blob: 381b09bb562b277620479fa92313cc6631995630 [file] [log] [blame]
Vivek Goyale43473b2010-09-15 17:06:35 -04001/*
2 * Interface for controlling IO bandwidth on a request queue
3 *
4 * Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com>
5 */
6
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"
13
14/* Max dispatch from a group in 1 round */
15static int throtl_grp_quantum = 8;
16
17/* Total max dispatch from all groups in one round */
18static int throtl_quantum = 32;
19
20/* Throttling is performed over 100ms slice and after that slice is renewed */
21static unsigned long throtl_slice = HZ/10; /* 100 ms */
22
23struct throtl_rb_root {
24 struct rb_root rb;
25 struct rb_node *left;
26 unsigned int count;
27 unsigned long min_disptime;
28};
29
30#define THROTL_RB_ROOT (struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \
31 .count = 0, .min_disptime = 0}
32
33#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
34
35struct throtl_grp {
36 /* List of throtl groups on the request queue*/
37 struct hlist_node tg_node;
38
39 /* active throtl group service_tree member */
40 struct rb_node rb_node;
41
42 /*
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.
46 */
47 unsigned long disptime;
48
49 struct blkio_group blkg;
50 atomic_t ref;
51 unsigned int flags;
52
53 /* Two lists for READ and WRITE */
54 struct bio_list bio_lists[2];
55
56 /* Number of queued bios on READ and WRITE lists */
57 unsigned int nr_queued[2];
58
59 /* bytes per second rate limits */
60 uint64_t bps[2];
61
Vivek Goyal8e89d132010-09-15 17:06:37 -040062 /* IOPS limits */
63 unsigned int iops[2];
64
Vivek Goyale43473b2010-09-15 17:06:35 -040065 /* Number of bytes disptached in current slice */
66 uint64_t bytes_disp[2];
Vivek Goyal8e89d132010-09-15 17:06:37 -040067 /* Number of bio's dispatched in current slice */
68 unsigned int io_disp[2];
Vivek Goyale43473b2010-09-15 17:06:35 -040069
70 /* When did we start a new slice */
71 unsigned long slice_start[2];
72 unsigned long slice_end[2];
Vivek Goyalfe071432010-10-01 14:49:49 +020073
74 /* Some throttle limits got updated for the group */
75 bool limits_changed;
Vivek Goyale43473b2010-09-15 17:06:35 -040076};
77
78struct throtl_data
79{
80 /* List of throtl groups */
81 struct hlist_head tg_list;
82
83 /* service tree for active throtl groups */
84 struct throtl_rb_root tg_service_tree;
85
86 struct throtl_grp root_tg;
87 struct request_queue *queue;
88
89 /* Total Number of queued bios on READ and WRITE lists */
90 unsigned int nr_queued[2];
91
92 /*
Vivek Goyal02977e42010-10-01 14:49:48 +020093 * number of total undestroyed groups
Vivek Goyale43473b2010-09-15 17:06:35 -040094 */
95 unsigned int nr_undestroyed_grps;
96
97 /* Work for dispatching throttled bios */
98 struct delayed_work throtl_work;
Vivek Goyalfe071432010-10-01 14:49:49 +020099
100 atomic_t limits_changed;
Vivek Goyale43473b2010-09-15 17:06:35 -0400101};
102
103enum tg_state_flags {
104 THROTL_TG_FLAG_on_rr = 0, /* on round-robin busy list */
105};
106
107#define THROTL_TG_FNS(name) \
108static inline void throtl_mark_tg_##name(struct throtl_grp *tg) \
109{ \
110 (tg)->flags |= (1 << THROTL_TG_FLAG_##name); \
111} \
112static inline void throtl_clear_tg_##name(struct throtl_grp *tg) \
113{ \
114 (tg)->flags &= ~(1 << THROTL_TG_FLAG_##name); \
115} \
116static inline int throtl_tg_##name(const struct throtl_grp *tg) \
117{ \
118 return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0; \
119}
120
121THROTL_TG_FNS(on_rr);
122
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); \
126
127#define throtl_log(td, fmt, args...) \
128 blk_add_trace_msg((td)->queue, "throtl " fmt, ##args)
129
130static inline struct throtl_grp *tg_of_blkg(struct blkio_group *blkg)
131{
132 if (blkg)
133 return container_of(blkg, struct throtl_grp, blkg);
134
135 return NULL;
136}
137
138static inline int total_nr_queued(struct throtl_data *td)
139{
140 return (td->nr_queued[0] + td->nr_queued[1]);
141}
142
143static inline struct throtl_grp *throtl_ref_get_tg(struct throtl_grp *tg)
144{
145 atomic_inc(&tg->ref);
146 return tg;
147}
148
149static void throtl_put_tg(struct throtl_grp *tg)
150{
151 BUG_ON(atomic_read(&tg->ref) <= 0);
152 if (!atomic_dec_and_test(&tg->ref))
153 return;
154 kfree(tg);
155}
156
157static struct throtl_grp * throtl_find_alloc_tg(struct throtl_data *td,
158 struct cgroup *cgroup)
159{
160 struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
161 struct throtl_grp *tg = NULL;
162 void *key = td;
163 struct backing_dev_info *bdi = &td->queue->backing_dev_info;
164 unsigned int major, minor;
165
166 /*
167 * TODO: Speed up blkiocg_lookup_group() by maintaining a radix
168 * tree of blkg (instead of traversing through hash list all
169 * the time.
170 */
171 tg = tg_of_blkg(blkiocg_lookup_group(blkcg, key));
172
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);
177 goto done;
178 }
179
180 if (tg)
181 goto done;
182
183 tg = kzalloc_node(sizeof(*tg), GFP_ATOMIC, td->queue->node);
184 if (!tg)
185 goto done;
186
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]);
191
192 /*
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.
197 */
198 atomic_set(&tg->ref, 1);
199
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);
204
205 tg->bps[READ] = blkcg_get_read_bps(blkcg, tg->blkg.dev);
206 tg->bps[WRITE] = blkcg_get_write_bps(blkcg, tg->blkg.dev);
Vivek Goyal8e89d132010-09-15 17:06:37 -0400207 tg->iops[READ] = blkcg_get_read_iops(blkcg, tg->blkg.dev);
208 tg->iops[WRITE] = blkcg_get_write_iops(blkcg, tg->blkg.dev);
Vivek Goyale43473b2010-09-15 17:06:35 -0400209
210 hlist_add_head(&tg->tg_node, &td->tg_list);
211 td->nr_undestroyed_grps++;
212done:
213 return tg;
214}
215
216static struct throtl_grp * throtl_get_tg(struct throtl_data *td)
217{
218 struct cgroup *cgroup;
219 struct throtl_grp *tg = NULL;
220
221 rcu_read_lock();
222 cgroup = task_cgroup(current, blkio_subsys_id);
223 tg = throtl_find_alloc_tg(td, cgroup);
224 if (!tg)
225 tg = &td->root_tg;
226 rcu_read_unlock();
227 return tg;
228}
229
230static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root)
231{
232 /* Service tree is empty */
233 if (!root->count)
234 return NULL;
235
236 if (!root->left)
237 root->left = rb_first(&root->rb);
238
239 if (root->left)
240 return rb_entry_tg(root->left);
241
242 return NULL;
243}
244
245static void rb_erase_init(struct rb_node *n, struct rb_root *root)
246{
247 rb_erase(n, root);
248 RB_CLEAR_NODE(n);
249}
250
251static void throtl_rb_erase(struct rb_node *n, struct throtl_rb_root *root)
252{
253 if (root->left == n)
254 root->left = NULL;
255 rb_erase_init(n, &root->rb);
256 --root->count;
257}
258
259static void update_min_dispatch_time(struct throtl_rb_root *st)
260{
261 struct throtl_grp *tg;
262
263 tg = throtl_rb_first(st);
264 if (!tg)
265 return;
266
267 st->min_disptime = tg->disptime;
268}
269
270static void
271tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg)
272{
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;
277 int left = 1;
278
279 while (*node != NULL) {
280 parent = *node;
281 __tg = rb_entry_tg(parent);
282
283 if (time_before(key, __tg->disptime))
284 node = &parent->rb_left;
285 else {
286 node = &parent->rb_right;
287 left = 0;
288 }
289 }
290
291 if (left)
292 st->left = &tg->rb_node;
293
294 rb_link_node(&tg->rb_node, parent, node);
295 rb_insert_color(&tg->rb_node, &st->rb);
296}
297
298static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
299{
300 struct throtl_rb_root *st = &td->tg_service_tree;
301
302 tg_service_tree_add(st, tg);
303 throtl_mark_tg_on_rr(tg);
304 st->count++;
305}
306
307static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
308{
309 if (!throtl_tg_on_rr(tg))
310 __throtl_enqueue_tg(td, tg);
311}
312
313static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
314{
315 throtl_rb_erase(&tg->rb_node, &td->tg_service_tree);
316 throtl_clear_tg_on_rr(tg);
317}
318
319static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
320{
321 if (throtl_tg_on_rr(tg))
322 __throtl_dequeue_tg(td, tg);
323}
324
325static void throtl_schedule_next_dispatch(struct throtl_data *td)
326{
327 struct throtl_rb_root *st = &td->tg_service_tree;
328
329 /*
330 * If there are more bios pending, schedule more work.
331 */
332 if (!total_nr_queued(td))
333 return;
334
335 BUG_ON(!st->count);
336
337 update_min_dispatch_time(st);
338
339 if (time_before_eq(st->min_disptime, jiffies))
340 throtl_schedule_delayed_work(td->queue, 0);
341 else
342 throtl_schedule_delayed_work(td->queue,
343 (st->min_disptime - jiffies));
344}
345
346static inline void
347throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
348{
349 tg->bytes_disp[rw] = 0;
Vivek Goyal8e89d132010-09-15 17:06:37 -0400350 tg->io_disp[rw] = 0;
Vivek Goyale43473b2010-09-15 17:06:35 -0400351 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);
356}
357
Vivek Goyald1ae8ff2010-12-01 19:34:46 +0100358static inline void throtl_set_slice_end(struct throtl_data *td,
359 struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
360{
361 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
362}
363
Vivek Goyale43473b2010-09-15 17:06:35 -0400364static inline void throtl_extend_slice(struct throtl_data *td,
365 struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
366{
367 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
368 throtl_log_tg(td, tg, "[%c] extend slice start=%lu end=%lu jiffies=%lu",
369 rw == READ ? 'R' : 'W', tg->slice_start[rw],
370 tg->slice_end[rw], jiffies);
371}
372
373/* Determine if previously allocated or extended slice is complete or not */
374static bool
375throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw)
376{
377 if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
378 return 0;
379
380 return 1;
381}
382
383/* Trim the used slices and adjust slice start accordingly */
384static inline void
385throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
386{
Vivek Goyal3aad5d32010-10-01 14:51:14 +0200387 unsigned long nr_slices, time_elapsed, io_trim;
388 u64 bytes_trim, tmp;
Vivek Goyale43473b2010-09-15 17:06:35 -0400389
390 BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
391
392 /*
393 * If bps are unlimited (-1), then time slice don't get
394 * renewed. Don't try to trim the slice if slice is used. A new
395 * slice will start when appropriate.
396 */
397 if (throtl_slice_used(td, tg, rw))
398 return;
399
Vivek Goyald1ae8ff2010-12-01 19:34:46 +0100400 /*
401 * A bio has been dispatched. Also adjust slice_end. It might happen
402 * that initially cgroup limit was very low resulting in high
403 * slice_end, but later limit was bumped up and bio was dispached
404 * sooner, then we need to reduce slice_end. A high bogus slice_end
405 * is bad because it does not allow new slice to start.
406 */
407
408 throtl_set_slice_end(td, tg, rw, jiffies + throtl_slice);
409
Vivek Goyale43473b2010-09-15 17:06:35 -0400410 time_elapsed = jiffies - tg->slice_start[rw];
411
412 nr_slices = time_elapsed / throtl_slice;
413
414 if (!nr_slices)
415 return;
Vivek Goyal3aad5d32010-10-01 14:51:14 +0200416 tmp = tg->bps[rw] * throtl_slice * nr_slices;
417 do_div(tmp, HZ);
418 bytes_trim = tmp;
Vivek Goyale43473b2010-09-15 17:06:35 -0400419
Vivek Goyal8e89d132010-09-15 17:06:37 -0400420 io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ;
Vivek Goyale43473b2010-09-15 17:06:35 -0400421
Vivek Goyal8e89d132010-09-15 17:06:37 -0400422 if (!bytes_trim && !io_trim)
Vivek Goyale43473b2010-09-15 17:06:35 -0400423 return;
424
425 if (tg->bytes_disp[rw] >= bytes_trim)
426 tg->bytes_disp[rw] -= bytes_trim;
427 else
428 tg->bytes_disp[rw] = 0;
429
Vivek Goyal8e89d132010-09-15 17:06:37 -0400430 if (tg->io_disp[rw] >= io_trim)
431 tg->io_disp[rw] -= io_trim;
432 else
433 tg->io_disp[rw] = 0;
434
Vivek Goyale43473b2010-09-15 17:06:35 -0400435 tg->slice_start[rw] += nr_slices * throtl_slice;
436
Vivek Goyal3aad5d32010-10-01 14:51:14 +0200437 throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%llu io=%lu"
Vivek Goyale43473b2010-09-15 17:06:35 -0400438 " start=%lu end=%lu jiffies=%lu",
Vivek Goyal8e89d132010-09-15 17:06:37 -0400439 rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
Vivek Goyale43473b2010-09-15 17:06:35 -0400440 tg->slice_start[rw], tg->slice_end[rw], jiffies);
441}
442
Vivek Goyal8e89d132010-09-15 17:06:37 -0400443static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg,
444 struct bio *bio, unsigned long *wait)
Vivek Goyale43473b2010-09-15 17:06:35 -0400445{
446 bool rw = bio_data_dir(bio);
Vivek Goyal8e89d132010-09-15 17:06:37 -0400447 unsigned int io_allowed;
Vivek Goyale43473b2010-09-15 17:06:35 -0400448 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
Vivek Goyalc49c06e2010-10-01 21:16:42 +0200449 u64 tmp;
Vivek Goyale43473b2010-09-15 17:06:35 -0400450
Vivek Goyal8e89d132010-09-15 17:06:37 -0400451 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
Vivek Goyale43473b2010-09-15 17:06:35 -0400452
Vivek Goyal8e89d132010-09-15 17:06:37 -0400453 /* Slice has just started. Consider one slice interval */
454 if (!jiffy_elapsed)
455 jiffy_elapsed_rnd = throtl_slice;
456
457 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
458
Vivek Goyalc49c06e2010-10-01 21:16:42 +0200459 /*
460 * jiffy_elapsed_rnd should not be a big value as minimum iops can be
461 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
462 * will allow dispatch after 1 second and after that slice should
463 * have been trimmed.
464 */
465
466 tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd;
467 do_div(tmp, HZ);
468
469 if (tmp > UINT_MAX)
470 io_allowed = UINT_MAX;
471 else
472 io_allowed = tmp;
Vivek Goyal8e89d132010-09-15 17:06:37 -0400473
474 if (tg->io_disp[rw] + 1 <= io_allowed) {
Vivek Goyale43473b2010-09-15 17:06:35 -0400475 if (wait)
476 *wait = 0;
477 return 1;
478 }
479
Vivek Goyal8e89d132010-09-15 17:06:37 -0400480 /* Calc approx time to dispatch */
481 jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;
482
483 if (jiffy_wait > jiffy_elapsed)
484 jiffy_wait = jiffy_wait - jiffy_elapsed;
485 else
486 jiffy_wait = 1;
487
488 if (wait)
489 *wait = jiffy_wait;
490 return 0;
491}
492
493static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg,
494 struct bio *bio, unsigned long *wait)
495{
496 bool rw = bio_data_dir(bio);
Vivek Goyal3aad5d32010-10-01 14:51:14 +0200497 u64 bytes_allowed, extra_bytes, tmp;
Vivek Goyal8e89d132010-09-15 17:06:37 -0400498 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
Vivek Goyale43473b2010-09-15 17:06:35 -0400499
500 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
501
502 /* Slice has just started. Consider one slice interval */
503 if (!jiffy_elapsed)
504 jiffy_elapsed_rnd = throtl_slice;
505
506 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
507
Vivek Goyal5e901a22010-10-01 21:16:38 +0200508 tmp = tg->bps[rw] * jiffy_elapsed_rnd;
509 do_div(tmp, HZ);
Vivek Goyal3aad5d32010-10-01 14:51:14 +0200510 bytes_allowed = tmp;
Vivek Goyale43473b2010-09-15 17:06:35 -0400511
512 if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) {
513 if (wait)
514 *wait = 0;
515 return 1;
516 }
517
518 /* Calc approx time to dispatch */
519 extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed;
520 jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]);
521
522 if (!jiffy_wait)
523 jiffy_wait = 1;
524
525 /*
526 * This wait time is without taking into consideration the rounding
527 * up we did. Add that time also.
528 */
529 jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
Vivek Goyale43473b2010-09-15 17:06:35 -0400530 if (wait)
531 *wait = jiffy_wait;
Vivek Goyal8e89d132010-09-15 17:06:37 -0400532 return 0;
533}
Vivek Goyale43473b2010-09-15 17:06:35 -0400534
Vivek Goyal8e89d132010-09-15 17:06:37 -0400535/*
536 * Returns whether one can dispatch a bio or not. Also returns approx number
537 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
538 */
539static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
540 struct bio *bio, unsigned long *wait)
541{
542 bool rw = bio_data_dir(bio);
543 unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
544
545 /*
546 * Currently whole state machine of group depends on first bio
547 * queued in the group bio list. So one should not be calling
548 * this function with a different bio if there are other bios
549 * queued.
550 */
551 BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));
552
553 /* If tg->bps = -1, then BW is unlimited */
554 if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
555 if (wait)
556 *wait = 0;
557 return 1;
558 }
559
560 /*
561 * If previous slice expired, start a new one otherwise renew/extend
562 * existing slice to make sure it is at least throtl_slice interval
563 * long since now.
564 */
565 if (throtl_slice_used(td, tg, rw))
566 throtl_start_new_slice(td, tg, rw);
567 else {
568 if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
569 throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);
570 }
571
572 if (tg_with_in_bps_limit(td, tg, bio, &bps_wait)
573 && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) {
574 if (wait)
575 *wait = 0;
576 return 1;
577 }
578
579 max_wait = max(bps_wait, iops_wait);
580
581 if (wait)
582 *wait = max_wait;
583
584 if (time_before(tg->slice_end[rw], jiffies + max_wait))
585 throtl_extend_slice(td, tg, rw, jiffies + max_wait);
Vivek Goyale43473b2010-09-15 17:06:35 -0400586
587 return 0;
588}
589
590static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
591{
592 bool rw = bio_data_dir(bio);
593 bool sync = bio->bi_rw & REQ_SYNC;
594
595 /* Charge the bio to the group */
596 tg->bytes_disp[rw] += bio->bi_size;
Vivek Goyal8e89d132010-09-15 17:06:37 -0400597 tg->io_disp[rw]++;
Vivek Goyale43473b2010-09-15 17:06:35 -0400598
599 /*
600 * TODO: This will take blkg->stats_lock. Figure out a way
601 * to avoid this cost.
602 */
603 blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size, rw, sync);
Vivek Goyale43473b2010-09-15 17:06:35 -0400604}
605
606static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg,
607 struct bio *bio)
608{
609 bool rw = bio_data_dir(bio);
610
611 bio_list_add(&tg->bio_lists[rw], bio);
612 /* Take a bio reference on tg */
613 throtl_ref_get_tg(tg);
614 tg->nr_queued[rw]++;
615 td->nr_queued[rw]++;
616 throtl_enqueue_tg(td, tg);
617}
618
619static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg)
620{
621 unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
622 struct bio *bio;
623
624 if ((bio = bio_list_peek(&tg->bio_lists[READ])))
625 tg_may_dispatch(td, tg, bio, &read_wait);
626
627 if ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
628 tg_may_dispatch(td, tg, bio, &write_wait);
629
630 min_wait = min(read_wait, write_wait);
631 disptime = jiffies + min_wait;
632
Vivek Goyale43473b2010-09-15 17:06:35 -0400633 /* Update dispatch time */
634 throtl_dequeue_tg(td, tg);
635 tg->disptime = disptime;
636 throtl_enqueue_tg(td, tg);
637}
638
639static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg,
640 bool rw, struct bio_list *bl)
641{
642 struct bio *bio;
643
644 bio = bio_list_pop(&tg->bio_lists[rw]);
645 tg->nr_queued[rw]--;
646 /* Drop bio reference on tg */
647 throtl_put_tg(tg);
648
649 BUG_ON(td->nr_queued[rw] <= 0);
650 td->nr_queued[rw]--;
651
652 throtl_charge_bio(tg, bio);
653 bio_list_add(bl, bio);
654 bio->bi_rw |= REQ_THROTTLED;
655
656 throtl_trim_slice(td, tg, rw);
657}
658
659static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg,
660 struct bio_list *bl)
661{
662 unsigned int nr_reads = 0, nr_writes = 0;
663 unsigned int max_nr_reads = throtl_grp_quantum*3/4;
Vivek Goyalc2f68052010-11-15 19:32:42 +0100664 unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
Vivek Goyale43473b2010-09-15 17:06:35 -0400665 struct bio *bio;
666
667 /* Try to dispatch 75% READS and 25% WRITES */
668
669 while ((bio = bio_list_peek(&tg->bio_lists[READ]))
670 && tg_may_dispatch(td, tg, bio, NULL)) {
671
672 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
673 nr_reads++;
674
675 if (nr_reads >= max_nr_reads)
676 break;
677 }
678
679 while ((bio = bio_list_peek(&tg->bio_lists[WRITE]))
680 && tg_may_dispatch(td, tg, bio, NULL)) {
681
682 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
683 nr_writes++;
684
685 if (nr_writes >= max_nr_writes)
686 break;
687 }
688
689 return nr_reads + nr_writes;
690}
691
692static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl)
693{
694 unsigned int nr_disp = 0;
695 struct throtl_grp *tg;
696 struct throtl_rb_root *st = &td->tg_service_tree;
697
698 while (1) {
699 tg = throtl_rb_first(st);
700
701 if (!tg)
702 break;
703
704 if (time_before(jiffies, tg->disptime))
705 break;
706
707 throtl_dequeue_tg(td, tg);
708
709 nr_disp += throtl_dispatch_tg(td, tg, bl);
710
711 if (tg->nr_queued[0] || tg->nr_queued[1]) {
712 tg_update_disptime(td, tg);
713 throtl_enqueue_tg(td, tg);
714 }
715
716 if (nr_disp >= throtl_quantum)
717 break;
718 }
719
720 return nr_disp;
721}
722
Vivek Goyalfe071432010-10-01 14:49:49 +0200723static void throtl_process_limit_change(struct throtl_data *td)
724{
725 struct throtl_grp *tg;
726 struct hlist_node *pos, *n;
727
Vivek Goyalfe071432010-10-01 14:49:49 +0200728 if (!atomic_read(&td->limits_changed))
729 return;
730
731 throtl_log(td, "limit changed =%d", atomic_read(&td->limits_changed));
732
Vivek Goyal04a6b512010-12-01 19:34:52 +0100733 /*
734 * Make sure updates from throtl_update_blkio_group_read_bps() group
735 * of functions to tg->limits_changed are visible. We do not
736 * want update td->limits_changed to be visible but update to
737 * tg->limits_changed not being visible yet on this cpu. Hence
738 * the read barrier.
739 */
740 smp_rmb();
Vivek Goyalfe071432010-10-01 14:49:49 +0200741
Vivek Goyal04a6b512010-12-01 19:34:52 +0100742 hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) {
Vivek Goyalfe071432010-10-01 14:49:49 +0200743 if (throtl_tg_on_rr(tg) && tg->limits_changed) {
744 throtl_log_tg(td, tg, "limit change rbps=%llu wbps=%llu"
745 " riops=%u wiops=%u", tg->bps[READ],
746 tg->bps[WRITE], tg->iops[READ],
747 tg->iops[WRITE]);
748 tg_update_disptime(td, tg);
749 tg->limits_changed = false;
750 }
751 }
752
753 smp_mb__before_atomic_dec();
754 atomic_dec(&td->limits_changed);
755 smp_mb__after_atomic_dec();
756}
757
Vivek Goyale43473b2010-09-15 17:06:35 -0400758/* Dispatch throttled bios. Should be called without queue lock held. */
759static int throtl_dispatch(struct request_queue *q)
760{
761 struct throtl_data *td = q->td;
762 unsigned int nr_disp = 0;
763 struct bio_list bio_list_on_stack;
764 struct bio *bio;
765
766 spin_lock_irq(q->queue_lock);
767
Vivek Goyalfe071432010-10-01 14:49:49 +0200768 throtl_process_limit_change(td);
769
Vivek Goyale43473b2010-09-15 17:06:35 -0400770 if (!total_nr_queued(td))
771 goto out;
772
773 bio_list_init(&bio_list_on_stack);
774
775 throtl_log(td, "dispatch nr_queued=%lu read=%u write=%u",
776 total_nr_queued(td), td->nr_queued[READ],
777 td->nr_queued[WRITE]);
778
779 nr_disp = throtl_select_dispatch(td, &bio_list_on_stack);
780
781 if (nr_disp)
782 throtl_log(td, "bios disp=%u", nr_disp);
783
784 throtl_schedule_next_dispatch(td);
785out:
786 spin_unlock_irq(q->queue_lock);
787
788 /*
789 * If we dispatched some requests, unplug the queue to make sure
790 * immediate dispatch
791 */
792 if (nr_disp) {
793 while((bio = bio_list_pop(&bio_list_on_stack)))
794 generic_make_request(bio);
795 blk_unplug(q);
796 }
797 return nr_disp;
798}
799
800void blk_throtl_work(struct work_struct *work)
801{
802 struct throtl_data *td = container_of(work, struct throtl_data,
803 throtl_work.work);
804 struct request_queue *q = td->queue;
805
806 throtl_dispatch(q);
807}
808
809/* Call with queue lock held */
810void throtl_schedule_delayed_work(struct request_queue *q, unsigned long delay)
811{
812
813 struct throtl_data *td = q->td;
814 struct delayed_work *dwork = &td->throtl_work;
815
816 if (total_nr_queued(td) > 0) {
817 /*
818 * We might have a work scheduled to be executed in future.
819 * Cancel that and schedule a new one.
820 */
821 __cancel_delayed_work(dwork);
822 kblockd_schedule_delayed_work(q, dwork, delay);
823 throtl_log(td, "schedule work. delay=%lu jiffies=%lu",
824 delay, jiffies);
825 }
826}
827EXPORT_SYMBOL(throtl_schedule_delayed_work);
828
829static void
830throtl_destroy_tg(struct throtl_data *td, struct throtl_grp *tg)
831{
832 /* Something wrong if we are trying to remove same group twice */
833 BUG_ON(hlist_unhashed(&tg->tg_node));
834
835 hlist_del_init(&tg->tg_node);
836
837 /*
838 * Put the reference taken at the time of creation so that when all
839 * queues are gone, group can be destroyed.
840 */
841 throtl_put_tg(tg);
842 td->nr_undestroyed_grps--;
843}
844
845static void throtl_release_tgs(struct throtl_data *td)
846{
847 struct hlist_node *pos, *n;
848 struct throtl_grp *tg;
849
850 hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) {
851 /*
852 * If cgroup removal path got to blk_group first and removed
853 * it from cgroup list, then it will take care of destroying
854 * cfqg also.
855 */
856 if (!blkiocg_del_blkio_group(&tg->blkg))
857 throtl_destroy_tg(td, tg);
858 }
859}
860
861static void throtl_td_free(struct throtl_data *td)
862{
863 kfree(td);
864}
865
866/*
867 * Blk cgroup controller notification saying that blkio_group object is being
868 * delinked as associated cgroup object is going away. That also means that
869 * no new IO will come in this group. So get rid of this group as soon as
870 * any pending IO in the group is finished.
871 *
872 * This function is called under rcu_read_lock(). key is the rcu protected
873 * pointer. That means "key" is a valid throtl_data pointer as long as we are
874 * rcu read lock.
875 *
876 * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
877 * it should not be NULL as even if queue was going away, cgroup deltion
878 * path got to it first.
879 */
880void throtl_unlink_blkio_group(void *key, struct blkio_group *blkg)
881{
882 unsigned long flags;
883 struct throtl_data *td = key;
884
885 spin_lock_irqsave(td->queue->queue_lock, flags);
886 throtl_destroy_tg(td, tg_of_blkg(blkg));
887 spin_unlock_irqrestore(td->queue->queue_lock, flags);
888}
889
Vivek Goyalfe071432010-10-01 14:49:49 +0200890/*
891 * For all update functions, key should be a valid pointer because these
892 * update functions are called under blkcg_lock, that means, blkg is
893 * valid and in turn key is valid. queue exit path can not race becuase
894 * of blkcg_lock
895 *
896 * Can not take queue lock in update functions as queue lock under blkcg_lock
897 * is not allowed. Under other paths we take blkcg_lock under queue_lock.
898 */
899static void throtl_update_blkio_group_read_bps(void *key,
900 struct blkio_group *blkg, u64 read_bps)
Vivek Goyale43473b2010-09-15 17:06:35 -0400901{
Vivek Goyalfe071432010-10-01 14:49:49 +0200902 struct throtl_data *td = key;
903
Vivek Goyale43473b2010-09-15 17:06:35 -0400904 tg_of_blkg(blkg)->bps[READ] = read_bps;
Vivek Goyalfe071432010-10-01 14:49:49 +0200905 /* Make sure read_bps is updated before setting limits_changed */
906 smp_wmb();
907 tg_of_blkg(blkg)->limits_changed = true;
908
909 /* Make sure tg->limits_changed is updated before td->limits_changed */
910 smp_mb__before_atomic_inc();
911 atomic_inc(&td->limits_changed);
912 smp_mb__after_atomic_inc();
913
914 /* Schedule a work now to process the limit change */
915 throtl_schedule_delayed_work(td->queue, 0);
Vivek Goyale43473b2010-09-15 17:06:35 -0400916}
917
Vivek Goyalfe071432010-10-01 14:49:49 +0200918static void throtl_update_blkio_group_write_bps(void *key,
919 struct blkio_group *blkg, u64 write_bps)
Vivek Goyale43473b2010-09-15 17:06:35 -0400920{
Vivek Goyalfe071432010-10-01 14:49:49 +0200921 struct throtl_data *td = key;
922
Vivek Goyale43473b2010-09-15 17:06:35 -0400923 tg_of_blkg(blkg)->bps[WRITE] = write_bps;
Vivek Goyalfe071432010-10-01 14:49:49 +0200924 smp_wmb();
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);
Vivek Goyale43473b2010-09-15 17:06:35 -0400930}
931
Vivek Goyalfe071432010-10-01 14:49:49 +0200932static void throtl_update_blkio_group_read_iops(void *key,
933 struct blkio_group *blkg, unsigned int read_iops)
Vivek Goyal8e89d132010-09-15 17:06:37 -0400934{
Vivek Goyalfe071432010-10-01 14:49:49 +0200935 struct throtl_data *td = key;
936
Vivek Goyal8e89d132010-09-15 17:06:37 -0400937 tg_of_blkg(blkg)->iops[READ] = read_iops;
Vivek Goyalfe071432010-10-01 14:49:49 +0200938 smp_wmb();
939 tg_of_blkg(blkg)->limits_changed = true;
940 smp_mb__before_atomic_inc();
941 atomic_inc(&td->limits_changed);
942 smp_mb__after_atomic_inc();
943 throtl_schedule_delayed_work(td->queue, 0);
Vivek Goyal8e89d132010-09-15 17:06:37 -0400944}
945
Vivek Goyalfe071432010-10-01 14:49:49 +0200946static void throtl_update_blkio_group_write_iops(void *key,
947 struct blkio_group *blkg, unsigned int write_iops)
Vivek Goyal8e89d132010-09-15 17:06:37 -0400948{
Vivek Goyalfe071432010-10-01 14:49:49 +0200949 struct throtl_data *td = key;
950
Vivek Goyal8e89d132010-09-15 17:06:37 -0400951 tg_of_blkg(blkg)->iops[WRITE] = write_iops;
Vivek Goyalfe071432010-10-01 14:49:49 +0200952 smp_wmb();
953 tg_of_blkg(blkg)->limits_changed = true;
954 smp_mb__before_atomic_inc();
955 atomic_inc(&td->limits_changed);
956 smp_mb__after_atomic_inc();
957 throtl_schedule_delayed_work(td->queue, 0);
Vivek Goyal8e89d132010-09-15 17:06:37 -0400958}
959
Vivek Goyale43473b2010-09-15 17:06:35 -0400960void throtl_shutdown_timer_wq(struct request_queue *q)
961{
962 struct throtl_data *td = q->td;
963
964 cancel_delayed_work_sync(&td->throtl_work);
965}
966
967static struct blkio_policy_type blkio_policy_throtl = {
968 .ops = {
969 .blkio_unlink_group_fn = throtl_unlink_blkio_group,
970 .blkio_update_group_read_bps_fn =
971 throtl_update_blkio_group_read_bps,
972 .blkio_update_group_write_bps_fn =
973 throtl_update_blkio_group_write_bps,
Vivek Goyal8e89d132010-09-15 17:06:37 -0400974 .blkio_update_group_read_iops_fn =
975 throtl_update_blkio_group_read_iops,
976 .blkio_update_group_write_iops_fn =
977 throtl_update_blkio_group_write_iops,
Vivek Goyale43473b2010-09-15 17:06:35 -0400978 },
Vivek Goyal8e89d132010-09-15 17:06:37 -0400979 .plid = BLKIO_POLICY_THROTL,
Vivek Goyale43473b2010-09-15 17:06:35 -0400980};
981
982int blk_throtl_bio(struct request_queue *q, struct bio **biop)
983{
984 struct throtl_data *td = q->td;
985 struct throtl_grp *tg;
986 struct bio *bio = *biop;
987 bool rw = bio_data_dir(bio), update_disptime = true;
988
989 if (bio->bi_rw & REQ_THROTTLED) {
990 bio->bi_rw &= ~REQ_THROTTLED;
991 return 0;
992 }
993
994 spin_lock_irq(q->queue_lock);
995 tg = throtl_get_tg(td);
996
997 if (tg->nr_queued[rw]) {
998 /*
999 * There is already another bio queued in same dir. No
1000 * need to update dispatch time.
Vivek Goyalfe071432010-10-01 14:49:49 +02001001 * Still update the disptime if rate limits on this group
1002 * were changed.
Vivek Goyale43473b2010-09-15 17:06:35 -04001003 */
Vivek Goyalfe071432010-10-01 14:49:49 +02001004 if (!tg->limits_changed)
1005 update_disptime = false;
1006 else
1007 tg->limits_changed = false;
1008
Vivek Goyale43473b2010-09-15 17:06:35 -04001009 goto queue_bio;
1010 }
1011
1012 /* Bio is with-in rate limit of group */
1013 if (tg_may_dispatch(td, tg, bio, NULL)) {
1014 throtl_charge_bio(tg, bio);
1015 goto out;
1016 }
1017
1018queue_bio:
Vivek Goyal8e89d132010-09-15 17:06:37 -04001019 throtl_log_tg(td, tg, "[%c] bio. bdisp=%u sz=%u bps=%llu"
1020 " iodisp=%u iops=%u queued=%d/%d",
1021 rw == READ ? 'R' : 'W',
Vivek Goyale43473b2010-09-15 17:06:35 -04001022 tg->bytes_disp[rw], bio->bi_size, tg->bps[rw],
Vivek Goyal8e89d132010-09-15 17:06:37 -04001023 tg->io_disp[rw], tg->iops[rw],
Vivek Goyale43473b2010-09-15 17:06:35 -04001024 tg->nr_queued[READ], tg->nr_queued[WRITE]);
1025
1026 throtl_add_bio_tg(q->td, tg, bio);
1027 *biop = NULL;
1028
1029 if (update_disptime) {
1030 tg_update_disptime(td, tg);
1031 throtl_schedule_next_dispatch(td);
1032 }
1033
1034out:
1035 spin_unlock_irq(q->queue_lock);
1036 return 0;
1037}
1038
1039int blk_throtl_init(struct request_queue *q)
1040{
1041 struct throtl_data *td;
1042 struct throtl_grp *tg;
1043
1044 td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
1045 if (!td)
1046 return -ENOMEM;
1047
1048 INIT_HLIST_HEAD(&td->tg_list);
1049 td->tg_service_tree = THROTL_RB_ROOT;
Vivek Goyalfe071432010-10-01 14:49:49 +02001050 atomic_set(&td->limits_changed, 0);
Vivek Goyale43473b2010-09-15 17:06:35 -04001051
1052 /* Init root group */
1053 tg = &td->root_tg;
1054 INIT_HLIST_NODE(&tg->tg_node);
1055 RB_CLEAR_NODE(&tg->rb_node);
1056 bio_list_init(&tg->bio_lists[0]);
1057 bio_list_init(&tg->bio_lists[1]);
1058
1059 /* Practically unlimited BW */
1060 tg->bps[0] = tg->bps[1] = -1;
Vivek Goyal8e89d132010-09-15 17:06:37 -04001061 tg->iops[0] = tg->iops[1] = -1;
Vivek Goyal02977e42010-10-01 14:49:48 +02001062
1063 /*
1064 * Set root group reference to 2. One reference will be dropped when
1065 * all groups on tg_list are being deleted during queue exit. Other
1066 * reference will remain there as we don't want to delete this group
1067 * as it is statically allocated and gets destroyed when throtl_data
1068 * goes away.
1069 */
1070 atomic_set(&tg->ref, 2);
1071 hlist_add_head(&tg->tg_node, &td->tg_list);
1072 td->nr_undestroyed_grps++;
Vivek Goyale43473b2010-09-15 17:06:35 -04001073
1074 INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work);
1075
1076 rcu_read_lock();
1077 blkiocg_add_blkio_group(&blkio_root_cgroup, &tg->blkg, (void *)td,
1078 0, BLKIO_POLICY_THROTL);
1079 rcu_read_unlock();
1080
1081 /* Attach throtl data to request queue */
1082 td->queue = q;
1083 q->td = td;
1084 return 0;
1085}
1086
1087void blk_throtl_exit(struct request_queue *q)
1088{
1089 struct throtl_data *td = q->td;
1090 bool wait = false;
1091
1092 BUG_ON(!td);
1093
1094 throtl_shutdown_timer_wq(q);
1095
1096 spin_lock_irq(q->queue_lock);
1097 throtl_release_tgs(td);
Vivek Goyale43473b2010-09-15 17:06:35 -04001098
1099 /* If there are other groups */
Vivek Goyal02977e42010-10-01 14:49:48 +02001100 if (td->nr_undestroyed_grps > 0)
Vivek Goyale43473b2010-09-15 17:06:35 -04001101 wait = true;
1102
1103 spin_unlock_irq(q->queue_lock);
1104
1105 /*
1106 * Wait for tg->blkg->key accessors to exit their grace periods.
1107 * Do this wait only if there are other undestroyed groups out
1108 * there (other than root group). This can happen if cgroup deletion
1109 * path claimed the responsibility of cleaning up a group before
1110 * queue cleanup code get to the group.
1111 *
1112 * Do not call synchronize_rcu() unconditionally as there are drivers
1113 * which create/delete request queue hundreds of times during scan/boot
1114 * and synchronize_rcu() can take significant time and slow down boot.
1115 */
1116 if (wait)
1117 synchronize_rcu();
Vivek Goyalfe071432010-10-01 14:49:49 +02001118
1119 /*
1120 * Just being safe to make sure after previous flush if some body did
1121 * update limits through cgroup and another work got queued, cancel
1122 * it.
1123 */
1124 throtl_shutdown_timer_wq(q);
Vivek Goyale43473b2010-09-15 17:06:35 -04001125 throtl_td_free(td);
1126}
1127
1128static int __init throtl_init(void)
1129{
1130 blkio_policy_register(&blkio_policy_throtl);
1131 return 0;
1132}
1133
1134module_init(throtl_init);