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 <linux/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 /* are there any throtl rules between this group and td? */
130 /* bytes per second rate limits */
134 unsigned int iops
[2];
136 /* Number of bytes disptached in current slice */
137 uint64_t bytes_disp
[2];
138 /* Number of bio's dispatched in current slice */
139 unsigned int io_disp
[2];
141 /* When did we start a new slice */
142 unsigned long slice_start
[2];
143 unsigned long slice_end
[2];
145 /* Per cpu stats pointer */
146 struct tg_stats_cpu __percpu
*stats_cpu
;
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 static void throtl_pending_timer_fn(unsigned long arg
);
170 static inline struct throtl_grp
*pd_to_tg(struct blkg_policy_data
*pd
)
172 return pd
? container_of(pd
, struct throtl_grp
, pd
) : NULL
;
175 static inline struct throtl_grp
*blkg_to_tg(struct blkcg_gq
*blkg
)
177 return pd_to_tg(blkg_to_pd(blkg
, &blkcg_policy_throtl
));
180 static inline struct blkcg_gq
*tg_to_blkg(struct throtl_grp
*tg
)
182 return pd_to_blkg(&tg
->pd
);
185 static inline struct throtl_grp
*td_root_tg(struct throtl_data
*td
)
187 return blkg_to_tg(td
->queue
->root_blkg
);
191 * sq_to_tg - return the throl_grp the specified service queue belongs to
192 * @sq: the throtl_service_queue of interest
194 * Return the throtl_grp @sq belongs to. If @sq is the top-level one
195 * embedded in throtl_data, %NULL is returned.
197 static struct throtl_grp
*sq_to_tg(struct throtl_service_queue
*sq
)
199 if (sq
&& sq
->parent_sq
)
200 return container_of(sq
, struct throtl_grp
, service_queue
);
206 * sq_to_td - return throtl_data the specified service queue belongs to
207 * @sq: the throtl_service_queue of interest
209 * A service_queue can be embeded in either a throtl_grp or throtl_data.
210 * Determine the associated throtl_data accordingly and return it.
212 static struct throtl_data
*sq_to_td(struct throtl_service_queue
*sq
)
214 struct throtl_grp
*tg
= sq_to_tg(sq
);
219 return container_of(sq
, struct throtl_data
, service_queue
);
223 * throtl_log - log debug message via blktrace
224 * @sq: the service_queue being reported
225 * @fmt: printf format string
228 * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
229 * throtl_grp; otherwise, just "throtl".
231 * TODO: this should be made a function and name formatting should happen
232 * after testing whether blktrace is enabled.
234 #define throtl_log(sq, fmt, args...) do { \
235 struct throtl_grp *__tg = sq_to_tg((sq)); \
236 struct throtl_data *__td = sq_to_td((sq)); \
242 blkg_path(tg_to_blkg(__tg), __pbuf, sizeof(__pbuf)); \
243 blk_add_trace_msg(__td->queue, "throtl %s " fmt, __pbuf, ##args); \
245 blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \
249 static void throtl_qnode_init(struct throtl_qnode
*qn
, struct throtl_grp
*tg
)
251 INIT_LIST_HEAD(&qn
->node
);
252 bio_list_init(&qn
->bios
);
257 * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it
258 * @bio: bio being added
259 * @qn: qnode to add bio to
260 * @queued: the service_queue->queued[] list @qn belongs to
262 * Add @bio to @qn and put @qn on @queued if it's not already on.
263 * @qn->tg's reference count is bumped when @qn is activated. See the
264 * comment on top of throtl_qnode definition for details.
266 static void throtl_qnode_add_bio(struct bio
*bio
, struct throtl_qnode
*qn
,
267 struct list_head
*queued
)
269 bio_list_add(&qn
->bios
, bio
);
270 if (list_empty(&qn
->node
)) {
271 list_add_tail(&qn
->node
, queued
);
272 blkg_get(tg_to_blkg(qn
->tg
));
277 * throtl_peek_queued - peek the first bio on a qnode list
278 * @queued: the qnode list to peek
280 static struct bio
*throtl_peek_queued(struct list_head
*queued
)
282 struct throtl_qnode
*qn
= list_first_entry(queued
, struct throtl_qnode
, node
);
285 if (list_empty(queued
))
288 bio
= bio_list_peek(&qn
->bios
);
294 * throtl_pop_queued - pop the first bio form a qnode list
295 * @queued: the qnode list to pop a bio from
296 * @tg_to_put: optional out argument for throtl_grp to put
298 * Pop the first bio from the qnode list @queued. After popping, the first
299 * qnode is removed from @queued if empty or moved to the end of @queued so
300 * that the popping order is round-robin.
302 * When the first qnode is removed, its associated throtl_grp should be put
303 * too. If @tg_to_put is NULL, this function automatically puts it;
304 * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is
305 * responsible for putting it.
307 static struct bio
*throtl_pop_queued(struct list_head
*queued
,
308 struct throtl_grp
**tg_to_put
)
310 struct throtl_qnode
*qn
= list_first_entry(queued
, struct throtl_qnode
, node
);
313 if (list_empty(queued
))
316 bio
= bio_list_pop(&qn
->bios
);
319 if (bio_list_empty(&qn
->bios
)) {
320 list_del_init(&qn
->node
);
324 blkg_put(tg_to_blkg(qn
->tg
));
326 list_move_tail(&qn
->node
, queued
);
332 /* init a service_queue, assumes the caller zeroed it */
333 static void throtl_service_queue_init(struct throtl_service_queue
*sq
)
335 INIT_LIST_HEAD(&sq
->queued
[0]);
336 INIT_LIST_HEAD(&sq
->queued
[1]);
337 sq
->pending_tree
= RB_ROOT
;
338 setup_timer(&sq
->pending_timer
, throtl_pending_timer_fn
,
342 static struct blkg_policy_data
*throtl_pd_alloc(gfp_t gfp
, int node
)
344 struct throtl_grp
*tg
;
347 tg
= kzalloc_node(sizeof(*tg
), gfp
, node
);
351 tg
->stats_cpu
= alloc_percpu_gfp(struct tg_stats_cpu
, gfp
);
352 if (!tg
->stats_cpu
) {
357 throtl_service_queue_init(&tg
->service_queue
);
359 for (rw
= READ
; rw
<= WRITE
; rw
++) {
360 throtl_qnode_init(&tg
->qnode_on_self
[rw
], tg
);
361 throtl_qnode_init(&tg
->qnode_on_parent
[rw
], tg
);
364 RB_CLEAR_NODE(&tg
->rb_node
);
368 tg
->iops
[WRITE
] = -1;
370 for_each_possible_cpu(cpu
) {
371 struct tg_stats_cpu
*stats_cpu
= per_cpu_ptr(tg
->stats_cpu
, cpu
);
373 blkg_rwstat_init(&stats_cpu
->service_bytes
);
374 blkg_rwstat_init(&stats_cpu
->serviced
);
380 static void throtl_pd_init(struct blkcg_gq
*blkg
)
382 struct throtl_grp
*tg
= blkg_to_tg(blkg
);
383 struct throtl_data
*td
= blkg
->q
->td
;
384 struct throtl_service_queue
*sq
= &tg
->service_queue
;
387 * If on the default hierarchy, we switch to properly hierarchical
388 * behavior where limits on a given throtl_grp are applied to the
389 * whole subtree rather than just the group itself. e.g. If 16M
390 * read_bps limit is set on the root group, the whole system can't
391 * exceed 16M for the device.
393 * If not on the default hierarchy, the broken flat hierarchy
394 * behavior is retained where all throtl_grps are treated as if
395 * they're all separate root groups right below throtl_data.
396 * Limits of a group don't interact with limits of other groups
397 * regardless of the position of the group in the hierarchy.
399 sq
->parent_sq
= &td
->service_queue
;
400 if (cgroup_on_dfl(blkg
->blkcg
->css
.cgroup
) && blkg
->parent
)
401 sq
->parent_sq
= &blkg_to_tg(blkg
->parent
)->service_queue
;
406 * Set has_rules[] if @tg or any of its parents have limits configured.
407 * This doesn't require walking up to the top of the hierarchy as the
408 * parent's has_rules[] is guaranteed to be correct.
410 static void tg_update_has_rules(struct throtl_grp
*tg
)
412 struct throtl_grp
*parent_tg
= sq_to_tg(tg
->service_queue
.parent_sq
);
415 for (rw
= READ
; rw
<= WRITE
; rw
++)
416 tg
->has_rules
[rw
] = (parent_tg
&& parent_tg
->has_rules
[rw
]) ||
417 (tg
->bps
[rw
] != -1 || tg
->iops
[rw
] != -1);
420 static void throtl_pd_online(struct blkcg_gq
*blkg
)
423 * We don't want new groups to escape the limits of its ancestors.
424 * Update has_rules[] after a new group is brought online.
426 tg_update_has_rules(blkg_to_tg(blkg
));
429 static void throtl_pd_free(struct blkg_policy_data
*pd
)
431 struct throtl_grp
*tg
= pd_to_tg(pd
);
433 del_timer_sync(&tg
->service_queue
.pending_timer
);
434 free_percpu(tg
->stats_cpu
);
438 static void throtl_pd_reset_stats(struct blkcg_gq
*blkg
)
440 struct throtl_grp
*tg
= blkg_to_tg(blkg
);
443 for_each_possible_cpu(cpu
) {
444 struct tg_stats_cpu
*sc
= per_cpu_ptr(tg
->stats_cpu
, cpu
);
446 blkg_rwstat_reset(&sc
->service_bytes
);
447 blkg_rwstat_reset(&sc
->serviced
);
451 static struct throtl_grp
*throtl_lookup_tg(struct throtl_data
*td
,
455 * This is the common case when there are no blkcgs. Avoid lookup
458 if (blkcg
== &blkcg_root
)
459 return td_root_tg(td
);
461 return blkg_to_tg(blkg_lookup(blkcg
, td
->queue
));
464 static struct throtl_grp
*throtl_lookup_create_tg(struct throtl_data
*td
,
467 struct request_queue
*q
= td
->queue
;
468 struct throtl_grp
*tg
= NULL
;
471 * This is the common case when there are no blkcgs. Avoid lookup
474 if (blkcg
== &blkcg_root
) {
477 struct blkcg_gq
*blkg
;
479 blkg
= blkg_lookup_create(blkcg
, q
);
481 /* if %NULL and @q is alive, fall back to root_tg */
483 tg
= blkg_to_tg(blkg
);
484 else if (!blk_queue_dying(q
))
491 static struct throtl_grp
*
492 throtl_rb_first(struct throtl_service_queue
*parent_sq
)
494 /* Service tree is empty */
495 if (!parent_sq
->nr_pending
)
498 if (!parent_sq
->first_pending
)
499 parent_sq
->first_pending
= rb_first(&parent_sq
->pending_tree
);
501 if (parent_sq
->first_pending
)
502 return rb_entry_tg(parent_sq
->first_pending
);
507 static void rb_erase_init(struct rb_node
*n
, struct rb_root
*root
)
513 static void throtl_rb_erase(struct rb_node
*n
,
514 struct throtl_service_queue
*parent_sq
)
516 if (parent_sq
->first_pending
== n
)
517 parent_sq
->first_pending
= NULL
;
518 rb_erase_init(n
, &parent_sq
->pending_tree
);
519 --parent_sq
->nr_pending
;
522 static void update_min_dispatch_time(struct throtl_service_queue
*parent_sq
)
524 struct throtl_grp
*tg
;
526 tg
= throtl_rb_first(parent_sq
);
530 parent_sq
->first_pending_disptime
= tg
->disptime
;
533 static void tg_service_queue_add(struct throtl_grp
*tg
)
535 struct throtl_service_queue
*parent_sq
= tg
->service_queue
.parent_sq
;
536 struct rb_node
**node
= &parent_sq
->pending_tree
.rb_node
;
537 struct rb_node
*parent
= NULL
;
538 struct throtl_grp
*__tg
;
539 unsigned long key
= tg
->disptime
;
542 while (*node
!= NULL
) {
544 __tg
= rb_entry_tg(parent
);
546 if (time_before(key
, __tg
->disptime
))
547 node
= &parent
->rb_left
;
549 node
= &parent
->rb_right
;
555 parent_sq
->first_pending
= &tg
->rb_node
;
557 rb_link_node(&tg
->rb_node
, parent
, node
);
558 rb_insert_color(&tg
->rb_node
, &parent_sq
->pending_tree
);
561 static void __throtl_enqueue_tg(struct throtl_grp
*tg
)
563 tg_service_queue_add(tg
);
564 tg
->flags
|= THROTL_TG_PENDING
;
565 tg
->service_queue
.parent_sq
->nr_pending
++;
568 static void throtl_enqueue_tg(struct throtl_grp
*tg
)
570 if (!(tg
->flags
& THROTL_TG_PENDING
))
571 __throtl_enqueue_tg(tg
);
574 static void __throtl_dequeue_tg(struct throtl_grp
*tg
)
576 throtl_rb_erase(&tg
->rb_node
, tg
->service_queue
.parent_sq
);
577 tg
->flags
&= ~THROTL_TG_PENDING
;
580 static void throtl_dequeue_tg(struct throtl_grp
*tg
)
582 if (tg
->flags
& THROTL_TG_PENDING
)
583 __throtl_dequeue_tg(tg
);
586 /* Call with queue lock held */
587 static void throtl_schedule_pending_timer(struct throtl_service_queue
*sq
,
588 unsigned long expires
)
590 mod_timer(&sq
->pending_timer
, expires
);
591 throtl_log(sq
, "schedule timer. delay=%lu jiffies=%lu",
592 expires
- jiffies
, jiffies
);
596 * throtl_schedule_next_dispatch - schedule the next dispatch cycle
597 * @sq: the service_queue to schedule dispatch for
598 * @force: force scheduling
600 * Arm @sq->pending_timer so that the next dispatch cycle starts on the
601 * dispatch time of the first pending child. Returns %true if either timer
602 * is armed or there's no pending child left. %false if the current
603 * dispatch window is still open and the caller should continue
606 * If @force is %true, the dispatch timer is always scheduled and this
607 * function is guaranteed to return %true. This is to be used when the
608 * caller can't dispatch itself and needs to invoke pending_timer
609 * unconditionally. Note that forced scheduling is likely to induce short
610 * delay before dispatch starts even if @sq->first_pending_disptime is not
611 * in the future and thus shouldn't be used in hot paths.
613 static bool throtl_schedule_next_dispatch(struct throtl_service_queue
*sq
,
616 /* any pending children left? */
620 update_min_dispatch_time(sq
);
622 /* is the next dispatch time in the future? */
623 if (force
|| time_after(sq
->first_pending_disptime
, jiffies
)) {
624 throtl_schedule_pending_timer(sq
, sq
->first_pending_disptime
);
628 /* tell the caller to continue dispatching */
632 static inline void throtl_start_new_slice_with_credit(struct throtl_grp
*tg
,
633 bool rw
, unsigned long start
)
635 tg
->bytes_disp
[rw
] = 0;
639 * Previous slice has expired. We must have trimmed it after last
640 * bio dispatch. That means since start of last slice, we never used
641 * that bandwidth. Do try to make use of that bandwidth while giving
644 if (time_after_eq(start
, tg
->slice_start
[rw
]))
645 tg
->slice_start
[rw
] = start
;
647 tg
->slice_end
[rw
] = jiffies
+ throtl_slice
;
648 throtl_log(&tg
->service_queue
,
649 "[%c] new slice with credit start=%lu end=%lu jiffies=%lu",
650 rw
== READ
? 'R' : 'W', tg
->slice_start
[rw
],
651 tg
->slice_end
[rw
], jiffies
);
654 static inline void throtl_start_new_slice(struct throtl_grp
*tg
, bool rw
)
656 tg
->bytes_disp
[rw
] = 0;
658 tg
->slice_start
[rw
] = jiffies
;
659 tg
->slice_end
[rw
] = jiffies
+ throtl_slice
;
660 throtl_log(&tg
->service_queue
,
661 "[%c] new slice start=%lu end=%lu jiffies=%lu",
662 rw
== READ
? 'R' : 'W', tg
->slice_start
[rw
],
663 tg
->slice_end
[rw
], jiffies
);
666 static inline void throtl_set_slice_end(struct throtl_grp
*tg
, bool rw
,
667 unsigned long jiffy_end
)
669 tg
->slice_end
[rw
] = roundup(jiffy_end
, throtl_slice
);
672 static inline void throtl_extend_slice(struct throtl_grp
*tg
, bool rw
,
673 unsigned long jiffy_end
)
675 tg
->slice_end
[rw
] = roundup(jiffy_end
, throtl_slice
);
676 throtl_log(&tg
->service_queue
,
677 "[%c] extend slice start=%lu end=%lu jiffies=%lu",
678 rw
== READ
? 'R' : 'W', tg
->slice_start
[rw
],
679 tg
->slice_end
[rw
], jiffies
);
682 /* Determine if previously allocated or extended slice is complete or not */
683 static bool throtl_slice_used(struct throtl_grp
*tg
, bool rw
)
685 if (time_in_range(jiffies
, tg
->slice_start
[rw
], tg
->slice_end
[rw
]))
691 /* Trim the used slices and adjust slice start accordingly */
692 static inline void throtl_trim_slice(struct throtl_grp
*tg
, bool rw
)
694 unsigned long nr_slices
, time_elapsed
, io_trim
;
697 BUG_ON(time_before(tg
->slice_end
[rw
], tg
->slice_start
[rw
]));
700 * If bps are unlimited (-1), then time slice don't get
701 * renewed. Don't try to trim the slice if slice is used. A new
702 * slice will start when appropriate.
704 if (throtl_slice_used(tg
, rw
))
708 * A bio has been dispatched. Also adjust slice_end. It might happen
709 * that initially cgroup limit was very low resulting in high
710 * slice_end, but later limit was bumped up and bio was dispached
711 * sooner, then we need to reduce slice_end. A high bogus slice_end
712 * is bad because it does not allow new slice to start.
715 throtl_set_slice_end(tg
, rw
, jiffies
+ throtl_slice
);
717 time_elapsed
= jiffies
- tg
->slice_start
[rw
];
719 nr_slices
= time_elapsed
/ throtl_slice
;
723 tmp
= tg
->bps
[rw
] * throtl_slice
* nr_slices
;
727 io_trim
= (tg
->iops
[rw
] * throtl_slice
* nr_slices
)/HZ
;
729 if (!bytes_trim
&& !io_trim
)
732 if (tg
->bytes_disp
[rw
] >= bytes_trim
)
733 tg
->bytes_disp
[rw
] -= bytes_trim
;
735 tg
->bytes_disp
[rw
] = 0;
737 if (tg
->io_disp
[rw
] >= io_trim
)
738 tg
->io_disp
[rw
] -= io_trim
;
742 tg
->slice_start
[rw
] += nr_slices
* throtl_slice
;
744 throtl_log(&tg
->service_queue
,
745 "[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu",
746 rw
== READ
? 'R' : 'W', nr_slices
, bytes_trim
, io_trim
,
747 tg
->slice_start
[rw
], tg
->slice_end
[rw
], jiffies
);
750 static bool tg_with_in_iops_limit(struct throtl_grp
*tg
, struct bio
*bio
,
753 bool rw
= bio_data_dir(bio
);
754 unsigned int io_allowed
;
755 unsigned long jiffy_elapsed
, jiffy_wait
, jiffy_elapsed_rnd
;
758 jiffy_elapsed
= jiffy_elapsed_rnd
= jiffies
- tg
->slice_start
[rw
];
760 /* Slice has just started. Consider one slice interval */
762 jiffy_elapsed_rnd
= throtl_slice
;
764 jiffy_elapsed_rnd
= roundup(jiffy_elapsed_rnd
, throtl_slice
);
767 * jiffy_elapsed_rnd should not be a big value as minimum iops can be
768 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
769 * will allow dispatch after 1 second and after that slice should
773 tmp
= (u64
)tg
->iops
[rw
] * jiffy_elapsed_rnd
;
777 io_allowed
= UINT_MAX
;
781 if (tg
->io_disp
[rw
] + 1 <= io_allowed
) {
787 /* Calc approx time to dispatch */
788 jiffy_wait
= ((tg
->io_disp
[rw
] + 1) * HZ
)/tg
->iops
[rw
] + 1;
790 if (jiffy_wait
> jiffy_elapsed
)
791 jiffy_wait
= jiffy_wait
- jiffy_elapsed
;
800 static bool tg_with_in_bps_limit(struct throtl_grp
*tg
, struct bio
*bio
,
803 bool rw
= bio_data_dir(bio
);
804 u64 bytes_allowed
, extra_bytes
, tmp
;
805 unsigned long jiffy_elapsed
, jiffy_wait
, jiffy_elapsed_rnd
;
807 jiffy_elapsed
= jiffy_elapsed_rnd
= jiffies
- tg
->slice_start
[rw
];
809 /* Slice has just started. Consider one slice interval */
811 jiffy_elapsed_rnd
= throtl_slice
;
813 jiffy_elapsed_rnd
= roundup(jiffy_elapsed_rnd
, throtl_slice
);
815 tmp
= tg
->bps
[rw
] * jiffy_elapsed_rnd
;
819 if (tg
->bytes_disp
[rw
] + bio
->bi_iter
.bi_size
<= bytes_allowed
) {
825 /* Calc approx time to dispatch */
826 extra_bytes
= tg
->bytes_disp
[rw
] + bio
->bi_iter
.bi_size
- bytes_allowed
;
827 jiffy_wait
= div64_u64(extra_bytes
* HZ
, tg
->bps
[rw
]);
833 * This wait time is without taking into consideration the rounding
834 * up we did. Add that time also.
836 jiffy_wait
= jiffy_wait
+ (jiffy_elapsed_rnd
- jiffy_elapsed
);
843 * Returns whether one can dispatch a bio or not. Also returns approx number
844 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
846 static bool tg_may_dispatch(struct throtl_grp
*tg
, struct bio
*bio
,
849 bool rw
= bio_data_dir(bio
);
850 unsigned long bps_wait
= 0, iops_wait
= 0, max_wait
= 0;
853 * Currently whole state machine of group depends on first bio
854 * queued in the group bio list. So one should not be calling
855 * this function with a different bio if there are other bios
858 BUG_ON(tg
->service_queue
.nr_queued
[rw
] &&
859 bio
!= throtl_peek_queued(&tg
->service_queue
.queued
[rw
]));
861 /* If tg->bps = -1, then BW is unlimited */
862 if (tg
->bps
[rw
] == -1 && tg
->iops
[rw
] == -1) {
869 * If previous slice expired, start a new one otherwise renew/extend
870 * existing slice to make sure it is at least throtl_slice interval
873 if (throtl_slice_used(tg
, rw
))
874 throtl_start_new_slice(tg
, rw
);
876 if (time_before(tg
->slice_end
[rw
], jiffies
+ throtl_slice
))
877 throtl_extend_slice(tg
, rw
, jiffies
+ throtl_slice
);
880 if (tg_with_in_bps_limit(tg
, bio
, &bps_wait
) &&
881 tg_with_in_iops_limit(tg
, bio
, &iops_wait
)) {
887 max_wait
= max(bps_wait
, iops_wait
);
892 if (time_before(tg
->slice_end
[rw
], jiffies
+ max_wait
))
893 throtl_extend_slice(tg
, rw
, jiffies
+ max_wait
);
898 static void throtl_update_dispatch_stats(struct blkcg_gq
*blkg
, u64 bytes
,
901 struct throtl_grp
*tg
= blkg_to_tg(blkg
);
902 struct tg_stats_cpu
*stats_cpu
;
906 * Disabling interrupts to provide mutual exclusion between two
907 * writes on same cpu. It probably is not needed for 64bit. Not
908 * optimizing that case yet.
910 local_irq_save(flags
);
912 stats_cpu
= this_cpu_ptr(tg
->stats_cpu
);
914 blkg_rwstat_add(&stats_cpu
->serviced
, rw
, 1);
915 blkg_rwstat_add(&stats_cpu
->service_bytes
, rw
, bytes
);
917 local_irq_restore(flags
);
920 static void throtl_charge_bio(struct throtl_grp
*tg
, struct bio
*bio
)
922 bool rw
= bio_data_dir(bio
);
924 /* Charge the bio to the group */
925 tg
->bytes_disp
[rw
] += bio
->bi_iter
.bi_size
;
929 * REQ_THROTTLED is used to prevent the same bio to be throttled
930 * more than once as a throttled bio will go through blk-throtl the
931 * second time when it eventually gets issued. Set it when a bio
932 * is being charged to a tg.
934 * Dispatch stats aren't recursive and each @bio should only be
935 * accounted by the @tg it was originally associated with. Let's
936 * update the stats when setting REQ_THROTTLED for the first time
937 * which is guaranteed to be for the @bio's original tg.
939 if (!(bio
->bi_rw
& REQ_THROTTLED
)) {
940 bio
->bi_rw
|= REQ_THROTTLED
;
941 throtl_update_dispatch_stats(tg_to_blkg(tg
),
942 bio
->bi_iter
.bi_size
, bio
->bi_rw
);
947 * throtl_add_bio_tg - add a bio to the specified throtl_grp
950 * @tg: the target throtl_grp
952 * Add @bio to @tg's service_queue using @qn. If @qn is not specified,
953 * tg->qnode_on_self[] is used.
955 static void throtl_add_bio_tg(struct bio
*bio
, struct throtl_qnode
*qn
,
956 struct throtl_grp
*tg
)
958 struct throtl_service_queue
*sq
= &tg
->service_queue
;
959 bool rw
= bio_data_dir(bio
);
962 qn
= &tg
->qnode_on_self
[rw
];
965 * If @tg doesn't currently have any bios queued in the same
966 * direction, queueing @bio can change when @tg should be
967 * dispatched. Mark that @tg was empty. This is automatically
968 * cleaered on the next tg_update_disptime().
970 if (!sq
->nr_queued
[rw
])
971 tg
->flags
|= THROTL_TG_WAS_EMPTY
;
973 throtl_qnode_add_bio(bio
, qn
, &sq
->queued
[rw
]);
976 throtl_enqueue_tg(tg
);
979 static void tg_update_disptime(struct throtl_grp
*tg
)
981 struct throtl_service_queue
*sq
= &tg
->service_queue
;
982 unsigned long read_wait
= -1, write_wait
= -1, min_wait
= -1, disptime
;
985 if ((bio
= throtl_peek_queued(&sq
->queued
[READ
])))
986 tg_may_dispatch(tg
, bio
, &read_wait
);
988 if ((bio
= throtl_peek_queued(&sq
->queued
[WRITE
])))
989 tg_may_dispatch(tg
, bio
, &write_wait
);
991 min_wait
= min(read_wait
, write_wait
);
992 disptime
= jiffies
+ min_wait
;
994 /* Update dispatch time */
995 throtl_dequeue_tg(tg
);
996 tg
->disptime
= disptime
;
997 throtl_enqueue_tg(tg
);
999 /* see throtl_add_bio_tg() */
1000 tg
->flags
&= ~THROTL_TG_WAS_EMPTY
;
1003 static void start_parent_slice_with_credit(struct throtl_grp
*child_tg
,
1004 struct throtl_grp
*parent_tg
, bool rw
)
1006 if (throtl_slice_used(parent_tg
, rw
)) {
1007 throtl_start_new_slice_with_credit(parent_tg
, rw
,
1008 child_tg
->slice_start
[rw
]);
1013 static void tg_dispatch_one_bio(struct throtl_grp
*tg
, bool rw
)
1015 struct throtl_service_queue
*sq
= &tg
->service_queue
;
1016 struct throtl_service_queue
*parent_sq
= sq
->parent_sq
;
1017 struct throtl_grp
*parent_tg
= sq_to_tg(parent_sq
);
1018 struct throtl_grp
*tg_to_put
= NULL
;
1022 * @bio is being transferred from @tg to @parent_sq. Popping a bio
1023 * from @tg may put its reference and @parent_sq might end up
1024 * getting released prematurely. Remember the tg to put and put it
1025 * after @bio is transferred to @parent_sq.
1027 bio
= throtl_pop_queued(&sq
->queued
[rw
], &tg_to_put
);
1028 sq
->nr_queued
[rw
]--;
1030 throtl_charge_bio(tg
, bio
);
1033 * If our parent is another tg, we just need to transfer @bio to
1034 * the parent using throtl_add_bio_tg(). If our parent is
1035 * @td->service_queue, @bio is ready to be issued. Put it on its
1036 * bio_lists[] and decrease total number queued. The caller is
1037 * responsible for issuing these bios.
1040 throtl_add_bio_tg(bio
, &tg
->qnode_on_parent
[rw
], parent_tg
);
1041 start_parent_slice_with_credit(tg
, parent_tg
, rw
);
1043 throtl_qnode_add_bio(bio
, &tg
->qnode_on_parent
[rw
],
1044 &parent_sq
->queued
[rw
]);
1045 BUG_ON(tg
->td
->nr_queued
[rw
] <= 0);
1046 tg
->td
->nr_queued
[rw
]--;
1049 throtl_trim_slice(tg
, rw
);
1052 blkg_put(tg_to_blkg(tg_to_put
));
1055 static int throtl_dispatch_tg(struct throtl_grp
*tg
)
1057 struct throtl_service_queue
*sq
= &tg
->service_queue
;
1058 unsigned int nr_reads
= 0, nr_writes
= 0;
1059 unsigned int max_nr_reads
= throtl_grp_quantum
*3/4;
1060 unsigned int max_nr_writes
= throtl_grp_quantum
- max_nr_reads
;
1063 /* Try to dispatch 75% READS and 25% WRITES */
1065 while ((bio
= throtl_peek_queued(&sq
->queued
[READ
])) &&
1066 tg_may_dispatch(tg
, bio
, NULL
)) {
1068 tg_dispatch_one_bio(tg
, bio_data_dir(bio
));
1071 if (nr_reads
>= max_nr_reads
)
1075 while ((bio
= throtl_peek_queued(&sq
->queued
[WRITE
])) &&
1076 tg_may_dispatch(tg
, bio
, NULL
)) {
1078 tg_dispatch_one_bio(tg
, bio_data_dir(bio
));
1081 if (nr_writes
>= max_nr_writes
)
1085 return nr_reads
+ nr_writes
;
1088 static int throtl_select_dispatch(struct throtl_service_queue
*parent_sq
)
1090 unsigned int nr_disp
= 0;
1093 struct throtl_grp
*tg
= throtl_rb_first(parent_sq
);
1094 struct throtl_service_queue
*sq
= &tg
->service_queue
;
1099 if (time_before(jiffies
, tg
->disptime
))
1102 throtl_dequeue_tg(tg
);
1104 nr_disp
+= throtl_dispatch_tg(tg
);
1106 if (sq
->nr_queued
[0] || sq
->nr_queued
[1])
1107 tg_update_disptime(tg
);
1109 if (nr_disp
>= throtl_quantum
)
1117 * throtl_pending_timer_fn - timer function for service_queue->pending_timer
1118 * @arg: the throtl_service_queue being serviced
1120 * This timer is armed when a child throtl_grp with active bio's become
1121 * pending and queued on the service_queue's pending_tree and expires when
1122 * the first child throtl_grp should be dispatched. This function
1123 * dispatches bio's from the children throtl_grps to the parent
1126 * If the parent's parent is another throtl_grp, dispatching is propagated
1127 * by either arming its pending_timer or repeating dispatch directly. If
1128 * the top-level service_tree is reached, throtl_data->dispatch_work is
1129 * kicked so that the ready bio's are issued.
1131 static void throtl_pending_timer_fn(unsigned long arg
)
1133 struct throtl_service_queue
*sq
= (void *)arg
;
1134 struct throtl_grp
*tg
= sq_to_tg(sq
);
1135 struct throtl_data
*td
= sq_to_td(sq
);
1136 struct request_queue
*q
= td
->queue
;
1137 struct throtl_service_queue
*parent_sq
;
1141 spin_lock_irq(q
->queue_lock
);
1143 parent_sq
= sq
->parent_sq
;
1147 throtl_log(sq
, "dispatch nr_queued=%u read=%u write=%u",
1148 sq
->nr_queued
[READ
] + sq
->nr_queued
[WRITE
],
1149 sq
->nr_queued
[READ
], sq
->nr_queued
[WRITE
]);
1151 ret
= throtl_select_dispatch(sq
);
1153 throtl_log(sq
, "bios disp=%u", ret
);
1157 if (throtl_schedule_next_dispatch(sq
, false))
1160 /* this dispatch windows is still open, relax and repeat */
1161 spin_unlock_irq(q
->queue_lock
);
1163 spin_lock_irq(q
->queue_lock
);
1170 /* @parent_sq is another throl_grp, propagate dispatch */
1171 if (tg
->flags
& THROTL_TG_WAS_EMPTY
) {
1172 tg_update_disptime(tg
);
1173 if (!throtl_schedule_next_dispatch(parent_sq
, false)) {
1174 /* window is already open, repeat dispatching */
1181 /* reached the top-level, queue issueing */
1182 queue_work(kthrotld_workqueue
, &td
->dispatch_work
);
1185 spin_unlock_irq(q
->queue_lock
);
1189 * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work
1190 * @work: work item being executed
1192 * This function is queued for execution when bio's reach the bio_lists[]
1193 * of throtl_data->service_queue. Those bio's are ready and issued by this
1196 static void blk_throtl_dispatch_work_fn(struct work_struct
*work
)
1198 struct throtl_data
*td
= container_of(work
, struct throtl_data
,
1200 struct throtl_service_queue
*td_sq
= &td
->service_queue
;
1201 struct request_queue
*q
= td
->queue
;
1202 struct bio_list bio_list_on_stack
;
1204 struct blk_plug plug
;
1207 bio_list_init(&bio_list_on_stack
);
1209 spin_lock_irq(q
->queue_lock
);
1210 for (rw
= READ
; rw
<= WRITE
; rw
++)
1211 while ((bio
= throtl_pop_queued(&td_sq
->queued
[rw
], NULL
)))
1212 bio_list_add(&bio_list_on_stack
, bio
);
1213 spin_unlock_irq(q
->queue_lock
);
1215 if (!bio_list_empty(&bio_list_on_stack
)) {
1216 blk_start_plug(&plug
);
1217 while((bio
= bio_list_pop(&bio_list_on_stack
)))
1218 generic_make_request(bio
);
1219 blk_finish_plug(&plug
);
1223 static u64
tg_prfill_cpu_rwstat(struct seq_file
*sf
,
1224 struct blkg_policy_data
*pd
, int off
)
1226 struct throtl_grp
*tg
= pd_to_tg(pd
);
1227 struct blkg_rwstat rwstat
= { }, tmp
;
1230 for_each_possible_cpu(cpu
) {
1231 struct tg_stats_cpu
*sc
= per_cpu_ptr(tg
->stats_cpu
, cpu
);
1233 tmp
= blkg_rwstat_read((void *)sc
+ off
);
1234 for (i
= 0; i
< BLKG_RWSTAT_NR
; i
++)
1235 rwstat
.cnt
[i
] += tmp
.cnt
[i
];
1238 return __blkg_prfill_rwstat(sf
, pd
, &rwstat
);
1241 static int tg_print_cpu_rwstat(struct seq_file
*sf
, void *v
)
1243 blkcg_print_blkgs(sf
, css_to_blkcg(seq_css(sf
)), tg_prfill_cpu_rwstat
,
1244 &blkcg_policy_throtl
, seq_cft(sf
)->private, true);
1248 static u64
tg_prfill_conf_u64(struct seq_file
*sf
, struct blkg_policy_data
*pd
,
1251 struct throtl_grp
*tg
= pd_to_tg(pd
);
1252 u64 v
= *(u64
*)((void *)tg
+ off
);
1256 return __blkg_prfill_u64(sf
, pd
, v
);
1259 static u64
tg_prfill_conf_uint(struct seq_file
*sf
, struct blkg_policy_data
*pd
,
1262 struct throtl_grp
*tg
= pd_to_tg(pd
);
1263 unsigned int v
= *(unsigned int *)((void *)tg
+ off
);
1267 return __blkg_prfill_u64(sf
, pd
, v
);
1270 static int tg_print_conf_u64(struct seq_file
*sf
, void *v
)
1272 blkcg_print_blkgs(sf
, css_to_blkcg(seq_css(sf
)), tg_prfill_conf_u64
,
1273 &blkcg_policy_throtl
, seq_cft(sf
)->private, false);
1277 static int tg_print_conf_uint(struct seq_file
*sf
, void *v
)
1279 blkcg_print_blkgs(sf
, css_to_blkcg(seq_css(sf
)), tg_prfill_conf_uint
,
1280 &blkcg_policy_throtl
, seq_cft(sf
)->private, false);
1284 static ssize_t
tg_set_conf(struct kernfs_open_file
*of
,
1285 char *buf
, size_t nbytes
, loff_t off
, bool is_u64
)
1287 struct blkcg
*blkcg
= css_to_blkcg(of_css(of
));
1288 struct blkg_conf_ctx ctx
;
1289 struct throtl_grp
*tg
;
1290 struct throtl_service_queue
*sq
;
1291 struct blkcg_gq
*blkg
;
1292 struct cgroup_subsys_state
*pos_css
;
1295 ret
= blkg_conf_prep(blkcg
, &blkcg_policy_throtl
, buf
, &ctx
);
1299 tg
= blkg_to_tg(ctx
.blkg
);
1300 sq
= &tg
->service_queue
;
1306 *(u64
*)((void *)tg
+ of_cft(of
)->private) = ctx
.v
;
1308 *(unsigned int *)((void *)tg
+ of_cft(of
)->private) = ctx
.v
;
1310 throtl_log(&tg
->service_queue
,
1311 "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
1312 tg
->bps
[READ
], tg
->bps
[WRITE
],
1313 tg
->iops
[READ
], tg
->iops
[WRITE
]);
1316 * Update has_rules[] flags for the updated tg's subtree. A tg is
1317 * considered to have rules if either the tg itself or any of its
1318 * ancestors has rules. This identifies groups without any
1319 * restrictions in the whole hierarchy and allows them to bypass
1322 blkg_for_each_descendant_pre(blkg
, pos_css
, ctx
.blkg
)
1323 tg_update_has_rules(blkg_to_tg(blkg
));
1326 * We're already holding queue_lock and know @tg is valid. Let's
1327 * apply the new config directly.
1329 * Restart the slices for both READ and WRITES. It might happen
1330 * that a group's limit are dropped suddenly and we don't want to
1331 * account recently dispatched IO with new low rate.
1333 throtl_start_new_slice(tg
, 0);
1334 throtl_start_new_slice(tg
, 1);
1336 if (tg
->flags
& THROTL_TG_PENDING
) {
1337 tg_update_disptime(tg
);
1338 throtl_schedule_next_dispatch(sq
->parent_sq
, true);
1341 blkg_conf_finish(&ctx
);
1345 static ssize_t
tg_set_conf_u64(struct kernfs_open_file
*of
,
1346 char *buf
, size_t nbytes
, loff_t off
)
1348 return tg_set_conf(of
, buf
, nbytes
, off
, true);
1351 static ssize_t
tg_set_conf_uint(struct kernfs_open_file
*of
,
1352 char *buf
, size_t nbytes
, loff_t off
)
1354 return tg_set_conf(of
, buf
, nbytes
, off
, false);
1357 static struct cftype throtl_files
[] = {
1359 .name
= "throttle.read_bps_device",
1360 .private = offsetof(struct throtl_grp
, bps
[READ
]),
1361 .seq_show
= tg_print_conf_u64
,
1362 .write
= tg_set_conf_u64
,
1365 .name
= "throttle.write_bps_device",
1366 .private = offsetof(struct throtl_grp
, bps
[WRITE
]),
1367 .seq_show
= tg_print_conf_u64
,
1368 .write
= tg_set_conf_u64
,
1371 .name
= "throttle.read_iops_device",
1372 .private = offsetof(struct throtl_grp
, iops
[READ
]),
1373 .seq_show
= tg_print_conf_uint
,
1374 .write
= tg_set_conf_uint
,
1377 .name
= "throttle.write_iops_device",
1378 .private = offsetof(struct throtl_grp
, iops
[WRITE
]),
1379 .seq_show
= tg_print_conf_uint
,
1380 .write
= tg_set_conf_uint
,
1383 .name
= "throttle.io_service_bytes",
1384 .private = offsetof(struct tg_stats_cpu
, service_bytes
),
1385 .seq_show
= tg_print_cpu_rwstat
,
1388 .name
= "throttle.io_serviced",
1389 .private = offsetof(struct tg_stats_cpu
, serviced
),
1390 .seq_show
= tg_print_cpu_rwstat
,
1395 static void throtl_shutdown_wq(struct request_queue
*q
)
1397 struct throtl_data
*td
= q
->td
;
1399 cancel_work_sync(&td
->dispatch_work
);
1402 static struct blkcg_policy blkcg_policy_throtl
= {
1403 .cftypes
= throtl_files
,
1405 .pd_alloc_fn
= throtl_pd_alloc
,
1406 .pd_init_fn
= throtl_pd_init
,
1407 .pd_online_fn
= throtl_pd_online
,
1408 .pd_free_fn
= throtl_pd_free
,
1409 .pd_reset_stats_fn
= throtl_pd_reset_stats
,
1412 bool blk_throtl_bio(struct request_queue
*q
, struct bio
*bio
)
1414 struct throtl_data
*td
= q
->td
;
1415 struct throtl_qnode
*qn
= NULL
;
1416 struct throtl_grp
*tg
;
1417 struct throtl_service_queue
*sq
;
1418 bool rw
= bio_data_dir(bio
);
1419 struct blkcg
*blkcg
;
1420 bool throttled
= false;
1422 /* see throtl_charge_bio() */
1423 if (bio
->bi_rw
& REQ_THROTTLED
)
1427 * A throtl_grp pointer retrieved under rcu can be used to access
1428 * basic fields like stats and io rates. If a group has no rules,
1429 * just update the dispatch stats in lockless manner and return.
1432 blkcg
= bio_blkcg(bio
);
1433 tg
= throtl_lookup_tg(td
, blkcg
);
1435 if (!tg
->has_rules
[rw
]) {
1436 throtl_update_dispatch_stats(tg_to_blkg(tg
),
1437 bio
->bi_iter
.bi_size
, bio
->bi_rw
);
1438 goto out_unlock_rcu
;
1443 * Either group has not been allocated yet or it is not an unlimited
1446 spin_lock_irq(q
->queue_lock
);
1447 tg
= throtl_lookup_create_tg(td
, blkcg
);
1451 sq
= &tg
->service_queue
;
1454 /* throtl is FIFO - if bios are already queued, should queue */
1455 if (sq
->nr_queued
[rw
])
1458 /* if above limits, break to queue */
1459 if (!tg_may_dispatch(tg
, bio
, NULL
))
1462 /* within limits, let's charge and dispatch directly */
1463 throtl_charge_bio(tg
, bio
);
1466 * We need to trim slice even when bios are not being queued
1467 * otherwise it might happen that a bio is not queued for
1468 * a long time and slice keeps on extending and trim is not
1469 * called for a long time. Now if limits are reduced suddenly
1470 * we take into account all the IO dispatched so far at new
1471 * low rate and * newly queued IO gets a really long dispatch
1474 * So keep on trimming slice even if bio is not queued.
1476 throtl_trim_slice(tg
, rw
);
1479 * @bio passed through this layer without being throttled.
1480 * Climb up the ladder. If we''re already at the top, it
1481 * can be executed directly.
1483 qn
= &tg
->qnode_on_parent
[rw
];
1490 /* out-of-limit, queue to @tg */
1491 throtl_log(sq
, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
1492 rw
== READ
? 'R' : 'W',
1493 tg
->bytes_disp
[rw
], bio
->bi_iter
.bi_size
, tg
->bps
[rw
],
1494 tg
->io_disp
[rw
], tg
->iops
[rw
],
1495 sq
->nr_queued
[READ
], sq
->nr_queued
[WRITE
]);
1497 bio_associate_current(bio
);
1498 tg
->td
->nr_queued
[rw
]++;
1499 throtl_add_bio_tg(bio
, qn
, tg
);
1503 * Update @tg's dispatch time and force schedule dispatch if @tg
1504 * was empty before @bio. The forced scheduling isn't likely to
1505 * cause undue delay as @bio is likely to be dispatched directly if
1506 * its @tg's disptime is not in the future.
1508 if (tg
->flags
& THROTL_TG_WAS_EMPTY
) {
1509 tg_update_disptime(tg
);
1510 throtl_schedule_next_dispatch(tg
->service_queue
.parent_sq
, true);
1514 spin_unlock_irq(q
->queue_lock
);
1519 * As multiple blk-throtls may stack in the same issue path, we
1520 * don't want bios to leave with the flag set. Clear the flag if
1524 bio
->bi_rw
&= ~REQ_THROTTLED
;
1529 * Dispatch all bios from all children tg's queued on @parent_sq. On
1530 * return, @parent_sq is guaranteed to not have any active children tg's
1531 * and all bios from previously active tg's are on @parent_sq->bio_lists[].
1533 static void tg_drain_bios(struct throtl_service_queue
*parent_sq
)
1535 struct throtl_grp
*tg
;
1537 while ((tg
= throtl_rb_first(parent_sq
))) {
1538 struct throtl_service_queue
*sq
= &tg
->service_queue
;
1541 throtl_dequeue_tg(tg
);
1543 while ((bio
= throtl_peek_queued(&sq
->queued
[READ
])))
1544 tg_dispatch_one_bio(tg
, bio_data_dir(bio
));
1545 while ((bio
= throtl_peek_queued(&sq
->queued
[WRITE
])))
1546 tg_dispatch_one_bio(tg
, bio_data_dir(bio
));
1551 * blk_throtl_drain - drain throttled bios
1552 * @q: request_queue to drain throttled bios for
1554 * Dispatch all currently throttled bios on @q through ->make_request_fn().
1556 void blk_throtl_drain(struct request_queue
*q
)
1557 __releases(q
->queue_lock
) __acquires(q
->queue_lock
)
1559 struct throtl_data
*td
= q
->td
;
1560 struct blkcg_gq
*blkg
;
1561 struct cgroup_subsys_state
*pos_css
;
1565 queue_lockdep_assert_held(q
);
1569 * Drain each tg while doing post-order walk on the blkg tree, so
1570 * that all bios are propagated to td->service_queue. It'd be
1571 * better to walk service_queue tree directly but blkg walk is
1574 blkg_for_each_descendant_post(blkg
, pos_css
, td
->queue
->root_blkg
)
1575 tg_drain_bios(&blkg_to_tg(blkg
)->service_queue
);
1577 /* finally, transfer bios from top-level tg's into the td */
1578 tg_drain_bios(&td
->service_queue
);
1581 spin_unlock_irq(q
->queue_lock
);
1583 /* all bios now should be in td->service_queue, issue them */
1584 for (rw
= READ
; rw
<= WRITE
; rw
++)
1585 while ((bio
= throtl_pop_queued(&td
->service_queue
.queued
[rw
],
1587 generic_make_request(bio
);
1589 spin_lock_irq(q
->queue_lock
);
1592 int blk_throtl_init(struct request_queue
*q
)
1594 struct throtl_data
*td
;
1597 td
= kzalloc_node(sizeof(*td
), GFP_KERNEL
, q
->node
);
1601 INIT_WORK(&td
->dispatch_work
, blk_throtl_dispatch_work_fn
);
1602 throtl_service_queue_init(&td
->service_queue
);
1607 /* activate policy */
1608 ret
= blkcg_activate_policy(q
, &blkcg_policy_throtl
);
1614 void blk_throtl_exit(struct request_queue
*q
)
1617 throtl_shutdown_wq(q
);
1618 blkcg_deactivate_policy(q
, &blkcg_policy_throtl
);
1622 static int __init
throtl_init(void)
1624 kthrotld_workqueue
= alloc_workqueue("kthrotld", WQ_MEM_RECLAIM
, 0);
1625 if (!kthrotld_workqueue
)
1626 panic("Failed to create kthrotld\n");
1628 return blkcg_policy_register(&blkcg_policy_throtl
);
1631 module_init(throtl_init
);