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
{
31 * Bios queued directly to this service_queue or dispatched from
32 * children throtl_grp's.
34 struct bio_list bio_lists
[2]; /* queued bios [READ/WRITE] */
35 unsigned int nr_queued
[2]; /* number of queued bios */
38 * RB tree of active children throtl_grp's, which are sorted by
41 struct rb_root pending_tree
; /* RB tree of active tgs */
42 struct rb_node
*first_pending
; /* first node in the tree */
43 unsigned int nr_pending
; /* # queued in the tree */
44 unsigned long first_pending_disptime
; /* disptime of the first tg */
48 THROTL_TG_PENDING
= 1 << 0, /* on parent's pending tree */
51 #define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
53 /* Per-cpu group stats */
55 /* total bytes transferred */
56 struct blkg_rwstat service_bytes
;
57 /* total IOs serviced, post merge */
58 struct blkg_rwstat serviced
;
62 /* must be the first member */
63 struct blkg_policy_data pd
;
65 /* active throtl group service_queue member */
66 struct rb_node rb_node
;
68 /* throtl_data this group belongs to */
69 struct throtl_data
*td
;
71 /* this group's service queue */
72 struct throtl_service_queue service_queue
;
75 * Dispatch time in jiffies. This is the estimated time when group
76 * will unthrottle and is ready to dispatch more bio. It is used as
77 * key to sort active groups in service tree.
79 unsigned long disptime
;
83 /* bytes per second rate limits */
89 /* Number of bytes disptached in current slice */
90 uint64_t bytes_disp
[2];
91 /* Number of bio's dispatched in current slice */
92 unsigned int io_disp
[2];
94 /* When did we start a new slice */
95 unsigned long slice_start
[2];
96 unsigned long slice_end
[2];
98 /* Per cpu stats pointer */
99 struct tg_stats_cpu __percpu
*stats_cpu
;
101 /* List of tgs waiting for per cpu stats memory to be allocated */
102 struct list_head stats_alloc_node
;
107 /* service tree for active throtl groups */
108 struct throtl_service_queue service_queue
;
110 struct request_queue
*queue
;
112 /* Total Number of queued bios on READ and WRITE lists */
113 unsigned int nr_queued
[2];
116 * number of total undestroyed groups
118 unsigned int nr_undestroyed_grps
;
120 /* Work for dispatching throttled bios */
121 struct delayed_work dispatch_work
;
124 /* list and work item to allocate percpu group stats */
125 static DEFINE_SPINLOCK(tg_stats_alloc_lock
);
126 static LIST_HEAD(tg_stats_alloc_list
);
128 static void tg_stats_alloc_fn(struct work_struct
*);
129 static DECLARE_DELAYED_WORK(tg_stats_alloc_work
, tg_stats_alloc_fn
);
131 static inline struct throtl_grp
*pd_to_tg(struct blkg_policy_data
*pd
)
133 return pd
? container_of(pd
, struct throtl_grp
, pd
) : NULL
;
136 static inline struct throtl_grp
*blkg_to_tg(struct blkcg_gq
*blkg
)
138 return pd_to_tg(blkg_to_pd(blkg
, &blkcg_policy_throtl
));
141 static inline struct blkcg_gq
*tg_to_blkg(struct throtl_grp
*tg
)
143 return pd_to_blkg(&tg
->pd
);
146 static inline struct throtl_grp
*td_root_tg(struct throtl_data
*td
)
148 return blkg_to_tg(td
->queue
->root_blkg
);
151 #define throtl_log_tg(tg, fmt, args...) do { \
154 blkg_path(tg_to_blkg(tg), __pbuf, sizeof(__pbuf)); \
155 blk_add_trace_msg((tg)->td->queue, "throtl %s " fmt, __pbuf, ##args); \
158 #define throtl_log(td, fmt, args...) \
159 blk_add_trace_msg((td)->queue, "throtl " fmt, ##args)
162 * Worker for allocating per cpu stat for tgs. This is scheduled on the
163 * system_wq once there are some groups on the alloc_list waiting for
166 static void tg_stats_alloc_fn(struct work_struct
*work
)
168 static struct tg_stats_cpu
*stats_cpu
; /* this fn is non-reentrant */
169 struct delayed_work
*dwork
= to_delayed_work(work
);
174 stats_cpu
= alloc_percpu(struct tg_stats_cpu
);
176 /* allocation failed, try again after some time */
177 schedule_delayed_work(dwork
, msecs_to_jiffies(10));
182 spin_lock_irq(&tg_stats_alloc_lock
);
184 if (!list_empty(&tg_stats_alloc_list
)) {
185 struct throtl_grp
*tg
= list_first_entry(&tg_stats_alloc_list
,
188 swap(tg
->stats_cpu
, stats_cpu
);
189 list_del_init(&tg
->stats_alloc_node
);
192 empty
= list_empty(&tg_stats_alloc_list
);
193 spin_unlock_irq(&tg_stats_alloc_lock
);
198 /* init a service_queue, assumes the caller zeroed it */
199 static void throtl_service_queue_init(struct throtl_service_queue
*sq
)
201 bio_list_init(&sq
->bio_lists
[0]);
202 bio_list_init(&sq
->bio_lists
[1]);
203 sq
->pending_tree
= RB_ROOT
;
206 static void throtl_pd_init(struct blkcg_gq
*blkg
)
208 struct throtl_grp
*tg
= blkg_to_tg(blkg
);
211 throtl_service_queue_init(&tg
->service_queue
);
212 RB_CLEAR_NODE(&tg
->rb_node
);
213 tg
->td
= blkg
->q
->td
;
218 tg
->iops
[WRITE
] = -1;
221 * Ugh... We need to perform per-cpu allocation for tg->stats_cpu
222 * but percpu allocator can't be called from IO path. Queue tg on
223 * tg_stats_alloc_list and allocate from work item.
225 spin_lock_irqsave(&tg_stats_alloc_lock
, flags
);
226 list_add(&tg
->stats_alloc_node
, &tg_stats_alloc_list
);
227 schedule_delayed_work(&tg_stats_alloc_work
, 0);
228 spin_unlock_irqrestore(&tg_stats_alloc_lock
, flags
);
231 static void throtl_pd_exit(struct blkcg_gq
*blkg
)
233 struct throtl_grp
*tg
= blkg_to_tg(blkg
);
236 spin_lock_irqsave(&tg_stats_alloc_lock
, flags
);
237 list_del_init(&tg
->stats_alloc_node
);
238 spin_unlock_irqrestore(&tg_stats_alloc_lock
, flags
);
240 free_percpu(tg
->stats_cpu
);
243 static void throtl_pd_reset_stats(struct blkcg_gq
*blkg
)
245 struct throtl_grp
*tg
= blkg_to_tg(blkg
);
248 if (tg
->stats_cpu
== NULL
)
251 for_each_possible_cpu(cpu
) {
252 struct tg_stats_cpu
*sc
= per_cpu_ptr(tg
->stats_cpu
, cpu
);
254 blkg_rwstat_reset(&sc
->service_bytes
);
255 blkg_rwstat_reset(&sc
->serviced
);
259 static struct throtl_grp
*throtl_lookup_tg(struct throtl_data
*td
,
263 * This is the common case when there are no blkcgs. Avoid lookup
266 if (blkcg
== &blkcg_root
)
267 return td_root_tg(td
);
269 return blkg_to_tg(blkg_lookup(blkcg
, td
->queue
));
272 static struct throtl_grp
*throtl_lookup_create_tg(struct throtl_data
*td
,
275 struct request_queue
*q
= td
->queue
;
276 struct throtl_grp
*tg
= NULL
;
279 * This is the common case when there are no blkcgs. Avoid lookup
282 if (blkcg
== &blkcg_root
) {
285 struct blkcg_gq
*blkg
;
287 blkg
= blkg_lookup_create(blkcg
, q
);
289 /* if %NULL and @q is alive, fall back to root_tg */
291 tg
= blkg_to_tg(blkg
);
292 else if (!blk_queue_dying(q
))
299 static struct throtl_grp
*
300 throtl_rb_first(struct throtl_service_queue
*parent_sq
)
302 /* Service tree is empty */
303 if (!parent_sq
->nr_pending
)
306 if (!parent_sq
->first_pending
)
307 parent_sq
->first_pending
= rb_first(&parent_sq
->pending_tree
);
309 if (parent_sq
->first_pending
)
310 return rb_entry_tg(parent_sq
->first_pending
);
315 static void rb_erase_init(struct rb_node
*n
, struct rb_root
*root
)
321 static void throtl_rb_erase(struct rb_node
*n
,
322 struct throtl_service_queue
*parent_sq
)
324 if (parent_sq
->first_pending
== n
)
325 parent_sq
->first_pending
= NULL
;
326 rb_erase_init(n
, &parent_sq
->pending_tree
);
327 --parent_sq
->nr_pending
;
330 static void update_min_dispatch_time(struct throtl_service_queue
*parent_sq
)
332 struct throtl_grp
*tg
;
334 tg
= throtl_rb_first(parent_sq
);
338 parent_sq
->first_pending_disptime
= tg
->disptime
;
341 static void tg_service_queue_add(struct throtl_grp
*tg
,
342 struct throtl_service_queue
*parent_sq
)
344 struct rb_node
**node
= &parent_sq
->pending_tree
.rb_node
;
345 struct rb_node
*parent
= NULL
;
346 struct throtl_grp
*__tg
;
347 unsigned long key
= tg
->disptime
;
350 while (*node
!= NULL
) {
352 __tg
= rb_entry_tg(parent
);
354 if (time_before(key
, __tg
->disptime
))
355 node
= &parent
->rb_left
;
357 node
= &parent
->rb_right
;
363 parent_sq
->first_pending
= &tg
->rb_node
;
365 rb_link_node(&tg
->rb_node
, parent
, node
);
366 rb_insert_color(&tg
->rb_node
, &parent_sq
->pending_tree
);
369 static void __throtl_enqueue_tg(struct throtl_grp
*tg
,
370 struct throtl_service_queue
*parent_sq
)
372 tg_service_queue_add(tg
, parent_sq
);
373 tg
->flags
|= THROTL_TG_PENDING
;
374 parent_sq
->nr_pending
++;
377 static void throtl_enqueue_tg(struct throtl_grp
*tg
,
378 struct throtl_service_queue
*parent_sq
)
380 if (!(tg
->flags
& THROTL_TG_PENDING
))
381 __throtl_enqueue_tg(tg
, parent_sq
);
384 static void __throtl_dequeue_tg(struct throtl_grp
*tg
,
385 struct throtl_service_queue
*parent_sq
)
387 throtl_rb_erase(&tg
->rb_node
, parent_sq
);
388 tg
->flags
&= ~THROTL_TG_PENDING
;
391 static void throtl_dequeue_tg(struct throtl_grp
*tg
,
392 struct throtl_service_queue
*parent_sq
)
394 if (tg
->flags
& THROTL_TG_PENDING
)
395 __throtl_dequeue_tg(tg
, parent_sq
);
398 /* Call with queue lock held */
399 static void throtl_schedule_delayed_work(struct throtl_data
*td
,
402 struct delayed_work
*dwork
= &td
->dispatch_work
;
404 mod_delayed_work(kthrotld_workqueue
, dwork
, delay
);
405 throtl_log(td
, "schedule work. delay=%lu jiffies=%lu", delay
, jiffies
);
408 static void throtl_schedule_next_dispatch(struct throtl_data
*td
)
410 struct throtl_service_queue
*sq
= &td
->service_queue
;
412 /* any pending children left? */
416 update_min_dispatch_time(sq
);
418 if (time_before_eq(sq
->first_pending_disptime
, jiffies
))
419 throtl_schedule_delayed_work(td
, 0);
421 throtl_schedule_delayed_work(td
, sq
->first_pending_disptime
- jiffies
);
424 static inline void throtl_start_new_slice(struct throtl_grp
*tg
, bool rw
)
426 tg
->bytes_disp
[rw
] = 0;
428 tg
->slice_start
[rw
] = jiffies
;
429 tg
->slice_end
[rw
] = jiffies
+ throtl_slice
;
430 throtl_log_tg(tg
, "[%c] new slice start=%lu end=%lu jiffies=%lu",
431 rw
== READ
? 'R' : 'W', tg
->slice_start
[rw
],
432 tg
->slice_end
[rw
], jiffies
);
435 static inline void throtl_set_slice_end(struct throtl_grp
*tg
, bool rw
,
436 unsigned long jiffy_end
)
438 tg
->slice_end
[rw
] = roundup(jiffy_end
, throtl_slice
);
441 static inline void throtl_extend_slice(struct throtl_grp
*tg
, bool rw
,
442 unsigned long jiffy_end
)
444 tg
->slice_end
[rw
] = roundup(jiffy_end
, throtl_slice
);
445 throtl_log_tg(tg
, "[%c] extend slice start=%lu end=%lu jiffies=%lu",
446 rw
== READ
? 'R' : 'W', tg
->slice_start
[rw
],
447 tg
->slice_end
[rw
], jiffies
);
450 /* Determine if previously allocated or extended slice is complete or not */
451 static bool throtl_slice_used(struct throtl_grp
*tg
, bool rw
)
453 if (time_in_range(jiffies
, tg
->slice_start
[rw
], tg
->slice_end
[rw
]))
459 /* Trim the used slices and adjust slice start accordingly */
460 static inline void throtl_trim_slice(struct throtl_grp
*tg
, bool rw
)
462 unsigned long nr_slices
, time_elapsed
, io_trim
;
465 BUG_ON(time_before(tg
->slice_end
[rw
], tg
->slice_start
[rw
]));
468 * If bps are unlimited (-1), then time slice don't get
469 * renewed. Don't try to trim the slice if slice is used. A new
470 * slice will start when appropriate.
472 if (throtl_slice_used(tg
, rw
))
476 * A bio has been dispatched. Also adjust slice_end. It might happen
477 * that initially cgroup limit was very low resulting in high
478 * slice_end, but later limit was bumped up and bio was dispached
479 * sooner, then we need to reduce slice_end. A high bogus slice_end
480 * is bad because it does not allow new slice to start.
483 throtl_set_slice_end(tg
, rw
, jiffies
+ throtl_slice
);
485 time_elapsed
= jiffies
- tg
->slice_start
[rw
];
487 nr_slices
= time_elapsed
/ throtl_slice
;
491 tmp
= tg
->bps
[rw
] * throtl_slice
* nr_slices
;
495 io_trim
= (tg
->iops
[rw
] * throtl_slice
* nr_slices
)/HZ
;
497 if (!bytes_trim
&& !io_trim
)
500 if (tg
->bytes_disp
[rw
] >= bytes_trim
)
501 tg
->bytes_disp
[rw
] -= bytes_trim
;
503 tg
->bytes_disp
[rw
] = 0;
505 if (tg
->io_disp
[rw
] >= io_trim
)
506 tg
->io_disp
[rw
] -= io_trim
;
510 tg
->slice_start
[rw
] += nr_slices
* throtl_slice
;
512 throtl_log_tg(tg
, "[%c] trim slice nr=%lu bytes=%llu io=%lu"
513 " start=%lu end=%lu jiffies=%lu",
514 rw
== READ
? 'R' : 'W', nr_slices
, bytes_trim
, io_trim
,
515 tg
->slice_start
[rw
], tg
->slice_end
[rw
], jiffies
);
518 static bool tg_with_in_iops_limit(struct throtl_grp
*tg
, struct bio
*bio
,
521 bool rw
= bio_data_dir(bio
);
522 unsigned int io_allowed
;
523 unsigned long jiffy_elapsed
, jiffy_wait
, jiffy_elapsed_rnd
;
526 jiffy_elapsed
= jiffy_elapsed_rnd
= jiffies
- tg
->slice_start
[rw
];
528 /* Slice has just started. Consider one slice interval */
530 jiffy_elapsed_rnd
= throtl_slice
;
532 jiffy_elapsed_rnd
= roundup(jiffy_elapsed_rnd
, throtl_slice
);
535 * jiffy_elapsed_rnd should not be a big value as minimum iops can be
536 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
537 * will allow dispatch after 1 second and after that slice should
541 tmp
= (u64
)tg
->iops
[rw
] * jiffy_elapsed_rnd
;
545 io_allowed
= UINT_MAX
;
549 if (tg
->io_disp
[rw
] + 1 <= io_allowed
) {
555 /* Calc approx time to dispatch */
556 jiffy_wait
= ((tg
->io_disp
[rw
] + 1) * HZ
)/tg
->iops
[rw
] + 1;
558 if (jiffy_wait
> jiffy_elapsed
)
559 jiffy_wait
= jiffy_wait
- jiffy_elapsed
;
568 static bool tg_with_in_bps_limit(struct throtl_grp
*tg
, struct bio
*bio
,
571 bool rw
= bio_data_dir(bio
);
572 u64 bytes_allowed
, extra_bytes
, tmp
;
573 unsigned long jiffy_elapsed
, jiffy_wait
, jiffy_elapsed_rnd
;
575 jiffy_elapsed
= jiffy_elapsed_rnd
= jiffies
- tg
->slice_start
[rw
];
577 /* Slice has just started. Consider one slice interval */
579 jiffy_elapsed_rnd
= throtl_slice
;
581 jiffy_elapsed_rnd
= roundup(jiffy_elapsed_rnd
, throtl_slice
);
583 tmp
= tg
->bps
[rw
] * jiffy_elapsed_rnd
;
587 if (tg
->bytes_disp
[rw
] + bio
->bi_size
<= bytes_allowed
) {
593 /* Calc approx time to dispatch */
594 extra_bytes
= tg
->bytes_disp
[rw
] + bio
->bi_size
- bytes_allowed
;
595 jiffy_wait
= div64_u64(extra_bytes
* HZ
, tg
->bps
[rw
]);
601 * This wait time is without taking into consideration the rounding
602 * up we did. Add that time also.
604 jiffy_wait
= jiffy_wait
+ (jiffy_elapsed_rnd
- jiffy_elapsed
);
610 static bool tg_no_rule_group(struct throtl_grp
*tg
, bool rw
) {
611 if (tg
->bps
[rw
] == -1 && tg
->iops
[rw
] == -1)
617 * Returns whether one can dispatch a bio or not. Also returns approx number
618 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
620 static bool tg_may_dispatch(struct throtl_grp
*tg
, struct bio
*bio
,
623 bool rw
= bio_data_dir(bio
);
624 unsigned long bps_wait
= 0, iops_wait
= 0, max_wait
= 0;
627 * Currently whole state machine of group depends on first bio
628 * queued in the group bio list. So one should not be calling
629 * this function with a different bio if there are other bios
632 BUG_ON(tg
->service_queue
.nr_queued
[rw
] &&
633 bio
!= bio_list_peek(&tg
->service_queue
.bio_lists
[rw
]));
635 /* If tg->bps = -1, then BW is unlimited */
636 if (tg
->bps
[rw
] == -1 && tg
->iops
[rw
] == -1) {
643 * If previous slice expired, start a new one otherwise renew/extend
644 * existing slice to make sure it is at least throtl_slice interval
647 if (throtl_slice_used(tg
, rw
))
648 throtl_start_new_slice(tg
, rw
);
650 if (time_before(tg
->slice_end
[rw
], jiffies
+ throtl_slice
))
651 throtl_extend_slice(tg
, rw
, jiffies
+ throtl_slice
);
654 if (tg_with_in_bps_limit(tg
, bio
, &bps_wait
) &&
655 tg_with_in_iops_limit(tg
, bio
, &iops_wait
)) {
661 max_wait
= max(bps_wait
, iops_wait
);
666 if (time_before(tg
->slice_end
[rw
], jiffies
+ max_wait
))
667 throtl_extend_slice(tg
, rw
, jiffies
+ max_wait
);
672 static void throtl_update_dispatch_stats(struct blkcg_gq
*blkg
, u64 bytes
,
675 struct throtl_grp
*tg
= blkg_to_tg(blkg
);
676 struct tg_stats_cpu
*stats_cpu
;
679 /* If per cpu stats are not allocated yet, don't do any accounting. */
680 if (tg
->stats_cpu
== NULL
)
684 * Disabling interrupts to provide mutual exclusion between two
685 * writes on same cpu. It probably is not needed for 64bit. Not
686 * optimizing that case yet.
688 local_irq_save(flags
);
690 stats_cpu
= this_cpu_ptr(tg
->stats_cpu
);
692 blkg_rwstat_add(&stats_cpu
->serviced
, rw
, 1);
693 blkg_rwstat_add(&stats_cpu
->service_bytes
, rw
, bytes
);
695 local_irq_restore(flags
);
698 static void throtl_charge_bio(struct throtl_grp
*tg
, struct bio
*bio
)
700 bool rw
= bio_data_dir(bio
);
702 /* Charge the bio to the group */
703 tg
->bytes_disp
[rw
] += bio
->bi_size
;
706 throtl_update_dispatch_stats(tg_to_blkg(tg
), bio
->bi_size
, bio
->bi_rw
);
709 static void throtl_add_bio_tg(struct bio
*bio
, struct throtl_grp
*tg
,
710 struct throtl_service_queue
*parent_sq
)
712 struct throtl_service_queue
*sq
= &tg
->service_queue
;
713 bool rw
= bio_data_dir(bio
);
715 bio_list_add(&sq
->bio_lists
[rw
], bio
);
716 /* Take a bio reference on tg */
717 blkg_get(tg_to_blkg(tg
));
719 tg
->td
->nr_queued
[rw
]++;
720 throtl_enqueue_tg(tg
, parent_sq
);
723 static void tg_update_disptime(struct throtl_grp
*tg
,
724 struct throtl_service_queue
*parent_sq
)
726 struct throtl_service_queue
*sq
= &tg
->service_queue
;
727 unsigned long read_wait
= -1, write_wait
= -1, min_wait
= -1, disptime
;
730 if ((bio
= bio_list_peek(&sq
->bio_lists
[READ
])))
731 tg_may_dispatch(tg
, bio
, &read_wait
);
733 if ((bio
= bio_list_peek(&sq
->bio_lists
[WRITE
])))
734 tg_may_dispatch(tg
, bio
, &write_wait
);
736 min_wait
= min(read_wait
, write_wait
);
737 disptime
= jiffies
+ min_wait
;
739 /* Update dispatch time */
740 throtl_dequeue_tg(tg
, parent_sq
);
741 tg
->disptime
= disptime
;
742 throtl_enqueue_tg(tg
, parent_sq
);
745 static void tg_dispatch_one_bio(struct throtl_grp
*tg
, bool rw
,
748 struct throtl_service_queue
*sq
= &tg
->service_queue
;
751 bio
= bio_list_pop(&sq
->bio_lists
[rw
]);
753 /* Drop bio reference on blkg */
754 blkg_put(tg_to_blkg(tg
));
756 BUG_ON(tg
->td
->nr_queued
[rw
] <= 0);
757 tg
->td
->nr_queued
[rw
]--;
759 throtl_charge_bio(tg
, bio
);
760 bio_list_add(bl
, bio
);
761 bio
->bi_rw
|= REQ_THROTTLED
;
763 throtl_trim_slice(tg
, rw
);
766 static int throtl_dispatch_tg(struct throtl_grp
*tg
, struct bio_list
*bl
)
768 struct throtl_service_queue
*sq
= &tg
->service_queue
;
769 unsigned int nr_reads
= 0, nr_writes
= 0;
770 unsigned int max_nr_reads
= throtl_grp_quantum
*3/4;
771 unsigned int max_nr_writes
= throtl_grp_quantum
- max_nr_reads
;
774 /* Try to dispatch 75% READS and 25% WRITES */
776 while ((bio
= bio_list_peek(&sq
->bio_lists
[READ
])) &&
777 tg_may_dispatch(tg
, bio
, NULL
)) {
779 tg_dispatch_one_bio(tg
, bio_data_dir(bio
), bl
);
782 if (nr_reads
>= max_nr_reads
)
786 while ((bio
= bio_list_peek(&sq
->bio_lists
[WRITE
])) &&
787 tg_may_dispatch(tg
, bio
, NULL
)) {
789 tg_dispatch_one_bio(tg
, bio_data_dir(bio
), bl
);
792 if (nr_writes
>= max_nr_writes
)
796 return nr_reads
+ nr_writes
;
799 static int throtl_select_dispatch(struct throtl_service_queue
*parent_sq
,
802 unsigned int nr_disp
= 0;
805 struct throtl_grp
*tg
= throtl_rb_first(parent_sq
);
806 struct throtl_service_queue
*sq
= &tg
->service_queue
;
811 if (time_before(jiffies
, tg
->disptime
))
814 throtl_dequeue_tg(tg
, parent_sq
);
816 nr_disp
+= throtl_dispatch_tg(tg
, bl
);
818 if (sq
->nr_queued
[0] || sq
->nr_queued
[1])
819 tg_update_disptime(tg
, parent_sq
);
821 if (nr_disp
>= throtl_quantum
)
828 /* work function to dispatch throttled bios */
829 void blk_throtl_dispatch_work_fn(struct work_struct
*work
)
831 struct throtl_data
*td
= container_of(to_delayed_work(work
),
832 struct throtl_data
, dispatch_work
);
833 struct request_queue
*q
= td
->queue
;
834 unsigned int nr_disp
= 0;
835 struct bio_list bio_list_on_stack
;
837 struct blk_plug plug
;
839 spin_lock_irq(q
->queue_lock
);
841 bio_list_init(&bio_list_on_stack
);
843 throtl_log(td
, "dispatch nr_queued=%u read=%u write=%u",
844 td
->nr_queued
[READ
] + td
->nr_queued
[WRITE
],
845 td
->nr_queued
[READ
], td
->nr_queued
[WRITE
]);
847 nr_disp
= throtl_select_dispatch(&td
->service_queue
, &bio_list_on_stack
);
850 throtl_log(td
, "bios disp=%u", nr_disp
);
852 throtl_schedule_next_dispatch(td
);
854 spin_unlock_irq(q
->queue_lock
);
857 * If we dispatched some requests, unplug the queue to make sure
861 blk_start_plug(&plug
);
862 while((bio
= bio_list_pop(&bio_list_on_stack
)))
863 generic_make_request(bio
);
864 blk_finish_plug(&plug
);
868 static u64
tg_prfill_cpu_rwstat(struct seq_file
*sf
,
869 struct blkg_policy_data
*pd
, int off
)
871 struct throtl_grp
*tg
= pd_to_tg(pd
);
872 struct blkg_rwstat rwstat
= { }, tmp
;
875 for_each_possible_cpu(cpu
) {
876 struct tg_stats_cpu
*sc
= per_cpu_ptr(tg
->stats_cpu
, cpu
);
878 tmp
= blkg_rwstat_read((void *)sc
+ off
);
879 for (i
= 0; i
< BLKG_RWSTAT_NR
; i
++)
880 rwstat
.cnt
[i
] += tmp
.cnt
[i
];
883 return __blkg_prfill_rwstat(sf
, pd
, &rwstat
);
886 static int tg_print_cpu_rwstat(struct cgroup
*cgrp
, struct cftype
*cft
,
889 struct blkcg
*blkcg
= cgroup_to_blkcg(cgrp
);
891 blkcg_print_blkgs(sf
, blkcg
, tg_prfill_cpu_rwstat
, &blkcg_policy_throtl
,
896 static u64
tg_prfill_conf_u64(struct seq_file
*sf
, struct blkg_policy_data
*pd
,
899 struct throtl_grp
*tg
= pd_to_tg(pd
);
900 u64 v
= *(u64
*)((void *)tg
+ off
);
904 return __blkg_prfill_u64(sf
, pd
, v
);
907 static u64
tg_prfill_conf_uint(struct seq_file
*sf
, struct blkg_policy_data
*pd
,
910 struct throtl_grp
*tg
= pd_to_tg(pd
);
911 unsigned int v
= *(unsigned int *)((void *)tg
+ off
);
915 return __blkg_prfill_u64(sf
, pd
, v
);
918 static int tg_print_conf_u64(struct cgroup
*cgrp
, struct cftype
*cft
,
921 blkcg_print_blkgs(sf
, cgroup_to_blkcg(cgrp
), tg_prfill_conf_u64
,
922 &blkcg_policy_throtl
, cft
->private, false);
926 static int tg_print_conf_uint(struct cgroup
*cgrp
, struct cftype
*cft
,
929 blkcg_print_blkgs(sf
, cgroup_to_blkcg(cgrp
), tg_prfill_conf_uint
,
930 &blkcg_policy_throtl
, cft
->private, false);
934 static int tg_set_conf(struct cgroup
*cgrp
, struct cftype
*cft
, const char *buf
,
937 struct blkcg
*blkcg
= cgroup_to_blkcg(cgrp
);
938 struct blkg_conf_ctx ctx
;
939 struct throtl_grp
*tg
;
940 struct throtl_data
*td
;
943 ret
= blkg_conf_prep(blkcg
, &blkcg_policy_throtl
, buf
, &ctx
);
947 tg
= blkg_to_tg(ctx
.blkg
);
948 td
= ctx
.blkg
->q
->td
;
954 *(u64
*)((void *)tg
+ cft
->private) = ctx
.v
;
956 *(unsigned int *)((void *)tg
+ cft
->private) = ctx
.v
;
958 throtl_log_tg(tg
, "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
959 tg
->bps
[READ
], tg
->bps
[WRITE
],
960 tg
->iops
[READ
], tg
->iops
[WRITE
]);
963 * We're already holding queue_lock and know @tg is valid. Let's
964 * apply the new config directly.
966 * Restart the slices for both READ and WRITES. It might happen
967 * that a group's limit are dropped suddenly and we don't want to
968 * account recently dispatched IO with new low rate.
970 throtl_start_new_slice(tg
, 0);
971 throtl_start_new_slice(tg
, 1);
973 if (tg
->flags
& THROTL_TG_PENDING
) {
974 tg_update_disptime(tg
, &td
->service_queue
);
975 throtl_schedule_next_dispatch(td
);
978 blkg_conf_finish(&ctx
);
982 static int tg_set_conf_u64(struct cgroup
*cgrp
, struct cftype
*cft
,
985 return tg_set_conf(cgrp
, cft
, buf
, true);
988 static int tg_set_conf_uint(struct cgroup
*cgrp
, struct cftype
*cft
,
991 return tg_set_conf(cgrp
, cft
, buf
, false);
994 static struct cftype throtl_files
[] = {
996 .name
= "throttle.read_bps_device",
997 .private = offsetof(struct throtl_grp
, bps
[READ
]),
998 .read_seq_string
= tg_print_conf_u64
,
999 .write_string
= tg_set_conf_u64
,
1000 .max_write_len
= 256,
1003 .name
= "throttle.write_bps_device",
1004 .private = offsetof(struct throtl_grp
, bps
[WRITE
]),
1005 .read_seq_string
= tg_print_conf_u64
,
1006 .write_string
= tg_set_conf_u64
,
1007 .max_write_len
= 256,
1010 .name
= "throttle.read_iops_device",
1011 .private = offsetof(struct throtl_grp
, iops
[READ
]),
1012 .read_seq_string
= tg_print_conf_uint
,
1013 .write_string
= tg_set_conf_uint
,
1014 .max_write_len
= 256,
1017 .name
= "throttle.write_iops_device",
1018 .private = offsetof(struct throtl_grp
, iops
[WRITE
]),
1019 .read_seq_string
= tg_print_conf_uint
,
1020 .write_string
= tg_set_conf_uint
,
1021 .max_write_len
= 256,
1024 .name
= "throttle.io_service_bytes",
1025 .private = offsetof(struct tg_stats_cpu
, service_bytes
),
1026 .read_seq_string
= tg_print_cpu_rwstat
,
1029 .name
= "throttle.io_serviced",
1030 .private = offsetof(struct tg_stats_cpu
, serviced
),
1031 .read_seq_string
= tg_print_cpu_rwstat
,
1036 static void throtl_shutdown_wq(struct request_queue
*q
)
1038 struct throtl_data
*td
= q
->td
;
1040 cancel_delayed_work_sync(&td
->dispatch_work
);
1043 static struct blkcg_policy blkcg_policy_throtl
= {
1044 .pd_size
= sizeof(struct throtl_grp
),
1045 .cftypes
= throtl_files
,
1047 .pd_init_fn
= throtl_pd_init
,
1048 .pd_exit_fn
= throtl_pd_exit
,
1049 .pd_reset_stats_fn
= throtl_pd_reset_stats
,
1052 bool blk_throtl_bio(struct request_queue
*q
, struct bio
*bio
)
1054 struct throtl_data
*td
= q
->td
;
1055 struct throtl_grp
*tg
;
1056 struct throtl_service_queue
*sq
;
1057 bool rw
= bio_data_dir(bio
), update_disptime
= true;
1058 struct blkcg
*blkcg
;
1059 bool throttled
= false;
1061 if (bio
->bi_rw
& REQ_THROTTLED
) {
1062 bio
->bi_rw
&= ~REQ_THROTTLED
;
1067 * A throtl_grp pointer retrieved under rcu can be used to access
1068 * basic fields like stats and io rates. If a group has no rules,
1069 * just update the dispatch stats in lockless manner and return.
1072 blkcg
= bio_blkcg(bio
);
1073 tg
= throtl_lookup_tg(td
, blkcg
);
1075 if (tg_no_rule_group(tg
, rw
)) {
1076 throtl_update_dispatch_stats(tg_to_blkg(tg
),
1077 bio
->bi_size
, bio
->bi_rw
);
1078 goto out_unlock_rcu
;
1083 * Either group has not been allocated yet or it is not an unlimited
1086 spin_lock_irq(q
->queue_lock
);
1087 tg
= throtl_lookup_create_tg(td
, blkcg
);
1091 sq
= &tg
->service_queue
;
1093 if (sq
->nr_queued
[rw
]) {
1095 * There is already another bio queued in same dir. No
1096 * need to update dispatch time.
1098 update_disptime
= false;
1103 /* Bio is with-in rate limit of group */
1104 if (tg_may_dispatch(tg
, bio
, NULL
)) {
1105 throtl_charge_bio(tg
, bio
);
1108 * We need to trim slice even when bios are not being queued
1109 * otherwise it might happen that a bio is not queued for
1110 * a long time and slice keeps on extending and trim is not
1111 * called for a long time. Now if limits are reduced suddenly
1112 * we take into account all the IO dispatched so far at new
1113 * low rate and * newly queued IO gets a really long dispatch
1116 * So keep on trimming slice even if bio is not queued.
1118 throtl_trim_slice(tg
, rw
);
1123 throtl_log_tg(tg
, "[%c] bio. bdisp=%llu sz=%u bps=%llu"
1124 " iodisp=%u iops=%u queued=%d/%d",
1125 rw
== READ
? 'R' : 'W',
1126 tg
->bytes_disp
[rw
], bio
->bi_size
, tg
->bps
[rw
],
1127 tg
->io_disp
[rw
], tg
->iops
[rw
],
1128 sq
->nr_queued
[READ
], sq
->nr_queued
[WRITE
]);
1130 bio_associate_current(bio
);
1131 throtl_add_bio_tg(bio
, tg
, &q
->td
->service_queue
);
1134 if (update_disptime
) {
1135 tg_update_disptime(tg
, &td
->service_queue
);
1136 throtl_schedule_next_dispatch(td
);
1140 spin_unlock_irq(q
->queue_lock
);
1148 * blk_throtl_drain - drain throttled bios
1149 * @q: request_queue to drain throttled bios for
1151 * Dispatch all currently throttled bios on @q through ->make_request_fn().
1153 void blk_throtl_drain(struct request_queue
*q
)
1154 __releases(q
->queue_lock
) __acquires(q
->queue_lock
)
1156 struct throtl_data
*td
= q
->td
;
1157 struct throtl_service_queue
*parent_sq
= &td
->service_queue
;
1158 struct throtl_grp
*tg
;
1162 queue_lockdep_assert_held(q
);
1166 while ((tg
= throtl_rb_first(parent_sq
))) {
1167 struct throtl_service_queue
*sq
= &tg
->service_queue
;
1169 throtl_dequeue_tg(tg
, parent_sq
);
1171 while ((bio
= bio_list_peek(&sq
->bio_lists
[READ
])))
1172 tg_dispatch_one_bio(tg
, bio_data_dir(bio
), &bl
);
1173 while ((bio
= bio_list_peek(&sq
->bio_lists
[WRITE
])))
1174 tg_dispatch_one_bio(tg
, bio_data_dir(bio
), &bl
);
1176 spin_unlock_irq(q
->queue_lock
);
1178 while ((bio
= bio_list_pop(&bl
)))
1179 generic_make_request(bio
);
1181 spin_lock_irq(q
->queue_lock
);
1184 int blk_throtl_init(struct request_queue
*q
)
1186 struct throtl_data
*td
;
1189 td
= kzalloc_node(sizeof(*td
), GFP_KERNEL
, q
->node
);
1193 INIT_DELAYED_WORK(&td
->dispatch_work
, blk_throtl_dispatch_work_fn
);
1194 throtl_service_queue_init(&td
->service_queue
);
1199 /* activate policy */
1200 ret
= blkcg_activate_policy(q
, &blkcg_policy_throtl
);
1206 void blk_throtl_exit(struct request_queue
*q
)
1209 throtl_shutdown_wq(q
);
1210 blkcg_deactivate_policy(q
, &blkcg_policy_throtl
);
1214 static int __init
throtl_init(void)
1216 kthrotld_workqueue
= alloc_workqueue("kthrotld", WQ_MEM_RECLAIM
, 0);
1217 if (!kthrotld_workqueue
)
1218 panic("Failed to create kthrotld\n");
1220 return blkcg_policy_register(&blkcg_policy_throtl
);
1223 module_init(throtl_init
);