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>
9 #include <linux/module.h>
10 #include <linux/blkdev.h>
11 #include <linux/elevator.h>
12 #include <linux/hash.h>
13 #include <linux/rbtree.h>
14 #include <linux/ioprio.h>
19 static const int cfq_quantum
= 4; /* max queue in one round of service */
20 static const int cfq_fifo_expire
[2] = { HZ
/ 4, HZ
/ 8 };
21 static const int cfq_back_max
= 16 * 1024; /* maximum backwards seek, in KiB */
22 static const int cfq_back_penalty
= 2; /* penalty of a backwards seek */
24 static const int cfq_slice_sync
= HZ
/ 10;
25 static int cfq_slice_async
= HZ
/ 25;
26 static const int cfq_slice_async_rq
= 2;
27 static int cfq_slice_idle
= HZ
/ 125;
29 #define CFQ_IDLE_GRACE (HZ / 10)
30 #define CFQ_SLICE_SCALE (5)
32 #define CFQ_KEY_ASYNC (0)
35 * for the hash of cfqq inside the cfqd
37 #define CFQ_QHASH_SHIFT 6
38 #define CFQ_QHASH_ENTRIES (1 << CFQ_QHASH_SHIFT)
39 #define list_entry_qhash(entry) hlist_entry((entry), struct cfq_queue, cfq_hash)
41 #define list_entry_cfqq(ptr) list_entry((ptr), struct cfq_queue, cfq_list)
43 #define RQ_CIC(rq) ((struct cfq_io_context*)(rq)->elevator_private)
44 #define RQ_CFQQ(rq) ((rq)->elevator_private2)
46 static struct kmem_cache
*cfq_pool
;
47 static struct kmem_cache
*cfq_ioc_pool
;
49 static DEFINE_PER_CPU(unsigned long, ioc_count
);
50 static struct completion
*ioc_gone
;
52 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
53 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
54 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
59 #define cfq_cfqq_dispatched(cfqq) \
60 ((cfqq)->on_dispatch[ASYNC] + (cfqq)->on_dispatch[SYNC])
62 #define cfq_cfqq_class_sync(cfqq) ((cfqq)->key != CFQ_KEY_ASYNC)
64 #define cfq_cfqq_sync(cfqq) \
65 (cfq_cfqq_class_sync(cfqq) || (cfqq)->on_dispatch[SYNC])
67 #define sample_valid(samples) ((samples) > 80)
70 * Per block device queue structure
73 request_queue_t
*queue
;
76 * rr list of queues with requests and the count of them
78 struct list_head rr_list
[CFQ_PRIO_LISTS
];
79 struct list_head busy_rr
;
80 struct list_head cur_rr
;
81 struct list_head idle_rr
;
82 unsigned int busy_queues
;
87 struct hlist_head
*cfq_hash
;
93 * idle window management
95 struct timer_list idle_slice_timer
;
96 struct work_struct unplug_work
;
98 struct cfq_queue
*active_queue
;
99 struct cfq_io_context
*active_cic
;
100 int cur_prio
, cur_end_prio
;
101 unsigned int dispatch_slice
;
103 struct timer_list idle_class_timer
;
105 sector_t last_sector
;
106 unsigned long last_end_request
;
109 * tunables, see top of file
111 unsigned int cfq_quantum
;
112 unsigned int cfq_fifo_expire
[2];
113 unsigned int cfq_back_penalty
;
114 unsigned int cfq_back_max
;
115 unsigned int cfq_slice
[2];
116 unsigned int cfq_slice_async_rq
;
117 unsigned int cfq_slice_idle
;
119 struct list_head cic_list
;
123 * Per process-grouping structure
126 /* reference count */
128 /* parent cfq_data */
129 struct cfq_data
*cfqd
;
130 /* cfqq lookup hash */
131 struct hlist_node cfq_hash
;
134 /* member of the rr/busy/cur/idle cfqd list */
135 struct list_head cfq_list
;
136 /* sorted list of pending requests */
137 struct rb_root sort_list
;
138 /* if fifo isn't expired, next request to serve */
139 struct request
*next_rq
;
140 /* requests queued in sort_list */
142 /* currently allocated requests */
144 /* pending metadata requests */
146 /* fifo list of requests in sort_list */
147 struct list_head fifo
;
149 unsigned long slice_end
;
150 unsigned long slice_left
;
151 unsigned long service_last
;
153 /* number of requests that are on the dispatch list */
156 /* io prio of this group */
157 unsigned short ioprio
, org_ioprio
;
158 unsigned short ioprio_class
, org_ioprio_class
;
160 /* various state flags, see below */
164 enum cfqq_state_flags
{
165 CFQ_CFQQ_FLAG_on_rr
= 0, /* on round-robin busy list */
166 CFQ_CFQQ_FLAG_wait_request
, /* waiting for a request */
167 CFQ_CFQQ_FLAG_must_alloc
, /* must be allowed rq alloc */
168 CFQ_CFQQ_FLAG_must_alloc_slice
, /* per-slice must_alloc flag */
169 CFQ_CFQQ_FLAG_must_dispatch
, /* must dispatch, even if expired */
170 CFQ_CFQQ_FLAG_fifo_expire
, /* FIFO checked in this slice */
171 CFQ_CFQQ_FLAG_idle_window
, /* slice idling enabled */
172 CFQ_CFQQ_FLAG_prio_changed
, /* task priority has changed */
173 CFQ_CFQQ_FLAG_queue_new
, /* queue never been serviced */
174 CFQ_CFQQ_FLAG_slice_new
, /* no requests dispatched in slice */
177 #define CFQ_CFQQ_FNS(name) \
178 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
180 cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
182 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
184 cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
186 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
188 return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
192 CFQ_CFQQ_FNS(wait_request
);
193 CFQ_CFQQ_FNS(must_alloc
);
194 CFQ_CFQQ_FNS(must_alloc_slice
);
195 CFQ_CFQQ_FNS(must_dispatch
);
196 CFQ_CFQQ_FNS(fifo_expire
);
197 CFQ_CFQQ_FNS(idle_window
);
198 CFQ_CFQQ_FNS(prio_changed
);
199 CFQ_CFQQ_FNS(queue_new
);
200 CFQ_CFQQ_FNS(slice_new
);
203 static struct cfq_queue
*cfq_find_cfq_hash(struct cfq_data
*, unsigned int, unsigned short);
204 static void cfq_dispatch_insert(request_queue_t
*, struct request
*);
205 static struct cfq_queue
*cfq_get_queue(struct cfq_data
*cfqd
, unsigned int key
, struct task_struct
*tsk
, gfp_t gfp_mask
);
208 * scheduler run of queue, if there are requests pending and no one in the
209 * driver that will restart queueing
211 static inline void cfq_schedule_dispatch(struct cfq_data
*cfqd
)
213 if (cfqd
->busy_queues
)
214 kblockd_schedule_work(&cfqd
->unplug_work
);
217 static int cfq_queue_empty(request_queue_t
*q
)
219 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
221 return !cfqd
->busy_queues
;
224 static inline pid_t
cfq_queue_pid(struct task_struct
*task
, int rw
, int is_sync
)
227 * Use the per-process queue, for read requests and syncronous writes
229 if (!(rw
& REQ_RW
) || is_sync
)
232 return CFQ_KEY_ASYNC
;
236 * Scale schedule slice based on io priority. Use the sync time slice only
237 * if a queue is marked sync and has sync io queued. A sync queue with async
238 * io only, should not get full sync slice length.
241 cfq_prio_to_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
243 const int base_slice
= cfqd
->cfq_slice
[cfq_cfqq_sync(cfqq
)];
245 WARN_ON(cfqq
->ioprio
>= IOPRIO_BE_NR
);
247 return base_slice
+ (base_slice
/CFQ_SLICE_SCALE
* (4 - cfqq
->ioprio
));
251 cfq_set_prio_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
253 cfqq
->slice_end
= cfq_prio_to_slice(cfqd
, cfqq
) + jiffies
;
257 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
258 * isn't valid until the first request from the dispatch is activated
259 * and the slice time set.
261 static inline int cfq_slice_used(struct cfq_queue
*cfqq
)
263 if (cfq_cfqq_slice_new(cfqq
))
265 if (time_before(jiffies
, cfqq
->slice_end
))
272 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
273 * We choose the request that is closest to the head right now. Distance
274 * behind the head is penalized and only allowed to a certain extent.
276 static struct request
*
277 cfq_choose_req(struct cfq_data
*cfqd
, struct request
*rq1
, struct request
*rq2
)
279 sector_t last
, s1
, s2
, d1
= 0, d2
= 0;
280 unsigned long back_max
;
281 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
282 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
283 unsigned wrap
= 0; /* bit mask: requests behind the disk head? */
285 if (rq1
== NULL
|| rq1
== rq2
)
290 if (rq_is_sync(rq1
) && !rq_is_sync(rq2
))
292 else if (rq_is_sync(rq2
) && !rq_is_sync(rq1
))
294 if (rq_is_meta(rq1
) && !rq_is_meta(rq2
))
296 else if (rq_is_meta(rq2
) && !rq_is_meta(rq1
))
302 last
= cfqd
->last_sector
;
305 * by definition, 1KiB is 2 sectors
307 back_max
= cfqd
->cfq_back_max
* 2;
310 * Strict one way elevator _except_ in the case where we allow
311 * short backward seeks which are biased as twice the cost of a
312 * similar forward seek.
316 else if (s1
+ back_max
>= last
)
317 d1
= (last
- s1
) * cfqd
->cfq_back_penalty
;
319 wrap
|= CFQ_RQ1_WRAP
;
323 else if (s2
+ back_max
>= last
)
324 d2
= (last
- s2
) * cfqd
->cfq_back_penalty
;
326 wrap
|= CFQ_RQ2_WRAP
;
328 /* Found required data */
331 * By doing switch() on the bit mask "wrap" we avoid having to
332 * check two variables for all permutations: --> faster!
335 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
351 case (CFQ_RQ1_WRAP
|CFQ_RQ2_WRAP
): /* both rqs wrapped */
354 * Since both rqs are wrapped,
355 * start with the one that's further behind head
356 * (--> only *one* back seek required),
357 * since back seek takes more time than forward.
367 * would be nice to take fifo expire time into account as well
369 static struct request
*
370 cfq_find_next_rq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
371 struct request
*last
)
373 struct rb_node
*rbnext
= rb_next(&last
->rb_node
);
374 struct rb_node
*rbprev
= rb_prev(&last
->rb_node
);
375 struct request
*next
= NULL
, *prev
= NULL
;
377 BUG_ON(RB_EMPTY_NODE(&last
->rb_node
));
380 prev
= rb_entry_rq(rbprev
);
383 next
= rb_entry_rq(rbnext
);
385 rbnext
= rb_first(&cfqq
->sort_list
);
386 if (rbnext
&& rbnext
!= &last
->rb_node
)
387 next
= rb_entry_rq(rbnext
);
390 return cfq_choose_req(cfqd
, next
, prev
);
393 static void cfq_resort_rr_list(struct cfq_queue
*cfqq
, int preempted
)
395 struct cfq_data
*cfqd
= cfqq
->cfqd
;
396 struct list_head
*list
, *n
;
397 struct cfq_queue
*__cfqq
;
400 * Resorting requires the cfqq to be on the RR list already.
402 if (!cfq_cfqq_on_rr(cfqq
))
405 list_del(&cfqq
->cfq_list
);
407 if (cfq_class_rt(cfqq
))
408 list
= &cfqd
->cur_rr
;
409 else if (cfq_class_idle(cfqq
))
410 list
= &cfqd
->idle_rr
;
413 * if cfqq has requests in flight, don't allow it to be
414 * found in cfq_set_active_queue before it has finished them.
415 * this is done to increase fairness between a process that
416 * has lots of io pending vs one that only generates one
417 * sporadically or synchronously
419 if (cfq_cfqq_dispatched(cfqq
))
420 list
= &cfqd
->busy_rr
;
422 list
= &cfqd
->rr_list
[cfqq
->ioprio
];
425 if (preempted
|| cfq_cfqq_queue_new(cfqq
)) {
427 * If this queue was preempted or is new (never been serviced),
428 * let it be added first for fairness but beind other new
432 while (n
->next
!= list
) {
433 __cfqq
= list_entry_cfqq(n
->next
);
434 if (!cfq_cfqq_queue_new(__cfqq
))
439 list_add_tail(&cfqq
->cfq_list
, n
);
440 } else if (!cfq_cfqq_class_sync(cfqq
)) {
442 * async queue always goes to the end. this wont be overly
443 * unfair to writes, as the sort of the sync queue wont be
444 * allowed to pass the async queue again.
446 list_add_tail(&cfqq
->cfq_list
, list
);
449 * sort by last service, but don't cross a new or async
450 * queue. we don't cross a new queue because it hasn't been
451 * service before, and we don't cross an async queue because
452 * it gets added to the end on expire.
455 while ((n
= n
->prev
) != list
) {
456 struct cfq_queue
*__cfqq
= list_entry_cfqq(n
);
458 if (!cfq_cfqq_class_sync(cfqq
) || !__cfqq
->service_last
)
460 if (time_before(__cfqq
->service_last
, cfqq
->service_last
))
463 list_add(&cfqq
->cfq_list
, n
);
468 * add to busy list of queues for service, trying to be fair in ordering
469 * the pending list according to last request service
472 cfq_add_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
474 BUG_ON(cfq_cfqq_on_rr(cfqq
));
475 cfq_mark_cfqq_on_rr(cfqq
);
478 cfq_resort_rr_list(cfqq
, 0);
482 cfq_del_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
484 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
485 cfq_clear_cfqq_on_rr(cfqq
);
486 list_del_init(&cfqq
->cfq_list
);
488 BUG_ON(!cfqd
->busy_queues
);
493 * rb tree support functions
495 static inline void cfq_del_rq_rb(struct request
*rq
)
497 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
498 struct cfq_data
*cfqd
= cfqq
->cfqd
;
499 const int sync
= rq_is_sync(rq
);
501 BUG_ON(!cfqq
->queued
[sync
]);
502 cfqq
->queued
[sync
]--;
504 elv_rb_del(&cfqq
->sort_list
, rq
);
506 if (cfq_cfqq_on_rr(cfqq
) && RB_EMPTY_ROOT(&cfqq
->sort_list
))
507 cfq_del_cfqq_rr(cfqd
, cfqq
);
510 static void cfq_add_rq_rb(struct request
*rq
)
512 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
513 struct cfq_data
*cfqd
= cfqq
->cfqd
;
514 struct request
*__alias
;
516 cfqq
->queued
[rq_is_sync(rq
)]++;
519 * looks a little odd, but the first insert might return an alias.
520 * if that happens, put the alias on the dispatch list
522 while ((__alias
= elv_rb_add(&cfqq
->sort_list
, rq
)) != NULL
)
523 cfq_dispatch_insert(cfqd
->queue
, __alias
);
525 if (!cfq_cfqq_on_rr(cfqq
))
526 cfq_add_cfqq_rr(cfqd
, cfqq
);
530 cfq_reposition_rq_rb(struct cfq_queue
*cfqq
, struct request
*rq
)
532 elv_rb_del(&cfqq
->sort_list
, rq
);
533 cfqq
->queued
[rq_is_sync(rq
)]--;
537 static struct request
*
538 cfq_find_rq_fmerge(struct cfq_data
*cfqd
, struct bio
*bio
)
540 struct task_struct
*tsk
= current
;
541 pid_t key
= cfq_queue_pid(tsk
, bio_data_dir(bio
), bio_sync(bio
));
542 struct cfq_queue
*cfqq
;
544 cfqq
= cfq_find_cfq_hash(cfqd
, key
, tsk
->ioprio
);
546 sector_t sector
= bio
->bi_sector
+ bio_sectors(bio
);
548 return elv_rb_find(&cfqq
->sort_list
, sector
);
554 static void cfq_activate_request(request_queue_t
*q
, struct request
*rq
)
556 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
558 cfqd
->rq_in_driver
++;
561 * If the depth is larger 1, it really could be queueing. But lets
562 * make the mark a little higher - idling could still be good for
563 * low queueing, and a low queueing number could also just indicate
564 * a SCSI mid layer like behaviour where limit+1 is often seen.
566 if (!cfqd
->hw_tag
&& cfqd
->rq_in_driver
> 4)
570 static void cfq_deactivate_request(request_queue_t
*q
, struct request
*rq
)
572 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
574 WARN_ON(!cfqd
->rq_in_driver
);
575 cfqd
->rq_in_driver
--;
578 static void cfq_remove_request(struct request
*rq
)
580 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
582 if (cfqq
->next_rq
== rq
)
583 cfqq
->next_rq
= cfq_find_next_rq(cfqq
->cfqd
, cfqq
, rq
);
585 list_del_init(&rq
->queuelist
);
588 if (rq_is_meta(rq
)) {
589 WARN_ON(!cfqq
->meta_pending
);
590 cfqq
->meta_pending
--;
595 cfq_merge(request_queue_t
*q
, struct request
**req
, struct bio
*bio
)
597 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
598 struct request
*__rq
;
600 __rq
= cfq_find_rq_fmerge(cfqd
, bio
);
601 if (__rq
&& elv_rq_merge_ok(__rq
, bio
)) {
603 return ELEVATOR_FRONT_MERGE
;
606 return ELEVATOR_NO_MERGE
;
609 static void cfq_merged_request(request_queue_t
*q
, struct request
*req
,
612 if (type
== ELEVATOR_FRONT_MERGE
) {
613 struct cfq_queue
*cfqq
= RQ_CFQQ(req
);
615 cfq_reposition_rq_rb(cfqq
, req
);
620 cfq_merged_requests(request_queue_t
*q
, struct request
*rq
,
621 struct request
*next
)
624 * reposition in fifo if next is older than rq
626 if (!list_empty(&rq
->queuelist
) && !list_empty(&next
->queuelist
) &&
627 time_before(next
->start_time
, rq
->start_time
))
628 list_move(&rq
->queuelist
, &next
->queuelist
);
630 cfq_remove_request(next
);
633 static int cfq_allow_merge(request_queue_t
*q
, struct request
*rq
,
636 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
637 const int rw
= bio_data_dir(bio
);
638 struct cfq_queue
*cfqq
;
642 * Disallow merge of a sync bio into an async request.
644 if ((bio_data_dir(bio
) == READ
|| bio_sync(bio
)) && !rq_is_sync(rq
))
648 * Lookup the cfqq that this bio will be queued with. Allow
649 * merge only if rq is queued there.
651 key
= cfq_queue_pid(current
, rw
, bio_sync(bio
));
652 cfqq
= cfq_find_cfq_hash(cfqd
, key
, current
->ioprio
);
654 if (cfqq
== RQ_CFQQ(rq
))
661 __cfq_set_active_queue(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
665 * stop potential idle class queues waiting service
667 del_timer(&cfqd
->idle_class_timer
);
670 cfqq
->slice_left
= 0;
671 cfq_clear_cfqq_must_alloc_slice(cfqq
);
672 cfq_clear_cfqq_fifo_expire(cfqq
);
673 cfq_mark_cfqq_slice_new(cfqq
);
676 cfqd
->active_queue
= cfqq
;
680 * current cfqq expired its slice (or was too idle), select new one
683 __cfq_slice_expired(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
686 unsigned long now
= jiffies
;
688 if (cfq_cfqq_wait_request(cfqq
))
689 del_timer(&cfqd
->idle_slice_timer
);
691 if (!preempted
&& !cfq_cfqq_dispatched(cfqq
))
692 cfq_schedule_dispatch(cfqd
);
694 cfq_clear_cfqq_must_dispatch(cfqq
);
695 cfq_clear_cfqq_wait_request(cfqq
);
696 cfq_clear_cfqq_queue_new(cfqq
);
699 * store what was left of this slice, if the queue idled out
702 if (cfq_slice_used(cfqq
))
703 cfqq
->slice_left
= cfqq
->slice_end
- now
;
705 cfqq
->slice_left
= 0;
707 cfq_resort_rr_list(cfqq
, preempted
);
709 if (cfqq
== cfqd
->active_queue
)
710 cfqd
->active_queue
= NULL
;
712 if (cfqd
->active_cic
) {
713 put_io_context(cfqd
->active_cic
->ioc
);
714 cfqd
->active_cic
= NULL
;
717 cfqd
->dispatch_slice
= 0;
720 static inline void cfq_slice_expired(struct cfq_data
*cfqd
, int preempted
)
722 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
725 __cfq_slice_expired(cfqd
, cfqq
, preempted
);
738 static int cfq_get_next_prio_level(struct cfq_data
*cfqd
)
747 for (p
= cfqd
->cur_prio
; p
<= cfqd
->cur_end_prio
; p
++) {
748 if (!list_empty(&cfqd
->rr_list
[p
])) {
757 if (++cfqd
->cur_end_prio
== CFQ_PRIO_LISTS
) {
758 cfqd
->cur_end_prio
= 0;
765 if (unlikely(prio
== -1))
768 BUG_ON(prio
>= CFQ_PRIO_LISTS
);
770 list_splice_init(&cfqd
->rr_list
[prio
], &cfqd
->cur_rr
);
772 cfqd
->cur_prio
= prio
+ 1;
773 if (cfqd
->cur_prio
> cfqd
->cur_end_prio
) {
774 cfqd
->cur_end_prio
= cfqd
->cur_prio
;
777 if (cfqd
->cur_end_prio
== CFQ_PRIO_LISTS
) {
779 cfqd
->cur_end_prio
= 0;
785 static struct cfq_queue
*cfq_set_active_queue(struct cfq_data
*cfqd
)
787 struct cfq_queue
*cfqq
= NULL
;
789 if (!list_empty(&cfqd
->cur_rr
) || cfq_get_next_prio_level(cfqd
) != -1) {
791 * if current list is non-empty, grab first entry. if it is
792 * empty, get next prio level and grab first entry then if any
795 cfqq
= list_entry_cfqq(cfqd
->cur_rr
.next
);
796 } else if (!list_empty(&cfqd
->busy_rr
)) {
798 * If no new queues are available, check if the busy list has
799 * some before falling back to idle io.
801 cfqq
= list_entry_cfqq(cfqd
->busy_rr
.next
);
802 } else if (!list_empty(&cfqd
->idle_rr
)) {
804 * if we have idle queues and no rt or be queues had pending
805 * requests, either allow immediate service if the grace period
806 * has passed or arm the idle grace timer
808 unsigned long end
= cfqd
->last_end_request
+ CFQ_IDLE_GRACE
;
810 if (time_after_eq(jiffies
, end
))
811 cfqq
= list_entry_cfqq(cfqd
->idle_rr
.next
);
813 mod_timer(&cfqd
->idle_class_timer
, end
);
816 __cfq_set_active_queue(cfqd
, cfqq
);
820 #define CIC_SEEKY(cic) ((cic)->seek_mean > (128 * 1024))
822 static int cfq_arm_slice_timer(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
825 struct cfq_io_context
*cic
;
828 WARN_ON(!RB_EMPTY_ROOT(&cfqq
->sort_list
));
829 WARN_ON(cfqq
!= cfqd
->active_queue
);
832 * idle is disabled, either manually or by past process history
834 if (!cfqd
->cfq_slice_idle
)
836 if (!cfq_cfqq_idle_window(cfqq
))
839 * task has exited, don't wait
841 cic
= cfqd
->active_cic
;
842 if (!cic
|| !cic
->ioc
->task
)
845 cfq_mark_cfqq_must_dispatch(cfqq
);
846 cfq_mark_cfqq_wait_request(cfqq
);
848 sl
= min(cfqq
->slice_end
- 1, (unsigned long) cfqd
->cfq_slice_idle
);
851 * we don't want to idle for seeks, but we do want to allow
852 * fair distribution of slice time for a process doing back-to-back
853 * seeks. so allow a little bit of time for him to submit a new rq
855 if (sample_valid(cic
->seek_samples
) && CIC_SEEKY(cic
))
856 sl
= min(sl
, msecs_to_jiffies(2));
858 mod_timer(&cfqd
->idle_slice_timer
, jiffies
+ sl
);
862 static void cfq_dispatch_insert(request_queue_t
*q
, struct request
*rq
)
864 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
865 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
867 cfq_remove_request(rq
);
868 cfqq
->on_dispatch
[rq_is_sync(rq
)]++;
869 elv_dispatch_sort(q
, rq
);
871 rq
= list_entry(q
->queue_head
.prev
, struct request
, queuelist
);
872 cfqd
->last_sector
= rq
->sector
+ rq
->nr_sectors
;
876 * return expired entry, or NULL to just start from scratch in rbtree
878 static inline struct request
*cfq_check_fifo(struct cfq_queue
*cfqq
)
880 struct cfq_data
*cfqd
= cfqq
->cfqd
;
884 if (cfq_cfqq_fifo_expire(cfqq
))
886 if (list_empty(&cfqq
->fifo
))
889 fifo
= cfq_cfqq_class_sync(cfqq
);
890 rq
= rq_entry_fifo(cfqq
->fifo
.next
);
892 if (time_after(jiffies
, rq
->start_time
+ cfqd
->cfq_fifo_expire
[fifo
])) {
893 cfq_mark_cfqq_fifo_expire(cfqq
);
901 cfq_prio_to_maxrq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
903 const int base_rq
= cfqd
->cfq_slice_async_rq
;
905 WARN_ON(cfqq
->ioprio
>= IOPRIO_BE_NR
);
907 return 2 * (base_rq
+ base_rq
* (CFQ_PRIO_LISTS
- 1 - cfqq
->ioprio
));
911 * get next queue for service
913 static struct cfq_queue
*cfq_select_queue(struct cfq_data
*cfqd
)
915 struct cfq_queue
*cfqq
;
917 cfqq
= cfqd
->active_queue
;
924 if (!cfq_cfqq_must_dispatch(cfqq
) && cfq_slice_used(cfqq
))
928 * if queue has requests, dispatch one. if not, check if
929 * enough slice is left to wait for one
931 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
))
933 else if (cfq_cfqq_slice_new(cfqq
) || cfq_cfqq_dispatched(cfqq
)) {
936 } else if (cfq_cfqq_class_sync(cfqq
)) {
937 if (cfq_arm_slice_timer(cfqd
, cfqq
))
942 cfq_slice_expired(cfqd
, 0);
944 cfqq
= cfq_set_active_queue(cfqd
);
950 __cfq_dispatch_requests(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
955 BUG_ON(RB_EMPTY_ROOT(&cfqq
->sort_list
));
961 * follow expired path, else get first next available
963 if ((rq
= cfq_check_fifo(cfqq
)) == NULL
)
967 * finally, insert request into driver dispatch list
969 cfq_dispatch_insert(cfqd
->queue
, rq
);
971 cfqd
->dispatch_slice
++;
974 if (!cfqd
->active_cic
) {
975 atomic_inc(&RQ_CIC(rq
)->ioc
->refcount
);
976 cfqd
->active_cic
= RQ_CIC(rq
);
979 if (RB_EMPTY_ROOT(&cfqq
->sort_list
))
982 } while (dispatched
< max_dispatch
);
985 * expire an async queue immediately if it has used up its slice. idle
986 * queue always expire after 1 dispatch round.
988 if ((!cfq_cfqq_sync(cfqq
) &&
989 cfqd
->dispatch_slice
>= cfq_prio_to_maxrq(cfqd
, cfqq
)) ||
990 cfq_class_idle(cfqq
)) {
991 cfqq
->slice_end
= jiffies
+ 1;
992 cfq_slice_expired(cfqd
, 0);
999 cfq_forced_dispatch_cfqqs(struct list_head
*list
)
1001 struct cfq_queue
*cfqq
, *next
;
1005 list_for_each_entry_safe(cfqq
, next
, list
, cfq_list
) {
1006 while (cfqq
->next_rq
) {
1007 cfq_dispatch_insert(cfqq
->cfqd
->queue
, cfqq
->next_rq
);
1010 BUG_ON(!list_empty(&cfqq
->fifo
));
1017 cfq_forced_dispatch(struct cfq_data
*cfqd
)
1019 int i
, dispatched
= 0;
1021 for (i
= 0; i
< CFQ_PRIO_LISTS
; i
++)
1022 dispatched
+= cfq_forced_dispatch_cfqqs(&cfqd
->rr_list
[i
]);
1024 dispatched
+= cfq_forced_dispatch_cfqqs(&cfqd
->busy_rr
);
1025 dispatched
+= cfq_forced_dispatch_cfqqs(&cfqd
->cur_rr
);
1026 dispatched
+= cfq_forced_dispatch_cfqqs(&cfqd
->idle_rr
);
1028 cfq_slice_expired(cfqd
, 0);
1030 BUG_ON(cfqd
->busy_queues
);
1036 cfq_dispatch_requests(request_queue_t
*q
, int force
)
1038 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1039 struct cfq_queue
*cfqq
, *prev_cfqq
;
1042 if (!cfqd
->busy_queues
)
1045 if (unlikely(force
))
1046 return cfq_forced_dispatch(cfqd
);
1050 while ((cfqq
= cfq_select_queue(cfqd
)) != NULL
) {
1054 * Don't repeat dispatch from the previous queue.
1056 if (prev_cfqq
== cfqq
)
1059 cfq_clear_cfqq_must_dispatch(cfqq
);
1060 cfq_clear_cfqq_wait_request(cfqq
);
1061 del_timer(&cfqd
->idle_slice_timer
);
1063 max_dispatch
= cfqd
->cfq_quantum
;
1064 if (cfq_class_idle(cfqq
))
1067 dispatched
+= __cfq_dispatch_requests(cfqd
, cfqq
, max_dispatch
);
1070 * If the dispatch cfqq has idling enabled and is still
1071 * the active queue, break out.
1073 if (cfq_cfqq_idle_window(cfqq
) && cfqd
->active_queue
)
1083 * task holds one reference to the queue, dropped when task exits. each rq
1084 * in-flight on this queue also holds a reference, dropped when rq is freed.
1086 * queue lock must be held here.
1088 static void cfq_put_queue(struct cfq_queue
*cfqq
)
1090 struct cfq_data
*cfqd
= cfqq
->cfqd
;
1092 BUG_ON(atomic_read(&cfqq
->ref
) <= 0);
1094 if (!atomic_dec_and_test(&cfqq
->ref
))
1097 BUG_ON(rb_first(&cfqq
->sort_list
));
1098 BUG_ON(cfqq
->allocated
[READ
] + cfqq
->allocated
[WRITE
]);
1099 BUG_ON(cfq_cfqq_on_rr(cfqq
));
1101 if (unlikely(cfqd
->active_queue
== cfqq
))
1102 __cfq_slice_expired(cfqd
, cfqq
, 0);
1105 * it's on the empty list and still hashed
1107 list_del(&cfqq
->cfq_list
);
1108 hlist_del(&cfqq
->cfq_hash
);
1109 kmem_cache_free(cfq_pool
, cfqq
);
1112 static struct cfq_queue
*
1113 __cfq_find_cfq_hash(struct cfq_data
*cfqd
, unsigned int key
, unsigned int prio
,
1116 struct hlist_head
*hash_list
= &cfqd
->cfq_hash
[hashval
];
1117 struct hlist_node
*entry
;
1118 struct cfq_queue
*__cfqq
;
1120 hlist_for_each_entry(__cfqq
, entry
, hash_list
, cfq_hash
) {
1121 const unsigned short __p
= IOPRIO_PRIO_VALUE(__cfqq
->org_ioprio_class
, __cfqq
->org_ioprio
);
1123 if (__cfqq
->key
== key
&& (__p
== prio
|| !prio
))
1130 static struct cfq_queue
*
1131 cfq_find_cfq_hash(struct cfq_data
*cfqd
, unsigned int key
, unsigned short prio
)
1133 return __cfq_find_cfq_hash(cfqd
, key
, prio
, hash_long(key
, CFQ_QHASH_SHIFT
));
1136 static void cfq_free_io_context(struct io_context
*ioc
)
1138 struct cfq_io_context
*__cic
;
1142 while ((n
= rb_first(&ioc
->cic_root
)) != NULL
) {
1143 __cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1144 rb_erase(&__cic
->rb_node
, &ioc
->cic_root
);
1145 kmem_cache_free(cfq_ioc_pool
, __cic
);
1149 elv_ioc_count_mod(ioc_count
, -freed
);
1151 if (ioc_gone
&& !elv_ioc_count_read(ioc_count
))
1155 static void cfq_exit_cfqq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1157 if (unlikely(cfqq
== cfqd
->active_queue
))
1158 __cfq_slice_expired(cfqd
, cfqq
, 0);
1160 cfq_put_queue(cfqq
);
1163 static void __cfq_exit_single_io_context(struct cfq_data
*cfqd
,
1164 struct cfq_io_context
*cic
)
1166 list_del_init(&cic
->queue_list
);
1170 if (cic
->cfqq
[ASYNC
]) {
1171 cfq_exit_cfqq(cfqd
, cic
->cfqq
[ASYNC
]);
1172 cic
->cfqq
[ASYNC
] = NULL
;
1175 if (cic
->cfqq
[SYNC
]) {
1176 cfq_exit_cfqq(cfqd
, cic
->cfqq
[SYNC
]);
1177 cic
->cfqq
[SYNC
] = NULL
;
1183 * Called with interrupts disabled
1185 static void cfq_exit_single_io_context(struct cfq_io_context
*cic
)
1187 struct cfq_data
*cfqd
= cic
->key
;
1190 request_queue_t
*q
= cfqd
->queue
;
1192 spin_lock_irq(q
->queue_lock
);
1193 __cfq_exit_single_io_context(cfqd
, cic
);
1194 spin_unlock_irq(q
->queue_lock
);
1198 static void cfq_exit_io_context(struct io_context
*ioc
)
1200 struct cfq_io_context
*__cic
;
1204 * put the reference this task is holding to the various queues
1207 n
= rb_first(&ioc
->cic_root
);
1209 __cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1211 cfq_exit_single_io_context(__cic
);
1216 static struct cfq_io_context
*
1217 cfq_alloc_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
1219 struct cfq_io_context
*cic
;
1221 cic
= kmem_cache_alloc_node(cfq_ioc_pool
, gfp_mask
, cfqd
->queue
->node
);
1223 memset(cic
, 0, sizeof(*cic
));
1224 cic
->last_end_request
= jiffies
;
1225 INIT_LIST_HEAD(&cic
->queue_list
);
1226 cic
->dtor
= cfq_free_io_context
;
1227 cic
->exit
= cfq_exit_io_context
;
1228 elv_ioc_count_inc(ioc_count
);
1234 static void cfq_init_prio_data(struct cfq_queue
*cfqq
)
1236 struct task_struct
*tsk
= current
;
1239 if (!cfq_cfqq_prio_changed(cfqq
))
1242 ioprio_class
= IOPRIO_PRIO_CLASS(tsk
->ioprio
);
1243 switch (ioprio_class
) {
1245 printk(KERN_ERR
"cfq: bad prio %x\n", ioprio_class
);
1246 case IOPRIO_CLASS_NONE
:
1248 * no prio set, place us in the middle of the BE classes
1250 cfqq
->ioprio
= task_nice_ioprio(tsk
);
1251 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1253 case IOPRIO_CLASS_RT
:
1254 cfqq
->ioprio
= task_ioprio(tsk
);
1255 cfqq
->ioprio_class
= IOPRIO_CLASS_RT
;
1257 case IOPRIO_CLASS_BE
:
1258 cfqq
->ioprio
= task_ioprio(tsk
);
1259 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1261 case IOPRIO_CLASS_IDLE
:
1262 cfqq
->ioprio_class
= IOPRIO_CLASS_IDLE
;
1264 cfq_clear_cfqq_idle_window(cfqq
);
1269 * keep track of original prio settings in case we have to temporarily
1270 * elevate the priority of this queue
1272 cfqq
->org_ioprio
= cfqq
->ioprio
;
1273 cfqq
->org_ioprio_class
= cfqq
->ioprio_class
;
1275 cfq_resort_rr_list(cfqq
, 0);
1276 cfq_clear_cfqq_prio_changed(cfqq
);
1279 static inline void changed_ioprio(struct cfq_io_context
*cic
)
1281 struct cfq_data
*cfqd
= cic
->key
;
1282 struct cfq_queue
*cfqq
;
1283 unsigned long flags
;
1285 if (unlikely(!cfqd
))
1288 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
1290 cfqq
= cic
->cfqq
[ASYNC
];
1292 struct cfq_queue
*new_cfqq
;
1293 new_cfqq
= cfq_get_queue(cfqd
, CFQ_KEY_ASYNC
, cic
->ioc
->task
,
1296 cic
->cfqq
[ASYNC
] = new_cfqq
;
1297 cfq_put_queue(cfqq
);
1301 cfqq
= cic
->cfqq
[SYNC
];
1303 cfq_mark_cfqq_prio_changed(cfqq
);
1305 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
1308 static void cfq_ioc_set_ioprio(struct io_context
*ioc
)
1310 struct cfq_io_context
*cic
;
1313 ioc
->ioprio_changed
= 0;
1315 n
= rb_first(&ioc
->cic_root
);
1317 cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1319 changed_ioprio(cic
);
1324 static struct cfq_queue
*
1325 cfq_get_queue(struct cfq_data
*cfqd
, unsigned int key
, struct task_struct
*tsk
,
1328 const int hashval
= hash_long(key
, CFQ_QHASH_SHIFT
);
1329 struct cfq_queue
*cfqq
, *new_cfqq
= NULL
;
1330 unsigned short ioprio
;
1333 ioprio
= tsk
->ioprio
;
1334 cfqq
= __cfq_find_cfq_hash(cfqd
, key
, ioprio
, hashval
);
1340 } else if (gfp_mask
& __GFP_WAIT
) {
1342 * Inform the allocator of the fact that we will
1343 * just repeat this allocation if it fails, to allow
1344 * the allocator to do whatever it needs to attempt to
1347 spin_unlock_irq(cfqd
->queue
->queue_lock
);
1348 new_cfqq
= kmem_cache_alloc_node(cfq_pool
, gfp_mask
|__GFP_NOFAIL
, cfqd
->queue
->node
);
1349 spin_lock_irq(cfqd
->queue
->queue_lock
);
1352 cfqq
= kmem_cache_alloc_node(cfq_pool
, gfp_mask
, cfqd
->queue
->node
);
1357 memset(cfqq
, 0, sizeof(*cfqq
));
1359 INIT_HLIST_NODE(&cfqq
->cfq_hash
);
1360 INIT_LIST_HEAD(&cfqq
->cfq_list
);
1361 INIT_LIST_HEAD(&cfqq
->fifo
);
1364 hlist_add_head(&cfqq
->cfq_hash
, &cfqd
->cfq_hash
[hashval
]);
1365 atomic_set(&cfqq
->ref
, 0);
1368 * set ->slice_left to allow preemption for a new process
1370 cfqq
->slice_left
= 2 * cfqd
->cfq_slice_idle
;
1371 cfq_mark_cfqq_idle_window(cfqq
);
1372 cfq_mark_cfqq_prio_changed(cfqq
);
1373 cfq_mark_cfqq_queue_new(cfqq
);
1374 cfq_init_prio_data(cfqq
);
1378 kmem_cache_free(cfq_pool
, new_cfqq
);
1380 atomic_inc(&cfqq
->ref
);
1382 WARN_ON((gfp_mask
& __GFP_WAIT
) && !cfqq
);
1387 cfq_drop_dead_cic(struct io_context
*ioc
, struct cfq_io_context
*cic
)
1389 WARN_ON(!list_empty(&cic
->queue_list
));
1390 rb_erase(&cic
->rb_node
, &ioc
->cic_root
);
1391 kmem_cache_free(cfq_ioc_pool
, cic
);
1392 elv_ioc_count_dec(ioc_count
);
1395 static struct cfq_io_context
*
1396 cfq_cic_rb_lookup(struct cfq_data
*cfqd
, struct io_context
*ioc
)
1399 struct cfq_io_context
*cic
;
1400 void *k
, *key
= cfqd
;
1403 n
= ioc
->cic_root
.rb_node
;
1405 cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1406 /* ->key must be copied to avoid race with cfq_exit_queue() */
1409 cfq_drop_dead_cic(ioc
, cic
);
1425 cfq_cic_link(struct cfq_data
*cfqd
, struct io_context
*ioc
,
1426 struct cfq_io_context
*cic
)
1429 struct rb_node
*parent
;
1430 struct cfq_io_context
*__cic
;
1431 unsigned long flags
;
1439 p
= &ioc
->cic_root
.rb_node
;
1442 __cic
= rb_entry(parent
, struct cfq_io_context
, rb_node
);
1443 /* ->key must be copied to avoid race with cfq_exit_queue() */
1446 cfq_drop_dead_cic(ioc
, __cic
);
1452 else if (cic
->key
> k
)
1453 p
= &(*p
)->rb_right
;
1458 rb_link_node(&cic
->rb_node
, parent
, p
);
1459 rb_insert_color(&cic
->rb_node
, &ioc
->cic_root
);
1461 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
1462 list_add(&cic
->queue_list
, &cfqd
->cic_list
);
1463 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
1467 * Setup general io context and cfq io context. There can be several cfq
1468 * io contexts per general io context, if this process is doing io to more
1469 * than one device managed by cfq.
1471 static struct cfq_io_context
*
1472 cfq_get_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
1474 struct io_context
*ioc
= NULL
;
1475 struct cfq_io_context
*cic
;
1477 might_sleep_if(gfp_mask
& __GFP_WAIT
);
1479 ioc
= get_io_context(gfp_mask
, cfqd
->queue
->node
);
1483 cic
= cfq_cic_rb_lookup(cfqd
, ioc
);
1487 cic
= cfq_alloc_io_context(cfqd
, gfp_mask
);
1491 cfq_cic_link(cfqd
, ioc
, cic
);
1493 smp_read_barrier_depends();
1494 if (unlikely(ioc
->ioprio_changed
))
1495 cfq_ioc_set_ioprio(ioc
);
1499 put_io_context(ioc
);
1504 cfq_update_io_thinktime(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
)
1506 unsigned long elapsed
= jiffies
- cic
->last_end_request
;
1507 unsigned long ttime
= min(elapsed
, 2UL * cfqd
->cfq_slice_idle
);
1509 cic
->ttime_samples
= (7*cic
->ttime_samples
+ 256) / 8;
1510 cic
->ttime_total
= (7*cic
->ttime_total
+ 256*ttime
) / 8;
1511 cic
->ttime_mean
= (cic
->ttime_total
+ 128) / cic
->ttime_samples
;
1515 cfq_update_io_seektime(struct cfq_io_context
*cic
, struct request
*rq
)
1520 if (cic
->last_request_pos
< rq
->sector
)
1521 sdist
= rq
->sector
- cic
->last_request_pos
;
1523 sdist
= cic
->last_request_pos
- rq
->sector
;
1526 * Don't allow the seek distance to get too large from the
1527 * odd fragment, pagein, etc
1529 if (cic
->seek_samples
<= 60) /* second&third seek */
1530 sdist
= min(sdist
, (cic
->seek_mean
* 4) + 2*1024*1024);
1532 sdist
= min(sdist
, (cic
->seek_mean
* 4) + 2*1024*64);
1534 cic
->seek_samples
= (7*cic
->seek_samples
+ 256) / 8;
1535 cic
->seek_total
= (7*cic
->seek_total
+ (u64
)256*sdist
) / 8;
1536 total
= cic
->seek_total
+ (cic
->seek_samples
/2);
1537 do_div(total
, cic
->seek_samples
);
1538 cic
->seek_mean
= (sector_t
)total
;
1542 * Disable idle window if the process thinks too long or seeks so much that
1546 cfq_update_idle_window(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1547 struct cfq_io_context
*cic
)
1549 int enable_idle
= cfq_cfqq_idle_window(cfqq
);
1551 if (!cic
->ioc
->task
|| !cfqd
->cfq_slice_idle
||
1552 (cfqd
->hw_tag
&& CIC_SEEKY(cic
)))
1554 else if (sample_valid(cic
->ttime_samples
)) {
1555 if (cic
->ttime_mean
> cfqd
->cfq_slice_idle
)
1562 cfq_mark_cfqq_idle_window(cfqq
);
1564 cfq_clear_cfqq_idle_window(cfqq
);
1569 * Check if new_cfqq should preempt the currently active queue. Return 0 for
1570 * no or if we aren't sure, a 1 will cause a preempt.
1573 cfq_should_preempt(struct cfq_data
*cfqd
, struct cfq_queue
*new_cfqq
,
1576 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
1578 if (cfq_class_idle(new_cfqq
))
1584 if (cfq_class_idle(cfqq
))
1586 if (!cfq_cfqq_wait_request(new_cfqq
))
1589 * if it doesn't have slice left, forget it
1591 if (new_cfqq
->slice_left
< cfqd
->cfq_slice_idle
)
1594 * if the new request is sync, but the currently running queue is
1595 * not, let the sync request have priority.
1597 if (rq_is_sync(rq
) && !cfq_cfqq_sync(cfqq
))
1600 * So both queues are sync. Let the new request get disk time if
1601 * it's a metadata request and the current queue is doing regular IO.
1603 if (rq_is_meta(rq
) && !cfqq
->meta_pending
)
1610 * cfqq preempts the active queue. if we allowed preempt with no slice left,
1611 * let it have half of its nominal slice.
1613 static void cfq_preempt_queue(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1615 cfq_slice_expired(cfqd
, 1);
1617 if (!cfqq
->slice_left
)
1618 cfqq
->slice_left
= cfq_prio_to_slice(cfqd
, cfqq
) / 2;
1621 * Put the new queue at the front of the of the current list,
1622 * so we know that it will be selected next.
1624 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
1625 list_move(&cfqq
->cfq_list
, &cfqd
->cur_rr
);
1627 cfqq
->slice_end
= 0;
1628 cfq_mark_cfqq_slice_new(cfqq
);
1632 * Called when a new fs request (rq) is added (to cfqq). Check if there's
1633 * something we should do about it
1636 cfq_rq_enqueued(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1639 struct cfq_io_context
*cic
= RQ_CIC(rq
);
1642 cfqq
->meta_pending
++;
1645 * check if this request is a better next-serve candidate)) {
1647 cfqq
->next_rq
= cfq_choose_req(cfqd
, cfqq
->next_rq
, rq
);
1648 BUG_ON(!cfqq
->next_rq
);
1651 * we never wait for an async request and we don't allow preemption
1652 * of an async request. so just return early
1654 if (!rq_is_sync(rq
)) {
1656 * sync process issued an async request, if it's waiting
1657 * then expire it and kick rq handling.
1659 if (cic
== cfqd
->active_cic
&&
1660 del_timer(&cfqd
->idle_slice_timer
)) {
1661 cfq_slice_expired(cfqd
, 0);
1662 blk_start_queueing(cfqd
->queue
);
1667 cfq_update_io_thinktime(cfqd
, cic
);
1668 cfq_update_io_seektime(cic
, rq
);
1669 cfq_update_idle_window(cfqd
, cfqq
, cic
);
1671 cic
->last_request_pos
= rq
->sector
+ rq
->nr_sectors
;
1673 if (cfqq
== cfqd
->active_queue
) {
1675 * if we are waiting for a request for this queue, let it rip
1676 * immediately and flag that we must not expire this queue
1679 if (cfq_cfqq_wait_request(cfqq
)) {
1680 cfq_mark_cfqq_must_dispatch(cfqq
);
1681 del_timer(&cfqd
->idle_slice_timer
);
1682 blk_start_queueing(cfqd
->queue
);
1684 } else if (cfq_should_preempt(cfqd
, cfqq
, rq
)) {
1686 * not the active queue - expire current slice if it is
1687 * idle and has expired it's mean thinktime or this new queue
1688 * has some old slice time left and is of higher priority
1690 cfq_preempt_queue(cfqd
, cfqq
);
1691 cfq_mark_cfqq_must_dispatch(cfqq
);
1692 blk_start_queueing(cfqd
->queue
);
1696 static void cfq_insert_request(request_queue_t
*q
, struct request
*rq
)
1698 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1699 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1701 cfq_init_prio_data(cfqq
);
1705 list_add_tail(&rq
->queuelist
, &cfqq
->fifo
);
1707 cfq_rq_enqueued(cfqd
, cfqq
, rq
);
1710 static void cfq_completed_request(request_queue_t
*q
, struct request
*rq
)
1712 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1713 struct cfq_data
*cfqd
= cfqq
->cfqd
;
1714 const int sync
= rq_is_sync(rq
);
1719 WARN_ON(!cfqd
->rq_in_driver
);
1720 WARN_ON(!cfqq
->on_dispatch
[sync
]);
1721 cfqd
->rq_in_driver
--;
1722 cfqq
->on_dispatch
[sync
]--;
1723 cfqq
->service_last
= now
;
1725 if (!cfq_class_idle(cfqq
))
1726 cfqd
->last_end_request
= now
;
1728 cfq_resort_rr_list(cfqq
, 0);
1731 RQ_CIC(rq
)->last_end_request
= now
;
1734 * If this is the active queue, check if it needs to be expired,
1735 * or if we want to idle in case it has no pending requests.
1737 if (cfqd
->active_queue
== cfqq
) {
1738 if (cfq_cfqq_slice_new(cfqq
)) {
1739 cfq_set_prio_slice(cfqd
, cfqq
);
1740 cfq_clear_cfqq_slice_new(cfqq
);
1742 if (cfq_slice_used(cfqq
))
1743 cfq_slice_expired(cfqd
, 0);
1744 else if (sync
&& RB_EMPTY_ROOT(&cfqq
->sort_list
)) {
1745 if (!cfq_arm_slice_timer(cfqd
, cfqq
))
1746 cfq_schedule_dispatch(cfqd
);
1752 * we temporarily boost lower priority queues if they are holding fs exclusive
1753 * resources. they are boosted to normal prio (CLASS_BE/4)
1755 static void cfq_prio_boost(struct cfq_queue
*cfqq
)
1757 const int ioprio_class
= cfqq
->ioprio_class
;
1758 const int ioprio
= cfqq
->ioprio
;
1760 if (has_fs_excl()) {
1762 * boost idle prio on transactions that would lock out other
1763 * users of the filesystem
1765 if (cfq_class_idle(cfqq
))
1766 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1767 if (cfqq
->ioprio
> IOPRIO_NORM
)
1768 cfqq
->ioprio
= IOPRIO_NORM
;
1771 * check if we need to unboost the queue
1773 if (cfqq
->ioprio_class
!= cfqq
->org_ioprio_class
)
1774 cfqq
->ioprio_class
= cfqq
->org_ioprio_class
;
1775 if (cfqq
->ioprio
!= cfqq
->org_ioprio
)
1776 cfqq
->ioprio
= cfqq
->org_ioprio
;
1780 * refile between round-robin lists if we moved the priority class
1782 if ((ioprio_class
!= cfqq
->ioprio_class
|| ioprio
!= cfqq
->ioprio
))
1783 cfq_resort_rr_list(cfqq
, 0);
1786 static inline int __cfq_may_queue(struct cfq_queue
*cfqq
)
1788 if ((cfq_cfqq_wait_request(cfqq
) || cfq_cfqq_must_alloc(cfqq
)) &&
1789 !cfq_cfqq_must_alloc_slice(cfqq
)) {
1790 cfq_mark_cfqq_must_alloc_slice(cfqq
);
1791 return ELV_MQUEUE_MUST
;
1794 return ELV_MQUEUE_MAY
;
1797 static int cfq_may_queue(request_queue_t
*q
, int rw
)
1799 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1800 struct task_struct
*tsk
= current
;
1801 struct cfq_queue
*cfqq
;
1804 key
= cfq_queue_pid(tsk
, rw
, rw
& REQ_RW_SYNC
);
1807 * don't force setup of a queue from here, as a call to may_queue
1808 * does not necessarily imply that a request actually will be queued.
1809 * so just lookup a possibly existing queue, or return 'may queue'
1812 cfqq
= cfq_find_cfq_hash(cfqd
, key
, tsk
->ioprio
);
1814 cfq_init_prio_data(cfqq
);
1815 cfq_prio_boost(cfqq
);
1817 return __cfq_may_queue(cfqq
);
1820 return ELV_MQUEUE_MAY
;
1824 * queue lock held here
1826 static void cfq_put_request(struct request
*rq
)
1828 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1831 const int rw
= rq_data_dir(rq
);
1833 BUG_ON(!cfqq
->allocated
[rw
]);
1834 cfqq
->allocated
[rw
]--;
1836 put_io_context(RQ_CIC(rq
)->ioc
);
1838 rq
->elevator_private
= NULL
;
1839 rq
->elevator_private2
= NULL
;
1841 cfq_put_queue(cfqq
);
1846 * Allocate cfq data structures associated with this request.
1849 cfq_set_request(request_queue_t
*q
, struct request
*rq
, gfp_t gfp_mask
)
1851 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1852 struct task_struct
*tsk
= current
;
1853 struct cfq_io_context
*cic
;
1854 const int rw
= rq_data_dir(rq
);
1855 const int is_sync
= rq_is_sync(rq
);
1856 pid_t key
= cfq_queue_pid(tsk
, rw
, is_sync
);
1857 struct cfq_queue
*cfqq
;
1858 unsigned long flags
;
1860 might_sleep_if(gfp_mask
& __GFP_WAIT
);
1862 cic
= cfq_get_io_context(cfqd
, gfp_mask
);
1864 spin_lock_irqsave(q
->queue_lock
, flags
);
1869 if (!cic
->cfqq
[is_sync
]) {
1870 cfqq
= cfq_get_queue(cfqd
, key
, tsk
, gfp_mask
);
1874 cic
->cfqq
[is_sync
] = cfqq
;
1876 cfqq
= cic
->cfqq
[is_sync
];
1878 cfqq
->allocated
[rw
]++;
1879 cfq_clear_cfqq_must_alloc(cfqq
);
1880 atomic_inc(&cfqq
->ref
);
1882 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1884 rq
->elevator_private
= cic
;
1885 rq
->elevator_private2
= cfqq
;
1890 put_io_context(cic
->ioc
);
1892 cfq_schedule_dispatch(cfqd
);
1893 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1897 static void cfq_kick_queue(struct work_struct
*work
)
1899 struct cfq_data
*cfqd
=
1900 container_of(work
, struct cfq_data
, unplug_work
);
1901 request_queue_t
*q
= cfqd
->queue
;
1902 unsigned long flags
;
1904 spin_lock_irqsave(q
->queue_lock
, flags
);
1905 blk_start_queueing(q
);
1906 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1910 * Timer running if the active_queue is currently idling inside its time slice
1912 static void cfq_idle_slice_timer(unsigned long data
)
1914 struct cfq_data
*cfqd
= (struct cfq_data
*) data
;
1915 struct cfq_queue
*cfqq
;
1916 unsigned long flags
;
1918 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
1920 if ((cfqq
= cfqd
->active_queue
) != NULL
) {
1924 if (cfq_slice_used(cfqq
))
1928 * only expire and reinvoke request handler, if there are
1929 * other queues with pending requests
1931 if (!cfqd
->busy_queues
)
1935 * not expired and it has a request pending, let it dispatch
1937 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
)) {
1938 cfq_mark_cfqq_must_dispatch(cfqq
);
1943 cfq_slice_expired(cfqd
, 0);
1945 cfq_schedule_dispatch(cfqd
);
1947 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
1951 * Timer running if an idle class queue is waiting for service
1953 static void cfq_idle_class_timer(unsigned long data
)
1955 struct cfq_data
*cfqd
= (struct cfq_data
*) data
;
1956 unsigned long flags
, end
;
1958 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
1961 * race with a non-idle queue, reset timer
1963 end
= cfqd
->last_end_request
+ CFQ_IDLE_GRACE
;
1964 if (!time_after_eq(jiffies
, end
))
1965 mod_timer(&cfqd
->idle_class_timer
, end
);
1967 cfq_schedule_dispatch(cfqd
);
1969 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
1972 static void cfq_shutdown_timer_wq(struct cfq_data
*cfqd
)
1974 del_timer_sync(&cfqd
->idle_slice_timer
);
1975 del_timer_sync(&cfqd
->idle_class_timer
);
1976 blk_sync_queue(cfqd
->queue
);
1979 static void cfq_exit_queue(elevator_t
*e
)
1981 struct cfq_data
*cfqd
= e
->elevator_data
;
1982 request_queue_t
*q
= cfqd
->queue
;
1984 cfq_shutdown_timer_wq(cfqd
);
1986 spin_lock_irq(q
->queue_lock
);
1988 if (cfqd
->active_queue
)
1989 __cfq_slice_expired(cfqd
, cfqd
->active_queue
, 0);
1991 while (!list_empty(&cfqd
->cic_list
)) {
1992 struct cfq_io_context
*cic
= list_entry(cfqd
->cic_list
.next
,
1993 struct cfq_io_context
,
1996 __cfq_exit_single_io_context(cfqd
, cic
);
1999 spin_unlock_irq(q
->queue_lock
);
2001 cfq_shutdown_timer_wq(cfqd
);
2003 kfree(cfqd
->cfq_hash
);
2007 static void *cfq_init_queue(request_queue_t
*q
)
2009 struct cfq_data
*cfqd
;
2012 cfqd
= kmalloc_node(sizeof(*cfqd
), GFP_KERNEL
, q
->node
);
2016 memset(cfqd
, 0, sizeof(*cfqd
));
2018 for (i
= 0; i
< CFQ_PRIO_LISTS
; i
++)
2019 INIT_LIST_HEAD(&cfqd
->rr_list
[i
]);
2021 INIT_LIST_HEAD(&cfqd
->busy_rr
);
2022 INIT_LIST_HEAD(&cfqd
->cur_rr
);
2023 INIT_LIST_HEAD(&cfqd
->idle_rr
);
2024 INIT_LIST_HEAD(&cfqd
->cic_list
);
2026 cfqd
->cfq_hash
= kmalloc_node(sizeof(struct hlist_head
) * CFQ_QHASH_ENTRIES
, GFP_KERNEL
, q
->node
);
2027 if (!cfqd
->cfq_hash
)
2030 for (i
= 0; i
< CFQ_QHASH_ENTRIES
; i
++)
2031 INIT_HLIST_HEAD(&cfqd
->cfq_hash
[i
]);
2035 init_timer(&cfqd
->idle_slice_timer
);
2036 cfqd
->idle_slice_timer
.function
= cfq_idle_slice_timer
;
2037 cfqd
->idle_slice_timer
.data
= (unsigned long) cfqd
;
2039 init_timer(&cfqd
->idle_class_timer
);
2040 cfqd
->idle_class_timer
.function
= cfq_idle_class_timer
;
2041 cfqd
->idle_class_timer
.data
= (unsigned long) cfqd
;
2043 INIT_WORK(&cfqd
->unplug_work
, cfq_kick_queue
);
2045 cfqd
->cfq_quantum
= cfq_quantum
;
2046 cfqd
->cfq_fifo_expire
[0] = cfq_fifo_expire
[0];
2047 cfqd
->cfq_fifo_expire
[1] = cfq_fifo_expire
[1];
2048 cfqd
->cfq_back_max
= cfq_back_max
;
2049 cfqd
->cfq_back_penalty
= cfq_back_penalty
;
2050 cfqd
->cfq_slice
[0] = cfq_slice_async
;
2051 cfqd
->cfq_slice
[1] = cfq_slice_sync
;
2052 cfqd
->cfq_slice_async_rq
= cfq_slice_async_rq
;
2053 cfqd
->cfq_slice_idle
= cfq_slice_idle
;
2061 static void cfq_slab_kill(void)
2064 kmem_cache_destroy(cfq_pool
);
2066 kmem_cache_destroy(cfq_ioc_pool
);
2069 static int __init
cfq_slab_setup(void)
2071 cfq_pool
= kmem_cache_create("cfq_pool", sizeof(struct cfq_queue
), 0, 0,
2076 cfq_ioc_pool
= kmem_cache_create("cfq_ioc_pool",
2077 sizeof(struct cfq_io_context
), 0, 0, NULL
, NULL
);
2088 * sysfs parts below -->
2092 cfq_var_show(unsigned int var
, char *page
)
2094 return sprintf(page
, "%d\n", var
);
2098 cfq_var_store(unsigned int *var
, const char *page
, size_t count
)
2100 char *p
= (char *) page
;
2102 *var
= simple_strtoul(p
, &p
, 10);
2106 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
2107 static ssize_t __FUNC(elevator_t *e, char *page) \
2109 struct cfq_data *cfqd = e->elevator_data; \
2110 unsigned int __data = __VAR; \
2112 __data = jiffies_to_msecs(__data); \
2113 return cfq_var_show(__data, (page)); \
2115 SHOW_FUNCTION(cfq_quantum_show
, cfqd
->cfq_quantum
, 0);
2116 SHOW_FUNCTION(cfq_fifo_expire_sync_show
, cfqd
->cfq_fifo_expire
[1], 1);
2117 SHOW_FUNCTION(cfq_fifo_expire_async_show
, cfqd
->cfq_fifo_expire
[0], 1);
2118 SHOW_FUNCTION(cfq_back_seek_max_show
, cfqd
->cfq_back_max
, 0);
2119 SHOW_FUNCTION(cfq_back_seek_penalty_show
, cfqd
->cfq_back_penalty
, 0);
2120 SHOW_FUNCTION(cfq_slice_idle_show
, cfqd
->cfq_slice_idle
, 1);
2121 SHOW_FUNCTION(cfq_slice_sync_show
, cfqd
->cfq_slice
[1], 1);
2122 SHOW_FUNCTION(cfq_slice_async_show
, cfqd
->cfq_slice
[0], 1);
2123 SHOW_FUNCTION(cfq_slice_async_rq_show
, cfqd
->cfq_slice_async_rq
, 0);
2124 #undef SHOW_FUNCTION
2126 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
2127 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
2129 struct cfq_data *cfqd = e->elevator_data; \
2130 unsigned int __data; \
2131 int ret = cfq_var_store(&__data, (page), count); \
2132 if (__data < (MIN)) \
2134 else if (__data > (MAX)) \
2137 *(__PTR) = msecs_to_jiffies(__data); \
2139 *(__PTR) = __data; \
2142 STORE_FUNCTION(cfq_quantum_store
, &cfqd
->cfq_quantum
, 1, UINT_MAX
, 0);
2143 STORE_FUNCTION(cfq_fifo_expire_sync_store
, &cfqd
->cfq_fifo_expire
[1], 1, UINT_MAX
, 1);
2144 STORE_FUNCTION(cfq_fifo_expire_async_store
, &cfqd
->cfq_fifo_expire
[0], 1, UINT_MAX
, 1);
2145 STORE_FUNCTION(cfq_back_seek_max_store
, &cfqd
->cfq_back_max
, 0, UINT_MAX
, 0);
2146 STORE_FUNCTION(cfq_back_seek_penalty_store
, &cfqd
->cfq_back_penalty
, 1, UINT_MAX
, 0);
2147 STORE_FUNCTION(cfq_slice_idle_store
, &cfqd
->cfq_slice_idle
, 0, UINT_MAX
, 1);
2148 STORE_FUNCTION(cfq_slice_sync_store
, &cfqd
->cfq_slice
[1], 1, UINT_MAX
, 1);
2149 STORE_FUNCTION(cfq_slice_async_store
, &cfqd
->cfq_slice
[0], 1, UINT_MAX
, 1);
2150 STORE_FUNCTION(cfq_slice_async_rq_store
, &cfqd
->cfq_slice_async_rq
, 1, UINT_MAX
, 0);
2151 #undef STORE_FUNCTION
2153 #define CFQ_ATTR(name) \
2154 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2156 static struct elv_fs_entry cfq_attrs
[] = {
2158 CFQ_ATTR(fifo_expire_sync
),
2159 CFQ_ATTR(fifo_expire_async
),
2160 CFQ_ATTR(back_seek_max
),
2161 CFQ_ATTR(back_seek_penalty
),
2162 CFQ_ATTR(slice_sync
),
2163 CFQ_ATTR(slice_async
),
2164 CFQ_ATTR(slice_async_rq
),
2165 CFQ_ATTR(slice_idle
),
2169 static struct elevator_type iosched_cfq
= {
2171 .elevator_merge_fn
= cfq_merge
,
2172 .elevator_merged_fn
= cfq_merged_request
,
2173 .elevator_merge_req_fn
= cfq_merged_requests
,
2174 .elevator_allow_merge_fn
= cfq_allow_merge
,
2175 .elevator_dispatch_fn
= cfq_dispatch_requests
,
2176 .elevator_add_req_fn
= cfq_insert_request
,
2177 .elevator_activate_req_fn
= cfq_activate_request
,
2178 .elevator_deactivate_req_fn
= cfq_deactivate_request
,
2179 .elevator_queue_empty_fn
= cfq_queue_empty
,
2180 .elevator_completed_req_fn
= cfq_completed_request
,
2181 .elevator_former_req_fn
= elv_rb_former_request
,
2182 .elevator_latter_req_fn
= elv_rb_latter_request
,
2183 .elevator_set_req_fn
= cfq_set_request
,
2184 .elevator_put_req_fn
= cfq_put_request
,
2185 .elevator_may_queue_fn
= cfq_may_queue
,
2186 .elevator_init_fn
= cfq_init_queue
,
2187 .elevator_exit_fn
= cfq_exit_queue
,
2188 .trim
= cfq_free_io_context
,
2190 .elevator_attrs
= cfq_attrs
,
2191 .elevator_name
= "cfq",
2192 .elevator_owner
= THIS_MODULE
,
2195 static int __init
cfq_init(void)
2200 * could be 0 on HZ < 1000 setups
2202 if (!cfq_slice_async
)
2203 cfq_slice_async
= 1;
2204 if (!cfq_slice_idle
)
2207 if (cfq_slab_setup())
2210 ret
= elv_register(&iosched_cfq
);
2217 static void __exit
cfq_exit(void)
2219 DECLARE_COMPLETION_ONSTACK(all_gone
);
2220 elv_unregister(&iosched_cfq
);
2221 ioc_gone
= &all_gone
;
2222 /* ioc_gone's update must be visible before reading ioc_count */
2224 if (elv_ioc_count_read(ioc_count
))
2225 wait_for_completion(ioc_gone
);
2230 module_init(cfq_init
);
2231 module_exit(cfq_exit
);
2233 MODULE_AUTHOR("Jens Axboe");
2234 MODULE_LICENSE("GPL");
2235 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");