Commit | Line | Data |
---|---|---|
1da177e4 | 1 | /* |
1da177e4 LT |
2 | * Anticipatory & deadline i/o scheduler. |
3 | * | |
0fe23479 | 4 | * Copyright (C) 2002 Jens Axboe <axboe@kernel.dk> |
f5b3db00 | 5 | * Nick Piggin <nickpiggin@yahoo.com.au> |
1da177e4 LT |
6 | * |
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> | |
1da177e4 LT |
13 | #include <linux/module.h> |
14 | #include <linux/slab.h> | |
15 | #include <linux/init.h> | |
16 | #include <linux/compiler.h> | |
1da177e4 LT |
17 | #include <linux/rbtree.h> |
18 | #include <linux/interrupt.h> | |
19 | ||
1da177e4 LT |
20 | /* |
21 | * See Documentation/block/as-iosched.txt | |
22 | */ | |
23 | ||
24 | /* | |
25 | * max time before a read is submitted. | |
26 | */ | |
27 | #define default_read_expire (HZ / 8) | |
28 | ||
29 | /* | |
30 | * ditto for writes, these limits are not hard, even | |
31 | * if the disk is capable of satisfying them. | |
32 | */ | |
33 | #define default_write_expire (HZ / 4) | |
34 | ||
35 | /* | |
36 | * read_batch_expire describes how long we will allow a stream of reads to | |
37 | * persist before looking to see whether it is time to switch over to writes. | |
38 | */ | |
39 | #define default_read_batch_expire (HZ / 2) | |
40 | ||
41 | /* | |
42 | * write_batch_expire describes how long we want a stream of writes to run for. | |
43 | * This is not a hard limit, but a target we set for the auto-tuning thingy. | |
44 | * See, the problem is: we can send a lot of writes to disk cache / TCQ in | |
45 | * a short amount of time... | |
46 | */ | |
47 | #define default_write_batch_expire (HZ / 8) | |
48 | ||
49 | /* | |
50 | * max time we may wait to anticipate a read (default around 6ms) | |
51 | */ | |
52 | #define default_antic_expire ((HZ / 150) ? HZ / 150 : 1) | |
53 | ||
54 | /* | |
55 | * Keep track of up to 20ms thinktimes. We can go as big as we like here, | |
56 | * however huge values tend to interfere and not decay fast enough. A program | |
57 | * might be in a non-io phase of operation. Waiting on user input for example, | |
58 | * or doing a lengthy computation. A small penalty can be justified there, and | |
59 | * will still catch out those processes that constantly have large thinktimes. | |
60 | */ | |
61 | #define MAX_THINKTIME (HZ/50UL) | |
62 | ||
63 | /* Bits in as_io_context.state */ | |
64 | enum as_io_states { | |
f5b3db00 | 65 | AS_TASK_RUNNING=0, /* Process has not exited */ |
1da177e4 LT |
66 | AS_TASK_IOSTARTED, /* Process has started some IO */ |
67 | AS_TASK_IORUNNING, /* Process has completed some IO */ | |
68 | }; | |
69 | ||
70 | enum anticipation_status { | |
71 | ANTIC_OFF=0, /* Not anticipating (normal operation) */ | |
72 | ANTIC_WAIT_REQ, /* The last read has not yet completed */ | |
73 | ANTIC_WAIT_NEXT, /* Currently anticipating a request vs | |
74 | last read (which has completed) */ | |
75 | ANTIC_FINISHED, /* Anticipating but have found a candidate | |
76 | * or timed out */ | |
77 | }; | |
78 | ||
79 | struct as_data { | |
80 | /* | |
81 | * run time data | |
82 | */ | |
83 | ||
84 | struct request_queue *q; /* the "owner" queue */ | |
85 | ||
86 | /* | |
87 | * requests (as_rq s) are present on both sort_list and fifo_list | |
88 | */ | |
89 | struct rb_root sort_list[2]; | |
90 | struct list_head fifo_list[2]; | |
91 | ||
8a8e674c | 92 | struct request *next_rq[2]; /* next in sort order */ |
1d6bfbdf | 93 | sector_t last_sector[2]; /* last SYNC & ASYNC sectors */ |
1da177e4 LT |
94 | |
95 | unsigned long exit_prob; /* probability a task will exit while | |
96 | being waited on */ | |
f5b3db00 NP |
97 | unsigned long exit_no_coop; /* probablility an exited task will |
98 | not be part of a later cooperating | |
99 | request */ | |
1da177e4 LT |
100 | unsigned long new_ttime_total; /* mean thinktime on new proc */ |
101 | unsigned long new_ttime_mean; | |
102 | u64 new_seek_total; /* mean seek on new proc */ | |
103 | sector_t new_seek_mean; | |
104 | ||
105 | unsigned long current_batch_expires; | |
106 | unsigned long last_check_fifo[2]; | |
107 | int changed_batch; /* 1: waiting for old batch to end */ | |
108 | int new_batch; /* 1: waiting on first read complete */ | |
1d6bfbdf | 109 | int batch_data_dir; /* current batch SYNC / ASYNC */ |
1da177e4 LT |
110 | int write_batch_count; /* max # of reqs in a write batch */ |
111 | int current_write_count; /* how many requests left this batch */ | |
112 | int write_batch_idled; /* has the write batch gone idle? */ | |
1da177e4 LT |
113 | |
114 | enum anticipation_status antic_status; | |
115 | unsigned long antic_start; /* jiffies: when it started */ | |
116 | struct timer_list antic_timer; /* anticipatory scheduling timer */ | |
117 | struct work_struct antic_work; /* Deferred unplugging */ | |
118 | struct io_context *io_context; /* Identify the expected process */ | |
119 | int ioc_finished; /* IO associated with io_context is finished */ | |
120 | int nr_dispatched; | |
121 | ||
122 | /* | |
123 | * settings that change how the i/o scheduler behaves | |
124 | */ | |
125 | unsigned long fifo_expire[2]; | |
126 | unsigned long batch_expire[2]; | |
127 | unsigned long antic_expire; | |
128 | }; | |
129 | ||
1da177e4 LT |
130 | /* |
131 | * per-request data. | |
132 | */ | |
133 | enum arq_state { | |
134 | AS_RQ_NEW=0, /* New - not referenced and not on any lists */ | |
135 | AS_RQ_QUEUED, /* In the request queue. It belongs to the | |
136 | scheduler */ | |
137 | AS_RQ_DISPATCHED, /* On the dispatch list. It belongs to the | |
138 | driver now */ | |
139 | AS_RQ_PRESCHED, /* Debug poisoning for requests being used */ | |
140 | AS_RQ_REMOVED, | |
141 | AS_RQ_MERGED, | |
142 | AS_RQ_POSTSCHED, /* when they shouldn't be */ | |
143 | }; | |
144 | ||
8a8e674c JA |
145 | #define RQ_IOC(rq) ((struct io_context *) (rq)->elevator_private) |
146 | #define RQ_STATE(rq) ((enum arq_state)(rq)->elevator_private2) | |
147 | #define RQ_SET_STATE(rq, state) ((rq)->elevator_private2 = (void *) state) | |
1da177e4 | 148 | |
e4313dd4 | 149 | static DEFINE_PER_CPU(unsigned long, ioc_count); |
334e94de | 150 | static struct completion *ioc_gone; |
863fddcb | 151 | static DEFINE_SPINLOCK(ioc_gone_lock); |
334e94de | 152 | |
8a8e674c | 153 | static void as_move_to_dispatch(struct as_data *ad, struct request *rq); |
ef9be1d3 TH |
154 | static void as_antic_stop(struct as_data *ad); |
155 | ||
1da177e4 LT |
156 | /* |
157 | * IO Context helper functions | |
158 | */ | |
159 | ||
160 | /* Called to deallocate the as_io_context */ | |
161 | static void free_as_io_context(struct as_io_context *aic) | |
162 | { | |
163 | kfree(aic); | |
e4313dd4 | 164 | elv_ioc_count_dec(ioc_count); |
863fddcb JA |
165 | if (ioc_gone) { |
166 | /* | |
167 | * AS scheduler is exiting, grab exit lock and check | |
168 | * the pending io context count. If it hits zero, | |
169 | * complete ioc_gone and set it back to NULL. | |
170 | */ | |
171 | spin_lock(&ioc_gone_lock); | |
172 | if (ioc_gone && !elv_ioc_count_read(ioc_count)) { | |
173 | complete(ioc_gone); | |
174 | ioc_gone = NULL; | |
175 | } | |
176 | spin_unlock(&ioc_gone_lock); | |
177 | } | |
1da177e4 LT |
178 | } |
179 | ||
e17a9489 AV |
180 | static void as_trim(struct io_context *ioc) |
181 | { | |
8bdd3f8a | 182 | spin_lock_irq(&ioc->lock); |
334e94de AV |
183 | if (ioc->aic) |
184 | free_as_io_context(ioc->aic); | |
e17a9489 | 185 | ioc->aic = NULL; |
8bdd3f8a | 186 | spin_unlock_irq(&ioc->lock); |
e17a9489 AV |
187 | } |
188 | ||
1da177e4 LT |
189 | /* Called when the task exits */ |
190 | static void exit_as_io_context(struct as_io_context *aic) | |
191 | { | |
192 | WARN_ON(!test_bit(AS_TASK_RUNNING, &aic->state)); | |
193 | clear_bit(AS_TASK_RUNNING, &aic->state); | |
194 | } | |
195 | ||
196 | static struct as_io_context *alloc_as_io_context(void) | |
197 | { | |
198 | struct as_io_context *ret; | |
199 | ||
200 | ret = kmalloc(sizeof(*ret), GFP_ATOMIC); | |
201 | if (ret) { | |
202 | ret->dtor = free_as_io_context; | |
203 | ret->exit = exit_as_io_context; | |
204 | ret->state = 1 << AS_TASK_RUNNING; | |
205 | atomic_set(&ret->nr_queued, 0); | |
206 | atomic_set(&ret->nr_dispatched, 0); | |
207 | spin_lock_init(&ret->lock); | |
208 | ret->ttime_total = 0; | |
209 | ret->ttime_samples = 0; | |
210 | ret->ttime_mean = 0; | |
211 | ret->seek_total = 0; | |
212 | ret->seek_samples = 0; | |
213 | ret->seek_mean = 0; | |
e4313dd4 | 214 | elv_ioc_count_inc(ioc_count); |
1da177e4 LT |
215 | } |
216 | ||
217 | return ret; | |
218 | } | |
219 | ||
220 | /* | |
221 | * If the current task has no AS IO context then create one and initialise it. | |
222 | * Then take a ref on the task's io context and return it. | |
223 | */ | |
b5deef90 | 224 | static struct io_context *as_get_io_context(int node) |
1da177e4 | 225 | { |
b5deef90 | 226 | struct io_context *ioc = get_io_context(GFP_ATOMIC, node); |
1da177e4 LT |
227 | if (ioc && !ioc->aic) { |
228 | ioc->aic = alloc_as_io_context(); | |
229 | if (!ioc->aic) { | |
230 | put_io_context(ioc); | |
231 | ioc = NULL; | |
232 | } | |
233 | } | |
234 | return ioc; | |
235 | } | |
236 | ||
8a8e674c | 237 | static void as_put_io_context(struct request *rq) |
b4878f24 JA |
238 | { |
239 | struct as_io_context *aic; | |
240 | ||
8a8e674c | 241 | if (unlikely(!RQ_IOC(rq))) |
b4878f24 JA |
242 | return; |
243 | ||
8a8e674c | 244 | aic = RQ_IOC(rq)->aic; |
b4878f24 | 245 | |
8a8e674c | 246 | if (rq_is_sync(rq) && aic) { |
8bdd3f8a JA |
247 | unsigned long flags; |
248 | ||
249 | spin_lock_irqsave(&aic->lock, flags); | |
b4878f24 JA |
250 | set_bit(AS_TASK_IORUNNING, &aic->state); |
251 | aic->last_end_request = jiffies; | |
8bdd3f8a | 252 | spin_unlock_irqrestore(&aic->lock, flags); |
b4878f24 JA |
253 | } |
254 | ||
8a8e674c | 255 | put_io_context(RQ_IOC(rq)); |
b4878f24 JA |
256 | } |
257 | ||
1da177e4 LT |
258 | /* |
259 | * rb tree support functions | |
260 | */ | |
9e2585a8 | 261 | #define RQ_RB_ROOT(ad, rq) (&(ad)->sort_list[rq_is_sync((rq))]) |
1da177e4 | 262 | |
8a8e674c | 263 | static void as_add_rq_rb(struct as_data *ad, struct request *rq) |
ef9be1d3 | 264 | { |
e37f346e | 265 | struct request *alias; |
ef9be1d3 | 266 | |
9e2585a8 | 267 | while ((unlikely(alias = elv_rb_add(RQ_RB_ROOT(ad, rq), rq)))) { |
8a8e674c | 268 | as_move_to_dispatch(ad, alias); |
ef9be1d3 TH |
269 | as_antic_stop(ad); |
270 | } | |
271 | } | |
272 | ||
8a8e674c | 273 | static inline void as_del_rq_rb(struct as_data *ad, struct request *rq) |
1da177e4 | 274 | { |
9e2585a8 | 275 | elv_rb_del(RQ_RB_ROOT(ad, rq), rq); |
1da177e4 LT |
276 | } |
277 | ||
278 | /* | |
279 | * IO Scheduler proper | |
280 | */ | |
281 | ||
282 | #define MAXBACK (1024 * 1024) /* | |
283 | * Maximum distance the disk will go backward | |
284 | * for a request. | |
285 | */ | |
286 | ||
287 | #define BACK_PENALTY 2 | |
288 | ||
289 | /* | |
290 | * as_choose_req selects the preferred one of two requests of the same data_dir | |
291 | * ignoring time - eg. timeouts, which is the job of as_dispatch_request | |
292 | */ | |
8a8e674c JA |
293 | static struct request * |
294 | as_choose_req(struct as_data *ad, struct request *rq1, struct request *rq2) | |
1da177e4 LT |
295 | { |
296 | int data_dir; | |
297 | sector_t last, s1, s2, d1, d2; | |
298 | int r1_wrap=0, r2_wrap=0; /* requests are behind the disk head */ | |
299 | const sector_t maxback = MAXBACK; | |
300 | ||
8a8e674c JA |
301 | if (rq1 == NULL || rq1 == rq2) |
302 | return rq2; | |
303 | if (rq2 == NULL) | |
304 | return rq1; | |
1da177e4 | 305 | |
8a8e674c | 306 | data_dir = rq_is_sync(rq1); |
1da177e4 LT |
307 | |
308 | last = ad->last_sector[data_dir]; | |
8a8e674c JA |
309 | s1 = rq1->sector; |
310 | s2 = rq2->sector; | |
1da177e4 | 311 | |
8a8e674c | 312 | BUG_ON(data_dir != rq_is_sync(rq2)); |
1da177e4 LT |
313 | |
314 | /* | |
315 | * Strict one way elevator _except_ in the case where we allow | |
316 | * short backward seeks which are biased as twice the cost of a | |
317 | * similar forward seek. | |
318 | */ | |
319 | if (s1 >= last) | |
320 | d1 = s1 - last; | |
321 | else if (s1+maxback >= last) | |
322 | d1 = (last - s1)*BACK_PENALTY; | |
323 | else { | |
324 | r1_wrap = 1; | |
325 | d1 = 0; /* shut up, gcc */ | |
326 | } | |
327 | ||
328 | if (s2 >= last) | |
329 | d2 = s2 - last; | |
330 | else if (s2+maxback >= last) | |
331 | d2 = (last - s2)*BACK_PENALTY; | |
332 | else { | |
333 | r2_wrap = 1; | |
334 | d2 = 0; | |
335 | } | |
336 | ||
337 | /* Found required data */ | |
338 | if (!r1_wrap && r2_wrap) | |
8a8e674c | 339 | return rq1; |
1da177e4 | 340 | else if (!r2_wrap && r1_wrap) |
8a8e674c | 341 | return rq2; |
1da177e4 LT |
342 | else if (r1_wrap && r2_wrap) { |
343 | /* both behind the head */ | |
344 | if (s1 <= s2) | |
8a8e674c | 345 | return rq1; |
1da177e4 | 346 | else |
8a8e674c | 347 | return rq2; |
1da177e4 LT |
348 | } |
349 | ||
350 | /* Both requests in front of the head */ | |
351 | if (d1 < d2) | |
8a8e674c | 352 | return rq1; |
1da177e4 | 353 | else if (d2 < d1) |
8a8e674c | 354 | return rq2; |
1da177e4 LT |
355 | else { |
356 | if (s1 >= s2) | |
8a8e674c | 357 | return rq1; |
1da177e4 | 358 | else |
8a8e674c | 359 | return rq2; |
1da177e4 LT |
360 | } |
361 | } | |
362 | ||
363 | /* | |
8a8e674c | 364 | * as_find_next_rq finds the next request after @prev in elevator order. |
1da177e4 LT |
365 | * this with as_choose_req form the basis for how the scheduler chooses |
366 | * what request to process next. Anticipation works on top of this. | |
367 | */ | |
8a8e674c JA |
368 | static struct request * |
369 | as_find_next_rq(struct as_data *ad, struct request *last) | |
1da177e4 | 370 | { |
1da177e4 LT |
371 | struct rb_node *rbnext = rb_next(&last->rb_node); |
372 | struct rb_node *rbprev = rb_prev(&last->rb_node); | |
8a8e674c | 373 | struct request *next = NULL, *prev = NULL; |
1da177e4 | 374 | |
e37f346e | 375 | BUG_ON(RB_EMPTY_NODE(&last->rb_node)); |
1da177e4 LT |
376 | |
377 | if (rbprev) | |
8a8e674c | 378 | prev = rb_entry_rq(rbprev); |
1da177e4 LT |
379 | |
380 | if (rbnext) | |
8a8e674c | 381 | next = rb_entry_rq(rbnext); |
1da177e4 | 382 | else { |
9e2585a8 | 383 | const int data_dir = rq_is_sync(last); |
1da177e4 | 384 | |
e37f346e JA |
385 | rbnext = rb_first(&ad->sort_list[data_dir]); |
386 | if (rbnext && rbnext != &last->rb_node) | |
8a8e674c | 387 | next = rb_entry_rq(rbnext); |
e37f346e | 388 | } |
1da177e4 | 389 | |
e37f346e | 390 | return as_choose_req(ad, next, prev); |
1da177e4 LT |
391 | } |
392 | ||
393 | /* | |
394 | * anticipatory scheduling functions follow | |
395 | */ | |
396 | ||
397 | /* | |
398 | * as_antic_expired tells us when we have anticipated too long. | |
399 | * The funny "absolute difference" math on the elapsed time is to handle | |
400 | * jiffy wraps, and disks which have been idle for 0x80000000 jiffies. | |
401 | */ | |
402 | static int as_antic_expired(struct as_data *ad) | |
403 | { | |
404 | long delta_jif; | |
405 | ||
406 | delta_jif = jiffies - ad->antic_start; | |
407 | if (unlikely(delta_jif < 0)) | |
408 | delta_jif = -delta_jif; | |
409 | if (delta_jif < ad->antic_expire) | |
410 | return 0; | |
411 | ||
412 | return 1; | |
413 | } | |
414 | ||
415 | /* | |
416 | * as_antic_waitnext starts anticipating that a nice request will soon be | |
417 | * submitted. See also as_antic_waitreq | |
418 | */ | |
419 | static void as_antic_waitnext(struct as_data *ad) | |
420 | { | |
421 | unsigned long timeout; | |
422 | ||
423 | BUG_ON(ad->antic_status != ANTIC_OFF | |
424 | && ad->antic_status != ANTIC_WAIT_REQ); | |
425 | ||
426 | timeout = ad->antic_start + ad->antic_expire; | |
427 | ||
428 | mod_timer(&ad->antic_timer, timeout); | |
429 | ||
430 | ad->antic_status = ANTIC_WAIT_NEXT; | |
431 | } | |
432 | ||
433 | /* | |
434 | * as_antic_waitreq starts anticipating. We don't start timing the anticipation | |
435 | * until the request that we're anticipating on has finished. This means we | |
436 | * are timing from when the candidate process wakes up hopefully. | |
437 | */ | |
438 | static void as_antic_waitreq(struct as_data *ad) | |
439 | { | |
440 | BUG_ON(ad->antic_status == ANTIC_FINISHED); | |
441 | if (ad->antic_status == ANTIC_OFF) { | |
442 | if (!ad->io_context || ad->ioc_finished) | |
443 | as_antic_waitnext(ad); | |
444 | else | |
445 | ad->antic_status = ANTIC_WAIT_REQ; | |
446 | } | |
447 | } | |
448 | ||
449 | /* | |
450 | * This is called directly by the functions in this file to stop anticipation. | |
451 | * We kill the timer and schedule a call to the request_fn asap. | |
452 | */ | |
453 | static void as_antic_stop(struct as_data *ad) | |
454 | { | |
455 | int status = ad->antic_status; | |
456 | ||
457 | if (status == ANTIC_WAIT_REQ || status == ANTIC_WAIT_NEXT) { | |
458 | if (status == ANTIC_WAIT_NEXT) | |
459 | del_timer(&ad->antic_timer); | |
460 | ad->antic_status = ANTIC_FINISHED; | |
461 | /* see as_work_handler */ | |
18887ad9 | 462 | kblockd_schedule_work(ad->q, &ad->antic_work); |
1da177e4 LT |
463 | } |
464 | } | |
465 | ||
466 | /* | |
467 | * as_antic_timeout is the timer function set by as_antic_waitnext. | |
468 | */ | |
469 | static void as_antic_timeout(unsigned long data) | |
470 | { | |
471 | struct request_queue *q = (struct request_queue *)data; | |
472 | struct as_data *ad = q->elevator->elevator_data; | |
473 | unsigned long flags; | |
474 | ||
475 | spin_lock_irqsave(q->queue_lock, flags); | |
476 | if (ad->antic_status == ANTIC_WAIT_REQ | |
477 | || ad->antic_status == ANTIC_WAIT_NEXT) { | |
521f3bbd JA |
478 | struct as_io_context *aic; |
479 | spin_lock(&ad->io_context->lock); | |
480 | aic = ad->io_context->aic; | |
1da177e4 LT |
481 | |
482 | ad->antic_status = ANTIC_FINISHED; | |
18887ad9 | 483 | kblockd_schedule_work(q, &ad->antic_work); |
1da177e4 LT |
484 | |
485 | if (aic->ttime_samples == 0) { | |
f5b3db00 | 486 | /* process anticipated on has exited or timed out*/ |
1da177e4 LT |
487 | ad->exit_prob = (7*ad->exit_prob + 256)/8; |
488 | } | |
f5b3db00 NP |
489 | if (!test_bit(AS_TASK_RUNNING, &aic->state)) { |
490 | /* process not "saved" by a cooperating request */ | |
491 | ad->exit_no_coop = (7*ad->exit_no_coop + 256)/8; | |
492 | } | |
521f3bbd | 493 | spin_unlock(&ad->io_context->lock); |
1da177e4 LT |
494 | } |
495 | spin_unlock_irqrestore(q->queue_lock, flags); | |
496 | } | |
497 | ||
f5b3db00 NP |
498 | static void as_update_thinktime(struct as_data *ad, struct as_io_context *aic, |
499 | unsigned long ttime) | |
500 | { | |
501 | /* fixed point: 1.0 == 1<<8 */ | |
502 | if (aic->ttime_samples == 0) { | |
503 | ad->new_ttime_total = (7*ad->new_ttime_total + 256*ttime) / 8; | |
504 | ad->new_ttime_mean = ad->new_ttime_total / 256; | |
505 | ||
506 | ad->exit_prob = (7*ad->exit_prob)/8; | |
507 | } | |
508 | aic->ttime_samples = (7*aic->ttime_samples + 256) / 8; | |
509 | aic->ttime_total = (7*aic->ttime_total + 256*ttime) / 8; | |
510 | aic->ttime_mean = (aic->ttime_total + 128) / aic->ttime_samples; | |
511 | } | |
512 | ||
513 | static void as_update_seekdist(struct as_data *ad, struct as_io_context *aic, | |
514 | sector_t sdist) | |
515 | { | |
516 | u64 total; | |
517 | ||
518 | if (aic->seek_samples == 0) { | |
519 | ad->new_seek_total = (7*ad->new_seek_total + 256*(u64)sdist)/8; | |
520 | ad->new_seek_mean = ad->new_seek_total / 256; | |
521 | } | |
522 | ||
523 | /* | |
524 | * Don't allow the seek distance to get too large from the | |
525 | * odd fragment, pagein, etc | |
526 | */ | |
527 | if (aic->seek_samples <= 60) /* second&third seek */ | |
528 | sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*1024); | |
529 | else | |
530 | sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*64); | |
531 | ||
532 | aic->seek_samples = (7*aic->seek_samples + 256) / 8; | |
533 | aic->seek_total = (7*aic->seek_total + (u64)256*sdist) / 8; | |
534 | total = aic->seek_total + (aic->seek_samples/2); | |
535 | do_div(total, aic->seek_samples); | |
536 | aic->seek_mean = (sector_t)total; | |
537 | } | |
538 | ||
539 | /* | |
540 | * as_update_iohist keeps a decaying histogram of IO thinktimes, and | |
541 | * updates @aic->ttime_mean based on that. It is called when a new | |
542 | * request is queued. | |
543 | */ | |
544 | static void as_update_iohist(struct as_data *ad, struct as_io_context *aic, | |
545 | struct request *rq) | |
546 | { | |
9e2585a8 | 547 | int data_dir = rq_is_sync(rq); |
f5b3db00 NP |
548 | unsigned long thinktime = 0; |
549 | sector_t seek_dist; | |
550 | ||
551 | if (aic == NULL) | |
552 | return; | |
553 | ||
1d6bfbdf | 554 | if (data_dir == BLK_RW_SYNC) { |
f5b3db00 NP |
555 | unsigned long in_flight = atomic_read(&aic->nr_queued) |
556 | + atomic_read(&aic->nr_dispatched); | |
557 | spin_lock(&aic->lock); | |
558 | if (test_bit(AS_TASK_IORUNNING, &aic->state) || | |
559 | test_bit(AS_TASK_IOSTARTED, &aic->state)) { | |
560 | /* Calculate read -> read thinktime */ | |
561 | if (test_bit(AS_TASK_IORUNNING, &aic->state) | |
562 | && in_flight == 0) { | |
563 | thinktime = jiffies - aic->last_end_request; | |
564 | thinktime = min(thinktime, MAX_THINKTIME-1); | |
565 | } | |
566 | as_update_thinktime(ad, aic, thinktime); | |
567 | ||
568 | /* Calculate read -> read seek distance */ | |
569 | if (aic->last_request_pos < rq->sector) | |
570 | seek_dist = rq->sector - aic->last_request_pos; | |
571 | else | |
572 | seek_dist = aic->last_request_pos - rq->sector; | |
573 | as_update_seekdist(ad, aic, seek_dist); | |
574 | } | |
575 | aic->last_request_pos = rq->sector + rq->nr_sectors; | |
576 | set_bit(AS_TASK_IOSTARTED, &aic->state); | |
577 | spin_unlock(&aic->lock); | |
578 | } | |
579 | } | |
580 | ||
1da177e4 LT |
581 | /* |
582 | * as_close_req decides if one request is considered "close" to the | |
583 | * previous one issued. | |
584 | */ | |
f5b3db00 | 585 | static int as_close_req(struct as_data *ad, struct as_io_context *aic, |
8a8e674c | 586 | struct request *rq) |
1da177e4 | 587 | { |
c6a632a2 | 588 | unsigned long delay; /* jiffies */ |
1da177e4 | 589 | sector_t last = ad->last_sector[ad->batch_data_dir]; |
8a8e674c | 590 | sector_t next = rq->sector; |
1da177e4 | 591 | sector_t delta; /* acceptable close offset (in sectors) */ |
f5b3db00 | 592 | sector_t s; |
1da177e4 LT |
593 | |
594 | if (ad->antic_status == ANTIC_OFF || !ad->ioc_finished) | |
595 | delay = 0; | |
596 | else | |
c6a632a2 | 597 | delay = jiffies - ad->antic_start; |
1da177e4 | 598 | |
f5b3db00 NP |
599 | if (delay == 0) |
600 | delta = 8192; | |
c6a632a2 | 601 | else if (delay <= (20 * HZ / 1000) && delay <= ad->antic_expire) |
f5b3db00 | 602 | delta = 8192 << delay; |
1da177e4 LT |
603 | else |
604 | return 1; | |
605 | ||
f5b3db00 NP |
606 | if ((last <= next + (delta>>1)) && (next <= last + delta)) |
607 | return 1; | |
608 | ||
609 | if (last < next) | |
610 | s = next - last; | |
611 | else | |
612 | s = last - next; | |
613 | ||
614 | if (aic->seek_samples == 0) { | |
615 | /* | |
616 | * Process has just started IO. Use past statistics to | |
617 | * gauge success possibility | |
618 | */ | |
619 | if (ad->new_seek_mean > s) { | |
620 | /* this request is better than what we're expecting */ | |
621 | return 1; | |
622 | } | |
623 | ||
624 | } else { | |
625 | if (aic->seek_mean > s) { | |
626 | /* this request is better than what we're expecting */ | |
627 | return 1; | |
628 | } | |
629 | } | |
630 | ||
631 | return 0; | |
1da177e4 LT |
632 | } |
633 | ||
634 | /* | |
635 | * as_can_break_anticipation returns true if we have been anticipating this | |
636 | * request. | |
637 | * | |
638 | * It also returns true if the process against which we are anticipating | |
639 | * submits a write - that's presumably an fsync, O_SYNC write, etc. We want to | |
640 | * dispatch it ASAP, because we know that application will not be submitting | |
641 | * any new reads. | |
642 | * | |
f5b3db00 | 643 | * If the task which has submitted the request has exited, break anticipation. |
1da177e4 LT |
644 | * |
645 | * If this task has queued some other IO, do not enter enticipation. | |
646 | */ | |
8a8e674c | 647 | static int as_can_break_anticipation(struct as_data *ad, struct request *rq) |
1da177e4 LT |
648 | { |
649 | struct io_context *ioc; | |
650 | struct as_io_context *aic; | |
1da177e4 LT |
651 | |
652 | ioc = ad->io_context; | |
653 | BUG_ON(!ioc); | |
521f3bbd | 654 | spin_lock(&ioc->lock); |
1da177e4 | 655 | |
8a8e674c | 656 | if (rq && ioc == RQ_IOC(rq)) { |
1da177e4 | 657 | /* request from same process */ |
521f3bbd | 658 | spin_unlock(&ioc->lock); |
1da177e4 LT |
659 | return 1; |
660 | } | |
661 | ||
662 | if (ad->ioc_finished && as_antic_expired(ad)) { | |
663 | /* | |
664 | * In this situation status should really be FINISHED, | |
665 | * however the timer hasn't had the chance to run yet. | |
666 | */ | |
521f3bbd | 667 | spin_unlock(&ioc->lock); |
1da177e4 LT |
668 | return 1; |
669 | } | |
670 | ||
671 | aic = ioc->aic; | |
521f3bbd JA |
672 | if (!aic) { |
673 | spin_unlock(&ioc->lock); | |
1da177e4 | 674 | return 0; |
521f3bbd | 675 | } |
1da177e4 | 676 | |
1da177e4 LT |
677 | if (atomic_read(&aic->nr_queued) > 0) { |
678 | /* process has more requests queued */ | |
521f3bbd | 679 | spin_unlock(&ioc->lock); |
1da177e4 LT |
680 | return 1; |
681 | } | |
682 | ||
683 | if (atomic_read(&aic->nr_dispatched) > 0) { | |
684 | /* process has more requests dispatched */ | |
521f3bbd | 685 | spin_unlock(&ioc->lock); |
1da177e4 LT |
686 | return 1; |
687 | } | |
688 | ||
8a8e674c | 689 | if (rq && rq_is_sync(rq) && as_close_req(ad, aic, rq)) { |
1da177e4 LT |
690 | /* |
691 | * Found a close request that is not one of ours. | |
692 | * | |
f5b3db00 NP |
693 | * This makes close requests from another process update |
694 | * our IO history. Is generally useful when there are | |
1da177e4 LT |
695 | * two or more cooperating processes working in the same |
696 | * area. | |
697 | */ | |
f5b3db00 NP |
698 | if (!test_bit(AS_TASK_RUNNING, &aic->state)) { |
699 | if (aic->ttime_samples == 0) | |
700 | ad->exit_prob = (7*ad->exit_prob + 256)/8; | |
701 | ||
702 | ad->exit_no_coop = (7*ad->exit_no_coop)/8; | |
703 | } | |
704 | ||
8a8e674c | 705 | as_update_iohist(ad, aic, rq); |
521f3bbd | 706 | spin_unlock(&ioc->lock); |
1da177e4 LT |
707 | return 1; |
708 | } | |
709 | ||
f5b3db00 NP |
710 | if (!test_bit(AS_TASK_RUNNING, &aic->state)) { |
711 | /* process anticipated on has exited */ | |
712 | if (aic->ttime_samples == 0) | |
713 | ad->exit_prob = (7*ad->exit_prob + 256)/8; | |
714 | ||
521f3bbd JA |
715 | if (ad->exit_no_coop > 128) { |
716 | spin_unlock(&ioc->lock); | |
f5b3db00 | 717 | return 1; |
521f3bbd | 718 | } |
f5b3db00 | 719 | } |
1da177e4 LT |
720 | |
721 | if (aic->ttime_samples == 0) { | |
521f3bbd JA |
722 | if (ad->new_ttime_mean > ad->antic_expire) { |
723 | spin_unlock(&ioc->lock); | |
1da177e4 | 724 | return 1; |
521f3bbd JA |
725 | } |
726 | if (ad->exit_prob * ad->exit_no_coop > 128*256) { | |
727 | spin_unlock(&ioc->lock); | |
1da177e4 | 728 | return 1; |
521f3bbd | 729 | } |
1da177e4 LT |
730 | } else if (aic->ttime_mean > ad->antic_expire) { |
731 | /* the process thinks too much between requests */ | |
521f3bbd | 732 | spin_unlock(&ioc->lock); |
1da177e4 LT |
733 | return 1; |
734 | } | |
521f3bbd | 735 | spin_unlock(&ioc->lock); |
1da177e4 LT |
736 | return 0; |
737 | } | |
738 | ||
739 | /* | |
8a8e674c | 740 | * as_can_anticipate indicates whether we should either run rq |
1da177e4 LT |
741 | * or keep anticipating a better request. |
742 | */ | |
8a8e674c | 743 | static int as_can_anticipate(struct as_data *ad, struct request *rq) |
1da177e4 | 744 | { |
f7d7b7a7 | 745 | #if 0 /* disable for now, we need to check tag level as well */ |
a68bbddb JA |
746 | /* |
747 | * SSD device without seek penalty, disable idling | |
748 | */ | |
f7d7b7a7 | 749 | if (blk_queue_nonrot(ad->q)) axman |
a68bbddb | 750 | return 0; |
f7d7b7a7 | 751 | #endif |
a68bbddb | 752 | |
1da177e4 LT |
753 | if (!ad->io_context) |
754 | /* | |
755 | * Last request submitted was a write | |
756 | */ | |
757 | return 0; | |
758 | ||
759 | if (ad->antic_status == ANTIC_FINISHED) | |
760 | /* | |
761 | * Don't restart if we have just finished. Run the next request | |
762 | */ | |
763 | return 0; | |
764 | ||
8a8e674c | 765 | if (as_can_break_anticipation(ad, rq)) |
1da177e4 LT |
766 | /* |
767 | * This request is a good candidate. Don't keep anticipating, | |
768 | * run it. | |
769 | */ | |
770 | return 0; | |
771 | ||
772 | /* | |
773 | * OK from here, we haven't finished, and don't have a decent request! | |
774 | * Status is either ANTIC_OFF so start waiting, | |
775 | * ANTIC_WAIT_REQ so continue waiting for request to finish | |
776 | * or ANTIC_WAIT_NEXT so continue waiting for an acceptable request. | |
1da177e4 LT |
777 | */ |
778 | ||
779 | return 1; | |
780 | } | |
781 | ||
1da177e4 | 782 | /* |
8a8e674c | 783 | * as_update_rq must be called whenever a request (rq) is added to |
1da177e4 LT |
784 | * the sort_list. This function keeps caches up to date, and checks if the |
785 | * request might be one we are "anticipating" | |
786 | */ | |
8a8e674c | 787 | static void as_update_rq(struct as_data *ad, struct request *rq) |
1da177e4 | 788 | { |
8a8e674c | 789 | const int data_dir = rq_is_sync(rq); |
1da177e4 | 790 | |
8a8e674c JA |
791 | /* keep the next_rq cache up to date */ |
792 | ad->next_rq[data_dir] = as_choose_req(ad, rq, ad->next_rq[data_dir]); | |
1da177e4 LT |
793 | |
794 | /* | |
795 | * have we been anticipating this request? | |
796 | * or does it come from the same process as the one we are anticipating | |
797 | * for? | |
798 | */ | |
799 | if (ad->antic_status == ANTIC_WAIT_REQ | |
800 | || ad->antic_status == ANTIC_WAIT_NEXT) { | |
8a8e674c | 801 | if (as_can_break_anticipation(ad, rq)) |
1da177e4 LT |
802 | as_antic_stop(ad); |
803 | } | |
804 | } | |
805 | ||
806 | /* | |
807 | * Gathers timings and resizes the write batch automatically | |
808 | */ | |
809 | static void update_write_batch(struct as_data *ad) | |
810 | { | |
1d6bfbdf | 811 | unsigned long batch = ad->batch_expire[BLK_RW_ASYNC]; |
1da177e4 LT |
812 | long write_time; |
813 | ||
814 | write_time = (jiffies - ad->current_batch_expires) + batch; | |
815 | if (write_time < 0) | |
816 | write_time = 0; | |
817 | ||
818 | if (write_time > batch && !ad->write_batch_idled) { | |
819 | if (write_time > batch * 3) | |
820 | ad->write_batch_count /= 2; | |
821 | else | |
822 | ad->write_batch_count--; | |
823 | } else if (write_time < batch && ad->current_write_count == 0) { | |
824 | if (batch > write_time * 3) | |
825 | ad->write_batch_count *= 2; | |
826 | else | |
827 | ad->write_batch_count++; | |
828 | } | |
829 | ||
830 | if (ad->write_batch_count < 1) | |
831 | ad->write_batch_count = 1; | |
832 | } | |
833 | ||
834 | /* | |
835 | * as_completed_request is to be called when a request has completed and | |
836 | * returned something to the requesting process, be it an error or data. | |
837 | */ | |
165125e1 | 838 | static void as_completed_request(struct request_queue *q, struct request *rq) |
1da177e4 LT |
839 | { |
840 | struct as_data *ad = q->elevator->elevator_data; | |
1da177e4 LT |
841 | |
842 | WARN_ON(!list_empty(&rq->queuelist)); | |
843 | ||
8a8e674c | 844 | if (RQ_STATE(rq) != AS_RQ_REMOVED) { |
12e00368 | 845 | WARN(1, "rq->state %d\n", RQ_STATE(rq)); |
1da177e4 LT |
846 | goto out; |
847 | } | |
848 | ||
1da177e4 | 849 | if (ad->changed_batch && ad->nr_dispatched == 1) { |
d585d0b9 DS |
850 | ad->current_batch_expires = jiffies + |
851 | ad->batch_expire[ad->batch_data_dir]; | |
18887ad9 | 852 | kblockd_schedule_work(q, &ad->antic_work); |
1da177e4 LT |
853 | ad->changed_batch = 0; |
854 | ||
1d6bfbdf | 855 | if (ad->batch_data_dir == BLK_RW_SYNC) |
1da177e4 LT |
856 | ad->new_batch = 1; |
857 | } | |
858 | WARN_ON(ad->nr_dispatched == 0); | |
859 | ad->nr_dispatched--; | |
860 | ||
861 | /* | |
862 | * Start counting the batch from when a request of that direction is | |
863 | * actually serviced. This should help devices with big TCQ windows | |
864 | * and writeback caches | |
865 | */ | |
9e2585a8 | 866 | if (ad->new_batch && ad->batch_data_dir == rq_is_sync(rq)) { |
1da177e4 LT |
867 | update_write_batch(ad); |
868 | ad->current_batch_expires = jiffies + | |
1d6bfbdf | 869 | ad->batch_expire[BLK_RW_SYNC]; |
1da177e4 LT |
870 | ad->new_batch = 0; |
871 | } | |
872 | ||
8a8e674c | 873 | if (ad->io_context == RQ_IOC(rq) && ad->io_context) { |
1da177e4 LT |
874 | ad->antic_start = jiffies; |
875 | ad->ioc_finished = 1; | |
876 | if (ad->antic_status == ANTIC_WAIT_REQ) { | |
877 | /* | |
878 | * We were waiting on this request, now anticipate | |
879 | * the next one | |
880 | */ | |
881 | as_antic_waitnext(ad); | |
882 | } | |
883 | } | |
884 | ||
8a8e674c | 885 | as_put_io_context(rq); |
1da177e4 | 886 | out: |
8a8e674c | 887 | RQ_SET_STATE(rq, AS_RQ_POSTSCHED); |
1da177e4 LT |
888 | } |
889 | ||
890 | /* | |
891 | * as_remove_queued_request removes a request from the pre dispatch queue | |
892 | * without updating refcounts. It is expected the caller will drop the | |
893 | * reference unless it replaces the request at somepart of the elevator | |
894 | * (ie. the dispatch queue) | |
895 | */ | |
165125e1 JA |
896 | static void as_remove_queued_request(struct request_queue *q, |
897 | struct request *rq) | |
1da177e4 | 898 | { |
9e2585a8 | 899 | const int data_dir = rq_is_sync(rq); |
1da177e4 | 900 | struct as_data *ad = q->elevator->elevator_data; |
8a8e674c | 901 | struct io_context *ioc; |
1da177e4 | 902 | |
8a8e674c | 903 | WARN_ON(RQ_STATE(rq) != AS_RQ_QUEUED); |
1da177e4 | 904 | |
8a8e674c JA |
905 | ioc = RQ_IOC(rq); |
906 | if (ioc && ioc->aic) { | |
907 | BUG_ON(!atomic_read(&ioc->aic->nr_queued)); | |
908 | atomic_dec(&ioc->aic->nr_queued); | |
1da177e4 LT |
909 | } |
910 | ||
911 | /* | |
8a8e674c | 912 | * Update the "next_rq" cache if we are about to remove its |
1da177e4 LT |
913 | * entry |
914 | */ | |
8a8e674c JA |
915 | if (ad->next_rq[data_dir] == rq) |
916 | ad->next_rq[data_dir] = as_find_next_rq(ad, rq); | |
1da177e4 | 917 | |
d4f2f462 | 918 | rq_fifo_clear(rq); |
8a8e674c | 919 | as_del_rq_rb(ad, rq); |
1da177e4 LT |
920 | } |
921 | ||
1da177e4 | 922 | /* |
8896f3c0 | 923 | * as_fifo_expired returns 0 if there are no expired requests on the fifo, |
1da177e4 LT |
924 | * 1 otherwise. It is ratelimited so that we only perform the check once per |
925 | * `fifo_expire' interval. Otherwise a large number of expired requests | |
926 | * would create a hopeless seekstorm. | |
927 | * | |
928 | * See as_antic_expired comment. | |
929 | */ | |
930 | static int as_fifo_expired(struct as_data *ad, int adir) | |
931 | { | |
d4f2f462 | 932 | struct request *rq; |
1da177e4 LT |
933 | long delta_jif; |
934 | ||
935 | delta_jif = jiffies - ad->last_check_fifo[adir]; | |
936 | if (unlikely(delta_jif < 0)) | |
937 | delta_jif = -delta_jif; | |
938 | if (delta_jif < ad->fifo_expire[adir]) | |
939 | return 0; | |
940 | ||
941 | ad->last_check_fifo[adir] = jiffies; | |
942 | ||
943 | if (list_empty(&ad->fifo_list[adir])) | |
944 | return 0; | |
945 | ||
d4f2f462 | 946 | rq = rq_entry_fifo(ad->fifo_list[adir].next); |
1da177e4 | 947 | |
d4f2f462 | 948 | return time_after(jiffies, rq_fifo_time(rq)); |
1da177e4 LT |
949 | } |
950 | ||
951 | /* | |
952 | * as_batch_expired returns true if the current batch has expired. A batch | |
953 | * is a set of reads or a set of writes. | |
954 | */ | |
955 | static inline int as_batch_expired(struct as_data *ad) | |
956 | { | |
957 | if (ad->changed_batch || ad->new_batch) | |
958 | return 0; | |
959 | ||
1d6bfbdf | 960 | if (ad->batch_data_dir == BLK_RW_SYNC) |
1da177e4 LT |
961 | /* TODO! add a check so a complete fifo gets written? */ |
962 | return time_after(jiffies, ad->current_batch_expires); | |
963 | ||
964 | return time_after(jiffies, ad->current_batch_expires) | |
965 | || ad->current_write_count == 0; | |
966 | } | |
967 | ||
968 | /* | |
969 | * move an entry to dispatch queue | |
970 | */ | |
8a8e674c | 971 | static void as_move_to_dispatch(struct as_data *ad, struct request *rq) |
1da177e4 | 972 | { |
9e2585a8 | 973 | const int data_dir = rq_is_sync(rq); |
1da177e4 | 974 | |
e37f346e | 975 | BUG_ON(RB_EMPTY_NODE(&rq->rb_node)); |
1da177e4 LT |
976 | |
977 | as_antic_stop(ad); | |
978 | ad->antic_status = ANTIC_OFF; | |
979 | ||
980 | /* | |
981 | * This has to be set in order to be correctly updated by | |
8a8e674c | 982 | * as_find_next_rq |
1da177e4 LT |
983 | */ |
984 | ad->last_sector[data_dir] = rq->sector + rq->nr_sectors; | |
985 | ||
1d6bfbdf | 986 | if (data_dir == BLK_RW_SYNC) { |
8a8e674c | 987 | struct io_context *ioc = RQ_IOC(rq); |
1da177e4 | 988 | /* In case we have to anticipate after this */ |
8a8e674c | 989 | copy_io_context(&ad->io_context, &ioc); |
1da177e4 LT |
990 | } else { |
991 | if (ad->io_context) { | |
992 | put_io_context(ad->io_context); | |
993 | ad->io_context = NULL; | |
994 | } | |
995 | ||
996 | if (ad->current_write_count != 0) | |
997 | ad->current_write_count--; | |
998 | } | |
999 | ad->ioc_finished = 0; | |
1000 | ||
8a8e674c | 1001 | ad->next_rq[data_dir] = as_find_next_rq(ad, rq); |
1da177e4 LT |
1002 | |
1003 | /* | |
1004 | * take it off the sort and fifo list, add to dispatch queue | |
1005 | */ | |
1da177e4 | 1006 | as_remove_queued_request(ad->q, rq); |
8a8e674c | 1007 | WARN_ON(RQ_STATE(rq) != AS_RQ_QUEUED); |
1da177e4 | 1008 | |
b4878f24 JA |
1009 | elv_dispatch_sort(ad->q, rq); |
1010 | ||
8a8e674c JA |
1011 | RQ_SET_STATE(rq, AS_RQ_DISPATCHED); |
1012 | if (RQ_IOC(rq) && RQ_IOC(rq)->aic) | |
1013 | atomic_inc(&RQ_IOC(rq)->aic->nr_dispatched); | |
1da177e4 LT |
1014 | ad->nr_dispatched++; |
1015 | } | |
1016 | ||
1017 | /* | |
1018 | * as_dispatch_request selects the best request according to | |
1019 | * read/write expire, batch expire, etc, and moves it to the dispatch | |
1020 | * queue. Returns 1 if a request was found, 0 otherwise. | |
1021 | */ | |
165125e1 | 1022 | static int as_dispatch_request(struct request_queue *q, int force) |
1da177e4 | 1023 | { |
b4878f24 | 1024 | struct as_data *ad = q->elevator->elevator_data; |
1d6bfbdf JA |
1025 | const int reads = !list_empty(&ad->fifo_list[BLK_RW_SYNC]); |
1026 | const int writes = !list_empty(&ad->fifo_list[BLK_RW_ASYNC]); | |
8a8e674c | 1027 | struct request *rq; |
1da177e4 | 1028 | |
b4878f24 JA |
1029 | if (unlikely(force)) { |
1030 | /* | |
1031 | * Forced dispatch, accounting is useless. Reset | |
1032 | * accounting states and dump fifo_lists. Note that | |
1d6bfbdf | 1033 | * batch_data_dir is reset to BLK_RW_SYNC to avoid |
b4878f24 JA |
1034 | * screwing write batch accounting as write batch |
1035 | * accounting occurs on W->R transition. | |
1036 | */ | |
1037 | int dispatched = 0; | |
1038 | ||
1d6bfbdf | 1039 | ad->batch_data_dir = BLK_RW_SYNC; |
b4878f24 JA |
1040 | ad->changed_batch = 0; |
1041 | ad->new_batch = 0; | |
1042 | ||
1d6bfbdf JA |
1043 | while (ad->next_rq[BLK_RW_SYNC]) { |
1044 | as_move_to_dispatch(ad, ad->next_rq[BLK_RW_SYNC]); | |
b4878f24 JA |
1045 | dispatched++; |
1046 | } | |
1d6bfbdf | 1047 | ad->last_check_fifo[BLK_RW_SYNC] = jiffies; |
b4878f24 | 1048 | |
1d6bfbdf JA |
1049 | while (ad->next_rq[BLK_RW_ASYNC]) { |
1050 | as_move_to_dispatch(ad, ad->next_rq[BLK_RW_ASYNC]); | |
b4878f24 JA |
1051 | dispatched++; |
1052 | } | |
1d6bfbdf | 1053 | ad->last_check_fifo[BLK_RW_ASYNC] = jiffies; |
b4878f24 JA |
1054 | |
1055 | return dispatched; | |
1056 | } | |
1057 | ||
1da177e4 | 1058 | /* Signal that the write batch was uncontended, so we can't time it */ |
1d6bfbdf | 1059 | if (ad->batch_data_dir == BLK_RW_ASYNC && !reads) { |
1da177e4 LT |
1060 | if (ad->current_write_count == 0 || !writes) |
1061 | ad->write_batch_idled = 1; | |
1062 | } | |
1063 | ||
1064 | if (!(reads || writes) | |
1065 | || ad->antic_status == ANTIC_WAIT_REQ | |
1066 | || ad->antic_status == ANTIC_WAIT_NEXT | |
1067 | || ad->changed_batch) | |
1068 | return 0; | |
1069 | ||
f5b3db00 | 1070 | if (!(reads && writes && as_batch_expired(ad))) { |
1da177e4 LT |
1071 | /* |
1072 | * batch is still running or no reads or no writes | |
1073 | */ | |
8a8e674c | 1074 | rq = ad->next_rq[ad->batch_data_dir]; |
1da177e4 | 1075 | |
1d6bfbdf JA |
1076 | if (ad->batch_data_dir == BLK_RW_SYNC && ad->antic_expire) { |
1077 | if (as_fifo_expired(ad, BLK_RW_SYNC)) | |
1da177e4 LT |
1078 | goto fifo_expired; |
1079 | ||
8a8e674c | 1080 | if (as_can_anticipate(ad, rq)) { |
1da177e4 LT |
1081 | as_antic_waitreq(ad); |
1082 | return 0; | |
1083 | } | |
1084 | } | |
1085 | ||
8a8e674c | 1086 | if (rq) { |
1da177e4 LT |
1087 | /* we have a "next request" */ |
1088 | if (reads && !writes) | |
1089 | ad->current_batch_expires = | |
1d6bfbdf | 1090 | jiffies + ad->batch_expire[BLK_RW_SYNC]; |
1da177e4 LT |
1091 | goto dispatch_request; |
1092 | } | |
1093 | } | |
1094 | ||
1095 | /* | |
1096 | * at this point we are not running a batch. select the appropriate | |
1097 | * data direction (read / write) | |
1098 | */ | |
1099 | ||
1100 | if (reads) { | |
1d6bfbdf | 1101 | BUG_ON(RB_EMPTY_ROOT(&ad->sort_list[BLK_RW_SYNC])); |
1da177e4 | 1102 | |
1d6bfbdf | 1103 | if (writes && ad->batch_data_dir == BLK_RW_SYNC) |
1da177e4 LT |
1104 | /* |
1105 | * Last batch was a read, switch to writes | |
1106 | */ | |
1107 | goto dispatch_writes; | |
1108 | ||
1d6bfbdf | 1109 | if (ad->batch_data_dir == BLK_RW_ASYNC) { |
1da177e4 LT |
1110 | WARN_ON(ad->new_batch); |
1111 | ad->changed_batch = 1; | |
1112 | } | |
1d6bfbdf JA |
1113 | ad->batch_data_dir = BLK_RW_SYNC; |
1114 | rq = rq_entry_fifo(ad->fifo_list[BLK_RW_SYNC].next); | |
1da177e4 LT |
1115 | ad->last_check_fifo[ad->batch_data_dir] = jiffies; |
1116 | goto dispatch_request; | |
1117 | } | |
1118 | ||
1119 | /* | |
1120 | * the last batch was a read | |
1121 | */ | |
1122 | ||
1123 | if (writes) { | |
1124 | dispatch_writes: | |
1d6bfbdf | 1125 | BUG_ON(RB_EMPTY_ROOT(&ad->sort_list[BLK_RW_ASYNC])); |
1da177e4 | 1126 | |
1d6bfbdf | 1127 | if (ad->batch_data_dir == BLK_RW_SYNC) { |
1da177e4 LT |
1128 | ad->changed_batch = 1; |
1129 | ||
1130 | /* | |
1131 | * new_batch might be 1 when the queue runs out of | |
1132 | * reads. A subsequent submission of a write might | |
1133 | * cause a change of batch before the read is finished. | |
1134 | */ | |
1135 | ad->new_batch = 0; | |
1136 | } | |
1d6bfbdf | 1137 | ad->batch_data_dir = BLK_RW_ASYNC; |
1da177e4 LT |
1138 | ad->current_write_count = ad->write_batch_count; |
1139 | ad->write_batch_idled = 0; | |
1d6bfbdf JA |
1140 | rq = rq_entry_fifo(ad->fifo_list[BLK_RW_ASYNC].next); |
1141 | ad->last_check_fifo[BLK_RW_ASYNC] = jiffies; | |
1da177e4 LT |
1142 | goto dispatch_request; |
1143 | } | |
1144 | ||
1145 | BUG(); | |
1146 | return 0; | |
1147 | ||
1148 | dispatch_request: | |
1149 | /* | |
1150 | * If a request has expired, service it. | |
1151 | */ | |
1152 | ||
1153 | if (as_fifo_expired(ad, ad->batch_data_dir)) { | |
1154 | fifo_expired: | |
8a8e674c | 1155 | rq = rq_entry_fifo(ad->fifo_list[ad->batch_data_dir].next); |
1da177e4 LT |
1156 | } |
1157 | ||
1158 | if (ad->changed_batch) { | |
1159 | WARN_ON(ad->new_batch); | |
1160 | ||
1161 | if (ad->nr_dispatched) | |
1162 | return 0; | |
1163 | ||
1d6bfbdf | 1164 | if (ad->batch_data_dir == BLK_RW_ASYNC) |
1da177e4 | 1165 | ad->current_batch_expires = jiffies + |
1d6bfbdf | 1166 | ad->batch_expire[BLK_RW_ASYNC]; |
1da177e4 LT |
1167 | else |
1168 | ad->new_batch = 1; | |
1169 | ||
1170 | ad->changed_batch = 0; | |
1171 | } | |
1172 | ||
1173 | /* | |
8a8e674c | 1174 | * rq is the selected appropriate request. |
1da177e4 | 1175 | */ |
8a8e674c | 1176 | as_move_to_dispatch(ad, rq); |
1da177e4 LT |
1177 | |
1178 | return 1; | |
1179 | } | |
1180 | ||
1da177e4 | 1181 | /* |
8a8e674c | 1182 | * add rq to rbtree and fifo |
1da177e4 | 1183 | */ |
165125e1 | 1184 | static void as_add_request(struct request_queue *q, struct request *rq) |
1da177e4 | 1185 | { |
b4878f24 | 1186 | struct as_data *ad = q->elevator->elevator_data; |
1da177e4 LT |
1187 | int data_dir; |
1188 | ||
8a8e674c | 1189 | RQ_SET_STATE(rq, AS_RQ_NEW); |
b4878f24 | 1190 | |
9e2585a8 | 1191 | data_dir = rq_is_sync(rq); |
1da177e4 | 1192 | |
b5deef90 | 1193 | rq->elevator_private = as_get_io_context(q->node); |
1da177e4 | 1194 | |
8a8e674c JA |
1195 | if (RQ_IOC(rq)) { |
1196 | as_update_iohist(ad, RQ_IOC(rq)->aic, rq); | |
1197 | atomic_inc(&RQ_IOC(rq)->aic->nr_queued); | |
1da177e4 LT |
1198 | } |
1199 | ||
8a8e674c | 1200 | as_add_rq_rb(ad, rq); |
1da177e4 | 1201 | |
ef9be1d3 | 1202 | /* |
8896f3c0 | 1203 | * set expire time and add to fifo list |
ef9be1d3 | 1204 | */ |
d4f2f462 JA |
1205 | rq_set_fifo_time(rq, jiffies + ad->fifo_expire[data_dir]); |
1206 | list_add_tail(&rq->queuelist, &ad->fifo_list[data_dir]); | |
1da177e4 | 1207 | |
8a8e674c JA |
1208 | as_update_rq(ad, rq); /* keep state machine up to date */ |
1209 | RQ_SET_STATE(rq, AS_RQ_QUEUED); | |
1da177e4 LT |
1210 | } |
1211 | ||
165125e1 | 1212 | static void as_activate_request(struct request_queue *q, struct request *rq) |
1da177e4 | 1213 | { |
8a8e674c JA |
1214 | WARN_ON(RQ_STATE(rq) != AS_RQ_DISPATCHED); |
1215 | RQ_SET_STATE(rq, AS_RQ_REMOVED); | |
1216 | if (RQ_IOC(rq) && RQ_IOC(rq)->aic) | |
1217 | atomic_dec(&RQ_IOC(rq)->aic->nr_dispatched); | |
1da177e4 LT |
1218 | } |
1219 | ||
165125e1 | 1220 | static void as_deactivate_request(struct request_queue *q, struct request *rq) |
1da177e4 | 1221 | { |
8a8e674c JA |
1222 | WARN_ON(RQ_STATE(rq) != AS_RQ_REMOVED); |
1223 | RQ_SET_STATE(rq, AS_RQ_DISPATCHED); | |
1224 | if (RQ_IOC(rq) && RQ_IOC(rq)->aic) | |
1225 | atomic_inc(&RQ_IOC(rq)->aic->nr_dispatched); | |
1da177e4 LT |
1226 | } |
1227 | ||
1228 | /* | |
1229 | * as_queue_empty tells us if there are requests left in the device. It may | |
1230 | * not be the case that a driver can get the next request even if the queue | |
1231 | * is not empty - it is used in the block layer to check for plugging and | |
1232 | * merging opportunities | |
1233 | */ | |
165125e1 | 1234 | static int as_queue_empty(struct request_queue *q) |
1da177e4 LT |
1235 | { |
1236 | struct as_data *ad = q->elevator->elevator_data; | |
1237 | ||
1d6bfbdf JA |
1238 | return list_empty(&ad->fifo_list[BLK_RW_ASYNC]) |
1239 | && list_empty(&ad->fifo_list[BLK_RW_SYNC]); | |
1da177e4 LT |
1240 | } |
1241 | ||
1da177e4 | 1242 | static int |
165125e1 | 1243 | as_merge(struct request_queue *q, struct request **req, struct bio *bio) |
1da177e4 LT |
1244 | { |
1245 | struct as_data *ad = q->elevator->elevator_data; | |
1246 | sector_t rb_key = bio->bi_sector + bio_sectors(bio); | |
1247 | struct request *__rq; | |
1da177e4 LT |
1248 | |
1249 | /* | |
1250 | * check for front merge | |
1251 | */ | |
e37f346e | 1252 | __rq = elv_rb_find(&ad->sort_list[bio_data_dir(bio)], rb_key); |
9817064b JA |
1253 | if (__rq && elv_rq_merge_ok(__rq, bio)) { |
1254 | *req = __rq; | |
1255 | return ELEVATOR_FRONT_MERGE; | |
1da177e4 LT |
1256 | } |
1257 | ||
1258 | return ELEVATOR_NO_MERGE; | |
1da177e4 LT |
1259 | } |
1260 | ||
165125e1 JA |
1261 | static void as_merged_request(struct request_queue *q, struct request *req, |
1262 | int type) | |
1da177e4 LT |
1263 | { |
1264 | struct as_data *ad = q->elevator->elevator_data; | |
1da177e4 | 1265 | |
1da177e4 LT |
1266 | /* |
1267 | * if the merge was a front merge, we need to reposition request | |
1268 | */ | |
e37f346e | 1269 | if (type == ELEVATOR_FRONT_MERGE) { |
8a8e674c JA |
1270 | as_del_rq_rb(ad, req); |
1271 | as_add_rq_rb(ad, req); | |
1da177e4 LT |
1272 | /* |
1273 | * Note! At this stage of this and the next function, our next | |
1274 | * request may not be optimal - eg the request may have "grown" | |
1275 | * behind the disk head. We currently don't bother adjusting. | |
1276 | */ | |
1277 | } | |
1da177e4 LT |
1278 | } |
1279 | ||
165125e1 | 1280 | static void as_merged_requests(struct request_queue *q, struct request *req, |
f5b3db00 | 1281 | struct request *next) |
1da177e4 | 1282 | { |
1da177e4 | 1283 | /* |
8a8e674c JA |
1284 | * if next expires before rq, assign its expire time to arq |
1285 | * and move into next position (next will be deleted) in fifo | |
1da177e4 | 1286 | */ |
d4f2f462 JA |
1287 | if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) { |
1288 | if (time_before(rq_fifo_time(next), rq_fifo_time(req))) { | |
1289 | list_move(&req->queuelist, &next->queuelist); | |
1290 | rq_set_fifo_time(req, rq_fifo_time(next)); | |
1da177e4 LT |
1291 | } |
1292 | } | |
1293 | ||
1da177e4 LT |
1294 | /* |
1295 | * kill knowledge of next, this one is a goner | |
1296 | */ | |
1297 | as_remove_queued_request(q, next); | |
8a8e674c | 1298 | as_put_io_context(next); |
1da177e4 | 1299 | |
8a8e674c | 1300 | RQ_SET_STATE(next, AS_RQ_MERGED); |
1da177e4 LT |
1301 | } |
1302 | ||
1303 | /* | |
1304 | * This is executed in a "deferred" process context, by kblockd. It calls the | |
1305 | * driver's request_fn so the driver can submit that request. | |
1306 | * | |
1307 | * IMPORTANT! This guy will reenter the elevator, so set up all queue global | |
1308 | * state before calling, and don't rely on any state over calls. | |
1309 | * | |
1310 | * FIXME! dispatch queue is not a queue at all! | |
1311 | */ | |
65f27f38 | 1312 | static void as_work_handler(struct work_struct *work) |
1da177e4 | 1313 | { |
65f27f38 DH |
1314 | struct as_data *ad = container_of(work, struct as_data, antic_work); |
1315 | struct request_queue *q = ad->q; | |
1da177e4 LT |
1316 | unsigned long flags; |
1317 | ||
1318 | spin_lock_irqsave(q->queue_lock, flags); | |
dc72ef4a | 1319 | blk_start_queueing(q); |
1da177e4 LT |
1320 | spin_unlock_irqrestore(q->queue_lock, flags); |
1321 | } | |
1322 | ||
165125e1 | 1323 | static int as_may_queue(struct request_queue *q, int rw) |
1da177e4 LT |
1324 | { |
1325 | int ret = ELV_MQUEUE_MAY; | |
1326 | struct as_data *ad = q->elevator->elevator_data; | |
1327 | struct io_context *ioc; | |
1328 | if (ad->antic_status == ANTIC_WAIT_REQ || | |
1329 | ad->antic_status == ANTIC_WAIT_NEXT) { | |
b5deef90 | 1330 | ioc = as_get_io_context(q->node); |
1da177e4 LT |
1331 | if (ad->io_context == ioc) |
1332 | ret = ELV_MQUEUE_MUST; | |
1333 | put_io_context(ioc); | |
1334 | } | |
1335 | ||
1336 | return ret; | |
1337 | } | |
1338 | ||
b374d18a | 1339 | static void as_exit_queue(struct elevator_queue *e) |
1da177e4 LT |
1340 | { |
1341 | struct as_data *ad = e->elevator_data; | |
1342 | ||
1343 | del_timer_sync(&ad->antic_timer); | |
64d01dc9 | 1344 | cancel_work_sync(&ad->antic_work); |
1da177e4 | 1345 | |
1d6bfbdf JA |
1346 | BUG_ON(!list_empty(&ad->fifo_list[BLK_RW_SYNC])); |
1347 | BUG_ON(!list_empty(&ad->fifo_list[BLK_RW_ASYNC])); | |
1da177e4 | 1348 | |
1da177e4 | 1349 | put_io_context(ad->io_context); |
1da177e4 LT |
1350 | kfree(ad); |
1351 | } | |
1352 | ||
1353 | /* | |
8a8e674c | 1354 | * initialize elevator private data (as_data). |
1da177e4 | 1355 | */ |
165125e1 | 1356 | static void *as_init_queue(struct request_queue *q) |
1da177e4 LT |
1357 | { |
1358 | struct as_data *ad; | |
1da177e4 | 1359 | |
94f6030c | 1360 | ad = kmalloc_node(sizeof(*ad), GFP_KERNEL | __GFP_ZERO, q->node); |
1da177e4 | 1361 | if (!ad) |
bc1c1169 | 1362 | return NULL; |
1da177e4 LT |
1363 | |
1364 | ad->q = q; /* Identify what queue the data belongs to */ | |
1365 | ||
1da177e4 LT |
1366 | /* anticipatory scheduling helpers */ |
1367 | ad->antic_timer.function = as_antic_timeout; | |
1368 | ad->antic_timer.data = (unsigned long)q; | |
1369 | init_timer(&ad->antic_timer); | |
65f27f38 | 1370 | INIT_WORK(&ad->antic_work, as_work_handler); |
1da177e4 | 1371 | |
1d6bfbdf JA |
1372 | INIT_LIST_HEAD(&ad->fifo_list[BLK_RW_SYNC]); |
1373 | INIT_LIST_HEAD(&ad->fifo_list[BLK_RW_ASYNC]); | |
1374 | ad->sort_list[BLK_RW_SYNC] = RB_ROOT; | |
1375 | ad->sort_list[BLK_RW_ASYNC] = RB_ROOT; | |
1376 | ad->fifo_expire[BLK_RW_SYNC] = default_read_expire; | |
1377 | ad->fifo_expire[BLK_RW_ASYNC] = default_write_expire; | |
1da177e4 | 1378 | ad->antic_expire = default_antic_expire; |
1d6bfbdf JA |
1379 | ad->batch_expire[BLK_RW_SYNC] = default_read_batch_expire; |
1380 | ad->batch_expire[BLK_RW_ASYNC] = default_write_batch_expire; | |
1da177e4 | 1381 | |
1d6bfbdf JA |
1382 | ad->current_batch_expires = jiffies + ad->batch_expire[BLK_RW_SYNC]; |
1383 | ad->write_batch_count = ad->batch_expire[BLK_RW_ASYNC] / 10; | |
1da177e4 LT |
1384 | if (ad->write_batch_count < 2) |
1385 | ad->write_batch_count = 2; | |
1386 | ||
bc1c1169 | 1387 | return ad; |
1da177e4 LT |
1388 | } |
1389 | ||
1390 | /* | |
1391 | * sysfs parts below | |
1392 | */ | |
1da177e4 LT |
1393 | |
1394 | static ssize_t | |
1395 | as_var_show(unsigned int var, char *page) | |
1396 | { | |
1da177e4 LT |
1397 | return sprintf(page, "%d\n", var); |
1398 | } | |
1399 | ||
1400 | static ssize_t | |
1401 | as_var_store(unsigned long *var, const char *page, size_t count) | |
1402 | { | |
1da177e4 LT |
1403 | char *p = (char *) page; |
1404 | ||
c9b3ad67 | 1405 | *var = simple_strtoul(p, &p, 10); |
1da177e4 LT |
1406 | return count; |
1407 | } | |
1408 | ||
b374d18a | 1409 | static ssize_t est_time_show(struct elevator_queue *e, char *page) |
1da177e4 | 1410 | { |
3d1ab40f | 1411 | struct as_data *ad = e->elevator_data; |
1da177e4 LT |
1412 | int pos = 0; |
1413 | ||
f5b3db00 NP |
1414 | pos += sprintf(page+pos, "%lu %% exit probability\n", |
1415 | 100*ad->exit_prob/256); | |
1416 | pos += sprintf(page+pos, "%lu %% probability of exiting without a " | |
1417 | "cooperating process submitting IO\n", | |
1418 | 100*ad->exit_no_coop/256); | |
1da177e4 | 1419 | pos += sprintf(page+pos, "%lu ms new thinktime\n", ad->new_ttime_mean); |
f5b3db00 NP |
1420 | pos += sprintf(page+pos, "%llu sectors new seek distance\n", |
1421 | (unsigned long long)ad->new_seek_mean); | |
1da177e4 LT |
1422 | |
1423 | return pos; | |
1424 | } | |
1425 | ||
1426 | #define SHOW_FUNCTION(__FUNC, __VAR) \ | |
b374d18a | 1427 | static ssize_t __FUNC(struct elevator_queue *e, char *page) \ |
1da177e4 | 1428 | { \ |
3d1ab40f | 1429 | struct as_data *ad = e->elevator_data; \ |
1da177e4 LT |
1430 | return as_var_show(jiffies_to_msecs((__VAR)), (page)); \ |
1431 | } | |
1d6bfbdf JA |
1432 | SHOW_FUNCTION(as_read_expire_show, ad->fifo_expire[BLK_RW_SYNC]); |
1433 | SHOW_FUNCTION(as_write_expire_show, ad->fifo_expire[BLK_RW_ASYNC]); | |
e572ec7e | 1434 | SHOW_FUNCTION(as_antic_expire_show, ad->antic_expire); |
1d6bfbdf JA |
1435 | SHOW_FUNCTION(as_read_batch_expire_show, ad->batch_expire[BLK_RW_SYNC]); |
1436 | SHOW_FUNCTION(as_write_batch_expire_show, ad->batch_expire[BLK_RW_ASYNC]); | |
1da177e4 LT |
1437 | #undef SHOW_FUNCTION |
1438 | ||
1439 | #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \ | |
b374d18a | 1440 | static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ |
1da177e4 | 1441 | { \ |
3d1ab40f AV |
1442 | struct as_data *ad = e->elevator_data; \ |
1443 | int ret = as_var_store(__PTR, (page), count); \ | |
1da177e4 LT |
1444 | if (*(__PTR) < (MIN)) \ |
1445 | *(__PTR) = (MIN); \ | |
1446 | else if (*(__PTR) > (MAX)) \ | |
1447 | *(__PTR) = (MAX); \ | |
1448 | *(__PTR) = msecs_to_jiffies(*(__PTR)); \ | |
1449 | return ret; \ | |
1450 | } | |
1d6bfbdf JA |
1451 | STORE_FUNCTION(as_read_expire_store, &ad->fifo_expire[BLK_RW_SYNC], 0, INT_MAX); |
1452 | STORE_FUNCTION(as_write_expire_store, | |
1453 | &ad->fifo_expire[BLK_RW_ASYNC], 0, INT_MAX); | |
e572ec7e AV |
1454 | STORE_FUNCTION(as_antic_expire_store, &ad->antic_expire, 0, INT_MAX); |
1455 | STORE_FUNCTION(as_read_batch_expire_store, | |
1d6bfbdf | 1456 | &ad->batch_expire[BLK_RW_SYNC], 0, INT_MAX); |
e572ec7e | 1457 | STORE_FUNCTION(as_write_batch_expire_store, |
1d6bfbdf | 1458 | &ad->batch_expire[BLK_RW_ASYNC], 0, INT_MAX); |
1da177e4 LT |
1459 | #undef STORE_FUNCTION |
1460 | ||
e572ec7e AV |
1461 | #define AS_ATTR(name) \ |
1462 | __ATTR(name, S_IRUGO|S_IWUSR, as_##name##_show, as_##name##_store) | |
1463 | ||
1464 | static struct elv_fs_entry as_attrs[] = { | |
1465 | __ATTR_RO(est_time), | |
1466 | AS_ATTR(read_expire), | |
1467 | AS_ATTR(write_expire), | |
1468 | AS_ATTR(antic_expire), | |
1469 | AS_ATTR(read_batch_expire), | |
1470 | AS_ATTR(write_batch_expire), | |
1471 | __ATTR_NULL | |
1da177e4 LT |
1472 | }; |
1473 | ||
1da177e4 LT |
1474 | static struct elevator_type iosched_as = { |
1475 | .ops = { | |
1476 | .elevator_merge_fn = as_merge, | |
1477 | .elevator_merged_fn = as_merged_request, | |
1478 | .elevator_merge_req_fn = as_merged_requests, | |
b4878f24 JA |
1479 | .elevator_dispatch_fn = as_dispatch_request, |
1480 | .elevator_add_req_fn = as_add_request, | |
1481 | .elevator_activate_req_fn = as_activate_request, | |
1da177e4 LT |
1482 | .elevator_deactivate_req_fn = as_deactivate_request, |
1483 | .elevator_queue_empty_fn = as_queue_empty, | |
1484 | .elevator_completed_req_fn = as_completed_request, | |
e37f346e JA |
1485 | .elevator_former_req_fn = elv_rb_former_request, |
1486 | .elevator_latter_req_fn = elv_rb_latter_request, | |
1da177e4 LT |
1487 | .elevator_may_queue_fn = as_may_queue, |
1488 | .elevator_init_fn = as_init_queue, | |
1489 | .elevator_exit_fn = as_exit_queue, | |
e17a9489 | 1490 | .trim = as_trim, |
1da177e4 LT |
1491 | }, |
1492 | ||
3d1ab40f | 1493 | .elevator_attrs = as_attrs, |
1da177e4 LT |
1494 | .elevator_name = "anticipatory", |
1495 | .elevator_owner = THIS_MODULE, | |
1496 | }; | |
1497 | ||
1498 | static int __init as_init(void) | |
1499 | { | |
2fdd82bd AB |
1500 | elv_register(&iosched_as); |
1501 | ||
1502 | return 0; | |
1da177e4 LT |
1503 | } |
1504 | ||
1505 | static void __exit as_exit(void) | |
1506 | { | |
6e9a4738 | 1507 | DECLARE_COMPLETION_ONSTACK(all_gone); |
1da177e4 | 1508 | elv_unregister(&iosched_as); |
334e94de | 1509 | ioc_gone = &all_gone; |
fba82272 OH |
1510 | /* ioc_gone's update must be visible before reading ioc_count */ |
1511 | smp_wmb(); | |
e4313dd4 | 1512 | if (elv_ioc_count_read(ioc_count)) |
863fddcb | 1513 | wait_for_completion(&all_gone); |
334e94de | 1514 | synchronize_rcu(); |
1da177e4 LT |
1515 | } |
1516 | ||
1517 | module_init(as_init); | |
1518 | module_exit(as_exit); | |
1519 | ||
1520 | MODULE_AUTHOR("Nick Piggin"); | |
1521 | MODULE_LICENSE("GPL"); | |
1522 | MODULE_DESCRIPTION("anticipatory IO scheduler"); |