2 * CFQ, or complete fairness queueing, disk scheduler.
4 * Based on ideas from a previously unfinished io
5 * scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
7 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
9 #include <linux/module.h>
10 #include <linux/blkdev.h>
11 #include <linux/elevator.h>
12 #include <linux/hash.h>
13 #include <linux/rbtree.h>
14 #include <linux/ioprio.h>
19 static const int cfq_quantum
= 4; /* max queue in one round of service */
20 static const int cfq_fifo_expire
[2] = { HZ
/ 4, HZ
/ 8 };
21 static const int cfq_back_max
= 16 * 1024; /* maximum backwards seek, in KiB */
22 static const int cfq_back_penalty
= 2; /* penalty of a backwards seek */
24 static const int cfq_slice_sync
= HZ
/ 10;
25 static int cfq_slice_async
= HZ
/ 25;
26 static const int cfq_slice_async_rq
= 2;
27 static int cfq_slice_idle
= HZ
/ 125;
30 * grace period before allowing idle class to get disk access
32 #define CFQ_IDLE_GRACE (HZ / 10)
35 * below this threshold, we consider thinktime immediate
37 #define CFQ_MIN_TT (2)
39 #define CFQ_SLICE_SCALE (5)
41 #define CFQ_KEY_ASYNC (0)
44 * for the hash of cfqq inside the cfqd
46 #define CFQ_QHASH_SHIFT 6
47 #define CFQ_QHASH_ENTRIES (1 << CFQ_QHASH_SHIFT)
48 #define list_entry_qhash(entry) hlist_entry((entry), struct cfq_queue, cfq_hash)
50 #define list_entry_cfqq(ptr) list_entry((ptr), struct cfq_queue, cfq_list)
52 #define RQ_CIC(rq) ((struct cfq_io_context*)(rq)->elevator_private)
53 #define RQ_CFQQ(rq) ((rq)->elevator_private2)
55 static struct kmem_cache
*cfq_pool
;
56 static struct kmem_cache
*cfq_ioc_pool
;
58 static DEFINE_PER_CPU(unsigned long, ioc_count
);
59 static struct completion
*ioc_gone
;
61 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
62 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
63 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
68 #define cfq_cfqq_sync(cfqq) ((cfqq)->key != CFQ_KEY_ASYNC)
70 #define sample_valid(samples) ((samples) > 80)
73 * Most of our rbtree usage is for sorting with min extraction, so
74 * if we cache the leftmost node we don't have to walk down the tree
75 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
76 * move this into the elevator for the rq sorting as well.
82 #define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, }
85 * Per block device queue structure
88 request_queue_t
*queue
;
91 * rr list of queues with requests and the count of them
93 struct cfq_rb_root service_tree
;
94 struct list_head cur_rr
;
95 unsigned int busy_queues
;
100 struct hlist_head
*cfq_hash
;
106 * idle window management
108 struct timer_list idle_slice_timer
;
109 struct work_struct unplug_work
;
111 struct cfq_queue
*active_queue
;
112 struct cfq_io_context
*active_cic
;
113 unsigned int dispatch_slice
;
115 struct timer_list idle_class_timer
;
117 sector_t last_position
;
118 unsigned long last_end_request
;
121 * tunables, see top of file
123 unsigned int cfq_quantum
;
124 unsigned int cfq_fifo_expire
[2];
125 unsigned int cfq_back_penalty
;
126 unsigned int cfq_back_max
;
127 unsigned int cfq_slice
[2];
128 unsigned int cfq_slice_async_rq
;
129 unsigned int cfq_slice_idle
;
131 struct list_head cic_list
;
133 sector_t new_seek_mean
;
138 * Per process-grouping structure
141 /* reference count */
143 /* parent cfq_data */
144 struct cfq_data
*cfqd
;
145 /* cfqq lookup hash */
146 struct hlist_node cfq_hash
;
149 /* member of the rr/busy/cur/idle cfqd list */
150 struct list_head cfq_list
;
151 /* service_tree member */
152 struct rb_node rb_node
;
153 /* service_tree key */
154 unsigned long rb_key
;
155 /* sorted list of pending requests */
156 struct rb_root sort_list
;
157 /* if fifo isn't expired, next request to serve */
158 struct request
*next_rq
;
159 /* requests queued in sort_list */
161 /* currently allocated requests */
163 /* pending metadata requests */
165 /* fifo list of requests in sort_list */
166 struct list_head fifo
;
168 unsigned long slice_end
;
171 /* number of requests that are on the dispatch list or inside driver */
174 /* io prio of this group */
175 unsigned short ioprio
, org_ioprio
;
176 unsigned short ioprio_class
, org_ioprio_class
;
178 /* various state flags, see below */
181 sector_t last_request_pos
;
184 enum cfqq_state_flags
{
185 CFQ_CFQQ_FLAG_on_rr
= 0, /* on round-robin busy list */
186 CFQ_CFQQ_FLAG_wait_request
, /* waiting for a request */
187 CFQ_CFQQ_FLAG_must_alloc
, /* must be allowed rq alloc */
188 CFQ_CFQQ_FLAG_must_alloc_slice
, /* per-slice must_alloc flag */
189 CFQ_CFQQ_FLAG_must_dispatch
, /* must dispatch, even if expired */
190 CFQ_CFQQ_FLAG_fifo_expire
, /* FIFO checked in this slice */
191 CFQ_CFQQ_FLAG_idle_window
, /* slice idling enabled */
192 CFQ_CFQQ_FLAG_prio_changed
, /* task priority has changed */
193 CFQ_CFQQ_FLAG_queue_new
, /* queue never been serviced */
194 CFQ_CFQQ_FLAG_slice_new
, /* no requests dispatched in slice */
197 #define CFQ_CFQQ_FNS(name) \
198 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
200 cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
202 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
204 cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
206 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
208 return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
212 CFQ_CFQQ_FNS(wait_request
);
213 CFQ_CFQQ_FNS(must_alloc
);
214 CFQ_CFQQ_FNS(must_alloc_slice
);
215 CFQ_CFQQ_FNS(must_dispatch
);
216 CFQ_CFQQ_FNS(fifo_expire
);
217 CFQ_CFQQ_FNS(idle_window
);
218 CFQ_CFQQ_FNS(prio_changed
);
219 CFQ_CFQQ_FNS(queue_new
);
220 CFQ_CFQQ_FNS(slice_new
);
223 static struct cfq_queue
*cfq_find_cfq_hash(struct cfq_data
*, unsigned int, unsigned short);
224 static void cfq_dispatch_insert(request_queue_t
*, struct request
*);
225 static struct cfq_queue
*cfq_get_queue(struct cfq_data
*cfqd
, unsigned int key
, struct task_struct
*tsk
, gfp_t gfp_mask
);
228 * scheduler run of queue, if there are requests pending and no one in the
229 * driver that will restart queueing
231 static inline void cfq_schedule_dispatch(struct cfq_data
*cfqd
)
233 if (cfqd
->busy_queues
)
234 kblockd_schedule_work(&cfqd
->unplug_work
);
237 static int cfq_queue_empty(request_queue_t
*q
)
239 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
241 return !cfqd
->busy_queues
;
244 static inline pid_t
cfq_queue_pid(struct task_struct
*task
, int rw
, int is_sync
)
247 * Use the per-process queue, for read requests and syncronous writes
249 if (!(rw
& REQ_RW
) || is_sync
)
252 return CFQ_KEY_ASYNC
;
256 * Scale schedule slice based on io priority. Use the sync time slice only
257 * if a queue is marked sync and has sync io queued. A sync queue with async
258 * io only, should not get full sync slice length.
260 static inline int cfq_prio_slice(struct cfq_data
*cfqd
, int sync
,
263 const int base_slice
= cfqd
->cfq_slice
[sync
];
265 WARN_ON(prio
>= IOPRIO_BE_NR
);
267 return base_slice
+ (base_slice
/CFQ_SLICE_SCALE
* (4 - prio
));
271 cfq_prio_to_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
273 return cfq_prio_slice(cfqd
, cfq_cfqq_sync(cfqq
), cfqq
->ioprio
);
277 cfq_set_prio_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
279 cfqq
->slice_end
= cfq_prio_to_slice(cfqd
, cfqq
) + jiffies
;
283 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
284 * isn't valid until the first request from the dispatch is activated
285 * and the slice time set.
287 static inline int cfq_slice_used(struct cfq_queue
*cfqq
)
289 if (cfq_cfqq_slice_new(cfqq
))
291 if (time_before(jiffies
, cfqq
->slice_end
))
298 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
299 * We choose the request that is closest to the head right now. Distance
300 * behind the head is penalized and only allowed to a certain extent.
302 static struct request
*
303 cfq_choose_req(struct cfq_data
*cfqd
, struct request
*rq1
, struct request
*rq2
)
305 sector_t last
, s1
, s2
, d1
= 0, d2
= 0;
306 unsigned long back_max
;
307 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
308 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
309 unsigned wrap
= 0; /* bit mask: requests behind the disk head? */
311 if (rq1
== NULL
|| rq1
== rq2
)
316 if (rq_is_sync(rq1
) && !rq_is_sync(rq2
))
318 else if (rq_is_sync(rq2
) && !rq_is_sync(rq1
))
320 if (rq_is_meta(rq1
) && !rq_is_meta(rq2
))
322 else if (rq_is_meta(rq2
) && !rq_is_meta(rq1
))
328 last
= cfqd
->last_position
;
331 * by definition, 1KiB is 2 sectors
333 back_max
= cfqd
->cfq_back_max
* 2;
336 * Strict one way elevator _except_ in the case where we allow
337 * short backward seeks which are biased as twice the cost of a
338 * similar forward seek.
342 else if (s1
+ back_max
>= last
)
343 d1
= (last
- s1
) * cfqd
->cfq_back_penalty
;
345 wrap
|= CFQ_RQ1_WRAP
;
349 else if (s2
+ back_max
>= last
)
350 d2
= (last
- s2
) * cfqd
->cfq_back_penalty
;
352 wrap
|= CFQ_RQ2_WRAP
;
354 /* Found required data */
357 * By doing switch() on the bit mask "wrap" we avoid having to
358 * check two variables for all permutations: --> faster!
361 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
377 case (CFQ_RQ1_WRAP
|CFQ_RQ2_WRAP
): /* both rqs wrapped */
380 * Since both rqs are wrapped,
381 * start with the one that's further behind head
382 * (--> only *one* back seek required),
383 * since back seek takes more time than forward.
392 static struct rb_node
*cfq_rb_first(struct cfq_rb_root
*root
)
395 root
->left
= rb_first(&root
->rb
);
400 static void cfq_rb_erase(struct rb_node
*n
, struct cfq_rb_root
*root
)
405 rb_erase(n
, &root
->rb
);
410 * would be nice to take fifo expire time into account as well
412 static struct request
*
413 cfq_find_next_rq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
414 struct request
*last
)
416 struct rb_node
*rbnext
= rb_next(&last
->rb_node
);
417 struct rb_node
*rbprev
= rb_prev(&last
->rb_node
);
418 struct request
*next
= NULL
, *prev
= NULL
;
420 BUG_ON(RB_EMPTY_NODE(&last
->rb_node
));
423 prev
= rb_entry_rq(rbprev
);
426 next
= rb_entry_rq(rbnext
);
428 rbnext
= rb_first(&cfqq
->sort_list
);
429 if (rbnext
&& rbnext
!= &last
->rb_node
)
430 next
= rb_entry_rq(rbnext
);
433 return cfq_choose_req(cfqd
, next
, prev
);
436 static unsigned long cfq_slice_offset(struct cfq_data
*cfqd
,
437 struct cfq_queue
*cfqq
)
440 * just an approximation, should be ok.
442 return ((cfqd
->busy_queues
- 1) * cfq_prio_slice(cfqd
, 1, 0));
445 static void cfq_service_tree_add(struct cfq_data
*cfqd
,
446 struct cfq_queue
*cfqq
)
448 struct rb_node
**p
= &cfqd
->service_tree
.rb
.rb_node
;
449 struct rb_node
*parent
= NULL
;
450 unsigned long rb_key
;
453 rb_key
= cfq_slice_offset(cfqd
, cfqq
) + jiffies
;
454 rb_key
+= cfqq
->slice_resid
;
455 cfqq
->slice_resid
= 0;
457 if (!RB_EMPTY_NODE(&cfqq
->rb_node
)) {
459 * same position, nothing more to do
461 if (rb_key
== cfqq
->rb_key
)
464 cfq_rb_erase(&cfqq
->rb_node
, &cfqd
->service_tree
);
468 struct cfq_queue
*__cfqq
;
472 __cfqq
= rb_entry(parent
, struct cfq_queue
, rb_node
);
475 * sort RT queues first, we always want to give
476 * preference to them. IDLE queues goes to the back.
477 * after that, sort on the next service time.
479 if (cfq_class_rt(cfqq
) > cfq_class_rt(__cfqq
))
481 else if (cfq_class_rt(cfqq
) < cfq_class_rt(__cfqq
))
483 else if (cfq_class_idle(cfqq
) < cfq_class_idle(__cfqq
))
485 else if (cfq_class_idle(cfqq
) > cfq_class_idle(__cfqq
))
487 else if (rb_key
< __cfqq
->rb_key
)
492 if (n
== &(*p
)->rb_right
)
499 cfqd
->service_tree
.left
= &cfqq
->rb_node
;
501 cfqq
->rb_key
= rb_key
;
502 rb_link_node(&cfqq
->rb_node
, parent
, p
);
503 rb_insert_color(&cfqq
->rb_node
, &cfqd
->service_tree
.rb
);
506 static void cfq_resort_rr_list(struct cfq_queue
*cfqq
, int preempted
)
508 struct cfq_data
*cfqd
= cfqq
->cfqd
;
511 * Resorting requires the cfqq to be on the RR list already.
513 if (!cfq_cfqq_on_rr(cfqq
))
516 cfq_service_tree_add(cfqd
, cfqq
);
520 * add to busy list of queues for service, trying to be fair in ordering
521 * the pending list according to last request service
524 cfq_add_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
526 BUG_ON(cfq_cfqq_on_rr(cfqq
));
527 cfq_mark_cfqq_on_rr(cfqq
);
530 cfq_resort_rr_list(cfqq
, 0);
534 cfq_del_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
536 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
537 cfq_clear_cfqq_on_rr(cfqq
);
538 list_del_init(&cfqq
->cfq_list
);
540 if (!RB_EMPTY_NODE(&cfqq
->rb_node
))
541 cfq_rb_erase(&cfqq
->rb_node
, &cfqd
->service_tree
);
543 BUG_ON(!cfqd
->busy_queues
);
548 * rb tree support functions
550 static inline void cfq_del_rq_rb(struct request
*rq
)
552 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
553 struct cfq_data
*cfqd
= cfqq
->cfqd
;
554 const int sync
= rq_is_sync(rq
);
556 BUG_ON(!cfqq
->queued
[sync
]);
557 cfqq
->queued
[sync
]--;
559 elv_rb_del(&cfqq
->sort_list
, rq
);
561 if (cfq_cfqq_on_rr(cfqq
) && RB_EMPTY_ROOT(&cfqq
->sort_list
))
562 cfq_del_cfqq_rr(cfqd
, cfqq
);
565 static void cfq_add_rq_rb(struct request
*rq
)
567 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
568 struct cfq_data
*cfqd
= cfqq
->cfqd
;
569 struct request
*__alias
;
571 cfqq
->queued
[rq_is_sync(rq
)]++;
574 * looks a little odd, but the first insert might return an alias.
575 * if that happens, put the alias on the dispatch list
577 while ((__alias
= elv_rb_add(&cfqq
->sort_list
, rq
)) != NULL
)
578 cfq_dispatch_insert(cfqd
->queue
, __alias
);
580 if (!cfq_cfqq_on_rr(cfqq
))
581 cfq_add_cfqq_rr(cfqd
, cfqq
);
584 * check if this request is a better next-serve candidate
586 cfqq
->next_rq
= cfq_choose_req(cfqd
, cfqq
->next_rq
, rq
);
587 BUG_ON(!cfqq
->next_rq
);
591 cfq_reposition_rq_rb(struct cfq_queue
*cfqq
, struct request
*rq
)
593 elv_rb_del(&cfqq
->sort_list
, rq
);
594 cfqq
->queued
[rq_is_sync(rq
)]--;
598 static struct request
*
599 cfq_find_rq_fmerge(struct cfq_data
*cfqd
, struct bio
*bio
)
601 struct task_struct
*tsk
= current
;
602 pid_t key
= cfq_queue_pid(tsk
, bio_data_dir(bio
), bio_sync(bio
));
603 struct cfq_queue
*cfqq
;
605 cfqq
= cfq_find_cfq_hash(cfqd
, key
, tsk
->ioprio
);
607 sector_t sector
= bio
->bi_sector
+ bio_sectors(bio
);
609 return elv_rb_find(&cfqq
->sort_list
, sector
);
615 static void cfq_activate_request(request_queue_t
*q
, struct request
*rq
)
617 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
619 cfqd
->rq_in_driver
++;
622 * If the depth is larger 1, it really could be queueing. But lets
623 * make the mark a little higher - idling could still be good for
624 * low queueing, and a low queueing number could also just indicate
625 * a SCSI mid layer like behaviour where limit+1 is often seen.
627 if (!cfqd
->hw_tag
&& cfqd
->rq_in_driver
> 4)
630 cfqd
->last_position
= rq
->hard_sector
+ rq
->hard_nr_sectors
;
633 static void cfq_deactivate_request(request_queue_t
*q
, struct request
*rq
)
635 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
637 WARN_ON(!cfqd
->rq_in_driver
);
638 cfqd
->rq_in_driver
--;
641 static void cfq_remove_request(struct request
*rq
)
643 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
645 if (cfqq
->next_rq
== rq
)
646 cfqq
->next_rq
= cfq_find_next_rq(cfqq
->cfqd
, cfqq
, rq
);
648 list_del_init(&rq
->queuelist
);
651 if (rq_is_meta(rq
)) {
652 WARN_ON(!cfqq
->meta_pending
);
653 cfqq
->meta_pending
--;
658 cfq_merge(request_queue_t
*q
, struct request
**req
, struct bio
*bio
)
660 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
661 struct request
*__rq
;
663 __rq
= cfq_find_rq_fmerge(cfqd
, bio
);
664 if (__rq
&& elv_rq_merge_ok(__rq
, bio
)) {
666 return ELEVATOR_FRONT_MERGE
;
669 return ELEVATOR_NO_MERGE
;
672 static void cfq_merged_request(request_queue_t
*q
, struct request
*req
,
675 if (type
== ELEVATOR_FRONT_MERGE
) {
676 struct cfq_queue
*cfqq
= RQ_CFQQ(req
);
678 cfq_reposition_rq_rb(cfqq
, req
);
683 cfq_merged_requests(request_queue_t
*q
, struct request
*rq
,
684 struct request
*next
)
687 * reposition in fifo if next is older than rq
689 if (!list_empty(&rq
->queuelist
) && !list_empty(&next
->queuelist
) &&
690 time_before(next
->start_time
, rq
->start_time
))
691 list_move(&rq
->queuelist
, &next
->queuelist
);
693 cfq_remove_request(next
);
696 static int cfq_allow_merge(request_queue_t
*q
, struct request
*rq
,
699 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
700 const int rw
= bio_data_dir(bio
);
701 struct cfq_queue
*cfqq
;
705 * Disallow merge of a sync bio into an async request.
707 if ((bio_data_dir(bio
) == READ
|| bio_sync(bio
)) && !rq_is_sync(rq
))
711 * Lookup the cfqq that this bio will be queued with. Allow
712 * merge only if rq is queued there.
714 key
= cfq_queue_pid(current
, rw
, bio_sync(bio
));
715 cfqq
= cfq_find_cfq_hash(cfqd
, key
, current
->ioprio
);
717 if (cfqq
== RQ_CFQQ(rq
))
724 __cfq_set_active_queue(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
728 * stop potential idle class queues waiting service
730 del_timer(&cfqd
->idle_class_timer
);
733 cfq_clear_cfqq_must_alloc_slice(cfqq
);
734 cfq_clear_cfqq_fifo_expire(cfqq
);
735 cfq_mark_cfqq_slice_new(cfqq
);
736 cfq_clear_cfqq_queue_new(cfqq
);
739 cfqd
->active_queue
= cfqq
;
743 * current cfqq expired its slice (or was too idle), select new one
746 __cfq_slice_expired(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
747 int preempted
, int timed_out
)
749 if (cfq_cfqq_wait_request(cfqq
))
750 del_timer(&cfqd
->idle_slice_timer
);
752 cfq_clear_cfqq_must_dispatch(cfqq
);
753 cfq_clear_cfqq_wait_request(cfqq
);
756 * store what was left of this slice, if the queue idled out
759 if (timed_out
&& !cfq_cfqq_slice_new(cfqq
))
760 cfqq
->slice_resid
= cfqq
->slice_end
- jiffies
;
762 cfq_resort_rr_list(cfqq
, preempted
);
764 if (cfqq
== cfqd
->active_queue
)
765 cfqd
->active_queue
= NULL
;
767 if (cfqd
->active_cic
) {
768 put_io_context(cfqd
->active_cic
->ioc
);
769 cfqd
->active_cic
= NULL
;
772 cfqd
->dispatch_slice
= 0;
775 static inline void cfq_slice_expired(struct cfq_data
*cfqd
, int preempted
,
778 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
781 __cfq_slice_expired(cfqd
, cfqq
, preempted
, timed_out
);
784 static struct cfq_queue
*cfq_get_next_queue(struct cfq_data
*cfqd
)
786 struct cfq_queue
*cfqq
= NULL
;
788 if (!list_empty(&cfqd
->cur_rr
)) {
790 * if current list is non-empty, grab first entry.
792 cfqq
= list_entry_cfqq(cfqd
->cur_rr
.next
);
793 } else if (!RB_EMPTY_ROOT(&cfqd
->service_tree
.rb
)) {
794 struct rb_node
*n
= cfq_rb_first(&cfqd
->service_tree
);
797 cfqq
= rb_entry(n
, struct cfq_queue
, rb_node
);
798 if (cfq_class_idle(cfqq
)) {
800 * if we have idle queues and no rt or be queues had
801 * pending requests, either allow immediate service if
802 * the grace period has passed or arm the idle grace
805 end
= cfqd
->last_end_request
+ CFQ_IDLE_GRACE
;
806 if (time_before(jiffies
, end
)) {
807 mod_timer(&cfqd
->idle_class_timer
, end
);
816 static struct cfq_queue
*cfq_set_active_queue(struct cfq_data
*cfqd
)
818 struct cfq_queue
*cfqq
;
820 cfqq
= cfq_get_next_queue(cfqd
);
821 __cfq_set_active_queue(cfqd
, cfqq
);
825 static inline sector_t
cfq_dist_from_last(struct cfq_data
*cfqd
,
828 if (rq
->sector
>= cfqd
->last_position
)
829 return rq
->sector
- cfqd
->last_position
;
831 return cfqd
->last_position
- rq
->sector
;
834 static inline int cfq_rq_close(struct cfq_data
*cfqd
, struct request
*rq
)
836 struct cfq_io_context
*cic
= cfqd
->active_cic
;
838 if (!sample_valid(cic
->seek_samples
))
841 return cfq_dist_from_last(cfqd
, rq
) <= cic
->seek_mean
;
844 static int cfq_close_cooperator(struct cfq_data
*cfq_data
,
845 struct cfq_queue
*cfqq
)
848 * We should notice if some of the queues are cooperating, eg
849 * working closely on the same area of the disk. In that case,
850 * we can group them together and don't waste time idling.
855 #define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024))
857 static void cfq_arm_slice_timer(struct cfq_data
*cfqd
)
859 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
860 struct cfq_io_context
*cic
;
863 WARN_ON(!RB_EMPTY_ROOT(&cfqq
->sort_list
));
864 WARN_ON(cfq_cfqq_slice_new(cfqq
));
867 * idle is disabled, either manually or by past process history
869 if (!cfqd
->cfq_slice_idle
|| !cfq_cfqq_idle_window(cfqq
))
873 * task has exited, don't wait
875 cic
= cfqd
->active_cic
;
876 if (!cic
|| !cic
->ioc
->task
)
880 * See if this prio level has a good candidate
882 if (cfq_close_cooperator(cfqd
, cfqq
) &&
883 (sample_valid(cic
->ttime_samples
) && cic
->ttime_mean
> 2))
886 cfq_mark_cfqq_must_dispatch(cfqq
);
887 cfq_mark_cfqq_wait_request(cfqq
);
890 * we don't want to idle for seeks, but we do want to allow
891 * fair distribution of slice time for a process doing back-to-back
892 * seeks. so allow a little bit of time for him to submit a new rq
894 sl
= cfqd
->cfq_slice_idle
;
895 if (sample_valid(cic
->seek_samples
) && CIC_SEEKY(cic
))
896 sl
= min(sl
, msecs_to_jiffies(CFQ_MIN_TT
));
898 mod_timer(&cfqd
->idle_slice_timer
, jiffies
+ sl
);
901 static void cfq_dispatch_insert(request_queue_t
*q
, struct request
*rq
)
903 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
905 cfq_remove_request(rq
);
907 elv_dispatch_sort(q
, rq
);
911 * return expired entry, or NULL to just start from scratch in rbtree
913 static inline struct request
*cfq_check_fifo(struct cfq_queue
*cfqq
)
915 struct cfq_data
*cfqd
= cfqq
->cfqd
;
919 if (cfq_cfqq_fifo_expire(cfqq
))
922 cfq_mark_cfqq_fifo_expire(cfqq
);
924 if (list_empty(&cfqq
->fifo
))
927 fifo
= cfq_cfqq_sync(cfqq
);
928 rq
= rq_entry_fifo(cfqq
->fifo
.next
);
930 if (time_before(jiffies
, rq
->start_time
+ cfqd
->cfq_fifo_expire
[fifo
]))
937 cfq_prio_to_maxrq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
939 const int base_rq
= cfqd
->cfq_slice_async_rq
;
941 WARN_ON(cfqq
->ioprio
>= IOPRIO_BE_NR
);
943 return 2 * (base_rq
+ base_rq
* (CFQ_PRIO_LISTS
- 1 - cfqq
->ioprio
));
947 * get next queue for service
949 static struct cfq_queue
*cfq_select_queue(struct cfq_data
*cfqd
)
951 struct cfq_queue
*cfqq
;
953 cfqq
= cfqd
->active_queue
;
958 * The active queue has run out of time, expire it and select new.
960 if (cfq_slice_used(cfqq
))
964 * The active queue has requests and isn't expired, allow it to
967 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
))
971 * No requests pending. If the active queue still has requests in
972 * flight or is idling for a new request, allow either of these
973 * conditions to happen (or time out) before selecting a new queue.
975 if (cfqq
->dispatched
|| timer_pending(&cfqd
->idle_slice_timer
)) {
981 cfq_slice_expired(cfqd
, 0, 0);
983 cfqq
= cfq_set_active_queue(cfqd
);
989 __cfq_dispatch_requests(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
994 BUG_ON(RB_EMPTY_ROOT(&cfqq
->sort_list
));
1000 * follow expired path, else get first next available
1002 if ((rq
= cfq_check_fifo(cfqq
)) == NULL
)
1006 * finally, insert request into driver dispatch list
1008 cfq_dispatch_insert(cfqd
->queue
, rq
);
1010 cfqd
->dispatch_slice
++;
1013 if (!cfqd
->active_cic
) {
1014 atomic_inc(&RQ_CIC(rq
)->ioc
->refcount
);
1015 cfqd
->active_cic
= RQ_CIC(rq
);
1018 if (RB_EMPTY_ROOT(&cfqq
->sort_list
))
1021 } while (dispatched
< max_dispatch
);
1024 * expire an async queue immediately if it has used up its slice. idle
1025 * queue always expire after 1 dispatch round.
1027 if (cfqd
->busy_queues
> 1 && ((!cfq_cfqq_sync(cfqq
) &&
1028 cfqd
->dispatch_slice
>= cfq_prio_to_maxrq(cfqd
, cfqq
)) ||
1029 cfq_class_idle(cfqq
))) {
1030 cfqq
->slice_end
= jiffies
+ 1;
1031 cfq_slice_expired(cfqd
, 0, 0);
1037 static inline int __cfq_forced_dispatch_cfqq(struct cfq_queue
*cfqq
)
1041 while (cfqq
->next_rq
) {
1042 cfq_dispatch_insert(cfqq
->cfqd
->queue
, cfqq
->next_rq
);
1046 BUG_ON(!list_empty(&cfqq
->fifo
));
1050 static int cfq_forced_dispatch_cfqqs(struct list_head
*list
)
1052 struct cfq_queue
*cfqq
, *next
;
1056 list_for_each_entry_safe(cfqq
, next
, list
, cfq_list
)
1057 dispatched
+= __cfq_forced_dispatch_cfqq(cfqq
);
1062 static int cfq_forced_dispatch(struct cfq_data
*cfqd
)
1067 while ((n
= cfq_rb_first(&cfqd
->service_tree
)) != NULL
) {
1068 struct cfq_queue
*cfqq
= rb_entry(n
, struct cfq_queue
, rb_node
);
1070 dispatched
+= __cfq_forced_dispatch_cfqq(cfqq
);
1073 dispatched
+= cfq_forced_dispatch_cfqqs(&cfqd
->cur_rr
);
1075 cfq_slice_expired(cfqd
, 0, 0);
1077 BUG_ON(cfqd
->busy_queues
);
1082 static int cfq_dispatch_requests(request_queue_t
*q
, int force
)
1084 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1085 struct cfq_queue
*cfqq
;
1088 if (!cfqd
->busy_queues
)
1091 if (unlikely(force
))
1092 return cfq_forced_dispatch(cfqd
);
1095 while ((cfqq
= cfq_select_queue(cfqd
)) != NULL
) {
1098 if (cfqd
->busy_queues
> 1) {
1100 * So we have dispatched before in this round, if the
1101 * next queue has idling enabled (must be sync), don't
1102 * allow it service until the previous have completed.
1104 if (cfqd
->rq_in_driver
&& cfq_cfqq_idle_window(cfqq
) &&
1107 if (cfqq
->dispatched
>= cfqd
->cfq_quantum
)
1111 cfq_clear_cfqq_must_dispatch(cfqq
);
1112 cfq_clear_cfqq_wait_request(cfqq
);
1113 del_timer(&cfqd
->idle_slice_timer
);
1115 max_dispatch
= cfqd
->cfq_quantum
;
1116 if (cfq_class_idle(cfqq
))
1119 dispatched
+= __cfq_dispatch_requests(cfqd
, cfqq
, max_dispatch
);
1126 * task holds one reference to the queue, dropped when task exits. each rq
1127 * in-flight on this queue also holds a reference, dropped when rq is freed.
1129 * queue lock must be held here.
1131 static void cfq_put_queue(struct cfq_queue
*cfqq
)
1133 struct cfq_data
*cfqd
= cfqq
->cfqd
;
1135 BUG_ON(atomic_read(&cfqq
->ref
) <= 0);
1137 if (!atomic_dec_and_test(&cfqq
->ref
))
1140 BUG_ON(rb_first(&cfqq
->sort_list
));
1141 BUG_ON(cfqq
->allocated
[READ
] + cfqq
->allocated
[WRITE
]);
1142 BUG_ON(cfq_cfqq_on_rr(cfqq
));
1144 if (unlikely(cfqd
->active_queue
== cfqq
)) {
1145 __cfq_slice_expired(cfqd
, cfqq
, 0, 0);
1146 cfq_schedule_dispatch(cfqd
);
1150 * it's on the empty list and still hashed
1152 hlist_del(&cfqq
->cfq_hash
);
1153 kmem_cache_free(cfq_pool
, cfqq
);
1156 static struct cfq_queue
*
1157 __cfq_find_cfq_hash(struct cfq_data
*cfqd
, unsigned int key
, unsigned int prio
,
1160 struct hlist_head
*hash_list
= &cfqd
->cfq_hash
[hashval
];
1161 struct hlist_node
*entry
;
1162 struct cfq_queue
*__cfqq
;
1164 hlist_for_each_entry(__cfqq
, entry
, hash_list
, cfq_hash
) {
1165 const unsigned short __p
= IOPRIO_PRIO_VALUE(__cfqq
->org_ioprio_class
, __cfqq
->org_ioprio
);
1167 if (__cfqq
->key
== key
&& (__p
== prio
|| !prio
))
1174 static struct cfq_queue
*
1175 cfq_find_cfq_hash(struct cfq_data
*cfqd
, unsigned int key
, unsigned short prio
)
1177 return __cfq_find_cfq_hash(cfqd
, key
, prio
, hash_long(key
, CFQ_QHASH_SHIFT
));
1180 static void cfq_free_io_context(struct io_context
*ioc
)
1182 struct cfq_io_context
*__cic
;
1186 while ((n
= rb_first(&ioc
->cic_root
)) != NULL
) {
1187 __cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1188 rb_erase(&__cic
->rb_node
, &ioc
->cic_root
);
1189 kmem_cache_free(cfq_ioc_pool
, __cic
);
1193 elv_ioc_count_mod(ioc_count
, -freed
);
1195 if (ioc_gone
&& !elv_ioc_count_read(ioc_count
))
1199 static void cfq_exit_cfqq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1201 if (unlikely(cfqq
== cfqd
->active_queue
)) {
1202 __cfq_slice_expired(cfqd
, cfqq
, 0, 0);
1203 cfq_schedule_dispatch(cfqd
);
1206 cfq_put_queue(cfqq
);
1209 static void __cfq_exit_single_io_context(struct cfq_data
*cfqd
,
1210 struct cfq_io_context
*cic
)
1212 list_del_init(&cic
->queue_list
);
1216 if (cic
->cfqq
[ASYNC
]) {
1217 cfq_exit_cfqq(cfqd
, cic
->cfqq
[ASYNC
]);
1218 cic
->cfqq
[ASYNC
] = NULL
;
1221 if (cic
->cfqq
[SYNC
]) {
1222 cfq_exit_cfqq(cfqd
, cic
->cfqq
[SYNC
]);
1223 cic
->cfqq
[SYNC
] = NULL
;
1229 * Called with interrupts disabled
1231 static void cfq_exit_single_io_context(struct cfq_io_context
*cic
)
1233 struct cfq_data
*cfqd
= cic
->key
;
1236 request_queue_t
*q
= cfqd
->queue
;
1238 spin_lock_irq(q
->queue_lock
);
1239 __cfq_exit_single_io_context(cfqd
, cic
);
1240 spin_unlock_irq(q
->queue_lock
);
1244 static void cfq_exit_io_context(struct io_context
*ioc
)
1246 struct cfq_io_context
*__cic
;
1250 * put the reference this task is holding to the various queues
1253 n
= rb_first(&ioc
->cic_root
);
1255 __cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1257 cfq_exit_single_io_context(__cic
);
1262 static struct cfq_io_context
*
1263 cfq_alloc_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
1265 struct cfq_io_context
*cic
;
1267 cic
= kmem_cache_alloc_node(cfq_ioc_pool
, gfp_mask
, cfqd
->queue
->node
);
1269 memset(cic
, 0, sizeof(*cic
));
1270 cic
->last_end_request
= jiffies
;
1271 INIT_LIST_HEAD(&cic
->queue_list
);
1272 cic
->dtor
= cfq_free_io_context
;
1273 cic
->exit
= cfq_exit_io_context
;
1274 elv_ioc_count_inc(ioc_count
);
1280 static void cfq_init_prio_data(struct cfq_queue
*cfqq
)
1282 struct task_struct
*tsk
= current
;
1285 if (!cfq_cfqq_prio_changed(cfqq
))
1288 ioprio_class
= IOPRIO_PRIO_CLASS(tsk
->ioprio
);
1289 switch (ioprio_class
) {
1291 printk(KERN_ERR
"cfq: bad prio %x\n", ioprio_class
);
1292 case IOPRIO_CLASS_NONE
:
1294 * no prio set, place us in the middle of the BE classes
1296 cfqq
->ioprio
= task_nice_ioprio(tsk
);
1297 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1299 case IOPRIO_CLASS_RT
:
1300 cfqq
->ioprio
= task_ioprio(tsk
);
1301 cfqq
->ioprio_class
= IOPRIO_CLASS_RT
;
1303 case IOPRIO_CLASS_BE
:
1304 cfqq
->ioprio
= task_ioprio(tsk
);
1305 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1307 case IOPRIO_CLASS_IDLE
:
1308 cfqq
->ioprio_class
= IOPRIO_CLASS_IDLE
;
1310 cfq_clear_cfqq_idle_window(cfqq
);
1315 * keep track of original prio settings in case we have to temporarily
1316 * elevate the priority of this queue
1318 cfqq
->org_ioprio
= cfqq
->ioprio
;
1319 cfqq
->org_ioprio_class
= cfqq
->ioprio_class
;
1320 cfq_clear_cfqq_prio_changed(cfqq
);
1323 static inline void changed_ioprio(struct cfq_io_context
*cic
)
1325 struct cfq_data
*cfqd
= cic
->key
;
1326 struct cfq_queue
*cfqq
;
1327 unsigned long flags
;
1329 if (unlikely(!cfqd
))
1332 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
1334 cfqq
= cic
->cfqq
[ASYNC
];
1336 struct cfq_queue
*new_cfqq
;
1337 new_cfqq
= cfq_get_queue(cfqd
, CFQ_KEY_ASYNC
, cic
->ioc
->task
,
1340 cic
->cfqq
[ASYNC
] = new_cfqq
;
1341 cfq_put_queue(cfqq
);
1345 cfqq
= cic
->cfqq
[SYNC
];
1347 cfq_mark_cfqq_prio_changed(cfqq
);
1349 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
1352 static void cfq_ioc_set_ioprio(struct io_context
*ioc
)
1354 struct cfq_io_context
*cic
;
1357 ioc
->ioprio_changed
= 0;
1359 n
= rb_first(&ioc
->cic_root
);
1361 cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1363 changed_ioprio(cic
);
1368 static struct cfq_queue
*
1369 cfq_get_queue(struct cfq_data
*cfqd
, unsigned int key
, struct task_struct
*tsk
,
1372 const int hashval
= hash_long(key
, CFQ_QHASH_SHIFT
);
1373 struct cfq_queue
*cfqq
, *new_cfqq
= NULL
;
1374 unsigned short ioprio
;
1377 ioprio
= tsk
->ioprio
;
1378 cfqq
= __cfq_find_cfq_hash(cfqd
, key
, ioprio
, hashval
);
1384 } else if (gfp_mask
& __GFP_WAIT
) {
1386 * Inform the allocator of the fact that we will
1387 * just repeat this allocation if it fails, to allow
1388 * the allocator to do whatever it needs to attempt to
1391 spin_unlock_irq(cfqd
->queue
->queue_lock
);
1392 new_cfqq
= kmem_cache_alloc_node(cfq_pool
, gfp_mask
|__GFP_NOFAIL
, cfqd
->queue
->node
);
1393 spin_lock_irq(cfqd
->queue
->queue_lock
);
1396 cfqq
= kmem_cache_alloc_node(cfq_pool
, gfp_mask
, cfqd
->queue
->node
);
1401 memset(cfqq
, 0, sizeof(*cfqq
));
1403 INIT_HLIST_NODE(&cfqq
->cfq_hash
);
1404 INIT_LIST_HEAD(&cfqq
->cfq_list
);
1405 RB_CLEAR_NODE(&cfqq
->rb_node
);
1406 INIT_LIST_HEAD(&cfqq
->fifo
);
1409 hlist_add_head(&cfqq
->cfq_hash
, &cfqd
->cfq_hash
[hashval
]);
1410 atomic_set(&cfqq
->ref
, 0);
1413 if (key
!= CFQ_KEY_ASYNC
)
1414 cfq_mark_cfqq_idle_window(cfqq
);
1416 cfq_mark_cfqq_prio_changed(cfqq
);
1417 cfq_mark_cfqq_queue_new(cfqq
);
1418 cfq_init_prio_data(cfqq
);
1422 kmem_cache_free(cfq_pool
, new_cfqq
);
1424 atomic_inc(&cfqq
->ref
);
1426 WARN_ON((gfp_mask
& __GFP_WAIT
) && !cfqq
);
1431 cfq_drop_dead_cic(struct io_context
*ioc
, struct cfq_io_context
*cic
)
1433 WARN_ON(!list_empty(&cic
->queue_list
));
1434 rb_erase(&cic
->rb_node
, &ioc
->cic_root
);
1435 kmem_cache_free(cfq_ioc_pool
, cic
);
1436 elv_ioc_count_dec(ioc_count
);
1439 static struct cfq_io_context
*
1440 cfq_cic_rb_lookup(struct cfq_data
*cfqd
, struct io_context
*ioc
)
1443 struct cfq_io_context
*cic
;
1444 void *k
, *key
= cfqd
;
1447 n
= ioc
->cic_root
.rb_node
;
1449 cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1450 /* ->key must be copied to avoid race with cfq_exit_queue() */
1453 cfq_drop_dead_cic(ioc
, cic
);
1469 cfq_cic_link(struct cfq_data
*cfqd
, struct io_context
*ioc
,
1470 struct cfq_io_context
*cic
)
1473 struct rb_node
*parent
;
1474 struct cfq_io_context
*__cic
;
1475 unsigned long flags
;
1483 p
= &ioc
->cic_root
.rb_node
;
1486 __cic
= rb_entry(parent
, struct cfq_io_context
, rb_node
);
1487 /* ->key must be copied to avoid race with cfq_exit_queue() */
1490 cfq_drop_dead_cic(ioc
, __cic
);
1496 else if (cic
->key
> k
)
1497 p
= &(*p
)->rb_right
;
1502 rb_link_node(&cic
->rb_node
, parent
, p
);
1503 rb_insert_color(&cic
->rb_node
, &ioc
->cic_root
);
1505 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
1506 list_add(&cic
->queue_list
, &cfqd
->cic_list
);
1507 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
1511 * Setup general io context and cfq io context. There can be several cfq
1512 * io contexts per general io context, if this process is doing io to more
1513 * than one device managed by cfq.
1515 static struct cfq_io_context
*
1516 cfq_get_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
1518 struct io_context
*ioc
= NULL
;
1519 struct cfq_io_context
*cic
;
1521 might_sleep_if(gfp_mask
& __GFP_WAIT
);
1523 ioc
= get_io_context(gfp_mask
, cfqd
->queue
->node
);
1527 cic
= cfq_cic_rb_lookup(cfqd
, ioc
);
1531 cic
= cfq_alloc_io_context(cfqd
, gfp_mask
);
1535 cfq_cic_link(cfqd
, ioc
, cic
);
1537 smp_read_barrier_depends();
1538 if (unlikely(ioc
->ioprio_changed
))
1539 cfq_ioc_set_ioprio(ioc
);
1543 put_io_context(ioc
);
1548 cfq_update_io_thinktime(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
)
1550 unsigned long elapsed
= jiffies
- cic
->last_end_request
;
1551 unsigned long ttime
= min(elapsed
, 2UL * cfqd
->cfq_slice_idle
);
1553 cic
->ttime_samples
= (7*cic
->ttime_samples
+ 256) / 8;
1554 cic
->ttime_total
= (7*cic
->ttime_total
+ 256*ttime
) / 8;
1555 cic
->ttime_mean
= (cic
->ttime_total
+ 128) / cic
->ttime_samples
;
1559 cfq_update_io_seektime(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
,
1565 if (cic
->last_request_pos
< rq
->sector
)
1566 sdist
= rq
->sector
- cic
->last_request_pos
;
1568 sdist
= cic
->last_request_pos
- rq
->sector
;
1570 if (!cic
->seek_samples
) {
1571 cfqd
->new_seek_total
= (7*cic
->seek_total
+ (u64
)256*sdist
) / 8;
1572 cfqd
->new_seek_mean
= cfqd
->new_seek_total
/ 256;
1576 * Don't allow the seek distance to get too large from the
1577 * odd fragment, pagein, etc
1579 if (cic
->seek_samples
<= 60) /* second&third seek */
1580 sdist
= min(sdist
, (cic
->seek_mean
* 4) + 2*1024*1024);
1582 sdist
= min(sdist
, (cic
->seek_mean
* 4) + 2*1024*64);
1584 cic
->seek_samples
= (7*cic
->seek_samples
+ 256) / 8;
1585 cic
->seek_total
= (7*cic
->seek_total
+ (u64
)256*sdist
) / 8;
1586 total
= cic
->seek_total
+ (cic
->seek_samples
/2);
1587 do_div(total
, cic
->seek_samples
);
1588 cic
->seek_mean
= (sector_t
)total
;
1592 * Disable idle window if the process thinks too long or seeks so much that
1596 cfq_update_idle_window(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1597 struct cfq_io_context
*cic
)
1599 int enable_idle
= cfq_cfqq_idle_window(cfqq
);
1601 if (!cic
->ioc
->task
|| !cfqd
->cfq_slice_idle
||
1602 (cfqd
->hw_tag
&& CIC_SEEKY(cic
)))
1604 else if (sample_valid(cic
->ttime_samples
)) {
1605 if (cic
->ttime_mean
> cfqd
->cfq_slice_idle
)
1612 cfq_mark_cfqq_idle_window(cfqq
);
1614 cfq_clear_cfqq_idle_window(cfqq
);
1618 * Check if new_cfqq should preempt the currently active queue. Return 0 for
1619 * no or if we aren't sure, a 1 will cause a preempt.
1622 cfq_should_preempt(struct cfq_data
*cfqd
, struct cfq_queue
*new_cfqq
,
1625 struct cfq_queue
*cfqq
;
1627 cfqq
= cfqd
->active_queue
;
1631 if (cfq_slice_used(cfqq
))
1634 if (cfq_class_idle(new_cfqq
))
1637 if (cfq_class_idle(cfqq
))
1641 * if the new request is sync, but the currently running queue is
1642 * not, let the sync request have priority.
1644 if (rq_is_sync(rq
) && !cfq_cfqq_sync(cfqq
))
1648 * So both queues are sync. Let the new request get disk time if
1649 * it's a metadata request and the current queue is doing regular IO.
1651 if (rq_is_meta(rq
) && !cfqq
->meta_pending
)
1654 if (!cfqd
->active_cic
|| !cfq_cfqq_wait_request(cfqq
))
1658 * if this request is as-good as one we would expect from the
1659 * current cfqq, let it preempt
1661 if (cfq_rq_close(cfqd
, rq
))
1668 * cfqq preempts the active queue. if we allowed preempt with no slice left,
1669 * let it have half of its nominal slice.
1671 static void cfq_preempt_queue(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1673 cfq_slice_expired(cfqd
, 1, 1);
1676 * Put the new queue at the front of the of the current list,
1677 * so we know that it will be selected next.
1679 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
1680 list_del_init(&cfqq
->cfq_list
);
1681 list_add(&cfqq
->cfq_list
, &cfqd
->cur_rr
);
1683 cfqq
->slice_end
= 0;
1684 cfq_mark_cfqq_slice_new(cfqq
);
1688 * Called when a new fs request (rq) is added (to cfqq). Check if there's
1689 * something we should do about it
1692 cfq_rq_enqueued(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1695 struct cfq_io_context
*cic
= RQ_CIC(rq
);
1698 cfqq
->meta_pending
++;
1700 cfq_update_io_thinktime(cfqd
, cic
);
1701 cfq_update_io_seektime(cfqd
, cic
, rq
);
1702 cfq_update_idle_window(cfqd
, cfqq
, cic
);
1704 cic
->last_request_pos
= rq
->sector
+ rq
->nr_sectors
;
1705 cfqq
->last_request_pos
= cic
->last_request_pos
;
1707 if (cfqq
== cfqd
->active_queue
) {
1709 * if we are waiting for a request for this queue, let it rip
1710 * immediately and flag that we must not expire this queue
1713 if (cfq_cfqq_wait_request(cfqq
)) {
1714 cfq_mark_cfqq_must_dispatch(cfqq
);
1715 del_timer(&cfqd
->idle_slice_timer
);
1716 blk_start_queueing(cfqd
->queue
);
1718 } else if (cfq_should_preempt(cfqd
, cfqq
, rq
)) {
1720 * not the active queue - expire current slice if it is
1721 * idle and has expired it's mean thinktime or this new queue
1722 * has some old slice time left and is of higher priority
1724 cfq_preempt_queue(cfqd
, cfqq
);
1725 cfq_mark_cfqq_must_dispatch(cfqq
);
1726 blk_start_queueing(cfqd
->queue
);
1730 static void cfq_insert_request(request_queue_t
*q
, struct request
*rq
)
1732 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1733 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1735 cfq_init_prio_data(cfqq
);
1739 list_add_tail(&rq
->queuelist
, &cfqq
->fifo
);
1741 cfq_rq_enqueued(cfqd
, cfqq
, rq
);
1744 static void cfq_completed_request(request_queue_t
*q
, struct request
*rq
)
1746 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1747 struct cfq_data
*cfqd
= cfqq
->cfqd
;
1748 const int sync
= rq_is_sync(rq
);
1753 WARN_ON(!cfqd
->rq_in_driver
);
1754 WARN_ON(!cfqq
->dispatched
);
1755 cfqd
->rq_in_driver
--;
1758 if (!cfq_class_idle(cfqq
))
1759 cfqd
->last_end_request
= now
;
1762 RQ_CIC(rq
)->last_end_request
= now
;
1765 * If this is the active queue, check if it needs to be expired,
1766 * or if we want to idle in case it has no pending requests.
1768 if (cfqd
->active_queue
== cfqq
) {
1769 if (cfq_cfqq_slice_new(cfqq
)) {
1770 cfq_set_prio_slice(cfqd
, cfqq
);
1771 cfq_clear_cfqq_slice_new(cfqq
);
1773 if (cfq_slice_used(cfqq
))
1774 cfq_slice_expired(cfqd
, 0, 1);
1775 else if (sync
&& RB_EMPTY_ROOT(&cfqq
->sort_list
))
1776 cfq_arm_slice_timer(cfqd
);
1779 if (!cfqd
->rq_in_driver
)
1780 cfq_schedule_dispatch(cfqd
);
1784 * we temporarily boost lower priority queues if they are holding fs exclusive
1785 * resources. they are boosted to normal prio (CLASS_BE/4)
1787 static void cfq_prio_boost(struct cfq_queue
*cfqq
)
1789 if (has_fs_excl()) {
1791 * boost idle prio on transactions that would lock out other
1792 * users of the filesystem
1794 if (cfq_class_idle(cfqq
))
1795 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1796 if (cfqq
->ioprio
> IOPRIO_NORM
)
1797 cfqq
->ioprio
= IOPRIO_NORM
;
1800 * check if we need to unboost the queue
1802 if (cfqq
->ioprio_class
!= cfqq
->org_ioprio_class
)
1803 cfqq
->ioprio_class
= cfqq
->org_ioprio_class
;
1804 if (cfqq
->ioprio
!= cfqq
->org_ioprio
)
1805 cfqq
->ioprio
= cfqq
->org_ioprio
;
1809 static inline int __cfq_may_queue(struct cfq_queue
*cfqq
)
1811 if ((cfq_cfqq_wait_request(cfqq
) || cfq_cfqq_must_alloc(cfqq
)) &&
1812 !cfq_cfqq_must_alloc_slice(cfqq
)) {
1813 cfq_mark_cfqq_must_alloc_slice(cfqq
);
1814 return ELV_MQUEUE_MUST
;
1817 return ELV_MQUEUE_MAY
;
1820 static int cfq_may_queue(request_queue_t
*q
, int rw
)
1822 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1823 struct task_struct
*tsk
= current
;
1824 struct cfq_queue
*cfqq
;
1827 key
= cfq_queue_pid(tsk
, rw
, rw
& REQ_RW_SYNC
);
1830 * don't force setup of a queue from here, as a call to may_queue
1831 * does not necessarily imply that a request actually will be queued.
1832 * so just lookup a possibly existing queue, or return 'may queue'
1835 cfqq
= cfq_find_cfq_hash(cfqd
, key
, tsk
->ioprio
);
1837 cfq_init_prio_data(cfqq
);
1838 cfq_prio_boost(cfqq
);
1840 return __cfq_may_queue(cfqq
);
1843 return ELV_MQUEUE_MAY
;
1847 * queue lock held here
1849 static void cfq_put_request(struct request
*rq
)
1851 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1854 const int rw
= rq_data_dir(rq
);
1856 BUG_ON(!cfqq
->allocated
[rw
]);
1857 cfqq
->allocated
[rw
]--;
1859 put_io_context(RQ_CIC(rq
)->ioc
);
1861 rq
->elevator_private
= NULL
;
1862 rq
->elevator_private2
= NULL
;
1864 cfq_put_queue(cfqq
);
1869 * Allocate cfq data structures associated with this request.
1872 cfq_set_request(request_queue_t
*q
, struct request
*rq
, gfp_t gfp_mask
)
1874 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1875 struct task_struct
*tsk
= current
;
1876 struct cfq_io_context
*cic
;
1877 const int rw
= rq_data_dir(rq
);
1878 const int is_sync
= rq_is_sync(rq
);
1879 pid_t key
= cfq_queue_pid(tsk
, rw
, is_sync
);
1880 struct cfq_queue
*cfqq
;
1881 unsigned long flags
;
1883 might_sleep_if(gfp_mask
& __GFP_WAIT
);
1885 cic
= cfq_get_io_context(cfqd
, gfp_mask
);
1887 spin_lock_irqsave(q
->queue_lock
, flags
);
1892 if (!cic
->cfqq
[is_sync
]) {
1893 cfqq
= cfq_get_queue(cfqd
, key
, tsk
, gfp_mask
);
1897 cic
->cfqq
[is_sync
] = cfqq
;
1899 cfqq
= cic
->cfqq
[is_sync
];
1901 cfqq
->allocated
[rw
]++;
1902 cfq_clear_cfqq_must_alloc(cfqq
);
1903 atomic_inc(&cfqq
->ref
);
1905 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1907 rq
->elevator_private
= cic
;
1908 rq
->elevator_private2
= cfqq
;
1913 put_io_context(cic
->ioc
);
1915 cfq_schedule_dispatch(cfqd
);
1916 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1920 static void cfq_kick_queue(struct work_struct
*work
)
1922 struct cfq_data
*cfqd
=
1923 container_of(work
, struct cfq_data
, unplug_work
);
1924 request_queue_t
*q
= cfqd
->queue
;
1925 unsigned long flags
;
1927 spin_lock_irqsave(q
->queue_lock
, flags
);
1928 blk_start_queueing(q
);
1929 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1933 * Timer running if the active_queue is currently idling inside its time slice
1935 static void cfq_idle_slice_timer(unsigned long data
)
1937 struct cfq_data
*cfqd
= (struct cfq_data
*) data
;
1938 struct cfq_queue
*cfqq
;
1939 unsigned long flags
;
1942 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
1944 if ((cfqq
= cfqd
->active_queue
) != NULL
) {
1950 if (cfq_slice_used(cfqq
))
1954 * only expire and reinvoke request handler, if there are
1955 * other queues with pending requests
1957 if (!cfqd
->busy_queues
)
1961 * not expired and it has a request pending, let it dispatch
1963 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
)) {
1964 cfq_mark_cfqq_must_dispatch(cfqq
);
1969 cfq_slice_expired(cfqd
, 0, timed_out
);
1971 cfq_schedule_dispatch(cfqd
);
1973 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
1977 * Timer running if an idle class queue is waiting for service
1979 static void cfq_idle_class_timer(unsigned long data
)
1981 struct cfq_data
*cfqd
= (struct cfq_data
*) data
;
1982 unsigned long flags
, end
;
1984 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
1987 * race with a non-idle queue, reset timer
1989 end
= cfqd
->last_end_request
+ CFQ_IDLE_GRACE
;
1990 if (!time_after_eq(jiffies
, end
))
1991 mod_timer(&cfqd
->idle_class_timer
, end
);
1993 cfq_schedule_dispatch(cfqd
);
1995 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
1998 static void cfq_shutdown_timer_wq(struct cfq_data
*cfqd
)
2000 del_timer_sync(&cfqd
->idle_slice_timer
);
2001 del_timer_sync(&cfqd
->idle_class_timer
);
2002 blk_sync_queue(cfqd
->queue
);
2005 static void cfq_exit_queue(elevator_t
*e
)
2007 struct cfq_data
*cfqd
= e
->elevator_data
;
2008 request_queue_t
*q
= cfqd
->queue
;
2010 cfq_shutdown_timer_wq(cfqd
);
2012 spin_lock_irq(q
->queue_lock
);
2014 if (cfqd
->active_queue
)
2015 __cfq_slice_expired(cfqd
, cfqd
->active_queue
, 0, 0);
2017 while (!list_empty(&cfqd
->cic_list
)) {
2018 struct cfq_io_context
*cic
= list_entry(cfqd
->cic_list
.next
,
2019 struct cfq_io_context
,
2022 __cfq_exit_single_io_context(cfqd
, cic
);
2025 spin_unlock_irq(q
->queue_lock
);
2027 cfq_shutdown_timer_wq(cfqd
);
2029 kfree(cfqd
->cfq_hash
);
2033 static void *cfq_init_queue(request_queue_t
*q
)
2035 struct cfq_data
*cfqd
;
2038 cfqd
= kmalloc_node(sizeof(*cfqd
), GFP_KERNEL
, q
->node
);
2042 memset(cfqd
, 0, sizeof(*cfqd
));
2044 cfqd
->service_tree
= CFQ_RB_ROOT
;
2045 INIT_LIST_HEAD(&cfqd
->cur_rr
);
2046 INIT_LIST_HEAD(&cfqd
->cic_list
);
2048 cfqd
->cfq_hash
= kmalloc_node(sizeof(struct hlist_head
) * CFQ_QHASH_ENTRIES
, GFP_KERNEL
, q
->node
);
2049 if (!cfqd
->cfq_hash
)
2052 for (i
= 0; i
< CFQ_QHASH_ENTRIES
; i
++)
2053 INIT_HLIST_HEAD(&cfqd
->cfq_hash
[i
]);
2057 init_timer(&cfqd
->idle_slice_timer
);
2058 cfqd
->idle_slice_timer
.function
= cfq_idle_slice_timer
;
2059 cfqd
->idle_slice_timer
.data
= (unsigned long) cfqd
;
2061 init_timer(&cfqd
->idle_class_timer
);
2062 cfqd
->idle_class_timer
.function
= cfq_idle_class_timer
;
2063 cfqd
->idle_class_timer
.data
= (unsigned long) cfqd
;
2065 INIT_WORK(&cfqd
->unplug_work
, cfq_kick_queue
);
2067 cfqd
->cfq_quantum
= cfq_quantum
;
2068 cfqd
->cfq_fifo_expire
[0] = cfq_fifo_expire
[0];
2069 cfqd
->cfq_fifo_expire
[1] = cfq_fifo_expire
[1];
2070 cfqd
->cfq_back_max
= cfq_back_max
;
2071 cfqd
->cfq_back_penalty
= cfq_back_penalty
;
2072 cfqd
->cfq_slice
[0] = cfq_slice_async
;
2073 cfqd
->cfq_slice
[1] = cfq_slice_sync
;
2074 cfqd
->cfq_slice_async_rq
= cfq_slice_async_rq
;
2075 cfqd
->cfq_slice_idle
= cfq_slice_idle
;
2083 static void cfq_slab_kill(void)
2086 kmem_cache_destroy(cfq_pool
);
2088 kmem_cache_destroy(cfq_ioc_pool
);
2091 static int __init
cfq_slab_setup(void)
2093 cfq_pool
= kmem_cache_create("cfq_pool", sizeof(struct cfq_queue
), 0, 0,
2098 cfq_ioc_pool
= kmem_cache_create("cfq_ioc_pool",
2099 sizeof(struct cfq_io_context
), 0, 0, NULL
, NULL
);
2110 * sysfs parts below -->
2113 cfq_var_show(unsigned int var
, char *page
)
2115 return sprintf(page
, "%d\n", var
);
2119 cfq_var_store(unsigned int *var
, const char *page
, size_t count
)
2121 char *p
= (char *) page
;
2123 *var
= simple_strtoul(p
, &p
, 10);
2127 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
2128 static ssize_t __FUNC(elevator_t *e, char *page) \
2130 struct cfq_data *cfqd = e->elevator_data; \
2131 unsigned int __data = __VAR; \
2133 __data = jiffies_to_msecs(__data); \
2134 return cfq_var_show(__data, (page)); \
2136 SHOW_FUNCTION(cfq_quantum_show
, cfqd
->cfq_quantum
, 0);
2137 SHOW_FUNCTION(cfq_fifo_expire_sync_show
, cfqd
->cfq_fifo_expire
[1], 1);
2138 SHOW_FUNCTION(cfq_fifo_expire_async_show
, cfqd
->cfq_fifo_expire
[0], 1);
2139 SHOW_FUNCTION(cfq_back_seek_max_show
, cfqd
->cfq_back_max
, 0);
2140 SHOW_FUNCTION(cfq_back_seek_penalty_show
, cfqd
->cfq_back_penalty
, 0);
2141 SHOW_FUNCTION(cfq_slice_idle_show
, cfqd
->cfq_slice_idle
, 1);
2142 SHOW_FUNCTION(cfq_slice_sync_show
, cfqd
->cfq_slice
[1], 1);
2143 SHOW_FUNCTION(cfq_slice_async_show
, cfqd
->cfq_slice
[0], 1);
2144 SHOW_FUNCTION(cfq_slice_async_rq_show
, cfqd
->cfq_slice_async_rq
, 0);
2145 #undef SHOW_FUNCTION
2147 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
2148 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
2150 struct cfq_data *cfqd = e->elevator_data; \
2151 unsigned int __data; \
2152 int ret = cfq_var_store(&__data, (page), count); \
2153 if (__data < (MIN)) \
2155 else if (__data > (MAX)) \
2158 *(__PTR) = msecs_to_jiffies(__data); \
2160 *(__PTR) = __data; \
2163 STORE_FUNCTION(cfq_quantum_store
, &cfqd
->cfq_quantum
, 1, UINT_MAX
, 0);
2164 STORE_FUNCTION(cfq_fifo_expire_sync_store
, &cfqd
->cfq_fifo_expire
[1], 1, UINT_MAX
, 1);
2165 STORE_FUNCTION(cfq_fifo_expire_async_store
, &cfqd
->cfq_fifo_expire
[0], 1, UINT_MAX
, 1);
2166 STORE_FUNCTION(cfq_back_seek_max_store
, &cfqd
->cfq_back_max
, 0, UINT_MAX
, 0);
2167 STORE_FUNCTION(cfq_back_seek_penalty_store
, &cfqd
->cfq_back_penalty
, 1, UINT_MAX
, 0);
2168 STORE_FUNCTION(cfq_slice_idle_store
, &cfqd
->cfq_slice_idle
, 0, UINT_MAX
, 1);
2169 STORE_FUNCTION(cfq_slice_sync_store
, &cfqd
->cfq_slice
[1], 1, UINT_MAX
, 1);
2170 STORE_FUNCTION(cfq_slice_async_store
, &cfqd
->cfq_slice
[0], 1, UINT_MAX
, 1);
2171 STORE_FUNCTION(cfq_slice_async_rq_store
, &cfqd
->cfq_slice_async_rq
, 1, UINT_MAX
, 0);
2172 #undef STORE_FUNCTION
2174 #define CFQ_ATTR(name) \
2175 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2177 static struct elv_fs_entry cfq_attrs
[] = {
2179 CFQ_ATTR(fifo_expire_sync
),
2180 CFQ_ATTR(fifo_expire_async
),
2181 CFQ_ATTR(back_seek_max
),
2182 CFQ_ATTR(back_seek_penalty
),
2183 CFQ_ATTR(slice_sync
),
2184 CFQ_ATTR(slice_async
),
2185 CFQ_ATTR(slice_async_rq
),
2186 CFQ_ATTR(slice_idle
),
2190 static struct elevator_type iosched_cfq
= {
2192 .elevator_merge_fn
= cfq_merge
,
2193 .elevator_merged_fn
= cfq_merged_request
,
2194 .elevator_merge_req_fn
= cfq_merged_requests
,
2195 .elevator_allow_merge_fn
= cfq_allow_merge
,
2196 .elevator_dispatch_fn
= cfq_dispatch_requests
,
2197 .elevator_add_req_fn
= cfq_insert_request
,
2198 .elevator_activate_req_fn
= cfq_activate_request
,
2199 .elevator_deactivate_req_fn
= cfq_deactivate_request
,
2200 .elevator_queue_empty_fn
= cfq_queue_empty
,
2201 .elevator_completed_req_fn
= cfq_completed_request
,
2202 .elevator_former_req_fn
= elv_rb_former_request
,
2203 .elevator_latter_req_fn
= elv_rb_latter_request
,
2204 .elevator_set_req_fn
= cfq_set_request
,
2205 .elevator_put_req_fn
= cfq_put_request
,
2206 .elevator_may_queue_fn
= cfq_may_queue
,
2207 .elevator_init_fn
= cfq_init_queue
,
2208 .elevator_exit_fn
= cfq_exit_queue
,
2209 .trim
= cfq_free_io_context
,
2211 .elevator_attrs
= cfq_attrs
,
2212 .elevator_name
= "cfq",
2213 .elevator_owner
= THIS_MODULE
,
2216 static int __init
cfq_init(void)
2221 * could be 0 on HZ < 1000 setups
2223 if (!cfq_slice_async
)
2224 cfq_slice_async
= 1;
2225 if (!cfq_slice_idle
)
2228 if (cfq_slab_setup())
2231 ret
= elv_register(&iosched_cfq
);
2238 static void __exit
cfq_exit(void)
2240 DECLARE_COMPLETION_ONSTACK(all_gone
);
2241 elv_unregister(&iosched_cfq
);
2242 ioc_gone
= &all_gone
;
2243 /* ioc_gone's update must be visible before reading ioc_count */
2245 if (elv_ioc_count_read(ioc_count
))
2246 wait_for_completion(ioc_gone
);
2251 module_init(cfq_init
);
2252 module_exit(cfq_exit
);
2254 MODULE_AUTHOR("Jens Axboe");
2255 MODULE_LICENSE("GPL");
2256 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");