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@suse.de>
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_queued
= 8; /* minimum rq allocate limit per-queue*/
21 static const int cfq_fifo_expire
[2] = { HZ
/ 4, HZ
/ 8 };
22 static const int cfq_back_max
= 16 * 1024; /* maximum backwards seek, in KiB */
23 static const int cfq_back_penalty
= 2; /* penalty of a backwards seek */
25 static const int cfq_slice_sync
= HZ
/ 10;
26 static int cfq_slice_async
= HZ
/ 25;
27 static const int cfq_slice_async_rq
= 2;
28 static int cfq_slice_idle
= HZ
/ 125;
30 #define CFQ_IDLE_GRACE (HZ / 10)
31 #define CFQ_SLICE_SCALE (5)
33 #define CFQ_KEY_ASYNC (0)
35 static DEFINE_SPINLOCK(cfq_exit_lock
);
38 * for the hash of cfqq inside the cfqd
40 #define CFQ_QHASH_SHIFT 6
41 #define CFQ_QHASH_ENTRIES (1 << CFQ_QHASH_SHIFT)
42 #define list_entry_qhash(entry) hlist_entry((entry), struct cfq_queue, cfq_hash)
44 #define list_entry_cfqq(ptr) list_entry((ptr), struct cfq_queue, cfq_list)
46 #define RQ_DATA(rq) (rq)->elevator_private
48 static kmem_cache_t
*crq_pool
;
49 static kmem_cache_t
*cfq_pool
;
50 static kmem_cache_t
*cfq_ioc_pool
;
52 static atomic_t ioc_count
= ATOMIC_INIT(0);
53 static struct completion
*ioc_gone
;
55 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
56 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
57 #define cfq_class_be(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_BE)
58 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
63 #define cfq_cfqq_dispatched(cfqq) \
64 ((cfqq)->on_dispatch[ASYNC] + (cfqq)->on_dispatch[SYNC])
66 #define cfq_cfqq_class_sync(cfqq) ((cfqq)->key != CFQ_KEY_ASYNC)
68 #define cfq_cfqq_sync(cfqq) \
69 (cfq_cfqq_class_sync(cfqq) || (cfqq)->on_dispatch[SYNC])
71 #define sample_valid(samples) ((samples) > 80)
74 * Per block device queue structure
77 request_queue_t
*queue
;
80 * rr list of queues with requests and the count of them
82 struct list_head rr_list
[CFQ_PRIO_LISTS
];
83 struct list_head busy_rr
;
84 struct list_head cur_rr
;
85 struct list_head idle_rr
;
86 unsigned int busy_queues
;
89 * non-ordered list of empty cfqq's
91 struct list_head empty_list
;
96 struct hlist_head
*cfq_hash
;
104 * schedule slice state info
107 * idle window management
109 struct timer_list idle_slice_timer
;
110 struct work_struct unplug_work
;
112 struct cfq_queue
*active_queue
;
113 struct cfq_io_context
*active_cic
;
114 int cur_prio
, cur_end_prio
;
115 unsigned int dispatch_slice
;
117 struct timer_list idle_class_timer
;
119 sector_t last_sector
;
120 unsigned long last_end_request
;
122 unsigned int rq_starved
;
125 * tunables, see top of file
127 unsigned int cfq_quantum
;
128 unsigned int cfq_queued
;
129 unsigned int cfq_fifo_expire
[2];
130 unsigned int cfq_back_penalty
;
131 unsigned int cfq_back_max
;
132 unsigned int cfq_slice
[2];
133 unsigned int cfq_slice_async_rq
;
134 unsigned int cfq_slice_idle
;
136 struct list_head cic_list
;
140 * Per process-grouping structure
143 /* reference count */
145 /* parent cfq_data */
146 struct cfq_data
*cfqd
;
147 /* cfqq lookup hash */
148 struct hlist_node cfq_hash
;
151 /* on either rr or empty list of cfqd */
152 struct list_head cfq_list
;
153 /* sorted list of pending requests */
154 struct rb_root sort_list
;
155 /* if fifo isn't expired, next request to serve */
156 struct cfq_rq
*next_crq
;
157 /* requests queued in sort_list */
159 /* currently allocated requests */
161 /* fifo list of requests in sort_list */
162 struct list_head fifo
;
164 unsigned long slice_start
;
165 unsigned long slice_end
;
166 unsigned long slice_left
;
167 unsigned long service_last
;
169 /* number of requests that are on the dispatch list */
172 /* io prio of this group */
173 unsigned short ioprio
, org_ioprio
;
174 unsigned short ioprio_class
, org_ioprio_class
;
176 /* various state flags, see below */
181 struct request
*request
;
183 struct cfq_queue
*cfq_queue
;
184 struct cfq_io_context
*io_context
;
186 unsigned int crq_flags
;
189 enum cfqq_state_flags
{
190 CFQ_CFQQ_FLAG_on_rr
= 0,
191 CFQ_CFQQ_FLAG_wait_request
,
192 CFQ_CFQQ_FLAG_must_alloc
,
193 CFQ_CFQQ_FLAG_must_alloc_slice
,
194 CFQ_CFQQ_FLAG_must_dispatch
,
195 CFQ_CFQQ_FLAG_fifo_expire
,
196 CFQ_CFQQ_FLAG_idle_window
,
197 CFQ_CFQQ_FLAG_prio_changed
,
200 #define CFQ_CFQQ_FNS(name) \
201 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
203 cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
205 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
207 cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
209 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
211 return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
215 CFQ_CFQQ_FNS(wait_request
);
216 CFQ_CFQQ_FNS(must_alloc
);
217 CFQ_CFQQ_FNS(must_alloc_slice
);
218 CFQ_CFQQ_FNS(must_dispatch
);
219 CFQ_CFQQ_FNS(fifo_expire
);
220 CFQ_CFQQ_FNS(idle_window
);
221 CFQ_CFQQ_FNS(prio_changed
);
224 enum cfq_rq_state_flags
{
225 CFQ_CRQ_FLAG_is_sync
= 0,
228 #define CFQ_CRQ_FNS(name) \
229 static inline void cfq_mark_crq_##name(struct cfq_rq *crq) \
231 crq->crq_flags |= (1 << CFQ_CRQ_FLAG_##name); \
233 static inline void cfq_clear_crq_##name(struct cfq_rq *crq) \
235 crq->crq_flags &= ~(1 << CFQ_CRQ_FLAG_##name); \
237 static inline int cfq_crq_##name(const struct cfq_rq *crq) \
239 return (crq->crq_flags & (1 << CFQ_CRQ_FLAG_##name)) != 0; \
242 CFQ_CRQ_FNS(is_sync
);
245 static struct cfq_queue
*cfq_find_cfq_hash(struct cfq_data
*, unsigned int, unsigned short);
246 static void cfq_dispatch_insert(request_queue_t
*, struct cfq_rq
*);
247 static struct cfq_queue
*cfq_get_queue(struct cfq_data
*cfqd
, unsigned int key
, struct task_struct
*tsk
, gfp_t gfp_mask
);
250 * scheduler run of queue, if there are requests pending and no one in the
251 * driver that will restart queueing
253 static inline void cfq_schedule_dispatch(struct cfq_data
*cfqd
)
255 if (cfqd
->busy_queues
)
256 kblockd_schedule_work(&cfqd
->unplug_work
);
259 static int cfq_queue_empty(request_queue_t
*q
)
261 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
263 return !cfqd
->busy_queues
;
266 static inline pid_t
cfq_queue_pid(struct task_struct
*task
, int rw
)
268 if (rw
== READ
|| rw
== WRITE_SYNC
)
271 return CFQ_KEY_ASYNC
;
275 * Lifted from AS - choose which of crq1 and crq2 that is best served now.
276 * We choose the request that is closest to the head right now. Distance
277 * behind the head is penalized and only allowed to a certain extent.
279 static struct cfq_rq
*
280 cfq_choose_req(struct cfq_data
*cfqd
, struct cfq_rq
*crq1
, struct cfq_rq
*crq2
)
282 sector_t last
, s1
, s2
, d1
= 0, d2
= 0;
283 unsigned long back_max
;
284 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
285 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
286 unsigned wrap
= 0; /* bit mask: requests behind the disk head? */
288 if (crq1
== NULL
|| crq1
== crq2
)
293 if (cfq_crq_is_sync(crq1
) && !cfq_crq_is_sync(crq2
))
295 else if (cfq_crq_is_sync(crq2
) && !cfq_crq_is_sync(crq1
))
298 s1
= crq1
->request
->sector
;
299 s2
= crq2
->request
->sector
;
301 last
= cfqd
->last_sector
;
304 * by definition, 1KiB is 2 sectors
306 back_max
= cfqd
->cfq_back_max
* 2;
309 * Strict one way elevator _except_ in the case where we allow
310 * short backward seeks which are biased as twice the cost of a
311 * similar forward seek.
315 else if (s1
+ back_max
>= last
)
316 d1
= (last
- s1
) * cfqd
->cfq_back_penalty
;
318 wrap
|= CFQ_RQ1_WRAP
;
322 else if (s2
+ back_max
>= last
)
323 d2
= (last
- s2
) * cfqd
->cfq_back_penalty
;
325 wrap
|= CFQ_RQ2_WRAP
;
327 /* Found required data */
330 * By doing switch() on the bit mask "wrap" we avoid having to
331 * check two variables for all permutations: --> faster!
334 case 0: /* common case for CFQ: crq1 and crq2 not wrapped */
350 case (CFQ_RQ1_WRAP
|CFQ_RQ2_WRAP
): /* both crqs wrapped */
353 * Since both rqs are wrapped,
354 * start with the one that's further behind head
355 * (--> only *one* back seek required),
356 * since back seek takes more time than forward.
366 * would be nice to take fifo expire time into account as well
368 static struct cfq_rq
*
369 cfq_find_next_crq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
370 struct cfq_rq
*last_crq
)
372 struct request
*last
= last_crq
->request
;
373 struct rb_node
*rbnext
= rb_next(&last
->rb_node
);
374 struct rb_node
*rbprev
= rb_prev(&last
->rb_node
);
375 struct cfq_rq
*next
= NULL
, *prev
= NULL
;
377 BUG_ON(RB_EMPTY_NODE(&last
->rb_node
));
380 prev
= RQ_DATA(rb_entry_rq(rbprev
));
383 next
= RQ_DATA(rb_entry_rq(rbnext
));
385 rbnext
= rb_first(&cfqq
->sort_list
);
386 if (rbnext
&& rbnext
!= &last
->rb_node
)
387 next
= RQ_DATA(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
, *entry
;
398 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
400 list_del(&cfqq
->cfq_list
);
402 if (cfq_class_rt(cfqq
))
403 list
= &cfqd
->cur_rr
;
404 else if (cfq_class_idle(cfqq
))
405 list
= &cfqd
->idle_rr
;
408 * if cfqq has requests in flight, don't allow it to be
409 * found in cfq_set_active_queue before it has finished them.
410 * this is done to increase fairness between a process that
411 * has lots of io pending vs one that only generates one
412 * sporadically or synchronously
414 if (cfq_cfqq_dispatched(cfqq
))
415 list
= &cfqd
->busy_rr
;
417 list
= &cfqd
->rr_list
[cfqq
->ioprio
];
421 * if queue was preempted, just add to front to be fair. busy_rr
422 * isn't sorted, but insert at the back for fairness.
424 if (preempted
|| list
== &cfqd
->busy_rr
) {
428 list_add_tail(&cfqq
->cfq_list
, list
);
433 * sort by when queue was last serviced
436 while ((entry
= entry
->prev
) != list
) {
437 struct cfq_queue
*__cfqq
= list_entry_cfqq(entry
);
439 if (!__cfqq
->service_last
)
441 if (time_before(__cfqq
->service_last
, cfqq
->service_last
))
445 list_add(&cfqq
->cfq_list
, entry
);
449 * add to busy list of queues for service, trying to be fair in ordering
450 * the pending list according to last request service
453 cfq_add_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
455 BUG_ON(cfq_cfqq_on_rr(cfqq
));
456 cfq_mark_cfqq_on_rr(cfqq
);
459 cfq_resort_rr_list(cfqq
, 0);
463 cfq_del_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
465 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
466 cfq_clear_cfqq_on_rr(cfqq
);
467 list_move(&cfqq
->cfq_list
, &cfqd
->empty_list
);
469 BUG_ON(!cfqd
->busy_queues
);
474 * rb tree support functions
476 static inline void cfq_del_crq_rb(struct cfq_rq
*crq
)
478 struct cfq_queue
*cfqq
= crq
->cfq_queue
;
479 struct cfq_data
*cfqd
= cfqq
->cfqd
;
480 const int sync
= cfq_crq_is_sync(crq
);
482 BUG_ON(!cfqq
->queued
[sync
]);
483 cfqq
->queued
[sync
]--;
485 elv_rb_del(&cfqq
->sort_list
, crq
->request
);
487 if (cfq_cfqq_on_rr(cfqq
) && RB_EMPTY_ROOT(&cfqq
->sort_list
))
488 cfq_del_cfqq_rr(cfqd
, cfqq
);
491 static void cfq_add_crq_rb(struct cfq_rq
*crq
)
493 struct cfq_queue
*cfqq
= crq
->cfq_queue
;
494 struct cfq_data
*cfqd
= cfqq
->cfqd
;
495 struct request
*rq
= crq
->request
;
496 struct request
*__alias
;
498 cfqq
->queued
[cfq_crq_is_sync(crq
)]++;
501 * looks a little odd, but the first insert might return an alias.
502 * if that happens, put the alias on the dispatch list
504 while ((__alias
= elv_rb_add(&cfqq
->sort_list
, rq
)) != NULL
)
505 cfq_dispatch_insert(cfqd
->queue
, RQ_DATA(__alias
));
509 cfq_reposition_crq_rb(struct cfq_queue
*cfqq
, struct cfq_rq
*crq
)
511 elv_rb_del(&cfqq
->sort_list
, crq
->request
);
512 cfqq
->queued
[cfq_crq_is_sync(crq
)]--;
516 static struct request
*
517 cfq_find_rq_fmerge(struct cfq_data
*cfqd
, struct bio
*bio
)
519 struct task_struct
*tsk
= current
;
520 pid_t key
= cfq_queue_pid(tsk
, bio_data_dir(bio
));
521 sector_t sector
= bio
->bi_sector
+ bio_sectors(bio
);
522 struct cfq_queue
*cfqq
;
524 cfqq
= cfq_find_cfq_hash(cfqd
, key
, tsk
->ioprio
);
526 return elv_rb_find(&cfqq
->sort_list
, sector
);
531 static void cfq_activate_request(request_queue_t
*q
, struct request
*rq
)
533 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
535 cfqd
->rq_in_driver
++;
538 * If the depth is larger 1, it really could be queueing. But lets
539 * make the mark a little higher - idling could still be good for
540 * low queueing, and a low queueing number could also just indicate
541 * a SCSI mid layer like behaviour where limit+1 is often seen.
543 if (!cfqd
->hw_tag
&& cfqd
->rq_in_driver
> 4)
547 static void cfq_deactivate_request(request_queue_t
*q
, struct request
*rq
)
549 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
551 WARN_ON(!cfqd
->rq_in_driver
);
552 cfqd
->rq_in_driver
--;
555 static void cfq_remove_request(struct request
*rq
)
557 struct cfq_rq
*crq
= RQ_DATA(rq
);
558 struct cfq_queue
*cfqq
= crq
->cfq_queue
;
560 if (cfqq
->next_crq
== crq
)
561 cfqq
->next_crq
= cfq_find_next_crq(cfqq
->cfqd
, cfqq
, crq
);
563 list_del_init(&rq
->queuelist
);
568 cfq_merge(request_queue_t
*q
, struct request
**req
, struct bio
*bio
)
570 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
571 struct request
*__rq
;
573 __rq
= cfq_find_rq_fmerge(cfqd
, bio
);
574 if (__rq
&& elv_rq_merge_ok(__rq
, bio
)) {
576 return ELEVATOR_FRONT_MERGE
;
579 return ELEVATOR_NO_MERGE
;
582 static void cfq_merged_request(request_queue_t
*q
, struct request
*req
,
585 struct cfq_rq
*crq
= RQ_DATA(req
);
587 if (type
== ELEVATOR_FRONT_MERGE
) {
588 struct cfq_queue
*cfqq
= crq
->cfq_queue
;
590 cfq_reposition_crq_rb(cfqq
, crq
);
595 cfq_merged_requests(request_queue_t
*q
, struct request
*rq
,
596 struct request
*next
)
599 * reposition in fifo if next is older than rq
601 if (!list_empty(&rq
->queuelist
) && !list_empty(&next
->queuelist
) &&
602 time_before(next
->start_time
, rq
->start_time
))
603 list_move(&rq
->queuelist
, &next
->queuelist
);
605 cfq_remove_request(next
);
609 __cfq_set_active_queue(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
613 * stop potential idle class queues waiting service
615 del_timer(&cfqd
->idle_class_timer
);
617 cfqq
->slice_start
= jiffies
;
619 cfqq
->slice_left
= 0;
620 cfq_clear_cfqq_must_alloc_slice(cfqq
);
621 cfq_clear_cfqq_fifo_expire(cfqq
);
624 cfqd
->active_queue
= cfqq
;
628 * current cfqq expired its slice (or was too idle), select new one
631 __cfq_slice_expired(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
634 unsigned long now
= jiffies
;
636 if (cfq_cfqq_wait_request(cfqq
))
637 del_timer(&cfqd
->idle_slice_timer
);
639 if (!preempted
&& !cfq_cfqq_dispatched(cfqq
)) {
640 cfqq
->service_last
= now
;
641 cfq_schedule_dispatch(cfqd
);
644 cfq_clear_cfqq_must_dispatch(cfqq
);
645 cfq_clear_cfqq_wait_request(cfqq
);
648 * store what was left of this slice, if the queue idled out
651 if (time_after(cfqq
->slice_end
, now
))
652 cfqq
->slice_left
= cfqq
->slice_end
- now
;
654 cfqq
->slice_left
= 0;
656 if (cfq_cfqq_on_rr(cfqq
))
657 cfq_resort_rr_list(cfqq
, preempted
);
659 if (cfqq
== cfqd
->active_queue
)
660 cfqd
->active_queue
= NULL
;
662 if (cfqd
->active_cic
) {
663 put_io_context(cfqd
->active_cic
->ioc
);
664 cfqd
->active_cic
= NULL
;
667 cfqd
->dispatch_slice
= 0;
670 static inline void cfq_slice_expired(struct cfq_data
*cfqd
, int preempted
)
672 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
675 __cfq_slice_expired(cfqd
, cfqq
, preempted
);
688 static int cfq_get_next_prio_level(struct cfq_data
*cfqd
)
697 for (p
= cfqd
->cur_prio
; p
<= cfqd
->cur_end_prio
; p
++) {
698 if (!list_empty(&cfqd
->rr_list
[p
])) {
707 if (++cfqd
->cur_end_prio
== CFQ_PRIO_LISTS
) {
708 cfqd
->cur_end_prio
= 0;
715 if (unlikely(prio
== -1))
718 BUG_ON(prio
>= CFQ_PRIO_LISTS
);
720 list_splice_init(&cfqd
->rr_list
[prio
], &cfqd
->cur_rr
);
722 cfqd
->cur_prio
= prio
+ 1;
723 if (cfqd
->cur_prio
> cfqd
->cur_end_prio
) {
724 cfqd
->cur_end_prio
= cfqd
->cur_prio
;
727 if (cfqd
->cur_end_prio
== CFQ_PRIO_LISTS
) {
729 cfqd
->cur_end_prio
= 0;
735 static struct cfq_queue
*cfq_set_active_queue(struct cfq_data
*cfqd
)
737 struct cfq_queue
*cfqq
= NULL
;
740 * if current list is non-empty, grab first entry. if it is empty,
741 * get next prio level and grab first entry then if any are spliced
743 if (!list_empty(&cfqd
->cur_rr
) || cfq_get_next_prio_level(cfqd
) != -1)
744 cfqq
= list_entry_cfqq(cfqd
->cur_rr
.next
);
747 * If no new queues are available, check if the busy list has some
748 * before falling back to idle io.
750 if (!cfqq
&& !list_empty(&cfqd
->busy_rr
))
751 cfqq
= list_entry_cfqq(cfqd
->busy_rr
.next
);
754 * if we have idle queues and no rt or be queues had pending
755 * requests, either allow immediate service if the grace period
756 * has passed or arm the idle grace timer
758 if (!cfqq
&& !list_empty(&cfqd
->idle_rr
)) {
759 unsigned long end
= cfqd
->last_end_request
+ CFQ_IDLE_GRACE
;
761 if (time_after_eq(jiffies
, end
))
762 cfqq
= list_entry_cfqq(cfqd
->idle_rr
.next
);
764 mod_timer(&cfqd
->idle_class_timer
, end
);
767 __cfq_set_active_queue(cfqd
, cfqq
);
771 #define CIC_SEEKY(cic) ((cic)->seek_mean > (128 * 1024))
773 static int cfq_arm_slice_timer(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
776 struct cfq_io_context
*cic
;
779 WARN_ON(!RB_EMPTY_ROOT(&cfqq
->sort_list
));
780 WARN_ON(cfqq
!= cfqd
->active_queue
);
783 * idle is disabled, either manually or by past process history
785 if (!cfqd
->cfq_slice_idle
)
787 if (!cfq_cfqq_idle_window(cfqq
))
790 * task has exited, don't wait
792 cic
= cfqd
->active_cic
;
793 if (!cic
|| !cic
->ioc
->task
)
796 cfq_mark_cfqq_must_dispatch(cfqq
);
797 cfq_mark_cfqq_wait_request(cfqq
);
799 sl
= min(cfqq
->slice_end
- 1, (unsigned long) cfqd
->cfq_slice_idle
);
802 * we don't want to idle for seeks, but we do want to allow
803 * fair distribution of slice time for a process doing back-to-back
804 * seeks. so allow a little bit of time for him to submit a new rq
806 if (sample_valid(cic
->seek_samples
) && CIC_SEEKY(cic
))
807 sl
= min(sl
, msecs_to_jiffies(2));
809 mod_timer(&cfqd
->idle_slice_timer
, jiffies
+ sl
);
813 static void cfq_dispatch_insert(request_queue_t
*q
, struct cfq_rq
*crq
)
815 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
816 struct cfq_queue
*cfqq
= crq
->cfq_queue
;
819 cfq_remove_request(crq
->request
);
820 cfqq
->on_dispatch
[cfq_crq_is_sync(crq
)]++;
821 elv_dispatch_sort(q
, crq
->request
);
823 rq
= list_entry(q
->queue_head
.prev
, struct request
, queuelist
);
824 cfqd
->last_sector
= rq
->sector
+ rq
->nr_sectors
;
828 * return expired entry, or NULL to just start from scratch in rbtree
830 static inline struct cfq_rq
*cfq_check_fifo(struct cfq_queue
*cfqq
)
832 struct cfq_data
*cfqd
= cfqq
->cfqd
;
836 if (cfq_cfqq_fifo_expire(cfqq
))
839 if (!list_empty(&cfqq
->fifo
)) {
840 int fifo
= cfq_cfqq_class_sync(cfqq
);
842 crq
= RQ_DATA(rq_entry_fifo(cfqq
->fifo
.next
));
844 if (time_after(jiffies
, rq
->start_time
+ cfqd
->cfq_fifo_expire
[fifo
])) {
845 cfq_mark_cfqq_fifo_expire(cfqq
);
854 * Scale schedule slice based on io priority. Use the sync time slice only
855 * if a queue is marked sync and has sync io queued. A sync queue with async
856 * io only, should not get full sync slice length.
859 cfq_prio_to_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
861 const int base_slice
= cfqd
->cfq_slice
[cfq_cfqq_sync(cfqq
)];
863 WARN_ON(cfqq
->ioprio
>= IOPRIO_BE_NR
);
865 return base_slice
+ (base_slice
/CFQ_SLICE_SCALE
* (4 - cfqq
->ioprio
));
869 cfq_set_prio_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
871 cfqq
->slice_end
= cfq_prio_to_slice(cfqd
, cfqq
) + jiffies
;
875 cfq_prio_to_maxrq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
877 const int base_rq
= cfqd
->cfq_slice_async_rq
;
879 WARN_ON(cfqq
->ioprio
>= IOPRIO_BE_NR
);
881 return 2 * (base_rq
+ base_rq
* (CFQ_PRIO_LISTS
- 1 - cfqq
->ioprio
));
885 * get next queue for service
887 static struct cfq_queue
*cfq_select_queue(struct cfq_data
*cfqd
)
889 unsigned long now
= jiffies
;
890 struct cfq_queue
*cfqq
;
892 cfqq
= cfqd
->active_queue
;
899 if (!cfq_cfqq_must_dispatch(cfqq
) && time_after(now
, cfqq
->slice_end
))
903 * if queue has requests, dispatch one. if not, check if
904 * enough slice is left to wait for one
906 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
))
908 else if (cfq_cfqq_dispatched(cfqq
)) {
911 } else if (cfq_cfqq_class_sync(cfqq
)) {
912 if (cfq_arm_slice_timer(cfqd
, cfqq
))
917 cfq_slice_expired(cfqd
, 0);
919 cfqq
= cfq_set_active_queue(cfqd
);
925 __cfq_dispatch_requests(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
930 BUG_ON(RB_EMPTY_ROOT(&cfqq
->sort_list
));
936 * follow expired path, else get first next available
938 if ((crq
= cfq_check_fifo(cfqq
)) == NULL
)
939 crq
= cfqq
->next_crq
;
942 * finally, insert request into driver dispatch list
944 cfq_dispatch_insert(cfqd
->queue
, crq
);
946 cfqd
->dispatch_slice
++;
949 if (!cfqd
->active_cic
) {
950 atomic_inc(&crq
->io_context
->ioc
->refcount
);
951 cfqd
->active_cic
= crq
->io_context
;
954 if (RB_EMPTY_ROOT(&cfqq
->sort_list
))
957 } while (dispatched
< max_dispatch
);
960 * if slice end isn't set yet, set it.
962 if (!cfqq
->slice_end
)
963 cfq_set_prio_slice(cfqd
, cfqq
);
966 * expire an async queue immediately if it has used up its slice. idle
967 * queue always expire after 1 dispatch round.
969 if ((!cfq_cfqq_sync(cfqq
) &&
970 cfqd
->dispatch_slice
>= cfq_prio_to_maxrq(cfqd
, cfqq
)) ||
971 cfq_class_idle(cfqq
) ||
972 !cfq_cfqq_idle_window(cfqq
))
973 cfq_slice_expired(cfqd
, 0);
979 cfq_forced_dispatch_cfqqs(struct list_head
*list
)
981 struct cfq_queue
*cfqq
, *next
;
986 list_for_each_entry_safe(cfqq
, next
, list
, cfq_list
) {
987 while ((crq
= cfqq
->next_crq
)) {
988 cfq_dispatch_insert(cfqq
->cfqd
->queue
, crq
);
991 BUG_ON(!list_empty(&cfqq
->fifo
));
998 cfq_forced_dispatch(struct cfq_data
*cfqd
)
1000 int i
, dispatched
= 0;
1002 for (i
= 0; i
< CFQ_PRIO_LISTS
; i
++)
1003 dispatched
+= cfq_forced_dispatch_cfqqs(&cfqd
->rr_list
[i
]);
1005 dispatched
+= cfq_forced_dispatch_cfqqs(&cfqd
->busy_rr
);
1006 dispatched
+= cfq_forced_dispatch_cfqqs(&cfqd
->cur_rr
);
1007 dispatched
+= cfq_forced_dispatch_cfqqs(&cfqd
->idle_rr
);
1009 cfq_slice_expired(cfqd
, 0);
1011 BUG_ON(cfqd
->busy_queues
);
1017 cfq_dispatch_requests(request_queue_t
*q
, int force
)
1019 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1020 struct cfq_queue
*cfqq
, *prev_cfqq
;
1023 if (!cfqd
->busy_queues
)
1026 if (unlikely(force
))
1027 return cfq_forced_dispatch(cfqd
);
1031 while ((cfqq
= cfq_select_queue(cfqd
)) != NULL
) {
1035 * Don't repeat dispatch from the previous queue.
1037 if (prev_cfqq
== cfqq
)
1040 cfq_clear_cfqq_must_dispatch(cfqq
);
1041 cfq_clear_cfqq_wait_request(cfqq
);
1042 del_timer(&cfqd
->idle_slice_timer
);
1044 max_dispatch
= cfqd
->cfq_quantum
;
1045 if (cfq_class_idle(cfqq
))
1048 dispatched
+= __cfq_dispatch_requests(cfqd
, cfqq
, max_dispatch
);
1051 * If the dispatch cfqq has idling enabled and is still
1052 * the active queue, break out.
1054 if (cfq_cfqq_idle_window(cfqq
) && cfqd
->active_queue
)
1064 * task holds one reference to the queue, dropped when task exits. each crq
1065 * in-flight on this queue also holds a reference, dropped when crq is freed.
1067 * queue lock must be held here.
1069 static void cfq_put_queue(struct cfq_queue
*cfqq
)
1071 struct cfq_data
*cfqd
= cfqq
->cfqd
;
1073 BUG_ON(atomic_read(&cfqq
->ref
) <= 0);
1075 if (!atomic_dec_and_test(&cfqq
->ref
))
1078 BUG_ON(rb_first(&cfqq
->sort_list
));
1079 BUG_ON(cfqq
->allocated
[READ
] + cfqq
->allocated
[WRITE
]);
1080 BUG_ON(cfq_cfqq_on_rr(cfqq
));
1082 if (unlikely(cfqd
->active_queue
== cfqq
))
1083 __cfq_slice_expired(cfqd
, cfqq
, 0);
1086 * it's on the empty list and still hashed
1088 list_del(&cfqq
->cfq_list
);
1089 hlist_del(&cfqq
->cfq_hash
);
1090 kmem_cache_free(cfq_pool
, cfqq
);
1093 static inline struct cfq_queue
*
1094 __cfq_find_cfq_hash(struct cfq_data
*cfqd
, unsigned int key
, unsigned int prio
,
1097 struct hlist_head
*hash_list
= &cfqd
->cfq_hash
[hashval
];
1098 struct hlist_node
*entry
;
1099 struct cfq_queue
*__cfqq
;
1101 hlist_for_each_entry(__cfqq
, entry
, hash_list
, cfq_hash
) {
1102 const unsigned short __p
= IOPRIO_PRIO_VALUE(__cfqq
->org_ioprio_class
, __cfqq
->org_ioprio
);
1104 if (__cfqq
->key
== key
&& (__p
== prio
|| !prio
))
1111 static struct cfq_queue
*
1112 cfq_find_cfq_hash(struct cfq_data
*cfqd
, unsigned int key
, unsigned short prio
)
1114 return __cfq_find_cfq_hash(cfqd
, key
, prio
, hash_long(key
, CFQ_QHASH_SHIFT
));
1117 static void cfq_free_io_context(struct io_context
*ioc
)
1119 struct cfq_io_context
*__cic
;
1123 while ((n
= rb_first(&ioc
->cic_root
)) != NULL
) {
1124 __cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1125 rb_erase(&__cic
->rb_node
, &ioc
->cic_root
);
1126 kmem_cache_free(cfq_ioc_pool
, __cic
);
1130 if (atomic_sub_and_test(freed
, &ioc_count
) && ioc_gone
)
1134 static void cfq_trim(struct io_context
*ioc
)
1136 ioc
->set_ioprio
= NULL
;
1137 cfq_free_io_context(ioc
);
1141 * Called with interrupts disabled
1143 static void cfq_exit_single_io_context(struct cfq_io_context
*cic
)
1145 struct cfq_data
*cfqd
= cic
->key
;
1153 WARN_ON(!irqs_disabled());
1155 spin_lock(q
->queue_lock
);
1157 if (cic
->cfqq
[ASYNC
]) {
1158 if (unlikely(cic
->cfqq
[ASYNC
] == cfqd
->active_queue
))
1159 __cfq_slice_expired(cfqd
, cic
->cfqq
[ASYNC
], 0);
1160 cfq_put_queue(cic
->cfqq
[ASYNC
]);
1161 cic
->cfqq
[ASYNC
] = NULL
;
1164 if (cic
->cfqq
[SYNC
]) {
1165 if (unlikely(cic
->cfqq
[SYNC
] == cfqd
->active_queue
))
1166 __cfq_slice_expired(cfqd
, cic
->cfqq
[SYNC
], 0);
1167 cfq_put_queue(cic
->cfqq
[SYNC
]);
1168 cic
->cfqq
[SYNC
] = NULL
;
1172 list_del_init(&cic
->queue_list
);
1173 spin_unlock(q
->queue_lock
);
1176 static void cfq_exit_io_context(struct io_context
*ioc
)
1178 struct cfq_io_context
*__cic
;
1179 unsigned long flags
;
1183 * put the reference this task is holding to the various queues
1185 spin_lock_irqsave(&cfq_exit_lock
, flags
);
1187 n
= rb_first(&ioc
->cic_root
);
1189 __cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1191 cfq_exit_single_io_context(__cic
);
1195 spin_unlock_irqrestore(&cfq_exit_lock
, flags
);
1198 static struct cfq_io_context
*
1199 cfq_alloc_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
1201 struct cfq_io_context
*cic
= kmem_cache_alloc(cfq_ioc_pool
, gfp_mask
);
1204 memset(cic
, 0, sizeof(*cic
));
1205 cic
->last_end_request
= jiffies
;
1206 INIT_LIST_HEAD(&cic
->queue_list
);
1207 cic
->dtor
= cfq_free_io_context
;
1208 cic
->exit
= cfq_exit_io_context
;
1209 atomic_inc(&ioc_count
);
1215 static void cfq_init_prio_data(struct cfq_queue
*cfqq
)
1217 struct task_struct
*tsk
= current
;
1220 if (!cfq_cfqq_prio_changed(cfqq
))
1223 ioprio_class
= IOPRIO_PRIO_CLASS(tsk
->ioprio
);
1224 switch (ioprio_class
) {
1226 printk(KERN_ERR
"cfq: bad prio %x\n", ioprio_class
);
1227 case IOPRIO_CLASS_NONE
:
1229 * no prio set, place us in the middle of the BE classes
1231 cfqq
->ioprio
= task_nice_ioprio(tsk
);
1232 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1234 case IOPRIO_CLASS_RT
:
1235 cfqq
->ioprio
= task_ioprio(tsk
);
1236 cfqq
->ioprio_class
= IOPRIO_CLASS_RT
;
1238 case IOPRIO_CLASS_BE
:
1239 cfqq
->ioprio
= task_ioprio(tsk
);
1240 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1242 case IOPRIO_CLASS_IDLE
:
1243 cfqq
->ioprio_class
= IOPRIO_CLASS_IDLE
;
1245 cfq_clear_cfqq_idle_window(cfqq
);
1250 * keep track of original prio settings in case we have to temporarily
1251 * elevate the priority of this queue
1253 cfqq
->org_ioprio
= cfqq
->ioprio
;
1254 cfqq
->org_ioprio_class
= cfqq
->ioprio_class
;
1256 if (cfq_cfqq_on_rr(cfqq
))
1257 cfq_resort_rr_list(cfqq
, 0);
1259 cfq_clear_cfqq_prio_changed(cfqq
);
1262 static inline void changed_ioprio(struct cfq_io_context
*cic
)
1264 struct cfq_data
*cfqd
= cic
->key
;
1265 struct cfq_queue
*cfqq
;
1267 if (unlikely(!cfqd
))
1270 spin_lock(cfqd
->queue
->queue_lock
);
1272 cfqq
= cic
->cfqq
[ASYNC
];
1274 struct cfq_queue
*new_cfqq
;
1275 new_cfqq
= cfq_get_queue(cfqd
, CFQ_KEY_ASYNC
, cic
->ioc
->task
,
1278 cic
->cfqq
[ASYNC
] = new_cfqq
;
1279 cfq_put_queue(cfqq
);
1283 cfqq
= cic
->cfqq
[SYNC
];
1285 cfq_mark_cfqq_prio_changed(cfqq
);
1287 spin_unlock(cfqd
->queue
->queue_lock
);
1291 * callback from sys_ioprio_set, irqs are disabled
1293 static int cfq_ioc_set_ioprio(struct io_context
*ioc
, unsigned int ioprio
)
1295 struct cfq_io_context
*cic
;
1298 spin_lock(&cfq_exit_lock
);
1300 n
= rb_first(&ioc
->cic_root
);
1302 cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1304 changed_ioprio(cic
);
1308 spin_unlock(&cfq_exit_lock
);
1313 static struct cfq_queue
*
1314 cfq_get_queue(struct cfq_data
*cfqd
, unsigned int key
, struct task_struct
*tsk
,
1317 const int hashval
= hash_long(key
, CFQ_QHASH_SHIFT
);
1318 struct cfq_queue
*cfqq
, *new_cfqq
= NULL
;
1319 unsigned short ioprio
;
1322 ioprio
= tsk
->ioprio
;
1323 cfqq
= __cfq_find_cfq_hash(cfqd
, key
, ioprio
, hashval
);
1329 } else if (gfp_mask
& __GFP_WAIT
) {
1330 spin_unlock_irq(cfqd
->queue
->queue_lock
);
1331 new_cfqq
= kmem_cache_alloc(cfq_pool
, gfp_mask
);
1332 spin_lock_irq(cfqd
->queue
->queue_lock
);
1335 cfqq
= kmem_cache_alloc(cfq_pool
, gfp_mask
);
1340 memset(cfqq
, 0, sizeof(*cfqq
));
1342 INIT_HLIST_NODE(&cfqq
->cfq_hash
);
1343 INIT_LIST_HEAD(&cfqq
->cfq_list
);
1344 INIT_LIST_HEAD(&cfqq
->fifo
);
1347 hlist_add_head(&cfqq
->cfq_hash
, &cfqd
->cfq_hash
[hashval
]);
1348 atomic_set(&cfqq
->ref
, 0);
1350 cfqq
->service_last
= 0;
1352 * set ->slice_left to allow preemption for a new process
1354 cfqq
->slice_left
= 2 * cfqd
->cfq_slice_idle
;
1355 cfq_mark_cfqq_idle_window(cfqq
);
1356 cfq_mark_cfqq_prio_changed(cfqq
);
1357 cfq_init_prio_data(cfqq
);
1361 kmem_cache_free(cfq_pool
, new_cfqq
);
1363 atomic_inc(&cfqq
->ref
);
1365 WARN_ON((gfp_mask
& __GFP_WAIT
) && !cfqq
);
1370 cfq_drop_dead_cic(struct io_context
*ioc
, struct cfq_io_context
*cic
)
1372 spin_lock(&cfq_exit_lock
);
1373 rb_erase(&cic
->rb_node
, &ioc
->cic_root
);
1374 list_del_init(&cic
->queue_list
);
1375 spin_unlock(&cfq_exit_lock
);
1376 kmem_cache_free(cfq_ioc_pool
, cic
);
1377 atomic_dec(&ioc_count
);
1380 static struct cfq_io_context
*
1381 cfq_cic_rb_lookup(struct cfq_data
*cfqd
, struct io_context
*ioc
)
1384 struct cfq_io_context
*cic
;
1385 void *k
, *key
= cfqd
;
1388 n
= ioc
->cic_root
.rb_node
;
1390 cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1391 /* ->key must be copied to avoid race with cfq_exit_queue() */
1394 cfq_drop_dead_cic(ioc
, cic
);
1410 cfq_cic_link(struct cfq_data
*cfqd
, struct io_context
*ioc
,
1411 struct cfq_io_context
*cic
)
1414 struct rb_node
*parent
;
1415 struct cfq_io_context
*__cic
;
1421 ioc
->set_ioprio
= cfq_ioc_set_ioprio
;
1424 p
= &ioc
->cic_root
.rb_node
;
1427 __cic
= rb_entry(parent
, struct cfq_io_context
, rb_node
);
1428 /* ->key must be copied to avoid race with cfq_exit_queue() */
1431 cfq_drop_dead_cic(ioc
, __cic
);
1437 else if (cic
->key
> k
)
1438 p
= &(*p
)->rb_right
;
1443 spin_lock(&cfq_exit_lock
);
1444 rb_link_node(&cic
->rb_node
, parent
, p
);
1445 rb_insert_color(&cic
->rb_node
, &ioc
->cic_root
);
1446 list_add(&cic
->queue_list
, &cfqd
->cic_list
);
1447 spin_unlock(&cfq_exit_lock
);
1451 * Setup general io context and cfq io context. There can be several cfq
1452 * io contexts per general io context, if this process is doing io to more
1453 * than one device managed by cfq.
1455 static struct cfq_io_context
*
1456 cfq_get_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
1458 struct io_context
*ioc
= NULL
;
1459 struct cfq_io_context
*cic
;
1461 might_sleep_if(gfp_mask
& __GFP_WAIT
);
1463 ioc
= get_io_context(gfp_mask
);
1467 cic
= cfq_cic_rb_lookup(cfqd
, ioc
);
1471 cic
= cfq_alloc_io_context(cfqd
, gfp_mask
);
1475 cfq_cic_link(cfqd
, ioc
, cic
);
1479 put_io_context(ioc
);
1484 cfq_update_io_thinktime(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
)
1486 unsigned long elapsed
, ttime
;
1489 * if this context already has stuff queued, thinktime is from
1490 * last queue not last end
1493 if (time_after(cic
->last_end_request
, cic
->last_queue
))
1494 elapsed
= jiffies
- cic
->last_end_request
;
1496 elapsed
= jiffies
- cic
->last_queue
;
1498 elapsed
= jiffies
- cic
->last_end_request
;
1501 ttime
= min(elapsed
, 2UL * cfqd
->cfq_slice_idle
);
1503 cic
->ttime_samples
= (7*cic
->ttime_samples
+ 256) / 8;
1504 cic
->ttime_total
= (7*cic
->ttime_total
+ 256*ttime
) / 8;
1505 cic
->ttime_mean
= (cic
->ttime_total
+ 128) / cic
->ttime_samples
;
1509 cfq_update_io_seektime(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
,
1515 if (cic
->last_request_pos
< crq
->request
->sector
)
1516 sdist
= crq
->request
->sector
- cic
->last_request_pos
;
1518 sdist
= cic
->last_request_pos
- crq
->request
->sector
;
1521 * Don't allow the seek distance to get too large from the
1522 * odd fragment, pagein, etc
1524 if (cic
->seek_samples
<= 60) /* second&third seek */
1525 sdist
= min(sdist
, (cic
->seek_mean
* 4) + 2*1024*1024);
1527 sdist
= min(sdist
, (cic
->seek_mean
* 4) + 2*1024*64);
1529 cic
->seek_samples
= (7*cic
->seek_samples
+ 256) / 8;
1530 cic
->seek_total
= (7*cic
->seek_total
+ (u64
)256*sdist
) / 8;
1531 total
= cic
->seek_total
+ (cic
->seek_samples
/2);
1532 do_div(total
, cic
->seek_samples
);
1533 cic
->seek_mean
= (sector_t
)total
;
1537 * Disable idle window if the process thinks too long or seeks so much that
1541 cfq_update_idle_window(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1542 struct cfq_io_context
*cic
)
1544 int enable_idle
= cfq_cfqq_idle_window(cfqq
);
1546 if (!cic
->ioc
->task
|| !cfqd
->cfq_slice_idle
||
1547 (cfqd
->hw_tag
&& CIC_SEEKY(cic
)))
1549 else if (sample_valid(cic
->ttime_samples
)) {
1550 if (cic
->ttime_mean
> cfqd
->cfq_slice_idle
)
1557 cfq_mark_cfqq_idle_window(cfqq
);
1559 cfq_clear_cfqq_idle_window(cfqq
);
1564 * Check if new_cfqq should preempt the currently active queue. Return 0 for
1565 * no or if we aren't sure, a 1 will cause a preempt.
1568 cfq_should_preempt(struct cfq_data
*cfqd
, struct cfq_queue
*new_cfqq
,
1571 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
1573 if (cfq_class_idle(new_cfqq
))
1579 if (cfq_class_idle(cfqq
))
1581 if (!cfq_cfqq_wait_request(new_cfqq
))
1584 * if it doesn't have slice left, forget it
1586 if (new_cfqq
->slice_left
< cfqd
->cfq_slice_idle
)
1588 if (cfq_crq_is_sync(crq
) && !cfq_cfqq_sync(cfqq
))
1595 * cfqq preempts the active queue. if we allowed preempt with no slice left,
1596 * let it have half of its nominal slice.
1598 static void cfq_preempt_queue(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1600 struct cfq_queue
*__cfqq
, *next
;
1602 list_for_each_entry_safe(__cfqq
, next
, &cfqd
->cur_rr
, cfq_list
)
1603 cfq_resort_rr_list(__cfqq
, 1);
1605 if (!cfqq
->slice_left
)
1606 cfqq
->slice_left
= cfq_prio_to_slice(cfqd
, cfqq
) / 2;
1608 cfqq
->slice_end
= cfqq
->slice_left
+ jiffies
;
1609 cfq_slice_expired(cfqd
, 1);
1610 __cfq_set_active_queue(cfqd
, cfqq
);
1614 * should really be a ll_rw_blk.c helper
1616 static void cfq_start_queueing(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1618 request_queue_t
*q
= cfqd
->queue
;
1620 if (!blk_queue_plugged(q
))
1623 __generic_unplug_device(q
);
1627 * Called when a new fs request (crq) is added (to cfqq). Check if there's
1628 * something we should do about it
1631 cfq_crq_enqueued(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1634 struct cfq_io_context
*cic
= crq
->io_context
;
1637 * check if this request is a better next-serve candidate
1639 cfqq
->next_crq
= cfq_choose_req(cfqd
, cfqq
->next_crq
, crq
);
1640 BUG_ON(!cfqq
->next_crq
);
1643 * we never wait for an async request and we don't allow preemption
1644 * of an async request. so just return early
1646 if (!cfq_crq_is_sync(crq
)) {
1648 * sync process issued an async request, if it's waiting
1649 * then expire it and kick rq handling.
1651 if (cic
== cfqd
->active_cic
&&
1652 del_timer(&cfqd
->idle_slice_timer
)) {
1653 cfq_slice_expired(cfqd
, 0);
1654 cfq_start_queueing(cfqd
, cfqq
);
1659 cfq_update_io_thinktime(cfqd
, cic
);
1660 cfq_update_io_seektime(cfqd
, cic
, crq
);
1661 cfq_update_idle_window(cfqd
, cfqq
, cic
);
1663 cic
->last_queue
= jiffies
;
1664 cic
->last_request_pos
= crq
->request
->sector
+ crq
->request
->nr_sectors
;
1666 if (cfqq
== cfqd
->active_queue
) {
1668 * if we are waiting for a request for this queue, let it rip
1669 * immediately and flag that we must not expire this queue
1672 if (cfq_cfqq_wait_request(cfqq
)) {
1673 cfq_mark_cfqq_must_dispatch(cfqq
);
1674 del_timer(&cfqd
->idle_slice_timer
);
1675 cfq_start_queueing(cfqd
, cfqq
);
1677 } else if (cfq_should_preempt(cfqd
, cfqq
, crq
)) {
1679 * not the active queue - expire current slice if it is
1680 * idle and has expired it's mean thinktime or this new queue
1681 * has some old slice time left and is of higher priority
1683 cfq_preempt_queue(cfqd
, cfqq
);
1684 cfq_mark_cfqq_must_dispatch(cfqq
);
1685 cfq_start_queueing(cfqd
, cfqq
);
1689 static void cfq_insert_request(request_queue_t
*q
, struct request
*rq
)
1691 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1692 struct cfq_rq
*crq
= RQ_DATA(rq
);
1693 struct cfq_queue
*cfqq
= crq
->cfq_queue
;
1695 cfq_init_prio_data(cfqq
);
1697 cfq_add_crq_rb(crq
);
1699 if (!cfq_cfqq_on_rr(cfqq
))
1700 cfq_add_cfqq_rr(cfqd
, cfqq
);
1702 list_add_tail(&rq
->queuelist
, &cfqq
->fifo
);
1704 cfq_crq_enqueued(cfqd
, cfqq
, crq
);
1707 static void cfq_completed_request(request_queue_t
*q
, struct request
*rq
)
1709 struct cfq_rq
*crq
= RQ_DATA(rq
);
1710 struct cfq_queue
*cfqq
= crq
->cfq_queue
;
1711 struct cfq_data
*cfqd
= cfqq
->cfqd
;
1712 const int sync
= cfq_crq_is_sync(crq
);
1717 WARN_ON(!cfqd
->rq_in_driver
);
1718 WARN_ON(!cfqq
->on_dispatch
[sync
]);
1719 cfqd
->rq_in_driver
--;
1720 cfqq
->on_dispatch
[sync
]--;
1722 if (!cfq_class_idle(cfqq
))
1723 cfqd
->last_end_request
= now
;
1725 if (!cfq_cfqq_dispatched(cfqq
)) {
1726 if (cfq_cfqq_on_rr(cfqq
)) {
1727 cfqq
->service_last
= now
;
1728 cfq_resort_rr_list(cfqq
, 0);
1733 crq
->io_context
->last_end_request
= now
;
1736 * If this is the active queue, check if it needs to be expired,
1737 * or if we want to idle in case it has no pending requests.
1739 if (cfqd
->active_queue
== cfqq
) {
1740 if (time_after(now
, cfqq
->slice_end
))
1741 cfq_slice_expired(cfqd
, 0);
1742 else if (sync
&& RB_EMPTY_ROOT(&cfqq
->sort_list
)) {
1743 if (!cfq_arm_slice_timer(cfqd
, cfqq
))
1744 cfq_schedule_dispatch(cfqd
);
1750 * we temporarily boost lower priority queues if they are holding fs exclusive
1751 * resources. they are boosted to normal prio (CLASS_BE/4)
1753 static void cfq_prio_boost(struct cfq_queue
*cfqq
)
1755 const int ioprio_class
= cfqq
->ioprio_class
;
1756 const int ioprio
= cfqq
->ioprio
;
1758 if (has_fs_excl()) {
1760 * boost idle prio on transactions that would lock out other
1761 * users of the filesystem
1763 if (cfq_class_idle(cfqq
))
1764 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1765 if (cfqq
->ioprio
> IOPRIO_NORM
)
1766 cfqq
->ioprio
= IOPRIO_NORM
;
1769 * check if we need to unboost the queue
1771 if (cfqq
->ioprio_class
!= cfqq
->org_ioprio_class
)
1772 cfqq
->ioprio_class
= cfqq
->org_ioprio_class
;
1773 if (cfqq
->ioprio
!= cfqq
->org_ioprio
)
1774 cfqq
->ioprio
= cfqq
->org_ioprio
;
1778 * refile between round-robin lists if we moved the priority class
1780 if ((ioprio_class
!= cfqq
->ioprio_class
|| ioprio
!= cfqq
->ioprio
) &&
1781 cfq_cfqq_on_rr(cfqq
))
1782 cfq_resort_rr_list(cfqq
, 0);
1786 __cfq_may_queue(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1787 struct task_struct
*task
, int rw
)
1789 if ((cfq_cfqq_wait_request(cfqq
) || cfq_cfqq_must_alloc(cfqq
)) &&
1790 !cfq_cfqq_must_alloc_slice(cfqq
)) {
1791 cfq_mark_cfqq_must_alloc_slice(cfqq
);
1792 return ELV_MQUEUE_MUST
;
1795 return ELV_MQUEUE_MAY
;
1798 static int cfq_may_queue(request_queue_t
*q
, int rw
, struct bio
*bio
)
1800 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1801 struct task_struct
*tsk
= current
;
1802 struct cfq_queue
*cfqq
;
1805 * don't force setup of a queue from here, as a call to may_queue
1806 * does not necessarily imply that a request actually will be queued.
1807 * so just lookup a possibly existing queue, or return 'may queue'
1810 cfqq
= cfq_find_cfq_hash(cfqd
, cfq_queue_pid(tsk
, rw
), tsk
->ioprio
);
1812 cfq_init_prio_data(cfqq
);
1813 cfq_prio_boost(cfqq
);
1815 return __cfq_may_queue(cfqd
, cfqq
, tsk
, rw
);
1818 return ELV_MQUEUE_MAY
;
1821 static void cfq_check_waiters(request_queue_t
*q
, struct cfq_queue
*cfqq
)
1823 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1825 if (unlikely(cfqd
->rq_starved
)) {
1826 struct request_list
*rl
= &q
->rq
;
1829 if (waitqueue_active(&rl
->wait
[READ
]))
1830 wake_up(&rl
->wait
[READ
]);
1831 if (waitqueue_active(&rl
->wait
[WRITE
]))
1832 wake_up(&rl
->wait
[WRITE
]);
1837 * queue lock held here
1839 static void cfq_put_request(request_queue_t
*q
, struct request
*rq
)
1841 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1842 struct cfq_rq
*crq
= RQ_DATA(rq
);
1845 struct cfq_queue
*cfqq
= crq
->cfq_queue
;
1846 const int rw
= rq_data_dir(rq
);
1848 BUG_ON(!cfqq
->allocated
[rw
]);
1849 cfqq
->allocated
[rw
]--;
1851 put_io_context(crq
->io_context
->ioc
);
1853 mempool_free(crq
, cfqd
->crq_pool
);
1854 rq
->elevator_private
= NULL
;
1856 cfq_check_waiters(q
, cfqq
);
1857 cfq_put_queue(cfqq
);
1862 * Allocate cfq data structures associated with this request.
1865 cfq_set_request(request_queue_t
*q
, struct request
*rq
, struct bio
*bio
,
1868 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1869 struct task_struct
*tsk
= current
;
1870 struct cfq_io_context
*cic
;
1871 const int rw
= rq_data_dir(rq
);
1872 pid_t key
= cfq_queue_pid(tsk
, rw
);
1873 struct cfq_queue
*cfqq
;
1875 unsigned long flags
;
1876 int is_sync
= key
!= CFQ_KEY_ASYNC
;
1878 might_sleep_if(gfp_mask
& __GFP_WAIT
);
1880 cic
= cfq_get_io_context(cfqd
, gfp_mask
);
1882 spin_lock_irqsave(q
->queue_lock
, flags
);
1887 if (!cic
->cfqq
[is_sync
]) {
1888 cfqq
= cfq_get_queue(cfqd
, key
, tsk
, gfp_mask
);
1892 cic
->cfqq
[is_sync
] = cfqq
;
1894 cfqq
= cic
->cfqq
[is_sync
];
1896 cfqq
->allocated
[rw
]++;
1897 cfq_clear_cfqq_must_alloc(cfqq
);
1898 cfqd
->rq_starved
= 0;
1899 atomic_inc(&cfqq
->ref
);
1900 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1902 crq
= mempool_alloc(cfqd
->crq_pool
, gfp_mask
);
1905 crq
->cfq_queue
= cfqq
;
1906 crq
->io_context
= cic
;
1909 cfq_mark_crq_is_sync(crq
);
1911 cfq_clear_crq_is_sync(crq
);
1913 rq
->elevator_private
= crq
;
1917 spin_lock_irqsave(q
->queue_lock
, flags
);
1918 cfqq
->allocated
[rw
]--;
1919 if (!(cfqq
->allocated
[0] + cfqq
->allocated
[1]))
1920 cfq_mark_cfqq_must_alloc(cfqq
);
1921 cfq_put_queue(cfqq
);
1924 put_io_context(cic
->ioc
);
1926 * mark us rq allocation starved. we need to kickstart the process
1927 * ourselves if there are no pending requests that can do it for us.
1928 * that would be an extremely rare OOM situation
1930 cfqd
->rq_starved
= 1;
1931 cfq_schedule_dispatch(cfqd
);
1932 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1936 static void cfq_kick_queue(void *data
)
1938 request_queue_t
*q
= data
;
1939 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1940 unsigned long flags
;
1942 spin_lock_irqsave(q
->queue_lock
, flags
);
1944 if (cfqd
->rq_starved
) {
1945 struct request_list
*rl
= &q
->rq
;
1948 * we aren't guaranteed to get a request after this, but we
1949 * have to be opportunistic
1952 if (waitqueue_active(&rl
->wait
[READ
]))
1953 wake_up(&rl
->wait
[READ
]);
1954 if (waitqueue_active(&rl
->wait
[WRITE
]))
1955 wake_up(&rl
->wait
[WRITE
]);
1960 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1964 * Timer running if the active_queue is currently idling inside its time slice
1966 static void cfq_idle_slice_timer(unsigned long data
)
1968 struct cfq_data
*cfqd
= (struct cfq_data
*) data
;
1969 struct cfq_queue
*cfqq
;
1970 unsigned long flags
;
1972 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
1974 if ((cfqq
= cfqd
->active_queue
) != NULL
) {
1975 unsigned long now
= jiffies
;
1980 if (time_after(now
, cfqq
->slice_end
))
1984 * only expire and reinvoke request handler, if there are
1985 * other queues with pending requests
1987 if (!cfqd
->busy_queues
)
1991 * not expired and it has a request pending, let it dispatch
1993 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
)) {
1994 cfq_mark_cfqq_must_dispatch(cfqq
);
1999 cfq_slice_expired(cfqd
, 0);
2001 cfq_schedule_dispatch(cfqd
);
2003 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2007 * Timer running if an idle class queue is waiting for service
2009 static void cfq_idle_class_timer(unsigned long data
)
2011 struct cfq_data
*cfqd
= (struct cfq_data
*) data
;
2012 unsigned long flags
, end
;
2014 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
2017 * race with a non-idle queue, reset timer
2019 end
= cfqd
->last_end_request
+ CFQ_IDLE_GRACE
;
2020 if (!time_after_eq(jiffies
, end
))
2021 mod_timer(&cfqd
->idle_class_timer
, end
);
2023 cfq_schedule_dispatch(cfqd
);
2025 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2028 static void cfq_shutdown_timer_wq(struct cfq_data
*cfqd
)
2030 del_timer_sync(&cfqd
->idle_slice_timer
);
2031 del_timer_sync(&cfqd
->idle_class_timer
);
2032 blk_sync_queue(cfqd
->queue
);
2035 static void cfq_exit_queue(elevator_t
*e
)
2037 struct cfq_data
*cfqd
= e
->elevator_data
;
2038 request_queue_t
*q
= cfqd
->queue
;
2040 cfq_shutdown_timer_wq(cfqd
);
2042 spin_lock(&cfq_exit_lock
);
2043 spin_lock_irq(q
->queue_lock
);
2045 if (cfqd
->active_queue
)
2046 __cfq_slice_expired(cfqd
, cfqd
->active_queue
, 0);
2048 while (!list_empty(&cfqd
->cic_list
)) {
2049 struct cfq_io_context
*cic
= list_entry(cfqd
->cic_list
.next
,
2050 struct cfq_io_context
,
2052 if (cic
->cfqq
[ASYNC
]) {
2053 cfq_put_queue(cic
->cfqq
[ASYNC
]);
2054 cic
->cfqq
[ASYNC
] = NULL
;
2056 if (cic
->cfqq
[SYNC
]) {
2057 cfq_put_queue(cic
->cfqq
[SYNC
]);
2058 cic
->cfqq
[SYNC
] = NULL
;
2061 list_del_init(&cic
->queue_list
);
2064 spin_unlock_irq(q
->queue_lock
);
2065 spin_unlock(&cfq_exit_lock
);
2067 cfq_shutdown_timer_wq(cfqd
);
2069 mempool_destroy(cfqd
->crq_pool
);
2070 kfree(cfqd
->cfq_hash
);
2074 static void *cfq_init_queue(request_queue_t
*q
, elevator_t
*e
)
2076 struct cfq_data
*cfqd
;
2079 cfqd
= kmalloc(sizeof(*cfqd
), GFP_KERNEL
);
2083 memset(cfqd
, 0, sizeof(*cfqd
));
2085 for (i
= 0; i
< CFQ_PRIO_LISTS
; i
++)
2086 INIT_LIST_HEAD(&cfqd
->rr_list
[i
]);
2088 INIT_LIST_HEAD(&cfqd
->busy_rr
);
2089 INIT_LIST_HEAD(&cfqd
->cur_rr
);
2090 INIT_LIST_HEAD(&cfqd
->idle_rr
);
2091 INIT_LIST_HEAD(&cfqd
->empty_list
);
2092 INIT_LIST_HEAD(&cfqd
->cic_list
);
2094 cfqd
->cfq_hash
= kmalloc(sizeof(struct hlist_head
) * CFQ_QHASH_ENTRIES
, GFP_KERNEL
);
2095 if (!cfqd
->cfq_hash
)
2098 cfqd
->crq_pool
= mempool_create_slab_pool(BLKDEV_MIN_RQ
, crq_pool
);
2099 if (!cfqd
->crq_pool
)
2102 for (i
= 0; i
< CFQ_QHASH_ENTRIES
; i
++)
2103 INIT_HLIST_HEAD(&cfqd
->cfq_hash
[i
]);
2107 init_timer(&cfqd
->idle_slice_timer
);
2108 cfqd
->idle_slice_timer
.function
= cfq_idle_slice_timer
;
2109 cfqd
->idle_slice_timer
.data
= (unsigned long) cfqd
;
2111 init_timer(&cfqd
->idle_class_timer
);
2112 cfqd
->idle_class_timer
.function
= cfq_idle_class_timer
;
2113 cfqd
->idle_class_timer
.data
= (unsigned long) cfqd
;
2115 INIT_WORK(&cfqd
->unplug_work
, cfq_kick_queue
, q
);
2117 cfqd
->cfq_queued
= cfq_queued
;
2118 cfqd
->cfq_quantum
= cfq_quantum
;
2119 cfqd
->cfq_fifo_expire
[0] = cfq_fifo_expire
[0];
2120 cfqd
->cfq_fifo_expire
[1] = cfq_fifo_expire
[1];
2121 cfqd
->cfq_back_max
= cfq_back_max
;
2122 cfqd
->cfq_back_penalty
= cfq_back_penalty
;
2123 cfqd
->cfq_slice
[0] = cfq_slice_async
;
2124 cfqd
->cfq_slice
[1] = cfq_slice_sync
;
2125 cfqd
->cfq_slice_async_rq
= cfq_slice_async_rq
;
2126 cfqd
->cfq_slice_idle
= cfq_slice_idle
;
2130 kfree(cfqd
->cfq_hash
);
2136 static void cfq_slab_kill(void)
2139 kmem_cache_destroy(crq_pool
);
2141 kmem_cache_destroy(cfq_pool
);
2143 kmem_cache_destroy(cfq_ioc_pool
);
2146 static int __init
cfq_slab_setup(void)
2148 crq_pool
= kmem_cache_create("crq_pool", sizeof(struct cfq_rq
), 0, 0,
2153 cfq_pool
= kmem_cache_create("cfq_pool", sizeof(struct cfq_queue
), 0, 0,
2158 cfq_ioc_pool
= kmem_cache_create("cfq_ioc_pool",
2159 sizeof(struct cfq_io_context
), 0, 0, NULL
, NULL
);
2170 * sysfs parts below -->
2174 cfq_var_show(unsigned int var
, char *page
)
2176 return sprintf(page
, "%d\n", var
);
2180 cfq_var_store(unsigned int *var
, const char *page
, size_t count
)
2182 char *p
= (char *) page
;
2184 *var
= simple_strtoul(p
, &p
, 10);
2188 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
2189 static ssize_t __FUNC(elevator_t *e, char *page) \
2191 struct cfq_data *cfqd = e->elevator_data; \
2192 unsigned int __data = __VAR; \
2194 __data = jiffies_to_msecs(__data); \
2195 return cfq_var_show(__data, (page)); \
2197 SHOW_FUNCTION(cfq_quantum_show
, cfqd
->cfq_quantum
, 0);
2198 SHOW_FUNCTION(cfq_queued_show
, cfqd
->cfq_queued
, 0);
2199 SHOW_FUNCTION(cfq_fifo_expire_sync_show
, cfqd
->cfq_fifo_expire
[1], 1);
2200 SHOW_FUNCTION(cfq_fifo_expire_async_show
, cfqd
->cfq_fifo_expire
[0], 1);
2201 SHOW_FUNCTION(cfq_back_seek_max_show
, cfqd
->cfq_back_max
, 0);
2202 SHOW_FUNCTION(cfq_back_seek_penalty_show
, cfqd
->cfq_back_penalty
, 0);
2203 SHOW_FUNCTION(cfq_slice_idle_show
, cfqd
->cfq_slice_idle
, 1);
2204 SHOW_FUNCTION(cfq_slice_sync_show
, cfqd
->cfq_slice
[1], 1);
2205 SHOW_FUNCTION(cfq_slice_async_show
, cfqd
->cfq_slice
[0], 1);
2206 SHOW_FUNCTION(cfq_slice_async_rq_show
, cfqd
->cfq_slice_async_rq
, 0);
2207 #undef SHOW_FUNCTION
2209 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
2210 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
2212 struct cfq_data *cfqd = e->elevator_data; \
2213 unsigned int __data; \
2214 int ret = cfq_var_store(&__data, (page), count); \
2215 if (__data < (MIN)) \
2217 else if (__data > (MAX)) \
2220 *(__PTR) = msecs_to_jiffies(__data); \
2222 *(__PTR) = __data; \
2225 STORE_FUNCTION(cfq_quantum_store
, &cfqd
->cfq_quantum
, 1, UINT_MAX
, 0);
2226 STORE_FUNCTION(cfq_queued_store
, &cfqd
->cfq_queued
, 1, UINT_MAX
, 0);
2227 STORE_FUNCTION(cfq_fifo_expire_sync_store
, &cfqd
->cfq_fifo_expire
[1], 1, UINT_MAX
, 1);
2228 STORE_FUNCTION(cfq_fifo_expire_async_store
, &cfqd
->cfq_fifo_expire
[0], 1, UINT_MAX
, 1);
2229 STORE_FUNCTION(cfq_back_seek_max_store
, &cfqd
->cfq_back_max
, 0, UINT_MAX
, 0);
2230 STORE_FUNCTION(cfq_back_seek_penalty_store
, &cfqd
->cfq_back_penalty
, 1, UINT_MAX
, 0);
2231 STORE_FUNCTION(cfq_slice_idle_store
, &cfqd
->cfq_slice_idle
, 0, UINT_MAX
, 1);
2232 STORE_FUNCTION(cfq_slice_sync_store
, &cfqd
->cfq_slice
[1], 1, UINT_MAX
, 1);
2233 STORE_FUNCTION(cfq_slice_async_store
, &cfqd
->cfq_slice
[0], 1, UINT_MAX
, 1);
2234 STORE_FUNCTION(cfq_slice_async_rq_store
, &cfqd
->cfq_slice_async_rq
, 1, UINT_MAX
, 0);
2235 #undef STORE_FUNCTION
2237 #define CFQ_ATTR(name) \
2238 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2240 static struct elv_fs_entry cfq_attrs
[] = {
2243 CFQ_ATTR(fifo_expire_sync
),
2244 CFQ_ATTR(fifo_expire_async
),
2245 CFQ_ATTR(back_seek_max
),
2246 CFQ_ATTR(back_seek_penalty
),
2247 CFQ_ATTR(slice_sync
),
2248 CFQ_ATTR(slice_async
),
2249 CFQ_ATTR(slice_async_rq
),
2250 CFQ_ATTR(slice_idle
),
2254 static struct elevator_type iosched_cfq
= {
2256 .elevator_merge_fn
= cfq_merge
,
2257 .elevator_merged_fn
= cfq_merged_request
,
2258 .elevator_merge_req_fn
= cfq_merged_requests
,
2259 .elevator_dispatch_fn
= cfq_dispatch_requests
,
2260 .elevator_add_req_fn
= cfq_insert_request
,
2261 .elevator_activate_req_fn
= cfq_activate_request
,
2262 .elevator_deactivate_req_fn
= cfq_deactivate_request
,
2263 .elevator_queue_empty_fn
= cfq_queue_empty
,
2264 .elevator_completed_req_fn
= cfq_completed_request
,
2265 .elevator_former_req_fn
= elv_rb_former_request
,
2266 .elevator_latter_req_fn
= elv_rb_latter_request
,
2267 .elevator_set_req_fn
= cfq_set_request
,
2268 .elevator_put_req_fn
= cfq_put_request
,
2269 .elevator_may_queue_fn
= cfq_may_queue
,
2270 .elevator_init_fn
= cfq_init_queue
,
2271 .elevator_exit_fn
= cfq_exit_queue
,
2274 .elevator_attrs
= cfq_attrs
,
2275 .elevator_name
= "cfq",
2276 .elevator_owner
= THIS_MODULE
,
2279 static int __init
cfq_init(void)
2284 * could be 0 on HZ < 1000 setups
2286 if (!cfq_slice_async
)
2287 cfq_slice_async
= 1;
2288 if (!cfq_slice_idle
)
2291 if (cfq_slab_setup())
2294 ret
= elv_register(&iosched_cfq
);
2301 static void __exit
cfq_exit(void)
2303 DECLARE_COMPLETION(all_gone
);
2304 elv_unregister(&iosched_cfq
);
2305 ioc_gone
= &all_gone
;
2306 /* ioc_gone's update must be visible before reading ioc_count */
2308 if (atomic_read(&ioc_count
))
2309 wait_for_completion(ioc_gone
);
2314 module_init(cfq_init
);
2315 module_exit(cfq_exit
);
2317 MODULE_AUTHOR("Jens Axboe");
2318 MODULE_LICENSE("GPL");
2319 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");