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1 | /* |
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 | #include "blk.h" |
14 | |
15 | /* Max dispatch from a group in 1 round */ |
16 | static int throtl_grp_quantum = 8; |
17 | |
18 | /* Total max dispatch from all groups in one round */ |
19 | static int throtl_quantum = 32; |
20 | |
21 | /* Throttling is performed over 100ms slice and after that slice is renewed */ |
22 | static unsigned long throtl_slice = HZ/10; /* 100 ms */ |
23 | |
24 | static struct blkcg_policy blkcg_policy_throtl; |
25 | |
26 | /* A workqueue to queue throttle related work */ |
27 | static struct workqueue_struct *kthrotld_workqueue; |
28 | |
29 | /* |
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. |
36 | * |
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. |
41 | * |
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. |
45 | * |
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. |
51 | */ |
52 | struct throtl_qnode { |
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 */ |
56 | }; |
57 | |
58 | struct throtl_service_queue { |
59 | struct throtl_service_queue *parent_sq; /* the parent service_queue */ |
60 | |
61 | /* |
62 | * Bios queued directly to this service_queue or dispatched from |
63 | * children throtl_grp's. |
64 | */ |
65 | struct list_head queued[2]; /* throtl_qnode [READ/WRITE] */ |
66 | unsigned int nr_queued[2]; /* number of queued bios */ |
67 | |
68 | /* |
69 | * RB tree of active children throtl_grp's, which are sorted by |
70 | * their ->disptime. |
71 | */ |
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 */ |
77 | }; |
78 | |
79 | enum tg_state_flags { |
80 | THROTL_TG_PENDING = 1 << 0, /* on parent's pending tree */ |
81 | THROTL_TG_WAS_EMPTY = 1 << 1, /* bio_lists[] became non-empty */ |
82 | }; |
83 | |
84 | #define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node) |
85 | |
86 | /* Per-cpu group stats */ |
87 | struct tg_stats_cpu { |
88 | /* total bytes transferred */ |
89 | struct blkg_rwstat service_bytes; |
90 | /* total IOs serviced, post merge */ |
91 | struct blkg_rwstat serviced; |
92 | }; |
93 | |
94 | struct throtl_grp { |
95 | /* must be the first member */ |
96 | struct blkg_policy_data pd; |
97 | |
98 | /* active throtl group service_queue member */ |
99 | struct rb_node rb_node; |
100 | |
101 | /* throtl_data this group belongs to */ |
102 | struct throtl_data *td; |
103 | |
104 | /* this group's service queue */ |
105 | struct throtl_service_queue service_queue; |
106 | |
107 | /* |
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 |
113 | * qnode_on_self. |
114 | */ |
115 | struct throtl_qnode qnode_on_self[2]; |
116 | struct throtl_qnode qnode_on_parent[2]; |
117 | |
118 | /* |
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. |
122 | */ |
123 | unsigned long disptime; |
124 | |
125 | unsigned int flags; |
126 | |
127 | /* are there any throtl rules between this group and td? */ |
128 | bool has_rules[2]; |
129 | |
130 | /* bytes per second rate limits */ |
131 | uint64_t bps[2]; |
132 | |
133 | /* IOPS limits */ |
134 | unsigned int iops[2]; |
135 | |
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]; |
140 | |
141 | /* When did we start a new slice */ |
142 | unsigned long slice_start[2]; |
143 | unsigned long slice_end[2]; |
144 | |
145 | /* Per cpu stats pointer */ |
146 | struct tg_stats_cpu __percpu *stats_cpu; |
147 | |
148 | /* List of tgs waiting for per cpu stats memory to be allocated */ |
149 | struct list_head stats_alloc_node; |
150 | }; |
151 | |
152 | struct throtl_data |
153 | { |
154 | /* service tree for active throtl groups */ |
155 | struct throtl_service_queue service_queue; |
156 | |
157 | struct request_queue *queue; |
158 | |
159 | /* Total Number of queued bios on READ and WRITE lists */ |
160 | unsigned int nr_queued[2]; |
161 | |
162 | /* |
163 | * number of total undestroyed groups |
164 | */ |
165 | unsigned int nr_undestroyed_grps; |
166 | |
167 | /* Work for dispatching throttled bios */ |
168 | struct work_struct dispatch_work; |
169 | }; |
170 | |
171 | /* list and work item to allocate percpu group stats */ |
172 | static DEFINE_SPINLOCK(tg_stats_alloc_lock); |
173 | static LIST_HEAD(tg_stats_alloc_list); |
174 | |
175 | static void tg_stats_alloc_fn(struct work_struct *); |
176 | static DECLARE_DELAYED_WORK(tg_stats_alloc_work, tg_stats_alloc_fn); |
177 | |
178 | static void throtl_pending_timer_fn(unsigned long arg); |
179 | |
180 | static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd) |
181 | { |
182 | return pd ? container_of(pd, struct throtl_grp, pd) : NULL; |
183 | } |
184 | |
185 | static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg) |
186 | { |
187 | return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl)); |
188 | } |
189 | |
190 | static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg) |
191 | { |
192 | return pd_to_blkg(&tg->pd); |
193 | } |
194 | |
195 | static inline struct throtl_grp *td_root_tg(struct throtl_data *td) |
196 | { |
197 | return blkg_to_tg(td->queue->root_blkg); |
198 | } |
199 | |
200 | /** |
201 | * sq_to_tg - return the throl_grp the specified service queue belongs to |
202 | * @sq: the throtl_service_queue of interest |
203 | * |
204 | * Return the throtl_grp @sq belongs to. If @sq is the top-level one |
205 | * embedded in throtl_data, %NULL is returned. |
206 | */ |
207 | static struct throtl_grp *sq_to_tg(struct throtl_service_queue *sq) |
208 | { |
209 | if (sq && sq->parent_sq) |
210 | return container_of(sq, struct throtl_grp, service_queue); |
211 | else |
212 | return NULL; |
213 | } |
214 | |
215 | /** |
216 | * sq_to_td - return throtl_data the specified service queue belongs to |
217 | * @sq: the throtl_service_queue of interest |
218 | * |
219 | * A service_queue can be embeded in either a throtl_grp or throtl_data. |
220 | * Determine the associated throtl_data accordingly and return it. |
221 | */ |
222 | static struct throtl_data *sq_to_td(struct throtl_service_queue *sq) |
223 | { |
224 | struct throtl_grp *tg = sq_to_tg(sq); |
225 | |
226 | if (tg) |
227 | return tg->td; |
228 | else |
229 | return container_of(sq, struct throtl_data, service_queue); |
230 | } |
231 | |
232 | /** |
233 | * throtl_log - log debug message via blktrace |
234 | * @sq: the service_queue being reported |
235 | * @fmt: printf format string |
236 | * @args: printf args |
237 | * |
238 | * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a |
239 | * throtl_grp; otherwise, just "throtl". |
240 | * |
241 | * TODO: this should be made a function and name formatting should happen |
242 | * after testing whether blktrace is enabled. |
243 | */ |
244 | #define throtl_log(sq, fmt, args...) do { \ |
245 | struct throtl_grp *__tg = sq_to_tg((sq)); \ |
246 | struct throtl_data *__td = sq_to_td((sq)); \ |
247 | \ |
248 | (void)__td; \ |
249 | if ((__tg)) { \ |
250 | char __pbuf[128]; \ |
251 | \ |
252 | blkg_path(tg_to_blkg(__tg), __pbuf, sizeof(__pbuf)); \ |
253 | blk_add_trace_msg(__td->queue, "throtl %s " fmt, __pbuf, ##args); \ |
254 | } else { \ |
255 | blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \ |
256 | } \ |
257 | } while (0) |
258 | |
259 | /* |
260 | * Worker for allocating per cpu stat for tgs. This is scheduled on the |
261 | * system_wq once there are some groups on the alloc_list waiting for |
262 | * allocation. |
263 | */ |
264 | static void tg_stats_alloc_fn(struct work_struct *work) |
265 | { |
266 | static struct tg_stats_cpu *stats_cpu; /* this fn is non-reentrant */ |
267 | struct delayed_work *dwork = to_delayed_work(work); |
268 | bool empty = false; |
269 | |
270 | alloc_stats: |
271 | if (!stats_cpu) { |
272 | stats_cpu = alloc_percpu(struct tg_stats_cpu); |
273 | if (!stats_cpu) { |
274 | /* allocation failed, try again after some time */ |
275 | schedule_delayed_work(dwork, msecs_to_jiffies(10)); |
276 | return; |
277 | } |
278 | } |
279 | |
280 | spin_lock_irq(&tg_stats_alloc_lock); |
281 | |
282 | if (!list_empty(&tg_stats_alloc_list)) { |
283 | struct throtl_grp *tg = list_first_entry(&tg_stats_alloc_list, |
284 | struct throtl_grp, |
285 | stats_alloc_node); |
286 | swap(tg->stats_cpu, stats_cpu); |
287 | list_del_init(&tg->stats_alloc_node); |
288 | } |
289 | |
290 | empty = list_empty(&tg_stats_alloc_list); |
291 | spin_unlock_irq(&tg_stats_alloc_lock); |
292 | if (!empty) |
293 | goto alloc_stats; |
294 | } |
295 | |
296 | static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg) |
297 | { |
298 | INIT_LIST_HEAD(&qn->node); |
299 | bio_list_init(&qn->bios); |
300 | qn->tg = tg; |
301 | } |
302 | |
303 | /** |
304 | * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it |
305 | * @bio: bio being added |
306 | * @qn: qnode to add bio to |
307 | * @queued: the service_queue->queued[] list @qn belongs to |
308 | * |
309 | * Add @bio to @qn and put @qn on @queued if it's not already on. |
310 | * @qn->tg's reference count is bumped when @qn is activated. See the |
311 | * comment on top of throtl_qnode definition for details. |
312 | */ |
313 | static void throtl_qnode_add_bio(struct bio *bio, struct throtl_qnode *qn, |
314 | struct list_head *queued) |
315 | { |
316 | bio_list_add(&qn->bios, bio); |
317 | if (list_empty(&qn->node)) { |
318 | list_add_tail(&qn->node, queued); |
319 | blkg_get(tg_to_blkg(qn->tg)); |
320 | } |
321 | } |
322 | |
323 | /** |
324 | * throtl_peek_queued - peek the first bio on a qnode list |
325 | * @queued: the qnode list to peek |
326 | */ |
327 | static struct bio *throtl_peek_queued(struct list_head *queued) |
328 | { |
329 | struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node); |
330 | struct bio *bio; |
331 | |
332 | if (list_empty(queued)) |
333 | return NULL; |
334 | |
335 | bio = bio_list_peek(&qn->bios); |
336 | WARN_ON_ONCE(!bio); |
337 | return bio; |
338 | } |
339 | |
340 | /** |
341 | * throtl_pop_queued - pop the first bio form a qnode list |
342 | * @queued: the qnode list to pop a bio from |
343 | * @tg_to_put: optional out argument for throtl_grp to put |
344 | * |
345 | * Pop the first bio from the qnode list @queued. After popping, the first |
346 | * qnode is removed from @queued if empty or moved to the end of @queued so |
347 | * that the popping order is round-robin. |
348 | * |
349 | * When the first qnode is removed, its associated throtl_grp should be put |
350 | * too. If @tg_to_put is NULL, this function automatically puts it; |
351 | * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is |
352 | * responsible for putting it. |
353 | */ |
354 | static struct bio *throtl_pop_queued(struct list_head *queued, |
355 | struct throtl_grp **tg_to_put) |
356 | { |
357 | struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node); |
358 | struct bio *bio; |
359 | |
360 | if (list_empty(queued)) |
361 | return NULL; |
362 | |
363 | bio = bio_list_pop(&qn->bios); |
364 | WARN_ON_ONCE(!bio); |
365 | |
366 | if (bio_list_empty(&qn->bios)) { |
367 | list_del_init(&qn->node); |
368 | if (tg_to_put) |
369 | *tg_to_put = qn->tg; |
370 | else |
371 | blkg_put(tg_to_blkg(qn->tg)); |
372 | } else { |
373 | list_move_tail(&qn->node, queued); |
374 | } |
375 | |
376 | return bio; |
377 | } |
378 | |
379 | /* init a service_queue, assumes the caller zeroed it */ |
380 | static void throtl_service_queue_init(struct throtl_service_queue *sq, |
381 | struct throtl_service_queue *parent_sq) |
382 | { |
383 | INIT_LIST_HEAD(&sq->queued[0]); |
384 | INIT_LIST_HEAD(&sq->queued[1]); |
385 | sq->pending_tree = RB_ROOT; |
386 | sq->parent_sq = parent_sq; |
387 | setup_timer(&sq->pending_timer, throtl_pending_timer_fn, |
388 | (unsigned long)sq); |
389 | } |
390 | |
391 | static void throtl_service_queue_exit(struct throtl_service_queue *sq) |
392 | { |
393 | del_timer_sync(&sq->pending_timer); |
394 | } |
395 | |
396 | static void throtl_pd_init(struct blkcg_gq *blkg) |
397 | { |
398 | struct throtl_grp *tg = blkg_to_tg(blkg); |
399 | struct throtl_data *td = blkg->q->td; |
400 | struct throtl_service_queue *parent_sq; |
401 | unsigned long flags; |
402 | int rw; |
403 | |
404 | /* |
405 | * If sane_hierarchy is enabled, we switch to properly hierarchical |
406 | * behavior where limits on a given throtl_grp are applied to the |
407 | * whole subtree rather than just the group itself. e.g. If 16M |
408 | * read_bps limit is set on the root group, the whole system can't |
409 | * exceed 16M for the device. |
410 | * |
411 | * If sane_hierarchy is not enabled, the broken flat hierarchy |
412 | * behavior is retained where all throtl_grps are treated as if |
413 | * they're all separate root groups right below throtl_data. |
414 | * Limits of a group don't interact with limits of other groups |
415 | * regardless of the position of the group in the hierarchy. |
416 | */ |
417 | parent_sq = &td->service_queue; |
418 | |
419 | if (cgroup_sane_behavior(blkg->blkcg->css.cgroup) && blkg->parent) |
420 | parent_sq = &blkg_to_tg(blkg->parent)->service_queue; |
421 | |
422 | throtl_service_queue_init(&tg->service_queue, parent_sq); |
423 | |
424 | for (rw = READ; rw <= WRITE; rw++) { |
425 | throtl_qnode_init(&tg->qnode_on_self[rw], tg); |
426 | throtl_qnode_init(&tg->qnode_on_parent[rw], tg); |
427 | } |
428 | |
429 | RB_CLEAR_NODE(&tg->rb_node); |
430 | tg->td = td; |
431 | |
432 | tg->bps[READ] = -1; |
433 | tg->bps[WRITE] = -1; |
434 | tg->iops[READ] = -1; |
435 | tg->iops[WRITE] = -1; |
436 | |
437 | /* |
438 | * Ugh... We need to perform per-cpu allocation for tg->stats_cpu |
439 | * but percpu allocator can't be called from IO path. Queue tg on |
440 | * tg_stats_alloc_list and allocate from work item. |
441 | */ |
442 | spin_lock_irqsave(&tg_stats_alloc_lock, flags); |
443 | list_add(&tg->stats_alloc_node, &tg_stats_alloc_list); |
444 | schedule_delayed_work(&tg_stats_alloc_work, 0); |
445 | spin_unlock_irqrestore(&tg_stats_alloc_lock, flags); |
446 | } |
447 | |
448 | /* |
449 | * Set has_rules[] if @tg or any of its parents have limits configured. |
450 | * This doesn't require walking up to the top of the hierarchy as the |
451 | * parent's has_rules[] is guaranteed to be correct. |
452 | */ |
453 | static void tg_update_has_rules(struct throtl_grp *tg) |
454 | { |
455 | struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq); |
456 | int rw; |
457 | |
458 | for (rw = READ; rw <= WRITE; rw++) |
459 | tg->has_rules[rw] = (parent_tg && parent_tg->has_rules[rw]) || |
460 | (tg->bps[rw] != -1 || tg->iops[rw] != -1); |
461 | } |
462 | |
463 | static void throtl_pd_online(struct blkcg_gq *blkg) |
464 | { |
465 | /* |
466 | * We don't want new groups to escape the limits of its ancestors. |
467 | * Update has_rules[] after a new group is brought online. |
468 | */ |
469 | tg_update_has_rules(blkg_to_tg(blkg)); |
470 | } |
471 | |
472 | static void throtl_pd_exit(struct blkcg_gq *blkg) |
473 | { |
474 | struct throtl_grp *tg = blkg_to_tg(blkg); |
475 | unsigned long flags; |
476 | |
477 | spin_lock_irqsave(&tg_stats_alloc_lock, flags); |
478 | list_del_init(&tg->stats_alloc_node); |
479 | spin_unlock_irqrestore(&tg_stats_alloc_lock, flags); |
480 | |
481 | free_percpu(tg->stats_cpu); |
482 | |
483 | throtl_service_queue_exit(&tg->service_queue); |
484 | } |
485 | |
486 | static void throtl_pd_reset_stats(struct blkcg_gq *blkg) |
487 | { |
488 | struct throtl_grp *tg = blkg_to_tg(blkg); |
489 | int cpu; |
490 | |
491 | if (tg->stats_cpu == NULL) |
492 | return; |
493 | |
494 | for_each_possible_cpu(cpu) { |
495 | struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu); |
496 | |
497 | blkg_rwstat_reset(&sc->service_bytes); |
498 | blkg_rwstat_reset(&sc->serviced); |
499 | } |
500 | } |
501 | |
502 | static struct throtl_grp *throtl_lookup_tg(struct throtl_data *td, |
503 | struct blkcg *blkcg) |
504 | { |
505 | /* |
506 | * This is the common case when there are no blkcgs. Avoid lookup |
507 | * in this case |
508 | */ |
509 | if (blkcg == &blkcg_root) |
510 | return td_root_tg(td); |
511 | |
512 | return blkg_to_tg(blkg_lookup(blkcg, td->queue)); |
513 | } |
514 | |
515 | static struct throtl_grp *throtl_lookup_create_tg(struct throtl_data *td, |
516 | struct blkcg *blkcg) |
517 | { |
518 | struct request_queue *q = td->queue; |
519 | struct throtl_grp *tg = NULL; |
520 | |
521 | /* |
522 | * This is the common case when there are no blkcgs. Avoid lookup |
523 | * in this case |
524 | */ |
525 | if (blkcg == &blkcg_root) { |
526 | tg = td_root_tg(td); |
527 | } else { |
528 | struct blkcg_gq *blkg; |
529 | |
530 | blkg = blkg_lookup_create(blkcg, q); |
531 | |
532 | /* if %NULL and @q is alive, fall back to root_tg */ |
533 | if (!IS_ERR(blkg)) |
534 | tg = blkg_to_tg(blkg); |
535 | else if (!blk_queue_dying(q)) |
536 | tg = td_root_tg(td); |
537 | } |
538 | |
539 | return tg; |
540 | } |
541 | |
542 | static struct throtl_grp * |
543 | throtl_rb_first(struct throtl_service_queue *parent_sq) |
544 | { |
545 | /* Service tree is empty */ |
546 | if (!parent_sq->nr_pending) |
547 | return NULL; |
548 | |
549 | if (!parent_sq->first_pending) |
550 | parent_sq->first_pending = rb_first(&parent_sq->pending_tree); |
551 | |
552 | if (parent_sq->first_pending) |
553 | return rb_entry_tg(parent_sq->first_pending); |
554 | |
555 | return NULL; |
556 | } |
557 | |
558 | static void rb_erase_init(struct rb_node *n, struct rb_root *root) |
559 | { |
560 | rb_erase(n, root); |
561 | RB_CLEAR_NODE(n); |
562 | } |
563 | |
564 | static void throtl_rb_erase(struct rb_node *n, |
565 | struct throtl_service_queue *parent_sq) |
566 | { |
567 | if (parent_sq->first_pending == n) |
568 | parent_sq->first_pending = NULL; |
569 | rb_erase_init(n, &parent_sq->pending_tree); |
570 | --parent_sq->nr_pending; |
571 | } |
572 | |
573 | static void update_min_dispatch_time(struct throtl_service_queue *parent_sq) |
574 | { |
575 | struct throtl_grp *tg; |
576 | |
577 | tg = throtl_rb_first(parent_sq); |
578 | if (!tg) |
579 | return; |
580 | |
581 | parent_sq->first_pending_disptime = tg->disptime; |
582 | } |
583 | |
584 | static void tg_service_queue_add(struct throtl_grp *tg) |
585 | { |
586 | struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq; |
587 | struct rb_node **node = &parent_sq->pending_tree.rb_node; |
588 | struct rb_node *parent = NULL; |
589 | struct throtl_grp *__tg; |
590 | unsigned long key = tg->disptime; |
591 | int left = 1; |
592 | |
593 | while (*node != NULL) { |
594 | parent = *node; |
595 | __tg = rb_entry_tg(parent); |
596 | |
597 | if (time_before(key, __tg->disptime)) |
598 | node = &parent->rb_left; |
599 | else { |
600 | node = &parent->rb_right; |
601 | left = 0; |
602 | } |
603 | } |
604 | |
605 | if (left) |
606 | parent_sq->first_pending = &tg->rb_node; |
607 | |
608 | rb_link_node(&tg->rb_node, parent, node); |
609 | rb_insert_color(&tg->rb_node, &parent_sq->pending_tree); |
610 | } |
611 | |
612 | static void __throtl_enqueue_tg(struct throtl_grp *tg) |
613 | { |
614 | tg_service_queue_add(tg); |
615 | tg->flags |= THROTL_TG_PENDING; |
616 | tg->service_queue.parent_sq->nr_pending++; |
617 | } |
618 | |
619 | static void throtl_enqueue_tg(struct throtl_grp *tg) |
620 | { |
621 | if (!(tg->flags & THROTL_TG_PENDING)) |
622 | __throtl_enqueue_tg(tg); |
623 | } |
624 | |
625 | static void __throtl_dequeue_tg(struct throtl_grp *tg) |
626 | { |
627 | throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq); |
628 | tg->flags &= ~THROTL_TG_PENDING; |
629 | } |
630 | |
631 | static void throtl_dequeue_tg(struct throtl_grp *tg) |
632 | { |
633 | if (tg->flags & THROTL_TG_PENDING) |
634 | __throtl_dequeue_tg(tg); |
635 | } |
636 | |
637 | /* Call with queue lock held */ |
638 | static void throtl_schedule_pending_timer(struct throtl_service_queue *sq, |
639 | unsigned long expires) |
640 | { |
641 | mod_timer(&sq->pending_timer, expires); |
642 | throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu", |
643 | expires - jiffies, jiffies); |
644 | } |
645 | |
646 | /** |
647 | * throtl_schedule_next_dispatch - schedule the next dispatch cycle |
648 | * @sq: the service_queue to schedule dispatch for |
649 | * @force: force scheduling |
650 | * |
651 | * Arm @sq->pending_timer so that the next dispatch cycle starts on the |
652 | * dispatch time of the first pending child. Returns %true if either timer |
653 | * is armed or there's no pending child left. %false if the current |
654 | * dispatch window is still open and the caller should continue |
655 | * dispatching. |
656 | * |
657 | * If @force is %true, the dispatch timer is always scheduled and this |
658 | * function is guaranteed to return %true. This is to be used when the |
659 | * caller can't dispatch itself and needs to invoke pending_timer |
660 | * unconditionally. Note that forced scheduling is likely to induce short |
661 | * delay before dispatch starts even if @sq->first_pending_disptime is not |
662 | * in the future and thus shouldn't be used in hot paths. |
663 | */ |
664 | static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq, |
665 | bool force) |
666 | { |
667 | /* any pending children left? */ |
668 | if (!sq->nr_pending) |
669 | return true; |
670 | |
671 | update_min_dispatch_time(sq); |
672 | |
673 | /* is the next dispatch time in the future? */ |
674 | if (force || time_after(sq->first_pending_disptime, jiffies)) { |
675 | throtl_schedule_pending_timer(sq, sq->first_pending_disptime); |
676 | return true; |
677 | } |
678 | |
679 | /* tell the caller to continue dispatching */ |
680 | return false; |
681 | } |
682 | |
683 | static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg, |
684 | bool rw, unsigned long start) |
685 | { |
686 | tg->bytes_disp[rw] = 0; |
687 | tg->io_disp[rw] = 0; |
688 | |
689 | /* |
690 | * Previous slice has expired. We must have trimmed it after last |
691 | * bio dispatch. That means since start of last slice, we never used |
692 | * that bandwidth. Do try to make use of that bandwidth while giving |
693 | * credit. |
694 | */ |
695 | if (time_after_eq(start, tg->slice_start[rw])) |
696 | tg->slice_start[rw] = start; |
697 | |
698 | tg->slice_end[rw] = jiffies + throtl_slice; |
699 | throtl_log(&tg->service_queue, |
700 | "[%c] new slice with credit start=%lu end=%lu jiffies=%lu", |
701 | rw == READ ? 'R' : 'W', tg->slice_start[rw], |
702 | tg->slice_end[rw], jiffies); |
703 | } |
704 | |
705 | static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw) |
706 | { |
707 | tg->bytes_disp[rw] = 0; |
708 | tg->io_disp[rw] = 0; |
709 | tg->slice_start[rw] = jiffies; |
710 | tg->slice_end[rw] = jiffies + throtl_slice; |
711 | throtl_log(&tg->service_queue, |
712 | "[%c] new slice start=%lu end=%lu jiffies=%lu", |
713 | rw == READ ? 'R' : 'W', tg->slice_start[rw], |
714 | tg->slice_end[rw], jiffies); |
715 | } |
716 | |
717 | static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw, |
718 | unsigned long jiffy_end) |
719 | { |
720 | tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); |
721 | } |
722 | |
723 | static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw, |
724 | unsigned long jiffy_end) |
725 | { |
726 | tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); |
727 | throtl_log(&tg->service_queue, |
728 | "[%c] extend slice start=%lu end=%lu jiffies=%lu", |
729 | rw == READ ? 'R' : 'W', tg->slice_start[rw], |
730 | tg->slice_end[rw], jiffies); |
731 | } |
732 | |
733 | /* Determine if previously allocated or extended slice is complete or not */ |
734 | static bool throtl_slice_used(struct throtl_grp *tg, bool rw) |
735 | { |
736 | if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw])) |
737 | return 0; |
738 | |
739 | return 1; |
740 | } |
741 | |
742 | /* Trim the used slices and adjust slice start accordingly */ |
743 | static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw) |
744 | { |
745 | unsigned long nr_slices, time_elapsed, io_trim; |
746 | u64 bytes_trim, tmp; |
747 | |
748 | BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw])); |
749 | |
750 | /* |
751 | * If bps are unlimited (-1), then time slice don't get |
752 | * renewed. Don't try to trim the slice if slice is used. A new |
753 | * slice will start when appropriate. |
754 | */ |
755 | if (throtl_slice_used(tg, rw)) |
756 | return; |
757 | |
758 | /* |
759 | * A bio has been dispatched. Also adjust slice_end. It might happen |
760 | * that initially cgroup limit was very low resulting in high |
761 | * slice_end, but later limit was bumped up and bio was dispached |
762 | * sooner, then we need to reduce slice_end. A high bogus slice_end |
763 | * is bad because it does not allow new slice to start. |
764 | */ |
765 | |
766 | throtl_set_slice_end(tg, rw, jiffies + throtl_slice); |
767 | |
768 | time_elapsed = jiffies - tg->slice_start[rw]; |
769 | |
770 | nr_slices = time_elapsed / throtl_slice; |
771 | |
772 | if (!nr_slices) |
773 | return; |
774 | tmp = tg->bps[rw] * throtl_slice * nr_slices; |
775 | do_div(tmp, HZ); |
776 | bytes_trim = tmp; |
777 | |
778 | io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ; |
779 | |
780 | if (!bytes_trim && !io_trim) |
781 | return; |
782 | |
783 | if (tg->bytes_disp[rw] >= bytes_trim) |
784 | tg->bytes_disp[rw] -= bytes_trim; |
785 | else |
786 | tg->bytes_disp[rw] = 0; |
787 | |
788 | if (tg->io_disp[rw] >= io_trim) |
789 | tg->io_disp[rw] -= io_trim; |
790 | else |
791 | tg->io_disp[rw] = 0; |
792 | |
793 | tg->slice_start[rw] += nr_slices * throtl_slice; |
794 | |
795 | throtl_log(&tg->service_queue, |
796 | "[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu", |
797 | rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim, |
798 | tg->slice_start[rw], tg->slice_end[rw], jiffies); |
799 | } |
800 | |
801 | static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio, |
802 | unsigned long *wait) |
803 | { |
804 | bool rw = bio_data_dir(bio); |
805 | unsigned int io_allowed; |
806 | unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; |
807 | u64 tmp; |
808 | |
809 | jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; |
810 | |
811 | /* Slice has just started. Consider one slice interval */ |
812 | if (!jiffy_elapsed) |
813 | jiffy_elapsed_rnd = throtl_slice; |
814 | |
815 | jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice); |
816 | |
817 | /* |
818 | * jiffy_elapsed_rnd should not be a big value as minimum iops can be |
819 | * 1 then at max jiffy elapsed should be equivalent of 1 second as we |
820 | * will allow dispatch after 1 second and after that slice should |
821 | * have been trimmed. |
822 | */ |
823 | |
824 | tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd; |
825 | do_div(tmp, HZ); |
826 | |
827 | if (tmp > UINT_MAX) |
828 | io_allowed = UINT_MAX; |
829 | else |
830 | io_allowed = tmp; |
831 | |
832 | if (tg->io_disp[rw] + 1 <= io_allowed) { |
833 | if (wait) |
834 | *wait = 0; |
835 | return 1; |
836 | } |
837 | |
838 | /* Calc approx time to dispatch */ |
839 | jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1; |
840 | |
841 | if (jiffy_wait > jiffy_elapsed) |
842 | jiffy_wait = jiffy_wait - jiffy_elapsed; |
843 | else |
844 | jiffy_wait = 1; |
845 | |
846 | if (wait) |
847 | *wait = jiffy_wait; |
848 | return 0; |
849 | } |
850 | |
851 | static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio, |
852 | unsigned long *wait) |
853 | { |
854 | bool rw = bio_data_dir(bio); |
855 | u64 bytes_allowed, extra_bytes, tmp; |
856 | unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; |
857 | |
858 | jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; |
859 | |
860 | /* Slice has just started. Consider one slice interval */ |
861 | if (!jiffy_elapsed) |
862 | jiffy_elapsed_rnd = throtl_slice; |
863 | |
864 | jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice); |
865 | |
866 | tmp = tg->bps[rw] * jiffy_elapsed_rnd; |
867 | do_div(tmp, HZ); |
868 | bytes_allowed = tmp; |
869 | |
870 | if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) { |
871 | if (wait) |
872 | *wait = 0; |
873 | return 1; |
874 | } |
875 | |
876 | /* Calc approx time to dispatch */ |
877 | extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed; |
878 | jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]); |
879 | |
880 | if (!jiffy_wait) |
881 | jiffy_wait = 1; |
882 | |
883 | /* |
884 | * This wait time is without taking into consideration the rounding |
885 | * up we did. Add that time also. |
886 | */ |
887 | jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed); |
888 | if (wait) |
889 | *wait = jiffy_wait; |
890 | return 0; |
891 | } |
892 | |
893 | /* |
894 | * Returns whether one can dispatch a bio or not. Also returns approx number |
895 | * of jiffies to wait before this bio is with-in IO rate and can be dispatched |
896 | */ |
897 | static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio, |
898 | unsigned long *wait) |
899 | { |
900 | bool rw = bio_data_dir(bio); |
901 | unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0; |
902 | |
903 | /* |
904 | * Currently whole state machine of group depends on first bio |
905 | * queued in the group bio list. So one should not be calling |
906 | * this function with a different bio if there are other bios |
907 | * queued. |
908 | */ |
909 | BUG_ON(tg->service_queue.nr_queued[rw] && |
910 | bio != throtl_peek_queued(&tg->service_queue.queued[rw])); |
911 | |
912 | /* If tg->bps = -1, then BW is unlimited */ |
913 | if (tg->bps[rw] == -1 && tg->iops[rw] == -1) { |
914 | if (wait) |
915 | *wait = 0; |
916 | return 1; |
917 | } |
918 | |
919 | /* |
920 | * If previous slice expired, start a new one otherwise renew/extend |
921 | * existing slice to make sure it is at least throtl_slice interval |
922 | * long since now. |
923 | */ |
924 | if (throtl_slice_used(tg, rw)) |
925 | throtl_start_new_slice(tg, rw); |
926 | else { |
927 | if (time_before(tg->slice_end[rw], jiffies + throtl_slice)) |
928 | throtl_extend_slice(tg, rw, jiffies + throtl_slice); |
929 | } |
930 | |
931 | if (tg_with_in_bps_limit(tg, bio, &bps_wait) && |
932 | tg_with_in_iops_limit(tg, bio, &iops_wait)) { |
933 | if (wait) |
934 | *wait = 0; |
935 | return 1; |
936 | } |
937 | |
938 | max_wait = max(bps_wait, iops_wait); |
939 | |
940 | if (wait) |
941 | *wait = max_wait; |
942 | |
943 | if (time_before(tg->slice_end[rw], jiffies + max_wait)) |
944 | throtl_extend_slice(tg, rw, jiffies + max_wait); |
945 | |
946 | return 0; |
947 | } |
948 | |
949 | static void throtl_update_dispatch_stats(struct blkcg_gq *blkg, u64 bytes, |
950 | int rw) |
951 | { |
952 | struct throtl_grp *tg = blkg_to_tg(blkg); |
953 | struct tg_stats_cpu *stats_cpu; |
954 | unsigned long flags; |
955 | |
956 | /* If per cpu stats are not allocated yet, don't do any accounting. */ |
957 | if (tg->stats_cpu == NULL) |
958 | return; |
959 | |
960 | /* |
961 | * Disabling interrupts to provide mutual exclusion between two |
962 | * writes on same cpu. It probably is not needed for 64bit. Not |
963 | * optimizing that case yet. |
964 | */ |
965 | local_irq_save(flags); |
966 | |
967 | stats_cpu = this_cpu_ptr(tg->stats_cpu); |
968 | |
969 | blkg_rwstat_add(&stats_cpu->serviced, rw, 1); |
970 | blkg_rwstat_add(&stats_cpu->service_bytes, rw, bytes); |
971 | |
972 | local_irq_restore(flags); |
973 | } |
974 | |
975 | static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio) |
976 | { |
977 | bool rw = bio_data_dir(bio); |
978 | |
979 | /* Charge the bio to the group */ |
980 | tg->bytes_disp[rw] += bio->bi_size; |
981 | tg->io_disp[rw]++; |
982 | |
983 | /* |
984 | * REQ_THROTTLED is used to prevent the same bio to be throttled |
985 | * more than once as a throttled bio will go through blk-throtl the |
986 | * second time when it eventually gets issued. Set it when a bio |
987 | * is being charged to a tg. |
988 | * |
989 | * Dispatch stats aren't recursive and each @bio should only be |
990 | * accounted by the @tg it was originally associated with. Let's |
991 | * update the stats when setting REQ_THROTTLED for the first time |
992 | * which is guaranteed to be for the @bio's original tg. |
993 | */ |
994 | if (!(bio->bi_rw & REQ_THROTTLED)) { |
995 | bio->bi_rw |= REQ_THROTTLED; |
996 | throtl_update_dispatch_stats(tg_to_blkg(tg), bio->bi_size, |
997 | bio->bi_rw); |
998 | } |
999 | } |
1000 | |
1001 | /** |
1002 | * throtl_add_bio_tg - add a bio to the specified throtl_grp |
1003 | * @bio: bio to add |
1004 | * @qn: qnode to use |
1005 | * @tg: the target throtl_grp |
1006 | * |
1007 | * Add @bio to @tg's service_queue using @qn. If @qn is not specified, |
1008 | * tg->qnode_on_self[] is used. |
1009 | */ |
1010 | static void throtl_add_bio_tg(struct bio *bio, struct throtl_qnode *qn, |
1011 | struct throtl_grp *tg) |
1012 | { |
1013 | struct throtl_service_queue *sq = &tg->service_queue; |
1014 | bool rw = bio_data_dir(bio); |
1015 | |
1016 | if (!qn) |
1017 | qn = &tg->qnode_on_self[rw]; |
1018 | |
1019 | /* |
1020 | * If @tg doesn't currently have any bios queued in the same |
1021 | * direction, queueing @bio can change when @tg should be |
1022 | * dispatched. Mark that @tg was empty. This is automatically |
1023 | * cleaered on the next tg_update_disptime(). |
1024 | */ |
1025 | if (!sq->nr_queued[rw]) |
1026 | tg->flags |= THROTL_TG_WAS_EMPTY; |
1027 | |
1028 | throtl_qnode_add_bio(bio, qn, &sq->queued[rw]); |
1029 | |
1030 | sq->nr_queued[rw]++; |
1031 | throtl_enqueue_tg(tg); |
1032 | } |
1033 | |
1034 | static void tg_update_disptime(struct throtl_grp *tg) |
1035 | { |
1036 | struct throtl_service_queue *sq = &tg->service_queue; |
1037 | unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime; |
1038 | struct bio *bio; |
1039 | |
1040 | if ((bio = throtl_peek_queued(&sq->queued[READ]))) |
1041 | tg_may_dispatch(tg, bio, &read_wait); |
1042 | |
1043 | if ((bio = throtl_peek_queued(&sq->queued[WRITE]))) |
1044 | tg_may_dispatch(tg, bio, &write_wait); |
1045 | |
1046 | min_wait = min(read_wait, write_wait); |
1047 | disptime = jiffies + min_wait; |
1048 | |
1049 | /* Update dispatch time */ |
1050 | throtl_dequeue_tg(tg); |
1051 | tg->disptime = disptime; |
1052 | throtl_enqueue_tg(tg); |
1053 | |
1054 | /* see throtl_add_bio_tg() */ |
1055 | tg->flags &= ~THROTL_TG_WAS_EMPTY; |
1056 | } |
1057 | |
1058 | static void start_parent_slice_with_credit(struct throtl_grp *child_tg, |
1059 | struct throtl_grp *parent_tg, bool rw) |
1060 | { |
1061 | if (throtl_slice_used(parent_tg, rw)) { |
1062 | throtl_start_new_slice_with_credit(parent_tg, rw, |
1063 | child_tg->slice_start[rw]); |
1064 | } |
1065 | |
1066 | } |
1067 | |
1068 | static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw) |
1069 | { |
1070 | struct throtl_service_queue *sq = &tg->service_queue; |
1071 | struct throtl_service_queue *parent_sq = sq->parent_sq; |
1072 | struct throtl_grp *parent_tg = sq_to_tg(parent_sq); |
1073 | struct throtl_grp *tg_to_put = NULL; |
1074 | struct bio *bio; |
1075 | |
1076 | /* |
1077 | * @bio is being transferred from @tg to @parent_sq. Popping a bio |
1078 | * from @tg may put its reference and @parent_sq might end up |
1079 | * getting released prematurely. Remember the tg to put and put it |
1080 | * after @bio is transferred to @parent_sq. |
1081 | */ |
1082 | bio = throtl_pop_queued(&sq->queued[rw], &tg_to_put); |
1083 | sq->nr_queued[rw]--; |
1084 | |
1085 | throtl_charge_bio(tg, bio); |
1086 | |
1087 | /* |
1088 | * If our parent is another tg, we just need to transfer @bio to |
1089 | * the parent using throtl_add_bio_tg(). If our parent is |
1090 | * @td->service_queue, @bio is ready to be issued. Put it on its |
1091 | * bio_lists[] and decrease total number queued. The caller is |
1092 | * responsible for issuing these bios. |
1093 | */ |
1094 | if (parent_tg) { |
1095 | throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg); |
1096 | start_parent_slice_with_credit(tg, parent_tg, rw); |
1097 | } else { |
1098 | throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw], |
1099 | &parent_sq->queued[rw]); |
1100 | BUG_ON(tg->td->nr_queued[rw] <= 0); |
1101 | tg->td->nr_queued[rw]--; |
1102 | } |
1103 | |
1104 | throtl_trim_slice(tg, rw); |
1105 | |
1106 | if (tg_to_put) |
1107 | blkg_put(tg_to_blkg(tg_to_put)); |
1108 | } |
1109 | |
1110 | static int throtl_dispatch_tg(struct throtl_grp *tg) |
1111 | { |
1112 | struct throtl_service_queue *sq = &tg->service_queue; |
1113 | unsigned int nr_reads = 0, nr_writes = 0; |
1114 | unsigned int max_nr_reads = throtl_grp_quantum*3/4; |
1115 | unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads; |
1116 | struct bio *bio; |
1117 | |
1118 | /* Try to dispatch 75% READS and 25% WRITES */ |
1119 | |
1120 | while ((bio = throtl_peek_queued(&sq->queued[READ])) && |
1121 | tg_may_dispatch(tg, bio, NULL)) { |
1122 | |
1123 | tg_dispatch_one_bio(tg, bio_data_dir(bio)); |
1124 | nr_reads++; |
1125 | |
1126 | if (nr_reads >= max_nr_reads) |
1127 | break; |
1128 | } |
1129 | |
1130 | while ((bio = throtl_peek_queued(&sq->queued[WRITE])) && |
1131 | tg_may_dispatch(tg, bio, NULL)) { |
1132 | |
1133 | tg_dispatch_one_bio(tg, bio_data_dir(bio)); |
1134 | nr_writes++; |
1135 | |
1136 | if (nr_writes >= max_nr_writes) |
1137 | break; |
1138 | } |
1139 | |
1140 | return nr_reads + nr_writes; |
1141 | } |
1142 | |
1143 | static int throtl_select_dispatch(struct throtl_service_queue *parent_sq) |
1144 | { |
1145 | unsigned int nr_disp = 0; |
1146 | |
1147 | while (1) { |
1148 | struct throtl_grp *tg = throtl_rb_first(parent_sq); |
1149 | struct throtl_service_queue *sq = &tg->service_queue; |
1150 | |
1151 | if (!tg) |
1152 | break; |
1153 | |
1154 | if (time_before(jiffies, tg->disptime)) |
1155 | break; |
1156 | |
1157 | throtl_dequeue_tg(tg); |
1158 | |
1159 | nr_disp += throtl_dispatch_tg(tg); |
1160 | |
1161 | if (sq->nr_queued[0] || sq->nr_queued[1]) |
1162 | tg_update_disptime(tg); |
1163 | |
1164 | if (nr_disp >= throtl_quantum) |
1165 | break; |
1166 | } |
1167 | |
1168 | return nr_disp; |
1169 | } |
1170 | |
1171 | /** |
1172 | * throtl_pending_timer_fn - timer function for service_queue->pending_timer |
1173 | * @arg: the throtl_service_queue being serviced |
1174 | * |
1175 | * This timer is armed when a child throtl_grp with active bio's become |
1176 | * pending and queued on the service_queue's pending_tree and expires when |
1177 | * the first child throtl_grp should be dispatched. This function |
1178 | * dispatches bio's from the children throtl_grps to the parent |
1179 | * service_queue. |
1180 | * |
1181 | * If the parent's parent is another throtl_grp, dispatching is propagated |
1182 | * by either arming its pending_timer or repeating dispatch directly. If |
1183 | * the top-level service_tree is reached, throtl_data->dispatch_work is |
1184 | * kicked so that the ready bio's are issued. |
1185 | */ |
1186 | static void throtl_pending_timer_fn(unsigned long arg) |
1187 | { |
1188 | struct throtl_service_queue *sq = (void *)arg; |
1189 | struct throtl_grp *tg = sq_to_tg(sq); |
1190 | struct throtl_data *td = sq_to_td(sq); |
1191 | struct request_queue *q = td->queue; |
1192 | struct throtl_service_queue *parent_sq; |
1193 | bool dispatched; |
1194 | int ret; |
1195 | |
1196 | spin_lock_irq(q->queue_lock); |
1197 | again: |
1198 | parent_sq = sq->parent_sq; |
1199 | dispatched = false; |
1200 | |
1201 | while (true) { |
1202 | throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u", |
1203 | sq->nr_queued[READ] + sq->nr_queued[WRITE], |
1204 | sq->nr_queued[READ], sq->nr_queued[WRITE]); |
1205 | |
1206 | ret = throtl_select_dispatch(sq); |
1207 | if (ret) { |
1208 | throtl_log(sq, "bios disp=%u", ret); |
1209 | dispatched = true; |
1210 | } |
1211 | |
1212 | if (throtl_schedule_next_dispatch(sq, false)) |
1213 | break; |
1214 | |
1215 | /* this dispatch windows is still open, relax and repeat */ |
1216 | spin_unlock_irq(q->queue_lock); |
1217 | cpu_relax(); |
1218 | spin_lock_irq(q->queue_lock); |
1219 | } |
1220 | |
1221 | if (!dispatched) |
1222 | goto out_unlock; |
1223 | |
1224 | if (parent_sq) { |
1225 | /* @parent_sq is another throl_grp, propagate dispatch */ |
1226 | if (tg->flags & THROTL_TG_WAS_EMPTY) { |
1227 | tg_update_disptime(tg); |
1228 | if (!throtl_schedule_next_dispatch(parent_sq, false)) { |
1229 | /* window is already open, repeat dispatching */ |
1230 | sq = parent_sq; |
1231 | tg = sq_to_tg(sq); |
1232 | goto again; |
1233 | } |
1234 | } |
1235 | } else { |
1236 | /* reached the top-level, queue issueing */ |
1237 | queue_work(kthrotld_workqueue, &td->dispatch_work); |
1238 | } |
1239 | out_unlock: |
1240 | spin_unlock_irq(q->queue_lock); |
1241 | } |
1242 | |
1243 | /** |
1244 | * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work |
1245 | * @work: work item being executed |
1246 | * |
1247 | * This function is queued for execution when bio's reach the bio_lists[] |
1248 | * of throtl_data->service_queue. Those bio's are ready and issued by this |
1249 | * function. |
1250 | */ |
1251 | void blk_throtl_dispatch_work_fn(struct work_struct *work) |
1252 | { |
1253 | struct throtl_data *td = container_of(work, struct throtl_data, |
1254 | dispatch_work); |
1255 | struct throtl_service_queue *td_sq = &td->service_queue; |
1256 | struct request_queue *q = td->queue; |
1257 | struct bio_list bio_list_on_stack; |
1258 | struct bio *bio; |
1259 | struct blk_plug plug; |
1260 | int rw; |
1261 | |
1262 | bio_list_init(&bio_list_on_stack); |
1263 | |
1264 | spin_lock_irq(q->queue_lock); |
1265 | for (rw = READ; rw <= WRITE; rw++) |
1266 | while ((bio = throtl_pop_queued(&td_sq->queued[rw], NULL))) |
1267 | bio_list_add(&bio_list_on_stack, bio); |
1268 | spin_unlock_irq(q->queue_lock); |
1269 | |
1270 | if (!bio_list_empty(&bio_list_on_stack)) { |
1271 | blk_start_plug(&plug); |
1272 | while((bio = bio_list_pop(&bio_list_on_stack))) |
1273 | generic_make_request(bio); |
1274 | blk_finish_plug(&plug); |
1275 | } |
1276 | } |
1277 | |
1278 | static u64 tg_prfill_cpu_rwstat(struct seq_file *sf, |
1279 | struct blkg_policy_data *pd, int off) |
1280 | { |
1281 | struct throtl_grp *tg = pd_to_tg(pd); |
1282 | struct blkg_rwstat rwstat = { }, tmp; |
1283 | int i, cpu; |
1284 | |
1285 | for_each_possible_cpu(cpu) { |
1286 | struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu); |
1287 | |
1288 | tmp = blkg_rwstat_read((void *)sc + off); |
1289 | for (i = 0; i < BLKG_RWSTAT_NR; i++) |
1290 | rwstat.cnt[i] += tmp.cnt[i]; |
1291 | } |
1292 | |
1293 | return __blkg_prfill_rwstat(sf, pd, &rwstat); |
1294 | } |
1295 | |
1296 | static int tg_print_cpu_rwstat(struct cgroup_subsys_state *css, |
1297 | struct cftype *cft, struct seq_file *sf) |
1298 | { |
1299 | struct blkcg *blkcg = css_to_blkcg(css); |
1300 | |
1301 | blkcg_print_blkgs(sf, blkcg, tg_prfill_cpu_rwstat, &blkcg_policy_throtl, |
1302 | cft->private, true); |
1303 | return 0; |
1304 | } |
1305 | |
1306 | static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd, |
1307 | int off) |
1308 | { |
1309 | struct throtl_grp *tg = pd_to_tg(pd); |
1310 | u64 v = *(u64 *)((void *)tg + off); |
1311 | |
1312 | if (v == -1) |
1313 | return 0; |
1314 | return __blkg_prfill_u64(sf, pd, v); |
1315 | } |
1316 | |
1317 | static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd, |
1318 | int off) |
1319 | { |
1320 | struct throtl_grp *tg = pd_to_tg(pd); |
1321 | unsigned int v = *(unsigned int *)((void *)tg + off); |
1322 | |
1323 | if (v == -1) |
1324 | return 0; |
1325 | return __blkg_prfill_u64(sf, pd, v); |
1326 | } |
1327 | |
1328 | static int tg_print_conf_u64(struct cgroup_subsys_state *css, |
1329 | struct cftype *cft, struct seq_file *sf) |
1330 | { |
1331 | blkcg_print_blkgs(sf, css_to_blkcg(css), tg_prfill_conf_u64, |
1332 | &blkcg_policy_throtl, cft->private, false); |
1333 | return 0; |
1334 | } |
1335 | |
1336 | static int tg_print_conf_uint(struct cgroup_subsys_state *css, |
1337 | struct cftype *cft, struct seq_file *sf) |
1338 | { |
1339 | blkcg_print_blkgs(sf, css_to_blkcg(css), tg_prfill_conf_uint, |
1340 | &blkcg_policy_throtl, cft->private, false); |
1341 | return 0; |
1342 | } |
1343 | |
1344 | static int tg_set_conf(struct cgroup_subsys_state *css, struct cftype *cft, |
1345 | const char *buf, bool is_u64) |
1346 | { |
1347 | struct blkcg *blkcg = css_to_blkcg(css); |
1348 | struct blkg_conf_ctx ctx; |
1349 | struct throtl_grp *tg; |
1350 | struct throtl_service_queue *sq; |
1351 | struct blkcg_gq *blkg; |
1352 | struct cgroup_subsys_state *pos_css; |
1353 | int ret; |
1354 | |
1355 | ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx); |
1356 | if (ret) |
1357 | return ret; |
1358 | |
1359 | tg = blkg_to_tg(ctx.blkg); |
1360 | sq = &tg->service_queue; |
1361 | |
1362 | if (!ctx.v) |
1363 | ctx.v = -1; |
1364 | |
1365 | if (is_u64) |
1366 | *(u64 *)((void *)tg + cft->private) = ctx.v; |
1367 | else |
1368 | *(unsigned int *)((void *)tg + cft->private) = ctx.v; |
1369 | |
1370 | throtl_log(&tg->service_queue, |
1371 | "limit change rbps=%llu wbps=%llu riops=%u wiops=%u", |
1372 | tg->bps[READ], tg->bps[WRITE], |
1373 | tg->iops[READ], tg->iops[WRITE]); |
1374 | |
1375 | /* |
1376 | * Update has_rules[] flags for the updated tg's subtree. A tg is |
1377 | * considered to have rules if either the tg itself or any of its |
1378 | * ancestors has rules. This identifies groups without any |
1379 | * restrictions in the whole hierarchy and allows them to bypass |
1380 | * blk-throttle. |
1381 | */ |
1382 | blkg_for_each_descendant_pre(blkg, pos_css, ctx.blkg) |
1383 | tg_update_has_rules(blkg_to_tg(blkg)); |
1384 | |
1385 | /* |
1386 | * We're already holding queue_lock and know @tg is valid. Let's |
1387 | * apply the new config directly. |
1388 | * |
1389 | * Restart the slices for both READ and WRITES. It might happen |
1390 | * that a group's limit are dropped suddenly and we don't want to |
1391 | * account recently dispatched IO with new low rate. |
1392 | */ |
1393 | throtl_start_new_slice(tg, 0); |
1394 | throtl_start_new_slice(tg, 1); |
1395 | |
1396 | if (tg->flags & THROTL_TG_PENDING) { |
1397 | tg_update_disptime(tg); |
1398 | throtl_schedule_next_dispatch(sq->parent_sq, true); |
1399 | } |
1400 | |
1401 | blkg_conf_finish(&ctx); |
1402 | return 0; |
1403 | } |
1404 | |
1405 | static int tg_set_conf_u64(struct cgroup_subsys_state *css, struct cftype *cft, |
1406 | const char *buf) |
1407 | { |
1408 | return tg_set_conf(css, cft, buf, true); |
1409 | } |
1410 | |
1411 | static int tg_set_conf_uint(struct cgroup_subsys_state *css, struct cftype *cft, |
1412 | const char *buf) |
1413 | { |
1414 | return tg_set_conf(css, cft, buf, false); |
1415 | } |
1416 | |
1417 | static struct cftype throtl_files[] = { |
1418 | { |
1419 | .name = "throttle.read_bps_device", |
1420 | .private = offsetof(struct throtl_grp, bps[READ]), |
1421 | .read_seq_string = tg_print_conf_u64, |
1422 | .write_string = tg_set_conf_u64, |
1423 | .max_write_len = 256, |
1424 | }, |
1425 | { |
1426 | .name = "throttle.write_bps_device", |
1427 | .private = offsetof(struct throtl_grp, bps[WRITE]), |
1428 | .read_seq_string = tg_print_conf_u64, |
1429 | .write_string = tg_set_conf_u64, |
1430 | .max_write_len = 256, |
1431 | }, |
1432 | { |
1433 | .name = "throttle.read_iops_device", |
1434 | .private = offsetof(struct throtl_grp, iops[READ]), |
1435 | .read_seq_string = tg_print_conf_uint, |
1436 | .write_string = tg_set_conf_uint, |
1437 | .max_write_len = 256, |
1438 | }, |
1439 | { |
1440 | .name = "throttle.write_iops_device", |
1441 | .private = offsetof(struct throtl_grp, iops[WRITE]), |
1442 | .read_seq_string = tg_print_conf_uint, |
1443 | .write_string = tg_set_conf_uint, |
1444 | .max_write_len = 256, |
1445 | }, |
1446 | { |
1447 | .name = "throttle.io_service_bytes", |
1448 | .private = offsetof(struct tg_stats_cpu, service_bytes), |
1449 | .read_seq_string = tg_print_cpu_rwstat, |
1450 | }, |
1451 | { |
1452 | .name = "throttle.io_serviced", |
1453 | .private = offsetof(struct tg_stats_cpu, serviced), |
1454 | .read_seq_string = tg_print_cpu_rwstat, |
1455 | }, |
1456 | { } /* terminate */ |
1457 | }; |
1458 | |
1459 | static void throtl_shutdown_wq(struct request_queue *q) |
1460 | { |
1461 | struct throtl_data *td = q->td; |
1462 | |
1463 | cancel_work_sync(&td->dispatch_work); |
1464 | } |
1465 | |
1466 | static struct blkcg_policy blkcg_policy_throtl = { |
1467 | .pd_size = sizeof(struct throtl_grp), |
1468 | .cftypes = throtl_files, |
1469 | |
1470 | .pd_init_fn = throtl_pd_init, |
1471 | .pd_online_fn = throtl_pd_online, |
1472 | .pd_exit_fn = throtl_pd_exit, |
1473 | .pd_reset_stats_fn = throtl_pd_reset_stats, |
1474 | }; |
1475 | |
1476 | bool blk_throtl_bio(struct request_queue *q, struct bio *bio) |
1477 | { |
1478 | struct throtl_data *td = q->td; |
1479 | struct throtl_qnode *qn = NULL; |
1480 | struct throtl_grp *tg; |
1481 | struct throtl_service_queue *sq; |
1482 | bool rw = bio_data_dir(bio); |
1483 | struct blkcg *blkcg; |
1484 | bool throttled = false; |
1485 | |
1486 | /* see throtl_charge_bio() */ |
1487 | if (bio->bi_rw & REQ_THROTTLED) |
1488 | goto out; |
1489 | |
1490 | /* |
1491 | * A throtl_grp pointer retrieved under rcu can be used to access |
1492 | * basic fields like stats and io rates. If a group has no rules, |
1493 | * just update the dispatch stats in lockless manner and return. |
1494 | */ |
1495 | rcu_read_lock(); |
1496 | blkcg = bio_blkcg(bio); |
1497 | tg = throtl_lookup_tg(td, blkcg); |
1498 | if (tg) { |
1499 | if (!tg->has_rules[rw]) { |
1500 | throtl_update_dispatch_stats(tg_to_blkg(tg), |
1501 | bio->bi_size, bio->bi_rw); |
1502 | goto out_unlock_rcu; |
1503 | } |
1504 | } |
1505 | |
1506 | /* |
1507 | * Either group has not been allocated yet or it is not an unlimited |
1508 | * IO group |
1509 | */ |
1510 | spin_lock_irq(q->queue_lock); |
1511 | tg = throtl_lookup_create_tg(td, blkcg); |
1512 | if (unlikely(!tg)) |
1513 | goto out_unlock; |
1514 | |
1515 | sq = &tg->service_queue; |
1516 | |
1517 | while (true) { |
1518 | /* throtl is FIFO - if bios are already queued, should queue */ |
1519 | if (sq->nr_queued[rw]) |
1520 | break; |
1521 | |
1522 | /* if above limits, break to queue */ |
1523 | if (!tg_may_dispatch(tg, bio, NULL)) |
1524 | break; |
1525 | |
1526 | /* within limits, let's charge and dispatch directly */ |
1527 | throtl_charge_bio(tg, bio); |
1528 | |
1529 | /* |
1530 | * We need to trim slice even when bios are not being queued |
1531 | * otherwise it might happen that a bio is not queued for |
1532 | * a long time and slice keeps on extending and trim is not |
1533 | * called for a long time. Now if limits are reduced suddenly |
1534 | * we take into account all the IO dispatched so far at new |
1535 | * low rate and * newly queued IO gets a really long dispatch |
1536 | * time. |
1537 | * |
1538 | * So keep on trimming slice even if bio is not queued. |
1539 | */ |
1540 | throtl_trim_slice(tg, rw); |
1541 | |
1542 | /* |
1543 | * @bio passed through this layer without being throttled. |
1544 | * Climb up the ladder. If we''re already at the top, it |
1545 | * can be executed directly. |
1546 | */ |
1547 | qn = &tg->qnode_on_parent[rw]; |
1548 | sq = sq->parent_sq; |
1549 | tg = sq_to_tg(sq); |
1550 | if (!tg) |
1551 | goto out_unlock; |
1552 | } |
1553 | |
1554 | /* out-of-limit, queue to @tg */ |
1555 | throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d", |
1556 | rw == READ ? 'R' : 'W', |
1557 | tg->bytes_disp[rw], bio->bi_size, tg->bps[rw], |
1558 | tg->io_disp[rw], tg->iops[rw], |
1559 | sq->nr_queued[READ], sq->nr_queued[WRITE]); |
1560 | |
1561 | bio_associate_current(bio); |
1562 | tg->td->nr_queued[rw]++; |
1563 | throtl_add_bio_tg(bio, qn, tg); |
1564 | throttled = true; |
1565 | |
1566 | /* |
1567 | * Update @tg's dispatch time and force schedule dispatch if @tg |
1568 | * was empty before @bio. The forced scheduling isn't likely to |
1569 | * cause undue delay as @bio is likely to be dispatched directly if |
1570 | * its @tg's disptime is not in the future. |
1571 | */ |
1572 | if (tg->flags & THROTL_TG_WAS_EMPTY) { |
1573 | tg_update_disptime(tg); |
1574 | throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true); |
1575 | } |
1576 | |
1577 | out_unlock: |
1578 | spin_unlock_irq(q->queue_lock); |
1579 | out_unlock_rcu: |
1580 | rcu_read_unlock(); |
1581 | out: |
1582 | /* |
1583 | * As multiple blk-throtls may stack in the same issue path, we |
1584 | * don't want bios to leave with the flag set. Clear the flag if |
1585 | * being issued. |
1586 | */ |
1587 | if (!throttled) |
1588 | bio->bi_rw &= ~REQ_THROTTLED; |
1589 | return throttled; |
1590 | } |
1591 | |
1592 | /* |
1593 | * Dispatch all bios from all children tg's queued on @parent_sq. On |
1594 | * return, @parent_sq is guaranteed to not have any active children tg's |
1595 | * and all bios from previously active tg's are on @parent_sq->bio_lists[]. |
1596 | */ |
1597 | static void tg_drain_bios(struct throtl_service_queue *parent_sq) |
1598 | { |
1599 | struct throtl_grp *tg; |
1600 | |
1601 | while ((tg = throtl_rb_first(parent_sq))) { |
1602 | struct throtl_service_queue *sq = &tg->service_queue; |
1603 | struct bio *bio; |
1604 | |
1605 | throtl_dequeue_tg(tg); |
1606 | |
1607 | while ((bio = throtl_peek_queued(&sq->queued[READ]))) |
1608 | tg_dispatch_one_bio(tg, bio_data_dir(bio)); |
1609 | while ((bio = throtl_peek_queued(&sq->queued[WRITE]))) |
1610 | tg_dispatch_one_bio(tg, bio_data_dir(bio)); |
1611 | } |
1612 | } |
1613 | |
1614 | /** |
1615 | * blk_throtl_drain - drain throttled bios |
1616 | * @q: request_queue to drain throttled bios for |
1617 | * |
1618 | * Dispatch all currently throttled bios on @q through ->make_request_fn(). |
1619 | */ |
1620 | void blk_throtl_drain(struct request_queue *q) |
1621 | __releases(q->queue_lock) __acquires(q->queue_lock) |
1622 | { |
1623 | struct throtl_data *td = q->td; |
1624 | struct blkcg_gq *blkg; |
1625 | struct cgroup_subsys_state *pos_css; |
1626 | struct bio *bio; |
1627 | int rw; |
1628 | |
1629 | queue_lockdep_assert_held(q); |
1630 | rcu_read_lock(); |
1631 | |
1632 | /* |
1633 | * Drain each tg while doing post-order walk on the blkg tree, so |
1634 | * that all bios are propagated to td->service_queue. It'd be |
1635 | * better to walk service_queue tree directly but blkg walk is |
1636 | * easier. |
1637 | */ |
1638 | blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) |
1639 | tg_drain_bios(&blkg_to_tg(blkg)->service_queue); |
1640 | |
1641 | /* finally, transfer bios from top-level tg's into the td */ |
1642 | tg_drain_bios(&td->service_queue); |
1643 | |
1644 | rcu_read_unlock(); |
1645 | spin_unlock_irq(q->queue_lock); |
1646 | |
1647 | /* all bios now should be in td->service_queue, issue them */ |
1648 | for (rw = READ; rw <= WRITE; rw++) |
1649 | while ((bio = throtl_pop_queued(&td->service_queue.queued[rw], |
1650 | NULL))) |
1651 | generic_make_request(bio); |
1652 | |
1653 | spin_lock_irq(q->queue_lock); |
1654 | } |
1655 | |
1656 | int blk_throtl_init(struct request_queue *q) |
1657 | { |
1658 | struct throtl_data *td; |
1659 | int ret; |
1660 | |
1661 | td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node); |
1662 | if (!td) |
1663 | return -ENOMEM; |
1664 | |
1665 | INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn); |
1666 | throtl_service_queue_init(&td->service_queue, NULL); |
1667 | |
1668 | q->td = td; |
1669 | td->queue = q; |
1670 | |
1671 | /* activate policy */ |
1672 | ret = blkcg_activate_policy(q, &blkcg_policy_throtl); |
1673 | if (ret) |
1674 | kfree(td); |
1675 | return ret; |
1676 | } |
1677 | |
1678 | void blk_throtl_exit(struct request_queue *q) |
1679 | { |
1680 | BUG_ON(!q->td); |
1681 | throtl_shutdown_wq(q); |
1682 | blkcg_deactivate_policy(q, &blkcg_policy_throtl); |
1683 | kfree(q->td); |
1684 | } |
1685 | |
1686 | static int __init throtl_init(void) |
1687 | { |
1688 | kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0); |
1689 | if (!kthrotld_workqueue) |
1690 | panic("Failed to create kthrotld\n"); |
1691 | |
1692 | return blkcg_policy_register(&blkcg_policy_throtl); |
1693 | } |
1694 | |
1695 | module_init(throtl_init); |
1696 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9