure all children has lower idle time threshold and
1440 * higher latency target
1441 */
1442 this_tg->idletime_threshold = min(this_tg->idletime_threshold,
1443 parent_tg->idletime_threshold);
1444 this_tg->latency_target = max(this_tg->latency_target,
1445 parent_tg->latency_target);
1446 }
1447
1448 /*
1449 * We're already holding queue_lock and know @tg is valid. Let's
1450 * apply the new config directly.
1451 *
1452 * Restart the slices for both READ and WRITES. It might happen
1453 * that a group's limit are dropped suddenly and we don't want to
1454 * account recently dispatched IO with new low rate.
1455 */
1456 throtl_start_new_slice(tg, READ);
1457 throtl_start_new_slice(tg, WRITE);
1458
1459 if (tg->flags & THROTL_TG_PENDING) {
1460 tg_update_disptime(tg);
1461 throtl_schedule_next_dispatch(sq->parent_sq, true);
1462 }
1463}
1464
1465static ssize_t tg_set_conf(struct kernfs_open_file *of,
1466 char *buf, size_t nbytes, loff_t off, bool is_u64)
1467{
1468 struct blkcg *blkcg = css_to_blkcg(of_css(of));
1469 struct blkg_conf_ctx ctx;
1470 struct throtl_grp *tg;
1471 int ret;
1472 u64 v;
1473
1474 ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
1475 if (ret)
1476 return ret;
1477
1478 ret = -EINVAL;
1479 if (sscanf(ctx.body, "%llu", &v) != 1)
1480 goto out_finish;
1481 if (!v)
1482 v = U64_MAX;
1483
1484 tg = blkg_to_tg(ctx.blkg);
1485
1486 if (is_u64)
1487 *(u64 *)((void *)tg + of_cft(of)->private) = v;
1488 else
1489 *(unsigned int *)((void *)tg + of_cft(of)->private) = v;
1490
1491 tg_conf_updated(tg, false);
1492 ret = 0;
1493out_finish:
1494 blkg_conf_finish(&ctx);
1495 return ret ?: nbytes;
1496}
1497
1498static ssize_t tg_set_conf_u64(struct kernfs_open_file *of,
1499 char *buf, size_t nbytes, loff_t off)
1500{
1501 return tg_set_conf(of, buf, nbytes, off, true);
1502}
1503
1504static ssize_t tg_set_conf_uint(struct kernfs_open_file *of,
1505 char *buf, size_t nbytes, loff_t off)
1506{
1507 return tg_set_conf(of, buf, nbytes, off, false);
1508}
1509
1510static int tg_print_rwstat(struct seq_file *sf, void *v)
1511{
1512 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1513 blkg_prfill_rwstat, &blkcg_policy_throtl,
1514 seq_cft(sf)->private, true);
1515 return 0;
1516}
1517
1518static u64 tg_prfill_rwstat_recursive(struct seq_file *sf,
1519 struct blkg_policy_data *pd, int off)
1520{
1521 struct blkg_rwstat_sample sum;
1522
1523 blkg_rwstat_recursive_sum(pd_to_blkg(pd), &blkcg_policy_throtl, off,
1524 &sum);
1525 return __blkg_prfill_rwstat(sf, pd, &sum);
1526}
1527
1528static int tg_print_rwstat_recursive(struct seq_file *sf, void *v)
1529{
1530 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1531 tg_prfill_rwstat_recursive, &blkcg_policy_throtl,
1532 seq_cft(sf)->private, true);
1533 return 0;
1534}
1535
1536static struct cftype throtl_legacy_files[] = {
1537 {
1538 .name = "throttle.read_bps_device",
1539 .private = offsetof(struct throtl_grp, bps[READ][LIMIT_MAX]),
1540 .seq_show = tg_print_conf_u64,
1541 .write = tg_set_conf_u64,
1542 },
1543 {
1544 .name = "throttle.write_bps_device",
1545 .private = offsetof(struct throtl_grp, bps[WRITE][LIMIT_MAX]),
1546 .seq_show = tg_print_conf_u64,
1547 .write = tg_set_conf_u64,
1548 },
1549 {
1550 .name = "throttle.read_iops_device",
1551 .private = offsetof(struct throtl_grp, iops[READ][LIMIT_MAX]),
1552 .seq_show = tg_print_conf_uint,
1553 .write = tg_set_conf_uint,
1554 },
1555 {
1556 .name = "throttle.write_iops_device",
1557 .private = offsetof(struct throtl_grp, iops[WRITE][LIMIT_MAX]),
1558 .seq_show = tg_print_conf_uint,
1559 .write = tg_set_conf_uint,
1560 },
1561 {
1562 .name = "throttle.io_service_bytes",
1563 .private = offsetof(struct throtl_grp, stat_bytes),
1564 .seq_show = tg_print_rwstat,
1565 },
1566 {
1567 .name = "throttle.io_service_bytes_recursive",
1568 .private = offsetof(struct throtl_grp, stat_bytes),
1569 .seq_show = tg_print_rwstat_recursive,
1570 },
1571 {
1572 .name = "throttle.io_serviced",
1573 .private = offsetof(struct throtl_grp, stat_ios),
1574 .seq_show = tg_print_rwstat,
1575 },
1576 {
1577 .name = "throttle.io_serviced_recursive",
1578 .private = offsetof(struct throtl_grp, stat_ios),
1579 .seq_show = tg_print_rwstat_recursive,
1580 },
1581 { } /* terminate */
1582};
1583
1584static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
1585 int off)
1586{
1587 struct throtl_grp *tg = pd_to_tg(pd);
1588 const char *dname = blkg_dev_name(pd->blkg);
1589 char bufs[4][21] = { "max", "max", "max", "max" };
1590 u64 bps_dft;
1591 unsigned int iops_dft;
1592 char idle_time[26] = "";
1593 char latency_time[26] = "";
1594
1595 if (!dname)
1596 return 0;
1597
1598 if (off == LIMIT_LOW) {
1599 bps_dft = 0;
1600 iops_dft = 0;
1601 } else {
1602 bps_dft = U64_MAX;
1603 iops_dft = UINT_MAX;
1604 }
1605
1606 if (tg->bps_conf[READ][off] == bps_dft &&
1607 tg->bps_conf[WRITE][off] == bps_dft &&
1608 tg->iops_conf[READ][off] == iops_dft &&
1609 tg->iops_conf[WRITE][off] == iops_dft &&
1610 (off != LIMIT_LOW ||
1611 (tg->idletime_threshold_conf == DFL_IDLE_THRESHOLD &&
1612 tg->latency_target_conf == DFL_LATENCY_TARGET)))
1613 return 0;
1614
1615 if (tg->bps_conf[READ][off] != U64_MAX)
1616 snprintf(bufs[0], sizeof(bufs[0]), "%llu",
1617 tg->bps_conf[READ][off]);
1618 if (tg->bps_conf[WRITE][off] != U64_MAX)
1619 snprintf(bufs[1], sizeof(bufs[1]), "%llu",
1620 tg->bps_conf[WRITE][off]);
1621 if (tg->iops_conf[READ][off] != UINT_MAX)
1622 snprintf(bufs[2], sizeof(bufs[2]), "%u",
1623 tg->iops_conf[READ][off]);
1624 if (tg->iops_conf[WRITE][off] != UINT_MAX)
1625 snprintf(bufs[3], sizeof(bufs[3]), "%u",
1626 tg->iops_conf[WRITE][off]);
1627 if (off == LIMIT_LOW) {
1628 if (tg->idletime_threshold_conf == ULONG_MAX)
1629 strcpy(idle_time, " idle=max");
1630 else
1631 snprintf(idle_time, sizeof(idle_time), " idle=%lu",
1632 tg->idletime_threshold_conf);
1633
1634 if (tg->latency_target_conf == ULONG_MAX)
1635 strcpy(latency_time, " latency=max");
1636 else
1637 snprintf(latency_time, sizeof(latency_time),
1638 " latency=%lu", tg->latency_target_conf);
1639 }
1640
1641 seq_printf(sf, "%s rbps=%s wbps=%s riops=%s wiops=%s%s%s\n",
1642 dname, bufs[0], bufs[1], bufs[2], bufs[3], idle_time,
1643 latency_time);
1644 return 0;
1645}
1646
1647static int tg_print_limit(struct seq_file *sf, void *v)
1648{
1649 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_limit,
1650 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1651 return 0;
1652}
1653
1654static ssize_t tg_set_limit(struct kernfs_open_file *of,
1655 char *buf, size_t nbytes, loff_t off)
1656{
1657 struct blkcg *blkcg = css_to_blkcg(of_css(of));
1658 struct blkg_conf_ctx ctx;
1659 struct throtl_grp *tg;
1660 u64 v[4];
1661 unsigned long idle_time;
1662 unsigned long latency_time;
1663 int ret;
1664 int index = of_cft(of)->private;
1665
1666 ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
1667 if (ret)
1668 return ret;
1669
1670 tg = blkg_to_tg(ctx.blkg);
1671
1672 v[0] = tg->bps_conf[READ][index];
1673 v[1] = tg->bps_conf[WRITE][index];
1674 v[2] = tg->iops_conf[READ][index];
1675 v[3] = tg->iops_conf[WRITE][index];
1676
1677 idle_time = tg->idletime_threshold_conf;
1678 latency_time = tg->latency_target_conf;
1679 while (true) {
1680 char tok[27]; /* wiops=18446744073709551616 */
1681 char *p;
1682 u64 val = U64_MAX;
1683 int len;
1684
1685 if (sscanf(ctx.body, "%26s%n", tok, &len) != 1)
1686 break;
1687 if (tok[0] == '\0')
1688 break;
1689 ctx.body += len;
1690
1691 ret = -EINVAL;
1692 p = tok;
1693 strsep(&p, "=");
1694 if (!p || (sscanf(p, "%llu", &val) != 1 && strcmp(p, "max")))
1695 goto out_finish;
1696
1697 ret = -ERANGE;
1698 if (!val)
1699 goto out_finish;
1700
1701 ret = -EINVAL;
1702 if (!strcmp(tok, "rbps") && val > 1)
1703 v[0] = val;
1704 else if (!strcmp(tok, "wbps") && val > 1)
1705 v[1] = val;
1706 else if (!strcmp(tok, "riops") && val > 1)
1707 v[2] = min_t(u64, val, UINT_MAX);
1708 else if (!strcmp(tok, "wiops") && val > 1)
1709 v[3] = min_t(u64, val, UINT_MAX);
1710 else if (off == LIMIT_LOW && !strcmp(tok, "idle"))
1711 idle_time = val;
1712 else if (off == LIMIT_LOW && !strcmp(tok, "latency"))
1713 latency_time = val;
1714 else
1715 goto out_finish;
1716 }
1717
1718 tg->bps_conf[READ][index] = v[0];
1719 tg->bps_conf[WRITE][index] = v[1];
1720 tg->iops_conf[READ][index] = v[2];
1721 tg->iops_conf[WRITE][index] = v[3];
1722
1723 if (index == LIMIT_MAX) {
1724 tg->bps[READ][index] = v[0];
1725 tg->bps[WRITE][index] = v[1];
1726 tg->iops[READ][index] = v[2];
1727 tg->iops[WRITE][index] = v[3];
1728 }
1729 tg->bps[READ][LIMIT_LOW] = min(tg->bps_conf[READ][LIMIT_LOW],
1730 tg->bps_conf[READ][LIMIT_MAX]);
1731 tg->bps[WRITE][LIMIT_LOW] = min(tg->bps_conf[WRITE][LIMIT_LOW],
1732 tg->bps_conf[WRITE][LIMIT_MAX]);
1733 tg->iops[READ][LIMIT_LOW] = min(tg->iops_conf[READ][LIMIT_LOW],
1734 tg->iops_conf[READ][LIMIT_MAX]);
1735 tg->iops[WRITE][LIMIT_LOW] = min(tg->iops_conf[WRITE][LIMIT_LOW],
1736 tg->iops_conf[WRITE][LIMIT_MAX]);
1737 tg->idletime_threshold_conf = idle_time;
1738 tg->latency_target_conf = latency_time;
1739
1740 /* force user to configure all settings for low limit */
1741 if (!(tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW] ||
1742 tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW]) ||
1743 tg->idletime_threshold_conf == DFL_IDLE_THRESHOLD ||
1744 tg->latency_target_conf == DFL_LATENCY_TARGET) {
1745 tg->bps[READ][LIMIT_LOW] = 0;
1746 tg->bps[WRITE][LIMIT_LOW] = 0;
1747 tg->iops[READ][LIMIT_LOW] = 0;
1748 tg->iops[WRITE][LIMIT_LOW] = 0;
1749 tg->idletime_threshold = DFL_IDLE_THRESHOLD;
1750 tg->latency_target = DFL_LATENCY_TARGET;
1751 } else if (index == LIMIT_LOW) {
1752 tg->idletime_threshold = tg->idletime_threshold_conf;
1753 tg->latency_target = tg->latency_target_conf;
1754 }
1755
1756 blk_throtl_update_limit_valid(tg->td);
1757 if (tg->td->limit_valid[LIMIT_LOW]) {
1758 if (index == LIMIT_LOW)
1759 tg->td->limit_index = LIMIT_LOW;
1760 } else
1761 tg->td->limit_index = LIMIT_MAX;
1762 tg_conf_updated(tg, index == LIMIT_LOW &&
1763 tg->td->limit_valid[LIMIT_LOW]);
1764 ret = 0;
1765out_finish:
1766 blkg_conf_finish(&ctx);
1767 return ret ?: nbytes;
1768}
1769
1770static struct cftype throtl_files[] = {
1771#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
1772 {
1773 .name = "low",
1774 .flags = CFTYPE_NOT_ON_ROOT,
1775 .seq_show = tg_print_limit,
1776 .write = tg_set_limit,
1777 .private = LIMIT_LOW,
1778 },
1779#endif
1780 {
1781 .name = "max",
1782 .flags = CFTYPE_NOT_ON_ROOT,
1783 .seq_show = tg_print_limit,
1784 .write = tg_set_limit,
1785 .private = LIMIT_MAX,
1786 },
1787 { } /* terminate */
1788};
1789
1790static void throtl_shutdown_wq(struct request_queue *q)
1791{
1792 struct throtl_data *td = q->td;
1793
1794 cancel_work_sync(&td->dispatch_work);
1795}
1796
1797static struct blkcg_policy blkcg_policy_throtl = {
1798 .dfl_cftypes = throtl_files,
1799 .legacy_cftypes = throtl_legacy_files,
1800
1801 .pd_alloc_fn = throtl_pd_alloc,
1802 .pd_init_fn = throtl_pd_init,
1803 .pd_online_fn = throtl_pd_online,
1804 .pd_offline_fn = throtl_pd_offline,
1805 .pd_free_fn = throtl_pd_free,
1806};
1807
1808static unsigned long __tg_last_low_overflow_time(struct throtl_grp *tg)
1809{
1810 unsigned long rtime = jiffies, wtime = jiffies;
1811
1812 if (tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW])
1813 rtime = tg->last_low_overflow_time[READ];
1814 if (tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW])
1815 wtime = tg->last_low_overflow_time[WRITE];
1816 return min(rtime, wtime);
1817}
1818
1819/* tg should not be an intermediate node */
1820static unsigned long tg_last_low_overflow_time(struct throtl_grp *tg)
1821{
1822 struct throtl_service_queue *parent_sq;
1823 struct throtl_grp *parent = tg;
1824 unsigned long ret = __tg_last_low_overflow_time(tg);
1825
1826 while (true) {
1827 parent_sq = parent->service_queue.parent_sq;
1828 parent = sq_to_tg(parent_sq);
1829 if (!parent)
1830 break;
1831
1832 /*
1833 * The parent doesn't have low limit, it always reaches low
1834 * limit. Its overflow time is useless for children
1835 */
1836 if (!parent->bps[READ][LIMIT_LOW] &&
1837 !parent->iops[READ][LIMIT_LOW] &&
1838 !parent->bps[WRITE][LIMIT_LOW] &&
1839 !parent->iops[WRITE][LIMIT_LOW])
1840 continue;
1841 if (time_after(__tg_last_low_overflow_time(parent), ret))
1842 ret = __tg_last_low_overflow_time(parent);
1843 }
1844 return ret;
1845}
1846
1847static bool throtl_tg_is_idle(struct throtl_grp *tg)
1848{
1849 /*
1850 * cgroup is idle if:
1851 * - single idle is too long, longer than a fixed value (in case user
1852 * configure a too big threshold) or 4 times of idletime threshold
1853 * - average think time is more than threshold
1854 * - IO latency is largely below threshold
1855 */
1856 unsigned long time;
1857 bool ret;
1858
1859 time = min_t(unsigned long, MAX_IDLE_TIME, 4 * tg->idletime_threshold);
1860 ret = tg->latency_target == DFL_LATENCY_TARGET ||
1861 tg->idletime_threshold == DFL_IDLE_THRESHOLD ||
1862 (ktime_get_ns() >> 10) - tg->last_finish_time > time ||
1863 tg->avg_idletime > tg->idletime_threshold ||
1864 (tg->latency_target && tg->bio_cnt &&
1865 tg->bad_bio_cnt * 5 < tg->bio_cnt);
1866 throtl_log(&tg->service_queue,
1867 "avg_idle=%ld, idle_threshold=%ld, bad_bio=%d, total_bio=%d, is_idle=%d, scale=%d",
1868 tg->avg_idletime, tg->idletime_threshold, tg->bad_bio_cnt,
1869 tg->bio_cnt, ret, tg->td->scale);
1870 return ret;
1871}
1872
1873static bool throtl_tg_can_upgrade(struct throtl_grp *tg)
1874{
1875 struct throtl_service_queue *sq = &tg->service_queue;
1876 bool read_limit, write_limit;
1877
1878 /*
1879 * if cgroup reaches low limit (if low limit is 0, the cgroup always
1880 * reaches), it's ok to upgrade to next limit
1881 */
1882 read_limit = tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW];
1883 write_limit = tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW];
1884 if (!read_limit && !write_limit)
1885 return true;
1886 if (read_limit && sq->nr_queued[READ] &&
1887 (!write_limit || sq->nr_queued[WRITE]))
1888 return true;
1889 if (write_limit && sq->nr_queued[WRITE] &&
1890 (!read_limit || sq->nr_queued[READ]))
1891 return true;
1892
1893 if (time_after_eq(jiffies,
1894 tg_last_low_overflow_time(tg) + tg->td->throtl_slice) &&
1895 throtl_tg_is_idle(tg))
1896 return true;
1897 return false;
1898}
1899
1900static bool throtl_hierarchy_can_upgrade(struct throtl_grp *tg)
1901{
1902 while (true) {
1903 if (throtl_tg_can_upgrade(tg))
1904 return true;
1905 tg = sq_to_tg(tg->service_queue.parent_sq);
1906 if (!tg || !tg_to_blkg(tg)->parent)
1907 return false;
1908 }
1909 return false;
1910}
1911
1912static bool throtl_can_upgrade(struct throtl_data *td,
1913 struct throtl_grp *this_tg)
1914{
1915 struct cgroup_subsys_state *pos_css;
1916 struct blkcg_gq *blkg;
1917
1918 if (td->limit_index != LIMIT_LOW)
1919 return false;
1920
1921 if (time_before(jiffies, td->low_downgrade_time + td->throtl_slice))
1922 return false;
1923
1924 rcu_read_lock();
1925 blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
1926 struct throtl_grp *tg = blkg_to_tg(blkg);
1927
1928 if (tg == this_tg)
1929 continue;
1930 if (!list_empty(&tg_to_blkg(tg)->blkcg->css.children))
1931 continue;
1932 if (!throtl_hierarchy_can_upgrade(tg)) {
1933 rcu_read_unlock();
1934 return false;
1935 }
1936 }
1937 rcu_read_unlock();
1938 return true;
1939}
1940
1941static void throtl_upgrade_check(struct throtl_grp *tg)
1942{
1943 unsigned long now = jiffies;
1944
1945 if (tg->td->limit_index != LIMIT_LOW)
1946 return;
1947
1948 if (time_after(tg->last_check_time + tg->td->throtl_slice, now))
1949 return;
1950
1951 tg->last_check_time = now;
1952
1953 if (!time_after_eq(now,
1954 __tg_last_low_overflow_time(tg) + tg->td->throtl_slice))
1955 return;
1956
1957 if (throtl_can_upgrade(tg->td, NULL))
1958 throtl_upgrade_state(tg->td);
1959}
1960
1961static void throtl_upgrade_state(struct throtl_data *td)
1962{
1963 struct cgroup_subsys_state *pos_css;
1964 struct blkcg_gq *blkg;
1965
1966 throtl_log(&td->service_queue, "upgrade to max");
1967 td->limit_index = LIMIT_MAX;
1968 td->low_upgrade_time = jiffies;
1969 td->scale = 0;
1970 rcu_read_lock();
1971 blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
1972 struct throtl_grp *tg = blkg_to_tg(blkg);
1973 struct throtl_service_queue *sq = &tg->service_queue;
1974
1975 tg->disptime = jiffies - 1;
1976 throtl_select_dispatch(sq);
1977 throtl_schedule_next_dispatch(sq, true);
1978 }
1979 rcu_read_unlock();
1980 throtl_select_dispatch(&td->service_queue);
1981 throtl_schedule_next_dispatch(&td->service_queue, true);
1982 queue_work(kthrotld_workqueue, &td->dispatch_work);
1983}
1984
1985static void throtl_downgrade_state(struct throtl_data *td)
1986{
1987 td->scale /= 2;
1988
1989 throtl_log(&td->service_queue, "downgrade, scale %d", td->scale);
1990 if (td->scale) {
1991 td->low_upgrade_time = jiffies - td->scale * td->throtl_slice;
1992 return;
1993 }
1994
1995 td->limit_index = LIMIT_LOW;
1996 td->low_downgrade_time = jiffies;
1997}
1998
1999static bool throtl_tg_can_downgrade(struct throtl_grp *tg)
2000{
2001 struct throtl_data *td = tg->td;
2002 unsigned long now = jiffies;
2003
2004 /*
2005 * If cgroup is below low limit, consider downgrade and throttle other
2006 * cgroups
2007 */
2008 if (time_after_eq(now, td->low_upgrade_time + td->throtl_slice) &&
2009 time_after_eq(now, tg_last_low_overflow_time(tg) +
2010 td->throtl_slice) &&
2011 (!throtl_tg_is_idle(tg) ||
2012 !list_empty(&tg_to_blkg(tg)->blkcg->css.children)))
2013 return true;
2014 return false;
2015}
2016
2017static bool throtl_hierarchy_can_downgrade(struct throtl_grp *tg)
2018{
2019 while (true) {
2020 if (!throtl_tg_can_downgrade(tg))
2021 return false;
2022 tg = sq_to_tg(tg->service_queue.parent_sq);
2023 if (!tg || !tg_to_blkg(tg)->parent)
2024 break;
2025 }
2026 return true;
2027}
2028
2029static void throtl_downgrade_check(struct throtl_grp *tg)
2030{
2031 uint64_t bps;
2032 unsigned int iops;
2033 unsigned long elapsed_time;
2034 unsigned long now = jiffies;
2035
2036 if (tg->td->limit_index != LIMIT_MAX ||
2037 !tg->td->limit_valid[LIMIT_LOW])
2038 return;
2039 if (!list_empty(&tg_to_blkg(tg)->blkcg->css.children))
2040 return;
2041 if (time_after(tg->last_check_time + tg->td->throtl_slice, now))
2042 return;
2043
2044 elapsed_time = now - tg->last_check_time;
2045 tg->last_check_time = now;
2046
2047 if (time_before(now, tg_last_low_overflow_time(tg) +
2048 tg->td->throtl_slice))
2049 return;
2050
2051 if (tg->bps[READ][LIMIT_LOW]) {
2052 bps = tg->last_bytes_disp[READ] * HZ;
2053 do_div(bps, elapsed_time);
2054 if (bps >= tg->bps[READ][LIMIT_LOW])
2055 tg->last_low_overflow_time[READ] = now;
2056 }
2057
2058 if (tg->bps[WRITE][LIMIT_LOW]) {
2059 bps = tg->last_bytes_disp[WRITE] * HZ;
2060 do_div(bps, elapsed_time);
2061 if (bps >= tg->bps[WRITE][LIMIT_LOW])
2062 tg->last_low_overflow_time[WRITE] = now;
2063 }
2064
2065 if (tg->iops[READ][LIMIT_LOW]) {
2066 tg->last_io_disp[READ] += atomic_xchg(&tg->last_io_split_cnt[READ], 0);
2067 iops = tg->last_io_disp[READ] * HZ / elapsed_time;
2068 if (iops >= tg->iops[READ][LIMIT_LOW])
2069 tg->last_low_overflow_time[READ] = now;
2070 }
2071
2072 if (tg->iops[WRITE][LIMIT_LOW]) {
2073 tg->last_io_disp[WRITE] += atomic_xchg(&tg->last_io_split_cnt[WRITE], 0);
2074 iops = tg->last_io_disp[WRITE] * HZ / elapsed_time;
2075 if (iops >= tg->iops[WRITE][LIMIT_LOW])
2076 tg->last_low_overflow_time[WRITE] = now;
2077 }
2078
2079 /*
2080 * If cgroup is below low limit, consider downgrade and throttle other
2081 * cgroups
2082 */
2083 if (throtl_hierarchy_can_downgrade(tg))
2084 throtl_downgrade_state(tg->td);
2085
2086 tg->last_bytes_disp[READ] = 0;
2087 tg->last_bytes_disp[WRITE] = 0;
2088 tg->last_io_disp[READ] = 0;
2089 tg->last_io_disp[WRITE] = 0;
2090}
2091
2092static void blk_throtl_update_idletime(struct throtl_grp *tg)
2093{
2094 unsigned long now;
2095 unsigned long last_finish_time = tg->last_finish_time;
2096
2097 if (last_finish_time == 0)
2098 return;
2099
2100 now = ktime_get_ns() >> 10;
2101 if (now <= last_finish_time ||
2102 last_finish_time == tg->checked_last_finish_time)
2103 return;
2104
2105 tg->avg_idletime = (tg->avg_idletime * 7 + now - last_finish_time) >> 3;
2106 tg->checked_last_finish_time = last_finish_time;
2107}
2108
2109#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2110static void throtl_update_latency_buckets(struct throtl_data *td)
2111{
2112 struct avg_latency_bucket avg_latency[2][LATENCY_BUCKET_SIZE];
2113 int i, cpu, rw;
2114 unsigned long last_latency[2] = { 0 };
2115 unsigned long latency[2];
2116
2117 if (!blk_queue_nonrot(td->queue) || !td->limit_valid[LIMIT_LOW])
2118 return;
2119 if (time_before(jiffies, td->last_calculate_time + HZ))
2120 return;
2121 td->last_calculate_time = jiffies;
2122
2123 memset(avg_latency, 0, sizeof(avg_latency));
2124 for (rw = READ; rw <= WRITE; rw++) {
2125 for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
2126 struct latency_bucket *tmp = &td->tmp_buckets[rw][i];
2127
2128 for_each_possible_cpu(cpu) {
2129 struct latency_bucket *bucket;
2130
2131 /* this isn't race free, but ok in practice */
2132 bucket = per_cpu_ptr(td->latency_buckets[rw],
2133 cpu);
2134 tmp->total_latency += bucket[i].total_latency;
2135 tmp->samples += bucket[i].samples;
2136 bucket[i].total_latency = 0;
2137 bucket[i].samples = 0;
2138 }
2139
2140 if (tmp->samples >= 32) {
2141 int samples = tmp->samples;
2142
2143 latency[rw] = tmp->total_latency;
2144
2145 tmp->total_latency = 0;
2146 tmp->samples = 0;
2147 latency[rw] /= samples;
2148 if (latency[rw] == 0)
2149 continue;
2150 avg_latency[rw][i].latency = latency[rw];
2151 }
2152 }
2153 }
2154
2155 for (rw = READ; rw <= WRITE; rw++) {
2156 for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
2157 if (!avg_latency[rw][i].latency) {
2158 if (td->avg_buckets[rw][i].latency < last_latency[rw])
2159 td->avg_buckets[rw][i].latency =
2160 last_latency[rw];
2161 continue;
2162 }
2163
2164 if (!td->avg_buckets[rw][i].valid)
2165 latency[rw] = avg_latency[rw][i].latency;
2166 else
2167 latency[rw] = (td->avg_buckets[rw][i].latency * 7 +
2168 avg_latency[rw][i].latency) >> 3;
2169
2170 td->avg_buckets[rw][i].latency = max(latency[rw],
2171 last_latency[rw]);
2172 td->avg_buckets[rw][i].valid = true;
2173 last_latency[rw] = td->avg_buckets[rw][i].latency;
2174 }
2175 }
2176
2177 for (i = 0; i < LATENCY_BUCKET_SIZE; i++)
2178 throtl_log(&td->service_queue,
2179 "Latency bucket %d: read latency=%ld, read valid=%d, "
2180 "write latency=%ld, write valid=%d", i,
2181 td->avg_buckets[READ][i].latency,
2182 td->avg_buckets[READ][i].valid,
2183 td->avg_buckets[WRITE][i].latency,
2184 td->avg_buckets[WRITE][i].valid);
2185}
2186#else
2187static inline void throtl_update_latency_buckets(struct throtl_data *td)
2188{
2189}
2190#endif
2191
2192void blk_throtl_charge_bio_split(struct bio *bio)
2193{
2194 struct blkcg_gq *blkg = bio->bi_blkg;
2195 struct throtl_grp *parent = blkg_to_tg(blkg);
2196 struct throtl_service_queue *parent_sq;
2197 bool rw = bio_data_dir(bio);
2198
2199 do {
2200 if (!parent->has_rules[rw])
2201 break;
2202
2203 atomic_inc(&parent->io_split_cnt[rw]);
2204 atomic_inc(&parent->last_io_split_cnt[rw]);
2205
2206 parent_sq = parent->service_queue.parent_sq;
2207 parent = sq_to_tg(parent_sq);
2208 } while (parent);
2209}
2210
2211bool blk_throtl_bio(struct bio *bio)
2212{
2213 struct request_queue *q = bio->bi_bdev->bd_disk->queue;
2214 struct blkcg_gq *blkg = bio->bi_blkg;
2215 struct throtl_qnode *qn = NULL;
2216 struct throtl_grp *tg = blkg_to_tg(blkg);
2217 struct throtl_service_queue *sq;
2218 bool rw = bio_data_dir(bio);
2219 bool throttled = false;
2220 struct throtl_data *td = tg->td;
2221
2222 rcu_read_lock();
2223
2224 /* see throtl_charge_bio() */
2225 if (bio_flagged(bio, BIO_THROTTLED))
2226 goto out;
2227
2228 if (!cgroup_subsys_on_dfl(io_cgrp_subsys)) {
2229 blkg_rwstat_add(&tg->stat_bytes, bio->bi_opf,
2230 bio->bi_iter.bi_size);
2231 blkg_rwstat_add(&tg->stat_ios, bio->bi_opf, 1);
2232 }
2233
2234 if (!tg->has_rules[rw])
2235 goto out;
2236
2237 spin_lock_irq(&q->queue_lock);
2238
2239 throtl_update_latency_buckets(td);
2240
2241 blk_throtl_update_idletime(tg);
2242
2243 sq = &tg->service_queue;
2244
2245again:
2246 while (true) {
2247 if (tg->last_low_overflow_time[rw] == 0)
2248 tg->last_low_overflow_time[rw] = jiffies;
2249 throtl_downgrade_check(tg);
2250 throtl_upgrade_check(tg);
2251 /* throtl is FIFO - if bios are already queued, should queue */
2252 if (sq->nr_queued[rw])
2253 break;
2254
2255 /* if above limits, break to queue */
2256 if (!tg_may_dispatch(tg, bio, NULL)) {
2257 tg->last_low_overflow_time[rw] = jiffies;
2258 if (throtl_can_upgrade(td, tg)) {
2259 throtl_upgrade_state(td);
2260 goto again;
2261 }
2262 break;
2263 }
2264
2265 /* within limits, let's charge and dispatch directly */
2266 throtl_charge_bio(tg, bio);
2267
2268 /*
2269 * We need to trim slice even when bios are not being queued
2270 * otherwise it might happen that a bio is not queued for
2271 * a long time and slice keeps on extending and trim is not
2272 * called for a long time. Now if limits are reduced suddenly
2273 * we take into account all the IO dispatched so far at new
2274 * low rate and * newly queued IO gets a really long dispatch
2275 * time.
2276 *
2277 * So keep on trimming slice even if bio is not queued.
2278 */
2279 throtl_trim_slice(tg, rw);
2280
2281 /*
2282 * @bio passed through this layer without being throttled.
2283 * Climb up the ladder. If we're already at the top, it
2284 * can be executed directly.
2285 */
2286 qn = &tg->qnode_on_parent[rw];
2287 sq = sq->parent_sq;
2288 tg = sq_to_tg(sq);
2289 if (!tg)
2290 goto out_unlock;
2291 }
2292
2293 /* out-of-limit, queue to @tg */
2294 throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
2295 rw == READ ? 'R' : 'W',
2296 tg->bytes_disp[rw], bio->bi_iter.bi_size,
2297 tg_bps_limit(tg, rw),
2298 tg->io_disp[rw], tg_iops_limit(tg, rw),
2299 sq->nr_queued[READ], sq->nr_queued[WRITE]);
2300
2301 tg->last_low_overflow_time[rw] = jiffies;
2302
2303 td->nr_queued[rw]++;
2304 throtl_add_bio_tg(bio, qn, tg);
2305 throttled = true;
2306
2307 /*
2308 * Update @tg's dispatch time and force schedule dispatch if @tg
2309 * was empty before @bio. The forced scheduling isn't likely to
2310 * cause undue delay as @bio is likely to be dispatched directly if
2311 * its @tg's disptime is not in the future.
2312 */
2313 if (tg->flags & THROTL_TG_WAS_EMPTY) {
2314 tg_update_disptime(tg);
2315 throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true);
2316 }
2317
2318out_unlock:
2319 spin_unlock_irq(&q->queue_lock);
2320out:
2321 bio_set_flag(bio, BIO_THROTTLED);
2322
2323#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2324 if (throttled || !td->track_bio_latency)
2325 bio->bi_issue.value |= BIO_ISSUE_THROTL_SKIP_LATENCY;
2326#endif
2327 rcu_read_unlock();
2328 return throttled;
2329}
2330
2331#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2332static void throtl_track_latency(struct throtl_data *td, sector_t size,
2333 int op, unsigned long time)
2334{
2335 struct latency_bucket *latency;
2336 int index;
2337
2338 if (!td || td->limit_index != LIMIT_LOW ||
2339 !(op == REQ_OP_READ || op == REQ_OP_WRITE) ||
2340 !blk_queue_nonrot(td->queue))
2341 return;
2342
2343 index = request_bucket_index(size);
2344
2345 latency = get_cpu_ptr(td->latency_buckets[op]);
2346 latency[index].total_latency += time;
2347 latency[index].samples++;
2348 put_cpu_ptr(td->latency_buckets[op]);
2349}
2350
2351void blk_throtl_stat_add(struct request *rq, u64 time_ns)
2352{
2353 struct request_queue *q = rq->q;
2354 struct throtl_data *td = q->td;
2355
2356 throtl_track_latency(td, blk_rq_stats_sectors(rq), req_op(rq),
2357 time_ns >> 10);
2358}
2359
2360void blk_throtl_bio_endio(struct bio *bio)
2361{
2362 struct blkcg_gq *blkg;
2363 struct throtl_grp *tg;
2364 u64 finish_time_ns;
2365 unsigned long finish_time;
2366 unsigned long start_time;
2367 unsigned long lat;
2368 int rw = bio_data_dir(bio);
2369
2370 blkg = bio->bi_blkg;
2371 if (!blkg)
2372 return;
2373 tg = blkg_to_tg(blkg);
2374 if (!tg->td->limit_valid[LIMIT_LOW])
2375 return;
2376
2377 finish_time_ns = ktime_get_ns();
2378 tg->last_finish_time = finish_time_ns >> 10;
2379
2380 start_time = bio_issue_time(&bio->bi_issue) >> 10;
2381 finish_time = __bio_issue_time(finish_time_ns) >> 10;
2382 if (!start_time || finish_time <= start_time)
2383 return;
2384
2385 lat = finish_time - start_time;
2386 /* this is only for bio based driver */
2387 if (!(bio->bi_issue.value & BIO_ISSUE_THROTL_SKIP_LATENCY))
2388 throtl_track_latency(tg->td, bio_issue_size(&bio->bi_issue),
2389 bio_op(bio), lat);
2390
2391 if (tg->latency_target && lat >= tg->td->filtered_latency) {
2392 int bucket;
2393 unsigned int threshold;
2394
2395 bucket = request_bucket_index(bio_issue_size(&bio->bi_issue));
2396 threshold = tg->td->avg_buckets[rw][bucket].latency +
2397 tg->latency_target;
2398 if (lat > threshold)
2399 tg->bad_bio_cnt++;
2400 /*
2401 * Not race free, could get wrong count, which means cgroups
2402 * will be throttled
2403 */
2404 tg->bio_cnt++;
2405 }
2406
2407 if (time_after(jiffies, tg->bio_cnt_reset_time) || tg->bio_cnt > 1024) {
2408 tg->bio_cnt_reset_time = tg->td->throtl_slice + jiffies;
2409 tg->bio_cnt /= 2;
2410 tg->bad_bio_cnt /= 2;
2411 }
2412}
2413#endif
2414
2415int blk_throtl_init(struct request_queue *q)
2416{
2417 struct throtl_data *td;
2418 int ret;
2419
2420 td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
2421 if (!td)
2422 return -ENOMEM;
2423 td->latency_buckets[READ] = __alloc_percpu(sizeof(struct latency_bucket) *
2424 LATENCY_BUCKET_SIZE, __alignof__(u64));
2425 if (!td->latency_buckets[READ]) {
2426 kfree(td);
2427 return -ENOMEM;
2428 }
2429 td->latency_buckets[WRITE] = __alloc_percpu(sizeof(struct latency_bucket) *
2430 LATENCY_BUCKET_SIZE, __alignof__(u64));
2431 if (!td->latency_buckets[WRITE]) {
2432 free_percpu(td->latency_buckets[READ]);
2433 kfree(td);
2434 return -ENOMEM;
2435 }
2436
2437 INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
2438 throtl_service_queue_init(&td->service_queue);
2439
2440 q->td = td;
2441 td->queue = q;
2442
2443 td->limit_valid[LIMIT_MAX] = true;
2444 td->limit_index = LIMIT_MAX;
2445 td->low_upgrade_time = jiffies;
2446 td->low_downgrade_time = jiffies;
2447
2448 /* activate policy */
2449 ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
2450 if (ret) {
2451 free_percpu(td->latency_buckets[READ]);
2452 free_percpu(td->latency_buckets[WRITE]);
2453 kfree(td);
2454 }
2455 return ret;
2456}
2457
2458void blk_throtl_exit(struct request_queue *q)
2459{
2460 BUG_ON(!q->td);
2461 del_timer_sync(&q->td->service_queue.pending_timer);
2462 throtl_shutdown_wq(q);
2463 blkcg_deactivate_policy(q, &blkcg_policy_throtl);
2464 free_percpu(q->td->latency_buckets[READ]);
2465 free_percpu(q->td->latency_buckets[WRITE]);
2466 kfree(q->td);
2467}
2468
2469void blk_throtl_register_queue(struct request_queue *q)
2470{
2471 struct throtl_data *td;
2472 int i;
2473
2474 td = q->td;
2475 BUG_ON(!td);
2476
2477 if (blk_queue_nonrot(q)) {
2478 td->throtl_slice = DFL_THROTL_SLICE_SSD;
2479 td->filtered_latency = LATENCY_FILTERED_SSD;
2480 } else {
2481 td->throtl_slice = DFL_THROTL_SLICE_HD;
2482 td->filtered_latency = LATENCY_FILTERED_HD;
2483 for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
2484 td->avg_buckets[READ][i].latency = DFL_HD_BASELINE_LATENCY;
2485 td->avg_buckets[WRITE][i].latency = DFL_HD_BASELINE_LATENCY;
2486 }
2487 }
2488#ifndef CONFIG_BLK_DEV_THROTTLING_LOW
2489 /* if no low limit, use previous default */
2490 td->throtl_slice = DFL_THROTL_SLICE_HD;
2491#endif
2492
2493 td->track_bio_latency = !queue_is_mq(q);
2494 if (!td->track_bio_latency)
2495 blk_stat_enable_accounting(q);
2496}
2497
2498#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2499ssize_t blk_throtl_sample_time_show(struct request_queue *q, char *page)
2500{
2501 if (!q->td)
2502 return -EINVAL;
2503 return sprintf(page, "%u\n", jiffies_to_msecs(q->td->throtl_slice));
2504}
2505
2506ssize_t blk_throtl_sample_time_store(struct request_queue *q,
2507 const char *page, size_t count)
2508{
2509 unsigned long v;
2510 unsigned long t;
2511
2512 if (!q->td)
2513 return -EINVAL;
2514 if (kstrtoul(page, 10, &v))
2515 return -EINVAL;
2516 t = msecs_to_jiffies(v);
2517 if (t == 0 || t > MAX_THROTL_SLICE)
2518 return -EINVAL;
2519 q->td->throtl_slice = t;
2520 return count;
2521}
2522#endif
2523
2524static int __init throtl_init(void)
2525{
2526 kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
2527 if (!kthrotld_workqueue)
2528 panic("Failed to create kthrotld\n");
2529
2530 return blkcg_policy_register(&blkcg_policy_throtl);
2531}
2532
2533module_init(throtl_init);