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
;
30 * To implement hierarchical throttling, throtl_grps form a tree and bios
31 * are dispatched upwards level by level until they reach the top and get
32 * issued. When dispatching bios from the children and local group at each
33 * level, if the bios are dispatched into a single bio_list, there's a risk
34 * of a local or child group which can queue many bios at once filling up
35 * the list starving others.
37 * To avoid such starvation, dispatched bios are queued separately
38 * according to where they came from. When they are again dispatched to
39 * the parent, they're popped in round-robin order so that no single source
40 * hogs the dispatch window.
42 * throtl_qnode is used to keep the queued bios separated by their sources.
43 * Bios are queued to throtl_qnode which in turn is queued to
44 * throtl_service_queue and then dispatched in round-robin order.
46 * It's also used to track the reference counts on blkg's. A qnode always
47 * belongs to a throtl_grp and gets queued on itself or the parent, so
48 * incrementing the reference of the associated throtl_grp when a qnode is
49 * queued and decrementing when dequeued is enough to keep the whole blkg
50 * tree pinned while bios are in flight.
53 struct list_head node
; /* service_queue->queued[] */
54 struct bio_list bios
; /* queued bios */
55 struct throtl_grp
*tg
; /* tg this qnode belongs to */
58 struct throtl_service_queue
{
59 struct throtl_service_queue
*parent_sq
; /* the parent service_queue */
62 * Bios queued directly to this service_queue or dispatched from
63 * children throtl_grp's.
65 struct list_head queued
[2]; /* throtl_qnode [READ/WRITE] */
66 unsigned int nr_queued
[2]; /* number of queued bios */
69 * RB tree of active children throtl_grp's, which are sorted by
72 struct rb_root pending_tree
; /* RB tree of active tgs */
73 struct rb_node
*first_pending
; /* first node in the tree */
74 unsigned int nr_pending
; /* # queued in the tree */
75 unsigned long first_pending_disptime
; /* disptime of the first tg */
76 struct timer_list pending_timer
; /* fires on first_pending_disptime */
80 THROTL_TG_PENDING
= 1 << 0, /* on parent's pending tree */
81 THROTL_TG_WAS_EMPTY
= 1 << 1, /* bio_lists[] became non-empty */
84 #define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
86 /* Per-cpu group stats */
88 /* total bytes transferred */
89 struct blkg_rwstat service_bytes
;
90 /* total IOs serviced, post merge */
91 struct blkg_rwstat serviced
;
95 /* must be the first member */
96 struct blkg_policy_data pd
;
98 /* active throtl group service_queue member */
99 struct rb_node rb_node
;
101 /* throtl_data this group belongs to */
102 struct throtl_data
*td
;
104 /* this group's service queue */
105 struct throtl_service_queue service_queue
;
108 * qnode_on_self is used when bios are directly queued to this
109 * throtl_grp so that local bios compete fairly with bios
110 * dispatched from children. qnode_on_parent is used when bios are
111 * dispatched from this throtl_grp into its parent and will compete
112 * with the sibling qnode_on_parents and the parent's
115 struct throtl_qnode qnode_on_self
[2];
116 struct throtl_qnode qnode_on_parent
[2];
119 * Dispatch time in jiffies. This is the estimated time when group
120 * will unthrottle and is ready to dispatch more bio. It is used as
121 * key to sort active groups in service tree.
123 unsigned long disptime
;
127 /* bytes per second rate limits */
131 unsigned int iops
[2];
133 /* Number of bytes disptached in current slice */
134 uint64_t bytes_disp
[2];
135 /* Number of bio's dispatched in current slice */
136 unsigned int io_disp
[2];
138 /* When did we start a new slice */
139 unsigned long slice_start
[2];
140 unsigned long slice_end
[2];
142 /* Per cpu stats pointer */
143 struct tg_stats_cpu __percpu
*stats_cpu
;
145 /* List of tgs waiting for per cpu stats memory to be allocated */
146 struct list_head stats_alloc_node
;
151 /* service tree for active throtl groups */
152 struct throtl_service_queue service_queue
;
154 struct request_queue
*queue
;
156 /* Total Number of queued bios on READ and WRITE lists */
157 unsigned int nr_queued
[2];
160 * number of total undestroyed groups
162 unsigned int nr_undestroyed_grps
;
164 /* Work for dispatching throttled bios */
165 struct work_struct dispatch_work
;
168 /* list and work item to allocate percpu group stats */
169 static DEFINE_SPINLOCK(tg_stats_alloc_lock
);
170 static LIST_HEAD(tg_stats_alloc_list
);
172 static void tg_stats_alloc_fn(struct work_struct
*);
173 static DECLARE_DELAYED_WORK(tg_stats_alloc_work
, tg_stats_alloc_fn
);
175 static void throtl_pending_timer_fn(unsigned long arg
);
177 static inline struct throtl_grp
*pd_to_tg(struct blkg_policy_data
*pd
)
179 return pd
? container_of(pd
, struct throtl_grp
, pd
) : NULL
;
182 static inline struct throtl_grp
*blkg_to_tg(struct blkcg_gq
*blkg
)
184 return pd_to_tg(blkg_to_pd(blkg
, &blkcg_policy_throtl
));
187 static inline struct blkcg_gq
*tg_to_blkg(struct throtl_grp
*tg
)
189 return pd_to_blkg(&tg
->pd
);
192 static inline struct throtl_grp
*td_root_tg(struct throtl_data
*td
)
194 return blkg_to_tg(td
->queue
->root_blkg
);
198 * sq_to_tg - return the throl_grp the specified service queue belongs to
199 * @sq: the throtl_service_queue of interest
201 * Return the throtl_grp @sq belongs to. If @sq is the top-level one
202 * embedded in throtl_data, %NULL is returned.
204 static struct throtl_grp
*sq_to_tg(struct throtl_service_queue
*sq
)
206 if (sq
&& sq
->parent_sq
)
207 return container_of(sq
, struct throtl_grp
, service_queue
);
213 * sq_to_td - return throtl_data the specified service queue belongs to
214 * @sq: the throtl_service_queue of interest
216 * A service_queue can be embeded in either a throtl_grp or throtl_data.
217 * Determine the associated throtl_data accordingly and return it.
219 static struct throtl_data
*sq_to_td(struct throtl_service_queue
*sq
)
221 struct throtl_grp
*tg
= sq_to_tg(sq
);
226 return container_of(sq
, struct throtl_data
, service_queue
);
230 * throtl_log - log debug message via blktrace
231 * @sq: the service_queue being reported
232 * @fmt: printf format string
235 * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
236 * throtl_grp; otherwise, just "throtl".
238 * TODO: this should be made a function and name formatting should happen
239 * after testing whether blktrace is enabled.
241 #define throtl_log(sq, fmt, args...) do { \
242 struct throtl_grp *__tg = sq_to_tg((sq)); \
243 struct throtl_data *__td = sq_to_td((sq)); \
249 blkg_path(tg_to_blkg(__tg), __pbuf, sizeof(__pbuf)); \
250 blk_add_trace_msg(__td->queue, "throtl %s " fmt, __pbuf, ##args); \
252 blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \
257 * Worker for allocating per cpu stat for tgs. This is scheduled on the
258 * system_wq once there are some groups on the alloc_list waiting for
261 static void tg_stats_alloc_fn(struct work_struct
*work
)
263 static struct tg_stats_cpu
*stats_cpu
; /* this fn is non-reentrant */
264 struct delayed_work
*dwork
= to_delayed_work(work
);
269 stats_cpu
= alloc_percpu(struct tg_stats_cpu
);
271 /* allocation failed, try again after some time */
272 schedule_delayed_work(dwork
, msecs_to_jiffies(10));
277 spin_lock_irq(&tg_stats_alloc_lock
);
279 if (!list_empty(&tg_stats_alloc_list
)) {
280 struct throtl_grp
*tg
= list_first_entry(&tg_stats_alloc_list
,
283 swap(tg
->stats_cpu
, stats_cpu
);
284 list_del_init(&tg
->stats_alloc_node
);
287 empty
= list_empty(&tg_stats_alloc_list
);
288 spin_unlock_irq(&tg_stats_alloc_lock
);
293 static void throtl_qnode_init(struct throtl_qnode
*qn
, struct throtl_grp
*tg
)
295 INIT_LIST_HEAD(&qn
->node
);
296 bio_list_init(&qn
->bios
);
301 * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it
302 * @bio: bio being added
303 * @qn: qnode to add bio to
304 * @queued: the service_queue->queued[] list @qn belongs to
306 * Add @bio to @qn and put @qn on @queued if it's not already on.
307 * @qn->tg's reference count is bumped when @qn is activated. See the
308 * comment on top of throtl_qnode definition for details.
310 static void throtl_qnode_add_bio(struct bio
*bio
, struct throtl_qnode
*qn
,
311 struct list_head
*queued
)
313 bio_list_add(&qn
->bios
, bio
);
314 if (list_empty(&qn
->node
)) {
315 list_add_tail(&qn
->node
, queued
);
316 blkg_get(tg_to_blkg(qn
->tg
));
321 * throtl_peek_queued - peek the first bio on a qnode list
322 * @queued: the qnode list to peek
324 static struct bio
*throtl_peek_queued(struct list_head
*queued
)
326 struct throtl_qnode
*qn
= list_first_entry(queued
, struct throtl_qnode
, node
);
329 if (list_empty(queued
))
332 bio
= bio_list_peek(&qn
->bios
);
338 * throtl_pop_queued - pop the first bio form a qnode list
339 * @queued: the qnode list to pop a bio from
340 * @tg_to_put: optional out argument for throtl_grp to put
342 * Pop the first bio from the qnode list @queued. After popping, the first
343 * qnode is removed from @queued if empty or moved to the end of @queued so
344 * that the popping order is round-robin.
346 * When the first qnode is removed, its associated throtl_grp should be put
347 * too. If @tg_to_put is NULL, this function automatically puts it;
348 * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is
349 * responsible for putting it.
351 static struct bio
*throtl_pop_queued(struct list_head
*queued
,
352 struct throtl_grp
**tg_to_put
)
354 struct throtl_qnode
*qn
= list_first_entry(queued
, struct throtl_qnode
, node
);
357 if (list_empty(queued
))
360 bio
= bio_list_pop(&qn
->bios
);
363 if (bio_list_empty(&qn
->bios
)) {
364 list_del_init(&qn
->node
);
368 blkg_put(tg_to_blkg(qn
->tg
));
370 list_move_tail(&qn
->node
, queued
);
376 /* init a service_queue, assumes the caller zeroed it */
377 static void throtl_service_queue_init(struct throtl_service_queue
*sq
,
378 struct throtl_service_queue
*parent_sq
)
380 INIT_LIST_HEAD(&sq
->queued
[0]);
381 INIT_LIST_HEAD(&sq
->queued
[1]);
382 sq
->pending_tree
= RB_ROOT
;
383 sq
->parent_sq
= parent_sq
;
384 setup_timer(&sq
->pending_timer
, throtl_pending_timer_fn
,
388 static void throtl_service_queue_exit(struct throtl_service_queue
*sq
)
390 del_timer_sync(&sq
->pending_timer
);
393 static void throtl_pd_init(struct blkcg_gq
*blkg
)
395 struct throtl_grp
*tg
= blkg_to_tg(blkg
);
396 struct throtl_data
*td
= blkg
->q
->td
;
400 throtl_service_queue_init(&tg
->service_queue
, &td
->service_queue
);
401 for (rw
= READ
; rw
<= WRITE
; rw
++) {
402 throtl_qnode_init(&tg
->qnode_on_self
[rw
], tg
);
403 throtl_qnode_init(&tg
->qnode_on_parent
[rw
], tg
);
406 RB_CLEAR_NODE(&tg
->rb_node
);
412 tg
->iops
[WRITE
] = -1;
415 * Ugh... We need to perform per-cpu allocation for tg->stats_cpu
416 * but percpu allocator can't be called from IO path. Queue tg on
417 * tg_stats_alloc_list and allocate from work item.
419 spin_lock_irqsave(&tg_stats_alloc_lock
, flags
);
420 list_add(&tg
->stats_alloc_node
, &tg_stats_alloc_list
);
421 schedule_delayed_work(&tg_stats_alloc_work
, 0);
422 spin_unlock_irqrestore(&tg_stats_alloc_lock
, flags
);
425 static void throtl_pd_exit(struct blkcg_gq
*blkg
)
427 struct throtl_grp
*tg
= blkg_to_tg(blkg
);
430 spin_lock_irqsave(&tg_stats_alloc_lock
, flags
);
431 list_del_init(&tg
->stats_alloc_node
);
432 spin_unlock_irqrestore(&tg_stats_alloc_lock
, flags
);
434 free_percpu(tg
->stats_cpu
);
436 throtl_service_queue_exit(&tg
->service_queue
);
439 static void throtl_pd_reset_stats(struct blkcg_gq
*blkg
)
441 struct throtl_grp
*tg
= blkg_to_tg(blkg
);
444 if (tg
->stats_cpu
== NULL
)
447 for_each_possible_cpu(cpu
) {
448 struct tg_stats_cpu
*sc
= per_cpu_ptr(tg
->stats_cpu
, cpu
);
450 blkg_rwstat_reset(&sc
->service_bytes
);
451 blkg_rwstat_reset(&sc
->serviced
);
455 static struct throtl_grp
*throtl_lookup_tg(struct throtl_data
*td
,
459 * This is the common case when there are no blkcgs. Avoid lookup
462 if (blkcg
== &blkcg_root
)
463 return td_root_tg(td
);
465 return blkg_to_tg(blkg_lookup(blkcg
, td
->queue
));
468 static struct throtl_grp
*throtl_lookup_create_tg(struct throtl_data
*td
,
471 struct request_queue
*q
= td
->queue
;
472 struct throtl_grp
*tg
= NULL
;
475 * This is the common case when there are no blkcgs. Avoid lookup
478 if (blkcg
== &blkcg_root
) {
481 struct blkcg_gq
*blkg
;
483 blkg
= blkg_lookup_create(blkcg
, q
);
485 /* if %NULL and @q is alive, fall back to root_tg */
487 tg
= blkg_to_tg(blkg
);
488 else if (!blk_queue_dying(q
))
495 static struct throtl_grp
*
496 throtl_rb_first(struct throtl_service_queue
*parent_sq
)
498 /* Service tree is empty */
499 if (!parent_sq
->nr_pending
)
502 if (!parent_sq
->first_pending
)
503 parent_sq
->first_pending
= rb_first(&parent_sq
->pending_tree
);
505 if (parent_sq
->first_pending
)
506 return rb_entry_tg(parent_sq
->first_pending
);
511 static void rb_erase_init(struct rb_node
*n
, struct rb_root
*root
)
517 static void throtl_rb_erase(struct rb_node
*n
,
518 struct throtl_service_queue
*parent_sq
)
520 if (parent_sq
->first_pending
== n
)
521 parent_sq
->first_pending
= NULL
;
522 rb_erase_init(n
, &parent_sq
->pending_tree
);
523 --parent_sq
->nr_pending
;
526 static void update_min_dispatch_time(struct throtl_service_queue
*parent_sq
)
528 struct throtl_grp
*tg
;
530 tg
= throtl_rb_first(parent_sq
);
534 parent_sq
->first_pending_disptime
= tg
->disptime
;
537 static void tg_service_queue_add(struct throtl_grp
*tg
)
539 struct throtl_service_queue
*parent_sq
= tg
->service_queue
.parent_sq
;
540 struct rb_node
**node
= &parent_sq
->pending_tree
.rb_node
;
541 struct rb_node
*parent
= NULL
;
542 struct throtl_grp
*__tg
;
543 unsigned long key
= tg
->disptime
;
546 while (*node
!= NULL
) {
548 __tg
= rb_entry_tg(parent
);
550 if (time_before(key
, __tg
->disptime
))
551 node
= &parent
->rb_left
;
553 node
= &parent
->rb_right
;
559 parent_sq
->first_pending
= &tg
->rb_node
;
561 rb_link_node(&tg
->rb_node
, parent
, node
);
562 rb_insert_color(&tg
->rb_node
, &parent_sq
->pending_tree
);
565 static void __throtl_enqueue_tg(struct throtl_grp
*tg
)
567 tg_service_queue_add(tg
);
568 tg
->flags
|= THROTL_TG_PENDING
;
569 tg
->service_queue
.parent_sq
->nr_pending
++;
572 static void throtl_enqueue_tg(struct throtl_grp
*tg
)
574 if (!(tg
->flags
& THROTL_TG_PENDING
))
575 __throtl_enqueue_tg(tg
);
578 static void __throtl_dequeue_tg(struct throtl_grp
*tg
)
580 throtl_rb_erase(&tg
->rb_node
, tg
->service_queue
.parent_sq
);
581 tg
->flags
&= ~THROTL_TG_PENDING
;
584 static void throtl_dequeue_tg(struct throtl_grp
*tg
)
586 if (tg
->flags
& THROTL_TG_PENDING
)
587 __throtl_dequeue_tg(tg
);
590 /* Call with queue lock held */
591 static void throtl_schedule_pending_timer(struct throtl_service_queue
*sq
,
592 unsigned long expires
)
594 mod_timer(&sq
->pending_timer
, expires
);
595 throtl_log(sq
, "schedule timer. delay=%lu jiffies=%lu",
596 expires
- jiffies
, jiffies
);
600 * throtl_schedule_next_dispatch - schedule the next dispatch cycle
601 * @sq: the service_queue to schedule dispatch for
602 * @force: force scheduling
604 * Arm @sq->pending_timer so that the next dispatch cycle starts on the
605 * dispatch time of the first pending child. Returns %true if either timer
606 * is armed or there's no pending child left. %false if the current
607 * dispatch window is still open and the caller should continue
610 * If @force is %true, the dispatch timer is always scheduled and this
611 * function is guaranteed to return %true. This is to be used when the
612 * caller can't dispatch itself and needs to invoke pending_timer
613 * unconditionally. Note that forced scheduling is likely to induce short
614 * delay before dispatch starts even if @sq->first_pending_disptime is not
615 * in the future and thus shouldn't be used in hot paths.
617 static bool throtl_schedule_next_dispatch(struct throtl_service_queue
*sq
,
620 /* any pending children left? */
624 update_min_dispatch_time(sq
);
626 /* is the next dispatch time in the future? */
627 if (force
|| time_after(sq
->first_pending_disptime
, jiffies
)) {
628 throtl_schedule_pending_timer(sq
, sq
->first_pending_disptime
);
632 /* tell the caller to continue dispatching */
636 static inline void throtl_start_new_slice(struct throtl_grp
*tg
, bool rw
)
638 tg
->bytes_disp
[rw
] = 0;
640 tg
->slice_start
[rw
] = jiffies
;
641 tg
->slice_end
[rw
] = jiffies
+ throtl_slice
;
642 throtl_log(&tg
->service_queue
,
643 "[%c] new slice start=%lu end=%lu jiffies=%lu",
644 rw
== READ
? 'R' : 'W', tg
->slice_start
[rw
],
645 tg
->slice_end
[rw
], jiffies
);
648 static inline void throtl_set_slice_end(struct throtl_grp
*tg
, bool rw
,
649 unsigned long jiffy_end
)
651 tg
->slice_end
[rw
] = roundup(jiffy_end
, throtl_slice
);
654 static inline void throtl_extend_slice(struct throtl_grp
*tg
, bool rw
,
655 unsigned long jiffy_end
)
657 tg
->slice_end
[rw
] = roundup(jiffy_end
, throtl_slice
);
658 throtl_log(&tg
->service_queue
,
659 "[%c] extend slice start=%lu end=%lu jiffies=%lu",
660 rw
== READ
? 'R' : 'W', tg
->slice_start
[rw
],
661 tg
->slice_end
[rw
], jiffies
);
664 /* Determine if previously allocated or extended slice is complete or not */
665 static bool throtl_slice_used(struct throtl_grp
*tg
, bool rw
)
667 if (time_in_range(jiffies
, tg
->slice_start
[rw
], tg
->slice_end
[rw
]))
673 /* Trim the used slices and adjust slice start accordingly */
674 static inline void throtl_trim_slice(struct throtl_grp
*tg
, bool rw
)
676 unsigned long nr_slices
, time_elapsed
, io_trim
;
679 BUG_ON(time_before(tg
->slice_end
[rw
], tg
->slice_start
[rw
]));
682 * If bps are unlimited (-1), then time slice don't get
683 * renewed. Don't try to trim the slice if slice is used. A new
684 * slice will start when appropriate.
686 if (throtl_slice_used(tg
, rw
))
690 * A bio has been dispatched. Also adjust slice_end. It might happen
691 * that initially cgroup limit was very low resulting in high
692 * slice_end, but later limit was bumped up and bio was dispached
693 * sooner, then we need to reduce slice_end. A high bogus slice_end
694 * is bad because it does not allow new slice to start.
697 throtl_set_slice_end(tg
, rw
, jiffies
+ throtl_slice
);
699 time_elapsed
= jiffies
- tg
->slice_start
[rw
];
701 nr_slices
= time_elapsed
/ throtl_slice
;
705 tmp
= tg
->bps
[rw
] * throtl_slice
* nr_slices
;
709 io_trim
= (tg
->iops
[rw
] * throtl_slice
* nr_slices
)/HZ
;
711 if (!bytes_trim
&& !io_trim
)
714 if (tg
->bytes_disp
[rw
] >= bytes_trim
)
715 tg
->bytes_disp
[rw
] -= bytes_trim
;
717 tg
->bytes_disp
[rw
] = 0;
719 if (tg
->io_disp
[rw
] >= io_trim
)
720 tg
->io_disp
[rw
] -= io_trim
;
724 tg
->slice_start
[rw
] += nr_slices
* throtl_slice
;
726 throtl_log(&tg
->service_queue
,
727 "[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu",
728 rw
== READ
? 'R' : 'W', nr_slices
, bytes_trim
, io_trim
,
729 tg
->slice_start
[rw
], tg
->slice_end
[rw
], jiffies
);
732 static bool tg_with_in_iops_limit(struct throtl_grp
*tg
, struct bio
*bio
,
735 bool rw
= bio_data_dir(bio
);
736 unsigned int io_allowed
;
737 unsigned long jiffy_elapsed
, jiffy_wait
, jiffy_elapsed_rnd
;
740 jiffy_elapsed
= jiffy_elapsed_rnd
= jiffies
- tg
->slice_start
[rw
];
742 /* Slice has just started. Consider one slice interval */
744 jiffy_elapsed_rnd
= throtl_slice
;
746 jiffy_elapsed_rnd
= roundup(jiffy_elapsed_rnd
, throtl_slice
);
749 * jiffy_elapsed_rnd should not be a big value as minimum iops can be
750 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
751 * will allow dispatch after 1 second and after that slice should
755 tmp
= (u64
)tg
->iops
[rw
] * jiffy_elapsed_rnd
;
759 io_allowed
= UINT_MAX
;
763 if (tg
->io_disp
[rw
] + 1 <= io_allowed
) {
769 /* Calc approx time to dispatch */
770 jiffy_wait
= ((tg
->io_disp
[rw
] + 1) * HZ
)/tg
->iops
[rw
] + 1;
772 if (jiffy_wait
> jiffy_elapsed
)
773 jiffy_wait
= jiffy_wait
- jiffy_elapsed
;
782 static bool tg_with_in_bps_limit(struct throtl_grp
*tg
, struct bio
*bio
,
785 bool rw
= bio_data_dir(bio
);
786 u64 bytes_allowed
, extra_bytes
, tmp
;
787 unsigned long jiffy_elapsed
, jiffy_wait
, jiffy_elapsed_rnd
;
789 jiffy_elapsed
= jiffy_elapsed_rnd
= jiffies
- tg
->slice_start
[rw
];
791 /* Slice has just started. Consider one slice interval */
793 jiffy_elapsed_rnd
= throtl_slice
;
795 jiffy_elapsed_rnd
= roundup(jiffy_elapsed_rnd
, throtl_slice
);
797 tmp
= tg
->bps
[rw
] * jiffy_elapsed_rnd
;
801 if (tg
->bytes_disp
[rw
] + bio
->bi_size
<= bytes_allowed
) {
807 /* Calc approx time to dispatch */
808 extra_bytes
= tg
->bytes_disp
[rw
] + bio
->bi_size
- bytes_allowed
;
809 jiffy_wait
= div64_u64(extra_bytes
* HZ
, tg
->bps
[rw
]);
815 * This wait time is without taking into consideration the rounding
816 * up we did. Add that time also.
818 jiffy_wait
= jiffy_wait
+ (jiffy_elapsed_rnd
- jiffy_elapsed
);
824 static bool tg_no_rule_group(struct throtl_grp
*tg
, bool rw
) {
825 if (tg
->bps
[rw
] == -1 && tg
->iops
[rw
] == -1)
831 * Returns whether one can dispatch a bio or not. Also returns approx number
832 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
834 static bool tg_may_dispatch(struct throtl_grp
*tg
, struct bio
*bio
,
837 bool rw
= bio_data_dir(bio
);
838 unsigned long bps_wait
= 0, iops_wait
= 0, max_wait
= 0;
841 * Currently whole state machine of group depends on first bio
842 * queued in the group bio list. So one should not be calling
843 * this function with a different bio if there are other bios
846 BUG_ON(tg
->service_queue
.nr_queued
[rw
] &&
847 bio
!= throtl_peek_queued(&tg
->service_queue
.queued
[rw
]));
849 /* If tg->bps = -1, then BW is unlimited */
850 if (tg
->bps
[rw
] == -1 && tg
->iops
[rw
] == -1) {
857 * If previous slice expired, start a new one otherwise renew/extend
858 * existing slice to make sure it is at least throtl_slice interval
861 if (throtl_slice_used(tg
, rw
))
862 throtl_start_new_slice(tg
, rw
);
864 if (time_before(tg
->slice_end
[rw
], jiffies
+ throtl_slice
))
865 throtl_extend_slice(tg
, rw
, jiffies
+ throtl_slice
);
868 if (tg_with_in_bps_limit(tg
, bio
, &bps_wait
) &&
869 tg_with_in_iops_limit(tg
, bio
, &iops_wait
)) {
875 max_wait
= max(bps_wait
, iops_wait
);
880 if (time_before(tg
->slice_end
[rw
], jiffies
+ max_wait
))
881 throtl_extend_slice(tg
, rw
, jiffies
+ max_wait
);
886 static void throtl_update_dispatch_stats(struct blkcg_gq
*blkg
, u64 bytes
,
889 struct throtl_grp
*tg
= blkg_to_tg(blkg
);
890 struct tg_stats_cpu
*stats_cpu
;
893 /* If per cpu stats are not allocated yet, don't do any accounting. */
894 if (tg
->stats_cpu
== NULL
)
898 * Disabling interrupts to provide mutual exclusion between two
899 * writes on same cpu. It probably is not needed for 64bit. Not
900 * optimizing that case yet.
902 local_irq_save(flags
);
904 stats_cpu
= this_cpu_ptr(tg
->stats_cpu
);
906 blkg_rwstat_add(&stats_cpu
->serviced
, rw
, 1);
907 blkg_rwstat_add(&stats_cpu
->service_bytes
, rw
, bytes
);
909 local_irq_restore(flags
);
912 static void throtl_charge_bio(struct throtl_grp
*tg
, struct bio
*bio
)
914 bool rw
= bio_data_dir(bio
);
916 /* Charge the bio to the group */
917 tg
->bytes_disp
[rw
] += bio
->bi_size
;
921 * REQ_THROTTLED is used to prevent the same bio to be throttled
922 * more than once as a throttled bio will go through blk-throtl the
923 * second time when it eventually gets issued. Set it when a bio
924 * is being charged to a tg.
926 * Dispatch stats aren't recursive and each @bio should only be
927 * accounted by the @tg it was originally associated with. Let's
928 * update the stats when setting REQ_THROTTLED for the first time
929 * which is guaranteed to be for the @bio's original tg.
931 if (!(bio
->bi_rw
& REQ_THROTTLED
)) {
932 bio
->bi_rw
|= REQ_THROTTLED
;
933 throtl_update_dispatch_stats(tg_to_blkg(tg
), bio
->bi_size
,
939 * throtl_add_bio_tg - add a bio to the specified throtl_grp
942 * @tg: the target throtl_grp
944 * Add @bio to @tg's service_queue using @qn. If @qn is not specified,
945 * tg->qnode_on_self[] is used.
947 static void throtl_add_bio_tg(struct bio
*bio
, struct throtl_qnode
*qn
,
948 struct throtl_grp
*tg
)
950 struct throtl_service_queue
*sq
= &tg
->service_queue
;
951 bool rw
= bio_data_dir(bio
);
954 qn
= &tg
->qnode_on_self
[rw
];
957 * If @tg doesn't currently have any bios queued in the same
958 * direction, queueing @bio can change when @tg should be
959 * dispatched. Mark that @tg was empty. This is automatically
960 * cleaered on the next tg_update_disptime().
962 if (!sq
->nr_queued
[rw
])
963 tg
->flags
|= THROTL_TG_WAS_EMPTY
;
965 throtl_qnode_add_bio(bio
, qn
, &sq
->queued
[rw
]);
968 throtl_enqueue_tg(tg
);
971 static void tg_update_disptime(struct throtl_grp
*tg
)
973 struct throtl_service_queue
*sq
= &tg
->service_queue
;
974 unsigned long read_wait
= -1, write_wait
= -1, min_wait
= -1, disptime
;
977 if ((bio
= throtl_peek_queued(&sq
->queued
[READ
])))
978 tg_may_dispatch(tg
, bio
, &read_wait
);
980 if ((bio
= throtl_peek_queued(&sq
->queued
[WRITE
])))
981 tg_may_dispatch(tg
, bio
, &write_wait
);
983 min_wait
= min(read_wait
, write_wait
);
984 disptime
= jiffies
+ min_wait
;
986 /* Update dispatch time */
987 throtl_dequeue_tg(tg
);
988 tg
->disptime
= disptime
;
989 throtl_enqueue_tg(tg
);
991 /* see throtl_add_bio_tg() */
992 tg
->flags
&= ~THROTL_TG_WAS_EMPTY
;
995 static void tg_dispatch_one_bio(struct throtl_grp
*tg
, bool rw
)
997 struct throtl_service_queue
*sq
= &tg
->service_queue
;
998 struct throtl_service_queue
*parent_sq
= sq
->parent_sq
;
999 struct throtl_grp
*parent_tg
= sq_to_tg(parent_sq
);
1000 struct throtl_grp
*tg_to_put
= NULL
;
1004 * @bio is being transferred from @tg to @parent_sq. Popping a bio
1005 * from @tg may put its reference and @parent_sq might end up
1006 * getting released prematurely. Remember the tg to put and put it
1007 * after @bio is transferred to @parent_sq.
1009 bio
= throtl_pop_queued(&sq
->queued
[rw
], &tg_to_put
);
1010 sq
->nr_queued
[rw
]--;
1012 throtl_charge_bio(tg
, bio
);
1015 * If our parent is another tg, we just need to transfer @bio to
1016 * the parent using throtl_add_bio_tg(). If our parent is
1017 * @td->service_queue, @bio is ready to be issued. Put it on its
1018 * bio_lists[] and decrease total number queued. The caller is
1019 * responsible for issuing these bios.
1022 throtl_add_bio_tg(bio
, &tg
->qnode_on_parent
[rw
], parent_tg
);
1024 throtl_qnode_add_bio(bio
, &tg
->qnode_on_parent
[rw
],
1025 &parent_sq
->queued
[rw
]);
1026 BUG_ON(tg
->td
->nr_queued
[rw
] <= 0);
1027 tg
->td
->nr_queued
[rw
]--;
1030 throtl_trim_slice(tg
, rw
);
1033 blkg_put(tg_to_blkg(tg_to_put
));
1036 static int throtl_dispatch_tg(struct throtl_grp
*tg
)
1038 struct throtl_service_queue
*sq
= &tg
->service_queue
;
1039 unsigned int nr_reads
= 0, nr_writes
= 0;
1040 unsigned int max_nr_reads
= throtl_grp_quantum
*3/4;
1041 unsigned int max_nr_writes
= throtl_grp_quantum
- max_nr_reads
;
1044 /* Try to dispatch 75% READS and 25% WRITES */
1046 while ((bio
= throtl_peek_queued(&sq
->queued
[READ
])) &&
1047 tg_may_dispatch(tg
, bio
, NULL
)) {
1049 tg_dispatch_one_bio(tg
, bio_data_dir(bio
));
1052 if (nr_reads
>= max_nr_reads
)
1056 while ((bio
= throtl_peek_queued(&sq
->queued
[WRITE
])) &&
1057 tg_may_dispatch(tg
, bio
, NULL
)) {
1059 tg_dispatch_one_bio(tg
, bio_data_dir(bio
));
1062 if (nr_writes
>= max_nr_writes
)
1066 return nr_reads
+ nr_writes
;
1069 static int throtl_select_dispatch(struct throtl_service_queue
*parent_sq
)
1071 unsigned int nr_disp
= 0;
1074 struct throtl_grp
*tg
= throtl_rb_first(parent_sq
);
1075 struct throtl_service_queue
*sq
= &tg
->service_queue
;
1080 if (time_before(jiffies
, tg
->disptime
))
1083 throtl_dequeue_tg(tg
);
1085 nr_disp
+= throtl_dispatch_tg(tg
);
1087 if (sq
->nr_queued
[0] || sq
->nr_queued
[1])
1088 tg_update_disptime(tg
);
1090 if (nr_disp
>= throtl_quantum
)
1098 * throtl_pending_timer_fn - timer function for service_queue->pending_timer
1099 * @arg: the throtl_service_queue being serviced
1101 * This timer is armed when a child throtl_grp with active bio's become
1102 * pending and queued on the service_queue's pending_tree and expires when
1103 * the first child throtl_grp should be dispatched. This function
1104 * dispatches bio's from the children throtl_grps to the parent
1107 * If the parent's parent is another throtl_grp, dispatching is propagated
1108 * by either arming its pending_timer or repeating dispatch directly. If
1109 * the top-level service_tree is reached, throtl_data->dispatch_work is
1110 * kicked so that the ready bio's are issued.
1112 static void throtl_pending_timer_fn(unsigned long arg
)
1114 struct throtl_service_queue
*sq
= (void *)arg
;
1115 struct throtl_grp
*tg
= sq_to_tg(sq
);
1116 struct throtl_data
*td
= sq_to_td(sq
);
1117 struct request_queue
*q
= td
->queue
;
1118 struct throtl_service_queue
*parent_sq
;
1122 spin_lock_irq(q
->queue_lock
);
1124 parent_sq
= sq
->parent_sq
;
1128 throtl_log(sq
, "dispatch nr_queued=%u read=%u write=%u",
1129 sq
->nr_queued
[READ
] + sq
->nr_queued
[WRITE
],
1130 sq
->nr_queued
[READ
], sq
->nr_queued
[WRITE
]);
1132 ret
= throtl_select_dispatch(sq
);
1134 throtl_log(sq
, "bios disp=%u", ret
);
1138 if (throtl_schedule_next_dispatch(sq
, false))
1141 /* this dispatch windows is still open, relax and repeat */
1142 spin_unlock_irq(q
->queue_lock
);
1144 spin_lock_irq(q
->queue_lock
);
1151 /* @parent_sq is another throl_grp, propagate dispatch */
1152 if (tg
->flags
& THROTL_TG_WAS_EMPTY
) {
1153 tg_update_disptime(tg
);
1154 if (!throtl_schedule_next_dispatch(parent_sq
, false)) {
1155 /* window is already open, repeat dispatching */
1162 /* reached the top-level, queue issueing */
1163 queue_work(kthrotld_workqueue
, &td
->dispatch_work
);
1166 spin_unlock_irq(q
->queue_lock
);
1170 * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work
1171 * @work: work item being executed
1173 * This function is queued for execution when bio's reach the bio_lists[]
1174 * of throtl_data->service_queue. Those bio's are ready and issued by this
1177 void blk_throtl_dispatch_work_fn(struct work_struct
*work
)
1179 struct throtl_data
*td
= container_of(work
, struct throtl_data
,
1181 struct throtl_service_queue
*td_sq
= &td
->service_queue
;
1182 struct request_queue
*q
= td
->queue
;
1183 struct bio_list bio_list_on_stack
;
1185 struct blk_plug plug
;
1188 bio_list_init(&bio_list_on_stack
);
1190 spin_lock_irq(q
->queue_lock
);
1191 for (rw
= READ
; rw
<= WRITE
; rw
++)
1192 while ((bio
= throtl_pop_queued(&td_sq
->queued
[rw
], NULL
)))
1193 bio_list_add(&bio_list_on_stack
, bio
);
1194 spin_unlock_irq(q
->queue_lock
);
1196 if (!bio_list_empty(&bio_list_on_stack
)) {
1197 blk_start_plug(&plug
);
1198 while((bio
= bio_list_pop(&bio_list_on_stack
)))
1199 generic_make_request(bio
);
1200 blk_finish_plug(&plug
);
1204 static u64
tg_prfill_cpu_rwstat(struct seq_file
*sf
,
1205 struct blkg_policy_data
*pd
, int off
)
1207 struct throtl_grp
*tg
= pd_to_tg(pd
);
1208 struct blkg_rwstat rwstat
= { }, tmp
;
1211 for_each_possible_cpu(cpu
) {
1212 struct tg_stats_cpu
*sc
= per_cpu_ptr(tg
->stats_cpu
, cpu
);
1214 tmp
= blkg_rwstat_read((void *)sc
+ off
);
1215 for (i
= 0; i
< BLKG_RWSTAT_NR
; i
++)
1216 rwstat
.cnt
[i
] += tmp
.cnt
[i
];
1219 return __blkg_prfill_rwstat(sf
, pd
, &rwstat
);
1222 static int tg_print_cpu_rwstat(struct cgroup
*cgrp
, struct cftype
*cft
,
1223 struct seq_file
*sf
)
1225 struct blkcg
*blkcg
= cgroup_to_blkcg(cgrp
);
1227 blkcg_print_blkgs(sf
, blkcg
, tg_prfill_cpu_rwstat
, &blkcg_policy_throtl
,
1228 cft
->private, true);
1232 static u64
tg_prfill_conf_u64(struct seq_file
*sf
, struct blkg_policy_data
*pd
,
1235 struct throtl_grp
*tg
= pd_to_tg(pd
);
1236 u64 v
= *(u64
*)((void *)tg
+ off
);
1240 return __blkg_prfill_u64(sf
, pd
, v
);
1243 static u64
tg_prfill_conf_uint(struct seq_file
*sf
, struct blkg_policy_data
*pd
,
1246 struct throtl_grp
*tg
= pd_to_tg(pd
);
1247 unsigned int v
= *(unsigned int *)((void *)tg
+ off
);
1251 return __blkg_prfill_u64(sf
, pd
, v
);
1254 static int tg_print_conf_u64(struct cgroup
*cgrp
, struct cftype
*cft
,
1255 struct seq_file
*sf
)
1257 blkcg_print_blkgs(sf
, cgroup_to_blkcg(cgrp
), tg_prfill_conf_u64
,
1258 &blkcg_policy_throtl
, cft
->private, false);
1262 static int tg_print_conf_uint(struct cgroup
*cgrp
, struct cftype
*cft
,
1263 struct seq_file
*sf
)
1265 blkcg_print_blkgs(sf
, cgroup_to_blkcg(cgrp
), tg_prfill_conf_uint
,
1266 &blkcg_policy_throtl
, cft
->private, false);
1270 static int tg_set_conf(struct cgroup
*cgrp
, struct cftype
*cft
, const char *buf
,
1273 struct blkcg
*blkcg
= cgroup_to_blkcg(cgrp
);
1274 struct blkg_conf_ctx ctx
;
1275 struct throtl_grp
*tg
;
1276 struct throtl_service_queue
*sq
;
1279 ret
= blkg_conf_prep(blkcg
, &blkcg_policy_throtl
, buf
, &ctx
);
1283 tg
= blkg_to_tg(ctx
.blkg
);
1284 sq
= &tg
->service_queue
;
1290 *(u64
*)((void *)tg
+ cft
->private) = ctx
.v
;
1292 *(unsigned int *)((void *)tg
+ cft
->private) = ctx
.v
;
1294 throtl_log(&tg
->service_queue
,
1295 "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
1296 tg
->bps
[READ
], tg
->bps
[WRITE
],
1297 tg
->iops
[READ
], tg
->iops
[WRITE
]);
1300 * We're already holding queue_lock and know @tg is valid. Let's
1301 * apply the new config directly.
1303 * Restart the slices for both READ and WRITES. It might happen
1304 * that a group's limit are dropped suddenly and we don't want to
1305 * account recently dispatched IO with new low rate.
1307 throtl_start_new_slice(tg
, 0);
1308 throtl_start_new_slice(tg
, 1);
1310 if (tg
->flags
& THROTL_TG_PENDING
) {
1311 tg_update_disptime(tg
);
1312 throtl_schedule_next_dispatch(sq
->parent_sq
, true);
1315 blkg_conf_finish(&ctx
);
1319 static int tg_set_conf_u64(struct cgroup
*cgrp
, struct cftype
*cft
,
1322 return tg_set_conf(cgrp
, cft
, buf
, true);
1325 static int tg_set_conf_uint(struct cgroup
*cgrp
, struct cftype
*cft
,
1328 return tg_set_conf(cgrp
, cft
, buf
, false);
1331 static struct cftype throtl_files
[] = {
1333 .name
= "throttle.read_bps_device",
1334 .private = offsetof(struct throtl_grp
, bps
[READ
]),
1335 .read_seq_string
= tg_print_conf_u64
,
1336 .write_string
= tg_set_conf_u64
,
1337 .max_write_len
= 256,
1340 .name
= "throttle.write_bps_device",
1341 .private = offsetof(struct throtl_grp
, bps
[WRITE
]),
1342 .read_seq_string
= tg_print_conf_u64
,
1343 .write_string
= tg_set_conf_u64
,
1344 .max_write_len
= 256,
1347 .name
= "throttle.read_iops_device",
1348 .private = offsetof(struct throtl_grp
, iops
[READ
]),
1349 .read_seq_string
= tg_print_conf_uint
,
1350 .write_string
= tg_set_conf_uint
,
1351 .max_write_len
= 256,
1354 .name
= "throttle.write_iops_device",
1355 .private = offsetof(struct throtl_grp
, iops
[WRITE
]),
1356 .read_seq_string
= tg_print_conf_uint
,
1357 .write_string
= tg_set_conf_uint
,
1358 .max_write_len
= 256,
1361 .name
= "throttle.io_service_bytes",
1362 .private = offsetof(struct tg_stats_cpu
, service_bytes
),
1363 .read_seq_string
= tg_print_cpu_rwstat
,
1366 .name
= "throttle.io_serviced",
1367 .private = offsetof(struct tg_stats_cpu
, serviced
),
1368 .read_seq_string
= tg_print_cpu_rwstat
,
1373 static void throtl_shutdown_wq(struct request_queue
*q
)
1375 struct throtl_data
*td
= q
->td
;
1377 cancel_work_sync(&td
->dispatch_work
);
1380 static struct blkcg_policy blkcg_policy_throtl
= {
1381 .pd_size
= sizeof(struct throtl_grp
),
1382 .cftypes
= throtl_files
,
1384 .pd_init_fn
= throtl_pd_init
,
1385 .pd_exit_fn
= throtl_pd_exit
,
1386 .pd_reset_stats_fn
= throtl_pd_reset_stats
,
1389 bool blk_throtl_bio(struct request_queue
*q
, struct bio
*bio
)
1391 struct throtl_data
*td
= q
->td
;
1392 struct throtl_qnode
*qn
= NULL
;
1393 struct throtl_grp
*tg
;
1394 struct throtl_service_queue
*sq
;
1395 bool rw
= bio_data_dir(bio
);
1396 struct blkcg
*blkcg
;
1397 bool throttled
= false;
1399 /* see throtl_charge_bio() */
1400 if (bio
->bi_rw
& REQ_THROTTLED
)
1404 * A throtl_grp pointer retrieved under rcu can be used to access
1405 * basic fields like stats and io rates. If a group has no rules,
1406 * just update the dispatch stats in lockless manner and return.
1409 blkcg
= bio_blkcg(bio
);
1410 tg
= throtl_lookup_tg(td
, blkcg
);
1412 if (tg_no_rule_group(tg
, rw
)) {
1413 throtl_update_dispatch_stats(tg_to_blkg(tg
),
1414 bio
->bi_size
, bio
->bi_rw
);
1415 goto out_unlock_rcu
;
1420 * Either group has not been allocated yet or it is not an unlimited
1423 spin_lock_irq(q
->queue_lock
);
1424 tg
= throtl_lookup_create_tg(td
, blkcg
);
1428 sq
= &tg
->service_queue
;
1431 /* throtl is FIFO - if bios are already queued, should queue */
1432 if (sq
->nr_queued
[rw
])
1435 /* if above limits, break to queue */
1436 if (!tg_may_dispatch(tg
, bio
, NULL
))
1439 /* within limits, let's charge and dispatch directly */
1440 throtl_charge_bio(tg
, bio
);
1443 * We need to trim slice even when bios are not being queued
1444 * otherwise it might happen that a bio is not queued for
1445 * a long time and slice keeps on extending and trim is not
1446 * called for a long time. Now if limits are reduced suddenly
1447 * we take into account all the IO dispatched so far at new
1448 * low rate and * newly queued IO gets a really long dispatch
1451 * So keep on trimming slice even if bio is not queued.
1453 throtl_trim_slice(tg
, rw
);
1456 * @bio passed through this layer without being throttled.
1457 * Climb up the ladder. If we''re already at the top, it
1458 * can be executed directly.
1460 qn
= &tg
->qnode_on_parent
[rw
];
1467 /* out-of-limit, queue to @tg */
1468 throtl_log(sq
, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
1469 rw
== READ
? 'R' : 'W',
1470 tg
->bytes_disp
[rw
], bio
->bi_size
, tg
->bps
[rw
],
1471 tg
->io_disp
[rw
], tg
->iops
[rw
],
1472 sq
->nr_queued
[READ
], sq
->nr_queued
[WRITE
]);
1474 bio_associate_current(bio
);
1475 tg
->td
->nr_queued
[rw
]++;
1476 throtl_add_bio_tg(bio
, qn
, tg
);
1480 * Update @tg's dispatch time and force schedule dispatch if @tg
1481 * was empty before @bio. The forced scheduling isn't likely to
1482 * cause undue delay as @bio is likely to be dispatched directly if
1483 * its @tg's disptime is not in the future.
1485 if (tg
->flags
& THROTL_TG_WAS_EMPTY
) {
1486 tg_update_disptime(tg
);
1487 throtl_schedule_next_dispatch(tg
->service_queue
.parent_sq
, true);
1491 spin_unlock_irq(q
->queue_lock
);
1496 * As multiple blk-throtls may stack in the same issue path, we
1497 * don't want bios to leave with the flag set. Clear the flag if
1501 bio
->bi_rw
&= ~REQ_THROTTLED
;
1506 * Dispatch all bios from all children tg's queued on @parent_sq. On
1507 * return, @parent_sq is guaranteed to not have any active children tg's
1508 * and all bios from previously active tg's are on @parent_sq->bio_lists[].
1510 static void tg_drain_bios(struct throtl_service_queue
*parent_sq
)
1512 struct throtl_grp
*tg
;
1514 while ((tg
= throtl_rb_first(parent_sq
))) {
1515 struct throtl_service_queue
*sq
= &tg
->service_queue
;
1518 throtl_dequeue_tg(tg
);
1520 while ((bio
= throtl_peek_queued(&sq
->queued
[READ
])))
1521 tg_dispatch_one_bio(tg
, bio_data_dir(bio
));
1522 while ((bio
= throtl_peek_queued(&sq
->queued
[WRITE
])))
1523 tg_dispatch_one_bio(tg
, bio_data_dir(bio
));
1528 * blk_throtl_drain - drain throttled bios
1529 * @q: request_queue to drain throttled bios for
1531 * Dispatch all currently throttled bios on @q through ->make_request_fn().
1533 void blk_throtl_drain(struct request_queue
*q
)
1534 __releases(q
->queue_lock
) __acquires(q
->queue_lock
)
1536 struct throtl_data
*td
= q
->td
;
1537 struct blkcg_gq
*blkg
;
1538 struct cgroup
*pos_cgrp
;
1542 queue_lockdep_assert_held(q
);
1546 * Drain each tg while doing post-order walk on the blkg tree, so
1547 * that all bios are propagated to td->service_queue. It'd be
1548 * better to walk service_queue tree directly but blkg walk is
1551 blkg_for_each_descendant_post(blkg
, pos_cgrp
, td
->queue
->root_blkg
)
1552 tg_drain_bios(&blkg_to_tg(blkg
)->service_queue
);
1554 tg_drain_bios(&td_root_tg(td
)->service_queue
);
1556 /* finally, transfer bios from top-level tg's into the td */
1557 tg_drain_bios(&td
->service_queue
);
1560 spin_unlock_irq(q
->queue_lock
);
1562 /* all bios now should be in td->service_queue, issue them */
1563 for (rw
= READ
; rw
<= WRITE
; rw
++)
1564 while ((bio
= throtl_pop_queued(&td
->service_queue
.queued
[rw
],
1566 generic_make_request(bio
);
1568 spin_lock_irq(q
->queue_lock
);
1571 int blk_throtl_init(struct request_queue
*q
)
1573 struct throtl_data
*td
;
1576 td
= kzalloc_node(sizeof(*td
), GFP_KERNEL
, q
->node
);
1580 INIT_WORK(&td
->dispatch_work
, blk_throtl_dispatch_work_fn
);
1581 throtl_service_queue_init(&td
->service_queue
, NULL
);
1586 /* activate policy */
1587 ret
= blkcg_activate_policy(q
, &blkcg_policy_throtl
);
1593 void blk_throtl_exit(struct request_queue
*q
)
1596 throtl_shutdown_wq(q
);
1597 blkcg_deactivate_policy(q
, &blkcg_policy_throtl
);
1601 static int __init
throtl_init(void)
1603 kthrotld_workqueue
= alloc_workqueue("kthrotld", WQ_MEM_RECLAIM
, 0);
1604 if (!kthrotld_workqueue
)
1605 panic("Failed to create kthrotld\n");
1607 return blkcg_policy_register(&blkcg_policy_throtl
);
1610 module_init(throtl_init
);