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_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 kmem_cache_t
*cfq_pool
;
47 static kmem_cache_t
*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 /* fifo list of requests in sort_list */
145 struct list_head fifo
;
147 unsigned long slice_start
;
148 unsigned long slice_end
;
149 unsigned long slice_left
;
151 /* number of requests that are on the dispatch list */
154 /* io prio of this group */
155 unsigned short ioprio
, org_ioprio
;
156 unsigned short ioprio_class
, org_ioprio_class
;
158 /* various state flags, see below */
162 enum cfqq_state_flags
{
163 CFQ_CFQQ_FLAG_on_rr
= 0,
164 CFQ_CFQQ_FLAG_wait_request
,
165 CFQ_CFQQ_FLAG_must_alloc
,
166 CFQ_CFQQ_FLAG_must_alloc_slice
,
167 CFQ_CFQQ_FLAG_must_dispatch
,
168 CFQ_CFQQ_FLAG_fifo_expire
,
169 CFQ_CFQQ_FLAG_idle_window
,
170 CFQ_CFQQ_FLAG_prio_changed
,
171 CFQ_CFQQ_FLAG_queue_new
,
174 #define CFQ_CFQQ_FNS(name) \
175 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
177 cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
179 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
181 cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
183 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
185 return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
189 CFQ_CFQQ_FNS(wait_request
);
190 CFQ_CFQQ_FNS(must_alloc
);
191 CFQ_CFQQ_FNS(must_alloc_slice
);
192 CFQ_CFQQ_FNS(must_dispatch
);
193 CFQ_CFQQ_FNS(fifo_expire
);
194 CFQ_CFQQ_FNS(idle_window
);
195 CFQ_CFQQ_FNS(prio_changed
);
196 CFQ_CFQQ_FNS(queue_new
);
199 static struct cfq_queue
*cfq_find_cfq_hash(struct cfq_data
*, unsigned int, unsigned short);
200 static void cfq_dispatch_insert(request_queue_t
*, struct request
*);
201 static struct cfq_queue
*cfq_get_queue(struct cfq_data
*cfqd
, unsigned int key
, struct task_struct
*tsk
, gfp_t gfp_mask
);
204 * scheduler run of queue, if there are requests pending and no one in the
205 * driver that will restart queueing
207 static inline void cfq_schedule_dispatch(struct cfq_data
*cfqd
)
209 if (cfqd
->busy_queues
)
210 kblockd_schedule_work(&cfqd
->unplug_work
);
213 static int cfq_queue_empty(request_queue_t
*q
)
215 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
217 return !cfqd
->busy_queues
;
220 static inline pid_t
cfq_queue_pid(struct task_struct
*task
, int rw
)
222 if (rw
== READ
|| rw
== WRITE_SYNC
)
225 return CFQ_KEY_ASYNC
;
229 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
230 * We choose the request that is closest to the head right now. Distance
231 * behind the head is penalized and only allowed to a certain extent.
233 static struct request
*
234 cfq_choose_req(struct cfq_data
*cfqd
, struct request
*rq1
, struct request
*rq2
)
236 sector_t last
, s1
, s2
, d1
= 0, d2
= 0;
237 unsigned long back_max
;
238 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
239 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
240 unsigned wrap
= 0; /* bit mask: requests behind the disk head? */
242 if (rq1
== NULL
|| rq1
== rq2
)
247 if (rq_is_sync(rq1
) && !rq_is_sync(rq2
))
249 else if (rq_is_sync(rq2
) && !rq_is_sync(rq1
))
255 last
= cfqd
->last_sector
;
258 * by definition, 1KiB is 2 sectors
260 back_max
= cfqd
->cfq_back_max
* 2;
263 * Strict one way elevator _except_ in the case where we allow
264 * short backward seeks which are biased as twice the cost of a
265 * similar forward seek.
269 else if (s1
+ back_max
>= last
)
270 d1
= (last
- s1
) * cfqd
->cfq_back_penalty
;
272 wrap
|= CFQ_RQ1_WRAP
;
276 else if (s2
+ back_max
>= last
)
277 d2
= (last
- s2
) * cfqd
->cfq_back_penalty
;
279 wrap
|= CFQ_RQ2_WRAP
;
281 /* Found required data */
284 * By doing switch() on the bit mask "wrap" we avoid having to
285 * check two variables for all permutations: --> faster!
288 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
304 case (CFQ_RQ1_WRAP
|CFQ_RQ2_WRAP
): /* both rqs wrapped */
307 * Since both rqs are wrapped,
308 * start with the one that's further behind head
309 * (--> only *one* back seek required),
310 * since back seek takes more time than forward.
320 * would be nice to take fifo expire time into account as well
322 static struct request
*
323 cfq_find_next_rq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
324 struct request
*last
)
326 struct rb_node
*rbnext
= rb_next(&last
->rb_node
);
327 struct rb_node
*rbprev
= rb_prev(&last
->rb_node
);
328 struct request
*next
= NULL
, *prev
= NULL
;
330 BUG_ON(RB_EMPTY_NODE(&last
->rb_node
));
333 prev
= rb_entry_rq(rbprev
);
336 next
= rb_entry_rq(rbnext
);
338 rbnext
= rb_first(&cfqq
->sort_list
);
339 if (rbnext
&& rbnext
!= &last
->rb_node
)
340 next
= rb_entry_rq(rbnext
);
343 return cfq_choose_req(cfqd
, next
, prev
);
346 static void cfq_resort_rr_list(struct cfq_queue
*cfqq
, int preempted
)
348 struct cfq_data
*cfqd
= cfqq
->cfqd
;
349 struct list_head
*list
;
351 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
353 list_del(&cfqq
->cfq_list
);
355 if (cfq_class_rt(cfqq
))
356 list
= &cfqd
->cur_rr
;
357 else if (cfq_class_idle(cfqq
))
358 list
= &cfqd
->idle_rr
;
361 * if cfqq has requests in flight, don't allow it to be
362 * found in cfq_set_active_queue before it has finished them.
363 * this is done to increase fairness between a process that
364 * has lots of io pending vs one that only generates one
365 * sporadically or synchronously
367 if (cfq_cfqq_dispatched(cfqq
))
368 list
= &cfqd
->busy_rr
;
370 list
= &cfqd
->rr_list
[cfqq
->ioprio
];
374 * If this queue was preempted or is new (never been serviced), let
375 * it be added first for fairness but beind other new queues.
376 * Otherwise, just add to the back of the list.
378 if (preempted
|| cfq_cfqq_queue_new(cfqq
)) {
379 struct list_head
*n
= list
;
380 struct cfq_queue
*__cfqq
;
382 while (n
->next
!= list
) {
383 __cfqq
= list_entry_cfqq(n
->next
);
384 if (!cfq_cfqq_queue_new(__cfqq
))
393 list_add_tail(&cfqq
->cfq_list
, list
);
397 * add to busy list of queues for service, trying to be fair in ordering
398 * the pending list according to last request service
401 cfq_add_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
403 BUG_ON(cfq_cfqq_on_rr(cfqq
));
404 cfq_mark_cfqq_on_rr(cfqq
);
407 cfq_resort_rr_list(cfqq
, 0);
411 cfq_del_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
413 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
414 cfq_clear_cfqq_on_rr(cfqq
);
415 list_del_init(&cfqq
->cfq_list
);
417 BUG_ON(!cfqd
->busy_queues
);
422 * rb tree support functions
424 static inline void cfq_del_rq_rb(struct request
*rq
)
426 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
427 struct cfq_data
*cfqd
= cfqq
->cfqd
;
428 const int sync
= rq_is_sync(rq
);
430 BUG_ON(!cfqq
->queued
[sync
]);
431 cfqq
->queued
[sync
]--;
433 elv_rb_del(&cfqq
->sort_list
, rq
);
435 if (cfq_cfqq_on_rr(cfqq
) && RB_EMPTY_ROOT(&cfqq
->sort_list
))
436 cfq_del_cfqq_rr(cfqd
, cfqq
);
439 static void cfq_add_rq_rb(struct request
*rq
)
441 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
442 struct cfq_data
*cfqd
= cfqq
->cfqd
;
443 struct request
*__alias
;
445 cfqq
->queued
[rq_is_sync(rq
)]++;
448 * looks a little odd, but the first insert might return an alias.
449 * if that happens, put the alias on the dispatch list
451 while ((__alias
= elv_rb_add(&cfqq
->sort_list
, rq
)) != NULL
)
452 cfq_dispatch_insert(cfqd
->queue
, __alias
);
456 cfq_reposition_rq_rb(struct cfq_queue
*cfqq
, struct request
*rq
)
458 elv_rb_del(&cfqq
->sort_list
, rq
);
459 cfqq
->queued
[rq_is_sync(rq
)]--;
463 static struct request
*
464 cfq_find_rq_fmerge(struct cfq_data
*cfqd
, struct bio
*bio
)
466 struct task_struct
*tsk
= current
;
467 pid_t key
= cfq_queue_pid(tsk
, bio_data_dir(bio
));
468 struct cfq_queue
*cfqq
;
470 cfqq
= cfq_find_cfq_hash(cfqd
, key
, tsk
->ioprio
);
472 sector_t sector
= bio
->bi_sector
+ bio_sectors(bio
);
474 return elv_rb_find(&cfqq
->sort_list
, sector
);
480 static void cfq_activate_request(request_queue_t
*q
, struct request
*rq
)
482 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
484 cfqd
->rq_in_driver
++;
487 * If the depth is larger 1, it really could be queueing. But lets
488 * make the mark a little higher - idling could still be good for
489 * low queueing, and a low queueing number could also just indicate
490 * a SCSI mid layer like behaviour where limit+1 is often seen.
492 if (!cfqd
->hw_tag
&& cfqd
->rq_in_driver
> 4)
496 static void cfq_deactivate_request(request_queue_t
*q
, struct request
*rq
)
498 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
500 WARN_ON(!cfqd
->rq_in_driver
);
501 cfqd
->rq_in_driver
--;
504 static void cfq_remove_request(struct request
*rq
)
506 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
508 if (cfqq
->next_rq
== rq
)
509 cfqq
->next_rq
= cfq_find_next_rq(cfqq
->cfqd
, cfqq
, rq
);
511 list_del_init(&rq
->queuelist
);
516 cfq_merge(request_queue_t
*q
, struct request
**req
, struct bio
*bio
)
518 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
519 struct request
*__rq
;
521 __rq
= cfq_find_rq_fmerge(cfqd
, bio
);
522 if (__rq
&& elv_rq_merge_ok(__rq
, bio
)) {
524 return ELEVATOR_FRONT_MERGE
;
527 return ELEVATOR_NO_MERGE
;
530 static void cfq_merged_request(request_queue_t
*q
, struct request
*req
,
533 if (type
== ELEVATOR_FRONT_MERGE
) {
534 struct cfq_queue
*cfqq
= RQ_CFQQ(req
);
536 cfq_reposition_rq_rb(cfqq
, req
);
541 cfq_merged_requests(request_queue_t
*q
, struct request
*rq
,
542 struct request
*next
)
545 * reposition in fifo if next is older than rq
547 if (!list_empty(&rq
->queuelist
) && !list_empty(&next
->queuelist
) &&
548 time_before(next
->start_time
, rq
->start_time
))
549 list_move(&rq
->queuelist
, &next
->queuelist
);
551 cfq_remove_request(next
);
555 __cfq_set_active_queue(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
559 * stop potential idle class queues waiting service
561 del_timer(&cfqd
->idle_class_timer
);
563 cfqq
->slice_start
= jiffies
;
565 cfqq
->slice_left
= 0;
566 cfq_clear_cfqq_must_alloc_slice(cfqq
);
567 cfq_clear_cfqq_fifo_expire(cfqq
);
570 cfqd
->active_queue
= cfqq
;
574 * current cfqq expired its slice (or was too idle), select new one
577 __cfq_slice_expired(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
580 unsigned long now
= jiffies
;
582 if (cfq_cfqq_wait_request(cfqq
))
583 del_timer(&cfqd
->idle_slice_timer
);
585 if (!preempted
&& !cfq_cfqq_dispatched(cfqq
))
586 cfq_schedule_dispatch(cfqd
);
588 cfq_clear_cfqq_must_dispatch(cfqq
);
589 cfq_clear_cfqq_wait_request(cfqq
);
590 cfq_clear_cfqq_queue_new(cfqq
);
593 * store what was left of this slice, if the queue idled out
596 if (time_after(cfqq
->slice_end
, now
))
597 cfqq
->slice_left
= cfqq
->slice_end
- now
;
599 cfqq
->slice_left
= 0;
601 if (cfq_cfqq_on_rr(cfqq
))
602 cfq_resort_rr_list(cfqq
, preempted
);
604 if (cfqq
== cfqd
->active_queue
)
605 cfqd
->active_queue
= NULL
;
607 if (cfqd
->active_cic
) {
608 put_io_context(cfqd
->active_cic
->ioc
);
609 cfqd
->active_cic
= NULL
;
612 cfqd
->dispatch_slice
= 0;
615 static inline void cfq_slice_expired(struct cfq_data
*cfqd
, int preempted
)
617 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
620 __cfq_slice_expired(cfqd
, cfqq
, preempted
);
633 static int cfq_get_next_prio_level(struct cfq_data
*cfqd
)
642 for (p
= cfqd
->cur_prio
; p
<= cfqd
->cur_end_prio
; p
++) {
643 if (!list_empty(&cfqd
->rr_list
[p
])) {
652 if (++cfqd
->cur_end_prio
== CFQ_PRIO_LISTS
) {
653 cfqd
->cur_end_prio
= 0;
660 if (unlikely(prio
== -1))
663 BUG_ON(prio
>= CFQ_PRIO_LISTS
);
665 list_splice_init(&cfqd
->rr_list
[prio
], &cfqd
->cur_rr
);
667 cfqd
->cur_prio
= prio
+ 1;
668 if (cfqd
->cur_prio
> cfqd
->cur_end_prio
) {
669 cfqd
->cur_end_prio
= cfqd
->cur_prio
;
672 if (cfqd
->cur_end_prio
== CFQ_PRIO_LISTS
) {
674 cfqd
->cur_end_prio
= 0;
680 static struct cfq_queue
*cfq_set_active_queue(struct cfq_data
*cfqd
)
682 struct cfq_queue
*cfqq
= NULL
;
684 if (!list_empty(&cfqd
->cur_rr
) || cfq_get_next_prio_level(cfqd
) != -1) {
686 * if current list is non-empty, grab first entry. if it is
687 * empty, get next prio level and grab first entry then if any
690 cfqq
= list_entry_cfqq(cfqd
->cur_rr
.next
);
691 } else if (!list_empty(&cfqd
->busy_rr
)) {
693 * If no new queues are available, check if the busy list has
694 * some before falling back to idle io.
696 cfqq
= list_entry_cfqq(cfqd
->busy_rr
.next
);
697 } else if (!list_empty(&cfqd
->idle_rr
)) {
699 * if we have idle queues and no rt or be queues had pending
700 * requests, either allow immediate service if the grace period
701 * has passed or arm the idle grace timer
703 unsigned long end
= cfqd
->last_end_request
+ CFQ_IDLE_GRACE
;
705 if (time_after_eq(jiffies
, end
))
706 cfqq
= list_entry_cfqq(cfqd
->idle_rr
.next
);
708 mod_timer(&cfqd
->idle_class_timer
, end
);
711 __cfq_set_active_queue(cfqd
, cfqq
);
715 #define CIC_SEEKY(cic) ((cic)->seek_mean > (128 * 1024))
717 static int cfq_arm_slice_timer(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
720 struct cfq_io_context
*cic
;
723 WARN_ON(!RB_EMPTY_ROOT(&cfqq
->sort_list
));
724 WARN_ON(cfqq
!= cfqd
->active_queue
);
727 * idle is disabled, either manually or by past process history
729 if (!cfqd
->cfq_slice_idle
)
731 if (!cfq_cfqq_idle_window(cfqq
))
734 * task has exited, don't wait
736 cic
= cfqd
->active_cic
;
737 if (!cic
|| !cic
->ioc
->task
)
740 cfq_mark_cfqq_must_dispatch(cfqq
);
741 cfq_mark_cfqq_wait_request(cfqq
);
743 sl
= min(cfqq
->slice_end
- 1, (unsigned long) cfqd
->cfq_slice_idle
);
746 * we don't want to idle for seeks, but we do want to allow
747 * fair distribution of slice time for a process doing back-to-back
748 * seeks. so allow a little bit of time for him to submit a new rq
750 if (sample_valid(cic
->seek_samples
) && CIC_SEEKY(cic
))
751 sl
= min(sl
, msecs_to_jiffies(2));
753 mod_timer(&cfqd
->idle_slice_timer
, jiffies
+ sl
);
757 static void cfq_dispatch_insert(request_queue_t
*q
, struct request
*rq
)
759 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
760 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
762 cfq_remove_request(rq
);
763 cfqq
->on_dispatch
[rq_is_sync(rq
)]++;
764 elv_dispatch_sort(q
, rq
);
766 rq
= list_entry(q
->queue_head
.prev
, struct request
, queuelist
);
767 cfqd
->last_sector
= rq
->sector
+ rq
->nr_sectors
;
771 * return expired entry, or NULL to just start from scratch in rbtree
773 static inline struct request
*cfq_check_fifo(struct cfq_queue
*cfqq
)
775 struct cfq_data
*cfqd
= cfqq
->cfqd
;
779 if (cfq_cfqq_fifo_expire(cfqq
))
781 if (list_empty(&cfqq
->fifo
))
784 fifo
= cfq_cfqq_class_sync(cfqq
);
785 rq
= rq_entry_fifo(cfqq
->fifo
.next
);
787 if (time_after(jiffies
, rq
->start_time
+ cfqd
->cfq_fifo_expire
[fifo
])) {
788 cfq_mark_cfqq_fifo_expire(cfqq
);
796 * Scale schedule slice based on io priority. Use the sync time slice only
797 * if a queue is marked sync and has sync io queued. A sync queue with async
798 * io only, should not get full sync slice length.
801 cfq_prio_to_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
803 const int base_slice
= cfqd
->cfq_slice
[cfq_cfqq_sync(cfqq
)];
805 WARN_ON(cfqq
->ioprio
>= IOPRIO_BE_NR
);
807 return base_slice
+ (base_slice
/CFQ_SLICE_SCALE
* (4 - cfqq
->ioprio
));
811 cfq_set_prio_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
813 cfqq
->slice_end
= cfq_prio_to_slice(cfqd
, cfqq
) + jiffies
;
817 cfq_prio_to_maxrq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
819 const int base_rq
= cfqd
->cfq_slice_async_rq
;
821 WARN_ON(cfqq
->ioprio
>= IOPRIO_BE_NR
);
823 return 2 * (base_rq
+ base_rq
* (CFQ_PRIO_LISTS
- 1 - cfqq
->ioprio
));
827 * get next queue for service
829 static struct cfq_queue
*cfq_select_queue(struct cfq_data
*cfqd
)
831 unsigned long now
= jiffies
;
832 struct cfq_queue
*cfqq
;
834 cfqq
= cfqd
->active_queue
;
841 if (!cfq_cfqq_must_dispatch(cfqq
) && time_after(now
, cfqq
->slice_end
))
845 * if queue has requests, dispatch one. if not, check if
846 * enough slice is left to wait for one
848 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
))
850 else if (cfq_cfqq_dispatched(cfqq
)) {
853 } else if (cfq_cfqq_class_sync(cfqq
)) {
854 if (cfq_arm_slice_timer(cfqd
, cfqq
))
859 cfq_slice_expired(cfqd
, 0);
861 cfqq
= cfq_set_active_queue(cfqd
);
867 __cfq_dispatch_requests(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
872 BUG_ON(RB_EMPTY_ROOT(&cfqq
->sort_list
));
878 * follow expired path, else get first next available
880 if ((rq
= cfq_check_fifo(cfqq
)) == NULL
)
884 * finally, insert request into driver dispatch list
886 cfq_dispatch_insert(cfqd
->queue
, rq
);
888 cfqd
->dispatch_slice
++;
891 if (!cfqd
->active_cic
) {
892 atomic_inc(&RQ_CIC(rq
)->ioc
->refcount
);
893 cfqd
->active_cic
= RQ_CIC(rq
);
896 if (RB_EMPTY_ROOT(&cfqq
->sort_list
))
899 } while (dispatched
< max_dispatch
);
902 * if slice end isn't set yet, set it.
904 if (!cfqq
->slice_end
)
905 cfq_set_prio_slice(cfqd
, cfqq
);
908 * expire an async queue immediately if it has used up its slice. idle
909 * queue always expire after 1 dispatch round.
911 if ((!cfq_cfqq_sync(cfqq
) &&
912 cfqd
->dispatch_slice
>= cfq_prio_to_maxrq(cfqd
, cfqq
)) ||
913 cfq_class_idle(cfqq
) ||
914 !cfq_cfqq_idle_window(cfqq
))
915 cfq_slice_expired(cfqd
, 0);
921 cfq_forced_dispatch_cfqqs(struct list_head
*list
)
923 struct cfq_queue
*cfqq
, *next
;
927 list_for_each_entry_safe(cfqq
, next
, list
, cfq_list
) {
928 while (cfqq
->next_rq
) {
929 cfq_dispatch_insert(cfqq
->cfqd
->queue
, cfqq
->next_rq
);
932 BUG_ON(!list_empty(&cfqq
->fifo
));
939 cfq_forced_dispatch(struct cfq_data
*cfqd
)
941 int i
, dispatched
= 0;
943 for (i
= 0; i
< CFQ_PRIO_LISTS
; i
++)
944 dispatched
+= cfq_forced_dispatch_cfqqs(&cfqd
->rr_list
[i
]);
946 dispatched
+= cfq_forced_dispatch_cfqqs(&cfqd
->busy_rr
);
947 dispatched
+= cfq_forced_dispatch_cfqqs(&cfqd
->cur_rr
);
948 dispatched
+= cfq_forced_dispatch_cfqqs(&cfqd
->idle_rr
);
950 cfq_slice_expired(cfqd
, 0);
952 BUG_ON(cfqd
->busy_queues
);
958 cfq_dispatch_requests(request_queue_t
*q
, int force
)
960 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
961 struct cfq_queue
*cfqq
, *prev_cfqq
;
964 if (!cfqd
->busy_queues
)
968 return cfq_forced_dispatch(cfqd
);
972 while ((cfqq
= cfq_select_queue(cfqd
)) != NULL
) {
976 * Don't repeat dispatch from the previous queue.
978 if (prev_cfqq
== cfqq
)
981 cfq_clear_cfqq_must_dispatch(cfqq
);
982 cfq_clear_cfqq_wait_request(cfqq
);
983 del_timer(&cfqd
->idle_slice_timer
);
985 max_dispatch
= cfqd
->cfq_quantum
;
986 if (cfq_class_idle(cfqq
))
989 dispatched
+= __cfq_dispatch_requests(cfqd
, cfqq
, max_dispatch
);
992 * If the dispatch cfqq has idling enabled and is still
993 * the active queue, break out.
995 if (cfq_cfqq_idle_window(cfqq
) && cfqd
->active_queue
)
1005 * task holds one reference to the queue, dropped when task exits. each rq
1006 * in-flight on this queue also holds a reference, dropped when rq is freed.
1008 * queue lock must be held here.
1010 static void cfq_put_queue(struct cfq_queue
*cfqq
)
1012 struct cfq_data
*cfqd
= cfqq
->cfqd
;
1014 BUG_ON(atomic_read(&cfqq
->ref
) <= 0);
1016 if (!atomic_dec_and_test(&cfqq
->ref
))
1019 BUG_ON(rb_first(&cfqq
->sort_list
));
1020 BUG_ON(cfqq
->allocated
[READ
] + cfqq
->allocated
[WRITE
]);
1021 BUG_ON(cfq_cfqq_on_rr(cfqq
));
1023 if (unlikely(cfqd
->active_queue
== cfqq
))
1024 __cfq_slice_expired(cfqd
, cfqq
, 0);
1027 * it's on the empty list and still hashed
1029 list_del(&cfqq
->cfq_list
);
1030 hlist_del(&cfqq
->cfq_hash
);
1031 kmem_cache_free(cfq_pool
, cfqq
);
1034 static struct cfq_queue
*
1035 __cfq_find_cfq_hash(struct cfq_data
*cfqd
, unsigned int key
, unsigned int prio
,
1038 struct hlist_head
*hash_list
= &cfqd
->cfq_hash
[hashval
];
1039 struct hlist_node
*entry
;
1040 struct cfq_queue
*__cfqq
;
1042 hlist_for_each_entry(__cfqq
, entry
, hash_list
, cfq_hash
) {
1043 const unsigned short __p
= IOPRIO_PRIO_VALUE(__cfqq
->org_ioprio_class
, __cfqq
->org_ioprio
);
1045 if (__cfqq
->key
== key
&& (__p
== prio
|| !prio
))
1052 static struct cfq_queue
*
1053 cfq_find_cfq_hash(struct cfq_data
*cfqd
, unsigned int key
, unsigned short prio
)
1055 return __cfq_find_cfq_hash(cfqd
, key
, prio
, hash_long(key
, CFQ_QHASH_SHIFT
));
1058 static void cfq_free_io_context(struct io_context
*ioc
)
1060 struct cfq_io_context
*__cic
;
1064 while ((n
= rb_first(&ioc
->cic_root
)) != NULL
) {
1065 __cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1066 rb_erase(&__cic
->rb_node
, &ioc
->cic_root
);
1067 kmem_cache_free(cfq_ioc_pool
, __cic
);
1071 elv_ioc_count_mod(ioc_count
, -freed
);
1073 if (ioc_gone
&& !elv_ioc_count_read(ioc_count
))
1077 static void cfq_exit_cfqq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1079 if (unlikely(cfqq
== cfqd
->active_queue
))
1080 __cfq_slice_expired(cfqd
, cfqq
, 0);
1082 cfq_put_queue(cfqq
);
1085 static void __cfq_exit_single_io_context(struct cfq_data
*cfqd
,
1086 struct cfq_io_context
*cic
)
1088 list_del_init(&cic
->queue_list
);
1092 if (cic
->cfqq
[ASYNC
]) {
1093 cfq_exit_cfqq(cfqd
, cic
->cfqq
[ASYNC
]);
1094 cic
->cfqq
[ASYNC
] = NULL
;
1097 if (cic
->cfqq
[SYNC
]) {
1098 cfq_exit_cfqq(cfqd
, cic
->cfqq
[SYNC
]);
1099 cic
->cfqq
[SYNC
] = NULL
;
1105 * Called with interrupts disabled
1107 static void cfq_exit_single_io_context(struct cfq_io_context
*cic
)
1109 struct cfq_data
*cfqd
= cic
->key
;
1112 request_queue_t
*q
= cfqd
->queue
;
1114 spin_lock_irq(q
->queue_lock
);
1115 __cfq_exit_single_io_context(cfqd
, cic
);
1116 spin_unlock_irq(q
->queue_lock
);
1120 static void cfq_exit_io_context(struct io_context
*ioc
)
1122 struct cfq_io_context
*__cic
;
1126 * put the reference this task is holding to the various queues
1129 n
= rb_first(&ioc
->cic_root
);
1131 __cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1133 cfq_exit_single_io_context(__cic
);
1138 static struct cfq_io_context
*
1139 cfq_alloc_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
1141 struct cfq_io_context
*cic
;
1143 cic
= kmem_cache_alloc_node(cfq_ioc_pool
, gfp_mask
, cfqd
->queue
->node
);
1145 memset(cic
, 0, sizeof(*cic
));
1146 cic
->last_end_request
= jiffies
;
1147 INIT_LIST_HEAD(&cic
->queue_list
);
1148 cic
->dtor
= cfq_free_io_context
;
1149 cic
->exit
= cfq_exit_io_context
;
1150 elv_ioc_count_inc(ioc_count
);
1156 static void cfq_init_prio_data(struct cfq_queue
*cfqq
)
1158 struct task_struct
*tsk
= current
;
1161 if (!cfq_cfqq_prio_changed(cfqq
))
1164 ioprio_class
= IOPRIO_PRIO_CLASS(tsk
->ioprio
);
1165 switch (ioprio_class
) {
1167 printk(KERN_ERR
"cfq: bad prio %x\n", ioprio_class
);
1168 case IOPRIO_CLASS_NONE
:
1170 * no prio set, place us in the middle of the BE classes
1172 cfqq
->ioprio
= task_nice_ioprio(tsk
);
1173 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1175 case IOPRIO_CLASS_RT
:
1176 cfqq
->ioprio
= task_ioprio(tsk
);
1177 cfqq
->ioprio_class
= IOPRIO_CLASS_RT
;
1179 case IOPRIO_CLASS_BE
:
1180 cfqq
->ioprio
= task_ioprio(tsk
);
1181 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1183 case IOPRIO_CLASS_IDLE
:
1184 cfqq
->ioprio_class
= IOPRIO_CLASS_IDLE
;
1186 cfq_clear_cfqq_idle_window(cfqq
);
1191 * keep track of original prio settings in case we have to temporarily
1192 * elevate the priority of this queue
1194 cfqq
->org_ioprio
= cfqq
->ioprio
;
1195 cfqq
->org_ioprio_class
= cfqq
->ioprio_class
;
1197 if (cfq_cfqq_on_rr(cfqq
))
1198 cfq_resort_rr_list(cfqq
, 0);
1200 cfq_clear_cfqq_prio_changed(cfqq
);
1203 static inline void changed_ioprio(struct cfq_io_context
*cic
)
1205 struct cfq_data
*cfqd
= cic
->key
;
1206 struct cfq_queue
*cfqq
;
1208 if (unlikely(!cfqd
))
1211 spin_lock(cfqd
->queue
->queue_lock
);
1213 cfqq
= cic
->cfqq
[ASYNC
];
1215 struct cfq_queue
*new_cfqq
;
1216 new_cfqq
= cfq_get_queue(cfqd
, CFQ_KEY_ASYNC
, cic
->ioc
->task
,
1219 cic
->cfqq
[ASYNC
] = new_cfqq
;
1220 cfq_put_queue(cfqq
);
1224 cfqq
= cic
->cfqq
[SYNC
];
1226 cfq_mark_cfqq_prio_changed(cfqq
);
1228 spin_unlock(cfqd
->queue
->queue_lock
);
1231 static void cfq_ioc_set_ioprio(struct io_context
*ioc
)
1233 struct cfq_io_context
*cic
;
1236 ioc
->ioprio_changed
= 0;
1238 n
= rb_first(&ioc
->cic_root
);
1240 cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1242 changed_ioprio(cic
);
1247 static struct cfq_queue
*
1248 cfq_get_queue(struct cfq_data
*cfqd
, unsigned int key
, struct task_struct
*tsk
,
1251 const int hashval
= hash_long(key
, CFQ_QHASH_SHIFT
);
1252 struct cfq_queue
*cfqq
, *new_cfqq
= NULL
;
1253 unsigned short ioprio
;
1256 ioprio
= tsk
->ioprio
;
1257 cfqq
= __cfq_find_cfq_hash(cfqd
, key
, ioprio
, hashval
);
1263 } else if (gfp_mask
& __GFP_WAIT
) {
1265 * Inform the allocator of the fact that we will
1266 * just repeat this allocation if it fails, to allow
1267 * the allocator to do whatever it needs to attempt to
1270 spin_unlock_irq(cfqd
->queue
->queue_lock
);
1271 new_cfqq
= kmem_cache_alloc_node(cfq_pool
, gfp_mask
|__GFP_NOFAIL
, cfqd
->queue
->node
);
1272 spin_lock_irq(cfqd
->queue
->queue_lock
);
1275 cfqq
= kmem_cache_alloc_node(cfq_pool
, gfp_mask
, cfqd
->queue
->node
);
1280 memset(cfqq
, 0, sizeof(*cfqq
));
1282 INIT_HLIST_NODE(&cfqq
->cfq_hash
);
1283 INIT_LIST_HEAD(&cfqq
->cfq_list
);
1284 INIT_LIST_HEAD(&cfqq
->fifo
);
1287 hlist_add_head(&cfqq
->cfq_hash
, &cfqd
->cfq_hash
[hashval
]);
1288 atomic_set(&cfqq
->ref
, 0);
1291 * set ->slice_left to allow preemption for a new process
1293 cfqq
->slice_left
= 2 * cfqd
->cfq_slice_idle
;
1294 cfq_mark_cfqq_idle_window(cfqq
);
1295 cfq_mark_cfqq_prio_changed(cfqq
);
1296 cfq_mark_cfqq_queue_new(cfqq
);
1297 cfq_init_prio_data(cfqq
);
1301 kmem_cache_free(cfq_pool
, new_cfqq
);
1303 atomic_inc(&cfqq
->ref
);
1305 WARN_ON((gfp_mask
& __GFP_WAIT
) && !cfqq
);
1310 cfq_drop_dead_cic(struct io_context
*ioc
, struct cfq_io_context
*cic
)
1312 WARN_ON(!list_empty(&cic
->queue_list
));
1313 rb_erase(&cic
->rb_node
, &ioc
->cic_root
);
1314 kmem_cache_free(cfq_ioc_pool
, cic
);
1315 elv_ioc_count_dec(ioc_count
);
1318 static struct cfq_io_context
*
1319 cfq_cic_rb_lookup(struct cfq_data
*cfqd
, struct io_context
*ioc
)
1322 struct cfq_io_context
*cic
;
1323 void *k
, *key
= cfqd
;
1326 n
= ioc
->cic_root
.rb_node
;
1328 cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1329 /* ->key must be copied to avoid race with cfq_exit_queue() */
1332 cfq_drop_dead_cic(ioc
, cic
);
1348 cfq_cic_link(struct cfq_data
*cfqd
, struct io_context
*ioc
,
1349 struct cfq_io_context
*cic
)
1352 struct rb_node
*parent
;
1353 struct cfq_io_context
*__cic
;
1361 p
= &ioc
->cic_root
.rb_node
;
1364 __cic
= rb_entry(parent
, struct cfq_io_context
, rb_node
);
1365 /* ->key must be copied to avoid race with cfq_exit_queue() */
1368 cfq_drop_dead_cic(ioc
, __cic
);
1374 else if (cic
->key
> k
)
1375 p
= &(*p
)->rb_right
;
1380 rb_link_node(&cic
->rb_node
, parent
, p
);
1381 rb_insert_color(&cic
->rb_node
, &ioc
->cic_root
);
1383 spin_lock_irq(cfqd
->queue
->queue_lock
);
1384 list_add(&cic
->queue_list
, &cfqd
->cic_list
);
1385 spin_unlock_irq(cfqd
->queue
->queue_lock
);
1389 * Setup general io context and cfq io context. There can be several cfq
1390 * io contexts per general io context, if this process is doing io to more
1391 * than one device managed by cfq.
1393 static struct cfq_io_context
*
1394 cfq_get_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
1396 struct io_context
*ioc
= NULL
;
1397 struct cfq_io_context
*cic
;
1399 might_sleep_if(gfp_mask
& __GFP_WAIT
);
1401 ioc
= get_io_context(gfp_mask
, cfqd
->queue
->node
);
1405 cic
= cfq_cic_rb_lookup(cfqd
, ioc
);
1409 cic
= cfq_alloc_io_context(cfqd
, gfp_mask
);
1413 cfq_cic_link(cfqd
, ioc
, cic
);
1415 smp_read_barrier_depends();
1416 if (unlikely(ioc
->ioprio_changed
))
1417 cfq_ioc_set_ioprio(ioc
);
1421 put_io_context(ioc
);
1426 cfq_update_io_thinktime(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
)
1428 unsigned long elapsed
, ttime
;
1431 * if this context already has stuff queued, thinktime is from
1432 * last queue not last end
1435 if (time_after(cic
->last_end_request
, cic
->last_queue
))
1436 elapsed
= jiffies
- cic
->last_end_request
;
1438 elapsed
= jiffies
- cic
->last_queue
;
1440 elapsed
= jiffies
- cic
->last_end_request
;
1443 ttime
= min(elapsed
, 2UL * cfqd
->cfq_slice_idle
);
1445 cic
->ttime_samples
= (7*cic
->ttime_samples
+ 256) / 8;
1446 cic
->ttime_total
= (7*cic
->ttime_total
+ 256*ttime
) / 8;
1447 cic
->ttime_mean
= (cic
->ttime_total
+ 128) / cic
->ttime_samples
;
1451 cfq_update_io_seektime(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
,
1457 if (cic
->last_request_pos
< rq
->sector
)
1458 sdist
= rq
->sector
- cic
->last_request_pos
;
1460 sdist
= cic
->last_request_pos
- rq
->sector
;
1463 * Don't allow the seek distance to get too large from the
1464 * odd fragment, pagein, etc
1466 if (cic
->seek_samples
<= 60) /* second&third seek */
1467 sdist
= min(sdist
, (cic
->seek_mean
* 4) + 2*1024*1024);
1469 sdist
= min(sdist
, (cic
->seek_mean
* 4) + 2*1024*64);
1471 cic
->seek_samples
= (7*cic
->seek_samples
+ 256) / 8;
1472 cic
->seek_total
= (7*cic
->seek_total
+ (u64
)256*sdist
) / 8;
1473 total
= cic
->seek_total
+ (cic
->seek_samples
/2);
1474 do_div(total
, cic
->seek_samples
);
1475 cic
->seek_mean
= (sector_t
)total
;
1479 * Disable idle window if the process thinks too long or seeks so much that
1483 cfq_update_idle_window(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1484 struct cfq_io_context
*cic
)
1486 int enable_idle
= cfq_cfqq_idle_window(cfqq
);
1488 if (!cic
->ioc
->task
|| !cfqd
->cfq_slice_idle
||
1489 (cfqd
->hw_tag
&& CIC_SEEKY(cic
)))
1491 else if (sample_valid(cic
->ttime_samples
)) {
1492 if (cic
->ttime_mean
> cfqd
->cfq_slice_idle
)
1499 cfq_mark_cfqq_idle_window(cfqq
);
1501 cfq_clear_cfqq_idle_window(cfqq
);
1506 * Check if new_cfqq should preempt the currently active queue. Return 0 for
1507 * no or if we aren't sure, a 1 will cause a preempt.
1510 cfq_should_preempt(struct cfq_data
*cfqd
, struct cfq_queue
*new_cfqq
,
1513 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
1515 if (cfq_class_idle(new_cfqq
))
1521 if (cfq_class_idle(cfqq
))
1523 if (!cfq_cfqq_wait_request(new_cfqq
))
1526 * if it doesn't have slice left, forget it
1528 if (new_cfqq
->slice_left
< cfqd
->cfq_slice_idle
)
1530 if (rq_is_sync(rq
) && !cfq_cfqq_sync(cfqq
))
1537 * cfqq preempts the active queue. if we allowed preempt with no slice left,
1538 * let it have half of its nominal slice.
1540 static void cfq_preempt_queue(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1542 struct cfq_queue
*__cfqq
, *next
;
1544 list_for_each_entry_safe(__cfqq
, next
, &cfqd
->cur_rr
, cfq_list
)
1545 cfq_resort_rr_list(__cfqq
, 1);
1547 if (!cfqq
->slice_left
)
1548 cfqq
->slice_left
= cfq_prio_to_slice(cfqd
, cfqq
) / 2;
1550 cfqq
->slice_end
= cfqq
->slice_left
+ jiffies
;
1551 cfq_slice_expired(cfqd
, 1);
1552 __cfq_set_active_queue(cfqd
, cfqq
);
1556 * should really be a ll_rw_blk.c helper
1558 static void cfq_start_queueing(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1560 request_queue_t
*q
= cfqd
->queue
;
1562 if (!blk_queue_plugged(q
))
1565 __generic_unplug_device(q
);
1569 * Called when a new fs request (rq) is added (to cfqq). Check if there's
1570 * something we should do about it
1573 cfq_rq_enqueued(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1576 struct cfq_io_context
*cic
= RQ_CIC(rq
);
1579 * check if this request is a better next-serve candidate)) {
1581 cfqq
->next_rq
= cfq_choose_req(cfqd
, cfqq
->next_rq
, rq
);
1582 BUG_ON(!cfqq
->next_rq
);
1585 * we never wait for an async request and we don't allow preemption
1586 * of an async request. so just return early
1588 if (!rq_is_sync(rq
)) {
1590 * sync process issued an async request, if it's waiting
1591 * then expire it and kick rq handling.
1593 if (cic
== cfqd
->active_cic
&&
1594 del_timer(&cfqd
->idle_slice_timer
)) {
1595 cfq_slice_expired(cfqd
, 0);
1596 cfq_start_queueing(cfqd
, cfqq
);
1601 cfq_update_io_thinktime(cfqd
, cic
);
1602 cfq_update_io_seektime(cfqd
, cic
, rq
);
1603 cfq_update_idle_window(cfqd
, cfqq
, cic
);
1605 cic
->last_queue
= jiffies
;
1606 cic
->last_request_pos
= rq
->sector
+ rq
->nr_sectors
;
1608 if (cfqq
== cfqd
->active_queue
) {
1610 * if we are waiting for a request for this queue, let it rip
1611 * immediately and flag that we must not expire this queue
1614 if (cfq_cfqq_wait_request(cfqq
)) {
1615 cfq_mark_cfqq_must_dispatch(cfqq
);
1616 del_timer(&cfqd
->idle_slice_timer
);
1617 cfq_start_queueing(cfqd
, cfqq
);
1619 } else if (cfq_should_preempt(cfqd
, cfqq
, rq
)) {
1621 * not the active queue - expire current slice if it is
1622 * idle and has expired it's mean thinktime or this new queue
1623 * has some old slice time left and is of higher priority
1625 cfq_preempt_queue(cfqd
, cfqq
);
1626 cfq_mark_cfqq_must_dispatch(cfqq
);
1627 cfq_start_queueing(cfqd
, cfqq
);
1631 static void cfq_insert_request(request_queue_t
*q
, struct request
*rq
)
1633 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1634 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1636 cfq_init_prio_data(cfqq
);
1640 if (!cfq_cfqq_on_rr(cfqq
))
1641 cfq_add_cfqq_rr(cfqd
, cfqq
);
1643 list_add_tail(&rq
->queuelist
, &cfqq
->fifo
);
1645 cfq_rq_enqueued(cfqd
, cfqq
, rq
);
1648 static void cfq_completed_request(request_queue_t
*q
, struct request
*rq
)
1650 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1651 struct cfq_data
*cfqd
= cfqq
->cfqd
;
1652 const int sync
= rq_is_sync(rq
);
1657 WARN_ON(!cfqd
->rq_in_driver
);
1658 WARN_ON(!cfqq
->on_dispatch
[sync
]);
1659 cfqd
->rq_in_driver
--;
1660 cfqq
->on_dispatch
[sync
]--;
1662 if (!cfq_class_idle(cfqq
))
1663 cfqd
->last_end_request
= now
;
1665 if (!cfq_cfqq_dispatched(cfqq
) && cfq_cfqq_on_rr(cfqq
))
1666 cfq_resort_rr_list(cfqq
, 0);
1669 RQ_CIC(rq
)->last_end_request
= now
;
1672 * If this is the active queue, check if it needs to be expired,
1673 * or if we want to idle in case it has no pending requests.
1675 if (cfqd
->active_queue
== cfqq
) {
1676 if (time_after(now
, cfqq
->slice_end
))
1677 cfq_slice_expired(cfqd
, 0);
1678 else if (sync
&& RB_EMPTY_ROOT(&cfqq
->sort_list
)) {
1679 if (!cfq_arm_slice_timer(cfqd
, cfqq
))
1680 cfq_schedule_dispatch(cfqd
);
1686 * we temporarily boost lower priority queues if they are holding fs exclusive
1687 * resources. they are boosted to normal prio (CLASS_BE/4)
1689 static void cfq_prio_boost(struct cfq_queue
*cfqq
)
1691 const int ioprio_class
= cfqq
->ioprio_class
;
1692 const int ioprio
= cfqq
->ioprio
;
1694 if (has_fs_excl()) {
1696 * boost idle prio on transactions that would lock out other
1697 * users of the filesystem
1699 if (cfq_class_idle(cfqq
))
1700 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1701 if (cfqq
->ioprio
> IOPRIO_NORM
)
1702 cfqq
->ioprio
= IOPRIO_NORM
;
1705 * check if we need to unboost the queue
1707 if (cfqq
->ioprio_class
!= cfqq
->org_ioprio_class
)
1708 cfqq
->ioprio_class
= cfqq
->org_ioprio_class
;
1709 if (cfqq
->ioprio
!= cfqq
->org_ioprio
)
1710 cfqq
->ioprio
= cfqq
->org_ioprio
;
1714 * refile between round-robin lists if we moved the priority class
1716 if ((ioprio_class
!= cfqq
->ioprio_class
|| ioprio
!= cfqq
->ioprio
) &&
1717 cfq_cfqq_on_rr(cfqq
))
1718 cfq_resort_rr_list(cfqq
, 0);
1721 static inline int __cfq_may_queue(struct cfq_queue
*cfqq
)
1723 if ((cfq_cfqq_wait_request(cfqq
) || cfq_cfqq_must_alloc(cfqq
)) &&
1724 !cfq_cfqq_must_alloc_slice(cfqq
)) {
1725 cfq_mark_cfqq_must_alloc_slice(cfqq
);
1726 return ELV_MQUEUE_MUST
;
1729 return ELV_MQUEUE_MAY
;
1732 static int cfq_may_queue(request_queue_t
*q
, int rw
)
1734 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1735 struct task_struct
*tsk
= current
;
1736 struct cfq_queue
*cfqq
;
1739 * don't force setup of a queue from here, as a call to may_queue
1740 * does not necessarily imply that a request actually will be queued.
1741 * so just lookup a possibly existing queue, or return 'may queue'
1744 cfqq
= cfq_find_cfq_hash(cfqd
, cfq_queue_pid(tsk
, rw
), tsk
->ioprio
);
1746 cfq_init_prio_data(cfqq
);
1747 cfq_prio_boost(cfqq
);
1749 return __cfq_may_queue(cfqq
);
1752 return ELV_MQUEUE_MAY
;
1756 * queue lock held here
1758 static void cfq_put_request(request_queue_t
*q
, struct request
*rq
)
1760 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1763 const int rw
= rq_data_dir(rq
);
1765 BUG_ON(!cfqq
->allocated
[rw
]);
1766 cfqq
->allocated
[rw
]--;
1768 put_io_context(RQ_CIC(rq
)->ioc
);
1770 rq
->elevator_private
= NULL
;
1771 rq
->elevator_private2
= NULL
;
1773 cfq_put_queue(cfqq
);
1778 * Allocate cfq data structures associated with this request.
1781 cfq_set_request(request_queue_t
*q
, struct request
*rq
, gfp_t gfp_mask
)
1783 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1784 struct task_struct
*tsk
= current
;
1785 struct cfq_io_context
*cic
;
1786 const int rw
= rq_data_dir(rq
);
1787 pid_t key
= cfq_queue_pid(tsk
, rw
);
1788 struct cfq_queue
*cfqq
;
1789 unsigned long flags
;
1790 int is_sync
= key
!= CFQ_KEY_ASYNC
;
1792 might_sleep_if(gfp_mask
& __GFP_WAIT
);
1794 cic
= cfq_get_io_context(cfqd
, gfp_mask
);
1796 spin_lock_irqsave(q
->queue_lock
, flags
);
1801 if (!cic
->cfqq
[is_sync
]) {
1802 cfqq
= cfq_get_queue(cfqd
, key
, tsk
, gfp_mask
);
1806 cic
->cfqq
[is_sync
] = cfqq
;
1808 cfqq
= cic
->cfqq
[is_sync
];
1810 cfqq
->allocated
[rw
]++;
1811 cfq_clear_cfqq_must_alloc(cfqq
);
1812 atomic_inc(&cfqq
->ref
);
1814 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1816 rq
->elevator_private
= cic
;
1817 rq
->elevator_private2
= cfqq
;
1822 put_io_context(cic
->ioc
);
1824 cfq_schedule_dispatch(cfqd
);
1825 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1829 static void cfq_kick_queue(void *data
)
1831 request_queue_t
*q
= data
;
1832 unsigned long flags
;
1834 spin_lock_irqsave(q
->queue_lock
, flags
);
1837 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1841 * Timer running if the active_queue is currently idling inside its time slice
1843 static void cfq_idle_slice_timer(unsigned long data
)
1845 struct cfq_data
*cfqd
= (struct cfq_data
*) data
;
1846 struct cfq_queue
*cfqq
;
1847 unsigned long flags
;
1849 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
1851 if ((cfqq
= cfqd
->active_queue
) != NULL
) {
1852 unsigned long now
= jiffies
;
1857 if (time_after(now
, cfqq
->slice_end
))
1861 * only expire and reinvoke request handler, if there are
1862 * other queues with pending requests
1864 if (!cfqd
->busy_queues
)
1868 * not expired and it has a request pending, let it dispatch
1870 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
)) {
1871 cfq_mark_cfqq_must_dispatch(cfqq
);
1876 cfq_slice_expired(cfqd
, 0);
1878 cfq_schedule_dispatch(cfqd
);
1880 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
1884 * Timer running if an idle class queue is waiting for service
1886 static void cfq_idle_class_timer(unsigned long data
)
1888 struct cfq_data
*cfqd
= (struct cfq_data
*) data
;
1889 unsigned long flags
, end
;
1891 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
1894 * race with a non-idle queue, reset timer
1896 end
= cfqd
->last_end_request
+ CFQ_IDLE_GRACE
;
1897 if (!time_after_eq(jiffies
, end
))
1898 mod_timer(&cfqd
->idle_class_timer
, end
);
1900 cfq_schedule_dispatch(cfqd
);
1902 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
1905 static void cfq_shutdown_timer_wq(struct cfq_data
*cfqd
)
1907 del_timer_sync(&cfqd
->idle_slice_timer
);
1908 del_timer_sync(&cfqd
->idle_class_timer
);
1909 blk_sync_queue(cfqd
->queue
);
1912 static void cfq_exit_queue(elevator_t
*e
)
1914 struct cfq_data
*cfqd
= e
->elevator_data
;
1915 request_queue_t
*q
= cfqd
->queue
;
1917 cfq_shutdown_timer_wq(cfqd
);
1919 spin_lock_irq(q
->queue_lock
);
1921 if (cfqd
->active_queue
)
1922 __cfq_slice_expired(cfqd
, cfqd
->active_queue
, 0);
1924 while (!list_empty(&cfqd
->cic_list
)) {
1925 struct cfq_io_context
*cic
= list_entry(cfqd
->cic_list
.next
,
1926 struct cfq_io_context
,
1929 __cfq_exit_single_io_context(cfqd
, cic
);
1932 spin_unlock_irq(q
->queue_lock
);
1934 cfq_shutdown_timer_wq(cfqd
);
1936 kfree(cfqd
->cfq_hash
);
1940 static void *cfq_init_queue(request_queue_t
*q
, elevator_t
*e
)
1942 struct cfq_data
*cfqd
;
1945 cfqd
= kmalloc_node(sizeof(*cfqd
), GFP_KERNEL
, q
->node
);
1949 memset(cfqd
, 0, sizeof(*cfqd
));
1951 for (i
= 0; i
< CFQ_PRIO_LISTS
; i
++)
1952 INIT_LIST_HEAD(&cfqd
->rr_list
[i
]);
1954 INIT_LIST_HEAD(&cfqd
->busy_rr
);
1955 INIT_LIST_HEAD(&cfqd
->cur_rr
);
1956 INIT_LIST_HEAD(&cfqd
->idle_rr
);
1957 INIT_LIST_HEAD(&cfqd
->cic_list
);
1959 cfqd
->cfq_hash
= kmalloc_node(sizeof(struct hlist_head
) * CFQ_QHASH_ENTRIES
, GFP_KERNEL
, q
->node
);
1960 if (!cfqd
->cfq_hash
)
1963 for (i
= 0; i
< CFQ_QHASH_ENTRIES
; i
++)
1964 INIT_HLIST_HEAD(&cfqd
->cfq_hash
[i
]);
1968 init_timer(&cfqd
->idle_slice_timer
);
1969 cfqd
->idle_slice_timer
.function
= cfq_idle_slice_timer
;
1970 cfqd
->idle_slice_timer
.data
= (unsigned long) cfqd
;
1972 init_timer(&cfqd
->idle_class_timer
);
1973 cfqd
->idle_class_timer
.function
= cfq_idle_class_timer
;
1974 cfqd
->idle_class_timer
.data
= (unsigned long) cfqd
;
1976 INIT_WORK(&cfqd
->unplug_work
, cfq_kick_queue
, q
);
1978 cfqd
->cfq_quantum
= cfq_quantum
;
1979 cfqd
->cfq_fifo_expire
[0] = cfq_fifo_expire
[0];
1980 cfqd
->cfq_fifo_expire
[1] = cfq_fifo_expire
[1];
1981 cfqd
->cfq_back_max
= cfq_back_max
;
1982 cfqd
->cfq_back_penalty
= cfq_back_penalty
;
1983 cfqd
->cfq_slice
[0] = cfq_slice_async
;
1984 cfqd
->cfq_slice
[1] = cfq_slice_sync
;
1985 cfqd
->cfq_slice_async_rq
= cfq_slice_async_rq
;
1986 cfqd
->cfq_slice_idle
= cfq_slice_idle
;
1994 static void cfq_slab_kill(void)
1997 kmem_cache_destroy(cfq_pool
);
1999 kmem_cache_destroy(cfq_ioc_pool
);
2002 static int __init
cfq_slab_setup(void)
2004 cfq_pool
= kmem_cache_create("cfq_pool", sizeof(struct cfq_queue
), 0, 0,
2009 cfq_ioc_pool
= kmem_cache_create("cfq_ioc_pool",
2010 sizeof(struct cfq_io_context
), 0, 0, NULL
, NULL
);
2021 * sysfs parts below -->
2025 cfq_var_show(unsigned int var
, char *page
)
2027 return sprintf(page
, "%d\n", var
);
2031 cfq_var_store(unsigned int *var
, const char *page
, size_t count
)
2033 char *p
= (char *) page
;
2035 *var
= simple_strtoul(p
, &p
, 10);
2039 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
2040 static ssize_t __FUNC(elevator_t *e, char *page) \
2042 struct cfq_data *cfqd = e->elevator_data; \
2043 unsigned int __data = __VAR; \
2045 __data = jiffies_to_msecs(__data); \
2046 return cfq_var_show(__data, (page)); \
2048 SHOW_FUNCTION(cfq_quantum_show
, cfqd
->cfq_quantum
, 0);
2049 SHOW_FUNCTION(cfq_fifo_expire_sync_show
, cfqd
->cfq_fifo_expire
[1], 1);
2050 SHOW_FUNCTION(cfq_fifo_expire_async_show
, cfqd
->cfq_fifo_expire
[0], 1);
2051 SHOW_FUNCTION(cfq_back_seek_max_show
, cfqd
->cfq_back_max
, 0);
2052 SHOW_FUNCTION(cfq_back_seek_penalty_show
, cfqd
->cfq_back_penalty
, 0);
2053 SHOW_FUNCTION(cfq_slice_idle_show
, cfqd
->cfq_slice_idle
, 1);
2054 SHOW_FUNCTION(cfq_slice_sync_show
, cfqd
->cfq_slice
[1], 1);
2055 SHOW_FUNCTION(cfq_slice_async_show
, cfqd
->cfq_slice
[0], 1);
2056 SHOW_FUNCTION(cfq_slice_async_rq_show
, cfqd
->cfq_slice_async_rq
, 0);
2057 #undef SHOW_FUNCTION
2059 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
2060 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
2062 struct cfq_data *cfqd = e->elevator_data; \
2063 unsigned int __data; \
2064 int ret = cfq_var_store(&__data, (page), count); \
2065 if (__data < (MIN)) \
2067 else if (__data > (MAX)) \
2070 *(__PTR) = msecs_to_jiffies(__data); \
2072 *(__PTR) = __data; \
2075 STORE_FUNCTION(cfq_quantum_store
, &cfqd
->cfq_quantum
, 1, UINT_MAX
, 0);
2076 STORE_FUNCTION(cfq_fifo_expire_sync_store
, &cfqd
->cfq_fifo_expire
[1], 1, UINT_MAX
, 1);
2077 STORE_FUNCTION(cfq_fifo_expire_async_store
, &cfqd
->cfq_fifo_expire
[0], 1, UINT_MAX
, 1);
2078 STORE_FUNCTION(cfq_back_seek_max_store
, &cfqd
->cfq_back_max
, 0, UINT_MAX
, 0);
2079 STORE_FUNCTION(cfq_back_seek_penalty_store
, &cfqd
->cfq_back_penalty
, 1, UINT_MAX
, 0);
2080 STORE_FUNCTION(cfq_slice_idle_store
, &cfqd
->cfq_slice_idle
, 0, UINT_MAX
, 1);
2081 STORE_FUNCTION(cfq_slice_sync_store
, &cfqd
->cfq_slice
[1], 1, UINT_MAX
, 1);
2082 STORE_FUNCTION(cfq_slice_async_store
, &cfqd
->cfq_slice
[0], 1, UINT_MAX
, 1);
2083 STORE_FUNCTION(cfq_slice_async_rq_store
, &cfqd
->cfq_slice_async_rq
, 1, UINT_MAX
, 0);
2084 #undef STORE_FUNCTION
2086 #define CFQ_ATTR(name) \
2087 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2089 static struct elv_fs_entry cfq_attrs
[] = {
2091 CFQ_ATTR(fifo_expire_sync
),
2092 CFQ_ATTR(fifo_expire_async
),
2093 CFQ_ATTR(back_seek_max
),
2094 CFQ_ATTR(back_seek_penalty
),
2095 CFQ_ATTR(slice_sync
),
2096 CFQ_ATTR(slice_async
),
2097 CFQ_ATTR(slice_async_rq
),
2098 CFQ_ATTR(slice_idle
),
2102 static struct elevator_type iosched_cfq
= {
2104 .elevator_merge_fn
= cfq_merge
,
2105 .elevator_merged_fn
= cfq_merged_request
,
2106 .elevator_merge_req_fn
= cfq_merged_requests
,
2107 .elevator_dispatch_fn
= cfq_dispatch_requests
,
2108 .elevator_add_req_fn
= cfq_insert_request
,
2109 .elevator_activate_req_fn
= cfq_activate_request
,
2110 .elevator_deactivate_req_fn
= cfq_deactivate_request
,
2111 .elevator_queue_empty_fn
= cfq_queue_empty
,
2112 .elevator_completed_req_fn
= cfq_completed_request
,
2113 .elevator_former_req_fn
= elv_rb_former_request
,
2114 .elevator_latter_req_fn
= elv_rb_latter_request
,
2115 .elevator_set_req_fn
= cfq_set_request
,
2116 .elevator_put_req_fn
= cfq_put_request
,
2117 .elevator_may_queue_fn
= cfq_may_queue
,
2118 .elevator_init_fn
= cfq_init_queue
,
2119 .elevator_exit_fn
= cfq_exit_queue
,
2120 .trim
= cfq_free_io_context
,
2122 .elevator_attrs
= cfq_attrs
,
2123 .elevator_name
= "cfq",
2124 .elevator_owner
= THIS_MODULE
,
2127 static int __init
cfq_init(void)
2132 * could be 0 on HZ < 1000 setups
2134 if (!cfq_slice_async
)
2135 cfq_slice_async
= 1;
2136 if (!cfq_slice_idle
)
2139 if (cfq_slab_setup())
2142 ret
= elv_register(&iosched_cfq
);
2149 static void __exit
cfq_exit(void)
2151 DECLARE_COMPLETION(all_gone
);
2152 elv_unregister(&iosched_cfq
);
2153 ioc_gone
= &all_gone
;
2154 /* ioc_gone's update must be visible before reading ioc_count */
2156 if (elv_ioc_count_read(ioc_count
))
2157 wait_for_completion(ioc_gone
);
2162 module_init(cfq_init
);
2163 module_exit(cfq_exit
);
2165 MODULE_AUTHOR("Jens Axboe");
2166 MODULE_LICENSE("GPL");
2167 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");