2 * CFQ, or complete fairness queueing, disk scheduler.
4 * Based on ideas from a previously unfinished io
5 * scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
7 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
9 #include <linux/module.h>
10 #include <linux/blkdev.h>
11 #include <linux/elevator.h>
12 #include <linux/jiffies.h>
13 #include <linux/rbtree.h>
14 #include <linux/ioprio.h>
15 #include <linux/blktrace_api.h>
20 /* max queue in one round of service */
21 static const int cfq_quantum
= 4;
22 static const int cfq_fifo_expire
[2] = { HZ
/ 4, HZ
/ 8 };
23 /* maximum backwards seek, in KiB */
24 static const int cfq_back_max
= 16 * 1024;
25 /* penalty of a backwards seek */
26 static const int cfq_back_penalty
= 2;
27 static const int cfq_slice_sync
= HZ
/ 10;
28 static int cfq_slice_async
= HZ
/ 25;
29 static const int cfq_slice_async_rq
= 2;
30 static int cfq_slice_idle
= HZ
/ 125;
31 static const int cfq_target_latency
= HZ
* 3/10; /* 300 ms */
32 static const int cfq_hist_divisor
= 4;
35 * offset from end of service tree
37 #define CFQ_IDLE_DELAY (HZ / 5)
40 * below this threshold, we consider thinktime immediate
42 #define CFQ_MIN_TT (2)
45 * Allow merged cfqqs to perform this amount of seeky I/O before
46 * deciding to break the queues up again.
48 #define CFQQ_COOP_TOUT (HZ)
50 #define CFQ_SLICE_SCALE (5)
51 #define CFQ_HW_QUEUE_MIN (5)
54 ((struct cfq_io_context *) (rq)->elevator_private)
55 #define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2)
57 static struct kmem_cache
*cfq_pool
;
58 static struct kmem_cache
*cfq_ioc_pool
;
60 static DEFINE_PER_CPU(unsigned long, cfq_ioc_count
);
61 static struct completion
*ioc_gone
;
62 static DEFINE_SPINLOCK(ioc_gone_lock
);
64 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
65 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
66 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
68 #define sample_valid(samples) ((samples) > 80)
71 * Most of our rbtree usage is for sorting with min extraction, so
72 * if we cache the leftmost node we don't have to walk down the tree
73 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
74 * move this into the elevator for the rq sorting as well.
81 #define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, 0, }
84 * Per process-grouping structure
89 /* various state flags, see below */
92 struct cfq_data
*cfqd
;
93 /* service_tree member */
94 struct rb_node rb_node
;
95 /* service_tree key */
97 /* prio tree member */
98 struct rb_node p_node
;
99 /* prio tree root we belong to, if any */
100 struct rb_root
*p_root
;
101 /* sorted list of pending requests */
102 struct rb_root sort_list
;
103 /* if fifo isn't expired, next request to serve */
104 struct request
*next_rq
;
105 /* requests queued in sort_list */
107 /* currently allocated requests */
109 /* fifo list of requests in sort_list */
110 struct list_head fifo
;
112 unsigned long slice_end
;
114 unsigned int slice_dispatch
;
116 /* pending metadata requests */
118 /* number of requests that are on the dispatch list or inside driver */
121 /* io prio of this group */
122 unsigned short ioprio
, org_ioprio
;
123 unsigned short ioprio_class
, org_ioprio_class
;
125 unsigned int seek_samples
;
128 sector_t last_request_pos
;
129 unsigned long seeky_start
;
133 struct cfq_rb_root
*service_tree
;
134 struct cfq_queue
*new_cfqq
;
138 * First index in the service_trees.
139 * IDLE is handled separately, so it has negative index
148 * Second index in the service_trees.
152 SYNC_NOIDLE_WORKLOAD
= 1,
158 * Per block device queue structure
161 struct request_queue
*queue
;
164 * rr lists of queues with requests, onle rr for each priority class.
165 * Counts are embedded in the cfq_rb_root
167 struct cfq_rb_root service_trees
[2][3];
168 struct cfq_rb_root service_tree_idle
;
170 * The priority currently being served
172 enum wl_prio_t serving_prio
;
173 enum wl_type_t serving_type
;
174 unsigned long workload_expires
;
177 * Each priority tree is sorted by next_request position. These
178 * trees are used when determining if two or more queues are
179 * interleaving requests (see cfq_close_cooperator).
181 struct rb_root prio_trees
[CFQ_PRIO_LISTS
];
183 unsigned int busy_queues
;
184 unsigned int busy_queues_avg
[2];
190 * queue-depth detection
196 * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
197 * 1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
200 int hw_tag_est_depth
;
201 unsigned int hw_tag_samples
;
204 * idle window management
206 struct timer_list idle_slice_timer
;
207 struct work_struct unplug_work
;
209 struct cfq_queue
*active_queue
;
210 struct cfq_io_context
*active_cic
;
213 * async queue for each priority case
215 struct cfq_queue
*async_cfqq
[2][IOPRIO_BE_NR
];
216 struct cfq_queue
*async_idle_cfqq
;
218 sector_t last_position
;
221 * tunables, see top of file
223 unsigned int cfq_quantum
;
224 unsigned int cfq_fifo_expire
[2];
225 unsigned int cfq_back_penalty
;
226 unsigned int cfq_back_max
;
227 unsigned int cfq_slice
[2];
228 unsigned int cfq_slice_async_rq
;
229 unsigned int cfq_slice_idle
;
230 unsigned int cfq_latency
;
232 struct list_head cic_list
;
235 * Fallback dummy cfqq for extreme OOM conditions
237 struct cfq_queue oom_cfqq
;
239 unsigned long last_end_sync_rq
;
242 static struct cfq_rb_root
*service_tree_for(enum wl_prio_t prio
,
244 struct cfq_data
*cfqd
)
246 if (prio
== IDLE_WORKLOAD
)
247 return &cfqd
->service_tree_idle
;
249 return &cfqd
->service_trees
[prio
][type
];
252 enum cfqq_state_flags
{
253 CFQ_CFQQ_FLAG_on_rr
= 0, /* on round-robin busy list */
254 CFQ_CFQQ_FLAG_wait_request
, /* waiting for a request */
255 CFQ_CFQQ_FLAG_must_dispatch
, /* must be allowed a dispatch */
256 CFQ_CFQQ_FLAG_must_alloc_slice
, /* per-slice must_alloc flag */
257 CFQ_CFQQ_FLAG_fifo_expire
, /* FIFO checked in this slice */
258 CFQ_CFQQ_FLAG_idle_window
, /* slice idling enabled */
259 CFQ_CFQQ_FLAG_prio_changed
, /* task priority has changed */
260 CFQ_CFQQ_FLAG_slice_new
, /* no requests dispatched in slice */
261 CFQ_CFQQ_FLAG_sync
, /* synchronous queue */
262 CFQ_CFQQ_FLAG_coop
, /* cfqq is shared */
263 CFQ_CFQQ_FLAG_deep
, /* sync cfqq experienced large depth */
266 #define CFQ_CFQQ_FNS(name) \
267 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
269 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
271 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
273 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
275 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
277 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
281 CFQ_CFQQ_FNS(wait_request
);
282 CFQ_CFQQ_FNS(must_dispatch
);
283 CFQ_CFQQ_FNS(must_alloc_slice
);
284 CFQ_CFQQ_FNS(fifo_expire
);
285 CFQ_CFQQ_FNS(idle_window
);
286 CFQ_CFQQ_FNS(prio_changed
);
287 CFQ_CFQQ_FNS(slice_new
);
293 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
294 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
295 #define cfq_log(cfqd, fmt, args...) \
296 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
298 static inline enum wl_prio_t
cfqq_prio(struct cfq_queue
*cfqq
)
300 if (cfq_class_idle(cfqq
))
301 return IDLE_WORKLOAD
;
302 if (cfq_class_rt(cfqq
))
308 static enum wl_type_t
cfqq_type(struct cfq_queue
*cfqq
)
310 if (!cfq_cfqq_sync(cfqq
))
311 return ASYNC_WORKLOAD
;
312 if (!cfq_cfqq_idle_window(cfqq
))
313 return SYNC_NOIDLE_WORKLOAD
;
314 return SYNC_WORKLOAD
;
317 static inline int cfq_busy_queues_wl(enum wl_prio_t wl
, struct cfq_data
*cfqd
)
319 if (wl
== IDLE_WORKLOAD
)
320 return cfqd
->service_tree_idle
.count
;
322 return cfqd
->service_trees
[wl
][ASYNC_WORKLOAD
].count
323 + cfqd
->service_trees
[wl
][SYNC_NOIDLE_WORKLOAD
].count
324 + cfqd
->service_trees
[wl
][SYNC_WORKLOAD
].count
;
327 static void cfq_dispatch_insert(struct request_queue
*, struct request
*);
328 static struct cfq_queue
*cfq_get_queue(struct cfq_data
*, bool,
329 struct io_context
*, gfp_t
);
330 static struct cfq_io_context
*cfq_cic_lookup(struct cfq_data
*,
331 struct io_context
*);
333 static inline int rq_in_driver(struct cfq_data
*cfqd
)
335 return cfqd
->rq_in_driver
[0] + cfqd
->rq_in_driver
[1];
338 static inline struct cfq_queue
*cic_to_cfqq(struct cfq_io_context
*cic
,
341 return cic
->cfqq
[is_sync
];
344 static inline void cic_set_cfqq(struct cfq_io_context
*cic
,
345 struct cfq_queue
*cfqq
, bool is_sync
)
347 cic
->cfqq
[is_sync
] = cfqq
;
351 * We regard a request as SYNC, if it's either a read or has the SYNC bit
352 * set (in which case it could also be direct WRITE).
354 static inline bool cfq_bio_sync(struct bio
*bio
)
356 return bio_data_dir(bio
) == READ
|| bio_rw_flagged(bio
, BIO_RW_SYNCIO
);
360 * scheduler run of queue, if there are requests pending and no one in the
361 * driver that will restart queueing
363 static inline void cfq_schedule_dispatch(struct cfq_data
*cfqd
)
365 if (cfqd
->busy_queues
) {
366 cfq_log(cfqd
, "schedule dispatch");
367 kblockd_schedule_work(cfqd
->queue
, &cfqd
->unplug_work
);
371 static int cfq_queue_empty(struct request_queue
*q
)
373 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
375 return !cfqd
->busy_queues
;
379 * Scale schedule slice based on io priority. Use the sync time slice only
380 * if a queue is marked sync and has sync io queued. A sync queue with async
381 * io only, should not get full sync slice length.
383 static inline int cfq_prio_slice(struct cfq_data
*cfqd
, bool sync
,
386 const int base_slice
= cfqd
->cfq_slice
[sync
];
388 WARN_ON(prio
>= IOPRIO_BE_NR
);
390 return base_slice
+ (base_slice
/CFQ_SLICE_SCALE
* (4 - prio
));
394 cfq_prio_to_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
396 return cfq_prio_slice(cfqd
, cfq_cfqq_sync(cfqq
), cfqq
->ioprio
);
400 * get averaged number of queues of RT/BE priority.
401 * average is updated, with a formula that gives more weight to higher numbers,
402 * to quickly follows sudden increases and decrease slowly
405 static inline unsigned cfq_get_avg_queues(struct cfq_data
*cfqd
, bool rt
)
407 unsigned min_q
, max_q
;
408 unsigned mult
= cfq_hist_divisor
- 1;
409 unsigned round
= cfq_hist_divisor
/ 2;
410 unsigned busy
= cfq_busy_queues_wl(rt
, cfqd
);
412 min_q
= min(cfqd
->busy_queues_avg
[rt
], busy
);
413 max_q
= max(cfqd
->busy_queues_avg
[rt
], busy
);
414 cfqd
->busy_queues_avg
[rt
] = (mult
* max_q
+ min_q
+ round
) /
416 return cfqd
->busy_queues_avg
[rt
];
420 cfq_set_prio_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
422 unsigned slice
= cfq_prio_to_slice(cfqd
, cfqq
);
423 if (cfqd
->cfq_latency
) {
424 /* interested queues (we consider only the ones with the same
426 unsigned iq
= cfq_get_avg_queues(cfqd
, cfq_class_rt(cfqq
));
427 unsigned sync_slice
= cfqd
->cfq_slice
[1];
428 unsigned expect_latency
= sync_slice
* iq
;
429 if (expect_latency
> cfq_target_latency
) {
430 unsigned base_low_slice
= 2 * cfqd
->cfq_slice_idle
;
431 /* scale low_slice according to IO priority
432 * and sync vs async */
434 min(slice
, base_low_slice
* slice
/ sync_slice
);
435 /* the adapted slice value is scaled to fit all iqs
436 * into the target latency */
437 slice
= max(slice
* cfq_target_latency
/ expect_latency
,
441 cfqq
->slice_end
= jiffies
+ slice
;
442 cfq_log_cfqq(cfqd
, cfqq
, "set_slice=%lu", cfqq
->slice_end
- jiffies
);
446 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
447 * isn't valid until the first request from the dispatch is activated
448 * and the slice time set.
450 static inline bool cfq_slice_used(struct cfq_queue
*cfqq
)
452 if (cfq_cfqq_slice_new(cfqq
))
454 if (time_before(jiffies
, cfqq
->slice_end
))
461 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
462 * We choose the request that is closest to the head right now. Distance
463 * behind the head is penalized and only allowed to a certain extent.
465 static struct request
*
466 cfq_choose_req(struct cfq_data
*cfqd
, struct request
*rq1
, struct request
*rq2
, sector_t last
)
468 sector_t s1
, s2
, d1
= 0, d2
= 0;
469 unsigned long back_max
;
470 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
471 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
472 unsigned wrap
= 0; /* bit mask: requests behind the disk head? */
474 if (rq1
== NULL
|| rq1
== rq2
)
479 if (rq_is_sync(rq1
) && !rq_is_sync(rq2
))
481 else if (rq_is_sync(rq2
) && !rq_is_sync(rq1
))
483 if (rq_is_meta(rq1
) && !rq_is_meta(rq2
))
485 else if (rq_is_meta(rq2
) && !rq_is_meta(rq1
))
488 s1
= blk_rq_pos(rq1
);
489 s2
= blk_rq_pos(rq2
);
492 * by definition, 1KiB is 2 sectors
494 back_max
= cfqd
->cfq_back_max
* 2;
497 * Strict one way elevator _except_ in the case where we allow
498 * short backward seeks which are biased as twice the cost of a
499 * similar forward seek.
503 else if (s1
+ back_max
>= last
)
504 d1
= (last
- s1
) * cfqd
->cfq_back_penalty
;
506 wrap
|= CFQ_RQ1_WRAP
;
510 else if (s2
+ back_max
>= last
)
511 d2
= (last
- s2
) * cfqd
->cfq_back_penalty
;
513 wrap
|= CFQ_RQ2_WRAP
;
515 /* Found required data */
518 * By doing switch() on the bit mask "wrap" we avoid having to
519 * check two variables for all permutations: --> faster!
522 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
538 case (CFQ_RQ1_WRAP
|CFQ_RQ2_WRAP
): /* both rqs wrapped */
541 * Since both rqs are wrapped,
542 * start with the one that's further behind head
543 * (--> only *one* back seek required),
544 * since back seek takes more time than forward.
554 * The below is leftmost cache rbtree addon
556 static struct cfq_queue
*cfq_rb_first(struct cfq_rb_root
*root
)
559 root
->left
= rb_first(&root
->rb
);
562 return rb_entry(root
->left
, struct cfq_queue
, rb_node
);
567 static void rb_erase_init(struct rb_node
*n
, struct rb_root
*root
)
573 static void cfq_rb_erase(struct rb_node
*n
, struct cfq_rb_root
*root
)
577 rb_erase_init(n
, &root
->rb
);
582 * would be nice to take fifo expire time into account as well
584 static struct request
*
585 cfq_find_next_rq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
586 struct request
*last
)
588 struct rb_node
*rbnext
= rb_next(&last
->rb_node
);
589 struct rb_node
*rbprev
= rb_prev(&last
->rb_node
);
590 struct request
*next
= NULL
, *prev
= NULL
;
592 BUG_ON(RB_EMPTY_NODE(&last
->rb_node
));
595 prev
= rb_entry_rq(rbprev
);
598 next
= rb_entry_rq(rbnext
);
600 rbnext
= rb_first(&cfqq
->sort_list
);
601 if (rbnext
&& rbnext
!= &last
->rb_node
)
602 next
= rb_entry_rq(rbnext
);
605 return cfq_choose_req(cfqd
, next
, prev
, blk_rq_pos(last
));
608 static unsigned long cfq_slice_offset(struct cfq_data
*cfqd
,
609 struct cfq_queue
*cfqq
)
611 struct cfq_rb_root
*service_tree
;
613 service_tree
= service_tree_for(cfqq_prio(cfqq
), cfqq_type(cfqq
), cfqd
);
616 * just an approximation, should be ok.
618 return service_tree
->count
* (cfq_prio_slice(cfqd
, 1, 0) -
619 cfq_prio_slice(cfqd
, cfq_cfqq_sync(cfqq
), cfqq
->ioprio
));
623 * The cfqd->service_trees holds all pending cfq_queue's that have
624 * requests waiting to be processed. It is sorted in the order that
625 * we will service the queues.
627 static void cfq_service_tree_add(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
630 struct rb_node
**p
, *parent
;
631 struct cfq_queue
*__cfqq
;
632 unsigned long rb_key
;
633 struct cfq_rb_root
*service_tree
;
636 service_tree
= service_tree_for(cfqq_prio(cfqq
), cfqq_type(cfqq
), cfqd
);
637 if (cfq_class_idle(cfqq
)) {
638 rb_key
= CFQ_IDLE_DELAY
;
639 parent
= rb_last(&service_tree
->rb
);
640 if (parent
&& parent
!= &cfqq
->rb_node
) {
641 __cfqq
= rb_entry(parent
, struct cfq_queue
, rb_node
);
642 rb_key
+= __cfqq
->rb_key
;
645 } else if (!add_front
) {
647 * Get our rb key offset. Subtract any residual slice
648 * value carried from last service. A negative resid
649 * count indicates slice overrun, and this should position
650 * the next service time further away in the tree.
652 rb_key
= cfq_slice_offset(cfqd
, cfqq
) + jiffies
;
653 rb_key
-= cfqq
->slice_resid
;
654 cfqq
->slice_resid
= 0;
657 __cfqq
= cfq_rb_first(service_tree
);
658 rb_key
+= __cfqq
? __cfqq
->rb_key
: jiffies
;
661 if (!RB_EMPTY_NODE(&cfqq
->rb_node
)) {
663 * same position, nothing more to do
665 if (rb_key
== cfqq
->rb_key
&&
666 cfqq
->service_tree
== service_tree
)
669 cfq_rb_erase(&cfqq
->rb_node
, cfqq
->service_tree
);
670 cfqq
->service_tree
= NULL
;
675 cfqq
->service_tree
= service_tree
;
676 p
= &service_tree
->rb
.rb_node
;
681 __cfqq
= rb_entry(parent
, struct cfq_queue
, rb_node
);
684 * sort by key, that represents service time.
686 if (time_before(rb_key
, __cfqq
->rb_key
))
697 service_tree
->left
= &cfqq
->rb_node
;
699 cfqq
->rb_key
= rb_key
;
700 rb_link_node(&cfqq
->rb_node
, parent
, p
);
701 rb_insert_color(&cfqq
->rb_node
, &service_tree
->rb
);
702 service_tree
->count
++;
705 static struct cfq_queue
*
706 cfq_prio_tree_lookup(struct cfq_data
*cfqd
, struct rb_root
*root
,
707 sector_t sector
, struct rb_node
**ret_parent
,
708 struct rb_node
***rb_link
)
710 struct rb_node
**p
, *parent
;
711 struct cfq_queue
*cfqq
= NULL
;
719 cfqq
= rb_entry(parent
, struct cfq_queue
, p_node
);
722 * Sort strictly based on sector. Smallest to the left,
723 * largest to the right.
725 if (sector
> blk_rq_pos(cfqq
->next_rq
))
727 else if (sector
< blk_rq_pos(cfqq
->next_rq
))
735 *ret_parent
= parent
;
741 static void cfq_prio_tree_add(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
743 struct rb_node
**p
, *parent
;
744 struct cfq_queue
*__cfqq
;
747 rb_erase(&cfqq
->p_node
, cfqq
->p_root
);
751 if (cfq_class_idle(cfqq
))
756 cfqq
->p_root
= &cfqd
->prio_trees
[cfqq
->org_ioprio
];
757 __cfqq
= cfq_prio_tree_lookup(cfqd
, cfqq
->p_root
,
758 blk_rq_pos(cfqq
->next_rq
), &parent
, &p
);
760 rb_link_node(&cfqq
->p_node
, parent
, p
);
761 rb_insert_color(&cfqq
->p_node
, cfqq
->p_root
);
767 * Update cfqq's position in the service tree.
769 static void cfq_resort_rr_list(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
772 * Resorting requires the cfqq to be on the RR list already.
774 if (cfq_cfqq_on_rr(cfqq
)) {
775 cfq_service_tree_add(cfqd
, cfqq
, 0);
776 cfq_prio_tree_add(cfqd
, cfqq
);
781 * add to busy list of queues for service, trying to be fair in ordering
782 * the pending list according to last request service
784 static void cfq_add_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
786 cfq_log_cfqq(cfqd
, cfqq
, "add_to_rr");
787 BUG_ON(cfq_cfqq_on_rr(cfqq
));
788 cfq_mark_cfqq_on_rr(cfqq
);
791 cfq_resort_rr_list(cfqd
, cfqq
);
795 * Called when the cfqq no longer has requests pending, remove it from
798 static void cfq_del_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
800 cfq_log_cfqq(cfqd
, cfqq
, "del_from_rr");
801 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
802 cfq_clear_cfqq_on_rr(cfqq
);
804 if (!RB_EMPTY_NODE(&cfqq
->rb_node
)) {
805 cfq_rb_erase(&cfqq
->rb_node
, cfqq
->service_tree
);
806 cfqq
->service_tree
= NULL
;
809 rb_erase(&cfqq
->p_node
, cfqq
->p_root
);
813 BUG_ON(!cfqd
->busy_queues
);
818 * rb tree support functions
820 static void cfq_del_rq_rb(struct request
*rq
)
822 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
823 struct cfq_data
*cfqd
= cfqq
->cfqd
;
824 const int sync
= rq_is_sync(rq
);
826 BUG_ON(!cfqq
->queued
[sync
]);
827 cfqq
->queued
[sync
]--;
829 elv_rb_del(&cfqq
->sort_list
, rq
);
831 if (cfq_cfqq_on_rr(cfqq
) && RB_EMPTY_ROOT(&cfqq
->sort_list
))
832 cfq_del_cfqq_rr(cfqd
, cfqq
);
835 static void cfq_add_rq_rb(struct request
*rq
)
837 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
838 struct cfq_data
*cfqd
= cfqq
->cfqd
;
839 struct request
*__alias
, *prev
;
841 cfqq
->queued
[rq_is_sync(rq
)]++;
844 * looks a little odd, but the first insert might return an alias.
845 * if that happens, put the alias on the dispatch list
847 while ((__alias
= elv_rb_add(&cfqq
->sort_list
, rq
)) != NULL
)
848 cfq_dispatch_insert(cfqd
->queue
, __alias
);
850 if (!cfq_cfqq_on_rr(cfqq
))
851 cfq_add_cfqq_rr(cfqd
, cfqq
);
854 * check if this request is a better next-serve candidate
856 prev
= cfqq
->next_rq
;
857 cfqq
->next_rq
= cfq_choose_req(cfqd
, cfqq
->next_rq
, rq
, cfqd
->last_position
);
860 * adjust priority tree position, if ->next_rq changes
862 if (prev
!= cfqq
->next_rq
)
863 cfq_prio_tree_add(cfqd
, cfqq
);
865 BUG_ON(!cfqq
->next_rq
);
868 static void cfq_reposition_rq_rb(struct cfq_queue
*cfqq
, struct request
*rq
)
870 elv_rb_del(&cfqq
->sort_list
, rq
);
871 cfqq
->queued
[rq_is_sync(rq
)]--;
875 static struct request
*
876 cfq_find_rq_fmerge(struct cfq_data
*cfqd
, struct bio
*bio
)
878 struct task_struct
*tsk
= current
;
879 struct cfq_io_context
*cic
;
880 struct cfq_queue
*cfqq
;
882 cic
= cfq_cic_lookup(cfqd
, tsk
->io_context
);
886 cfqq
= cic_to_cfqq(cic
, cfq_bio_sync(bio
));
888 sector_t sector
= bio
->bi_sector
+ bio_sectors(bio
);
890 return elv_rb_find(&cfqq
->sort_list
, sector
);
896 static void cfq_activate_request(struct request_queue
*q
, struct request
*rq
)
898 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
900 cfqd
->rq_in_driver
[rq_is_sync(rq
)]++;
901 cfq_log_cfqq(cfqd
, RQ_CFQQ(rq
), "activate rq, drv=%d",
904 cfqd
->last_position
= blk_rq_pos(rq
) + blk_rq_sectors(rq
);
907 static void cfq_deactivate_request(struct request_queue
*q
, struct request
*rq
)
909 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
910 const int sync
= rq_is_sync(rq
);
912 WARN_ON(!cfqd
->rq_in_driver
[sync
]);
913 cfqd
->rq_in_driver
[sync
]--;
914 cfq_log_cfqq(cfqd
, RQ_CFQQ(rq
), "deactivate rq, drv=%d",
918 static void cfq_remove_request(struct request
*rq
)
920 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
922 if (cfqq
->next_rq
== rq
)
923 cfqq
->next_rq
= cfq_find_next_rq(cfqq
->cfqd
, cfqq
, rq
);
925 list_del_init(&rq
->queuelist
);
928 cfqq
->cfqd
->rq_queued
--;
929 if (rq_is_meta(rq
)) {
930 WARN_ON(!cfqq
->meta_pending
);
931 cfqq
->meta_pending
--;
935 static int cfq_merge(struct request_queue
*q
, struct request
**req
,
938 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
939 struct request
*__rq
;
941 __rq
= cfq_find_rq_fmerge(cfqd
, bio
);
942 if (__rq
&& elv_rq_merge_ok(__rq
, bio
)) {
944 return ELEVATOR_FRONT_MERGE
;
947 return ELEVATOR_NO_MERGE
;
950 static void cfq_merged_request(struct request_queue
*q
, struct request
*req
,
953 if (type
== ELEVATOR_FRONT_MERGE
) {
954 struct cfq_queue
*cfqq
= RQ_CFQQ(req
);
956 cfq_reposition_rq_rb(cfqq
, req
);
961 cfq_merged_requests(struct request_queue
*q
, struct request
*rq
,
962 struct request
*next
)
964 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
966 * reposition in fifo if next is older than rq
968 if (!list_empty(&rq
->queuelist
) && !list_empty(&next
->queuelist
) &&
969 time_before(rq_fifo_time(next
), rq_fifo_time(rq
))) {
970 list_move(&rq
->queuelist
, &next
->queuelist
);
971 rq_set_fifo_time(rq
, rq_fifo_time(next
));
974 if (cfqq
->next_rq
== next
)
976 cfq_remove_request(next
);
979 static int cfq_allow_merge(struct request_queue
*q
, struct request
*rq
,
982 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
983 struct cfq_io_context
*cic
;
984 struct cfq_queue
*cfqq
;
987 * Disallow merge of a sync bio into an async request.
989 if (cfq_bio_sync(bio
) && !rq_is_sync(rq
))
993 * Lookup the cfqq that this bio will be queued with. Allow
994 * merge only if rq is queued there.
996 cic
= cfq_cic_lookup(cfqd
, current
->io_context
);
1000 cfqq
= cic_to_cfqq(cic
, cfq_bio_sync(bio
));
1001 return cfqq
== RQ_CFQQ(rq
);
1004 static void __cfq_set_active_queue(struct cfq_data
*cfqd
,
1005 struct cfq_queue
*cfqq
)
1008 cfq_log_cfqq(cfqd
, cfqq
, "set_active");
1009 cfqq
->slice_end
= 0;
1010 cfqq
->slice_dispatch
= 0;
1012 cfq_clear_cfqq_wait_request(cfqq
);
1013 cfq_clear_cfqq_must_dispatch(cfqq
);
1014 cfq_clear_cfqq_must_alloc_slice(cfqq
);
1015 cfq_clear_cfqq_fifo_expire(cfqq
);
1016 cfq_mark_cfqq_slice_new(cfqq
);
1018 del_timer(&cfqd
->idle_slice_timer
);
1021 cfqd
->active_queue
= cfqq
;
1025 * current cfqq expired its slice (or was too idle), select new one
1028 __cfq_slice_expired(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1031 cfq_log_cfqq(cfqd
, cfqq
, "slice expired t=%d", timed_out
);
1033 if (cfq_cfqq_wait_request(cfqq
))
1034 del_timer(&cfqd
->idle_slice_timer
);
1036 cfq_clear_cfqq_wait_request(cfqq
);
1039 * store what was left of this slice, if the queue idled/timed out
1041 if (timed_out
&& !cfq_cfqq_slice_new(cfqq
)) {
1042 cfqq
->slice_resid
= cfqq
->slice_end
- jiffies
;
1043 cfq_log_cfqq(cfqd
, cfqq
, "resid=%ld", cfqq
->slice_resid
);
1046 cfq_resort_rr_list(cfqd
, cfqq
);
1048 if (cfqq
== cfqd
->active_queue
)
1049 cfqd
->active_queue
= NULL
;
1051 if (cfqd
->active_cic
) {
1052 put_io_context(cfqd
->active_cic
->ioc
);
1053 cfqd
->active_cic
= NULL
;
1057 static inline void cfq_slice_expired(struct cfq_data
*cfqd
, bool timed_out
)
1059 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
1062 __cfq_slice_expired(cfqd
, cfqq
, timed_out
);
1066 * Get next queue for service. Unless we have a queue preemption,
1067 * we'll simply select the first cfqq in the service tree.
1069 static struct cfq_queue
*cfq_get_next_queue(struct cfq_data
*cfqd
)
1071 struct cfq_rb_root
*service_tree
=
1072 service_tree_for(cfqd
->serving_prio
, cfqd
->serving_type
, cfqd
);
1074 if (RB_EMPTY_ROOT(&service_tree
->rb
))
1076 return cfq_rb_first(service_tree
);
1080 * Get and set a new active queue for service.
1082 static struct cfq_queue
*cfq_set_active_queue(struct cfq_data
*cfqd
,
1083 struct cfq_queue
*cfqq
)
1086 cfqq
= cfq_get_next_queue(cfqd
);
1088 __cfq_set_active_queue(cfqd
, cfqq
);
1092 static inline sector_t
cfq_dist_from_last(struct cfq_data
*cfqd
,
1095 if (blk_rq_pos(rq
) >= cfqd
->last_position
)
1096 return blk_rq_pos(rq
) - cfqd
->last_position
;
1098 return cfqd
->last_position
- blk_rq_pos(rq
);
1101 #define CFQQ_SEEK_THR 8 * 1024
1102 #define CFQQ_SEEKY(cfqq) ((cfqq)->seek_mean > CFQQ_SEEK_THR)
1104 static inline int cfq_rq_close(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1107 sector_t sdist
= cfqq
->seek_mean
;
1109 if (!sample_valid(cfqq
->seek_samples
))
1110 sdist
= CFQQ_SEEK_THR
;
1112 return cfq_dist_from_last(cfqd
, rq
) <= sdist
;
1115 static struct cfq_queue
*cfqq_close(struct cfq_data
*cfqd
,
1116 struct cfq_queue
*cur_cfqq
)
1118 struct rb_root
*root
= &cfqd
->prio_trees
[cur_cfqq
->org_ioprio
];
1119 struct rb_node
*parent
, *node
;
1120 struct cfq_queue
*__cfqq
;
1121 sector_t sector
= cfqd
->last_position
;
1123 if (RB_EMPTY_ROOT(root
))
1127 * First, if we find a request starting at the end of the last
1128 * request, choose it.
1130 __cfqq
= cfq_prio_tree_lookup(cfqd
, root
, sector
, &parent
, NULL
);
1135 * If the exact sector wasn't found, the parent of the NULL leaf
1136 * will contain the closest sector.
1138 __cfqq
= rb_entry(parent
, struct cfq_queue
, p_node
);
1139 if (cfq_rq_close(cfqd
, cur_cfqq
, __cfqq
->next_rq
))
1142 if (blk_rq_pos(__cfqq
->next_rq
) < sector
)
1143 node
= rb_next(&__cfqq
->p_node
);
1145 node
= rb_prev(&__cfqq
->p_node
);
1149 __cfqq
= rb_entry(node
, struct cfq_queue
, p_node
);
1150 if (cfq_rq_close(cfqd
, cur_cfqq
, __cfqq
->next_rq
))
1158 * cur_cfqq - passed in so that we don't decide that the current queue is
1159 * closely cooperating with itself.
1161 * So, basically we're assuming that that cur_cfqq has dispatched at least
1162 * one request, and that cfqd->last_position reflects a position on the disk
1163 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
1166 static struct cfq_queue
*cfq_close_cooperator(struct cfq_data
*cfqd
,
1167 struct cfq_queue
*cur_cfqq
)
1169 struct cfq_queue
*cfqq
;
1171 if (!cfq_cfqq_sync(cur_cfqq
))
1173 if (CFQQ_SEEKY(cur_cfqq
))
1177 * We should notice if some of the queues are cooperating, eg
1178 * working closely on the same area of the disk. In that case,
1179 * we can group them together and don't waste time idling.
1181 cfqq
= cfqq_close(cfqd
, cur_cfqq
);
1186 * It only makes sense to merge sync queues.
1188 if (!cfq_cfqq_sync(cfqq
))
1190 if (CFQQ_SEEKY(cfqq
))
1194 * Do not merge queues of different priority classes
1196 if (cfq_class_rt(cfqq
) != cfq_class_rt(cur_cfqq
))
1203 * Determine whether we should enforce idle window for this queue.
1206 static bool cfq_should_idle(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1208 enum wl_prio_t prio
= cfqq_prio(cfqq
);
1209 struct cfq_rb_root
*service_tree
= cfqq
->service_tree
;
1211 /* We never do for idle class queues. */
1212 if (prio
== IDLE_WORKLOAD
)
1215 /* We do for queues that were marked with idle window flag. */
1216 if (cfq_cfqq_idle_window(cfqq
))
1220 * Otherwise, we do only if they are the last ones
1221 * in their service tree.
1224 service_tree
= service_tree_for(prio
, cfqq_type(cfqq
), cfqd
);
1226 if (service_tree
->count
== 0)
1229 return (service_tree
->count
== 1 && cfq_rb_first(service_tree
) == cfqq
);
1232 static void cfq_arm_slice_timer(struct cfq_data
*cfqd
)
1234 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
1235 struct cfq_io_context
*cic
;
1239 * SSD device without seek penalty, disable idling. But only do so
1240 * for devices that support queuing, otherwise we still have a problem
1241 * with sync vs async workloads.
1243 if (blk_queue_nonrot(cfqd
->queue
) && cfqd
->hw_tag
)
1246 WARN_ON(!RB_EMPTY_ROOT(&cfqq
->sort_list
));
1247 WARN_ON(cfq_cfqq_slice_new(cfqq
));
1250 * idle is disabled, either manually or by past process history
1252 if (!cfqd
->cfq_slice_idle
|| !cfq_should_idle(cfqd
, cfqq
))
1256 * still requests with the driver, don't idle
1258 if (rq_in_driver(cfqd
))
1262 * task has exited, don't wait
1264 cic
= cfqd
->active_cic
;
1265 if (!cic
|| !atomic_read(&cic
->ioc
->nr_tasks
))
1269 * If our average think time is larger than the remaining time
1270 * slice, then don't idle. This avoids overrunning the allotted
1273 if (sample_valid(cic
->ttime_samples
) &&
1274 (cfqq
->slice_end
- jiffies
< cic
->ttime_mean
))
1277 cfq_mark_cfqq_wait_request(cfqq
);
1279 sl
= cfqd
->cfq_slice_idle
;
1281 mod_timer(&cfqd
->idle_slice_timer
, jiffies
+ sl
);
1282 cfq_log_cfqq(cfqd
, cfqq
, "arm_idle: %lu", sl
);
1286 * Move request from internal lists to the request queue dispatch list.
1288 static void cfq_dispatch_insert(struct request_queue
*q
, struct request
*rq
)
1290 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1291 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1293 cfq_log_cfqq(cfqd
, cfqq
, "dispatch_insert");
1295 cfqq
->next_rq
= cfq_find_next_rq(cfqd
, cfqq
, rq
);
1296 cfq_remove_request(rq
);
1298 elv_dispatch_sort(q
, rq
);
1300 if (cfq_cfqq_sync(cfqq
))
1301 cfqd
->sync_flight
++;
1305 * return expired entry, or NULL to just start from scratch in rbtree
1307 static struct request
*cfq_check_fifo(struct cfq_queue
*cfqq
)
1309 struct request
*rq
= NULL
;
1311 if (cfq_cfqq_fifo_expire(cfqq
))
1314 cfq_mark_cfqq_fifo_expire(cfqq
);
1316 if (list_empty(&cfqq
->fifo
))
1319 rq
= rq_entry_fifo(cfqq
->fifo
.next
);
1320 if (time_before(jiffies
, rq_fifo_time(rq
)))
1323 cfq_log_cfqq(cfqq
->cfqd
, cfqq
, "fifo=%p", rq
);
1328 cfq_prio_to_maxrq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1330 const int base_rq
= cfqd
->cfq_slice_async_rq
;
1332 WARN_ON(cfqq
->ioprio
>= IOPRIO_BE_NR
);
1334 return 2 * (base_rq
+ base_rq
* (CFQ_PRIO_LISTS
- 1 - cfqq
->ioprio
));
1338 * Must be called with the queue_lock held.
1340 static int cfqq_process_refs(struct cfq_queue
*cfqq
)
1342 int process_refs
, io_refs
;
1344 io_refs
= cfqq
->allocated
[READ
] + cfqq
->allocated
[WRITE
];
1345 process_refs
= atomic_read(&cfqq
->ref
) - io_refs
;
1346 BUG_ON(process_refs
< 0);
1347 return process_refs
;
1350 static void cfq_setup_merge(struct cfq_queue
*cfqq
, struct cfq_queue
*new_cfqq
)
1352 int process_refs
, new_process_refs
;
1353 struct cfq_queue
*__cfqq
;
1355 /* Avoid a circular list and skip interim queue merges */
1356 while ((__cfqq
= new_cfqq
->new_cfqq
)) {
1362 process_refs
= cfqq_process_refs(cfqq
);
1364 * If the process for the cfqq has gone away, there is no
1365 * sense in merging the queues.
1367 if (process_refs
== 0)
1371 * Merge in the direction of the lesser amount of work.
1373 new_process_refs
= cfqq_process_refs(new_cfqq
);
1374 if (new_process_refs
>= process_refs
) {
1375 cfqq
->new_cfqq
= new_cfqq
;
1376 atomic_add(process_refs
, &new_cfqq
->ref
);
1378 new_cfqq
->new_cfqq
= cfqq
;
1379 atomic_add(new_process_refs
, &cfqq
->ref
);
1383 static enum wl_type_t
cfq_choose_wl(struct cfq_data
*cfqd
, enum wl_prio_t prio
,
1386 struct cfq_queue
*queue
;
1388 bool key_valid
= false;
1389 unsigned long lowest_key
= 0;
1390 enum wl_type_t cur_best
= SYNC_NOIDLE_WORKLOAD
;
1394 * When priorities switched, we prefer starting
1395 * from SYNC_NOIDLE (first choice), or just SYNC
1398 if (service_tree_for(prio
, cur_best
, cfqd
)->count
)
1400 cur_best
= SYNC_WORKLOAD
;
1401 if (service_tree_for(prio
, cur_best
, cfqd
)->count
)
1404 return ASYNC_WORKLOAD
;
1407 for (i
= 0; i
< 3; ++i
) {
1408 /* otherwise, select the one with lowest rb_key */
1409 queue
= cfq_rb_first(service_tree_for(prio
, i
, cfqd
));
1411 (!key_valid
|| time_before(queue
->rb_key
, lowest_key
))) {
1412 lowest_key
= queue
->rb_key
;
1421 static void choose_service_tree(struct cfq_data
*cfqd
)
1423 enum wl_prio_t previous_prio
= cfqd
->serving_prio
;
1428 /* Choose next priority. RT > BE > IDLE */
1429 if (cfq_busy_queues_wl(RT_WORKLOAD
, cfqd
))
1430 cfqd
->serving_prio
= RT_WORKLOAD
;
1431 else if (cfq_busy_queues_wl(BE_WORKLOAD
, cfqd
))
1432 cfqd
->serving_prio
= BE_WORKLOAD
;
1434 cfqd
->serving_prio
= IDLE_WORKLOAD
;
1435 cfqd
->workload_expires
= jiffies
+ 1;
1440 * For RT and BE, we have to choose also the type
1441 * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
1444 prio_changed
= (cfqd
->serving_prio
!= previous_prio
);
1445 count
= service_tree_for(cfqd
->serving_prio
, cfqd
->serving_type
, cfqd
)
1449 * If priority didn't change, check workload expiration,
1450 * and that we still have other queues ready
1452 if (!prio_changed
&& count
&&
1453 !time_after(jiffies
, cfqd
->workload_expires
))
1456 /* otherwise select new workload type */
1457 cfqd
->serving_type
=
1458 cfq_choose_wl(cfqd
, cfqd
->serving_prio
, prio_changed
);
1459 count
= service_tree_for(cfqd
->serving_prio
, cfqd
->serving_type
, cfqd
)
1463 * the workload slice is computed as a fraction of target latency
1464 * proportional to the number of queues in that workload, over
1465 * all the queues in the same priority class
1467 slice
= cfq_target_latency
* count
/
1468 max_t(unsigned, cfqd
->busy_queues_avg
[cfqd
->serving_prio
],
1469 cfq_busy_queues_wl(cfqd
->serving_prio
, cfqd
));
1471 if (cfqd
->serving_type
== ASYNC_WORKLOAD
)
1472 /* async workload slice is scaled down according to
1473 * the sync/async slice ratio. */
1474 slice
= slice
* cfqd
->cfq_slice
[0] / cfqd
->cfq_slice
[1];
1476 /* sync workload slice is at least 2 * cfq_slice_idle */
1477 slice
= max(slice
, 2 * cfqd
->cfq_slice_idle
);
1479 slice
= max_t(unsigned, slice
, CFQ_MIN_TT
);
1480 cfqd
->workload_expires
= jiffies
+ slice
;
1484 * Select a queue for service. If we have a current active queue,
1485 * check whether to continue servicing it, or retrieve and set a new one.
1487 static struct cfq_queue
*cfq_select_queue(struct cfq_data
*cfqd
)
1489 struct cfq_queue
*cfqq
, *new_cfqq
= NULL
;
1491 cfqq
= cfqd
->active_queue
;
1496 * The active queue has run out of time, expire it and select new.
1498 if (cfq_slice_used(cfqq
) && !cfq_cfqq_must_dispatch(cfqq
))
1502 * The active queue has requests and isn't expired, allow it to
1505 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
))
1509 * If another queue has a request waiting within our mean seek
1510 * distance, let it run. The expire code will check for close
1511 * cooperators and put the close queue at the front of the service
1512 * tree. If possible, merge the expiring queue with the new cfqq.
1514 new_cfqq
= cfq_close_cooperator(cfqd
, cfqq
);
1516 if (!cfqq
->new_cfqq
)
1517 cfq_setup_merge(cfqq
, new_cfqq
);
1522 * No requests pending. If the active queue still has requests in
1523 * flight or is idling for a new request, allow either of these
1524 * conditions to happen (or time out) before selecting a new queue.
1526 if (timer_pending(&cfqd
->idle_slice_timer
) ||
1527 (cfqq
->dispatched
&& cfq_should_idle(cfqd
, cfqq
))) {
1533 cfq_slice_expired(cfqd
, 0);
1536 * Current queue expired. Check if we have to switch to a new
1540 choose_service_tree(cfqd
);
1542 cfqq
= cfq_set_active_queue(cfqd
, new_cfqq
);
1547 static int __cfq_forced_dispatch_cfqq(struct cfq_queue
*cfqq
)
1551 while (cfqq
->next_rq
) {
1552 cfq_dispatch_insert(cfqq
->cfqd
->queue
, cfqq
->next_rq
);
1556 BUG_ON(!list_empty(&cfqq
->fifo
));
1561 * Drain our current requests. Used for barriers and when switching
1562 * io schedulers on-the-fly.
1564 static int cfq_forced_dispatch(struct cfq_data
*cfqd
)
1566 struct cfq_queue
*cfqq
;
1569 for (i
= 0; i
< 2; ++i
)
1570 for (j
= 0; j
< 3; ++j
)
1571 while ((cfqq
= cfq_rb_first(&cfqd
->service_trees
[i
][j
]))
1573 dispatched
+= __cfq_forced_dispatch_cfqq(cfqq
);
1575 while ((cfqq
= cfq_rb_first(&cfqd
->service_tree_idle
)) != NULL
)
1576 dispatched
+= __cfq_forced_dispatch_cfqq(cfqq
);
1578 cfq_slice_expired(cfqd
, 0);
1580 BUG_ON(cfqd
->busy_queues
);
1582 cfq_log(cfqd
, "forced_dispatch=%d", dispatched
);
1586 static bool cfq_may_dispatch(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1588 unsigned int max_dispatch
;
1591 * Drain async requests before we start sync IO
1593 if (cfq_should_idle(cfqd
, cfqq
) && cfqd
->rq_in_driver
[BLK_RW_ASYNC
])
1597 * If this is an async queue and we have sync IO in flight, let it wait
1599 if (cfqd
->sync_flight
&& !cfq_cfqq_sync(cfqq
))
1602 max_dispatch
= cfqd
->cfq_quantum
;
1603 if (cfq_class_idle(cfqq
))
1607 * Does this cfqq already have too much IO in flight?
1609 if (cfqq
->dispatched
>= max_dispatch
) {
1611 * idle queue must always only have a single IO in flight
1613 if (cfq_class_idle(cfqq
))
1617 * We have other queues, don't allow more IO from this one
1619 if (cfqd
->busy_queues
> 1)
1623 * Sole queue user, allow bigger slice
1629 * Async queues must wait a bit before being allowed dispatch.
1630 * We also ramp up the dispatch depth gradually for async IO,
1631 * based on the last sync IO we serviced
1633 if (!cfq_cfqq_sync(cfqq
) && cfqd
->cfq_latency
) {
1634 unsigned long last_sync
= jiffies
- cfqd
->last_end_sync_rq
;
1637 depth
= last_sync
/ cfqd
->cfq_slice
[1];
1638 if (!depth
&& !cfqq
->dispatched
)
1640 if (depth
< max_dispatch
)
1641 max_dispatch
= depth
;
1645 * If we're below the current max, allow a dispatch
1647 return cfqq
->dispatched
< max_dispatch
;
1651 * Dispatch a request from cfqq, moving them to the request queue
1654 static bool cfq_dispatch_request(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1658 BUG_ON(RB_EMPTY_ROOT(&cfqq
->sort_list
));
1660 if (!cfq_may_dispatch(cfqd
, cfqq
))
1664 * follow expired path, else get first next available
1666 rq
= cfq_check_fifo(cfqq
);
1671 * insert request into driver dispatch list
1673 cfq_dispatch_insert(cfqd
->queue
, rq
);
1675 if (!cfqd
->active_cic
) {
1676 struct cfq_io_context
*cic
= RQ_CIC(rq
);
1678 atomic_long_inc(&cic
->ioc
->refcount
);
1679 cfqd
->active_cic
= cic
;
1686 * Find the cfqq that we need to service and move a request from that to the
1689 static int cfq_dispatch_requests(struct request_queue
*q
, int force
)
1691 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1692 struct cfq_queue
*cfqq
;
1694 if (!cfqd
->busy_queues
)
1697 if (unlikely(force
))
1698 return cfq_forced_dispatch(cfqd
);
1700 cfqq
= cfq_select_queue(cfqd
);
1705 * Dispatch a request from this cfqq, if it is allowed
1707 if (!cfq_dispatch_request(cfqd
, cfqq
))
1710 cfqq
->slice_dispatch
++;
1711 cfq_clear_cfqq_must_dispatch(cfqq
);
1714 * expire an async queue immediately if it has used up its slice. idle
1715 * queue always expire after 1 dispatch round.
1717 if (cfqd
->busy_queues
> 1 && ((!cfq_cfqq_sync(cfqq
) &&
1718 cfqq
->slice_dispatch
>= cfq_prio_to_maxrq(cfqd
, cfqq
)) ||
1719 cfq_class_idle(cfqq
))) {
1720 cfqq
->slice_end
= jiffies
+ 1;
1721 cfq_slice_expired(cfqd
, 0);
1724 cfq_log_cfqq(cfqd
, cfqq
, "dispatched a request");
1729 * task holds one reference to the queue, dropped when task exits. each rq
1730 * in-flight on this queue also holds a reference, dropped when rq is freed.
1732 * queue lock must be held here.
1734 static void cfq_put_queue(struct cfq_queue
*cfqq
)
1736 struct cfq_data
*cfqd
= cfqq
->cfqd
;
1738 BUG_ON(atomic_read(&cfqq
->ref
) <= 0);
1740 if (!atomic_dec_and_test(&cfqq
->ref
))
1743 cfq_log_cfqq(cfqd
, cfqq
, "put_queue");
1744 BUG_ON(rb_first(&cfqq
->sort_list
));
1745 BUG_ON(cfqq
->allocated
[READ
] + cfqq
->allocated
[WRITE
]);
1746 BUG_ON(cfq_cfqq_on_rr(cfqq
));
1748 if (unlikely(cfqd
->active_queue
== cfqq
)) {
1749 __cfq_slice_expired(cfqd
, cfqq
, 0);
1750 cfq_schedule_dispatch(cfqd
);
1753 kmem_cache_free(cfq_pool
, cfqq
);
1757 * Must always be called with the rcu_read_lock() held
1760 __call_for_each_cic(struct io_context
*ioc
,
1761 void (*func
)(struct io_context
*, struct cfq_io_context
*))
1763 struct cfq_io_context
*cic
;
1764 struct hlist_node
*n
;
1766 hlist_for_each_entry_rcu(cic
, n
, &ioc
->cic_list
, cic_list
)
1771 * Call func for each cic attached to this ioc.
1774 call_for_each_cic(struct io_context
*ioc
,
1775 void (*func
)(struct io_context
*, struct cfq_io_context
*))
1778 __call_for_each_cic(ioc
, func
);
1782 static void cfq_cic_free_rcu(struct rcu_head
*head
)
1784 struct cfq_io_context
*cic
;
1786 cic
= container_of(head
, struct cfq_io_context
, rcu_head
);
1788 kmem_cache_free(cfq_ioc_pool
, cic
);
1789 elv_ioc_count_dec(cfq_ioc_count
);
1793 * CFQ scheduler is exiting, grab exit lock and check
1794 * the pending io context count. If it hits zero,
1795 * complete ioc_gone and set it back to NULL
1797 spin_lock(&ioc_gone_lock
);
1798 if (ioc_gone
&& !elv_ioc_count_read(cfq_ioc_count
)) {
1802 spin_unlock(&ioc_gone_lock
);
1806 static void cfq_cic_free(struct cfq_io_context
*cic
)
1808 call_rcu(&cic
->rcu_head
, cfq_cic_free_rcu
);
1811 static void cic_free_func(struct io_context
*ioc
, struct cfq_io_context
*cic
)
1813 unsigned long flags
;
1815 BUG_ON(!cic
->dead_key
);
1817 spin_lock_irqsave(&ioc
->lock
, flags
);
1818 radix_tree_delete(&ioc
->radix_root
, cic
->dead_key
);
1819 hlist_del_rcu(&cic
->cic_list
);
1820 spin_unlock_irqrestore(&ioc
->lock
, flags
);
1826 * Must be called with rcu_read_lock() held or preemption otherwise disabled.
1827 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
1828 * and ->trim() which is called with the task lock held
1830 static void cfq_free_io_context(struct io_context
*ioc
)
1833 * ioc->refcount is zero here, or we are called from elv_unregister(),
1834 * so no more cic's are allowed to be linked into this ioc. So it
1835 * should be ok to iterate over the known list, we will see all cic's
1836 * since no new ones are added.
1838 __call_for_each_cic(ioc
, cic_free_func
);
1841 static void cfq_exit_cfqq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1843 struct cfq_queue
*__cfqq
, *next
;
1845 if (unlikely(cfqq
== cfqd
->active_queue
)) {
1846 __cfq_slice_expired(cfqd
, cfqq
, 0);
1847 cfq_schedule_dispatch(cfqd
);
1851 * If this queue was scheduled to merge with another queue, be
1852 * sure to drop the reference taken on that queue (and others in
1853 * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs.
1855 __cfqq
= cfqq
->new_cfqq
;
1857 if (__cfqq
== cfqq
) {
1858 WARN(1, "cfqq->new_cfqq loop detected\n");
1861 next
= __cfqq
->new_cfqq
;
1862 cfq_put_queue(__cfqq
);
1866 cfq_put_queue(cfqq
);
1869 static void __cfq_exit_single_io_context(struct cfq_data
*cfqd
,
1870 struct cfq_io_context
*cic
)
1872 struct io_context
*ioc
= cic
->ioc
;
1874 list_del_init(&cic
->queue_list
);
1877 * Make sure key == NULL is seen for dead queues
1880 cic
->dead_key
= (unsigned long) cic
->key
;
1883 if (ioc
->ioc_data
== cic
)
1884 rcu_assign_pointer(ioc
->ioc_data
, NULL
);
1886 if (cic
->cfqq
[BLK_RW_ASYNC
]) {
1887 cfq_exit_cfqq(cfqd
, cic
->cfqq
[BLK_RW_ASYNC
]);
1888 cic
->cfqq
[BLK_RW_ASYNC
] = NULL
;
1891 if (cic
->cfqq
[BLK_RW_SYNC
]) {
1892 cfq_exit_cfqq(cfqd
, cic
->cfqq
[BLK_RW_SYNC
]);
1893 cic
->cfqq
[BLK_RW_SYNC
] = NULL
;
1897 static void cfq_exit_single_io_context(struct io_context
*ioc
,
1898 struct cfq_io_context
*cic
)
1900 struct cfq_data
*cfqd
= cic
->key
;
1903 struct request_queue
*q
= cfqd
->queue
;
1904 unsigned long flags
;
1906 spin_lock_irqsave(q
->queue_lock
, flags
);
1909 * Ensure we get a fresh copy of the ->key to prevent
1910 * race between exiting task and queue
1912 smp_read_barrier_depends();
1914 __cfq_exit_single_io_context(cfqd
, cic
);
1916 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1921 * The process that ioc belongs to has exited, we need to clean up
1922 * and put the internal structures we have that belongs to that process.
1924 static void cfq_exit_io_context(struct io_context
*ioc
)
1926 call_for_each_cic(ioc
, cfq_exit_single_io_context
);
1929 static struct cfq_io_context
*
1930 cfq_alloc_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
1932 struct cfq_io_context
*cic
;
1934 cic
= kmem_cache_alloc_node(cfq_ioc_pool
, gfp_mask
| __GFP_ZERO
,
1937 cic
->last_end_request
= jiffies
;
1938 INIT_LIST_HEAD(&cic
->queue_list
);
1939 INIT_HLIST_NODE(&cic
->cic_list
);
1940 cic
->dtor
= cfq_free_io_context
;
1941 cic
->exit
= cfq_exit_io_context
;
1942 elv_ioc_count_inc(cfq_ioc_count
);
1948 static void cfq_init_prio_data(struct cfq_queue
*cfqq
, struct io_context
*ioc
)
1950 struct task_struct
*tsk
= current
;
1953 if (!cfq_cfqq_prio_changed(cfqq
))
1956 ioprio_class
= IOPRIO_PRIO_CLASS(ioc
->ioprio
);
1957 switch (ioprio_class
) {
1959 printk(KERN_ERR
"cfq: bad prio %x\n", ioprio_class
);
1960 case IOPRIO_CLASS_NONE
:
1962 * no prio set, inherit CPU scheduling settings
1964 cfqq
->ioprio
= task_nice_ioprio(tsk
);
1965 cfqq
->ioprio_class
= task_nice_ioclass(tsk
);
1967 case IOPRIO_CLASS_RT
:
1968 cfqq
->ioprio
= task_ioprio(ioc
);
1969 cfqq
->ioprio_class
= IOPRIO_CLASS_RT
;
1971 case IOPRIO_CLASS_BE
:
1972 cfqq
->ioprio
= task_ioprio(ioc
);
1973 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1975 case IOPRIO_CLASS_IDLE
:
1976 cfqq
->ioprio_class
= IOPRIO_CLASS_IDLE
;
1978 cfq_clear_cfqq_idle_window(cfqq
);
1983 * keep track of original prio settings in case we have to temporarily
1984 * elevate the priority of this queue
1986 cfqq
->org_ioprio
= cfqq
->ioprio
;
1987 cfqq
->org_ioprio_class
= cfqq
->ioprio_class
;
1988 cfq_clear_cfqq_prio_changed(cfqq
);
1991 static void changed_ioprio(struct io_context
*ioc
, struct cfq_io_context
*cic
)
1993 struct cfq_data
*cfqd
= cic
->key
;
1994 struct cfq_queue
*cfqq
;
1995 unsigned long flags
;
1997 if (unlikely(!cfqd
))
2000 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
2002 cfqq
= cic
->cfqq
[BLK_RW_ASYNC
];
2004 struct cfq_queue
*new_cfqq
;
2005 new_cfqq
= cfq_get_queue(cfqd
, BLK_RW_ASYNC
, cic
->ioc
,
2008 cic
->cfqq
[BLK_RW_ASYNC
] = new_cfqq
;
2009 cfq_put_queue(cfqq
);
2013 cfqq
= cic
->cfqq
[BLK_RW_SYNC
];
2015 cfq_mark_cfqq_prio_changed(cfqq
);
2017 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2020 static void cfq_ioc_set_ioprio(struct io_context
*ioc
)
2022 call_for_each_cic(ioc
, changed_ioprio
);
2023 ioc
->ioprio_changed
= 0;
2026 static void cfq_init_cfqq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2027 pid_t pid
, bool is_sync
)
2029 RB_CLEAR_NODE(&cfqq
->rb_node
);
2030 RB_CLEAR_NODE(&cfqq
->p_node
);
2031 INIT_LIST_HEAD(&cfqq
->fifo
);
2033 atomic_set(&cfqq
->ref
, 0);
2036 cfq_mark_cfqq_prio_changed(cfqq
);
2039 if (!cfq_class_idle(cfqq
))
2040 cfq_mark_cfqq_idle_window(cfqq
);
2041 cfq_mark_cfqq_sync(cfqq
);
2046 static struct cfq_queue
*
2047 cfq_find_alloc_queue(struct cfq_data
*cfqd
, bool is_sync
,
2048 struct io_context
*ioc
, gfp_t gfp_mask
)
2050 struct cfq_queue
*cfqq
, *new_cfqq
= NULL
;
2051 struct cfq_io_context
*cic
;
2054 cic
= cfq_cic_lookup(cfqd
, ioc
);
2055 /* cic always exists here */
2056 cfqq
= cic_to_cfqq(cic
, is_sync
);
2059 * Always try a new alloc if we fell back to the OOM cfqq
2060 * originally, since it should just be a temporary situation.
2062 if (!cfqq
|| cfqq
== &cfqd
->oom_cfqq
) {
2067 } else if (gfp_mask
& __GFP_WAIT
) {
2068 spin_unlock_irq(cfqd
->queue
->queue_lock
);
2069 new_cfqq
= kmem_cache_alloc_node(cfq_pool
,
2070 gfp_mask
| __GFP_ZERO
,
2072 spin_lock_irq(cfqd
->queue
->queue_lock
);
2076 cfqq
= kmem_cache_alloc_node(cfq_pool
,
2077 gfp_mask
| __GFP_ZERO
,
2082 cfq_init_cfqq(cfqd
, cfqq
, current
->pid
, is_sync
);
2083 cfq_init_prio_data(cfqq
, ioc
);
2084 cfq_log_cfqq(cfqd
, cfqq
, "alloced");
2086 cfqq
= &cfqd
->oom_cfqq
;
2090 kmem_cache_free(cfq_pool
, new_cfqq
);
2095 static struct cfq_queue
**
2096 cfq_async_queue_prio(struct cfq_data
*cfqd
, int ioprio_class
, int ioprio
)
2098 switch (ioprio_class
) {
2099 case IOPRIO_CLASS_RT
:
2100 return &cfqd
->async_cfqq
[0][ioprio
];
2101 case IOPRIO_CLASS_BE
:
2102 return &cfqd
->async_cfqq
[1][ioprio
];
2103 case IOPRIO_CLASS_IDLE
:
2104 return &cfqd
->async_idle_cfqq
;
2110 static struct cfq_queue
*
2111 cfq_get_queue(struct cfq_data
*cfqd
, bool is_sync
, struct io_context
*ioc
,
2114 const int ioprio
= task_ioprio(ioc
);
2115 const int ioprio_class
= task_ioprio_class(ioc
);
2116 struct cfq_queue
**async_cfqq
= NULL
;
2117 struct cfq_queue
*cfqq
= NULL
;
2120 async_cfqq
= cfq_async_queue_prio(cfqd
, ioprio_class
, ioprio
);
2125 cfqq
= cfq_find_alloc_queue(cfqd
, is_sync
, ioc
, gfp_mask
);
2128 * pin the queue now that it's allocated, scheduler exit will prune it
2130 if (!is_sync
&& !(*async_cfqq
)) {
2131 atomic_inc(&cfqq
->ref
);
2135 atomic_inc(&cfqq
->ref
);
2140 * We drop cfq io contexts lazily, so we may find a dead one.
2143 cfq_drop_dead_cic(struct cfq_data
*cfqd
, struct io_context
*ioc
,
2144 struct cfq_io_context
*cic
)
2146 unsigned long flags
;
2148 WARN_ON(!list_empty(&cic
->queue_list
));
2150 spin_lock_irqsave(&ioc
->lock
, flags
);
2152 BUG_ON(ioc
->ioc_data
== cic
);
2154 radix_tree_delete(&ioc
->radix_root
, (unsigned long) cfqd
);
2155 hlist_del_rcu(&cic
->cic_list
);
2156 spin_unlock_irqrestore(&ioc
->lock
, flags
);
2161 static struct cfq_io_context
*
2162 cfq_cic_lookup(struct cfq_data
*cfqd
, struct io_context
*ioc
)
2164 struct cfq_io_context
*cic
;
2165 unsigned long flags
;
2174 * we maintain a last-hit cache, to avoid browsing over the tree
2176 cic
= rcu_dereference(ioc
->ioc_data
);
2177 if (cic
&& cic
->key
== cfqd
) {
2183 cic
= radix_tree_lookup(&ioc
->radix_root
, (unsigned long) cfqd
);
2187 /* ->key must be copied to avoid race with cfq_exit_queue() */
2190 cfq_drop_dead_cic(cfqd
, ioc
, cic
);
2195 spin_lock_irqsave(&ioc
->lock
, flags
);
2196 rcu_assign_pointer(ioc
->ioc_data
, cic
);
2197 spin_unlock_irqrestore(&ioc
->lock
, flags
);
2205 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2206 * the process specific cfq io context when entered from the block layer.
2207 * Also adds the cic to a per-cfqd list, used when this queue is removed.
2209 static int cfq_cic_link(struct cfq_data
*cfqd
, struct io_context
*ioc
,
2210 struct cfq_io_context
*cic
, gfp_t gfp_mask
)
2212 unsigned long flags
;
2215 ret
= radix_tree_preload(gfp_mask
);
2220 spin_lock_irqsave(&ioc
->lock
, flags
);
2221 ret
= radix_tree_insert(&ioc
->radix_root
,
2222 (unsigned long) cfqd
, cic
);
2224 hlist_add_head_rcu(&cic
->cic_list
, &ioc
->cic_list
);
2225 spin_unlock_irqrestore(&ioc
->lock
, flags
);
2227 radix_tree_preload_end();
2230 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
2231 list_add(&cic
->queue_list
, &cfqd
->cic_list
);
2232 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2237 printk(KERN_ERR
"cfq: cic link failed!\n");
2243 * Setup general io context and cfq io context. There can be several cfq
2244 * io contexts per general io context, if this process is doing io to more
2245 * than one device managed by cfq.
2247 static struct cfq_io_context
*
2248 cfq_get_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
2250 struct io_context
*ioc
= NULL
;
2251 struct cfq_io_context
*cic
;
2253 might_sleep_if(gfp_mask
& __GFP_WAIT
);
2255 ioc
= get_io_context(gfp_mask
, cfqd
->queue
->node
);
2259 cic
= cfq_cic_lookup(cfqd
, ioc
);
2263 cic
= cfq_alloc_io_context(cfqd
, gfp_mask
);
2267 if (cfq_cic_link(cfqd
, ioc
, cic
, gfp_mask
))
2271 smp_read_barrier_depends();
2272 if (unlikely(ioc
->ioprio_changed
))
2273 cfq_ioc_set_ioprio(ioc
);
2279 put_io_context(ioc
);
2284 cfq_update_io_thinktime(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
)
2286 unsigned long elapsed
= jiffies
- cic
->last_end_request
;
2287 unsigned long ttime
= min(elapsed
, 2UL * cfqd
->cfq_slice_idle
);
2289 cic
->ttime_samples
= (7*cic
->ttime_samples
+ 256) / 8;
2290 cic
->ttime_total
= (7*cic
->ttime_total
+ 256*ttime
) / 8;
2291 cic
->ttime_mean
= (cic
->ttime_total
+ 128) / cic
->ttime_samples
;
2295 cfq_update_io_seektime(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2301 if (!cfqq
->last_request_pos
)
2303 else if (cfqq
->last_request_pos
< blk_rq_pos(rq
))
2304 sdist
= blk_rq_pos(rq
) - cfqq
->last_request_pos
;
2306 sdist
= cfqq
->last_request_pos
- blk_rq_pos(rq
);
2309 * Don't allow the seek distance to get too large from the
2310 * odd fragment, pagein, etc
2312 if (cfqq
->seek_samples
<= 60) /* second&third seek */
2313 sdist
= min(sdist
, (cfqq
->seek_mean
* 4) + 2*1024*1024);
2315 sdist
= min(sdist
, (cfqq
->seek_mean
* 4) + 2*1024*64);
2317 cfqq
->seek_samples
= (7*cfqq
->seek_samples
+ 256) / 8;
2318 cfqq
->seek_total
= (7*cfqq
->seek_total
+ (u64
)256*sdist
) / 8;
2319 total
= cfqq
->seek_total
+ (cfqq
->seek_samples
/2);
2320 do_div(total
, cfqq
->seek_samples
);
2321 cfqq
->seek_mean
= (sector_t
)total
;
2324 * If this cfqq is shared between multiple processes, check to
2325 * make sure that those processes are still issuing I/Os within
2326 * the mean seek distance. If not, it may be time to break the
2327 * queues apart again.
2329 if (cfq_cfqq_coop(cfqq
)) {
2330 if (CFQQ_SEEKY(cfqq
) && !cfqq
->seeky_start
)
2331 cfqq
->seeky_start
= jiffies
;
2332 else if (!CFQQ_SEEKY(cfqq
))
2333 cfqq
->seeky_start
= 0;
2338 * Disable idle window if the process thinks too long or seeks so much that
2342 cfq_update_idle_window(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2343 struct cfq_io_context
*cic
)
2345 int old_idle
, enable_idle
;
2348 * Don't idle for async or idle io prio class
2350 if (!cfq_cfqq_sync(cfqq
) || cfq_class_idle(cfqq
))
2353 enable_idle
= old_idle
= cfq_cfqq_idle_window(cfqq
);
2355 if (cfqq
->queued
[0] + cfqq
->queued
[1] >= 4)
2356 cfq_mark_cfqq_deep(cfqq
);
2358 if (!atomic_read(&cic
->ioc
->nr_tasks
) || !cfqd
->cfq_slice_idle
||
2359 (!cfq_cfqq_deep(cfqq
) && sample_valid(cfqq
->seek_samples
)
2360 && CFQQ_SEEKY(cfqq
)))
2362 else if (sample_valid(cic
->ttime_samples
)) {
2363 if (cic
->ttime_mean
> cfqd
->cfq_slice_idle
)
2369 if (old_idle
!= enable_idle
) {
2370 cfq_log_cfqq(cfqd
, cfqq
, "idle=%d", enable_idle
);
2372 cfq_mark_cfqq_idle_window(cfqq
);
2374 cfq_clear_cfqq_idle_window(cfqq
);
2379 * Check if new_cfqq should preempt the currently active queue. Return 0 for
2380 * no or if we aren't sure, a 1 will cause a preempt.
2383 cfq_should_preempt(struct cfq_data
*cfqd
, struct cfq_queue
*new_cfqq
,
2386 struct cfq_queue
*cfqq
;
2388 cfqq
= cfqd
->active_queue
;
2392 if (cfq_slice_used(cfqq
))
2395 if (cfq_class_idle(new_cfqq
))
2398 if (cfq_class_idle(cfqq
))
2401 if (cfqd
->serving_type
== SYNC_NOIDLE_WORKLOAD
&&
2402 cfqq_type(new_cfqq
) == SYNC_NOIDLE_WORKLOAD
&&
2403 new_cfqq
->service_tree
->count
== 1)
2407 * if the new request is sync, but the currently running queue is
2408 * not, let the sync request have priority.
2410 if (rq_is_sync(rq
) && !cfq_cfqq_sync(cfqq
))
2414 * So both queues are sync. Let the new request get disk time if
2415 * it's a metadata request and the current queue is doing regular IO.
2417 if (rq_is_meta(rq
) && !cfqq
->meta_pending
)
2421 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
2423 if (cfq_class_rt(new_cfqq
) && !cfq_class_rt(cfqq
))
2426 if (!cfqd
->active_cic
|| !cfq_cfqq_wait_request(cfqq
))
2430 * if this request is as-good as one we would expect from the
2431 * current cfqq, let it preempt
2433 if (cfq_rq_close(cfqd
, cfqq
, rq
))
2440 * cfqq preempts the active queue. if we allowed preempt with no slice left,
2441 * let it have half of its nominal slice.
2443 static void cfq_preempt_queue(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
2445 cfq_log_cfqq(cfqd
, cfqq
, "preempt");
2446 cfq_slice_expired(cfqd
, 1);
2449 * Put the new queue at the front of the of the current list,
2450 * so we know that it will be selected next.
2452 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
2454 cfq_service_tree_add(cfqd
, cfqq
, 1);
2456 cfqq
->slice_end
= 0;
2457 cfq_mark_cfqq_slice_new(cfqq
);
2461 * Called when a new fs request (rq) is added (to cfqq). Check if there's
2462 * something we should do about it
2465 cfq_rq_enqueued(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2468 struct cfq_io_context
*cic
= RQ_CIC(rq
);
2472 cfqq
->meta_pending
++;
2474 cfq_update_io_thinktime(cfqd
, cic
);
2475 cfq_update_io_seektime(cfqd
, cfqq
, rq
);
2476 cfq_update_idle_window(cfqd
, cfqq
, cic
);
2478 cfqq
->last_request_pos
= blk_rq_pos(rq
) + blk_rq_sectors(rq
);
2480 if (cfqq
== cfqd
->active_queue
) {
2482 * Remember that we saw a request from this process, but
2483 * don't start queuing just yet. Otherwise we risk seeing lots
2484 * of tiny requests, because we disrupt the normal plugging
2485 * and merging. If the request is already larger than a single
2486 * page, let it rip immediately. For that case we assume that
2487 * merging is already done. Ditto for a busy system that
2488 * has other work pending, don't risk delaying until the
2489 * idle timer unplug to continue working.
2491 if (cfq_cfqq_wait_request(cfqq
)) {
2492 if (blk_rq_bytes(rq
) > PAGE_CACHE_SIZE
||
2493 cfqd
->busy_queues
> 1) {
2494 del_timer(&cfqd
->idle_slice_timer
);
2495 __blk_run_queue(cfqd
->queue
);
2497 cfq_mark_cfqq_must_dispatch(cfqq
);
2499 } else if (cfq_should_preempt(cfqd
, cfqq
, rq
)) {
2501 * not the active queue - expire current slice if it is
2502 * idle and has expired it's mean thinktime or this new queue
2503 * has some old slice time left and is of higher priority or
2504 * this new queue is RT and the current one is BE
2506 cfq_preempt_queue(cfqd
, cfqq
);
2507 __blk_run_queue(cfqd
->queue
);
2511 static void cfq_insert_request(struct request_queue
*q
, struct request
*rq
)
2513 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
2514 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
2516 cfq_log_cfqq(cfqd
, cfqq
, "insert_request");
2517 cfq_init_prio_data(cfqq
, RQ_CIC(rq
)->ioc
);
2519 rq_set_fifo_time(rq
, jiffies
+ cfqd
->cfq_fifo_expire
[rq_is_sync(rq
)]);
2520 list_add_tail(&rq
->queuelist
, &cfqq
->fifo
);
2523 cfq_rq_enqueued(cfqd
, cfqq
, rq
);
2527 * Update hw_tag based on peak queue depth over 50 samples under
2530 static void cfq_update_hw_tag(struct cfq_data
*cfqd
)
2532 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
2534 if (rq_in_driver(cfqd
) > cfqd
->hw_tag_est_depth
)
2535 cfqd
->hw_tag_est_depth
= rq_in_driver(cfqd
);
2537 if (cfqd
->hw_tag
== 1)
2540 if (cfqd
->rq_queued
<= CFQ_HW_QUEUE_MIN
&&
2541 rq_in_driver(cfqd
) <= CFQ_HW_QUEUE_MIN
)
2545 * If active queue hasn't enough requests and can idle, cfq might not
2546 * dispatch sufficient requests to hardware. Don't zero hw_tag in this
2549 if (cfqq
&& cfq_cfqq_idle_window(cfqq
) &&
2550 cfqq
->dispatched
+ cfqq
->queued
[0] + cfqq
->queued
[1] <
2551 CFQ_HW_QUEUE_MIN
&& rq_in_driver(cfqd
) < CFQ_HW_QUEUE_MIN
)
2554 if (cfqd
->hw_tag_samples
++ < 50)
2557 if (cfqd
->hw_tag_est_depth
>= CFQ_HW_QUEUE_MIN
)
2563 static void cfq_completed_request(struct request_queue
*q
, struct request
*rq
)
2565 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
2566 struct cfq_data
*cfqd
= cfqq
->cfqd
;
2567 const int sync
= rq_is_sync(rq
);
2571 cfq_log_cfqq(cfqd
, cfqq
, "complete");
2573 cfq_update_hw_tag(cfqd
);
2575 WARN_ON(!cfqd
->rq_in_driver
[sync
]);
2576 WARN_ON(!cfqq
->dispatched
);
2577 cfqd
->rq_in_driver
[sync
]--;
2580 if (cfq_cfqq_sync(cfqq
))
2581 cfqd
->sync_flight
--;
2584 RQ_CIC(rq
)->last_end_request
= now
;
2585 cfqd
->last_end_sync_rq
= now
;
2589 * If this is the active queue, check if it needs to be expired,
2590 * or if we want to idle in case it has no pending requests.
2592 if (cfqd
->active_queue
== cfqq
) {
2593 const bool cfqq_empty
= RB_EMPTY_ROOT(&cfqq
->sort_list
);
2595 if (cfq_cfqq_slice_new(cfqq
)) {
2596 cfq_set_prio_slice(cfqd
, cfqq
);
2597 cfq_clear_cfqq_slice_new(cfqq
);
2600 * If there are no requests waiting in this queue, and
2601 * there are other queues ready to issue requests, AND
2602 * those other queues are issuing requests within our
2603 * mean seek distance, give them a chance to run instead
2606 if (cfq_slice_used(cfqq
) || cfq_class_idle(cfqq
))
2607 cfq_slice_expired(cfqd
, 1);
2608 else if (cfqq_empty
&& !cfq_close_cooperator(cfqd
, cfqq
) &&
2609 sync
&& !rq_noidle(rq
))
2610 cfq_arm_slice_timer(cfqd
);
2613 if (!rq_in_driver(cfqd
))
2614 cfq_schedule_dispatch(cfqd
);
2618 * we temporarily boost lower priority queues if they are holding fs exclusive
2619 * resources. they are boosted to normal prio (CLASS_BE/4)
2621 static void cfq_prio_boost(struct cfq_queue
*cfqq
)
2623 if (has_fs_excl()) {
2625 * boost idle prio on transactions that would lock out other
2626 * users of the filesystem
2628 if (cfq_class_idle(cfqq
))
2629 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
2630 if (cfqq
->ioprio
> IOPRIO_NORM
)
2631 cfqq
->ioprio
= IOPRIO_NORM
;
2634 * unboost the queue (if needed)
2636 cfqq
->ioprio_class
= cfqq
->org_ioprio_class
;
2637 cfqq
->ioprio
= cfqq
->org_ioprio
;
2641 static inline int __cfq_may_queue(struct cfq_queue
*cfqq
)
2643 if (cfq_cfqq_wait_request(cfqq
) && !cfq_cfqq_must_alloc_slice(cfqq
)) {
2644 cfq_mark_cfqq_must_alloc_slice(cfqq
);
2645 return ELV_MQUEUE_MUST
;
2648 return ELV_MQUEUE_MAY
;
2651 static int cfq_may_queue(struct request_queue
*q
, int rw
)
2653 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
2654 struct task_struct
*tsk
= current
;
2655 struct cfq_io_context
*cic
;
2656 struct cfq_queue
*cfqq
;
2659 * don't force setup of a queue from here, as a call to may_queue
2660 * does not necessarily imply that a request actually will be queued.
2661 * so just lookup a possibly existing queue, or return 'may queue'
2664 cic
= cfq_cic_lookup(cfqd
, tsk
->io_context
);
2666 return ELV_MQUEUE_MAY
;
2668 cfqq
= cic_to_cfqq(cic
, rw_is_sync(rw
));
2670 cfq_init_prio_data(cfqq
, cic
->ioc
);
2671 cfq_prio_boost(cfqq
);
2673 return __cfq_may_queue(cfqq
);
2676 return ELV_MQUEUE_MAY
;
2680 * queue lock held here
2682 static void cfq_put_request(struct request
*rq
)
2684 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
2687 const int rw
= rq_data_dir(rq
);
2689 BUG_ON(!cfqq
->allocated
[rw
]);
2690 cfqq
->allocated
[rw
]--;
2692 put_io_context(RQ_CIC(rq
)->ioc
);
2694 rq
->elevator_private
= NULL
;
2695 rq
->elevator_private2
= NULL
;
2697 cfq_put_queue(cfqq
);
2701 static struct cfq_queue
*
2702 cfq_merge_cfqqs(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
,
2703 struct cfq_queue
*cfqq
)
2705 cfq_log_cfqq(cfqd
, cfqq
, "merging with queue %p", cfqq
->new_cfqq
);
2706 cic_set_cfqq(cic
, cfqq
->new_cfqq
, 1);
2707 cfq_mark_cfqq_coop(cfqq
->new_cfqq
);
2708 cfq_put_queue(cfqq
);
2709 return cic_to_cfqq(cic
, 1);
2712 static int should_split_cfqq(struct cfq_queue
*cfqq
)
2714 if (cfqq
->seeky_start
&&
2715 time_after(jiffies
, cfqq
->seeky_start
+ CFQQ_COOP_TOUT
))
2721 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
2722 * was the last process referring to said cfqq.
2724 static struct cfq_queue
*
2725 split_cfqq(struct cfq_io_context
*cic
, struct cfq_queue
*cfqq
)
2727 if (cfqq_process_refs(cfqq
) == 1) {
2728 cfqq
->seeky_start
= 0;
2729 cfqq
->pid
= current
->pid
;
2730 cfq_clear_cfqq_coop(cfqq
);
2734 cic_set_cfqq(cic
, NULL
, 1);
2735 cfq_put_queue(cfqq
);
2739 * Allocate cfq data structures associated with this request.
2742 cfq_set_request(struct request_queue
*q
, struct request
*rq
, gfp_t gfp_mask
)
2744 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
2745 struct cfq_io_context
*cic
;
2746 const int rw
= rq_data_dir(rq
);
2747 const bool is_sync
= rq_is_sync(rq
);
2748 struct cfq_queue
*cfqq
;
2749 unsigned long flags
;
2751 might_sleep_if(gfp_mask
& __GFP_WAIT
);
2753 cic
= cfq_get_io_context(cfqd
, gfp_mask
);
2755 spin_lock_irqsave(q
->queue_lock
, flags
);
2761 cfqq
= cic_to_cfqq(cic
, is_sync
);
2762 if (!cfqq
|| cfqq
== &cfqd
->oom_cfqq
) {
2763 cfqq
= cfq_get_queue(cfqd
, is_sync
, cic
->ioc
, gfp_mask
);
2764 cic_set_cfqq(cic
, cfqq
, is_sync
);
2767 * If the queue was seeky for too long, break it apart.
2769 if (cfq_cfqq_coop(cfqq
) && should_split_cfqq(cfqq
)) {
2770 cfq_log_cfqq(cfqd
, cfqq
, "breaking apart cfqq");
2771 cfqq
= split_cfqq(cic
, cfqq
);
2777 * Check to see if this queue is scheduled to merge with
2778 * another, closely cooperating queue. The merging of
2779 * queues happens here as it must be done in process context.
2780 * The reference on new_cfqq was taken in merge_cfqqs.
2783 cfqq
= cfq_merge_cfqqs(cfqd
, cic
, cfqq
);
2786 cfqq
->allocated
[rw
]++;
2787 atomic_inc(&cfqq
->ref
);
2789 spin_unlock_irqrestore(q
->queue_lock
, flags
);
2791 rq
->elevator_private
= cic
;
2792 rq
->elevator_private2
= cfqq
;
2797 put_io_context(cic
->ioc
);
2799 cfq_schedule_dispatch(cfqd
);
2800 spin_unlock_irqrestore(q
->queue_lock
, flags
);
2801 cfq_log(cfqd
, "set_request fail");
2805 static void cfq_kick_queue(struct work_struct
*work
)
2807 struct cfq_data
*cfqd
=
2808 container_of(work
, struct cfq_data
, unplug_work
);
2809 struct request_queue
*q
= cfqd
->queue
;
2811 spin_lock_irq(q
->queue_lock
);
2812 __blk_run_queue(cfqd
->queue
);
2813 spin_unlock_irq(q
->queue_lock
);
2817 * Timer running if the active_queue is currently idling inside its time slice
2819 static void cfq_idle_slice_timer(unsigned long data
)
2821 struct cfq_data
*cfqd
= (struct cfq_data
*) data
;
2822 struct cfq_queue
*cfqq
;
2823 unsigned long flags
;
2826 cfq_log(cfqd
, "idle timer fired");
2828 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
2830 cfqq
= cfqd
->active_queue
;
2835 * We saw a request before the queue expired, let it through
2837 if (cfq_cfqq_must_dispatch(cfqq
))
2843 if (cfq_slice_used(cfqq
))
2847 * only expire and reinvoke request handler, if there are
2848 * other queues with pending requests
2850 if (!cfqd
->busy_queues
)
2854 * not expired and it has a request pending, let it dispatch
2856 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
))
2860 * Queue depth flag is reset only when the idle didn't succeed
2862 cfq_clear_cfqq_deep(cfqq
);
2865 cfq_slice_expired(cfqd
, timed_out
);
2867 cfq_schedule_dispatch(cfqd
);
2869 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2872 static void cfq_shutdown_timer_wq(struct cfq_data
*cfqd
)
2874 del_timer_sync(&cfqd
->idle_slice_timer
);
2875 cancel_work_sync(&cfqd
->unplug_work
);
2878 static void cfq_put_async_queues(struct cfq_data
*cfqd
)
2882 for (i
= 0; i
< IOPRIO_BE_NR
; i
++) {
2883 if (cfqd
->async_cfqq
[0][i
])
2884 cfq_put_queue(cfqd
->async_cfqq
[0][i
]);
2885 if (cfqd
->async_cfqq
[1][i
])
2886 cfq_put_queue(cfqd
->async_cfqq
[1][i
]);
2889 if (cfqd
->async_idle_cfqq
)
2890 cfq_put_queue(cfqd
->async_idle_cfqq
);
2893 static void cfq_exit_queue(struct elevator_queue
*e
)
2895 struct cfq_data
*cfqd
= e
->elevator_data
;
2896 struct request_queue
*q
= cfqd
->queue
;
2898 cfq_shutdown_timer_wq(cfqd
);
2900 spin_lock_irq(q
->queue_lock
);
2902 if (cfqd
->active_queue
)
2903 __cfq_slice_expired(cfqd
, cfqd
->active_queue
, 0);
2905 while (!list_empty(&cfqd
->cic_list
)) {
2906 struct cfq_io_context
*cic
= list_entry(cfqd
->cic_list
.next
,
2907 struct cfq_io_context
,
2910 __cfq_exit_single_io_context(cfqd
, cic
);
2913 cfq_put_async_queues(cfqd
);
2915 spin_unlock_irq(q
->queue_lock
);
2917 cfq_shutdown_timer_wq(cfqd
);
2922 static void *cfq_init_queue(struct request_queue
*q
)
2924 struct cfq_data
*cfqd
;
2927 cfqd
= kmalloc_node(sizeof(*cfqd
), GFP_KERNEL
| __GFP_ZERO
, q
->node
);
2931 for (i
= 0; i
< 2; ++i
)
2932 for (j
= 0; j
< 3; ++j
)
2933 cfqd
->service_trees
[i
][j
] = CFQ_RB_ROOT
;
2934 cfqd
->service_tree_idle
= CFQ_RB_ROOT
;
2937 * Not strictly needed (since RB_ROOT just clears the node and we
2938 * zeroed cfqd on alloc), but better be safe in case someone decides
2939 * to add magic to the rb code
2941 for (i
= 0; i
< CFQ_PRIO_LISTS
; i
++)
2942 cfqd
->prio_trees
[i
] = RB_ROOT
;
2945 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
2946 * Grab a permanent reference to it, so that the normal code flow
2947 * will not attempt to free it.
2949 cfq_init_cfqq(cfqd
, &cfqd
->oom_cfqq
, 1, 0);
2950 atomic_inc(&cfqd
->oom_cfqq
.ref
);
2952 INIT_LIST_HEAD(&cfqd
->cic_list
);
2956 init_timer(&cfqd
->idle_slice_timer
);
2957 cfqd
->idle_slice_timer
.function
= cfq_idle_slice_timer
;
2958 cfqd
->idle_slice_timer
.data
= (unsigned long) cfqd
;
2960 INIT_WORK(&cfqd
->unplug_work
, cfq_kick_queue
);
2962 cfqd
->cfq_quantum
= cfq_quantum
;
2963 cfqd
->cfq_fifo_expire
[0] = cfq_fifo_expire
[0];
2964 cfqd
->cfq_fifo_expire
[1] = cfq_fifo_expire
[1];
2965 cfqd
->cfq_back_max
= cfq_back_max
;
2966 cfqd
->cfq_back_penalty
= cfq_back_penalty
;
2967 cfqd
->cfq_slice
[0] = cfq_slice_async
;
2968 cfqd
->cfq_slice
[1] = cfq_slice_sync
;
2969 cfqd
->cfq_slice_async_rq
= cfq_slice_async_rq
;
2970 cfqd
->cfq_slice_idle
= cfq_slice_idle
;
2971 cfqd
->cfq_latency
= 1;
2973 cfqd
->last_end_sync_rq
= jiffies
;
2977 static void cfq_slab_kill(void)
2980 * Caller already ensured that pending RCU callbacks are completed,
2981 * so we should have no busy allocations at this point.
2984 kmem_cache_destroy(cfq_pool
);
2986 kmem_cache_destroy(cfq_ioc_pool
);
2989 static int __init
cfq_slab_setup(void)
2991 cfq_pool
= KMEM_CACHE(cfq_queue
, 0);
2995 cfq_ioc_pool
= KMEM_CACHE(cfq_io_context
, 0);
3006 * sysfs parts below -->
3009 cfq_var_show(unsigned int var
, char *page
)
3011 return sprintf(page
, "%d\n", var
);
3015 cfq_var_store(unsigned int *var
, const char *page
, size_t count
)
3017 char *p
= (char *) page
;
3019 *var
= simple_strtoul(p
, &p
, 10);
3023 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
3024 static ssize_t __FUNC(struct elevator_queue *e, char *page) \
3026 struct cfq_data *cfqd = e->elevator_data; \
3027 unsigned int __data = __VAR; \
3029 __data = jiffies_to_msecs(__data); \
3030 return cfq_var_show(__data, (page)); \
3032 SHOW_FUNCTION(cfq_quantum_show
, cfqd
->cfq_quantum
, 0);
3033 SHOW_FUNCTION(cfq_fifo_expire_sync_show
, cfqd
->cfq_fifo_expire
[1], 1);
3034 SHOW_FUNCTION(cfq_fifo_expire_async_show
, cfqd
->cfq_fifo_expire
[0], 1);
3035 SHOW_FUNCTION(cfq_back_seek_max_show
, cfqd
->cfq_back_max
, 0);
3036 SHOW_FUNCTION(cfq_back_seek_penalty_show
, cfqd
->cfq_back_penalty
, 0);
3037 SHOW_FUNCTION(cfq_slice_idle_show
, cfqd
->cfq_slice_idle
, 1);
3038 SHOW_FUNCTION(cfq_slice_sync_show
, cfqd
->cfq_slice
[1], 1);
3039 SHOW_FUNCTION(cfq_slice_async_show
, cfqd
->cfq_slice
[0], 1);
3040 SHOW_FUNCTION(cfq_slice_async_rq_show
, cfqd
->cfq_slice_async_rq
, 0);
3041 SHOW_FUNCTION(cfq_low_latency_show
, cfqd
->cfq_latency
, 0);
3042 #undef SHOW_FUNCTION
3044 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
3045 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3047 struct cfq_data *cfqd = e->elevator_data; \
3048 unsigned int __data; \
3049 int ret = cfq_var_store(&__data, (page), count); \
3050 if (__data < (MIN)) \
3052 else if (__data > (MAX)) \
3055 *(__PTR) = msecs_to_jiffies(__data); \
3057 *(__PTR) = __data; \
3060 STORE_FUNCTION(cfq_quantum_store
, &cfqd
->cfq_quantum
, 1, UINT_MAX
, 0);
3061 STORE_FUNCTION(cfq_fifo_expire_sync_store
, &cfqd
->cfq_fifo_expire
[1], 1,
3063 STORE_FUNCTION(cfq_fifo_expire_async_store
, &cfqd
->cfq_fifo_expire
[0], 1,
3065 STORE_FUNCTION(cfq_back_seek_max_store
, &cfqd
->cfq_back_max
, 0, UINT_MAX
, 0);
3066 STORE_FUNCTION(cfq_back_seek_penalty_store
, &cfqd
->cfq_back_penalty
, 1,
3068 STORE_FUNCTION(cfq_slice_idle_store
, &cfqd
->cfq_slice_idle
, 0, UINT_MAX
, 1);
3069 STORE_FUNCTION(cfq_slice_sync_store
, &cfqd
->cfq_slice
[1], 1, UINT_MAX
, 1);
3070 STORE_FUNCTION(cfq_slice_async_store
, &cfqd
->cfq_slice
[0], 1, UINT_MAX
, 1);
3071 STORE_FUNCTION(cfq_slice_async_rq_store
, &cfqd
->cfq_slice_async_rq
, 1,
3073 STORE_FUNCTION(cfq_low_latency_store
, &cfqd
->cfq_latency
, 0, 1, 0);
3074 #undef STORE_FUNCTION
3076 #define CFQ_ATTR(name) \
3077 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3079 static struct elv_fs_entry cfq_attrs
[] = {
3081 CFQ_ATTR(fifo_expire_sync
),
3082 CFQ_ATTR(fifo_expire_async
),
3083 CFQ_ATTR(back_seek_max
),
3084 CFQ_ATTR(back_seek_penalty
),
3085 CFQ_ATTR(slice_sync
),
3086 CFQ_ATTR(slice_async
),
3087 CFQ_ATTR(slice_async_rq
),
3088 CFQ_ATTR(slice_idle
),
3089 CFQ_ATTR(low_latency
),
3093 static struct elevator_type iosched_cfq
= {
3095 .elevator_merge_fn
= cfq_merge
,
3096 .elevator_merged_fn
= cfq_merged_request
,
3097 .elevator_merge_req_fn
= cfq_merged_requests
,
3098 .elevator_allow_merge_fn
= cfq_allow_merge
,
3099 .elevator_dispatch_fn
= cfq_dispatch_requests
,
3100 .elevator_add_req_fn
= cfq_insert_request
,
3101 .elevator_activate_req_fn
= cfq_activate_request
,
3102 .elevator_deactivate_req_fn
= cfq_deactivate_request
,
3103 .elevator_queue_empty_fn
= cfq_queue_empty
,
3104 .elevator_completed_req_fn
= cfq_completed_request
,
3105 .elevator_former_req_fn
= elv_rb_former_request
,
3106 .elevator_latter_req_fn
= elv_rb_latter_request
,
3107 .elevator_set_req_fn
= cfq_set_request
,
3108 .elevator_put_req_fn
= cfq_put_request
,
3109 .elevator_may_queue_fn
= cfq_may_queue
,
3110 .elevator_init_fn
= cfq_init_queue
,
3111 .elevator_exit_fn
= cfq_exit_queue
,
3112 .trim
= cfq_free_io_context
,
3114 .elevator_attrs
= cfq_attrs
,
3115 .elevator_name
= "cfq",
3116 .elevator_owner
= THIS_MODULE
,
3119 static int __init
cfq_init(void)
3122 * could be 0 on HZ < 1000 setups
3124 if (!cfq_slice_async
)
3125 cfq_slice_async
= 1;
3126 if (!cfq_slice_idle
)
3129 if (cfq_slab_setup())
3132 elv_register(&iosched_cfq
);
3137 static void __exit
cfq_exit(void)
3139 DECLARE_COMPLETION_ONSTACK(all_gone
);
3140 elv_unregister(&iosched_cfq
);
3141 ioc_gone
= &all_gone
;
3142 /* ioc_gone's update must be visible before reading ioc_count */
3146 * this also protects us from entering cfq_slab_kill() with
3147 * pending RCU callbacks
3149 if (elv_ioc_count_read(cfq_ioc_count
))
3150 wait_for_completion(&all_gone
);
3154 module_init(cfq_init
);
3155 module_exit(cfq_exit
);
3157 MODULE_AUTHOR("Jens Axboe");
3158 MODULE_LICENSE("GPL");
3159 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");