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[linux/fpc-iii.git] / block / cfq-iosched.c
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1 /*
2 * CFQ, or complete fairness queueing, disk scheduler.
4 * Based on ideas from a previously unfinished io
5 * scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
7 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
8 */
9 #include <linux/module.h>
10 #include <linux/blkdev.h>
11 #include <linux/elevator.h>
12 #include <linux/rbtree.h>
13 #include <linux/ioprio.h>
14 #include <linux/blktrace_api.h>
17 * tunables
19 /* max queue in one round of service */
20 static const int cfq_quantum = 4;
21 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
22 /* maximum backwards seek, in KiB */
23 static const int cfq_back_max = 16 * 1024;
24 /* penalty of a backwards seek */
25 static const int cfq_back_penalty = 2;
26 static const int cfq_slice_sync = HZ / 10;
27 static int cfq_slice_async = HZ / 25;
28 static const int cfq_slice_async_rq = 2;
29 static int cfq_slice_idle = HZ / 125;
32 * offset from end of service tree
34 #define CFQ_IDLE_DELAY (HZ / 5)
37 * below this threshold, we consider thinktime immediate
39 #define CFQ_MIN_TT (2)
41 #define CFQ_SLICE_SCALE (5)
42 #define CFQ_HW_QUEUE_MIN (5)
44 #define RQ_CIC(rq) \
45 ((struct cfq_io_context *) (rq)->elevator_private)
46 #define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2)
48 static struct kmem_cache *cfq_pool;
49 static struct kmem_cache *cfq_ioc_pool;
51 static DEFINE_PER_CPU(unsigned long, ioc_count);
52 static struct completion *ioc_gone;
53 static DEFINE_SPINLOCK(ioc_gone_lock);
55 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
56 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
57 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
59 #define sample_valid(samples) ((samples) > 80)
62 * Most of our rbtree usage is for sorting with min extraction, so
63 * if we cache the leftmost node we don't have to walk down the tree
64 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
65 * move this into the elevator for the rq sorting as well.
67 struct cfq_rb_root {
68 struct rb_root rb;
69 struct rb_node *left;
71 #define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, }
74 * Per process-grouping structure
76 struct cfq_queue {
77 /* reference count */
78 atomic_t ref;
79 /* various state flags, see below */
80 unsigned int flags;
81 /* parent cfq_data */
82 struct cfq_data *cfqd;
83 /* service_tree member */
84 struct rb_node rb_node;
85 /* service_tree key */
86 unsigned long rb_key;
87 /* prio tree member */
88 struct rb_node p_node;
89 /* prio tree root we belong to, if any */
90 struct rb_root *p_root;
91 /* sorted list of pending requests */
92 struct rb_root sort_list;
93 /* if fifo isn't expired, next request to serve */
94 struct request *next_rq;
95 /* requests queued in sort_list */
96 int queued[2];
97 /* currently allocated requests */
98 int allocated[2];
99 /* fifo list of requests in sort_list */
100 struct list_head fifo;
102 unsigned long slice_end;
103 long slice_resid;
104 unsigned int slice_dispatch;
106 /* pending metadata requests */
107 int meta_pending;
108 /* number of requests that are on the dispatch list or inside driver */
109 int dispatched;
111 /* io prio of this group */
112 unsigned short ioprio, org_ioprio;
113 unsigned short ioprio_class, org_ioprio_class;
115 pid_t pid;
119 * Per block device queue structure
121 struct cfq_data {
122 struct request_queue *queue;
125 * rr list of queues with requests and the count of them
127 struct cfq_rb_root service_tree;
130 * Each priority tree is sorted by next_request position. These
131 * trees are used when determining if two or more queues are
132 * interleaving requests (see cfq_close_cooperator).
134 struct rb_root prio_trees[CFQ_PRIO_LISTS];
136 unsigned int busy_queues;
138 * Used to track any pending rt requests so we can pre-empt current
139 * non-RT cfqq in service when this value is non-zero.
141 unsigned int busy_rt_queues;
143 int rq_in_driver;
144 int sync_flight;
147 * queue-depth detection
149 int rq_queued;
150 int hw_tag;
151 int hw_tag_samples;
152 int rq_in_driver_peak;
155 * idle window management
157 struct timer_list idle_slice_timer;
158 struct work_struct unplug_work;
160 struct cfq_queue *active_queue;
161 struct cfq_io_context *active_cic;
164 * async queue for each priority case
166 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
167 struct cfq_queue *async_idle_cfqq;
169 sector_t last_position;
172 * tunables, see top of file
174 unsigned int cfq_quantum;
175 unsigned int cfq_fifo_expire[2];
176 unsigned int cfq_back_penalty;
177 unsigned int cfq_back_max;
178 unsigned int cfq_slice[2];
179 unsigned int cfq_slice_async_rq;
180 unsigned int cfq_slice_idle;
182 struct list_head cic_list;
185 * Fallback dummy cfqq for extreme OOM conditions
187 struct cfq_queue oom_cfqq;
190 enum cfqq_state_flags {
191 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
192 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
193 CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */
194 CFQ_CFQQ_FLAG_must_alloc, /* must be allowed rq alloc */
195 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
196 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
197 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */
198 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
199 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
200 CFQ_CFQQ_FLAG_sync, /* synchronous queue */
201 CFQ_CFQQ_FLAG_coop, /* has done a coop jump of the queue */
204 #define CFQ_CFQQ_FNS(name) \
205 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
207 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
209 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
211 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
213 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
215 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
218 CFQ_CFQQ_FNS(on_rr);
219 CFQ_CFQQ_FNS(wait_request);
220 CFQ_CFQQ_FNS(must_dispatch);
221 CFQ_CFQQ_FNS(must_alloc);
222 CFQ_CFQQ_FNS(must_alloc_slice);
223 CFQ_CFQQ_FNS(fifo_expire);
224 CFQ_CFQQ_FNS(idle_window);
225 CFQ_CFQQ_FNS(prio_changed);
226 CFQ_CFQQ_FNS(slice_new);
227 CFQ_CFQQ_FNS(sync);
228 CFQ_CFQQ_FNS(coop);
229 #undef CFQ_CFQQ_FNS
231 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
232 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
233 #define cfq_log(cfqd, fmt, args...) \
234 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
236 static void cfq_dispatch_insert(struct request_queue *, struct request *);
237 static struct cfq_queue *cfq_get_queue(struct cfq_data *, int,
238 struct io_context *, gfp_t);
239 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
240 struct io_context *);
242 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
243 int is_sync)
245 return cic->cfqq[!!is_sync];
248 static inline void cic_set_cfqq(struct cfq_io_context *cic,
249 struct cfq_queue *cfqq, int is_sync)
251 cic->cfqq[!!is_sync] = cfqq;
255 * We regard a request as SYNC, if it's either a read or has the SYNC bit
256 * set (in which case it could also be direct WRITE).
258 static inline int cfq_bio_sync(struct bio *bio)
260 if (bio_data_dir(bio) == READ || bio_sync(bio))
261 return 1;
263 return 0;
267 * scheduler run of queue, if there are requests pending and no one in the
268 * driver that will restart queueing
270 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
272 if (cfqd->busy_queues) {
273 cfq_log(cfqd, "schedule dispatch");
274 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
278 static int cfq_queue_empty(struct request_queue *q)
280 struct cfq_data *cfqd = q->elevator->elevator_data;
282 return !cfqd->busy_queues;
286 * Scale schedule slice based on io priority. Use the sync time slice only
287 * if a queue is marked sync and has sync io queued. A sync queue with async
288 * io only, should not get full sync slice length.
290 static inline int cfq_prio_slice(struct cfq_data *cfqd, int sync,
291 unsigned short prio)
293 const int base_slice = cfqd->cfq_slice[sync];
295 WARN_ON(prio >= IOPRIO_BE_NR);
297 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
300 static inline int
301 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
303 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
306 static inline void
307 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
309 cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
310 cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
314 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
315 * isn't valid until the first request from the dispatch is activated
316 * and the slice time set.
318 static inline int cfq_slice_used(struct cfq_queue *cfqq)
320 if (cfq_cfqq_slice_new(cfqq))
321 return 0;
322 if (time_before(jiffies, cfqq->slice_end))
323 return 0;
325 return 1;
329 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
330 * We choose the request that is closest to the head right now. Distance
331 * behind the head is penalized and only allowed to a certain extent.
333 static struct request *
334 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2)
336 sector_t last, s1, s2, d1 = 0, d2 = 0;
337 unsigned long back_max;
338 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
339 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
340 unsigned wrap = 0; /* bit mask: requests behind the disk head? */
342 if (rq1 == NULL || rq1 == rq2)
343 return rq2;
344 if (rq2 == NULL)
345 return rq1;
347 if (rq_is_sync(rq1) && !rq_is_sync(rq2))
348 return rq1;
349 else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
350 return rq2;
351 if (rq_is_meta(rq1) && !rq_is_meta(rq2))
352 return rq1;
353 else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
354 return rq2;
356 s1 = blk_rq_pos(rq1);
357 s2 = blk_rq_pos(rq2);
359 last = cfqd->last_position;
362 * by definition, 1KiB is 2 sectors
364 back_max = cfqd->cfq_back_max * 2;
367 * Strict one way elevator _except_ in the case where we allow
368 * short backward seeks which are biased as twice the cost of a
369 * similar forward seek.
371 if (s1 >= last)
372 d1 = s1 - last;
373 else if (s1 + back_max >= last)
374 d1 = (last - s1) * cfqd->cfq_back_penalty;
375 else
376 wrap |= CFQ_RQ1_WRAP;
378 if (s2 >= last)
379 d2 = s2 - last;
380 else if (s2 + back_max >= last)
381 d2 = (last - s2) * cfqd->cfq_back_penalty;
382 else
383 wrap |= CFQ_RQ2_WRAP;
385 /* Found required data */
388 * By doing switch() on the bit mask "wrap" we avoid having to
389 * check two variables for all permutations: --> faster!
391 switch (wrap) {
392 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
393 if (d1 < d2)
394 return rq1;
395 else if (d2 < d1)
396 return rq2;
397 else {
398 if (s1 >= s2)
399 return rq1;
400 else
401 return rq2;
404 case CFQ_RQ2_WRAP:
405 return rq1;
406 case CFQ_RQ1_WRAP:
407 return rq2;
408 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
409 default:
411 * Since both rqs are wrapped,
412 * start with the one that's further behind head
413 * (--> only *one* back seek required),
414 * since back seek takes more time than forward.
416 if (s1 <= s2)
417 return rq1;
418 else
419 return rq2;
424 * The below is leftmost cache rbtree addon
426 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
428 if (!root->left)
429 root->left = rb_first(&root->rb);
431 if (root->left)
432 return rb_entry(root->left, struct cfq_queue, rb_node);
434 return NULL;
437 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
439 rb_erase(n, root);
440 RB_CLEAR_NODE(n);
443 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
445 if (root->left == n)
446 root->left = NULL;
447 rb_erase_init(n, &root->rb);
451 * would be nice to take fifo expire time into account as well
453 static struct request *
454 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
455 struct request *last)
457 struct rb_node *rbnext = rb_next(&last->rb_node);
458 struct rb_node *rbprev = rb_prev(&last->rb_node);
459 struct request *next = NULL, *prev = NULL;
461 BUG_ON(RB_EMPTY_NODE(&last->rb_node));
463 if (rbprev)
464 prev = rb_entry_rq(rbprev);
466 if (rbnext)
467 next = rb_entry_rq(rbnext);
468 else {
469 rbnext = rb_first(&cfqq->sort_list);
470 if (rbnext && rbnext != &last->rb_node)
471 next = rb_entry_rq(rbnext);
474 return cfq_choose_req(cfqd, next, prev);
477 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
478 struct cfq_queue *cfqq)
481 * just an approximation, should be ok.
483 return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) -
484 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
488 * The cfqd->service_tree holds all pending cfq_queue's that have
489 * requests waiting to be processed. It is sorted in the order that
490 * we will service the queues.
492 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
493 int add_front)
495 struct rb_node **p, *parent;
496 struct cfq_queue *__cfqq;
497 unsigned long rb_key;
498 int left;
500 if (cfq_class_idle(cfqq)) {
501 rb_key = CFQ_IDLE_DELAY;
502 parent = rb_last(&cfqd->service_tree.rb);
503 if (parent && parent != &cfqq->rb_node) {
504 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
505 rb_key += __cfqq->rb_key;
506 } else
507 rb_key += jiffies;
508 } else if (!add_front) {
509 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
510 rb_key += cfqq->slice_resid;
511 cfqq->slice_resid = 0;
512 } else
513 rb_key = 0;
515 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
517 * same position, nothing more to do
519 if (rb_key == cfqq->rb_key)
520 return;
522 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
525 left = 1;
526 parent = NULL;
527 p = &cfqd->service_tree.rb.rb_node;
528 while (*p) {
529 struct rb_node **n;
531 parent = *p;
532 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
535 * sort RT queues first, we always want to give
536 * preference to them. IDLE queues goes to the back.
537 * after that, sort on the next service time.
539 if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq))
540 n = &(*p)->rb_left;
541 else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq))
542 n = &(*p)->rb_right;
543 else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq))
544 n = &(*p)->rb_left;
545 else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq))
546 n = &(*p)->rb_right;
547 else if (rb_key < __cfqq->rb_key)
548 n = &(*p)->rb_left;
549 else
550 n = &(*p)->rb_right;
552 if (n == &(*p)->rb_right)
553 left = 0;
555 p = n;
558 if (left)
559 cfqd->service_tree.left = &cfqq->rb_node;
561 cfqq->rb_key = rb_key;
562 rb_link_node(&cfqq->rb_node, parent, p);
563 rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb);
566 static struct cfq_queue *
567 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
568 sector_t sector, struct rb_node **ret_parent,
569 struct rb_node ***rb_link)
571 struct rb_node **p, *parent;
572 struct cfq_queue *cfqq = NULL;
574 parent = NULL;
575 p = &root->rb_node;
576 while (*p) {
577 struct rb_node **n;
579 parent = *p;
580 cfqq = rb_entry(parent, struct cfq_queue, p_node);
583 * Sort strictly based on sector. Smallest to the left,
584 * largest to the right.
586 if (sector > blk_rq_pos(cfqq->next_rq))
587 n = &(*p)->rb_right;
588 else if (sector < blk_rq_pos(cfqq->next_rq))
589 n = &(*p)->rb_left;
590 else
591 break;
592 p = n;
593 cfqq = NULL;
596 *ret_parent = parent;
597 if (rb_link)
598 *rb_link = p;
599 return cfqq;
602 static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
604 struct rb_node **p, *parent;
605 struct cfq_queue *__cfqq;
607 if (cfqq->p_root) {
608 rb_erase(&cfqq->p_node, cfqq->p_root);
609 cfqq->p_root = NULL;
612 if (cfq_class_idle(cfqq))
613 return;
614 if (!cfqq->next_rq)
615 return;
617 cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
618 __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
619 blk_rq_pos(cfqq->next_rq), &parent, &p);
620 if (!__cfqq) {
621 rb_link_node(&cfqq->p_node, parent, p);
622 rb_insert_color(&cfqq->p_node, cfqq->p_root);
623 } else
624 cfqq->p_root = NULL;
628 * Update cfqq's position in the service tree.
630 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
633 * Resorting requires the cfqq to be on the RR list already.
635 if (cfq_cfqq_on_rr(cfqq)) {
636 cfq_service_tree_add(cfqd, cfqq, 0);
637 cfq_prio_tree_add(cfqd, cfqq);
642 * add to busy list of queues for service, trying to be fair in ordering
643 * the pending list according to last request service
645 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
647 cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
648 BUG_ON(cfq_cfqq_on_rr(cfqq));
649 cfq_mark_cfqq_on_rr(cfqq);
650 cfqd->busy_queues++;
651 if (cfq_class_rt(cfqq))
652 cfqd->busy_rt_queues++;
654 cfq_resort_rr_list(cfqd, cfqq);
658 * Called when the cfqq no longer has requests pending, remove it from
659 * the service tree.
661 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
663 cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
664 BUG_ON(!cfq_cfqq_on_rr(cfqq));
665 cfq_clear_cfqq_on_rr(cfqq);
667 if (!RB_EMPTY_NODE(&cfqq->rb_node))
668 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
669 if (cfqq->p_root) {
670 rb_erase(&cfqq->p_node, cfqq->p_root);
671 cfqq->p_root = NULL;
674 BUG_ON(!cfqd->busy_queues);
675 cfqd->busy_queues--;
676 if (cfq_class_rt(cfqq))
677 cfqd->busy_rt_queues--;
681 * rb tree support functions
683 static void cfq_del_rq_rb(struct request *rq)
685 struct cfq_queue *cfqq = RQ_CFQQ(rq);
686 struct cfq_data *cfqd = cfqq->cfqd;
687 const int sync = rq_is_sync(rq);
689 BUG_ON(!cfqq->queued[sync]);
690 cfqq->queued[sync]--;
692 elv_rb_del(&cfqq->sort_list, rq);
694 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
695 cfq_del_cfqq_rr(cfqd, cfqq);
698 static void cfq_add_rq_rb(struct request *rq)
700 struct cfq_queue *cfqq = RQ_CFQQ(rq);
701 struct cfq_data *cfqd = cfqq->cfqd;
702 struct request *__alias, *prev;
704 cfqq->queued[rq_is_sync(rq)]++;
707 * looks a little odd, but the first insert might return an alias.
708 * if that happens, put the alias on the dispatch list
710 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
711 cfq_dispatch_insert(cfqd->queue, __alias);
713 if (!cfq_cfqq_on_rr(cfqq))
714 cfq_add_cfqq_rr(cfqd, cfqq);
717 * check if this request is a better next-serve candidate
719 prev = cfqq->next_rq;
720 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq);
723 * adjust priority tree position, if ->next_rq changes
725 if (prev != cfqq->next_rq)
726 cfq_prio_tree_add(cfqd, cfqq);
728 BUG_ON(!cfqq->next_rq);
731 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
733 elv_rb_del(&cfqq->sort_list, rq);
734 cfqq->queued[rq_is_sync(rq)]--;
735 cfq_add_rq_rb(rq);
738 static struct request *
739 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
741 struct task_struct *tsk = current;
742 struct cfq_io_context *cic;
743 struct cfq_queue *cfqq;
745 cic = cfq_cic_lookup(cfqd, tsk->io_context);
746 if (!cic)
747 return NULL;
749 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
750 if (cfqq) {
751 sector_t sector = bio->bi_sector + bio_sectors(bio);
753 return elv_rb_find(&cfqq->sort_list, sector);
756 return NULL;
759 static void cfq_activate_request(struct request_queue *q, struct request *rq)
761 struct cfq_data *cfqd = q->elevator->elevator_data;
763 cfqd->rq_in_driver++;
764 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
765 cfqd->rq_in_driver);
767 cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
770 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
772 struct cfq_data *cfqd = q->elevator->elevator_data;
774 WARN_ON(!cfqd->rq_in_driver);
775 cfqd->rq_in_driver--;
776 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
777 cfqd->rq_in_driver);
780 static void cfq_remove_request(struct request *rq)
782 struct cfq_queue *cfqq = RQ_CFQQ(rq);
784 if (cfqq->next_rq == rq)
785 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
787 list_del_init(&rq->queuelist);
788 cfq_del_rq_rb(rq);
790 cfqq->cfqd->rq_queued--;
791 if (rq_is_meta(rq)) {
792 WARN_ON(!cfqq->meta_pending);
793 cfqq->meta_pending--;
797 static int cfq_merge(struct request_queue *q, struct request **req,
798 struct bio *bio)
800 struct cfq_data *cfqd = q->elevator->elevator_data;
801 struct request *__rq;
803 __rq = cfq_find_rq_fmerge(cfqd, bio);
804 if (__rq && elv_rq_merge_ok(__rq, bio)) {
805 *req = __rq;
806 return ELEVATOR_FRONT_MERGE;
809 return ELEVATOR_NO_MERGE;
812 static void cfq_merged_request(struct request_queue *q, struct request *req,
813 int type)
815 if (type == ELEVATOR_FRONT_MERGE) {
816 struct cfq_queue *cfqq = RQ_CFQQ(req);
818 cfq_reposition_rq_rb(cfqq, req);
822 static void
823 cfq_merged_requests(struct request_queue *q, struct request *rq,
824 struct request *next)
827 * reposition in fifo if next is older than rq
829 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
830 time_before(next->start_time, rq->start_time))
831 list_move(&rq->queuelist, &next->queuelist);
833 cfq_remove_request(next);
836 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
837 struct bio *bio)
839 struct cfq_data *cfqd = q->elevator->elevator_data;
840 struct cfq_io_context *cic;
841 struct cfq_queue *cfqq;
844 * Disallow merge of a sync bio into an async request.
846 if (cfq_bio_sync(bio) && !rq_is_sync(rq))
847 return 0;
850 * Lookup the cfqq that this bio will be queued with. Allow
851 * merge only if rq is queued there.
853 cic = cfq_cic_lookup(cfqd, current->io_context);
854 if (!cic)
855 return 0;
857 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
858 if (cfqq == RQ_CFQQ(rq))
859 return 1;
861 return 0;
864 static void __cfq_set_active_queue(struct cfq_data *cfqd,
865 struct cfq_queue *cfqq)
867 if (cfqq) {
868 cfq_log_cfqq(cfqd, cfqq, "set_active");
869 cfqq->slice_end = 0;
870 cfqq->slice_dispatch = 0;
872 cfq_clear_cfqq_wait_request(cfqq);
873 cfq_clear_cfqq_must_dispatch(cfqq);
874 cfq_clear_cfqq_must_alloc_slice(cfqq);
875 cfq_clear_cfqq_fifo_expire(cfqq);
876 cfq_mark_cfqq_slice_new(cfqq);
878 del_timer(&cfqd->idle_slice_timer);
881 cfqd->active_queue = cfqq;
885 * current cfqq expired its slice (or was too idle), select new one
887 static void
888 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
889 int timed_out)
891 cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
893 if (cfq_cfqq_wait_request(cfqq))
894 del_timer(&cfqd->idle_slice_timer);
896 cfq_clear_cfqq_wait_request(cfqq);
899 * store what was left of this slice, if the queue idled/timed out
901 if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
902 cfqq->slice_resid = cfqq->slice_end - jiffies;
903 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
906 cfq_resort_rr_list(cfqd, cfqq);
908 if (cfqq == cfqd->active_queue)
909 cfqd->active_queue = NULL;
911 if (cfqd->active_cic) {
912 put_io_context(cfqd->active_cic->ioc);
913 cfqd->active_cic = NULL;
917 static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out)
919 struct cfq_queue *cfqq = cfqd->active_queue;
921 if (cfqq)
922 __cfq_slice_expired(cfqd, cfqq, timed_out);
926 * Get next queue for service. Unless we have a queue preemption,
927 * we'll simply select the first cfqq in the service tree.
929 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
931 if (RB_EMPTY_ROOT(&cfqd->service_tree.rb))
932 return NULL;
934 return cfq_rb_first(&cfqd->service_tree);
938 * Get and set a new active queue for service.
940 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
941 struct cfq_queue *cfqq)
943 if (!cfqq) {
944 cfqq = cfq_get_next_queue(cfqd);
945 if (cfqq)
946 cfq_clear_cfqq_coop(cfqq);
949 __cfq_set_active_queue(cfqd, cfqq);
950 return cfqq;
953 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
954 struct request *rq)
956 if (blk_rq_pos(rq) >= cfqd->last_position)
957 return blk_rq_pos(rq) - cfqd->last_position;
958 else
959 return cfqd->last_position - blk_rq_pos(rq);
962 #define CIC_SEEK_THR 8 * 1024
963 #define CIC_SEEKY(cic) ((cic)->seek_mean > CIC_SEEK_THR)
965 static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq)
967 struct cfq_io_context *cic = cfqd->active_cic;
968 sector_t sdist = cic->seek_mean;
970 if (!sample_valid(cic->seek_samples))
971 sdist = CIC_SEEK_THR;
973 return cfq_dist_from_last(cfqd, rq) <= sdist;
976 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
977 struct cfq_queue *cur_cfqq)
979 struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
980 struct rb_node *parent, *node;
981 struct cfq_queue *__cfqq;
982 sector_t sector = cfqd->last_position;
984 if (RB_EMPTY_ROOT(root))
985 return NULL;
988 * First, if we find a request starting at the end of the last
989 * request, choose it.
991 __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
992 if (__cfqq)
993 return __cfqq;
996 * If the exact sector wasn't found, the parent of the NULL leaf
997 * will contain the closest sector.
999 __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1000 if (cfq_rq_close(cfqd, __cfqq->next_rq))
1001 return __cfqq;
1003 if (blk_rq_pos(__cfqq->next_rq) < sector)
1004 node = rb_next(&__cfqq->p_node);
1005 else
1006 node = rb_prev(&__cfqq->p_node);
1007 if (!node)
1008 return NULL;
1010 __cfqq = rb_entry(node, struct cfq_queue, p_node);
1011 if (cfq_rq_close(cfqd, __cfqq->next_rq))
1012 return __cfqq;
1014 return NULL;
1018 * cfqd - obvious
1019 * cur_cfqq - passed in so that we don't decide that the current queue is
1020 * closely cooperating with itself.
1022 * So, basically we're assuming that that cur_cfqq has dispatched at least
1023 * one request, and that cfqd->last_position reflects a position on the disk
1024 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
1025 * assumption.
1027 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1028 struct cfq_queue *cur_cfqq,
1029 int probe)
1031 struct cfq_queue *cfqq;
1034 * A valid cfq_io_context is necessary to compare requests against
1035 * the seek_mean of the current cfqq.
1037 if (!cfqd->active_cic)
1038 return NULL;
1041 * We should notice if some of the queues are cooperating, eg
1042 * working closely on the same area of the disk. In that case,
1043 * we can group them together and don't waste time idling.
1045 cfqq = cfqq_close(cfqd, cur_cfqq);
1046 if (!cfqq)
1047 return NULL;
1049 if (cfq_cfqq_coop(cfqq))
1050 return NULL;
1052 if (!probe)
1053 cfq_mark_cfqq_coop(cfqq);
1054 return cfqq;
1057 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
1059 struct cfq_queue *cfqq = cfqd->active_queue;
1060 struct cfq_io_context *cic;
1061 unsigned long sl;
1064 * SSD device without seek penalty, disable idling. But only do so
1065 * for devices that support queuing, otherwise we still have a problem
1066 * with sync vs async workloads.
1068 if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
1069 return;
1071 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
1072 WARN_ON(cfq_cfqq_slice_new(cfqq));
1075 * idle is disabled, either manually or by past process history
1077 if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq))
1078 return;
1081 * still requests with the driver, don't idle
1083 if (cfqd->rq_in_driver)
1084 return;
1087 * task has exited, don't wait
1089 cic = cfqd->active_cic;
1090 if (!cic || !atomic_read(&cic->ioc->nr_tasks))
1091 return;
1093 cfq_mark_cfqq_wait_request(cfqq);
1096 * we don't want to idle for seeks, but we do want to allow
1097 * fair distribution of slice time for a process doing back-to-back
1098 * seeks. so allow a little bit of time for him to submit a new rq
1100 sl = cfqd->cfq_slice_idle;
1101 if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
1102 sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT));
1104 mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
1105 cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
1109 * Move request from internal lists to the request queue dispatch list.
1111 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
1113 struct cfq_data *cfqd = q->elevator->elevator_data;
1114 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1116 cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
1118 cfq_remove_request(rq);
1119 cfqq->dispatched++;
1120 elv_dispatch_sort(q, rq);
1122 if (cfq_cfqq_sync(cfqq))
1123 cfqd->sync_flight++;
1127 * return expired entry, or NULL to just start from scratch in rbtree
1129 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
1131 struct cfq_data *cfqd = cfqq->cfqd;
1132 struct request *rq;
1133 int fifo;
1135 if (cfq_cfqq_fifo_expire(cfqq))
1136 return NULL;
1138 cfq_mark_cfqq_fifo_expire(cfqq);
1140 if (list_empty(&cfqq->fifo))
1141 return NULL;
1143 fifo = cfq_cfqq_sync(cfqq);
1144 rq = rq_entry_fifo(cfqq->fifo.next);
1146 if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo]))
1147 rq = NULL;
1149 cfq_log_cfqq(cfqd, cfqq, "fifo=%p", rq);
1150 return rq;
1153 static inline int
1154 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1156 const int base_rq = cfqd->cfq_slice_async_rq;
1158 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1160 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1164 * Select a queue for service. If we have a current active queue,
1165 * check whether to continue servicing it, or retrieve and set a new one.
1167 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
1169 struct cfq_queue *cfqq, *new_cfqq = NULL;
1171 cfqq = cfqd->active_queue;
1172 if (!cfqq)
1173 goto new_queue;
1176 * The active queue has run out of time, expire it and select new.
1178 if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq))
1179 goto expire;
1182 * If we have a RT cfqq waiting, then we pre-empt the current non-rt
1183 * cfqq.
1185 if (!cfq_class_rt(cfqq) && cfqd->busy_rt_queues) {
1187 * We simulate this as cfqq timed out so that it gets to bank
1188 * the remaining of its time slice.
1190 cfq_log_cfqq(cfqd, cfqq, "preempt");
1191 cfq_slice_expired(cfqd, 1);
1192 goto new_queue;
1196 * The active queue has requests and isn't expired, allow it to
1197 * dispatch.
1199 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
1200 goto keep_queue;
1203 * If another queue has a request waiting within our mean seek
1204 * distance, let it run. The expire code will check for close
1205 * cooperators and put the close queue at the front of the service
1206 * tree.
1208 new_cfqq = cfq_close_cooperator(cfqd, cfqq, 0);
1209 if (new_cfqq)
1210 goto expire;
1213 * No requests pending. If the active queue still has requests in
1214 * flight or is idling for a new request, allow either of these
1215 * conditions to happen (or time out) before selecting a new queue.
1217 if (timer_pending(&cfqd->idle_slice_timer) ||
1218 (cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) {
1219 cfqq = NULL;
1220 goto keep_queue;
1223 expire:
1224 cfq_slice_expired(cfqd, 0);
1225 new_queue:
1226 cfqq = cfq_set_active_queue(cfqd, new_cfqq);
1227 keep_queue:
1228 return cfqq;
1231 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
1233 int dispatched = 0;
1235 while (cfqq->next_rq) {
1236 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
1237 dispatched++;
1240 BUG_ON(!list_empty(&cfqq->fifo));
1241 return dispatched;
1245 * Drain our current requests. Used for barriers and when switching
1246 * io schedulers on-the-fly.
1248 static int cfq_forced_dispatch(struct cfq_data *cfqd)
1250 struct cfq_queue *cfqq;
1251 int dispatched = 0;
1253 while ((cfqq = cfq_rb_first(&cfqd->service_tree)) != NULL)
1254 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
1256 cfq_slice_expired(cfqd, 0);
1258 BUG_ON(cfqd->busy_queues);
1260 cfq_log(cfqd, "forced_dispatch=%d", dispatched);
1261 return dispatched;
1265 * Dispatch a request from cfqq, moving them to the request queue
1266 * dispatch list.
1268 static void cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1270 struct request *rq;
1272 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
1275 * follow expired path, else get first next available
1277 rq = cfq_check_fifo(cfqq);
1278 if (!rq)
1279 rq = cfqq->next_rq;
1282 * insert request into driver dispatch list
1284 cfq_dispatch_insert(cfqd->queue, rq);
1286 if (!cfqd->active_cic) {
1287 struct cfq_io_context *cic = RQ_CIC(rq);
1289 atomic_long_inc(&cic->ioc->refcount);
1290 cfqd->active_cic = cic;
1295 * Find the cfqq that we need to service and move a request from that to the
1296 * dispatch list
1298 static int cfq_dispatch_requests(struct request_queue *q, int force)
1300 struct cfq_data *cfqd = q->elevator->elevator_data;
1301 struct cfq_queue *cfqq;
1302 unsigned int max_dispatch;
1304 if (!cfqd->busy_queues)
1305 return 0;
1307 if (unlikely(force))
1308 return cfq_forced_dispatch(cfqd);
1310 cfqq = cfq_select_queue(cfqd);
1311 if (!cfqq)
1312 return 0;
1315 * If this is an async queue and we have sync IO in flight, let it wait
1317 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
1318 return 0;
1320 max_dispatch = cfqd->cfq_quantum;
1321 if (cfq_class_idle(cfqq))
1322 max_dispatch = 1;
1325 * Does this cfqq already have too much IO in flight?
1327 if (cfqq->dispatched >= max_dispatch) {
1329 * idle queue must always only have a single IO in flight
1331 if (cfq_class_idle(cfqq))
1332 return 0;
1335 * We have other queues, don't allow more IO from this one
1337 if (cfqd->busy_queues > 1)
1338 return 0;
1341 * we are the only queue, allow up to 4 times of 'quantum'
1343 if (cfqq->dispatched >= 4 * max_dispatch)
1344 return 0;
1348 * Dispatch a request from this cfqq
1350 cfq_dispatch_request(cfqd, cfqq);
1351 cfqq->slice_dispatch++;
1352 cfq_clear_cfqq_must_dispatch(cfqq);
1355 * expire an async queue immediately if it has used up its slice. idle
1356 * queue always expire after 1 dispatch round.
1358 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
1359 cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1360 cfq_class_idle(cfqq))) {
1361 cfqq->slice_end = jiffies + 1;
1362 cfq_slice_expired(cfqd, 0);
1365 cfq_log(cfqd, "dispatched a request");
1366 return 1;
1370 * task holds one reference to the queue, dropped when task exits. each rq
1371 * in-flight on this queue also holds a reference, dropped when rq is freed.
1373 * queue lock must be held here.
1375 static void cfq_put_queue(struct cfq_queue *cfqq)
1377 struct cfq_data *cfqd = cfqq->cfqd;
1379 BUG_ON(atomic_read(&cfqq->ref) <= 0);
1381 if (!atomic_dec_and_test(&cfqq->ref))
1382 return;
1384 cfq_log_cfqq(cfqd, cfqq, "put_queue");
1385 BUG_ON(rb_first(&cfqq->sort_list));
1386 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1387 BUG_ON(cfq_cfqq_on_rr(cfqq));
1389 if (unlikely(cfqd->active_queue == cfqq)) {
1390 __cfq_slice_expired(cfqd, cfqq, 0);
1391 cfq_schedule_dispatch(cfqd);
1394 kmem_cache_free(cfq_pool, cfqq);
1398 * Must always be called with the rcu_read_lock() held
1400 static void
1401 __call_for_each_cic(struct io_context *ioc,
1402 void (*func)(struct io_context *, struct cfq_io_context *))
1404 struct cfq_io_context *cic;
1405 struct hlist_node *n;
1407 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
1408 func(ioc, cic);
1412 * Call func for each cic attached to this ioc.
1414 static void
1415 call_for_each_cic(struct io_context *ioc,
1416 void (*func)(struct io_context *, struct cfq_io_context *))
1418 rcu_read_lock();
1419 __call_for_each_cic(ioc, func);
1420 rcu_read_unlock();
1423 static void cfq_cic_free_rcu(struct rcu_head *head)
1425 struct cfq_io_context *cic;
1427 cic = container_of(head, struct cfq_io_context, rcu_head);
1429 kmem_cache_free(cfq_ioc_pool, cic);
1430 elv_ioc_count_dec(ioc_count);
1432 if (ioc_gone) {
1434 * CFQ scheduler is exiting, grab exit lock and check
1435 * the pending io context count. If it hits zero,
1436 * complete ioc_gone and set it back to NULL
1438 spin_lock(&ioc_gone_lock);
1439 if (ioc_gone && !elv_ioc_count_read(ioc_count)) {
1440 complete(ioc_gone);
1441 ioc_gone = NULL;
1443 spin_unlock(&ioc_gone_lock);
1447 static void cfq_cic_free(struct cfq_io_context *cic)
1449 call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
1452 static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
1454 unsigned long flags;
1456 BUG_ON(!cic->dead_key);
1458 spin_lock_irqsave(&ioc->lock, flags);
1459 radix_tree_delete(&ioc->radix_root, cic->dead_key);
1460 hlist_del_rcu(&cic->cic_list);
1461 spin_unlock_irqrestore(&ioc->lock, flags);
1463 cfq_cic_free(cic);
1467 * Must be called with rcu_read_lock() held or preemption otherwise disabled.
1468 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
1469 * and ->trim() which is called with the task lock held
1471 static void cfq_free_io_context(struct io_context *ioc)
1474 * ioc->refcount is zero here, or we are called from elv_unregister(),
1475 * so no more cic's are allowed to be linked into this ioc. So it
1476 * should be ok to iterate over the known list, we will see all cic's
1477 * since no new ones are added.
1479 __call_for_each_cic(ioc, cic_free_func);
1482 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1484 if (unlikely(cfqq == cfqd->active_queue)) {
1485 __cfq_slice_expired(cfqd, cfqq, 0);
1486 cfq_schedule_dispatch(cfqd);
1489 cfq_put_queue(cfqq);
1492 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
1493 struct cfq_io_context *cic)
1495 struct io_context *ioc = cic->ioc;
1497 list_del_init(&cic->queue_list);
1500 * Make sure key == NULL is seen for dead queues
1502 smp_wmb();
1503 cic->dead_key = (unsigned long) cic->key;
1504 cic->key = NULL;
1506 if (ioc->ioc_data == cic)
1507 rcu_assign_pointer(ioc->ioc_data, NULL);
1509 if (cic->cfqq[BLK_RW_ASYNC]) {
1510 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
1511 cic->cfqq[BLK_RW_ASYNC] = NULL;
1514 if (cic->cfqq[BLK_RW_SYNC]) {
1515 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
1516 cic->cfqq[BLK_RW_SYNC] = NULL;
1520 static void cfq_exit_single_io_context(struct io_context *ioc,
1521 struct cfq_io_context *cic)
1523 struct cfq_data *cfqd = cic->key;
1525 if (cfqd) {
1526 struct request_queue *q = cfqd->queue;
1527 unsigned long flags;
1529 spin_lock_irqsave(q->queue_lock, flags);
1532 * Ensure we get a fresh copy of the ->key to prevent
1533 * race between exiting task and queue
1535 smp_read_barrier_depends();
1536 if (cic->key)
1537 __cfq_exit_single_io_context(cfqd, cic);
1539 spin_unlock_irqrestore(q->queue_lock, flags);
1544 * The process that ioc belongs to has exited, we need to clean up
1545 * and put the internal structures we have that belongs to that process.
1547 static void cfq_exit_io_context(struct io_context *ioc)
1549 call_for_each_cic(ioc, cfq_exit_single_io_context);
1552 static struct cfq_io_context *
1553 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1555 struct cfq_io_context *cic;
1557 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
1558 cfqd->queue->node);
1559 if (cic) {
1560 cic->last_end_request = jiffies;
1561 INIT_LIST_HEAD(&cic->queue_list);
1562 INIT_HLIST_NODE(&cic->cic_list);
1563 cic->dtor = cfq_free_io_context;
1564 cic->exit = cfq_exit_io_context;
1565 elv_ioc_count_inc(ioc_count);
1568 return cic;
1571 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
1573 struct task_struct *tsk = current;
1574 int ioprio_class;
1576 if (!cfq_cfqq_prio_changed(cfqq))
1577 return;
1579 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
1580 switch (ioprio_class) {
1581 default:
1582 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1583 case IOPRIO_CLASS_NONE:
1585 * no prio set, inherit CPU scheduling settings
1587 cfqq->ioprio = task_nice_ioprio(tsk);
1588 cfqq->ioprio_class = task_nice_ioclass(tsk);
1589 break;
1590 case IOPRIO_CLASS_RT:
1591 cfqq->ioprio = task_ioprio(ioc);
1592 cfqq->ioprio_class = IOPRIO_CLASS_RT;
1593 break;
1594 case IOPRIO_CLASS_BE:
1595 cfqq->ioprio = task_ioprio(ioc);
1596 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1597 break;
1598 case IOPRIO_CLASS_IDLE:
1599 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1600 cfqq->ioprio = 7;
1601 cfq_clear_cfqq_idle_window(cfqq);
1602 break;
1606 * keep track of original prio settings in case we have to temporarily
1607 * elevate the priority of this queue
1609 cfqq->org_ioprio = cfqq->ioprio;
1610 cfqq->org_ioprio_class = cfqq->ioprio_class;
1611 cfq_clear_cfqq_prio_changed(cfqq);
1614 static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
1616 struct cfq_data *cfqd = cic->key;
1617 struct cfq_queue *cfqq;
1618 unsigned long flags;
1620 if (unlikely(!cfqd))
1621 return;
1623 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1625 cfqq = cic->cfqq[BLK_RW_ASYNC];
1626 if (cfqq) {
1627 struct cfq_queue *new_cfqq;
1628 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
1629 GFP_ATOMIC);
1630 if (new_cfqq) {
1631 cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
1632 cfq_put_queue(cfqq);
1636 cfqq = cic->cfqq[BLK_RW_SYNC];
1637 if (cfqq)
1638 cfq_mark_cfqq_prio_changed(cfqq);
1640 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1643 static void cfq_ioc_set_ioprio(struct io_context *ioc)
1645 call_for_each_cic(ioc, changed_ioprio);
1646 ioc->ioprio_changed = 0;
1649 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1650 pid_t pid, int is_sync)
1652 RB_CLEAR_NODE(&cfqq->rb_node);
1653 RB_CLEAR_NODE(&cfqq->p_node);
1654 INIT_LIST_HEAD(&cfqq->fifo);
1656 atomic_set(&cfqq->ref, 0);
1657 cfqq->cfqd = cfqd;
1659 cfq_mark_cfqq_prio_changed(cfqq);
1661 if (is_sync) {
1662 if (!cfq_class_idle(cfqq))
1663 cfq_mark_cfqq_idle_window(cfqq);
1664 cfq_mark_cfqq_sync(cfqq);
1666 cfqq->pid = pid;
1669 static struct cfq_queue *
1670 cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
1671 struct io_context *ioc, gfp_t gfp_mask)
1673 struct cfq_queue *cfqq, *new_cfqq = NULL;
1674 struct cfq_io_context *cic;
1676 retry:
1677 cic = cfq_cic_lookup(cfqd, ioc);
1678 /* cic always exists here */
1679 cfqq = cic_to_cfqq(cic, is_sync);
1682 * Always try a new alloc if we fell back to the OOM cfqq
1683 * originally, since it should just be a temporary situation.
1685 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
1686 cfqq = NULL;
1687 if (new_cfqq) {
1688 cfqq = new_cfqq;
1689 new_cfqq = NULL;
1690 } else if (gfp_mask & __GFP_WAIT) {
1691 spin_unlock_irq(cfqd->queue->queue_lock);
1692 new_cfqq = kmem_cache_alloc_node(cfq_pool,
1693 gfp_mask | __GFP_ZERO,
1694 cfqd->queue->node);
1695 spin_lock_irq(cfqd->queue->queue_lock);
1696 if (new_cfqq)
1697 goto retry;
1698 } else {
1699 cfqq = kmem_cache_alloc_node(cfq_pool,
1700 gfp_mask | __GFP_ZERO,
1701 cfqd->queue->node);
1704 if (cfqq) {
1705 cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
1706 cfq_init_prio_data(cfqq, ioc);
1707 cfq_log_cfqq(cfqd, cfqq, "alloced");
1708 } else
1709 cfqq = &cfqd->oom_cfqq;
1712 if (new_cfqq)
1713 kmem_cache_free(cfq_pool, new_cfqq);
1715 return cfqq;
1718 static struct cfq_queue **
1719 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
1721 switch (ioprio_class) {
1722 case IOPRIO_CLASS_RT:
1723 return &cfqd->async_cfqq[0][ioprio];
1724 case IOPRIO_CLASS_BE:
1725 return &cfqd->async_cfqq[1][ioprio];
1726 case IOPRIO_CLASS_IDLE:
1727 return &cfqd->async_idle_cfqq;
1728 default:
1729 BUG();
1733 static struct cfq_queue *
1734 cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
1735 gfp_t gfp_mask)
1737 const int ioprio = task_ioprio(ioc);
1738 const int ioprio_class = task_ioprio_class(ioc);
1739 struct cfq_queue **async_cfqq = NULL;
1740 struct cfq_queue *cfqq = NULL;
1742 if (!is_sync) {
1743 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
1744 cfqq = *async_cfqq;
1747 if (!cfqq)
1748 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
1751 * pin the queue now that it's allocated, scheduler exit will prune it
1753 if (!is_sync && !(*async_cfqq)) {
1754 atomic_inc(&cfqq->ref);
1755 *async_cfqq = cfqq;
1758 atomic_inc(&cfqq->ref);
1759 return cfqq;
1763 * We drop cfq io contexts lazily, so we may find a dead one.
1765 static void
1766 cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
1767 struct cfq_io_context *cic)
1769 unsigned long flags;
1771 WARN_ON(!list_empty(&cic->queue_list));
1773 spin_lock_irqsave(&ioc->lock, flags);
1775 BUG_ON(ioc->ioc_data == cic);
1777 radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
1778 hlist_del_rcu(&cic->cic_list);
1779 spin_unlock_irqrestore(&ioc->lock, flags);
1781 cfq_cic_free(cic);
1784 static struct cfq_io_context *
1785 cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
1787 struct cfq_io_context *cic;
1788 unsigned long flags;
1789 void *k;
1791 if (unlikely(!ioc))
1792 return NULL;
1794 rcu_read_lock();
1797 * we maintain a last-hit cache, to avoid browsing over the tree
1799 cic = rcu_dereference(ioc->ioc_data);
1800 if (cic && cic->key == cfqd) {
1801 rcu_read_unlock();
1802 return cic;
1805 do {
1806 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
1807 rcu_read_unlock();
1808 if (!cic)
1809 break;
1810 /* ->key must be copied to avoid race with cfq_exit_queue() */
1811 k = cic->key;
1812 if (unlikely(!k)) {
1813 cfq_drop_dead_cic(cfqd, ioc, cic);
1814 rcu_read_lock();
1815 continue;
1818 spin_lock_irqsave(&ioc->lock, flags);
1819 rcu_assign_pointer(ioc->ioc_data, cic);
1820 spin_unlock_irqrestore(&ioc->lock, flags);
1821 break;
1822 } while (1);
1824 return cic;
1828 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
1829 * the process specific cfq io context when entered from the block layer.
1830 * Also adds the cic to a per-cfqd list, used when this queue is removed.
1832 static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
1833 struct cfq_io_context *cic, gfp_t gfp_mask)
1835 unsigned long flags;
1836 int ret;
1838 ret = radix_tree_preload(gfp_mask);
1839 if (!ret) {
1840 cic->ioc = ioc;
1841 cic->key = cfqd;
1843 spin_lock_irqsave(&ioc->lock, flags);
1844 ret = radix_tree_insert(&ioc->radix_root,
1845 (unsigned long) cfqd, cic);
1846 if (!ret)
1847 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
1848 spin_unlock_irqrestore(&ioc->lock, flags);
1850 radix_tree_preload_end();
1852 if (!ret) {
1853 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1854 list_add(&cic->queue_list, &cfqd->cic_list);
1855 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1859 if (ret)
1860 printk(KERN_ERR "cfq: cic link failed!\n");
1862 return ret;
1866 * Setup general io context and cfq io context. There can be several cfq
1867 * io contexts per general io context, if this process is doing io to more
1868 * than one device managed by cfq.
1870 static struct cfq_io_context *
1871 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1873 struct io_context *ioc = NULL;
1874 struct cfq_io_context *cic;
1876 might_sleep_if(gfp_mask & __GFP_WAIT);
1878 ioc = get_io_context(gfp_mask, cfqd->queue->node);
1879 if (!ioc)
1880 return NULL;
1882 cic = cfq_cic_lookup(cfqd, ioc);
1883 if (cic)
1884 goto out;
1886 cic = cfq_alloc_io_context(cfqd, gfp_mask);
1887 if (cic == NULL)
1888 goto err;
1890 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
1891 goto err_free;
1893 out:
1894 smp_read_barrier_depends();
1895 if (unlikely(ioc->ioprio_changed))
1896 cfq_ioc_set_ioprio(ioc);
1898 return cic;
1899 err_free:
1900 cfq_cic_free(cic);
1901 err:
1902 put_io_context(ioc);
1903 return NULL;
1906 static void
1907 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1909 unsigned long elapsed = jiffies - cic->last_end_request;
1910 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
1912 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1913 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1914 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1917 static void
1918 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
1919 struct request *rq)
1921 sector_t sdist;
1922 u64 total;
1924 if (!cic->last_request_pos)
1925 sdist = 0;
1926 else if (cic->last_request_pos < blk_rq_pos(rq))
1927 sdist = blk_rq_pos(rq) - cic->last_request_pos;
1928 else
1929 sdist = cic->last_request_pos - blk_rq_pos(rq);
1932 * Don't allow the seek distance to get too large from the
1933 * odd fragment, pagein, etc
1935 if (cic->seek_samples <= 60) /* second&third seek */
1936 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024);
1937 else
1938 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64);
1940 cic->seek_samples = (7*cic->seek_samples + 256) / 8;
1941 cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
1942 total = cic->seek_total + (cic->seek_samples/2);
1943 do_div(total, cic->seek_samples);
1944 cic->seek_mean = (sector_t)total;
1948 * Disable idle window if the process thinks too long or seeks so much that
1949 * it doesn't matter
1951 static void
1952 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1953 struct cfq_io_context *cic)
1955 int old_idle, enable_idle;
1958 * Don't idle for async or idle io prio class
1960 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
1961 return;
1963 enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
1965 if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
1966 (cfqd->hw_tag && CIC_SEEKY(cic)))
1967 enable_idle = 0;
1968 else if (sample_valid(cic->ttime_samples)) {
1969 if (cic->ttime_mean > cfqd->cfq_slice_idle)
1970 enable_idle = 0;
1971 else
1972 enable_idle = 1;
1975 if (old_idle != enable_idle) {
1976 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
1977 if (enable_idle)
1978 cfq_mark_cfqq_idle_window(cfqq);
1979 else
1980 cfq_clear_cfqq_idle_window(cfqq);
1985 * Check if new_cfqq should preempt the currently active queue. Return 0 for
1986 * no or if we aren't sure, a 1 will cause a preempt.
1988 static int
1989 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1990 struct request *rq)
1992 struct cfq_queue *cfqq;
1994 cfqq = cfqd->active_queue;
1995 if (!cfqq)
1996 return 0;
1998 if (cfq_slice_used(cfqq))
1999 return 1;
2001 if (cfq_class_idle(new_cfqq))
2002 return 0;
2004 if (cfq_class_idle(cfqq))
2005 return 1;
2008 * if the new request is sync, but the currently running queue is
2009 * not, let the sync request have priority.
2011 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
2012 return 1;
2015 * So both queues are sync. Let the new request get disk time if
2016 * it's a metadata request and the current queue is doing regular IO.
2018 if (rq_is_meta(rq) && !cfqq->meta_pending)
2019 return 1;
2022 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
2024 if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
2025 return 1;
2027 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
2028 return 0;
2031 * if this request is as-good as one we would expect from the
2032 * current cfqq, let it preempt
2034 if (cfq_rq_close(cfqd, rq))
2035 return 1;
2037 return 0;
2041 * cfqq preempts the active queue. if we allowed preempt with no slice left,
2042 * let it have half of its nominal slice.
2044 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2046 cfq_log_cfqq(cfqd, cfqq, "preempt");
2047 cfq_slice_expired(cfqd, 1);
2050 * Put the new queue at the front of the of the current list,
2051 * so we know that it will be selected next.
2053 BUG_ON(!cfq_cfqq_on_rr(cfqq));
2055 cfq_service_tree_add(cfqd, cfqq, 1);
2057 cfqq->slice_end = 0;
2058 cfq_mark_cfqq_slice_new(cfqq);
2062 * Called when a new fs request (rq) is added (to cfqq). Check if there's
2063 * something we should do about it
2065 static void
2066 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2067 struct request *rq)
2069 struct cfq_io_context *cic = RQ_CIC(rq);
2071 cfqd->rq_queued++;
2072 if (rq_is_meta(rq))
2073 cfqq->meta_pending++;
2075 cfq_update_io_thinktime(cfqd, cic);
2076 cfq_update_io_seektime(cfqd, cic, rq);
2077 cfq_update_idle_window(cfqd, cfqq, cic);
2079 cic->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
2081 if (cfqq == cfqd->active_queue) {
2083 * Remember that we saw a request from this process, but
2084 * don't start queuing just yet. Otherwise we risk seeing lots
2085 * of tiny requests, because we disrupt the normal plugging
2086 * and merging. If the request is already larger than a single
2087 * page, let it rip immediately. For that case we assume that
2088 * merging is already done. Ditto for a busy system that
2089 * has other work pending, don't risk delaying until the
2090 * idle timer unplug to continue working.
2092 if (cfq_cfqq_wait_request(cfqq)) {
2093 if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
2094 cfqd->busy_queues > 1) {
2095 del_timer(&cfqd->idle_slice_timer);
2096 __blk_run_queue(cfqd->queue);
2098 cfq_mark_cfqq_must_dispatch(cfqq);
2100 } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
2102 * not the active queue - expire current slice if it is
2103 * idle and has expired it's mean thinktime or this new queue
2104 * has some old slice time left and is of higher priority or
2105 * this new queue is RT and the current one is BE
2107 cfq_preempt_queue(cfqd, cfqq);
2108 __blk_run_queue(cfqd->queue);
2112 static void cfq_insert_request(struct request_queue *q, struct request *rq)
2114 struct cfq_data *cfqd = q->elevator->elevator_data;
2115 struct cfq_queue *cfqq = RQ_CFQQ(rq);
2117 cfq_log_cfqq(cfqd, cfqq, "insert_request");
2118 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
2120 cfq_add_rq_rb(rq);
2122 list_add_tail(&rq->queuelist, &cfqq->fifo);
2124 cfq_rq_enqueued(cfqd, cfqq, rq);
2128 * Update hw_tag based on peak queue depth over 50 samples under
2129 * sufficient load.
2131 static void cfq_update_hw_tag(struct cfq_data *cfqd)
2133 if (cfqd->rq_in_driver > cfqd->rq_in_driver_peak)
2134 cfqd->rq_in_driver_peak = cfqd->rq_in_driver;
2136 if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
2137 cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
2138 return;
2140 if (cfqd->hw_tag_samples++ < 50)
2141 return;
2143 if (cfqd->rq_in_driver_peak >= CFQ_HW_QUEUE_MIN)
2144 cfqd->hw_tag = 1;
2145 else
2146 cfqd->hw_tag = 0;
2148 cfqd->hw_tag_samples = 0;
2149 cfqd->rq_in_driver_peak = 0;
2152 static void cfq_completed_request(struct request_queue *q, struct request *rq)
2154 struct cfq_queue *cfqq = RQ_CFQQ(rq);
2155 struct cfq_data *cfqd = cfqq->cfqd;
2156 const int sync = rq_is_sync(rq);
2157 unsigned long now;
2159 now = jiffies;
2160 cfq_log_cfqq(cfqd, cfqq, "complete");
2162 cfq_update_hw_tag(cfqd);
2164 WARN_ON(!cfqd->rq_in_driver);
2165 WARN_ON(!cfqq->dispatched);
2166 cfqd->rq_in_driver--;
2167 cfqq->dispatched--;
2169 if (cfq_cfqq_sync(cfqq))
2170 cfqd->sync_flight--;
2172 if (sync)
2173 RQ_CIC(rq)->last_end_request = now;
2176 * If this is the active queue, check if it needs to be expired,
2177 * or if we want to idle in case it has no pending requests.
2179 if (cfqd->active_queue == cfqq) {
2180 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
2182 if (cfq_cfqq_slice_new(cfqq)) {
2183 cfq_set_prio_slice(cfqd, cfqq);
2184 cfq_clear_cfqq_slice_new(cfqq);
2187 * If there are no requests waiting in this queue, and
2188 * there are other queues ready to issue requests, AND
2189 * those other queues are issuing requests within our
2190 * mean seek distance, give them a chance to run instead
2191 * of idling.
2193 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
2194 cfq_slice_expired(cfqd, 1);
2195 else if (cfqq_empty && !cfq_close_cooperator(cfqd, cfqq, 1) &&
2196 sync && !rq_noidle(rq))
2197 cfq_arm_slice_timer(cfqd);
2200 if (!cfqd->rq_in_driver)
2201 cfq_schedule_dispatch(cfqd);
2205 * we temporarily boost lower priority queues if they are holding fs exclusive
2206 * resources. they are boosted to normal prio (CLASS_BE/4)
2208 static void cfq_prio_boost(struct cfq_queue *cfqq)
2210 if (has_fs_excl()) {
2212 * boost idle prio on transactions that would lock out other
2213 * users of the filesystem
2215 if (cfq_class_idle(cfqq))
2216 cfqq->ioprio_class = IOPRIO_CLASS_BE;
2217 if (cfqq->ioprio > IOPRIO_NORM)
2218 cfqq->ioprio = IOPRIO_NORM;
2219 } else {
2221 * check if we need to unboost the queue
2223 if (cfqq->ioprio_class != cfqq->org_ioprio_class)
2224 cfqq->ioprio_class = cfqq->org_ioprio_class;
2225 if (cfqq->ioprio != cfqq->org_ioprio)
2226 cfqq->ioprio = cfqq->org_ioprio;
2230 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
2232 if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
2233 !cfq_cfqq_must_alloc_slice(cfqq)) {
2234 cfq_mark_cfqq_must_alloc_slice(cfqq);
2235 return ELV_MQUEUE_MUST;
2238 return ELV_MQUEUE_MAY;
2241 static int cfq_may_queue(struct request_queue *q, int rw)
2243 struct cfq_data *cfqd = q->elevator->elevator_data;
2244 struct task_struct *tsk = current;
2245 struct cfq_io_context *cic;
2246 struct cfq_queue *cfqq;
2249 * don't force setup of a queue from here, as a call to may_queue
2250 * does not necessarily imply that a request actually will be queued.
2251 * so just lookup a possibly existing queue, or return 'may queue'
2252 * if that fails
2254 cic = cfq_cic_lookup(cfqd, tsk->io_context);
2255 if (!cic)
2256 return ELV_MQUEUE_MAY;
2258 cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
2259 if (cfqq) {
2260 cfq_init_prio_data(cfqq, cic->ioc);
2261 cfq_prio_boost(cfqq);
2263 return __cfq_may_queue(cfqq);
2266 return ELV_MQUEUE_MAY;
2270 * queue lock held here
2272 static void cfq_put_request(struct request *rq)
2274 struct cfq_queue *cfqq = RQ_CFQQ(rq);
2276 if (cfqq) {
2277 const int rw = rq_data_dir(rq);
2279 BUG_ON(!cfqq->allocated[rw]);
2280 cfqq->allocated[rw]--;
2282 put_io_context(RQ_CIC(rq)->ioc);
2284 rq->elevator_private = NULL;
2285 rq->elevator_private2 = NULL;
2287 cfq_put_queue(cfqq);
2292 * Allocate cfq data structures associated with this request.
2294 static int
2295 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
2297 struct cfq_data *cfqd = q->elevator->elevator_data;
2298 struct cfq_io_context *cic;
2299 const int rw = rq_data_dir(rq);
2300 const int is_sync = rq_is_sync(rq);
2301 struct cfq_queue *cfqq;
2302 unsigned long flags;
2304 might_sleep_if(gfp_mask & __GFP_WAIT);
2306 cic = cfq_get_io_context(cfqd, gfp_mask);
2308 spin_lock_irqsave(q->queue_lock, flags);
2310 if (!cic)
2311 goto queue_fail;
2313 cfqq = cic_to_cfqq(cic, is_sync);
2314 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2315 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
2316 cic_set_cfqq(cic, cfqq, is_sync);
2319 cfqq->allocated[rw]++;
2320 cfq_clear_cfqq_must_alloc(cfqq);
2321 atomic_inc(&cfqq->ref);
2323 spin_unlock_irqrestore(q->queue_lock, flags);
2325 rq->elevator_private = cic;
2326 rq->elevator_private2 = cfqq;
2327 return 0;
2329 queue_fail:
2330 if (cic)
2331 put_io_context(cic->ioc);
2333 cfq_schedule_dispatch(cfqd);
2334 spin_unlock_irqrestore(q->queue_lock, flags);
2335 cfq_log(cfqd, "set_request fail");
2336 return 1;
2339 static void cfq_kick_queue(struct work_struct *work)
2341 struct cfq_data *cfqd =
2342 container_of(work, struct cfq_data, unplug_work);
2343 struct request_queue *q = cfqd->queue;
2345 spin_lock_irq(q->queue_lock);
2346 __blk_run_queue(cfqd->queue);
2347 spin_unlock_irq(q->queue_lock);
2351 * Timer running if the active_queue is currently idling inside its time slice
2353 static void cfq_idle_slice_timer(unsigned long data)
2355 struct cfq_data *cfqd = (struct cfq_data *) data;
2356 struct cfq_queue *cfqq;
2357 unsigned long flags;
2358 int timed_out = 1;
2360 cfq_log(cfqd, "idle timer fired");
2362 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2364 cfqq = cfqd->active_queue;
2365 if (cfqq) {
2366 timed_out = 0;
2369 * We saw a request before the queue expired, let it through
2371 if (cfq_cfqq_must_dispatch(cfqq))
2372 goto out_kick;
2375 * expired
2377 if (cfq_slice_used(cfqq))
2378 goto expire;
2381 * only expire and reinvoke request handler, if there are
2382 * other queues with pending requests
2384 if (!cfqd->busy_queues)
2385 goto out_cont;
2388 * not expired and it has a request pending, let it dispatch
2390 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
2391 goto out_kick;
2393 expire:
2394 cfq_slice_expired(cfqd, timed_out);
2395 out_kick:
2396 cfq_schedule_dispatch(cfqd);
2397 out_cont:
2398 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2401 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
2403 del_timer_sync(&cfqd->idle_slice_timer);
2404 cancel_work_sync(&cfqd->unplug_work);
2407 static void cfq_put_async_queues(struct cfq_data *cfqd)
2409 int i;
2411 for (i = 0; i < IOPRIO_BE_NR; i++) {
2412 if (cfqd->async_cfqq[0][i])
2413 cfq_put_queue(cfqd->async_cfqq[0][i]);
2414 if (cfqd->async_cfqq[1][i])
2415 cfq_put_queue(cfqd->async_cfqq[1][i]);
2418 if (cfqd->async_idle_cfqq)
2419 cfq_put_queue(cfqd->async_idle_cfqq);
2422 static void cfq_exit_queue(struct elevator_queue *e)
2424 struct cfq_data *cfqd = e->elevator_data;
2425 struct request_queue *q = cfqd->queue;
2427 cfq_shutdown_timer_wq(cfqd);
2429 spin_lock_irq(q->queue_lock);
2431 if (cfqd->active_queue)
2432 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
2434 while (!list_empty(&cfqd->cic_list)) {
2435 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2436 struct cfq_io_context,
2437 queue_list);
2439 __cfq_exit_single_io_context(cfqd, cic);
2442 cfq_put_async_queues(cfqd);
2444 spin_unlock_irq(q->queue_lock);
2446 cfq_shutdown_timer_wq(cfqd);
2448 kfree(cfqd);
2451 static void *cfq_init_queue(struct request_queue *q)
2453 struct cfq_data *cfqd;
2454 int i;
2456 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
2457 if (!cfqd)
2458 return NULL;
2460 cfqd->service_tree = CFQ_RB_ROOT;
2463 * Not strictly needed (since RB_ROOT just clears the node and we
2464 * zeroed cfqd on alloc), but better be safe in case someone decides
2465 * to add magic to the rb code
2467 for (i = 0; i < CFQ_PRIO_LISTS; i++)
2468 cfqd->prio_trees[i] = RB_ROOT;
2471 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
2472 * Grab a permanent reference to it, so that the normal code flow
2473 * will not attempt to free it.
2475 cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
2476 atomic_inc(&cfqd->oom_cfqq.ref);
2478 INIT_LIST_HEAD(&cfqd->cic_list);
2480 cfqd->queue = q;
2482 init_timer(&cfqd->idle_slice_timer);
2483 cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2484 cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2486 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
2488 cfqd->cfq_quantum = cfq_quantum;
2489 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2490 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2491 cfqd->cfq_back_max = cfq_back_max;
2492 cfqd->cfq_back_penalty = cfq_back_penalty;
2493 cfqd->cfq_slice[0] = cfq_slice_async;
2494 cfqd->cfq_slice[1] = cfq_slice_sync;
2495 cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2496 cfqd->cfq_slice_idle = cfq_slice_idle;
2497 cfqd->hw_tag = 1;
2499 return cfqd;
2502 static void cfq_slab_kill(void)
2505 * Caller already ensured that pending RCU callbacks are completed,
2506 * so we should have no busy allocations at this point.
2508 if (cfq_pool)
2509 kmem_cache_destroy(cfq_pool);
2510 if (cfq_ioc_pool)
2511 kmem_cache_destroy(cfq_ioc_pool);
2514 static int __init cfq_slab_setup(void)
2516 cfq_pool = KMEM_CACHE(cfq_queue, 0);
2517 if (!cfq_pool)
2518 goto fail;
2520 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
2521 if (!cfq_ioc_pool)
2522 goto fail;
2524 return 0;
2525 fail:
2526 cfq_slab_kill();
2527 return -ENOMEM;
2531 * sysfs parts below -->
2533 static ssize_t
2534 cfq_var_show(unsigned int var, char *page)
2536 return sprintf(page, "%d\n", var);
2539 static ssize_t
2540 cfq_var_store(unsigned int *var, const char *page, size_t count)
2542 char *p = (char *) page;
2544 *var = simple_strtoul(p, &p, 10);
2545 return count;
2548 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
2549 static ssize_t __FUNC(struct elevator_queue *e, char *page) \
2551 struct cfq_data *cfqd = e->elevator_data; \
2552 unsigned int __data = __VAR; \
2553 if (__CONV) \
2554 __data = jiffies_to_msecs(__data); \
2555 return cfq_var_show(__data, (page)); \
2557 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
2558 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2559 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
2560 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
2561 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
2562 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2563 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2564 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2565 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
2566 #undef SHOW_FUNCTION
2568 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
2569 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
2571 struct cfq_data *cfqd = e->elevator_data; \
2572 unsigned int __data; \
2573 int ret = cfq_var_store(&__data, (page), count); \
2574 if (__data < (MIN)) \
2575 __data = (MIN); \
2576 else if (__data > (MAX)) \
2577 __data = (MAX); \
2578 if (__CONV) \
2579 *(__PTR) = msecs_to_jiffies(__data); \
2580 else \
2581 *(__PTR) = __data; \
2582 return ret; \
2584 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
2585 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
2586 UINT_MAX, 1);
2587 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
2588 UINT_MAX, 1);
2589 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
2590 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
2591 UINT_MAX, 0);
2592 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2593 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2594 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
2595 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
2596 UINT_MAX, 0);
2597 #undef STORE_FUNCTION
2599 #define CFQ_ATTR(name) \
2600 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2602 static struct elv_fs_entry cfq_attrs[] = {
2603 CFQ_ATTR(quantum),
2604 CFQ_ATTR(fifo_expire_sync),
2605 CFQ_ATTR(fifo_expire_async),
2606 CFQ_ATTR(back_seek_max),
2607 CFQ_ATTR(back_seek_penalty),
2608 CFQ_ATTR(slice_sync),
2609 CFQ_ATTR(slice_async),
2610 CFQ_ATTR(slice_async_rq),
2611 CFQ_ATTR(slice_idle),
2612 __ATTR_NULL
2615 static struct elevator_type iosched_cfq = {
2616 .ops = {
2617 .elevator_merge_fn = cfq_merge,
2618 .elevator_merged_fn = cfq_merged_request,
2619 .elevator_merge_req_fn = cfq_merged_requests,
2620 .elevator_allow_merge_fn = cfq_allow_merge,
2621 .elevator_dispatch_fn = cfq_dispatch_requests,
2622 .elevator_add_req_fn = cfq_insert_request,
2623 .elevator_activate_req_fn = cfq_activate_request,
2624 .elevator_deactivate_req_fn = cfq_deactivate_request,
2625 .elevator_queue_empty_fn = cfq_queue_empty,
2626 .elevator_completed_req_fn = cfq_completed_request,
2627 .elevator_former_req_fn = elv_rb_former_request,
2628 .elevator_latter_req_fn = elv_rb_latter_request,
2629 .elevator_set_req_fn = cfq_set_request,
2630 .elevator_put_req_fn = cfq_put_request,
2631 .elevator_may_queue_fn = cfq_may_queue,
2632 .elevator_init_fn = cfq_init_queue,
2633 .elevator_exit_fn = cfq_exit_queue,
2634 .trim = cfq_free_io_context,
2636 .elevator_attrs = cfq_attrs,
2637 .elevator_name = "cfq",
2638 .elevator_owner = THIS_MODULE,
2641 static int __init cfq_init(void)
2644 * could be 0 on HZ < 1000 setups
2646 if (!cfq_slice_async)
2647 cfq_slice_async = 1;
2648 if (!cfq_slice_idle)
2649 cfq_slice_idle = 1;
2651 if (cfq_slab_setup())
2652 return -ENOMEM;
2654 elv_register(&iosched_cfq);
2656 return 0;
2659 static void __exit cfq_exit(void)
2661 DECLARE_COMPLETION_ONSTACK(all_gone);
2662 elv_unregister(&iosched_cfq);
2663 ioc_gone = &all_gone;
2664 /* ioc_gone's update must be visible before reading ioc_count */
2665 smp_wmb();
2668 * this also protects us from entering cfq_slab_kill() with
2669 * pending RCU callbacks
2671 if (elv_ioc_count_read(ioc_count))
2672 wait_for_completion(&all_gone);
2673 cfq_slab_kill();
2676 module_init(cfq_init);
2677 module_exit(cfq_exit);
2679 MODULE_AUTHOR("Jens Axboe");
2680 MODULE_LICENSE("GPL");
2681 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");