2 * Anticipatory & deadline i/o scheduler.
4 * Copyright (C) 2002 Jens Axboe <axboe@suse.de>
5 * Nick Piggin <nickpiggin@yahoo.com.au>
8 #include <linux/kernel.h>
10 #include <linux/blkdev.h>
11 #include <linux/elevator.h>
12 #include <linux/bio.h>
13 #include <linux/module.h>
14 #include <linux/slab.h>
15 #include <linux/init.h>
16 #include <linux/compiler.h>
17 #include <linux/rbtree.h>
18 #include <linux/interrupt.h>
24 * See Documentation/block/as-iosched.txt
28 * max time before a read is submitted.
30 #define default_read_expire (HZ / 8)
33 * ditto for writes, these limits are not hard, even
34 * if the disk is capable of satisfying them.
36 #define default_write_expire (HZ / 4)
39 * read_batch_expire describes how long we will allow a stream of reads to
40 * persist before looking to see whether it is time to switch over to writes.
42 #define default_read_batch_expire (HZ / 2)
45 * write_batch_expire describes how long we want a stream of writes to run for.
46 * This is not a hard limit, but a target we set for the auto-tuning thingy.
47 * See, the problem is: we can send a lot of writes to disk cache / TCQ in
48 * a short amount of time...
50 #define default_write_batch_expire (HZ / 8)
53 * max time we may wait to anticipate a read (default around 6ms)
55 #define default_antic_expire ((HZ / 150) ? HZ / 150 : 1)
58 * Keep track of up to 20ms thinktimes. We can go as big as we like here,
59 * however huge values tend to interfere and not decay fast enough. A program
60 * might be in a non-io phase of operation. Waiting on user input for example,
61 * or doing a lengthy computation. A small penalty can be justified there, and
62 * will still catch out those processes that constantly have large thinktimes.
64 #define MAX_THINKTIME (HZ/50UL)
66 /* Bits in as_io_context.state */
68 AS_TASK_RUNNING
=0, /* Process has not exited */
69 AS_TASK_IOSTARTED
, /* Process has started some IO */
70 AS_TASK_IORUNNING
, /* Process has completed some IO */
73 enum anticipation_status
{
74 ANTIC_OFF
=0, /* Not anticipating (normal operation) */
75 ANTIC_WAIT_REQ
, /* The last read has not yet completed */
76 ANTIC_WAIT_NEXT
, /* Currently anticipating a request vs
77 last read (which has completed) */
78 ANTIC_FINISHED
, /* Anticipating but have found a candidate
87 struct request_queue
*q
; /* the "owner" queue */
90 * requests (as_rq s) are present on both sort_list and fifo_list
92 struct rb_root sort_list
[2];
93 struct list_head fifo_list
[2];
95 struct as_rq
*next_arq
[2]; /* next in sort order */
96 sector_t last_sector
[2]; /* last REQ_SYNC & REQ_ASYNC sectors */
98 unsigned long exit_prob
; /* probability a task will exit while
100 unsigned long exit_no_coop
; /* probablility an exited task will
101 not be part of a later cooperating
103 unsigned long new_ttime_total
; /* mean thinktime on new proc */
104 unsigned long new_ttime_mean
;
105 u64 new_seek_total
; /* mean seek on new proc */
106 sector_t new_seek_mean
;
108 unsigned long current_batch_expires
;
109 unsigned long last_check_fifo
[2];
110 int changed_batch
; /* 1: waiting for old batch to end */
111 int new_batch
; /* 1: waiting on first read complete */
112 int batch_data_dir
; /* current batch REQ_SYNC / REQ_ASYNC */
113 int write_batch_count
; /* max # of reqs in a write batch */
114 int current_write_count
; /* how many requests left this batch */
115 int write_batch_idled
; /* has the write batch gone idle? */
118 enum anticipation_status antic_status
;
119 unsigned long antic_start
; /* jiffies: when it started */
120 struct timer_list antic_timer
; /* anticipatory scheduling timer */
121 struct work_struct antic_work
; /* Deferred unplugging */
122 struct io_context
*io_context
; /* Identify the expected process */
123 int ioc_finished
; /* IO associated with io_context is finished */
127 * settings that change how the i/o scheduler behaves
129 unsigned long fifo_expire
[2];
130 unsigned long batch_expire
[2];
131 unsigned long antic_expire
;
134 #define list_entry_fifo(ptr) list_entry((ptr), struct as_rq, fifo)
140 AS_RQ_NEW
=0, /* New - not referenced and not on any lists */
141 AS_RQ_QUEUED
, /* In the request queue. It belongs to the
143 AS_RQ_DISPATCHED
, /* On the dispatch list. It belongs to the
145 AS_RQ_PRESCHED
, /* Debug poisoning for requests being used */
148 AS_RQ_POSTSCHED
, /* when they shouldn't be */
153 * rbtree index, key is the starting offset
155 struct rb_node rb_node
;
158 struct request
*request
;
160 struct io_context
*io_context
; /* The submitting task */
165 struct list_head fifo
;
166 unsigned long expires
;
168 unsigned int is_sync
;
169 enum arq_state state
;
172 #define RQ_DATA(rq) ((struct as_rq *) (rq)->elevator_private)
174 static kmem_cache_t
*arq_pool
;
176 static atomic_t ioc_count
= ATOMIC_INIT(0);
177 static struct completion
*ioc_gone
;
179 static void as_move_to_dispatch(struct as_data
*ad
, struct as_rq
*arq
);
180 static void as_antic_stop(struct as_data
*ad
);
183 * IO Context helper functions
186 /* Called to deallocate the as_io_context */
187 static void free_as_io_context(struct as_io_context
*aic
)
190 if (atomic_dec_and_test(&ioc_count
) && ioc_gone
)
194 static void as_trim(struct io_context
*ioc
)
197 free_as_io_context(ioc
->aic
);
201 /* Called when the task exits */
202 static void exit_as_io_context(struct as_io_context
*aic
)
204 WARN_ON(!test_bit(AS_TASK_RUNNING
, &aic
->state
));
205 clear_bit(AS_TASK_RUNNING
, &aic
->state
);
208 static struct as_io_context
*alloc_as_io_context(void)
210 struct as_io_context
*ret
;
212 ret
= kmalloc(sizeof(*ret
), GFP_ATOMIC
);
214 ret
->dtor
= free_as_io_context
;
215 ret
->exit
= exit_as_io_context
;
216 ret
->state
= 1 << AS_TASK_RUNNING
;
217 atomic_set(&ret
->nr_queued
, 0);
218 atomic_set(&ret
->nr_dispatched
, 0);
219 spin_lock_init(&ret
->lock
);
220 ret
->ttime_total
= 0;
221 ret
->ttime_samples
= 0;
224 ret
->seek_samples
= 0;
226 atomic_inc(&ioc_count
);
233 * If the current task has no AS IO context then create one and initialise it.
234 * Then take a ref on the task's io context and return it.
236 static struct io_context
*as_get_io_context(void)
238 struct io_context
*ioc
= get_io_context(GFP_ATOMIC
);
239 if (ioc
&& !ioc
->aic
) {
240 ioc
->aic
= alloc_as_io_context();
249 static void as_put_io_context(struct as_rq
*arq
)
251 struct as_io_context
*aic
;
253 if (unlikely(!arq
->io_context
))
256 aic
= arq
->io_context
->aic
;
258 if (arq
->is_sync
== REQ_SYNC
&& aic
) {
259 spin_lock(&aic
->lock
);
260 set_bit(AS_TASK_IORUNNING
, &aic
->state
);
261 aic
->last_end_request
= jiffies
;
262 spin_unlock(&aic
->lock
);
265 put_io_context(arq
->io_context
);
269 * rb tree support functions
271 #define rb_entry_arq(node) rb_entry((node), struct as_rq, rb_node)
272 #define ARQ_RB_ROOT(ad, arq) (&(ad)->sort_list[(arq)->is_sync])
273 #define rq_rb_key(rq) (rq)->sector
276 * as_find_first_arq finds the first (lowest sector numbered) request
277 * for the specified data_dir. Used to sweep back to the start of the disk
278 * (1-way elevator) after we process the last (highest sector) request.
280 static struct as_rq
*as_find_first_arq(struct as_data
*ad
, int data_dir
)
282 struct rb_node
*n
= ad
->sort_list
[data_dir
].rb_node
;
288 if (n
->rb_left
== NULL
)
289 return rb_entry_arq(n
);
296 * Add the request to the rb tree if it is unique. If there is an alias (an
297 * existing request against the same sector), which can happen when using
298 * direct IO, then return the alias.
300 static struct as_rq
*__as_add_arq_rb(struct as_data
*ad
, struct as_rq
*arq
)
302 struct rb_node
**p
= &ARQ_RB_ROOT(ad
, arq
)->rb_node
;
303 struct rb_node
*parent
= NULL
;
305 struct request
*rq
= arq
->request
;
307 arq
->rb_key
= rq_rb_key(rq
);
311 __arq
= rb_entry_arq(parent
);
313 if (arq
->rb_key
< __arq
->rb_key
)
315 else if (arq
->rb_key
> __arq
->rb_key
)
321 rb_link_node(&arq
->rb_node
, parent
, p
);
322 rb_insert_color(&arq
->rb_node
, ARQ_RB_ROOT(ad
, arq
));
327 static void as_add_arq_rb(struct as_data
*ad
, struct as_rq
*arq
)
331 while ((unlikely(alias
= __as_add_arq_rb(ad
, arq
)))) {
332 as_move_to_dispatch(ad
, alias
);
337 static inline void as_del_arq_rb(struct as_data
*ad
, struct as_rq
*arq
)
339 if (RB_EMPTY_NODE(&arq
->rb_node
)) {
344 rb_erase(&arq
->rb_node
, ARQ_RB_ROOT(ad
, arq
));
345 RB_CLEAR_NODE(&arq
->rb_node
);
348 static struct request
*
349 as_find_arq_rb(struct as_data
*ad
, sector_t sector
, int data_dir
)
351 struct rb_node
*n
= ad
->sort_list
[data_dir
].rb_node
;
355 arq
= rb_entry_arq(n
);
357 if (sector
< arq
->rb_key
)
359 else if (sector
> arq
->rb_key
)
369 * IO Scheduler proper
372 #define MAXBACK (1024 * 1024) /*
373 * Maximum distance the disk will go backward
377 #define BACK_PENALTY 2
380 * as_choose_req selects the preferred one of two requests of the same data_dir
381 * ignoring time - eg. timeouts, which is the job of as_dispatch_request
383 static struct as_rq
*
384 as_choose_req(struct as_data
*ad
, struct as_rq
*arq1
, struct as_rq
*arq2
)
387 sector_t last
, s1
, s2
, d1
, d2
;
388 int r1_wrap
=0, r2_wrap
=0; /* requests are behind the disk head */
389 const sector_t maxback
= MAXBACK
;
391 if (arq1
== NULL
|| arq1
== arq2
)
396 data_dir
= arq1
->is_sync
;
398 last
= ad
->last_sector
[data_dir
];
399 s1
= arq1
->request
->sector
;
400 s2
= arq2
->request
->sector
;
402 BUG_ON(data_dir
!= arq2
->is_sync
);
405 * Strict one way elevator _except_ in the case where we allow
406 * short backward seeks which are biased as twice the cost of a
407 * similar forward seek.
411 else if (s1
+maxback
>= last
)
412 d1
= (last
- s1
)*BACK_PENALTY
;
415 d1
= 0; /* shut up, gcc */
420 else if (s2
+maxback
>= last
)
421 d2
= (last
- s2
)*BACK_PENALTY
;
427 /* Found required data */
428 if (!r1_wrap
&& r2_wrap
)
430 else if (!r2_wrap
&& r1_wrap
)
432 else if (r1_wrap
&& r2_wrap
) {
433 /* both behind the head */
440 /* Both requests in front of the head */
454 * as_find_next_arq finds the next request after @prev in elevator order.
455 * this with as_choose_req form the basis for how the scheduler chooses
456 * what request to process next. Anticipation works on top of this.
458 static struct as_rq
*as_find_next_arq(struct as_data
*ad
, struct as_rq
*last
)
460 const int data_dir
= last
->is_sync
;
462 struct rb_node
*rbnext
= rb_next(&last
->rb_node
);
463 struct rb_node
*rbprev
= rb_prev(&last
->rb_node
);
464 struct as_rq
*arq_next
, *arq_prev
;
466 BUG_ON(!RB_EMPTY_NODE(&last
->rb_node
));
469 arq_prev
= rb_entry_arq(rbprev
);
474 arq_next
= rb_entry_arq(rbnext
);
476 arq_next
= as_find_first_arq(ad
, data_dir
);
477 if (arq_next
== last
)
481 ret
= as_choose_req(ad
, arq_next
, arq_prev
);
487 * anticipatory scheduling functions follow
491 * as_antic_expired tells us when we have anticipated too long.
492 * The funny "absolute difference" math on the elapsed time is to handle
493 * jiffy wraps, and disks which have been idle for 0x80000000 jiffies.
495 static int as_antic_expired(struct as_data
*ad
)
499 delta_jif
= jiffies
- ad
->antic_start
;
500 if (unlikely(delta_jif
< 0))
501 delta_jif
= -delta_jif
;
502 if (delta_jif
< ad
->antic_expire
)
509 * as_antic_waitnext starts anticipating that a nice request will soon be
510 * submitted. See also as_antic_waitreq
512 static void as_antic_waitnext(struct as_data
*ad
)
514 unsigned long timeout
;
516 BUG_ON(ad
->antic_status
!= ANTIC_OFF
517 && ad
->antic_status
!= ANTIC_WAIT_REQ
);
519 timeout
= ad
->antic_start
+ ad
->antic_expire
;
521 mod_timer(&ad
->antic_timer
, timeout
);
523 ad
->antic_status
= ANTIC_WAIT_NEXT
;
527 * as_antic_waitreq starts anticipating. We don't start timing the anticipation
528 * until the request that we're anticipating on has finished. This means we
529 * are timing from when the candidate process wakes up hopefully.
531 static void as_antic_waitreq(struct as_data
*ad
)
533 BUG_ON(ad
->antic_status
== ANTIC_FINISHED
);
534 if (ad
->antic_status
== ANTIC_OFF
) {
535 if (!ad
->io_context
|| ad
->ioc_finished
)
536 as_antic_waitnext(ad
);
538 ad
->antic_status
= ANTIC_WAIT_REQ
;
543 * This is called directly by the functions in this file to stop anticipation.
544 * We kill the timer and schedule a call to the request_fn asap.
546 static void as_antic_stop(struct as_data
*ad
)
548 int status
= ad
->antic_status
;
550 if (status
== ANTIC_WAIT_REQ
|| status
== ANTIC_WAIT_NEXT
) {
551 if (status
== ANTIC_WAIT_NEXT
)
552 del_timer(&ad
->antic_timer
);
553 ad
->antic_status
= ANTIC_FINISHED
;
554 /* see as_work_handler */
555 kblockd_schedule_work(&ad
->antic_work
);
560 * as_antic_timeout is the timer function set by as_antic_waitnext.
562 static void as_antic_timeout(unsigned long data
)
564 struct request_queue
*q
= (struct request_queue
*)data
;
565 struct as_data
*ad
= q
->elevator
->elevator_data
;
568 spin_lock_irqsave(q
->queue_lock
, flags
);
569 if (ad
->antic_status
== ANTIC_WAIT_REQ
570 || ad
->antic_status
== ANTIC_WAIT_NEXT
) {
571 struct as_io_context
*aic
= ad
->io_context
->aic
;
573 ad
->antic_status
= ANTIC_FINISHED
;
574 kblockd_schedule_work(&ad
->antic_work
);
576 if (aic
->ttime_samples
== 0) {
577 /* process anticipated on has exited or timed out*/
578 ad
->exit_prob
= (7*ad
->exit_prob
+ 256)/8;
580 if (!test_bit(AS_TASK_RUNNING
, &aic
->state
)) {
581 /* process not "saved" by a cooperating request */
582 ad
->exit_no_coop
= (7*ad
->exit_no_coop
+ 256)/8;
585 spin_unlock_irqrestore(q
->queue_lock
, flags
);
588 static void as_update_thinktime(struct as_data
*ad
, struct as_io_context
*aic
,
591 /* fixed point: 1.0 == 1<<8 */
592 if (aic
->ttime_samples
== 0) {
593 ad
->new_ttime_total
= (7*ad
->new_ttime_total
+ 256*ttime
) / 8;
594 ad
->new_ttime_mean
= ad
->new_ttime_total
/ 256;
596 ad
->exit_prob
= (7*ad
->exit_prob
)/8;
598 aic
->ttime_samples
= (7*aic
->ttime_samples
+ 256) / 8;
599 aic
->ttime_total
= (7*aic
->ttime_total
+ 256*ttime
) / 8;
600 aic
->ttime_mean
= (aic
->ttime_total
+ 128) / aic
->ttime_samples
;
603 static void as_update_seekdist(struct as_data
*ad
, struct as_io_context
*aic
,
608 if (aic
->seek_samples
== 0) {
609 ad
->new_seek_total
= (7*ad
->new_seek_total
+ 256*(u64
)sdist
)/8;
610 ad
->new_seek_mean
= ad
->new_seek_total
/ 256;
614 * Don't allow the seek distance to get too large from the
615 * odd fragment, pagein, etc
617 if (aic
->seek_samples
<= 60) /* second&third seek */
618 sdist
= min(sdist
, (aic
->seek_mean
* 4) + 2*1024*1024);
620 sdist
= min(sdist
, (aic
->seek_mean
* 4) + 2*1024*64);
622 aic
->seek_samples
= (7*aic
->seek_samples
+ 256) / 8;
623 aic
->seek_total
= (7*aic
->seek_total
+ (u64
)256*sdist
) / 8;
624 total
= aic
->seek_total
+ (aic
->seek_samples
/2);
625 do_div(total
, aic
->seek_samples
);
626 aic
->seek_mean
= (sector_t
)total
;
630 * as_update_iohist keeps a decaying histogram of IO thinktimes, and
631 * updates @aic->ttime_mean based on that. It is called when a new
634 static void as_update_iohist(struct as_data
*ad
, struct as_io_context
*aic
,
637 struct as_rq
*arq
= RQ_DATA(rq
);
638 int data_dir
= arq
->is_sync
;
639 unsigned long thinktime
= 0;
645 if (data_dir
== REQ_SYNC
) {
646 unsigned long in_flight
= atomic_read(&aic
->nr_queued
)
647 + atomic_read(&aic
->nr_dispatched
);
648 spin_lock(&aic
->lock
);
649 if (test_bit(AS_TASK_IORUNNING
, &aic
->state
) ||
650 test_bit(AS_TASK_IOSTARTED
, &aic
->state
)) {
651 /* Calculate read -> read thinktime */
652 if (test_bit(AS_TASK_IORUNNING
, &aic
->state
)
654 thinktime
= jiffies
- aic
->last_end_request
;
655 thinktime
= min(thinktime
, MAX_THINKTIME
-1);
657 as_update_thinktime(ad
, aic
, thinktime
);
659 /* Calculate read -> read seek distance */
660 if (aic
->last_request_pos
< rq
->sector
)
661 seek_dist
= rq
->sector
- aic
->last_request_pos
;
663 seek_dist
= aic
->last_request_pos
- rq
->sector
;
664 as_update_seekdist(ad
, aic
, seek_dist
);
666 aic
->last_request_pos
= rq
->sector
+ rq
->nr_sectors
;
667 set_bit(AS_TASK_IOSTARTED
, &aic
->state
);
668 spin_unlock(&aic
->lock
);
673 * as_close_req decides if one request is considered "close" to the
674 * previous one issued.
676 static int as_close_req(struct as_data
*ad
, struct as_io_context
*aic
,
679 unsigned long delay
; /* milliseconds */
680 sector_t last
= ad
->last_sector
[ad
->batch_data_dir
];
681 sector_t next
= arq
->request
->sector
;
682 sector_t delta
; /* acceptable close offset (in sectors) */
685 if (ad
->antic_status
== ANTIC_OFF
|| !ad
->ioc_finished
)
688 delay
= ((jiffies
- ad
->antic_start
) * 1000) / HZ
;
692 else if (delay
<= 20 && delay
<= ad
->antic_expire
)
693 delta
= 8192 << delay
;
697 if ((last
<= next
+ (delta
>>1)) && (next
<= last
+ delta
))
705 if (aic
->seek_samples
== 0) {
707 * Process has just started IO. Use past statistics to
708 * gauge success possibility
710 if (ad
->new_seek_mean
> s
) {
711 /* this request is better than what we're expecting */
716 if (aic
->seek_mean
> s
) {
717 /* this request is better than what we're expecting */
726 * as_can_break_anticipation returns true if we have been anticipating this
729 * It also returns true if the process against which we are anticipating
730 * submits a write - that's presumably an fsync, O_SYNC write, etc. We want to
731 * dispatch it ASAP, because we know that application will not be submitting
734 * If the task which has submitted the request has exited, break anticipation.
736 * If this task has queued some other IO, do not enter enticipation.
738 static int as_can_break_anticipation(struct as_data
*ad
, struct as_rq
*arq
)
740 struct io_context
*ioc
;
741 struct as_io_context
*aic
;
743 ioc
= ad
->io_context
;
746 if (arq
&& ioc
== arq
->io_context
) {
747 /* request from same process */
751 if (ad
->ioc_finished
&& as_antic_expired(ad
)) {
753 * In this situation status should really be FINISHED,
754 * however the timer hasn't had the chance to run yet.
763 if (atomic_read(&aic
->nr_queued
) > 0) {
764 /* process has more requests queued */
768 if (atomic_read(&aic
->nr_dispatched
) > 0) {
769 /* process has more requests dispatched */
773 if (arq
&& arq
->is_sync
== REQ_SYNC
&& as_close_req(ad
, aic
, arq
)) {
775 * Found a close request that is not one of ours.
777 * This makes close requests from another process update
778 * our IO history. Is generally useful when there are
779 * two or more cooperating processes working in the same
782 if (!test_bit(AS_TASK_RUNNING
, &aic
->state
)) {
783 if (aic
->ttime_samples
== 0)
784 ad
->exit_prob
= (7*ad
->exit_prob
+ 256)/8;
786 ad
->exit_no_coop
= (7*ad
->exit_no_coop
)/8;
789 as_update_iohist(ad
, aic
, arq
->request
);
793 if (!test_bit(AS_TASK_RUNNING
, &aic
->state
)) {
794 /* process anticipated on has exited */
795 if (aic
->ttime_samples
== 0)
796 ad
->exit_prob
= (7*ad
->exit_prob
+ 256)/8;
798 if (ad
->exit_no_coop
> 128)
802 if (aic
->ttime_samples
== 0) {
803 if (ad
->new_ttime_mean
> ad
->antic_expire
)
805 if (ad
->exit_prob
* ad
->exit_no_coop
> 128*256)
807 } else if (aic
->ttime_mean
> ad
->antic_expire
) {
808 /* the process thinks too much between requests */
816 * as_can_anticipate indicates whether we should either run arq
817 * or keep anticipating a better request.
819 static int as_can_anticipate(struct as_data
*ad
, struct as_rq
*arq
)
823 * Last request submitted was a write
827 if (ad
->antic_status
== ANTIC_FINISHED
)
829 * Don't restart if we have just finished. Run the next request
833 if (as_can_break_anticipation(ad
, arq
))
835 * This request is a good candidate. Don't keep anticipating,
841 * OK from here, we haven't finished, and don't have a decent request!
842 * Status is either ANTIC_OFF so start waiting,
843 * ANTIC_WAIT_REQ so continue waiting for request to finish
844 * or ANTIC_WAIT_NEXT so continue waiting for an acceptable request.
851 * as_update_arq must be called whenever a request (arq) is added to
852 * the sort_list. This function keeps caches up to date, and checks if the
853 * request might be one we are "anticipating"
855 static void as_update_arq(struct as_data
*ad
, struct as_rq
*arq
)
857 const int data_dir
= arq
->is_sync
;
859 /* keep the next_arq cache up to date */
860 ad
->next_arq
[data_dir
] = as_choose_req(ad
, arq
, ad
->next_arq
[data_dir
]);
863 * have we been anticipating this request?
864 * or does it come from the same process as the one we are anticipating
867 if (ad
->antic_status
== ANTIC_WAIT_REQ
868 || ad
->antic_status
== ANTIC_WAIT_NEXT
) {
869 if (as_can_break_anticipation(ad
, arq
))
875 * Gathers timings and resizes the write batch automatically
877 static void update_write_batch(struct as_data
*ad
)
879 unsigned long batch
= ad
->batch_expire
[REQ_ASYNC
];
882 write_time
= (jiffies
- ad
->current_batch_expires
) + batch
;
886 if (write_time
> batch
&& !ad
->write_batch_idled
) {
887 if (write_time
> batch
* 3)
888 ad
->write_batch_count
/= 2;
890 ad
->write_batch_count
--;
891 } else if (write_time
< batch
&& ad
->current_write_count
== 0) {
892 if (batch
> write_time
* 3)
893 ad
->write_batch_count
*= 2;
895 ad
->write_batch_count
++;
898 if (ad
->write_batch_count
< 1)
899 ad
->write_batch_count
= 1;
903 * as_completed_request is to be called when a request has completed and
904 * returned something to the requesting process, be it an error or data.
906 static void as_completed_request(request_queue_t
*q
, struct request
*rq
)
908 struct as_data
*ad
= q
->elevator
->elevator_data
;
909 struct as_rq
*arq
= RQ_DATA(rq
);
911 WARN_ON(!list_empty(&rq
->queuelist
));
913 if (arq
->state
!= AS_RQ_REMOVED
) {
914 printk("arq->state %d\n", arq
->state
);
919 if (ad
->changed_batch
&& ad
->nr_dispatched
== 1) {
920 kblockd_schedule_work(&ad
->antic_work
);
921 ad
->changed_batch
= 0;
923 if (ad
->batch_data_dir
== REQ_SYNC
)
926 WARN_ON(ad
->nr_dispatched
== 0);
930 * Start counting the batch from when a request of that direction is
931 * actually serviced. This should help devices with big TCQ windows
932 * and writeback caches
934 if (ad
->new_batch
&& ad
->batch_data_dir
== arq
->is_sync
) {
935 update_write_batch(ad
);
936 ad
->current_batch_expires
= jiffies
+
937 ad
->batch_expire
[REQ_SYNC
];
941 if (ad
->io_context
== arq
->io_context
&& ad
->io_context
) {
942 ad
->antic_start
= jiffies
;
943 ad
->ioc_finished
= 1;
944 if (ad
->antic_status
== ANTIC_WAIT_REQ
) {
946 * We were waiting on this request, now anticipate
949 as_antic_waitnext(ad
);
953 as_put_io_context(arq
);
955 arq
->state
= AS_RQ_POSTSCHED
;
959 * as_remove_queued_request removes a request from the pre dispatch queue
960 * without updating refcounts. It is expected the caller will drop the
961 * reference unless it replaces the request at somepart of the elevator
962 * (ie. the dispatch queue)
964 static void as_remove_queued_request(request_queue_t
*q
, struct request
*rq
)
966 struct as_rq
*arq
= RQ_DATA(rq
);
967 const int data_dir
= arq
->is_sync
;
968 struct as_data
*ad
= q
->elevator
->elevator_data
;
970 WARN_ON(arq
->state
!= AS_RQ_QUEUED
);
972 if (arq
->io_context
&& arq
->io_context
->aic
) {
973 BUG_ON(!atomic_read(&arq
->io_context
->aic
->nr_queued
));
974 atomic_dec(&arq
->io_context
->aic
->nr_queued
);
978 * Update the "next_arq" cache if we are about to remove its
981 if (ad
->next_arq
[data_dir
] == arq
)
982 ad
->next_arq
[data_dir
] = as_find_next_arq(ad
, arq
);
984 list_del_init(&arq
->fifo
);
985 as_del_arq_rb(ad
, arq
);
989 * as_fifo_expired returns 0 if there are no expired reads on the fifo,
990 * 1 otherwise. It is ratelimited so that we only perform the check once per
991 * `fifo_expire' interval. Otherwise a large number of expired requests
992 * would create a hopeless seekstorm.
994 * See as_antic_expired comment.
996 static int as_fifo_expired(struct as_data
*ad
, int adir
)
1001 delta_jif
= jiffies
- ad
->last_check_fifo
[adir
];
1002 if (unlikely(delta_jif
< 0))
1003 delta_jif
= -delta_jif
;
1004 if (delta_jif
< ad
->fifo_expire
[adir
])
1007 ad
->last_check_fifo
[adir
] = jiffies
;
1009 if (list_empty(&ad
->fifo_list
[adir
]))
1012 arq
= list_entry_fifo(ad
->fifo_list
[adir
].next
);
1014 return time_after(jiffies
, arq
->expires
);
1018 * as_batch_expired returns true if the current batch has expired. A batch
1019 * is a set of reads or a set of writes.
1021 static inline int as_batch_expired(struct as_data
*ad
)
1023 if (ad
->changed_batch
|| ad
->new_batch
)
1026 if (ad
->batch_data_dir
== REQ_SYNC
)
1027 /* TODO! add a check so a complete fifo gets written? */
1028 return time_after(jiffies
, ad
->current_batch_expires
);
1030 return time_after(jiffies
, ad
->current_batch_expires
)
1031 || ad
->current_write_count
== 0;
1035 * move an entry to dispatch queue
1037 static void as_move_to_dispatch(struct as_data
*ad
, struct as_rq
*arq
)
1039 struct request
*rq
= arq
->request
;
1040 const int data_dir
= arq
->is_sync
;
1042 BUG_ON(RB_EMPTY_NODE(&arq
->rb_node
));
1045 ad
->antic_status
= ANTIC_OFF
;
1048 * This has to be set in order to be correctly updated by
1051 ad
->last_sector
[data_dir
] = rq
->sector
+ rq
->nr_sectors
;
1053 if (data_dir
== REQ_SYNC
) {
1054 /* In case we have to anticipate after this */
1055 copy_io_context(&ad
->io_context
, &arq
->io_context
);
1057 if (ad
->io_context
) {
1058 put_io_context(ad
->io_context
);
1059 ad
->io_context
= NULL
;
1062 if (ad
->current_write_count
!= 0)
1063 ad
->current_write_count
--;
1065 ad
->ioc_finished
= 0;
1067 ad
->next_arq
[data_dir
] = as_find_next_arq(ad
, arq
);
1070 * take it off the sort and fifo list, add to dispatch queue
1072 as_remove_queued_request(ad
->q
, rq
);
1073 WARN_ON(arq
->state
!= AS_RQ_QUEUED
);
1075 elv_dispatch_sort(ad
->q
, rq
);
1077 arq
->state
= AS_RQ_DISPATCHED
;
1078 if (arq
->io_context
&& arq
->io_context
->aic
)
1079 atomic_inc(&arq
->io_context
->aic
->nr_dispatched
);
1080 ad
->nr_dispatched
++;
1084 * as_dispatch_request selects the best request according to
1085 * read/write expire, batch expire, etc, and moves it to the dispatch
1086 * queue. Returns 1 if a request was found, 0 otherwise.
1088 static int as_dispatch_request(request_queue_t
*q
, int force
)
1090 struct as_data
*ad
= q
->elevator
->elevator_data
;
1092 const int reads
= !list_empty(&ad
->fifo_list
[REQ_SYNC
]);
1093 const int writes
= !list_empty(&ad
->fifo_list
[REQ_ASYNC
]);
1095 if (unlikely(force
)) {
1097 * Forced dispatch, accounting is useless. Reset
1098 * accounting states and dump fifo_lists. Note that
1099 * batch_data_dir is reset to REQ_SYNC to avoid
1100 * screwing write batch accounting as write batch
1101 * accounting occurs on W->R transition.
1105 ad
->batch_data_dir
= REQ_SYNC
;
1106 ad
->changed_batch
= 0;
1109 while (ad
->next_arq
[REQ_SYNC
]) {
1110 as_move_to_dispatch(ad
, ad
->next_arq
[REQ_SYNC
]);
1113 ad
->last_check_fifo
[REQ_SYNC
] = jiffies
;
1115 while (ad
->next_arq
[REQ_ASYNC
]) {
1116 as_move_to_dispatch(ad
, ad
->next_arq
[REQ_ASYNC
]);
1119 ad
->last_check_fifo
[REQ_ASYNC
] = jiffies
;
1124 /* Signal that the write batch was uncontended, so we can't time it */
1125 if (ad
->batch_data_dir
== REQ_ASYNC
&& !reads
) {
1126 if (ad
->current_write_count
== 0 || !writes
)
1127 ad
->write_batch_idled
= 1;
1130 if (!(reads
|| writes
)
1131 || ad
->antic_status
== ANTIC_WAIT_REQ
1132 || ad
->antic_status
== ANTIC_WAIT_NEXT
1133 || ad
->changed_batch
)
1136 if (!(reads
&& writes
&& as_batch_expired(ad
))) {
1138 * batch is still running or no reads or no writes
1140 arq
= ad
->next_arq
[ad
->batch_data_dir
];
1142 if (ad
->batch_data_dir
== REQ_SYNC
&& ad
->antic_expire
) {
1143 if (as_fifo_expired(ad
, REQ_SYNC
))
1146 if (as_can_anticipate(ad
, arq
)) {
1147 as_antic_waitreq(ad
);
1153 /* we have a "next request" */
1154 if (reads
&& !writes
)
1155 ad
->current_batch_expires
=
1156 jiffies
+ ad
->batch_expire
[REQ_SYNC
];
1157 goto dispatch_request
;
1162 * at this point we are not running a batch. select the appropriate
1163 * data direction (read / write)
1167 BUG_ON(RB_EMPTY_ROOT(&ad
->sort_list
[REQ_SYNC
]));
1169 if (writes
&& ad
->batch_data_dir
== REQ_SYNC
)
1171 * Last batch was a read, switch to writes
1173 goto dispatch_writes
;
1175 if (ad
->batch_data_dir
== REQ_ASYNC
) {
1176 WARN_ON(ad
->new_batch
);
1177 ad
->changed_batch
= 1;
1179 ad
->batch_data_dir
= REQ_SYNC
;
1180 arq
= list_entry_fifo(ad
->fifo_list
[ad
->batch_data_dir
].next
);
1181 ad
->last_check_fifo
[ad
->batch_data_dir
] = jiffies
;
1182 goto dispatch_request
;
1186 * the last batch was a read
1191 BUG_ON(RB_EMPTY_ROOT(&ad
->sort_list
[REQ_ASYNC
]));
1193 if (ad
->batch_data_dir
== REQ_SYNC
) {
1194 ad
->changed_batch
= 1;
1197 * new_batch might be 1 when the queue runs out of
1198 * reads. A subsequent submission of a write might
1199 * cause a change of batch before the read is finished.
1203 ad
->batch_data_dir
= REQ_ASYNC
;
1204 ad
->current_write_count
= ad
->write_batch_count
;
1205 ad
->write_batch_idled
= 0;
1206 arq
= ad
->next_arq
[ad
->batch_data_dir
];
1207 goto dispatch_request
;
1215 * If a request has expired, service it.
1218 if (as_fifo_expired(ad
, ad
->batch_data_dir
)) {
1220 arq
= list_entry_fifo(ad
->fifo_list
[ad
->batch_data_dir
].next
);
1221 BUG_ON(arq
== NULL
);
1224 if (ad
->changed_batch
) {
1225 WARN_ON(ad
->new_batch
);
1227 if (ad
->nr_dispatched
)
1230 if (ad
->batch_data_dir
== REQ_ASYNC
)
1231 ad
->current_batch_expires
= jiffies
+
1232 ad
->batch_expire
[REQ_ASYNC
];
1236 ad
->changed_batch
= 0;
1240 * arq is the selected appropriate request.
1242 as_move_to_dispatch(ad
, arq
);
1248 * add arq to rbtree and fifo
1250 static void as_add_request(request_queue_t
*q
, struct request
*rq
)
1252 struct as_data
*ad
= q
->elevator
->elevator_data
;
1253 struct as_rq
*arq
= RQ_DATA(rq
);
1256 arq
->state
= AS_RQ_NEW
;
1258 if (rq_data_dir(arq
->request
) == READ
1259 || (arq
->request
->cmd_flags
& REQ_RW_SYNC
))
1263 data_dir
= arq
->is_sync
;
1265 arq
->io_context
= as_get_io_context();
1267 if (arq
->io_context
) {
1268 as_update_iohist(ad
, arq
->io_context
->aic
, arq
->request
);
1269 atomic_inc(&arq
->io_context
->aic
->nr_queued
);
1272 as_add_arq_rb(ad
, arq
);
1275 * set expire time (only used for reads) and add to fifo list
1277 arq
->expires
= jiffies
+ ad
->fifo_expire
[data_dir
];
1278 list_add_tail(&arq
->fifo
, &ad
->fifo_list
[data_dir
]);
1280 as_update_arq(ad
, arq
); /* keep state machine up to date */
1281 arq
->state
= AS_RQ_QUEUED
;
1284 static void as_activate_request(request_queue_t
*q
, struct request
*rq
)
1286 struct as_rq
*arq
= RQ_DATA(rq
);
1288 WARN_ON(arq
->state
!= AS_RQ_DISPATCHED
);
1289 arq
->state
= AS_RQ_REMOVED
;
1290 if (arq
->io_context
&& arq
->io_context
->aic
)
1291 atomic_dec(&arq
->io_context
->aic
->nr_dispatched
);
1294 static void as_deactivate_request(request_queue_t
*q
, struct request
*rq
)
1296 struct as_rq
*arq
= RQ_DATA(rq
);
1298 WARN_ON(arq
->state
!= AS_RQ_REMOVED
);
1299 arq
->state
= AS_RQ_DISPATCHED
;
1300 if (arq
->io_context
&& arq
->io_context
->aic
)
1301 atomic_inc(&arq
->io_context
->aic
->nr_dispatched
);
1305 * as_queue_empty tells us if there are requests left in the device. It may
1306 * not be the case that a driver can get the next request even if the queue
1307 * is not empty - it is used in the block layer to check for plugging and
1308 * merging opportunities
1310 static int as_queue_empty(request_queue_t
*q
)
1312 struct as_data
*ad
= q
->elevator
->elevator_data
;
1314 return list_empty(&ad
->fifo_list
[REQ_ASYNC
])
1315 && list_empty(&ad
->fifo_list
[REQ_SYNC
]);
1318 static struct request
*as_former_request(request_queue_t
*q
,
1321 struct as_rq
*arq
= RQ_DATA(rq
);
1322 struct rb_node
*rbprev
= rb_prev(&arq
->rb_node
);
1323 struct request
*ret
= NULL
;
1326 ret
= rb_entry_arq(rbprev
)->request
;
1331 static struct request
*as_latter_request(request_queue_t
*q
,
1334 struct as_rq
*arq
= RQ_DATA(rq
);
1335 struct rb_node
*rbnext
= rb_next(&arq
->rb_node
);
1336 struct request
*ret
= NULL
;
1339 ret
= rb_entry_arq(rbnext
)->request
;
1345 as_merge(request_queue_t
*q
, struct request
**req
, struct bio
*bio
)
1347 struct as_data
*ad
= q
->elevator
->elevator_data
;
1348 sector_t rb_key
= bio
->bi_sector
+ bio_sectors(bio
);
1349 struct request
*__rq
;
1352 * check for front merge
1354 __rq
= as_find_arq_rb(ad
, rb_key
, bio_data_dir(bio
));
1355 if (__rq
&& elv_rq_merge_ok(__rq
, bio
)) {
1357 return ELEVATOR_FRONT_MERGE
;
1360 return ELEVATOR_NO_MERGE
;
1363 static void as_merged_request(request_queue_t
*q
, struct request
*req
)
1365 struct as_data
*ad
= q
->elevator
->elevator_data
;
1366 struct as_rq
*arq
= RQ_DATA(req
);
1369 * if the merge was a front merge, we need to reposition request
1371 if (rq_rb_key(req
) != arq
->rb_key
) {
1372 as_del_arq_rb(ad
, arq
);
1373 as_add_arq_rb(ad
, arq
);
1375 * Note! At this stage of this and the next function, our next
1376 * request may not be optimal - eg the request may have "grown"
1377 * behind the disk head. We currently don't bother adjusting.
1382 static void as_merged_requests(request_queue_t
*q
, struct request
*req
,
1383 struct request
*next
)
1385 struct as_data
*ad
= q
->elevator
->elevator_data
;
1386 struct as_rq
*arq
= RQ_DATA(req
);
1387 struct as_rq
*anext
= RQ_DATA(next
);
1392 if (rq_rb_key(req
) != arq
->rb_key
) {
1393 as_del_arq_rb(ad
, arq
);
1394 as_add_arq_rb(ad
, arq
);
1398 * if anext expires before arq, assign its expire time to arq
1399 * and move into anext position (anext will be deleted) in fifo
1401 if (!list_empty(&arq
->fifo
) && !list_empty(&anext
->fifo
)) {
1402 if (time_before(anext
->expires
, arq
->expires
)) {
1403 list_move(&arq
->fifo
, &anext
->fifo
);
1404 arq
->expires
= anext
->expires
;
1406 * Don't copy here but swap, because when anext is
1407 * removed below, it must contain the unused context
1409 swap_io_context(&arq
->io_context
, &anext
->io_context
);
1414 * kill knowledge of next, this one is a goner
1416 as_remove_queued_request(q
, next
);
1417 as_put_io_context(anext
);
1419 anext
->state
= AS_RQ_MERGED
;
1423 * This is executed in a "deferred" process context, by kblockd. It calls the
1424 * driver's request_fn so the driver can submit that request.
1426 * IMPORTANT! This guy will reenter the elevator, so set up all queue global
1427 * state before calling, and don't rely on any state over calls.
1429 * FIXME! dispatch queue is not a queue at all!
1431 static void as_work_handler(void *data
)
1433 struct request_queue
*q
= data
;
1434 unsigned long flags
;
1436 spin_lock_irqsave(q
->queue_lock
, flags
);
1437 if (!as_queue_empty(q
))
1439 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1442 static void as_put_request(request_queue_t
*q
, struct request
*rq
)
1444 struct as_data
*ad
= q
->elevator
->elevator_data
;
1445 struct as_rq
*arq
= RQ_DATA(rq
);
1452 if (unlikely(arq
->state
!= AS_RQ_POSTSCHED
&&
1453 arq
->state
!= AS_RQ_PRESCHED
&&
1454 arq
->state
!= AS_RQ_MERGED
)) {
1455 printk("arq->state %d\n", arq
->state
);
1459 mempool_free(arq
, ad
->arq_pool
);
1460 rq
->elevator_private
= NULL
;
1463 static int as_set_request(request_queue_t
*q
, struct request
*rq
,
1464 struct bio
*bio
, gfp_t gfp_mask
)
1466 struct as_data
*ad
= q
->elevator
->elevator_data
;
1467 struct as_rq
*arq
= mempool_alloc(ad
->arq_pool
, gfp_mask
);
1470 memset(arq
, 0, sizeof(*arq
));
1471 RB_CLEAR_NODE(&arq
->rb_node
);
1473 arq
->state
= AS_RQ_PRESCHED
;
1474 arq
->io_context
= NULL
;
1475 INIT_LIST_HEAD(&arq
->fifo
);
1476 rq
->elevator_private
= arq
;
1483 static int as_may_queue(request_queue_t
*q
, int rw
, struct bio
*bio
)
1485 int ret
= ELV_MQUEUE_MAY
;
1486 struct as_data
*ad
= q
->elevator
->elevator_data
;
1487 struct io_context
*ioc
;
1488 if (ad
->antic_status
== ANTIC_WAIT_REQ
||
1489 ad
->antic_status
== ANTIC_WAIT_NEXT
) {
1490 ioc
= as_get_io_context();
1491 if (ad
->io_context
== ioc
)
1492 ret
= ELV_MQUEUE_MUST
;
1493 put_io_context(ioc
);
1499 static void as_exit_queue(elevator_t
*e
)
1501 struct as_data
*ad
= e
->elevator_data
;
1503 del_timer_sync(&ad
->antic_timer
);
1506 BUG_ON(!list_empty(&ad
->fifo_list
[REQ_SYNC
]));
1507 BUG_ON(!list_empty(&ad
->fifo_list
[REQ_ASYNC
]));
1509 mempool_destroy(ad
->arq_pool
);
1510 put_io_context(ad
->io_context
);
1515 * initialize elevator private data (as_data), and alloc a arq for
1516 * each request on the free lists
1518 static void *as_init_queue(request_queue_t
*q
, elevator_t
*e
)
1525 ad
= kmalloc_node(sizeof(*ad
), GFP_KERNEL
, q
->node
);
1528 memset(ad
, 0, sizeof(*ad
));
1530 ad
->q
= q
; /* Identify what queue the data belongs to */
1532 ad
->arq_pool
= mempool_create_node(BLKDEV_MIN_RQ
, mempool_alloc_slab
,
1533 mempool_free_slab
, arq_pool
, q
->node
);
1534 if (!ad
->arq_pool
) {
1539 /* anticipatory scheduling helpers */
1540 ad
->antic_timer
.function
= as_antic_timeout
;
1541 ad
->antic_timer
.data
= (unsigned long)q
;
1542 init_timer(&ad
->antic_timer
);
1543 INIT_WORK(&ad
->antic_work
, as_work_handler
, q
);
1545 INIT_LIST_HEAD(&ad
->fifo_list
[REQ_SYNC
]);
1546 INIT_LIST_HEAD(&ad
->fifo_list
[REQ_ASYNC
]);
1547 ad
->sort_list
[REQ_SYNC
] = RB_ROOT
;
1548 ad
->sort_list
[REQ_ASYNC
] = RB_ROOT
;
1549 ad
->fifo_expire
[REQ_SYNC
] = default_read_expire
;
1550 ad
->fifo_expire
[REQ_ASYNC
] = default_write_expire
;
1551 ad
->antic_expire
= default_antic_expire
;
1552 ad
->batch_expire
[REQ_SYNC
] = default_read_batch_expire
;
1553 ad
->batch_expire
[REQ_ASYNC
] = default_write_batch_expire
;
1555 ad
->current_batch_expires
= jiffies
+ ad
->batch_expire
[REQ_SYNC
];
1556 ad
->write_batch_count
= ad
->batch_expire
[REQ_ASYNC
] / 10;
1557 if (ad
->write_batch_count
< 2)
1558 ad
->write_batch_count
= 2;
1568 as_var_show(unsigned int var
, char *page
)
1570 return sprintf(page
, "%d\n", var
);
1574 as_var_store(unsigned long *var
, const char *page
, size_t count
)
1576 char *p
= (char *) page
;
1578 *var
= simple_strtoul(p
, &p
, 10);
1582 static ssize_t
est_time_show(elevator_t
*e
, char *page
)
1584 struct as_data
*ad
= e
->elevator_data
;
1587 pos
+= sprintf(page
+pos
, "%lu %% exit probability\n",
1588 100*ad
->exit_prob
/256);
1589 pos
+= sprintf(page
+pos
, "%lu %% probability of exiting without a "
1590 "cooperating process submitting IO\n",
1591 100*ad
->exit_no_coop
/256);
1592 pos
+= sprintf(page
+pos
, "%lu ms new thinktime\n", ad
->new_ttime_mean
);
1593 pos
+= sprintf(page
+pos
, "%llu sectors new seek distance\n",
1594 (unsigned long long)ad
->new_seek_mean
);
1599 #define SHOW_FUNCTION(__FUNC, __VAR) \
1600 static ssize_t __FUNC(elevator_t *e, char *page) \
1602 struct as_data *ad = e->elevator_data; \
1603 return as_var_show(jiffies_to_msecs((__VAR)), (page)); \
1605 SHOW_FUNCTION(as_read_expire_show
, ad
->fifo_expire
[REQ_SYNC
]);
1606 SHOW_FUNCTION(as_write_expire_show
, ad
->fifo_expire
[REQ_ASYNC
]);
1607 SHOW_FUNCTION(as_antic_expire_show
, ad
->antic_expire
);
1608 SHOW_FUNCTION(as_read_batch_expire_show
, ad
->batch_expire
[REQ_SYNC
]);
1609 SHOW_FUNCTION(as_write_batch_expire_show
, ad
->batch_expire
[REQ_ASYNC
]);
1610 #undef SHOW_FUNCTION
1612 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \
1613 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
1615 struct as_data *ad = e->elevator_data; \
1616 int ret = as_var_store(__PTR, (page), count); \
1617 if (*(__PTR) < (MIN)) \
1619 else if (*(__PTR) > (MAX)) \
1621 *(__PTR) = msecs_to_jiffies(*(__PTR)); \
1624 STORE_FUNCTION(as_read_expire_store
, &ad
->fifo_expire
[REQ_SYNC
], 0, INT_MAX
);
1625 STORE_FUNCTION(as_write_expire_store
, &ad
->fifo_expire
[REQ_ASYNC
], 0, INT_MAX
);
1626 STORE_FUNCTION(as_antic_expire_store
, &ad
->antic_expire
, 0, INT_MAX
);
1627 STORE_FUNCTION(as_read_batch_expire_store
,
1628 &ad
->batch_expire
[REQ_SYNC
], 0, INT_MAX
);
1629 STORE_FUNCTION(as_write_batch_expire_store
,
1630 &ad
->batch_expire
[REQ_ASYNC
], 0, INT_MAX
);
1631 #undef STORE_FUNCTION
1633 #define AS_ATTR(name) \
1634 __ATTR(name, S_IRUGO|S_IWUSR, as_##name##_show, as_##name##_store)
1636 static struct elv_fs_entry as_attrs
[] = {
1637 __ATTR_RO(est_time
),
1638 AS_ATTR(read_expire
),
1639 AS_ATTR(write_expire
),
1640 AS_ATTR(antic_expire
),
1641 AS_ATTR(read_batch_expire
),
1642 AS_ATTR(write_batch_expire
),
1646 static struct elevator_type iosched_as
= {
1648 .elevator_merge_fn
= as_merge
,
1649 .elevator_merged_fn
= as_merged_request
,
1650 .elevator_merge_req_fn
= as_merged_requests
,
1651 .elevator_dispatch_fn
= as_dispatch_request
,
1652 .elevator_add_req_fn
= as_add_request
,
1653 .elevator_activate_req_fn
= as_activate_request
,
1654 .elevator_deactivate_req_fn
= as_deactivate_request
,
1655 .elevator_queue_empty_fn
= as_queue_empty
,
1656 .elevator_completed_req_fn
= as_completed_request
,
1657 .elevator_former_req_fn
= as_former_request
,
1658 .elevator_latter_req_fn
= as_latter_request
,
1659 .elevator_set_req_fn
= as_set_request
,
1660 .elevator_put_req_fn
= as_put_request
,
1661 .elevator_may_queue_fn
= as_may_queue
,
1662 .elevator_init_fn
= as_init_queue
,
1663 .elevator_exit_fn
= as_exit_queue
,
1667 .elevator_attrs
= as_attrs
,
1668 .elevator_name
= "anticipatory",
1669 .elevator_owner
= THIS_MODULE
,
1672 static int __init
as_init(void)
1676 arq_pool
= kmem_cache_create("as_arq", sizeof(struct as_rq
),
1681 ret
= elv_register(&iosched_as
);
1684 * don't allow AS to get unregistered, since we would have
1685 * to browse all tasks in the system and release their
1686 * as_io_context first
1688 __module_get(THIS_MODULE
);
1692 kmem_cache_destroy(arq_pool
);
1696 static void __exit
as_exit(void)
1698 DECLARE_COMPLETION(all_gone
);
1699 elv_unregister(&iosched_as
);
1700 ioc_gone
= &all_gone
;
1701 /* ioc_gone's update must be visible before reading ioc_count */
1703 if (atomic_read(&ioc_count
))
1704 wait_for_completion(ioc_gone
);
1706 kmem_cache_destroy(arq_pool
);
1709 module_init(as_init
);
1710 module_exit(as_exit
);
1712 MODULE_AUTHOR("Nick Piggin");
1713 MODULE_LICENSE("GPL");
1714 MODULE_DESCRIPTION("anticipatory IO scheduler");