2 * CFQ, or complete fairness queueing, disk scheduler.
4 * Based on ideas from a previously unfinished io
5 * scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
7 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
9 #include <linux/module.h>
10 #include <linux/blkdev.h>
11 #include <linux/elevator.h>
12 #include <linux/rbtree.h>
13 #include <linux/ioprio.h>
14 #include <linux/blktrace_api.h>
19 /* max queue in one round of service */
20 static const int cfq_quantum
= 4;
21 static const int cfq_fifo_expire
[2] = { HZ
/ 4, HZ
/ 8 };
22 /* maximum backwards seek, in KiB */
23 static const int cfq_back_max
= 16 * 1024;
24 /* penalty of a backwards seek */
25 static const int cfq_back_penalty
= 2;
26 static const int cfq_slice_sync
= HZ
/ 10;
27 static int cfq_slice_async
= HZ
/ 25;
28 static const int cfq_slice_async_rq
= 2;
29 static int cfq_slice_idle
= HZ
/ 125;
30 static const int cfq_target_latency
= HZ
* 3/10; /* 300 ms */
31 static const int cfq_hist_divisor
= 4;
34 * offset from end of service tree
36 #define CFQ_IDLE_DELAY (HZ / 5)
39 * below this threshold, we consider thinktime immediate
41 #define CFQ_MIN_TT (2)
44 * Allow merged cfqqs to perform this amount of seeky I/O before
45 * deciding to break the queues up again.
47 #define CFQQ_COOP_TOUT (HZ)
49 #define CFQ_SLICE_SCALE (5)
50 #define CFQ_HW_QUEUE_MIN (5)
53 ((struct cfq_io_context *) (rq)->elevator_private)
54 #define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2)
56 static struct kmem_cache
*cfq_pool
;
57 static struct kmem_cache
*cfq_ioc_pool
;
59 static DEFINE_PER_CPU(unsigned long, cfq_ioc_count
);
60 static struct completion
*ioc_gone
;
61 static DEFINE_SPINLOCK(ioc_gone_lock
);
63 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
64 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
65 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
67 #define sample_valid(samples) ((samples) > 80)
70 * Most of our rbtree usage is for sorting with min extraction, so
71 * if we cache the leftmost node we don't have to walk down the tree
72 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
73 * move this into the elevator for the rq sorting as well.
80 #define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, 0, }
83 * Per process-grouping structure
88 /* various state flags, see below */
91 struct cfq_data
*cfqd
;
92 /* service_tree member */
93 struct rb_node rb_node
;
94 /* service_tree key */
96 /* prio tree member */
97 struct rb_node p_node
;
98 /* prio tree root we belong to, if any */
99 struct rb_root
*p_root
;
100 /* sorted list of pending requests */
101 struct rb_root sort_list
;
102 /* if fifo isn't expired, next request to serve */
103 struct request
*next_rq
;
104 /* requests queued in sort_list */
106 /* currently allocated requests */
108 /* fifo list of requests in sort_list */
109 struct list_head fifo
;
111 unsigned long slice_end
;
113 unsigned int slice_dispatch
;
115 /* pending metadata requests */
117 /* number of requests that are on the dispatch list or inside driver */
120 /* io prio of this group */
121 unsigned short ioprio
, org_ioprio
;
122 unsigned short ioprio_class
, org_ioprio_class
;
124 unsigned int seek_samples
;
127 sector_t last_request_pos
;
128 unsigned long seeky_start
;
132 struct cfq_rb_root
*service_tree
;
133 struct cfq_queue
*new_cfqq
;
137 * First index in the service_trees.
138 * IDLE is handled separately, so it has negative index
147 * Second index in the service_trees.
151 SYNC_NOIDLE_WORKLOAD
= 1,
157 * Per block device queue structure
160 struct request_queue
*queue
;
163 * rr lists of queues with requests, onle rr for each priority class.
164 * Counts are embedded in the cfq_rb_root
166 struct cfq_rb_root service_trees
[2][3];
167 struct cfq_rb_root service_tree_idle
;
169 * The priority currently being served
171 enum wl_prio_t serving_prio
;
172 enum wl_type_t serving_type
;
173 unsigned long workload_expires
;
176 * Each priority tree is sorted by next_request position. These
177 * trees are used when determining if two or more queues are
178 * interleaving requests (see cfq_close_cooperator).
180 struct rb_root prio_trees
[CFQ_PRIO_LISTS
];
182 unsigned int busy_queues
;
183 unsigned int busy_queues_avg
[2];
189 * queue-depth detection
194 int rq_in_driver_peak
;
197 * idle window management
199 struct timer_list idle_slice_timer
;
200 struct work_struct unplug_work
;
202 struct cfq_queue
*active_queue
;
203 struct cfq_io_context
*active_cic
;
206 * async queue for each priority case
208 struct cfq_queue
*async_cfqq
[2][IOPRIO_BE_NR
];
209 struct cfq_queue
*async_idle_cfqq
;
211 sector_t last_position
;
214 * tunables, see top of file
216 unsigned int cfq_quantum
;
217 unsigned int cfq_fifo_expire
[2];
218 unsigned int cfq_back_penalty
;
219 unsigned int cfq_back_max
;
220 unsigned int cfq_slice
[2];
221 unsigned int cfq_slice_async_rq
;
222 unsigned int cfq_slice_idle
;
223 unsigned int cfq_latency
;
225 struct list_head cic_list
;
228 * Fallback dummy cfqq for extreme OOM conditions
230 struct cfq_queue oom_cfqq
;
232 unsigned long last_end_sync_rq
;
235 static struct cfq_rb_root
*service_tree_for(enum wl_prio_t prio
,
237 struct cfq_data
*cfqd
)
239 if (prio
== IDLE_WORKLOAD
)
240 return &cfqd
->service_tree_idle
;
242 return &cfqd
->service_trees
[prio
][type
];
245 enum cfqq_state_flags
{
246 CFQ_CFQQ_FLAG_on_rr
= 0, /* on round-robin busy list */
247 CFQ_CFQQ_FLAG_wait_request
, /* waiting for a request */
248 CFQ_CFQQ_FLAG_must_dispatch
, /* must be allowed a dispatch */
249 CFQ_CFQQ_FLAG_must_alloc_slice
, /* per-slice must_alloc flag */
250 CFQ_CFQQ_FLAG_fifo_expire
, /* FIFO checked in this slice */
251 CFQ_CFQQ_FLAG_idle_window
, /* slice idling enabled */
252 CFQ_CFQQ_FLAG_prio_changed
, /* task priority has changed */
253 CFQ_CFQQ_FLAG_slice_new
, /* no requests dispatched in slice */
254 CFQ_CFQQ_FLAG_sync
, /* synchronous queue */
255 CFQ_CFQQ_FLAG_coop
, /* cfqq is shared */
258 #define CFQ_CFQQ_FNS(name) \
259 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
261 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
263 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
265 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
267 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
269 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
273 CFQ_CFQQ_FNS(wait_request
);
274 CFQ_CFQQ_FNS(must_dispatch
);
275 CFQ_CFQQ_FNS(must_alloc_slice
);
276 CFQ_CFQQ_FNS(fifo_expire
);
277 CFQ_CFQQ_FNS(idle_window
);
278 CFQ_CFQQ_FNS(prio_changed
);
279 CFQ_CFQQ_FNS(slice_new
);
284 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
285 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
286 #define cfq_log(cfqd, fmt, args...) \
287 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
289 static inline enum wl_prio_t
cfqq_prio(struct cfq_queue
*cfqq
)
291 if (cfq_class_idle(cfqq
))
292 return IDLE_WORKLOAD
;
293 if (cfq_class_rt(cfqq
))
299 static enum wl_type_t
cfqq_type(struct cfq_queue
*cfqq
)
301 if (!cfq_cfqq_sync(cfqq
))
302 return ASYNC_WORKLOAD
;
303 if (!cfq_cfqq_idle_window(cfqq
))
304 return SYNC_NOIDLE_WORKLOAD
;
305 return SYNC_WORKLOAD
;
308 static inline int cfq_busy_queues_wl(enum wl_prio_t wl
, struct cfq_data
*cfqd
)
310 if (wl
== IDLE_WORKLOAD
)
311 return cfqd
->service_tree_idle
.count
;
313 return cfqd
->service_trees
[wl
][ASYNC_WORKLOAD
].count
314 + cfqd
->service_trees
[wl
][SYNC_NOIDLE_WORKLOAD
].count
315 + cfqd
->service_trees
[wl
][SYNC_WORKLOAD
].count
;
318 static void cfq_dispatch_insert(struct request_queue
*, struct request
*);
319 static struct cfq_queue
*cfq_get_queue(struct cfq_data
*, bool,
320 struct io_context
*, gfp_t
);
321 static struct cfq_io_context
*cfq_cic_lookup(struct cfq_data
*,
322 struct io_context
*);
324 static inline int rq_in_driver(struct cfq_data
*cfqd
)
326 return cfqd
->rq_in_driver
[0] + cfqd
->rq_in_driver
[1];
329 static inline struct cfq_queue
*cic_to_cfqq(struct cfq_io_context
*cic
,
332 return cic
->cfqq
[is_sync
];
335 static inline void cic_set_cfqq(struct cfq_io_context
*cic
,
336 struct cfq_queue
*cfqq
, bool is_sync
)
338 cic
->cfqq
[is_sync
] = cfqq
;
342 * We regard a request as SYNC, if it's either a read or has the SYNC bit
343 * set (in which case it could also be direct WRITE).
345 static inline bool cfq_bio_sync(struct bio
*bio
)
347 return bio_data_dir(bio
) == READ
|| bio_rw_flagged(bio
, BIO_RW_SYNCIO
);
351 * scheduler run of queue, if there are requests pending and no one in the
352 * driver that will restart queueing
354 static inline void cfq_schedule_dispatch(struct cfq_data
*cfqd
)
356 if (cfqd
->busy_queues
) {
357 cfq_log(cfqd
, "schedule dispatch");
358 kblockd_schedule_work(cfqd
->queue
, &cfqd
->unplug_work
);
362 static int cfq_queue_empty(struct request_queue
*q
)
364 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
366 return !cfqd
->busy_queues
;
370 * Scale schedule slice based on io priority. Use the sync time slice only
371 * if a queue is marked sync and has sync io queued. A sync queue with async
372 * io only, should not get full sync slice length.
374 static inline int cfq_prio_slice(struct cfq_data
*cfqd
, bool sync
,
377 const int base_slice
= cfqd
->cfq_slice
[sync
];
379 WARN_ON(prio
>= IOPRIO_BE_NR
);
381 return base_slice
+ (base_slice
/CFQ_SLICE_SCALE
* (4 - prio
));
385 cfq_prio_to_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
387 return cfq_prio_slice(cfqd
, cfq_cfqq_sync(cfqq
), cfqq
->ioprio
);
391 * get averaged number of queues of RT/BE priority.
392 * average is updated, with a formula that gives more weight to higher numbers,
393 * to quickly follows sudden increases and decrease slowly
396 static inline unsigned cfq_get_avg_queues(struct cfq_data
*cfqd
, bool rt
)
398 unsigned min_q
, max_q
;
399 unsigned mult
= cfq_hist_divisor
- 1;
400 unsigned round
= cfq_hist_divisor
/ 2;
401 unsigned busy
= cfq_busy_queues_wl(rt
, cfqd
);
403 min_q
= min(cfqd
->busy_queues_avg
[rt
], busy
);
404 max_q
= max(cfqd
->busy_queues_avg
[rt
], busy
);
405 cfqd
->busy_queues_avg
[rt
] = (mult
* max_q
+ min_q
+ round
) /
407 return cfqd
->busy_queues_avg
[rt
];
411 cfq_set_prio_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
413 unsigned slice
= cfq_prio_to_slice(cfqd
, cfqq
);
414 if (cfqd
->cfq_latency
) {
415 /* interested queues (we consider only the ones with the same
417 unsigned iq
= cfq_get_avg_queues(cfqd
, cfq_class_rt(cfqq
));
418 unsigned sync_slice
= cfqd
->cfq_slice
[1];
419 unsigned expect_latency
= sync_slice
* iq
;
420 if (expect_latency
> cfq_target_latency
) {
421 unsigned base_low_slice
= 2 * cfqd
->cfq_slice_idle
;
422 /* scale low_slice according to IO priority
423 * and sync vs async */
425 min(slice
, base_low_slice
* slice
/ sync_slice
);
426 /* the adapted slice value is scaled to fit all iqs
427 * into the target latency */
428 slice
= max(slice
* cfq_target_latency
/ expect_latency
,
432 cfqq
->slice_end
= jiffies
+ slice
;
433 cfq_log_cfqq(cfqd
, cfqq
, "set_slice=%lu", cfqq
->slice_end
- jiffies
);
437 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
438 * isn't valid until the first request from the dispatch is activated
439 * and the slice time set.
441 static inline bool cfq_slice_used(struct cfq_queue
*cfqq
)
443 if (cfq_cfqq_slice_new(cfqq
))
445 if (time_before(jiffies
, cfqq
->slice_end
))
452 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
453 * We choose the request that is closest to the head right now. Distance
454 * behind the head is penalized and only allowed to a certain extent.
456 static struct request
*
457 cfq_choose_req(struct cfq_data
*cfqd
, struct request
*rq1
, struct request
*rq2
)
459 sector_t last
, s1
, s2
, d1
= 0, d2
= 0;
460 unsigned long back_max
;
461 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
462 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
463 unsigned wrap
= 0; /* bit mask: requests behind the disk head? */
465 if (rq1
== NULL
|| rq1
== rq2
)
470 if (rq_is_sync(rq1
) && !rq_is_sync(rq2
))
472 else if (rq_is_sync(rq2
) && !rq_is_sync(rq1
))
474 if (rq_is_meta(rq1
) && !rq_is_meta(rq2
))
476 else if (rq_is_meta(rq2
) && !rq_is_meta(rq1
))
479 s1
= blk_rq_pos(rq1
);
480 s2
= blk_rq_pos(rq2
);
482 last
= cfqd
->last_position
;
485 * by definition, 1KiB is 2 sectors
487 back_max
= cfqd
->cfq_back_max
* 2;
490 * Strict one way elevator _except_ in the case where we allow
491 * short backward seeks which are biased as twice the cost of a
492 * similar forward seek.
496 else if (s1
+ back_max
>= last
)
497 d1
= (last
- s1
) * cfqd
->cfq_back_penalty
;
499 wrap
|= CFQ_RQ1_WRAP
;
503 else if (s2
+ back_max
>= last
)
504 d2
= (last
- s2
) * cfqd
->cfq_back_penalty
;
506 wrap
|= CFQ_RQ2_WRAP
;
508 /* Found required data */
511 * By doing switch() on the bit mask "wrap" we avoid having to
512 * check two variables for all permutations: --> faster!
515 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
531 case (CFQ_RQ1_WRAP
|CFQ_RQ2_WRAP
): /* both rqs wrapped */
534 * Since both rqs are wrapped,
535 * start with the one that's further behind head
536 * (--> only *one* back seek required),
537 * since back seek takes more time than forward.
547 * The below is leftmost cache rbtree addon
549 static struct cfq_queue
*cfq_rb_first(struct cfq_rb_root
*root
)
552 root
->left
= rb_first(&root
->rb
);
555 return rb_entry(root
->left
, struct cfq_queue
, rb_node
);
560 static void rb_erase_init(struct rb_node
*n
, struct rb_root
*root
)
566 static void cfq_rb_erase(struct rb_node
*n
, struct cfq_rb_root
*root
)
570 rb_erase_init(n
, &root
->rb
);
575 * would be nice to take fifo expire time into account as well
577 static struct request
*
578 cfq_find_next_rq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
579 struct request
*last
)
581 struct rb_node
*rbnext
= rb_next(&last
->rb_node
);
582 struct rb_node
*rbprev
= rb_prev(&last
->rb_node
);
583 struct request
*next
= NULL
, *prev
= NULL
;
585 BUG_ON(RB_EMPTY_NODE(&last
->rb_node
));
588 prev
= rb_entry_rq(rbprev
);
591 next
= rb_entry_rq(rbnext
);
593 rbnext
= rb_first(&cfqq
->sort_list
);
594 if (rbnext
&& rbnext
!= &last
->rb_node
)
595 next
= rb_entry_rq(rbnext
);
598 return cfq_choose_req(cfqd
, next
, prev
);
601 static unsigned long cfq_slice_offset(struct cfq_data
*cfqd
,
602 struct cfq_queue
*cfqq
)
605 * just an approximation, should be ok.
607 return (cfqd
->busy_queues
- 1) * (cfq_prio_slice(cfqd
, 1, 0) -
608 cfq_prio_slice(cfqd
, cfq_cfqq_sync(cfqq
), cfqq
->ioprio
));
612 * The cfqd->service_trees holds all pending cfq_queue's that have
613 * requests waiting to be processed. It is sorted in the order that
614 * we will service the queues.
616 static void cfq_service_tree_add(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
619 struct rb_node
**p
, *parent
;
620 struct cfq_queue
*__cfqq
;
621 unsigned long rb_key
;
622 struct cfq_rb_root
*service_tree
;
625 service_tree
= service_tree_for(cfqq_prio(cfqq
), cfqq_type(cfqq
), cfqd
);
626 if (cfq_class_idle(cfqq
)) {
627 rb_key
= CFQ_IDLE_DELAY
;
628 parent
= rb_last(&service_tree
->rb
);
629 if (parent
&& parent
!= &cfqq
->rb_node
) {
630 __cfqq
= rb_entry(parent
, struct cfq_queue
, rb_node
);
631 rb_key
+= __cfqq
->rb_key
;
634 } else if (!add_front
) {
636 * Get our rb key offset. Subtract any residual slice
637 * value carried from last service. A negative resid
638 * count indicates slice overrun, and this should position
639 * the next service time further away in the tree.
641 rb_key
= cfq_slice_offset(cfqd
, cfqq
) + jiffies
;
642 rb_key
-= cfqq
->slice_resid
;
643 cfqq
->slice_resid
= 0;
646 __cfqq
= cfq_rb_first(service_tree
);
647 rb_key
+= __cfqq
? __cfqq
->rb_key
: jiffies
;
650 if (!RB_EMPTY_NODE(&cfqq
->rb_node
)) {
652 * same position, nothing more to do
654 if (rb_key
== cfqq
->rb_key
&&
655 cfqq
->service_tree
== service_tree
)
658 cfq_rb_erase(&cfqq
->rb_node
, cfqq
->service_tree
);
659 cfqq
->service_tree
= NULL
;
664 cfqq
->service_tree
= service_tree
;
665 p
= &service_tree
->rb
.rb_node
;
670 __cfqq
= rb_entry(parent
, struct cfq_queue
, rb_node
);
673 * sort by key, that represents service time.
675 if (time_before(rb_key
, __cfqq
->rb_key
))
686 service_tree
->left
= &cfqq
->rb_node
;
688 cfqq
->rb_key
= rb_key
;
689 rb_link_node(&cfqq
->rb_node
, parent
, p
);
690 rb_insert_color(&cfqq
->rb_node
, &service_tree
->rb
);
691 service_tree
->count
++;
694 static struct cfq_queue
*
695 cfq_prio_tree_lookup(struct cfq_data
*cfqd
, struct rb_root
*root
,
696 sector_t sector
, struct rb_node
**ret_parent
,
697 struct rb_node
***rb_link
)
699 struct rb_node
**p
, *parent
;
700 struct cfq_queue
*cfqq
= NULL
;
708 cfqq
= rb_entry(parent
, struct cfq_queue
, p_node
);
711 * Sort strictly based on sector. Smallest to the left,
712 * largest to the right.
714 if (sector
> blk_rq_pos(cfqq
->next_rq
))
716 else if (sector
< blk_rq_pos(cfqq
->next_rq
))
724 *ret_parent
= parent
;
730 static void cfq_prio_tree_add(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
732 struct rb_node
**p
, *parent
;
733 struct cfq_queue
*__cfqq
;
736 rb_erase(&cfqq
->p_node
, cfqq
->p_root
);
740 if (cfq_class_idle(cfqq
))
745 cfqq
->p_root
= &cfqd
->prio_trees
[cfqq
->org_ioprio
];
746 __cfqq
= cfq_prio_tree_lookup(cfqd
, cfqq
->p_root
,
747 blk_rq_pos(cfqq
->next_rq
), &parent
, &p
);
749 rb_link_node(&cfqq
->p_node
, parent
, p
);
750 rb_insert_color(&cfqq
->p_node
, cfqq
->p_root
);
756 * Update cfqq's position in the service tree.
758 static void cfq_resort_rr_list(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
761 * Resorting requires the cfqq to be on the RR list already.
763 if (cfq_cfqq_on_rr(cfqq
)) {
764 cfq_service_tree_add(cfqd
, cfqq
, 0);
765 cfq_prio_tree_add(cfqd
, cfqq
);
770 * add to busy list of queues for service, trying to be fair in ordering
771 * the pending list according to last request service
773 static void cfq_add_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
775 cfq_log_cfqq(cfqd
, cfqq
, "add_to_rr");
776 BUG_ON(cfq_cfqq_on_rr(cfqq
));
777 cfq_mark_cfqq_on_rr(cfqq
);
780 cfq_resort_rr_list(cfqd
, cfqq
);
784 * Called when the cfqq no longer has requests pending, remove it from
787 static void cfq_del_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
789 cfq_log_cfqq(cfqd
, cfqq
, "del_from_rr");
790 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
791 cfq_clear_cfqq_on_rr(cfqq
);
793 if (!RB_EMPTY_NODE(&cfqq
->rb_node
)) {
794 cfq_rb_erase(&cfqq
->rb_node
, cfqq
->service_tree
);
795 cfqq
->service_tree
= NULL
;
798 rb_erase(&cfqq
->p_node
, cfqq
->p_root
);
802 BUG_ON(!cfqd
->busy_queues
);
807 * rb tree support functions
809 static void cfq_del_rq_rb(struct request
*rq
)
811 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
812 struct cfq_data
*cfqd
= cfqq
->cfqd
;
813 const int sync
= rq_is_sync(rq
);
815 BUG_ON(!cfqq
->queued
[sync
]);
816 cfqq
->queued
[sync
]--;
818 elv_rb_del(&cfqq
->sort_list
, rq
);
820 if (cfq_cfqq_on_rr(cfqq
) && RB_EMPTY_ROOT(&cfqq
->sort_list
))
821 cfq_del_cfqq_rr(cfqd
, cfqq
);
824 static void cfq_add_rq_rb(struct request
*rq
)
826 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
827 struct cfq_data
*cfqd
= cfqq
->cfqd
;
828 struct request
*__alias
, *prev
;
830 cfqq
->queued
[rq_is_sync(rq
)]++;
833 * looks a little odd, but the first insert might return an alias.
834 * if that happens, put the alias on the dispatch list
836 while ((__alias
= elv_rb_add(&cfqq
->sort_list
, rq
)) != NULL
)
837 cfq_dispatch_insert(cfqd
->queue
, __alias
);
839 if (!cfq_cfqq_on_rr(cfqq
))
840 cfq_add_cfqq_rr(cfqd
, cfqq
);
843 * check if this request is a better next-serve candidate
845 prev
= cfqq
->next_rq
;
846 cfqq
->next_rq
= cfq_choose_req(cfqd
, cfqq
->next_rq
, rq
);
849 * adjust priority tree position, if ->next_rq changes
851 if (prev
!= cfqq
->next_rq
)
852 cfq_prio_tree_add(cfqd
, cfqq
);
854 BUG_ON(!cfqq
->next_rq
);
857 static void cfq_reposition_rq_rb(struct cfq_queue
*cfqq
, struct request
*rq
)
859 elv_rb_del(&cfqq
->sort_list
, rq
);
860 cfqq
->queued
[rq_is_sync(rq
)]--;
864 static struct request
*
865 cfq_find_rq_fmerge(struct cfq_data
*cfqd
, struct bio
*bio
)
867 struct task_struct
*tsk
= current
;
868 struct cfq_io_context
*cic
;
869 struct cfq_queue
*cfqq
;
871 cic
= cfq_cic_lookup(cfqd
, tsk
->io_context
);
875 cfqq
= cic_to_cfqq(cic
, cfq_bio_sync(bio
));
877 sector_t sector
= bio
->bi_sector
+ bio_sectors(bio
);
879 return elv_rb_find(&cfqq
->sort_list
, sector
);
885 static void cfq_activate_request(struct request_queue
*q
, struct request
*rq
)
887 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
889 cfqd
->rq_in_driver
[rq_is_sync(rq
)]++;
890 cfq_log_cfqq(cfqd
, RQ_CFQQ(rq
), "activate rq, drv=%d",
893 cfqd
->last_position
= blk_rq_pos(rq
) + blk_rq_sectors(rq
);
896 static void cfq_deactivate_request(struct request_queue
*q
, struct request
*rq
)
898 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
899 const int sync
= rq_is_sync(rq
);
901 WARN_ON(!cfqd
->rq_in_driver
[sync
]);
902 cfqd
->rq_in_driver
[sync
]--;
903 cfq_log_cfqq(cfqd
, RQ_CFQQ(rq
), "deactivate rq, drv=%d",
907 static void cfq_remove_request(struct request
*rq
)
909 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
911 if (cfqq
->next_rq
== rq
)
912 cfqq
->next_rq
= cfq_find_next_rq(cfqq
->cfqd
, cfqq
, rq
);
914 list_del_init(&rq
->queuelist
);
917 cfqq
->cfqd
->rq_queued
--;
918 if (rq_is_meta(rq
)) {
919 WARN_ON(!cfqq
->meta_pending
);
920 cfqq
->meta_pending
--;
924 static int cfq_merge(struct request_queue
*q
, struct request
**req
,
927 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
928 struct request
*__rq
;
930 __rq
= cfq_find_rq_fmerge(cfqd
, bio
);
931 if (__rq
&& elv_rq_merge_ok(__rq
, bio
)) {
933 return ELEVATOR_FRONT_MERGE
;
936 return ELEVATOR_NO_MERGE
;
939 static void cfq_merged_request(struct request_queue
*q
, struct request
*req
,
942 if (type
== ELEVATOR_FRONT_MERGE
) {
943 struct cfq_queue
*cfqq
= RQ_CFQQ(req
);
945 cfq_reposition_rq_rb(cfqq
, req
);
950 cfq_merged_requests(struct request_queue
*q
, struct request
*rq
,
951 struct request
*next
)
954 * reposition in fifo if next is older than rq
956 if (!list_empty(&rq
->queuelist
) && !list_empty(&next
->queuelist
) &&
957 time_before(rq_fifo_time(next
), rq_fifo_time(rq
))) {
958 list_move(&rq
->queuelist
, &next
->queuelist
);
959 rq_set_fifo_time(rq
, rq_fifo_time(next
));
962 cfq_remove_request(next
);
965 static int cfq_allow_merge(struct request_queue
*q
, struct request
*rq
,
968 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
969 struct cfq_io_context
*cic
;
970 struct cfq_queue
*cfqq
;
973 * Disallow merge of a sync bio into an async request.
975 if (cfq_bio_sync(bio
) && !rq_is_sync(rq
))
979 * Lookup the cfqq that this bio will be queued with. Allow
980 * merge only if rq is queued there.
982 cic
= cfq_cic_lookup(cfqd
, current
->io_context
);
986 cfqq
= cic_to_cfqq(cic
, cfq_bio_sync(bio
));
987 return cfqq
== RQ_CFQQ(rq
);
990 static void __cfq_set_active_queue(struct cfq_data
*cfqd
,
991 struct cfq_queue
*cfqq
)
994 cfq_log_cfqq(cfqd
, cfqq
, "set_active");
996 cfqq
->slice_dispatch
= 0;
998 cfq_clear_cfqq_wait_request(cfqq
);
999 cfq_clear_cfqq_must_dispatch(cfqq
);
1000 cfq_clear_cfqq_must_alloc_slice(cfqq
);
1001 cfq_clear_cfqq_fifo_expire(cfqq
);
1002 cfq_mark_cfqq_slice_new(cfqq
);
1004 del_timer(&cfqd
->idle_slice_timer
);
1007 cfqd
->active_queue
= cfqq
;
1011 * current cfqq expired its slice (or was too idle), select new one
1014 __cfq_slice_expired(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1017 cfq_log_cfqq(cfqd
, cfqq
, "slice expired t=%d", timed_out
);
1019 if (cfq_cfqq_wait_request(cfqq
))
1020 del_timer(&cfqd
->idle_slice_timer
);
1022 cfq_clear_cfqq_wait_request(cfqq
);
1025 * store what was left of this slice, if the queue idled/timed out
1027 if (timed_out
&& !cfq_cfqq_slice_new(cfqq
)) {
1028 cfqq
->slice_resid
= cfqq
->slice_end
- jiffies
;
1029 cfq_log_cfqq(cfqd
, cfqq
, "resid=%ld", cfqq
->slice_resid
);
1032 cfq_resort_rr_list(cfqd
, cfqq
);
1034 if (cfqq
== cfqd
->active_queue
)
1035 cfqd
->active_queue
= NULL
;
1037 if (cfqd
->active_cic
) {
1038 put_io_context(cfqd
->active_cic
->ioc
);
1039 cfqd
->active_cic
= NULL
;
1043 static inline void cfq_slice_expired(struct cfq_data
*cfqd
, bool timed_out
)
1045 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
1048 __cfq_slice_expired(cfqd
, cfqq
, timed_out
);
1052 * Get next queue for service. Unless we have a queue preemption,
1053 * we'll simply select the first cfqq in the service tree.
1055 static struct cfq_queue
*cfq_get_next_queue(struct cfq_data
*cfqd
)
1057 struct cfq_rb_root
*service_tree
=
1058 service_tree_for(cfqd
->serving_prio
, cfqd
->serving_type
, cfqd
);
1060 if (RB_EMPTY_ROOT(&service_tree
->rb
))
1062 return cfq_rb_first(service_tree
);
1066 * Get and set a new active queue for service.
1068 static struct cfq_queue
*cfq_set_active_queue(struct cfq_data
*cfqd
,
1069 struct cfq_queue
*cfqq
)
1072 cfqq
= cfq_get_next_queue(cfqd
);
1074 __cfq_set_active_queue(cfqd
, cfqq
);
1078 static inline sector_t
cfq_dist_from_last(struct cfq_data
*cfqd
,
1081 if (blk_rq_pos(rq
) >= cfqd
->last_position
)
1082 return blk_rq_pos(rq
) - cfqd
->last_position
;
1084 return cfqd
->last_position
- blk_rq_pos(rq
);
1087 #define CFQQ_SEEK_THR 8 * 1024
1088 #define CFQQ_SEEKY(cfqq) ((cfqq)->seek_mean > CFQQ_SEEK_THR)
1090 static inline int cfq_rq_close(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1093 sector_t sdist
= cfqq
->seek_mean
;
1095 if (!sample_valid(cfqq
->seek_samples
))
1096 sdist
= CFQQ_SEEK_THR
;
1098 return cfq_dist_from_last(cfqd
, rq
) <= sdist
;
1101 static struct cfq_queue
*cfqq_close(struct cfq_data
*cfqd
,
1102 struct cfq_queue
*cur_cfqq
)
1104 struct rb_root
*root
= &cfqd
->prio_trees
[cur_cfqq
->org_ioprio
];
1105 struct rb_node
*parent
, *node
;
1106 struct cfq_queue
*__cfqq
;
1107 sector_t sector
= cfqd
->last_position
;
1109 if (RB_EMPTY_ROOT(root
))
1113 * First, if we find a request starting at the end of the last
1114 * request, choose it.
1116 __cfqq
= cfq_prio_tree_lookup(cfqd
, root
, sector
, &parent
, NULL
);
1121 * If the exact sector wasn't found, the parent of the NULL leaf
1122 * will contain the closest sector.
1124 __cfqq
= rb_entry(parent
, struct cfq_queue
, p_node
);
1125 if (cfq_rq_close(cfqd
, cur_cfqq
, __cfqq
->next_rq
))
1128 if (blk_rq_pos(__cfqq
->next_rq
) < sector
)
1129 node
= rb_next(&__cfqq
->p_node
);
1131 node
= rb_prev(&__cfqq
->p_node
);
1135 __cfqq
= rb_entry(node
, struct cfq_queue
, p_node
);
1136 if (cfq_rq_close(cfqd
, cur_cfqq
, __cfqq
->next_rq
))
1144 * cur_cfqq - passed in so that we don't decide that the current queue is
1145 * closely cooperating with itself.
1147 * So, basically we're assuming that that cur_cfqq has dispatched at least
1148 * one request, and that cfqd->last_position reflects a position on the disk
1149 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
1152 static struct cfq_queue
*cfq_close_cooperator(struct cfq_data
*cfqd
,
1153 struct cfq_queue
*cur_cfqq
)
1155 struct cfq_queue
*cfqq
;
1157 if (!cfq_cfqq_sync(cur_cfqq
))
1159 if (CFQQ_SEEKY(cur_cfqq
))
1163 * We should notice if some of the queues are cooperating, eg
1164 * working closely on the same area of the disk. In that case,
1165 * we can group them together and don't waste time idling.
1167 cfqq
= cfqq_close(cfqd
, cur_cfqq
);
1172 * It only makes sense to merge sync queues.
1174 if (!cfq_cfqq_sync(cfqq
))
1176 if (CFQQ_SEEKY(cfqq
))
1180 * Do not merge queues of different priority classes
1182 if (cfq_class_rt(cfqq
) != cfq_class_rt(cur_cfqq
))
1189 * Determine whether we should enforce idle window for this queue.
1192 static bool cfq_should_idle(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1194 enum wl_prio_t prio
= cfqq_prio(cfqq
);
1195 struct cfq_rb_root
*service_tree
= cfqq
->service_tree
;
1197 /* We never do for idle class queues. */
1198 if (prio
== IDLE_WORKLOAD
)
1201 /* We do for queues that were marked with idle window flag. */
1202 if (cfq_cfqq_idle_window(cfqq
))
1206 * Otherwise, we do only if they are the last ones
1207 * in their service tree.
1210 service_tree
= service_tree_for(prio
, cfqq_type(cfqq
), cfqd
);
1212 if (service_tree
->count
== 0)
1215 return (service_tree
->count
== 1 && cfq_rb_first(service_tree
) == cfqq
);
1218 static void cfq_arm_slice_timer(struct cfq_data
*cfqd
)
1220 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
1221 struct cfq_io_context
*cic
;
1225 * SSD device without seek penalty, disable idling. But only do so
1226 * for devices that support queuing, otherwise we still have a problem
1227 * with sync vs async workloads.
1229 if (blk_queue_nonrot(cfqd
->queue
) && cfqd
->hw_tag
)
1232 WARN_ON(!RB_EMPTY_ROOT(&cfqq
->sort_list
));
1233 WARN_ON(cfq_cfqq_slice_new(cfqq
));
1236 * idle is disabled, either manually or by past process history
1238 if (!cfqd
->cfq_slice_idle
|| !cfq_should_idle(cfqd
, cfqq
))
1242 * still requests with the driver, don't idle
1244 if (rq_in_driver(cfqd
))
1248 * task has exited, don't wait
1250 cic
= cfqd
->active_cic
;
1251 if (!cic
|| !atomic_read(&cic
->ioc
->nr_tasks
))
1255 * If our average think time is larger than the remaining time
1256 * slice, then don't idle. This avoids overrunning the allotted
1259 if (sample_valid(cic
->ttime_samples
) &&
1260 (cfqq
->slice_end
- jiffies
< cic
->ttime_mean
))
1263 cfq_mark_cfqq_wait_request(cfqq
);
1265 sl
= cfqd
->cfq_slice_idle
;
1266 /* are we servicing noidle tree, and there are more queues?
1267 * non-rotational or NCQ: no idle
1268 * non-NCQ rotational : very small idle, to allow
1269 * fair distribution of slice time for a process doing back-to-back
1272 if (cfqd
->serving_type
== SYNC_NOIDLE_WORKLOAD
&&
1273 service_tree_for(cfqd
->serving_prio
, SYNC_NOIDLE_WORKLOAD
, cfqd
)
1275 if (blk_queue_nonrot(cfqd
->queue
) || cfqd
->hw_tag
)
1277 sl
= min(sl
, msecs_to_jiffies(CFQ_MIN_TT
));
1280 mod_timer(&cfqd
->idle_slice_timer
, jiffies
+ sl
);
1281 cfq_log_cfqq(cfqd
, cfqq
, "arm_idle: %lu", sl
);
1285 * Move request from internal lists to the request queue dispatch list.
1287 static void cfq_dispatch_insert(struct request_queue
*q
, struct request
*rq
)
1289 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1290 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1292 cfq_log_cfqq(cfqd
, cfqq
, "dispatch_insert");
1294 cfqq
->next_rq
= cfq_find_next_rq(cfqd
, cfqq
, rq
);
1295 cfq_remove_request(rq
);
1297 elv_dispatch_sort(q
, rq
);
1299 if (cfq_cfqq_sync(cfqq
))
1300 cfqd
->sync_flight
++;
1304 * return expired entry, or NULL to just start from scratch in rbtree
1306 static struct request
*cfq_check_fifo(struct cfq_queue
*cfqq
)
1308 struct request
*rq
= NULL
;
1310 if (cfq_cfqq_fifo_expire(cfqq
))
1313 cfq_mark_cfqq_fifo_expire(cfqq
);
1315 if (list_empty(&cfqq
->fifo
))
1318 rq
= rq_entry_fifo(cfqq
->fifo
.next
);
1319 if (time_before(jiffies
, rq_fifo_time(rq
)))
1322 cfq_log_cfqq(cfqq
->cfqd
, cfqq
, "fifo=%p", rq
);
1327 cfq_prio_to_maxrq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1329 const int base_rq
= cfqd
->cfq_slice_async_rq
;
1331 WARN_ON(cfqq
->ioprio
>= IOPRIO_BE_NR
);
1333 return 2 * (base_rq
+ base_rq
* (CFQ_PRIO_LISTS
- 1 - cfqq
->ioprio
));
1337 * Must be called with the queue_lock held.
1339 static int cfqq_process_refs(struct cfq_queue
*cfqq
)
1341 int process_refs
, io_refs
;
1343 io_refs
= cfqq
->allocated
[READ
] + cfqq
->allocated
[WRITE
];
1344 process_refs
= atomic_read(&cfqq
->ref
) - io_refs
;
1345 BUG_ON(process_refs
< 0);
1346 return process_refs
;
1349 static void cfq_setup_merge(struct cfq_queue
*cfqq
, struct cfq_queue
*new_cfqq
)
1351 int process_refs
, new_process_refs
;
1352 struct cfq_queue
*__cfqq
;
1354 /* Avoid a circular list and skip interim queue merges */
1355 while ((__cfqq
= new_cfqq
->new_cfqq
)) {
1361 process_refs
= cfqq_process_refs(cfqq
);
1363 * If the process for the cfqq has gone away, there is no
1364 * sense in merging the queues.
1366 if (process_refs
== 0)
1370 * Merge in the direction of the lesser amount of work.
1372 new_process_refs
= cfqq_process_refs(new_cfqq
);
1373 if (new_process_refs
>= process_refs
) {
1374 cfqq
->new_cfqq
= new_cfqq
;
1375 atomic_add(process_refs
, &new_cfqq
->ref
);
1377 new_cfqq
->new_cfqq
= cfqq
;
1378 atomic_add(new_process_refs
, &cfqq
->ref
);
1382 static enum wl_type_t
cfq_choose_wl(struct cfq_data
*cfqd
, enum wl_prio_t prio
,
1385 struct cfq_queue
*queue
;
1387 bool key_valid
= false;
1388 unsigned long lowest_key
= 0;
1389 enum wl_type_t cur_best
= SYNC_NOIDLE_WORKLOAD
;
1393 * When priorities switched, we prefer starting
1394 * from SYNC_NOIDLE (first choice), or just SYNC
1397 if (service_tree_for(prio
, cur_best
, cfqd
)->count
)
1399 cur_best
= SYNC_WORKLOAD
;
1400 if (service_tree_for(prio
, cur_best
, cfqd
)->count
)
1403 return ASYNC_WORKLOAD
;
1406 for (i
= 0; i
< 3; ++i
) {
1407 /* otherwise, select the one with lowest rb_key */
1408 queue
= cfq_rb_first(service_tree_for(prio
, i
, cfqd
));
1410 (!key_valid
|| time_before(queue
->rb_key
, lowest_key
))) {
1411 lowest_key
= queue
->rb_key
;
1420 static void choose_service_tree(struct cfq_data
*cfqd
)
1422 enum wl_prio_t previous_prio
= cfqd
->serving_prio
;
1427 /* Choose next priority. RT > BE > IDLE */
1428 if (cfq_busy_queues_wl(RT_WORKLOAD
, cfqd
))
1429 cfqd
->serving_prio
= RT_WORKLOAD
;
1430 else if (cfq_busy_queues_wl(BE_WORKLOAD
, cfqd
))
1431 cfqd
->serving_prio
= BE_WORKLOAD
;
1433 cfqd
->serving_prio
= IDLE_WORKLOAD
;
1434 cfqd
->workload_expires
= jiffies
+ 1;
1439 * For RT and BE, we have to choose also the type
1440 * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
1443 prio_changed
= (cfqd
->serving_prio
!= previous_prio
);
1444 count
= service_tree_for(cfqd
->serving_prio
, cfqd
->serving_type
, cfqd
)
1448 * If priority didn't change, check workload expiration,
1449 * and that we still have other queues ready
1451 if (!prio_changed
&& count
&&
1452 !time_after(jiffies
, cfqd
->workload_expires
))
1455 /* otherwise select new workload type */
1456 cfqd
->serving_type
=
1457 cfq_choose_wl(cfqd
, cfqd
->serving_prio
, prio_changed
);
1458 count
= service_tree_for(cfqd
->serving_prio
, cfqd
->serving_type
, cfqd
)
1462 * the workload slice is computed as a fraction of target latency
1463 * proportional to the number of queues in that workload, over
1464 * all the queues in the same priority class
1466 slice
= cfq_target_latency
* count
/
1467 max_t(unsigned, cfqd
->busy_queues_avg
[cfqd
->serving_prio
],
1468 cfq_busy_queues_wl(cfqd
->serving_prio
, cfqd
));
1470 if (cfqd
->serving_type
== ASYNC_WORKLOAD
)
1471 /* async workload slice is scaled down according to
1472 * the sync/async slice ratio. */
1473 slice
= slice
* cfqd
->cfq_slice
[0] / cfqd
->cfq_slice
[1];
1475 /* sync workload slice is at least 2 * cfq_slice_idle */
1476 slice
= max(slice
, 2 * cfqd
->cfq_slice_idle
);
1478 slice
= max_t(unsigned, slice
, CFQ_MIN_TT
);
1479 cfqd
->workload_expires
= jiffies
+ slice
;
1483 * Select a queue for service. If we have a current active queue,
1484 * check whether to continue servicing it, or retrieve and set a new one.
1486 static struct cfq_queue
*cfq_select_queue(struct cfq_data
*cfqd
)
1488 struct cfq_queue
*cfqq
, *new_cfqq
= NULL
;
1490 cfqq
= cfqd
->active_queue
;
1495 * The active queue has run out of time, expire it and select new.
1497 if (cfq_slice_used(cfqq
) && !cfq_cfqq_must_dispatch(cfqq
))
1501 * The active queue has requests and isn't expired, allow it to
1504 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
))
1508 * If another queue has a request waiting within our mean seek
1509 * distance, let it run. The expire code will check for close
1510 * cooperators and put the close queue at the front of the service
1511 * tree. If possible, merge the expiring queue with the new cfqq.
1513 new_cfqq
= cfq_close_cooperator(cfqd
, cfqq
);
1515 if (!cfqq
->new_cfqq
)
1516 cfq_setup_merge(cfqq
, new_cfqq
);
1521 * No requests pending. If the active queue still has requests in
1522 * flight or is idling for a new request, allow either of these
1523 * conditions to happen (or time out) before selecting a new queue.
1525 if (timer_pending(&cfqd
->idle_slice_timer
) ||
1526 (cfqq
->dispatched
&& cfq_should_idle(cfqd
, cfqq
))) {
1532 cfq_slice_expired(cfqd
, 0);
1535 * Current queue expired. Check if we have to switch to a new
1539 choose_service_tree(cfqd
);
1541 cfqq
= cfq_set_active_queue(cfqd
, new_cfqq
);
1546 static int __cfq_forced_dispatch_cfqq(struct cfq_queue
*cfqq
)
1550 while (cfqq
->next_rq
) {
1551 cfq_dispatch_insert(cfqq
->cfqd
->queue
, cfqq
->next_rq
);
1555 BUG_ON(!list_empty(&cfqq
->fifo
));
1560 * Drain our current requests. Used for barriers and when switching
1561 * io schedulers on-the-fly.
1563 static int cfq_forced_dispatch(struct cfq_data
*cfqd
)
1565 struct cfq_queue
*cfqq
;
1568 for (i
= 0; i
< 2; ++i
)
1569 for (j
= 0; j
< 3; ++j
)
1570 while ((cfqq
= cfq_rb_first(&cfqd
->service_trees
[i
][j
]))
1572 dispatched
+= __cfq_forced_dispatch_cfqq(cfqq
);
1574 while ((cfqq
= cfq_rb_first(&cfqd
->service_tree_idle
)) != NULL
)
1575 dispatched
+= __cfq_forced_dispatch_cfqq(cfqq
);
1577 cfq_slice_expired(cfqd
, 0);
1579 BUG_ON(cfqd
->busy_queues
);
1581 cfq_log(cfqd
, "forced_dispatch=%d", dispatched
);
1585 static bool cfq_may_dispatch(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1587 unsigned int max_dispatch
;
1590 * Drain async requests before we start sync IO
1592 if (cfq_should_idle(cfqd
, cfqq
) && cfqd
->rq_in_driver
[BLK_RW_ASYNC
])
1596 * If this is an async queue and we have sync IO in flight, let it wait
1598 if (cfqd
->sync_flight
&& !cfq_cfqq_sync(cfqq
))
1601 max_dispatch
= cfqd
->cfq_quantum
;
1602 if (cfq_class_idle(cfqq
))
1606 * Does this cfqq already have too much IO in flight?
1608 if (cfqq
->dispatched
>= max_dispatch
) {
1610 * idle queue must always only have a single IO in flight
1612 if (cfq_class_idle(cfqq
))
1616 * We have other queues, don't allow more IO from this one
1618 if (cfqd
->busy_queues
> 1)
1622 * Sole queue user, allow bigger slice
1628 * Async queues must wait a bit before being allowed dispatch.
1629 * We also ramp up the dispatch depth gradually for async IO,
1630 * based on the last sync IO we serviced
1632 if (!cfq_cfqq_sync(cfqq
) && cfqd
->cfq_latency
) {
1633 unsigned long last_sync
= jiffies
- cfqd
->last_end_sync_rq
;
1636 depth
= last_sync
/ cfqd
->cfq_slice
[1];
1637 if (!depth
&& !cfqq
->dispatched
)
1639 if (depth
< max_dispatch
)
1640 max_dispatch
= depth
;
1644 * If we're below the current max, allow a dispatch
1646 return cfqq
->dispatched
< max_dispatch
;
1650 * Dispatch a request from cfqq, moving them to the request queue
1653 static bool cfq_dispatch_request(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1657 BUG_ON(RB_EMPTY_ROOT(&cfqq
->sort_list
));
1659 if (!cfq_may_dispatch(cfqd
, cfqq
))
1663 * follow expired path, else get first next available
1665 rq
= cfq_check_fifo(cfqq
);
1670 * insert request into driver dispatch list
1672 cfq_dispatch_insert(cfqd
->queue
, rq
);
1674 if (!cfqd
->active_cic
) {
1675 struct cfq_io_context
*cic
= RQ_CIC(rq
);
1677 atomic_long_inc(&cic
->ioc
->refcount
);
1678 cfqd
->active_cic
= cic
;
1685 * Find the cfqq that we need to service and move a request from that to the
1688 static int cfq_dispatch_requests(struct request_queue
*q
, int force
)
1690 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1691 struct cfq_queue
*cfqq
;
1693 if (!cfqd
->busy_queues
)
1696 if (unlikely(force
))
1697 return cfq_forced_dispatch(cfqd
);
1699 cfqq
= cfq_select_queue(cfqd
);
1704 * Dispatch a request from this cfqq, if it is allowed
1706 if (!cfq_dispatch_request(cfqd
, cfqq
))
1709 cfqq
->slice_dispatch
++;
1710 cfq_clear_cfqq_must_dispatch(cfqq
);
1713 * expire an async queue immediately if it has used up its slice. idle
1714 * queue always expire after 1 dispatch round.
1716 if (cfqd
->busy_queues
> 1 && ((!cfq_cfqq_sync(cfqq
) &&
1717 cfqq
->slice_dispatch
>= cfq_prio_to_maxrq(cfqd
, cfqq
)) ||
1718 cfq_class_idle(cfqq
))) {
1719 cfqq
->slice_end
= jiffies
+ 1;
1720 cfq_slice_expired(cfqd
, 0);
1723 cfq_log_cfqq(cfqd
, cfqq
, "dispatched a request");
1728 * task holds one reference to the queue, dropped when task exits. each rq
1729 * in-flight on this queue also holds a reference, dropped when rq is freed.
1731 * queue lock must be held here.
1733 static void cfq_put_queue(struct cfq_queue
*cfqq
)
1735 struct cfq_data
*cfqd
= cfqq
->cfqd
;
1737 BUG_ON(atomic_read(&cfqq
->ref
) <= 0);
1739 if (!atomic_dec_and_test(&cfqq
->ref
))
1742 cfq_log_cfqq(cfqd
, cfqq
, "put_queue");
1743 BUG_ON(rb_first(&cfqq
->sort_list
));
1744 BUG_ON(cfqq
->allocated
[READ
] + cfqq
->allocated
[WRITE
]);
1745 BUG_ON(cfq_cfqq_on_rr(cfqq
));
1747 if (unlikely(cfqd
->active_queue
== cfqq
)) {
1748 __cfq_slice_expired(cfqd
, cfqq
, 0);
1749 cfq_schedule_dispatch(cfqd
);
1752 kmem_cache_free(cfq_pool
, cfqq
);
1756 * Must always be called with the rcu_read_lock() held
1759 __call_for_each_cic(struct io_context
*ioc
,
1760 void (*func
)(struct io_context
*, struct cfq_io_context
*))
1762 struct cfq_io_context
*cic
;
1763 struct hlist_node
*n
;
1765 hlist_for_each_entry_rcu(cic
, n
, &ioc
->cic_list
, cic_list
)
1770 * Call func for each cic attached to this ioc.
1773 call_for_each_cic(struct io_context
*ioc
,
1774 void (*func
)(struct io_context
*, struct cfq_io_context
*))
1777 __call_for_each_cic(ioc
, func
);
1781 static void cfq_cic_free_rcu(struct rcu_head
*head
)
1783 struct cfq_io_context
*cic
;
1785 cic
= container_of(head
, struct cfq_io_context
, rcu_head
);
1787 kmem_cache_free(cfq_ioc_pool
, cic
);
1788 elv_ioc_count_dec(cfq_ioc_count
);
1792 * CFQ scheduler is exiting, grab exit lock and check
1793 * the pending io context count. If it hits zero,
1794 * complete ioc_gone and set it back to NULL
1796 spin_lock(&ioc_gone_lock
);
1797 if (ioc_gone
&& !elv_ioc_count_read(cfq_ioc_count
)) {
1801 spin_unlock(&ioc_gone_lock
);
1805 static void cfq_cic_free(struct cfq_io_context
*cic
)
1807 call_rcu(&cic
->rcu_head
, cfq_cic_free_rcu
);
1810 static void cic_free_func(struct io_context
*ioc
, struct cfq_io_context
*cic
)
1812 unsigned long flags
;
1814 BUG_ON(!cic
->dead_key
);
1816 spin_lock_irqsave(&ioc
->lock
, flags
);
1817 radix_tree_delete(&ioc
->radix_root
, cic
->dead_key
);
1818 hlist_del_rcu(&cic
->cic_list
);
1819 spin_unlock_irqrestore(&ioc
->lock
, flags
);
1825 * Must be called with rcu_read_lock() held or preemption otherwise disabled.
1826 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
1827 * and ->trim() which is called with the task lock held
1829 static void cfq_free_io_context(struct io_context
*ioc
)
1832 * ioc->refcount is zero here, or we are called from elv_unregister(),
1833 * so no more cic's are allowed to be linked into this ioc. So it
1834 * should be ok to iterate over the known list, we will see all cic's
1835 * since no new ones are added.
1837 __call_for_each_cic(ioc
, cic_free_func
);
1840 static void cfq_exit_cfqq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1842 struct cfq_queue
*__cfqq
, *next
;
1844 if (unlikely(cfqq
== cfqd
->active_queue
)) {
1845 __cfq_slice_expired(cfqd
, cfqq
, 0);
1846 cfq_schedule_dispatch(cfqd
);
1850 * If this queue was scheduled to merge with another queue, be
1851 * sure to drop the reference taken on that queue (and others in
1852 * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs.
1854 __cfqq
= cfqq
->new_cfqq
;
1856 if (__cfqq
== cfqq
) {
1857 WARN(1, "cfqq->new_cfqq loop detected\n");
1860 next
= __cfqq
->new_cfqq
;
1861 cfq_put_queue(__cfqq
);
1865 cfq_put_queue(cfqq
);
1868 static void __cfq_exit_single_io_context(struct cfq_data
*cfqd
,
1869 struct cfq_io_context
*cic
)
1871 struct io_context
*ioc
= cic
->ioc
;
1873 list_del_init(&cic
->queue_list
);
1876 * Make sure key == NULL is seen for dead queues
1879 cic
->dead_key
= (unsigned long) cic
->key
;
1882 if (ioc
->ioc_data
== cic
)
1883 rcu_assign_pointer(ioc
->ioc_data
, NULL
);
1885 if (cic
->cfqq
[BLK_RW_ASYNC
]) {
1886 cfq_exit_cfqq(cfqd
, cic
->cfqq
[BLK_RW_ASYNC
]);
1887 cic
->cfqq
[BLK_RW_ASYNC
] = NULL
;
1890 if (cic
->cfqq
[BLK_RW_SYNC
]) {
1891 cfq_exit_cfqq(cfqd
, cic
->cfqq
[BLK_RW_SYNC
]);
1892 cic
->cfqq
[BLK_RW_SYNC
] = NULL
;
1896 static void cfq_exit_single_io_context(struct io_context
*ioc
,
1897 struct cfq_io_context
*cic
)
1899 struct cfq_data
*cfqd
= cic
->key
;
1902 struct request_queue
*q
= cfqd
->queue
;
1903 unsigned long flags
;
1905 spin_lock_irqsave(q
->queue_lock
, flags
);
1908 * Ensure we get a fresh copy of the ->key to prevent
1909 * race between exiting task and queue
1911 smp_read_barrier_depends();
1913 __cfq_exit_single_io_context(cfqd
, cic
);
1915 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1920 * The process that ioc belongs to has exited, we need to clean up
1921 * and put the internal structures we have that belongs to that process.
1923 static void cfq_exit_io_context(struct io_context
*ioc
)
1925 call_for_each_cic(ioc
, cfq_exit_single_io_context
);
1928 static struct cfq_io_context
*
1929 cfq_alloc_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
1931 struct cfq_io_context
*cic
;
1933 cic
= kmem_cache_alloc_node(cfq_ioc_pool
, gfp_mask
| __GFP_ZERO
,
1936 cic
->last_end_request
= jiffies
;
1937 INIT_LIST_HEAD(&cic
->queue_list
);
1938 INIT_HLIST_NODE(&cic
->cic_list
);
1939 cic
->dtor
= cfq_free_io_context
;
1940 cic
->exit
= cfq_exit_io_context
;
1941 elv_ioc_count_inc(cfq_ioc_count
);
1947 static void cfq_init_prio_data(struct cfq_queue
*cfqq
, struct io_context
*ioc
)
1949 struct task_struct
*tsk
= current
;
1952 if (!cfq_cfqq_prio_changed(cfqq
))
1955 ioprio_class
= IOPRIO_PRIO_CLASS(ioc
->ioprio
);
1956 switch (ioprio_class
) {
1958 printk(KERN_ERR
"cfq: bad prio %x\n", ioprio_class
);
1959 case IOPRIO_CLASS_NONE
:
1961 * no prio set, inherit CPU scheduling settings
1963 cfqq
->ioprio
= task_nice_ioprio(tsk
);
1964 cfqq
->ioprio_class
= task_nice_ioclass(tsk
);
1966 case IOPRIO_CLASS_RT
:
1967 cfqq
->ioprio
= task_ioprio(ioc
);
1968 cfqq
->ioprio_class
= IOPRIO_CLASS_RT
;
1970 case IOPRIO_CLASS_BE
:
1971 cfqq
->ioprio
= task_ioprio(ioc
);
1972 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1974 case IOPRIO_CLASS_IDLE
:
1975 cfqq
->ioprio_class
= IOPRIO_CLASS_IDLE
;
1977 cfq_clear_cfqq_idle_window(cfqq
);
1982 * keep track of original prio settings in case we have to temporarily
1983 * elevate the priority of this queue
1985 cfqq
->org_ioprio
= cfqq
->ioprio
;
1986 cfqq
->org_ioprio_class
= cfqq
->ioprio_class
;
1987 cfq_clear_cfqq_prio_changed(cfqq
);
1990 static void changed_ioprio(struct io_context
*ioc
, struct cfq_io_context
*cic
)
1992 struct cfq_data
*cfqd
= cic
->key
;
1993 struct cfq_queue
*cfqq
;
1994 unsigned long flags
;
1996 if (unlikely(!cfqd
))
1999 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
2001 cfqq
= cic
->cfqq
[BLK_RW_ASYNC
];
2003 struct cfq_queue
*new_cfqq
;
2004 new_cfqq
= cfq_get_queue(cfqd
, BLK_RW_ASYNC
, cic
->ioc
,
2007 cic
->cfqq
[BLK_RW_ASYNC
] = new_cfqq
;
2008 cfq_put_queue(cfqq
);
2012 cfqq
= cic
->cfqq
[BLK_RW_SYNC
];
2014 cfq_mark_cfqq_prio_changed(cfqq
);
2016 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2019 static void cfq_ioc_set_ioprio(struct io_context
*ioc
)
2021 call_for_each_cic(ioc
, changed_ioprio
);
2022 ioc
->ioprio_changed
= 0;
2025 static void cfq_init_cfqq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2026 pid_t pid
, bool is_sync
)
2028 RB_CLEAR_NODE(&cfqq
->rb_node
);
2029 RB_CLEAR_NODE(&cfqq
->p_node
);
2030 INIT_LIST_HEAD(&cfqq
->fifo
);
2032 atomic_set(&cfqq
->ref
, 0);
2035 cfq_mark_cfqq_prio_changed(cfqq
);
2038 if (!cfq_class_idle(cfqq
))
2039 cfq_mark_cfqq_idle_window(cfqq
);
2040 cfq_mark_cfqq_sync(cfqq
);
2045 static struct cfq_queue
*
2046 cfq_find_alloc_queue(struct cfq_data
*cfqd
, bool is_sync
,
2047 struct io_context
*ioc
, gfp_t gfp_mask
)
2049 struct cfq_queue
*cfqq
, *new_cfqq
= NULL
;
2050 struct cfq_io_context
*cic
;
2053 cic
= cfq_cic_lookup(cfqd
, ioc
);
2054 /* cic always exists here */
2055 cfqq
= cic_to_cfqq(cic
, is_sync
);
2058 * Always try a new alloc if we fell back to the OOM cfqq
2059 * originally, since it should just be a temporary situation.
2061 if (!cfqq
|| cfqq
== &cfqd
->oom_cfqq
) {
2066 } else if (gfp_mask
& __GFP_WAIT
) {
2067 spin_unlock_irq(cfqd
->queue
->queue_lock
);
2068 new_cfqq
= kmem_cache_alloc_node(cfq_pool
,
2069 gfp_mask
| __GFP_ZERO
,
2071 spin_lock_irq(cfqd
->queue
->queue_lock
);
2075 cfqq
= kmem_cache_alloc_node(cfq_pool
,
2076 gfp_mask
| __GFP_ZERO
,
2081 cfq_init_cfqq(cfqd
, cfqq
, current
->pid
, is_sync
);
2082 cfq_init_prio_data(cfqq
, ioc
);
2083 cfq_log_cfqq(cfqd
, cfqq
, "alloced");
2085 cfqq
= &cfqd
->oom_cfqq
;
2089 kmem_cache_free(cfq_pool
, new_cfqq
);
2094 static struct cfq_queue
**
2095 cfq_async_queue_prio(struct cfq_data
*cfqd
, int ioprio_class
, int ioprio
)
2097 switch (ioprio_class
) {
2098 case IOPRIO_CLASS_RT
:
2099 return &cfqd
->async_cfqq
[0][ioprio
];
2100 case IOPRIO_CLASS_BE
:
2101 return &cfqd
->async_cfqq
[1][ioprio
];
2102 case IOPRIO_CLASS_IDLE
:
2103 return &cfqd
->async_idle_cfqq
;
2109 static struct cfq_queue
*
2110 cfq_get_queue(struct cfq_data
*cfqd
, bool is_sync
, struct io_context
*ioc
,
2113 const int ioprio
= task_ioprio(ioc
);
2114 const int ioprio_class
= task_ioprio_class(ioc
);
2115 struct cfq_queue
**async_cfqq
= NULL
;
2116 struct cfq_queue
*cfqq
= NULL
;
2119 async_cfqq
= cfq_async_queue_prio(cfqd
, ioprio_class
, ioprio
);
2124 cfqq
= cfq_find_alloc_queue(cfqd
, is_sync
, ioc
, gfp_mask
);
2127 * pin the queue now that it's allocated, scheduler exit will prune it
2129 if (!is_sync
&& !(*async_cfqq
)) {
2130 atomic_inc(&cfqq
->ref
);
2134 atomic_inc(&cfqq
->ref
);
2139 * We drop cfq io contexts lazily, so we may find a dead one.
2142 cfq_drop_dead_cic(struct cfq_data
*cfqd
, struct io_context
*ioc
,
2143 struct cfq_io_context
*cic
)
2145 unsigned long flags
;
2147 WARN_ON(!list_empty(&cic
->queue_list
));
2149 spin_lock_irqsave(&ioc
->lock
, flags
);
2151 BUG_ON(ioc
->ioc_data
== cic
);
2153 radix_tree_delete(&ioc
->radix_root
, (unsigned long) cfqd
);
2154 hlist_del_rcu(&cic
->cic_list
);
2155 spin_unlock_irqrestore(&ioc
->lock
, flags
);
2160 static struct cfq_io_context
*
2161 cfq_cic_lookup(struct cfq_data
*cfqd
, struct io_context
*ioc
)
2163 struct cfq_io_context
*cic
;
2164 unsigned long flags
;
2173 * we maintain a last-hit cache, to avoid browsing over the tree
2175 cic
= rcu_dereference(ioc
->ioc_data
);
2176 if (cic
&& cic
->key
== cfqd
) {
2182 cic
= radix_tree_lookup(&ioc
->radix_root
, (unsigned long) cfqd
);
2186 /* ->key must be copied to avoid race with cfq_exit_queue() */
2189 cfq_drop_dead_cic(cfqd
, ioc
, cic
);
2194 spin_lock_irqsave(&ioc
->lock
, flags
);
2195 rcu_assign_pointer(ioc
->ioc_data
, cic
);
2196 spin_unlock_irqrestore(&ioc
->lock
, flags
);
2204 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2205 * the process specific cfq io context when entered from the block layer.
2206 * Also adds the cic to a per-cfqd list, used when this queue is removed.
2208 static int cfq_cic_link(struct cfq_data
*cfqd
, struct io_context
*ioc
,
2209 struct cfq_io_context
*cic
, gfp_t gfp_mask
)
2211 unsigned long flags
;
2214 ret
= radix_tree_preload(gfp_mask
);
2219 spin_lock_irqsave(&ioc
->lock
, flags
);
2220 ret
= radix_tree_insert(&ioc
->radix_root
,
2221 (unsigned long) cfqd
, cic
);
2223 hlist_add_head_rcu(&cic
->cic_list
, &ioc
->cic_list
);
2224 spin_unlock_irqrestore(&ioc
->lock
, flags
);
2226 radix_tree_preload_end();
2229 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
2230 list_add(&cic
->queue_list
, &cfqd
->cic_list
);
2231 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2236 printk(KERN_ERR
"cfq: cic link failed!\n");
2242 * Setup general io context and cfq io context. There can be several cfq
2243 * io contexts per general io context, if this process is doing io to more
2244 * than one device managed by cfq.
2246 static struct cfq_io_context
*
2247 cfq_get_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
2249 struct io_context
*ioc
= NULL
;
2250 struct cfq_io_context
*cic
;
2252 might_sleep_if(gfp_mask
& __GFP_WAIT
);
2254 ioc
= get_io_context(gfp_mask
, cfqd
->queue
->node
);
2258 cic
= cfq_cic_lookup(cfqd
, ioc
);
2262 cic
= cfq_alloc_io_context(cfqd
, gfp_mask
);
2266 if (cfq_cic_link(cfqd
, ioc
, cic
, gfp_mask
))
2270 smp_read_barrier_depends();
2271 if (unlikely(ioc
->ioprio_changed
))
2272 cfq_ioc_set_ioprio(ioc
);
2278 put_io_context(ioc
);
2283 cfq_update_io_thinktime(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
)
2285 unsigned long elapsed
= jiffies
- cic
->last_end_request
;
2286 unsigned long ttime
= min(elapsed
, 2UL * cfqd
->cfq_slice_idle
);
2288 cic
->ttime_samples
= (7*cic
->ttime_samples
+ 256) / 8;
2289 cic
->ttime_total
= (7*cic
->ttime_total
+ 256*ttime
) / 8;
2290 cic
->ttime_mean
= (cic
->ttime_total
+ 128) / cic
->ttime_samples
;
2294 cfq_update_io_seektime(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2300 if (!cfqq
->last_request_pos
)
2302 else if (cfqq
->last_request_pos
< blk_rq_pos(rq
))
2303 sdist
= blk_rq_pos(rq
) - cfqq
->last_request_pos
;
2305 sdist
= cfqq
->last_request_pos
- blk_rq_pos(rq
);
2308 * Don't allow the seek distance to get too large from the
2309 * odd fragment, pagein, etc
2311 if (cfqq
->seek_samples
<= 60) /* second&third seek */
2312 sdist
= min(sdist
, (cfqq
->seek_mean
* 4) + 2*1024*1024);
2314 sdist
= min(sdist
, (cfqq
->seek_mean
* 4) + 2*1024*64);
2316 cfqq
->seek_samples
= (7*cfqq
->seek_samples
+ 256) / 8;
2317 cfqq
->seek_total
= (7*cfqq
->seek_total
+ (u64
)256*sdist
) / 8;
2318 total
= cfqq
->seek_total
+ (cfqq
->seek_samples
/2);
2319 do_div(total
, cfqq
->seek_samples
);
2320 cfqq
->seek_mean
= (sector_t
)total
;
2323 * If this cfqq is shared between multiple processes, check to
2324 * make sure that those processes are still issuing I/Os within
2325 * the mean seek distance. If not, it may be time to break the
2326 * queues apart again.
2328 if (cfq_cfqq_coop(cfqq
)) {
2329 if (CFQQ_SEEKY(cfqq
) && !cfqq
->seeky_start
)
2330 cfqq
->seeky_start
= jiffies
;
2331 else if (!CFQQ_SEEKY(cfqq
))
2332 cfqq
->seeky_start
= 0;
2337 * Disable idle window if the process thinks too long or seeks so much that
2341 cfq_update_idle_window(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2342 struct cfq_io_context
*cic
)
2344 int old_idle
, enable_idle
;
2347 * Don't idle for async or idle io prio class
2349 if (!cfq_cfqq_sync(cfqq
) || cfq_class_idle(cfqq
))
2352 enable_idle
= old_idle
= cfq_cfqq_idle_window(cfqq
);
2354 if (!atomic_read(&cic
->ioc
->nr_tasks
) || !cfqd
->cfq_slice_idle
||
2355 (sample_valid(cfqq
->seek_samples
) && CFQQ_SEEKY(cfqq
)))
2357 else if (sample_valid(cic
->ttime_samples
)) {
2358 if (cic
->ttime_mean
> cfqd
->cfq_slice_idle
)
2364 if (old_idle
!= enable_idle
) {
2365 cfq_log_cfqq(cfqd
, cfqq
, "idle=%d", enable_idle
);
2367 cfq_mark_cfqq_idle_window(cfqq
);
2369 cfq_clear_cfqq_idle_window(cfqq
);
2374 * Check if new_cfqq should preempt the currently active queue. Return 0 for
2375 * no or if we aren't sure, a 1 will cause a preempt.
2378 cfq_should_preempt(struct cfq_data
*cfqd
, struct cfq_queue
*new_cfqq
,
2381 struct cfq_queue
*cfqq
;
2383 cfqq
= cfqd
->active_queue
;
2387 if (cfq_slice_used(cfqq
))
2390 if (cfq_class_idle(new_cfqq
))
2393 if (cfq_class_idle(cfqq
))
2396 if (cfqd
->serving_type
== SYNC_NOIDLE_WORKLOAD
2397 && new_cfqq
->service_tree
== cfqq
->service_tree
)
2401 * if the new request is sync, but the currently running queue is
2402 * not, let the sync request have priority.
2404 if (rq_is_sync(rq
) && !cfq_cfqq_sync(cfqq
))
2408 * So both queues are sync. Let the new request get disk time if
2409 * it's a metadata request and the current queue is doing regular IO.
2411 if (rq_is_meta(rq
) && !cfqq
->meta_pending
)
2415 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
2417 if (cfq_class_rt(new_cfqq
) && !cfq_class_rt(cfqq
))
2420 if (!cfqd
->active_cic
|| !cfq_cfqq_wait_request(cfqq
))
2424 * if this request is as-good as one we would expect from the
2425 * current cfqq, let it preempt
2427 if (cfq_rq_close(cfqd
, cfqq
, rq
))
2434 * cfqq preempts the active queue. if we allowed preempt with no slice left,
2435 * let it have half of its nominal slice.
2437 static void cfq_preempt_queue(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
2439 cfq_log_cfqq(cfqd
, cfqq
, "preempt");
2440 cfq_slice_expired(cfqd
, 1);
2443 * Put the new queue at the front of the of the current list,
2444 * so we know that it will be selected next.
2446 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
2448 cfq_service_tree_add(cfqd
, cfqq
, 1);
2450 cfqq
->slice_end
= 0;
2451 cfq_mark_cfqq_slice_new(cfqq
);
2455 * Called when a new fs request (rq) is added (to cfqq). Check if there's
2456 * something we should do about it
2459 cfq_rq_enqueued(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2462 struct cfq_io_context
*cic
= RQ_CIC(rq
);
2466 cfqq
->meta_pending
++;
2468 cfq_update_io_thinktime(cfqd
, cic
);
2469 cfq_update_io_seektime(cfqd
, cfqq
, rq
);
2470 cfq_update_idle_window(cfqd
, cfqq
, cic
);
2472 cfqq
->last_request_pos
= blk_rq_pos(rq
) + blk_rq_sectors(rq
);
2474 if (cfqq
== cfqd
->active_queue
) {
2476 * Remember that we saw a request from this process, but
2477 * don't start queuing just yet. Otherwise we risk seeing lots
2478 * of tiny requests, because we disrupt the normal plugging
2479 * and merging. If the request is already larger than a single
2480 * page, let it rip immediately. For that case we assume that
2481 * merging is already done. Ditto for a busy system that
2482 * has other work pending, don't risk delaying until the
2483 * idle timer unplug to continue working.
2485 if (cfq_cfqq_wait_request(cfqq
)) {
2486 if (blk_rq_bytes(rq
) > PAGE_CACHE_SIZE
||
2487 cfqd
->busy_queues
> 1) {
2488 del_timer(&cfqd
->idle_slice_timer
);
2489 __blk_run_queue(cfqd
->queue
);
2491 cfq_mark_cfqq_must_dispatch(cfqq
);
2493 } else if (cfq_should_preempt(cfqd
, cfqq
, rq
)) {
2495 * not the active queue - expire current slice if it is
2496 * idle and has expired it's mean thinktime or this new queue
2497 * has some old slice time left and is of higher priority or
2498 * this new queue is RT and the current one is BE
2500 cfq_preempt_queue(cfqd
, cfqq
);
2501 __blk_run_queue(cfqd
->queue
);
2505 static void cfq_insert_request(struct request_queue
*q
, struct request
*rq
)
2507 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
2508 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
2510 cfq_log_cfqq(cfqd
, cfqq
, "insert_request");
2511 cfq_init_prio_data(cfqq
, RQ_CIC(rq
)->ioc
);
2513 rq_set_fifo_time(rq
, jiffies
+ cfqd
->cfq_fifo_expire
[rq_is_sync(rq
)]);
2514 list_add_tail(&rq
->queuelist
, &cfqq
->fifo
);
2517 cfq_rq_enqueued(cfqd
, cfqq
, rq
);
2521 * Update hw_tag based on peak queue depth over 50 samples under
2524 static void cfq_update_hw_tag(struct cfq_data
*cfqd
)
2526 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
2528 if (rq_in_driver(cfqd
) > cfqd
->rq_in_driver_peak
)
2529 cfqd
->rq_in_driver_peak
= rq_in_driver(cfqd
);
2531 if (cfqd
->rq_queued
<= CFQ_HW_QUEUE_MIN
&&
2532 rq_in_driver(cfqd
) <= CFQ_HW_QUEUE_MIN
)
2536 * If active queue hasn't enough requests and can idle, cfq might not
2537 * dispatch sufficient requests to hardware. Don't zero hw_tag in this
2540 if (cfqq
&& cfq_cfqq_idle_window(cfqq
) &&
2541 cfqq
->dispatched
+ cfqq
->queued
[0] + cfqq
->queued
[1] <
2542 CFQ_HW_QUEUE_MIN
&& rq_in_driver(cfqd
) < CFQ_HW_QUEUE_MIN
)
2545 if (cfqd
->hw_tag_samples
++ < 50)
2548 if (cfqd
->rq_in_driver_peak
>= CFQ_HW_QUEUE_MIN
)
2553 cfqd
->hw_tag_samples
= 0;
2554 cfqd
->rq_in_driver_peak
= 0;
2557 static void cfq_completed_request(struct request_queue
*q
, struct request
*rq
)
2559 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
2560 struct cfq_data
*cfqd
= cfqq
->cfqd
;
2561 const int sync
= rq_is_sync(rq
);
2565 cfq_log_cfqq(cfqd
, cfqq
, "complete");
2567 cfq_update_hw_tag(cfqd
);
2569 WARN_ON(!cfqd
->rq_in_driver
[sync
]);
2570 WARN_ON(!cfqq
->dispatched
);
2571 cfqd
->rq_in_driver
[sync
]--;
2574 if (cfq_cfqq_sync(cfqq
))
2575 cfqd
->sync_flight
--;
2578 RQ_CIC(rq
)->last_end_request
= now
;
2579 cfqd
->last_end_sync_rq
= now
;
2583 * If this is the active queue, check if it needs to be expired,
2584 * or if we want to idle in case it has no pending requests.
2586 if (cfqd
->active_queue
== cfqq
) {
2587 const bool cfqq_empty
= RB_EMPTY_ROOT(&cfqq
->sort_list
);
2589 if (cfq_cfqq_slice_new(cfqq
)) {
2590 cfq_set_prio_slice(cfqd
, cfqq
);
2591 cfq_clear_cfqq_slice_new(cfqq
);
2594 * If there are no requests waiting in this queue, and
2595 * there are other queues ready to issue requests, AND
2596 * those other queues are issuing requests within our
2597 * mean seek distance, give them a chance to run instead
2600 if (cfq_slice_used(cfqq
) || cfq_class_idle(cfqq
))
2601 cfq_slice_expired(cfqd
, 1);
2602 else if (cfqq_empty
&& !cfq_close_cooperator(cfqd
, cfqq
) &&
2603 sync
&& !rq_noidle(rq
))
2604 cfq_arm_slice_timer(cfqd
);
2607 if (!rq_in_driver(cfqd
))
2608 cfq_schedule_dispatch(cfqd
);
2612 * we temporarily boost lower priority queues if they are holding fs exclusive
2613 * resources. they are boosted to normal prio (CLASS_BE/4)
2615 static void cfq_prio_boost(struct cfq_queue
*cfqq
)
2617 if (has_fs_excl()) {
2619 * boost idle prio on transactions that would lock out other
2620 * users of the filesystem
2622 if (cfq_class_idle(cfqq
))
2623 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
2624 if (cfqq
->ioprio
> IOPRIO_NORM
)
2625 cfqq
->ioprio
= IOPRIO_NORM
;
2628 * unboost the queue (if needed)
2630 cfqq
->ioprio_class
= cfqq
->org_ioprio_class
;
2631 cfqq
->ioprio
= cfqq
->org_ioprio
;
2635 static inline int __cfq_may_queue(struct cfq_queue
*cfqq
)
2637 if (cfq_cfqq_wait_request(cfqq
) && !cfq_cfqq_must_alloc_slice(cfqq
)) {
2638 cfq_mark_cfqq_must_alloc_slice(cfqq
);
2639 return ELV_MQUEUE_MUST
;
2642 return ELV_MQUEUE_MAY
;
2645 static int cfq_may_queue(struct request_queue
*q
, int rw
)
2647 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
2648 struct task_struct
*tsk
= current
;
2649 struct cfq_io_context
*cic
;
2650 struct cfq_queue
*cfqq
;
2653 * don't force setup of a queue from here, as a call to may_queue
2654 * does not necessarily imply that a request actually will be queued.
2655 * so just lookup a possibly existing queue, or return 'may queue'
2658 cic
= cfq_cic_lookup(cfqd
, tsk
->io_context
);
2660 return ELV_MQUEUE_MAY
;
2662 cfqq
= cic_to_cfqq(cic
, rw_is_sync(rw
));
2664 cfq_init_prio_data(cfqq
, cic
->ioc
);
2665 cfq_prio_boost(cfqq
);
2667 return __cfq_may_queue(cfqq
);
2670 return ELV_MQUEUE_MAY
;
2674 * queue lock held here
2676 static void cfq_put_request(struct request
*rq
)
2678 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
2681 const int rw
= rq_data_dir(rq
);
2683 BUG_ON(!cfqq
->allocated
[rw
]);
2684 cfqq
->allocated
[rw
]--;
2686 put_io_context(RQ_CIC(rq
)->ioc
);
2688 rq
->elevator_private
= NULL
;
2689 rq
->elevator_private2
= NULL
;
2691 cfq_put_queue(cfqq
);
2695 static struct cfq_queue
*
2696 cfq_merge_cfqqs(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
,
2697 struct cfq_queue
*cfqq
)
2699 cfq_log_cfqq(cfqd
, cfqq
, "merging with queue %p", cfqq
->new_cfqq
);
2700 cic_set_cfqq(cic
, cfqq
->new_cfqq
, 1);
2701 cfq_mark_cfqq_coop(cfqq
->new_cfqq
);
2702 cfq_put_queue(cfqq
);
2703 return cic_to_cfqq(cic
, 1);
2706 static int should_split_cfqq(struct cfq_queue
*cfqq
)
2708 if (cfqq
->seeky_start
&&
2709 time_after(jiffies
, cfqq
->seeky_start
+ CFQQ_COOP_TOUT
))
2715 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
2716 * was the last process referring to said cfqq.
2718 static struct cfq_queue
*
2719 split_cfqq(struct cfq_io_context
*cic
, struct cfq_queue
*cfqq
)
2721 if (cfqq_process_refs(cfqq
) == 1) {
2722 cfqq
->seeky_start
= 0;
2723 cfqq
->pid
= current
->pid
;
2724 cfq_clear_cfqq_coop(cfqq
);
2728 cic_set_cfqq(cic
, NULL
, 1);
2729 cfq_put_queue(cfqq
);
2733 * Allocate cfq data structures associated with this request.
2736 cfq_set_request(struct request_queue
*q
, struct request
*rq
, gfp_t gfp_mask
)
2738 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
2739 struct cfq_io_context
*cic
;
2740 const int rw
= rq_data_dir(rq
);
2741 const bool is_sync
= rq_is_sync(rq
);
2742 struct cfq_queue
*cfqq
;
2743 unsigned long flags
;
2745 might_sleep_if(gfp_mask
& __GFP_WAIT
);
2747 cic
= cfq_get_io_context(cfqd
, gfp_mask
);
2749 spin_lock_irqsave(q
->queue_lock
, flags
);
2755 cfqq
= cic_to_cfqq(cic
, is_sync
);
2756 if (!cfqq
|| cfqq
== &cfqd
->oom_cfqq
) {
2757 cfqq
= cfq_get_queue(cfqd
, is_sync
, cic
->ioc
, gfp_mask
);
2758 cic_set_cfqq(cic
, cfqq
, is_sync
);
2761 * If the queue was seeky for too long, break it apart.
2763 if (cfq_cfqq_coop(cfqq
) && should_split_cfqq(cfqq
)) {
2764 cfq_log_cfqq(cfqd
, cfqq
, "breaking apart cfqq");
2765 cfqq
= split_cfqq(cic
, cfqq
);
2771 * Check to see if this queue is scheduled to merge with
2772 * another, closely cooperating queue. The merging of
2773 * queues happens here as it must be done in process context.
2774 * The reference on new_cfqq was taken in merge_cfqqs.
2777 cfqq
= cfq_merge_cfqqs(cfqd
, cic
, cfqq
);
2780 cfqq
->allocated
[rw
]++;
2781 atomic_inc(&cfqq
->ref
);
2783 spin_unlock_irqrestore(q
->queue_lock
, flags
);
2785 rq
->elevator_private
= cic
;
2786 rq
->elevator_private2
= cfqq
;
2791 put_io_context(cic
->ioc
);
2793 cfq_schedule_dispatch(cfqd
);
2794 spin_unlock_irqrestore(q
->queue_lock
, flags
);
2795 cfq_log(cfqd
, "set_request fail");
2799 static void cfq_kick_queue(struct work_struct
*work
)
2801 struct cfq_data
*cfqd
=
2802 container_of(work
, struct cfq_data
, unplug_work
);
2803 struct request_queue
*q
= cfqd
->queue
;
2805 spin_lock_irq(q
->queue_lock
);
2806 __blk_run_queue(cfqd
->queue
);
2807 spin_unlock_irq(q
->queue_lock
);
2811 * Timer running if the active_queue is currently idling inside its time slice
2813 static void cfq_idle_slice_timer(unsigned long data
)
2815 struct cfq_data
*cfqd
= (struct cfq_data
*) data
;
2816 struct cfq_queue
*cfqq
;
2817 unsigned long flags
;
2820 cfq_log(cfqd
, "idle timer fired");
2822 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
2824 cfqq
= cfqd
->active_queue
;
2829 * We saw a request before the queue expired, let it through
2831 if (cfq_cfqq_must_dispatch(cfqq
))
2837 if (cfq_slice_used(cfqq
))
2841 * only expire and reinvoke request handler, if there are
2842 * other queues with pending requests
2844 if (!cfqd
->busy_queues
)
2848 * not expired and it has a request pending, let it dispatch
2850 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
))
2854 cfq_slice_expired(cfqd
, timed_out
);
2856 cfq_schedule_dispatch(cfqd
);
2858 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2861 static void cfq_shutdown_timer_wq(struct cfq_data
*cfqd
)
2863 del_timer_sync(&cfqd
->idle_slice_timer
);
2864 cancel_work_sync(&cfqd
->unplug_work
);
2867 static void cfq_put_async_queues(struct cfq_data
*cfqd
)
2871 for (i
= 0; i
< IOPRIO_BE_NR
; i
++) {
2872 if (cfqd
->async_cfqq
[0][i
])
2873 cfq_put_queue(cfqd
->async_cfqq
[0][i
]);
2874 if (cfqd
->async_cfqq
[1][i
])
2875 cfq_put_queue(cfqd
->async_cfqq
[1][i
]);
2878 if (cfqd
->async_idle_cfqq
)
2879 cfq_put_queue(cfqd
->async_idle_cfqq
);
2882 static void cfq_exit_queue(struct elevator_queue
*e
)
2884 struct cfq_data
*cfqd
= e
->elevator_data
;
2885 struct request_queue
*q
= cfqd
->queue
;
2887 cfq_shutdown_timer_wq(cfqd
);
2889 spin_lock_irq(q
->queue_lock
);
2891 if (cfqd
->active_queue
)
2892 __cfq_slice_expired(cfqd
, cfqd
->active_queue
, 0);
2894 while (!list_empty(&cfqd
->cic_list
)) {
2895 struct cfq_io_context
*cic
= list_entry(cfqd
->cic_list
.next
,
2896 struct cfq_io_context
,
2899 __cfq_exit_single_io_context(cfqd
, cic
);
2902 cfq_put_async_queues(cfqd
);
2904 spin_unlock_irq(q
->queue_lock
);
2906 cfq_shutdown_timer_wq(cfqd
);
2911 static void *cfq_init_queue(struct request_queue
*q
)
2913 struct cfq_data
*cfqd
;
2916 cfqd
= kmalloc_node(sizeof(*cfqd
), GFP_KERNEL
| __GFP_ZERO
, q
->node
);
2920 for (i
= 0; i
< 2; ++i
)
2921 for (j
= 0; j
< 3; ++j
)
2922 cfqd
->service_trees
[i
][j
] = CFQ_RB_ROOT
;
2923 cfqd
->service_tree_idle
= CFQ_RB_ROOT
;
2926 * Not strictly needed (since RB_ROOT just clears the node and we
2927 * zeroed cfqd on alloc), but better be safe in case someone decides
2928 * to add magic to the rb code
2930 for (i
= 0; i
< CFQ_PRIO_LISTS
; i
++)
2931 cfqd
->prio_trees
[i
] = RB_ROOT
;
2934 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
2935 * Grab a permanent reference to it, so that the normal code flow
2936 * will not attempt to free it.
2938 cfq_init_cfqq(cfqd
, &cfqd
->oom_cfqq
, 1, 0);
2939 atomic_inc(&cfqd
->oom_cfqq
.ref
);
2941 INIT_LIST_HEAD(&cfqd
->cic_list
);
2945 init_timer(&cfqd
->idle_slice_timer
);
2946 cfqd
->idle_slice_timer
.function
= cfq_idle_slice_timer
;
2947 cfqd
->idle_slice_timer
.data
= (unsigned long) cfqd
;
2949 INIT_WORK(&cfqd
->unplug_work
, cfq_kick_queue
);
2951 cfqd
->cfq_quantum
= cfq_quantum
;
2952 cfqd
->cfq_fifo_expire
[0] = cfq_fifo_expire
[0];
2953 cfqd
->cfq_fifo_expire
[1] = cfq_fifo_expire
[1];
2954 cfqd
->cfq_back_max
= cfq_back_max
;
2955 cfqd
->cfq_back_penalty
= cfq_back_penalty
;
2956 cfqd
->cfq_slice
[0] = cfq_slice_async
;
2957 cfqd
->cfq_slice
[1] = cfq_slice_sync
;
2958 cfqd
->cfq_slice_async_rq
= cfq_slice_async_rq
;
2959 cfqd
->cfq_slice_idle
= cfq_slice_idle
;
2960 cfqd
->cfq_latency
= 1;
2962 cfqd
->last_end_sync_rq
= jiffies
;
2966 static void cfq_slab_kill(void)
2969 * Caller already ensured that pending RCU callbacks are completed,
2970 * so we should have no busy allocations at this point.
2973 kmem_cache_destroy(cfq_pool
);
2975 kmem_cache_destroy(cfq_ioc_pool
);
2978 static int __init
cfq_slab_setup(void)
2980 cfq_pool
= KMEM_CACHE(cfq_queue
, 0);
2984 cfq_ioc_pool
= KMEM_CACHE(cfq_io_context
, 0);
2995 * sysfs parts below -->
2998 cfq_var_show(unsigned int var
, char *page
)
3000 return sprintf(page
, "%d\n", var
);
3004 cfq_var_store(unsigned int *var
, const char *page
, size_t count
)
3006 char *p
= (char *) page
;
3008 *var
= simple_strtoul(p
, &p
, 10);
3012 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
3013 static ssize_t __FUNC(struct elevator_queue *e, char *page) \
3015 struct cfq_data *cfqd = e->elevator_data; \
3016 unsigned int __data = __VAR; \
3018 __data = jiffies_to_msecs(__data); \
3019 return cfq_var_show(__data, (page)); \
3021 SHOW_FUNCTION(cfq_quantum_show
, cfqd
->cfq_quantum
, 0);
3022 SHOW_FUNCTION(cfq_fifo_expire_sync_show
, cfqd
->cfq_fifo_expire
[1], 1);
3023 SHOW_FUNCTION(cfq_fifo_expire_async_show
, cfqd
->cfq_fifo_expire
[0], 1);
3024 SHOW_FUNCTION(cfq_back_seek_max_show
, cfqd
->cfq_back_max
, 0);
3025 SHOW_FUNCTION(cfq_back_seek_penalty_show
, cfqd
->cfq_back_penalty
, 0);
3026 SHOW_FUNCTION(cfq_slice_idle_show
, cfqd
->cfq_slice_idle
, 1);
3027 SHOW_FUNCTION(cfq_slice_sync_show
, cfqd
->cfq_slice
[1], 1);
3028 SHOW_FUNCTION(cfq_slice_async_show
, cfqd
->cfq_slice
[0], 1);
3029 SHOW_FUNCTION(cfq_slice_async_rq_show
, cfqd
->cfq_slice_async_rq
, 0);
3030 SHOW_FUNCTION(cfq_low_latency_show
, cfqd
->cfq_latency
, 0);
3031 #undef SHOW_FUNCTION
3033 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
3034 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3036 struct cfq_data *cfqd = e->elevator_data; \
3037 unsigned int __data; \
3038 int ret = cfq_var_store(&__data, (page), count); \
3039 if (__data < (MIN)) \
3041 else if (__data > (MAX)) \
3044 *(__PTR) = msecs_to_jiffies(__data); \
3046 *(__PTR) = __data; \
3049 STORE_FUNCTION(cfq_quantum_store
, &cfqd
->cfq_quantum
, 1, UINT_MAX
, 0);
3050 STORE_FUNCTION(cfq_fifo_expire_sync_store
, &cfqd
->cfq_fifo_expire
[1], 1,
3052 STORE_FUNCTION(cfq_fifo_expire_async_store
, &cfqd
->cfq_fifo_expire
[0], 1,
3054 STORE_FUNCTION(cfq_back_seek_max_store
, &cfqd
->cfq_back_max
, 0, UINT_MAX
, 0);
3055 STORE_FUNCTION(cfq_back_seek_penalty_store
, &cfqd
->cfq_back_penalty
, 1,
3057 STORE_FUNCTION(cfq_slice_idle_store
, &cfqd
->cfq_slice_idle
, 0, UINT_MAX
, 1);
3058 STORE_FUNCTION(cfq_slice_sync_store
, &cfqd
->cfq_slice
[1], 1, UINT_MAX
, 1);
3059 STORE_FUNCTION(cfq_slice_async_store
, &cfqd
->cfq_slice
[0], 1, UINT_MAX
, 1);
3060 STORE_FUNCTION(cfq_slice_async_rq_store
, &cfqd
->cfq_slice_async_rq
, 1,
3062 STORE_FUNCTION(cfq_low_latency_store
, &cfqd
->cfq_latency
, 0, 1, 0);
3063 #undef STORE_FUNCTION
3065 #define CFQ_ATTR(name) \
3066 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3068 static struct elv_fs_entry cfq_attrs
[] = {
3070 CFQ_ATTR(fifo_expire_sync
),
3071 CFQ_ATTR(fifo_expire_async
),
3072 CFQ_ATTR(back_seek_max
),
3073 CFQ_ATTR(back_seek_penalty
),
3074 CFQ_ATTR(slice_sync
),
3075 CFQ_ATTR(slice_async
),
3076 CFQ_ATTR(slice_async_rq
),
3077 CFQ_ATTR(slice_idle
),
3078 CFQ_ATTR(low_latency
),
3082 static struct elevator_type iosched_cfq
= {
3084 .elevator_merge_fn
= cfq_merge
,
3085 .elevator_merged_fn
= cfq_merged_request
,
3086 .elevator_merge_req_fn
= cfq_merged_requests
,
3087 .elevator_allow_merge_fn
= cfq_allow_merge
,
3088 .elevator_dispatch_fn
= cfq_dispatch_requests
,
3089 .elevator_add_req_fn
= cfq_insert_request
,
3090 .elevator_activate_req_fn
= cfq_activate_request
,
3091 .elevator_deactivate_req_fn
= cfq_deactivate_request
,
3092 .elevator_queue_empty_fn
= cfq_queue_empty
,
3093 .elevator_completed_req_fn
= cfq_completed_request
,
3094 .elevator_former_req_fn
= elv_rb_former_request
,
3095 .elevator_latter_req_fn
= elv_rb_latter_request
,
3096 .elevator_set_req_fn
= cfq_set_request
,
3097 .elevator_put_req_fn
= cfq_put_request
,
3098 .elevator_may_queue_fn
= cfq_may_queue
,
3099 .elevator_init_fn
= cfq_init_queue
,
3100 .elevator_exit_fn
= cfq_exit_queue
,
3101 .trim
= cfq_free_io_context
,
3103 .elevator_attrs
= cfq_attrs
,
3104 .elevator_name
= "cfq",
3105 .elevator_owner
= THIS_MODULE
,
3108 static int __init
cfq_init(void)
3111 * could be 0 on HZ < 1000 setups
3113 if (!cfq_slice_async
)
3114 cfq_slice_async
= 1;
3115 if (!cfq_slice_idle
)
3118 if (cfq_slab_setup())
3121 elv_register(&iosched_cfq
);
3126 static void __exit
cfq_exit(void)
3128 DECLARE_COMPLETION_ONSTACK(all_gone
);
3129 elv_unregister(&iosched_cfq
);
3130 ioc_gone
= &all_gone
;
3131 /* ioc_gone's update must be visible before reading ioc_count */
3135 * this also protects us from entering cfq_slab_kill() with
3136 * pending RCU callbacks
3138 if (elv_ioc_count_read(cfq_ioc_count
))
3139 wait_for_completion(&all_gone
);
3143 module_init(cfq_init
);
3144 module_exit(cfq_exit
);
3146 MODULE_AUTHOR("Jens Axboe");
3147 MODULE_LICENSE("GPL");
3148 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");