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"
14 /* Max dispatch from a group in 1 round */
15 static int throtl_grp_quantum
= 8;
17 /* Total max dispatch from all groups in one round */
18 static int throtl_quantum
= 32;
20 /* Throttling is performed over 100ms slice and after that slice is renewed */
21 static unsigned long throtl_slice
= HZ
/10; /* 100 ms */
23 struct throtl_rb_root
{
27 unsigned long min_disptime
;
30 #define THROTL_RB_ROOT (struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \
31 .count = 0, .min_disptime = 0}
33 #define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
36 /* List of throtl groups on the request queue*/
37 struct hlist_node tg_node
;
39 /* active throtl group service_tree member */
40 struct rb_node rb_node
;
43 * Dispatch time in jiffies. This is the estimated time when group
44 * will unthrottle and is ready to dispatch more bio. It is used as
45 * key to sort active groups in service tree.
47 unsigned long disptime
;
49 struct blkio_group blkg
;
53 /* Two lists for READ and WRITE */
54 struct bio_list bio_lists
[2];
56 /* Number of queued bios on READ and WRITE lists */
57 unsigned int nr_queued
[2];
59 /* bytes per second rate limits */
65 /* Number of bytes disptached in current slice */
66 uint64_t bytes_disp
[2];
67 /* Number of bio's dispatched in current slice */
68 unsigned int io_disp
[2];
70 /* When did we start a new slice */
71 unsigned long slice_start
[2];
72 unsigned long slice_end
[2];
74 /* Some throttle limits got updated for the group */
80 /* List of throtl groups */
81 struct hlist_head tg_list
;
83 /* service tree for active throtl groups */
84 struct throtl_rb_root tg_service_tree
;
86 struct throtl_grp root_tg
;
87 struct request_queue
*queue
;
89 /* Total Number of queued bios on READ and WRITE lists */
90 unsigned int nr_queued
[2];
93 * number of total undestroyed groups
95 unsigned int nr_undestroyed_grps
;
97 /* Work for dispatching throttled bios */
98 struct delayed_work throtl_work
;
100 atomic_t limits_changed
;
103 enum tg_state_flags
{
104 THROTL_TG_FLAG_on_rr
= 0, /* on round-robin busy list */
107 #define THROTL_TG_FNS(name) \
108 static inline void throtl_mark_tg_##name(struct throtl_grp *tg) \
110 (tg)->flags |= (1 << THROTL_TG_FLAG_##name); \
112 static inline void throtl_clear_tg_##name(struct throtl_grp *tg) \
114 (tg)->flags &= ~(1 << THROTL_TG_FLAG_##name); \
116 static inline int throtl_tg_##name(const struct throtl_grp *tg) \
118 return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0; \
121 THROTL_TG_FNS(on_rr
);
123 #define throtl_log_tg(td, tg, fmt, args...) \
124 blk_add_trace_msg((td)->queue, "throtl %s " fmt, \
125 blkg_path(&(tg)->blkg), ##args); \
127 #define throtl_log(td, fmt, args...) \
128 blk_add_trace_msg((td)->queue, "throtl " fmt, ##args)
130 static inline struct throtl_grp
*tg_of_blkg(struct blkio_group
*blkg
)
133 return container_of(blkg
, struct throtl_grp
, blkg
);
138 static inline int total_nr_queued(struct throtl_data
*td
)
140 return (td
->nr_queued
[0] + td
->nr_queued
[1]);
143 static inline struct throtl_grp
*throtl_ref_get_tg(struct throtl_grp
*tg
)
145 atomic_inc(&tg
->ref
);
149 static void throtl_put_tg(struct throtl_grp
*tg
)
151 BUG_ON(atomic_read(&tg
->ref
) <= 0);
152 if (!atomic_dec_and_test(&tg
->ref
))
157 static struct throtl_grp
* throtl_find_alloc_tg(struct throtl_data
*td
,
158 struct cgroup
*cgroup
)
160 struct blkio_cgroup
*blkcg
= cgroup_to_blkio_cgroup(cgroup
);
161 struct throtl_grp
*tg
= NULL
;
163 struct backing_dev_info
*bdi
= &td
->queue
->backing_dev_info
;
164 unsigned int major
, minor
;
167 * TODO: Speed up blkiocg_lookup_group() by maintaining a radix
168 * tree of blkg (instead of traversing through hash list all
171 tg
= tg_of_blkg(blkiocg_lookup_group(blkcg
, key
));
173 /* Fill in device details for root group */
174 if (tg
&& !tg
->blkg
.dev
&& bdi
->dev
&& dev_name(bdi
->dev
)) {
175 sscanf(dev_name(bdi
->dev
), "%u:%u", &major
, &minor
);
176 tg
->blkg
.dev
= MKDEV(major
, minor
);
183 tg
= kzalloc_node(sizeof(*tg
), GFP_ATOMIC
, td
->queue
->node
);
187 INIT_HLIST_NODE(&tg
->tg_node
);
188 RB_CLEAR_NODE(&tg
->rb_node
);
189 bio_list_init(&tg
->bio_lists
[0]);
190 bio_list_init(&tg
->bio_lists
[1]);
193 * Take the initial reference that will be released on destroy
194 * This can be thought of a joint reference by cgroup and
195 * request queue which will be dropped by either request queue
196 * exit or cgroup deletion path depending on who is exiting first.
198 atomic_set(&tg
->ref
, 1);
200 /* Add group onto cgroup list */
201 sscanf(dev_name(bdi
->dev
), "%u:%u", &major
, &minor
);
202 blkiocg_add_blkio_group(blkcg
, &tg
->blkg
, (void *)td
,
203 MKDEV(major
, minor
), BLKIO_POLICY_THROTL
);
205 tg
->bps
[READ
] = blkcg_get_read_bps(blkcg
, tg
->blkg
.dev
);
206 tg
->bps
[WRITE
] = blkcg_get_write_bps(blkcg
, tg
->blkg
.dev
);
207 tg
->iops
[READ
] = blkcg_get_read_iops(blkcg
, tg
->blkg
.dev
);
208 tg
->iops
[WRITE
] = blkcg_get_write_iops(blkcg
, tg
->blkg
.dev
);
210 hlist_add_head(&tg
->tg_node
, &td
->tg_list
);
211 td
->nr_undestroyed_grps
++;
216 static struct throtl_grp
* throtl_get_tg(struct throtl_data
*td
)
218 struct cgroup
*cgroup
;
219 struct throtl_grp
*tg
= NULL
;
222 cgroup
= task_cgroup(current
, blkio_subsys_id
);
223 tg
= throtl_find_alloc_tg(td
, cgroup
);
230 static struct throtl_grp
*throtl_rb_first(struct throtl_rb_root
*root
)
232 /* Service tree is empty */
237 root
->left
= rb_first(&root
->rb
);
240 return rb_entry_tg(root
->left
);
245 static void rb_erase_init(struct rb_node
*n
, struct rb_root
*root
)
251 static void throtl_rb_erase(struct rb_node
*n
, struct throtl_rb_root
*root
)
255 rb_erase_init(n
, &root
->rb
);
259 static void update_min_dispatch_time(struct throtl_rb_root
*st
)
261 struct throtl_grp
*tg
;
263 tg
= throtl_rb_first(st
);
267 st
->min_disptime
= tg
->disptime
;
271 tg_service_tree_add(struct throtl_rb_root
*st
, struct throtl_grp
*tg
)
273 struct rb_node
**node
= &st
->rb
.rb_node
;
274 struct rb_node
*parent
= NULL
;
275 struct throtl_grp
*__tg
;
276 unsigned long key
= tg
->disptime
;
279 while (*node
!= NULL
) {
281 __tg
= rb_entry_tg(parent
);
283 if (time_before(key
, __tg
->disptime
))
284 node
= &parent
->rb_left
;
286 node
= &parent
->rb_right
;
292 st
->left
= &tg
->rb_node
;
294 rb_link_node(&tg
->rb_node
, parent
, node
);
295 rb_insert_color(&tg
->rb_node
, &st
->rb
);
298 static void __throtl_enqueue_tg(struct throtl_data
*td
, struct throtl_grp
*tg
)
300 struct throtl_rb_root
*st
= &td
->tg_service_tree
;
302 tg_service_tree_add(st
, tg
);
303 throtl_mark_tg_on_rr(tg
);
307 static void throtl_enqueue_tg(struct throtl_data
*td
, struct throtl_grp
*tg
)
309 if (!throtl_tg_on_rr(tg
))
310 __throtl_enqueue_tg(td
, tg
);
313 static void __throtl_dequeue_tg(struct throtl_data
*td
, struct throtl_grp
*tg
)
315 throtl_rb_erase(&tg
->rb_node
, &td
->tg_service_tree
);
316 throtl_clear_tg_on_rr(tg
);
319 static void throtl_dequeue_tg(struct throtl_data
*td
, struct throtl_grp
*tg
)
321 if (throtl_tg_on_rr(tg
))
322 __throtl_dequeue_tg(td
, tg
);
325 static void throtl_schedule_next_dispatch(struct throtl_data
*td
)
327 struct throtl_rb_root
*st
= &td
->tg_service_tree
;
330 * If there are more bios pending, schedule more work.
332 if (!total_nr_queued(td
))
337 update_min_dispatch_time(st
);
339 if (time_before_eq(st
->min_disptime
, jiffies
))
340 throtl_schedule_delayed_work(td
->queue
, 0);
342 throtl_schedule_delayed_work(td
->queue
,
343 (st
->min_disptime
- jiffies
));
347 throtl_start_new_slice(struct throtl_data
*td
, struct throtl_grp
*tg
, bool rw
)
349 tg
->bytes_disp
[rw
] = 0;
351 tg
->slice_start
[rw
] = jiffies
;
352 tg
->slice_end
[rw
] = jiffies
+ throtl_slice
;
353 throtl_log_tg(td
, tg
, "[%c] new slice start=%lu end=%lu jiffies=%lu",
354 rw
== READ
? 'R' : 'W', tg
->slice_start
[rw
],
355 tg
->slice_end
[rw
], jiffies
);
358 static inline void throtl_extend_slice(struct throtl_data
*td
,
359 struct throtl_grp
*tg
, bool rw
, unsigned long jiffy_end
)
361 tg
->slice_end
[rw
] = roundup(jiffy_end
, throtl_slice
);
362 throtl_log_tg(td
, tg
, "[%c] extend slice start=%lu end=%lu jiffies=%lu",
363 rw
== READ
? 'R' : 'W', tg
->slice_start
[rw
],
364 tg
->slice_end
[rw
], jiffies
);
367 /* Determine if previously allocated or extended slice is complete or not */
369 throtl_slice_used(struct throtl_data
*td
, struct throtl_grp
*tg
, bool rw
)
371 if (time_in_range(jiffies
, tg
->slice_start
[rw
], tg
->slice_end
[rw
]))
377 /* Trim the used slices and adjust slice start accordingly */
379 throtl_trim_slice(struct throtl_data
*td
, struct throtl_grp
*tg
, bool rw
)
381 unsigned long nr_slices
, bytes_trim
, time_elapsed
, io_trim
;
383 BUG_ON(time_before(tg
->slice_end
[rw
], tg
->slice_start
[rw
]));
386 * If bps are unlimited (-1), then time slice don't get
387 * renewed. Don't try to trim the slice if slice is used. A new
388 * slice will start when appropriate.
390 if (throtl_slice_used(td
, tg
, rw
))
393 time_elapsed
= jiffies
- tg
->slice_start
[rw
];
395 nr_slices
= time_elapsed
/ throtl_slice
;
400 bytes_trim
= (tg
->bps
[rw
] * throtl_slice
* nr_slices
)/HZ
;
401 io_trim
= (tg
->iops
[rw
] * throtl_slice
* nr_slices
)/HZ
;
403 if (!bytes_trim
&& !io_trim
)
406 if (tg
->bytes_disp
[rw
] >= bytes_trim
)
407 tg
->bytes_disp
[rw
] -= bytes_trim
;
409 tg
->bytes_disp
[rw
] = 0;
411 if (tg
->io_disp
[rw
] >= io_trim
)
412 tg
->io_disp
[rw
] -= io_trim
;
416 tg
->slice_start
[rw
] += nr_slices
* throtl_slice
;
418 throtl_log_tg(td
, tg
, "[%c] trim slice nr=%lu bytes=%lu io=%lu"
419 " start=%lu end=%lu jiffies=%lu",
420 rw
== READ
? 'R' : 'W', nr_slices
, bytes_trim
, io_trim
,
421 tg
->slice_start
[rw
], tg
->slice_end
[rw
], jiffies
);
424 static bool tg_with_in_iops_limit(struct throtl_data
*td
, struct throtl_grp
*tg
,
425 struct bio
*bio
, unsigned long *wait
)
427 bool rw
= bio_data_dir(bio
);
428 unsigned int io_allowed
;
429 unsigned long jiffy_elapsed
, jiffy_wait
, jiffy_elapsed_rnd
;
431 jiffy_elapsed
= jiffy_elapsed_rnd
= jiffies
- tg
->slice_start
[rw
];
433 /* Slice has just started. Consider one slice interval */
435 jiffy_elapsed_rnd
= throtl_slice
;
437 jiffy_elapsed_rnd
= roundup(jiffy_elapsed_rnd
, throtl_slice
);
439 io_allowed
= (tg
->iops
[rw
] * jiffies_to_msecs(jiffy_elapsed_rnd
))
442 if (tg
->io_disp
[rw
] + 1 <= io_allowed
) {
448 /* Calc approx time to dispatch */
449 jiffy_wait
= ((tg
->io_disp
[rw
] + 1) * HZ
)/tg
->iops
[rw
] + 1;
451 if (jiffy_wait
> jiffy_elapsed
)
452 jiffy_wait
= jiffy_wait
- jiffy_elapsed
;
461 static bool tg_with_in_bps_limit(struct throtl_data
*td
, struct throtl_grp
*tg
,
462 struct bio
*bio
, unsigned long *wait
)
464 bool rw
= bio_data_dir(bio
);
465 u64 bytes_allowed
, extra_bytes
;
466 unsigned long jiffy_elapsed
, jiffy_wait
, jiffy_elapsed_rnd
;
468 jiffy_elapsed
= jiffy_elapsed_rnd
= jiffies
- tg
->slice_start
[rw
];
470 /* Slice has just started. Consider one slice interval */
472 jiffy_elapsed_rnd
= throtl_slice
;
474 jiffy_elapsed_rnd
= roundup(jiffy_elapsed_rnd
, throtl_slice
);
476 bytes_allowed
= (tg
->bps
[rw
] * jiffies_to_msecs(jiffy_elapsed_rnd
))
479 if (tg
->bytes_disp
[rw
] + bio
->bi_size
<= bytes_allowed
) {
485 /* Calc approx time to dispatch */
486 extra_bytes
= tg
->bytes_disp
[rw
] + bio
->bi_size
- bytes_allowed
;
487 jiffy_wait
= div64_u64(extra_bytes
* HZ
, tg
->bps
[rw
]);
493 * This wait time is without taking into consideration the rounding
494 * up we did. Add that time also.
496 jiffy_wait
= jiffy_wait
+ (jiffy_elapsed_rnd
- jiffy_elapsed
);
503 * Returns whether one can dispatch a bio or not. Also returns approx number
504 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
506 static bool tg_may_dispatch(struct throtl_data
*td
, struct throtl_grp
*tg
,
507 struct bio
*bio
, unsigned long *wait
)
509 bool rw
= bio_data_dir(bio
);
510 unsigned long bps_wait
= 0, iops_wait
= 0, max_wait
= 0;
513 * Currently whole state machine of group depends on first bio
514 * queued in the group bio list. So one should not be calling
515 * this function with a different bio if there are other bios
518 BUG_ON(tg
->nr_queued
[rw
] && bio
!= bio_list_peek(&tg
->bio_lists
[rw
]));
520 /* If tg->bps = -1, then BW is unlimited */
521 if (tg
->bps
[rw
] == -1 && tg
->iops
[rw
] == -1) {
528 * If previous slice expired, start a new one otherwise renew/extend
529 * existing slice to make sure it is at least throtl_slice interval
532 if (throtl_slice_used(td
, tg
, rw
))
533 throtl_start_new_slice(td
, tg
, rw
);
535 if (time_before(tg
->slice_end
[rw
], jiffies
+ throtl_slice
))
536 throtl_extend_slice(td
, tg
, rw
, jiffies
+ throtl_slice
);
539 if (tg_with_in_bps_limit(td
, tg
, bio
, &bps_wait
)
540 && tg_with_in_iops_limit(td
, tg
, bio
, &iops_wait
)) {
546 max_wait
= max(bps_wait
, iops_wait
);
551 if (time_before(tg
->slice_end
[rw
], jiffies
+ max_wait
))
552 throtl_extend_slice(td
, tg
, rw
, jiffies
+ max_wait
);
557 static void throtl_charge_bio(struct throtl_grp
*tg
, struct bio
*bio
)
559 bool rw
= bio_data_dir(bio
);
560 bool sync
= bio
->bi_rw
& REQ_SYNC
;
562 /* Charge the bio to the group */
563 tg
->bytes_disp
[rw
] += bio
->bi_size
;
567 * TODO: This will take blkg->stats_lock. Figure out a way
568 * to avoid this cost.
570 blkiocg_update_dispatch_stats(&tg
->blkg
, bio
->bi_size
, rw
, sync
);
573 static void throtl_add_bio_tg(struct throtl_data
*td
, struct throtl_grp
*tg
,
576 bool rw
= bio_data_dir(bio
);
578 bio_list_add(&tg
->bio_lists
[rw
], bio
);
579 /* Take a bio reference on tg */
580 throtl_ref_get_tg(tg
);
583 throtl_enqueue_tg(td
, tg
);
586 static void tg_update_disptime(struct throtl_data
*td
, struct throtl_grp
*tg
)
588 unsigned long read_wait
= -1, write_wait
= -1, min_wait
= -1, disptime
;
591 if ((bio
= bio_list_peek(&tg
->bio_lists
[READ
])))
592 tg_may_dispatch(td
, tg
, bio
, &read_wait
);
594 if ((bio
= bio_list_peek(&tg
->bio_lists
[WRITE
])))
595 tg_may_dispatch(td
, tg
, bio
, &write_wait
);
597 min_wait
= min(read_wait
, write_wait
);
598 disptime
= jiffies
+ min_wait
;
600 /* Update dispatch time */
601 throtl_dequeue_tg(td
, tg
);
602 tg
->disptime
= disptime
;
603 throtl_enqueue_tg(td
, tg
);
606 static void tg_dispatch_one_bio(struct throtl_data
*td
, struct throtl_grp
*tg
,
607 bool rw
, struct bio_list
*bl
)
611 bio
= bio_list_pop(&tg
->bio_lists
[rw
]);
613 /* Drop bio reference on tg */
616 BUG_ON(td
->nr_queued
[rw
] <= 0);
619 throtl_charge_bio(tg
, bio
);
620 bio_list_add(bl
, bio
);
621 bio
->bi_rw
|= REQ_THROTTLED
;
623 throtl_trim_slice(td
, tg
, rw
);
626 static int throtl_dispatch_tg(struct throtl_data
*td
, struct throtl_grp
*tg
,
629 unsigned int nr_reads
= 0, nr_writes
= 0;
630 unsigned int max_nr_reads
= throtl_grp_quantum
*3/4;
631 unsigned int max_nr_writes
= throtl_grp_quantum
- nr_reads
;
634 /* Try to dispatch 75% READS and 25% WRITES */
636 while ((bio
= bio_list_peek(&tg
->bio_lists
[READ
]))
637 && tg_may_dispatch(td
, tg
, bio
, NULL
)) {
639 tg_dispatch_one_bio(td
, tg
, bio_data_dir(bio
), bl
);
642 if (nr_reads
>= max_nr_reads
)
646 while ((bio
= bio_list_peek(&tg
->bio_lists
[WRITE
]))
647 && tg_may_dispatch(td
, tg
, bio
, NULL
)) {
649 tg_dispatch_one_bio(td
, tg
, bio_data_dir(bio
), bl
);
652 if (nr_writes
>= max_nr_writes
)
656 return nr_reads
+ nr_writes
;
659 static int throtl_select_dispatch(struct throtl_data
*td
, struct bio_list
*bl
)
661 unsigned int nr_disp
= 0;
662 struct throtl_grp
*tg
;
663 struct throtl_rb_root
*st
= &td
->tg_service_tree
;
666 tg
= throtl_rb_first(st
);
671 if (time_before(jiffies
, tg
->disptime
))
674 throtl_dequeue_tg(td
, tg
);
676 nr_disp
+= throtl_dispatch_tg(td
, tg
, bl
);
678 if (tg
->nr_queued
[0] || tg
->nr_queued
[1]) {
679 tg_update_disptime(td
, tg
);
680 throtl_enqueue_tg(td
, tg
);
683 if (nr_disp
>= throtl_quantum
)
690 static void throtl_process_limit_change(struct throtl_data
*td
)
692 struct throtl_grp
*tg
;
693 struct hlist_node
*pos
, *n
;
696 * Make sure atomic_inc() effects from
697 * throtl_update_blkio_group_read_bps(), group of functions are
699 * Is this required or smp_mb__after_atomic_inc() was suffcient
700 * after the atomic_inc().
703 if (!atomic_read(&td
->limits_changed
))
706 throtl_log(td
, "limit changed =%d", atomic_read(&td
->limits_changed
));
708 hlist_for_each_entry_safe(tg
, pos
, n
, &td
->tg_list
, tg_node
) {
710 * Do I need an smp_rmb() here to make sure tg->limits_changed
711 * update is visible. I am relying on smp_rmb() at the
712 * beginning of function and not putting a new one here.
715 if (throtl_tg_on_rr(tg
) && tg
->limits_changed
) {
716 throtl_log_tg(td
, tg
, "limit change rbps=%llu wbps=%llu"
717 " riops=%u wiops=%u", tg
->bps
[READ
],
718 tg
->bps
[WRITE
], tg
->iops
[READ
],
720 tg_update_disptime(td
, tg
);
721 tg
->limits_changed
= false;
725 smp_mb__before_atomic_dec();
726 atomic_dec(&td
->limits_changed
);
727 smp_mb__after_atomic_dec();
730 /* Dispatch throttled bios. Should be called without queue lock held. */
731 static int throtl_dispatch(struct request_queue
*q
)
733 struct throtl_data
*td
= q
->td
;
734 unsigned int nr_disp
= 0;
735 struct bio_list bio_list_on_stack
;
738 spin_lock_irq(q
->queue_lock
);
740 throtl_process_limit_change(td
);
742 if (!total_nr_queued(td
))
745 bio_list_init(&bio_list_on_stack
);
747 throtl_log(td
, "dispatch nr_queued=%lu read=%u write=%u",
748 total_nr_queued(td
), td
->nr_queued
[READ
],
749 td
->nr_queued
[WRITE
]);
751 nr_disp
= throtl_select_dispatch(td
, &bio_list_on_stack
);
754 throtl_log(td
, "bios disp=%u", nr_disp
);
756 throtl_schedule_next_dispatch(td
);
758 spin_unlock_irq(q
->queue_lock
);
761 * If we dispatched some requests, unplug the queue to make sure
765 while((bio
= bio_list_pop(&bio_list_on_stack
)))
766 generic_make_request(bio
);
772 void blk_throtl_work(struct work_struct
*work
)
774 struct throtl_data
*td
= container_of(work
, struct throtl_data
,
776 struct request_queue
*q
= td
->queue
;
781 /* Call with queue lock held */
782 void throtl_schedule_delayed_work(struct request_queue
*q
, unsigned long delay
)
785 struct throtl_data
*td
= q
->td
;
786 struct delayed_work
*dwork
= &td
->throtl_work
;
788 if (total_nr_queued(td
) > 0) {
790 * We might have a work scheduled to be executed in future.
791 * Cancel that and schedule a new one.
793 __cancel_delayed_work(dwork
);
794 kblockd_schedule_delayed_work(q
, dwork
, delay
);
795 throtl_log(td
, "schedule work. delay=%lu jiffies=%lu",
799 EXPORT_SYMBOL(throtl_schedule_delayed_work
);
802 throtl_destroy_tg(struct throtl_data
*td
, struct throtl_grp
*tg
)
804 /* Something wrong if we are trying to remove same group twice */
805 BUG_ON(hlist_unhashed(&tg
->tg_node
));
807 hlist_del_init(&tg
->tg_node
);
810 * Put the reference taken at the time of creation so that when all
811 * queues are gone, group can be destroyed.
814 td
->nr_undestroyed_grps
--;
817 static void throtl_release_tgs(struct throtl_data
*td
)
819 struct hlist_node
*pos
, *n
;
820 struct throtl_grp
*tg
;
822 hlist_for_each_entry_safe(tg
, pos
, n
, &td
->tg_list
, tg_node
) {
824 * If cgroup removal path got to blk_group first and removed
825 * it from cgroup list, then it will take care of destroying
828 if (!blkiocg_del_blkio_group(&tg
->blkg
))
829 throtl_destroy_tg(td
, tg
);
833 static void throtl_td_free(struct throtl_data
*td
)
839 * Blk cgroup controller notification saying that blkio_group object is being
840 * delinked as associated cgroup object is going away. That also means that
841 * no new IO will come in this group. So get rid of this group as soon as
842 * any pending IO in the group is finished.
844 * This function is called under rcu_read_lock(). key is the rcu protected
845 * pointer. That means "key" is a valid throtl_data pointer as long as we are
848 * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
849 * it should not be NULL as even if queue was going away, cgroup deltion
850 * path got to it first.
852 void throtl_unlink_blkio_group(void *key
, struct blkio_group
*blkg
)
855 struct throtl_data
*td
= key
;
857 spin_lock_irqsave(td
->queue
->queue_lock
, flags
);
858 throtl_destroy_tg(td
, tg_of_blkg(blkg
));
859 spin_unlock_irqrestore(td
->queue
->queue_lock
, flags
);
863 * For all update functions, key should be a valid pointer because these
864 * update functions are called under blkcg_lock, that means, blkg is
865 * valid and in turn key is valid. queue exit path can not race becuase
868 * Can not take queue lock in update functions as queue lock under blkcg_lock
869 * is not allowed. Under other paths we take blkcg_lock under queue_lock.
871 static void throtl_update_blkio_group_read_bps(void *key
,
872 struct blkio_group
*blkg
, u64 read_bps
)
874 struct throtl_data
*td
= key
;
876 tg_of_blkg(blkg
)->bps
[READ
] = read_bps
;
877 /* Make sure read_bps is updated before setting limits_changed */
879 tg_of_blkg(blkg
)->limits_changed
= true;
881 /* Make sure tg->limits_changed is updated before td->limits_changed */
882 smp_mb__before_atomic_inc();
883 atomic_inc(&td
->limits_changed
);
884 smp_mb__after_atomic_inc();
886 /* Schedule a work now to process the limit change */
887 throtl_schedule_delayed_work(td
->queue
, 0);
890 static void throtl_update_blkio_group_write_bps(void *key
,
891 struct blkio_group
*blkg
, u64 write_bps
)
893 struct throtl_data
*td
= key
;
895 tg_of_blkg(blkg
)->bps
[WRITE
] = write_bps
;
897 tg_of_blkg(blkg
)->limits_changed
= true;
898 smp_mb__before_atomic_inc();
899 atomic_inc(&td
->limits_changed
);
900 smp_mb__after_atomic_inc();
901 throtl_schedule_delayed_work(td
->queue
, 0);
904 static void throtl_update_blkio_group_read_iops(void *key
,
905 struct blkio_group
*blkg
, unsigned int read_iops
)
907 struct throtl_data
*td
= key
;
909 tg_of_blkg(blkg
)->iops
[READ
] = read_iops
;
911 tg_of_blkg(blkg
)->limits_changed
= true;
912 smp_mb__before_atomic_inc();
913 atomic_inc(&td
->limits_changed
);
914 smp_mb__after_atomic_inc();
915 throtl_schedule_delayed_work(td
->queue
, 0);
918 static void throtl_update_blkio_group_write_iops(void *key
,
919 struct blkio_group
*blkg
, unsigned int write_iops
)
921 struct throtl_data
*td
= key
;
923 tg_of_blkg(blkg
)->iops
[WRITE
] = write_iops
;
925 tg_of_blkg(blkg
)->limits_changed
= true;
926 smp_mb__before_atomic_inc();
927 atomic_inc(&td
->limits_changed
);
928 smp_mb__after_atomic_inc();
929 throtl_schedule_delayed_work(td
->queue
, 0);
932 void throtl_shutdown_timer_wq(struct request_queue
*q
)
934 struct throtl_data
*td
= q
->td
;
936 cancel_delayed_work_sync(&td
->throtl_work
);
939 static struct blkio_policy_type blkio_policy_throtl
= {
941 .blkio_unlink_group_fn
= throtl_unlink_blkio_group
,
942 .blkio_update_group_read_bps_fn
=
943 throtl_update_blkio_group_read_bps
,
944 .blkio_update_group_write_bps_fn
=
945 throtl_update_blkio_group_write_bps
,
946 .blkio_update_group_read_iops_fn
=
947 throtl_update_blkio_group_read_iops
,
948 .blkio_update_group_write_iops_fn
=
949 throtl_update_blkio_group_write_iops
,
951 .plid
= BLKIO_POLICY_THROTL
,
954 int blk_throtl_bio(struct request_queue
*q
, struct bio
**biop
)
956 struct throtl_data
*td
= q
->td
;
957 struct throtl_grp
*tg
;
958 struct bio
*bio
= *biop
;
959 bool rw
= bio_data_dir(bio
), update_disptime
= true;
961 if (bio
->bi_rw
& REQ_THROTTLED
) {
962 bio
->bi_rw
&= ~REQ_THROTTLED
;
966 spin_lock_irq(q
->queue_lock
);
967 tg
= throtl_get_tg(td
);
969 if (tg
->nr_queued
[rw
]) {
971 * There is already another bio queued in same dir. No
972 * need to update dispatch time.
973 * Still update the disptime if rate limits on this group
976 if (!tg
->limits_changed
)
977 update_disptime
= false;
979 tg
->limits_changed
= false;
984 /* Bio is with-in rate limit of group */
985 if (tg_may_dispatch(td
, tg
, bio
, NULL
)) {
986 throtl_charge_bio(tg
, bio
);
991 throtl_log_tg(td
, tg
, "[%c] bio. bdisp=%u sz=%u bps=%llu"
992 " iodisp=%u iops=%u queued=%d/%d",
993 rw
== READ
? 'R' : 'W',
994 tg
->bytes_disp
[rw
], bio
->bi_size
, tg
->bps
[rw
],
995 tg
->io_disp
[rw
], tg
->iops
[rw
],
996 tg
->nr_queued
[READ
], tg
->nr_queued
[WRITE
]);
998 throtl_add_bio_tg(q
->td
, tg
, bio
);
1001 if (update_disptime
) {
1002 tg_update_disptime(td
, tg
);
1003 throtl_schedule_next_dispatch(td
);
1007 spin_unlock_irq(q
->queue_lock
);
1011 int blk_throtl_init(struct request_queue
*q
)
1013 struct throtl_data
*td
;
1014 struct throtl_grp
*tg
;
1016 td
= kzalloc_node(sizeof(*td
), GFP_KERNEL
, q
->node
);
1020 INIT_HLIST_HEAD(&td
->tg_list
);
1021 td
->tg_service_tree
= THROTL_RB_ROOT
;
1022 atomic_set(&td
->limits_changed
, 0);
1024 /* Init root group */
1026 INIT_HLIST_NODE(&tg
->tg_node
);
1027 RB_CLEAR_NODE(&tg
->rb_node
);
1028 bio_list_init(&tg
->bio_lists
[0]);
1029 bio_list_init(&tg
->bio_lists
[1]);
1031 /* Practically unlimited BW */
1032 tg
->bps
[0] = tg
->bps
[1] = -1;
1033 tg
->iops
[0] = tg
->iops
[1] = -1;
1036 * Set root group reference to 2. One reference will be dropped when
1037 * all groups on tg_list are being deleted during queue exit. Other
1038 * reference will remain there as we don't want to delete this group
1039 * as it is statically allocated and gets destroyed when throtl_data
1042 atomic_set(&tg
->ref
, 2);
1043 hlist_add_head(&tg
->tg_node
, &td
->tg_list
);
1044 td
->nr_undestroyed_grps
++;
1046 INIT_DELAYED_WORK(&td
->throtl_work
, blk_throtl_work
);
1049 blkiocg_add_blkio_group(&blkio_root_cgroup
, &tg
->blkg
, (void *)td
,
1050 0, BLKIO_POLICY_THROTL
);
1053 /* Attach throtl data to request queue */
1059 void blk_throtl_exit(struct request_queue
*q
)
1061 struct throtl_data
*td
= q
->td
;
1066 throtl_shutdown_timer_wq(q
);
1068 spin_lock_irq(q
->queue_lock
);
1069 throtl_release_tgs(td
);
1071 /* If there are other groups */
1072 if (td
->nr_undestroyed_grps
> 0)
1075 spin_unlock_irq(q
->queue_lock
);
1078 * Wait for tg->blkg->key accessors to exit their grace periods.
1079 * Do this wait only if there are other undestroyed groups out
1080 * there (other than root group). This can happen if cgroup deletion
1081 * path claimed the responsibility of cleaning up a group before
1082 * queue cleanup code get to the group.
1084 * Do not call synchronize_rcu() unconditionally as there are drivers
1085 * which create/delete request queue hundreds of times during scan/boot
1086 * and synchronize_rcu() can take significant time and slow down boot.
1092 * Just being safe to make sure after previous flush if some body did
1093 * update limits through cgroup and another work got queued, cancel
1096 throtl_shutdown_timer_wq(q
);
1100 static int __init
throtl_init(void)
1102 blkio_policy_register(&blkio_policy_throtl
);
1106 module_init(throtl_init
);