blob: 296708ceceb2d62a8bacd8a954efeb1108d5547e [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002 * Anticipatory & deadline i/o scheduler.
3 *
4 * Copyright (C) 2002 Jens Axboe <axboe@suse.de>
Nick Pigginf5b3db02005-11-07 00:59:53 -08005 * Nick Piggin <nickpiggin@yahoo.com.au>
Linus Torvalds1da177e2005-04-16 15:20:36 -07006 *
7 */
8#include <linux/kernel.h>
9#include <linux/fs.h>
10#include <linux/blkdev.h>
11#include <linux/elevator.h>
12#include <linux/bio.h>
13#include <linux/config.h>
14#include <linux/module.h>
15#include <linux/slab.h>
16#include <linux/init.h>
17#include <linux/compiler.h>
18#include <linux/hash.h>
19#include <linux/rbtree.h>
20#include <linux/interrupt.h>
21
22#define REQ_SYNC 1
23#define REQ_ASYNC 0
24
25/*
26 * See Documentation/block/as-iosched.txt
27 */
28
29/*
30 * max time before a read is submitted.
31 */
32#define default_read_expire (HZ / 8)
33
34/*
35 * ditto for writes, these limits are not hard, even
36 * if the disk is capable of satisfying them.
37 */
38#define default_write_expire (HZ / 4)
39
40/*
41 * read_batch_expire describes how long we will allow a stream of reads to
42 * persist before looking to see whether it is time to switch over to writes.
43 */
44#define default_read_batch_expire (HZ / 2)
45
46/*
47 * write_batch_expire describes how long we want a stream of writes to run for.
48 * This is not a hard limit, but a target we set for the auto-tuning thingy.
49 * See, the problem is: we can send a lot of writes to disk cache / TCQ in
50 * a short amount of time...
51 */
52#define default_write_batch_expire (HZ / 8)
53
54/*
55 * max time we may wait to anticipate a read (default around 6ms)
56 */
57#define default_antic_expire ((HZ / 150) ? HZ / 150 : 1)
58
59/*
60 * Keep track of up to 20ms thinktimes. We can go as big as we like here,
61 * however huge values tend to interfere and not decay fast enough. A program
62 * might be in a non-io phase of operation. Waiting on user input for example,
63 * or doing a lengthy computation. A small penalty can be justified there, and
64 * will still catch out those processes that constantly have large thinktimes.
65 */
66#define MAX_THINKTIME (HZ/50UL)
67
68/* Bits in as_io_context.state */
69enum as_io_states {
Nick Pigginf5b3db02005-11-07 00:59:53 -080070 AS_TASK_RUNNING=0, /* Process has not exited */
Linus Torvalds1da177e2005-04-16 15:20:36 -070071 AS_TASK_IOSTARTED, /* Process has started some IO */
72 AS_TASK_IORUNNING, /* Process has completed some IO */
73};
74
75enum anticipation_status {
76 ANTIC_OFF=0, /* Not anticipating (normal operation) */
77 ANTIC_WAIT_REQ, /* The last read has not yet completed */
78 ANTIC_WAIT_NEXT, /* Currently anticipating a request vs
79 last read (which has completed) */
80 ANTIC_FINISHED, /* Anticipating but have found a candidate
81 * or timed out */
82};
83
84struct as_data {
85 /*
86 * run time data
87 */
88
89 struct request_queue *q; /* the "owner" queue */
90
91 /*
92 * requests (as_rq s) are present on both sort_list and fifo_list
93 */
94 struct rb_root sort_list[2];
95 struct list_head fifo_list[2];
96
97 struct as_rq *next_arq[2]; /* next in sort order */
98 sector_t last_sector[2]; /* last REQ_SYNC & REQ_ASYNC sectors */
Linus Torvalds1da177e2005-04-16 15:20:36 -070099 struct list_head *hash; /* request hash */
100
101 unsigned long exit_prob; /* probability a task will exit while
102 being waited on */
Nick Pigginf5b3db02005-11-07 00:59:53 -0800103 unsigned long exit_no_coop; /* probablility an exited task will
104 not be part of a later cooperating
105 request */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106 unsigned long new_ttime_total; /* mean thinktime on new proc */
107 unsigned long new_ttime_mean;
108 u64 new_seek_total; /* mean seek on new proc */
109 sector_t new_seek_mean;
110
111 unsigned long current_batch_expires;
112 unsigned long last_check_fifo[2];
113 int changed_batch; /* 1: waiting for old batch to end */
114 int new_batch; /* 1: waiting on first read complete */
115 int batch_data_dir; /* current batch REQ_SYNC / REQ_ASYNC */
116 int write_batch_count; /* max # of reqs in a write batch */
117 int current_write_count; /* how many requests left this batch */
118 int write_batch_idled; /* has the write batch gone idle? */
119 mempool_t *arq_pool;
120
121 enum anticipation_status antic_status;
122 unsigned long antic_start; /* jiffies: when it started */
123 struct timer_list antic_timer; /* anticipatory scheduling timer */
124 struct work_struct antic_work; /* Deferred unplugging */
125 struct io_context *io_context; /* Identify the expected process */
126 int ioc_finished; /* IO associated with io_context is finished */
127 int nr_dispatched;
128
129 /*
130 * settings that change how the i/o scheduler behaves
131 */
132 unsigned long fifo_expire[2];
133 unsigned long batch_expire[2];
134 unsigned long antic_expire;
135};
136
137#define list_entry_fifo(ptr) list_entry((ptr), struct as_rq, fifo)
138
139/*
140 * per-request data.
141 */
142enum arq_state {
143 AS_RQ_NEW=0, /* New - not referenced and not on any lists */
144 AS_RQ_QUEUED, /* In the request queue. It belongs to the
145 scheduler */
146 AS_RQ_DISPATCHED, /* On the dispatch list. It belongs to the
147 driver now */
148 AS_RQ_PRESCHED, /* Debug poisoning for requests being used */
149 AS_RQ_REMOVED,
150 AS_RQ_MERGED,
151 AS_RQ_POSTSCHED, /* when they shouldn't be */
152};
153
154struct as_rq {
155 /*
156 * rbtree index, key is the starting offset
157 */
158 struct rb_node rb_node;
159 sector_t rb_key;
160
161 struct request *request;
162
163 struct io_context *io_context; /* The submitting task */
164
165 /*
166 * request hash, key is the ending offset (for back merge lookup)
167 */
168 struct list_head hash;
169 unsigned int on_hash;
170
171 /*
172 * expire fifo
173 */
174 struct list_head fifo;
175 unsigned long expires;
176
177 unsigned int is_sync;
178 enum arq_state state;
179};
180
181#define RQ_DATA(rq) ((struct as_rq *) (rq)->elevator_private)
182
183static kmem_cache_t *arq_pool;
184
Al Viro334e94d2006-03-18 15:05:53 -0500185static atomic_t ioc_count = ATOMIC_INIT(0);
186static struct completion *ioc_gone;
187
Tejun Heoef9be1d2005-11-11 14:27:09 +0100188static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq);
189static void as_antic_stop(struct as_data *ad);
190
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191/*
192 * IO Context helper functions
193 */
194
195/* Called to deallocate the as_io_context */
196static void free_as_io_context(struct as_io_context *aic)
197{
198 kfree(aic);
Al Viro334e94d2006-03-18 15:05:53 -0500199 if (atomic_dec_and_test(&ioc_count) && ioc_gone)
200 complete(ioc_gone);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700201}
202
Al Viroe17a9482006-03-18 13:21:20 -0500203static void as_trim(struct io_context *ioc)
204{
Al Viro334e94d2006-03-18 15:05:53 -0500205 if (ioc->aic)
206 free_as_io_context(ioc->aic);
Al Viroe17a9482006-03-18 13:21:20 -0500207 ioc->aic = NULL;
208}
209
Linus Torvalds1da177e2005-04-16 15:20:36 -0700210/* Called when the task exits */
211static void exit_as_io_context(struct as_io_context *aic)
212{
213 WARN_ON(!test_bit(AS_TASK_RUNNING, &aic->state));
214 clear_bit(AS_TASK_RUNNING, &aic->state);
215}
216
217static struct as_io_context *alloc_as_io_context(void)
218{
219 struct as_io_context *ret;
220
221 ret = kmalloc(sizeof(*ret), GFP_ATOMIC);
222 if (ret) {
223 ret->dtor = free_as_io_context;
224 ret->exit = exit_as_io_context;
225 ret->state = 1 << AS_TASK_RUNNING;
226 atomic_set(&ret->nr_queued, 0);
227 atomic_set(&ret->nr_dispatched, 0);
228 spin_lock_init(&ret->lock);
229 ret->ttime_total = 0;
230 ret->ttime_samples = 0;
231 ret->ttime_mean = 0;
232 ret->seek_total = 0;
233 ret->seek_samples = 0;
234 ret->seek_mean = 0;
Al Viro334e94d2006-03-18 15:05:53 -0500235 atomic_inc(&ioc_count);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700236 }
237
238 return ret;
239}
240
241/*
242 * If the current task has no AS IO context then create one and initialise it.
243 * Then take a ref on the task's io context and return it.
244 */
245static struct io_context *as_get_io_context(void)
246{
247 struct io_context *ioc = get_io_context(GFP_ATOMIC);
248 if (ioc && !ioc->aic) {
249 ioc->aic = alloc_as_io_context();
250 if (!ioc->aic) {
251 put_io_context(ioc);
252 ioc = NULL;
253 }
254 }
255 return ioc;
256}
257
Jens Axboeb4878f22005-10-20 16:42:29 +0200258static void as_put_io_context(struct as_rq *arq)
259{
260 struct as_io_context *aic;
261
262 if (unlikely(!arq->io_context))
263 return;
264
265 aic = arq->io_context->aic;
266
267 if (arq->is_sync == REQ_SYNC && aic) {
268 spin_lock(&aic->lock);
269 set_bit(AS_TASK_IORUNNING, &aic->state);
270 aic->last_end_request = jiffies;
271 spin_unlock(&aic->lock);
272 }
273
274 put_io_context(arq->io_context);
275}
276
Linus Torvalds1da177e2005-04-16 15:20:36 -0700277/*
278 * the back merge hash support functions
279 */
280static const int as_hash_shift = 6;
281#define AS_HASH_BLOCK(sec) ((sec) >> 3)
282#define AS_HASH_FN(sec) (hash_long(AS_HASH_BLOCK((sec)), as_hash_shift))
283#define AS_HASH_ENTRIES (1 << as_hash_shift)
284#define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors)
285#define list_entry_hash(ptr) list_entry((ptr), struct as_rq, hash)
286
287static inline void __as_del_arq_hash(struct as_rq *arq)
288{
289 arq->on_hash = 0;
290 list_del_init(&arq->hash);
291}
292
293static inline void as_del_arq_hash(struct as_rq *arq)
294{
295 if (arq->on_hash)
296 __as_del_arq_hash(arq);
297}
298
Linus Torvalds1da177e2005-04-16 15:20:36 -0700299static void as_add_arq_hash(struct as_data *ad, struct as_rq *arq)
300{
301 struct request *rq = arq->request;
302
303 BUG_ON(arq->on_hash);
304
305 arq->on_hash = 1;
306 list_add(&arq->hash, &ad->hash[AS_HASH_FN(rq_hash_key(rq))]);
307}
308
309/*
310 * move hot entry to front of chain
311 */
312static inline void as_hot_arq_hash(struct as_data *ad, struct as_rq *arq)
313{
314 struct request *rq = arq->request;
315 struct list_head *head = &ad->hash[AS_HASH_FN(rq_hash_key(rq))];
316
317 if (!arq->on_hash) {
318 WARN_ON(1);
319 return;
320 }
321
322 if (arq->hash.prev != head) {
323 list_del(&arq->hash);
324 list_add(&arq->hash, head);
325 }
326}
327
328static struct request *as_find_arq_hash(struct as_data *ad, sector_t offset)
329{
330 struct list_head *hash_list = &ad->hash[AS_HASH_FN(offset)];
331 struct list_head *entry, *next = hash_list->next;
332
333 while ((entry = next) != hash_list) {
334 struct as_rq *arq = list_entry_hash(entry);
335 struct request *__rq = arq->request;
336
337 next = entry->next;
338
339 BUG_ON(!arq->on_hash);
340
341 if (!rq_mergeable(__rq)) {
Tejun Heo98b11472005-10-20 16:46:54 +0200342 as_del_arq_hash(arq);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700343 continue;
344 }
345
346 if (rq_hash_key(__rq) == offset)
347 return __rq;
348 }
349
350 return NULL;
351}
352
353/*
354 * rb tree support functions
355 */
356#define RB_NONE (2)
357#define RB_EMPTY(root) ((root)->rb_node == NULL)
358#define ON_RB(node) ((node)->rb_color != RB_NONE)
359#define RB_CLEAR(node) ((node)->rb_color = RB_NONE)
360#define rb_entry_arq(node) rb_entry((node), struct as_rq, rb_node)
361#define ARQ_RB_ROOT(ad, arq) (&(ad)->sort_list[(arq)->is_sync])
362#define rq_rb_key(rq) (rq)->sector
363
364/*
365 * as_find_first_arq finds the first (lowest sector numbered) request
366 * for the specified data_dir. Used to sweep back to the start of the disk
367 * (1-way elevator) after we process the last (highest sector) request.
368 */
369static struct as_rq *as_find_first_arq(struct as_data *ad, int data_dir)
370{
371 struct rb_node *n = ad->sort_list[data_dir].rb_node;
372
373 if (n == NULL)
374 return NULL;
375
376 for (;;) {
377 if (n->rb_left == NULL)
378 return rb_entry_arq(n);
379
380 n = n->rb_left;
381 }
382}
383
384/*
385 * Add the request to the rb tree if it is unique. If there is an alias (an
386 * existing request against the same sector), which can happen when using
387 * direct IO, then return the alias.
388 */
Tejun Heoef9be1d2005-11-11 14:27:09 +0100389static struct as_rq *__as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700390{
391 struct rb_node **p = &ARQ_RB_ROOT(ad, arq)->rb_node;
392 struct rb_node *parent = NULL;
393 struct as_rq *__arq;
394 struct request *rq = arq->request;
395
396 arq->rb_key = rq_rb_key(rq);
397
398 while (*p) {
399 parent = *p;
400 __arq = rb_entry_arq(parent);
401
402 if (arq->rb_key < __arq->rb_key)
403 p = &(*p)->rb_left;
404 else if (arq->rb_key > __arq->rb_key)
405 p = &(*p)->rb_right;
406 else
407 return __arq;
408 }
409
410 rb_link_node(&arq->rb_node, parent, p);
411 rb_insert_color(&arq->rb_node, ARQ_RB_ROOT(ad, arq));
412
413 return NULL;
414}
415
Tejun Heoef9be1d2005-11-11 14:27:09 +0100416static void as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
417{
418 struct as_rq *alias;
419
420 while ((unlikely(alias = __as_add_arq_rb(ad, arq)))) {
421 as_move_to_dispatch(ad, alias);
422 as_antic_stop(ad);
423 }
424}
425
Linus Torvalds1da177e2005-04-16 15:20:36 -0700426static inline void as_del_arq_rb(struct as_data *ad, struct as_rq *arq)
427{
428 if (!ON_RB(&arq->rb_node)) {
429 WARN_ON(1);
430 return;
431 }
432
433 rb_erase(&arq->rb_node, ARQ_RB_ROOT(ad, arq));
434 RB_CLEAR(&arq->rb_node);
435}
436
437static struct request *
438as_find_arq_rb(struct as_data *ad, sector_t sector, int data_dir)
439{
440 struct rb_node *n = ad->sort_list[data_dir].rb_node;
441 struct as_rq *arq;
442
443 while (n) {
444 arq = rb_entry_arq(n);
445
446 if (sector < arq->rb_key)
447 n = n->rb_left;
448 else if (sector > arq->rb_key)
449 n = n->rb_right;
450 else
451 return arq->request;
452 }
453
454 return NULL;
455}
456
457/*
458 * IO Scheduler proper
459 */
460
461#define MAXBACK (1024 * 1024) /*
462 * Maximum distance the disk will go backward
463 * for a request.
464 */
465
466#define BACK_PENALTY 2
467
468/*
469 * as_choose_req selects the preferred one of two requests of the same data_dir
470 * ignoring time - eg. timeouts, which is the job of as_dispatch_request
471 */
472static struct as_rq *
473as_choose_req(struct as_data *ad, struct as_rq *arq1, struct as_rq *arq2)
474{
475 int data_dir;
476 sector_t last, s1, s2, d1, d2;
477 int r1_wrap=0, r2_wrap=0; /* requests are behind the disk head */
478 const sector_t maxback = MAXBACK;
479
480 if (arq1 == NULL || arq1 == arq2)
481 return arq2;
482 if (arq2 == NULL)
483 return arq1;
484
485 data_dir = arq1->is_sync;
486
487 last = ad->last_sector[data_dir];
488 s1 = arq1->request->sector;
489 s2 = arq2->request->sector;
490
491 BUG_ON(data_dir != arq2->is_sync);
492
493 /*
494 * Strict one way elevator _except_ in the case where we allow
495 * short backward seeks which are biased as twice the cost of a
496 * similar forward seek.
497 */
498 if (s1 >= last)
499 d1 = s1 - last;
500 else if (s1+maxback >= last)
501 d1 = (last - s1)*BACK_PENALTY;
502 else {
503 r1_wrap = 1;
504 d1 = 0; /* shut up, gcc */
505 }
506
507 if (s2 >= last)
508 d2 = s2 - last;
509 else if (s2+maxback >= last)
510 d2 = (last - s2)*BACK_PENALTY;
511 else {
512 r2_wrap = 1;
513 d2 = 0;
514 }
515
516 /* Found required data */
517 if (!r1_wrap && r2_wrap)
518 return arq1;
519 else if (!r2_wrap && r1_wrap)
520 return arq2;
521 else if (r1_wrap && r2_wrap) {
522 /* both behind the head */
523 if (s1 <= s2)
524 return arq1;
525 else
526 return arq2;
527 }
528
529 /* Both requests in front of the head */
530 if (d1 < d2)
531 return arq1;
532 else if (d2 < d1)
533 return arq2;
534 else {
535 if (s1 >= s2)
536 return arq1;
537 else
538 return arq2;
539 }
540}
541
542/*
543 * as_find_next_arq finds the next request after @prev in elevator order.
544 * this with as_choose_req form the basis for how the scheduler chooses
545 * what request to process next. Anticipation works on top of this.
546 */
547static struct as_rq *as_find_next_arq(struct as_data *ad, struct as_rq *last)
548{
549 const int data_dir = last->is_sync;
550 struct as_rq *ret;
551 struct rb_node *rbnext = rb_next(&last->rb_node);
552 struct rb_node *rbprev = rb_prev(&last->rb_node);
553 struct as_rq *arq_next, *arq_prev;
554
555 BUG_ON(!ON_RB(&last->rb_node));
556
557 if (rbprev)
558 arq_prev = rb_entry_arq(rbprev);
559 else
560 arq_prev = NULL;
561
562 if (rbnext)
563 arq_next = rb_entry_arq(rbnext);
564 else {
565 arq_next = as_find_first_arq(ad, data_dir);
566 if (arq_next == last)
567 arq_next = NULL;
568 }
569
570 ret = as_choose_req(ad, arq_next, arq_prev);
571
572 return ret;
573}
574
575/*
576 * anticipatory scheduling functions follow
577 */
578
579/*
580 * as_antic_expired tells us when we have anticipated too long.
581 * The funny "absolute difference" math on the elapsed time is to handle
582 * jiffy wraps, and disks which have been idle for 0x80000000 jiffies.
583 */
584static int as_antic_expired(struct as_data *ad)
585{
586 long delta_jif;
587
588 delta_jif = jiffies - ad->antic_start;
589 if (unlikely(delta_jif < 0))
590 delta_jif = -delta_jif;
591 if (delta_jif < ad->antic_expire)
592 return 0;
593
594 return 1;
595}
596
597/*
598 * as_antic_waitnext starts anticipating that a nice request will soon be
599 * submitted. See also as_antic_waitreq
600 */
601static void as_antic_waitnext(struct as_data *ad)
602{
603 unsigned long timeout;
604
605 BUG_ON(ad->antic_status != ANTIC_OFF
606 && ad->antic_status != ANTIC_WAIT_REQ);
607
608 timeout = ad->antic_start + ad->antic_expire;
609
610 mod_timer(&ad->antic_timer, timeout);
611
612 ad->antic_status = ANTIC_WAIT_NEXT;
613}
614
615/*
616 * as_antic_waitreq starts anticipating. We don't start timing the anticipation
617 * until the request that we're anticipating on has finished. This means we
618 * are timing from when the candidate process wakes up hopefully.
619 */
620static void as_antic_waitreq(struct as_data *ad)
621{
622 BUG_ON(ad->antic_status == ANTIC_FINISHED);
623 if (ad->antic_status == ANTIC_OFF) {
624 if (!ad->io_context || ad->ioc_finished)
625 as_antic_waitnext(ad);
626 else
627 ad->antic_status = ANTIC_WAIT_REQ;
628 }
629}
630
631/*
632 * This is called directly by the functions in this file to stop anticipation.
633 * We kill the timer and schedule a call to the request_fn asap.
634 */
635static void as_antic_stop(struct as_data *ad)
636{
637 int status = ad->antic_status;
638
639 if (status == ANTIC_WAIT_REQ || status == ANTIC_WAIT_NEXT) {
640 if (status == ANTIC_WAIT_NEXT)
641 del_timer(&ad->antic_timer);
642 ad->antic_status = ANTIC_FINISHED;
643 /* see as_work_handler */
644 kblockd_schedule_work(&ad->antic_work);
645 }
646}
647
648/*
649 * as_antic_timeout is the timer function set by as_antic_waitnext.
650 */
651static void as_antic_timeout(unsigned long data)
652{
653 struct request_queue *q = (struct request_queue *)data;
654 struct as_data *ad = q->elevator->elevator_data;
655 unsigned long flags;
656
657 spin_lock_irqsave(q->queue_lock, flags);
658 if (ad->antic_status == ANTIC_WAIT_REQ
659 || ad->antic_status == ANTIC_WAIT_NEXT) {
660 struct as_io_context *aic = ad->io_context->aic;
661
662 ad->antic_status = ANTIC_FINISHED;
663 kblockd_schedule_work(&ad->antic_work);
664
665 if (aic->ttime_samples == 0) {
Nick Pigginf5b3db02005-11-07 00:59:53 -0800666 /* process anticipated on has exited or timed out*/
Linus Torvalds1da177e2005-04-16 15:20:36 -0700667 ad->exit_prob = (7*ad->exit_prob + 256)/8;
668 }
Nick Pigginf5b3db02005-11-07 00:59:53 -0800669 if (!test_bit(AS_TASK_RUNNING, &aic->state)) {
670 /* process not "saved" by a cooperating request */
671 ad->exit_no_coop = (7*ad->exit_no_coop + 256)/8;
672 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700673 }
674 spin_unlock_irqrestore(q->queue_lock, flags);
675}
676
Nick Pigginf5b3db02005-11-07 00:59:53 -0800677static void as_update_thinktime(struct as_data *ad, struct as_io_context *aic,
678 unsigned long ttime)
679{
680 /* fixed point: 1.0 == 1<<8 */
681 if (aic->ttime_samples == 0) {
682 ad->new_ttime_total = (7*ad->new_ttime_total + 256*ttime) / 8;
683 ad->new_ttime_mean = ad->new_ttime_total / 256;
684
685 ad->exit_prob = (7*ad->exit_prob)/8;
686 }
687 aic->ttime_samples = (7*aic->ttime_samples + 256) / 8;
688 aic->ttime_total = (7*aic->ttime_total + 256*ttime) / 8;
689 aic->ttime_mean = (aic->ttime_total + 128) / aic->ttime_samples;
690}
691
692static void as_update_seekdist(struct as_data *ad, struct as_io_context *aic,
693 sector_t sdist)
694{
695 u64 total;
696
697 if (aic->seek_samples == 0) {
698 ad->new_seek_total = (7*ad->new_seek_total + 256*(u64)sdist)/8;
699 ad->new_seek_mean = ad->new_seek_total / 256;
700 }
701
702 /*
703 * Don't allow the seek distance to get too large from the
704 * odd fragment, pagein, etc
705 */
706 if (aic->seek_samples <= 60) /* second&third seek */
707 sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*1024);
708 else
709 sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*64);
710
711 aic->seek_samples = (7*aic->seek_samples + 256) / 8;
712 aic->seek_total = (7*aic->seek_total + (u64)256*sdist) / 8;
713 total = aic->seek_total + (aic->seek_samples/2);
714 do_div(total, aic->seek_samples);
715 aic->seek_mean = (sector_t)total;
716}
717
718/*
719 * as_update_iohist keeps a decaying histogram of IO thinktimes, and
720 * updates @aic->ttime_mean based on that. It is called when a new
721 * request is queued.
722 */
723static void as_update_iohist(struct as_data *ad, struct as_io_context *aic,
724 struct request *rq)
725{
726 struct as_rq *arq = RQ_DATA(rq);
727 int data_dir = arq->is_sync;
728 unsigned long thinktime = 0;
729 sector_t seek_dist;
730
731 if (aic == NULL)
732 return;
733
734 if (data_dir == REQ_SYNC) {
735 unsigned long in_flight = atomic_read(&aic->nr_queued)
736 + atomic_read(&aic->nr_dispatched);
737 spin_lock(&aic->lock);
738 if (test_bit(AS_TASK_IORUNNING, &aic->state) ||
739 test_bit(AS_TASK_IOSTARTED, &aic->state)) {
740 /* Calculate read -> read thinktime */
741 if (test_bit(AS_TASK_IORUNNING, &aic->state)
742 && in_flight == 0) {
743 thinktime = jiffies - aic->last_end_request;
744 thinktime = min(thinktime, MAX_THINKTIME-1);
745 }
746 as_update_thinktime(ad, aic, thinktime);
747
748 /* Calculate read -> read seek distance */
749 if (aic->last_request_pos < rq->sector)
750 seek_dist = rq->sector - aic->last_request_pos;
751 else
752 seek_dist = aic->last_request_pos - rq->sector;
753 as_update_seekdist(ad, aic, seek_dist);
754 }
755 aic->last_request_pos = rq->sector + rq->nr_sectors;
756 set_bit(AS_TASK_IOSTARTED, &aic->state);
757 spin_unlock(&aic->lock);
758 }
759}
760
Linus Torvalds1da177e2005-04-16 15:20:36 -0700761/*
762 * as_close_req decides if one request is considered "close" to the
763 * previous one issued.
764 */
Nick Pigginf5b3db02005-11-07 00:59:53 -0800765static int as_close_req(struct as_data *ad, struct as_io_context *aic,
766 struct as_rq *arq)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700767{
768 unsigned long delay; /* milliseconds */
769 sector_t last = ad->last_sector[ad->batch_data_dir];
770 sector_t next = arq->request->sector;
771 sector_t delta; /* acceptable close offset (in sectors) */
Nick Pigginf5b3db02005-11-07 00:59:53 -0800772 sector_t s;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700773
774 if (ad->antic_status == ANTIC_OFF || !ad->ioc_finished)
775 delay = 0;
776 else
777 delay = ((jiffies - ad->antic_start) * 1000) / HZ;
778
Nick Pigginf5b3db02005-11-07 00:59:53 -0800779 if (delay == 0)
780 delta = 8192;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700781 else if (delay <= 20 && delay <= ad->antic_expire)
Nick Pigginf5b3db02005-11-07 00:59:53 -0800782 delta = 8192 << delay;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700783 else
784 return 1;
785
Nick Pigginf5b3db02005-11-07 00:59:53 -0800786 if ((last <= next + (delta>>1)) && (next <= last + delta))
787 return 1;
788
789 if (last < next)
790 s = next - last;
791 else
792 s = last - next;
793
794 if (aic->seek_samples == 0) {
795 /*
796 * Process has just started IO. Use past statistics to
797 * gauge success possibility
798 */
799 if (ad->new_seek_mean > s) {
800 /* this request is better than what we're expecting */
801 return 1;
802 }
803
804 } else {
805 if (aic->seek_mean > s) {
806 /* this request is better than what we're expecting */
807 return 1;
808 }
809 }
810
811 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700812}
813
814/*
815 * as_can_break_anticipation returns true if we have been anticipating this
816 * request.
817 *
818 * It also returns true if the process against which we are anticipating
819 * submits a write - that's presumably an fsync, O_SYNC write, etc. We want to
820 * dispatch it ASAP, because we know that application will not be submitting
821 * any new reads.
822 *
Nick Pigginf5b3db02005-11-07 00:59:53 -0800823 * If the task which has submitted the request has exited, break anticipation.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700824 *
825 * If this task has queued some other IO, do not enter enticipation.
826 */
827static int as_can_break_anticipation(struct as_data *ad, struct as_rq *arq)
828{
829 struct io_context *ioc;
830 struct as_io_context *aic;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700831
832 ioc = ad->io_context;
833 BUG_ON(!ioc);
834
835 if (arq && ioc == arq->io_context) {
836 /* request from same process */
837 return 1;
838 }
839
840 if (ad->ioc_finished && as_antic_expired(ad)) {
841 /*
842 * In this situation status should really be FINISHED,
843 * however the timer hasn't had the chance to run yet.
844 */
845 return 1;
846 }
847
848 aic = ioc->aic;
849 if (!aic)
850 return 0;
851
Linus Torvalds1da177e2005-04-16 15:20:36 -0700852 if (atomic_read(&aic->nr_queued) > 0) {
853 /* process has more requests queued */
854 return 1;
855 }
856
857 if (atomic_read(&aic->nr_dispatched) > 0) {
858 /* process has more requests dispatched */
859 return 1;
860 }
861
Nick Pigginf5b3db02005-11-07 00:59:53 -0800862 if (arq && arq->is_sync == REQ_SYNC && as_close_req(ad, aic, arq)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700863 /*
864 * Found a close request that is not one of ours.
865 *
Nick Pigginf5b3db02005-11-07 00:59:53 -0800866 * This makes close requests from another process update
867 * our IO history. Is generally useful when there are
Linus Torvalds1da177e2005-04-16 15:20:36 -0700868 * two or more cooperating processes working in the same
869 * area.
870 */
Nick Pigginf5b3db02005-11-07 00:59:53 -0800871 if (!test_bit(AS_TASK_RUNNING, &aic->state)) {
872 if (aic->ttime_samples == 0)
873 ad->exit_prob = (7*ad->exit_prob + 256)/8;
874
875 ad->exit_no_coop = (7*ad->exit_no_coop)/8;
876 }
877
878 as_update_iohist(ad, aic, arq->request);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700879 return 1;
880 }
881
Nick Pigginf5b3db02005-11-07 00:59:53 -0800882 if (!test_bit(AS_TASK_RUNNING, &aic->state)) {
883 /* process anticipated on has exited */
884 if (aic->ttime_samples == 0)
885 ad->exit_prob = (7*ad->exit_prob + 256)/8;
886
887 if (ad->exit_no_coop > 128)
888 return 1;
889 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700890
891 if (aic->ttime_samples == 0) {
892 if (ad->new_ttime_mean > ad->antic_expire)
893 return 1;
Nick Pigginf5b3db02005-11-07 00:59:53 -0800894 if (ad->exit_prob * ad->exit_no_coop > 128*256)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700895 return 1;
896 } else if (aic->ttime_mean > ad->antic_expire) {
897 /* the process thinks too much between requests */
898 return 1;
899 }
900
Linus Torvalds1da177e2005-04-16 15:20:36 -0700901 return 0;
902}
903
904/*
905 * as_can_anticipate indicates weather we should either run arq
906 * or keep anticipating a better request.
907 */
908static int as_can_anticipate(struct as_data *ad, struct as_rq *arq)
909{
910 if (!ad->io_context)
911 /*
912 * Last request submitted was a write
913 */
914 return 0;
915
916 if (ad->antic_status == ANTIC_FINISHED)
917 /*
918 * Don't restart if we have just finished. Run the next request
919 */
920 return 0;
921
922 if (as_can_break_anticipation(ad, arq))
923 /*
924 * This request is a good candidate. Don't keep anticipating,
925 * run it.
926 */
927 return 0;
928
929 /*
930 * OK from here, we haven't finished, and don't have a decent request!
931 * Status is either ANTIC_OFF so start waiting,
932 * ANTIC_WAIT_REQ so continue waiting for request to finish
933 * or ANTIC_WAIT_NEXT so continue waiting for an acceptable request.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700934 */
935
936 return 1;
937}
938
Linus Torvalds1da177e2005-04-16 15:20:36 -0700939/*
940 * as_update_arq must be called whenever a request (arq) is added to
941 * the sort_list. This function keeps caches up to date, and checks if the
942 * request might be one we are "anticipating"
943 */
944static void as_update_arq(struct as_data *ad, struct as_rq *arq)
945{
946 const int data_dir = arq->is_sync;
947
948 /* keep the next_arq cache up to date */
949 ad->next_arq[data_dir] = as_choose_req(ad, arq, ad->next_arq[data_dir]);
950
951 /*
952 * have we been anticipating this request?
953 * or does it come from the same process as the one we are anticipating
954 * for?
955 */
956 if (ad->antic_status == ANTIC_WAIT_REQ
957 || ad->antic_status == ANTIC_WAIT_NEXT) {
958 if (as_can_break_anticipation(ad, arq))
959 as_antic_stop(ad);
960 }
961}
962
963/*
964 * Gathers timings and resizes the write batch automatically
965 */
966static void update_write_batch(struct as_data *ad)
967{
968 unsigned long batch = ad->batch_expire[REQ_ASYNC];
969 long write_time;
970
971 write_time = (jiffies - ad->current_batch_expires) + batch;
972 if (write_time < 0)
973 write_time = 0;
974
975 if (write_time > batch && !ad->write_batch_idled) {
976 if (write_time > batch * 3)
977 ad->write_batch_count /= 2;
978 else
979 ad->write_batch_count--;
980 } else if (write_time < batch && ad->current_write_count == 0) {
981 if (batch > write_time * 3)
982 ad->write_batch_count *= 2;
983 else
984 ad->write_batch_count++;
985 }
986
987 if (ad->write_batch_count < 1)
988 ad->write_batch_count = 1;
989}
990
991/*
992 * as_completed_request is to be called when a request has completed and
993 * returned something to the requesting process, be it an error or data.
994 */
995static void as_completed_request(request_queue_t *q, struct request *rq)
996{
997 struct as_data *ad = q->elevator->elevator_data;
998 struct as_rq *arq = RQ_DATA(rq);
999
1000 WARN_ON(!list_empty(&rq->queuelist));
1001
Linus Torvalds1da177e2005-04-16 15:20:36 -07001002 if (arq->state != AS_RQ_REMOVED) {
1003 printk("arq->state %d\n", arq->state);
1004 WARN_ON(1);
1005 goto out;
1006 }
1007
Linus Torvalds1da177e2005-04-16 15:20:36 -07001008 if (ad->changed_batch && ad->nr_dispatched == 1) {
1009 kblockd_schedule_work(&ad->antic_work);
1010 ad->changed_batch = 0;
1011
1012 if (ad->batch_data_dir == REQ_SYNC)
1013 ad->new_batch = 1;
1014 }
1015 WARN_ON(ad->nr_dispatched == 0);
1016 ad->nr_dispatched--;
1017
1018 /*
1019 * Start counting the batch from when a request of that direction is
1020 * actually serviced. This should help devices with big TCQ windows
1021 * and writeback caches
1022 */
1023 if (ad->new_batch && ad->batch_data_dir == arq->is_sync) {
1024 update_write_batch(ad);
1025 ad->current_batch_expires = jiffies +
1026 ad->batch_expire[REQ_SYNC];
1027 ad->new_batch = 0;
1028 }
1029
1030 if (ad->io_context == arq->io_context && ad->io_context) {
1031 ad->antic_start = jiffies;
1032 ad->ioc_finished = 1;
1033 if (ad->antic_status == ANTIC_WAIT_REQ) {
1034 /*
1035 * We were waiting on this request, now anticipate
1036 * the next one
1037 */
1038 as_antic_waitnext(ad);
1039 }
1040 }
1041
Jens Axboeb4878f22005-10-20 16:42:29 +02001042 as_put_io_context(arq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001043out:
1044 arq->state = AS_RQ_POSTSCHED;
1045}
1046
1047/*
1048 * as_remove_queued_request removes a request from the pre dispatch queue
1049 * without updating refcounts. It is expected the caller will drop the
1050 * reference unless it replaces the request at somepart of the elevator
1051 * (ie. the dispatch queue)
1052 */
1053static void as_remove_queued_request(request_queue_t *q, struct request *rq)
1054{
1055 struct as_rq *arq = RQ_DATA(rq);
1056 const int data_dir = arq->is_sync;
1057 struct as_data *ad = q->elevator->elevator_data;
1058
1059 WARN_ON(arq->state != AS_RQ_QUEUED);
1060
1061 if (arq->io_context && arq->io_context->aic) {
1062 BUG_ON(!atomic_read(&arq->io_context->aic->nr_queued));
1063 atomic_dec(&arq->io_context->aic->nr_queued);
1064 }
1065
1066 /*
1067 * Update the "next_arq" cache if we are about to remove its
1068 * entry
1069 */
1070 if (ad->next_arq[data_dir] == arq)
1071 ad->next_arq[data_dir] = as_find_next_arq(ad, arq);
1072
1073 list_del_init(&arq->fifo);
Tejun Heo98b11472005-10-20 16:46:54 +02001074 as_del_arq_hash(arq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001075 as_del_arq_rb(ad, arq);
1076}
1077
1078/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001079 * as_fifo_expired returns 0 if there are no expired reads on the fifo,
1080 * 1 otherwise. It is ratelimited so that we only perform the check once per
1081 * `fifo_expire' interval. Otherwise a large number of expired requests
1082 * would create a hopeless seekstorm.
1083 *
1084 * See as_antic_expired comment.
1085 */
1086static int as_fifo_expired(struct as_data *ad, int adir)
1087{
1088 struct as_rq *arq;
1089 long delta_jif;
1090
1091 delta_jif = jiffies - ad->last_check_fifo[adir];
1092 if (unlikely(delta_jif < 0))
1093 delta_jif = -delta_jif;
1094 if (delta_jif < ad->fifo_expire[adir])
1095 return 0;
1096
1097 ad->last_check_fifo[adir] = jiffies;
1098
1099 if (list_empty(&ad->fifo_list[adir]))
1100 return 0;
1101
1102 arq = list_entry_fifo(ad->fifo_list[adir].next);
1103
1104 return time_after(jiffies, arq->expires);
1105}
1106
1107/*
1108 * as_batch_expired returns true if the current batch has expired. A batch
1109 * is a set of reads or a set of writes.
1110 */
1111static inline int as_batch_expired(struct as_data *ad)
1112{
1113 if (ad->changed_batch || ad->new_batch)
1114 return 0;
1115
1116 if (ad->batch_data_dir == REQ_SYNC)
1117 /* TODO! add a check so a complete fifo gets written? */
1118 return time_after(jiffies, ad->current_batch_expires);
1119
1120 return time_after(jiffies, ad->current_batch_expires)
1121 || ad->current_write_count == 0;
1122}
1123
1124/*
1125 * move an entry to dispatch queue
1126 */
1127static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq)
1128{
1129 struct request *rq = arq->request;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001130 const int data_dir = arq->is_sync;
1131
1132 BUG_ON(!ON_RB(&arq->rb_node));
1133
1134 as_antic_stop(ad);
1135 ad->antic_status = ANTIC_OFF;
1136
1137 /*
1138 * This has to be set in order to be correctly updated by
1139 * as_find_next_arq
1140 */
1141 ad->last_sector[data_dir] = rq->sector + rq->nr_sectors;
1142
1143 if (data_dir == REQ_SYNC) {
1144 /* In case we have to anticipate after this */
1145 copy_io_context(&ad->io_context, &arq->io_context);
1146 } else {
1147 if (ad->io_context) {
1148 put_io_context(ad->io_context);
1149 ad->io_context = NULL;
1150 }
1151
1152 if (ad->current_write_count != 0)
1153 ad->current_write_count--;
1154 }
1155 ad->ioc_finished = 0;
1156
1157 ad->next_arq[data_dir] = as_find_next_arq(ad, arq);
1158
1159 /*
1160 * take it off the sort and fifo list, add to dispatch queue
1161 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001162 as_remove_queued_request(ad->q, rq);
1163 WARN_ON(arq->state != AS_RQ_QUEUED);
1164
Jens Axboeb4878f22005-10-20 16:42:29 +02001165 elv_dispatch_sort(ad->q, rq);
1166
Linus Torvalds1da177e2005-04-16 15:20:36 -07001167 arq->state = AS_RQ_DISPATCHED;
1168 if (arq->io_context && arq->io_context->aic)
1169 atomic_inc(&arq->io_context->aic->nr_dispatched);
1170 ad->nr_dispatched++;
1171}
1172
1173/*
1174 * as_dispatch_request selects the best request according to
1175 * read/write expire, batch expire, etc, and moves it to the dispatch
1176 * queue. Returns 1 if a request was found, 0 otherwise.
1177 */
Jens Axboeb4878f22005-10-20 16:42:29 +02001178static int as_dispatch_request(request_queue_t *q, int force)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001179{
Jens Axboeb4878f22005-10-20 16:42:29 +02001180 struct as_data *ad = q->elevator->elevator_data;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001181 struct as_rq *arq;
1182 const int reads = !list_empty(&ad->fifo_list[REQ_SYNC]);
1183 const int writes = !list_empty(&ad->fifo_list[REQ_ASYNC]);
1184
Jens Axboeb4878f22005-10-20 16:42:29 +02001185 if (unlikely(force)) {
1186 /*
1187 * Forced dispatch, accounting is useless. Reset
1188 * accounting states and dump fifo_lists. Note that
1189 * batch_data_dir is reset to REQ_SYNC to avoid
1190 * screwing write batch accounting as write batch
1191 * accounting occurs on W->R transition.
1192 */
1193 int dispatched = 0;
1194
1195 ad->batch_data_dir = REQ_SYNC;
1196 ad->changed_batch = 0;
1197 ad->new_batch = 0;
1198
1199 while (ad->next_arq[REQ_SYNC]) {
1200 as_move_to_dispatch(ad, ad->next_arq[REQ_SYNC]);
1201 dispatched++;
1202 }
1203 ad->last_check_fifo[REQ_SYNC] = jiffies;
1204
1205 while (ad->next_arq[REQ_ASYNC]) {
1206 as_move_to_dispatch(ad, ad->next_arq[REQ_ASYNC]);
1207 dispatched++;
1208 }
1209 ad->last_check_fifo[REQ_ASYNC] = jiffies;
1210
1211 return dispatched;
1212 }
1213
Linus Torvalds1da177e2005-04-16 15:20:36 -07001214 /* Signal that the write batch was uncontended, so we can't time it */
1215 if (ad->batch_data_dir == REQ_ASYNC && !reads) {
1216 if (ad->current_write_count == 0 || !writes)
1217 ad->write_batch_idled = 1;
1218 }
1219
1220 if (!(reads || writes)
1221 || ad->antic_status == ANTIC_WAIT_REQ
1222 || ad->antic_status == ANTIC_WAIT_NEXT
1223 || ad->changed_batch)
1224 return 0;
1225
Nick Pigginf5b3db02005-11-07 00:59:53 -08001226 if (!(reads && writes && as_batch_expired(ad))) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001227 /*
1228 * batch is still running or no reads or no writes
1229 */
1230 arq = ad->next_arq[ad->batch_data_dir];
1231
1232 if (ad->batch_data_dir == REQ_SYNC && ad->antic_expire) {
1233 if (as_fifo_expired(ad, REQ_SYNC))
1234 goto fifo_expired;
1235
1236 if (as_can_anticipate(ad, arq)) {
1237 as_antic_waitreq(ad);
1238 return 0;
1239 }
1240 }
1241
1242 if (arq) {
1243 /* we have a "next request" */
1244 if (reads && !writes)
1245 ad->current_batch_expires =
1246 jiffies + ad->batch_expire[REQ_SYNC];
1247 goto dispatch_request;
1248 }
1249 }
1250
1251 /*
1252 * at this point we are not running a batch. select the appropriate
1253 * data direction (read / write)
1254 */
1255
1256 if (reads) {
1257 BUG_ON(RB_EMPTY(&ad->sort_list[REQ_SYNC]));
1258
1259 if (writes && ad->batch_data_dir == REQ_SYNC)
1260 /*
1261 * Last batch was a read, switch to writes
1262 */
1263 goto dispatch_writes;
1264
1265 if (ad->batch_data_dir == REQ_ASYNC) {
1266 WARN_ON(ad->new_batch);
1267 ad->changed_batch = 1;
1268 }
1269 ad->batch_data_dir = REQ_SYNC;
1270 arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next);
1271 ad->last_check_fifo[ad->batch_data_dir] = jiffies;
1272 goto dispatch_request;
1273 }
1274
1275 /*
1276 * the last batch was a read
1277 */
1278
1279 if (writes) {
1280dispatch_writes:
1281 BUG_ON(RB_EMPTY(&ad->sort_list[REQ_ASYNC]));
1282
1283 if (ad->batch_data_dir == REQ_SYNC) {
1284 ad->changed_batch = 1;
1285
1286 /*
1287 * new_batch might be 1 when the queue runs out of
1288 * reads. A subsequent submission of a write might
1289 * cause a change of batch before the read is finished.
1290 */
1291 ad->new_batch = 0;
1292 }
1293 ad->batch_data_dir = REQ_ASYNC;
1294 ad->current_write_count = ad->write_batch_count;
1295 ad->write_batch_idled = 0;
1296 arq = ad->next_arq[ad->batch_data_dir];
1297 goto dispatch_request;
1298 }
1299
1300 BUG();
1301 return 0;
1302
1303dispatch_request:
1304 /*
1305 * If a request has expired, service it.
1306 */
1307
1308 if (as_fifo_expired(ad, ad->batch_data_dir)) {
1309fifo_expired:
1310 arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next);
1311 BUG_ON(arq == NULL);
1312 }
1313
1314 if (ad->changed_batch) {
1315 WARN_ON(ad->new_batch);
1316
1317 if (ad->nr_dispatched)
1318 return 0;
1319
1320 if (ad->batch_data_dir == REQ_ASYNC)
1321 ad->current_batch_expires = jiffies +
1322 ad->batch_expire[REQ_ASYNC];
1323 else
1324 ad->new_batch = 1;
1325
1326 ad->changed_batch = 0;
1327 }
1328
1329 /*
1330 * arq is the selected appropriate request.
1331 */
1332 as_move_to_dispatch(ad, arq);
1333
1334 return 1;
1335}
1336
Linus Torvalds1da177e2005-04-16 15:20:36 -07001337/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001338 * add arq to rbtree and fifo
1339 */
Jens Axboeb4878f22005-10-20 16:42:29 +02001340static void as_add_request(request_queue_t *q, struct request *rq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001341{
Jens Axboeb4878f22005-10-20 16:42:29 +02001342 struct as_data *ad = q->elevator->elevator_data;
1343 struct as_rq *arq = RQ_DATA(rq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001344 int data_dir;
1345
Jens Axboeb4878f22005-10-20 16:42:29 +02001346 arq->state = AS_RQ_NEW;
1347
Linus Torvalds1da177e2005-04-16 15:20:36 -07001348 if (rq_data_dir(arq->request) == READ
1349 || current->flags&PF_SYNCWRITE)
1350 arq->is_sync = 1;
1351 else
1352 arq->is_sync = 0;
1353 data_dir = arq->is_sync;
1354
1355 arq->io_context = as_get_io_context();
1356
1357 if (arq->io_context) {
1358 as_update_iohist(ad, arq->io_context->aic, arq->request);
1359 atomic_inc(&arq->io_context->aic->nr_queued);
1360 }
1361
Tejun Heoef9be1d2005-11-11 14:27:09 +01001362 as_add_arq_rb(ad, arq);
1363 if (rq_mergeable(arq->request))
1364 as_add_arq_hash(ad, arq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001365
Tejun Heoef9be1d2005-11-11 14:27:09 +01001366 /*
1367 * set expire time (only used for reads) and add to fifo list
1368 */
1369 arq->expires = jiffies + ad->fifo_expire[data_dir];
1370 list_add_tail(&arq->fifo, &ad->fifo_list[data_dir]);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001371
Tejun Heoef9be1d2005-11-11 14:27:09 +01001372 as_update_arq(ad, arq); /* keep state machine up to date */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001373 arq->state = AS_RQ_QUEUED;
1374}
1375
Jens Axboeb4878f22005-10-20 16:42:29 +02001376static void as_activate_request(request_queue_t *q, struct request *rq)
1377{
1378 struct as_rq *arq = RQ_DATA(rq);
1379
1380 WARN_ON(arq->state != AS_RQ_DISPATCHED);
1381 arq->state = AS_RQ_REMOVED;
1382 if (arq->io_context && arq->io_context->aic)
1383 atomic_dec(&arq->io_context->aic->nr_dispatched);
1384}
1385
Linus Torvalds1da177e2005-04-16 15:20:36 -07001386static void as_deactivate_request(request_queue_t *q, struct request *rq)
1387{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001388 struct as_rq *arq = RQ_DATA(rq);
1389
Jens Axboeb4878f22005-10-20 16:42:29 +02001390 WARN_ON(arq->state != AS_RQ_REMOVED);
1391 arq->state = AS_RQ_DISPATCHED;
1392 if (arq->io_context && arq->io_context->aic)
1393 atomic_inc(&arq->io_context->aic->nr_dispatched);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001394}
1395
1396/*
1397 * as_queue_empty tells us if there are requests left in the device. It may
1398 * not be the case that a driver can get the next request even if the queue
1399 * is not empty - it is used in the block layer to check for plugging and
1400 * merging opportunities
1401 */
1402static int as_queue_empty(request_queue_t *q)
1403{
1404 struct as_data *ad = q->elevator->elevator_data;
1405
Jens Axboeb4878f22005-10-20 16:42:29 +02001406 return list_empty(&ad->fifo_list[REQ_ASYNC])
1407 && list_empty(&ad->fifo_list[REQ_SYNC]);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001408}
1409
Nick Pigginf5b3db02005-11-07 00:59:53 -08001410static struct request *as_former_request(request_queue_t *q,
1411 struct request *rq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001412{
1413 struct as_rq *arq = RQ_DATA(rq);
1414 struct rb_node *rbprev = rb_prev(&arq->rb_node);
1415 struct request *ret = NULL;
1416
1417 if (rbprev)
1418 ret = rb_entry_arq(rbprev)->request;
1419
1420 return ret;
1421}
1422
Nick Pigginf5b3db02005-11-07 00:59:53 -08001423static struct request *as_latter_request(request_queue_t *q,
1424 struct request *rq)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001425{
1426 struct as_rq *arq = RQ_DATA(rq);
1427 struct rb_node *rbnext = rb_next(&arq->rb_node);
1428 struct request *ret = NULL;
1429
1430 if (rbnext)
1431 ret = rb_entry_arq(rbnext)->request;
1432
1433 return ret;
1434}
1435
1436static int
1437as_merge(request_queue_t *q, struct request **req, struct bio *bio)
1438{
1439 struct as_data *ad = q->elevator->elevator_data;
1440 sector_t rb_key = bio->bi_sector + bio_sectors(bio);
1441 struct request *__rq;
1442 int ret;
1443
1444 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001445 * see if the merge hash can satisfy a back merge
1446 */
1447 __rq = as_find_arq_hash(ad, bio->bi_sector);
1448 if (__rq) {
1449 BUG_ON(__rq->sector + __rq->nr_sectors != bio->bi_sector);
1450
1451 if (elv_rq_merge_ok(__rq, bio)) {
1452 ret = ELEVATOR_BACK_MERGE;
1453 goto out;
1454 }
1455 }
1456
1457 /*
1458 * check for front merge
1459 */
1460 __rq = as_find_arq_rb(ad, rb_key, bio_data_dir(bio));
1461 if (__rq) {
1462 BUG_ON(rb_key != rq_rb_key(__rq));
1463
1464 if (elv_rq_merge_ok(__rq, bio)) {
1465 ret = ELEVATOR_FRONT_MERGE;
1466 goto out;
1467 }
1468 }
1469
1470 return ELEVATOR_NO_MERGE;
1471out:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001472 if (ret) {
1473 if (rq_mergeable(__rq))
1474 as_hot_arq_hash(ad, RQ_DATA(__rq));
1475 }
1476 *req = __rq;
1477 return ret;
1478}
1479
1480static void as_merged_request(request_queue_t *q, struct request *req)
1481{
1482 struct as_data *ad = q->elevator->elevator_data;
1483 struct as_rq *arq = RQ_DATA(req);
1484
1485 /*
1486 * hash always needs to be repositioned, key is end sector
1487 */
1488 as_del_arq_hash(arq);
1489 as_add_arq_hash(ad, arq);
1490
1491 /*
1492 * if the merge was a front merge, we need to reposition request
1493 */
1494 if (rq_rb_key(req) != arq->rb_key) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001495 as_del_arq_rb(ad, arq);
Tejun Heoef9be1d2005-11-11 14:27:09 +01001496 as_add_arq_rb(ad, arq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001497 /*
1498 * Note! At this stage of this and the next function, our next
1499 * request may not be optimal - eg the request may have "grown"
1500 * behind the disk head. We currently don't bother adjusting.
1501 */
1502 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001503}
1504
Nick Pigginf5b3db02005-11-07 00:59:53 -08001505static void as_merged_requests(request_queue_t *q, struct request *req,
1506 struct request *next)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001507{
1508 struct as_data *ad = q->elevator->elevator_data;
1509 struct as_rq *arq = RQ_DATA(req);
1510 struct as_rq *anext = RQ_DATA(next);
1511
1512 BUG_ON(!arq);
1513 BUG_ON(!anext);
1514
1515 /*
1516 * reposition arq (this is the merged request) in hash, and in rbtree
1517 * in case of a front merge
1518 */
1519 as_del_arq_hash(arq);
1520 as_add_arq_hash(ad, arq);
1521
1522 if (rq_rb_key(req) != arq->rb_key) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001523 as_del_arq_rb(ad, arq);
Tejun Heoef9be1d2005-11-11 14:27:09 +01001524 as_add_arq_rb(ad, arq);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001525 }
1526
1527 /*
1528 * if anext expires before arq, assign its expire time to arq
1529 * and move into anext position (anext will be deleted) in fifo
1530 */
1531 if (!list_empty(&arq->fifo) && !list_empty(&anext->fifo)) {
1532 if (time_before(anext->expires, arq->expires)) {
1533 list_move(&arq->fifo, &anext->fifo);
1534 arq->expires = anext->expires;
1535 /*
1536 * Don't copy here but swap, because when anext is
1537 * removed below, it must contain the unused context
1538 */
1539 swap_io_context(&arq->io_context, &anext->io_context);
1540 }
1541 }
1542
1543 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001544 * kill knowledge of next, this one is a goner
1545 */
1546 as_remove_queued_request(q, next);
Jens Axboeb4878f22005-10-20 16:42:29 +02001547 as_put_io_context(anext);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001548
1549 anext->state = AS_RQ_MERGED;
1550}
1551
1552/*
1553 * This is executed in a "deferred" process context, by kblockd. It calls the
1554 * driver's request_fn so the driver can submit that request.
1555 *
1556 * IMPORTANT! This guy will reenter the elevator, so set up all queue global
1557 * state before calling, and don't rely on any state over calls.
1558 *
1559 * FIXME! dispatch queue is not a queue at all!
1560 */
1561static void as_work_handler(void *data)
1562{
1563 struct request_queue *q = data;
1564 unsigned long flags;
1565
1566 spin_lock_irqsave(q->queue_lock, flags);
Jens Axboeb4878f22005-10-20 16:42:29 +02001567 if (!as_queue_empty(q))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001568 q->request_fn(q);
1569 spin_unlock_irqrestore(q->queue_lock, flags);
1570}
1571
1572static void as_put_request(request_queue_t *q, struct request *rq)
1573{
1574 struct as_data *ad = q->elevator->elevator_data;
1575 struct as_rq *arq = RQ_DATA(rq);
1576
1577 if (!arq) {
1578 WARN_ON(1);
1579 return;
1580 }
1581
Jens Axboeb4878f22005-10-20 16:42:29 +02001582 if (unlikely(arq->state != AS_RQ_POSTSCHED &&
1583 arq->state != AS_RQ_PRESCHED &&
1584 arq->state != AS_RQ_MERGED)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001585 printk("arq->state %d\n", arq->state);
1586 WARN_ON(1);
1587 }
1588
1589 mempool_free(arq, ad->arq_pool);
1590 rq->elevator_private = NULL;
1591}
1592
Jens Axboe22e2c502005-06-27 10:55:12 +02001593static int as_set_request(request_queue_t *q, struct request *rq,
Al Viro8267e262005-10-21 03:20:53 -04001594 struct bio *bio, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001595{
1596 struct as_data *ad = q->elevator->elevator_data;
1597 struct as_rq *arq = mempool_alloc(ad->arq_pool, gfp_mask);
1598
1599 if (arq) {
1600 memset(arq, 0, sizeof(*arq));
1601 RB_CLEAR(&arq->rb_node);
1602 arq->request = rq;
1603 arq->state = AS_RQ_PRESCHED;
1604 arq->io_context = NULL;
1605 INIT_LIST_HEAD(&arq->hash);
1606 arq->on_hash = 0;
1607 INIT_LIST_HEAD(&arq->fifo);
1608 rq->elevator_private = arq;
1609 return 0;
1610 }
1611
1612 return 1;
1613}
1614
Jens Axboe22e2c502005-06-27 10:55:12 +02001615static int as_may_queue(request_queue_t *q, int rw, struct bio *bio)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001616{
1617 int ret = ELV_MQUEUE_MAY;
1618 struct as_data *ad = q->elevator->elevator_data;
1619 struct io_context *ioc;
1620 if (ad->antic_status == ANTIC_WAIT_REQ ||
1621 ad->antic_status == ANTIC_WAIT_NEXT) {
1622 ioc = as_get_io_context();
1623 if (ad->io_context == ioc)
1624 ret = ELV_MQUEUE_MUST;
1625 put_io_context(ioc);
1626 }
1627
1628 return ret;
1629}
1630
1631static void as_exit_queue(elevator_t *e)
1632{
1633 struct as_data *ad = e->elevator_data;
1634
1635 del_timer_sync(&ad->antic_timer);
1636 kblockd_flush();
1637
1638 BUG_ON(!list_empty(&ad->fifo_list[REQ_SYNC]));
1639 BUG_ON(!list_empty(&ad->fifo_list[REQ_ASYNC]));
1640
1641 mempool_destroy(ad->arq_pool);
1642 put_io_context(ad->io_context);
1643 kfree(ad->hash);
1644 kfree(ad);
1645}
1646
1647/*
1648 * initialize elevator private data (as_data), and alloc a arq for
1649 * each request on the free lists
1650 */
1651static int as_init_queue(request_queue_t *q, elevator_t *e)
1652{
1653 struct as_data *ad;
1654 int i;
1655
1656 if (!arq_pool)
1657 return -ENOMEM;
1658
Christoph Lameter19460892005-06-23 00:08:19 -07001659 ad = kmalloc_node(sizeof(*ad), GFP_KERNEL, q->node);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001660 if (!ad)
1661 return -ENOMEM;
1662 memset(ad, 0, sizeof(*ad));
1663
1664 ad->q = q; /* Identify what queue the data belongs to */
1665
Christoph Lameter19460892005-06-23 00:08:19 -07001666 ad->hash = kmalloc_node(sizeof(struct list_head)*AS_HASH_ENTRIES,
1667 GFP_KERNEL, q->node);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001668 if (!ad->hash) {
1669 kfree(ad);
1670 return -ENOMEM;
1671 }
1672
Christoph Lameter19460892005-06-23 00:08:19 -07001673 ad->arq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
1674 mempool_free_slab, arq_pool, q->node);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001675 if (!ad->arq_pool) {
1676 kfree(ad->hash);
1677 kfree(ad);
1678 return -ENOMEM;
1679 }
1680
1681 /* anticipatory scheduling helpers */
1682 ad->antic_timer.function = as_antic_timeout;
1683 ad->antic_timer.data = (unsigned long)q;
1684 init_timer(&ad->antic_timer);
1685 INIT_WORK(&ad->antic_work, as_work_handler, q);
1686
1687 for (i = 0; i < AS_HASH_ENTRIES; i++)
1688 INIT_LIST_HEAD(&ad->hash[i]);
1689
1690 INIT_LIST_HEAD(&ad->fifo_list[REQ_SYNC]);
1691 INIT_LIST_HEAD(&ad->fifo_list[REQ_ASYNC]);
1692 ad->sort_list[REQ_SYNC] = RB_ROOT;
1693 ad->sort_list[REQ_ASYNC] = RB_ROOT;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001694 ad->fifo_expire[REQ_SYNC] = default_read_expire;
1695 ad->fifo_expire[REQ_ASYNC] = default_write_expire;
1696 ad->antic_expire = default_antic_expire;
1697 ad->batch_expire[REQ_SYNC] = default_read_batch_expire;
1698 ad->batch_expire[REQ_ASYNC] = default_write_batch_expire;
1699 e->elevator_data = ad;
1700
1701 ad->current_batch_expires = jiffies + ad->batch_expire[REQ_SYNC];
1702 ad->write_batch_count = ad->batch_expire[REQ_ASYNC] / 10;
1703 if (ad->write_batch_count < 2)
1704 ad->write_batch_count = 2;
1705
1706 return 0;
1707}
1708
1709/*
1710 * sysfs parts below
1711 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001712
1713static ssize_t
1714as_var_show(unsigned int var, char *page)
1715{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001716 return sprintf(page, "%d\n", var);
1717}
1718
1719static ssize_t
1720as_var_store(unsigned long *var, const char *page, size_t count)
1721{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001722 char *p = (char *) page;
1723
Jens Axboec9b3ad62005-07-27 11:43:37 -07001724 *var = simple_strtoul(p, &p, 10);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001725 return count;
1726}
1727
Al Viroe572ec72006-03-18 22:27:18 -05001728static ssize_t est_time_show(elevator_t *e, char *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001729{
Al Viro3d1ab402006-03-18 18:35:43 -05001730 struct as_data *ad = e->elevator_data;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001731 int pos = 0;
1732
Nick Pigginf5b3db02005-11-07 00:59:53 -08001733 pos += sprintf(page+pos, "%lu %% exit probability\n",
1734 100*ad->exit_prob/256);
1735 pos += sprintf(page+pos, "%lu %% probability of exiting without a "
1736 "cooperating process submitting IO\n",
1737 100*ad->exit_no_coop/256);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001738 pos += sprintf(page+pos, "%lu ms new thinktime\n", ad->new_ttime_mean);
Nick Pigginf5b3db02005-11-07 00:59:53 -08001739 pos += sprintf(page+pos, "%llu sectors new seek distance\n",
1740 (unsigned long long)ad->new_seek_mean);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001741
1742 return pos;
1743}
1744
1745#define SHOW_FUNCTION(__FUNC, __VAR) \
Al Viro3d1ab402006-03-18 18:35:43 -05001746static ssize_t __FUNC(elevator_t *e, char *page) \
Linus Torvalds1da177e2005-04-16 15:20:36 -07001747{ \
Al Viro3d1ab402006-03-18 18:35:43 -05001748 struct as_data *ad = e->elevator_data; \
Linus Torvalds1da177e2005-04-16 15:20:36 -07001749 return as_var_show(jiffies_to_msecs((__VAR)), (page)); \
1750}
Al Viroe572ec72006-03-18 22:27:18 -05001751SHOW_FUNCTION(as_read_expire_show, ad->fifo_expire[REQ_SYNC]);
1752SHOW_FUNCTION(as_write_expire_show, ad->fifo_expire[REQ_ASYNC]);
1753SHOW_FUNCTION(as_antic_expire_show, ad->antic_expire);
1754SHOW_FUNCTION(as_read_batch_expire_show, ad->batch_expire[REQ_SYNC]);
1755SHOW_FUNCTION(as_write_batch_expire_show, ad->batch_expire[REQ_ASYNC]);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001756#undef SHOW_FUNCTION
1757
1758#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \
Al Viro3d1ab402006-03-18 18:35:43 -05001759static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
Linus Torvalds1da177e2005-04-16 15:20:36 -07001760{ \
Al Viro3d1ab402006-03-18 18:35:43 -05001761 struct as_data *ad = e->elevator_data; \
1762 int ret = as_var_store(__PTR, (page), count); \
Linus Torvalds1da177e2005-04-16 15:20:36 -07001763 if (*(__PTR) < (MIN)) \
1764 *(__PTR) = (MIN); \
1765 else if (*(__PTR) > (MAX)) \
1766 *(__PTR) = (MAX); \
1767 *(__PTR) = msecs_to_jiffies(*(__PTR)); \
1768 return ret; \
1769}
Al Viroe572ec72006-03-18 22:27:18 -05001770STORE_FUNCTION(as_read_expire_store, &ad->fifo_expire[REQ_SYNC], 0, INT_MAX);
1771STORE_FUNCTION(as_write_expire_store, &ad->fifo_expire[REQ_ASYNC], 0, INT_MAX);
1772STORE_FUNCTION(as_antic_expire_store, &ad->antic_expire, 0, INT_MAX);
1773STORE_FUNCTION(as_read_batch_expire_store,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001774 &ad->batch_expire[REQ_SYNC], 0, INT_MAX);
Al Viroe572ec72006-03-18 22:27:18 -05001775STORE_FUNCTION(as_write_batch_expire_store,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001776 &ad->batch_expire[REQ_ASYNC], 0, INT_MAX);
1777#undef STORE_FUNCTION
1778
Al Viroe572ec72006-03-18 22:27:18 -05001779#define AS_ATTR(name) \
1780 __ATTR(name, S_IRUGO|S_IWUSR, as_##name##_show, as_##name##_store)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001781
Al Viroe572ec72006-03-18 22:27:18 -05001782static struct elv_fs_entry as_attrs[] = {
1783 __ATTR_RO(est_time),
1784 AS_ATTR(read_expire),
1785 AS_ATTR(write_expire),
1786 AS_ATTR(antic_expire),
1787 AS_ATTR(read_batch_expire),
1788 AS_ATTR(write_batch_expire),
1789 __ATTR_NULL
Linus Torvalds1da177e2005-04-16 15:20:36 -07001790};
1791
Linus Torvalds1da177e2005-04-16 15:20:36 -07001792static struct elevator_type iosched_as = {
1793 .ops = {
1794 .elevator_merge_fn = as_merge,
1795 .elevator_merged_fn = as_merged_request,
1796 .elevator_merge_req_fn = as_merged_requests,
Jens Axboeb4878f22005-10-20 16:42:29 +02001797 .elevator_dispatch_fn = as_dispatch_request,
1798 .elevator_add_req_fn = as_add_request,
1799 .elevator_activate_req_fn = as_activate_request,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001800 .elevator_deactivate_req_fn = as_deactivate_request,
1801 .elevator_queue_empty_fn = as_queue_empty,
1802 .elevator_completed_req_fn = as_completed_request,
1803 .elevator_former_req_fn = as_former_request,
1804 .elevator_latter_req_fn = as_latter_request,
1805 .elevator_set_req_fn = as_set_request,
1806 .elevator_put_req_fn = as_put_request,
1807 .elevator_may_queue_fn = as_may_queue,
1808 .elevator_init_fn = as_init_queue,
1809 .elevator_exit_fn = as_exit_queue,
Al Viroe17a9482006-03-18 13:21:20 -05001810 .trim = as_trim,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001811 },
1812
Al Viro3d1ab402006-03-18 18:35:43 -05001813 .elevator_attrs = as_attrs,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001814 .elevator_name = "anticipatory",
1815 .elevator_owner = THIS_MODULE,
1816};
1817
1818static int __init as_init(void)
1819{
1820 int ret;
1821
1822 arq_pool = kmem_cache_create("as_arq", sizeof(struct as_rq),
1823 0, 0, NULL, NULL);
1824 if (!arq_pool)
1825 return -ENOMEM;
1826
1827 ret = elv_register(&iosched_as);
1828 if (!ret) {
1829 /*
1830 * don't allow AS to get unregistered, since we would have
1831 * to browse all tasks in the system and release their
1832 * as_io_context first
1833 */
1834 __module_get(THIS_MODULE);
1835 return 0;
1836 }
1837
1838 kmem_cache_destroy(arq_pool);
1839 return ret;
1840}
1841
1842static void __exit as_exit(void)
1843{
Al Viro334e94d2006-03-18 15:05:53 -05001844 DECLARE_COMPLETION(all_gone);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001845 elv_unregister(&iosched_as);
Al Viro334e94d2006-03-18 15:05:53 -05001846 ioc_gone = &all_gone;
1847 barrier();
1848 if (atomic_read(&ioc_count))
1849 complete(ioc_gone);
1850 synchronize_rcu();
Christoph Hellwig83521d32005-10-30 15:01:39 -08001851 kmem_cache_destroy(arq_pool);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001852}
1853
1854module_init(as_init);
1855module_exit(as_exit);
1856
1857MODULE_AUTHOR("Nick Piggin");
1858MODULE_LICENSE("GPL");
1859MODULE_DESCRIPTION("anticipatory IO scheduler");