2 * linux/drivers/block/as-iosched.c
4 * Anticipatory & deadline i/o scheduler.
6 * Copyright (C) 2002 Jens Axboe <axboe@suse.de>
7 * Nick Piggin <piggin@cyberone.com.au>
10 #include <linux/kernel.h>
12 #include <linux/blkdev.h>
13 #include <linux/elevator.h>
14 #include <linux/bio.h>
15 #include <linux/config.h>
16 #include <linux/module.h>
17 #include <linux/slab.h>
18 #include <linux/init.h>
19 #include <linux/compiler.h>
20 #include <linux/hash.h>
21 #include <linux/rbtree.h>
22 #include <linux/interrupt.h>
28 * See Documentation/block/as-iosched.txt
32 * max time before a read is submitted.
34 #define default_read_expire (HZ / 8)
37 * ditto for writes, these limits are not hard, even
38 * if the disk is capable of satisfying them.
40 #define default_write_expire (HZ / 4)
43 * read_batch_expire describes how long we will allow a stream of reads to
44 * persist before looking to see whether it is time to switch over to writes.
46 #define default_read_batch_expire (HZ / 2)
49 * write_batch_expire describes how long we want a stream of writes to run for.
50 * This is not a hard limit, but a target we set for the auto-tuning thingy.
51 * See, the problem is: we can send a lot of writes to disk cache / TCQ in
52 * a short amount of time...
54 #define default_write_batch_expire (HZ / 8)
57 * max time we may wait to anticipate a read (default around 6ms)
59 #define default_antic_expire ((HZ / 150) ? HZ / 150 : 1)
62 * Keep track of up to 20ms thinktimes. We can go as big as we like here,
63 * however huge values tend to interfere and not decay fast enough. A program
64 * might be in a non-io phase of operation. Waiting on user input for example,
65 * or doing a lengthy computation. A small penalty can be justified there, and
66 * will still catch out those processes that constantly have large thinktimes.
68 #define MAX_THINKTIME (HZ/50UL)
70 /* Bits in as_io_context.state */
72 AS_TASK_RUNNING=0, /* Process has not exitted */
73 AS_TASK_IOSTARTED, /* Process has started some IO */
74 AS_TASK_IORUNNING, /* Process has completed some IO */
77 enum anticipation_status {
78 ANTIC_OFF=0, /* Not anticipating (normal operation) */
79 ANTIC_WAIT_REQ, /* The last read has not yet completed */
80 ANTIC_WAIT_NEXT, /* Currently anticipating a request vs
81 last read (which has completed) */
82 ANTIC_FINISHED, /* Anticipating but have found a candidate
91 struct request_queue *q; /* the "owner" queue */
94 * requests (as_rq s) are present on both sort_list and fifo_list
96 struct rb_root sort_list[2];
97 struct list_head fifo_list[2];
99 struct as_rq *next_arq[2]; /* next in sort order */
100 sector_t last_sector[2]; /* last REQ_SYNC & REQ_ASYNC sectors */
101 struct list_head *hash; /* request hash */
103 unsigned long exit_prob; /* probability a task will exit while
105 unsigned long new_ttime_total; /* mean thinktime on new proc */
106 unsigned long new_ttime_mean;
107 u64 new_seek_total; /* mean seek on new proc */
108 sector_t new_seek_mean;
110 unsigned long current_batch_expires;
111 unsigned long last_check_fifo[2];
112 int changed_batch; /* 1: waiting for old batch to end */
113 int new_batch; /* 1: waiting on first read complete */
114 int batch_data_dir; /* current batch REQ_SYNC / REQ_ASYNC */
115 int write_batch_count; /* max # of reqs in a write batch */
116 int current_write_count; /* how many requests left this batch */
117 int write_batch_idled; /* has the write batch gone idle? */
120 enum anticipation_status antic_status;
121 unsigned long antic_start; /* jiffies: when it started */
122 struct timer_list antic_timer; /* anticipatory scheduling timer */
123 struct work_struct antic_work; /* Deferred unplugging */
124 struct io_context *io_context; /* Identify the expected process */
125 int ioc_finished; /* IO associated with io_context is finished */
129 * settings that change how the i/o scheduler behaves
131 unsigned long fifo_expire[2];
132 unsigned long batch_expire[2];
133 unsigned long antic_expire;
136 #define list_entry_fifo(ptr) list_entry((ptr), struct as_rq, fifo)
142 AS_RQ_NEW=0, /* New - not referenced and not on any lists */
143 AS_RQ_QUEUED, /* In the request queue. It belongs to the
145 AS_RQ_DISPATCHED, /* On the dispatch list. It belongs to the
147 AS_RQ_PRESCHED, /* Debug poisoning for requests being used */
150 AS_RQ_POSTSCHED, /* when they shouldn't be */
155 * rbtree index, key is the starting offset
157 struct rb_node rb_node;
160 struct request *request;
162 struct io_context *io_context; /* The submitting task */
165 * request hash, key is the ending offset (for back merge lookup)
167 struct list_head hash;
168 unsigned int on_hash;
173 struct list_head fifo;
174 unsigned long expires;
176 unsigned int is_sync;
177 enum arq_state state;
180 #define RQ_DATA(rq) ((struct as_rq *) (rq)->elevator_private)
182 static kmem_cache_t *arq_pool;
185 * IO Context helper functions
188 /* Called to deallocate the as_io_context */
189 static void free_as_io_context(struct as_io_context *aic)
194 /* Called when the task exits */
195 static void exit_as_io_context(struct as_io_context *aic)
197 WARN_ON(!test_bit(AS_TASK_RUNNING, &aic->state));
198 clear_bit(AS_TASK_RUNNING, &aic->state);
201 static struct as_io_context *alloc_as_io_context(void)
203 struct as_io_context *ret;
205 ret = kmalloc(sizeof(*ret), GFP_ATOMIC);
207 ret->dtor = free_as_io_context;
208 ret->exit = exit_as_io_context;
209 ret->state = 1 << AS_TASK_RUNNING;
210 atomic_set(&ret->nr_queued, 0);
211 atomic_set(&ret->nr_dispatched, 0);
212 spin_lock_init(&ret->lock);
213 ret->ttime_total = 0;
214 ret->ttime_samples = 0;
217 ret->seek_samples = 0;
225 * If the current task has no AS IO context then create one and initialise it.
226 * Then take a ref on the task's io context and return it.
228 static struct io_context *as_get_io_context(void)
230 struct io_context *ioc = get_io_context(GFP_ATOMIC);
231 if (ioc && !ioc->aic) {
232 ioc->aic = alloc_as_io_context();
241 static void as_put_io_context(struct as_rq *arq)
243 struct as_io_context *aic;
245 if (unlikely(!arq->io_context))
248 aic = arq->io_context->aic;
250 if (arq->is_sync == REQ_SYNC && aic) {
251 spin_lock(&aic->lock);
252 set_bit(AS_TASK_IORUNNING, &aic->state);
253 aic->last_end_request = jiffies;
254 spin_unlock(&aic->lock);
257 put_io_context(arq->io_context);
261 * the back merge hash support functions
263 static const int as_hash_shift = 6;
264 #define AS_HASH_BLOCK(sec) ((sec) >> 3)
265 #define AS_HASH_FN(sec) (hash_long(AS_HASH_BLOCK((sec)), as_hash_shift))
266 #define AS_HASH_ENTRIES (1 << as_hash_shift)
267 #define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors)
268 #define list_entry_hash(ptr) list_entry((ptr), struct as_rq, hash)
270 static inline void __as_del_arq_hash(struct as_rq *arq)
273 list_del_init(&arq->hash);
276 static inline void as_del_arq_hash(struct as_rq *arq)
279 __as_del_arq_hash(arq);
282 static void as_remove_merge_hints(request_queue_t *q, struct as_rq *arq)
284 as_del_arq_hash(arq);
286 if (q->last_merge == arq->request)
287 q->last_merge = NULL;
290 static void as_add_arq_hash(struct as_data *ad, struct as_rq *arq)
292 struct request *rq = arq->request;
294 BUG_ON(arq->on_hash);
297 list_add(&arq->hash, &ad->hash[AS_HASH_FN(rq_hash_key(rq))]);
301 * move hot entry to front of chain
303 static inline void as_hot_arq_hash(struct as_data *ad, struct as_rq *arq)
305 struct request *rq = arq->request;
306 struct list_head *head = &ad->hash[AS_HASH_FN(rq_hash_key(rq))];
313 if (arq->hash.prev != head) {
314 list_del(&arq->hash);
315 list_add(&arq->hash, head);
319 static struct request *as_find_arq_hash(struct as_data *ad, sector_t offset)
321 struct list_head *hash_list = &ad->hash[AS_HASH_FN(offset)];
322 struct list_head *entry, *next = hash_list->next;
324 while ((entry = next) != hash_list) {
325 struct as_rq *arq = list_entry_hash(entry);
326 struct request *__rq = arq->request;
330 BUG_ON(!arq->on_hash);
332 if (!rq_mergeable(__rq)) {
333 as_remove_merge_hints(ad->q, arq);
337 if (rq_hash_key(__rq) == offset)
345 * rb tree support functions
348 #define RB_EMPTY(root) ((root)->rb_node == NULL)
349 #define ON_RB(node) ((node)->rb_color != RB_NONE)
350 #define RB_CLEAR(node) ((node)->rb_color = RB_NONE)
351 #define rb_entry_arq(node) rb_entry((node), struct as_rq, rb_node)
352 #define ARQ_RB_ROOT(ad, arq) (&(ad)->sort_list[(arq)->is_sync])
353 #define rq_rb_key(rq) (rq)->sector
356 * as_find_first_arq finds the first (lowest sector numbered) request
357 * for the specified data_dir. Used to sweep back to the start of the disk
358 * (1-way elevator) after we process the last (highest sector) request.
360 static struct as_rq *as_find_first_arq(struct as_data *ad, int data_dir)
362 struct rb_node *n = ad->sort_list[data_dir].rb_node;
368 if (n->rb_left == NULL)
369 return rb_entry_arq(n);
376 * Add the request to the rb tree if it is unique. If there is an alias (an
377 * existing request against the same sector), which can happen when using
378 * direct IO, then return the alias.
380 static struct as_rq *as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
382 struct rb_node **p = &ARQ_RB_ROOT(ad, arq)->rb_node;
383 struct rb_node *parent = NULL;
385 struct request *rq = arq->request;
387 arq->rb_key = rq_rb_key(rq);
391 __arq = rb_entry_arq(parent);
393 if (arq->rb_key < __arq->rb_key)
395 else if (arq->rb_key > __arq->rb_key)
401 rb_link_node(&arq->rb_node, parent, p);
402 rb_insert_color(&arq->rb_node, ARQ_RB_ROOT(ad, arq));
407 static inline void as_del_arq_rb(struct as_data *ad, struct as_rq *arq)
409 if (!ON_RB(&arq->rb_node)) {
414 rb_erase(&arq->rb_node, ARQ_RB_ROOT(ad, arq));
415 RB_CLEAR(&arq->rb_node);
418 static struct request *
419 as_find_arq_rb(struct as_data *ad, sector_t sector, int data_dir)
421 struct rb_node *n = ad->sort_list[data_dir].rb_node;
425 arq = rb_entry_arq(n);
427 if (sector < arq->rb_key)
429 else if (sector > arq->rb_key)
439 * IO Scheduler proper
442 #define MAXBACK (1024 * 1024) /*
443 * Maximum distance the disk will go backward
447 #define BACK_PENALTY 2
450 * as_choose_req selects the preferred one of two requests of the same data_dir
451 * ignoring time - eg. timeouts, which is the job of as_dispatch_request
453 static struct as_rq *
454 as_choose_req(struct as_data *ad, struct as_rq *arq1, struct as_rq *arq2)
457 sector_t last, s1, s2, d1, d2;
458 int r1_wrap=0, r2_wrap=0; /* requests are behind the disk head */
459 const sector_t maxback = MAXBACK;
461 if (arq1 == NULL || arq1 == arq2)
466 data_dir = arq1->is_sync;
468 last = ad->last_sector[data_dir];
469 s1 = arq1->request->sector;
470 s2 = arq2->request->sector;
472 BUG_ON(data_dir != arq2->is_sync);
475 * Strict one way elevator _except_ in the case where we allow
476 * short backward seeks which are biased as twice the cost of a
477 * similar forward seek.
481 else if (s1+maxback >= last)
482 d1 = (last - s1)*BACK_PENALTY;
485 d1 = 0; /* shut up, gcc */
490 else if (s2+maxback >= last)
491 d2 = (last - s2)*BACK_PENALTY;
497 /* Found required data */
498 if (!r1_wrap && r2_wrap)
500 else if (!r2_wrap && r1_wrap)
502 else if (r1_wrap && r2_wrap) {
503 /* both behind the head */
510 /* Both requests in front of the head */
524 * as_find_next_arq finds the next request after @prev in elevator order.
525 * this with as_choose_req form the basis for how the scheduler chooses
526 * what request to process next. Anticipation works on top of this.
528 static struct as_rq *as_find_next_arq(struct as_data *ad, struct as_rq *last)
530 const int data_dir = last->is_sync;
532 struct rb_node *rbnext = rb_next(&last->rb_node);
533 struct rb_node *rbprev = rb_prev(&last->rb_node);
534 struct as_rq *arq_next, *arq_prev;
536 BUG_ON(!ON_RB(&last->rb_node));
539 arq_prev = rb_entry_arq(rbprev);
544 arq_next = rb_entry_arq(rbnext);
546 arq_next = as_find_first_arq(ad, data_dir);
547 if (arq_next == last)
551 ret = as_choose_req(ad, arq_next, arq_prev);
557 * anticipatory scheduling functions follow
561 * as_antic_expired tells us when we have anticipated too long.
562 * The funny "absolute difference" math on the elapsed time is to handle
563 * jiffy wraps, and disks which have been idle for 0x80000000 jiffies.
565 static int as_antic_expired(struct as_data *ad)
569 delta_jif = jiffies - ad->antic_start;
570 if (unlikely(delta_jif < 0))
571 delta_jif = -delta_jif;
572 if (delta_jif < ad->antic_expire)
579 * as_antic_waitnext starts anticipating that a nice request will soon be
580 * submitted. See also as_antic_waitreq
582 static void as_antic_waitnext(struct as_data *ad)
584 unsigned long timeout;
586 BUG_ON(ad->antic_status != ANTIC_OFF
587 && ad->antic_status != ANTIC_WAIT_REQ);
589 timeout = ad->antic_start + ad->antic_expire;
591 mod_timer(&ad->antic_timer, timeout);
593 ad->antic_status = ANTIC_WAIT_NEXT;
597 * as_antic_waitreq starts anticipating. We don't start timing the anticipation
598 * until the request that we're anticipating on has finished. This means we
599 * are timing from when the candidate process wakes up hopefully.
601 static void as_antic_waitreq(struct as_data *ad)
603 BUG_ON(ad->antic_status == ANTIC_FINISHED);
604 if (ad->antic_status == ANTIC_OFF) {
605 if (!ad->io_context || ad->ioc_finished)
606 as_antic_waitnext(ad);
608 ad->antic_status = ANTIC_WAIT_REQ;
613 * This is called directly by the functions in this file to stop anticipation.
614 * We kill the timer and schedule a call to the request_fn asap.
616 static void as_antic_stop(struct as_data *ad)
618 int status = ad->antic_status;
620 if (status == ANTIC_WAIT_REQ || status == ANTIC_WAIT_NEXT) {
621 if (status == ANTIC_WAIT_NEXT)
622 del_timer(&ad->antic_timer);
623 ad->antic_status = ANTIC_FINISHED;
624 /* see as_work_handler */
625 kblockd_schedule_work(&ad->antic_work);
630 * as_antic_timeout is the timer function set by as_antic_waitnext.
632 static void as_antic_timeout(unsigned long data)
634 struct request_queue *q = (struct request_queue *)data;
635 struct as_data *ad = q->elevator->elevator_data;
638 spin_lock_irqsave(q->queue_lock, flags);
639 if (ad->antic_status == ANTIC_WAIT_REQ
640 || ad->antic_status == ANTIC_WAIT_NEXT) {
641 struct as_io_context *aic = ad->io_context->aic;
643 ad->antic_status = ANTIC_FINISHED;
644 kblockd_schedule_work(&ad->antic_work);
646 if (aic->ttime_samples == 0) {
647 /* process anticipated on has exitted or timed out*/
648 ad->exit_prob = (7*ad->exit_prob + 256)/8;
651 spin_unlock_irqrestore(q->queue_lock, flags);
655 * as_close_req decides if one request is considered "close" to the
656 * previous one issued.
658 static int as_close_req(struct as_data *ad, struct as_rq *arq)
660 unsigned long delay; /* milliseconds */
661 sector_t last = ad->last_sector[ad->batch_data_dir];
662 sector_t next = arq->request->sector;
663 sector_t delta; /* acceptable close offset (in sectors) */
665 if (ad->antic_status == ANTIC_OFF || !ad->ioc_finished)
668 delay = ((jiffies - ad->antic_start) * 1000) / HZ;
672 else if (delay <= 20 && delay <= ad->antic_expire)
673 delta = 64 << (delay-1);
677 return (last - (delta>>1) <= next) && (next <= last + delta);
681 * as_can_break_anticipation returns true if we have been anticipating this
684 * It also returns true if the process against which we are anticipating
685 * submits a write - that's presumably an fsync, O_SYNC write, etc. We want to
686 * dispatch it ASAP, because we know that application will not be submitting
689 * If the task which has submitted the request has exitted, break anticipation.
691 * If this task has queued some other IO, do not enter enticipation.
693 static int as_can_break_anticipation(struct as_data *ad, struct as_rq *arq)
695 struct io_context *ioc;
696 struct as_io_context *aic;
699 ioc = ad->io_context;
702 if (arq && ioc == arq->io_context) {
703 /* request from same process */
707 if (ad->ioc_finished && as_antic_expired(ad)) {
709 * In this situation status should really be FINISHED,
710 * however the timer hasn't had the chance to run yet.
719 if (!test_bit(AS_TASK_RUNNING, &aic->state)) {
720 /* process anticipated on has exitted */
721 if (aic->ttime_samples == 0)
722 ad->exit_prob = (7*ad->exit_prob + 256)/8;
726 if (atomic_read(&aic->nr_queued) > 0) {
727 /* process has more requests queued */
731 if (atomic_read(&aic->nr_dispatched) > 0) {
732 /* process has more requests dispatched */
736 if (arq && arq->is_sync == REQ_SYNC && as_close_req(ad, arq)) {
738 * Found a close request that is not one of ours.
740 * This makes close requests from another process reset
741 * our thinktime delay. Is generally useful when there are
742 * two or more cooperating processes working in the same
745 spin_lock(&aic->lock);
746 aic->last_end_request = jiffies;
747 spin_unlock(&aic->lock);
752 if (aic->ttime_samples == 0) {
753 if (ad->new_ttime_mean > ad->antic_expire)
755 if (ad->exit_prob > 128)
757 } else if (aic->ttime_mean > ad->antic_expire) {
758 /* the process thinks too much between requests */
765 if (ad->last_sector[REQ_SYNC] < arq->request->sector)
766 s = arq->request->sector - ad->last_sector[REQ_SYNC];
768 s = ad->last_sector[REQ_SYNC] - arq->request->sector;
770 if (aic->seek_samples == 0) {
772 * Process has just started IO. Use past statistics to
773 * guage success possibility
775 if (ad->new_seek_mean > s) {
776 /* this request is better than what we're expecting */
781 if (aic->seek_mean > s) {
782 /* this request is better than what we're expecting */
791 * as_can_anticipate indicates weather we should either run arq
792 * or keep anticipating a better request.
794 static int as_can_anticipate(struct as_data *ad, struct as_rq *arq)
798 * Last request submitted was a write
802 if (ad->antic_status == ANTIC_FINISHED)
804 * Don't restart if we have just finished. Run the next request
808 if (as_can_break_anticipation(ad, arq))
810 * This request is a good candidate. Don't keep anticipating,
816 * OK from here, we haven't finished, and don't have a decent request!
817 * Status is either ANTIC_OFF so start waiting,
818 * ANTIC_WAIT_REQ so continue waiting for request to finish
819 * or ANTIC_WAIT_NEXT so continue waiting for an acceptable request.
826 static void as_update_thinktime(struct as_data *ad, struct as_io_context *aic, unsigned long ttime)
828 /* fixed point: 1.0 == 1<<8 */
829 if (aic->ttime_samples == 0) {
830 ad->new_ttime_total = (7*ad->new_ttime_total + 256*ttime) / 8;
831 ad->new_ttime_mean = ad->new_ttime_total / 256;
833 ad->exit_prob = (7*ad->exit_prob)/8;
835 aic->ttime_samples = (7*aic->ttime_samples + 256) / 8;
836 aic->ttime_total = (7*aic->ttime_total + 256*ttime) / 8;
837 aic->ttime_mean = (aic->ttime_total + 128) / aic->ttime_samples;
840 static void as_update_seekdist(struct as_data *ad, struct as_io_context *aic, sector_t sdist)
844 if (aic->seek_samples == 0) {
845 ad->new_seek_total = (7*ad->new_seek_total + 256*(u64)sdist)/8;
846 ad->new_seek_mean = ad->new_seek_total / 256;
850 * Don't allow the seek distance to get too large from the
851 * odd fragment, pagein, etc
853 if (aic->seek_samples <= 60) /* second&third seek */
854 sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*1024);
856 sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*64);
858 aic->seek_samples = (7*aic->seek_samples + 256) / 8;
859 aic->seek_total = (7*aic->seek_total + (u64)256*sdist) / 8;
860 total = aic->seek_total + (aic->seek_samples/2);
861 do_div(total, aic->seek_samples);
862 aic->seek_mean = (sector_t)total;
866 * as_update_iohist keeps a decaying histogram of IO thinktimes, and
867 * updates @aic->ttime_mean based on that. It is called when a new
870 static void as_update_iohist(struct as_data *ad, struct as_io_context *aic, struct request *rq)
872 struct as_rq *arq = RQ_DATA(rq);
873 int data_dir = arq->is_sync;
874 unsigned long thinktime;
880 if (data_dir == REQ_SYNC) {
881 unsigned long in_flight = atomic_read(&aic->nr_queued)
882 + atomic_read(&aic->nr_dispatched);
883 spin_lock(&aic->lock);
884 if (test_bit(AS_TASK_IORUNNING, &aic->state) ||
885 test_bit(AS_TASK_IOSTARTED, &aic->state)) {
886 /* Calculate read -> read thinktime */
887 if (test_bit(AS_TASK_IORUNNING, &aic->state)
889 thinktime = jiffies - aic->last_end_request;
890 thinktime = min(thinktime, MAX_THINKTIME-1);
893 as_update_thinktime(ad, aic, thinktime);
895 /* Calculate read -> read seek distance */
896 if (aic->last_request_pos < rq->sector)
897 seek_dist = rq->sector - aic->last_request_pos;
899 seek_dist = aic->last_request_pos - rq->sector;
900 as_update_seekdist(ad, aic, seek_dist);
902 aic->last_request_pos = rq->sector + rq->nr_sectors;
903 set_bit(AS_TASK_IOSTARTED, &aic->state);
904 spin_unlock(&aic->lock);
909 * as_update_arq must be called whenever a request (arq) is added to
910 * the sort_list. This function keeps caches up to date, and checks if the
911 * request might be one we are "anticipating"
913 static void as_update_arq(struct as_data *ad, struct as_rq *arq)
915 const int data_dir = arq->is_sync;
917 /* keep the next_arq cache up to date */
918 ad->next_arq[data_dir] = as_choose_req(ad, arq, ad->next_arq[data_dir]);
921 * have we been anticipating this request?
922 * or does it come from the same process as the one we are anticipating
925 if (ad->antic_status == ANTIC_WAIT_REQ
926 || ad->antic_status == ANTIC_WAIT_NEXT) {
927 if (as_can_break_anticipation(ad, arq))
933 * Gathers timings and resizes the write batch automatically
935 static void update_write_batch(struct as_data *ad)
937 unsigned long batch = ad->batch_expire[REQ_ASYNC];
940 write_time = (jiffies - ad->current_batch_expires) + batch;
944 if (write_time > batch && !ad->write_batch_idled) {
945 if (write_time > batch * 3)
946 ad->write_batch_count /= 2;
948 ad->write_batch_count--;
949 } else if (write_time < batch && ad->current_write_count == 0) {
950 if (batch > write_time * 3)
951 ad->write_batch_count *= 2;
953 ad->write_batch_count++;
956 if (ad->write_batch_count < 1)
957 ad->write_batch_count = 1;
961 * as_completed_request is to be called when a request has completed and
962 * returned something to the requesting process, be it an error or data.
964 static void as_completed_request(request_queue_t *q, struct request *rq)
966 struct as_data *ad = q->elevator->elevator_data;
967 struct as_rq *arq = RQ_DATA(rq);
969 WARN_ON(!list_empty(&rq->queuelist));
971 if (arq->state != AS_RQ_REMOVED) {
972 printk("arq->state %d\n", arq->state);
977 if (ad->changed_batch && ad->nr_dispatched == 1) {
978 kblockd_schedule_work(&ad->antic_work);
979 ad->changed_batch = 0;
981 if (ad->batch_data_dir == REQ_SYNC)
984 WARN_ON(ad->nr_dispatched == 0);
988 * Start counting the batch from when a request of that direction is
989 * actually serviced. This should help devices with big TCQ windows
990 * and writeback caches
992 if (ad->new_batch && ad->batch_data_dir == arq->is_sync) {
993 update_write_batch(ad);
994 ad->current_batch_expires = jiffies +
995 ad->batch_expire[REQ_SYNC];
999 if (ad->io_context == arq->io_context && ad->io_context) {
1000 ad->antic_start = jiffies;
1001 ad->ioc_finished = 1;
1002 if (ad->antic_status == ANTIC_WAIT_REQ) {
1004 * We were waiting on this request, now anticipate
1007 as_antic_waitnext(ad);
1011 as_put_io_context(arq);
1013 arq->state = AS_RQ_POSTSCHED;
1017 * as_remove_queued_request removes a request from the pre dispatch queue
1018 * without updating refcounts. It is expected the caller will drop the
1019 * reference unless it replaces the request at somepart of the elevator
1020 * (ie. the dispatch queue)
1022 static void as_remove_queued_request(request_queue_t *q, struct request *rq)
1024 struct as_rq *arq = RQ_DATA(rq);
1025 const int data_dir = arq->is_sync;
1026 struct as_data *ad = q->elevator->elevator_data;
1028 WARN_ON(arq->state != AS_RQ_QUEUED);
1030 if (arq->io_context && arq->io_context->aic) {
1031 BUG_ON(!atomic_read(&arq->io_context->aic->nr_queued));
1032 atomic_dec(&arq->io_context->aic->nr_queued);
1036 * Update the "next_arq" cache if we are about to remove its
1039 if (ad->next_arq[data_dir] == arq)
1040 ad->next_arq[data_dir] = as_find_next_arq(ad, arq);
1042 list_del_init(&arq->fifo);
1043 as_remove_merge_hints(q, arq);
1044 as_del_arq_rb(ad, arq);
1048 * as_fifo_expired returns 0 if there are no expired reads on the fifo,
1049 * 1 otherwise. It is ratelimited so that we only perform the check once per
1050 * `fifo_expire' interval. Otherwise a large number of expired requests
1051 * would create a hopeless seekstorm.
1053 * See as_antic_expired comment.
1055 static int as_fifo_expired(struct as_data *ad, int adir)
1060 delta_jif = jiffies - ad->last_check_fifo[adir];
1061 if (unlikely(delta_jif < 0))
1062 delta_jif = -delta_jif;
1063 if (delta_jif < ad->fifo_expire[adir])
1066 ad->last_check_fifo[adir] = jiffies;
1068 if (list_empty(&ad->fifo_list[adir]))
1071 arq = list_entry_fifo(ad->fifo_list[adir].next);
1073 return time_after(jiffies, arq->expires);
1077 * as_batch_expired returns true if the current batch has expired. A batch
1078 * is a set of reads or a set of writes.
1080 static inline int as_batch_expired(struct as_data *ad)
1082 if (ad->changed_batch || ad->new_batch)
1085 if (ad->batch_data_dir == REQ_SYNC)
1086 /* TODO! add a check so a complete fifo gets written? */
1087 return time_after(jiffies, ad->current_batch_expires);
1089 return time_after(jiffies, ad->current_batch_expires)
1090 || ad->current_write_count == 0;
1094 * move an entry to dispatch queue
1096 static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq)
1098 struct request *rq = arq->request;
1099 const int data_dir = arq->is_sync;
1101 BUG_ON(!ON_RB(&arq->rb_node));
1104 ad->antic_status = ANTIC_OFF;
1107 * This has to be set in order to be correctly updated by
1110 ad->last_sector[data_dir] = rq->sector + rq->nr_sectors;
1112 if (data_dir == REQ_SYNC) {
1113 /* In case we have to anticipate after this */
1114 copy_io_context(&ad->io_context, &arq->io_context);
1116 if (ad->io_context) {
1117 put_io_context(ad->io_context);
1118 ad->io_context = NULL;
1121 if (ad->current_write_count != 0)
1122 ad->current_write_count--;
1124 ad->ioc_finished = 0;
1126 ad->next_arq[data_dir] = as_find_next_arq(ad, arq);
1129 * take it off the sort and fifo list, add to dispatch queue
1131 while (!list_empty(&rq->queuelist)) {
1132 struct request *__rq = list_entry_rq(rq->queuelist.next);
1133 struct as_rq *__arq = RQ_DATA(__rq);
1135 list_del(&__rq->queuelist);
1137 elv_dispatch_add_tail(ad->q, __rq);
1139 if (__arq->io_context && __arq->io_context->aic)
1140 atomic_inc(&__arq->io_context->aic->nr_dispatched);
1142 WARN_ON(__arq->state != AS_RQ_QUEUED);
1143 __arq->state = AS_RQ_DISPATCHED;
1145 ad->nr_dispatched++;
1148 as_remove_queued_request(ad->q, rq);
1149 WARN_ON(arq->state != AS_RQ_QUEUED);
1151 elv_dispatch_sort(ad->q, rq);
1153 arq->state = AS_RQ_DISPATCHED;
1154 if (arq->io_context && arq->io_context->aic)
1155 atomic_inc(&arq->io_context->aic->nr_dispatched);
1156 ad->nr_dispatched++;
1160 * as_dispatch_request selects the best request according to
1161 * read/write expire, batch expire, etc, and moves it to the dispatch
1162 * queue. Returns 1 if a request was found, 0 otherwise.
1164 static int as_dispatch_request(request_queue_t *q, int force)
1166 struct as_data *ad = q->elevator->elevator_data;
1168 const int reads = !list_empty(&ad->fifo_list[REQ_SYNC]);
1169 const int writes = !list_empty(&ad->fifo_list[REQ_ASYNC]);
1171 if (unlikely(force)) {
1173 * Forced dispatch, accounting is useless. Reset
1174 * accounting states and dump fifo_lists. Note that
1175 * batch_data_dir is reset to REQ_SYNC to avoid
1176 * screwing write batch accounting as write batch
1177 * accounting occurs on W->R transition.
1181 ad->batch_data_dir = REQ_SYNC;
1182 ad->changed_batch = 0;
1185 while (ad->next_arq[REQ_SYNC]) {
1186 as_move_to_dispatch(ad, ad->next_arq[REQ_SYNC]);
1189 ad->last_check_fifo[REQ_SYNC] = jiffies;
1191 while (ad->next_arq[REQ_ASYNC]) {
1192 as_move_to_dispatch(ad, ad->next_arq[REQ_ASYNC]);
1195 ad->last_check_fifo[REQ_ASYNC] = jiffies;
1200 /* Signal that the write batch was uncontended, so we can't time it */
1201 if (ad->batch_data_dir == REQ_ASYNC && !reads) {
1202 if (ad->current_write_count == 0 || !writes)
1203 ad->write_batch_idled = 1;
1206 if (!(reads || writes)
1207 || ad->antic_status == ANTIC_WAIT_REQ
1208 || ad->antic_status == ANTIC_WAIT_NEXT
1209 || ad->changed_batch)
1212 if (!(reads && writes && as_batch_expired(ad)) ) {
1214 * batch is still running or no reads or no writes
1216 arq = ad->next_arq[ad->batch_data_dir];
1218 if (ad->batch_data_dir == REQ_SYNC && ad->antic_expire) {
1219 if (as_fifo_expired(ad, REQ_SYNC))
1222 if (as_can_anticipate(ad, arq)) {
1223 as_antic_waitreq(ad);
1229 /* we have a "next request" */
1230 if (reads && !writes)
1231 ad->current_batch_expires =
1232 jiffies + ad->batch_expire[REQ_SYNC];
1233 goto dispatch_request;
1238 * at this point we are not running a batch. select the appropriate
1239 * data direction (read / write)
1243 BUG_ON(RB_EMPTY(&ad->sort_list[REQ_SYNC]));
1245 if (writes && ad->batch_data_dir == REQ_SYNC)
1247 * Last batch was a read, switch to writes
1249 goto dispatch_writes;
1251 if (ad->batch_data_dir == REQ_ASYNC) {
1252 WARN_ON(ad->new_batch);
1253 ad->changed_batch = 1;
1255 ad->batch_data_dir = REQ_SYNC;
1256 arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next);
1257 ad->last_check_fifo[ad->batch_data_dir] = jiffies;
1258 goto dispatch_request;
1262 * the last batch was a read
1267 BUG_ON(RB_EMPTY(&ad->sort_list[REQ_ASYNC]));
1269 if (ad->batch_data_dir == REQ_SYNC) {
1270 ad->changed_batch = 1;
1273 * new_batch might be 1 when the queue runs out of
1274 * reads. A subsequent submission of a write might
1275 * cause a change of batch before the read is finished.
1279 ad->batch_data_dir = REQ_ASYNC;
1280 ad->current_write_count = ad->write_batch_count;
1281 ad->write_batch_idled = 0;
1282 arq = ad->next_arq[ad->batch_data_dir];
1283 goto dispatch_request;
1291 * If a request has expired, service it.
1294 if (as_fifo_expired(ad, ad->batch_data_dir)) {
1296 arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next);
1297 BUG_ON(arq == NULL);
1300 if (ad->changed_batch) {
1301 WARN_ON(ad->new_batch);
1303 if (ad->nr_dispatched)
1306 if (ad->batch_data_dir == REQ_ASYNC)
1307 ad->current_batch_expires = jiffies +
1308 ad->batch_expire[REQ_ASYNC];
1312 ad->changed_batch = 0;
1316 * arq is the selected appropriate request.
1318 as_move_to_dispatch(ad, arq);
1324 * Add arq to a list behind alias
1327 as_add_aliased_request(struct as_data *ad, struct as_rq *arq, struct as_rq *alias)
1329 struct request *req = arq->request;
1330 struct list_head *insert = alias->request->queuelist.prev;
1333 * Transfer list of aliases
1335 while (!list_empty(&req->queuelist)) {
1336 struct request *__rq = list_entry_rq(req->queuelist.next);
1337 struct as_rq *__arq = RQ_DATA(__rq);
1339 list_move_tail(&__rq->queuelist, &alias->request->queuelist);
1341 WARN_ON(__arq->state != AS_RQ_QUEUED);
1345 * Another request with the same start sector on the rbtree.
1346 * Link this request to that sector. They are untangled in
1347 * as_move_to_dispatch
1349 list_add(&arq->request->queuelist, insert);
1352 * Don't want to have to handle merges.
1354 as_remove_merge_hints(ad->q, arq);
1358 * add arq to rbtree and fifo
1360 static void as_add_request(request_queue_t *q, struct request *rq)
1362 struct as_data *ad = q->elevator->elevator_data;
1363 struct as_rq *arq = RQ_DATA(rq);
1364 struct as_rq *alias;
1367 if (arq->state != AS_RQ_PRESCHED) {
1368 printk("arq->state: %d\n", arq->state);
1371 arq->state = AS_RQ_NEW;
1373 if (rq_data_dir(arq->request) == READ
1374 || current->flags&PF_SYNCWRITE)
1378 data_dir = arq->is_sync;
1380 arq->io_context = as_get_io_context();
1382 if (arq->io_context) {
1383 as_update_iohist(ad, arq->io_context->aic, arq->request);
1384 atomic_inc(&arq->io_context->aic->nr_queued);
1387 alias = as_add_arq_rb(ad, arq);
1390 * set expire time (only used for reads) and add to fifo list
1392 arq->expires = jiffies + ad->fifo_expire[data_dir];
1393 list_add_tail(&arq->fifo, &ad->fifo_list[data_dir]);
1395 if (rq_mergeable(arq->request)) {
1396 as_add_arq_hash(ad, arq);
1398 if (!ad->q->last_merge)
1399 ad->q->last_merge = arq->request;
1401 as_update_arq(ad, arq); /* keep state machine up to date */
1404 as_add_aliased_request(ad, arq, alias);
1407 * have we been anticipating this request?
1408 * or does it come from the same process as the one we are
1411 if (ad->antic_status == ANTIC_WAIT_REQ
1412 || ad->antic_status == ANTIC_WAIT_NEXT) {
1413 if (as_can_break_anticipation(ad, arq))
1418 arq->state = AS_RQ_QUEUED;
1421 static void as_activate_request(request_queue_t *q, struct request *rq)
1423 struct as_rq *arq = RQ_DATA(rq);
1425 WARN_ON(arq->state != AS_RQ_DISPATCHED);
1426 arq->state = AS_RQ_REMOVED;
1427 if (arq->io_context && arq->io_context->aic)
1428 atomic_dec(&arq->io_context->aic->nr_dispatched);
1431 static void as_deactivate_request(request_queue_t *q, struct request *rq)
1433 struct as_rq *arq = RQ_DATA(rq);
1435 WARN_ON(arq->state != AS_RQ_REMOVED);
1436 arq->state = AS_RQ_DISPATCHED;
1437 if (arq->io_context && arq->io_context->aic)
1438 atomic_inc(&arq->io_context->aic->nr_dispatched);
1442 * as_queue_empty tells us if there are requests left in the device. It may
1443 * not be the case that a driver can get the next request even if the queue
1444 * is not empty - it is used in the block layer to check for plugging and
1445 * merging opportunities
1447 static int as_queue_empty(request_queue_t *q)
1449 struct as_data *ad = q->elevator->elevator_data;
1451 return list_empty(&ad->fifo_list[REQ_ASYNC])
1452 && list_empty(&ad->fifo_list[REQ_SYNC]);
1455 static struct request *
1456 as_former_request(request_queue_t *q, struct request *rq)
1458 struct as_rq *arq = RQ_DATA(rq);
1459 struct rb_node *rbprev = rb_prev(&arq->rb_node);
1460 struct request *ret = NULL;
1463 ret = rb_entry_arq(rbprev)->request;
1468 static struct request *
1469 as_latter_request(request_queue_t *q, struct request *rq)
1471 struct as_rq *arq = RQ_DATA(rq);
1472 struct rb_node *rbnext = rb_next(&arq->rb_node);
1473 struct request *ret = NULL;
1476 ret = rb_entry_arq(rbnext)->request;
1482 as_merge(request_queue_t *q, struct request **req, struct bio *bio)
1484 struct as_data *ad = q->elevator->elevator_data;
1485 sector_t rb_key = bio->bi_sector + bio_sectors(bio);
1486 struct request *__rq;
1490 * try last_merge to avoid going to hash
1492 ret = elv_try_last_merge(q, bio);
1493 if (ret != ELEVATOR_NO_MERGE) {
1494 __rq = q->last_merge;
1499 * see if the merge hash can satisfy a back merge
1501 __rq = as_find_arq_hash(ad, bio->bi_sector);
1503 BUG_ON(__rq->sector + __rq->nr_sectors != bio->bi_sector);
1505 if (elv_rq_merge_ok(__rq, bio)) {
1506 ret = ELEVATOR_BACK_MERGE;
1512 * check for front merge
1514 __rq = as_find_arq_rb(ad, rb_key, bio_data_dir(bio));
1516 BUG_ON(rb_key != rq_rb_key(__rq));
1518 if (elv_rq_merge_ok(__rq, bio)) {
1519 ret = ELEVATOR_FRONT_MERGE;
1524 return ELEVATOR_NO_MERGE;
1526 if (rq_mergeable(__rq))
1527 q->last_merge = __rq;
1530 if (rq_mergeable(__rq))
1531 as_hot_arq_hash(ad, RQ_DATA(__rq));
1537 static void as_merged_request(request_queue_t *q, struct request *req)
1539 struct as_data *ad = q->elevator->elevator_data;
1540 struct as_rq *arq = RQ_DATA(req);
1543 * hash always needs to be repositioned, key is end sector
1545 as_del_arq_hash(arq);
1546 as_add_arq_hash(ad, arq);
1549 * if the merge was a front merge, we need to reposition request
1551 if (rq_rb_key(req) != arq->rb_key) {
1552 struct as_rq *alias, *next_arq = NULL;
1554 if (ad->next_arq[arq->is_sync] == arq)
1555 next_arq = as_find_next_arq(ad, arq);
1558 * Note! We should really be moving any old aliased requests
1559 * off this request and try to insert them into the rbtree. We
1560 * currently don't bother. Ditto the next function.
1562 as_del_arq_rb(ad, arq);
1563 if ((alias = as_add_arq_rb(ad, arq)) ) {
1564 list_del_init(&arq->fifo);
1565 as_add_aliased_request(ad, arq, alias);
1567 ad->next_arq[arq->is_sync] = next_arq;
1570 * Note! At this stage of this and the next function, our next
1571 * request may not be optimal - eg the request may have "grown"
1572 * behind the disk head. We currently don't bother adjusting.
1577 q->last_merge = req;
1581 as_merged_requests(request_queue_t *q, struct request *req,
1582 struct request *next)
1584 struct as_data *ad = q->elevator->elevator_data;
1585 struct as_rq *arq = RQ_DATA(req);
1586 struct as_rq *anext = RQ_DATA(next);
1592 * reposition arq (this is the merged request) in hash, and in rbtree
1593 * in case of a front merge
1595 as_del_arq_hash(arq);
1596 as_add_arq_hash(ad, arq);
1598 if (rq_rb_key(req) != arq->rb_key) {
1599 struct as_rq *alias, *next_arq = NULL;
1601 if (ad->next_arq[arq->is_sync] == arq)
1602 next_arq = as_find_next_arq(ad, arq);
1604 as_del_arq_rb(ad, arq);
1605 if ((alias = as_add_arq_rb(ad, arq)) ) {
1606 list_del_init(&arq->fifo);
1607 as_add_aliased_request(ad, arq, alias);
1609 ad->next_arq[arq->is_sync] = next_arq;
1614 * if anext expires before arq, assign its expire time to arq
1615 * and move into anext position (anext will be deleted) in fifo
1617 if (!list_empty(&arq->fifo) && !list_empty(&anext->fifo)) {
1618 if (time_before(anext->expires, arq->expires)) {
1619 list_move(&arq->fifo, &anext->fifo);
1620 arq->expires = anext->expires;
1622 * Don't copy here but swap, because when anext is
1623 * removed below, it must contain the unused context
1625 swap_io_context(&arq->io_context, &anext->io_context);
1630 * Transfer list of aliases
1632 while (!list_empty(&next->queuelist)) {
1633 struct request *__rq = list_entry_rq(next->queuelist.next);
1634 struct as_rq *__arq = RQ_DATA(__rq);
1636 list_move_tail(&__rq->queuelist, &req->queuelist);
1638 WARN_ON(__arq->state != AS_RQ_QUEUED);
1642 * kill knowledge of next, this one is a goner
1644 as_remove_queued_request(q, next);
1645 as_put_io_context(anext);
1647 anext->state = AS_RQ_MERGED;
1651 * This is executed in a "deferred" process context, by kblockd. It calls the
1652 * driver's request_fn so the driver can submit that request.
1654 * IMPORTANT! This guy will reenter the elevator, so set up all queue global
1655 * state before calling, and don't rely on any state over calls.
1657 * FIXME! dispatch queue is not a queue at all!
1659 static void as_work_handler(void *data)
1661 struct request_queue *q = data;
1662 unsigned long flags;
1664 spin_lock_irqsave(q->queue_lock, flags);
1665 if (!as_queue_empty(q))
1667 spin_unlock_irqrestore(q->queue_lock, flags);
1670 static void as_put_request(request_queue_t *q, struct request *rq)
1672 struct as_data *ad = q->elevator->elevator_data;
1673 struct as_rq *arq = RQ_DATA(rq);
1680 if (unlikely(arq->state != AS_RQ_POSTSCHED &&
1681 arq->state != AS_RQ_PRESCHED &&
1682 arq->state != AS_RQ_MERGED)) {
1683 printk("arq->state %d\n", arq->state);
1687 mempool_free(arq, ad->arq_pool);
1688 rq->elevator_private = NULL;
1691 static int as_set_request(request_queue_t *q, struct request *rq,
1692 struct bio *bio, int gfp_mask)
1694 struct as_data *ad = q->elevator->elevator_data;
1695 struct as_rq *arq = mempool_alloc(ad->arq_pool, gfp_mask);
1698 memset(arq, 0, sizeof(*arq));
1699 RB_CLEAR(&arq->rb_node);
1701 arq->state = AS_RQ_PRESCHED;
1702 arq->io_context = NULL;
1703 INIT_LIST_HEAD(&arq->hash);
1705 INIT_LIST_HEAD(&arq->fifo);
1706 rq->elevator_private = arq;
1713 static int as_may_queue(request_queue_t *q, int rw, struct bio *bio)
1715 int ret = ELV_MQUEUE_MAY;
1716 struct as_data *ad = q->elevator->elevator_data;
1717 struct io_context *ioc;
1718 if (ad->antic_status == ANTIC_WAIT_REQ ||
1719 ad->antic_status == ANTIC_WAIT_NEXT) {
1720 ioc = as_get_io_context();
1721 if (ad->io_context == ioc)
1722 ret = ELV_MQUEUE_MUST;
1723 put_io_context(ioc);
1729 static void as_exit_queue(elevator_t *e)
1731 struct as_data *ad = e->elevator_data;
1733 del_timer_sync(&ad->antic_timer);
1736 BUG_ON(!list_empty(&ad->fifo_list[REQ_SYNC]));
1737 BUG_ON(!list_empty(&ad->fifo_list[REQ_ASYNC]));
1739 mempool_destroy(ad->arq_pool);
1740 put_io_context(ad->io_context);
1746 * initialize elevator private data (as_data), and alloc a arq for
1747 * each request on the free lists
1749 static int as_init_queue(request_queue_t *q, elevator_t *e)
1757 ad = kmalloc_node(sizeof(*ad), GFP_KERNEL, q->node);
1760 memset(ad, 0, sizeof(*ad));
1762 ad->q = q; /* Identify what queue the data belongs to */
1764 ad->hash = kmalloc_node(sizeof(struct list_head)*AS_HASH_ENTRIES,
1765 GFP_KERNEL, q->node);
1771 ad->arq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
1772 mempool_free_slab, arq_pool, q->node);
1773 if (!ad->arq_pool) {
1779 /* anticipatory scheduling helpers */
1780 ad->antic_timer.function = as_antic_timeout;
1781 ad->antic_timer.data = (unsigned long)q;
1782 init_timer(&ad->antic_timer);
1783 INIT_WORK(&ad->antic_work, as_work_handler, q);
1785 for (i = 0; i < AS_HASH_ENTRIES; i++)
1786 INIT_LIST_HEAD(&ad->hash[i]);
1788 INIT_LIST_HEAD(&ad->fifo_list[REQ_SYNC]);
1789 INIT_LIST_HEAD(&ad->fifo_list[REQ_ASYNC]);
1790 ad->sort_list[REQ_SYNC] = RB_ROOT;
1791 ad->sort_list[REQ_ASYNC] = RB_ROOT;
1792 ad->fifo_expire[REQ_SYNC] = default_read_expire;
1793 ad->fifo_expire[REQ_ASYNC] = default_write_expire;
1794 ad->antic_expire = default_antic_expire;
1795 ad->batch_expire[REQ_SYNC] = default_read_batch_expire;
1796 ad->batch_expire[REQ_ASYNC] = default_write_batch_expire;
1797 e->elevator_data = ad;
1799 ad->current_batch_expires = jiffies + ad->batch_expire[REQ_SYNC];
1800 ad->write_batch_count = ad->batch_expire[REQ_ASYNC] / 10;
1801 if (ad->write_batch_count < 2)
1802 ad->write_batch_count = 2;
1810 struct as_fs_entry {
1811 struct attribute attr;
1812 ssize_t (*show)(struct as_data *, char *);
1813 ssize_t (*store)(struct as_data *, const char *, size_t);
1817 as_var_show(unsigned int var, char *page)
1819 return sprintf(page, "%d\n", var);
1823 as_var_store(unsigned long *var, const char *page, size_t count)
1825 char *p = (char *) page;
1827 *var = simple_strtoul(p, &p, 10);
1831 static ssize_t as_est_show(struct as_data *ad, char *page)
1835 pos += sprintf(page+pos, "%lu %% exit probability\n", 100*ad->exit_prob/256);
1836 pos += sprintf(page+pos, "%lu ms new thinktime\n", ad->new_ttime_mean);
1837 pos += sprintf(page+pos, "%llu sectors new seek distance\n", (unsigned long long)ad->new_seek_mean);
1842 #define SHOW_FUNCTION(__FUNC, __VAR) \
1843 static ssize_t __FUNC(struct as_data *ad, char *page) \
1845 return as_var_show(jiffies_to_msecs((__VAR)), (page)); \
1847 SHOW_FUNCTION(as_readexpire_show, ad->fifo_expire[REQ_SYNC]);
1848 SHOW_FUNCTION(as_writeexpire_show, ad->fifo_expire[REQ_ASYNC]);
1849 SHOW_FUNCTION(as_anticexpire_show, ad->antic_expire);
1850 SHOW_FUNCTION(as_read_batchexpire_show, ad->batch_expire[REQ_SYNC]);
1851 SHOW_FUNCTION(as_write_batchexpire_show, ad->batch_expire[REQ_ASYNC]);
1852 #undef SHOW_FUNCTION
1854 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \
1855 static ssize_t __FUNC(struct as_data *ad, const char *page, size_t count) \
1857 int ret = as_var_store(__PTR, (page), count); \
1858 if (*(__PTR) < (MIN)) \
1860 else if (*(__PTR) > (MAX)) \
1862 *(__PTR) = msecs_to_jiffies(*(__PTR)); \
1865 STORE_FUNCTION(as_readexpire_store, &ad->fifo_expire[REQ_SYNC], 0, INT_MAX);
1866 STORE_FUNCTION(as_writeexpire_store, &ad->fifo_expire[REQ_ASYNC], 0, INT_MAX);
1867 STORE_FUNCTION(as_anticexpire_store, &ad->antic_expire, 0, INT_MAX);
1868 STORE_FUNCTION(as_read_batchexpire_store,
1869 &ad->batch_expire[REQ_SYNC], 0, INT_MAX);
1870 STORE_FUNCTION(as_write_batchexpire_store,
1871 &ad->batch_expire[REQ_ASYNC], 0, INT_MAX);
1872 #undef STORE_FUNCTION
1874 static struct as_fs_entry as_est_entry = {
1875 .attr = {.name = "est_time", .mode = S_IRUGO },
1876 .show = as_est_show,
1878 static struct as_fs_entry as_readexpire_entry = {
1879 .attr = {.name = "read_expire", .mode = S_IRUGO | S_IWUSR },
1880 .show = as_readexpire_show,
1881 .store = as_readexpire_store,
1883 static struct as_fs_entry as_writeexpire_entry = {
1884 .attr = {.name = "write_expire", .mode = S_IRUGO | S_IWUSR },
1885 .show = as_writeexpire_show,
1886 .store = as_writeexpire_store,
1888 static struct as_fs_entry as_anticexpire_entry = {
1889 .attr = {.name = "antic_expire", .mode = S_IRUGO | S_IWUSR },
1890 .show = as_anticexpire_show,
1891 .store = as_anticexpire_store,
1893 static struct as_fs_entry as_read_batchexpire_entry = {
1894 .attr = {.name = "read_batch_expire", .mode = S_IRUGO | S_IWUSR },
1895 .show = as_read_batchexpire_show,
1896 .store = as_read_batchexpire_store,
1898 static struct as_fs_entry as_write_batchexpire_entry = {
1899 .attr = {.name = "write_batch_expire", .mode = S_IRUGO | S_IWUSR },
1900 .show = as_write_batchexpire_show,
1901 .store = as_write_batchexpire_store,
1904 static struct attribute *default_attrs[] = {
1906 &as_readexpire_entry.attr,
1907 &as_writeexpire_entry.attr,
1908 &as_anticexpire_entry.attr,
1909 &as_read_batchexpire_entry.attr,
1910 &as_write_batchexpire_entry.attr,
1914 #define to_as(atr) container_of((atr), struct as_fs_entry, attr)
1917 as_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
1919 elevator_t *e = container_of(kobj, elevator_t, kobj);
1920 struct as_fs_entry *entry = to_as(attr);
1925 return entry->show(e->elevator_data, page);
1929 as_attr_store(struct kobject *kobj, struct attribute *attr,
1930 const char *page, size_t length)
1932 elevator_t *e = container_of(kobj, elevator_t, kobj);
1933 struct as_fs_entry *entry = to_as(attr);
1938 return entry->store(e->elevator_data, page, length);
1941 static struct sysfs_ops as_sysfs_ops = {
1942 .show = as_attr_show,
1943 .store = as_attr_store,
1946 static struct kobj_type as_ktype = {
1947 .sysfs_ops = &as_sysfs_ops,
1948 .default_attrs = default_attrs,
1951 static struct elevator_type iosched_as = {
1953 .elevator_merge_fn = as_merge,
1954 .elevator_merged_fn = as_merged_request,
1955 .elevator_merge_req_fn = as_merged_requests,
1956 .elevator_dispatch_fn = as_dispatch_request,
1957 .elevator_add_req_fn = as_add_request,
1958 .elevator_activate_req_fn = as_activate_request,
1959 .elevator_deactivate_req_fn = as_deactivate_request,
1960 .elevator_queue_empty_fn = as_queue_empty,
1961 .elevator_completed_req_fn = as_completed_request,
1962 .elevator_former_req_fn = as_former_request,
1963 .elevator_latter_req_fn = as_latter_request,
1964 .elevator_set_req_fn = as_set_request,
1965 .elevator_put_req_fn = as_put_request,
1966 .elevator_may_queue_fn = as_may_queue,
1967 .elevator_init_fn = as_init_queue,
1968 .elevator_exit_fn = as_exit_queue,
1971 .elevator_ktype = &as_ktype,
1972 .elevator_name = "anticipatory",
1973 .elevator_owner = THIS_MODULE,
1976 static int __init as_init(void)
1980 arq_pool = kmem_cache_create("as_arq", sizeof(struct as_rq),
1985 ret = elv_register(&iosched_as);
1988 * don't allow AS to get unregistered, since we would have
1989 * to browse all tasks in the system and release their
1990 * as_io_context first
1992 __module_get(THIS_MODULE);
1996 kmem_cache_destroy(arq_pool);
2000 static void __exit as_exit(void)
2002 kmem_cache_destroy(arq_pool);
2003 elv_unregister(&iosched_as);
2006 module_init(as_init);
2007 module_exit(as_exit);
2009 MODULE_AUTHOR("Nick Piggin");
2010 MODULE_LICENSE("GPL");
2011 MODULE_DESCRIPTION("anticipatory IO scheduler");