Root/
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 | static void tg_stats_init(struct tg_stats_cpu *tg_stats) |
260 | { |
261 | blkg_rwstat_init(&tg_stats->service_bytes); |
262 | blkg_rwstat_init(&tg_stats->serviced); |
263 | } |
264 | |
265 | /* |
266 | * Worker for allocating per cpu stat for tgs. This is scheduled on the |
267 | * system_wq once there are some groups on the alloc_list waiting for |
268 | * allocation. |
269 | */ |
270 | static void tg_stats_alloc_fn(struct work_struct *work) |
271 | { |
272 | static struct tg_stats_cpu *stats_cpu; /* this fn is non-reentrant */ |
273 | struct delayed_work *dwork = to_delayed_work(work); |
274 | bool empty = false; |
275 | |
276 | alloc_stats: |
277 | if (!stats_cpu) { |
278 | int cpu; |
279 | |
280 | stats_cpu = alloc_percpu(struct tg_stats_cpu); |
281 | if (!stats_cpu) { |
282 | /* allocation failed, try again after some time */ |
283 | schedule_delayed_work(dwork, msecs_to_jiffies(10)); |
284 | return; |
285 | } |
286 | for_each_possible_cpu(cpu) |
287 | tg_stats_init(per_cpu_ptr(stats_cpu, cpu)); |
288 | } |
289 | |
290 | spin_lock_irq(&tg_stats_alloc_lock); |
291 | |
292 | if (!list_empty(&tg_stats_alloc_list)) { |
293 | struct throtl_grp *tg = list_first_entry(&tg_stats_alloc_list, |
294 | struct throtl_grp, |
295 | stats_alloc_node); |
296 | swap(tg->stats_cpu, stats_cpu); |
297 | list_del_init(&tg->stats_alloc_node); |
298 | } |
299 | |
300 | empty = list_empty(&tg_stats_alloc_list); |
301 | spin_unlock_irq(&tg_stats_alloc_lock); |
302 | if (!empty) |
303 | goto alloc_stats; |
304 | } |
305 | |
306 | static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg) |
307 | { |
308 | INIT_LIST_HEAD(&qn->node); |
309 | bio_list_init(&qn->bios); |
310 | qn->tg = tg; |
311 | } |
312 | |
313 | /** |
314 | * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it |
315 | * @bio: bio being added |
316 | * @qn: qnode to add bio to |
317 | * @queued: the service_queue->queued[] list @qn belongs to |
318 | * |
319 | * Add @bio to @qn and put @qn on @queued if it's not already on. |
320 | * @qn->tg's reference count is bumped when @qn is activated. See the |
321 | * comment on top of throtl_qnode definition for details. |
322 | */ |
323 | static void throtl_qnode_add_bio(struct bio *bio, struct throtl_qnode *qn, |
324 | struct list_head *queued) |
325 | { |
326 | bio_list_add(&qn->bios, bio); |
327 | if (list_empty(&qn->node)) { |
328 | list_add_tail(&qn->node, queued); |
329 | blkg_get(tg_to_blkg(qn->tg)); |
330 | } |
331 | } |
332 | |
333 | /** |
334 | * throtl_peek_queued - peek the first bio on a qnode list |
335 | * @queued: the qnode list to peek |
336 | */ |
337 | static struct bio *throtl_peek_queued(struct list_head *queued) |
338 | { |
339 | struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node); |
340 | struct bio *bio; |
341 | |
342 | if (list_empty(queued)) |
343 | return NULL; |
344 | |
345 | bio = bio_list_peek(&qn->bios); |
346 | WARN_ON_ONCE(!bio); |
347 | return bio; |
348 | } |
349 | |
350 | /** |
351 | * throtl_pop_queued - pop the first bio form a qnode list |
352 | * @queued: the qnode list to pop a bio from |
353 | * @tg_to_put: optional out argument for throtl_grp to put |
354 | * |
355 | * Pop the first bio from the qnode list @queued. After popping, the first |
356 | * qnode is removed from @queued if empty or moved to the end of @queued so |
357 | * that the popping order is round-robin. |
358 | * |
359 | * When the first qnode is removed, its associated throtl_grp should be put |
360 | * too. If @tg_to_put is NULL, this function automatically puts it; |
361 | * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is |
362 | * responsible for putting it. |
363 | */ |
364 | static struct bio *throtl_pop_queued(struct list_head *queued, |
365 | struct throtl_grp **tg_to_put) |
366 | { |
367 | struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node); |
368 | struct bio *bio; |
369 | |
370 | if (list_empty(queued)) |
371 | return NULL; |
372 | |
373 | bio = bio_list_pop(&qn->bios); |
374 | WARN_ON_ONCE(!bio); |
375 | |
376 | if (bio_list_empty(&qn->bios)) { |
377 | list_del_init(&qn->node); |
378 | if (tg_to_put) |
379 | *tg_to_put = qn->tg; |
380 | else |
381 | blkg_put(tg_to_blkg(qn->tg)); |
382 | } else { |
383 | list_move_tail(&qn->node, queued); |
384 | } |
385 | |
386 | return bio; |
387 | } |
388 | |
389 | /* init a service_queue, assumes the caller zeroed it */ |
390 | static void throtl_service_queue_init(struct throtl_service_queue *sq, |
391 | struct throtl_service_queue *parent_sq) |
392 | { |
393 | INIT_LIST_HEAD(&sq->queued[0]); |
394 | INIT_LIST_HEAD(&sq->queued[1]); |
395 | sq->pending_tree = RB_ROOT; |
396 | sq->parent_sq = parent_sq; |
397 | setup_timer(&sq->pending_timer, throtl_pending_timer_fn, |
398 | (unsigned long)sq); |
399 | } |
400 | |
401 | static void throtl_service_queue_exit(struct throtl_service_queue *sq) |
402 | { |
403 | del_timer_sync(&sq->pending_timer); |
404 | } |
405 | |
406 | static void throtl_pd_init(struct blkcg_gq *blkg) |
407 | { |
408 | struct throtl_grp *tg = blkg_to_tg(blkg); |
409 | struct throtl_data *td = blkg->q->td; |
410 | struct throtl_service_queue *parent_sq; |
411 | unsigned long flags; |
412 | int rw; |
413 | |
414 | /* |
415 | * If sane_hierarchy is enabled, we switch to properly hierarchical |
416 | * behavior where limits on a given throtl_grp are applied to the |
417 | * whole subtree rather than just the group itself. e.g. If 16M |
418 | * read_bps limit is set on the root group, the whole system can't |
419 | * exceed 16M for the device. |
420 | * |
421 | * If sane_hierarchy is not enabled, the broken flat hierarchy |
422 | * behavior is retained where all throtl_grps are treated as if |
423 | * they're all separate root groups right below throtl_data. |
424 | * Limits of a group don't interact with limits of other groups |
425 | * regardless of the position of the group in the hierarchy. |
426 | */ |
427 | parent_sq = &td->service_queue; |
428 | |
429 | if (cgroup_sane_behavior(blkg->blkcg->css.cgroup) && blkg->parent) |
430 | parent_sq = &blkg_to_tg(blkg->parent)->service_queue; |
431 | |
432 | throtl_service_queue_init(&tg->service_queue, parent_sq); |
433 | |
434 | for (rw = READ; rw <= WRITE; rw++) { |
435 | throtl_qnode_init(&tg->qnode_on_self[rw], tg); |
436 | throtl_qnode_init(&tg->qnode_on_parent[rw], tg); |
437 | } |
438 | |
439 | RB_CLEAR_NODE(&tg->rb_node); |
440 | tg->td = td; |
441 | |
442 | tg->bps[READ] = -1; |
443 | tg->bps[WRITE] = -1; |
444 | tg->iops[READ] = -1; |
445 | tg->iops[WRITE] = -1; |
446 | |
447 | /* |
448 | * Ugh... We need to perform per-cpu allocation for tg->stats_cpu |
449 | * but percpu allocator can't be called from IO path. Queue tg on |
450 | * tg_stats_alloc_list and allocate from work item. |
451 | */ |
452 | spin_lock_irqsave(&tg_stats_alloc_lock, flags); |
453 | list_add(&tg->stats_alloc_node, &tg_stats_alloc_list); |
454 | schedule_delayed_work(&tg_stats_alloc_work, 0); |
455 | spin_unlock_irqrestore(&tg_stats_alloc_lock, flags); |
456 | } |
457 | |
458 | /* |
459 | * Set has_rules[] if @tg or any of its parents have limits configured. |
460 | * This doesn't require walking up to the top of the hierarchy as the |
461 | * parent's has_rules[] is guaranteed to be correct. |
462 | */ |
463 | static void tg_update_has_rules(struct throtl_grp *tg) |
464 | { |
465 | struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq); |
466 | int rw; |
467 | |
468 | for (rw = READ; rw <= WRITE; rw++) |
469 | tg->has_rules[rw] = (parent_tg && parent_tg->has_rules[rw]) || |
470 | (tg->bps[rw] != -1 || tg->iops[rw] != -1); |
471 | } |
472 | |
473 | static void throtl_pd_online(struct blkcg_gq *blkg) |
474 | { |
475 | /* |
476 | * We don't want new groups to escape the limits of its ancestors. |
477 | * Update has_rules[] after a new group is brought online. |
478 | */ |
479 | tg_update_has_rules(blkg_to_tg(blkg)); |
480 | } |
481 | |
482 | static void throtl_pd_exit(struct blkcg_gq *blkg) |
483 | { |
484 | struct throtl_grp *tg = blkg_to_tg(blkg); |
485 | unsigned long flags; |
486 | |
487 | spin_lock_irqsave(&tg_stats_alloc_lock, flags); |
488 | list_del_init(&tg->stats_alloc_node); |
489 | spin_unlock_irqrestore(&tg_stats_alloc_lock, flags); |
490 | |
491 | free_percpu(tg->stats_cpu); |
492 | |
493 | throtl_service_queue_exit(&tg->service_queue); |
494 | } |
495 | |
496 | static void throtl_pd_reset_stats(struct blkcg_gq *blkg) |
497 | { |
498 | struct throtl_grp *tg = blkg_to_tg(blkg); |
499 | int cpu; |
500 | |
501 | if (tg->stats_cpu == NULL) |
502 | return; |
503 | |
504 | for_each_possible_cpu(cpu) { |
505 | struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu); |
506 | |
507 | blkg_rwstat_reset(&sc->service_bytes); |
508 | blkg_rwstat_reset(&sc->serviced); |
509 | } |
510 | } |
511 | |
512 | static struct throtl_grp *throtl_lookup_tg(struct throtl_data *td, |
513 | struct blkcg *blkcg) |
514 | { |
515 | /* |
516 | * This is the common case when there are no blkcgs. Avoid lookup |
517 | * in this case |
518 | */ |
519 | if (blkcg == &blkcg_root) |
520 | return td_root_tg(td); |
521 | |
522 | return blkg_to_tg(blkg_lookup(blkcg, td->queue)); |
523 | } |
524 | |
525 | static struct throtl_grp *throtl_lookup_create_tg(struct throtl_data *td, |
526 | struct blkcg *blkcg) |
527 | { |
528 | struct request_queue *q = td->queue; |
529 | struct throtl_grp *tg = NULL; |
530 | |
531 | /* |
532 | * This is the common case when there are no blkcgs. Avoid lookup |
533 | * in this case |
534 | */ |
535 | if (blkcg == &blkcg_root) { |
536 | tg = td_root_tg(td); |
537 | } else { |
538 | struct blkcg_gq *blkg; |
539 | |
540 | blkg = blkg_lookup_create(blkcg, q); |
541 | |
542 | /* if %NULL and @q is alive, fall back to root_tg */ |
543 | if (!IS_ERR(blkg)) |
544 | tg = blkg_to_tg(blkg); |
545 | else if (!blk_queue_dying(q)) |
546 | tg = td_root_tg(td); |
547 | } |
548 | |
549 | return tg; |
550 | } |
551 | |
552 | static struct throtl_grp * |
553 | throtl_rb_first(struct throtl_service_queue *parent_sq) |
554 | { |
555 | /* Service tree is empty */ |
556 | if (!parent_sq->nr_pending) |
557 | return NULL; |
558 | |
559 | if (!parent_sq->first_pending) |
560 | parent_sq->first_pending = rb_first(&parent_sq->pending_tree); |
561 | |
562 | if (parent_sq->first_pending) |
563 | return rb_entry_tg(parent_sq->first_pending); |
564 | |
565 | return NULL; |
566 | } |
567 | |
568 | static void rb_erase_init(struct rb_node *n, struct rb_root *root) |
569 | { |
570 | rb_erase(n, root); |
571 | RB_CLEAR_NODE(n); |
572 | } |
573 | |
574 | static void throtl_rb_erase(struct rb_node *n, |
575 | struct throtl_service_queue *parent_sq) |
576 | { |
577 | if (parent_sq->first_pending == n) |
578 | parent_sq->first_pending = NULL; |
579 | rb_erase_init(n, &parent_sq->pending_tree); |
580 | --parent_sq->nr_pending; |
581 | } |
582 | |
583 | static void update_min_dispatch_time(struct throtl_service_queue *parent_sq) |
584 | { |
585 | struct throtl_grp *tg; |
586 | |
587 | tg = throtl_rb_first(parent_sq); |
588 | if (!tg) |
589 | return; |
590 | |
591 | parent_sq->first_pending_disptime = tg->disptime; |
592 | } |
593 | |
594 | static void tg_service_queue_add(struct throtl_grp *tg) |
595 | { |
596 | struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq; |
597 | struct rb_node **node = &parent_sq->pending_tree.rb_node; |
598 | struct rb_node *parent = NULL; |
599 | struct throtl_grp *__tg; |
600 | unsigned long key = tg->disptime; |
601 | int left = 1; |
602 | |
603 | while (*node != NULL) { |
604 | parent = *node; |
605 | __tg = rb_entry_tg(parent); |
606 | |
607 | if (time_before(key, __tg->disptime)) |
608 | node = &parent->rb_left; |
609 | else { |
610 | node = &parent->rb_right; |
611 | left = 0; |
612 | } |
613 | } |
614 | |
615 | if (left) |
616 | parent_sq->first_pending = &tg->rb_node; |
617 | |
618 | rb_link_node(&tg->rb_node, parent, node); |
619 | rb_insert_color(&tg->rb_node, &parent_sq->pending_tree); |
620 | } |
621 | |
622 | static void __throtl_enqueue_tg(struct throtl_grp *tg) |
623 | { |
624 | tg_service_queue_add(tg); |
625 | tg->flags |= THROTL_TG_PENDING; |
626 | tg->service_queue.parent_sq->nr_pending++; |
627 | } |
628 | |
629 | static void throtl_enqueue_tg(struct throtl_grp *tg) |
630 | { |
631 | if (!(tg->flags & THROTL_TG_PENDING)) |
632 | __throtl_enqueue_tg(tg); |
633 | } |
634 | |
635 | static void __throtl_dequeue_tg(struct throtl_grp *tg) |
636 | { |
637 | throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq); |
638 | tg->flags &= ~THROTL_TG_PENDING; |
639 | } |
640 | |
641 | static void throtl_dequeue_tg(struct throtl_grp *tg) |
642 | { |
643 | if (tg->flags & THROTL_TG_PENDING) |
644 | __throtl_dequeue_tg(tg); |
645 | } |
646 | |
647 | /* Call with queue lock held */ |
648 | static void throtl_schedule_pending_timer(struct throtl_service_queue *sq, |
649 | unsigned long expires) |
650 | { |
651 | mod_timer(&sq->pending_timer, expires); |
652 | throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu", |
653 | expires - jiffies, jiffies); |
654 | } |
655 | |
656 | /** |
657 | * throtl_schedule_next_dispatch - schedule the next dispatch cycle |
658 | * @sq: the service_queue to schedule dispatch for |
659 | * @force: force scheduling |
660 | * |
661 | * Arm @sq->pending_timer so that the next dispatch cycle starts on the |
662 | * dispatch time of the first pending child. Returns %true if either timer |
663 | * is armed or there's no pending child left. %false if the current |
664 | * dispatch window is still open and the caller should continue |
665 | * dispatching. |
666 | * |
667 | * If @force is %true, the dispatch timer is always scheduled and this |
668 | * function is guaranteed to return %true. This is to be used when the |
669 | * caller can't dispatch itself and needs to invoke pending_timer |
670 | * unconditionally. Note that forced scheduling is likely to induce short |
671 | * delay before dispatch starts even if @sq->first_pending_disptime is not |
672 | * in the future and thus shouldn't be used in hot paths. |
673 | */ |
674 | static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq, |
675 | bool force) |
676 | { |
677 | /* any pending children left? */ |
678 | if (!sq->nr_pending) |
679 | return true; |
680 | |
681 | update_min_dispatch_time(sq); |
682 | |
683 | /* is the next dispatch time in the future? */ |
684 | if (force || time_after(sq->first_pending_disptime, jiffies)) { |
685 | throtl_schedule_pending_timer(sq, sq->first_pending_disptime); |
686 | return true; |
687 | } |
688 | |
689 | /* tell the caller to continue dispatching */ |
690 | return false; |
691 | } |
692 | |
693 | static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg, |
694 | bool rw, unsigned long start) |
695 | { |
696 | tg->bytes_disp[rw] = 0; |
697 | tg->io_disp[rw] = 0; |
698 | |
699 | /* |
700 | * Previous slice has expired. We must have trimmed it after last |
701 | * bio dispatch. That means since start of last slice, we never used |
702 | * that bandwidth. Do try to make use of that bandwidth while giving |
703 | * credit. |
704 | */ |
705 | if (time_after_eq(start, tg->slice_start[rw])) |
706 | tg->slice_start[rw] = start; |
707 | |
708 | tg->slice_end[rw] = jiffies + throtl_slice; |
709 | throtl_log(&tg->service_queue, |
710 | "[%c] new slice with credit start=%lu end=%lu jiffies=%lu", |
711 | rw == READ ? 'R' : 'W', tg->slice_start[rw], |
712 | tg->slice_end[rw], jiffies); |
713 | } |
714 | |
715 | static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw) |
716 | { |
717 | tg->bytes_disp[rw] = 0; |
718 | tg->io_disp[rw] = 0; |
719 | tg->slice_start[rw] = jiffies; |
720 | tg->slice_end[rw] = jiffies + throtl_slice; |
721 | throtl_log(&tg->service_queue, |
722 | "[%c] new slice start=%lu end=%lu jiffies=%lu", |
723 | rw == READ ? 'R' : 'W', tg->slice_start[rw], |
724 | tg->slice_end[rw], jiffies); |
725 | } |
726 | |
727 | static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw, |
728 | unsigned long jiffy_end) |
729 | { |
730 | tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); |
731 | } |
732 | |
733 | static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw, |
734 | unsigned long jiffy_end) |
735 | { |
736 | tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); |
737 | throtl_log(&tg->service_queue, |
738 | "[%c] extend slice start=%lu end=%lu jiffies=%lu", |
739 | rw == READ ? 'R' : 'W', tg->slice_start[rw], |
740 | tg->slice_end[rw], jiffies); |
741 | } |
742 | |
743 | /* Determine if previously allocated or extended slice is complete or not */ |
744 | static bool throtl_slice_used(struct throtl_grp *tg, bool rw) |
745 | { |
746 | if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw])) |
747 | return 0; |
748 | |
749 | return 1; |
750 | } |
751 | |
752 | /* Trim the used slices and adjust slice start accordingly */ |
753 | static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw) |
754 | { |
755 | unsigned long nr_slices, time_elapsed, io_trim; |
756 | u64 bytes_trim, tmp; |
757 | |
758 | BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw])); |
759 | |
760 | /* |
761 | * If bps are unlimited (-1), then time slice don't get |
762 | * renewed. Don't try to trim the slice if slice is used. A new |
763 | * slice will start when appropriate. |
764 | */ |
765 | if (throtl_slice_used(tg, rw)) |
766 | return; |
767 | |
768 | /* |
769 | * A bio has been dispatched. Also adjust slice_end. It might happen |
770 | * that initially cgroup limit was very low resulting in high |
771 | * slice_end, but later limit was bumped up and bio was dispached |
772 | * sooner, then we need to reduce slice_end. A high bogus slice_end |
773 | * is bad because it does not allow new slice to start. |
774 | */ |
775 | |
776 | throtl_set_slice_end(tg, rw, jiffies + throtl_slice); |
777 | |
778 | time_elapsed = jiffies - tg->slice_start[rw]; |
779 | |
780 | nr_slices = time_elapsed / throtl_slice; |
781 | |
782 | if (!nr_slices) |
783 | return; |
784 | tmp = tg->bps[rw] * throtl_slice * nr_slices; |
785 | do_div(tmp, HZ); |
786 | bytes_trim = tmp; |
787 | |
788 | io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ; |
789 | |
790 | if (!bytes_trim && !io_trim) |
791 | return; |
792 | |
793 | if (tg->bytes_disp[rw] >= bytes_trim) |
794 | tg->bytes_disp[rw] -= bytes_trim; |
795 | else |
796 | tg->bytes_disp[rw] = 0; |
797 | |
798 | if (tg->io_disp[rw] >= io_trim) |
799 | tg->io_disp[rw] -= io_trim; |
800 | else |
801 | tg->io_disp[rw] = 0; |
802 | |
803 | tg->slice_start[rw] += nr_slices * throtl_slice; |
804 | |
805 | throtl_log(&tg->service_queue, |
806 | "[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu", |
807 | rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim, |
808 | tg->slice_start[rw], tg->slice_end[rw], jiffies); |
809 | } |
810 | |
811 | static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio, |
812 | unsigned long *wait) |
813 | { |
814 | bool rw = bio_data_dir(bio); |
815 | unsigned int io_allowed; |
816 | unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; |
817 | u64 tmp; |
818 | |
819 | jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; |
820 | |
821 | /* Slice has just started. Consider one slice interval */ |
822 | if (!jiffy_elapsed) |
823 | jiffy_elapsed_rnd = throtl_slice; |
824 | |
825 | jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice); |
826 | |
827 | /* |
828 | * jiffy_elapsed_rnd should not be a big value as minimum iops can be |
829 | * 1 then at max jiffy elapsed should be equivalent of 1 second as we |
830 | * will allow dispatch after 1 second and after that slice should |
831 | * have been trimmed. |
832 | */ |
833 | |
834 | tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd; |
835 | do_div(tmp, HZ); |
836 | |
837 | if (tmp > UINT_MAX) |
838 | io_allowed = UINT_MAX; |
839 | else |
840 | io_allowed = tmp; |
841 | |
842 | if (tg->io_disp[rw] + 1 <= io_allowed) { |
843 | if (wait) |
844 | *wait = 0; |
845 | return 1; |
846 | } |
847 | |
848 | /* Calc approx time to dispatch */ |
849 | jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1; |
850 | |
851 | if (jiffy_wait > jiffy_elapsed) |
852 | jiffy_wait = jiffy_wait - jiffy_elapsed; |
853 | else |
854 | jiffy_wait = 1; |
855 | |
856 | if (wait) |
857 | *wait = jiffy_wait; |
858 | return 0; |
859 | } |
860 | |
861 | static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio, |
862 | unsigned long *wait) |
863 | { |
864 | bool rw = bio_data_dir(bio); |
865 | u64 bytes_allowed, extra_bytes, tmp; |
866 | unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; |
867 | |
868 | jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; |
869 | |
870 | /* Slice has just started. Consider one slice interval */ |
871 | if (!jiffy_elapsed) |
872 | jiffy_elapsed_rnd = throtl_slice; |
873 | |
874 | jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice); |
875 | |
876 | tmp = tg->bps[rw] * jiffy_elapsed_rnd; |
877 | do_div(tmp, HZ); |
878 | bytes_allowed = tmp; |
879 | |
880 | if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) { |
881 | if (wait) |
882 | *wait = 0; |
883 | return 1; |
884 | } |
885 | |
886 | /* Calc approx time to dispatch */ |
887 | extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed; |
888 | jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]); |
889 | |
890 | if (!jiffy_wait) |
891 | jiffy_wait = 1; |
892 | |
893 | /* |
894 | * This wait time is without taking into consideration the rounding |
895 | * up we did. Add that time also. |
896 | */ |
897 | jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed); |
898 | if (wait) |
899 | *wait = jiffy_wait; |
900 | return 0; |
901 | } |
902 | |
903 | /* |
904 | * Returns whether one can dispatch a bio or not. Also returns approx number |
905 | * of jiffies to wait before this bio is with-in IO rate and can be dispatched |
906 | */ |
907 | static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio, |
908 | unsigned long *wait) |
909 | { |
910 | bool rw = bio_data_dir(bio); |
911 | unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0; |
912 | |
913 | /* |
914 | * Currently whole state machine of group depends on first bio |
915 | * queued in the group bio list. So one should not be calling |
916 | * this function with a different bio if there are other bios |
917 | * queued. |
918 | */ |
919 | BUG_ON(tg->service_queue.nr_queued[rw] && |
920 | bio != throtl_peek_queued(&tg->service_queue.queued[rw])); |
921 | |
922 | /* If tg->bps = -1, then BW is unlimited */ |
923 | if (tg->bps[rw] == -1 && tg->iops[rw] == -1) { |
924 | if (wait) |
925 | *wait = 0; |
926 | return 1; |
927 | } |
928 | |
929 | /* |
930 | * If previous slice expired, start a new one otherwise renew/extend |
931 | * existing slice to make sure it is at least throtl_slice interval |
932 | * long since now. |
933 | */ |
934 | if (throtl_slice_used(tg, rw)) |
935 | throtl_start_new_slice(tg, rw); |
936 | else { |
937 | if (time_before(tg->slice_end[rw], jiffies + throtl_slice)) |
938 | throtl_extend_slice(tg, rw, jiffies + throtl_slice); |
939 | } |
940 | |
941 | if (tg_with_in_bps_limit(tg, bio, &bps_wait) && |
942 | tg_with_in_iops_limit(tg, bio, &iops_wait)) { |
943 | if (wait) |
944 | *wait = 0; |
945 | return 1; |
946 | } |
947 | |
948 | max_wait = max(bps_wait, iops_wait); |
949 | |
950 | if (wait) |
951 | *wait = max_wait; |
952 | |
953 | if (time_before(tg->slice_end[rw], jiffies + max_wait)) |
954 | throtl_extend_slice(tg, rw, jiffies + max_wait); |
955 | |
956 | return 0; |
957 | } |
958 | |
959 | static void throtl_update_dispatch_stats(struct blkcg_gq *blkg, u64 bytes, |
960 | int rw) |
961 | { |
962 | struct throtl_grp *tg = blkg_to_tg(blkg); |
963 | struct tg_stats_cpu *stats_cpu; |
964 | unsigned long flags; |
965 | |
966 | /* If per cpu stats are not allocated yet, don't do any accounting. */ |
967 | if (tg->stats_cpu == NULL) |
968 | return; |
969 | |
970 | /* |
971 | * Disabling interrupts to provide mutual exclusion between two |
972 | * writes on same cpu. It probably is not needed for 64bit. Not |
973 | * optimizing that case yet. |
974 | */ |
975 | local_irq_save(flags); |
976 | |
977 | stats_cpu = this_cpu_ptr(tg->stats_cpu); |
978 | |
979 | blkg_rwstat_add(&stats_cpu->serviced, rw, 1); |
980 | blkg_rwstat_add(&stats_cpu->service_bytes, rw, bytes); |
981 | |
982 | local_irq_restore(flags); |
983 | } |
984 | |
985 | static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio) |
986 | { |
987 | bool rw = bio_data_dir(bio); |
988 | |
989 | /* Charge the bio to the group */ |
990 | tg->bytes_disp[rw] += bio->bi_size; |
991 | tg->io_disp[rw]++; |
992 | |
993 | /* |
994 | * REQ_THROTTLED is used to prevent the same bio to be throttled |
995 | * more than once as a throttled bio will go through blk-throtl the |
996 | * second time when it eventually gets issued. Set it when a bio |
997 | * is being charged to a tg. |
998 | * |
999 | * Dispatch stats aren't recursive and each @bio should only be |
1000 | * accounted by the @tg it was originally associated with. Let's |
1001 | * update the stats when setting REQ_THROTTLED for the first time |
1002 | * which is guaranteed to be for the @bio's original tg. |
1003 | */ |
1004 | if (!(bio->bi_rw & REQ_THROTTLED)) { |
1005 | bio->bi_rw |= REQ_THROTTLED; |
1006 | throtl_update_dispatch_stats(tg_to_blkg(tg), bio->bi_size, |
1007 | bio->bi_rw); |
1008 | } |
1009 | } |
1010 | |
1011 | /** |
1012 | * throtl_add_bio_tg - add a bio to the specified throtl_grp |
1013 | * @bio: bio to add |
1014 | * @qn: qnode to use |
1015 | * @tg: the target throtl_grp |
1016 | * |
1017 | * Add @bio to @tg's service_queue using @qn. If @qn is not specified, |
1018 | * tg->qnode_on_self[] is used. |
1019 | */ |
1020 | static void throtl_add_bio_tg(struct bio *bio, struct throtl_qnode *qn, |
1021 | struct throtl_grp *tg) |
1022 | { |
1023 | struct throtl_service_queue *sq = &tg->service_queue; |
1024 | bool rw = bio_data_dir(bio); |
1025 | |
1026 | if (!qn) |
1027 | qn = &tg->qnode_on_self[rw]; |
1028 | |
1029 | /* |
1030 | * If @tg doesn't currently have any bios queued in the same |
1031 | * direction, queueing @bio can change when @tg should be |
1032 | * dispatched. Mark that @tg was empty. This is automatically |
1033 | * cleaered on the next tg_update_disptime(). |
1034 | */ |
1035 | if (!sq->nr_queued[rw]) |
1036 | tg->flags |= THROTL_TG_WAS_EMPTY; |
1037 | |
1038 | throtl_qnode_add_bio(bio, qn, &sq->queued[rw]); |
1039 | |
1040 | sq->nr_queued[rw]++; |
1041 | throtl_enqueue_tg(tg); |
1042 | } |
1043 | |
1044 | static void tg_update_disptime(struct throtl_grp *tg) |
1045 | { |
1046 | struct throtl_service_queue *sq = &tg->service_queue; |
1047 | unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime; |
1048 | struct bio *bio; |
1049 | |
1050 | if ((bio = throtl_peek_queued(&sq->queued[READ]))) |
1051 | tg_may_dispatch(tg, bio, &read_wait); |
1052 | |
1053 | if ((bio = throtl_peek_queued(&sq->queued[WRITE]))) |
1054 | tg_may_dispatch(tg, bio, &write_wait); |
1055 | |
1056 | min_wait = min(read_wait, write_wait); |
1057 | disptime = jiffies + min_wait; |
1058 | |
1059 | /* Update dispatch time */ |
1060 | throtl_dequeue_tg(tg); |
1061 | tg->disptime = disptime; |
1062 | throtl_enqueue_tg(tg); |
1063 | |
1064 | /* see throtl_add_bio_tg() */ |
1065 | tg->flags &= ~THROTL_TG_WAS_EMPTY; |
1066 | } |
1067 | |
1068 | static void start_parent_slice_with_credit(struct throtl_grp *child_tg, |
1069 | struct throtl_grp *parent_tg, bool rw) |
1070 | { |
1071 | if (throtl_slice_used(parent_tg, rw)) { |
1072 | throtl_start_new_slice_with_credit(parent_tg, rw, |
1073 | child_tg->slice_start[rw]); |
1074 | } |
1075 | |
1076 | } |
1077 | |
1078 | static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw) |
1079 | { |
1080 | struct throtl_service_queue *sq = &tg->service_queue; |
1081 | struct throtl_service_queue *parent_sq = sq->parent_sq; |
1082 | struct throtl_grp *parent_tg = sq_to_tg(parent_sq); |
1083 | struct throtl_grp *tg_to_put = NULL; |
1084 | struct bio *bio; |
1085 | |
1086 | /* |
1087 | * @bio is being transferred from @tg to @parent_sq. Popping a bio |
1088 | * from @tg may put its reference and @parent_sq might end up |
1089 | * getting released prematurely. Remember the tg to put and put it |
1090 | * after @bio is transferred to @parent_sq. |
1091 | */ |
1092 | bio = throtl_pop_queued(&sq->queued[rw], &tg_to_put); |
1093 | sq->nr_queued[rw]--; |
1094 | |
1095 | throtl_charge_bio(tg, bio); |
1096 | |
1097 | /* |
1098 | * If our parent is another tg, we just need to transfer @bio to |
1099 | * the parent using throtl_add_bio_tg(). If our parent is |
1100 | * @td->service_queue, @bio is ready to be issued. Put it on its |
1101 | * bio_lists[] and decrease total number queued. The caller is |
1102 | * responsible for issuing these bios. |
1103 | */ |
1104 | if (parent_tg) { |
1105 | throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg); |
1106 | start_parent_slice_with_credit(tg, parent_tg, rw); |
1107 | } else { |
1108 | throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw], |
1109 | &parent_sq->queued[rw]); |
1110 | BUG_ON(tg->td->nr_queued[rw] <= 0); |
1111 | tg->td->nr_queued[rw]--; |
1112 | } |
1113 | |
1114 | throtl_trim_slice(tg, rw); |
1115 | |
1116 | if (tg_to_put) |
1117 | blkg_put(tg_to_blkg(tg_to_put)); |
1118 | } |
1119 | |
1120 | static int throtl_dispatch_tg(struct throtl_grp *tg) |
1121 | { |
1122 | struct throtl_service_queue *sq = &tg->service_queue; |
1123 | unsigned int nr_reads = 0, nr_writes = 0; |
1124 | unsigned int max_nr_reads = throtl_grp_quantum*3/4; |
1125 | unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads; |
1126 | struct bio *bio; |
1127 | |
1128 | /* Try to dispatch 75% READS and 25% WRITES */ |
1129 | |
1130 | while ((bio = throtl_peek_queued(&sq->queued[READ])) && |
1131 | tg_may_dispatch(tg, bio, NULL)) { |
1132 | |
1133 | tg_dispatch_one_bio(tg, bio_data_dir(bio)); |
1134 | nr_reads++; |
1135 | |
1136 | if (nr_reads >= max_nr_reads) |
1137 | break; |
1138 | } |
1139 | |
1140 | while ((bio = throtl_peek_queued(&sq->queued[WRITE])) && |
1141 | tg_may_dispatch(tg, bio, NULL)) { |
1142 | |
1143 | tg_dispatch_one_bio(tg, bio_data_dir(bio)); |
1144 | nr_writes++; |
1145 | |
1146 | if (nr_writes >= max_nr_writes) |
1147 | break; |
1148 | } |
1149 | |
1150 | return nr_reads + nr_writes; |
1151 | } |
1152 | |
1153 | static int throtl_select_dispatch(struct throtl_service_queue *parent_sq) |
1154 | { |
1155 | unsigned int nr_disp = 0; |
1156 | |
1157 | while (1) { |
1158 | struct throtl_grp *tg = throtl_rb_first(parent_sq); |
1159 | struct throtl_service_queue *sq = &tg->service_queue; |
1160 | |
1161 | if (!tg) |
1162 | break; |
1163 | |
1164 | if (time_before(jiffies, tg->disptime)) |
1165 | break; |
1166 | |
1167 | throtl_dequeue_tg(tg); |
1168 | |
1169 | nr_disp += throtl_dispatch_tg(tg); |
1170 | |
1171 | if (sq->nr_queued[0] || sq->nr_queued[1]) |
1172 | tg_update_disptime(tg); |
1173 | |
1174 | if (nr_disp >= throtl_quantum) |
1175 | break; |
1176 | } |
1177 | |
1178 | return nr_disp; |
1179 | } |
1180 | |
1181 | /** |
1182 | * throtl_pending_timer_fn - timer function for service_queue->pending_timer |
1183 | * @arg: the throtl_service_queue being serviced |
1184 | * |
1185 | * This timer is armed when a child throtl_grp with active bio's become |
1186 | * pending and queued on the service_queue's pending_tree and expires when |
1187 | * the first child throtl_grp should be dispatched. This function |
1188 | * dispatches bio's from the children throtl_grps to the parent |
1189 | * service_queue. |
1190 | * |
1191 | * If the parent's parent is another throtl_grp, dispatching is propagated |
1192 | * by either arming its pending_timer or repeating dispatch directly. If |
1193 | * the top-level service_tree is reached, throtl_data->dispatch_work is |
1194 | * kicked so that the ready bio's are issued. |
1195 | */ |
1196 | static void throtl_pending_timer_fn(unsigned long arg) |
1197 | { |
1198 | struct throtl_service_queue *sq = (void *)arg; |
1199 | struct throtl_grp *tg = sq_to_tg(sq); |
1200 | struct throtl_data *td = sq_to_td(sq); |
1201 | struct request_queue *q = td->queue; |
1202 | struct throtl_service_queue *parent_sq; |
1203 | bool dispatched; |
1204 | int ret; |
1205 | |
1206 | spin_lock_irq(q->queue_lock); |
1207 | again: |
1208 | parent_sq = sq->parent_sq; |
1209 | dispatched = false; |
1210 | |
1211 | while (true) { |
1212 | throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u", |
1213 | sq->nr_queued[READ] + sq->nr_queued[WRITE], |
1214 | sq->nr_queued[READ], sq->nr_queued[WRITE]); |
1215 | |
1216 | ret = throtl_select_dispatch(sq); |
1217 | if (ret) { |
1218 | throtl_log(sq, "bios disp=%u", ret); |
1219 | dispatched = true; |
1220 | } |
1221 | |
1222 | if (throtl_schedule_next_dispatch(sq, false)) |
1223 | break; |
1224 | |
1225 | /* this dispatch windows is still open, relax and repeat */ |
1226 | spin_unlock_irq(q->queue_lock); |
1227 | cpu_relax(); |
1228 | spin_lock_irq(q->queue_lock); |
1229 | } |
1230 | |
1231 | if (!dispatched) |
1232 | goto out_unlock; |
1233 | |
1234 | if (parent_sq) { |
1235 | /* @parent_sq is another throl_grp, propagate dispatch */ |
1236 | if (tg->flags & THROTL_TG_WAS_EMPTY) { |
1237 | tg_update_disptime(tg); |
1238 | if (!throtl_schedule_next_dispatch(parent_sq, false)) { |
1239 | /* window is already open, repeat dispatching */ |
1240 | sq = parent_sq; |
1241 | tg = sq_to_tg(sq); |
1242 | goto again; |
1243 | } |
1244 | } |
1245 | } else { |
1246 | /* reached the top-level, queue issueing */ |
1247 | queue_work(kthrotld_workqueue, &td->dispatch_work); |
1248 | } |
1249 | out_unlock: |
1250 | spin_unlock_irq(q->queue_lock); |
1251 | } |
1252 | |
1253 | /** |
1254 | * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work |
1255 | * @work: work item being executed |
1256 | * |
1257 | * This function is queued for execution when bio's reach the bio_lists[] |
1258 | * of throtl_data->service_queue. Those bio's are ready and issued by this |
1259 | * function. |
1260 | */ |
1261 | void blk_throtl_dispatch_work_fn(struct work_struct *work) |
1262 | { |
1263 | struct throtl_data *td = container_of(work, struct throtl_data, |
1264 | dispatch_work); |
1265 | struct throtl_service_queue *td_sq = &td->service_queue; |
1266 | struct request_queue *q = td->queue; |
1267 | struct bio_list bio_list_on_stack; |
1268 | struct bio *bio; |
1269 | struct blk_plug plug; |
1270 | int rw; |
1271 | |
1272 | bio_list_init(&bio_list_on_stack); |
1273 | |
1274 | spin_lock_irq(q->queue_lock); |
1275 | for (rw = READ; rw <= WRITE; rw++) |
1276 | while ((bio = throtl_pop_queued(&td_sq->queued[rw], NULL))) |
1277 | bio_list_add(&bio_list_on_stack, bio); |
1278 | spin_unlock_irq(q->queue_lock); |
1279 | |
1280 | if (!bio_list_empty(&bio_list_on_stack)) { |
1281 | blk_start_plug(&plug); |
1282 | while((bio = bio_list_pop(&bio_list_on_stack))) |
1283 | generic_make_request(bio); |
1284 | blk_finish_plug(&plug); |
1285 | } |
1286 | } |
1287 | |
1288 | static u64 tg_prfill_cpu_rwstat(struct seq_file *sf, |
1289 | struct blkg_policy_data *pd, int off) |
1290 | { |
1291 | struct throtl_grp *tg = pd_to_tg(pd); |
1292 | struct blkg_rwstat rwstat = { }, tmp; |
1293 | int i, cpu; |
1294 | |
1295 | for_each_possible_cpu(cpu) { |
1296 | struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu); |
1297 | |
1298 | tmp = blkg_rwstat_read((void *)sc + off); |
1299 | for (i = 0; i < BLKG_RWSTAT_NR; i++) |
1300 | rwstat.cnt[i] += tmp.cnt[i]; |
1301 | } |
1302 | |
1303 | return __blkg_prfill_rwstat(sf, pd, &rwstat); |
1304 | } |
1305 | |
1306 | static int tg_print_cpu_rwstat(struct cgroup_subsys_state *css, |
1307 | struct cftype *cft, struct seq_file *sf) |
1308 | { |
1309 | struct blkcg *blkcg = css_to_blkcg(css); |
1310 | |
1311 | blkcg_print_blkgs(sf, blkcg, tg_prfill_cpu_rwstat, &blkcg_policy_throtl, |
1312 | cft->private, true); |
1313 | return 0; |
1314 | } |
1315 | |
1316 | static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd, |
1317 | int off) |
1318 | { |
1319 | struct throtl_grp *tg = pd_to_tg(pd); |
1320 | u64 v = *(u64 *)((void *)tg + off); |
1321 | |
1322 | if (v == -1) |
1323 | return 0; |
1324 | return __blkg_prfill_u64(sf, pd, v); |
1325 | } |
1326 | |
1327 | static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd, |
1328 | int off) |
1329 | { |
1330 | struct throtl_grp *tg = pd_to_tg(pd); |
1331 | unsigned int v = *(unsigned int *)((void *)tg + off); |
1332 | |
1333 | if (v == -1) |
1334 | return 0; |
1335 | return __blkg_prfill_u64(sf, pd, v); |
1336 | } |
1337 | |
1338 | static int tg_print_conf_u64(struct cgroup_subsys_state *css, |
1339 | struct cftype *cft, struct seq_file *sf) |
1340 | { |
1341 | blkcg_print_blkgs(sf, css_to_blkcg(css), tg_prfill_conf_u64, |
1342 | &blkcg_policy_throtl, cft->private, false); |
1343 | return 0; |
1344 | } |
1345 | |
1346 | static int tg_print_conf_uint(struct cgroup_subsys_state *css, |
1347 | struct cftype *cft, struct seq_file *sf) |
1348 | { |
1349 | blkcg_print_blkgs(sf, css_to_blkcg(css), tg_prfill_conf_uint, |
1350 | &blkcg_policy_throtl, cft->private, false); |
1351 | return 0; |
1352 | } |
1353 | |
1354 | static int tg_set_conf(struct cgroup_subsys_state *css, struct cftype *cft, |
1355 | const char *buf, bool is_u64) |
1356 | { |
1357 | struct blkcg *blkcg = css_to_blkcg(css); |
1358 | struct blkg_conf_ctx ctx; |
1359 | struct throtl_grp *tg; |
1360 | struct throtl_service_queue *sq; |
1361 | struct blkcg_gq *blkg; |
1362 | struct cgroup_subsys_state *pos_css; |
1363 | int ret; |
1364 | |
1365 | ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx); |
1366 | if (ret) |
1367 | return ret; |
1368 | |
1369 | tg = blkg_to_tg(ctx.blkg); |
1370 | sq = &tg->service_queue; |
1371 | |
1372 | if (!ctx.v) |
1373 | ctx.v = -1; |
1374 | |
1375 | if (is_u64) |
1376 | *(u64 *)((void *)tg + cft->private) = ctx.v; |
1377 | else |
1378 | *(unsigned int *)((void *)tg + cft->private) = ctx.v; |
1379 | |
1380 | throtl_log(&tg->service_queue, |
1381 | "limit change rbps=%llu wbps=%llu riops=%u wiops=%u", |
1382 | tg->bps[READ], tg->bps[WRITE], |
1383 | tg->iops[READ], tg->iops[WRITE]); |
1384 | |
1385 | /* |
1386 | * Update has_rules[] flags for the updated tg's subtree. A tg is |
1387 | * considered to have rules if either the tg itself or any of its |
1388 | * ancestors has rules. This identifies groups without any |
1389 | * restrictions in the whole hierarchy and allows them to bypass |
1390 | * blk-throttle. |
1391 | */ |
1392 | blkg_for_each_descendant_pre(blkg, pos_css, ctx.blkg) |
1393 | tg_update_has_rules(blkg_to_tg(blkg)); |
1394 | |
1395 | /* |
1396 | * We're already holding queue_lock and know @tg is valid. Let's |
1397 | * apply the new config directly. |
1398 | * |
1399 | * Restart the slices for both READ and WRITES. It might happen |
1400 | * that a group's limit are dropped suddenly and we don't want to |
1401 | * account recently dispatched IO with new low rate. |
1402 | */ |
1403 | throtl_start_new_slice(tg, 0); |
1404 | throtl_start_new_slice(tg, 1); |
1405 | |
1406 | if (tg->flags & THROTL_TG_PENDING) { |
1407 | tg_update_disptime(tg); |
1408 | throtl_schedule_next_dispatch(sq->parent_sq, true); |
1409 | } |
1410 | |
1411 | blkg_conf_finish(&ctx); |
1412 | return 0; |
1413 | } |
1414 | |
1415 | static int tg_set_conf_u64(struct cgroup_subsys_state *css, struct cftype *cft, |
1416 | const char *buf) |
1417 | { |
1418 | return tg_set_conf(css, cft, buf, true); |
1419 | } |
1420 | |
1421 | static int tg_set_conf_uint(struct cgroup_subsys_state *css, struct cftype *cft, |
1422 | const char *buf) |
1423 | { |
1424 | return tg_set_conf(css, cft, buf, false); |
1425 | } |
1426 | |
1427 | static struct cftype throtl_files[] = { |
1428 | { |
1429 | .name = "throttle.read_bps_device", |
1430 | .private = offsetof(struct throtl_grp, bps[READ]), |
1431 | .read_seq_string = tg_print_conf_u64, |
1432 | .write_string = tg_set_conf_u64, |
1433 | .max_write_len = 256, |
1434 | }, |
1435 | { |
1436 | .name = "throttle.write_bps_device", |
1437 | .private = offsetof(struct throtl_grp, bps[WRITE]), |
1438 | .read_seq_string = tg_print_conf_u64, |
1439 | .write_string = tg_set_conf_u64, |
1440 | .max_write_len = 256, |
1441 | }, |
1442 | { |
1443 | .name = "throttle.read_iops_device", |
1444 | .private = offsetof(struct throtl_grp, iops[READ]), |
1445 | .read_seq_string = tg_print_conf_uint, |
1446 | .write_string = tg_set_conf_uint, |
1447 | .max_write_len = 256, |
1448 | }, |
1449 | { |
1450 | .name = "throttle.write_iops_device", |
1451 | .private = offsetof(struct throtl_grp, iops[WRITE]), |
1452 | .read_seq_string = tg_print_conf_uint, |
1453 | .write_string = tg_set_conf_uint, |
1454 | .max_write_len = 256, |
1455 | }, |
1456 | { |
1457 | .name = "throttle.io_service_bytes", |
1458 | .private = offsetof(struct tg_stats_cpu, service_bytes), |
1459 | .read_seq_string = tg_print_cpu_rwstat, |
1460 | }, |
1461 | { |
1462 | .name = "throttle.io_serviced", |
1463 | .private = offsetof(struct tg_stats_cpu, serviced), |
1464 | .read_seq_string = tg_print_cpu_rwstat, |
1465 | }, |
1466 | { } /* terminate */ |
1467 | }; |
1468 | |
1469 | static void throtl_shutdown_wq(struct request_queue *q) |
1470 | { |
1471 | struct throtl_data *td = q->td; |
1472 | |
1473 | cancel_work_sync(&td->dispatch_work); |
1474 | } |
1475 | |
1476 | static struct blkcg_policy blkcg_policy_throtl = { |
1477 | .pd_size = sizeof(struct throtl_grp), |
1478 | .cftypes = throtl_files, |
1479 | |
1480 | .pd_init_fn = throtl_pd_init, |
1481 | .pd_online_fn = throtl_pd_online, |
1482 | .pd_exit_fn = throtl_pd_exit, |
1483 | .pd_reset_stats_fn = throtl_pd_reset_stats, |
1484 | }; |
1485 | |
1486 | bool blk_throtl_bio(struct request_queue *q, struct bio *bio) |
1487 | { |
1488 | struct throtl_data *td = q->td; |
1489 | struct throtl_qnode *qn = NULL; |
1490 | struct throtl_grp *tg; |
1491 | struct throtl_service_queue *sq; |
1492 | bool rw = bio_data_dir(bio); |
1493 | struct blkcg *blkcg; |
1494 | bool throttled = false; |
1495 | |
1496 | /* see throtl_charge_bio() */ |
1497 | if (bio->bi_rw & REQ_THROTTLED) |
1498 | goto out; |
1499 | |
1500 | /* |
1501 | * A throtl_grp pointer retrieved under rcu can be used to access |
1502 | * basic fields like stats and io rates. If a group has no rules, |
1503 | * just update the dispatch stats in lockless manner and return. |
1504 | */ |
1505 | rcu_read_lock(); |
1506 | blkcg = bio_blkcg(bio); |
1507 | tg = throtl_lookup_tg(td, blkcg); |
1508 | if (tg) { |
1509 | if (!tg->has_rules[rw]) { |
1510 | throtl_update_dispatch_stats(tg_to_blkg(tg), |
1511 | bio->bi_size, bio->bi_rw); |
1512 | goto out_unlock_rcu; |
1513 | } |
1514 | } |
1515 | |
1516 | /* |
1517 | * Either group has not been allocated yet or it is not an unlimited |
1518 | * IO group |
1519 | */ |
1520 | spin_lock_irq(q->queue_lock); |
1521 | tg = throtl_lookup_create_tg(td, blkcg); |
1522 | if (unlikely(!tg)) |
1523 | goto out_unlock; |
1524 | |
1525 | sq = &tg->service_queue; |
1526 | |
1527 | while (true) { |
1528 | /* throtl is FIFO - if bios are already queued, should queue */ |
1529 | if (sq->nr_queued[rw]) |
1530 | break; |
1531 | |
1532 | /* if above limits, break to queue */ |
1533 | if (!tg_may_dispatch(tg, bio, NULL)) |
1534 | break; |
1535 | |
1536 | /* within limits, let's charge and dispatch directly */ |
1537 | throtl_charge_bio(tg, bio); |
1538 | |
1539 | /* |
1540 | * We need to trim slice even when bios are not being queued |
1541 | * otherwise it might happen that a bio is not queued for |
1542 | * a long time and slice keeps on extending and trim is not |
1543 | * called for a long time. Now if limits are reduced suddenly |
1544 | * we take into account all the IO dispatched so far at new |
1545 | * low rate and * newly queued IO gets a really long dispatch |
1546 | * time. |
1547 | * |
1548 | * So keep on trimming slice even if bio is not queued. |
1549 | */ |
1550 | throtl_trim_slice(tg, rw); |
1551 | |
1552 | /* |
1553 | * @bio passed through this layer without being throttled. |
1554 | * Climb up the ladder. If we''re already at the top, it |
1555 | * can be executed directly. |
1556 | */ |
1557 | qn = &tg->qnode_on_parent[rw]; |
1558 | sq = sq->parent_sq; |
1559 | tg = sq_to_tg(sq); |
1560 | if (!tg) |
1561 | goto out_unlock; |
1562 | } |
1563 | |
1564 | /* out-of-limit, queue to @tg */ |
1565 | throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d", |
1566 | rw == READ ? 'R' : 'W', |
1567 | tg->bytes_disp[rw], bio->bi_size, tg->bps[rw], |
1568 | tg->io_disp[rw], tg->iops[rw], |
1569 | sq->nr_queued[READ], sq->nr_queued[WRITE]); |
1570 | |
1571 | bio_associate_current(bio); |
1572 | tg->td->nr_queued[rw]++; |
1573 | throtl_add_bio_tg(bio, qn, tg); |
1574 | throttled = true; |
1575 | |
1576 | /* |
1577 | * Update @tg's dispatch time and force schedule dispatch if @tg |
1578 | * was empty before @bio. The forced scheduling isn't likely to |
1579 | * cause undue delay as @bio is likely to be dispatched directly if |
1580 | * its @tg's disptime is not in the future. |
1581 | */ |
1582 | if (tg->flags & THROTL_TG_WAS_EMPTY) { |
1583 | tg_update_disptime(tg); |
1584 | throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true); |
1585 | } |
1586 | |
1587 | out_unlock: |
1588 | spin_unlock_irq(q->queue_lock); |
1589 | out_unlock_rcu: |
1590 | rcu_read_unlock(); |
1591 | out: |
1592 | /* |
1593 | * As multiple blk-throtls may stack in the same issue path, we |
1594 | * don't want bios to leave with the flag set. Clear the flag if |
1595 | * being issued. |
1596 | */ |
1597 | if (!throttled) |
1598 | bio->bi_rw &= ~REQ_THROTTLED; |
1599 | return throttled; |
1600 | } |
1601 | |
1602 | /* |
1603 | * Dispatch all bios from all children tg's queued on @parent_sq. On |
1604 | * return, @parent_sq is guaranteed to not have any active children tg's |
1605 | * and all bios from previously active tg's are on @parent_sq->bio_lists[]. |
1606 | */ |
1607 | static void tg_drain_bios(struct throtl_service_queue *parent_sq) |
1608 | { |
1609 | struct throtl_grp *tg; |
1610 | |
1611 | while ((tg = throtl_rb_first(parent_sq))) { |
1612 | struct throtl_service_queue *sq = &tg->service_queue; |
1613 | struct bio *bio; |
1614 | |
1615 | throtl_dequeue_tg(tg); |
1616 | |
1617 | while ((bio = throtl_peek_queued(&sq->queued[READ]))) |
1618 | tg_dispatch_one_bio(tg, bio_data_dir(bio)); |
1619 | while ((bio = throtl_peek_queued(&sq->queued[WRITE]))) |
1620 | tg_dispatch_one_bio(tg, bio_data_dir(bio)); |
1621 | } |
1622 | } |
1623 | |
1624 | /** |
1625 | * blk_throtl_drain - drain throttled bios |
1626 | * @q: request_queue to drain throttled bios for |
1627 | * |
1628 | * Dispatch all currently throttled bios on @q through ->make_request_fn(). |
1629 | */ |
1630 | void blk_throtl_drain(struct request_queue *q) |
1631 | __releases(q->queue_lock) __acquires(q->queue_lock) |
1632 | { |
1633 | struct throtl_data *td = q->td; |
1634 | struct blkcg_gq *blkg; |
1635 | struct cgroup_subsys_state *pos_css; |
1636 | struct bio *bio; |
1637 | int rw; |
1638 | |
1639 | queue_lockdep_assert_held(q); |
1640 | rcu_read_lock(); |
1641 | |
1642 | /* |
1643 | * Drain each tg while doing post-order walk on the blkg tree, so |
1644 | * that all bios are propagated to td->service_queue. It'd be |
1645 | * better to walk service_queue tree directly but blkg walk is |
1646 | * easier. |
1647 | */ |
1648 | blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) |
1649 | tg_drain_bios(&blkg_to_tg(blkg)->service_queue); |
1650 | |
1651 | /* finally, transfer bios from top-level tg's into the td */ |
1652 | tg_drain_bios(&td->service_queue); |
1653 | |
1654 | rcu_read_unlock(); |
1655 | spin_unlock_irq(q->queue_lock); |
1656 | |
1657 | /* all bios now should be in td->service_queue, issue them */ |
1658 | for (rw = READ; rw <= WRITE; rw++) |
1659 | while ((bio = throtl_pop_queued(&td->service_queue.queued[rw], |
1660 | NULL))) |
1661 | generic_make_request(bio); |
1662 | |
1663 | spin_lock_irq(q->queue_lock); |
1664 | } |
1665 | |
1666 | int blk_throtl_init(struct request_queue *q) |
1667 | { |
1668 | struct throtl_data *td; |
1669 | int ret; |
1670 | |
1671 | td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node); |
1672 | if (!td) |
1673 | return -ENOMEM; |
1674 | |
1675 | INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn); |
1676 | throtl_service_queue_init(&td->service_queue, NULL); |
1677 | |
1678 | q->td = td; |
1679 | td->queue = q; |
1680 | |
1681 | /* activate policy */ |
1682 | ret = blkcg_activate_policy(q, &blkcg_policy_throtl); |
1683 | if (ret) |
1684 | kfree(td); |
1685 | return ret; |
1686 | } |
1687 | |
1688 | void blk_throtl_exit(struct request_queue *q) |
1689 | { |
1690 | BUG_ON(!q->td); |
1691 | throtl_shutdown_wq(q); |
1692 | blkcg_deactivate_policy(q, &blkcg_policy_throtl); |
1693 | kfree(q->td); |
1694 | } |
1695 | |
1696 | static int __init throtl_init(void) |
1697 | { |
1698 | kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0); |
1699 | if (!kthrotld_workqueue) |
1700 | panic("Failed to create kthrotld\n"); |
1701 | |
1702 | return blkcg_policy_register(&blkcg_policy_throtl); |
1703 | } |
1704 | |
1705 | module_init(throtl_init); |
1706 |
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