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