Commit | Line | Data |
---|---|---|
1da177e4 | 1 | /* |
1da177e4 LT |
2 | * Anticipatory & deadline i/o scheduler. |
3 | * | |
4 | * Copyright (C) 2002 Jens Axboe <axboe@suse.de> | |
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 | ||
20 | #define REQ_SYNC 1 | |
21 | #define REQ_ASYNC 0 | |
22 | ||
23 | /* | |
24 | * See Documentation/block/as-iosched.txt | |
25 | */ | |
26 | ||
27 | /* | |
28 | * max time before a read is submitted. | |
29 | */ | |
30 | #define default_read_expire (HZ / 8) | |
31 | ||
32 | /* | |
33 | * ditto for writes, these limits are not hard, even | |
34 | * if the disk is capable of satisfying them. | |
35 | */ | |
36 | #define default_write_expire (HZ / 4) | |
37 | ||
38 | /* | |
39 | * read_batch_expire describes how long we will allow a stream of reads to | |
40 | * persist before looking to see whether it is time to switch over to writes. | |
41 | */ | |
42 | #define default_read_batch_expire (HZ / 2) | |
43 | ||
44 | /* | |
45 | * write_batch_expire describes how long we want a stream of writes to run for. | |
46 | * This is not a hard limit, but a target we set for the auto-tuning thingy. | |
47 | * See, the problem is: we can send a lot of writes to disk cache / TCQ in | |
48 | * a short amount of time... | |
49 | */ | |
50 | #define default_write_batch_expire (HZ / 8) | |
51 | ||
52 | /* | |
53 | * max time we may wait to anticipate a read (default around 6ms) | |
54 | */ | |
55 | #define default_antic_expire ((HZ / 150) ? HZ / 150 : 1) | |
56 | ||
57 | /* | |
58 | * Keep track of up to 20ms thinktimes. We can go as big as we like here, | |
59 | * however huge values tend to interfere and not decay fast enough. A program | |
60 | * might be in a non-io phase of operation. Waiting on user input for example, | |
61 | * or doing a lengthy computation. A small penalty can be justified there, and | |
62 | * will still catch out those processes that constantly have large thinktimes. | |
63 | */ | |
64 | #define MAX_THINKTIME (HZ/50UL) | |
65 | ||
66 | /* Bits in as_io_context.state */ | |
67 | enum as_io_states { | |
f5b3db00 | 68 | AS_TASK_RUNNING=0, /* Process has not exited */ |
1da177e4 LT |
69 | AS_TASK_IOSTARTED, /* Process has started some IO */ |
70 | AS_TASK_IORUNNING, /* Process has completed some IO */ | |
71 | }; | |
72 | ||
73 | enum anticipation_status { | |
74 | ANTIC_OFF=0, /* Not anticipating (normal operation) */ | |
75 | ANTIC_WAIT_REQ, /* The last read has not yet completed */ | |
76 | ANTIC_WAIT_NEXT, /* Currently anticipating a request vs | |
77 | last read (which has completed) */ | |
78 | ANTIC_FINISHED, /* Anticipating but have found a candidate | |
79 | * or timed out */ | |
80 | }; | |
81 | ||
82 | struct as_data { | |
83 | /* | |
84 | * run time data | |
85 | */ | |
86 | ||
87 | struct request_queue *q; /* the "owner" queue */ | |
88 | ||
89 | /* | |
90 | * requests (as_rq s) are present on both sort_list and fifo_list | |
91 | */ | |
92 | struct rb_root sort_list[2]; | |
93 | struct list_head fifo_list[2]; | |
94 | ||
95 | struct as_rq *next_arq[2]; /* next in sort order */ | |
96 | sector_t last_sector[2]; /* last REQ_SYNC & REQ_ASYNC sectors */ | |
1da177e4 LT |
97 | |
98 | unsigned long exit_prob; /* probability a task will exit while | |
99 | being waited on */ | |
f5b3db00 NP |
100 | unsigned long exit_no_coop; /* probablility an exited task will |
101 | not be part of a later cooperating | |
102 | request */ | |
1da177e4 LT |
103 | unsigned long new_ttime_total; /* mean thinktime on new proc */ |
104 | unsigned long new_ttime_mean; | |
105 | u64 new_seek_total; /* mean seek on new proc */ | |
106 | sector_t new_seek_mean; | |
107 | ||
108 | unsigned long current_batch_expires; | |
109 | unsigned long last_check_fifo[2]; | |
110 | int changed_batch; /* 1: waiting for old batch to end */ | |
111 | int new_batch; /* 1: waiting on first read complete */ | |
112 | int batch_data_dir; /* current batch REQ_SYNC / REQ_ASYNC */ | |
113 | int write_batch_count; /* max # of reqs in a write batch */ | |
114 | int current_write_count; /* how many requests left this batch */ | |
115 | int write_batch_idled; /* has the write batch gone idle? */ | |
116 | mempool_t *arq_pool; | |
117 | ||
118 | enum anticipation_status antic_status; | |
119 | unsigned long antic_start; /* jiffies: when it started */ | |
120 | struct timer_list antic_timer; /* anticipatory scheduling timer */ | |
121 | struct work_struct antic_work; /* Deferred unplugging */ | |
122 | struct io_context *io_context; /* Identify the expected process */ | |
123 | int ioc_finished; /* IO associated with io_context is finished */ | |
124 | int nr_dispatched; | |
125 | ||
126 | /* | |
127 | * settings that change how the i/o scheduler behaves | |
128 | */ | |
129 | unsigned long fifo_expire[2]; | |
130 | unsigned long batch_expire[2]; | |
131 | unsigned long antic_expire; | |
132 | }; | |
133 | ||
1da177e4 LT |
134 | /* |
135 | * per-request data. | |
136 | */ | |
137 | enum arq_state { | |
138 | AS_RQ_NEW=0, /* New - not referenced and not on any lists */ | |
139 | AS_RQ_QUEUED, /* In the request queue. It belongs to the | |
140 | scheduler */ | |
141 | AS_RQ_DISPATCHED, /* On the dispatch list. It belongs to the | |
142 | driver now */ | |
143 | AS_RQ_PRESCHED, /* Debug poisoning for requests being used */ | |
144 | AS_RQ_REMOVED, | |
145 | AS_RQ_MERGED, | |
146 | AS_RQ_POSTSCHED, /* when they shouldn't be */ | |
147 | }; | |
148 | ||
149 | struct as_rq { | |
1da177e4 LT |
150 | struct request *request; |
151 | ||
152 | struct io_context *io_context; /* The submitting task */ | |
153 | ||
1da177e4 LT |
154 | unsigned int is_sync; |
155 | enum arq_state state; | |
156 | }; | |
157 | ||
158 | #define RQ_DATA(rq) ((struct as_rq *) (rq)->elevator_private) | |
159 | ||
160 | static kmem_cache_t *arq_pool; | |
161 | ||
334e94de AV |
162 | static atomic_t ioc_count = ATOMIC_INIT(0); |
163 | static struct completion *ioc_gone; | |
164 | ||
ef9be1d3 TH |
165 | static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq); |
166 | static void as_antic_stop(struct as_data *ad); | |
167 | ||
1da177e4 LT |
168 | /* |
169 | * IO Context helper functions | |
170 | */ | |
171 | ||
172 | /* Called to deallocate the as_io_context */ | |
173 | static void free_as_io_context(struct as_io_context *aic) | |
174 | { | |
175 | kfree(aic); | |
334e94de AV |
176 | if (atomic_dec_and_test(&ioc_count) && ioc_gone) |
177 | complete(ioc_gone); | |
1da177e4 LT |
178 | } |
179 | ||
e17a9489 AV |
180 | static void as_trim(struct io_context *ioc) |
181 | { | |
334e94de AV |
182 | if (ioc->aic) |
183 | free_as_io_context(ioc->aic); | |
e17a9489 AV |
184 | ioc->aic = NULL; |
185 | } | |
186 | ||
1da177e4 LT |
187 | /* Called when the task exits */ |
188 | static void exit_as_io_context(struct as_io_context *aic) | |
189 | { | |
190 | WARN_ON(!test_bit(AS_TASK_RUNNING, &aic->state)); | |
191 | clear_bit(AS_TASK_RUNNING, &aic->state); | |
192 | } | |
193 | ||
194 | static struct as_io_context *alloc_as_io_context(void) | |
195 | { | |
196 | struct as_io_context *ret; | |
197 | ||
198 | ret = kmalloc(sizeof(*ret), GFP_ATOMIC); | |
199 | if (ret) { | |
200 | ret->dtor = free_as_io_context; | |
201 | ret->exit = exit_as_io_context; | |
202 | ret->state = 1 << AS_TASK_RUNNING; | |
203 | atomic_set(&ret->nr_queued, 0); | |
204 | atomic_set(&ret->nr_dispatched, 0); | |
205 | spin_lock_init(&ret->lock); | |
206 | ret->ttime_total = 0; | |
207 | ret->ttime_samples = 0; | |
208 | ret->ttime_mean = 0; | |
209 | ret->seek_total = 0; | |
210 | ret->seek_samples = 0; | |
211 | ret->seek_mean = 0; | |
334e94de | 212 | atomic_inc(&ioc_count); |
1da177e4 LT |
213 | } |
214 | ||
215 | return ret; | |
216 | } | |
217 | ||
218 | /* | |
219 | * If the current task has no AS IO context then create one and initialise it. | |
220 | * Then take a ref on the task's io context and return it. | |
221 | */ | |
222 | static struct io_context *as_get_io_context(void) | |
223 | { | |
224 | struct io_context *ioc = get_io_context(GFP_ATOMIC); | |
225 | if (ioc && !ioc->aic) { | |
226 | ioc->aic = alloc_as_io_context(); | |
227 | if (!ioc->aic) { | |
228 | put_io_context(ioc); | |
229 | ioc = NULL; | |
230 | } | |
231 | } | |
232 | return ioc; | |
233 | } | |
234 | ||
b4878f24 JA |
235 | static void as_put_io_context(struct as_rq *arq) |
236 | { | |
237 | struct as_io_context *aic; | |
238 | ||
239 | if (unlikely(!arq->io_context)) | |
240 | return; | |
241 | ||
242 | aic = arq->io_context->aic; | |
243 | ||
244 | if (arq->is_sync == REQ_SYNC && aic) { | |
245 | spin_lock(&aic->lock); | |
246 | set_bit(AS_TASK_IORUNNING, &aic->state); | |
247 | aic->last_end_request = jiffies; | |
248 | spin_unlock(&aic->lock); | |
249 | } | |
250 | ||
251 | put_io_context(arq->io_context); | |
252 | } | |
253 | ||
1da177e4 LT |
254 | /* |
255 | * rb tree support functions | |
256 | */ | |
1da177e4 | 257 | #define ARQ_RB_ROOT(ad, arq) (&(ad)->sort_list[(arq)->is_sync]) |
1da177e4 | 258 | |
e37f346e | 259 | static void as_add_arq_rb(struct as_data *ad, struct request *rq) |
ef9be1d3 | 260 | { |
e37f346e JA |
261 | struct as_rq *arq = RQ_DATA(rq); |
262 | struct request *alias; | |
ef9be1d3 | 263 | |
e37f346e JA |
264 | while ((unlikely(alias = elv_rb_add(ARQ_RB_ROOT(ad, arq), rq)))) { |
265 | as_move_to_dispatch(ad, RQ_DATA(alias)); | |
ef9be1d3 TH |
266 | as_antic_stop(ad); |
267 | } | |
268 | } | |
269 | ||
e37f346e | 270 | static inline void as_del_arq_rb(struct as_data *ad, struct request *rq) |
1da177e4 | 271 | { |
e37f346e | 272 | elv_rb_del(ARQ_RB_ROOT(ad, RQ_DATA(rq)), rq); |
1da177e4 LT |
273 | } |
274 | ||
275 | /* | |
276 | * IO Scheduler proper | |
277 | */ | |
278 | ||
279 | #define MAXBACK (1024 * 1024) /* | |
280 | * Maximum distance the disk will go backward | |
281 | * for a request. | |
282 | */ | |
283 | ||
284 | #define BACK_PENALTY 2 | |
285 | ||
286 | /* | |
287 | * as_choose_req selects the preferred one of two requests of the same data_dir | |
288 | * ignoring time - eg. timeouts, which is the job of as_dispatch_request | |
289 | */ | |
290 | static struct as_rq * | |
291 | as_choose_req(struct as_data *ad, struct as_rq *arq1, struct as_rq *arq2) | |
292 | { | |
293 | int data_dir; | |
294 | sector_t last, s1, s2, d1, d2; | |
295 | int r1_wrap=0, r2_wrap=0; /* requests are behind the disk head */ | |
296 | const sector_t maxback = MAXBACK; | |
297 | ||
298 | if (arq1 == NULL || arq1 == arq2) | |
299 | return arq2; | |
300 | if (arq2 == NULL) | |
301 | return arq1; | |
302 | ||
303 | data_dir = arq1->is_sync; | |
304 | ||
305 | last = ad->last_sector[data_dir]; | |
306 | s1 = arq1->request->sector; | |
307 | s2 = arq2->request->sector; | |
308 | ||
309 | BUG_ON(data_dir != arq2->is_sync); | |
310 | ||
311 | /* | |
312 | * Strict one way elevator _except_ in the case where we allow | |
313 | * short backward seeks which are biased as twice the cost of a | |
314 | * similar forward seek. | |
315 | */ | |
316 | if (s1 >= last) | |
317 | d1 = s1 - last; | |
318 | else if (s1+maxback >= last) | |
319 | d1 = (last - s1)*BACK_PENALTY; | |
320 | else { | |
321 | r1_wrap = 1; | |
322 | d1 = 0; /* shut up, gcc */ | |
323 | } | |
324 | ||
325 | if (s2 >= last) | |
326 | d2 = s2 - last; | |
327 | else if (s2+maxback >= last) | |
328 | d2 = (last - s2)*BACK_PENALTY; | |
329 | else { | |
330 | r2_wrap = 1; | |
331 | d2 = 0; | |
332 | } | |
333 | ||
334 | /* Found required data */ | |
335 | if (!r1_wrap && r2_wrap) | |
336 | return arq1; | |
337 | else if (!r2_wrap && r1_wrap) | |
338 | return arq2; | |
339 | else if (r1_wrap && r2_wrap) { | |
340 | /* both behind the head */ | |
341 | if (s1 <= s2) | |
342 | return arq1; | |
343 | else | |
344 | return arq2; | |
345 | } | |
346 | ||
347 | /* Both requests in front of the head */ | |
348 | if (d1 < d2) | |
349 | return arq1; | |
350 | else if (d2 < d1) | |
351 | return arq2; | |
352 | else { | |
353 | if (s1 >= s2) | |
354 | return arq1; | |
355 | else | |
356 | return arq2; | |
357 | } | |
358 | } | |
359 | ||
360 | /* | |
361 | * as_find_next_arq finds the next request after @prev in elevator order. | |
362 | * this with as_choose_req form the basis for how the scheduler chooses | |
363 | * what request to process next. Anticipation works on top of this. | |
364 | */ | |
e37f346e | 365 | static struct as_rq *as_find_next_arq(struct as_data *ad, struct as_rq *arq) |
1da177e4 | 366 | { |
e37f346e | 367 | struct request *last = arq->request; |
1da177e4 LT |
368 | struct rb_node *rbnext = rb_next(&last->rb_node); |
369 | struct rb_node *rbprev = rb_prev(&last->rb_node); | |
e37f346e | 370 | struct as_rq *next = NULL, *prev = NULL; |
1da177e4 | 371 | |
e37f346e | 372 | BUG_ON(RB_EMPTY_NODE(&last->rb_node)); |
1da177e4 LT |
373 | |
374 | if (rbprev) | |
e37f346e | 375 | prev = RQ_DATA(rb_entry_rq(rbprev)); |
1da177e4 LT |
376 | |
377 | if (rbnext) | |
e37f346e | 378 | next = RQ_DATA(rb_entry_rq(rbnext)); |
1da177e4 | 379 | else { |
e37f346e | 380 | const int data_dir = arq->is_sync; |
1da177e4 | 381 | |
e37f346e JA |
382 | rbnext = rb_first(&ad->sort_list[data_dir]); |
383 | if (rbnext && rbnext != &last->rb_node) | |
384 | next = RQ_DATA(rb_entry_rq(rbnext)); | |
385 | } | |
1da177e4 | 386 | |
e37f346e | 387 | return as_choose_req(ad, next, prev); |
1da177e4 LT |
388 | } |
389 | ||
390 | /* | |
391 | * anticipatory scheduling functions follow | |
392 | */ | |
393 | ||
394 | /* | |
395 | * as_antic_expired tells us when we have anticipated too long. | |
396 | * The funny "absolute difference" math on the elapsed time is to handle | |
397 | * jiffy wraps, and disks which have been idle for 0x80000000 jiffies. | |
398 | */ | |
399 | static int as_antic_expired(struct as_data *ad) | |
400 | { | |
401 | long delta_jif; | |
402 | ||
403 | delta_jif = jiffies - ad->antic_start; | |
404 | if (unlikely(delta_jif < 0)) | |
405 | delta_jif = -delta_jif; | |
406 | if (delta_jif < ad->antic_expire) | |
407 | return 0; | |
408 | ||
409 | return 1; | |
410 | } | |
411 | ||
412 | /* | |
413 | * as_antic_waitnext starts anticipating that a nice request will soon be | |
414 | * submitted. See also as_antic_waitreq | |
415 | */ | |
416 | static void as_antic_waitnext(struct as_data *ad) | |
417 | { | |
418 | unsigned long timeout; | |
419 | ||
420 | BUG_ON(ad->antic_status != ANTIC_OFF | |
421 | && ad->antic_status != ANTIC_WAIT_REQ); | |
422 | ||
423 | timeout = ad->antic_start + ad->antic_expire; | |
424 | ||
425 | mod_timer(&ad->antic_timer, timeout); | |
426 | ||
427 | ad->antic_status = ANTIC_WAIT_NEXT; | |
428 | } | |
429 | ||
430 | /* | |
431 | * as_antic_waitreq starts anticipating. We don't start timing the anticipation | |
432 | * until the request that we're anticipating on has finished. This means we | |
433 | * are timing from when the candidate process wakes up hopefully. | |
434 | */ | |
435 | static void as_antic_waitreq(struct as_data *ad) | |
436 | { | |
437 | BUG_ON(ad->antic_status == ANTIC_FINISHED); | |
438 | if (ad->antic_status == ANTIC_OFF) { | |
439 | if (!ad->io_context || ad->ioc_finished) | |
440 | as_antic_waitnext(ad); | |
441 | else | |
442 | ad->antic_status = ANTIC_WAIT_REQ; | |
443 | } | |
444 | } | |
445 | ||
446 | /* | |
447 | * This is called directly by the functions in this file to stop anticipation. | |
448 | * We kill the timer and schedule a call to the request_fn asap. | |
449 | */ | |
450 | static void as_antic_stop(struct as_data *ad) | |
451 | { | |
452 | int status = ad->antic_status; | |
453 | ||
454 | if (status == ANTIC_WAIT_REQ || status == ANTIC_WAIT_NEXT) { | |
455 | if (status == ANTIC_WAIT_NEXT) | |
456 | del_timer(&ad->antic_timer); | |
457 | ad->antic_status = ANTIC_FINISHED; | |
458 | /* see as_work_handler */ | |
459 | kblockd_schedule_work(&ad->antic_work); | |
460 | } | |
461 | } | |
462 | ||
463 | /* | |
464 | * as_antic_timeout is the timer function set by as_antic_waitnext. | |
465 | */ | |
466 | static void as_antic_timeout(unsigned long data) | |
467 | { | |
468 | struct request_queue *q = (struct request_queue *)data; | |
469 | struct as_data *ad = q->elevator->elevator_data; | |
470 | unsigned long flags; | |
471 | ||
472 | spin_lock_irqsave(q->queue_lock, flags); | |
473 | if (ad->antic_status == ANTIC_WAIT_REQ | |
474 | || ad->antic_status == ANTIC_WAIT_NEXT) { | |
475 | struct as_io_context *aic = ad->io_context->aic; | |
476 | ||
477 | ad->antic_status = ANTIC_FINISHED; | |
478 | kblockd_schedule_work(&ad->antic_work); | |
479 | ||
480 | if (aic->ttime_samples == 0) { | |
f5b3db00 | 481 | /* process anticipated on has exited or timed out*/ |
1da177e4 LT |
482 | ad->exit_prob = (7*ad->exit_prob + 256)/8; |
483 | } | |
f5b3db00 NP |
484 | if (!test_bit(AS_TASK_RUNNING, &aic->state)) { |
485 | /* process not "saved" by a cooperating request */ | |
486 | ad->exit_no_coop = (7*ad->exit_no_coop + 256)/8; | |
487 | } | |
1da177e4 LT |
488 | } |
489 | spin_unlock_irqrestore(q->queue_lock, flags); | |
490 | } | |
491 | ||
f5b3db00 NP |
492 | static void as_update_thinktime(struct as_data *ad, struct as_io_context *aic, |
493 | unsigned long ttime) | |
494 | { | |
495 | /* fixed point: 1.0 == 1<<8 */ | |
496 | if (aic->ttime_samples == 0) { | |
497 | ad->new_ttime_total = (7*ad->new_ttime_total + 256*ttime) / 8; | |
498 | ad->new_ttime_mean = ad->new_ttime_total / 256; | |
499 | ||
500 | ad->exit_prob = (7*ad->exit_prob)/8; | |
501 | } | |
502 | aic->ttime_samples = (7*aic->ttime_samples + 256) / 8; | |
503 | aic->ttime_total = (7*aic->ttime_total + 256*ttime) / 8; | |
504 | aic->ttime_mean = (aic->ttime_total + 128) / aic->ttime_samples; | |
505 | } | |
506 | ||
507 | static void as_update_seekdist(struct as_data *ad, struct as_io_context *aic, | |
508 | sector_t sdist) | |
509 | { | |
510 | u64 total; | |
511 | ||
512 | if (aic->seek_samples == 0) { | |
513 | ad->new_seek_total = (7*ad->new_seek_total + 256*(u64)sdist)/8; | |
514 | ad->new_seek_mean = ad->new_seek_total / 256; | |
515 | } | |
516 | ||
517 | /* | |
518 | * Don't allow the seek distance to get too large from the | |
519 | * odd fragment, pagein, etc | |
520 | */ | |
521 | if (aic->seek_samples <= 60) /* second&third seek */ | |
522 | sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*1024); | |
523 | else | |
524 | sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*64); | |
525 | ||
526 | aic->seek_samples = (7*aic->seek_samples + 256) / 8; | |
527 | aic->seek_total = (7*aic->seek_total + (u64)256*sdist) / 8; | |
528 | total = aic->seek_total + (aic->seek_samples/2); | |
529 | do_div(total, aic->seek_samples); | |
530 | aic->seek_mean = (sector_t)total; | |
531 | } | |
532 | ||
533 | /* | |
534 | * as_update_iohist keeps a decaying histogram of IO thinktimes, and | |
535 | * updates @aic->ttime_mean based on that. It is called when a new | |
536 | * request is queued. | |
537 | */ | |
538 | static void as_update_iohist(struct as_data *ad, struct as_io_context *aic, | |
539 | struct request *rq) | |
540 | { | |
541 | struct as_rq *arq = RQ_DATA(rq); | |
542 | int data_dir = arq->is_sync; | |
543 | unsigned long thinktime = 0; | |
544 | sector_t seek_dist; | |
545 | ||
546 | if (aic == NULL) | |
547 | return; | |
548 | ||
549 | if (data_dir == REQ_SYNC) { | |
550 | unsigned long in_flight = atomic_read(&aic->nr_queued) | |
551 | + atomic_read(&aic->nr_dispatched); | |
552 | spin_lock(&aic->lock); | |
553 | if (test_bit(AS_TASK_IORUNNING, &aic->state) || | |
554 | test_bit(AS_TASK_IOSTARTED, &aic->state)) { | |
555 | /* Calculate read -> read thinktime */ | |
556 | if (test_bit(AS_TASK_IORUNNING, &aic->state) | |
557 | && in_flight == 0) { | |
558 | thinktime = jiffies - aic->last_end_request; | |
559 | thinktime = min(thinktime, MAX_THINKTIME-1); | |
560 | } | |
561 | as_update_thinktime(ad, aic, thinktime); | |
562 | ||
563 | /* Calculate read -> read seek distance */ | |
564 | if (aic->last_request_pos < rq->sector) | |
565 | seek_dist = rq->sector - aic->last_request_pos; | |
566 | else | |
567 | seek_dist = aic->last_request_pos - rq->sector; | |
568 | as_update_seekdist(ad, aic, seek_dist); | |
569 | } | |
570 | aic->last_request_pos = rq->sector + rq->nr_sectors; | |
571 | set_bit(AS_TASK_IOSTARTED, &aic->state); | |
572 | spin_unlock(&aic->lock); | |
573 | } | |
574 | } | |
575 | ||
1da177e4 LT |
576 | /* |
577 | * as_close_req decides if one request is considered "close" to the | |
578 | * previous one issued. | |
579 | */ | |
f5b3db00 NP |
580 | static int as_close_req(struct as_data *ad, struct as_io_context *aic, |
581 | struct as_rq *arq) | |
1da177e4 LT |
582 | { |
583 | unsigned long delay; /* milliseconds */ | |
584 | sector_t last = ad->last_sector[ad->batch_data_dir]; | |
585 | sector_t next = arq->request->sector; | |
586 | sector_t delta; /* acceptable close offset (in sectors) */ | |
f5b3db00 | 587 | sector_t s; |
1da177e4 LT |
588 | |
589 | if (ad->antic_status == ANTIC_OFF || !ad->ioc_finished) | |
590 | delay = 0; | |
591 | else | |
592 | delay = ((jiffies - ad->antic_start) * 1000) / HZ; | |
593 | ||
f5b3db00 NP |
594 | if (delay == 0) |
595 | delta = 8192; | |
1da177e4 | 596 | else if (delay <= 20 && delay <= ad->antic_expire) |
f5b3db00 | 597 | delta = 8192 << delay; |
1da177e4 LT |
598 | else |
599 | return 1; | |
600 | ||
f5b3db00 NP |
601 | if ((last <= next + (delta>>1)) && (next <= last + delta)) |
602 | return 1; | |
603 | ||
604 | if (last < next) | |
605 | s = next - last; | |
606 | else | |
607 | s = last - next; | |
608 | ||
609 | if (aic->seek_samples == 0) { | |
610 | /* | |
611 | * Process has just started IO. Use past statistics to | |
612 | * gauge success possibility | |
613 | */ | |
614 | if (ad->new_seek_mean > s) { | |
615 | /* this request is better than what we're expecting */ | |
616 | return 1; | |
617 | } | |
618 | ||
619 | } else { | |
620 | if (aic->seek_mean > s) { | |
621 | /* this request is better than what we're expecting */ | |
622 | return 1; | |
623 | } | |
624 | } | |
625 | ||
626 | return 0; | |
1da177e4 LT |
627 | } |
628 | ||
629 | /* | |
630 | * as_can_break_anticipation returns true if we have been anticipating this | |
631 | * request. | |
632 | * | |
633 | * It also returns true if the process against which we are anticipating | |
634 | * submits a write - that's presumably an fsync, O_SYNC write, etc. We want to | |
635 | * dispatch it ASAP, because we know that application will not be submitting | |
636 | * any new reads. | |
637 | * | |
f5b3db00 | 638 | * If the task which has submitted the request has exited, break anticipation. |
1da177e4 LT |
639 | * |
640 | * If this task has queued some other IO, do not enter enticipation. | |
641 | */ | |
642 | static int as_can_break_anticipation(struct as_data *ad, struct as_rq *arq) | |
643 | { | |
644 | struct io_context *ioc; | |
645 | struct as_io_context *aic; | |
1da177e4 LT |
646 | |
647 | ioc = ad->io_context; | |
648 | BUG_ON(!ioc); | |
649 | ||
650 | if (arq && ioc == arq->io_context) { | |
651 | /* request from same process */ | |
652 | return 1; | |
653 | } | |
654 | ||
655 | if (ad->ioc_finished && as_antic_expired(ad)) { | |
656 | /* | |
657 | * In this situation status should really be FINISHED, | |
658 | * however the timer hasn't had the chance to run yet. | |
659 | */ | |
660 | return 1; | |
661 | } | |
662 | ||
663 | aic = ioc->aic; | |
664 | if (!aic) | |
665 | return 0; | |
666 | ||
1da177e4 LT |
667 | if (atomic_read(&aic->nr_queued) > 0) { |
668 | /* process has more requests queued */ | |
669 | return 1; | |
670 | } | |
671 | ||
672 | if (atomic_read(&aic->nr_dispatched) > 0) { | |
673 | /* process has more requests dispatched */ | |
674 | return 1; | |
675 | } | |
676 | ||
f5b3db00 | 677 | if (arq && arq->is_sync == REQ_SYNC && as_close_req(ad, aic, arq)) { |
1da177e4 LT |
678 | /* |
679 | * Found a close request that is not one of ours. | |
680 | * | |
f5b3db00 NP |
681 | * This makes close requests from another process update |
682 | * our IO history. Is generally useful when there are | |
1da177e4 LT |
683 | * two or more cooperating processes working in the same |
684 | * area. | |
685 | */ | |
f5b3db00 NP |
686 | if (!test_bit(AS_TASK_RUNNING, &aic->state)) { |
687 | if (aic->ttime_samples == 0) | |
688 | ad->exit_prob = (7*ad->exit_prob + 256)/8; | |
689 | ||
690 | ad->exit_no_coop = (7*ad->exit_no_coop)/8; | |
691 | } | |
692 | ||
693 | as_update_iohist(ad, aic, arq->request); | |
1da177e4 LT |
694 | return 1; |
695 | } | |
696 | ||
f5b3db00 NP |
697 | if (!test_bit(AS_TASK_RUNNING, &aic->state)) { |
698 | /* process anticipated on has exited */ | |
699 | if (aic->ttime_samples == 0) | |
700 | ad->exit_prob = (7*ad->exit_prob + 256)/8; | |
701 | ||
702 | if (ad->exit_no_coop > 128) | |
703 | return 1; | |
704 | } | |
1da177e4 LT |
705 | |
706 | if (aic->ttime_samples == 0) { | |
707 | if (ad->new_ttime_mean > ad->antic_expire) | |
708 | return 1; | |
f5b3db00 | 709 | if (ad->exit_prob * ad->exit_no_coop > 128*256) |
1da177e4 LT |
710 | return 1; |
711 | } else if (aic->ttime_mean > ad->antic_expire) { | |
712 | /* the process thinks too much between requests */ | |
713 | return 1; | |
714 | } | |
715 | ||
1da177e4 LT |
716 | return 0; |
717 | } | |
718 | ||
719 | /* | |
d6e05edc | 720 | * as_can_anticipate indicates whether we should either run arq |
1da177e4 LT |
721 | * or keep anticipating a better request. |
722 | */ | |
723 | static int as_can_anticipate(struct as_data *ad, struct as_rq *arq) | |
724 | { | |
725 | if (!ad->io_context) | |
726 | /* | |
727 | * Last request submitted was a write | |
728 | */ | |
729 | return 0; | |
730 | ||
731 | if (ad->antic_status == ANTIC_FINISHED) | |
732 | /* | |
733 | * Don't restart if we have just finished. Run the next request | |
734 | */ | |
735 | return 0; | |
736 | ||
737 | if (as_can_break_anticipation(ad, arq)) | |
738 | /* | |
739 | * This request is a good candidate. Don't keep anticipating, | |
740 | * run it. | |
741 | */ | |
742 | return 0; | |
743 | ||
744 | /* | |
745 | * OK from here, we haven't finished, and don't have a decent request! | |
746 | * Status is either ANTIC_OFF so start waiting, | |
747 | * ANTIC_WAIT_REQ so continue waiting for request to finish | |
748 | * or ANTIC_WAIT_NEXT so continue waiting for an acceptable request. | |
1da177e4 LT |
749 | */ |
750 | ||
751 | return 1; | |
752 | } | |
753 | ||
1da177e4 LT |
754 | /* |
755 | * as_update_arq must be called whenever a request (arq) is added to | |
756 | * the sort_list. This function keeps caches up to date, and checks if the | |
757 | * request might be one we are "anticipating" | |
758 | */ | |
759 | static void as_update_arq(struct as_data *ad, struct as_rq *arq) | |
760 | { | |
761 | const int data_dir = arq->is_sync; | |
762 | ||
763 | /* keep the next_arq cache up to date */ | |
764 | ad->next_arq[data_dir] = as_choose_req(ad, arq, ad->next_arq[data_dir]); | |
765 | ||
766 | /* | |
767 | * have we been anticipating this request? | |
768 | * or does it come from the same process as the one we are anticipating | |
769 | * for? | |
770 | */ | |
771 | if (ad->antic_status == ANTIC_WAIT_REQ | |
772 | || ad->antic_status == ANTIC_WAIT_NEXT) { | |
773 | if (as_can_break_anticipation(ad, arq)) | |
774 | as_antic_stop(ad); | |
775 | } | |
776 | } | |
777 | ||
778 | /* | |
779 | * Gathers timings and resizes the write batch automatically | |
780 | */ | |
781 | static void update_write_batch(struct as_data *ad) | |
782 | { | |
783 | unsigned long batch = ad->batch_expire[REQ_ASYNC]; | |
784 | long write_time; | |
785 | ||
786 | write_time = (jiffies - ad->current_batch_expires) + batch; | |
787 | if (write_time < 0) | |
788 | write_time = 0; | |
789 | ||
790 | if (write_time > batch && !ad->write_batch_idled) { | |
791 | if (write_time > batch * 3) | |
792 | ad->write_batch_count /= 2; | |
793 | else | |
794 | ad->write_batch_count--; | |
795 | } else if (write_time < batch && ad->current_write_count == 0) { | |
796 | if (batch > write_time * 3) | |
797 | ad->write_batch_count *= 2; | |
798 | else | |
799 | ad->write_batch_count++; | |
800 | } | |
801 | ||
802 | if (ad->write_batch_count < 1) | |
803 | ad->write_batch_count = 1; | |
804 | } | |
805 | ||
806 | /* | |
807 | * as_completed_request is to be called when a request has completed and | |
808 | * returned something to the requesting process, be it an error or data. | |
809 | */ | |
810 | static void as_completed_request(request_queue_t *q, struct request *rq) | |
811 | { | |
812 | struct as_data *ad = q->elevator->elevator_data; | |
813 | struct as_rq *arq = RQ_DATA(rq); | |
814 | ||
815 | WARN_ON(!list_empty(&rq->queuelist)); | |
816 | ||
1da177e4 LT |
817 | if (arq->state != AS_RQ_REMOVED) { |
818 | printk("arq->state %d\n", arq->state); | |
819 | WARN_ON(1); | |
820 | goto out; | |
821 | } | |
822 | ||
1da177e4 LT |
823 | if (ad->changed_batch && ad->nr_dispatched == 1) { |
824 | kblockd_schedule_work(&ad->antic_work); | |
825 | ad->changed_batch = 0; | |
826 | ||
827 | if (ad->batch_data_dir == REQ_SYNC) | |
828 | ad->new_batch = 1; | |
829 | } | |
830 | WARN_ON(ad->nr_dispatched == 0); | |
831 | ad->nr_dispatched--; | |
832 | ||
833 | /* | |
834 | * Start counting the batch from when a request of that direction is | |
835 | * actually serviced. This should help devices with big TCQ windows | |
836 | * and writeback caches | |
837 | */ | |
838 | if (ad->new_batch && ad->batch_data_dir == arq->is_sync) { | |
839 | update_write_batch(ad); | |
840 | ad->current_batch_expires = jiffies + | |
841 | ad->batch_expire[REQ_SYNC]; | |
842 | ad->new_batch = 0; | |
843 | } | |
844 | ||
845 | if (ad->io_context == arq->io_context && ad->io_context) { | |
846 | ad->antic_start = jiffies; | |
847 | ad->ioc_finished = 1; | |
848 | if (ad->antic_status == ANTIC_WAIT_REQ) { | |
849 | /* | |
850 | * We were waiting on this request, now anticipate | |
851 | * the next one | |
852 | */ | |
853 | as_antic_waitnext(ad); | |
854 | } | |
855 | } | |
856 | ||
b4878f24 | 857 | as_put_io_context(arq); |
1da177e4 LT |
858 | out: |
859 | arq->state = AS_RQ_POSTSCHED; | |
860 | } | |
861 | ||
862 | /* | |
863 | * as_remove_queued_request removes a request from the pre dispatch queue | |
864 | * without updating refcounts. It is expected the caller will drop the | |
865 | * reference unless it replaces the request at somepart of the elevator | |
866 | * (ie. the dispatch queue) | |
867 | */ | |
868 | static void as_remove_queued_request(request_queue_t *q, struct request *rq) | |
869 | { | |
870 | struct as_rq *arq = RQ_DATA(rq); | |
871 | const int data_dir = arq->is_sync; | |
872 | struct as_data *ad = q->elevator->elevator_data; | |
873 | ||
874 | WARN_ON(arq->state != AS_RQ_QUEUED); | |
875 | ||
876 | if (arq->io_context && arq->io_context->aic) { | |
877 | BUG_ON(!atomic_read(&arq->io_context->aic->nr_queued)); | |
878 | atomic_dec(&arq->io_context->aic->nr_queued); | |
879 | } | |
880 | ||
881 | /* | |
882 | * Update the "next_arq" cache if we are about to remove its | |
883 | * entry | |
884 | */ | |
885 | if (ad->next_arq[data_dir] == arq) | |
886 | ad->next_arq[data_dir] = as_find_next_arq(ad, arq); | |
887 | ||
d4f2f462 | 888 | rq_fifo_clear(rq); |
e37f346e | 889 | as_del_arq_rb(ad, rq); |
1da177e4 LT |
890 | } |
891 | ||
1da177e4 LT |
892 | /* |
893 | * as_fifo_expired returns 0 if there are no expired reads on the fifo, | |
894 | * 1 otherwise. It is ratelimited so that we only perform the check once per | |
895 | * `fifo_expire' interval. Otherwise a large number of expired requests | |
896 | * would create a hopeless seekstorm. | |
897 | * | |
898 | * See as_antic_expired comment. | |
899 | */ | |
900 | static int as_fifo_expired(struct as_data *ad, int adir) | |
901 | { | |
d4f2f462 | 902 | struct request *rq; |
1da177e4 LT |
903 | long delta_jif; |
904 | ||
905 | delta_jif = jiffies - ad->last_check_fifo[adir]; | |
906 | if (unlikely(delta_jif < 0)) | |
907 | delta_jif = -delta_jif; | |
908 | if (delta_jif < ad->fifo_expire[adir]) | |
909 | return 0; | |
910 | ||
911 | ad->last_check_fifo[adir] = jiffies; | |
912 | ||
913 | if (list_empty(&ad->fifo_list[adir])) | |
914 | return 0; | |
915 | ||
d4f2f462 | 916 | rq = rq_entry_fifo(ad->fifo_list[adir].next); |
1da177e4 | 917 | |
d4f2f462 | 918 | return time_after(jiffies, rq_fifo_time(rq)); |
1da177e4 LT |
919 | } |
920 | ||
921 | /* | |
922 | * as_batch_expired returns true if the current batch has expired. A batch | |
923 | * is a set of reads or a set of writes. | |
924 | */ | |
925 | static inline int as_batch_expired(struct as_data *ad) | |
926 | { | |
927 | if (ad->changed_batch || ad->new_batch) | |
928 | return 0; | |
929 | ||
930 | if (ad->batch_data_dir == REQ_SYNC) | |
931 | /* TODO! add a check so a complete fifo gets written? */ | |
932 | return time_after(jiffies, ad->current_batch_expires); | |
933 | ||
934 | return time_after(jiffies, ad->current_batch_expires) | |
935 | || ad->current_write_count == 0; | |
936 | } | |
937 | ||
938 | /* | |
939 | * move an entry to dispatch queue | |
940 | */ | |
941 | static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq) | |
942 | { | |
943 | struct request *rq = arq->request; | |
1da177e4 LT |
944 | const int data_dir = arq->is_sync; |
945 | ||
e37f346e | 946 | BUG_ON(RB_EMPTY_NODE(&rq->rb_node)); |
1da177e4 LT |
947 | |
948 | as_antic_stop(ad); | |
949 | ad->antic_status = ANTIC_OFF; | |
950 | ||
951 | /* | |
952 | * This has to be set in order to be correctly updated by | |
953 | * as_find_next_arq | |
954 | */ | |
955 | ad->last_sector[data_dir] = rq->sector + rq->nr_sectors; | |
956 | ||
957 | if (data_dir == REQ_SYNC) { | |
958 | /* In case we have to anticipate after this */ | |
959 | copy_io_context(&ad->io_context, &arq->io_context); | |
960 | } else { | |
961 | if (ad->io_context) { | |
962 | put_io_context(ad->io_context); | |
963 | ad->io_context = NULL; | |
964 | } | |
965 | ||
966 | if (ad->current_write_count != 0) | |
967 | ad->current_write_count--; | |
968 | } | |
969 | ad->ioc_finished = 0; | |
970 | ||
971 | ad->next_arq[data_dir] = as_find_next_arq(ad, arq); | |
972 | ||
973 | /* | |
974 | * take it off the sort and fifo list, add to dispatch queue | |
975 | */ | |
1da177e4 LT |
976 | as_remove_queued_request(ad->q, rq); |
977 | WARN_ON(arq->state != AS_RQ_QUEUED); | |
978 | ||
b4878f24 JA |
979 | elv_dispatch_sort(ad->q, rq); |
980 | ||
1da177e4 LT |
981 | arq->state = AS_RQ_DISPATCHED; |
982 | if (arq->io_context && arq->io_context->aic) | |
983 | atomic_inc(&arq->io_context->aic->nr_dispatched); | |
984 | ad->nr_dispatched++; | |
985 | } | |
986 | ||
987 | /* | |
988 | * as_dispatch_request selects the best request according to | |
989 | * read/write expire, batch expire, etc, and moves it to the dispatch | |
990 | * queue. Returns 1 if a request was found, 0 otherwise. | |
991 | */ | |
b4878f24 | 992 | static int as_dispatch_request(request_queue_t *q, int force) |
1da177e4 | 993 | { |
b4878f24 | 994 | struct as_data *ad = q->elevator->elevator_data; |
1da177e4 LT |
995 | struct as_rq *arq; |
996 | const int reads = !list_empty(&ad->fifo_list[REQ_SYNC]); | |
997 | const int writes = !list_empty(&ad->fifo_list[REQ_ASYNC]); | |
998 | ||
b4878f24 JA |
999 | if (unlikely(force)) { |
1000 | /* | |
1001 | * Forced dispatch, accounting is useless. Reset | |
1002 | * accounting states and dump fifo_lists. Note that | |
1003 | * batch_data_dir is reset to REQ_SYNC to avoid | |
1004 | * screwing write batch accounting as write batch | |
1005 | * accounting occurs on W->R transition. | |
1006 | */ | |
1007 | int dispatched = 0; | |
1008 | ||
1009 | ad->batch_data_dir = REQ_SYNC; | |
1010 | ad->changed_batch = 0; | |
1011 | ad->new_batch = 0; | |
1012 | ||
1013 | while (ad->next_arq[REQ_SYNC]) { | |
1014 | as_move_to_dispatch(ad, ad->next_arq[REQ_SYNC]); | |
1015 | dispatched++; | |
1016 | } | |
1017 | ad->last_check_fifo[REQ_SYNC] = jiffies; | |
1018 | ||
1019 | while (ad->next_arq[REQ_ASYNC]) { | |
1020 | as_move_to_dispatch(ad, ad->next_arq[REQ_ASYNC]); | |
1021 | dispatched++; | |
1022 | } | |
1023 | ad->last_check_fifo[REQ_ASYNC] = jiffies; | |
1024 | ||
1025 | return dispatched; | |
1026 | } | |
1027 | ||
1da177e4 LT |
1028 | /* Signal that the write batch was uncontended, so we can't time it */ |
1029 | if (ad->batch_data_dir == REQ_ASYNC && !reads) { | |
1030 | if (ad->current_write_count == 0 || !writes) | |
1031 | ad->write_batch_idled = 1; | |
1032 | } | |
1033 | ||
1034 | if (!(reads || writes) | |
1035 | || ad->antic_status == ANTIC_WAIT_REQ | |
1036 | || ad->antic_status == ANTIC_WAIT_NEXT | |
1037 | || ad->changed_batch) | |
1038 | return 0; | |
1039 | ||
f5b3db00 | 1040 | if (!(reads && writes && as_batch_expired(ad))) { |
1da177e4 LT |
1041 | /* |
1042 | * batch is still running or no reads or no writes | |
1043 | */ | |
1044 | arq = ad->next_arq[ad->batch_data_dir]; | |
1045 | ||
1046 | if (ad->batch_data_dir == REQ_SYNC && ad->antic_expire) { | |
1047 | if (as_fifo_expired(ad, REQ_SYNC)) | |
1048 | goto fifo_expired; | |
1049 | ||
1050 | if (as_can_anticipate(ad, arq)) { | |
1051 | as_antic_waitreq(ad); | |
1052 | return 0; | |
1053 | } | |
1054 | } | |
1055 | ||
1056 | if (arq) { | |
1057 | /* we have a "next request" */ | |
1058 | if (reads && !writes) | |
1059 | ad->current_batch_expires = | |
1060 | jiffies + ad->batch_expire[REQ_SYNC]; | |
1061 | goto dispatch_request; | |
1062 | } | |
1063 | } | |
1064 | ||
1065 | /* | |
1066 | * at this point we are not running a batch. select the appropriate | |
1067 | * data direction (read / write) | |
1068 | */ | |
1069 | ||
1070 | if (reads) { | |
dd67d051 | 1071 | BUG_ON(RB_EMPTY_ROOT(&ad->sort_list[REQ_SYNC])); |
1da177e4 LT |
1072 | |
1073 | if (writes && ad->batch_data_dir == REQ_SYNC) | |
1074 | /* | |
1075 | * Last batch was a read, switch to writes | |
1076 | */ | |
1077 | goto dispatch_writes; | |
1078 | ||
1079 | if (ad->batch_data_dir == REQ_ASYNC) { | |
1080 | WARN_ON(ad->new_batch); | |
1081 | ad->changed_batch = 1; | |
1082 | } | |
1083 | ad->batch_data_dir = REQ_SYNC; | |
d4f2f462 | 1084 | arq = RQ_DATA(rq_entry_fifo(ad->fifo_list[REQ_SYNC].next)); |
1da177e4 LT |
1085 | ad->last_check_fifo[ad->batch_data_dir] = jiffies; |
1086 | goto dispatch_request; | |
1087 | } | |
1088 | ||
1089 | /* | |
1090 | * the last batch was a read | |
1091 | */ | |
1092 | ||
1093 | if (writes) { | |
1094 | dispatch_writes: | |
dd67d051 | 1095 | BUG_ON(RB_EMPTY_ROOT(&ad->sort_list[REQ_ASYNC])); |
1da177e4 LT |
1096 | |
1097 | if (ad->batch_data_dir == REQ_SYNC) { | |
1098 | ad->changed_batch = 1; | |
1099 | ||
1100 | /* | |
1101 | * new_batch might be 1 when the queue runs out of | |
1102 | * reads. A subsequent submission of a write might | |
1103 | * cause a change of batch before the read is finished. | |
1104 | */ | |
1105 | ad->new_batch = 0; | |
1106 | } | |
1107 | ad->batch_data_dir = REQ_ASYNC; | |
1108 | ad->current_write_count = ad->write_batch_count; | |
1109 | ad->write_batch_idled = 0; | |
1110 | arq = ad->next_arq[ad->batch_data_dir]; | |
1111 | goto dispatch_request; | |
1112 | } | |
1113 | ||
1114 | BUG(); | |
1115 | return 0; | |
1116 | ||
1117 | dispatch_request: | |
1118 | /* | |
1119 | * If a request has expired, service it. | |
1120 | */ | |
1121 | ||
1122 | if (as_fifo_expired(ad, ad->batch_data_dir)) { | |
1123 | fifo_expired: | |
d4f2f462 | 1124 | arq = RQ_DATA(rq_entry_fifo(ad->fifo_list[ad->batch_data_dir].next)); |
1da177e4 LT |
1125 | } |
1126 | ||
1127 | if (ad->changed_batch) { | |
1128 | WARN_ON(ad->new_batch); | |
1129 | ||
1130 | if (ad->nr_dispatched) | |
1131 | return 0; | |
1132 | ||
1133 | if (ad->batch_data_dir == REQ_ASYNC) | |
1134 | ad->current_batch_expires = jiffies + | |
1135 | ad->batch_expire[REQ_ASYNC]; | |
1136 | else | |
1137 | ad->new_batch = 1; | |
1138 | ||
1139 | ad->changed_batch = 0; | |
1140 | } | |
1141 | ||
1142 | /* | |
1143 | * arq is the selected appropriate request. | |
1144 | */ | |
1145 | as_move_to_dispatch(ad, arq); | |
1146 | ||
1147 | return 1; | |
1148 | } | |
1149 | ||
1da177e4 LT |
1150 | /* |
1151 | * add arq to rbtree and fifo | |
1152 | */ | |
b4878f24 | 1153 | static void as_add_request(request_queue_t *q, struct request *rq) |
1da177e4 | 1154 | { |
b4878f24 JA |
1155 | struct as_data *ad = q->elevator->elevator_data; |
1156 | struct as_rq *arq = RQ_DATA(rq); | |
1da177e4 LT |
1157 | int data_dir; |
1158 | ||
b4878f24 JA |
1159 | arq->state = AS_RQ_NEW; |
1160 | ||
1da177e4 | 1161 | if (rq_data_dir(arq->request) == READ |
4aff5e23 | 1162 | || (arq->request->cmd_flags & REQ_RW_SYNC)) |
1da177e4 LT |
1163 | arq->is_sync = 1; |
1164 | else | |
1165 | arq->is_sync = 0; | |
1166 | data_dir = arq->is_sync; | |
1167 | ||
1168 | arq->io_context = as_get_io_context(); | |
1169 | ||
1170 | if (arq->io_context) { | |
1171 | as_update_iohist(ad, arq->io_context->aic, arq->request); | |
1172 | atomic_inc(&arq->io_context->aic->nr_queued); | |
1173 | } | |
1174 | ||
e37f346e | 1175 | as_add_arq_rb(ad, rq); |
1da177e4 | 1176 | |
ef9be1d3 TH |
1177 | /* |
1178 | * set expire time (only used for reads) and add to fifo list | |
1179 | */ | |
d4f2f462 JA |
1180 | rq_set_fifo_time(rq, jiffies + ad->fifo_expire[data_dir]); |
1181 | list_add_tail(&rq->queuelist, &ad->fifo_list[data_dir]); | |
1da177e4 | 1182 | |
ef9be1d3 | 1183 | as_update_arq(ad, arq); /* keep state machine up to date */ |
1da177e4 LT |
1184 | arq->state = AS_RQ_QUEUED; |
1185 | } | |
1186 | ||
b4878f24 | 1187 | static void as_activate_request(request_queue_t *q, struct request *rq) |
1da177e4 | 1188 | { |
1da177e4 LT |
1189 | struct as_rq *arq = RQ_DATA(rq); |
1190 | ||
b4878f24 JA |
1191 | WARN_ON(arq->state != AS_RQ_DISPATCHED); |
1192 | arq->state = AS_RQ_REMOVED; | |
1193 | if (arq->io_context && arq->io_context->aic) | |
1194 | atomic_dec(&arq->io_context->aic->nr_dispatched); | |
1da177e4 LT |
1195 | } |
1196 | ||
b4878f24 | 1197 | static void as_deactivate_request(request_queue_t *q, struct request *rq) |
1da177e4 | 1198 | { |
1da177e4 LT |
1199 | struct as_rq *arq = RQ_DATA(rq); |
1200 | ||
b4878f24 JA |
1201 | WARN_ON(arq->state != AS_RQ_REMOVED); |
1202 | arq->state = AS_RQ_DISPATCHED; | |
1203 | if (arq->io_context && arq->io_context->aic) | |
1204 | atomic_inc(&arq->io_context->aic->nr_dispatched); | |
1da177e4 LT |
1205 | } |
1206 | ||
1207 | /* | |
1208 | * as_queue_empty tells us if there are requests left in the device. It may | |
1209 | * not be the case that a driver can get the next request even if the queue | |
1210 | * is not empty - it is used in the block layer to check for plugging and | |
1211 | * merging opportunities | |
1212 | */ | |
1213 | static int as_queue_empty(request_queue_t *q) | |
1214 | { | |
1215 | struct as_data *ad = q->elevator->elevator_data; | |
1216 | ||
b4878f24 JA |
1217 | return list_empty(&ad->fifo_list[REQ_ASYNC]) |
1218 | && list_empty(&ad->fifo_list[REQ_SYNC]); | |
1da177e4 LT |
1219 | } |
1220 | ||
1da177e4 LT |
1221 | static int |
1222 | as_merge(request_queue_t *q, struct request **req, struct bio *bio) | |
1223 | { | |
1224 | struct as_data *ad = q->elevator->elevator_data; | |
1225 | sector_t rb_key = bio->bi_sector + bio_sectors(bio); | |
1226 | struct request *__rq; | |
1da177e4 LT |
1227 | |
1228 | /* | |
1229 | * check for front merge | |
1230 | */ | |
e37f346e | 1231 | __rq = elv_rb_find(&ad->sort_list[bio_data_dir(bio)], rb_key); |
9817064b JA |
1232 | if (__rq && elv_rq_merge_ok(__rq, bio)) { |
1233 | *req = __rq; | |
1234 | return ELEVATOR_FRONT_MERGE; | |
1da177e4 LT |
1235 | } |
1236 | ||
1237 | return ELEVATOR_NO_MERGE; | |
1da177e4 LT |
1238 | } |
1239 | ||
e37f346e | 1240 | static void as_merged_request(request_queue_t *q, struct request *req, int type) |
1da177e4 LT |
1241 | { |
1242 | struct as_data *ad = q->elevator->elevator_data; | |
1da177e4 | 1243 | |
1da177e4 LT |
1244 | /* |
1245 | * if the merge was a front merge, we need to reposition request | |
1246 | */ | |
e37f346e JA |
1247 | if (type == ELEVATOR_FRONT_MERGE) { |
1248 | as_del_arq_rb(ad, req); | |
1249 | as_add_arq_rb(ad, req); | |
1da177e4 LT |
1250 | /* |
1251 | * Note! At this stage of this and the next function, our next | |
1252 | * request may not be optimal - eg the request may have "grown" | |
1253 | * behind the disk head. We currently don't bother adjusting. | |
1254 | */ | |
1255 | } | |
1da177e4 LT |
1256 | } |
1257 | ||
f5b3db00 NP |
1258 | static void as_merged_requests(request_queue_t *q, struct request *req, |
1259 | struct request *next) | |
1da177e4 | 1260 | { |
1da177e4 LT |
1261 | struct as_rq *arq = RQ_DATA(req); |
1262 | struct as_rq *anext = RQ_DATA(next); | |
1263 | ||
1264 | BUG_ON(!arq); | |
1265 | BUG_ON(!anext); | |
1266 | ||
1da177e4 LT |
1267 | /* |
1268 | * if anext expires before arq, assign its expire time to arq | |
1269 | * and move into anext position (anext will be deleted) in fifo | |
1270 | */ | |
d4f2f462 JA |
1271 | if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) { |
1272 | if (time_before(rq_fifo_time(next), rq_fifo_time(req))) { | |
1273 | list_move(&req->queuelist, &next->queuelist); | |
1274 | rq_set_fifo_time(req, rq_fifo_time(next)); | |
1da177e4 LT |
1275 | /* |
1276 | * Don't copy here but swap, because when anext is | |
1277 | * removed below, it must contain the unused context | |
1278 | */ | |
1279 | swap_io_context(&arq->io_context, &anext->io_context); | |
1280 | } | |
1281 | } | |
1282 | ||
1da177e4 LT |
1283 | /* |
1284 | * kill knowledge of next, this one is a goner | |
1285 | */ | |
1286 | as_remove_queued_request(q, next); | |
b4878f24 | 1287 | as_put_io_context(anext); |
1da177e4 LT |
1288 | |
1289 | anext->state = AS_RQ_MERGED; | |
1290 | } | |
1291 | ||
1292 | /* | |
1293 | * This is executed in a "deferred" process context, by kblockd. It calls the | |
1294 | * driver's request_fn so the driver can submit that request. | |
1295 | * | |
1296 | * IMPORTANT! This guy will reenter the elevator, so set up all queue global | |
1297 | * state before calling, and don't rely on any state over calls. | |
1298 | * | |
1299 | * FIXME! dispatch queue is not a queue at all! | |
1300 | */ | |
1301 | static void as_work_handler(void *data) | |
1302 | { | |
1303 | struct request_queue *q = data; | |
1304 | unsigned long flags; | |
1305 | ||
1306 | spin_lock_irqsave(q->queue_lock, flags); | |
b4878f24 | 1307 | if (!as_queue_empty(q)) |
1da177e4 LT |
1308 | q->request_fn(q); |
1309 | spin_unlock_irqrestore(q->queue_lock, flags); | |
1310 | } | |
1311 | ||
1312 | static void as_put_request(request_queue_t *q, struct request *rq) | |
1313 | { | |
1314 | struct as_data *ad = q->elevator->elevator_data; | |
1315 | struct as_rq *arq = RQ_DATA(rq); | |
1316 | ||
1317 | if (!arq) { | |
1318 | WARN_ON(1); | |
1319 | return; | |
1320 | } | |
1321 | ||
b4878f24 JA |
1322 | if (unlikely(arq->state != AS_RQ_POSTSCHED && |
1323 | arq->state != AS_RQ_PRESCHED && | |
1324 | arq->state != AS_RQ_MERGED)) { | |
1da177e4 LT |
1325 | printk("arq->state %d\n", arq->state); |
1326 | WARN_ON(1); | |
1327 | } | |
1328 | ||
1329 | mempool_free(arq, ad->arq_pool); | |
1330 | rq->elevator_private = NULL; | |
1331 | } | |
1332 | ||
22e2c507 | 1333 | static int as_set_request(request_queue_t *q, struct request *rq, |
8267e268 | 1334 | struct bio *bio, gfp_t gfp_mask) |
1da177e4 LT |
1335 | { |
1336 | struct as_data *ad = q->elevator->elevator_data; | |
1337 | struct as_rq *arq = mempool_alloc(ad->arq_pool, gfp_mask); | |
1338 | ||
1339 | if (arq) { | |
1340 | memset(arq, 0, sizeof(*arq)); | |
1da177e4 LT |
1341 | arq->request = rq; |
1342 | arq->state = AS_RQ_PRESCHED; | |
1343 | arq->io_context = NULL; | |
1da177e4 LT |
1344 | rq->elevator_private = arq; |
1345 | return 0; | |
1346 | } | |
1347 | ||
1348 | return 1; | |
1349 | } | |
1350 | ||
22e2c507 | 1351 | static int as_may_queue(request_queue_t *q, int rw, struct bio *bio) |
1da177e4 LT |
1352 | { |
1353 | int ret = ELV_MQUEUE_MAY; | |
1354 | struct as_data *ad = q->elevator->elevator_data; | |
1355 | struct io_context *ioc; | |
1356 | if (ad->antic_status == ANTIC_WAIT_REQ || | |
1357 | ad->antic_status == ANTIC_WAIT_NEXT) { | |
1358 | ioc = as_get_io_context(); | |
1359 | if (ad->io_context == ioc) | |
1360 | ret = ELV_MQUEUE_MUST; | |
1361 | put_io_context(ioc); | |
1362 | } | |
1363 | ||
1364 | return ret; | |
1365 | } | |
1366 | ||
1367 | static void as_exit_queue(elevator_t *e) | |
1368 | { | |
1369 | struct as_data *ad = e->elevator_data; | |
1370 | ||
1371 | del_timer_sync(&ad->antic_timer); | |
1372 | kblockd_flush(); | |
1373 | ||
1374 | BUG_ON(!list_empty(&ad->fifo_list[REQ_SYNC])); | |
1375 | BUG_ON(!list_empty(&ad->fifo_list[REQ_ASYNC])); | |
1376 | ||
1377 | mempool_destroy(ad->arq_pool); | |
1378 | put_io_context(ad->io_context); | |
1da177e4 LT |
1379 | kfree(ad); |
1380 | } | |
1381 | ||
1382 | /* | |
1383 | * initialize elevator private data (as_data), and alloc a arq for | |
1384 | * each request on the free lists | |
1385 | */ | |
bc1c1169 | 1386 | static void *as_init_queue(request_queue_t *q, elevator_t *e) |
1da177e4 LT |
1387 | { |
1388 | struct as_data *ad; | |
1da177e4 LT |
1389 | |
1390 | if (!arq_pool) | |
bc1c1169 | 1391 | return NULL; |
1da177e4 | 1392 | |
1946089a | 1393 | ad = kmalloc_node(sizeof(*ad), GFP_KERNEL, q->node); |
1da177e4 | 1394 | if (!ad) |
bc1c1169 | 1395 | return NULL; |
1da177e4 LT |
1396 | memset(ad, 0, sizeof(*ad)); |
1397 | ||
1398 | ad->q = q; /* Identify what queue the data belongs to */ | |
1399 | ||
1946089a CL |
1400 | ad->arq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab, |
1401 | mempool_free_slab, arq_pool, q->node); | |
1da177e4 | 1402 | if (!ad->arq_pool) { |
1da177e4 | 1403 | kfree(ad); |
bc1c1169 | 1404 | return NULL; |
1da177e4 LT |
1405 | } |
1406 | ||
1407 | /* anticipatory scheduling helpers */ | |
1408 | ad->antic_timer.function = as_antic_timeout; | |
1409 | ad->antic_timer.data = (unsigned long)q; | |
1410 | init_timer(&ad->antic_timer); | |
1411 | INIT_WORK(&ad->antic_work, as_work_handler, q); | |
1412 | ||
1da177e4 LT |
1413 | INIT_LIST_HEAD(&ad->fifo_list[REQ_SYNC]); |
1414 | INIT_LIST_HEAD(&ad->fifo_list[REQ_ASYNC]); | |
1415 | ad->sort_list[REQ_SYNC] = RB_ROOT; | |
1416 | ad->sort_list[REQ_ASYNC] = RB_ROOT; | |
1da177e4 LT |
1417 | ad->fifo_expire[REQ_SYNC] = default_read_expire; |
1418 | ad->fifo_expire[REQ_ASYNC] = default_write_expire; | |
1419 | ad->antic_expire = default_antic_expire; | |
1420 | ad->batch_expire[REQ_SYNC] = default_read_batch_expire; | |
1421 | ad->batch_expire[REQ_ASYNC] = default_write_batch_expire; | |
1da177e4 LT |
1422 | |
1423 | ad->current_batch_expires = jiffies + ad->batch_expire[REQ_SYNC]; | |
1424 | ad->write_batch_count = ad->batch_expire[REQ_ASYNC] / 10; | |
1425 | if (ad->write_batch_count < 2) | |
1426 | ad->write_batch_count = 2; | |
1427 | ||
bc1c1169 | 1428 | return ad; |
1da177e4 LT |
1429 | } |
1430 | ||
1431 | /* | |
1432 | * sysfs parts below | |
1433 | */ | |
1da177e4 LT |
1434 | |
1435 | static ssize_t | |
1436 | as_var_show(unsigned int var, char *page) | |
1437 | { | |
1da177e4 LT |
1438 | return sprintf(page, "%d\n", var); |
1439 | } | |
1440 | ||
1441 | static ssize_t | |
1442 | as_var_store(unsigned long *var, const char *page, size_t count) | |
1443 | { | |
1da177e4 LT |
1444 | char *p = (char *) page; |
1445 | ||
c9b3ad67 | 1446 | *var = simple_strtoul(p, &p, 10); |
1da177e4 LT |
1447 | return count; |
1448 | } | |
1449 | ||
e572ec7e | 1450 | static ssize_t est_time_show(elevator_t *e, char *page) |
1da177e4 | 1451 | { |
3d1ab40f | 1452 | struct as_data *ad = e->elevator_data; |
1da177e4 LT |
1453 | int pos = 0; |
1454 | ||
f5b3db00 NP |
1455 | pos += sprintf(page+pos, "%lu %% exit probability\n", |
1456 | 100*ad->exit_prob/256); | |
1457 | pos += sprintf(page+pos, "%lu %% probability of exiting without a " | |
1458 | "cooperating process submitting IO\n", | |
1459 | 100*ad->exit_no_coop/256); | |
1da177e4 | 1460 | pos += sprintf(page+pos, "%lu ms new thinktime\n", ad->new_ttime_mean); |
f5b3db00 NP |
1461 | pos += sprintf(page+pos, "%llu sectors new seek distance\n", |
1462 | (unsigned long long)ad->new_seek_mean); | |
1da177e4 LT |
1463 | |
1464 | return pos; | |
1465 | } | |
1466 | ||
1467 | #define SHOW_FUNCTION(__FUNC, __VAR) \ | |
3d1ab40f | 1468 | static ssize_t __FUNC(elevator_t *e, char *page) \ |
1da177e4 | 1469 | { \ |
3d1ab40f | 1470 | struct as_data *ad = e->elevator_data; \ |
1da177e4 LT |
1471 | return as_var_show(jiffies_to_msecs((__VAR)), (page)); \ |
1472 | } | |
e572ec7e AV |
1473 | SHOW_FUNCTION(as_read_expire_show, ad->fifo_expire[REQ_SYNC]); |
1474 | SHOW_FUNCTION(as_write_expire_show, ad->fifo_expire[REQ_ASYNC]); | |
1475 | SHOW_FUNCTION(as_antic_expire_show, ad->antic_expire); | |
1476 | SHOW_FUNCTION(as_read_batch_expire_show, ad->batch_expire[REQ_SYNC]); | |
1477 | SHOW_FUNCTION(as_write_batch_expire_show, ad->batch_expire[REQ_ASYNC]); | |
1da177e4 LT |
1478 | #undef SHOW_FUNCTION |
1479 | ||
1480 | #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \ | |
3d1ab40f | 1481 | static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \ |
1da177e4 | 1482 | { \ |
3d1ab40f AV |
1483 | struct as_data *ad = e->elevator_data; \ |
1484 | int ret = as_var_store(__PTR, (page), count); \ | |
1da177e4 LT |
1485 | if (*(__PTR) < (MIN)) \ |
1486 | *(__PTR) = (MIN); \ | |
1487 | else if (*(__PTR) > (MAX)) \ | |
1488 | *(__PTR) = (MAX); \ | |
1489 | *(__PTR) = msecs_to_jiffies(*(__PTR)); \ | |
1490 | return ret; \ | |
1491 | } | |
e572ec7e AV |
1492 | STORE_FUNCTION(as_read_expire_store, &ad->fifo_expire[REQ_SYNC], 0, INT_MAX); |
1493 | STORE_FUNCTION(as_write_expire_store, &ad->fifo_expire[REQ_ASYNC], 0, INT_MAX); | |
1494 | STORE_FUNCTION(as_antic_expire_store, &ad->antic_expire, 0, INT_MAX); | |
1495 | STORE_FUNCTION(as_read_batch_expire_store, | |
1da177e4 | 1496 | &ad->batch_expire[REQ_SYNC], 0, INT_MAX); |
e572ec7e | 1497 | STORE_FUNCTION(as_write_batch_expire_store, |
1da177e4 LT |
1498 | &ad->batch_expire[REQ_ASYNC], 0, INT_MAX); |
1499 | #undef STORE_FUNCTION | |
1500 | ||
e572ec7e AV |
1501 | #define AS_ATTR(name) \ |
1502 | __ATTR(name, S_IRUGO|S_IWUSR, as_##name##_show, as_##name##_store) | |
1503 | ||
1504 | static struct elv_fs_entry as_attrs[] = { | |
1505 | __ATTR_RO(est_time), | |
1506 | AS_ATTR(read_expire), | |
1507 | AS_ATTR(write_expire), | |
1508 | AS_ATTR(antic_expire), | |
1509 | AS_ATTR(read_batch_expire), | |
1510 | AS_ATTR(write_batch_expire), | |
1511 | __ATTR_NULL | |
1da177e4 LT |
1512 | }; |
1513 | ||
1da177e4 LT |
1514 | static struct elevator_type iosched_as = { |
1515 | .ops = { | |
1516 | .elevator_merge_fn = as_merge, | |
1517 | .elevator_merged_fn = as_merged_request, | |
1518 | .elevator_merge_req_fn = as_merged_requests, | |
b4878f24 JA |
1519 | .elevator_dispatch_fn = as_dispatch_request, |
1520 | .elevator_add_req_fn = as_add_request, | |
1521 | .elevator_activate_req_fn = as_activate_request, | |
1da177e4 LT |
1522 | .elevator_deactivate_req_fn = as_deactivate_request, |
1523 | .elevator_queue_empty_fn = as_queue_empty, | |
1524 | .elevator_completed_req_fn = as_completed_request, | |
e37f346e JA |
1525 | .elevator_former_req_fn = elv_rb_former_request, |
1526 | .elevator_latter_req_fn = elv_rb_latter_request, | |
1da177e4 LT |
1527 | .elevator_set_req_fn = as_set_request, |
1528 | .elevator_put_req_fn = as_put_request, | |
1529 | .elevator_may_queue_fn = as_may_queue, | |
1530 | .elevator_init_fn = as_init_queue, | |
1531 | .elevator_exit_fn = as_exit_queue, | |
e17a9489 | 1532 | .trim = as_trim, |
1da177e4 LT |
1533 | }, |
1534 | ||
3d1ab40f | 1535 | .elevator_attrs = as_attrs, |
1da177e4 LT |
1536 | .elevator_name = "anticipatory", |
1537 | .elevator_owner = THIS_MODULE, | |
1538 | }; | |
1539 | ||
1540 | static int __init as_init(void) | |
1541 | { | |
1542 | int ret; | |
1543 | ||
1544 | arq_pool = kmem_cache_create("as_arq", sizeof(struct as_rq), | |
1545 | 0, 0, NULL, NULL); | |
1546 | if (!arq_pool) | |
1547 | return -ENOMEM; | |
1548 | ||
1549 | ret = elv_register(&iosched_as); | |
1550 | if (!ret) { | |
1551 | /* | |
1552 | * don't allow AS to get unregistered, since we would have | |
1553 | * to browse all tasks in the system and release their | |
1554 | * as_io_context first | |
1555 | */ | |
1556 | __module_get(THIS_MODULE); | |
1557 | return 0; | |
1558 | } | |
1559 | ||
1560 | kmem_cache_destroy(arq_pool); | |
1561 | return ret; | |
1562 | } | |
1563 | ||
1564 | static void __exit as_exit(void) | |
1565 | { | |
334e94de | 1566 | DECLARE_COMPLETION(all_gone); |
1da177e4 | 1567 | elv_unregister(&iosched_as); |
334e94de | 1568 | ioc_gone = &all_gone; |
fba82272 OH |
1569 | /* ioc_gone's update must be visible before reading ioc_count */ |
1570 | smp_wmb(); | |
334e94de | 1571 | if (atomic_read(&ioc_count)) |
fba82272 | 1572 | wait_for_completion(ioc_gone); |
334e94de | 1573 | synchronize_rcu(); |
83521d3e | 1574 | kmem_cache_destroy(arq_pool); |
1da177e4 LT |
1575 | } |
1576 | ||
1577 | module_init(as_init); | |
1578 | module_exit(as_exit); | |
1579 | ||
1580 | MODULE_AUTHOR("Nick Piggin"); | |
1581 | MODULE_LICENSE("GPL"); | |
1582 | MODULE_DESCRIPTION("anticipatory IO scheduler"); |