2 * Interface for controlling IO bandwidth on a request queue
4 * Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com>
7 #include <linux/module.h>
8 #include <linux/slab.h>
9 #include <linux/blkdev.h>
10 #include <linux/bio.h>
11 #include <linux/blktrace_api.h>
12 #include "blk-cgroup.h"
15 /* Max dispatch from a group in 1 round */
16 static int throtl_grp_quantum
= 8;
18 /* Total max dispatch from all groups in one round */
19 static int throtl_quantum
= 32;
21 /* Throttling is performed over 100ms slice and after that slice is renewed */
22 static unsigned long throtl_slice
= HZ
/10; /* 100 ms */
24 static struct blkcg_policy blkcg_policy_throtl
;
26 /* A workqueue to queue throttle related work */
27 static struct workqueue_struct
*kthrotld_workqueue
;
29 struct throtl_service_queue
{
30 struct throtl_service_queue
*parent_sq
; /* the parent service_queue */
33 * Bios queued directly to this service_queue or dispatched from
34 * children throtl_grp's.
36 struct bio_list bio_lists
[2]; /* queued bios [READ/WRITE] */
37 unsigned int nr_queued
[2]; /* number of queued bios */
40 * RB tree of active children throtl_grp's, which are sorted by
43 struct rb_root pending_tree
; /* RB tree of active tgs */
44 struct rb_node
*first_pending
; /* first node in the tree */
45 unsigned int nr_pending
; /* # queued in the tree */
46 unsigned long first_pending_disptime
; /* disptime of the first tg */
47 struct timer_list pending_timer
; /* fires on first_pending_disptime */
51 THROTL_TG_PENDING
= 1 << 0, /* on parent's pending tree */
52 THROTL_TG_WAS_EMPTY
= 1 << 1, /* bio_lists[] became non-empty */
55 #define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
57 /* Per-cpu group stats */
59 /* total bytes transferred */
60 struct blkg_rwstat service_bytes
;
61 /* total IOs serviced, post merge */
62 struct blkg_rwstat serviced
;
66 /* must be the first member */
67 struct blkg_policy_data pd
;
69 /* active throtl group service_queue member */
70 struct rb_node rb_node
;
72 /* throtl_data this group belongs to */
73 struct throtl_data
*td
;
75 /* this group's service queue */
76 struct throtl_service_queue service_queue
;
79 * Dispatch time in jiffies. This is the estimated time when group
80 * will unthrottle and is ready to dispatch more bio. It is used as
81 * key to sort active groups in service tree.
83 unsigned long disptime
;
87 /* bytes per second rate limits */
93 /* Number of bytes disptached in current slice */
94 uint64_t bytes_disp
[2];
95 /* Number of bio's dispatched in current slice */
96 unsigned int io_disp
[2];
98 /* When did we start a new slice */
99 unsigned long slice_start
[2];
100 unsigned long slice_end
[2];
102 /* Per cpu stats pointer */
103 struct tg_stats_cpu __percpu
*stats_cpu
;
105 /* List of tgs waiting for per cpu stats memory to be allocated */
106 struct list_head stats_alloc_node
;
111 /* service tree for active throtl groups */
112 struct throtl_service_queue service_queue
;
114 struct request_queue
*queue
;
116 /* Total Number of queued bios on READ and WRITE lists */
117 unsigned int nr_queued
[2];
120 * number of total undestroyed groups
122 unsigned int nr_undestroyed_grps
;
124 /* Work for dispatching throttled bios */
125 struct work_struct dispatch_work
;
128 /* list and work item to allocate percpu group stats */
129 static DEFINE_SPINLOCK(tg_stats_alloc_lock
);
130 static LIST_HEAD(tg_stats_alloc_list
);
132 static void tg_stats_alloc_fn(struct work_struct
*);
133 static DECLARE_DELAYED_WORK(tg_stats_alloc_work
, tg_stats_alloc_fn
);
135 static void throtl_pending_timer_fn(unsigned long arg
);
137 static inline struct throtl_grp
*pd_to_tg(struct blkg_policy_data
*pd
)
139 return pd
? container_of(pd
, struct throtl_grp
, pd
) : NULL
;
142 static inline struct throtl_grp
*blkg_to_tg(struct blkcg_gq
*blkg
)
144 return pd_to_tg(blkg_to_pd(blkg
, &blkcg_policy_throtl
));
147 static inline struct blkcg_gq
*tg_to_blkg(struct throtl_grp
*tg
)
149 return pd_to_blkg(&tg
->pd
);
152 static inline struct throtl_grp
*td_root_tg(struct throtl_data
*td
)
154 return blkg_to_tg(td
->queue
->root_blkg
);
158 * sq_to_tg - return the throl_grp the specified service queue belongs to
159 * @sq: the throtl_service_queue of interest
161 * Return the throtl_grp @sq belongs to. If @sq is the top-level one
162 * embedded in throtl_data, %NULL is returned.
164 static struct throtl_grp
*sq_to_tg(struct throtl_service_queue
*sq
)
166 if (sq
&& sq
->parent_sq
)
167 return container_of(sq
, struct throtl_grp
, service_queue
);
173 * sq_to_td - return throtl_data the specified service queue belongs to
174 * @sq: the throtl_service_queue of interest
176 * A service_queue can be embeded in either a throtl_grp or throtl_data.
177 * Determine the associated throtl_data accordingly and return it.
179 static struct throtl_data
*sq_to_td(struct throtl_service_queue
*sq
)
181 struct throtl_grp
*tg
= sq_to_tg(sq
);
186 return container_of(sq
, struct throtl_data
, service_queue
);
190 * throtl_log - log debug message via blktrace
191 * @sq: the service_queue being reported
192 * @fmt: printf format string
195 * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
196 * throtl_grp; otherwise, just "throtl".
198 * TODO: this should be made a function and name formatting should happen
199 * after testing whether blktrace is enabled.
201 #define throtl_log(sq, fmt, args...) do { \
202 struct throtl_grp *__tg = sq_to_tg((sq)); \
203 struct throtl_data *__td = sq_to_td((sq)); \
209 blkg_path(tg_to_blkg(__tg), __pbuf, sizeof(__pbuf)); \
210 blk_add_trace_msg(__td->queue, "throtl %s " fmt, __pbuf, ##args); \
212 blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \
217 * Worker for allocating per cpu stat for tgs. This is scheduled on the
218 * system_wq once there are some groups on the alloc_list waiting for
221 static void tg_stats_alloc_fn(struct work_struct
*work
)
223 static struct tg_stats_cpu
*stats_cpu
; /* this fn is non-reentrant */
224 struct delayed_work
*dwork
= to_delayed_work(work
);
229 stats_cpu
= alloc_percpu(struct tg_stats_cpu
);
231 /* allocation failed, try again after some time */
232 schedule_delayed_work(dwork
, msecs_to_jiffies(10));
237 spin_lock_irq(&tg_stats_alloc_lock
);
239 if (!list_empty(&tg_stats_alloc_list
)) {
240 struct throtl_grp
*tg
= list_first_entry(&tg_stats_alloc_list
,
243 swap(tg
->stats_cpu
, stats_cpu
);
244 list_del_init(&tg
->stats_alloc_node
);
247 empty
= list_empty(&tg_stats_alloc_list
);
248 spin_unlock_irq(&tg_stats_alloc_lock
);
253 /* init a service_queue, assumes the caller zeroed it */
254 static void throtl_service_queue_init(struct throtl_service_queue
*sq
,
255 struct throtl_service_queue
*parent_sq
)
257 bio_list_init(&sq
->bio_lists
[0]);
258 bio_list_init(&sq
->bio_lists
[1]);
259 sq
->pending_tree
= RB_ROOT
;
260 sq
->parent_sq
= parent_sq
;
261 setup_timer(&sq
->pending_timer
, throtl_pending_timer_fn
,
265 static void throtl_service_queue_exit(struct throtl_service_queue
*sq
)
267 del_timer_sync(&sq
->pending_timer
);
270 static void throtl_pd_init(struct blkcg_gq
*blkg
)
272 struct throtl_grp
*tg
= blkg_to_tg(blkg
);
273 struct throtl_data
*td
= blkg
->q
->td
;
276 throtl_service_queue_init(&tg
->service_queue
, &td
->service_queue
);
277 RB_CLEAR_NODE(&tg
->rb_node
);
283 tg
->iops
[WRITE
] = -1;
286 * Ugh... We need to perform per-cpu allocation for tg->stats_cpu
287 * but percpu allocator can't be called from IO path. Queue tg on
288 * tg_stats_alloc_list and allocate from work item.
290 spin_lock_irqsave(&tg_stats_alloc_lock
, flags
);
291 list_add(&tg
->stats_alloc_node
, &tg_stats_alloc_list
);
292 schedule_delayed_work(&tg_stats_alloc_work
, 0);
293 spin_unlock_irqrestore(&tg_stats_alloc_lock
, flags
);
296 static void throtl_pd_exit(struct blkcg_gq
*blkg
)
298 struct throtl_grp
*tg
= blkg_to_tg(blkg
);
301 spin_lock_irqsave(&tg_stats_alloc_lock
, flags
);
302 list_del_init(&tg
->stats_alloc_node
);
303 spin_unlock_irqrestore(&tg_stats_alloc_lock
, flags
);
305 free_percpu(tg
->stats_cpu
);
307 throtl_service_queue_exit(&tg
->service_queue
);
310 static void throtl_pd_reset_stats(struct blkcg_gq
*blkg
)
312 struct throtl_grp
*tg
= blkg_to_tg(blkg
);
315 if (tg
->stats_cpu
== NULL
)
318 for_each_possible_cpu(cpu
) {
319 struct tg_stats_cpu
*sc
= per_cpu_ptr(tg
->stats_cpu
, cpu
);
321 blkg_rwstat_reset(&sc
->service_bytes
);
322 blkg_rwstat_reset(&sc
->serviced
);
326 static struct throtl_grp
*throtl_lookup_tg(struct throtl_data
*td
,
330 * This is the common case when there are no blkcgs. Avoid lookup
333 if (blkcg
== &blkcg_root
)
334 return td_root_tg(td
);
336 return blkg_to_tg(blkg_lookup(blkcg
, td
->queue
));
339 static struct throtl_grp
*throtl_lookup_create_tg(struct throtl_data
*td
,
342 struct request_queue
*q
= td
->queue
;
343 struct throtl_grp
*tg
= NULL
;
346 * This is the common case when there are no blkcgs. Avoid lookup
349 if (blkcg
== &blkcg_root
) {
352 struct blkcg_gq
*blkg
;
354 blkg
= blkg_lookup_create(blkcg
, q
);
356 /* if %NULL and @q is alive, fall back to root_tg */
358 tg
= blkg_to_tg(blkg
);
359 else if (!blk_queue_dying(q
))
366 static struct throtl_grp
*
367 throtl_rb_first(struct throtl_service_queue
*parent_sq
)
369 /* Service tree is empty */
370 if (!parent_sq
->nr_pending
)
373 if (!parent_sq
->first_pending
)
374 parent_sq
->first_pending
= rb_first(&parent_sq
->pending_tree
);
376 if (parent_sq
->first_pending
)
377 return rb_entry_tg(parent_sq
->first_pending
);
382 static void rb_erase_init(struct rb_node
*n
, struct rb_root
*root
)
388 static void throtl_rb_erase(struct rb_node
*n
,
389 struct throtl_service_queue
*parent_sq
)
391 if (parent_sq
->first_pending
== n
)
392 parent_sq
->first_pending
= NULL
;
393 rb_erase_init(n
, &parent_sq
->pending_tree
);
394 --parent_sq
->nr_pending
;
397 static void update_min_dispatch_time(struct throtl_service_queue
*parent_sq
)
399 struct throtl_grp
*tg
;
401 tg
= throtl_rb_first(parent_sq
);
405 parent_sq
->first_pending_disptime
= tg
->disptime
;
408 static void tg_service_queue_add(struct throtl_grp
*tg
)
410 struct throtl_service_queue
*parent_sq
= tg
->service_queue
.parent_sq
;
411 struct rb_node
**node
= &parent_sq
->pending_tree
.rb_node
;
412 struct rb_node
*parent
= NULL
;
413 struct throtl_grp
*__tg
;
414 unsigned long key
= tg
->disptime
;
417 while (*node
!= NULL
) {
419 __tg
= rb_entry_tg(parent
);
421 if (time_before(key
, __tg
->disptime
))
422 node
= &parent
->rb_left
;
424 node
= &parent
->rb_right
;
430 parent_sq
->first_pending
= &tg
->rb_node
;
432 rb_link_node(&tg
->rb_node
, parent
, node
);
433 rb_insert_color(&tg
->rb_node
, &parent_sq
->pending_tree
);
436 static void __throtl_enqueue_tg(struct throtl_grp
*tg
)
438 tg_service_queue_add(tg
);
439 tg
->flags
|= THROTL_TG_PENDING
;
440 tg
->service_queue
.parent_sq
->nr_pending
++;
443 static void throtl_enqueue_tg(struct throtl_grp
*tg
)
445 if (!(tg
->flags
& THROTL_TG_PENDING
))
446 __throtl_enqueue_tg(tg
);
449 static void __throtl_dequeue_tg(struct throtl_grp
*tg
)
451 throtl_rb_erase(&tg
->rb_node
, tg
->service_queue
.parent_sq
);
452 tg
->flags
&= ~THROTL_TG_PENDING
;
455 static void throtl_dequeue_tg(struct throtl_grp
*tg
)
457 if (tg
->flags
& THROTL_TG_PENDING
)
458 __throtl_dequeue_tg(tg
);
461 /* Call with queue lock held */
462 static void throtl_schedule_pending_timer(struct throtl_service_queue
*sq
,
463 unsigned long expires
)
465 mod_timer(&sq
->pending_timer
, expires
);
466 throtl_log(sq
, "schedule timer. delay=%lu jiffies=%lu",
467 expires
- jiffies
, jiffies
);
470 static void throtl_schedule_next_dispatch(struct throtl_service_queue
*sq
)
472 struct throtl_data
*td
= sq_to_td(sq
);
474 /* any pending children left? */
478 update_min_dispatch_time(sq
);
480 /* is the next dispatch time in the future? */
481 if (time_after(sq
->first_pending_disptime
, jiffies
)) {
482 throtl_schedule_pending_timer(sq
, sq
->first_pending_disptime
);
486 /* kick immediate execution */
487 queue_work(kthrotld_workqueue
, &td
->dispatch_work
);
490 static inline void throtl_start_new_slice(struct throtl_grp
*tg
, bool rw
)
492 tg
->bytes_disp
[rw
] = 0;
494 tg
->slice_start
[rw
] = jiffies
;
495 tg
->slice_end
[rw
] = jiffies
+ throtl_slice
;
496 throtl_log(&tg
->service_queue
,
497 "[%c] new slice start=%lu end=%lu jiffies=%lu",
498 rw
== READ
? 'R' : 'W', tg
->slice_start
[rw
],
499 tg
->slice_end
[rw
], jiffies
);
502 static inline void throtl_set_slice_end(struct throtl_grp
*tg
, bool rw
,
503 unsigned long jiffy_end
)
505 tg
->slice_end
[rw
] = roundup(jiffy_end
, throtl_slice
);
508 static inline void throtl_extend_slice(struct throtl_grp
*tg
, bool rw
,
509 unsigned long jiffy_end
)
511 tg
->slice_end
[rw
] = roundup(jiffy_end
, throtl_slice
);
512 throtl_log(&tg
->service_queue
,
513 "[%c] extend slice start=%lu end=%lu jiffies=%lu",
514 rw
== READ
? 'R' : 'W', tg
->slice_start
[rw
],
515 tg
->slice_end
[rw
], jiffies
);
518 /* Determine if previously allocated or extended slice is complete or not */
519 static bool throtl_slice_used(struct throtl_grp
*tg
, bool rw
)
521 if (time_in_range(jiffies
, tg
->slice_start
[rw
], tg
->slice_end
[rw
]))
527 /* Trim the used slices and adjust slice start accordingly */
528 static inline void throtl_trim_slice(struct throtl_grp
*tg
, bool rw
)
530 unsigned long nr_slices
, time_elapsed
, io_trim
;
533 BUG_ON(time_before(tg
->slice_end
[rw
], tg
->slice_start
[rw
]));
536 * If bps are unlimited (-1), then time slice don't get
537 * renewed. Don't try to trim the slice if slice is used. A new
538 * slice will start when appropriate.
540 if (throtl_slice_used(tg
, rw
))
544 * A bio has been dispatched. Also adjust slice_end. It might happen
545 * that initially cgroup limit was very low resulting in high
546 * slice_end, but later limit was bumped up and bio was dispached
547 * sooner, then we need to reduce slice_end. A high bogus slice_end
548 * is bad because it does not allow new slice to start.
551 throtl_set_slice_end(tg
, rw
, jiffies
+ throtl_slice
);
553 time_elapsed
= jiffies
- tg
->slice_start
[rw
];
555 nr_slices
= time_elapsed
/ throtl_slice
;
559 tmp
= tg
->bps
[rw
] * throtl_slice
* nr_slices
;
563 io_trim
= (tg
->iops
[rw
] * throtl_slice
* nr_slices
)/HZ
;
565 if (!bytes_trim
&& !io_trim
)
568 if (tg
->bytes_disp
[rw
] >= bytes_trim
)
569 tg
->bytes_disp
[rw
] -= bytes_trim
;
571 tg
->bytes_disp
[rw
] = 0;
573 if (tg
->io_disp
[rw
] >= io_trim
)
574 tg
->io_disp
[rw
] -= io_trim
;
578 tg
->slice_start
[rw
] += nr_slices
* throtl_slice
;
580 throtl_log(&tg
->service_queue
,
581 "[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu",
582 rw
== READ
? 'R' : 'W', nr_slices
, bytes_trim
, io_trim
,
583 tg
->slice_start
[rw
], tg
->slice_end
[rw
], jiffies
);
586 static bool tg_with_in_iops_limit(struct throtl_grp
*tg
, struct bio
*bio
,
589 bool rw
= bio_data_dir(bio
);
590 unsigned int io_allowed
;
591 unsigned long jiffy_elapsed
, jiffy_wait
, jiffy_elapsed_rnd
;
594 jiffy_elapsed
= jiffy_elapsed_rnd
= jiffies
- tg
->slice_start
[rw
];
596 /* Slice has just started. Consider one slice interval */
598 jiffy_elapsed_rnd
= throtl_slice
;
600 jiffy_elapsed_rnd
= roundup(jiffy_elapsed_rnd
, throtl_slice
);
603 * jiffy_elapsed_rnd should not be a big value as minimum iops can be
604 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
605 * will allow dispatch after 1 second and after that slice should
609 tmp
= (u64
)tg
->iops
[rw
] * jiffy_elapsed_rnd
;
613 io_allowed
= UINT_MAX
;
617 if (tg
->io_disp
[rw
] + 1 <= io_allowed
) {
623 /* Calc approx time to dispatch */
624 jiffy_wait
= ((tg
->io_disp
[rw
] + 1) * HZ
)/tg
->iops
[rw
] + 1;
626 if (jiffy_wait
> jiffy_elapsed
)
627 jiffy_wait
= jiffy_wait
- jiffy_elapsed
;
636 static bool tg_with_in_bps_limit(struct throtl_grp
*tg
, struct bio
*bio
,
639 bool rw
= bio_data_dir(bio
);
640 u64 bytes_allowed
, extra_bytes
, tmp
;
641 unsigned long jiffy_elapsed
, jiffy_wait
, jiffy_elapsed_rnd
;
643 jiffy_elapsed
= jiffy_elapsed_rnd
= jiffies
- tg
->slice_start
[rw
];
645 /* Slice has just started. Consider one slice interval */
647 jiffy_elapsed_rnd
= throtl_slice
;
649 jiffy_elapsed_rnd
= roundup(jiffy_elapsed_rnd
, throtl_slice
);
651 tmp
= tg
->bps
[rw
] * jiffy_elapsed_rnd
;
655 if (tg
->bytes_disp
[rw
] + bio
->bi_size
<= bytes_allowed
) {
661 /* Calc approx time to dispatch */
662 extra_bytes
= tg
->bytes_disp
[rw
] + bio
->bi_size
- bytes_allowed
;
663 jiffy_wait
= div64_u64(extra_bytes
* HZ
, tg
->bps
[rw
]);
669 * This wait time is without taking into consideration the rounding
670 * up we did. Add that time also.
672 jiffy_wait
= jiffy_wait
+ (jiffy_elapsed_rnd
- jiffy_elapsed
);
678 static bool tg_no_rule_group(struct throtl_grp
*tg
, bool rw
) {
679 if (tg
->bps
[rw
] == -1 && tg
->iops
[rw
] == -1)
685 * Returns whether one can dispatch a bio or not. Also returns approx number
686 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
688 static bool tg_may_dispatch(struct throtl_grp
*tg
, struct bio
*bio
,
691 bool rw
= bio_data_dir(bio
);
692 unsigned long bps_wait
= 0, iops_wait
= 0, max_wait
= 0;
695 * Currently whole state machine of group depends on first bio
696 * queued in the group bio list. So one should not be calling
697 * this function with a different bio if there are other bios
700 BUG_ON(tg
->service_queue
.nr_queued
[rw
] &&
701 bio
!= bio_list_peek(&tg
->service_queue
.bio_lists
[rw
]));
703 /* If tg->bps = -1, then BW is unlimited */
704 if (tg
->bps
[rw
] == -1 && tg
->iops
[rw
] == -1) {
711 * If previous slice expired, start a new one otherwise renew/extend
712 * existing slice to make sure it is at least throtl_slice interval
715 if (throtl_slice_used(tg
, rw
))
716 throtl_start_new_slice(tg
, rw
);
718 if (time_before(tg
->slice_end
[rw
], jiffies
+ throtl_slice
))
719 throtl_extend_slice(tg
, rw
, jiffies
+ throtl_slice
);
722 if (tg_with_in_bps_limit(tg
, bio
, &bps_wait
) &&
723 tg_with_in_iops_limit(tg
, bio
, &iops_wait
)) {
729 max_wait
= max(bps_wait
, iops_wait
);
734 if (time_before(tg
->slice_end
[rw
], jiffies
+ max_wait
))
735 throtl_extend_slice(tg
, rw
, jiffies
+ max_wait
);
740 static void throtl_update_dispatch_stats(struct blkcg_gq
*blkg
, u64 bytes
,
743 struct throtl_grp
*tg
= blkg_to_tg(blkg
);
744 struct tg_stats_cpu
*stats_cpu
;
747 /* If per cpu stats are not allocated yet, don't do any accounting. */
748 if (tg
->stats_cpu
== NULL
)
752 * Disabling interrupts to provide mutual exclusion between two
753 * writes on same cpu. It probably is not needed for 64bit. Not
754 * optimizing that case yet.
756 local_irq_save(flags
);
758 stats_cpu
= this_cpu_ptr(tg
->stats_cpu
);
760 blkg_rwstat_add(&stats_cpu
->serviced
, rw
, 1);
761 blkg_rwstat_add(&stats_cpu
->service_bytes
, rw
, bytes
);
763 local_irq_restore(flags
);
766 static void throtl_charge_bio(struct throtl_grp
*tg
, struct bio
*bio
)
768 bool rw
= bio_data_dir(bio
);
770 /* Charge the bio to the group */
771 tg
->bytes_disp
[rw
] += bio
->bi_size
;
775 * REQ_THROTTLED is used to prevent the same bio to be throttled
776 * more than once as a throttled bio will go through blk-throtl the
777 * second time when it eventually gets issued. Set it when a bio
778 * is being charged to a tg.
780 * Dispatch stats aren't recursive and each @bio should only be
781 * accounted by the @tg it was originally associated with. Let's
782 * update the stats when setting REQ_THROTTLED for the first time
783 * which is guaranteed to be for the @bio's original tg.
785 if (!(bio
->bi_rw
& REQ_THROTTLED
)) {
786 bio
->bi_rw
|= REQ_THROTTLED
;
787 throtl_update_dispatch_stats(tg_to_blkg(tg
), bio
->bi_size
,
792 static void throtl_add_bio_tg(struct bio
*bio
, struct throtl_grp
*tg
)
794 struct throtl_service_queue
*sq
= &tg
->service_queue
;
795 bool rw
= bio_data_dir(bio
);
798 * If @tg doesn't currently have any bios queued in the same
799 * direction, queueing @bio can change when @tg should be
800 * dispatched. Mark that @tg was empty. This is automatically
801 * cleaered on the next tg_update_disptime().
803 if (!sq
->nr_queued
[rw
])
804 tg
->flags
|= THROTL_TG_WAS_EMPTY
;
806 bio_list_add(&sq
->bio_lists
[rw
], bio
);
807 /* Take a bio reference on tg */
808 blkg_get(tg_to_blkg(tg
));
810 tg
->td
->nr_queued
[rw
]++;
811 throtl_enqueue_tg(tg
);
814 static void tg_update_disptime(struct throtl_grp
*tg
)
816 struct throtl_service_queue
*sq
= &tg
->service_queue
;
817 unsigned long read_wait
= -1, write_wait
= -1, min_wait
= -1, disptime
;
820 if ((bio
= bio_list_peek(&sq
->bio_lists
[READ
])))
821 tg_may_dispatch(tg
, bio
, &read_wait
);
823 if ((bio
= bio_list_peek(&sq
->bio_lists
[WRITE
])))
824 tg_may_dispatch(tg
, bio
, &write_wait
);
826 min_wait
= min(read_wait
, write_wait
);
827 disptime
= jiffies
+ min_wait
;
829 /* Update dispatch time */
830 throtl_dequeue_tg(tg
);
831 tg
->disptime
= disptime
;
832 throtl_enqueue_tg(tg
);
834 /* see throtl_add_bio_tg() */
835 tg
->flags
&= ~THROTL_TG_WAS_EMPTY
;
838 static void tg_dispatch_one_bio(struct throtl_grp
*tg
, bool rw
)
840 struct throtl_service_queue
*sq
= &tg
->service_queue
;
843 bio
= bio_list_pop(&sq
->bio_lists
[rw
]);
845 /* Drop bio reference on blkg */
846 blkg_put(tg_to_blkg(tg
));
848 BUG_ON(tg
->td
->nr_queued
[rw
] <= 0);
849 tg
->td
->nr_queued
[rw
]--;
851 throtl_charge_bio(tg
, bio
);
852 bio_list_add(&sq
->parent_sq
->bio_lists
[rw
], bio
);
854 throtl_trim_slice(tg
, rw
);
857 static int throtl_dispatch_tg(struct throtl_grp
*tg
)
859 struct throtl_service_queue
*sq
= &tg
->service_queue
;
860 unsigned int nr_reads
= 0, nr_writes
= 0;
861 unsigned int max_nr_reads
= throtl_grp_quantum
*3/4;
862 unsigned int max_nr_writes
= throtl_grp_quantum
- max_nr_reads
;
865 /* Try to dispatch 75% READS and 25% WRITES */
867 while ((bio
= bio_list_peek(&sq
->bio_lists
[READ
])) &&
868 tg_may_dispatch(tg
, bio
, NULL
)) {
870 tg_dispatch_one_bio(tg
, bio_data_dir(bio
));
873 if (nr_reads
>= max_nr_reads
)
877 while ((bio
= bio_list_peek(&sq
->bio_lists
[WRITE
])) &&
878 tg_may_dispatch(tg
, bio
, NULL
)) {
880 tg_dispatch_one_bio(tg
, bio_data_dir(bio
));
883 if (nr_writes
>= max_nr_writes
)
887 return nr_reads
+ nr_writes
;
890 static int throtl_select_dispatch(struct throtl_service_queue
*parent_sq
)
892 unsigned int nr_disp
= 0;
895 struct throtl_grp
*tg
= throtl_rb_first(parent_sq
);
896 struct throtl_service_queue
*sq
= &tg
->service_queue
;
901 if (time_before(jiffies
, tg
->disptime
))
904 throtl_dequeue_tg(tg
);
906 nr_disp
+= throtl_dispatch_tg(tg
);
908 if (sq
->nr_queued
[0] || sq
->nr_queued
[1])
909 tg_update_disptime(tg
);
911 if (nr_disp
>= throtl_quantum
)
918 static void throtl_pending_timer_fn(unsigned long arg
)
920 struct throtl_service_queue
*sq
= (void *)arg
;
921 struct throtl_data
*td
= sq_to_td(sq
);
923 queue_work(kthrotld_workqueue
, &td
->dispatch_work
);
926 /* work function to dispatch throttled bios */
927 void blk_throtl_dispatch_work_fn(struct work_struct
*work
)
929 struct throtl_data
*td
= container_of(work
, struct throtl_data
,
931 struct throtl_service_queue
*sq
= &td
->service_queue
;
932 struct request_queue
*q
= td
->queue
;
933 unsigned int nr_disp
= 0;
934 struct bio_list bio_list_on_stack
;
936 struct blk_plug plug
;
939 spin_lock_irq(q
->queue_lock
);
941 bio_list_init(&bio_list_on_stack
);
943 throtl_log(sq
, "dispatch nr_queued=%u read=%u write=%u",
944 td
->nr_queued
[READ
] + td
->nr_queued
[WRITE
],
945 td
->nr_queued
[READ
], td
->nr_queued
[WRITE
]);
947 nr_disp
= throtl_select_dispatch(sq
);
950 for (rw
= READ
; rw
<= WRITE
; rw
++) {
951 bio_list_merge(&bio_list_on_stack
, &sq
->bio_lists
[rw
]);
952 bio_list_init(&sq
->bio_lists
[rw
]);
954 throtl_log(sq
, "bios disp=%u", nr_disp
);
957 throtl_schedule_next_dispatch(sq
);
959 spin_unlock_irq(q
->queue_lock
);
962 * If we dispatched some requests, unplug the queue to make sure
966 blk_start_plug(&plug
);
967 while((bio
= bio_list_pop(&bio_list_on_stack
)))
968 generic_make_request(bio
);
969 blk_finish_plug(&plug
);
973 static u64
tg_prfill_cpu_rwstat(struct seq_file
*sf
,
974 struct blkg_policy_data
*pd
, int off
)
976 struct throtl_grp
*tg
= pd_to_tg(pd
);
977 struct blkg_rwstat rwstat
= { }, tmp
;
980 for_each_possible_cpu(cpu
) {
981 struct tg_stats_cpu
*sc
= per_cpu_ptr(tg
->stats_cpu
, cpu
);
983 tmp
= blkg_rwstat_read((void *)sc
+ off
);
984 for (i
= 0; i
< BLKG_RWSTAT_NR
; i
++)
985 rwstat
.cnt
[i
] += tmp
.cnt
[i
];
988 return __blkg_prfill_rwstat(sf
, pd
, &rwstat
);
991 static int tg_print_cpu_rwstat(struct cgroup
*cgrp
, struct cftype
*cft
,
994 struct blkcg
*blkcg
= cgroup_to_blkcg(cgrp
);
996 blkcg_print_blkgs(sf
, blkcg
, tg_prfill_cpu_rwstat
, &blkcg_policy_throtl
,
1001 static u64
tg_prfill_conf_u64(struct seq_file
*sf
, struct blkg_policy_data
*pd
,
1004 struct throtl_grp
*tg
= pd_to_tg(pd
);
1005 u64 v
= *(u64
*)((void *)tg
+ off
);
1009 return __blkg_prfill_u64(sf
, pd
, v
);
1012 static u64
tg_prfill_conf_uint(struct seq_file
*sf
, struct blkg_policy_data
*pd
,
1015 struct throtl_grp
*tg
= pd_to_tg(pd
);
1016 unsigned int v
= *(unsigned int *)((void *)tg
+ off
);
1020 return __blkg_prfill_u64(sf
, pd
, v
);
1023 static int tg_print_conf_u64(struct cgroup
*cgrp
, struct cftype
*cft
,
1024 struct seq_file
*sf
)
1026 blkcg_print_blkgs(sf
, cgroup_to_blkcg(cgrp
), tg_prfill_conf_u64
,
1027 &blkcg_policy_throtl
, cft
->private, false);
1031 static int tg_print_conf_uint(struct cgroup
*cgrp
, struct cftype
*cft
,
1032 struct seq_file
*sf
)
1034 blkcg_print_blkgs(sf
, cgroup_to_blkcg(cgrp
), tg_prfill_conf_uint
,
1035 &blkcg_policy_throtl
, cft
->private, false);
1039 static int tg_set_conf(struct cgroup
*cgrp
, struct cftype
*cft
, const char *buf
,
1042 struct blkcg
*blkcg
= cgroup_to_blkcg(cgrp
);
1043 struct blkg_conf_ctx ctx
;
1044 struct throtl_grp
*tg
;
1045 struct throtl_service_queue
*sq
;
1048 ret
= blkg_conf_prep(blkcg
, &blkcg_policy_throtl
, buf
, &ctx
);
1052 tg
= blkg_to_tg(ctx
.blkg
);
1053 sq
= &tg
->service_queue
;
1059 *(u64
*)((void *)tg
+ cft
->private) = ctx
.v
;
1061 *(unsigned int *)((void *)tg
+ cft
->private) = ctx
.v
;
1063 throtl_log(&tg
->service_queue
,
1064 "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
1065 tg
->bps
[READ
], tg
->bps
[WRITE
],
1066 tg
->iops
[READ
], tg
->iops
[WRITE
]);
1069 * We're already holding queue_lock and know @tg is valid. Let's
1070 * apply the new config directly.
1072 * Restart the slices for both READ and WRITES. It might happen
1073 * that a group's limit are dropped suddenly and we don't want to
1074 * account recently dispatched IO with new low rate.
1076 throtl_start_new_slice(tg
, 0);
1077 throtl_start_new_slice(tg
, 1);
1079 if (tg
->flags
& THROTL_TG_PENDING
) {
1080 tg_update_disptime(tg
);
1081 throtl_schedule_next_dispatch(sq
->parent_sq
);
1084 blkg_conf_finish(&ctx
);
1088 static int tg_set_conf_u64(struct cgroup
*cgrp
, struct cftype
*cft
,
1091 return tg_set_conf(cgrp
, cft
, buf
, true);
1094 static int tg_set_conf_uint(struct cgroup
*cgrp
, struct cftype
*cft
,
1097 return tg_set_conf(cgrp
, cft
, buf
, false);
1100 static struct cftype throtl_files
[] = {
1102 .name
= "throttle.read_bps_device",
1103 .private = offsetof(struct throtl_grp
, bps
[READ
]),
1104 .read_seq_string
= tg_print_conf_u64
,
1105 .write_string
= tg_set_conf_u64
,
1106 .max_write_len
= 256,
1109 .name
= "throttle.write_bps_device",
1110 .private = offsetof(struct throtl_grp
, bps
[WRITE
]),
1111 .read_seq_string
= tg_print_conf_u64
,
1112 .write_string
= tg_set_conf_u64
,
1113 .max_write_len
= 256,
1116 .name
= "throttle.read_iops_device",
1117 .private = offsetof(struct throtl_grp
, iops
[READ
]),
1118 .read_seq_string
= tg_print_conf_uint
,
1119 .write_string
= tg_set_conf_uint
,
1120 .max_write_len
= 256,
1123 .name
= "throttle.write_iops_device",
1124 .private = offsetof(struct throtl_grp
, iops
[WRITE
]),
1125 .read_seq_string
= tg_print_conf_uint
,
1126 .write_string
= tg_set_conf_uint
,
1127 .max_write_len
= 256,
1130 .name
= "throttle.io_service_bytes",
1131 .private = offsetof(struct tg_stats_cpu
, service_bytes
),
1132 .read_seq_string
= tg_print_cpu_rwstat
,
1135 .name
= "throttle.io_serviced",
1136 .private = offsetof(struct tg_stats_cpu
, serviced
),
1137 .read_seq_string
= tg_print_cpu_rwstat
,
1142 static void throtl_shutdown_wq(struct request_queue
*q
)
1144 struct throtl_data
*td
= q
->td
;
1146 cancel_work_sync(&td
->dispatch_work
);
1149 static struct blkcg_policy blkcg_policy_throtl
= {
1150 .pd_size
= sizeof(struct throtl_grp
),
1151 .cftypes
= throtl_files
,
1153 .pd_init_fn
= throtl_pd_init
,
1154 .pd_exit_fn
= throtl_pd_exit
,
1155 .pd_reset_stats_fn
= throtl_pd_reset_stats
,
1158 bool blk_throtl_bio(struct request_queue
*q
, struct bio
*bio
)
1160 struct throtl_data
*td
= q
->td
;
1161 struct throtl_grp
*tg
;
1162 struct throtl_service_queue
*sq
;
1163 bool rw
= bio_data_dir(bio
);
1164 struct blkcg
*blkcg
;
1165 bool throttled
= false;
1167 /* see throtl_charge_bio() */
1168 if (bio
->bi_rw
& REQ_THROTTLED
)
1172 * A throtl_grp pointer retrieved under rcu can be used to access
1173 * basic fields like stats and io rates. If a group has no rules,
1174 * just update the dispatch stats in lockless manner and return.
1177 blkcg
= bio_blkcg(bio
);
1178 tg
= throtl_lookup_tg(td
, blkcg
);
1180 if (tg_no_rule_group(tg
, rw
)) {
1181 throtl_update_dispatch_stats(tg_to_blkg(tg
),
1182 bio
->bi_size
, bio
->bi_rw
);
1183 goto out_unlock_rcu
;
1188 * Either group has not been allocated yet or it is not an unlimited
1191 spin_lock_irq(q
->queue_lock
);
1192 tg
= throtl_lookup_create_tg(td
, blkcg
);
1196 sq
= &tg
->service_queue
;
1198 /* throtl is FIFO - if other bios are already queued, should queue */
1199 if (sq
->nr_queued
[rw
])
1202 /* Bio is with-in rate limit of group */
1203 if (tg_may_dispatch(tg
, bio
, NULL
)) {
1204 throtl_charge_bio(tg
, bio
);
1207 * We need to trim slice even when bios are not being queued
1208 * otherwise it might happen that a bio is not queued for
1209 * a long time and slice keeps on extending and trim is not
1210 * called for a long time. Now if limits are reduced suddenly
1211 * we take into account all the IO dispatched so far at new
1212 * low rate and * newly queued IO gets a really long dispatch
1215 * So keep on trimming slice even if bio is not queued.
1217 throtl_trim_slice(tg
, rw
);
1222 throtl_log(sq
, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
1223 rw
== READ
? 'R' : 'W',
1224 tg
->bytes_disp
[rw
], bio
->bi_size
, tg
->bps
[rw
],
1225 tg
->io_disp
[rw
], tg
->iops
[rw
],
1226 sq
->nr_queued
[READ
], sq
->nr_queued
[WRITE
]);
1228 bio_associate_current(bio
);
1229 throtl_add_bio_tg(bio
, tg
);
1232 /* update @tg's dispatch time if @tg was empty before @bio */
1233 if (tg
->flags
& THROTL_TG_WAS_EMPTY
) {
1234 tg_update_disptime(tg
);
1235 throtl_schedule_next_dispatch(tg
->service_queue
.parent_sq
);
1239 spin_unlock_irq(q
->queue_lock
);
1244 * As multiple blk-throtls may stack in the same issue path, we
1245 * don't want bios to leave with the flag set. Clear the flag if
1249 bio
->bi_rw
&= ~REQ_THROTTLED
;
1254 * blk_throtl_drain - drain throttled bios
1255 * @q: request_queue to drain throttled bios for
1257 * Dispatch all currently throttled bios on @q through ->make_request_fn().
1259 void blk_throtl_drain(struct request_queue
*q
)
1260 __releases(q
->queue_lock
) __acquires(q
->queue_lock
)
1262 struct throtl_data
*td
= q
->td
;
1263 struct throtl_service_queue
*parent_sq
= &td
->service_queue
;
1264 struct throtl_grp
*tg
;
1268 queue_lockdep_assert_held(q
);
1270 while ((tg
= throtl_rb_first(parent_sq
))) {
1271 struct throtl_service_queue
*sq
= &tg
->service_queue
;
1273 throtl_dequeue_tg(tg
);
1275 while ((bio
= bio_list_peek(&sq
->bio_lists
[READ
])))
1276 tg_dispatch_one_bio(tg
, bio_data_dir(bio
));
1277 while ((bio
= bio_list_peek(&sq
->bio_lists
[WRITE
])))
1278 tg_dispatch_one_bio(tg
, bio_data_dir(bio
));
1280 spin_unlock_irq(q
->queue_lock
);
1282 for (rw
= READ
; rw
<= WRITE
; rw
++)
1283 while ((bio
= bio_list_pop(&parent_sq
->bio_lists
[rw
])))
1284 generic_make_request(bio
);
1286 spin_lock_irq(q
->queue_lock
);
1289 int blk_throtl_init(struct request_queue
*q
)
1291 struct throtl_data
*td
;
1294 td
= kzalloc_node(sizeof(*td
), GFP_KERNEL
, q
->node
);
1298 INIT_WORK(&td
->dispatch_work
, blk_throtl_dispatch_work_fn
);
1299 throtl_service_queue_init(&td
->service_queue
, NULL
);
1304 /* activate policy */
1305 ret
= blkcg_activate_policy(q
, &blkcg_policy_throtl
);
1311 void blk_throtl_exit(struct request_queue
*q
)
1314 throtl_shutdown_wq(q
);
1315 blkcg_deactivate_policy(q
, &blkcg_policy_throtl
);
1319 static int __init
throtl_init(void)
1321 kthrotld_workqueue
= alloc_workqueue("kthrotld", WQ_MEM_RECLAIM
, 0);
1322 if (!kthrotld_workqueue
)
1323 panic("Failed to create kthrotld\n");
1325 return blkcg_policy_register(&blkcg_policy_throtl
);
1328 module_init(throtl_init
);