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/jiffies.h>
13 #include <linux/rbtree.h>
14 #include <linux/ioprio.h>
15 #include <linux/blktrace_api.h>
20 /* max queue in one round of service */
21 static const int cfq_quantum
= 4;
22 static const int cfq_fifo_expire
[2] = { HZ
/ 4, HZ
/ 8 };
23 /* maximum backwards seek, in KiB */
24 static const int cfq_back_max
= 16 * 1024;
25 /* penalty of a backwards seek */
26 static const int cfq_back_penalty
= 2;
27 static const int cfq_slice_sync
= HZ
/ 10;
28 static int cfq_slice_async
= HZ
/ 25;
29 static const int cfq_slice_async_rq
= 2;
30 static int cfq_slice_idle
= HZ
/ 125;
31 static const int cfq_target_latency
= HZ
* 3/10; /* 300 ms */
32 static const int cfq_hist_divisor
= 4;
35 * offset from end of service tree
37 #define CFQ_IDLE_DELAY (HZ / 5)
40 * below this threshold, we consider thinktime immediate
42 #define CFQ_MIN_TT (2)
45 * Allow merged cfqqs to perform this amount of seeky I/O before
46 * deciding to break the queues up again.
48 #define CFQQ_COOP_TOUT (HZ)
50 #define CFQ_SLICE_SCALE (5)
51 #define CFQ_HW_QUEUE_MIN (5)
54 ((struct cfq_io_context *) (rq)->elevator_private)
55 #define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2)
57 static struct kmem_cache
*cfq_pool
;
58 static struct kmem_cache
*cfq_ioc_pool
;
60 static DEFINE_PER_CPU(unsigned long, cfq_ioc_count
);
61 static struct completion
*ioc_gone
;
62 static DEFINE_SPINLOCK(ioc_gone_lock
);
64 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
65 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
66 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
68 #define sample_valid(samples) ((samples) > 80)
71 * Most of our rbtree usage is for sorting with min extraction, so
72 * if we cache the leftmost node we don't have to walk down the tree
73 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
74 * move this into the elevator for the rq sorting as well.
81 #define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, 0, }
84 * Per process-grouping structure
89 /* various state flags, see below */
92 struct cfq_data
*cfqd
;
93 /* service_tree member */
94 struct rb_node rb_node
;
95 /* service_tree key */
97 /* prio tree member */
98 struct rb_node p_node
;
99 /* prio tree root we belong to, if any */
100 struct rb_root
*p_root
;
101 /* sorted list of pending requests */
102 struct rb_root sort_list
;
103 /* if fifo isn't expired, next request to serve */
104 struct request
*next_rq
;
105 /* requests queued in sort_list */
107 /* currently allocated requests */
109 /* fifo list of requests in sort_list */
110 struct list_head fifo
;
112 unsigned long slice_end
;
114 unsigned int slice_dispatch
;
116 /* pending metadata requests */
118 /* number of requests that are on the dispatch list or inside driver */
121 /* io prio of this group */
122 unsigned short ioprio
, org_ioprio
;
123 unsigned short ioprio_class
, org_ioprio_class
;
125 unsigned int seek_samples
;
128 sector_t last_request_pos
;
129 unsigned long seeky_start
;
133 struct cfq_rb_root
*service_tree
;
134 struct cfq_queue
*new_cfqq
;
138 * First index in the service_trees.
139 * IDLE is handled separately, so it has negative index
148 * Second index in the service_trees.
152 SYNC_NOIDLE_WORKLOAD
= 1,
158 * Per block device queue structure
161 struct request_queue
*queue
;
164 * rr lists of queues with requests, onle rr for each priority class.
165 * Counts are embedded in the cfq_rb_root
167 struct cfq_rb_root service_trees
[2][3];
168 struct cfq_rb_root service_tree_idle
;
170 * The priority currently being served
172 enum wl_prio_t serving_prio
;
173 enum wl_type_t serving_type
;
174 unsigned long workload_expires
;
177 * Each priority tree is sorted by next_request position. These
178 * trees are used when determining if two or more queues are
179 * interleaving requests (see cfq_close_cooperator).
181 struct rb_root prio_trees
[CFQ_PRIO_LISTS
];
183 unsigned int busy_queues
;
184 unsigned int busy_queues_avg
[2];
190 * queue-depth detection
195 int rq_in_driver_peak
;
198 * idle window management
200 struct timer_list idle_slice_timer
;
201 struct work_struct unplug_work
;
203 struct cfq_queue
*active_queue
;
204 struct cfq_io_context
*active_cic
;
207 * async queue for each priority case
209 struct cfq_queue
*async_cfqq
[2][IOPRIO_BE_NR
];
210 struct cfq_queue
*async_idle_cfqq
;
212 sector_t last_position
;
215 * tunables, see top of file
217 unsigned int cfq_quantum
;
218 unsigned int cfq_fifo_expire
[2];
219 unsigned int cfq_back_penalty
;
220 unsigned int cfq_back_max
;
221 unsigned int cfq_slice
[2];
222 unsigned int cfq_slice_async_rq
;
223 unsigned int cfq_slice_idle
;
224 unsigned int cfq_latency
;
226 struct list_head cic_list
;
229 * Fallback dummy cfqq for extreme OOM conditions
231 struct cfq_queue oom_cfqq
;
233 unsigned long last_end_sync_rq
;
236 static struct cfq_rb_root
*service_tree_for(enum wl_prio_t prio
,
238 struct cfq_data
*cfqd
)
240 if (prio
== IDLE_WORKLOAD
)
241 return &cfqd
->service_tree_idle
;
243 return &cfqd
->service_trees
[prio
][type
];
246 enum cfqq_state_flags
{
247 CFQ_CFQQ_FLAG_on_rr
= 0, /* on round-robin busy list */
248 CFQ_CFQQ_FLAG_wait_request
, /* waiting for a request */
249 CFQ_CFQQ_FLAG_must_dispatch
, /* must be allowed a dispatch */
250 CFQ_CFQQ_FLAG_must_alloc_slice
, /* per-slice must_alloc flag */
251 CFQ_CFQQ_FLAG_fifo_expire
, /* FIFO checked in this slice */
252 CFQ_CFQQ_FLAG_idle_window
, /* slice idling enabled */
253 CFQ_CFQQ_FLAG_prio_changed
, /* task priority has changed */
254 CFQ_CFQQ_FLAG_slice_new
, /* no requests dispatched in slice */
255 CFQ_CFQQ_FLAG_sync
, /* synchronous queue */
256 CFQ_CFQQ_FLAG_coop
, /* cfqq is shared */
259 #define CFQ_CFQQ_FNS(name) \
260 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
262 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
264 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
266 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
268 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
270 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
274 CFQ_CFQQ_FNS(wait_request
);
275 CFQ_CFQQ_FNS(must_dispatch
);
276 CFQ_CFQQ_FNS(must_alloc_slice
);
277 CFQ_CFQQ_FNS(fifo_expire
);
278 CFQ_CFQQ_FNS(idle_window
);
279 CFQ_CFQQ_FNS(prio_changed
);
280 CFQ_CFQQ_FNS(slice_new
);
285 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
286 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
287 #define cfq_log(cfqd, fmt, args...) \
288 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
290 static inline enum wl_prio_t
cfqq_prio(struct cfq_queue
*cfqq
)
292 if (cfq_class_idle(cfqq
))
293 return IDLE_WORKLOAD
;
294 if (cfq_class_rt(cfqq
))
300 static enum wl_type_t
cfqq_type(struct cfq_queue
*cfqq
)
302 if (!cfq_cfqq_sync(cfqq
))
303 return ASYNC_WORKLOAD
;
304 if (!cfq_cfqq_idle_window(cfqq
))
305 return SYNC_NOIDLE_WORKLOAD
;
306 return SYNC_WORKLOAD
;
309 static inline int cfq_busy_queues_wl(enum wl_prio_t wl
, struct cfq_data
*cfqd
)
311 if (wl
== IDLE_WORKLOAD
)
312 return cfqd
->service_tree_idle
.count
;
314 return cfqd
->service_trees
[wl
][ASYNC_WORKLOAD
].count
315 + cfqd
->service_trees
[wl
][SYNC_NOIDLE_WORKLOAD
].count
316 + cfqd
->service_trees
[wl
][SYNC_WORKLOAD
].count
;
319 static void cfq_dispatch_insert(struct request_queue
*, struct request
*);
320 static struct cfq_queue
*cfq_get_queue(struct cfq_data
*, bool,
321 struct io_context
*, gfp_t
);
322 static struct cfq_io_context
*cfq_cic_lookup(struct cfq_data
*,
323 struct io_context
*);
325 static inline int rq_in_driver(struct cfq_data
*cfqd
)
327 return cfqd
->rq_in_driver
[0] + cfqd
->rq_in_driver
[1];
330 static inline struct cfq_queue
*cic_to_cfqq(struct cfq_io_context
*cic
,
333 return cic
->cfqq
[is_sync
];
336 static inline void cic_set_cfqq(struct cfq_io_context
*cic
,
337 struct cfq_queue
*cfqq
, bool is_sync
)
339 cic
->cfqq
[is_sync
] = cfqq
;
343 * We regard a request as SYNC, if it's either a read or has the SYNC bit
344 * set (in which case it could also be direct WRITE).
346 static inline bool cfq_bio_sync(struct bio
*bio
)
348 return bio_data_dir(bio
) == READ
|| bio_rw_flagged(bio
, BIO_RW_SYNCIO
);
352 * scheduler run of queue, if there are requests pending and no one in the
353 * driver that will restart queueing
355 static inline void cfq_schedule_dispatch(struct cfq_data
*cfqd
)
357 if (cfqd
->busy_queues
) {
358 cfq_log(cfqd
, "schedule dispatch");
359 kblockd_schedule_work(cfqd
->queue
, &cfqd
->unplug_work
);
363 static int cfq_queue_empty(struct request_queue
*q
)
365 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
367 return !cfqd
->busy_queues
;
371 * Scale schedule slice based on io priority. Use the sync time slice only
372 * if a queue is marked sync and has sync io queued. A sync queue with async
373 * io only, should not get full sync slice length.
375 static inline int cfq_prio_slice(struct cfq_data
*cfqd
, bool sync
,
378 const int base_slice
= cfqd
->cfq_slice
[sync
];
380 WARN_ON(prio
>= IOPRIO_BE_NR
);
382 return base_slice
+ (base_slice
/CFQ_SLICE_SCALE
* (4 - prio
));
386 cfq_prio_to_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
388 return cfq_prio_slice(cfqd
, cfq_cfqq_sync(cfqq
), cfqq
->ioprio
);
392 * get averaged number of queues of RT/BE priority.
393 * average is updated, with a formula that gives more weight to higher numbers,
394 * to quickly follows sudden increases and decrease slowly
397 static inline unsigned cfq_get_avg_queues(struct cfq_data
*cfqd
, bool rt
)
399 unsigned min_q
, max_q
;
400 unsigned mult
= cfq_hist_divisor
- 1;
401 unsigned round
= cfq_hist_divisor
/ 2;
402 unsigned busy
= cfq_busy_queues_wl(rt
, cfqd
);
404 min_q
= min(cfqd
->busy_queues_avg
[rt
], busy
);
405 max_q
= max(cfqd
->busy_queues_avg
[rt
], busy
);
406 cfqd
->busy_queues_avg
[rt
] = (mult
* max_q
+ min_q
+ round
) /
408 return cfqd
->busy_queues_avg
[rt
];
412 cfq_set_prio_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
414 unsigned slice
= cfq_prio_to_slice(cfqd
, cfqq
);
415 if (cfqd
->cfq_latency
) {
416 /* interested queues (we consider only the ones with the same
418 unsigned iq
= cfq_get_avg_queues(cfqd
, cfq_class_rt(cfqq
));
419 unsigned sync_slice
= cfqd
->cfq_slice
[1];
420 unsigned expect_latency
= sync_slice
* iq
;
421 if (expect_latency
> cfq_target_latency
) {
422 unsigned base_low_slice
= 2 * cfqd
->cfq_slice_idle
;
423 /* scale low_slice according to IO priority
424 * and sync vs async */
426 min(slice
, base_low_slice
* slice
/ sync_slice
);
427 /* the adapted slice value is scaled to fit all iqs
428 * into the target latency */
429 slice
= max(slice
* cfq_target_latency
/ expect_latency
,
433 cfqq
->slice_end
= jiffies
+ slice
;
434 cfq_log_cfqq(cfqd
, cfqq
, "set_slice=%lu", cfqq
->slice_end
- jiffies
);
438 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
439 * isn't valid until the first request from the dispatch is activated
440 * and the slice time set.
442 static inline bool cfq_slice_used(struct cfq_queue
*cfqq
)
444 if (cfq_cfqq_slice_new(cfqq
))
446 if (time_before(jiffies
, cfqq
->slice_end
))
453 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
454 * We choose the request that is closest to the head right now. Distance
455 * behind the head is penalized and only allowed to a certain extent.
457 static struct request
*
458 cfq_choose_req(struct cfq_data
*cfqd
, struct request
*rq1
, struct request
*rq2
, sector_t last
)
460 sector_t s1
, s2
, d1
= 0, d2
= 0;
461 unsigned long back_max
;
462 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
463 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
464 unsigned wrap
= 0; /* bit mask: requests behind the disk head? */
466 if (rq1
== NULL
|| rq1
== rq2
)
471 if (rq_is_sync(rq1
) && !rq_is_sync(rq2
))
473 else if (rq_is_sync(rq2
) && !rq_is_sync(rq1
))
475 if (rq_is_meta(rq1
) && !rq_is_meta(rq2
))
477 else if (rq_is_meta(rq2
) && !rq_is_meta(rq1
))
480 s1
= blk_rq_pos(rq1
);
481 s2
= blk_rq_pos(rq2
);
484 * by definition, 1KiB is 2 sectors
486 back_max
= cfqd
->cfq_back_max
* 2;
489 * Strict one way elevator _except_ in the case where we allow
490 * short backward seeks which are biased as twice the cost of a
491 * similar forward seek.
495 else if (s1
+ back_max
>= last
)
496 d1
= (last
- s1
) * cfqd
->cfq_back_penalty
;
498 wrap
|= CFQ_RQ1_WRAP
;
502 else if (s2
+ back_max
>= last
)
503 d2
= (last
- s2
) * cfqd
->cfq_back_penalty
;
505 wrap
|= CFQ_RQ2_WRAP
;
507 /* Found required data */
510 * By doing switch() on the bit mask "wrap" we avoid having to
511 * check two variables for all permutations: --> faster!
514 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
530 case (CFQ_RQ1_WRAP
|CFQ_RQ2_WRAP
): /* both rqs wrapped */
533 * Since both rqs are wrapped,
534 * start with the one that's further behind head
535 * (--> only *one* back seek required),
536 * since back seek takes more time than forward.
546 * The below is leftmost cache rbtree addon
548 static struct cfq_queue
*cfq_rb_first(struct cfq_rb_root
*root
)
551 root
->left
= rb_first(&root
->rb
);
554 return rb_entry(root
->left
, struct cfq_queue
, rb_node
);
559 static void rb_erase_init(struct rb_node
*n
, struct rb_root
*root
)
565 static void cfq_rb_erase(struct rb_node
*n
, struct cfq_rb_root
*root
)
569 rb_erase_init(n
, &root
->rb
);
574 * would be nice to take fifo expire time into account as well
576 static struct request
*
577 cfq_find_next_rq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
578 struct request
*last
)
580 struct rb_node
*rbnext
= rb_next(&last
->rb_node
);
581 struct rb_node
*rbprev
= rb_prev(&last
->rb_node
);
582 struct request
*next
= NULL
, *prev
= NULL
;
584 BUG_ON(RB_EMPTY_NODE(&last
->rb_node
));
587 prev
= rb_entry_rq(rbprev
);
590 next
= rb_entry_rq(rbnext
);
592 rbnext
= rb_first(&cfqq
->sort_list
);
593 if (rbnext
&& rbnext
!= &last
->rb_node
)
594 next
= rb_entry_rq(rbnext
);
597 return cfq_choose_req(cfqd
, next
, prev
, blk_rq_pos(last
));
600 static unsigned long cfq_slice_offset(struct cfq_data
*cfqd
,
601 struct cfq_queue
*cfqq
)
603 struct cfq_rb_root
*service_tree
;
605 service_tree
= service_tree_for(cfqq_prio(cfqq
), cfqq_type(cfqq
), cfqd
);
608 * just an approximation, should be ok.
610 return service_tree
->count
* (cfq_prio_slice(cfqd
, 1, 0) -
611 cfq_prio_slice(cfqd
, cfq_cfqq_sync(cfqq
), cfqq
->ioprio
));
615 * The cfqd->service_trees holds all pending cfq_queue's that have
616 * requests waiting to be processed. It is sorted in the order that
617 * we will service the queues.
619 static void cfq_service_tree_add(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
622 struct rb_node
**p
, *parent
;
623 struct cfq_queue
*__cfqq
;
624 unsigned long rb_key
;
625 struct cfq_rb_root
*service_tree
;
628 service_tree
= service_tree_for(cfqq_prio(cfqq
), cfqq_type(cfqq
), cfqd
);
629 if (cfq_class_idle(cfqq
)) {
630 rb_key
= CFQ_IDLE_DELAY
;
631 parent
= rb_last(&service_tree
->rb
);
632 if (parent
&& parent
!= &cfqq
->rb_node
) {
633 __cfqq
= rb_entry(parent
, struct cfq_queue
, rb_node
);
634 rb_key
+= __cfqq
->rb_key
;
637 } else if (!add_front
) {
639 * Get our rb key offset. Subtract any residual slice
640 * value carried from last service. A negative resid
641 * count indicates slice overrun, and this should position
642 * the next service time further away in the tree.
644 rb_key
= cfq_slice_offset(cfqd
, cfqq
) + jiffies
;
645 rb_key
-= cfqq
->slice_resid
;
646 cfqq
->slice_resid
= 0;
649 __cfqq
= cfq_rb_first(service_tree
);
650 rb_key
+= __cfqq
? __cfqq
->rb_key
: jiffies
;
653 if (!RB_EMPTY_NODE(&cfqq
->rb_node
)) {
655 * same position, nothing more to do
657 if (rb_key
== cfqq
->rb_key
&&
658 cfqq
->service_tree
== service_tree
)
661 cfq_rb_erase(&cfqq
->rb_node
, cfqq
->service_tree
);
662 cfqq
->service_tree
= NULL
;
667 cfqq
->service_tree
= service_tree
;
668 p
= &service_tree
->rb
.rb_node
;
673 __cfqq
= rb_entry(parent
, struct cfq_queue
, rb_node
);
676 * sort by key, that represents service time.
678 if (time_before(rb_key
, __cfqq
->rb_key
))
689 service_tree
->left
= &cfqq
->rb_node
;
691 cfqq
->rb_key
= rb_key
;
692 rb_link_node(&cfqq
->rb_node
, parent
, p
);
693 rb_insert_color(&cfqq
->rb_node
, &service_tree
->rb
);
694 service_tree
->count
++;
697 static struct cfq_queue
*
698 cfq_prio_tree_lookup(struct cfq_data
*cfqd
, struct rb_root
*root
,
699 sector_t sector
, struct rb_node
**ret_parent
,
700 struct rb_node
***rb_link
)
702 struct rb_node
**p
, *parent
;
703 struct cfq_queue
*cfqq
= NULL
;
711 cfqq
= rb_entry(parent
, struct cfq_queue
, p_node
);
714 * Sort strictly based on sector. Smallest to the left,
715 * largest to the right.
717 if (sector
> blk_rq_pos(cfqq
->next_rq
))
719 else if (sector
< blk_rq_pos(cfqq
->next_rq
))
727 *ret_parent
= parent
;
733 static void cfq_prio_tree_add(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
735 struct rb_node
**p
, *parent
;
736 struct cfq_queue
*__cfqq
;
739 rb_erase(&cfqq
->p_node
, cfqq
->p_root
);
743 if (cfq_class_idle(cfqq
))
748 cfqq
->p_root
= &cfqd
->prio_trees
[cfqq
->org_ioprio
];
749 __cfqq
= cfq_prio_tree_lookup(cfqd
, cfqq
->p_root
,
750 blk_rq_pos(cfqq
->next_rq
), &parent
, &p
);
752 rb_link_node(&cfqq
->p_node
, parent
, p
);
753 rb_insert_color(&cfqq
->p_node
, cfqq
->p_root
);
759 * Update cfqq's position in the service tree.
761 static void cfq_resort_rr_list(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
764 * Resorting requires the cfqq to be on the RR list already.
766 if (cfq_cfqq_on_rr(cfqq
)) {
767 cfq_service_tree_add(cfqd
, cfqq
, 0);
768 cfq_prio_tree_add(cfqd
, cfqq
);
773 * add to busy list of queues for service, trying to be fair in ordering
774 * the pending list according to last request service
776 static void cfq_add_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
778 cfq_log_cfqq(cfqd
, cfqq
, "add_to_rr");
779 BUG_ON(cfq_cfqq_on_rr(cfqq
));
780 cfq_mark_cfqq_on_rr(cfqq
);
783 cfq_resort_rr_list(cfqd
, cfqq
);
787 * Called when the cfqq no longer has requests pending, remove it from
790 static void cfq_del_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
792 cfq_log_cfqq(cfqd
, cfqq
, "del_from_rr");
793 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
794 cfq_clear_cfqq_on_rr(cfqq
);
796 if (!RB_EMPTY_NODE(&cfqq
->rb_node
)) {
797 cfq_rb_erase(&cfqq
->rb_node
, cfqq
->service_tree
);
798 cfqq
->service_tree
= NULL
;
801 rb_erase(&cfqq
->p_node
, cfqq
->p_root
);
805 BUG_ON(!cfqd
->busy_queues
);
810 * rb tree support functions
812 static void cfq_del_rq_rb(struct request
*rq
)
814 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
815 struct cfq_data
*cfqd
= cfqq
->cfqd
;
816 const int sync
= rq_is_sync(rq
);
818 BUG_ON(!cfqq
->queued
[sync
]);
819 cfqq
->queued
[sync
]--;
821 elv_rb_del(&cfqq
->sort_list
, rq
);
823 if (cfq_cfqq_on_rr(cfqq
) && RB_EMPTY_ROOT(&cfqq
->sort_list
))
824 cfq_del_cfqq_rr(cfqd
, cfqq
);
827 static void cfq_add_rq_rb(struct request
*rq
)
829 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
830 struct cfq_data
*cfqd
= cfqq
->cfqd
;
831 struct request
*__alias
, *prev
;
833 cfqq
->queued
[rq_is_sync(rq
)]++;
836 * looks a little odd, but the first insert might return an alias.
837 * if that happens, put the alias on the dispatch list
839 while ((__alias
= elv_rb_add(&cfqq
->sort_list
, rq
)) != NULL
)
840 cfq_dispatch_insert(cfqd
->queue
, __alias
);
842 if (!cfq_cfqq_on_rr(cfqq
))
843 cfq_add_cfqq_rr(cfqd
, cfqq
);
846 * check if this request is a better next-serve candidate
848 prev
= cfqq
->next_rq
;
849 cfqq
->next_rq
= cfq_choose_req(cfqd
, cfqq
->next_rq
, rq
, cfqd
->last_position
);
852 * adjust priority tree position, if ->next_rq changes
854 if (prev
!= cfqq
->next_rq
)
855 cfq_prio_tree_add(cfqd
, cfqq
);
857 BUG_ON(!cfqq
->next_rq
);
860 static void cfq_reposition_rq_rb(struct cfq_queue
*cfqq
, struct request
*rq
)
862 elv_rb_del(&cfqq
->sort_list
, rq
);
863 cfqq
->queued
[rq_is_sync(rq
)]--;
867 static struct request
*
868 cfq_find_rq_fmerge(struct cfq_data
*cfqd
, struct bio
*bio
)
870 struct task_struct
*tsk
= current
;
871 struct cfq_io_context
*cic
;
872 struct cfq_queue
*cfqq
;
874 cic
= cfq_cic_lookup(cfqd
, tsk
->io_context
);
878 cfqq
= cic_to_cfqq(cic
, cfq_bio_sync(bio
));
880 sector_t sector
= bio
->bi_sector
+ bio_sectors(bio
);
882 return elv_rb_find(&cfqq
->sort_list
, sector
);
888 static void cfq_activate_request(struct request_queue
*q
, struct request
*rq
)
890 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
892 cfqd
->rq_in_driver
[rq_is_sync(rq
)]++;
893 cfq_log_cfqq(cfqd
, RQ_CFQQ(rq
), "activate rq, drv=%d",
896 cfqd
->last_position
= blk_rq_pos(rq
) + blk_rq_sectors(rq
);
899 static void cfq_deactivate_request(struct request_queue
*q
, struct request
*rq
)
901 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
902 const int sync
= rq_is_sync(rq
);
904 WARN_ON(!cfqd
->rq_in_driver
[sync
]);
905 cfqd
->rq_in_driver
[sync
]--;
906 cfq_log_cfqq(cfqd
, RQ_CFQQ(rq
), "deactivate rq, drv=%d",
910 static void cfq_remove_request(struct request
*rq
)
912 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
914 if (cfqq
->next_rq
== rq
)
915 cfqq
->next_rq
= cfq_find_next_rq(cfqq
->cfqd
, cfqq
, rq
);
917 list_del_init(&rq
->queuelist
);
920 cfqq
->cfqd
->rq_queued
--;
921 if (rq_is_meta(rq
)) {
922 WARN_ON(!cfqq
->meta_pending
);
923 cfqq
->meta_pending
--;
927 static int cfq_merge(struct request_queue
*q
, struct request
**req
,
930 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
931 struct request
*__rq
;
933 __rq
= cfq_find_rq_fmerge(cfqd
, bio
);
934 if (__rq
&& elv_rq_merge_ok(__rq
, bio
)) {
936 return ELEVATOR_FRONT_MERGE
;
939 return ELEVATOR_NO_MERGE
;
942 static void cfq_merged_request(struct request_queue
*q
, struct request
*req
,
945 if (type
== ELEVATOR_FRONT_MERGE
) {
946 struct cfq_queue
*cfqq
= RQ_CFQQ(req
);
948 cfq_reposition_rq_rb(cfqq
, req
);
953 cfq_merged_requests(struct request_queue
*q
, struct request
*rq
,
954 struct request
*next
)
956 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
958 * reposition in fifo if next is older than rq
960 if (!list_empty(&rq
->queuelist
) && !list_empty(&next
->queuelist
) &&
961 time_before(rq_fifo_time(next
), rq_fifo_time(rq
))) {
962 list_move(&rq
->queuelist
, &next
->queuelist
);
963 rq_set_fifo_time(rq
, rq_fifo_time(next
));
966 if (cfqq
->next_rq
== next
)
968 cfq_remove_request(next
);
971 static int cfq_allow_merge(struct request_queue
*q
, struct request
*rq
,
974 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
975 struct cfq_io_context
*cic
;
976 struct cfq_queue
*cfqq
;
979 * Disallow merge of a sync bio into an async request.
981 if (cfq_bio_sync(bio
) && !rq_is_sync(rq
))
985 * Lookup the cfqq that this bio will be queued with. Allow
986 * merge only if rq is queued there.
988 cic
= cfq_cic_lookup(cfqd
, current
->io_context
);
992 cfqq
= cic_to_cfqq(cic
, cfq_bio_sync(bio
));
993 return cfqq
== RQ_CFQQ(rq
);
996 static void __cfq_set_active_queue(struct cfq_data
*cfqd
,
997 struct cfq_queue
*cfqq
)
1000 cfq_log_cfqq(cfqd
, cfqq
, "set_active");
1001 cfqq
->slice_end
= 0;
1002 cfqq
->slice_dispatch
= 0;
1004 cfq_clear_cfqq_wait_request(cfqq
);
1005 cfq_clear_cfqq_must_dispatch(cfqq
);
1006 cfq_clear_cfqq_must_alloc_slice(cfqq
);
1007 cfq_clear_cfqq_fifo_expire(cfqq
);
1008 cfq_mark_cfqq_slice_new(cfqq
);
1010 del_timer(&cfqd
->idle_slice_timer
);
1013 cfqd
->active_queue
= cfqq
;
1017 * current cfqq expired its slice (or was too idle), select new one
1020 __cfq_slice_expired(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1023 cfq_log_cfqq(cfqd
, cfqq
, "slice expired t=%d", timed_out
);
1025 if (cfq_cfqq_wait_request(cfqq
))
1026 del_timer(&cfqd
->idle_slice_timer
);
1028 cfq_clear_cfqq_wait_request(cfqq
);
1031 * store what was left of this slice, if the queue idled/timed out
1033 if (timed_out
&& !cfq_cfqq_slice_new(cfqq
)) {
1034 cfqq
->slice_resid
= cfqq
->slice_end
- jiffies
;
1035 cfq_log_cfqq(cfqd
, cfqq
, "resid=%ld", cfqq
->slice_resid
);
1038 cfq_resort_rr_list(cfqd
, cfqq
);
1040 if (cfqq
== cfqd
->active_queue
)
1041 cfqd
->active_queue
= NULL
;
1043 if (cfqd
->active_cic
) {
1044 put_io_context(cfqd
->active_cic
->ioc
);
1045 cfqd
->active_cic
= NULL
;
1049 static inline void cfq_slice_expired(struct cfq_data
*cfqd
, bool timed_out
)
1051 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
1054 __cfq_slice_expired(cfqd
, cfqq
, timed_out
);
1058 * Get next queue for service. Unless we have a queue preemption,
1059 * we'll simply select the first cfqq in the service tree.
1061 static struct cfq_queue
*cfq_get_next_queue(struct cfq_data
*cfqd
)
1063 struct cfq_rb_root
*service_tree
=
1064 service_tree_for(cfqd
->serving_prio
, cfqd
->serving_type
, cfqd
);
1066 if (RB_EMPTY_ROOT(&service_tree
->rb
))
1068 return cfq_rb_first(service_tree
);
1072 * Get and set a new active queue for service.
1074 static struct cfq_queue
*cfq_set_active_queue(struct cfq_data
*cfqd
,
1075 struct cfq_queue
*cfqq
)
1078 cfqq
= cfq_get_next_queue(cfqd
);
1080 __cfq_set_active_queue(cfqd
, cfqq
);
1084 static inline sector_t
cfq_dist_from_last(struct cfq_data
*cfqd
,
1087 if (blk_rq_pos(rq
) >= cfqd
->last_position
)
1088 return blk_rq_pos(rq
) - cfqd
->last_position
;
1090 return cfqd
->last_position
- blk_rq_pos(rq
);
1093 #define CFQQ_SEEK_THR 8 * 1024
1094 #define CFQQ_SEEKY(cfqq) ((cfqq)->seek_mean > CFQQ_SEEK_THR)
1096 static inline int cfq_rq_close(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1099 sector_t sdist
= cfqq
->seek_mean
;
1101 if (!sample_valid(cfqq
->seek_samples
))
1102 sdist
= CFQQ_SEEK_THR
;
1104 return cfq_dist_from_last(cfqd
, rq
) <= sdist
;
1107 static struct cfq_queue
*cfqq_close(struct cfq_data
*cfqd
,
1108 struct cfq_queue
*cur_cfqq
)
1110 struct rb_root
*root
= &cfqd
->prio_trees
[cur_cfqq
->org_ioprio
];
1111 struct rb_node
*parent
, *node
;
1112 struct cfq_queue
*__cfqq
;
1113 sector_t sector
= cfqd
->last_position
;
1115 if (RB_EMPTY_ROOT(root
))
1119 * First, if we find a request starting at the end of the last
1120 * request, choose it.
1122 __cfqq
= cfq_prio_tree_lookup(cfqd
, root
, sector
, &parent
, NULL
);
1127 * If the exact sector wasn't found, the parent of the NULL leaf
1128 * will contain the closest sector.
1130 __cfqq
= rb_entry(parent
, struct cfq_queue
, p_node
);
1131 if (cfq_rq_close(cfqd
, cur_cfqq
, __cfqq
->next_rq
))
1134 if (blk_rq_pos(__cfqq
->next_rq
) < sector
)
1135 node
= rb_next(&__cfqq
->p_node
);
1137 node
= rb_prev(&__cfqq
->p_node
);
1141 __cfqq
= rb_entry(node
, struct cfq_queue
, p_node
);
1142 if (cfq_rq_close(cfqd
, cur_cfqq
, __cfqq
->next_rq
))
1150 * cur_cfqq - passed in so that we don't decide that the current queue is
1151 * closely cooperating with itself.
1153 * So, basically we're assuming that that cur_cfqq has dispatched at least
1154 * one request, and that cfqd->last_position reflects a position on the disk
1155 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
1158 static struct cfq_queue
*cfq_close_cooperator(struct cfq_data
*cfqd
,
1159 struct cfq_queue
*cur_cfqq
)
1161 struct cfq_queue
*cfqq
;
1163 if (!cfq_cfqq_sync(cur_cfqq
))
1165 if (CFQQ_SEEKY(cur_cfqq
))
1169 * We should notice if some of the queues are cooperating, eg
1170 * working closely on the same area of the disk. In that case,
1171 * we can group them together and don't waste time idling.
1173 cfqq
= cfqq_close(cfqd
, cur_cfqq
);
1178 * It only makes sense to merge sync queues.
1180 if (!cfq_cfqq_sync(cfqq
))
1182 if (CFQQ_SEEKY(cfqq
))
1186 * Do not merge queues of different priority classes
1188 if (cfq_class_rt(cfqq
) != cfq_class_rt(cur_cfqq
))
1195 * Determine whether we should enforce idle window for this queue.
1198 static bool cfq_should_idle(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1200 enum wl_prio_t prio
= cfqq_prio(cfqq
);
1201 struct cfq_rb_root
*service_tree
= cfqq
->service_tree
;
1203 /* We never do for idle class queues. */
1204 if (prio
== IDLE_WORKLOAD
)
1207 /* We do for queues that were marked with idle window flag. */
1208 if (cfq_cfqq_idle_window(cfqq
))
1212 * Otherwise, we do only if they are the last ones
1213 * in their service tree.
1216 service_tree
= service_tree_for(prio
, cfqq_type(cfqq
), cfqd
);
1218 if (service_tree
->count
== 0)
1221 return (service_tree
->count
== 1 && cfq_rb_first(service_tree
) == cfqq
);
1224 static void cfq_arm_slice_timer(struct cfq_data
*cfqd
)
1226 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
1227 struct cfq_io_context
*cic
;
1231 * SSD device without seek penalty, disable idling. But only do so
1232 * for devices that support queuing, otherwise we still have a problem
1233 * with sync vs async workloads.
1235 if (blk_queue_nonrot(cfqd
->queue
) && cfqd
->hw_tag
)
1238 WARN_ON(!RB_EMPTY_ROOT(&cfqq
->sort_list
));
1239 WARN_ON(cfq_cfqq_slice_new(cfqq
));
1242 * idle is disabled, either manually or by past process history
1244 if (!cfqd
->cfq_slice_idle
|| !cfq_should_idle(cfqd
, cfqq
))
1248 * still requests with the driver, don't idle
1250 if (rq_in_driver(cfqd
))
1254 * task has exited, don't wait
1256 cic
= cfqd
->active_cic
;
1257 if (!cic
|| !atomic_read(&cic
->ioc
->nr_tasks
))
1261 * If our average think time is larger than the remaining time
1262 * slice, then don't idle. This avoids overrunning the allotted
1265 if (sample_valid(cic
->ttime_samples
) &&
1266 (cfqq
->slice_end
- jiffies
< cic
->ttime_mean
))
1269 cfq_mark_cfqq_wait_request(cfqq
);
1271 sl
= cfqd
->cfq_slice_idle
;
1273 mod_timer(&cfqd
->idle_slice_timer
, jiffies
+ sl
);
1274 cfq_log_cfqq(cfqd
, cfqq
, "arm_idle: %lu", sl
);
1278 * Move request from internal lists to the request queue dispatch list.
1280 static void cfq_dispatch_insert(struct request_queue
*q
, struct request
*rq
)
1282 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1283 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1285 cfq_log_cfqq(cfqd
, cfqq
, "dispatch_insert");
1287 cfqq
->next_rq
= cfq_find_next_rq(cfqd
, cfqq
, rq
);
1288 cfq_remove_request(rq
);
1290 elv_dispatch_sort(q
, rq
);
1292 if (cfq_cfqq_sync(cfqq
))
1293 cfqd
->sync_flight
++;
1297 * return expired entry, or NULL to just start from scratch in rbtree
1299 static struct request
*cfq_check_fifo(struct cfq_queue
*cfqq
)
1301 struct request
*rq
= NULL
;
1303 if (cfq_cfqq_fifo_expire(cfqq
))
1306 cfq_mark_cfqq_fifo_expire(cfqq
);
1308 if (list_empty(&cfqq
->fifo
))
1311 rq
= rq_entry_fifo(cfqq
->fifo
.next
);
1312 if (time_before(jiffies
, rq_fifo_time(rq
)))
1315 cfq_log_cfqq(cfqq
->cfqd
, cfqq
, "fifo=%p", rq
);
1320 cfq_prio_to_maxrq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1322 const int base_rq
= cfqd
->cfq_slice_async_rq
;
1324 WARN_ON(cfqq
->ioprio
>= IOPRIO_BE_NR
);
1326 return 2 * (base_rq
+ base_rq
* (CFQ_PRIO_LISTS
- 1 - cfqq
->ioprio
));
1330 * Must be called with the queue_lock held.
1332 static int cfqq_process_refs(struct cfq_queue
*cfqq
)
1334 int process_refs
, io_refs
;
1336 io_refs
= cfqq
->allocated
[READ
] + cfqq
->allocated
[WRITE
];
1337 process_refs
= atomic_read(&cfqq
->ref
) - io_refs
;
1338 BUG_ON(process_refs
< 0);
1339 return process_refs
;
1342 static void cfq_setup_merge(struct cfq_queue
*cfqq
, struct cfq_queue
*new_cfqq
)
1344 int process_refs
, new_process_refs
;
1345 struct cfq_queue
*__cfqq
;
1347 /* Avoid a circular list and skip interim queue merges */
1348 while ((__cfqq
= new_cfqq
->new_cfqq
)) {
1354 process_refs
= cfqq_process_refs(cfqq
);
1356 * If the process for the cfqq has gone away, there is no
1357 * sense in merging the queues.
1359 if (process_refs
== 0)
1363 * Merge in the direction of the lesser amount of work.
1365 new_process_refs
= cfqq_process_refs(new_cfqq
);
1366 if (new_process_refs
>= process_refs
) {
1367 cfqq
->new_cfqq
= new_cfqq
;
1368 atomic_add(process_refs
, &new_cfqq
->ref
);
1370 new_cfqq
->new_cfqq
= cfqq
;
1371 atomic_add(new_process_refs
, &cfqq
->ref
);
1375 static enum wl_type_t
cfq_choose_wl(struct cfq_data
*cfqd
, enum wl_prio_t prio
,
1378 struct cfq_queue
*queue
;
1380 bool key_valid
= false;
1381 unsigned long lowest_key
= 0;
1382 enum wl_type_t cur_best
= SYNC_NOIDLE_WORKLOAD
;
1386 * When priorities switched, we prefer starting
1387 * from SYNC_NOIDLE (first choice), or just SYNC
1390 if (service_tree_for(prio
, cur_best
, cfqd
)->count
)
1392 cur_best
= SYNC_WORKLOAD
;
1393 if (service_tree_for(prio
, cur_best
, cfqd
)->count
)
1396 return ASYNC_WORKLOAD
;
1399 for (i
= 0; i
< 3; ++i
) {
1400 /* otherwise, select the one with lowest rb_key */
1401 queue
= cfq_rb_first(service_tree_for(prio
, i
, cfqd
));
1403 (!key_valid
|| time_before(queue
->rb_key
, lowest_key
))) {
1404 lowest_key
= queue
->rb_key
;
1413 static void choose_service_tree(struct cfq_data
*cfqd
)
1415 enum wl_prio_t previous_prio
= cfqd
->serving_prio
;
1420 /* Choose next priority. RT > BE > IDLE */
1421 if (cfq_busy_queues_wl(RT_WORKLOAD
, cfqd
))
1422 cfqd
->serving_prio
= RT_WORKLOAD
;
1423 else if (cfq_busy_queues_wl(BE_WORKLOAD
, cfqd
))
1424 cfqd
->serving_prio
= BE_WORKLOAD
;
1426 cfqd
->serving_prio
= IDLE_WORKLOAD
;
1427 cfqd
->workload_expires
= jiffies
+ 1;
1432 * For RT and BE, we have to choose also the type
1433 * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
1436 prio_changed
= (cfqd
->serving_prio
!= previous_prio
);
1437 count
= service_tree_for(cfqd
->serving_prio
, cfqd
->serving_type
, cfqd
)
1441 * If priority didn't change, check workload expiration,
1442 * and that we still have other queues ready
1444 if (!prio_changed
&& count
&&
1445 !time_after(jiffies
, cfqd
->workload_expires
))
1448 /* otherwise select new workload type */
1449 cfqd
->serving_type
=
1450 cfq_choose_wl(cfqd
, cfqd
->serving_prio
, prio_changed
);
1451 count
= service_tree_for(cfqd
->serving_prio
, cfqd
->serving_type
, cfqd
)
1455 * the workload slice is computed as a fraction of target latency
1456 * proportional to the number of queues in that workload, over
1457 * all the queues in the same priority class
1459 slice
= cfq_target_latency
* count
/
1460 max_t(unsigned, cfqd
->busy_queues_avg
[cfqd
->serving_prio
],
1461 cfq_busy_queues_wl(cfqd
->serving_prio
, cfqd
));
1463 if (cfqd
->serving_type
== ASYNC_WORKLOAD
)
1464 /* async workload slice is scaled down according to
1465 * the sync/async slice ratio. */
1466 slice
= slice
* cfqd
->cfq_slice
[0] / cfqd
->cfq_slice
[1];
1468 /* sync workload slice is at least 2 * cfq_slice_idle */
1469 slice
= max(slice
, 2 * cfqd
->cfq_slice_idle
);
1471 slice
= max_t(unsigned, slice
, CFQ_MIN_TT
);
1472 cfqd
->workload_expires
= jiffies
+ slice
;
1476 * Select a queue for service. If we have a current active queue,
1477 * check whether to continue servicing it, or retrieve and set a new one.
1479 static struct cfq_queue
*cfq_select_queue(struct cfq_data
*cfqd
)
1481 struct cfq_queue
*cfqq
, *new_cfqq
= NULL
;
1483 cfqq
= cfqd
->active_queue
;
1488 * The active queue has run out of time, expire it and select new.
1490 if (cfq_slice_used(cfqq
) && !cfq_cfqq_must_dispatch(cfqq
))
1494 * The active queue has requests and isn't expired, allow it to
1497 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
))
1501 * If another queue has a request waiting within our mean seek
1502 * distance, let it run. The expire code will check for close
1503 * cooperators and put the close queue at the front of the service
1504 * tree. If possible, merge the expiring queue with the new cfqq.
1506 new_cfqq
= cfq_close_cooperator(cfqd
, cfqq
);
1508 if (!cfqq
->new_cfqq
)
1509 cfq_setup_merge(cfqq
, new_cfqq
);
1514 * No requests pending. If the active queue still has requests in
1515 * flight or is idling for a new request, allow either of these
1516 * conditions to happen (or time out) before selecting a new queue.
1518 if (timer_pending(&cfqd
->idle_slice_timer
) ||
1519 (cfqq
->dispatched
&& cfq_should_idle(cfqd
, cfqq
))) {
1525 cfq_slice_expired(cfqd
, 0);
1528 * Current queue expired. Check if we have to switch to a new
1532 choose_service_tree(cfqd
);
1534 cfqq
= cfq_set_active_queue(cfqd
, new_cfqq
);
1539 static int __cfq_forced_dispatch_cfqq(struct cfq_queue
*cfqq
)
1543 while (cfqq
->next_rq
) {
1544 cfq_dispatch_insert(cfqq
->cfqd
->queue
, cfqq
->next_rq
);
1548 BUG_ON(!list_empty(&cfqq
->fifo
));
1553 * Drain our current requests. Used for barriers and when switching
1554 * io schedulers on-the-fly.
1556 static int cfq_forced_dispatch(struct cfq_data
*cfqd
)
1558 struct cfq_queue
*cfqq
;
1561 for (i
= 0; i
< 2; ++i
)
1562 for (j
= 0; j
< 3; ++j
)
1563 while ((cfqq
= cfq_rb_first(&cfqd
->service_trees
[i
][j
]))
1565 dispatched
+= __cfq_forced_dispatch_cfqq(cfqq
);
1567 while ((cfqq
= cfq_rb_first(&cfqd
->service_tree_idle
)) != NULL
)
1568 dispatched
+= __cfq_forced_dispatch_cfqq(cfqq
);
1570 cfq_slice_expired(cfqd
, 0);
1572 BUG_ON(cfqd
->busy_queues
);
1574 cfq_log(cfqd
, "forced_dispatch=%d", dispatched
);
1578 static bool cfq_may_dispatch(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1580 unsigned int max_dispatch
;
1583 * Drain async requests before we start sync IO
1585 if (cfq_should_idle(cfqd
, cfqq
) && cfqd
->rq_in_driver
[BLK_RW_ASYNC
])
1589 * If this is an async queue and we have sync IO in flight, let it wait
1591 if (cfqd
->sync_flight
&& !cfq_cfqq_sync(cfqq
))
1594 max_dispatch
= cfqd
->cfq_quantum
;
1595 if (cfq_class_idle(cfqq
))
1599 * Does this cfqq already have too much IO in flight?
1601 if (cfqq
->dispatched
>= max_dispatch
) {
1603 * idle queue must always only have a single IO in flight
1605 if (cfq_class_idle(cfqq
))
1609 * We have other queues, don't allow more IO from this one
1611 if (cfqd
->busy_queues
> 1)
1615 * Sole queue user, allow bigger slice
1621 * Async queues must wait a bit before being allowed dispatch.
1622 * We also ramp up the dispatch depth gradually for async IO,
1623 * based on the last sync IO we serviced
1625 if (!cfq_cfqq_sync(cfqq
) && cfqd
->cfq_latency
) {
1626 unsigned long last_sync
= jiffies
- cfqd
->last_end_sync_rq
;
1629 depth
= last_sync
/ cfqd
->cfq_slice
[1];
1630 if (!depth
&& !cfqq
->dispatched
)
1632 if (depth
< max_dispatch
)
1633 max_dispatch
= depth
;
1637 * If we're below the current max, allow a dispatch
1639 return cfqq
->dispatched
< max_dispatch
;
1643 * Dispatch a request from cfqq, moving them to the request queue
1646 static bool cfq_dispatch_request(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1650 BUG_ON(RB_EMPTY_ROOT(&cfqq
->sort_list
));
1652 if (!cfq_may_dispatch(cfqd
, cfqq
))
1656 * follow expired path, else get first next available
1658 rq
= cfq_check_fifo(cfqq
);
1663 * insert request into driver dispatch list
1665 cfq_dispatch_insert(cfqd
->queue
, rq
);
1667 if (!cfqd
->active_cic
) {
1668 struct cfq_io_context
*cic
= RQ_CIC(rq
);
1670 atomic_long_inc(&cic
->ioc
->refcount
);
1671 cfqd
->active_cic
= cic
;
1678 * Find the cfqq that we need to service and move a request from that to the
1681 static int cfq_dispatch_requests(struct request_queue
*q
, int force
)
1683 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1684 struct cfq_queue
*cfqq
;
1686 if (!cfqd
->busy_queues
)
1689 if (unlikely(force
))
1690 return cfq_forced_dispatch(cfqd
);
1692 cfqq
= cfq_select_queue(cfqd
);
1697 * Dispatch a request from this cfqq, if it is allowed
1699 if (!cfq_dispatch_request(cfqd
, cfqq
))
1702 cfqq
->slice_dispatch
++;
1703 cfq_clear_cfqq_must_dispatch(cfqq
);
1706 * expire an async queue immediately if it has used up its slice. idle
1707 * queue always expire after 1 dispatch round.
1709 if (cfqd
->busy_queues
> 1 && ((!cfq_cfqq_sync(cfqq
) &&
1710 cfqq
->slice_dispatch
>= cfq_prio_to_maxrq(cfqd
, cfqq
)) ||
1711 cfq_class_idle(cfqq
))) {
1712 cfqq
->slice_end
= jiffies
+ 1;
1713 cfq_slice_expired(cfqd
, 0);
1716 cfq_log_cfqq(cfqd
, cfqq
, "dispatched a request");
1721 * task holds one reference to the queue, dropped when task exits. each rq
1722 * in-flight on this queue also holds a reference, dropped when rq is freed.
1724 * queue lock must be held here.
1726 static void cfq_put_queue(struct cfq_queue
*cfqq
)
1728 struct cfq_data
*cfqd
= cfqq
->cfqd
;
1730 BUG_ON(atomic_read(&cfqq
->ref
) <= 0);
1732 if (!atomic_dec_and_test(&cfqq
->ref
))
1735 cfq_log_cfqq(cfqd
, cfqq
, "put_queue");
1736 BUG_ON(rb_first(&cfqq
->sort_list
));
1737 BUG_ON(cfqq
->allocated
[READ
] + cfqq
->allocated
[WRITE
]);
1738 BUG_ON(cfq_cfqq_on_rr(cfqq
));
1740 if (unlikely(cfqd
->active_queue
== cfqq
)) {
1741 __cfq_slice_expired(cfqd
, cfqq
, 0);
1742 cfq_schedule_dispatch(cfqd
);
1745 kmem_cache_free(cfq_pool
, cfqq
);
1749 * Must always be called with the rcu_read_lock() held
1752 __call_for_each_cic(struct io_context
*ioc
,
1753 void (*func
)(struct io_context
*, struct cfq_io_context
*))
1755 struct cfq_io_context
*cic
;
1756 struct hlist_node
*n
;
1758 hlist_for_each_entry_rcu(cic
, n
, &ioc
->cic_list
, cic_list
)
1763 * Call func for each cic attached to this ioc.
1766 call_for_each_cic(struct io_context
*ioc
,
1767 void (*func
)(struct io_context
*, struct cfq_io_context
*))
1770 __call_for_each_cic(ioc
, func
);
1774 static void cfq_cic_free_rcu(struct rcu_head
*head
)
1776 struct cfq_io_context
*cic
;
1778 cic
= container_of(head
, struct cfq_io_context
, rcu_head
);
1780 kmem_cache_free(cfq_ioc_pool
, cic
);
1781 elv_ioc_count_dec(cfq_ioc_count
);
1785 * CFQ scheduler is exiting, grab exit lock and check
1786 * the pending io context count. If it hits zero,
1787 * complete ioc_gone and set it back to NULL
1789 spin_lock(&ioc_gone_lock
);
1790 if (ioc_gone
&& !elv_ioc_count_read(cfq_ioc_count
)) {
1794 spin_unlock(&ioc_gone_lock
);
1798 static void cfq_cic_free(struct cfq_io_context
*cic
)
1800 call_rcu(&cic
->rcu_head
, cfq_cic_free_rcu
);
1803 static void cic_free_func(struct io_context
*ioc
, struct cfq_io_context
*cic
)
1805 unsigned long flags
;
1807 BUG_ON(!cic
->dead_key
);
1809 spin_lock_irqsave(&ioc
->lock
, flags
);
1810 radix_tree_delete(&ioc
->radix_root
, cic
->dead_key
);
1811 hlist_del_rcu(&cic
->cic_list
);
1812 spin_unlock_irqrestore(&ioc
->lock
, flags
);
1818 * Must be called with rcu_read_lock() held or preemption otherwise disabled.
1819 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
1820 * and ->trim() which is called with the task lock held
1822 static void cfq_free_io_context(struct io_context
*ioc
)
1825 * ioc->refcount is zero here, or we are called from elv_unregister(),
1826 * so no more cic's are allowed to be linked into this ioc. So it
1827 * should be ok to iterate over the known list, we will see all cic's
1828 * since no new ones are added.
1830 __call_for_each_cic(ioc
, cic_free_func
);
1833 static void cfq_exit_cfqq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1835 struct cfq_queue
*__cfqq
, *next
;
1837 if (unlikely(cfqq
== cfqd
->active_queue
)) {
1838 __cfq_slice_expired(cfqd
, cfqq
, 0);
1839 cfq_schedule_dispatch(cfqd
);
1843 * If this queue was scheduled to merge with another queue, be
1844 * sure to drop the reference taken on that queue (and others in
1845 * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs.
1847 __cfqq
= cfqq
->new_cfqq
;
1849 if (__cfqq
== cfqq
) {
1850 WARN(1, "cfqq->new_cfqq loop detected\n");
1853 next
= __cfqq
->new_cfqq
;
1854 cfq_put_queue(__cfqq
);
1858 cfq_put_queue(cfqq
);
1861 static void __cfq_exit_single_io_context(struct cfq_data
*cfqd
,
1862 struct cfq_io_context
*cic
)
1864 struct io_context
*ioc
= cic
->ioc
;
1866 list_del_init(&cic
->queue_list
);
1869 * Make sure key == NULL is seen for dead queues
1872 cic
->dead_key
= (unsigned long) cic
->key
;
1875 if (ioc
->ioc_data
== cic
)
1876 rcu_assign_pointer(ioc
->ioc_data
, NULL
);
1878 if (cic
->cfqq
[BLK_RW_ASYNC
]) {
1879 cfq_exit_cfqq(cfqd
, cic
->cfqq
[BLK_RW_ASYNC
]);
1880 cic
->cfqq
[BLK_RW_ASYNC
] = NULL
;
1883 if (cic
->cfqq
[BLK_RW_SYNC
]) {
1884 cfq_exit_cfqq(cfqd
, cic
->cfqq
[BLK_RW_SYNC
]);
1885 cic
->cfqq
[BLK_RW_SYNC
] = NULL
;
1889 static void cfq_exit_single_io_context(struct io_context
*ioc
,
1890 struct cfq_io_context
*cic
)
1892 struct cfq_data
*cfqd
= cic
->key
;
1895 struct request_queue
*q
= cfqd
->queue
;
1896 unsigned long flags
;
1898 spin_lock_irqsave(q
->queue_lock
, flags
);
1901 * Ensure we get a fresh copy of the ->key to prevent
1902 * race between exiting task and queue
1904 smp_read_barrier_depends();
1906 __cfq_exit_single_io_context(cfqd
, cic
);
1908 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1913 * The process that ioc belongs to has exited, we need to clean up
1914 * and put the internal structures we have that belongs to that process.
1916 static void cfq_exit_io_context(struct io_context
*ioc
)
1918 call_for_each_cic(ioc
, cfq_exit_single_io_context
);
1921 static struct cfq_io_context
*
1922 cfq_alloc_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
1924 struct cfq_io_context
*cic
;
1926 cic
= kmem_cache_alloc_node(cfq_ioc_pool
, gfp_mask
| __GFP_ZERO
,
1929 cic
->last_end_request
= jiffies
;
1930 INIT_LIST_HEAD(&cic
->queue_list
);
1931 INIT_HLIST_NODE(&cic
->cic_list
);
1932 cic
->dtor
= cfq_free_io_context
;
1933 cic
->exit
= cfq_exit_io_context
;
1934 elv_ioc_count_inc(cfq_ioc_count
);
1940 static void cfq_init_prio_data(struct cfq_queue
*cfqq
, struct io_context
*ioc
)
1942 struct task_struct
*tsk
= current
;
1945 if (!cfq_cfqq_prio_changed(cfqq
))
1948 ioprio_class
= IOPRIO_PRIO_CLASS(ioc
->ioprio
);
1949 switch (ioprio_class
) {
1951 printk(KERN_ERR
"cfq: bad prio %x\n", ioprio_class
);
1952 case IOPRIO_CLASS_NONE
:
1954 * no prio set, inherit CPU scheduling settings
1956 cfqq
->ioprio
= task_nice_ioprio(tsk
);
1957 cfqq
->ioprio_class
= task_nice_ioclass(tsk
);
1959 case IOPRIO_CLASS_RT
:
1960 cfqq
->ioprio
= task_ioprio(ioc
);
1961 cfqq
->ioprio_class
= IOPRIO_CLASS_RT
;
1963 case IOPRIO_CLASS_BE
:
1964 cfqq
->ioprio
= task_ioprio(ioc
);
1965 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1967 case IOPRIO_CLASS_IDLE
:
1968 cfqq
->ioprio_class
= IOPRIO_CLASS_IDLE
;
1970 cfq_clear_cfqq_idle_window(cfqq
);
1975 * keep track of original prio settings in case we have to temporarily
1976 * elevate the priority of this queue
1978 cfqq
->org_ioprio
= cfqq
->ioprio
;
1979 cfqq
->org_ioprio_class
= cfqq
->ioprio_class
;
1980 cfq_clear_cfqq_prio_changed(cfqq
);
1983 static void changed_ioprio(struct io_context
*ioc
, struct cfq_io_context
*cic
)
1985 struct cfq_data
*cfqd
= cic
->key
;
1986 struct cfq_queue
*cfqq
;
1987 unsigned long flags
;
1989 if (unlikely(!cfqd
))
1992 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
1994 cfqq
= cic
->cfqq
[BLK_RW_ASYNC
];
1996 struct cfq_queue
*new_cfqq
;
1997 new_cfqq
= cfq_get_queue(cfqd
, BLK_RW_ASYNC
, cic
->ioc
,
2000 cic
->cfqq
[BLK_RW_ASYNC
] = new_cfqq
;
2001 cfq_put_queue(cfqq
);
2005 cfqq
= cic
->cfqq
[BLK_RW_SYNC
];
2007 cfq_mark_cfqq_prio_changed(cfqq
);
2009 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2012 static void cfq_ioc_set_ioprio(struct io_context
*ioc
)
2014 call_for_each_cic(ioc
, changed_ioprio
);
2015 ioc
->ioprio_changed
= 0;
2018 static void cfq_init_cfqq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2019 pid_t pid
, bool is_sync
)
2021 RB_CLEAR_NODE(&cfqq
->rb_node
);
2022 RB_CLEAR_NODE(&cfqq
->p_node
);
2023 INIT_LIST_HEAD(&cfqq
->fifo
);
2025 atomic_set(&cfqq
->ref
, 0);
2028 cfq_mark_cfqq_prio_changed(cfqq
);
2031 if (!cfq_class_idle(cfqq
))
2032 cfq_mark_cfqq_idle_window(cfqq
);
2033 cfq_mark_cfqq_sync(cfqq
);
2038 static struct cfq_queue
*
2039 cfq_find_alloc_queue(struct cfq_data
*cfqd
, bool is_sync
,
2040 struct io_context
*ioc
, gfp_t gfp_mask
)
2042 struct cfq_queue
*cfqq
, *new_cfqq
= NULL
;
2043 struct cfq_io_context
*cic
;
2046 cic
= cfq_cic_lookup(cfqd
, ioc
);
2047 /* cic always exists here */
2048 cfqq
= cic_to_cfqq(cic
, is_sync
);
2051 * Always try a new alloc if we fell back to the OOM cfqq
2052 * originally, since it should just be a temporary situation.
2054 if (!cfqq
|| cfqq
== &cfqd
->oom_cfqq
) {
2059 } else if (gfp_mask
& __GFP_WAIT
) {
2060 spin_unlock_irq(cfqd
->queue
->queue_lock
);
2061 new_cfqq
= kmem_cache_alloc_node(cfq_pool
,
2062 gfp_mask
| __GFP_ZERO
,
2064 spin_lock_irq(cfqd
->queue
->queue_lock
);
2068 cfqq
= kmem_cache_alloc_node(cfq_pool
,
2069 gfp_mask
| __GFP_ZERO
,
2074 cfq_init_cfqq(cfqd
, cfqq
, current
->pid
, is_sync
);
2075 cfq_init_prio_data(cfqq
, ioc
);
2076 cfq_log_cfqq(cfqd
, cfqq
, "alloced");
2078 cfqq
= &cfqd
->oom_cfqq
;
2082 kmem_cache_free(cfq_pool
, new_cfqq
);
2087 static struct cfq_queue
**
2088 cfq_async_queue_prio(struct cfq_data
*cfqd
, int ioprio_class
, int ioprio
)
2090 switch (ioprio_class
) {
2091 case IOPRIO_CLASS_RT
:
2092 return &cfqd
->async_cfqq
[0][ioprio
];
2093 case IOPRIO_CLASS_BE
:
2094 return &cfqd
->async_cfqq
[1][ioprio
];
2095 case IOPRIO_CLASS_IDLE
:
2096 return &cfqd
->async_idle_cfqq
;
2102 static struct cfq_queue
*
2103 cfq_get_queue(struct cfq_data
*cfqd
, bool is_sync
, struct io_context
*ioc
,
2106 const int ioprio
= task_ioprio(ioc
);
2107 const int ioprio_class
= task_ioprio_class(ioc
);
2108 struct cfq_queue
**async_cfqq
= NULL
;
2109 struct cfq_queue
*cfqq
= NULL
;
2112 async_cfqq
= cfq_async_queue_prio(cfqd
, ioprio_class
, ioprio
);
2117 cfqq
= cfq_find_alloc_queue(cfqd
, is_sync
, ioc
, gfp_mask
);
2120 * pin the queue now that it's allocated, scheduler exit will prune it
2122 if (!is_sync
&& !(*async_cfqq
)) {
2123 atomic_inc(&cfqq
->ref
);
2127 atomic_inc(&cfqq
->ref
);
2132 * We drop cfq io contexts lazily, so we may find a dead one.
2135 cfq_drop_dead_cic(struct cfq_data
*cfqd
, struct io_context
*ioc
,
2136 struct cfq_io_context
*cic
)
2138 unsigned long flags
;
2140 WARN_ON(!list_empty(&cic
->queue_list
));
2142 spin_lock_irqsave(&ioc
->lock
, flags
);
2144 BUG_ON(ioc
->ioc_data
== cic
);
2146 radix_tree_delete(&ioc
->radix_root
, (unsigned long) cfqd
);
2147 hlist_del_rcu(&cic
->cic_list
);
2148 spin_unlock_irqrestore(&ioc
->lock
, flags
);
2153 static struct cfq_io_context
*
2154 cfq_cic_lookup(struct cfq_data
*cfqd
, struct io_context
*ioc
)
2156 struct cfq_io_context
*cic
;
2157 unsigned long flags
;
2166 * we maintain a last-hit cache, to avoid browsing over the tree
2168 cic
= rcu_dereference(ioc
->ioc_data
);
2169 if (cic
&& cic
->key
== cfqd
) {
2175 cic
= radix_tree_lookup(&ioc
->radix_root
, (unsigned long) cfqd
);
2179 /* ->key must be copied to avoid race with cfq_exit_queue() */
2182 cfq_drop_dead_cic(cfqd
, ioc
, cic
);
2187 spin_lock_irqsave(&ioc
->lock
, flags
);
2188 rcu_assign_pointer(ioc
->ioc_data
, cic
);
2189 spin_unlock_irqrestore(&ioc
->lock
, flags
);
2197 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2198 * the process specific cfq io context when entered from the block layer.
2199 * Also adds the cic to a per-cfqd list, used when this queue is removed.
2201 static int cfq_cic_link(struct cfq_data
*cfqd
, struct io_context
*ioc
,
2202 struct cfq_io_context
*cic
, gfp_t gfp_mask
)
2204 unsigned long flags
;
2207 ret
= radix_tree_preload(gfp_mask
);
2212 spin_lock_irqsave(&ioc
->lock
, flags
);
2213 ret
= radix_tree_insert(&ioc
->radix_root
,
2214 (unsigned long) cfqd
, cic
);
2216 hlist_add_head_rcu(&cic
->cic_list
, &ioc
->cic_list
);
2217 spin_unlock_irqrestore(&ioc
->lock
, flags
);
2219 radix_tree_preload_end();
2222 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
2223 list_add(&cic
->queue_list
, &cfqd
->cic_list
);
2224 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2229 printk(KERN_ERR
"cfq: cic link failed!\n");
2235 * Setup general io context and cfq io context. There can be several cfq
2236 * io contexts per general io context, if this process is doing io to more
2237 * than one device managed by cfq.
2239 static struct cfq_io_context
*
2240 cfq_get_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
2242 struct io_context
*ioc
= NULL
;
2243 struct cfq_io_context
*cic
;
2245 might_sleep_if(gfp_mask
& __GFP_WAIT
);
2247 ioc
= get_io_context(gfp_mask
, cfqd
->queue
->node
);
2251 cic
= cfq_cic_lookup(cfqd
, ioc
);
2255 cic
= cfq_alloc_io_context(cfqd
, gfp_mask
);
2259 if (cfq_cic_link(cfqd
, ioc
, cic
, gfp_mask
))
2263 smp_read_barrier_depends();
2264 if (unlikely(ioc
->ioprio_changed
))
2265 cfq_ioc_set_ioprio(ioc
);
2271 put_io_context(ioc
);
2276 cfq_update_io_thinktime(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
)
2278 unsigned long elapsed
= jiffies
- cic
->last_end_request
;
2279 unsigned long ttime
= min(elapsed
, 2UL * cfqd
->cfq_slice_idle
);
2281 cic
->ttime_samples
= (7*cic
->ttime_samples
+ 256) / 8;
2282 cic
->ttime_total
= (7*cic
->ttime_total
+ 256*ttime
) / 8;
2283 cic
->ttime_mean
= (cic
->ttime_total
+ 128) / cic
->ttime_samples
;
2287 cfq_update_io_seektime(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2293 if (!cfqq
->last_request_pos
)
2295 else if (cfqq
->last_request_pos
< blk_rq_pos(rq
))
2296 sdist
= blk_rq_pos(rq
) - cfqq
->last_request_pos
;
2298 sdist
= cfqq
->last_request_pos
- blk_rq_pos(rq
);
2301 * Don't allow the seek distance to get too large from the
2302 * odd fragment, pagein, etc
2304 if (cfqq
->seek_samples
<= 60) /* second&third seek */
2305 sdist
= min(sdist
, (cfqq
->seek_mean
* 4) + 2*1024*1024);
2307 sdist
= min(sdist
, (cfqq
->seek_mean
* 4) + 2*1024*64);
2309 cfqq
->seek_samples
= (7*cfqq
->seek_samples
+ 256) / 8;
2310 cfqq
->seek_total
= (7*cfqq
->seek_total
+ (u64
)256*sdist
) / 8;
2311 total
= cfqq
->seek_total
+ (cfqq
->seek_samples
/2);
2312 do_div(total
, cfqq
->seek_samples
);
2313 cfqq
->seek_mean
= (sector_t
)total
;
2316 * If this cfqq is shared between multiple processes, check to
2317 * make sure that those processes are still issuing I/Os within
2318 * the mean seek distance. If not, it may be time to break the
2319 * queues apart again.
2321 if (cfq_cfqq_coop(cfqq
)) {
2322 if (CFQQ_SEEKY(cfqq
) && !cfqq
->seeky_start
)
2323 cfqq
->seeky_start
= jiffies
;
2324 else if (!CFQQ_SEEKY(cfqq
))
2325 cfqq
->seeky_start
= 0;
2330 * Disable idle window if the process thinks too long or seeks so much that
2334 cfq_update_idle_window(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2335 struct cfq_io_context
*cic
)
2337 int old_idle
, enable_idle
;
2340 * Don't idle for async or idle io prio class
2342 if (!cfq_cfqq_sync(cfqq
) || cfq_class_idle(cfqq
))
2345 enable_idle
= old_idle
= cfq_cfqq_idle_window(cfqq
);
2347 if (!atomic_read(&cic
->ioc
->nr_tasks
) || !cfqd
->cfq_slice_idle
||
2348 (sample_valid(cfqq
->seek_samples
) && CFQQ_SEEKY(cfqq
)))
2350 else if (sample_valid(cic
->ttime_samples
)) {
2351 if (cic
->ttime_mean
> cfqd
->cfq_slice_idle
)
2357 if (old_idle
!= enable_idle
) {
2358 cfq_log_cfqq(cfqd
, cfqq
, "idle=%d", enable_idle
);
2360 cfq_mark_cfqq_idle_window(cfqq
);
2362 cfq_clear_cfqq_idle_window(cfqq
);
2367 * Check if new_cfqq should preempt the currently active queue. Return 0 for
2368 * no or if we aren't sure, a 1 will cause a preempt.
2371 cfq_should_preempt(struct cfq_data
*cfqd
, struct cfq_queue
*new_cfqq
,
2374 struct cfq_queue
*cfqq
;
2376 cfqq
= cfqd
->active_queue
;
2380 if (cfq_slice_used(cfqq
))
2383 if (cfq_class_idle(new_cfqq
))
2386 if (cfq_class_idle(cfqq
))
2389 if (cfqd
->serving_type
== SYNC_NOIDLE_WORKLOAD
2390 && new_cfqq
->service_tree
== cfqq
->service_tree
)
2394 * if the new request is sync, but the currently running queue is
2395 * not, let the sync request have priority.
2397 if (rq_is_sync(rq
) && !cfq_cfqq_sync(cfqq
))
2401 * So both queues are sync. Let the new request get disk time if
2402 * it's a metadata request and the current queue is doing regular IO.
2404 if (rq_is_meta(rq
) && !cfqq
->meta_pending
)
2408 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
2410 if (cfq_class_rt(new_cfqq
) && !cfq_class_rt(cfqq
))
2413 if (!cfqd
->active_cic
|| !cfq_cfqq_wait_request(cfqq
))
2417 * if this request is as-good as one we would expect from the
2418 * current cfqq, let it preempt
2420 if (cfq_rq_close(cfqd
, cfqq
, rq
))
2427 * cfqq preempts the active queue. if we allowed preempt with no slice left,
2428 * let it have half of its nominal slice.
2430 static void cfq_preempt_queue(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
2432 cfq_log_cfqq(cfqd
, cfqq
, "preempt");
2433 cfq_slice_expired(cfqd
, 1);
2436 * Put the new queue at the front of the of the current list,
2437 * so we know that it will be selected next.
2439 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
2441 cfq_service_tree_add(cfqd
, cfqq
, 1);
2443 cfqq
->slice_end
= 0;
2444 cfq_mark_cfqq_slice_new(cfqq
);
2448 * Called when a new fs request (rq) is added (to cfqq). Check if there's
2449 * something we should do about it
2452 cfq_rq_enqueued(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2455 struct cfq_io_context
*cic
= RQ_CIC(rq
);
2459 cfqq
->meta_pending
++;
2461 cfq_update_io_thinktime(cfqd
, cic
);
2462 cfq_update_io_seektime(cfqd
, cfqq
, rq
);
2463 cfq_update_idle_window(cfqd
, cfqq
, cic
);
2465 cfqq
->last_request_pos
= blk_rq_pos(rq
) + blk_rq_sectors(rq
);
2467 if (cfqq
== cfqd
->active_queue
) {
2469 * Remember that we saw a request from this process, but
2470 * don't start queuing just yet. Otherwise we risk seeing lots
2471 * of tiny requests, because we disrupt the normal plugging
2472 * and merging. If the request is already larger than a single
2473 * page, let it rip immediately. For that case we assume that
2474 * merging is already done. Ditto for a busy system that
2475 * has other work pending, don't risk delaying until the
2476 * idle timer unplug to continue working.
2478 if (cfq_cfqq_wait_request(cfqq
)) {
2479 if (blk_rq_bytes(rq
) > PAGE_CACHE_SIZE
||
2480 cfqd
->busy_queues
> 1) {
2481 del_timer(&cfqd
->idle_slice_timer
);
2482 __blk_run_queue(cfqd
->queue
);
2484 cfq_mark_cfqq_must_dispatch(cfqq
);
2486 } else if (cfq_should_preempt(cfqd
, cfqq
, rq
)) {
2488 * not the active queue - expire current slice if it is
2489 * idle and has expired it's mean thinktime or this new queue
2490 * has some old slice time left and is of higher priority or
2491 * this new queue is RT and the current one is BE
2493 cfq_preempt_queue(cfqd
, cfqq
);
2494 __blk_run_queue(cfqd
->queue
);
2498 static void cfq_insert_request(struct request_queue
*q
, struct request
*rq
)
2500 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
2501 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
2503 cfq_log_cfqq(cfqd
, cfqq
, "insert_request");
2504 cfq_init_prio_data(cfqq
, RQ_CIC(rq
)->ioc
);
2506 rq_set_fifo_time(rq
, jiffies
+ cfqd
->cfq_fifo_expire
[rq_is_sync(rq
)]);
2507 list_add_tail(&rq
->queuelist
, &cfqq
->fifo
);
2510 cfq_rq_enqueued(cfqd
, cfqq
, rq
);
2514 * Update hw_tag based on peak queue depth over 50 samples under
2517 static void cfq_update_hw_tag(struct cfq_data
*cfqd
)
2519 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
2521 if (rq_in_driver(cfqd
) > cfqd
->rq_in_driver_peak
)
2522 cfqd
->rq_in_driver_peak
= rq_in_driver(cfqd
);
2524 if (cfqd
->rq_queued
<= CFQ_HW_QUEUE_MIN
&&
2525 rq_in_driver(cfqd
) <= CFQ_HW_QUEUE_MIN
)
2529 * If active queue hasn't enough requests and can idle, cfq might not
2530 * dispatch sufficient requests to hardware. Don't zero hw_tag in this
2533 if (cfqq
&& cfq_cfqq_idle_window(cfqq
) &&
2534 cfqq
->dispatched
+ cfqq
->queued
[0] + cfqq
->queued
[1] <
2535 CFQ_HW_QUEUE_MIN
&& rq_in_driver(cfqd
) < CFQ_HW_QUEUE_MIN
)
2538 if (cfqd
->hw_tag_samples
++ < 50)
2541 if (cfqd
->rq_in_driver_peak
>= CFQ_HW_QUEUE_MIN
)
2546 cfqd
->hw_tag_samples
= 0;
2547 cfqd
->rq_in_driver_peak
= 0;
2550 static void cfq_completed_request(struct request_queue
*q
, struct request
*rq
)
2552 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
2553 struct cfq_data
*cfqd
= cfqq
->cfqd
;
2554 const int sync
= rq_is_sync(rq
);
2558 cfq_log_cfqq(cfqd
, cfqq
, "complete");
2560 cfq_update_hw_tag(cfqd
);
2562 WARN_ON(!cfqd
->rq_in_driver
[sync
]);
2563 WARN_ON(!cfqq
->dispatched
);
2564 cfqd
->rq_in_driver
[sync
]--;
2567 if (cfq_cfqq_sync(cfqq
))
2568 cfqd
->sync_flight
--;
2571 RQ_CIC(rq
)->last_end_request
= now
;
2572 cfqd
->last_end_sync_rq
= now
;
2576 * If this is the active queue, check if it needs to be expired,
2577 * or if we want to idle in case it has no pending requests.
2579 if (cfqd
->active_queue
== cfqq
) {
2580 const bool cfqq_empty
= RB_EMPTY_ROOT(&cfqq
->sort_list
);
2582 if (cfq_cfqq_slice_new(cfqq
)) {
2583 cfq_set_prio_slice(cfqd
, cfqq
);
2584 cfq_clear_cfqq_slice_new(cfqq
);
2587 * If there are no requests waiting in this queue, and
2588 * there are other queues ready to issue requests, AND
2589 * those other queues are issuing requests within our
2590 * mean seek distance, give them a chance to run instead
2593 if (cfq_slice_used(cfqq
) || cfq_class_idle(cfqq
))
2594 cfq_slice_expired(cfqd
, 1);
2595 else if (cfqq_empty
&& !cfq_close_cooperator(cfqd
, cfqq
) &&
2596 sync
&& !rq_noidle(rq
))
2597 cfq_arm_slice_timer(cfqd
);
2600 if (!rq_in_driver(cfqd
))
2601 cfq_schedule_dispatch(cfqd
);
2605 * we temporarily boost lower priority queues if they are holding fs exclusive
2606 * resources. they are boosted to normal prio (CLASS_BE/4)
2608 static void cfq_prio_boost(struct cfq_queue
*cfqq
)
2610 if (has_fs_excl()) {
2612 * boost idle prio on transactions that would lock out other
2613 * users of the filesystem
2615 if (cfq_class_idle(cfqq
))
2616 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
2617 if (cfqq
->ioprio
> IOPRIO_NORM
)
2618 cfqq
->ioprio
= IOPRIO_NORM
;
2621 * unboost the queue (if needed)
2623 cfqq
->ioprio_class
= cfqq
->org_ioprio_class
;
2624 cfqq
->ioprio
= cfqq
->org_ioprio
;
2628 static inline int __cfq_may_queue(struct cfq_queue
*cfqq
)
2630 if (cfq_cfqq_wait_request(cfqq
) && !cfq_cfqq_must_alloc_slice(cfqq
)) {
2631 cfq_mark_cfqq_must_alloc_slice(cfqq
);
2632 return ELV_MQUEUE_MUST
;
2635 return ELV_MQUEUE_MAY
;
2638 static int cfq_may_queue(struct request_queue
*q
, int rw
)
2640 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
2641 struct task_struct
*tsk
= current
;
2642 struct cfq_io_context
*cic
;
2643 struct cfq_queue
*cfqq
;
2646 * don't force setup of a queue from here, as a call to may_queue
2647 * does not necessarily imply that a request actually will be queued.
2648 * so just lookup a possibly existing queue, or return 'may queue'
2651 cic
= cfq_cic_lookup(cfqd
, tsk
->io_context
);
2653 return ELV_MQUEUE_MAY
;
2655 cfqq
= cic_to_cfqq(cic
, rw_is_sync(rw
));
2657 cfq_init_prio_data(cfqq
, cic
->ioc
);
2658 cfq_prio_boost(cfqq
);
2660 return __cfq_may_queue(cfqq
);
2663 return ELV_MQUEUE_MAY
;
2667 * queue lock held here
2669 static void cfq_put_request(struct request
*rq
)
2671 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
2674 const int rw
= rq_data_dir(rq
);
2676 BUG_ON(!cfqq
->allocated
[rw
]);
2677 cfqq
->allocated
[rw
]--;
2679 put_io_context(RQ_CIC(rq
)->ioc
);
2681 rq
->elevator_private
= NULL
;
2682 rq
->elevator_private2
= NULL
;
2684 cfq_put_queue(cfqq
);
2688 static struct cfq_queue
*
2689 cfq_merge_cfqqs(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
,
2690 struct cfq_queue
*cfqq
)
2692 cfq_log_cfqq(cfqd
, cfqq
, "merging with queue %p", cfqq
->new_cfqq
);
2693 cic_set_cfqq(cic
, cfqq
->new_cfqq
, 1);
2694 cfq_mark_cfqq_coop(cfqq
->new_cfqq
);
2695 cfq_put_queue(cfqq
);
2696 return cic_to_cfqq(cic
, 1);
2699 static int should_split_cfqq(struct cfq_queue
*cfqq
)
2701 if (cfqq
->seeky_start
&&
2702 time_after(jiffies
, cfqq
->seeky_start
+ CFQQ_COOP_TOUT
))
2708 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
2709 * was the last process referring to said cfqq.
2711 static struct cfq_queue
*
2712 split_cfqq(struct cfq_io_context
*cic
, struct cfq_queue
*cfqq
)
2714 if (cfqq_process_refs(cfqq
) == 1) {
2715 cfqq
->seeky_start
= 0;
2716 cfqq
->pid
= current
->pid
;
2717 cfq_clear_cfqq_coop(cfqq
);
2721 cic_set_cfqq(cic
, NULL
, 1);
2722 cfq_put_queue(cfqq
);
2726 * Allocate cfq data structures associated with this request.
2729 cfq_set_request(struct request_queue
*q
, struct request
*rq
, gfp_t gfp_mask
)
2731 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
2732 struct cfq_io_context
*cic
;
2733 const int rw
= rq_data_dir(rq
);
2734 const bool is_sync
= rq_is_sync(rq
);
2735 struct cfq_queue
*cfqq
;
2736 unsigned long flags
;
2738 might_sleep_if(gfp_mask
& __GFP_WAIT
);
2740 cic
= cfq_get_io_context(cfqd
, gfp_mask
);
2742 spin_lock_irqsave(q
->queue_lock
, flags
);
2748 cfqq
= cic_to_cfqq(cic
, is_sync
);
2749 if (!cfqq
|| cfqq
== &cfqd
->oom_cfqq
) {
2750 cfqq
= cfq_get_queue(cfqd
, is_sync
, cic
->ioc
, gfp_mask
);
2751 cic_set_cfqq(cic
, cfqq
, is_sync
);
2754 * If the queue was seeky for too long, break it apart.
2756 if (cfq_cfqq_coop(cfqq
) && should_split_cfqq(cfqq
)) {
2757 cfq_log_cfqq(cfqd
, cfqq
, "breaking apart cfqq");
2758 cfqq
= split_cfqq(cic
, cfqq
);
2764 * Check to see if this queue is scheduled to merge with
2765 * another, closely cooperating queue. The merging of
2766 * queues happens here as it must be done in process context.
2767 * The reference on new_cfqq was taken in merge_cfqqs.
2770 cfqq
= cfq_merge_cfqqs(cfqd
, cic
, cfqq
);
2773 cfqq
->allocated
[rw
]++;
2774 atomic_inc(&cfqq
->ref
);
2776 spin_unlock_irqrestore(q
->queue_lock
, flags
);
2778 rq
->elevator_private
= cic
;
2779 rq
->elevator_private2
= cfqq
;
2784 put_io_context(cic
->ioc
);
2786 cfq_schedule_dispatch(cfqd
);
2787 spin_unlock_irqrestore(q
->queue_lock
, flags
);
2788 cfq_log(cfqd
, "set_request fail");
2792 static void cfq_kick_queue(struct work_struct
*work
)
2794 struct cfq_data
*cfqd
=
2795 container_of(work
, struct cfq_data
, unplug_work
);
2796 struct request_queue
*q
= cfqd
->queue
;
2798 spin_lock_irq(q
->queue_lock
);
2799 __blk_run_queue(cfqd
->queue
);
2800 spin_unlock_irq(q
->queue_lock
);
2804 * Timer running if the active_queue is currently idling inside its time slice
2806 static void cfq_idle_slice_timer(unsigned long data
)
2808 struct cfq_data
*cfqd
= (struct cfq_data
*) data
;
2809 struct cfq_queue
*cfqq
;
2810 unsigned long flags
;
2813 cfq_log(cfqd
, "idle timer fired");
2815 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
2817 cfqq
= cfqd
->active_queue
;
2822 * We saw a request before the queue expired, let it through
2824 if (cfq_cfqq_must_dispatch(cfqq
))
2830 if (cfq_slice_used(cfqq
))
2834 * only expire and reinvoke request handler, if there are
2835 * other queues with pending requests
2837 if (!cfqd
->busy_queues
)
2841 * not expired and it has a request pending, let it dispatch
2843 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
))
2847 cfq_slice_expired(cfqd
, timed_out
);
2849 cfq_schedule_dispatch(cfqd
);
2851 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2854 static void cfq_shutdown_timer_wq(struct cfq_data
*cfqd
)
2856 del_timer_sync(&cfqd
->idle_slice_timer
);
2857 cancel_work_sync(&cfqd
->unplug_work
);
2860 static void cfq_put_async_queues(struct cfq_data
*cfqd
)
2864 for (i
= 0; i
< IOPRIO_BE_NR
; i
++) {
2865 if (cfqd
->async_cfqq
[0][i
])
2866 cfq_put_queue(cfqd
->async_cfqq
[0][i
]);
2867 if (cfqd
->async_cfqq
[1][i
])
2868 cfq_put_queue(cfqd
->async_cfqq
[1][i
]);
2871 if (cfqd
->async_idle_cfqq
)
2872 cfq_put_queue(cfqd
->async_idle_cfqq
);
2875 static void cfq_exit_queue(struct elevator_queue
*e
)
2877 struct cfq_data
*cfqd
= e
->elevator_data
;
2878 struct request_queue
*q
= cfqd
->queue
;
2880 cfq_shutdown_timer_wq(cfqd
);
2882 spin_lock_irq(q
->queue_lock
);
2884 if (cfqd
->active_queue
)
2885 __cfq_slice_expired(cfqd
, cfqd
->active_queue
, 0);
2887 while (!list_empty(&cfqd
->cic_list
)) {
2888 struct cfq_io_context
*cic
= list_entry(cfqd
->cic_list
.next
,
2889 struct cfq_io_context
,
2892 __cfq_exit_single_io_context(cfqd
, cic
);
2895 cfq_put_async_queues(cfqd
);
2897 spin_unlock_irq(q
->queue_lock
);
2899 cfq_shutdown_timer_wq(cfqd
);
2904 static void *cfq_init_queue(struct request_queue
*q
)
2906 struct cfq_data
*cfqd
;
2909 cfqd
= kmalloc_node(sizeof(*cfqd
), GFP_KERNEL
| __GFP_ZERO
, q
->node
);
2913 for (i
= 0; i
< 2; ++i
)
2914 for (j
= 0; j
< 3; ++j
)
2915 cfqd
->service_trees
[i
][j
] = CFQ_RB_ROOT
;
2916 cfqd
->service_tree_idle
= CFQ_RB_ROOT
;
2919 * Not strictly needed (since RB_ROOT just clears the node and we
2920 * zeroed cfqd on alloc), but better be safe in case someone decides
2921 * to add magic to the rb code
2923 for (i
= 0; i
< CFQ_PRIO_LISTS
; i
++)
2924 cfqd
->prio_trees
[i
] = RB_ROOT
;
2927 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
2928 * Grab a permanent reference to it, so that the normal code flow
2929 * will not attempt to free it.
2931 cfq_init_cfqq(cfqd
, &cfqd
->oom_cfqq
, 1, 0);
2932 atomic_inc(&cfqd
->oom_cfqq
.ref
);
2934 INIT_LIST_HEAD(&cfqd
->cic_list
);
2938 init_timer(&cfqd
->idle_slice_timer
);
2939 cfqd
->idle_slice_timer
.function
= cfq_idle_slice_timer
;
2940 cfqd
->idle_slice_timer
.data
= (unsigned long) cfqd
;
2942 INIT_WORK(&cfqd
->unplug_work
, cfq_kick_queue
);
2944 cfqd
->cfq_quantum
= cfq_quantum
;
2945 cfqd
->cfq_fifo_expire
[0] = cfq_fifo_expire
[0];
2946 cfqd
->cfq_fifo_expire
[1] = cfq_fifo_expire
[1];
2947 cfqd
->cfq_back_max
= cfq_back_max
;
2948 cfqd
->cfq_back_penalty
= cfq_back_penalty
;
2949 cfqd
->cfq_slice
[0] = cfq_slice_async
;
2950 cfqd
->cfq_slice
[1] = cfq_slice_sync
;
2951 cfqd
->cfq_slice_async_rq
= cfq_slice_async_rq
;
2952 cfqd
->cfq_slice_idle
= cfq_slice_idle
;
2953 cfqd
->cfq_latency
= 1;
2955 cfqd
->last_end_sync_rq
= jiffies
;
2959 static void cfq_slab_kill(void)
2962 * Caller already ensured that pending RCU callbacks are completed,
2963 * so we should have no busy allocations at this point.
2966 kmem_cache_destroy(cfq_pool
);
2968 kmem_cache_destroy(cfq_ioc_pool
);
2971 static int __init
cfq_slab_setup(void)
2973 cfq_pool
= KMEM_CACHE(cfq_queue
, 0);
2977 cfq_ioc_pool
= KMEM_CACHE(cfq_io_context
, 0);
2988 * sysfs parts below -->
2991 cfq_var_show(unsigned int var
, char *page
)
2993 return sprintf(page
, "%d\n", var
);
2997 cfq_var_store(unsigned int *var
, const char *page
, size_t count
)
2999 char *p
= (char *) page
;
3001 *var
= simple_strtoul(p
, &p
, 10);
3005 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
3006 static ssize_t __FUNC(struct elevator_queue *e, char *page) \
3008 struct cfq_data *cfqd = e->elevator_data; \
3009 unsigned int __data = __VAR; \
3011 __data = jiffies_to_msecs(__data); \
3012 return cfq_var_show(__data, (page)); \
3014 SHOW_FUNCTION(cfq_quantum_show
, cfqd
->cfq_quantum
, 0);
3015 SHOW_FUNCTION(cfq_fifo_expire_sync_show
, cfqd
->cfq_fifo_expire
[1], 1);
3016 SHOW_FUNCTION(cfq_fifo_expire_async_show
, cfqd
->cfq_fifo_expire
[0], 1);
3017 SHOW_FUNCTION(cfq_back_seek_max_show
, cfqd
->cfq_back_max
, 0);
3018 SHOW_FUNCTION(cfq_back_seek_penalty_show
, cfqd
->cfq_back_penalty
, 0);
3019 SHOW_FUNCTION(cfq_slice_idle_show
, cfqd
->cfq_slice_idle
, 1);
3020 SHOW_FUNCTION(cfq_slice_sync_show
, cfqd
->cfq_slice
[1], 1);
3021 SHOW_FUNCTION(cfq_slice_async_show
, cfqd
->cfq_slice
[0], 1);
3022 SHOW_FUNCTION(cfq_slice_async_rq_show
, cfqd
->cfq_slice_async_rq
, 0);
3023 SHOW_FUNCTION(cfq_low_latency_show
, cfqd
->cfq_latency
, 0);
3024 #undef SHOW_FUNCTION
3026 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
3027 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3029 struct cfq_data *cfqd = e->elevator_data; \
3030 unsigned int __data; \
3031 int ret = cfq_var_store(&__data, (page), count); \
3032 if (__data < (MIN)) \
3034 else if (__data > (MAX)) \
3037 *(__PTR) = msecs_to_jiffies(__data); \
3039 *(__PTR) = __data; \
3042 STORE_FUNCTION(cfq_quantum_store
, &cfqd
->cfq_quantum
, 1, UINT_MAX
, 0);
3043 STORE_FUNCTION(cfq_fifo_expire_sync_store
, &cfqd
->cfq_fifo_expire
[1], 1,
3045 STORE_FUNCTION(cfq_fifo_expire_async_store
, &cfqd
->cfq_fifo_expire
[0], 1,
3047 STORE_FUNCTION(cfq_back_seek_max_store
, &cfqd
->cfq_back_max
, 0, UINT_MAX
, 0);
3048 STORE_FUNCTION(cfq_back_seek_penalty_store
, &cfqd
->cfq_back_penalty
, 1,
3050 STORE_FUNCTION(cfq_slice_idle_store
, &cfqd
->cfq_slice_idle
, 0, UINT_MAX
, 1);
3051 STORE_FUNCTION(cfq_slice_sync_store
, &cfqd
->cfq_slice
[1], 1, UINT_MAX
, 1);
3052 STORE_FUNCTION(cfq_slice_async_store
, &cfqd
->cfq_slice
[0], 1, UINT_MAX
, 1);
3053 STORE_FUNCTION(cfq_slice_async_rq_store
, &cfqd
->cfq_slice_async_rq
, 1,
3055 STORE_FUNCTION(cfq_low_latency_store
, &cfqd
->cfq_latency
, 0, 1, 0);
3056 #undef STORE_FUNCTION
3058 #define CFQ_ATTR(name) \
3059 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3061 static struct elv_fs_entry cfq_attrs
[] = {
3063 CFQ_ATTR(fifo_expire_sync
),
3064 CFQ_ATTR(fifo_expire_async
),
3065 CFQ_ATTR(back_seek_max
),
3066 CFQ_ATTR(back_seek_penalty
),
3067 CFQ_ATTR(slice_sync
),
3068 CFQ_ATTR(slice_async
),
3069 CFQ_ATTR(slice_async_rq
),
3070 CFQ_ATTR(slice_idle
),
3071 CFQ_ATTR(low_latency
),
3075 static struct elevator_type iosched_cfq
= {
3077 .elevator_merge_fn
= cfq_merge
,
3078 .elevator_merged_fn
= cfq_merged_request
,
3079 .elevator_merge_req_fn
= cfq_merged_requests
,
3080 .elevator_allow_merge_fn
= cfq_allow_merge
,
3081 .elevator_dispatch_fn
= cfq_dispatch_requests
,
3082 .elevator_add_req_fn
= cfq_insert_request
,
3083 .elevator_activate_req_fn
= cfq_activate_request
,
3084 .elevator_deactivate_req_fn
= cfq_deactivate_request
,
3085 .elevator_queue_empty_fn
= cfq_queue_empty
,
3086 .elevator_completed_req_fn
= cfq_completed_request
,
3087 .elevator_former_req_fn
= elv_rb_former_request
,
3088 .elevator_latter_req_fn
= elv_rb_latter_request
,
3089 .elevator_set_req_fn
= cfq_set_request
,
3090 .elevator_put_req_fn
= cfq_put_request
,
3091 .elevator_may_queue_fn
= cfq_may_queue
,
3092 .elevator_init_fn
= cfq_init_queue
,
3093 .elevator_exit_fn
= cfq_exit_queue
,
3094 .trim
= cfq_free_io_context
,
3096 .elevator_attrs
= cfq_attrs
,
3097 .elevator_name
= "cfq",
3098 .elevator_owner
= THIS_MODULE
,
3101 static int __init
cfq_init(void)
3104 * could be 0 on HZ < 1000 setups
3106 if (!cfq_slice_async
)
3107 cfq_slice_async
= 1;
3108 if (!cfq_slice_idle
)
3111 if (cfq_slab_setup())
3114 elv_register(&iosched_cfq
);
3119 static void __exit
cfq_exit(void)
3121 DECLARE_COMPLETION_ONSTACK(all_gone
);
3122 elv_unregister(&iosched_cfq
);
3123 ioc_gone
= &all_gone
;
3124 /* ioc_gone's update must be visible before reading ioc_count */
3128 * this also protects us from entering cfq_slab_kill() with
3129 * pending RCU callbacks
3131 if (elv_ioc_count_read(cfq_ioc_count
))
3132 wait_for_completion(&all_gone
);
3136 module_init(cfq_init
);
3137 module_exit(cfq_exit
);
3139 MODULE_AUTHOR("Jens Axboe");
3140 MODULE_LICENSE("GPL");
3141 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");