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>
16 #include "blk-cgroup.h"
21 /* max queue in one round of service */
22 static const int cfq_quantum
= 4;
23 static const int cfq_fifo_expire
[2] = { HZ
/ 4, HZ
/ 8 };
24 /* maximum backwards seek, in KiB */
25 static const int cfq_back_max
= 16 * 1024;
26 /* penalty of a backwards seek */
27 static const int cfq_back_penalty
= 2;
28 static const int cfq_slice_sync
= HZ
/ 10;
29 static int cfq_slice_async
= HZ
/ 25;
30 static const int cfq_slice_async_rq
= 2;
31 static int cfq_slice_idle
= HZ
/ 125;
32 static const int cfq_target_latency
= HZ
* 3/10; /* 300 ms */
33 static const int cfq_hist_divisor
= 4;
36 * offset from end of service tree
38 #define CFQ_IDLE_DELAY (HZ / 5)
41 * below this threshold, we consider thinktime immediate
43 #define CFQ_MIN_TT (2)
46 * Allow merged cfqqs to perform this amount of seeky I/O before
47 * deciding to break the queues up again.
49 #define CFQQ_COOP_TOUT (HZ)
51 #define CFQ_SLICE_SCALE (5)
52 #define CFQ_HW_QUEUE_MIN (5)
53 #define CFQ_SERVICE_SHIFT 12
56 ((struct cfq_io_context *) (rq)->elevator_private)
57 #define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2)
59 static struct kmem_cache
*cfq_pool
;
60 static struct kmem_cache
*cfq_ioc_pool
;
62 static DEFINE_PER_CPU(unsigned long, cfq_ioc_count
);
63 static struct completion
*ioc_gone
;
64 static DEFINE_SPINLOCK(ioc_gone_lock
);
66 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
67 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
68 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
70 #define sample_valid(samples) ((samples) > 80)
71 #define rb_entry_cfqg(node) rb_entry((node), struct cfq_group, rb_node)
74 * Most of our rbtree usage is for sorting with min extraction, so
75 * if we cache the leftmost node we don't have to walk down the tree
76 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
77 * move this into the elevator for the rq sorting as well.
84 struct rb_node
*active
;
85 unsigned total_weight
;
87 #define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, 0, 0, }
90 * Per process-grouping structure
95 /* various state flags, see below */
98 struct cfq_data
*cfqd
;
99 /* service_tree member */
100 struct rb_node rb_node
;
101 /* service_tree key */
102 unsigned long rb_key
;
103 /* prio tree member */
104 struct rb_node p_node
;
105 /* prio tree root we belong to, if any */
106 struct rb_root
*p_root
;
107 /* sorted list of pending requests */
108 struct rb_root sort_list
;
109 /* if fifo isn't expired, next request to serve */
110 struct request
*next_rq
;
111 /* requests queued in sort_list */
113 /* currently allocated requests */
115 /* fifo list of requests in sort_list */
116 struct list_head fifo
;
118 /* time when queue got scheduled in to dispatch first request. */
119 unsigned long dispatch_start
;
120 /* time when first request from queue completed and slice started. */
121 unsigned long slice_start
;
122 unsigned long slice_end
;
124 unsigned int slice_dispatch
;
126 /* pending metadata requests */
128 /* number of requests that are on the dispatch list or inside driver */
131 /* io prio of this group */
132 unsigned short ioprio
, org_ioprio
;
133 unsigned short ioprio_class
, org_ioprio_class
;
135 unsigned int seek_samples
;
138 sector_t last_request_pos
;
139 unsigned long seeky_start
;
143 struct cfq_rb_root
*service_tree
;
144 struct cfq_queue
*new_cfqq
;
145 struct cfq_group
*cfqg
;
146 /* Sectors dispatched in current dispatch round */
147 unsigned long nr_sectors
;
151 * First index in the service_trees.
152 * IDLE is handled separately, so it has negative index
161 * Second index in the service_trees.
165 SYNC_NOIDLE_WORKLOAD
= 1,
169 /* This is per cgroup per device grouping structure */
171 /* group service_tree member */
172 struct rb_node rb_node
;
174 /* group service_tree key */
179 /* number of cfqq currently on this group */
182 /* Per group busy queus average. Useful for workload slice calc. */
183 unsigned int busy_queues_avg
[2];
185 * rr lists of queues with requests, onle rr for each priority class.
186 * Counts are embedded in the cfq_rb_root
188 struct cfq_rb_root service_trees
[2][3];
189 struct cfq_rb_root service_tree_idle
;
191 unsigned long saved_workload_slice
;
192 enum wl_type_t saved_workload
;
193 enum wl_prio_t saved_serving_prio
;
194 struct blkio_group blkg
;
195 #ifdef CONFIG_CFQ_GROUP_IOSCHED
196 struct hlist_node cfqd_node
;
202 * Per block device queue structure
205 struct request_queue
*queue
;
206 /* Root service tree for cfq_groups */
207 struct cfq_rb_root grp_service_tree
;
208 struct cfq_group root_group
;
209 /* Number of active cfq groups on group service tree */
213 * The priority currently being served
215 enum wl_prio_t serving_prio
;
216 enum wl_type_t serving_type
;
217 unsigned long workload_expires
;
218 struct cfq_group
*serving_group
;
219 bool noidle_tree_requires_idle
;
222 * Each priority tree is sorted by next_request position. These
223 * trees are used when determining if two or more queues are
224 * interleaving requests (see cfq_close_cooperator).
226 struct rb_root prio_trees
[CFQ_PRIO_LISTS
];
228 unsigned int busy_queues
;
234 * queue-depth detection
240 * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
241 * 1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
244 int hw_tag_est_depth
;
245 unsigned int hw_tag_samples
;
248 * idle window management
250 struct timer_list idle_slice_timer
;
251 struct work_struct unplug_work
;
253 struct cfq_queue
*active_queue
;
254 struct cfq_io_context
*active_cic
;
257 * async queue for each priority case
259 struct cfq_queue
*async_cfqq
[2][IOPRIO_BE_NR
];
260 struct cfq_queue
*async_idle_cfqq
;
262 sector_t last_position
;
265 * tunables, see top of file
267 unsigned int cfq_quantum
;
268 unsigned int cfq_fifo_expire
[2];
269 unsigned int cfq_back_penalty
;
270 unsigned int cfq_back_max
;
271 unsigned int cfq_slice
[2];
272 unsigned int cfq_slice_async_rq
;
273 unsigned int cfq_slice_idle
;
274 unsigned int cfq_latency
;
276 struct list_head cic_list
;
279 * Fallback dummy cfqq for extreme OOM conditions
281 struct cfq_queue oom_cfqq
;
283 unsigned long last_end_sync_rq
;
285 /* List of cfq groups being managed on this device*/
286 struct hlist_head cfqg_list
;
289 static struct cfq_group
*cfq_get_next_cfqg(struct cfq_data
*cfqd
);
291 static struct cfq_rb_root
*service_tree_for(struct cfq_group
*cfqg
,
294 struct cfq_data
*cfqd
)
299 if (prio
== IDLE_WORKLOAD
)
300 return &cfqg
->service_tree_idle
;
302 return &cfqg
->service_trees
[prio
][type
];
305 enum cfqq_state_flags
{
306 CFQ_CFQQ_FLAG_on_rr
= 0, /* on round-robin busy list */
307 CFQ_CFQQ_FLAG_wait_request
, /* waiting for a request */
308 CFQ_CFQQ_FLAG_must_dispatch
, /* must be allowed a dispatch */
309 CFQ_CFQQ_FLAG_must_alloc_slice
, /* per-slice must_alloc flag */
310 CFQ_CFQQ_FLAG_fifo_expire
, /* FIFO checked in this slice */
311 CFQ_CFQQ_FLAG_idle_window
, /* slice idling enabled */
312 CFQ_CFQQ_FLAG_prio_changed
, /* task priority has changed */
313 CFQ_CFQQ_FLAG_slice_new
, /* no requests dispatched in slice */
314 CFQ_CFQQ_FLAG_sync
, /* synchronous queue */
315 CFQ_CFQQ_FLAG_coop
, /* cfqq is shared */
316 CFQ_CFQQ_FLAG_deep
, /* sync cfqq experienced large depth */
319 #define CFQ_CFQQ_FNS(name) \
320 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
322 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
324 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
326 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
328 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
330 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
334 CFQ_CFQQ_FNS(wait_request
);
335 CFQ_CFQQ_FNS(must_dispatch
);
336 CFQ_CFQQ_FNS(must_alloc_slice
);
337 CFQ_CFQQ_FNS(fifo_expire
);
338 CFQ_CFQQ_FNS(idle_window
);
339 CFQ_CFQQ_FNS(prio_changed
);
340 CFQ_CFQQ_FNS(slice_new
);
346 #ifdef CONFIG_DEBUG_CFQ_IOSCHED
347 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
348 blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
349 cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
350 blkg_path(&(cfqq)->cfqg->blkg), ##args);
352 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...) \
353 blk_add_trace_msg((cfqd)->queue, "%s " fmt, \
354 blkg_path(&(cfqg)->blkg), ##args); \
357 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
358 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
359 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...) do {} while (0);
361 #define cfq_log(cfqd, fmt, args...) \
362 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
364 /* Traverses through cfq group service trees */
365 #define for_each_cfqg_st(cfqg, i, j, st) \
366 for (i = 0; i <= IDLE_WORKLOAD; i++) \
367 for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
368 : &cfqg->service_tree_idle; \
369 (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
370 (i == IDLE_WORKLOAD && j == 0); \
371 j++, st = i < IDLE_WORKLOAD ? \
372 &cfqg->service_trees[i][j]: NULL) \
375 static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
377 if (cfq_class_idle(cfqq
))
378 return IDLE_WORKLOAD
;
379 if (cfq_class_rt(cfqq
))
385 static enum wl_type_t
cfqq_type(struct cfq_queue
*cfqq
)
387 if (!cfq_cfqq_sync(cfqq
))
388 return ASYNC_WORKLOAD
;
389 if (!cfq_cfqq_idle_window(cfqq
))
390 return SYNC_NOIDLE_WORKLOAD
;
391 return SYNC_WORKLOAD
;
394 static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl
,
395 struct cfq_data
*cfqd
,
396 struct cfq_group
*cfqg
)
398 if (wl
== IDLE_WORKLOAD
)
399 return cfqg
->service_tree_idle
.count
;
401 return cfqg
->service_trees
[wl
][ASYNC_WORKLOAD
].count
402 + cfqg
->service_trees
[wl
][SYNC_NOIDLE_WORKLOAD
].count
403 + cfqg
->service_trees
[wl
][SYNC_WORKLOAD
].count
;
406 static void cfq_dispatch_insert(struct request_queue
*, struct request
*);
407 static struct cfq_queue
*cfq_get_queue(struct cfq_data
*, bool,
408 struct io_context
*, gfp_t
);
409 static struct cfq_io_context
*cfq_cic_lookup(struct cfq_data
*,
410 struct io_context
*);
412 static inline int rq_in_driver(struct cfq_data
*cfqd
)
414 return cfqd
->rq_in_driver
[0] + cfqd
->rq_in_driver
[1];
417 static inline struct cfq_queue
*cic_to_cfqq(struct cfq_io_context
*cic
,
420 return cic
->cfqq
[is_sync
];
423 static inline void cic_set_cfqq(struct cfq_io_context
*cic
,
424 struct cfq_queue
*cfqq
, bool is_sync
)
426 cic
->cfqq
[is_sync
] = cfqq
;
430 * We regard a request as SYNC, if it's either a read or has the SYNC bit
431 * set (in which case it could also be direct WRITE).
433 static inline bool cfq_bio_sync(struct bio
*bio
)
435 return bio_data_dir(bio
) == READ
|| bio_rw_flagged(bio
, BIO_RW_SYNCIO
);
439 * scheduler run of queue, if there are requests pending and no one in the
440 * driver that will restart queueing
442 static inline void cfq_schedule_dispatch(struct cfq_data
*cfqd
)
444 if (cfqd
->busy_queues
) {
445 cfq_log(cfqd
, "schedule dispatch");
446 kblockd_schedule_work(cfqd
->queue
, &cfqd
->unplug_work
);
450 static int cfq_queue_empty(struct request_queue
*q
)
452 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
454 return !cfqd
->rq_queued
;
458 * Scale schedule slice based on io priority. Use the sync time slice only
459 * if a queue is marked sync and has sync io queued. A sync queue with async
460 * io only, should not get full sync slice length.
462 static inline int cfq_prio_slice(struct cfq_data
*cfqd
, bool sync
,
465 const int base_slice
= cfqd
->cfq_slice
[sync
];
467 WARN_ON(prio
>= IOPRIO_BE_NR
);
469 return base_slice
+ (base_slice
/CFQ_SLICE_SCALE
* (4 - prio
));
473 cfq_prio_to_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
475 return cfq_prio_slice(cfqd
, cfq_cfqq_sync(cfqq
), cfqq
->ioprio
);
478 static inline u64
cfq_scale_slice(unsigned long delta
, struct cfq_group
*cfqg
)
480 u64 d
= delta
<< CFQ_SERVICE_SHIFT
;
482 d
= d
* BLKIO_WEIGHT_DEFAULT
;
483 do_div(d
, cfqg
->weight
);
487 static inline u64
max_vdisktime(u64 min_vdisktime
, u64 vdisktime
)
489 s64 delta
= (s64
)(vdisktime
- min_vdisktime
);
491 min_vdisktime
= vdisktime
;
493 return min_vdisktime
;
496 static inline u64
min_vdisktime(u64 min_vdisktime
, u64 vdisktime
)
498 s64 delta
= (s64
)(vdisktime
- min_vdisktime
);
500 min_vdisktime
= vdisktime
;
502 return min_vdisktime
;
505 static void update_min_vdisktime(struct cfq_rb_root
*st
)
507 u64 vdisktime
= st
->min_vdisktime
;
508 struct cfq_group
*cfqg
;
511 cfqg
= rb_entry_cfqg(st
->active
);
512 vdisktime
= cfqg
->vdisktime
;
516 cfqg
= rb_entry_cfqg(st
->left
);
517 vdisktime
= min_vdisktime(vdisktime
, cfqg
->vdisktime
);
520 st
->min_vdisktime
= max_vdisktime(st
->min_vdisktime
, vdisktime
);
524 * get averaged number of queues of RT/BE priority.
525 * average is updated, with a formula that gives more weight to higher numbers,
526 * to quickly follows sudden increases and decrease slowly
529 static inline unsigned cfq_group_get_avg_queues(struct cfq_data
*cfqd
,
530 struct cfq_group
*cfqg
, bool rt
)
532 unsigned min_q
, max_q
;
533 unsigned mult
= cfq_hist_divisor
- 1;
534 unsigned round
= cfq_hist_divisor
/ 2;
535 unsigned busy
= cfq_group_busy_queues_wl(rt
, cfqd
, cfqg
);
537 min_q
= min(cfqg
->busy_queues_avg
[rt
], busy
);
538 max_q
= max(cfqg
->busy_queues_avg
[rt
], busy
);
539 cfqg
->busy_queues_avg
[rt
] = (mult
* max_q
+ min_q
+ round
) /
541 return cfqg
->busy_queues_avg
[rt
];
544 static inline unsigned
545 cfq_group_slice(struct cfq_data
*cfqd
, struct cfq_group
*cfqg
)
547 struct cfq_rb_root
*st
= &cfqd
->grp_service_tree
;
549 return cfq_target_latency
* cfqg
->weight
/ st
->total_weight
;
553 cfq_set_prio_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
555 unsigned slice
= cfq_prio_to_slice(cfqd
, cfqq
);
556 if (cfqd
->cfq_latency
) {
558 * interested queues (we consider only the ones with the same
559 * priority class in the cfq group)
561 unsigned iq
= cfq_group_get_avg_queues(cfqd
, cfqq
->cfqg
,
563 unsigned sync_slice
= cfqd
->cfq_slice
[1];
564 unsigned expect_latency
= sync_slice
* iq
;
565 unsigned group_slice
= cfq_group_slice(cfqd
, cfqq
->cfqg
);
567 if (expect_latency
> group_slice
) {
568 unsigned base_low_slice
= 2 * cfqd
->cfq_slice_idle
;
569 /* scale low_slice according to IO priority
570 * and sync vs async */
572 min(slice
, base_low_slice
* slice
/ sync_slice
);
573 /* the adapted slice value is scaled to fit all iqs
574 * into the target latency */
575 slice
= max(slice
* group_slice
/ expect_latency
,
579 cfqq
->slice_start
= jiffies
;
580 cfqq
->slice_end
= jiffies
+ slice
;
581 cfq_log_cfqq(cfqd
, cfqq
, "set_slice=%lu", cfqq
->slice_end
- jiffies
);
585 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
586 * isn't valid until the first request from the dispatch is activated
587 * and the slice time set.
589 static inline bool cfq_slice_used(struct cfq_queue
*cfqq
)
591 if (cfq_cfqq_slice_new(cfqq
))
593 if (time_before(jiffies
, cfqq
->slice_end
))
600 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
601 * We choose the request that is closest to the head right now. Distance
602 * behind the head is penalized and only allowed to a certain extent.
604 static struct request
*
605 cfq_choose_req(struct cfq_data
*cfqd
, struct request
*rq1
, struct request
*rq2
, sector_t last
)
607 sector_t s1
, s2
, d1
= 0, d2
= 0;
608 unsigned long back_max
;
609 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
610 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
611 unsigned wrap
= 0; /* bit mask: requests behind the disk head? */
613 if (rq1
== NULL
|| rq1
== rq2
)
618 if (rq_is_sync(rq1
) && !rq_is_sync(rq2
))
620 else if (rq_is_sync(rq2
) && !rq_is_sync(rq1
))
622 if (rq_is_meta(rq1
) && !rq_is_meta(rq2
))
624 else if (rq_is_meta(rq2
) && !rq_is_meta(rq1
))
627 s1
= blk_rq_pos(rq1
);
628 s2
= blk_rq_pos(rq2
);
631 * by definition, 1KiB is 2 sectors
633 back_max
= cfqd
->cfq_back_max
* 2;
636 * Strict one way elevator _except_ in the case where we allow
637 * short backward seeks which are biased as twice the cost of a
638 * similar forward seek.
642 else if (s1
+ back_max
>= last
)
643 d1
= (last
- s1
) * cfqd
->cfq_back_penalty
;
645 wrap
|= CFQ_RQ1_WRAP
;
649 else if (s2
+ back_max
>= last
)
650 d2
= (last
- s2
) * cfqd
->cfq_back_penalty
;
652 wrap
|= CFQ_RQ2_WRAP
;
654 /* Found required data */
657 * By doing switch() on the bit mask "wrap" we avoid having to
658 * check two variables for all permutations: --> faster!
661 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
677 case (CFQ_RQ1_WRAP
|CFQ_RQ2_WRAP
): /* both rqs wrapped */
680 * Since both rqs are wrapped,
681 * start with the one that's further behind head
682 * (--> only *one* back seek required),
683 * since back seek takes more time than forward.
693 * The below is leftmost cache rbtree addon
695 static struct cfq_queue
*cfq_rb_first(struct cfq_rb_root
*root
)
697 /* Service tree is empty */
702 root
->left
= rb_first(&root
->rb
);
705 return rb_entry(root
->left
, struct cfq_queue
, rb_node
);
710 static struct cfq_group
*cfq_rb_first_group(struct cfq_rb_root
*root
)
713 root
->left
= rb_first(&root
->rb
);
716 return rb_entry_cfqg(root
->left
);
721 static void rb_erase_init(struct rb_node
*n
, struct rb_root
*root
)
727 static void cfq_rb_erase(struct rb_node
*n
, struct cfq_rb_root
*root
)
731 rb_erase_init(n
, &root
->rb
);
736 * would be nice to take fifo expire time into account as well
738 static struct request
*
739 cfq_find_next_rq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
740 struct request
*last
)
742 struct rb_node
*rbnext
= rb_next(&last
->rb_node
);
743 struct rb_node
*rbprev
= rb_prev(&last
->rb_node
);
744 struct request
*next
= NULL
, *prev
= NULL
;
746 BUG_ON(RB_EMPTY_NODE(&last
->rb_node
));
749 prev
= rb_entry_rq(rbprev
);
752 next
= rb_entry_rq(rbnext
);
754 rbnext
= rb_first(&cfqq
->sort_list
);
755 if (rbnext
&& rbnext
!= &last
->rb_node
)
756 next
= rb_entry_rq(rbnext
);
759 return cfq_choose_req(cfqd
, next
, prev
, blk_rq_pos(last
));
762 static unsigned long cfq_slice_offset(struct cfq_data
*cfqd
,
763 struct cfq_queue
*cfqq
)
766 * just an approximation, should be ok.
768 return (cfqq
->cfqg
->nr_cfqq
- 1) * (cfq_prio_slice(cfqd
, 1, 0) -
769 cfq_prio_slice(cfqd
, cfq_cfqq_sync(cfqq
), cfqq
->ioprio
));
773 cfqg_key(struct cfq_rb_root
*st
, struct cfq_group
*cfqg
)
775 return cfqg
->vdisktime
- st
->min_vdisktime
;
779 __cfq_group_service_tree_add(struct cfq_rb_root
*st
, struct cfq_group
*cfqg
)
781 struct rb_node
**node
= &st
->rb
.rb_node
;
782 struct rb_node
*parent
= NULL
;
783 struct cfq_group
*__cfqg
;
784 s64 key
= cfqg_key(st
, cfqg
);
787 while (*node
!= NULL
) {
789 __cfqg
= rb_entry_cfqg(parent
);
791 if (key
< cfqg_key(st
, __cfqg
))
792 node
= &parent
->rb_left
;
794 node
= &parent
->rb_right
;
800 st
->left
= &cfqg
->rb_node
;
802 rb_link_node(&cfqg
->rb_node
, parent
, node
);
803 rb_insert_color(&cfqg
->rb_node
, &st
->rb
);
807 cfq_group_service_tree_add(struct cfq_data
*cfqd
, struct cfq_group
*cfqg
)
809 struct cfq_rb_root
*st
= &cfqd
->grp_service_tree
;
810 struct cfq_group
*__cfqg
;
818 * Currently put the group at the end. Later implement something
819 * so that groups get lesser vtime based on their weights, so that
820 * if group does not loose all if it was not continously backlogged.
822 n
= rb_last(&st
->rb
);
824 __cfqg
= rb_entry_cfqg(n
);
825 cfqg
->vdisktime
= __cfqg
->vdisktime
+ CFQ_IDLE_DELAY
;
827 cfqg
->vdisktime
= st
->min_vdisktime
;
829 __cfq_group_service_tree_add(st
, cfqg
);
832 st
->total_weight
+= cfqg
->weight
;
836 cfq_group_service_tree_del(struct cfq_data
*cfqd
, struct cfq_group
*cfqg
)
838 struct cfq_rb_root
*st
= &cfqd
->grp_service_tree
;
840 if (st
->active
== &cfqg
->rb_node
)
843 BUG_ON(cfqg
->nr_cfqq
< 1);
846 /* If there are other cfq queues under this group, don't delete it */
850 cfq_log_cfqg(cfqd
, cfqg
, "del_from_rr group");
853 st
->total_weight
-= cfqg
->weight
;
854 if (!RB_EMPTY_NODE(&cfqg
->rb_node
))
855 cfq_rb_erase(&cfqg
->rb_node
, st
);
856 cfqg
->saved_workload_slice
= 0;
857 blkiocg_update_blkio_group_dequeue_stats(&cfqg
->blkg
, 1);
860 static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue
*cfqq
)
862 unsigned int slice_used
, allocated_slice
;
865 * Queue got expired before even a single request completed or
866 * got expired immediately after first request completion.
868 if (!cfqq
->slice_start
|| cfqq
->slice_start
== jiffies
) {
870 * Also charge the seek time incurred to the group, otherwise
871 * if there are mutiple queues in the group, each can dispatch
872 * a single request on seeky media and cause lots of seek time
873 * and group will never know it.
875 slice_used
= max_t(unsigned, (jiffies
- cfqq
->dispatch_start
),
878 slice_used
= jiffies
- cfqq
->slice_start
;
879 allocated_slice
= cfqq
->slice_end
- cfqq
->slice_start
;
880 if (slice_used
> allocated_slice
)
881 slice_used
= allocated_slice
;
884 cfq_log_cfqq(cfqq
->cfqd
, cfqq
, "sl_used=%u sect=%lu", slice_used
,
889 static void cfq_group_served(struct cfq_data
*cfqd
, struct cfq_group
*cfqg
,
890 struct cfq_queue
*cfqq
)
892 struct cfq_rb_root
*st
= &cfqd
->grp_service_tree
;
893 unsigned int used_sl
;
895 used_sl
= cfq_cfqq_slice_usage(cfqq
);
897 /* Can't update vdisktime while group is on service tree */
898 cfq_rb_erase(&cfqg
->rb_node
, st
);
899 cfqg
->vdisktime
+= cfq_scale_slice(used_sl
, cfqg
);
900 __cfq_group_service_tree_add(st
, cfqg
);
902 /* This group is being expired. Save the context */
903 if (time_after(cfqd
->workload_expires
, jiffies
)) {
904 cfqg
->saved_workload_slice
= cfqd
->workload_expires
906 cfqg
->saved_workload
= cfqd
->serving_type
;
907 cfqg
->saved_serving_prio
= cfqd
->serving_prio
;
909 cfqg
->saved_workload_slice
= 0;
911 cfq_log_cfqg(cfqd
, cfqg
, "served: vt=%llu min_vt=%llu", cfqg
->vdisktime
,
913 blkiocg_update_blkio_group_stats(&cfqg
->blkg
, used_sl
,
917 #ifdef CONFIG_CFQ_GROUP_IOSCHED
918 static inline struct cfq_group
*cfqg_of_blkg(struct blkio_group
*blkg
)
921 return container_of(blkg
, struct cfq_group
, blkg
);
925 static struct cfq_group
*
926 cfq_find_alloc_cfqg(struct cfq_data
*cfqd
, struct cgroup
*cgroup
, int create
)
928 struct blkio_cgroup
*blkcg
= cgroup_to_blkio_cgroup(cgroup
);
929 struct cfq_group
*cfqg
= NULL
;
932 struct cfq_rb_root
*st
;
933 struct backing_dev_info
*bdi
= &cfqd
->queue
->backing_dev_info
;
934 unsigned int major
, minor
;
936 /* Do we need to take this reference */
937 if (!css_tryget(&blkcg
->css
))
940 cfqg
= cfqg_of_blkg(blkiocg_lookup_group(blkcg
, key
));
944 cfqg
= kzalloc_node(sizeof(*cfqg
), GFP_ATOMIC
, cfqd
->queue
->node
);
948 cfqg
->weight
= blkcg
->weight
;
949 for_each_cfqg_st(cfqg
, i
, j
, st
)
951 RB_CLEAR_NODE(&cfqg
->rb_node
);
954 * Take the initial reference that will be released on destroy
955 * This can be thought of a joint reference by cgroup and
956 * elevator which will be dropped by either elevator exit
957 * or cgroup deletion path depending on who is exiting first.
959 atomic_set(&cfqg
->ref
, 1);
961 /* Add group onto cgroup list */
962 sscanf(dev_name(bdi
->dev
), "%u:%u", &major
, &minor
);
963 blkiocg_add_blkio_group(blkcg
, &cfqg
->blkg
, (void *)cfqd
,
964 MKDEV(major
, minor
));
966 /* Add group on cfqd list */
967 hlist_add_head(&cfqg
->cfqd_node
, &cfqd
->cfqg_list
);
970 css_put(&blkcg
->css
);
975 * Search for the cfq group current task belongs to. If create = 1, then also
976 * create the cfq group if it does not exist. request_queue lock must be held.
978 static struct cfq_group
*cfq_get_cfqg(struct cfq_data
*cfqd
, int create
)
980 struct cgroup
*cgroup
;
981 struct cfq_group
*cfqg
= NULL
;
984 cgroup
= task_cgroup(current
, blkio_subsys_id
);
985 cfqg
= cfq_find_alloc_cfqg(cfqd
, cgroup
, create
);
987 cfqg
= &cfqd
->root_group
;
992 static void cfq_link_cfqq_cfqg(struct cfq_queue
*cfqq
, struct cfq_group
*cfqg
)
994 /* Currently, all async queues are mapped to root group */
995 if (!cfq_cfqq_sync(cfqq
))
996 cfqg
= &cfqq
->cfqd
->root_group
;
999 /* cfqq reference on cfqg */
1000 atomic_inc(&cfqq
->cfqg
->ref
);
1003 static void cfq_put_cfqg(struct cfq_group
*cfqg
)
1005 struct cfq_rb_root
*st
;
1008 BUG_ON(atomic_read(&cfqg
->ref
) <= 0);
1009 if (!atomic_dec_and_test(&cfqg
->ref
))
1011 for_each_cfqg_st(cfqg
, i
, j
, st
)
1012 BUG_ON(!RB_EMPTY_ROOT(&st
->rb
) || st
->active
!= NULL
);
1016 static void cfq_destroy_cfqg(struct cfq_data
*cfqd
, struct cfq_group
*cfqg
)
1018 /* Something wrong if we are trying to remove same group twice */
1019 BUG_ON(hlist_unhashed(&cfqg
->cfqd_node
));
1021 hlist_del_init(&cfqg
->cfqd_node
);
1024 * Put the reference taken at the time of creation so that when all
1025 * queues are gone, group can be destroyed.
1030 static void cfq_release_cfq_groups(struct cfq_data
*cfqd
)
1032 struct hlist_node
*pos
, *n
;
1033 struct cfq_group
*cfqg
;
1035 hlist_for_each_entry_safe(cfqg
, pos
, n
, &cfqd
->cfqg_list
, cfqd_node
) {
1037 * If cgroup removal path got to blk_group first and removed
1038 * it from cgroup list, then it will take care of destroying
1041 if (!blkiocg_del_blkio_group(&cfqg
->blkg
))
1042 cfq_destroy_cfqg(cfqd
, cfqg
);
1047 * Blk cgroup controller notification saying that blkio_group object is being
1048 * delinked as associated cgroup object is going away. That also means that
1049 * no new IO will come in this group. So get rid of this group as soon as
1050 * any pending IO in the group is finished.
1052 * This function is called under rcu_read_lock(). key is the rcu protected
1053 * pointer. That means "key" is a valid cfq_data pointer as long as we are rcu
1056 * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
1057 * it should not be NULL as even if elevator was exiting, cgroup deltion
1058 * path got to it first.
1060 void cfq_unlink_blkio_group(void *key
, struct blkio_group
*blkg
)
1062 unsigned long flags
;
1063 struct cfq_data
*cfqd
= key
;
1065 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
1066 cfq_destroy_cfqg(cfqd
, cfqg_of_blkg(blkg
));
1067 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
1070 #else /* GROUP_IOSCHED */
1071 static struct cfq_group
*cfq_get_cfqg(struct cfq_data
*cfqd
, int create
)
1073 return &cfqd
->root_group
;
1076 cfq_link_cfqq_cfqg(struct cfq_queue
*cfqq
, struct cfq_group
*cfqg
) {
1080 static void cfq_release_cfq_groups(struct cfq_data
*cfqd
) {}
1081 static inline void cfq_put_cfqg(struct cfq_group
*cfqg
) {}
1083 #endif /* GROUP_IOSCHED */
1086 * The cfqd->service_trees holds all pending cfq_queue's that have
1087 * requests waiting to be processed. It is sorted in the order that
1088 * we will service the queues.
1090 static void cfq_service_tree_add(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1093 struct rb_node
**p
, *parent
;
1094 struct cfq_queue
*__cfqq
;
1095 unsigned long rb_key
;
1096 struct cfq_rb_root
*service_tree
;
1100 service_tree
= service_tree_for(cfqq
->cfqg
, cfqq_prio(cfqq
),
1101 cfqq_type(cfqq
), cfqd
);
1102 if (cfq_class_idle(cfqq
)) {
1103 rb_key
= CFQ_IDLE_DELAY
;
1104 parent
= rb_last(&service_tree
->rb
);
1105 if (parent
&& parent
!= &cfqq
->rb_node
) {
1106 __cfqq
= rb_entry(parent
, struct cfq_queue
, rb_node
);
1107 rb_key
+= __cfqq
->rb_key
;
1110 } else if (!add_front
) {
1112 * Get our rb key offset. Subtract any residual slice
1113 * value carried from last service. A negative resid
1114 * count indicates slice overrun, and this should position
1115 * the next service time further away in the tree.
1117 rb_key
= cfq_slice_offset(cfqd
, cfqq
) + jiffies
;
1118 rb_key
-= cfqq
->slice_resid
;
1119 cfqq
->slice_resid
= 0;
1122 __cfqq
= cfq_rb_first(service_tree
);
1123 rb_key
+= __cfqq
? __cfqq
->rb_key
: jiffies
;
1126 if (!RB_EMPTY_NODE(&cfqq
->rb_node
)) {
1129 * same position, nothing more to do
1131 if (rb_key
== cfqq
->rb_key
&&
1132 cfqq
->service_tree
== service_tree
)
1135 cfq_rb_erase(&cfqq
->rb_node
, cfqq
->service_tree
);
1136 cfqq
->service_tree
= NULL
;
1141 cfqq
->service_tree
= service_tree
;
1142 p
= &service_tree
->rb
.rb_node
;
1147 __cfqq
= rb_entry(parent
, struct cfq_queue
, rb_node
);
1150 * sort by key, that represents service time.
1152 if (time_before(rb_key
, __cfqq
->rb_key
))
1155 n
= &(*p
)->rb_right
;
1163 service_tree
->left
= &cfqq
->rb_node
;
1165 cfqq
->rb_key
= rb_key
;
1166 rb_link_node(&cfqq
->rb_node
, parent
, p
);
1167 rb_insert_color(&cfqq
->rb_node
, &service_tree
->rb
);
1168 service_tree
->count
++;
1169 if (add_front
|| !new_cfqq
)
1171 cfq_group_service_tree_add(cfqd
, cfqq
->cfqg
);
1174 static struct cfq_queue
*
1175 cfq_prio_tree_lookup(struct cfq_data
*cfqd
, struct rb_root
*root
,
1176 sector_t sector
, struct rb_node
**ret_parent
,
1177 struct rb_node
***rb_link
)
1179 struct rb_node
**p
, *parent
;
1180 struct cfq_queue
*cfqq
= NULL
;
1188 cfqq
= rb_entry(parent
, struct cfq_queue
, p_node
);
1191 * Sort strictly based on sector. Smallest to the left,
1192 * largest to the right.
1194 if (sector
> blk_rq_pos(cfqq
->next_rq
))
1195 n
= &(*p
)->rb_right
;
1196 else if (sector
< blk_rq_pos(cfqq
->next_rq
))
1204 *ret_parent
= parent
;
1210 static void cfq_prio_tree_add(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1212 struct rb_node
**p
, *parent
;
1213 struct cfq_queue
*__cfqq
;
1216 rb_erase(&cfqq
->p_node
, cfqq
->p_root
);
1217 cfqq
->p_root
= NULL
;
1220 if (cfq_class_idle(cfqq
))
1225 cfqq
->p_root
= &cfqd
->prio_trees
[cfqq
->org_ioprio
];
1226 __cfqq
= cfq_prio_tree_lookup(cfqd
, cfqq
->p_root
,
1227 blk_rq_pos(cfqq
->next_rq
), &parent
, &p
);
1229 rb_link_node(&cfqq
->p_node
, parent
, p
);
1230 rb_insert_color(&cfqq
->p_node
, cfqq
->p_root
);
1232 cfqq
->p_root
= NULL
;
1236 * Update cfqq's position in the service tree.
1238 static void cfq_resort_rr_list(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1241 * Resorting requires the cfqq to be on the RR list already.
1243 if (cfq_cfqq_on_rr(cfqq
)) {
1244 cfq_service_tree_add(cfqd
, cfqq
, 0);
1245 cfq_prio_tree_add(cfqd
, cfqq
);
1250 * add to busy list of queues for service, trying to be fair in ordering
1251 * the pending list according to last request service
1253 static void cfq_add_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1255 cfq_log_cfqq(cfqd
, cfqq
, "add_to_rr");
1256 BUG_ON(cfq_cfqq_on_rr(cfqq
));
1257 cfq_mark_cfqq_on_rr(cfqq
);
1258 cfqd
->busy_queues
++;
1260 cfq_resort_rr_list(cfqd
, cfqq
);
1264 * Called when the cfqq no longer has requests pending, remove it from
1267 static void cfq_del_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1269 cfq_log_cfqq(cfqd
, cfqq
, "del_from_rr");
1270 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
1271 cfq_clear_cfqq_on_rr(cfqq
);
1273 if (!RB_EMPTY_NODE(&cfqq
->rb_node
)) {
1274 cfq_rb_erase(&cfqq
->rb_node
, cfqq
->service_tree
);
1275 cfqq
->service_tree
= NULL
;
1278 rb_erase(&cfqq
->p_node
, cfqq
->p_root
);
1279 cfqq
->p_root
= NULL
;
1282 cfq_group_service_tree_del(cfqd
, cfqq
->cfqg
);
1283 BUG_ON(!cfqd
->busy_queues
);
1284 cfqd
->busy_queues
--;
1288 * rb tree support functions
1290 static void cfq_del_rq_rb(struct request
*rq
)
1292 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1293 const int sync
= rq_is_sync(rq
);
1295 BUG_ON(!cfqq
->queued
[sync
]);
1296 cfqq
->queued
[sync
]--;
1298 elv_rb_del(&cfqq
->sort_list
, rq
);
1300 if (cfq_cfqq_on_rr(cfqq
) && RB_EMPTY_ROOT(&cfqq
->sort_list
)) {
1302 * Queue will be deleted from service tree when we actually
1303 * expire it later. Right now just remove it from prio tree
1307 rb_erase(&cfqq
->p_node
, cfqq
->p_root
);
1308 cfqq
->p_root
= NULL
;
1313 static void cfq_add_rq_rb(struct request
*rq
)
1315 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1316 struct cfq_data
*cfqd
= cfqq
->cfqd
;
1317 struct request
*__alias
, *prev
;
1319 cfqq
->queued
[rq_is_sync(rq
)]++;
1322 * looks a little odd, but the first insert might return an alias.
1323 * if that happens, put the alias on the dispatch list
1325 while ((__alias
= elv_rb_add(&cfqq
->sort_list
, rq
)) != NULL
)
1326 cfq_dispatch_insert(cfqd
->queue
, __alias
);
1328 if (!cfq_cfqq_on_rr(cfqq
))
1329 cfq_add_cfqq_rr(cfqd
, cfqq
);
1332 * check if this request is a better next-serve candidate
1334 prev
= cfqq
->next_rq
;
1335 cfqq
->next_rq
= cfq_choose_req(cfqd
, cfqq
->next_rq
, rq
, cfqd
->last_position
);
1338 * adjust priority tree position, if ->next_rq changes
1340 if (prev
!= cfqq
->next_rq
)
1341 cfq_prio_tree_add(cfqd
, cfqq
);
1343 BUG_ON(!cfqq
->next_rq
);
1346 static void cfq_reposition_rq_rb(struct cfq_queue
*cfqq
, struct request
*rq
)
1348 elv_rb_del(&cfqq
->sort_list
, rq
);
1349 cfqq
->queued
[rq_is_sync(rq
)]--;
1353 static struct request
*
1354 cfq_find_rq_fmerge(struct cfq_data
*cfqd
, struct bio
*bio
)
1356 struct task_struct
*tsk
= current
;
1357 struct cfq_io_context
*cic
;
1358 struct cfq_queue
*cfqq
;
1360 cic
= cfq_cic_lookup(cfqd
, tsk
->io_context
);
1364 cfqq
= cic_to_cfqq(cic
, cfq_bio_sync(bio
));
1366 sector_t sector
= bio
->bi_sector
+ bio_sectors(bio
);
1368 return elv_rb_find(&cfqq
->sort_list
, sector
);
1374 static void cfq_activate_request(struct request_queue
*q
, struct request
*rq
)
1376 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1378 cfqd
->rq_in_driver
[rq_is_sync(rq
)]++;
1379 cfq_log_cfqq(cfqd
, RQ_CFQQ(rq
), "activate rq, drv=%d",
1380 rq_in_driver(cfqd
));
1382 cfqd
->last_position
= blk_rq_pos(rq
) + blk_rq_sectors(rq
);
1385 static void cfq_deactivate_request(struct request_queue
*q
, struct request
*rq
)
1387 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1388 const int sync
= rq_is_sync(rq
);
1390 WARN_ON(!cfqd
->rq_in_driver
[sync
]);
1391 cfqd
->rq_in_driver
[sync
]--;
1392 cfq_log_cfqq(cfqd
, RQ_CFQQ(rq
), "deactivate rq, drv=%d",
1393 rq_in_driver(cfqd
));
1396 static void cfq_remove_request(struct request
*rq
)
1398 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1400 if (cfqq
->next_rq
== rq
)
1401 cfqq
->next_rq
= cfq_find_next_rq(cfqq
->cfqd
, cfqq
, rq
);
1403 list_del_init(&rq
->queuelist
);
1406 cfqq
->cfqd
->rq_queued
--;
1407 if (rq_is_meta(rq
)) {
1408 WARN_ON(!cfqq
->meta_pending
);
1409 cfqq
->meta_pending
--;
1413 static int cfq_merge(struct request_queue
*q
, struct request
**req
,
1416 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1417 struct request
*__rq
;
1419 __rq
= cfq_find_rq_fmerge(cfqd
, bio
);
1420 if (__rq
&& elv_rq_merge_ok(__rq
, bio
)) {
1422 return ELEVATOR_FRONT_MERGE
;
1425 return ELEVATOR_NO_MERGE
;
1428 static void cfq_merged_request(struct request_queue
*q
, struct request
*req
,
1431 if (type
== ELEVATOR_FRONT_MERGE
) {
1432 struct cfq_queue
*cfqq
= RQ_CFQQ(req
);
1434 cfq_reposition_rq_rb(cfqq
, req
);
1439 cfq_merged_requests(struct request_queue
*q
, struct request
*rq
,
1440 struct request
*next
)
1442 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1444 * reposition in fifo if next is older than rq
1446 if (!list_empty(&rq
->queuelist
) && !list_empty(&next
->queuelist
) &&
1447 time_before(rq_fifo_time(next
), rq_fifo_time(rq
))) {
1448 list_move(&rq
->queuelist
, &next
->queuelist
);
1449 rq_set_fifo_time(rq
, rq_fifo_time(next
));
1452 if (cfqq
->next_rq
== next
)
1454 cfq_remove_request(next
);
1457 static int cfq_allow_merge(struct request_queue
*q
, struct request
*rq
,
1460 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1461 struct cfq_io_context
*cic
;
1462 struct cfq_queue
*cfqq
;
1464 /* Deny merge if bio and rq don't belong to same cfq group */
1465 if ((RQ_CFQQ(rq
))->cfqg
!= cfq_get_cfqg(cfqd
, 0))
1468 * Disallow merge of a sync bio into an async request.
1470 if (cfq_bio_sync(bio
) && !rq_is_sync(rq
))
1474 * Lookup the cfqq that this bio will be queued with. Allow
1475 * merge only if rq is queued there.
1477 cic
= cfq_cic_lookup(cfqd
, current
->io_context
);
1481 cfqq
= cic_to_cfqq(cic
, cfq_bio_sync(bio
));
1482 return cfqq
== RQ_CFQQ(rq
);
1485 static void __cfq_set_active_queue(struct cfq_data
*cfqd
,
1486 struct cfq_queue
*cfqq
)
1489 cfq_log_cfqq(cfqd
, cfqq
, "set_active");
1490 cfqq
->slice_start
= 0;
1491 cfqq
->dispatch_start
= jiffies
;
1492 cfqq
->slice_end
= 0;
1493 cfqq
->slice_dispatch
= 0;
1494 cfqq
->nr_sectors
= 0;
1496 cfq_clear_cfqq_wait_request(cfqq
);
1497 cfq_clear_cfqq_must_dispatch(cfqq
);
1498 cfq_clear_cfqq_must_alloc_slice(cfqq
);
1499 cfq_clear_cfqq_fifo_expire(cfqq
);
1500 cfq_mark_cfqq_slice_new(cfqq
);
1502 del_timer(&cfqd
->idle_slice_timer
);
1505 cfqd
->active_queue
= cfqq
;
1509 * current cfqq expired its slice (or was too idle), select new one
1512 __cfq_slice_expired(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1515 cfq_log_cfqq(cfqd
, cfqq
, "slice expired t=%d", timed_out
);
1517 if (cfq_cfqq_wait_request(cfqq
))
1518 del_timer(&cfqd
->idle_slice_timer
);
1520 cfq_clear_cfqq_wait_request(cfqq
);
1523 * store what was left of this slice, if the queue idled/timed out
1525 if (timed_out
&& !cfq_cfqq_slice_new(cfqq
)) {
1526 cfqq
->slice_resid
= cfqq
->slice_end
- jiffies
;
1527 cfq_log_cfqq(cfqd
, cfqq
, "resid=%ld", cfqq
->slice_resid
);
1530 cfq_group_served(cfqd
, cfqq
->cfqg
, cfqq
);
1532 if (cfq_cfqq_on_rr(cfqq
) && RB_EMPTY_ROOT(&cfqq
->sort_list
))
1533 cfq_del_cfqq_rr(cfqd
, cfqq
);
1535 cfq_resort_rr_list(cfqd
, cfqq
);
1537 if (cfqq
== cfqd
->active_queue
)
1538 cfqd
->active_queue
= NULL
;
1540 if (&cfqq
->cfqg
->rb_node
== cfqd
->grp_service_tree
.active
)
1541 cfqd
->grp_service_tree
.active
= NULL
;
1543 if (cfqd
->active_cic
) {
1544 put_io_context(cfqd
->active_cic
->ioc
);
1545 cfqd
->active_cic
= NULL
;
1549 static inline void cfq_slice_expired(struct cfq_data
*cfqd
, bool timed_out
)
1551 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
1554 __cfq_slice_expired(cfqd
, cfqq
, timed_out
);
1558 * Get next queue for service. Unless we have a queue preemption,
1559 * we'll simply select the first cfqq in the service tree.
1561 static struct cfq_queue
*cfq_get_next_queue(struct cfq_data
*cfqd
)
1563 struct cfq_rb_root
*service_tree
=
1564 service_tree_for(cfqd
->serving_group
, cfqd
->serving_prio
,
1565 cfqd
->serving_type
, cfqd
);
1567 if (!cfqd
->rq_queued
)
1570 /* There is nothing to dispatch */
1573 if (RB_EMPTY_ROOT(&service_tree
->rb
))
1575 return cfq_rb_first(service_tree
);
1578 static struct cfq_queue
*cfq_get_next_queue_forced(struct cfq_data
*cfqd
)
1580 struct cfq_group
*cfqg
;
1581 struct cfq_queue
*cfqq
;
1583 struct cfq_rb_root
*st
;
1585 if (!cfqd
->rq_queued
)
1588 cfqg
= cfq_get_next_cfqg(cfqd
);
1592 for_each_cfqg_st(cfqg
, i
, j
, st
)
1593 if ((cfqq
= cfq_rb_first(st
)) != NULL
)
1599 * Get and set a new active queue for service.
1601 static struct cfq_queue
*cfq_set_active_queue(struct cfq_data
*cfqd
,
1602 struct cfq_queue
*cfqq
)
1605 cfqq
= cfq_get_next_queue(cfqd
);
1607 __cfq_set_active_queue(cfqd
, cfqq
);
1611 static inline sector_t
cfq_dist_from_last(struct cfq_data
*cfqd
,
1614 if (blk_rq_pos(rq
) >= cfqd
->last_position
)
1615 return blk_rq_pos(rq
) - cfqd
->last_position
;
1617 return cfqd
->last_position
- blk_rq_pos(rq
);
1620 #define CFQQ_SEEK_THR 8 * 1024
1621 #define CFQQ_SEEKY(cfqq) ((cfqq)->seek_mean > CFQQ_SEEK_THR)
1623 static inline int cfq_rq_close(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1626 sector_t sdist
= cfqq
->seek_mean
;
1628 if (!sample_valid(cfqq
->seek_samples
))
1629 sdist
= CFQQ_SEEK_THR
;
1631 return cfq_dist_from_last(cfqd
, rq
) <= sdist
;
1634 static struct cfq_queue
*cfqq_close(struct cfq_data
*cfqd
,
1635 struct cfq_queue
*cur_cfqq
)
1637 struct rb_root
*root
= &cfqd
->prio_trees
[cur_cfqq
->org_ioprio
];
1638 struct rb_node
*parent
, *node
;
1639 struct cfq_queue
*__cfqq
;
1640 sector_t sector
= cfqd
->last_position
;
1642 if (RB_EMPTY_ROOT(root
))
1646 * First, if we find a request starting at the end of the last
1647 * request, choose it.
1649 __cfqq
= cfq_prio_tree_lookup(cfqd
, root
, sector
, &parent
, NULL
);
1654 * If the exact sector wasn't found, the parent of the NULL leaf
1655 * will contain the closest sector.
1657 __cfqq
= rb_entry(parent
, struct cfq_queue
, p_node
);
1658 if (cfq_rq_close(cfqd
, cur_cfqq
, __cfqq
->next_rq
))
1661 if (blk_rq_pos(__cfqq
->next_rq
) < sector
)
1662 node
= rb_next(&__cfqq
->p_node
);
1664 node
= rb_prev(&__cfqq
->p_node
);
1668 __cfqq
= rb_entry(node
, struct cfq_queue
, p_node
);
1669 if (cfq_rq_close(cfqd
, cur_cfqq
, __cfqq
->next_rq
))
1677 * cur_cfqq - passed in so that we don't decide that the current queue is
1678 * closely cooperating with itself.
1680 * So, basically we're assuming that that cur_cfqq has dispatched at least
1681 * one request, and that cfqd->last_position reflects a position on the disk
1682 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
1685 static struct cfq_queue
*cfq_close_cooperator(struct cfq_data
*cfqd
,
1686 struct cfq_queue
*cur_cfqq
)
1688 struct cfq_queue
*cfqq
;
1690 if (!cfq_cfqq_sync(cur_cfqq
))
1692 if (CFQQ_SEEKY(cur_cfqq
))
1696 * We should notice if some of the queues are cooperating, eg
1697 * working closely on the same area of the disk. In that case,
1698 * we can group them together and don't waste time idling.
1700 cfqq
= cfqq_close(cfqd
, cur_cfqq
);
1704 /* If new queue belongs to different cfq_group, don't choose it */
1705 if (cur_cfqq
->cfqg
!= cfqq
->cfqg
)
1709 * It only makes sense to merge sync queues.
1711 if (!cfq_cfqq_sync(cfqq
))
1713 if (CFQQ_SEEKY(cfqq
))
1717 * Do not merge queues of different priority classes
1719 if (cfq_class_rt(cfqq
) != cfq_class_rt(cur_cfqq
))
1726 * Determine whether we should enforce idle window for this queue.
1729 static bool cfq_should_idle(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1731 enum wl_prio_t prio
= cfqq_prio(cfqq
);
1732 struct cfq_rb_root
*service_tree
= cfqq
->service_tree
;
1734 BUG_ON(!service_tree
);
1735 BUG_ON(!service_tree
->count
);
1737 /* We never do for idle class queues. */
1738 if (prio
== IDLE_WORKLOAD
)
1741 /* We do for queues that were marked with idle window flag. */
1742 if (cfq_cfqq_idle_window(cfqq
))
1746 * Otherwise, we do only if they are the last ones
1747 * in their service tree.
1749 return service_tree
->count
== 1;
1752 static void cfq_arm_slice_timer(struct cfq_data
*cfqd
)
1754 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
1755 struct cfq_io_context
*cic
;
1759 * SSD device without seek penalty, disable idling. But only do so
1760 * for devices that support queuing, otherwise we still have a problem
1761 * with sync vs async workloads.
1763 if (blk_queue_nonrot(cfqd
->queue
) && cfqd
->hw_tag
)
1766 WARN_ON(!RB_EMPTY_ROOT(&cfqq
->sort_list
));
1767 WARN_ON(cfq_cfqq_slice_new(cfqq
));
1770 * idle is disabled, either manually or by past process history
1772 if (!cfqd
->cfq_slice_idle
|| !cfq_should_idle(cfqd
, cfqq
))
1776 * still active requests from this queue, don't idle
1778 if (cfqq
->dispatched
)
1782 * task has exited, don't wait
1784 cic
= cfqd
->active_cic
;
1785 if (!cic
|| !atomic_read(&cic
->ioc
->nr_tasks
))
1789 * If our average think time is larger than the remaining time
1790 * slice, then don't idle. This avoids overrunning the allotted
1793 if (sample_valid(cic
->ttime_samples
) &&
1794 (cfqq
->slice_end
- jiffies
< cic
->ttime_mean
))
1797 cfq_mark_cfqq_wait_request(cfqq
);
1799 sl
= cfqd
->cfq_slice_idle
;
1801 mod_timer(&cfqd
->idle_slice_timer
, jiffies
+ sl
);
1802 cfq_log_cfqq(cfqd
, cfqq
, "arm_idle: %lu", sl
);
1806 * Move request from internal lists to the request queue dispatch list.
1808 static void cfq_dispatch_insert(struct request_queue
*q
, struct request
*rq
)
1810 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1811 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1813 cfq_log_cfqq(cfqd
, cfqq
, "dispatch_insert");
1815 cfqq
->next_rq
= cfq_find_next_rq(cfqd
, cfqq
, rq
);
1816 cfq_remove_request(rq
);
1818 elv_dispatch_sort(q
, rq
);
1820 if (cfq_cfqq_sync(cfqq
))
1821 cfqd
->sync_flight
++;
1822 cfqq
->nr_sectors
+= blk_rq_sectors(rq
);
1826 * return expired entry, or NULL to just start from scratch in rbtree
1828 static struct request
*cfq_check_fifo(struct cfq_queue
*cfqq
)
1830 struct request
*rq
= NULL
;
1832 if (cfq_cfqq_fifo_expire(cfqq
))
1835 cfq_mark_cfqq_fifo_expire(cfqq
);
1837 if (list_empty(&cfqq
->fifo
))
1840 rq
= rq_entry_fifo(cfqq
->fifo
.next
);
1841 if (time_before(jiffies
, rq_fifo_time(rq
)))
1844 cfq_log_cfqq(cfqq
->cfqd
, cfqq
, "fifo=%p", rq
);
1849 cfq_prio_to_maxrq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1851 const int base_rq
= cfqd
->cfq_slice_async_rq
;
1853 WARN_ON(cfqq
->ioprio
>= IOPRIO_BE_NR
);
1855 return 2 * (base_rq
+ base_rq
* (CFQ_PRIO_LISTS
- 1 - cfqq
->ioprio
));
1859 * Must be called with the queue_lock held.
1861 static int cfqq_process_refs(struct cfq_queue
*cfqq
)
1863 int process_refs
, io_refs
;
1865 io_refs
= cfqq
->allocated
[READ
] + cfqq
->allocated
[WRITE
];
1866 process_refs
= atomic_read(&cfqq
->ref
) - io_refs
;
1867 BUG_ON(process_refs
< 0);
1868 return process_refs
;
1871 static void cfq_setup_merge(struct cfq_queue
*cfqq
, struct cfq_queue
*new_cfqq
)
1873 int process_refs
, new_process_refs
;
1874 struct cfq_queue
*__cfqq
;
1876 /* Avoid a circular list and skip interim queue merges */
1877 while ((__cfqq
= new_cfqq
->new_cfqq
)) {
1883 process_refs
= cfqq_process_refs(cfqq
);
1885 * If the process for the cfqq has gone away, there is no
1886 * sense in merging the queues.
1888 if (process_refs
== 0)
1892 * Merge in the direction of the lesser amount of work.
1894 new_process_refs
= cfqq_process_refs(new_cfqq
);
1895 if (new_process_refs
>= process_refs
) {
1896 cfqq
->new_cfqq
= new_cfqq
;
1897 atomic_add(process_refs
, &new_cfqq
->ref
);
1899 new_cfqq
->new_cfqq
= cfqq
;
1900 atomic_add(new_process_refs
, &cfqq
->ref
);
1904 static enum wl_type_t
cfq_choose_wl(struct cfq_data
*cfqd
,
1905 struct cfq_group
*cfqg
, enum wl_prio_t prio
,
1908 struct cfq_queue
*queue
;
1910 bool key_valid
= false;
1911 unsigned long lowest_key
= 0;
1912 enum wl_type_t cur_best
= SYNC_NOIDLE_WORKLOAD
;
1916 * When priorities switched, we prefer starting
1917 * from SYNC_NOIDLE (first choice), or just SYNC
1920 if (service_tree_for(cfqg
, prio
, cur_best
, cfqd
)->count
)
1922 cur_best
= SYNC_WORKLOAD
;
1923 if (service_tree_for(cfqg
, prio
, cur_best
, cfqd
)->count
)
1926 return ASYNC_WORKLOAD
;
1929 for (i
= 0; i
< 3; ++i
) {
1930 /* otherwise, select the one with lowest rb_key */
1931 queue
= cfq_rb_first(service_tree_for(cfqg
, prio
, i
, cfqd
));
1933 (!key_valid
|| time_before(queue
->rb_key
, lowest_key
))) {
1934 lowest_key
= queue
->rb_key
;
1943 static void choose_service_tree(struct cfq_data
*cfqd
, struct cfq_group
*cfqg
)
1945 enum wl_prio_t previous_prio
= cfqd
->serving_prio
;
1949 struct cfq_rb_root
*st
;
1950 unsigned group_slice
;
1953 cfqd
->serving_prio
= IDLE_WORKLOAD
;
1954 cfqd
->workload_expires
= jiffies
+ 1;
1958 /* Choose next priority. RT > BE > IDLE */
1959 if (cfq_group_busy_queues_wl(RT_WORKLOAD
, cfqd
, cfqg
))
1960 cfqd
->serving_prio
= RT_WORKLOAD
;
1961 else if (cfq_group_busy_queues_wl(BE_WORKLOAD
, cfqd
, cfqg
))
1962 cfqd
->serving_prio
= BE_WORKLOAD
;
1964 cfqd
->serving_prio
= IDLE_WORKLOAD
;
1965 cfqd
->workload_expires
= jiffies
+ 1;
1970 * For RT and BE, we have to choose also the type
1971 * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
1974 prio_changed
= (cfqd
->serving_prio
!= previous_prio
);
1975 st
= service_tree_for(cfqg
, cfqd
->serving_prio
, cfqd
->serving_type
,
1980 * If priority didn't change, check workload expiration,
1981 * and that we still have other queues ready
1983 if (!prio_changed
&& count
&&
1984 !time_after(jiffies
, cfqd
->workload_expires
))
1987 /* otherwise select new workload type */
1988 cfqd
->serving_type
=
1989 cfq_choose_wl(cfqd
, cfqg
, cfqd
->serving_prio
, prio_changed
);
1990 st
= service_tree_for(cfqg
, cfqd
->serving_prio
, cfqd
->serving_type
,
1995 * the workload slice is computed as a fraction of target latency
1996 * proportional to the number of queues in that workload, over
1997 * all the queues in the same priority class
1999 group_slice
= cfq_group_slice(cfqd
, cfqg
);
2001 slice
= group_slice
* count
/
2002 max_t(unsigned, cfqg
->busy_queues_avg
[cfqd
->serving_prio
],
2003 cfq_group_busy_queues_wl(cfqd
->serving_prio
, cfqd
, cfqg
));
2005 if (cfqd
->serving_type
== ASYNC_WORKLOAD
)
2006 /* async workload slice is scaled down according to
2007 * the sync/async slice ratio. */
2008 slice
= slice
* cfqd
->cfq_slice
[0] / cfqd
->cfq_slice
[1];
2010 /* sync workload slice is at least 2 * cfq_slice_idle */
2011 slice
= max(slice
, 2 * cfqd
->cfq_slice_idle
);
2013 slice
= max_t(unsigned, slice
, CFQ_MIN_TT
);
2014 cfqd
->workload_expires
= jiffies
+ slice
;
2015 cfqd
->noidle_tree_requires_idle
= false;
2018 static struct cfq_group
*cfq_get_next_cfqg(struct cfq_data
*cfqd
)
2020 struct cfq_rb_root
*st
= &cfqd
->grp_service_tree
;
2021 struct cfq_group
*cfqg
;
2023 if (RB_EMPTY_ROOT(&st
->rb
))
2025 cfqg
= cfq_rb_first_group(st
);
2026 st
->active
= &cfqg
->rb_node
;
2027 update_min_vdisktime(st
);
2031 static void cfq_choose_cfqg(struct cfq_data
*cfqd
)
2033 struct cfq_group
*cfqg
= cfq_get_next_cfqg(cfqd
);
2035 cfqd
->serving_group
= cfqg
;
2037 /* Restore the workload type data */
2038 if (cfqg
->saved_workload_slice
) {
2039 cfqd
->workload_expires
= jiffies
+ cfqg
->saved_workload_slice
;
2040 cfqd
->serving_type
= cfqg
->saved_workload
;
2041 cfqd
->serving_prio
= cfqg
->saved_serving_prio
;
2043 choose_service_tree(cfqd
, cfqg
);
2047 * Select a queue for service. If we have a current active queue,
2048 * check whether to continue servicing it, or retrieve and set a new one.
2050 static struct cfq_queue
*cfq_select_queue(struct cfq_data
*cfqd
)
2052 struct cfq_queue
*cfqq
, *new_cfqq
= NULL
;
2054 cfqq
= cfqd
->active_queue
;
2058 if (!cfqd
->rq_queued
)
2061 * The active queue has run out of time, expire it and select new.
2063 if (cfq_slice_used(cfqq
) && !cfq_cfqq_must_dispatch(cfqq
))
2067 * The active queue has requests and isn't expired, allow it to
2070 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
))
2074 * If another queue has a request waiting within our mean seek
2075 * distance, let it run. The expire code will check for close
2076 * cooperators and put the close queue at the front of the service
2077 * tree. If possible, merge the expiring queue with the new cfqq.
2079 new_cfqq
= cfq_close_cooperator(cfqd
, cfqq
);
2081 if (!cfqq
->new_cfqq
)
2082 cfq_setup_merge(cfqq
, new_cfqq
);
2087 * No requests pending. If the active queue still has requests in
2088 * flight or is idling for a new request, allow either of these
2089 * conditions to happen (or time out) before selecting a new queue.
2091 if (timer_pending(&cfqd
->idle_slice_timer
) ||
2092 (cfqq
->dispatched
&& cfq_should_idle(cfqd
, cfqq
))) {
2098 cfq_slice_expired(cfqd
, 0);
2101 * Current queue expired. Check if we have to switch to a new
2105 cfq_choose_cfqg(cfqd
);
2107 cfqq
= cfq_set_active_queue(cfqd
, new_cfqq
);
2112 static int __cfq_forced_dispatch_cfqq(struct cfq_queue
*cfqq
)
2116 while (cfqq
->next_rq
) {
2117 cfq_dispatch_insert(cfqq
->cfqd
->queue
, cfqq
->next_rq
);
2121 BUG_ON(!list_empty(&cfqq
->fifo
));
2123 /* By default cfqq is not expired if it is empty. Do it explicitly */
2124 __cfq_slice_expired(cfqq
->cfqd
, cfqq
, 0);
2129 * Drain our current requests. Used for barriers and when switching
2130 * io schedulers on-the-fly.
2132 static int cfq_forced_dispatch(struct cfq_data
*cfqd
)
2134 struct cfq_queue
*cfqq
;
2137 while ((cfqq
= cfq_get_next_queue_forced(cfqd
)) != NULL
)
2138 dispatched
+= __cfq_forced_dispatch_cfqq(cfqq
);
2140 cfq_slice_expired(cfqd
, 0);
2141 BUG_ON(cfqd
->busy_queues
);
2143 cfq_log(cfqd
, "forced_dispatch=%d", dispatched
);
2147 static bool cfq_may_dispatch(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
2149 unsigned int max_dispatch
;
2152 * Drain async requests before we start sync IO
2154 if (cfq_should_idle(cfqd
, cfqq
) && cfqd
->rq_in_driver
[BLK_RW_ASYNC
])
2158 * If this is an async queue and we have sync IO in flight, let it wait
2160 if (cfqd
->sync_flight
&& !cfq_cfqq_sync(cfqq
))
2163 max_dispatch
= cfqd
->cfq_quantum
;
2164 if (cfq_class_idle(cfqq
))
2168 * Does this cfqq already have too much IO in flight?
2170 if (cfqq
->dispatched
>= max_dispatch
) {
2172 * idle queue must always only have a single IO in flight
2174 if (cfq_class_idle(cfqq
))
2178 * We have other queues, don't allow more IO from this one
2180 if (cfqd
->busy_queues
> 1)
2184 * Sole queue user, no limit
2190 * Async queues must wait a bit before being allowed dispatch.
2191 * We also ramp up the dispatch depth gradually for async IO,
2192 * based on the last sync IO we serviced
2194 if (!cfq_cfqq_sync(cfqq
) && cfqd
->cfq_latency
) {
2195 unsigned long last_sync
= jiffies
- cfqd
->last_end_sync_rq
;
2198 depth
= last_sync
/ cfqd
->cfq_slice
[1];
2199 if (!depth
&& !cfqq
->dispatched
)
2201 if (depth
< max_dispatch
)
2202 max_dispatch
= depth
;
2206 * If we're below the current max, allow a dispatch
2208 return cfqq
->dispatched
< max_dispatch
;
2212 * Dispatch a request from cfqq, moving them to the request queue
2215 static bool cfq_dispatch_request(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
2219 BUG_ON(RB_EMPTY_ROOT(&cfqq
->sort_list
));
2221 if (!cfq_may_dispatch(cfqd
, cfqq
))
2225 * follow expired path, else get first next available
2227 rq
= cfq_check_fifo(cfqq
);
2232 * insert request into driver dispatch list
2234 cfq_dispatch_insert(cfqd
->queue
, rq
);
2236 if (!cfqd
->active_cic
) {
2237 struct cfq_io_context
*cic
= RQ_CIC(rq
);
2239 atomic_long_inc(&cic
->ioc
->refcount
);
2240 cfqd
->active_cic
= cic
;
2247 * Find the cfqq that we need to service and move a request from that to the
2250 static int cfq_dispatch_requests(struct request_queue
*q
, int force
)
2252 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
2253 struct cfq_queue
*cfqq
;
2255 if (!cfqd
->busy_queues
)
2258 if (unlikely(force
))
2259 return cfq_forced_dispatch(cfqd
);
2261 cfqq
= cfq_select_queue(cfqd
);
2266 * Dispatch a request from this cfqq, if it is allowed
2268 if (!cfq_dispatch_request(cfqd
, cfqq
))
2271 cfqq
->slice_dispatch
++;
2272 cfq_clear_cfqq_must_dispatch(cfqq
);
2275 * expire an async queue immediately if it has used up its slice. idle
2276 * queue always expire after 1 dispatch round.
2278 if (cfqd
->busy_queues
> 1 && ((!cfq_cfqq_sync(cfqq
) &&
2279 cfqq
->slice_dispatch
>= cfq_prio_to_maxrq(cfqd
, cfqq
)) ||
2280 cfq_class_idle(cfqq
))) {
2281 cfqq
->slice_end
= jiffies
+ 1;
2282 cfq_slice_expired(cfqd
, 0);
2285 cfq_log_cfqq(cfqd
, cfqq
, "dispatched a request");
2290 * task holds one reference to the queue, dropped when task exits. each rq
2291 * in-flight on this queue also holds a reference, dropped when rq is freed.
2293 * Each cfq queue took a reference on the parent group. Drop it now.
2294 * queue lock must be held here.
2296 static void cfq_put_queue(struct cfq_queue
*cfqq
)
2298 struct cfq_data
*cfqd
= cfqq
->cfqd
;
2299 struct cfq_group
*cfqg
;
2301 BUG_ON(atomic_read(&cfqq
->ref
) <= 0);
2303 if (!atomic_dec_and_test(&cfqq
->ref
))
2306 cfq_log_cfqq(cfqd
, cfqq
, "put_queue");
2307 BUG_ON(rb_first(&cfqq
->sort_list
));
2308 BUG_ON(cfqq
->allocated
[READ
] + cfqq
->allocated
[WRITE
]);
2311 if (unlikely(cfqd
->active_queue
== cfqq
)) {
2312 __cfq_slice_expired(cfqd
, cfqq
, 0);
2313 cfq_schedule_dispatch(cfqd
);
2316 BUG_ON(cfq_cfqq_on_rr(cfqq
));
2317 kmem_cache_free(cfq_pool
, cfqq
);
2322 * Must always be called with the rcu_read_lock() held
2325 __call_for_each_cic(struct io_context
*ioc
,
2326 void (*func
)(struct io_context
*, struct cfq_io_context
*))
2328 struct cfq_io_context
*cic
;
2329 struct hlist_node
*n
;
2331 hlist_for_each_entry_rcu(cic
, n
, &ioc
->cic_list
, cic_list
)
2336 * Call func for each cic attached to this ioc.
2339 call_for_each_cic(struct io_context
*ioc
,
2340 void (*func
)(struct io_context
*, struct cfq_io_context
*))
2343 __call_for_each_cic(ioc
, func
);
2347 static void cfq_cic_free_rcu(struct rcu_head
*head
)
2349 struct cfq_io_context
*cic
;
2351 cic
= container_of(head
, struct cfq_io_context
, rcu_head
);
2353 kmem_cache_free(cfq_ioc_pool
, cic
);
2354 elv_ioc_count_dec(cfq_ioc_count
);
2358 * CFQ scheduler is exiting, grab exit lock and check
2359 * the pending io context count. If it hits zero,
2360 * complete ioc_gone and set it back to NULL
2362 spin_lock(&ioc_gone_lock
);
2363 if (ioc_gone
&& !elv_ioc_count_read(cfq_ioc_count
)) {
2367 spin_unlock(&ioc_gone_lock
);
2371 static void cfq_cic_free(struct cfq_io_context
*cic
)
2373 call_rcu(&cic
->rcu_head
, cfq_cic_free_rcu
);
2376 static void cic_free_func(struct io_context
*ioc
, struct cfq_io_context
*cic
)
2378 unsigned long flags
;
2380 BUG_ON(!cic
->dead_key
);
2382 spin_lock_irqsave(&ioc
->lock
, flags
);
2383 radix_tree_delete(&ioc
->radix_root
, cic
->dead_key
);
2384 hlist_del_rcu(&cic
->cic_list
);
2385 spin_unlock_irqrestore(&ioc
->lock
, flags
);
2391 * Must be called with rcu_read_lock() held or preemption otherwise disabled.
2392 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
2393 * and ->trim() which is called with the task lock held
2395 static void cfq_free_io_context(struct io_context
*ioc
)
2398 * ioc->refcount is zero here, or we are called from elv_unregister(),
2399 * so no more cic's are allowed to be linked into this ioc. So it
2400 * should be ok to iterate over the known list, we will see all cic's
2401 * since no new ones are added.
2403 __call_for_each_cic(ioc
, cic_free_func
);
2406 static void cfq_exit_cfqq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
2408 struct cfq_queue
*__cfqq
, *next
;
2410 if (unlikely(cfqq
== cfqd
->active_queue
)) {
2411 __cfq_slice_expired(cfqd
, cfqq
, 0);
2412 cfq_schedule_dispatch(cfqd
);
2416 * If this queue was scheduled to merge with another queue, be
2417 * sure to drop the reference taken on that queue (and others in
2418 * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs.
2420 __cfqq
= cfqq
->new_cfqq
;
2422 if (__cfqq
== cfqq
) {
2423 WARN(1, "cfqq->new_cfqq loop detected\n");
2426 next
= __cfqq
->new_cfqq
;
2427 cfq_put_queue(__cfqq
);
2431 cfq_put_queue(cfqq
);
2434 static void __cfq_exit_single_io_context(struct cfq_data
*cfqd
,
2435 struct cfq_io_context
*cic
)
2437 struct io_context
*ioc
= cic
->ioc
;
2439 list_del_init(&cic
->queue_list
);
2442 * Make sure key == NULL is seen for dead queues
2445 cic
->dead_key
= (unsigned long) cic
->key
;
2448 if (ioc
->ioc_data
== cic
)
2449 rcu_assign_pointer(ioc
->ioc_data
, NULL
);
2451 if (cic
->cfqq
[BLK_RW_ASYNC
]) {
2452 cfq_exit_cfqq(cfqd
, cic
->cfqq
[BLK_RW_ASYNC
]);
2453 cic
->cfqq
[BLK_RW_ASYNC
] = NULL
;
2456 if (cic
->cfqq
[BLK_RW_SYNC
]) {
2457 cfq_exit_cfqq(cfqd
, cic
->cfqq
[BLK_RW_SYNC
]);
2458 cic
->cfqq
[BLK_RW_SYNC
] = NULL
;
2462 static void cfq_exit_single_io_context(struct io_context
*ioc
,
2463 struct cfq_io_context
*cic
)
2465 struct cfq_data
*cfqd
= cic
->key
;
2468 struct request_queue
*q
= cfqd
->queue
;
2469 unsigned long flags
;
2471 spin_lock_irqsave(q
->queue_lock
, flags
);
2474 * Ensure we get a fresh copy of the ->key to prevent
2475 * race between exiting task and queue
2477 smp_read_barrier_depends();
2479 __cfq_exit_single_io_context(cfqd
, cic
);
2481 spin_unlock_irqrestore(q
->queue_lock
, flags
);
2486 * The process that ioc belongs to has exited, we need to clean up
2487 * and put the internal structures we have that belongs to that process.
2489 static void cfq_exit_io_context(struct io_context
*ioc
)
2491 call_for_each_cic(ioc
, cfq_exit_single_io_context
);
2494 static struct cfq_io_context
*
2495 cfq_alloc_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
2497 struct cfq_io_context
*cic
;
2499 cic
= kmem_cache_alloc_node(cfq_ioc_pool
, gfp_mask
| __GFP_ZERO
,
2502 cic
->last_end_request
= jiffies
;
2503 INIT_LIST_HEAD(&cic
->queue_list
);
2504 INIT_HLIST_NODE(&cic
->cic_list
);
2505 cic
->dtor
= cfq_free_io_context
;
2506 cic
->exit
= cfq_exit_io_context
;
2507 elv_ioc_count_inc(cfq_ioc_count
);
2513 static void cfq_init_prio_data(struct cfq_queue
*cfqq
, struct io_context
*ioc
)
2515 struct task_struct
*tsk
= current
;
2518 if (!cfq_cfqq_prio_changed(cfqq
))
2521 ioprio_class
= IOPRIO_PRIO_CLASS(ioc
->ioprio
);
2522 switch (ioprio_class
) {
2524 printk(KERN_ERR
"cfq: bad prio %x\n", ioprio_class
);
2525 case IOPRIO_CLASS_NONE
:
2527 * no prio set, inherit CPU scheduling settings
2529 cfqq
->ioprio
= task_nice_ioprio(tsk
);
2530 cfqq
->ioprio_class
= task_nice_ioclass(tsk
);
2532 case IOPRIO_CLASS_RT
:
2533 cfqq
->ioprio
= task_ioprio(ioc
);
2534 cfqq
->ioprio_class
= IOPRIO_CLASS_RT
;
2536 case IOPRIO_CLASS_BE
:
2537 cfqq
->ioprio
= task_ioprio(ioc
);
2538 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
2540 case IOPRIO_CLASS_IDLE
:
2541 cfqq
->ioprio_class
= IOPRIO_CLASS_IDLE
;
2543 cfq_clear_cfqq_idle_window(cfqq
);
2548 * keep track of original prio settings in case we have to temporarily
2549 * elevate the priority of this queue
2551 cfqq
->org_ioprio
= cfqq
->ioprio
;
2552 cfqq
->org_ioprio_class
= cfqq
->ioprio_class
;
2553 cfq_clear_cfqq_prio_changed(cfqq
);
2556 static void changed_ioprio(struct io_context
*ioc
, struct cfq_io_context
*cic
)
2558 struct cfq_data
*cfqd
= cic
->key
;
2559 struct cfq_queue
*cfqq
;
2560 unsigned long flags
;
2562 if (unlikely(!cfqd
))
2565 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
2567 cfqq
= cic
->cfqq
[BLK_RW_ASYNC
];
2569 struct cfq_queue
*new_cfqq
;
2570 new_cfqq
= cfq_get_queue(cfqd
, BLK_RW_ASYNC
, cic
->ioc
,
2573 cic
->cfqq
[BLK_RW_ASYNC
] = new_cfqq
;
2574 cfq_put_queue(cfqq
);
2578 cfqq
= cic
->cfqq
[BLK_RW_SYNC
];
2580 cfq_mark_cfqq_prio_changed(cfqq
);
2582 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2585 static void cfq_ioc_set_ioprio(struct io_context
*ioc
)
2587 call_for_each_cic(ioc
, changed_ioprio
);
2588 ioc
->ioprio_changed
= 0;
2591 static void cfq_init_cfqq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2592 pid_t pid
, bool is_sync
)
2594 RB_CLEAR_NODE(&cfqq
->rb_node
);
2595 RB_CLEAR_NODE(&cfqq
->p_node
);
2596 INIT_LIST_HEAD(&cfqq
->fifo
);
2598 atomic_set(&cfqq
->ref
, 0);
2601 cfq_mark_cfqq_prio_changed(cfqq
);
2604 if (!cfq_class_idle(cfqq
))
2605 cfq_mark_cfqq_idle_window(cfqq
);
2606 cfq_mark_cfqq_sync(cfqq
);
2611 static struct cfq_queue
*
2612 cfq_find_alloc_queue(struct cfq_data
*cfqd
, bool is_sync
,
2613 struct io_context
*ioc
, gfp_t gfp_mask
)
2615 struct cfq_queue
*cfqq
, *new_cfqq
= NULL
;
2616 struct cfq_io_context
*cic
;
2617 struct cfq_group
*cfqg
;
2620 cfqg
= cfq_get_cfqg(cfqd
, 1);
2621 cic
= cfq_cic_lookup(cfqd
, ioc
);
2622 /* cic always exists here */
2623 cfqq
= cic_to_cfqq(cic
, is_sync
);
2626 * Always try a new alloc if we fell back to the OOM cfqq
2627 * originally, since it should just be a temporary situation.
2629 if (!cfqq
|| cfqq
== &cfqd
->oom_cfqq
) {
2634 } else if (gfp_mask
& __GFP_WAIT
) {
2635 spin_unlock_irq(cfqd
->queue
->queue_lock
);
2636 new_cfqq
= kmem_cache_alloc_node(cfq_pool
,
2637 gfp_mask
| __GFP_ZERO
,
2639 spin_lock_irq(cfqd
->queue
->queue_lock
);
2643 cfqq
= kmem_cache_alloc_node(cfq_pool
,
2644 gfp_mask
| __GFP_ZERO
,
2649 cfq_init_cfqq(cfqd
, cfqq
, current
->pid
, is_sync
);
2650 cfq_init_prio_data(cfqq
, ioc
);
2651 cfq_link_cfqq_cfqg(cfqq
, cfqg
);
2652 cfq_log_cfqq(cfqd
, cfqq
, "alloced");
2654 cfqq
= &cfqd
->oom_cfqq
;
2658 kmem_cache_free(cfq_pool
, new_cfqq
);
2663 static struct cfq_queue
**
2664 cfq_async_queue_prio(struct cfq_data
*cfqd
, int ioprio_class
, int ioprio
)
2666 switch (ioprio_class
) {
2667 case IOPRIO_CLASS_RT
:
2668 return &cfqd
->async_cfqq
[0][ioprio
];
2669 case IOPRIO_CLASS_BE
:
2670 return &cfqd
->async_cfqq
[1][ioprio
];
2671 case IOPRIO_CLASS_IDLE
:
2672 return &cfqd
->async_idle_cfqq
;
2678 static struct cfq_queue
*
2679 cfq_get_queue(struct cfq_data
*cfqd
, bool is_sync
, struct io_context
*ioc
,
2682 const int ioprio
= task_ioprio(ioc
);
2683 const int ioprio_class
= task_ioprio_class(ioc
);
2684 struct cfq_queue
**async_cfqq
= NULL
;
2685 struct cfq_queue
*cfqq
= NULL
;
2688 async_cfqq
= cfq_async_queue_prio(cfqd
, ioprio_class
, ioprio
);
2693 cfqq
= cfq_find_alloc_queue(cfqd
, is_sync
, ioc
, gfp_mask
);
2696 * pin the queue now that it's allocated, scheduler exit will prune it
2698 if (!is_sync
&& !(*async_cfqq
)) {
2699 atomic_inc(&cfqq
->ref
);
2703 atomic_inc(&cfqq
->ref
);
2708 * We drop cfq io contexts lazily, so we may find a dead one.
2711 cfq_drop_dead_cic(struct cfq_data
*cfqd
, struct io_context
*ioc
,
2712 struct cfq_io_context
*cic
)
2714 unsigned long flags
;
2716 WARN_ON(!list_empty(&cic
->queue_list
));
2718 spin_lock_irqsave(&ioc
->lock
, flags
);
2720 BUG_ON(ioc
->ioc_data
== cic
);
2722 radix_tree_delete(&ioc
->radix_root
, (unsigned long) cfqd
);
2723 hlist_del_rcu(&cic
->cic_list
);
2724 spin_unlock_irqrestore(&ioc
->lock
, flags
);
2729 static struct cfq_io_context
*
2730 cfq_cic_lookup(struct cfq_data
*cfqd
, struct io_context
*ioc
)
2732 struct cfq_io_context
*cic
;
2733 unsigned long flags
;
2742 * we maintain a last-hit cache, to avoid browsing over the tree
2744 cic
= rcu_dereference(ioc
->ioc_data
);
2745 if (cic
&& cic
->key
== cfqd
) {
2751 cic
= radix_tree_lookup(&ioc
->radix_root
, (unsigned long) cfqd
);
2755 /* ->key must be copied to avoid race with cfq_exit_queue() */
2758 cfq_drop_dead_cic(cfqd
, ioc
, cic
);
2763 spin_lock_irqsave(&ioc
->lock
, flags
);
2764 rcu_assign_pointer(ioc
->ioc_data
, cic
);
2765 spin_unlock_irqrestore(&ioc
->lock
, flags
);
2773 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2774 * the process specific cfq io context when entered from the block layer.
2775 * Also adds the cic to a per-cfqd list, used when this queue is removed.
2777 static int cfq_cic_link(struct cfq_data
*cfqd
, struct io_context
*ioc
,
2778 struct cfq_io_context
*cic
, gfp_t gfp_mask
)
2780 unsigned long flags
;
2783 ret
= radix_tree_preload(gfp_mask
);
2788 spin_lock_irqsave(&ioc
->lock
, flags
);
2789 ret
= radix_tree_insert(&ioc
->radix_root
,
2790 (unsigned long) cfqd
, cic
);
2792 hlist_add_head_rcu(&cic
->cic_list
, &ioc
->cic_list
);
2793 spin_unlock_irqrestore(&ioc
->lock
, flags
);
2795 radix_tree_preload_end();
2798 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
2799 list_add(&cic
->queue_list
, &cfqd
->cic_list
);
2800 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2805 printk(KERN_ERR
"cfq: cic link failed!\n");
2811 * Setup general io context and cfq io context. There can be several cfq
2812 * io contexts per general io context, if this process is doing io to more
2813 * than one device managed by cfq.
2815 static struct cfq_io_context
*
2816 cfq_get_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
2818 struct io_context
*ioc
= NULL
;
2819 struct cfq_io_context
*cic
;
2821 might_sleep_if(gfp_mask
& __GFP_WAIT
);
2823 ioc
= get_io_context(gfp_mask
, cfqd
->queue
->node
);
2827 cic
= cfq_cic_lookup(cfqd
, ioc
);
2831 cic
= cfq_alloc_io_context(cfqd
, gfp_mask
);
2835 if (cfq_cic_link(cfqd
, ioc
, cic
, gfp_mask
))
2839 smp_read_barrier_depends();
2840 if (unlikely(ioc
->ioprio_changed
))
2841 cfq_ioc_set_ioprio(ioc
);
2847 put_io_context(ioc
);
2852 cfq_update_io_thinktime(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
)
2854 unsigned long elapsed
= jiffies
- cic
->last_end_request
;
2855 unsigned long ttime
= min(elapsed
, 2UL * cfqd
->cfq_slice_idle
);
2857 cic
->ttime_samples
= (7*cic
->ttime_samples
+ 256) / 8;
2858 cic
->ttime_total
= (7*cic
->ttime_total
+ 256*ttime
) / 8;
2859 cic
->ttime_mean
= (cic
->ttime_total
+ 128) / cic
->ttime_samples
;
2863 cfq_update_io_seektime(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2869 if (!cfqq
->last_request_pos
)
2871 else if (cfqq
->last_request_pos
< blk_rq_pos(rq
))
2872 sdist
= blk_rq_pos(rq
) - cfqq
->last_request_pos
;
2874 sdist
= cfqq
->last_request_pos
- blk_rq_pos(rq
);
2877 * Don't allow the seek distance to get too large from the
2878 * odd fragment, pagein, etc
2880 if (cfqq
->seek_samples
<= 60) /* second&third seek */
2881 sdist
= min(sdist
, (cfqq
->seek_mean
* 4) + 2*1024*1024);
2883 sdist
= min(sdist
, (cfqq
->seek_mean
* 4) + 2*1024*64);
2885 cfqq
->seek_samples
= (7*cfqq
->seek_samples
+ 256) / 8;
2886 cfqq
->seek_total
= (7*cfqq
->seek_total
+ (u64
)256*sdist
) / 8;
2887 total
= cfqq
->seek_total
+ (cfqq
->seek_samples
/2);
2888 do_div(total
, cfqq
->seek_samples
);
2889 cfqq
->seek_mean
= (sector_t
)total
;
2892 * If this cfqq is shared between multiple processes, check to
2893 * make sure that those processes are still issuing I/Os within
2894 * the mean seek distance. If not, it may be time to break the
2895 * queues apart again.
2897 if (cfq_cfqq_coop(cfqq
)) {
2898 if (CFQQ_SEEKY(cfqq
) && !cfqq
->seeky_start
)
2899 cfqq
->seeky_start
= jiffies
;
2900 else if (!CFQQ_SEEKY(cfqq
))
2901 cfqq
->seeky_start
= 0;
2906 * Disable idle window if the process thinks too long or seeks so much that
2910 cfq_update_idle_window(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2911 struct cfq_io_context
*cic
)
2913 int old_idle
, enable_idle
;
2916 * Don't idle for async or idle io prio class
2918 if (!cfq_cfqq_sync(cfqq
) || cfq_class_idle(cfqq
))
2921 enable_idle
= old_idle
= cfq_cfqq_idle_window(cfqq
);
2923 if (cfqq
->queued
[0] + cfqq
->queued
[1] >= 4)
2924 cfq_mark_cfqq_deep(cfqq
);
2926 if (!atomic_read(&cic
->ioc
->nr_tasks
) || !cfqd
->cfq_slice_idle
||
2927 (!cfq_cfqq_deep(cfqq
) && sample_valid(cfqq
->seek_samples
)
2928 && CFQQ_SEEKY(cfqq
)))
2930 else if (sample_valid(cic
->ttime_samples
)) {
2931 if (cic
->ttime_mean
> cfqd
->cfq_slice_idle
)
2937 if (old_idle
!= enable_idle
) {
2938 cfq_log_cfqq(cfqd
, cfqq
, "idle=%d", enable_idle
);
2940 cfq_mark_cfqq_idle_window(cfqq
);
2942 cfq_clear_cfqq_idle_window(cfqq
);
2947 * Check if new_cfqq should preempt the currently active queue. Return 0 for
2948 * no or if we aren't sure, a 1 will cause a preempt.
2951 cfq_should_preempt(struct cfq_data
*cfqd
, struct cfq_queue
*new_cfqq
,
2954 struct cfq_queue
*cfqq
;
2956 cfqq
= cfqd
->active_queue
;
2960 if (cfq_class_idle(new_cfqq
))
2963 if (cfq_class_idle(cfqq
))
2967 * if the new request is sync, but the currently running queue is
2968 * not, let the sync request have priority.
2970 if (rq_is_sync(rq
) && !cfq_cfqq_sync(cfqq
))
2973 if (new_cfqq
->cfqg
!= cfqq
->cfqg
)
2976 if (cfq_slice_used(cfqq
))
2979 /* Allow preemption only if we are idling on sync-noidle tree */
2980 if (cfqd
->serving_type
== SYNC_NOIDLE_WORKLOAD
&&
2981 cfqq_type(new_cfqq
) == SYNC_NOIDLE_WORKLOAD
&&
2982 new_cfqq
->service_tree
->count
== 2 &&
2983 RB_EMPTY_ROOT(&cfqq
->sort_list
))
2987 * So both queues are sync. Let the new request get disk time if
2988 * it's a metadata request and the current queue is doing regular IO.
2990 if (rq_is_meta(rq
) && !cfqq
->meta_pending
)
2994 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
2996 if (cfq_class_rt(new_cfqq
) && !cfq_class_rt(cfqq
))
2999 if (!cfqd
->active_cic
|| !cfq_cfqq_wait_request(cfqq
))
3003 * if this request is as-good as one we would expect from the
3004 * current cfqq, let it preempt
3006 if (cfq_rq_close(cfqd
, cfqq
, rq
))
3013 * cfqq preempts the active queue. if we allowed preempt with no slice left,
3014 * let it have half of its nominal slice.
3016 static void cfq_preempt_queue(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
3018 cfq_log_cfqq(cfqd
, cfqq
, "preempt");
3019 cfq_slice_expired(cfqd
, 1);
3022 * Put the new queue at the front of the of the current list,
3023 * so we know that it will be selected next.
3025 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
3027 cfq_service_tree_add(cfqd
, cfqq
, 1);
3029 cfqq
->slice_end
= 0;
3030 cfq_mark_cfqq_slice_new(cfqq
);
3034 * Called when a new fs request (rq) is added (to cfqq). Check if there's
3035 * something we should do about it
3038 cfq_rq_enqueued(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
3041 struct cfq_io_context
*cic
= RQ_CIC(rq
);
3045 cfqq
->meta_pending
++;
3047 cfq_update_io_thinktime(cfqd
, cic
);
3048 cfq_update_io_seektime(cfqd
, cfqq
, rq
);
3049 cfq_update_idle_window(cfqd
, cfqq
, cic
);
3051 cfqq
->last_request_pos
= blk_rq_pos(rq
) + blk_rq_sectors(rq
);
3053 if (cfqq
== cfqd
->active_queue
) {
3055 * Remember that we saw a request from this process, but
3056 * don't start queuing just yet. Otherwise we risk seeing lots
3057 * of tiny requests, because we disrupt the normal plugging
3058 * and merging. If the request is already larger than a single
3059 * page, let it rip immediately. For that case we assume that
3060 * merging is already done. Ditto for a busy system that
3061 * has other work pending, don't risk delaying until the
3062 * idle timer unplug to continue working.
3064 if (cfq_cfqq_wait_request(cfqq
)) {
3065 if (blk_rq_bytes(rq
) > PAGE_CACHE_SIZE
||
3066 cfqd
->busy_queues
> 1) {
3067 del_timer(&cfqd
->idle_slice_timer
);
3068 __blk_run_queue(cfqd
->queue
);
3070 cfq_mark_cfqq_must_dispatch(cfqq
);
3072 } else if (cfq_should_preempt(cfqd
, cfqq
, rq
)) {
3074 * not the active queue - expire current slice if it is
3075 * idle and has expired it's mean thinktime or this new queue
3076 * has some old slice time left and is of higher priority or
3077 * this new queue is RT and the current one is BE
3079 cfq_preempt_queue(cfqd
, cfqq
);
3080 __blk_run_queue(cfqd
->queue
);
3084 static void cfq_insert_request(struct request_queue
*q
, struct request
*rq
)
3086 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
3087 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
3089 cfq_log_cfqq(cfqd
, cfqq
, "insert_request");
3090 cfq_init_prio_data(cfqq
, RQ_CIC(rq
)->ioc
);
3092 rq_set_fifo_time(rq
, jiffies
+ cfqd
->cfq_fifo_expire
[rq_is_sync(rq
)]);
3093 list_add_tail(&rq
->queuelist
, &cfqq
->fifo
);
3096 cfq_rq_enqueued(cfqd
, cfqq
, rq
);
3100 * Update hw_tag based on peak queue depth over 50 samples under
3103 static void cfq_update_hw_tag(struct cfq_data
*cfqd
)
3105 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
3107 if (rq_in_driver(cfqd
) > cfqd
->hw_tag_est_depth
)
3108 cfqd
->hw_tag_est_depth
= rq_in_driver(cfqd
);
3110 if (cfqd
->hw_tag
== 1)
3113 if (cfqd
->rq_queued
<= CFQ_HW_QUEUE_MIN
&&
3114 rq_in_driver(cfqd
) <= CFQ_HW_QUEUE_MIN
)
3118 * If active queue hasn't enough requests and can idle, cfq might not
3119 * dispatch sufficient requests to hardware. Don't zero hw_tag in this
3122 if (cfqq
&& cfq_cfqq_idle_window(cfqq
) &&
3123 cfqq
->dispatched
+ cfqq
->queued
[0] + cfqq
->queued
[1] <
3124 CFQ_HW_QUEUE_MIN
&& rq_in_driver(cfqd
) < CFQ_HW_QUEUE_MIN
)
3127 if (cfqd
->hw_tag_samples
++ < 50)
3130 if (cfqd
->hw_tag_est_depth
>= CFQ_HW_QUEUE_MIN
)
3136 static void cfq_completed_request(struct request_queue
*q
, struct request
*rq
)
3138 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
3139 struct cfq_data
*cfqd
= cfqq
->cfqd
;
3140 const int sync
= rq_is_sync(rq
);
3144 cfq_log_cfqq(cfqd
, cfqq
, "complete rqnoidle %d", !!rq_noidle(rq
));
3146 cfq_update_hw_tag(cfqd
);
3148 WARN_ON(!cfqd
->rq_in_driver
[sync
]);
3149 WARN_ON(!cfqq
->dispatched
);
3150 cfqd
->rq_in_driver
[sync
]--;
3153 if (cfq_cfqq_sync(cfqq
))
3154 cfqd
->sync_flight
--;
3157 RQ_CIC(rq
)->last_end_request
= now
;
3158 cfqd
->last_end_sync_rq
= now
;
3162 * If this is the active queue, check if it needs to be expired,
3163 * or if we want to idle in case it has no pending requests.
3165 if (cfqd
->active_queue
== cfqq
) {
3166 const bool cfqq_empty
= RB_EMPTY_ROOT(&cfqq
->sort_list
);
3168 if (cfq_cfqq_slice_new(cfqq
)) {
3169 cfq_set_prio_slice(cfqd
, cfqq
);
3170 cfq_clear_cfqq_slice_new(cfqq
);
3173 * Idling is not enabled on:
3175 * - idle-priority queues
3177 * - queues with still some requests queued
3178 * - when there is a close cooperator
3180 if (cfq_slice_used(cfqq
) || cfq_class_idle(cfqq
))
3181 cfq_slice_expired(cfqd
, 1);
3182 else if (sync
&& cfqq_empty
&&
3183 !cfq_close_cooperator(cfqd
, cfqq
)) {
3184 cfqd
->noidle_tree_requires_idle
|= !rq_noidle(rq
);
3186 * Idling is enabled for SYNC_WORKLOAD.
3187 * SYNC_NOIDLE_WORKLOAD idles at the end of the tree
3188 * only if we processed at least one !rq_noidle request
3190 if (cfqd
->serving_type
== SYNC_WORKLOAD
3191 || cfqd
->noidle_tree_requires_idle
)
3192 cfq_arm_slice_timer(cfqd
);
3196 if (!rq_in_driver(cfqd
))
3197 cfq_schedule_dispatch(cfqd
);
3201 * we temporarily boost lower priority queues if they are holding fs exclusive
3202 * resources. they are boosted to normal prio (CLASS_BE/4)
3204 static void cfq_prio_boost(struct cfq_queue
*cfqq
)
3206 if (has_fs_excl()) {
3208 * boost idle prio on transactions that would lock out other
3209 * users of the filesystem
3211 if (cfq_class_idle(cfqq
))
3212 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
3213 if (cfqq
->ioprio
> IOPRIO_NORM
)
3214 cfqq
->ioprio
= IOPRIO_NORM
;
3217 * unboost the queue (if needed)
3219 cfqq
->ioprio_class
= cfqq
->org_ioprio_class
;
3220 cfqq
->ioprio
= cfqq
->org_ioprio
;
3224 static inline int __cfq_may_queue(struct cfq_queue
*cfqq
)
3226 if (cfq_cfqq_wait_request(cfqq
) && !cfq_cfqq_must_alloc_slice(cfqq
)) {
3227 cfq_mark_cfqq_must_alloc_slice(cfqq
);
3228 return ELV_MQUEUE_MUST
;
3231 return ELV_MQUEUE_MAY
;
3234 static int cfq_may_queue(struct request_queue
*q
, int rw
)
3236 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
3237 struct task_struct
*tsk
= current
;
3238 struct cfq_io_context
*cic
;
3239 struct cfq_queue
*cfqq
;
3242 * don't force setup of a queue from here, as a call to may_queue
3243 * does not necessarily imply that a request actually will be queued.
3244 * so just lookup a possibly existing queue, or return 'may queue'
3247 cic
= cfq_cic_lookup(cfqd
, tsk
->io_context
);
3249 return ELV_MQUEUE_MAY
;
3251 cfqq
= cic_to_cfqq(cic
, rw_is_sync(rw
));
3253 cfq_init_prio_data(cfqq
, cic
->ioc
);
3254 cfq_prio_boost(cfqq
);
3256 return __cfq_may_queue(cfqq
);
3259 return ELV_MQUEUE_MAY
;
3263 * queue lock held here
3265 static void cfq_put_request(struct request
*rq
)
3267 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
3270 const int rw
= rq_data_dir(rq
);
3272 BUG_ON(!cfqq
->allocated
[rw
]);
3273 cfqq
->allocated
[rw
]--;
3275 put_io_context(RQ_CIC(rq
)->ioc
);
3277 rq
->elevator_private
= NULL
;
3278 rq
->elevator_private2
= NULL
;
3280 cfq_put_queue(cfqq
);
3284 static struct cfq_queue
*
3285 cfq_merge_cfqqs(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
,
3286 struct cfq_queue
*cfqq
)
3288 cfq_log_cfqq(cfqd
, cfqq
, "merging with queue %p", cfqq
->new_cfqq
);
3289 cic_set_cfqq(cic
, cfqq
->new_cfqq
, 1);
3290 cfq_mark_cfqq_coop(cfqq
->new_cfqq
);
3291 cfq_put_queue(cfqq
);
3292 return cic_to_cfqq(cic
, 1);
3295 static int should_split_cfqq(struct cfq_queue
*cfqq
)
3297 if (cfqq
->seeky_start
&&
3298 time_after(jiffies
, cfqq
->seeky_start
+ CFQQ_COOP_TOUT
))
3304 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
3305 * was the last process referring to said cfqq.
3307 static struct cfq_queue
*
3308 split_cfqq(struct cfq_io_context
*cic
, struct cfq_queue
*cfqq
)
3310 if (cfqq_process_refs(cfqq
) == 1) {
3311 cfqq
->seeky_start
= 0;
3312 cfqq
->pid
= current
->pid
;
3313 cfq_clear_cfqq_coop(cfqq
);
3317 cic_set_cfqq(cic
, NULL
, 1);
3318 cfq_put_queue(cfqq
);
3322 * Allocate cfq data structures associated with this request.
3325 cfq_set_request(struct request_queue
*q
, struct request
*rq
, gfp_t gfp_mask
)
3327 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
3328 struct cfq_io_context
*cic
;
3329 const int rw
= rq_data_dir(rq
);
3330 const bool is_sync
= rq_is_sync(rq
);
3331 struct cfq_queue
*cfqq
;
3332 unsigned long flags
;
3334 might_sleep_if(gfp_mask
& __GFP_WAIT
);
3336 cic
= cfq_get_io_context(cfqd
, gfp_mask
);
3338 spin_lock_irqsave(q
->queue_lock
, flags
);
3344 cfqq
= cic_to_cfqq(cic
, is_sync
);
3345 if (!cfqq
|| cfqq
== &cfqd
->oom_cfqq
) {
3346 cfqq
= cfq_get_queue(cfqd
, is_sync
, cic
->ioc
, gfp_mask
);
3347 cic_set_cfqq(cic
, cfqq
, is_sync
);
3350 * If the queue was seeky for too long, break it apart.
3352 if (cfq_cfqq_coop(cfqq
) && should_split_cfqq(cfqq
)) {
3353 cfq_log_cfqq(cfqd
, cfqq
, "breaking apart cfqq");
3354 cfqq
= split_cfqq(cic
, cfqq
);
3360 * Check to see if this queue is scheduled to merge with
3361 * another, closely cooperating queue. The merging of
3362 * queues happens here as it must be done in process context.
3363 * The reference on new_cfqq was taken in merge_cfqqs.
3366 cfqq
= cfq_merge_cfqqs(cfqd
, cic
, cfqq
);
3369 cfqq
->allocated
[rw
]++;
3370 atomic_inc(&cfqq
->ref
);
3372 spin_unlock_irqrestore(q
->queue_lock
, flags
);
3374 rq
->elevator_private
= cic
;
3375 rq
->elevator_private2
= cfqq
;
3380 put_io_context(cic
->ioc
);
3382 cfq_schedule_dispatch(cfqd
);
3383 spin_unlock_irqrestore(q
->queue_lock
, flags
);
3384 cfq_log(cfqd
, "set_request fail");
3388 static void cfq_kick_queue(struct work_struct
*work
)
3390 struct cfq_data
*cfqd
=
3391 container_of(work
, struct cfq_data
, unplug_work
);
3392 struct request_queue
*q
= cfqd
->queue
;
3394 spin_lock_irq(q
->queue_lock
);
3395 __blk_run_queue(cfqd
->queue
);
3396 spin_unlock_irq(q
->queue_lock
);
3400 * Timer running if the active_queue is currently idling inside its time slice
3402 static void cfq_idle_slice_timer(unsigned long data
)
3404 struct cfq_data
*cfqd
= (struct cfq_data
*) data
;
3405 struct cfq_queue
*cfqq
;
3406 unsigned long flags
;
3409 cfq_log(cfqd
, "idle timer fired");
3411 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
3413 cfqq
= cfqd
->active_queue
;
3418 * We saw a request before the queue expired, let it through
3420 if (cfq_cfqq_must_dispatch(cfqq
))
3426 if (cfq_slice_used(cfqq
))
3430 * only expire and reinvoke request handler, if there are
3431 * other queues with pending requests
3433 if (!cfqd
->busy_queues
)
3437 * not expired and it has a request pending, let it dispatch
3439 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
))
3443 * Queue depth flag is reset only when the idle didn't succeed
3445 cfq_clear_cfqq_deep(cfqq
);
3448 cfq_slice_expired(cfqd
, timed_out
);
3450 cfq_schedule_dispatch(cfqd
);
3452 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
3455 static void cfq_shutdown_timer_wq(struct cfq_data
*cfqd
)
3457 del_timer_sync(&cfqd
->idle_slice_timer
);
3458 cancel_work_sync(&cfqd
->unplug_work
);
3461 static void cfq_put_async_queues(struct cfq_data
*cfqd
)
3465 for (i
= 0; i
< IOPRIO_BE_NR
; i
++) {
3466 if (cfqd
->async_cfqq
[0][i
])
3467 cfq_put_queue(cfqd
->async_cfqq
[0][i
]);
3468 if (cfqd
->async_cfqq
[1][i
])
3469 cfq_put_queue(cfqd
->async_cfqq
[1][i
]);
3472 if (cfqd
->async_idle_cfqq
)
3473 cfq_put_queue(cfqd
->async_idle_cfqq
);
3476 static void cfq_exit_queue(struct elevator_queue
*e
)
3478 struct cfq_data
*cfqd
= e
->elevator_data
;
3479 struct request_queue
*q
= cfqd
->queue
;
3481 cfq_shutdown_timer_wq(cfqd
);
3483 spin_lock_irq(q
->queue_lock
);
3485 if (cfqd
->active_queue
)
3486 __cfq_slice_expired(cfqd
, cfqd
->active_queue
, 0);
3488 while (!list_empty(&cfqd
->cic_list
)) {
3489 struct cfq_io_context
*cic
= list_entry(cfqd
->cic_list
.next
,
3490 struct cfq_io_context
,
3493 __cfq_exit_single_io_context(cfqd
, cic
);
3496 cfq_put_async_queues(cfqd
);
3497 cfq_release_cfq_groups(cfqd
);
3498 blkiocg_del_blkio_group(&cfqd
->root_group
.blkg
);
3500 spin_unlock_irq(q
->queue_lock
);
3502 cfq_shutdown_timer_wq(cfqd
);
3504 /* Wait for cfqg->blkg->key accessors to exit their grace periods. */
3509 static void *cfq_init_queue(struct request_queue
*q
)
3511 struct cfq_data
*cfqd
;
3513 struct cfq_group
*cfqg
;
3514 struct cfq_rb_root
*st
;
3516 cfqd
= kmalloc_node(sizeof(*cfqd
), GFP_KERNEL
| __GFP_ZERO
, q
->node
);
3520 /* Init root service tree */
3521 cfqd
->grp_service_tree
= CFQ_RB_ROOT
;
3523 /* Init root group */
3524 cfqg
= &cfqd
->root_group
;
3525 for_each_cfqg_st(cfqg
, i
, j
, st
)
3527 RB_CLEAR_NODE(&cfqg
->rb_node
);
3529 /* Give preference to root group over other groups */
3530 cfqg
->weight
= 2*BLKIO_WEIGHT_DEFAULT
;
3532 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3534 * Take a reference to root group which we never drop. This is just
3535 * to make sure that cfq_put_cfqg() does not try to kfree root group
3537 atomic_set(&cfqg
->ref
, 1);
3538 blkiocg_add_blkio_group(&blkio_root_cgroup
, &cfqg
->blkg
, (void *)cfqd
,
3542 * Not strictly needed (since RB_ROOT just clears the node and we
3543 * zeroed cfqd on alloc), but better be safe in case someone decides
3544 * to add magic to the rb code
3546 for (i
= 0; i
< CFQ_PRIO_LISTS
; i
++)
3547 cfqd
->prio_trees
[i
] = RB_ROOT
;
3550 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
3551 * Grab a permanent reference to it, so that the normal code flow
3552 * will not attempt to free it.
3554 cfq_init_cfqq(cfqd
, &cfqd
->oom_cfqq
, 1, 0);
3555 atomic_inc(&cfqd
->oom_cfqq
.ref
);
3556 cfq_link_cfqq_cfqg(&cfqd
->oom_cfqq
, &cfqd
->root_group
);
3558 INIT_LIST_HEAD(&cfqd
->cic_list
);
3562 init_timer(&cfqd
->idle_slice_timer
);
3563 cfqd
->idle_slice_timer
.function
= cfq_idle_slice_timer
;
3564 cfqd
->idle_slice_timer
.data
= (unsigned long) cfqd
;
3566 INIT_WORK(&cfqd
->unplug_work
, cfq_kick_queue
);
3568 cfqd
->cfq_quantum
= cfq_quantum
;
3569 cfqd
->cfq_fifo_expire
[0] = cfq_fifo_expire
[0];
3570 cfqd
->cfq_fifo_expire
[1] = cfq_fifo_expire
[1];
3571 cfqd
->cfq_back_max
= cfq_back_max
;
3572 cfqd
->cfq_back_penalty
= cfq_back_penalty
;
3573 cfqd
->cfq_slice
[0] = cfq_slice_async
;
3574 cfqd
->cfq_slice
[1] = cfq_slice_sync
;
3575 cfqd
->cfq_slice_async_rq
= cfq_slice_async_rq
;
3576 cfqd
->cfq_slice_idle
= cfq_slice_idle
;
3577 cfqd
->cfq_latency
= 1;
3579 cfqd
->last_end_sync_rq
= jiffies
;
3583 static void cfq_slab_kill(void)
3586 * Caller already ensured that pending RCU callbacks are completed,
3587 * so we should have no busy allocations at this point.
3590 kmem_cache_destroy(cfq_pool
);
3592 kmem_cache_destroy(cfq_ioc_pool
);
3595 static int __init
cfq_slab_setup(void)
3597 cfq_pool
= KMEM_CACHE(cfq_queue
, 0);
3601 cfq_ioc_pool
= KMEM_CACHE(cfq_io_context
, 0);
3612 * sysfs parts below -->
3615 cfq_var_show(unsigned int var
, char *page
)
3617 return sprintf(page
, "%d\n", var
);
3621 cfq_var_store(unsigned int *var
, const char *page
, size_t count
)
3623 char *p
= (char *) page
;
3625 *var
= simple_strtoul(p
, &p
, 10);
3629 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
3630 static ssize_t __FUNC(struct elevator_queue *e, char *page) \
3632 struct cfq_data *cfqd = e->elevator_data; \
3633 unsigned int __data = __VAR; \
3635 __data = jiffies_to_msecs(__data); \
3636 return cfq_var_show(__data, (page)); \
3638 SHOW_FUNCTION(cfq_quantum_show
, cfqd
->cfq_quantum
, 0);
3639 SHOW_FUNCTION(cfq_fifo_expire_sync_show
, cfqd
->cfq_fifo_expire
[1], 1);
3640 SHOW_FUNCTION(cfq_fifo_expire_async_show
, cfqd
->cfq_fifo_expire
[0], 1);
3641 SHOW_FUNCTION(cfq_back_seek_max_show
, cfqd
->cfq_back_max
, 0);
3642 SHOW_FUNCTION(cfq_back_seek_penalty_show
, cfqd
->cfq_back_penalty
, 0);
3643 SHOW_FUNCTION(cfq_slice_idle_show
, cfqd
->cfq_slice_idle
, 1);
3644 SHOW_FUNCTION(cfq_slice_sync_show
, cfqd
->cfq_slice
[1], 1);
3645 SHOW_FUNCTION(cfq_slice_async_show
, cfqd
->cfq_slice
[0], 1);
3646 SHOW_FUNCTION(cfq_slice_async_rq_show
, cfqd
->cfq_slice_async_rq
, 0);
3647 SHOW_FUNCTION(cfq_low_latency_show
, cfqd
->cfq_latency
, 0);
3648 #undef SHOW_FUNCTION
3650 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
3651 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3653 struct cfq_data *cfqd = e->elevator_data; \
3654 unsigned int __data; \
3655 int ret = cfq_var_store(&__data, (page), count); \
3656 if (__data < (MIN)) \
3658 else if (__data > (MAX)) \
3661 *(__PTR) = msecs_to_jiffies(__data); \
3663 *(__PTR) = __data; \
3666 STORE_FUNCTION(cfq_quantum_store
, &cfqd
->cfq_quantum
, 1, UINT_MAX
, 0);
3667 STORE_FUNCTION(cfq_fifo_expire_sync_store
, &cfqd
->cfq_fifo_expire
[1], 1,
3669 STORE_FUNCTION(cfq_fifo_expire_async_store
, &cfqd
->cfq_fifo_expire
[0], 1,
3671 STORE_FUNCTION(cfq_back_seek_max_store
, &cfqd
->cfq_back_max
, 0, UINT_MAX
, 0);
3672 STORE_FUNCTION(cfq_back_seek_penalty_store
, &cfqd
->cfq_back_penalty
, 1,
3674 STORE_FUNCTION(cfq_slice_idle_store
, &cfqd
->cfq_slice_idle
, 0, UINT_MAX
, 1);
3675 STORE_FUNCTION(cfq_slice_sync_store
, &cfqd
->cfq_slice
[1], 1, UINT_MAX
, 1);
3676 STORE_FUNCTION(cfq_slice_async_store
, &cfqd
->cfq_slice
[0], 1, UINT_MAX
, 1);
3677 STORE_FUNCTION(cfq_slice_async_rq_store
, &cfqd
->cfq_slice_async_rq
, 1,
3679 STORE_FUNCTION(cfq_low_latency_store
, &cfqd
->cfq_latency
, 0, 1, 0);
3680 #undef STORE_FUNCTION
3682 #define CFQ_ATTR(name) \
3683 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3685 static struct elv_fs_entry cfq_attrs
[] = {
3687 CFQ_ATTR(fifo_expire_sync
),
3688 CFQ_ATTR(fifo_expire_async
),
3689 CFQ_ATTR(back_seek_max
),
3690 CFQ_ATTR(back_seek_penalty
),
3691 CFQ_ATTR(slice_sync
),
3692 CFQ_ATTR(slice_async
),
3693 CFQ_ATTR(slice_async_rq
),
3694 CFQ_ATTR(slice_idle
),
3695 CFQ_ATTR(low_latency
),
3699 static struct elevator_type iosched_cfq
= {
3701 .elevator_merge_fn
= cfq_merge
,
3702 .elevator_merged_fn
= cfq_merged_request
,
3703 .elevator_merge_req_fn
= cfq_merged_requests
,
3704 .elevator_allow_merge_fn
= cfq_allow_merge
,
3705 .elevator_dispatch_fn
= cfq_dispatch_requests
,
3706 .elevator_add_req_fn
= cfq_insert_request
,
3707 .elevator_activate_req_fn
= cfq_activate_request
,
3708 .elevator_deactivate_req_fn
= cfq_deactivate_request
,
3709 .elevator_queue_empty_fn
= cfq_queue_empty
,
3710 .elevator_completed_req_fn
= cfq_completed_request
,
3711 .elevator_former_req_fn
= elv_rb_former_request
,
3712 .elevator_latter_req_fn
= elv_rb_latter_request
,
3713 .elevator_set_req_fn
= cfq_set_request
,
3714 .elevator_put_req_fn
= cfq_put_request
,
3715 .elevator_may_queue_fn
= cfq_may_queue
,
3716 .elevator_init_fn
= cfq_init_queue
,
3717 .elevator_exit_fn
= cfq_exit_queue
,
3718 .trim
= cfq_free_io_context
,
3720 .elevator_attrs
= cfq_attrs
,
3721 .elevator_name
= "cfq",
3722 .elevator_owner
= THIS_MODULE
,
3725 static int __init
cfq_init(void)
3728 * could be 0 on HZ < 1000 setups
3730 if (!cfq_slice_async
)
3731 cfq_slice_async
= 1;
3732 if (!cfq_slice_idle
)
3735 if (cfq_slab_setup())
3738 elv_register(&iosched_cfq
);
3743 static void __exit
cfq_exit(void)
3745 DECLARE_COMPLETION_ONSTACK(all_gone
);
3746 elv_unregister(&iosched_cfq
);
3747 ioc_gone
= &all_gone
;
3748 /* ioc_gone's update must be visible before reading ioc_count */
3752 * this also protects us from entering cfq_slab_kill() with
3753 * pending RCU callbacks
3755 if (elv_ioc_count_read(cfq_ioc_count
))
3756 wait_for_completion(&all_gone
);
3760 module_init(cfq_init
);
3761 module_exit(cfq_exit
);
3763 MODULE_AUTHOR("Jens Axboe");
3764 MODULE_LICENSE("GPL");
3765 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");