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/rbtree.h>
13 #include <linux/ioprio.h>
18 static const int cfq_quantum
= 4; /* max queue in one round of service */
19 static const int cfq_fifo_expire
[2] = { HZ
/ 4, HZ
/ 8 };
20 static const int cfq_back_max
= 16 * 1024; /* maximum backwards seek, in KiB */
21 static const int cfq_back_penalty
= 2; /* penalty of a backwards seek */
23 static const int cfq_slice_sync
= HZ
/ 10;
24 static int cfq_slice_async
= HZ
/ 25;
25 static const int cfq_slice_async_rq
= 2;
26 static int cfq_slice_idle
= HZ
/ 125;
29 * grace period before allowing idle class to get disk access
31 #define CFQ_IDLE_GRACE (HZ / 10)
34 * below this threshold, we consider thinktime immediate
36 #define CFQ_MIN_TT (2)
38 #define CFQ_SLICE_SCALE (5)
40 #define RQ_CIC(rq) ((struct cfq_io_context*)(rq)->elevator_private)
41 #define RQ_CFQQ(rq) ((rq)->elevator_private2)
43 static struct kmem_cache
*cfq_pool
;
44 static struct kmem_cache
*cfq_ioc_pool
;
46 static DEFINE_PER_CPU(unsigned long, ioc_count
);
47 static struct completion
*ioc_gone
;
49 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
50 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
51 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
56 #define sample_valid(samples) ((samples) > 80)
59 * Most of our rbtree usage is for sorting with min extraction, so
60 * if we cache the leftmost node we don't have to walk down the tree
61 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
62 * move this into the elevator for the rq sorting as well.
68 #define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, }
71 * Per block device queue structure
74 request_queue_t
*queue
;
77 * rr list of queues with requests and the count of them
79 struct cfq_rb_root service_tree
;
80 unsigned int busy_queues
;
87 * idle window management
89 struct timer_list idle_slice_timer
;
90 struct work_struct unplug_work
;
92 struct cfq_queue
*active_queue
;
93 struct cfq_io_context
*active_cic
;
96 * async queue for each priority case
98 struct cfq_queue
*async_cfqq
[2][IOPRIO_BE_NR
];
99 struct cfq_queue
*async_idle_cfqq
;
101 struct timer_list idle_class_timer
;
103 sector_t last_position
;
104 unsigned long last_end_request
;
107 * tunables, see top of file
109 unsigned int cfq_quantum
;
110 unsigned int cfq_fifo_expire
[2];
111 unsigned int cfq_back_penalty
;
112 unsigned int cfq_back_max
;
113 unsigned int cfq_slice
[2];
114 unsigned int cfq_slice_async_rq
;
115 unsigned int cfq_slice_idle
;
117 struct list_head cic_list
;
121 * Per process-grouping structure
124 /* reference count */
126 /* parent cfq_data */
127 struct cfq_data
*cfqd
;
128 /* service_tree member */
129 struct rb_node rb_node
;
130 /* service_tree key */
131 unsigned long rb_key
;
132 /* sorted list of pending requests */
133 struct rb_root sort_list
;
134 /* if fifo isn't expired, next request to serve */
135 struct request
*next_rq
;
136 /* requests queued in sort_list */
138 /* currently allocated requests */
140 /* pending metadata requests */
142 /* fifo list of requests in sort_list */
143 struct list_head fifo
;
145 unsigned long slice_end
;
148 /* number of requests that are on the dispatch list or inside driver */
151 /* io prio of this group */
152 unsigned short ioprio
, org_ioprio
;
153 unsigned short ioprio_class
, org_ioprio_class
;
155 /* various state flags, see below */
159 enum cfqq_state_flags
{
160 CFQ_CFQQ_FLAG_on_rr
= 0, /* on round-robin busy list */
161 CFQ_CFQQ_FLAG_wait_request
, /* waiting for a request */
162 CFQ_CFQQ_FLAG_must_alloc
, /* must be allowed rq alloc */
163 CFQ_CFQQ_FLAG_must_alloc_slice
, /* per-slice must_alloc flag */
164 CFQ_CFQQ_FLAG_must_dispatch
, /* must dispatch, even if expired */
165 CFQ_CFQQ_FLAG_fifo_expire
, /* FIFO checked in this slice */
166 CFQ_CFQQ_FLAG_idle_window
, /* slice idling enabled */
167 CFQ_CFQQ_FLAG_prio_changed
, /* task priority has changed */
168 CFQ_CFQQ_FLAG_queue_new
, /* queue never been serviced */
169 CFQ_CFQQ_FLAG_slice_new
, /* no requests dispatched in slice */
170 CFQ_CFQQ_FLAG_sync
, /* synchronous queue */
173 #define CFQ_CFQQ_FNS(name) \
174 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
176 cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
178 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
180 cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
182 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
184 return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
188 CFQ_CFQQ_FNS(wait_request
);
189 CFQ_CFQQ_FNS(must_alloc
);
190 CFQ_CFQQ_FNS(must_alloc_slice
);
191 CFQ_CFQQ_FNS(must_dispatch
);
192 CFQ_CFQQ_FNS(fifo_expire
);
193 CFQ_CFQQ_FNS(idle_window
);
194 CFQ_CFQQ_FNS(prio_changed
);
195 CFQ_CFQQ_FNS(queue_new
);
196 CFQ_CFQQ_FNS(slice_new
);
200 static void cfq_dispatch_insert(request_queue_t
*, struct request
*);
201 static struct cfq_queue
*cfq_get_queue(struct cfq_data
*, int,
202 struct task_struct
*, gfp_t
);
203 static struct cfq_io_context
*cfq_cic_rb_lookup(struct cfq_data
*,
204 struct io_context
*);
206 static inline struct cfq_queue
*cic_to_cfqq(struct cfq_io_context
*cic
,
209 return cic
->cfqq
[!!is_sync
];
212 static inline void cic_set_cfqq(struct cfq_io_context
*cic
,
213 struct cfq_queue
*cfqq
, int is_sync
)
215 cic
->cfqq
[!!is_sync
] = cfqq
;
219 * We regard a request as SYNC, if it's either a read or has the SYNC bit
220 * set (in which case it could also be direct WRITE).
222 static inline int cfq_bio_sync(struct bio
*bio
)
224 if (bio_data_dir(bio
) == READ
|| bio_sync(bio
))
231 * scheduler run of queue, if there are requests pending and no one in the
232 * driver that will restart queueing
234 static inline void cfq_schedule_dispatch(struct cfq_data
*cfqd
)
236 if (cfqd
->busy_queues
)
237 kblockd_schedule_work(&cfqd
->unplug_work
);
240 static int cfq_queue_empty(request_queue_t
*q
)
242 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
244 return !cfqd
->busy_queues
;
248 * Scale schedule slice based on io priority. Use the sync time slice only
249 * if a queue is marked sync and has sync io queued. A sync queue with async
250 * io only, should not get full sync slice length.
252 static inline int cfq_prio_slice(struct cfq_data
*cfqd
, int sync
,
255 const int base_slice
= cfqd
->cfq_slice
[sync
];
257 WARN_ON(prio
>= IOPRIO_BE_NR
);
259 return base_slice
+ (base_slice
/CFQ_SLICE_SCALE
* (4 - prio
));
263 cfq_prio_to_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
265 return cfq_prio_slice(cfqd
, cfq_cfqq_sync(cfqq
), cfqq
->ioprio
);
269 cfq_set_prio_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
271 cfqq
->slice_end
= cfq_prio_to_slice(cfqd
, cfqq
) + jiffies
;
275 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
276 * isn't valid until the first request from the dispatch is activated
277 * and the slice time set.
279 static inline int cfq_slice_used(struct cfq_queue
*cfqq
)
281 if (cfq_cfqq_slice_new(cfqq
))
283 if (time_before(jiffies
, cfqq
->slice_end
))
290 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
291 * We choose the request that is closest to the head right now. Distance
292 * behind the head is penalized and only allowed to a certain extent.
294 static struct request
*
295 cfq_choose_req(struct cfq_data
*cfqd
, struct request
*rq1
, struct request
*rq2
)
297 sector_t last
, s1
, s2
, d1
= 0, d2
= 0;
298 unsigned long back_max
;
299 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
300 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
301 unsigned wrap
= 0; /* bit mask: requests behind the disk head? */
303 if (rq1
== NULL
|| rq1
== rq2
)
308 if (rq_is_sync(rq1
) && !rq_is_sync(rq2
))
310 else if (rq_is_sync(rq2
) && !rq_is_sync(rq1
))
312 if (rq_is_meta(rq1
) && !rq_is_meta(rq2
))
314 else if (rq_is_meta(rq2
) && !rq_is_meta(rq1
))
320 last
= cfqd
->last_position
;
323 * by definition, 1KiB is 2 sectors
325 back_max
= cfqd
->cfq_back_max
* 2;
328 * Strict one way elevator _except_ in the case where we allow
329 * short backward seeks which are biased as twice the cost of a
330 * similar forward seek.
334 else if (s1
+ back_max
>= last
)
335 d1
= (last
- s1
) * cfqd
->cfq_back_penalty
;
337 wrap
|= CFQ_RQ1_WRAP
;
341 else if (s2
+ back_max
>= last
)
342 d2
= (last
- s2
) * cfqd
->cfq_back_penalty
;
344 wrap
|= CFQ_RQ2_WRAP
;
346 /* Found required data */
349 * By doing switch() on the bit mask "wrap" we avoid having to
350 * check two variables for all permutations: --> faster!
353 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
369 case (CFQ_RQ1_WRAP
|CFQ_RQ2_WRAP
): /* both rqs wrapped */
372 * Since both rqs are wrapped,
373 * start with the one that's further behind head
374 * (--> only *one* back seek required),
375 * since back seek takes more time than forward.
385 * The below is leftmost cache rbtree addon
387 static struct rb_node
*cfq_rb_first(struct cfq_rb_root
*root
)
390 root
->left
= rb_first(&root
->rb
);
395 static void cfq_rb_erase(struct rb_node
*n
, struct cfq_rb_root
*root
)
400 rb_erase(n
, &root
->rb
);
405 * would be nice to take fifo expire time into account as well
407 static struct request
*
408 cfq_find_next_rq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
409 struct request
*last
)
411 struct rb_node
*rbnext
= rb_next(&last
->rb_node
);
412 struct rb_node
*rbprev
= rb_prev(&last
->rb_node
);
413 struct request
*next
= NULL
, *prev
= NULL
;
415 BUG_ON(RB_EMPTY_NODE(&last
->rb_node
));
418 prev
= rb_entry_rq(rbprev
);
421 next
= rb_entry_rq(rbnext
);
423 rbnext
= rb_first(&cfqq
->sort_list
);
424 if (rbnext
&& rbnext
!= &last
->rb_node
)
425 next
= rb_entry_rq(rbnext
);
428 return cfq_choose_req(cfqd
, next
, prev
);
431 static unsigned long cfq_slice_offset(struct cfq_data
*cfqd
,
432 struct cfq_queue
*cfqq
)
435 * just an approximation, should be ok.
437 return (cfqd
->busy_queues
- 1) * (cfq_prio_slice(cfqd
, 1, 0) -
438 cfq_prio_slice(cfqd
, cfq_cfqq_sync(cfqq
), cfqq
->ioprio
));
442 * The cfqd->service_tree holds all pending cfq_queue's that have
443 * requests waiting to be processed. It is sorted in the order that
444 * we will service the queues.
446 static void cfq_service_tree_add(struct cfq_data
*cfqd
,
447 struct cfq_queue
*cfqq
, int add_front
)
449 struct rb_node
**p
= &cfqd
->service_tree
.rb
.rb_node
;
450 struct rb_node
*parent
= NULL
;
451 unsigned long rb_key
;
455 rb_key
= cfq_slice_offset(cfqd
, cfqq
) + jiffies
;
456 rb_key
+= cfqq
->slice_resid
;
457 cfqq
->slice_resid
= 0;
461 if (!RB_EMPTY_NODE(&cfqq
->rb_node
)) {
463 * same position, nothing more to do
465 if (rb_key
== cfqq
->rb_key
)
468 cfq_rb_erase(&cfqq
->rb_node
, &cfqd
->service_tree
);
473 struct cfq_queue
*__cfqq
;
477 __cfqq
= rb_entry(parent
, struct cfq_queue
, rb_node
);
480 * sort RT queues first, we always want to give
481 * preference to them. IDLE queues goes to the back.
482 * after that, sort on the next service time.
484 if (cfq_class_rt(cfqq
) > cfq_class_rt(__cfqq
))
486 else if (cfq_class_rt(cfqq
) < cfq_class_rt(__cfqq
))
488 else if (cfq_class_idle(cfqq
) < cfq_class_idle(__cfqq
))
490 else if (cfq_class_idle(cfqq
) > cfq_class_idle(__cfqq
))
492 else if (rb_key
< __cfqq
->rb_key
)
497 if (n
== &(*p
)->rb_right
)
504 cfqd
->service_tree
.left
= &cfqq
->rb_node
;
506 cfqq
->rb_key
= rb_key
;
507 rb_link_node(&cfqq
->rb_node
, parent
, p
);
508 rb_insert_color(&cfqq
->rb_node
, &cfqd
->service_tree
.rb
);
512 * Update cfqq's position in the service tree.
514 static void cfq_resort_rr_list(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
517 * Resorting requires the cfqq to be on the RR list already.
519 if (cfq_cfqq_on_rr(cfqq
))
520 cfq_service_tree_add(cfqd
, cfqq
, 0);
524 * add to busy list of queues for service, trying to be fair in ordering
525 * the pending list according to last request service
528 cfq_add_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
530 BUG_ON(cfq_cfqq_on_rr(cfqq
));
531 cfq_mark_cfqq_on_rr(cfqq
);
534 cfq_resort_rr_list(cfqd
, cfqq
);
538 * Called when the cfqq no longer has requests pending, remove it from
542 cfq_del_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
544 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
545 cfq_clear_cfqq_on_rr(cfqq
);
547 if (!RB_EMPTY_NODE(&cfqq
->rb_node
))
548 cfq_rb_erase(&cfqq
->rb_node
, &cfqd
->service_tree
);
550 BUG_ON(!cfqd
->busy_queues
);
555 * rb tree support functions
557 static inline void cfq_del_rq_rb(struct request
*rq
)
559 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
560 struct cfq_data
*cfqd
= cfqq
->cfqd
;
561 const int sync
= rq_is_sync(rq
);
563 BUG_ON(!cfqq
->queued
[sync
]);
564 cfqq
->queued
[sync
]--;
566 elv_rb_del(&cfqq
->sort_list
, rq
);
568 if (cfq_cfqq_on_rr(cfqq
) && RB_EMPTY_ROOT(&cfqq
->sort_list
))
569 cfq_del_cfqq_rr(cfqd
, cfqq
);
572 static void cfq_add_rq_rb(struct request
*rq
)
574 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
575 struct cfq_data
*cfqd
= cfqq
->cfqd
;
576 struct request
*__alias
;
578 cfqq
->queued
[rq_is_sync(rq
)]++;
581 * looks a little odd, but the first insert might return an alias.
582 * if that happens, put the alias on the dispatch list
584 while ((__alias
= elv_rb_add(&cfqq
->sort_list
, rq
)) != NULL
)
585 cfq_dispatch_insert(cfqd
->queue
, __alias
);
587 if (!cfq_cfqq_on_rr(cfqq
))
588 cfq_add_cfqq_rr(cfqd
, cfqq
);
591 * check if this request is a better next-serve candidate
593 cfqq
->next_rq
= cfq_choose_req(cfqd
, cfqq
->next_rq
, rq
);
594 BUG_ON(!cfqq
->next_rq
);
598 cfq_reposition_rq_rb(struct cfq_queue
*cfqq
, struct request
*rq
)
600 elv_rb_del(&cfqq
->sort_list
, rq
);
601 cfqq
->queued
[rq_is_sync(rq
)]--;
605 static struct request
*
606 cfq_find_rq_fmerge(struct cfq_data
*cfqd
, struct bio
*bio
)
608 struct task_struct
*tsk
= current
;
609 struct cfq_io_context
*cic
;
610 struct cfq_queue
*cfqq
;
612 cic
= cfq_cic_rb_lookup(cfqd
, tsk
->io_context
);
616 cfqq
= cic_to_cfqq(cic
, cfq_bio_sync(bio
));
618 sector_t sector
= bio
->bi_sector
+ bio_sectors(bio
);
620 return elv_rb_find(&cfqq
->sort_list
, sector
);
626 static void cfq_activate_request(request_queue_t
*q
, struct request
*rq
)
628 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
630 cfqd
->rq_in_driver
++;
633 * If the depth is larger 1, it really could be queueing. But lets
634 * make the mark a little higher - idling could still be good for
635 * low queueing, and a low queueing number could also just indicate
636 * a SCSI mid layer like behaviour where limit+1 is often seen.
638 if (!cfqd
->hw_tag
&& cfqd
->rq_in_driver
> 4)
641 cfqd
->last_position
= rq
->hard_sector
+ rq
->hard_nr_sectors
;
644 static void cfq_deactivate_request(request_queue_t
*q
, struct request
*rq
)
646 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
648 WARN_ON(!cfqd
->rq_in_driver
);
649 cfqd
->rq_in_driver
--;
652 static void cfq_remove_request(struct request
*rq
)
654 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
656 if (cfqq
->next_rq
== rq
)
657 cfqq
->next_rq
= cfq_find_next_rq(cfqq
->cfqd
, cfqq
, rq
);
659 list_del_init(&rq
->queuelist
);
662 if (rq_is_meta(rq
)) {
663 WARN_ON(!cfqq
->meta_pending
);
664 cfqq
->meta_pending
--;
668 static int cfq_merge(request_queue_t
*q
, struct request
**req
, struct bio
*bio
)
670 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
671 struct request
*__rq
;
673 __rq
= cfq_find_rq_fmerge(cfqd
, bio
);
674 if (__rq
&& elv_rq_merge_ok(__rq
, bio
)) {
676 return ELEVATOR_FRONT_MERGE
;
679 return ELEVATOR_NO_MERGE
;
682 static void cfq_merged_request(request_queue_t
*q
, struct request
*req
,
685 if (type
== ELEVATOR_FRONT_MERGE
) {
686 struct cfq_queue
*cfqq
= RQ_CFQQ(req
);
688 cfq_reposition_rq_rb(cfqq
, req
);
693 cfq_merged_requests(request_queue_t
*q
, struct request
*rq
,
694 struct request
*next
)
697 * reposition in fifo if next is older than rq
699 if (!list_empty(&rq
->queuelist
) && !list_empty(&next
->queuelist
) &&
700 time_before(next
->start_time
, rq
->start_time
))
701 list_move(&rq
->queuelist
, &next
->queuelist
);
703 cfq_remove_request(next
);
706 static int cfq_allow_merge(request_queue_t
*q
, struct request
*rq
,
709 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
710 struct cfq_io_context
*cic
;
711 struct cfq_queue
*cfqq
;
714 * Disallow merge of a sync bio into an async request.
716 if (cfq_bio_sync(bio
) && !rq_is_sync(rq
))
720 * Lookup the cfqq that this bio will be queued with. Allow
721 * merge only if rq is queued there.
723 cic
= cfq_cic_rb_lookup(cfqd
, current
->io_context
);
727 cfqq
= cic_to_cfqq(cic
, cfq_bio_sync(bio
));
728 if (cfqq
== RQ_CFQQ(rq
))
735 __cfq_set_active_queue(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
739 * stop potential idle class queues waiting service
741 del_timer(&cfqd
->idle_class_timer
);
744 cfq_clear_cfqq_must_alloc_slice(cfqq
);
745 cfq_clear_cfqq_fifo_expire(cfqq
);
746 cfq_mark_cfqq_slice_new(cfqq
);
747 cfq_clear_cfqq_queue_new(cfqq
);
750 cfqd
->active_queue
= cfqq
;
754 * current cfqq expired its slice (or was too idle), select new one
757 __cfq_slice_expired(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
760 if (cfq_cfqq_wait_request(cfqq
))
761 del_timer(&cfqd
->idle_slice_timer
);
763 cfq_clear_cfqq_must_dispatch(cfqq
);
764 cfq_clear_cfqq_wait_request(cfqq
);
767 * store what was left of this slice, if the queue idled/timed out
769 if (timed_out
&& !cfq_cfqq_slice_new(cfqq
))
770 cfqq
->slice_resid
= cfqq
->slice_end
- jiffies
;
772 cfq_resort_rr_list(cfqd
, cfqq
);
774 if (cfqq
== cfqd
->active_queue
)
775 cfqd
->active_queue
= NULL
;
777 if (cfqd
->active_cic
) {
778 put_io_context(cfqd
->active_cic
->ioc
);
779 cfqd
->active_cic
= NULL
;
783 static inline void cfq_slice_expired(struct cfq_data
*cfqd
, int timed_out
)
785 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
788 __cfq_slice_expired(cfqd
, cfqq
, timed_out
);
792 * Get next queue for service. Unless we have a queue preemption,
793 * we'll simply select the first cfqq in the service tree.
795 static struct cfq_queue
*cfq_get_next_queue(struct cfq_data
*cfqd
)
797 struct cfq_queue
*cfqq
;
800 if (RB_EMPTY_ROOT(&cfqd
->service_tree
.rb
))
803 n
= cfq_rb_first(&cfqd
->service_tree
);
804 cfqq
= rb_entry(n
, struct cfq_queue
, rb_node
);
806 if (cfq_class_idle(cfqq
)) {
810 * if we have idle queues and no rt or be queues had
811 * pending requests, either allow immediate service if
812 * the grace period has passed or arm the idle grace
815 end
= cfqd
->last_end_request
+ CFQ_IDLE_GRACE
;
816 if (time_before(jiffies
, end
)) {
817 mod_timer(&cfqd
->idle_class_timer
, end
);
826 * Get and set a new active queue for service.
828 static struct cfq_queue
*cfq_set_active_queue(struct cfq_data
*cfqd
)
830 struct cfq_queue
*cfqq
;
832 cfqq
= cfq_get_next_queue(cfqd
);
833 __cfq_set_active_queue(cfqd
, cfqq
);
837 static inline sector_t
cfq_dist_from_last(struct cfq_data
*cfqd
,
840 if (rq
->sector
>= cfqd
->last_position
)
841 return rq
->sector
- cfqd
->last_position
;
843 return cfqd
->last_position
- rq
->sector
;
846 static inline int cfq_rq_close(struct cfq_data
*cfqd
, struct request
*rq
)
848 struct cfq_io_context
*cic
= cfqd
->active_cic
;
850 if (!sample_valid(cic
->seek_samples
))
853 return cfq_dist_from_last(cfqd
, rq
) <= cic
->seek_mean
;
856 static int cfq_close_cooperator(struct cfq_data
*cfq_data
,
857 struct cfq_queue
*cfqq
)
860 * We should notice if some of the queues are cooperating, eg
861 * working closely on the same area of the disk. In that case,
862 * we can group them together and don't waste time idling.
867 #define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024))
869 static void cfq_arm_slice_timer(struct cfq_data
*cfqd
)
871 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
872 struct cfq_io_context
*cic
;
875 WARN_ON(!RB_EMPTY_ROOT(&cfqq
->sort_list
));
876 WARN_ON(cfq_cfqq_slice_new(cfqq
));
879 * idle is disabled, either manually or by past process history
881 if (!cfqd
->cfq_slice_idle
|| !cfq_cfqq_idle_window(cfqq
))
885 * task has exited, don't wait
887 cic
= cfqd
->active_cic
;
888 if (!cic
|| !cic
->ioc
->task
)
892 * See if this prio level has a good candidate
894 if (cfq_close_cooperator(cfqd
, cfqq
) &&
895 (sample_valid(cic
->ttime_samples
) && cic
->ttime_mean
> 2))
898 cfq_mark_cfqq_must_dispatch(cfqq
);
899 cfq_mark_cfqq_wait_request(cfqq
);
902 * we don't want to idle for seeks, but we do want to allow
903 * fair distribution of slice time for a process doing back-to-back
904 * seeks. so allow a little bit of time for him to submit a new rq
906 sl
= cfqd
->cfq_slice_idle
;
907 if (sample_valid(cic
->seek_samples
) && CIC_SEEKY(cic
))
908 sl
= min(sl
, msecs_to_jiffies(CFQ_MIN_TT
));
910 mod_timer(&cfqd
->idle_slice_timer
, jiffies
+ sl
);
914 * Move request from internal lists to the request queue dispatch list.
916 static void cfq_dispatch_insert(request_queue_t
*q
, struct request
*rq
)
918 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
919 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
921 cfq_remove_request(rq
);
923 elv_dispatch_sort(q
, rq
);
925 if (cfq_cfqq_sync(cfqq
))
930 * return expired entry, or NULL to just start from scratch in rbtree
932 static inline struct request
*cfq_check_fifo(struct cfq_queue
*cfqq
)
934 struct cfq_data
*cfqd
= cfqq
->cfqd
;
938 if (cfq_cfqq_fifo_expire(cfqq
))
941 cfq_mark_cfqq_fifo_expire(cfqq
);
943 if (list_empty(&cfqq
->fifo
))
946 fifo
= cfq_cfqq_sync(cfqq
);
947 rq
= rq_entry_fifo(cfqq
->fifo
.next
);
949 if (time_before(jiffies
, rq
->start_time
+ cfqd
->cfq_fifo_expire
[fifo
]))
956 cfq_prio_to_maxrq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
958 const int base_rq
= cfqd
->cfq_slice_async_rq
;
960 WARN_ON(cfqq
->ioprio
>= IOPRIO_BE_NR
);
962 return 2 * (base_rq
+ base_rq
* (CFQ_PRIO_LISTS
- 1 - cfqq
->ioprio
));
966 * Select a queue for service. If we have a current active queue,
967 * check whether to continue servicing it, or retrieve and set a new one.
969 static struct cfq_queue
*cfq_select_queue(struct cfq_data
*cfqd
)
971 struct cfq_queue
*cfqq
;
973 cfqq
= cfqd
->active_queue
;
978 * The active queue has run out of time, expire it and select new.
980 if (cfq_slice_used(cfqq
))
984 * The active queue has requests and isn't expired, allow it to
987 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
))
991 * No requests pending. If the active queue still has requests in
992 * flight or is idling for a new request, allow either of these
993 * conditions to happen (or time out) before selecting a new queue.
995 if (timer_pending(&cfqd
->idle_slice_timer
) ||
996 (cfqq
->dispatched
&& cfq_cfqq_idle_window(cfqq
))) {
1002 cfq_slice_expired(cfqd
, 0);
1004 cfqq
= cfq_set_active_queue(cfqd
);
1010 * Dispatch some requests from cfqq, moving them to the request queue
1014 __cfq_dispatch_requests(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1019 BUG_ON(RB_EMPTY_ROOT(&cfqq
->sort_list
));
1025 * follow expired path, else get first next available
1027 if ((rq
= cfq_check_fifo(cfqq
)) == NULL
)
1031 * finally, insert request into driver dispatch list
1033 cfq_dispatch_insert(cfqd
->queue
, rq
);
1037 if (!cfqd
->active_cic
) {
1038 atomic_inc(&RQ_CIC(rq
)->ioc
->refcount
);
1039 cfqd
->active_cic
= RQ_CIC(rq
);
1042 if (RB_EMPTY_ROOT(&cfqq
->sort_list
))
1045 } while (dispatched
< max_dispatch
);
1048 * expire an async queue immediately if it has used up its slice. idle
1049 * queue always expire after 1 dispatch round.
1051 if (cfqd
->busy_queues
> 1 && ((!cfq_cfqq_sync(cfqq
) &&
1052 dispatched
>= cfq_prio_to_maxrq(cfqd
, cfqq
)) ||
1053 cfq_class_idle(cfqq
))) {
1054 cfqq
->slice_end
= jiffies
+ 1;
1055 cfq_slice_expired(cfqd
, 0);
1061 static inline int __cfq_forced_dispatch_cfqq(struct cfq_queue
*cfqq
)
1065 while (cfqq
->next_rq
) {
1066 cfq_dispatch_insert(cfqq
->cfqd
->queue
, cfqq
->next_rq
);
1070 BUG_ON(!list_empty(&cfqq
->fifo
));
1075 * Drain our current requests. Used for barriers and when switching
1076 * io schedulers on-the-fly.
1078 static int cfq_forced_dispatch(struct cfq_data
*cfqd
)
1083 while ((n
= cfq_rb_first(&cfqd
->service_tree
)) != NULL
) {
1084 struct cfq_queue
*cfqq
= rb_entry(n
, struct cfq_queue
, rb_node
);
1086 dispatched
+= __cfq_forced_dispatch_cfqq(cfqq
);
1089 cfq_slice_expired(cfqd
, 0);
1091 BUG_ON(cfqd
->busy_queues
);
1096 static int cfq_dispatch_requests(request_queue_t
*q
, int force
)
1098 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1099 struct cfq_queue
*cfqq
;
1102 if (!cfqd
->busy_queues
)
1105 if (unlikely(force
))
1106 return cfq_forced_dispatch(cfqd
);
1109 while ((cfqq
= cfq_select_queue(cfqd
)) != NULL
) {
1112 max_dispatch
= cfqd
->cfq_quantum
;
1113 if (cfq_class_idle(cfqq
))
1116 if (cfqq
->dispatched
>= max_dispatch
) {
1117 if (cfqd
->busy_queues
> 1)
1119 if (cfqq
->dispatched
>= 4 * max_dispatch
)
1123 if (cfqd
->sync_flight
&& !cfq_cfqq_sync(cfqq
))
1126 cfq_clear_cfqq_must_dispatch(cfqq
);
1127 cfq_clear_cfqq_wait_request(cfqq
);
1128 del_timer(&cfqd
->idle_slice_timer
);
1130 dispatched
+= __cfq_dispatch_requests(cfqd
, cfqq
, max_dispatch
);
1137 * task holds one reference to the queue, dropped when task exits. each rq
1138 * in-flight on this queue also holds a reference, dropped when rq is freed.
1140 * queue lock must be held here.
1142 static void cfq_put_queue(struct cfq_queue
*cfqq
)
1144 struct cfq_data
*cfqd
= cfqq
->cfqd
;
1146 BUG_ON(atomic_read(&cfqq
->ref
) <= 0);
1148 if (!atomic_dec_and_test(&cfqq
->ref
))
1151 BUG_ON(rb_first(&cfqq
->sort_list
));
1152 BUG_ON(cfqq
->allocated
[READ
] + cfqq
->allocated
[WRITE
]);
1153 BUG_ON(cfq_cfqq_on_rr(cfqq
));
1155 if (unlikely(cfqd
->active_queue
== cfqq
)) {
1156 __cfq_slice_expired(cfqd
, cfqq
, 0);
1157 cfq_schedule_dispatch(cfqd
);
1160 kmem_cache_free(cfq_pool
, cfqq
);
1163 static void cfq_free_io_context(struct io_context
*ioc
)
1165 struct cfq_io_context
*__cic
;
1169 ioc
->ioc_data
= NULL
;
1171 while ((n
= rb_first(&ioc
->cic_root
)) != NULL
) {
1172 __cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1173 rb_erase(&__cic
->rb_node
, &ioc
->cic_root
);
1174 kmem_cache_free(cfq_ioc_pool
, __cic
);
1178 elv_ioc_count_mod(ioc_count
, -freed
);
1180 if (ioc_gone
&& !elv_ioc_count_read(ioc_count
))
1184 static void cfq_exit_cfqq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1186 if (unlikely(cfqq
== cfqd
->active_queue
)) {
1187 __cfq_slice_expired(cfqd
, cfqq
, 0);
1188 cfq_schedule_dispatch(cfqd
);
1191 cfq_put_queue(cfqq
);
1194 static void __cfq_exit_single_io_context(struct cfq_data
*cfqd
,
1195 struct cfq_io_context
*cic
)
1197 list_del_init(&cic
->queue_list
);
1201 if (cic
->cfqq
[ASYNC
]) {
1202 cfq_exit_cfqq(cfqd
, cic
->cfqq
[ASYNC
]);
1203 cic
->cfqq
[ASYNC
] = NULL
;
1206 if (cic
->cfqq
[SYNC
]) {
1207 cfq_exit_cfqq(cfqd
, cic
->cfqq
[SYNC
]);
1208 cic
->cfqq
[SYNC
] = NULL
;
1212 static void cfq_exit_single_io_context(struct cfq_io_context
*cic
)
1214 struct cfq_data
*cfqd
= cic
->key
;
1217 request_queue_t
*q
= cfqd
->queue
;
1219 spin_lock_irq(q
->queue_lock
);
1220 __cfq_exit_single_io_context(cfqd
, cic
);
1221 spin_unlock_irq(q
->queue_lock
);
1226 * The process that ioc belongs to has exited, we need to clean up
1227 * and put the internal structures we have that belongs to that process.
1229 static void cfq_exit_io_context(struct io_context
*ioc
)
1231 struct cfq_io_context
*__cic
;
1234 ioc
->ioc_data
= NULL
;
1237 * put the reference this task is holding to the various queues
1239 n
= rb_first(&ioc
->cic_root
);
1241 __cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1243 cfq_exit_single_io_context(__cic
);
1248 static struct cfq_io_context
*
1249 cfq_alloc_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
1251 struct cfq_io_context
*cic
;
1253 cic
= kmem_cache_alloc_node(cfq_ioc_pool
, gfp_mask
| __GFP_ZERO
,
1256 cic
->last_end_request
= jiffies
;
1257 INIT_LIST_HEAD(&cic
->queue_list
);
1258 cic
->dtor
= cfq_free_io_context
;
1259 cic
->exit
= cfq_exit_io_context
;
1260 elv_ioc_count_inc(ioc_count
);
1266 static void cfq_init_prio_data(struct cfq_queue
*cfqq
)
1268 struct task_struct
*tsk
= current
;
1271 if (!cfq_cfqq_prio_changed(cfqq
))
1274 ioprio_class
= IOPRIO_PRIO_CLASS(tsk
->ioprio
);
1275 switch (ioprio_class
) {
1277 printk(KERN_ERR
"cfq: bad prio %x\n", ioprio_class
);
1278 case IOPRIO_CLASS_NONE
:
1280 * no prio set, place us in the middle of the BE classes
1282 cfqq
->ioprio
= task_nice_ioprio(tsk
);
1283 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1285 case IOPRIO_CLASS_RT
:
1286 cfqq
->ioprio
= task_ioprio(tsk
);
1287 cfqq
->ioprio_class
= IOPRIO_CLASS_RT
;
1289 case IOPRIO_CLASS_BE
:
1290 cfqq
->ioprio
= task_ioprio(tsk
);
1291 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1293 case IOPRIO_CLASS_IDLE
:
1294 cfqq
->ioprio_class
= IOPRIO_CLASS_IDLE
;
1296 cfq_clear_cfqq_idle_window(cfqq
);
1301 * keep track of original prio settings in case we have to temporarily
1302 * elevate the priority of this queue
1304 cfqq
->org_ioprio
= cfqq
->ioprio
;
1305 cfqq
->org_ioprio_class
= cfqq
->ioprio_class
;
1306 cfq_clear_cfqq_prio_changed(cfqq
);
1309 static inline void changed_ioprio(struct cfq_io_context
*cic
)
1311 struct cfq_data
*cfqd
= cic
->key
;
1312 struct cfq_queue
*cfqq
;
1313 unsigned long flags
;
1315 if (unlikely(!cfqd
))
1318 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
1320 cfqq
= cic
->cfqq
[ASYNC
];
1322 struct cfq_queue
*new_cfqq
;
1323 new_cfqq
= cfq_get_queue(cfqd
, ASYNC
, cic
->ioc
->task
,
1326 cic
->cfqq
[ASYNC
] = new_cfqq
;
1327 cfq_put_queue(cfqq
);
1331 cfqq
= cic
->cfqq
[SYNC
];
1333 cfq_mark_cfqq_prio_changed(cfqq
);
1335 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
1338 static void cfq_ioc_set_ioprio(struct io_context
*ioc
)
1340 struct cfq_io_context
*cic
;
1343 ioc
->ioprio_changed
= 0;
1345 n
= rb_first(&ioc
->cic_root
);
1347 cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1349 changed_ioprio(cic
);
1354 static struct cfq_queue
*
1355 cfq_find_alloc_queue(struct cfq_data
*cfqd
, int is_sync
,
1356 struct task_struct
*tsk
, gfp_t gfp_mask
)
1358 struct cfq_queue
*cfqq
, *new_cfqq
= NULL
;
1359 struct cfq_io_context
*cic
;
1362 cic
= cfq_cic_rb_lookup(cfqd
, tsk
->io_context
);
1363 /* cic always exists here */
1364 cfqq
= cic_to_cfqq(cic
, is_sync
);
1370 } else if (gfp_mask
& __GFP_WAIT
) {
1372 * Inform the allocator of the fact that we will
1373 * just repeat this allocation if it fails, to allow
1374 * the allocator to do whatever it needs to attempt to
1377 spin_unlock_irq(cfqd
->queue
->queue_lock
);
1378 new_cfqq
= kmem_cache_alloc_node(cfq_pool
,
1379 gfp_mask
| __GFP_NOFAIL
| __GFP_ZERO
,
1381 spin_lock_irq(cfqd
->queue
->queue_lock
);
1384 cfqq
= kmem_cache_alloc_node(cfq_pool
,
1385 gfp_mask
| __GFP_ZERO
,
1391 RB_CLEAR_NODE(&cfqq
->rb_node
);
1392 INIT_LIST_HEAD(&cfqq
->fifo
);
1394 atomic_set(&cfqq
->ref
, 0);
1398 cfq_mark_cfqq_idle_window(cfqq
);
1399 cfq_mark_cfqq_sync(cfqq
);
1402 cfq_mark_cfqq_prio_changed(cfqq
);
1403 cfq_mark_cfqq_queue_new(cfqq
);
1405 cfq_init_prio_data(cfqq
);
1409 kmem_cache_free(cfq_pool
, new_cfqq
);
1412 WARN_ON((gfp_mask
& __GFP_WAIT
) && !cfqq
);
1416 static struct cfq_queue
**
1417 cfq_async_queue_prio(struct cfq_data
*cfqd
, int ioprio_class
, int ioprio
)
1419 switch(ioprio_class
) {
1420 case IOPRIO_CLASS_RT
:
1421 return &cfqd
->async_cfqq
[0][ioprio
];
1422 case IOPRIO_CLASS_BE
:
1423 return &cfqd
->async_cfqq
[1][ioprio
];
1424 case IOPRIO_CLASS_IDLE
:
1425 return &cfqd
->async_idle_cfqq
;
1431 static struct cfq_queue
*
1432 cfq_get_queue(struct cfq_data
*cfqd
, int is_sync
, struct task_struct
*tsk
,
1435 const int ioprio
= task_ioprio(tsk
);
1436 const int ioprio_class
= task_ioprio_class(tsk
);
1437 struct cfq_queue
**async_cfqq
= NULL
;
1438 struct cfq_queue
*cfqq
= NULL
;
1441 async_cfqq
= cfq_async_queue_prio(cfqd
, ioprio_class
, ioprio
);
1446 cfqq
= cfq_find_alloc_queue(cfqd
, is_sync
, tsk
, gfp_mask
);
1449 * pin the queue now that it's allocated, scheduler exit will prune it
1451 if (!is_sync
&& !(*async_cfqq
)) {
1452 atomic_inc(&cfqq
->ref
);
1456 atomic_inc(&cfqq
->ref
);
1461 * We drop cfq io contexts lazily, so we may find a dead one.
1464 cfq_drop_dead_cic(struct io_context
*ioc
, struct cfq_io_context
*cic
)
1466 WARN_ON(!list_empty(&cic
->queue_list
));
1468 if (ioc
->ioc_data
== cic
)
1469 ioc
->ioc_data
= NULL
;
1471 rb_erase(&cic
->rb_node
, &ioc
->cic_root
);
1472 kmem_cache_free(cfq_ioc_pool
, cic
);
1473 elv_ioc_count_dec(ioc_count
);
1476 static struct cfq_io_context
*
1477 cfq_cic_rb_lookup(struct cfq_data
*cfqd
, struct io_context
*ioc
)
1480 struct cfq_io_context
*cic
;
1481 void *k
, *key
= cfqd
;
1487 * we maintain a last-hit cache, to avoid browsing over the tree
1489 cic
= ioc
->ioc_data
;
1490 if (cic
&& cic
->key
== cfqd
)
1494 n
= ioc
->cic_root
.rb_node
;
1496 cic
= rb_entry(n
, struct cfq_io_context
, rb_node
);
1497 /* ->key must be copied to avoid race with cfq_exit_queue() */
1500 cfq_drop_dead_cic(ioc
, cic
);
1509 ioc
->ioc_data
= cic
;
1518 cfq_cic_link(struct cfq_data
*cfqd
, struct io_context
*ioc
,
1519 struct cfq_io_context
*cic
)
1522 struct rb_node
*parent
;
1523 struct cfq_io_context
*__cic
;
1524 unsigned long flags
;
1532 p
= &ioc
->cic_root
.rb_node
;
1535 __cic
= rb_entry(parent
, struct cfq_io_context
, rb_node
);
1536 /* ->key must be copied to avoid race with cfq_exit_queue() */
1539 cfq_drop_dead_cic(ioc
, __cic
);
1545 else if (cic
->key
> k
)
1546 p
= &(*p
)->rb_right
;
1551 rb_link_node(&cic
->rb_node
, parent
, p
);
1552 rb_insert_color(&cic
->rb_node
, &ioc
->cic_root
);
1554 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
1555 list_add(&cic
->queue_list
, &cfqd
->cic_list
);
1556 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
1560 * Setup general io context and cfq io context. There can be several cfq
1561 * io contexts per general io context, if this process is doing io to more
1562 * than one device managed by cfq.
1564 static struct cfq_io_context
*
1565 cfq_get_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
1567 struct io_context
*ioc
= NULL
;
1568 struct cfq_io_context
*cic
;
1570 might_sleep_if(gfp_mask
& __GFP_WAIT
);
1572 ioc
= get_io_context(gfp_mask
, cfqd
->queue
->node
);
1576 cic
= cfq_cic_rb_lookup(cfqd
, ioc
);
1580 cic
= cfq_alloc_io_context(cfqd
, gfp_mask
);
1584 cfq_cic_link(cfqd
, ioc
, cic
);
1586 smp_read_barrier_depends();
1587 if (unlikely(ioc
->ioprio_changed
))
1588 cfq_ioc_set_ioprio(ioc
);
1592 put_io_context(ioc
);
1597 cfq_update_io_thinktime(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
)
1599 unsigned long elapsed
= jiffies
- cic
->last_end_request
;
1600 unsigned long ttime
= min(elapsed
, 2UL * cfqd
->cfq_slice_idle
);
1602 cic
->ttime_samples
= (7*cic
->ttime_samples
+ 256) / 8;
1603 cic
->ttime_total
= (7*cic
->ttime_total
+ 256*ttime
) / 8;
1604 cic
->ttime_mean
= (cic
->ttime_total
+ 128) / cic
->ttime_samples
;
1608 cfq_update_io_seektime(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
,
1614 if (cic
->last_request_pos
< rq
->sector
)
1615 sdist
= rq
->sector
- cic
->last_request_pos
;
1617 sdist
= cic
->last_request_pos
- rq
->sector
;
1620 * Don't allow the seek distance to get too large from the
1621 * odd fragment, pagein, etc
1623 if (cic
->seek_samples
<= 60) /* second&third seek */
1624 sdist
= min(sdist
, (cic
->seek_mean
* 4) + 2*1024*1024);
1626 sdist
= min(sdist
, (cic
->seek_mean
* 4) + 2*1024*64);
1628 cic
->seek_samples
= (7*cic
->seek_samples
+ 256) / 8;
1629 cic
->seek_total
= (7*cic
->seek_total
+ (u64
)256*sdist
) / 8;
1630 total
= cic
->seek_total
+ (cic
->seek_samples
/2);
1631 do_div(total
, cic
->seek_samples
);
1632 cic
->seek_mean
= (sector_t
)total
;
1636 * Disable idle window if the process thinks too long or seeks so much that
1640 cfq_update_idle_window(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1641 struct cfq_io_context
*cic
)
1645 if (!cfq_cfqq_sync(cfqq
))
1648 enable_idle
= cfq_cfqq_idle_window(cfqq
);
1650 if (!cic
->ioc
->task
|| !cfqd
->cfq_slice_idle
||
1651 (cfqd
->hw_tag
&& CIC_SEEKY(cic
)))
1653 else if (sample_valid(cic
->ttime_samples
)) {
1654 if (cic
->ttime_mean
> cfqd
->cfq_slice_idle
)
1661 cfq_mark_cfqq_idle_window(cfqq
);
1663 cfq_clear_cfqq_idle_window(cfqq
);
1667 * Check if new_cfqq should preempt the currently active queue. Return 0 for
1668 * no or if we aren't sure, a 1 will cause a preempt.
1671 cfq_should_preempt(struct cfq_data
*cfqd
, struct cfq_queue
*new_cfqq
,
1674 struct cfq_queue
*cfqq
;
1676 cfqq
= cfqd
->active_queue
;
1680 if (cfq_slice_used(cfqq
))
1683 if (cfq_class_idle(new_cfqq
))
1686 if (cfq_class_idle(cfqq
))
1690 * if the new request is sync, but the currently running queue is
1691 * not, let the sync request have priority.
1693 if (rq_is_sync(rq
) && !cfq_cfqq_sync(cfqq
))
1697 * So both queues are sync. Let the new request get disk time if
1698 * it's a metadata request and the current queue is doing regular IO.
1700 if (rq_is_meta(rq
) && !cfqq
->meta_pending
)
1703 if (!cfqd
->active_cic
|| !cfq_cfqq_wait_request(cfqq
))
1707 * if this request is as-good as one we would expect from the
1708 * current cfqq, let it preempt
1710 if (cfq_rq_close(cfqd
, rq
))
1717 * cfqq preempts the active queue. if we allowed preempt with no slice left,
1718 * let it have half of its nominal slice.
1720 static void cfq_preempt_queue(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1722 cfq_slice_expired(cfqd
, 1);
1725 * Put the new queue at the front of the of the current list,
1726 * so we know that it will be selected next.
1728 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
1730 cfq_service_tree_add(cfqd
, cfqq
, 1);
1732 cfqq
->slice_end
= 0;
1733 cfq_mark_cfqq_slice_new(cfqq
);
1737 * Called when a new fs request (rq) is added (to cfqq). Check if there's
1738 * something we should do about it
1741 cfq_rq_enqueued(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1744 struct cfq_io_context
*cic
= RQ_CIC(rq
);
1747 cfqq
->meta_pending
++;
1749 cfq_update_io_thinktime(cfqd
, cic
);
1750 cfq_update_io_seektime(cfqd
, cic
, rq
);
1751 cfq_update_idle_window(cfqd
, cfqq
, cic
);
1753 cic
->last_request_pos
= rq
->sector
+ rq
->nr_sectors
;
1755 if (cfqq
== cfqd
->active_queue
) {
1757 * if we are waiting for a request for this queue, let it rip
1758 * immediately and flag that we must not expire this queue
1761 if (cfq_cfqq_wait_request(cfqq
)) {
1762 cfq_mark_cfqq_must_dispatch(cfqq
);
1763 del_timer(&cfqd
->idle_slice_timer
);
1764 blk_start_queueing(cfqd
->queue
);
1766 } else if (cfq_should_preempt(cfqd
, cfqq
, rq
)) {
1768 * not the active queue - expire current slice if it is
1769 * idle and has expired it's mean thinktime or this new queue
1770 * has some old slice time left and is of higher priority
1772 cfq_preempt_queue(cfqd
, cfqq
);
1773 cfq_mark_cfqq_must_dispatch(cfqq
);
1774 blk_start_queueing(cfqd
->queue
);
1778 static void cfq_insert_request(request_queue_t
*q
, struct request
*rq
)
1780 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1781 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1783 cfq_init_prio_data(cfqq
);
1787 list_add_tail(&rq
->queuelist
, &cfqq
->fifo
);
1789 cfq_rq_enqueued(cfqd
, cfqq
, rq
);
1792 static void cfq_completed_request(request_queue_t
*q
, struct request
*rq
)
1794 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1795 struct cfq_data
*cfqd
= cfqq
->cfqd
;
1796 const int sync
= rq_is_sync(rq
);
1801 WARN_ON(!cfqd
->rq_in_driver
);
1802 WARN_ON(!cfqq
->dispatched
);
1803 cfqd
->rq_in_driver
--;
1806 if (cfq_cfqq_sync(cfqq
))
1807 cfqd
->sync_flight
--;
1809 if (!cfq_class_idle(cfqq
))
1810 cfqd
->last_end_request
= now
;
1813 RQ_CIC(rq
)->last_end_request
= now
;
1816 * If this is the active queue, check if it needs to be expired,
1817 * or if we want to idle in case it has no pending requests.
1819 if (cfqd
->active_queue
== cfqq
) {
1820 if (cfq_cfqq_slice_new(cfqq
)) {
1821 cfq_set_prio_slice(cfqd
, cfqq
);
1822 cfq_clear_cfqq_slice_new(cfqq
);
1824 if (cfq_slice_used(cfqq
))
1825 cfq_slice_expired(cfqd
, 1);
1826 else if (sync
&& RB_EMPTY_ROOT(&cfqq
->sort_list
))
1827 cfq_arm_slice_timer(cfqd
);
1830 if (!cfqd
->rq_in_driver
)
1831 cfq_schedule_dispatch(cfqd
);
1835 * we temporarily boost lower priority queues if they are holding fs exclusive
1836 * resources. they are boosted to normal prio (CLASS_BE/4)
1838 static void cfq_prio_boost(struct cfq_queue
*cfqq
)
1840 if (has_fs_excl()) {
1842 * boost idle prio on transactions that would lock out other
1843 * users of the filesystem
1845 if (cfq_class_idle(cfqq
))
1846 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1847 if (cfqq
->ioprio
> IOPRIO_NORM
)
1848 cfqq
->ioprio
= IOPRIO_NORM
;
1851 * check if we need to unboost the queue
1853 if (cfqq
->ioprio_class
!= cfqq
->org_ioprio_class
)
1854 cfqq
->ioprio_class
= cfqq
->org_ioprio_class
;
1855 if (cfqq
->ioprio
!= cfqq
->org_ioprio
)
1856 cfqq
->ioprio
= cfqq
->org_ioprio
;
1860 static inline int __cfq_may_queue(struct cfq_queue
*cfqq
)
1862 if ((cfq_cfqq_wait_request(cfqq
) || cfq_cfqq_must_alloc(cfqq
)) &&
1863 !cfq_cfqq_must_alloc_slice(cfqq
)) {
1864 cfq_mark_cfqq_must_alloc_slice(cfqq
);
1865 return ELV_MQUEUE_MUST
;
1868 return ELV_MQUEUE_MAY
;
1871 static int cfq_may_queue(request_queue_t
*q
, int rw
)
1873 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1874 struct task_struct
*tsk
= current
;
1875 struct cfq_io_context
*cic
;
1876 struct cfq_queue
*cfqq
;
1879 * don't force setup of a queue from here, as a call to may_queue
1880 * does not necessarily imply that a request actually will be queued.
1881 * so just lookup a possibly existing queue, or return 'may queue'
1884 cic
= cfq_cic_rb_lookup(cfqd
, tsk
->io_context
);
1886 return ELV_MQUEUE_MAY
;
1888 cfqq
= cic_to_cfqq(cic
, rw
& REQ_RW_SYNC
);
1890 cfq_init_prio_data(cfqq
);
1891 cfq_prio_boost(cfqq
);
1893 return __cfq_may_queue(cfqq
);
1896 return ELV_MQUEUE_MAY
;
1900 * queue lock held here
1902 static void cfq_put_request(struct request
*rq
)
1904 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1907 const int rw
= rq_data_dir(rq
);
1909 BUG_ON(!cfqq
->allocated
[rw
]);
1910 cfqq
->allocated
[rw
]--;
1912 put_io_context(RQ_CIC(rq
)->ioc
);
1914 rq
->elevator_private
= NULL
;
1915 rq
->elevator_private2
= NULL
;
1917 cfq_put_queue(cfqq
);
1922 * Allocate cfq data structures associated with this request.
1925 cfq_set_request(request_queue_t
*q
, struct request
*rq
, gfp_t gfp_mask
)
1927 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1928 struct task_struct
*tsk
= current
;
1929 struct cfq_io_context
*cic
;
1930 const int rw
= rq_data_dir(rq
);
1931 const int is_sync
= rq_is_sync(rq
);
1932 struct cfq_queue
*cfqq
;
1933 unsigned long flags
;
1935 might_sleep_if(gfp_mask
& __GFP_WAIT
);
1937 cic
= cfq_get_io_context(cfqd
, gfp_mask
);
1939 spin_lock_irqsave(q
->queue_lock
, flags
);
1944 cfqq
= cic_to_cfqq(cic
, is_sync
);
1946 cfqq
= cfq_get_queue(cfqd
, is_sync
, tsk
, gfp_mask
);
1951 cic_set_cfqq(cic
, cfqq
, is_sync
);
1954 cfqq
->allocated
[rw
]++;
1955 cfq_clear_cfqq_must_alloc(cfqq
);
1956 atomic_inc(&cfqq
->ref
);
1958 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1960 rq
->elevator_private
= cic
;
1961 rq
->elevator_private2
= cfqq
;
1966 put_io_context(cic
->ioc
);
1968 cfq_schedule_dispatch(cfqd
);
1969 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1973 static void cfq_kick_queue(struct work_struct
*work
)
1975 struct cfq_data
*cfqd
=
1976 container_of(work
, struct cfq_data
, unplug_work
);
1977 request_queue_t
*q
= cfqd
->queue
;
1978 unsigned long flags
;
1980 spin_lock_irqsave(q
->queue_lock
, flags
);
1981 blk_start_queueing(q
);
1982 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1986 * Timer running if the active_queue is currently idling inside its time slice
1988 static void cfq_idle_slice_timer(unsigned long data
)
1990 struct cfq_data
*cfqd
= (struct cfq_data
*) data
;
1991 struct cfq_queue
*cfqq
;
1992 unsigned long flags
;
1995 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
1997 if ((cfqq
= cfqd
->active_queue
) != NULL
) {
2003 if (cfq_slice_used(cfqq
))
2007 * only expire and reinvoke request handler, if there are
2008 * other queues with pending requests
2010 if (!cfqd
->busy_queues
)
2014 * not expired and it has a request pending, let it dispatch
2016 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
)) {
2017 cfq_mark_cfqq_must_dispatch(cfqq
);
2022 cfq_slice_expired(cfqd
, timed_out
);
2024 cfq_schedule_dispatch(cfqd
);
2026 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2030 * Timer running if an idle class queue is waiting for service
2032 static void cfq_idle_class_timer(unsigned long data
)
2034 struct cfq_data
*cfqd
= (struct cfq_data
*) data
;
2035 unsigned long flags
, end
;
2037 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
2040 * race with a non-idle queue, reset timer
2042 end
= cfqd
->last_end_request
+ CFQ_IDLE_GRACE
;
2043 if (!time_after_eq(jiffies
, end
))
2044 mod_timer(&cfqd
->idle_class_timer
, end
);
2046 cfq_schedule_dispatch(cfqd
);
2048 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2051 static void cfq_shutdown_timer_wq(struct cfq_data
*cfqd
)
2053 del_timer_sync(&cfqd
->idle_slice_timer
);
2054 del_timer_sync(&cfqd
->idle_class_timer
);
2055 blk_sync_queue(cfqd
->queue
);
2058 static void cfq_put_async_queues(struct cfq_data
*cfqd
)
2062 for (i
= 0; i
< IOPRIO_BE_NR
; i
++) {
2063 if (cfqd
->async_cfqq
[0][i
])
2064 cfq_put_queue(cfqd
->async_cfqq
[0][i
]);
2065 if (cfqd
->async_cfqq
[1][i
])
2066 cfq_put_queue(cfqd
->async_cfqq
[1][i
]);
2067 if (cfqd
->async_idle_cfqq
)
2068 cfq_put_queue(cfqd
->async_idle_cfqq
);
2072 static void cfq_exit_queue(elevator_t
*e
)
2074 struct cfq_data
*cfqd
= e
->elevator_data
;
2075 request_queue_t
*q
= cfqd
->queue
;
2077 cfq_shutdown_timer_wq(cfqd
);
2079 spin_lock_irq(q
->queue_lock
);
2081 if (cfqd
->active_queue
)
2082 __cfq_slice_expired(cfqd
, cfqd
->active_queue
, 0);
2084 while (!list_empty(&cfqd
->cic_list
)) {
2085 struct cfq_io_context
*cic
= list_entry(cfqd
->cic_list
.next
,
2086 struct cfq_io_context
,
2089 __cfq_exit_single_io_context(cfqd
, cic
);
2092 cfq_put_async_queues(cfqd
);
2094 spin_unlock_irq(q
->queue_lock
);
2096 cfq_shutdown_timer_wq(cfqd
);
2101 static void *cfq_init_queue(request_queue_t
*q
)
2103 struct cfq_data
*cfqd
;
2105 cfqd
= kmalloc_node(sizeof(*cfqd
), GFP_KERNEL
| __GFP_ZERO
, q
->node
);
2109 cfqd
->service_tree
= CFQ_RB_ROOT
;
2110 INIT_LIST_HEAD(&cfqd
->cic_list
);
2114 init_timer(&cfqd
->idle_slice_timer
);
2115 cfqd
->idle_slice_timer
.function
= cfq_idle_slice_timer
;
2116 cfqd
->idle_slice_timer
.data
= (unsigned long) cfqd
;
2118 init_timer(&cfqd
->idle_class_timer
);
2119 cfqd
->idle_class_timer
.function
= cfq_idle_class_timer
;
2120 cfqd
->idle_class_timer
.data
= (unsigned long) cfqd
;
2122 INIT_WORK(&cfqd
->unplug_work
, cfq_kick_queue
);
2124 cfqd
->cfq_quantum
= cfq_quantum
;
2125 cfqd
->cfq_fifo_expire
[0] = cfq_fifo_expire
[0];
2126 cfqd
->cfq_fifo_expire
[1] = cfq_fifo_expire
[1];
2127 cfqd
->cfq_back_max
= cfq_back_max
;
2128 cfqd
->cfq_back_penalty
= cfq_back_penalty
;
2129 cfqd
->cfq_slice
[0] = cfq_slice_async
;
2130 cfqd
->cfq_slice
[1] = cfq_slice_sync
;
2131 cfqd
->cfq_slice_async_rq
= cfq_slice_async_rq
;
2132 cfqd
->cfq_slice_idle
= cfq_slice_idle
;
2137 static void cfq_slab_kill(void)
2140 kmem_cache_destroy(cfq_pool
);
2142 kmem_cache_destroy(cfq_ioc_pool
);
2145 static int __init
cfq_slab_setup(void)
2147 cfq_pool
= KMEM_CACHE(cfq_queue
, 0);
2151 cfq_ioc_pool
= KMEM_CACHE(cfq_io_context
, 0);
2162 * sysfs parts below -->
2165 cfq_var_show(unsigned int var
, char *page
)
2167 return sprintf(page
, "%d\n", var
);
2171 cfq_var_store(unsigned int *var
, const char *page
, size_t count
)
2173 char *p
= (char *) page
;
2175 *var
= simple_strtoul(p
, &p
, 10);
2179 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
2180 static ssize_t __FUNC(elevator_t *e, char *page) \
2182 struct cfq_data *cfqd = e->elevator_data; \
2183 unsigned int __data = __VAR; \
2185 __data = jiffies_to_msecs(__data); \
2186 return cfq_var_show(__data, (page)); \
2188 SHOW_FUNCTION(cfq_quantum_show
, cfqd
->cfq_quantum
, 0);
2189 SHOW_FUNCTION(cfq_fifo_expire_sync_show
, cfqd
->cfq_fifo_expire
[1], 1);
2190 SHOW_FUNCTION(cfq_fifo_expire_async_show
, cfqd
->cfq_fifo_expire
[0], 1);
2191 SHOW_FUNCTION(cfq_back_seek_max_show
, cfqd
->cfq_back_max
, 0);
2192 SHOW_FUNCTION(cfq_back_seek_penalty_show
, cfqd
->cfq_back_penalty
, 0);
2193 SHOW_FUNCTION(cfq_slice_idle_show
, cfqd
->cfq_slice_idle
, 1);
2194 SHOW_FUNCTION(cfq_slice_sync_show
, cfqd
->cfq_slice
[1], 1);
2195 SHOW_FUNCTION(cfq_slice_async_show
, cfqd
->cfq_slice
[0], 1);
2196 SHOW_FUNCTION(cfq_slice_async_rq_show
, cfqd
->cfq_slice_async_rq
, 0);
2197 #undef SHOW_FUNCTION
2199 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
2200 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
2202 struct cfq_data *cfqd = e->elevator_data; \
2203 unsigned int __data; \
2204 int ret = cfq_var_store(&__data, (page), count); \
2205 if (__data < (MIN)) \
2207 else if (__data > (MAX)) \
2210 *(__PTR) = msecs_to_jiffies(__data); \
2212 *(__PTR) = __data; \
2215 STORE_FUNCTION(cfq_quantum_store
, &cfqd
->cfq_quantum
, 1, UINT_MAX
, 0);
2216 STORE_FUNCTION(cfq_fifo_expire_sync_store
, &cfqd
->cfq_fifo_expire
[1], 1, UINT_MAX
, 1);
2217 STORE_FUNCTION(cfq_fifo_expire_async_store
, &cfqd
->cfq_fifo_expire
[0], 1, UINT_MAX
, 1);
2218 STORE_FUNCTION(cfq_back_seek_max_store
, &cfqd
->cfq_back_max
, 0, UINT_MAX
, 0);
2219 STORE_FUNCTION(cfq_back_seek_penalty_store
, &cfqd
->cfq_back_penalty
, 1, UINT_MAX
, 0);
2220 STORE_FUNCTION(cfq_slice_idle_store
, &cfqd
->cfq_slice_idle
, 0, UINT_MAX
, 1);
2221 STORE_FUNCTION(cfq_slice_sync_store
, &cfqd
->cfq_slice
[1], 1, UINT_MAX
, 1);
2222 STORE_FUNCTION(cfq_slice_async_store
, &cfqd
->cfq_slice
[0], 1, UINT_MAX
, 1);
2223 STORE_FUNCTION(cfq_slice_async_rq_store
, &cfqd
->cfq_slice_async_rq
, 1, UINT_MAX
, 0);
2224 #undef STORE_FUNCTION
2226 #define CFQ_ATTR(name) \
2227 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2229 static struct elv_fs_entry cfq_attrs
[] = {
2231 CFQ_ATTR(fifo_expire_sync
),
2232 CFQ_ATTR(fifo_expire_async
),
2233 CFQ_ATTR(back_seek_max
),
2234 CFQ_ATTR(back_seek_penalty
),
2235 CFQ_ATTR(slice_sync
),
2236 CFQ_ATTR(slice_async
),
2237 CFQ_ATTR(slice_async_rq
),
2238 CFQ_ATTR(slice_idle
),
2242 static struct elevator_type iosched_cfq
= {
2244 .elevator_merge_fn
= cfq_merge
,
2245 .elevator_merged_fn
= cfq_merged_request
,
2246 .elevator_merge_req_fn
= cfq_merged_requests
,
2247 .elevator_allow_merge_fn
= cfq_allow_merge
,
2248 .elevator_dispatch_fn
= cfq_dispatch_requests
,
2249 .elevator_add_req_fn
= cfq_insert_request
,
2250 .elevator_activate_req_fn
= cfq_activate_request
,
2251 .elevator_deactivate_req_fn
= cfq_deactivate_request
,
2252 .elevator_queue_empty_fn
= cfq_queue_empty
,
2253 .elevator_completed_req_fn
= cfq_completed_request
,
2254 .elevator_former_req_fn
= elv_rb_former_request
,
2255 .elevator_latter_req_fn
= elv_rb_latter_request
,
2256 .elevator_set_req_fn
= cfq_set_request
,
2257 .elevator_put_req_fn
= cfq_put_request
,
2258 .elevator_may_queue_fn
= cfq_may_queue
,
2259 .elevator_init_fn
= cfq_init_queue
,
2260 .elevator_exit_fn
= cfq_exit_queue
,
2261 .trim
= cfq_free_io_context
,
2263 .elevator_attrs
= cfq_attrs
,
2264 .elevator_name
= "cfq",
2265 .elevator_owner
= THIS_MODULE
,
2268 static int __init
cfq_init(void)
2273 * could be 0 on HZ < 1000 setups
2275 if (!cfq_slice_async
)
2276 cfq_slice_async
= 1;
2277 if (!cfq_slice_idle
)
2280 if (cfq_slab_setup())
2283 ret
= elv_register(&iosched_cfq
);
2290 static void __exit
cfq_exit(void)
2292 DECLARE_COMPLETION_ONSTACK(all_gone
);
2293 elv_unregister(&iosched_cfq
);
2294 ioc_gone
= &all_gone
;
2295 /* ioc_gone's update must be visible before reading ioc_count */
2297 if (elv_ioc_count_read(ioc_count
))
2298 wait_for_completion(ioc_gone
);
2303 module_init(cfq_init
);
2304 module_exit(cfq_exit
);
2306 MODULE_AUTHOR("Jens Axboe");
2307 MODULE_LICENSE("GPL");
2308 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");