Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * linux/drivers/block/as-iosched.c |
| 3 | * |
| 4 | * Anticipatory & deadline i/o scheduler. |
| 5 | * |
| 6 | * Copyright (C) 2002 Jens Axboe <axboe@suse.de> |
| 7 | * Nick Piggin <piggin@cyberone.com.au> |
| 8 | * |
| 9 | */ |
| 10 | #include <linux/kernel.h> |
| 11 | #include <linux/fs.h> |
| 12 | #include <linux/blkdev.h> |
| 13 | #include <linux/elevator.h> |
| 14 | #include <linux/bio.h> |
| 15 | #include <linux/config.h> |
| 16 | #include <linux/module.h> |
| 17 | #include <linux/slab.h> |
| 18 | #include <linux/init.h> |
| 19 | #include <linux/compiler.h> |
| 20 | #include <linux/hash.h> |
| 21 | #include <linux/rbtree.h> |
| 22 | #include <linux/interrupt.h> |
| 23 | |
| 24 | #define REQ_SYNC 1 |
| 25 | #define REQ_ASYNC 0 |
| 26 | |
| 27 | /* |
| 28 | * See Documentation/block/as-iosched.txt |
| 29 | */ |
| 30 | |
| 31 | /* |
| 32 | * max time before a read is submitted. |
| 33 | */ |
| 34 | #define default_read_expire (HZ / 8) |
| 35 | |
| 36 | /* |
| 37 | * ditto for writes, these limits are not hard, even |
| 38 | * if the disk is capable of satisfying them. |
| 39 | */ |
| 40 | #define default_write_expire (HZ / 4) |
| 41 | |
| 42 | /* |
| 43 | * read_batch_expire describes how long we will allow a stream of reads to |
| 44 | * persist before looking to see whether it is time to switch over to writes. |
| 45 | */ |
| 46 | #define default_read_batch_expire (HZ / 2) |
| 47 | |
| 48 | /* |
| 49 | * write_batch_expire describes how long we want a stream of writes to run for. |
| 50 | * This is not a hard limit, but a target we set for the auto-tuning thingy. |
| 51 | * See, the problem is: we can send a lot of writes to disk cache / TCQ in |
| 52 | * a short amount of time... |
| 53 | */ |
| 54 | #define default_write_batch_expire (HZ / 8) |
| 55 | |
| 56 | /* |
| 57 | * max time we may wait to anticipate a read (default around 6ms) |
| 58 | */ |
| 59 | #define default_antic_expire ((HZ / 150) ? HZ / 150 : 1) |
| 60 | |
| 61 | /* |
| 62 | * Keep track of up to 20ms thinktimes. We can go as big as we like here, |
| 63 | * however huge values tend to interfere and not decay fast enough. A program |
| 64 | * might be in a non-io phase of operation. Waiting on user input for example, |
| 65 | * or doing a lengthy computation. A small penalty can be justified there, and |
| 66 | * will still catch out those processes that constantly have large thinktimes. |
| 67 | */ |
| 68 | #define MAX_THINKTIME (HZ/50UL) |
| 69 | |
| 70 | /* Bits in as_io_context.state */ |
| 71 | enum as_io_states { |
| 72 | AS_TASK_RUNNING=0, /* Process has not exitted */ |
| 73 | AS_TASK_IOSTARTED, /* Process has started some IO */ |
| 74 | AS_TASK_IORUNNING, /* Process has completed some IO */ |
| 75 | }; |
| 76 | |
| 77 | enum anticipation_status { |
| 78 | ANTIC_OFF=0, /* Not anticipating (normal operation) */ |
| 79 | ANTIC_WAIT_REQ, /* The last read has not yet completed */ |
| 80 | ANTIC_WAIT_NEXT, /* Currently anticipating a request vs |
| 81 | last read (which has completed) */ |
| 82 | ANTIC_FINISHED, /* Anticipating but have found a candidate |
| 83 | * or timed out */ |
| 84 | }; |
| 85 | |
| 86 | struct as_data { |
| 87 | /* |
| 88 | * run time data |
| 89 | */ |
| 90 | |
| 91 | struct request_queue *q; /* the "owner" queue */ |
| 92 | |
| 93 | /* |
| 94 | * requests (as_rq s) are present on both sort_list and fifo_list |
| 95 | */ |
| 96 | struct rb_root sort_list[2]; |
| 97 | struct list_head fifo_list[2]; |
| 98 | |
| 99 | struct as_rq *next_arq[2]; /* next in sort order */ |
| 100 | sector_t last_sector[2]; /* last REQ_SYNC & REQ_ASYNC sectors */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 101 | struct list_head *hash; /* request hash */ |
| 102 | |
| 103 | unsigned long exit_prob; /* probability a task will exit while |
| 104 | being waited on */ |
| 105 | unsigned long new_ttime_total; /* mean thinktime on new proc */ |
| 106 | unsigned long new_ttime_mean; |
| 107 | u64 new_seek_total; /* mean seek on new proc */ |
| 108 | sector_t new_seek_mean; |
| 109 | |
| 110 | unsigned long current_batch_expires; |
| 111 | unsigned long last_check_fifo[2]; |
| 112 | int changed_batch; /* 1: waiting for old batch to end */ |
| 113 | int new_batch; /* 1: waiting on first read complete */ |
| 114 | int batch_data_dir; /* current batch REQ_SYNC / REQ_ASYNC */ |
| 115 | int write_batch_count; /* max # of reqs in a write batch */ |
| 116 | int current_write_count; /* how many requests left this batch */ |
| 117 | int write_batch_idled; /* has the write batch gone idle? */ |
| 118 | mempool_t *arq_pool; |
| 119 | |
| 120 | enum anticipation_status antic_status; |
| 121 | unsigned long antic_start; /* jiffies: when it started */ |
| 122 | struct timer_list antic_timer; /* anticipatory scheduling timer */ |
| 123 | struct work_struct antic_work; /* Deferred unplugging */ |
| 124 | struct io_context *io_context; /* Identify the expected process */ |
| 125 | int ioc_finished; /* IO associated with io_context is finished */ |
| 126 | int nr_dispatched; |
| 127 | |
| 128 | /* |
| 129 | * settings that change how the i/o scheduler behaves |
| 130 | */ |
| 131 | unsigned long fifo_expire[2]; |
| 132 | unsigned long batch_expire[2]; |
| 133 | unsigned long antic_expire; |
| 134 | }; |
| 135 | |
| 136 | #define list_entry_fifo(ptr) list_entry((ptr), struct as_rq, fifo) |
| 137 | |
| 138 | /* |
| 139 | * per-request data. |
| 140 | */ |
| 141 | enum arq_state { |
| 142 | AS_RQ_NEW=0, /* New - not referenced and not on any lists */ |
| 143 | AS_RQ_QUEUED, /* In the request queue. It belongs to the |
| 144 | scheduler */ |
| 145 | AS_RQ_DISPATCHED, /* On the dispatch list. It belongs to the |
| 146 | driver now */ |
| 147 | AS_RQ_PRESCHED, /* Debug poisoning for requests being used */ |
| 148 | AS_RQ_REMOVED, |
| 149 | AS_RQ_MERGED, |
| 150 | AS_RQ_POSTSCHED, /* when they shouldn't be */ |
| 151 | }; |
| 152 | |
| 153 | struct as_rq { |
| 154 | /* |
| 155 | * rbtree index, key is the starting offset |
| 156 | */ |
| 157 | struct rb_node rb_node; |
| 158 | sector_t rb_key; |
| 159 | |
| 160 | struct request *request; |
| 161 | |
| 162 | struct io_context *io_context; /* The submitting task */ |
| 163 | |
| 164 | /* |
| 165 | * request hash, key is the ending offset (for back merge lookup) |
| 166 | */ |
| 167 | struct list_head hash; |
| 168 | unsigned int on_hash; |
| 169 | |
| 170 | /* |
| 171 | * expire fifo |
| 172 | */ |
| 173 | struct list_head fifo; |
| 174 | unsigned long expires; |
| 175 | |
| 176 | unsigned int is_sync; |
| 177 | enum arq_state state; |
| 178 | }; |
| 179 | |
| 180 | #define RQ_DATA(rq) ((struct as_rq *) (rq)->elevator_private) |
| 181 | |
| 182 | static kmem_cache_t *arq_pool; |
| 183 | |
| 184 | /* |
| 185 | * IO Context helper functions |
| 186 | */ |
| 187 | |
| 188 | /* Called to deallocate the as_io_context */ |
| 189 | static void free_as_io_context(struct as_io_context *aic) |
| 190 | { |
| 191 | kfree(aic); |
| 192 | } |
| 193 | |
| 194 | /* Called when the task exits */ |
| 195 | static void exit_as_io_context(struct as_io_context *aic) |
| 196 | { |
| 197 | WARN_ON(!test_bit(AS_TASK_RUNNING, &aic->state)); |
| 198 | clear_bit(AS_TASK_RUNNING, &aic->state); |
| 199 | } |
| 200 | |
| 201 | static struct as_io_context *alloc_as_io_context(void) |
| 202 | { |
| 203 | struct as_io_context *ret; |
| 204 | |
| 205 | ret = kmalloc(sizeof(*ret), GFP_ATOMIC); |
| 206 | if (ret) { |
| 207 | ret->dtor = free_as_io_context; |
| 208 | ret->exit = exit_as_io_context; |
| 209 | ret->state = 1 << AS_TASK_RUNNING; |
| 210 | atomic_set(&ret->nr_queued, 0); |
| 211 | atomic_set(&ret->nr_dispatched, 0); |
| 212 | spin_lock_init(&ret->lock); |
| 213 | ret->ttime_total = 0; |
| 214 | ret->ttime_samples = 0; |
| 215 | ret->ttime_mean = 0; |
| 216 | ret->seek_total = 0; |
| 217 | ret->seek_samples = 0; |
| 218 | ret->seek_mean = 0; |
| 219 | } |
| 220 | |
| 221 | return ret; |
| 222 | } |
| 223 | |
| 224 | /* |
| 225 | * If the current task has no AS IO context then create one and initialise it. |
| 226 | * Then take a ref on the task's io context and return it. |
| 227 | */ |
| 228 | static struct io_context *as_get_io_context(void) |
| 229 | { |
| 230 | struct io_context *ioc = get_io_context(GFP_ATOMIC); |
| 231 | if (ioc && !ioc->aic) { |
| 232 | ioc->aic = alloc_as_io_context(); |
| 233 | if (!ioc->aic) { |
| 234 | put_io_context(ioc); |
| 235 | ioc = NULL; |
| 236 | } |
| 237 | } |
| 238 | return ioc; |
| 239 | } |
| 240 | |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 241 | static void as_put_io_context(struct as_rq *arq) |
| 242 | { |
| 243 | struct as_io_context *aic; |
| 244 | |
| 245 | if (unlikely(!arq->io_context)) |
| 246 | return; |
| 247 | |
| 248 | aic = arq->io_context->aic; |
| 249 | |
| 250 | if (arq->is_sync == REQ_SYNC && aic) { |
| 251 | spin_lock(&aic->lock); |
| 252 | set_bit(AS_TASK_IORUNNING, &aic->state); |
| 253 | aic->last_end_request = jiffies; |
| 254 | spin_unlock(&aic->lock); |
| 255 | } |
| 256 | |
| 257 | put_io_context(arq->io_context); |
| 258 | } |
| 259 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 260 | /* |
| 261 | * the back merge hash support functions |
| 262 | */ |
| 263 | static const int as_hash_shift = 6; |
| 264 | #define AS_HASH_BLOCK(sec) ((sec) >> 3) |
| 265 | #define AS_HASH_FN(sec) (hash_long(AS_HASH_BLOCK((sec)), as_hash_shift)) |
| 266 | #define AS_HASH_ENTRIES (1 << as_hash_shift) |
| 267 | #define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors) |
| 268 | #define list_entry_hash(ptr) list_entry((ptr), struct as_rq, hash) |
| 269 | |
| 270 | static inline void __as_del_arq_hash(struct as_rq *arq) |
| 271 | { |
| 272 | arq->on_hash = 0; |
| 273 | list_del_init(&arq->hash); |
| 274 | } |
| 275 | |
| 276 | static inline void as_del_arq_hash(struct as_rq *arq) |
| 277 | { |
| 278 | if (arq->on_hash) |
| 279 | __as_del_arq_hash(arq); |
| 280 | } |
| 281 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 282 | static void as_add_arq_hash(struct as_data *ad, struct as_rq *arq) |
| 283 | { |
| 284 | struct request *rq = arq->request; |
| 285 | |
| 286 | BUG_ON(arq->on_hash); |
| 287 | |
| 288 | arq->on_hash = 1; |
| 289 | list_add(&arq->hash, &ad->hash[AS_HASH_FN(rq_hash_key(rq))]); |
| 290 | } |
| 291 | |
| 292 | /* |
| 293 | * move hot entry to front of chain |
| 294 | */ |
| 295 | static inline void as_hot_arq_hash(struct as_data *ad, struct as_rq *arq) |
| 296 | { |
| 297 | struct request *rq = arq->request; |
| 298 | struct list_head *head = &ad->hash[AS_HASH_FN(rq_hash_key(rq))]; |
| 299 | |
| 300 | if (!arq->on_hash) { |
| 301 | WARN_ON(1); |
| 302 | return; |
| 303 | } |
| 304 | |
| 305 | if (arq->hash.prev != head) { |
| 306 | list_del(&arq->hash); |
| 307 | list_add(&arq->hash, head); |
| 308 | } |
| 309 | } |
| 310 | |
| 311 | static struct request *as_find_arq_hash(struct as_data *ad, sector_t offset) |
| 312 | { |
| 313 | struct list_head *hash_list = &ad->hash[AS_HASH_FN(offset)]; |
| 314 | struct list_head *entry, *next = hash_list->next; |
| 315 | |
| 316 | while ((entry = next) != hash_list) { |
| 317 | struct as_rq *arq = list_entry_hash(entry); |
| 318 | struct request *__rq = arq->request; |
| 319 | |
| 320 | next = entry->next; |
| 321 | |
| 322 | BUG_ON(!arq->on_hash); |
| 323 | |
| 324 | if (!rq_mergeable(__rq)) { |
Tejun Heo | 98b1147 | 2005-10-20 16:46:54 +0200 | [diff] [blame] | 325 | as_del_arq_hash(arq); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 326 | continue; |
| 327 | } |
| 328 | |
| 329 | if (rq_hash_key(__rq) == offset) |
| 330 | return __rq; |
| 331 | } |
| 332 | |
| 333 | return NULL; |
| 334 | } |
| 335 | |
| 336 | /* |
| 337 | * rb tree support functions |
| 338 | */ |
| 339 | #define RB_NONE (2) |
| 340 | #define RB_EMPTY(root) ((root)->rb_node == NULL) |
| 341 | #define ON_RB(node) ((node)->rb_color != RB_NONE) |
| 342 | #define RB_CLEAR(node) ((node)->rb_color = RB_NONE) |
| 343 | #define rb_entry_arq(node) rb_entry((node), struct as_rq, rb_node) |
| 344 | #define ARQ_RB_ROOT(ad, arq) (&(ad)->sort_list[(arq)->is_sync]) |
| 345 | #define rq_rb_key(rq) (rq)->sector |
| 346 | |
| 347 | /* |
| 348 | * as_find_first_arq finds the first (lowest sector numbered) request |
| 349 | * for the specified data_dir. Used to sweep back to the start of the disk |
| 350 | * (1-way elevator) after we process the last (highest sector) request. |
| 351 | */ |
| 352 | static struct as_rq *as_find_first_arq(struct as_data *ad, int data_dir) |
| 353 | { |
| 354 | struct rb_node *n = ad->sort_list[data_dir].rb_node; |
| 355 | |
| 356 | if (n == NULL) |
| 357 | return NULL; |
| 358 | |
| 359 | for (;;) { |
| 360 | if (n->rb_left == NULL) |
| 361 | return rb_entry_arq(n); |
| 362 | |
| 363 | n = n->rb_left; |
| 364 | } |
| 365 | } |
| 366 | |
| 367 | /* |
| 368 | * Add the request to the rb tree if it is unique. If there is an alias (an |
| 369 | * existing request against the same sector), which can happen when using |
| 370 | * direct IO, then return the alias. |
| 371 | */ |
| 372 | static struct as_rq *as_add_arq_rb(struct as_data *ad, struct as_rq *arq) |
| 373 | { |
| 374 | struct rb_node **p = &ARQ_RB_ROOT(ad, arq)->rb_node; |
| 375 | struct rb_node *parent = NULL; |
| 376 | struct as_rq *__arq; |
| 377 | struct request *rq = arq->request; |
| 378 | |
| 379 | arq->rb_key = rq_rb_key(rq); |
| 380 | |
| 381 | while (*p) { |
| 382 | parent = *p; |
| 383 | __arq = rb_entry_arq(parent); |
| 384 | |
| 385 | if (arq->rb_key < __arq->rb_key) |
| 386 | p = &(*p)->rb_left; |
| 387 | else if (arq->rb_key > __arq->rb_key) |
| 388 | p = &(*p)->rb_right; |
| 389 | else |
| 390 | return __arq; |
| 391 | } |
| 392 | |
| 393 | rb_link_node(&arq->rb_node, parent, p); |
| 394 | rb_insert_color(&arq->rb_node, ARQ_RB_ROOT(ad, arq)); |
| 395 | |
| 396 | return NULL; |
| 397 | } |
| 398 | |
| 399 | static inline void as_del_arq_rb(struct as_data *ad, struct as_rq *arq) |
| 400 | { |
| 401 | if (!ON_RB(&arq->rb_node)) { |
| 402 | WARN_ON(1); |
| 403 | return; |
| 404 | } |
| 405 | |
| 406 | rb_erase(&arq->rb_node, ARQ_RB_ROOT(ad, arq)); |
| 407 | RB_CLEAR(&arq->rb_node); |
| 408 | } |
| 409 | |
| 410 | static struct request * |
| 411 | as_find_arq_rb(struct as_data *ad, sector_t sector, int data_dir) |
| 412 | { |
| 413 | struct rb_node *n = ad->sort_list[data_dir].rb_node; |
| 414 | struct as_rq *arq; |
| 415 | |
| 416 | while (n) { |
| 417 | arq = rb_entry_arq(n); |
| 418 | |
| 419 | if (sector < arq->rb_key) |
| 420 | n = n->rb_left; |
| 421 | else if (sector > arq->rb_key) |
| 422 | n = n->rb_right; |
| 423 | else |
| 424 | return arq->request; |
| 425 | } |
| 426 | |
| 427 | return NULL; |
| 428 | } |
| 429 | |
| 430 | /* |
| 431 | * IO Scheduler proper |
| 432 | */ |
| 433 | |
| 434 | #define MAXBACK (1024 * 1024) /* |
| 435 | * Maximum distance the disk will go backward |
| 436 | * for a request. |
| 437 | */ |
| 438 | |
| 439 | #define BACK_PENALTY 2 |
| 440 | |
| 441 | /* |
| 442 | * as_choose_req selects the preferred one of two requests of the same data_dir |
| 443 | * ignoring time - eg. timeouts, which is the job of as_dispatch_request |
| 444 | */ |
| 445 | static struct as_rq * |
| 446 | as_choose_req(struct as_data *ad, struct as_rq *arq1, struct as_rq *arq2) |
| 447 | { |
| 448 | int data_dir; |
| 449 | sector_t last, s1, s2, d1, d2; |
| 450 | int r1_wrap=0, r2_wrap=0; /* requests are behind the disk head */ |
| 451 | const sector_t maxback = MAXBACK; |
| 452 | |
| 453 | if (arq1 == NULL || arq1 == arq2) |
| 454 | return arq2; |
| 455 | if (arq2 == NULL) |
| 456 | return arq1; |
| 457 | |
| 458 | data_dir = arq1->is_sync; |
| 459 | |
| 460 | last = ad->last_sector[data_dir]; |
| 461 | s1 = arq1->request->sector; |
| 462 | s2 = arq2->request->sector; |
| 463 | |
| 464 | BUG_ON(data_dir != arq2->is_sync); |
| 465 | |
| 466 | /* |
| 467 | * Strict one way elevator _except_ in the case where we allow |
| 468 | * short backward seeks which are biased as twice the cost of a |
| 469 | * similar forward seek. |
| 470 | */ |
| 471 | if (s1 >= last) |
| 472 | d1 = s1 - last; |
| 473 | else if (s1+maxback >= last) |
| 474 | d1 = (last - s1)*BACK_PENALTY; |
| 475 | else { |
| 476 | r1_wrap = 1; |
| 477 | d1 = 0; /* shut up, gcc */ |
| 478 | } |
| 479 | |
| 480 | if (s2 >= last) |
| 481 | d2 = s2 - last; |
| 482 | else if (s2+maxback >= last) |
| 483 | d2 = (last - s2)*BACK_PENALTY; |
| 484 | else { |
| 485 | r2_wrap = 1; |
| 486 | d2 = 0; |
| 487 | } |
| 488 | |
| 489 | /* Found required data */ |
| 490 | if (!r1_wrap && r2_wrap) |
| 491 | return arq1; |
| 492 | else if (!r2_wrap && r1_wrap) |
| 493 | return arq2; |
| 494 | else if (r1_wrap && r2_wrap) { |
| 495 | /* both behind the head */ |
| 496 | if (s1 <= s2) |
| 497 | return arq1; |
| 498 | else |
| 499 | return arq2; |
| 500 | } |
| 501 | |
| 502 | /* Both requests in front of the head */ |
| 503 | if (d1 < d2) |
| 504 | return arq1; |
| 505 | else if (d2 < d1) |
| 506 | return arq2; |
| 507 | else { |
| 508 | if (s1 >= s2) |
| 509 | return arq1; |
| 510 | else |
| 511 | return arq2; |
| 512 | } |
| 513 | } |
| 514 | |
| 515 | /* |
| 516 | * as_find_next_arq finds the next request after @prev in elevator order. |
| 517 | * this with as_choose_req form the basis for how the scheduler chooses |
| 518 | * what request to process next. Anticipation works on top of this. |
| 519 | */ |
| 520 | static struct as_rq *as_find_next_arq(struct as_data *ad, struct as_rq *last) |
| 521 | { |
| 522 | const int data_dir = last->is_sync; |
| 523 | struct as_rq *ret; |
| 524 | struct rb_node *rbnext = rb_next(&last->rb_node); |
| 525 | struct rb_node *rbprev = rb_prev(&last->rb_node); |
| 526 | struct as_rq *arq_next, *arq_prev; |
| 527 | |
| 528 | BUG_ON(!ON_RB(&last->rb_node)); |
| 529 | |
| 530 | if (rbprev) |
| 531 | arq_prev = rb_entry_arq(rbprev); |
| 532 | else |
| 533 | arq_prev = NULL; |
| 534 | |
| 535 | if (rbnext) |
| 536 | arq_next = rb_entry_arq(rbnext); |
| 537 | else { |
| 538 | arq_next = as_find_first_arq(ad, data_dir); |
| 539 | if (arq_next == last) |
| 540 | arq_next = NULL; |
| 541 | } |
| 542 | |
| 543 | ret = as_choose_req(ad, arq_next, arq_prev); |
| 544 | |
| 545 | return ret; |
| 546 | } |
| 547 | |
| 548 | /* |
| 549 | * anticipatory scheduling functions follow |
| 550 | */ |
| 551 | |
| 552 | /* |
| 553 | * as_antic_expired tells us when we have anticipated too long. |
| 554 | * The funny "absolute difference" math on the elapsed time is to handle |
| 555 | * jiffy wraps, and disks which have been idle for 0x80000000 jiffies. |
| 556 | */ |
| 557 | static int as_antic_expired(struct as_data *ad) |
| 558 | { |
| 559 | long delta_jif; |
| 560 | |
| 561 | delta_jif = jiffies - ad->antic_start; |
| 562 | if (unlikely(delta_jif < 0)) |
| 563 | delta_jif = -delta_jif; |
| 564 | if (delta_jif < ad->antic_expire) |
| 565 | return 0; |
| 566 | |
| 567 | return 1; |
| 568 | } |
| 569 | |
| 570 | /* |
| 571 | * as_antic_waitnext starts anticipating that a nice request will soon be |
| 572 | * submitted. See also as_antic_waitreq |
| 573 | */ |
| 574 | static void as_antic_waitnext(struct as_data *ad) |
| 575 | { |
| 576 | unsigned long timeout; |
| 577 | |
| 578 | BUG_ON(ad->antic_status != ANTIC_OFF |
| 579 | && ad->antic_status != ANTIC_WAIT_REQ); |
| 580 | |
| 581 | timeout = ad->antic_start + ad->antic_expire; |
| 582 | |
| 583 | mod_timer(&ad->antic_timer, timeout); |
| 584 | |
| 585 | ad->antic_status = ANTIC_WAIT_NEXT; |
| 586 | } |
| 587 | |
| 588 | /* |
| 589 | * as_antic_waitreq starts anticipating. We don't start timing the anticipation |
| 590 | * until the request that we're anticipating on has finished. This means we |
| 591 | * are timing from when the candidate process wakes up hopefully. |
| 592 | */ |
| 593 | static void as_antic_waitreq(struct as_data *ad) |
| 594 | { |
| 595 | BUG_ON(ad->antic_status == ANTIC_FINISHED); |
| 596 | if (ad->antic_status == ANTIC_OFF) { |
| 597 | if (!ad->io_context || ad->ioc_finished) |
| 598 | as_antic_waitnext(ad); |
| 599 | else |
| 600 | ad->antic_status = ANTIC_WAIT_REQ; |
| 601 | } |
| 602 | } |
| 603 | |
| 604 | /* |
| 605 | * This is called directly by the functions in this file to stop anticipation. |
| 606 | * We kill the timer and schedule a call to the request_fn asap. |
| 607 | */ |
| 608 | static void as_antic_stop(struct as_data *ad) |
| 609 | { |
| 610 | int status = ad->antic_status; |
| 611 | |
| 612 | if (status == ANTIC_WAIT_REQ || status == ANTIC_WAIT_NEXT) { |
| 613 | if (status == ANTIC_WAIT_NEXT) |
| 614 | del_timer(&ad->antic_timer); |
| 615 | ad->antic_status = ANTIC_FINISHED; |
| 616 | /* see as_work_handler */ |
| 617 | kblockd_schedule_work(&ad->antic_work); |
| 618 | } |
| 619 | } |
| 620 | |
| 621 | /* |
| 622 | * as_antic_timeout is the timer function set by as_antic_waitnext. |
| 623 | */ |
| 624 | static void as_antic_timeout(unsigned long data) |
| 625 | { |
| 626 | struct request_queue *q = (struct request_queue *)data; |
| 627 | struct as_data *ad = q->elevator->elevator_data; |
| 628 | unsigned long flags; |
| 629 | |
| 630 | spin_lock_irqsave(q->queue_lock, flags); |
| 631 | if (ad->antic_status == ANTIC_WAIT_REQ |
| 632 | || ad->antic_status == ANTIC_WAIT_NEXT) { |
| 633 | struct as_io_context *aic = ad->io_context->aic; |
| 634 | |
| 635 | ad->antic_status = ANTIC_FINISHED; |
| 636 | kblockd_schedule_work(&ad->antic_work); |
| 637 | |
| 638 | if (aic->ttime_samples == 0) { |
| 639 | /* process anticipated on has exitted or timed out*/ |
| 640 | ad->exit_prob = (7*ad->exit_prob + 256)/8; |
| 641 | } |
| 642 | } |
| 643 | spin_unlock_irqrestore(q->queue_lock, flags); |
| 644 | } |
| 645 | |
| 646 | /* |
| 647 | * as_close_req decides if one request is considered "close" to the |
| 648 | * previous one issued. |
| 649 | */ |
| 650 | static int as_close_req(struct as_data *ad, struct as_rq *arq) |
| 651 | { |
| 652 | unsigned long delay; /* milliseconds */ |
| 653 | sector_t last = ad->last_sector[ad->batch_data_dir]; |
| 654 | sector_t next = arq->request->sector; |
| 655 | sector_t delta; /* acceptable close offset (in sectors) */ |
| 656 | |
| 657 | if (ad->antic_status == ANTIC_OFF || !ad->ioc_finished) |
| 658 | delay = 0; |
| 659 | else |
| 660 | delay = ((jiffies - ad->antic_start) * 1000) / HZ; |
| 661 | |
| 662 | if (delay <= 1) |
| 663 | delta = 64; |
| 664 | else if (delay <= 20 && delay <= ad->antic_expire) |
| 665 | delta = 64 << (delay-1); |
| 666 | else |
| 667 | return 1; |
| 668 | |
| 669 | return (last - (delta>>1) <= next) && (next <= last + delta); |
| 670 | } |
| 671 | |
| 672 | /* |
| 673 | * as_can_break_anticipation returns true if we have been anticipating this |
| 674 | * request. |
| 675 | * |
| 676 | * It also returns true if the process against which we are anticipating |
| 677 | * submits a write - that's presumably an fsync, O_SYNC write, etc. We want to |
| 678 | * dispatch it ASAP, because we know that application will not be submitting |
| 679 | * any new reads. |
| 680 | * |
| 681 | * If the task which has submitted the request has exitted, break anticipation. |
| 682 | * |
| 683 | * If this task has queued some other IO, do not enter enticipation. |
| 684 | */ |
| 685 | static int as_can_break_anticipation(struct as_data *ad, struct as_rq *arq) |
| 686 | { |
| 687 | struct io_context *ioc; |
| 688 | struct as_io_context *aic; |
| 689 | sector_t s; |
| 690 | |
| 691 | ioc = ad->io_context; |
| 692 | BUG_ON(!ioc); |
| 693 | |
| 694 | if (arq && ioc == arq->io_context) { |
| 695 | /* request from same process */ |
| 696 | return 1; |
| 697 | } |
| 698 | |
| 699 | if (ad->ioc_finished && as_antic_expired(ad)) { |
| 700 | /* |
| 701 | * In this situation status should really be FINISHED, |
| 702 | * however the timer hasn't had the chance to run yet. |
| 703 | */ |
| 704 | return 1; |
| 705 | } |
| 706 | |
| 707 | aic = ioc->aic; |
| 708 | if (!aic) |
| 709 | return 0; |
| 710 | |
| 711 | if (!test_bit(AS_TASK_RUNNING, &aic->state)) { |
| 712 | /* process anticipated on has exitted */ |
| 713 | if (aic->ttime_samples == 0) |
| 714 | ad->exit_prob = (7*ad->exit_prob + 256)/8; |
| 715 | return 1; |
| 716 | } |
| 717 | |
| 718 | if (atomic_read(&aic->nr_queued) > 0) { |
| 719 | /* process has more requests queued */ |
| 720 | return 1; |
| 721 | } |
| 722 | |
| 723 | if (atomic_read(&aic->nr_dispatched) > 0) { |
| 724 | /* process has more requests dispatched */ |
| 725 | return 1; |
| 726 | } |
| 727 | |
| 728 | if (arq && arq->is_sync == REQ_SYNC && as_close_req(ad, arq)) { |
| 729 | /* |
| 730 | * Found a close request that is not one of ours. |
| 731 | * |
| 732 | * This makes close requests from another process reset |
| 733 | * our thinktime delay. Is generally useful when there are |
| 734 | * two or more cooperating processes working in the same |
| 735 | * area. |
| 736 | */ |
| 737 | spin_lock(&aic->lock); |
| 738 | aic->last_end_request = jiffies; |
| 739 | spin_unlock(&aic->lock); |
| 740 | return 1; |
| 741 | } |
| 742 | |
| 743 | |
| 744 | if (aic->ttime_samples == 0) { |
| 745 | if (ad->new_ttime_mean > ad->antic_expire) |
| 746 | return 1; |
| 747 | if (ad->exit_prob > 128) |
| 748 | return 1; |
| 749 | } else if (aic->ttime_mean > ad->antic_expire) { |
| 750 | /* the process thinks too much between requests */ |
| 751 | return 1; |
| 752 | } |
| 753 | |
| 754 | if (!arq) |
| 755 | return 0; |
| 756 | |
| 757 | if (ad->last_sector[REQ_SYNC] < arq->request->sector) |
| 758 | s = arq->request->sector - ad->last_sector[REQ_SYNC]; |
| 759 | else |
| 760 | s = ad->last_sector[REQ_SYNC] - arq->request->sector; |
| 761 | |
| 762 | if (aic->seek_samples == 0) { |
| 763 | /* |
| 764 | * Process has just started IO. Use past statistics to |
| 765 | * guage success possibility |
| 766 | */ |
| 767 | if (ad->new_seek_mean > s) { |
| 768 | /* this request is better than what we're expecting */ |
| 769 | return 1; |
| 770 | } |
| 771 | |
| 772 | } else { |
| 773 | if (aic->seek_mean > s) { |
| 774 | /* this request is better than what we're expecting */ |
| 775 | return 1; |
| 776 | } |
| 777 | } |
| 778 | |
| 779 | return 0; |
| 780 | } |
| 781 | |
| 782 | /* |
| 783 | * as_can_anticipate indicates weather we should either run arq |
| 784 | * or keep anticipating a better request. |
| 785 | */ |
| 786 | static int as_can_anticipate(struct as_data *ad, struct as_rq *arq) |
| 787 | { |
| 788 | if (!ad->io_context) |
| 789 | /* |
| 790 | * Last request submitted was a write |
| 791 | */ |
| 792 | return 0; |
| 793 | |
| 794 | if (ad->antic_status == ANTIC_FINISHED) |
| 795 | /* |
| 796 | * Don't restart if we have just finished. Run the next request |
| 797 | */ |
| 798 | return 0; |
| 799 | |
| 800 | if (as_can_break_anticipation(ad, arq)) |
| 801 | /* |
| 802 | * This request is a good candidate. Don't keep anticipating, |
| 803 | * run it. |
| 804 | */ |
| 805 | return 0; |
| 806 | |
| 807 | /* |
| 808 | * OK from here, we haven't finished, and don't have a decent request! |
| 809 | * Status is either ANTIC_OFF so start waiting, |
| 810 | * ANTIC_WAIT_REQ so continue waiting for request to finish |
| 811 | * or ANTIC_WAIT_NEXT so continue waiting for an acceptable request. |
| 812 | * |
| 813 | */ |
| 814 | |
| 815 | return 1; |
| 816 | } |
| 817 | |
| 818 | static void as_update_thinktime(struct as_data *ad, struct as_io_context *aic, unsigned long ttime) |
| 819 | { |
| 820 | /* fixed point: 1.0 == 1<<8 */ |
| 821 | if (aic->ttime_samples == 0) { |
| 822 | ad->new_ttime_total = (7*ad->new_ttime_total + 256*ttime) / 8; |
| 823 | ad->new_ttime_mean = ad->new_ttime_total / 256; |
| 824 | |
| 825 | ad->exit_prob = (7*ad->exit_prob)/8; |
| 826 | } |
| 827 | aic->ttime_samples = (7*aic->ttime_samples + 256) / 8; |
| 828 | aic->ttime_total = (7*aic->ttime_total + 256*ttime) / 8; |
| 829 | aic->ttime_mean = (aic->ttime_total + 128) / aic->ttime_samples; |
| 830 | } |
| 831 | |
| 832 | static void as_update_seekdist(struct as_data *ad, struct as_io_context *aic, sector_t sdist) |
| 833 | { |
| 834 | u64 total; |
| 835 | |
| 836 | if (aic->seek_samples == 0) { |
| 837 | ad->new_seek_total = (7*ad->new_seek_total + 256*(u64)sdist)/8; |
| 838 | ad->new_seek_mean = ad->new_seek_total / 256; |
| 839 | } |
| 840 | |
| 841 | /* |
| 842 | * Don't allow the seek distance to get too large from the |
| 843 | * odd fragment, pagein, etc |
| 844 | */ |
| 845 | if (aic->seek_samples <= 60) /* second&third seek */ |
| 846 | sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*1024); |
| 847 | else |
| 848 | sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*64); |
| 849 | |
| 850 | aic->seek_samples = (7*aic->seek_samples + 256) / 8; |
| 851 | aic->seek_total = (7*aic->seek_total + (u64)256*sdist) / 8; |
| 852 | total = aic->seek_total + (aic->seek_samples/2); |
| 853 | do_div(total, aic->seek_samples); |
| 854 | aic->seek_mean = (sector_t)total; |
| 855 | } |
| 856 | |
| 857 | /* |
| 858 | * as_update_iohist keeps a decaying histogram of IO thinktimes, and |
| 859 | * updates @aic->ttime_mean based on that. It is called when a new |
| 860 | * request is queued. |
| 861 | */ |
| 862 | static void as_update_iohist(struct as_data *ad, struct as_io_context *aic, struct request *rq) |
| 863 | { |
| 864 | struct as_rq *arq = RQ_DATA(rq); |
| 865 | int data_dir = arq->is_sync; |
| 866 | unsigned long thinktime; |
| 867 | sector_t seek_dist; |
| 868 | |
| 869 | if (aic == NULL) |
| 870 | return; |
| 871 | |
| 872 | if (data_dir == REQ_SYNC) { |
| 873 | unsigned long in_flight = atomic_read(&aic->nr_queued) |
| 874 | + atomic_read(&aic->nr_dispatched); |
| 875 | spin_lock(&aic->lock); |
| 876 | if (test_bit(AS_TASK_IORUNNING, &aic->state) || |
| 877 | test_bit(AS_TASK_IOSTARTED, &aic->state)) { |
| 878 | /* Calculate read -> read thinktime */ |
| 879 | if (test_bit(AS_TASK_IORUNNING, &aic->state) |
| 880 | && in_flight == 0) { |
| 881 | thinktime = jiffies - aic->last_end_request; |
| 882 | thinktime = min(thinktime, MAX_THINKTIME-1); |
| 883 | } else |
| 884 | thinktime = 0; |
| 885 | as_update_thinktime(ad, aic, thinktime); |
| 886 | |
| 887 | /* Calculate read -> read seek distance */ |
| 888 | if (aic->last_request_pos < rq->sector) |
| 889 | seek_dist = rq->sector - aic->last_request_pos; |
| 890 | else |
| 891 | seek_dist = aic->last_request_pos - rq->sector; |
| 892 | as_update_seekdist(ad, aic, seek_dist); |
| 893 | } |
| 894 | aic->last_request_pos = rq->sector + rq->nr_sectors; |
| 895 | set_bit(AS_TASK_IOSTARTED, &aic->state); |
| 896 | spin_unlock(&aic->lock); |
| 897 | } |
| 898 | } |
| 899 | |
| 900 | /* |
| 901 | * as_update_arq must be called whenever a request (arq) is added to |
| 902 | * the sort_list. This function keeps caches up to date, and checks if the |
| 903 | * request might be one we are "anticipating" |
| 904 | */ |
| 905 | static void as_update_arq(struct as_data *ad, struct as_rq *arq) |
| 906 | { |
| 907 | const int data_dir = arq->is_sync; |
| 908 | |
| 909 | /* keep the next_arq cache up to date */ |
| 910 | ad->next_arq[data_dir] = as_choose_req(ad, arq, ad->next_arq[data_dir]); |
| 911 | |
| 912 | /* |
| 913 | * have we been anticipating this request? |
| 914 | * or does it come from the same process as the one we are anticipating |
| 915 | * for? |
| 916 | */ |
| 917 | if (ad->antic_status == ANTIC_WAIT_REQ |
| 918 | || ad->antic_status == ANTIC_WAIT_NEXT) { |
| 919 | if (as_can_break_anticipation(ad, arq)) |
| 920 | as_antic_stop(ad); |
| 921 | } |
| 922 | } |
| 923 | |
| 924 | /* |
| 925 | * Gathers timings and resizes the write batch automatically |
| 926 | */ |
| 927 | static void update_write_batch(struct as_data *ad) |
| 928 | { |
| 929 | unsigned long batch = ad->batch_expire[REQ_ASYNC]; |
| 930 | long write_time; |
| 931 | |
| 932 | write_time = (jiffies - ad->current_batch_expires) + batch; |
| 933 | if (write_time < 0) |
| 934 | write_time = 0; |
| 935 | |
| 936 | if (write_time > batch && !ad->write_batch_idled) { |
| 937 | if (write_time > batch * 3) |
| 938 | ad->write_batch_count /= 2; |
| 939 | else |
| 940 | ad->write_batch_count--; |
| 941 | } else if (write_time < batch && ad->current_write_count == 0) { |
| 942 | if (batch > write_time * 3) |
| 943 | ad->write_batch_count *= 2; |
| 944 | else |
| 945 | ad->write_batch_count++; |
| 946 | } |
| 947 | |
| 948 | if (ad->write_batch_count < 1) |
| 949 | ad->write_batch_count = 1; |
| 950 | } |
| 951 | |
| 952 | /* |
| 953 | * as_completed_request is to be called when a request has completed and |
| 954 | * returned something to the requesting process, be it an error or data. |
| 955 | */ |
| 956 | static void as_completed_request(request_queue_t *q, struct request *rq) |
| 957 | { |
| 958 | struct as_data *ad = q->elevator->elevator_data; |
| 959 | struct as_rq *arq = RQ_DATA(rq); |
| 960 | |
| 961 | WARN_ON(!list_empty(&rq->queuelist)); |
| 962 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 963 | if (arq->state != AS_RQ_REMOVED) { |
| 964 | printk("arq->state %d\n", arq->state); |
| 965 | WARN_ON(1); |
| 966 | goto out; |
| 967 | } |
| 968 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 969 | if (ad->changed_batch && ad->nr_dispatched == 1) { |
| 970 | kblockd_schedule_work(&ad->antic_work); |
| 971 | ad->changed_batch = 0; |
| 972 | |
| 973 | if (ad->batch_data_dir == REQ_SYNC) |
| 974 | ad->new_batch = 1; |
| 975 | } |
| 976 | WARN_ON(ad->nr_dispatched == 0); |
| 977 | ad->nr_dispatched--; |
| 978 | |
| 979 | /* |
| 980 | * Start counting the batch from when a request of that direction is |
| 981 | * actually serviced. This should help devices with big TCQ windows |
| 982 | * and writeback caches |
| 983 | */ |
| 984 | if (ad->new_batch && ad->batch_data_dir == arq->is_sync) { |
| 985 | update_write_batch(ad); |
| 986 | ad->current_batch_expires = jiffies + |
| 987 | ad->batch_expire[REQ_SYNC]; |
| 988 | ad->new_batch = 0; |
| 989 | } |
| 990 | |
| 991 | if (ad->io_context == arq->io_context && ad->io_context) { |
| 992 | ad->antic_start = jiffies; |
| 993 | ad->ioc_finished = 1; |
| 994 | if (ad->antic_status == ANTIC_WAIT_REQ) { |
| 995 | /* |
| 996 | * We were waiting on this request, now anticipate |
| 997 | * the next one |
| 998 | */ |
| 999 | as_antic_waitnext(ad); |
| 1000 | } |
| 1001 | } |
| 1002 | |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 1003 | as_put_io_context(arq); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1004 | out: |
| 1005 | arq->state = AS_RQ_POSTSCHED; |
| 1006 | } |
| 1007 | |
| 1008 | /* |
| 1009 | * as_remove_queued_request removes a request from the pre dispatch queue |
| 1010 | * without updating refcounts. It is expected the caller will drop the |
| 1011 | * reference unless it replaces the request at somepart of the elevator |
| 1012 | * (ie. the dispatch queue) |
| 1013 | */ |
| 1014 | static void as_remove_queued_request(request_queue_t *q, struct request *rq) |
| 1015 | { |
| 1016 | struct as_rq *arq = RQ_DATA(rq); |
| 1017 | const int data_dir = arq->is_sync; |
| 1018 | struct as_data *ad = q->elevator->elevator_data; |
| 1019 | |
| 1020 | WARN_ON(arq->state != AS_RQ_QUEUED); |
| 1021 | |
| 1022 | if (arq->io_context && arq->io_context->aic) { |
| 1023 | BUG_ON(!atomic_read(&arq->io_context->aic->nr_queued)); |
| 1024 | atomic_dec(&arq->io_context->aic->nr_queued); |
| 1025 | } |
| 1026 | |
| 1027 | /* |
| 1028 | * Update the "next_arq" cache if we are about to remove its |
| 1029 | * entry |
| 1030 | */ |
| 1031 | if (ad->next_arq[data_dir] == arq) |
| 1032 | ad->next_arq[data_dir] = as_find_next_arq(ad, arq); |
| 1033 | |
| 1034 | list_del_init(&arq->fifo); |
Tejun Heo | 98b1147 | 2005-10-20 16:46:54 +0200 | [diff] [blame] | 1035 | as_del_arq_hash(arq); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1036 | as_del_arq_rb(ad, arq); |
| 1037 | } |
| 1038 | |
| 1039 | /* |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1040 | * as_fifo_expired returns 0 if there are no expired reads on the fifo, |
| 1041 | * 1 otherwise. It is ratelimited so that we only perform the check once per |
| 1042 | * `fifo_expire' interval. Otherwise a large number of expired requests |
| 1043 | * would create a hopeless seekstorm. |
| 1044 | * |
| 1045 | * See as_antic_expired comment. |
| 1046 | */ |
| 1047 | static int as_fifo_expired(struct as_data *ad, int adir) |
| 1048 | { |
| 1049 | struct as_rq *arq; |
| 1050 | long delta_jif; |
| 1051 | |
| 1052 | delta_jif = jiffies - ad->last_check_fifo[adir]; |
| 1053 | if (unlikely(delta_jif < 0)) |
| 1054 | delta_jif = -delta_jif; |
| 1055 | if (delta_jif < ad->fifo_expire[adir]) |
| 1056 | return 0; |
| 1057 | |
| 1058 | ad->last_check_fifo[adir] = jiffies; |
| 1059 | |
| 1060 | if (list_empty(&ad->fifo_list[adir])) |
| 1061 | return 0; |
| 1062 | |
| 1063 | arq = list_entry_fifo(ad->fifo_list[adir].next); |
| 1064 | |
| 1065 | return time_after(jiffies, arq->expires); |
| 1066 | } |
| 1067 | |
| 1068 | /* |
| 1069 | * as_batch_expired returns true if the current batch has expired. A batch |
| 1070 | * is a set of reads or a set of writes. |
| 1071 | */ |
| 1072 | static inline int as_batch_expired(struct as_data *ad) |
| 1073 | { |
| 1074 | if (ad->changed_batch || ad->new_batch) |
| 1075 | return 0; |
| 1076 | |
| 1077 | if (ad->batch_data_dir == REQ_SYNC) |
| 1078 | /* TODO! add a check so a complete fifo gets written? */ |
| 1079 | return time_after(jiffies, ad->current_batch_expires); |
| 1080 | |
| 1081 | return time_after(jiffies, ad->current_batch_expires) |
| 1082 | || ad->current_write_count == 0; |
| 1083 | } |
| 1084 | |
| 1085 | /* |
| 1086 | * move an entry to dispatch queue |
| 1087 | */ |
| 1088 | static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq) |
| 1089 | { |
| 1090 | struct request *rq = arq->request; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1091 | const int data_dir = arq->is_sync; |
| 1092 | |
| 1093 | BUG_ON(!ON_RB(&arq->rb_node)); |
| 1094 | |
| 1095 | as_antic_stop(ad); |
| 1096 | ad->antic_status = ANTIC_OFF; |
| 1097 | |
| 1098 | /* |
| 1099 | * This has to be set in order to be correctly updated by |
| 1100 | * as_find_next_arq |
| 1101 | */ |
| 1102 | ad->last_sector[data_dir] = rq->sector + rq->nr_sectors; |
| 1103 | |
| 1104 | if (data_dir == REQ_SYNC) { |
| 1105 | /* In case we have to anticipate after this */ |
| 1106 | copy_io_context(&ad->io_context, &arq->io_context); |
| 1107 | } else { |
| 1108 | if (ad->io_context) { |
| 1109 | put_io_context(ad->io_context); |
| 1110 | ad->io_context = NULL; |
| 1111 | } |
| 1112 | |
| 1113 | if (ad->current_write_count != 0) |
| 1114 | ad->current_write_count--; |
| 1115 | } |
| 1116 | ad->ioc_finished = 0; |
| 1117 | |
| 1118 | ad->next_arq[data_dir] = as_find_next_arq(ad, arq); |
| 1119 | |
| 1120 | /* |
| 1121 | * take it off the sort and fifo list, add to dispatch queue |
| 1122 | */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1123 | while (!list_empty(&rq->queuelist)) { |
| 1124 | struct request *__rq = list_entry_rq(rq->queuelist.next); |
| 1125 | struct as_rq *__arq = RQ_DATA(__rq); |
| 1126 | |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 1127 | list_del(&__rq->queuelist); |
| 1128 | |
| 1129 | elv_dispatch_add_tail(ad->q, __rq); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1130 | |
| 1131 | if (__arq->io_context && __arq->io_context->aic) |
| 1132 | atomic_inc(&__arq->io_context->aic->nr_dispatched); |
| 1133 | |
| 1134 | WARN_ON(__arq->state != AS_RQ_QUEUED); |
| 1135 | __arq->state = AS_RQ_DISPATCHED; |
| 1136 | |
| 1137 | ad->nr_dispatched++; |
| 1138 | } |
| 1139 | |
| 1140 | as_remove_queued_request(ad->q, rq); |
| 1141 | WARN_ON(arq->state != AS_RQ_QUEUED); |
| 1142 | |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 1143 | elv_dispatch_sort(ad->q, rq); |
| 1144 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1145 | arq->state = AS_RQ_DISPATCHED; |
| 1146 | if (arq->io_context && arq->io_context->aic) |
| 1147 | atomic_inc(&arq->io_context->aic->nr_dispatched); |
| 1148 | ad->nr_dispatched++; |
| 1149 | } |
| 1150 | |
| 1151 | /* |
| 1152 | * as_dispatch_request selects the best request according to |
| 1153 | * read/write expire, batch expire, etc, and moves it to the dispatch |
| 1154 | * queue. Returns 1 if a request was found, 0 otherwise. |
| 1155 | */ |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 1156 | static int as_dispatch_request(request_queue_t *q, int force) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1157 | { |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 1158 | struct as_data *ad = q->elevator->elevator_data; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1159 | struct as_rq *arq; |
| 1160 | const int reads = !list_empty(&ad->fifo_list[REQ_SYNC]); |
| 1161 | const int writes = !list_empty(&ad->fifo_list[REQ_ASYNC]); |
| 1162 | |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 1163 | if (unlikely(force)) { |
| 1164 | /* |
| 1165 | * Forced dispatch, accounting is useless. Reset |
| 1166 | * accounting states and dump fifo_lists. Note that |
| 1167 | * batch_data_dir is reset to REQ_SYNC to avoid |
| 1168 | * screwing write batch accounting as write batch |
| 1169 | * accounting occurs on W->R transition. |
| 1170 | */ |
| 1171 | int dispatched = 0; |
| 1172 | |
| 1173 | ad->batch_data_dir = REQ_SYNC; |
| 1174 | ad->changed_batch = 0; |
| 1175 | ad->new_batch = 0; |
| 1176 | |
| 1177 | while (ad->next_arq[REQ_SYNC]) { |
| 1178 | as_move_to_dispatch(ad, ad->next_arq[REQ_SYNC]); |
| 1179 | dispatched++; |
| 1180 | } |
| 1181 | ad->last_check_fifo[REQ_SYNC] = jiffies; |
| 1182 | |
| 1183 | while (ad->next_arq[REQ_ASYNC]) { |
| 1184 | as_move_to_dispatch(ad, ad->next_arq[REQ_ASYNC]); |
| 1185 | dispatched++; |
| 1186 | } |
| 1187 | ad->last_check_fifo[REQ_ASYNC] = jiffies; |
| 1188 | |
| 1189 | return dispatched; |
| 1190 | } |
| 1191 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1192 | /* Signal that the write batch was uncontended, so we can't time it */ |
| 1193 | if (ad->batch_data_dir == REQ_ASYNC && !reads) { |
| 1194 | if (ad->current_write_count == 0 || !writes) |
| 1195 | ad->write_batch_idled = 1; |
| 1196 | } |
| 1197 | |
| 1198 | if (!(reads || writes) |
| 1199 | || ad->antic_status == ANTIC_WAIT_REQ |
| 1200 | || ad->antic_status == ANTIC_WAIT_NEXT |
| 1201 | || ad->changed_batch) |
| 1202 | return 0; |
| 1203 | |
| 1204 | if (!(reads && writes && as_batch_expired(ad)) ) { |
| 1205 | /* |
| 1206 | * batch is still running or no reads or no writes |
| 1207 | */ |
| 1208 | arq = ad->next_arq[ad->batch_data_dir]; |
| 1209 | |
| 1210 | if (ad->batch_data_dir == REQ_SYNC && ad->antic_expire) { |
| 1211 | if (as_fifo_expired(ad, REQ_SYNC)) |
| 1212 | goto fifo_expired; |
| 1213 | |
| 1214 | if (as_can_anticipate(ad, arq)) { |
| 1215 | as_antic_waitreq(ad); |
| 1216 | return 0; |
| 1217 | } |
| 1218 | } |
| 1219 | |
| 1220 | if (arq) { |
| 1221 | /* we have a "next request" */ |
| 1222 | if (reads && !writes) |
| 1223 | ad->current_batch_expires = |
| 1224 | jiffies + ad->batch_expire[REQ_SYNC]; |
| 1225 | goto dispatch_request; |
| 1226 | } |
| 1227 | } |
| 1228 | |
| 1229 | /* |
| 1230 | * at this point we are not running a batch. select the appropriate |
| 1231 | * data direction (read / write) |
| 1232 | */ |
| 1233 | |
| 1234 | if (reads) { |
| 1235 | BUG_ON(RB_EMPTY(&ad->sort_list[REQ_SYNC])); |
| 1236 | |
| 1237 | if (writes && ad->batch_data_dir == REQ_SYNC) |
| 1238 | /* |
| 1239 | * Last batch was a read, switch to writes |
| 1240 | */ |
| 1241 | goto dispatch_writes; |
| 1242 | |
| 1243 | if (ad->batch_data_dir == REQ_ASYNC) { |
| 1244 | WARN_ON(ad->new_batch); |
| 1245 | ad->changed_batch = 1; |
| 1246 | } |
| 1247 | ad->batch_data_dir = REQ_SYNC; |
| 1248 | arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next); |
| 1249 | ad->last_check_fifo[ad->batch_data_dir] = jiffies; |
| 1250 | goto dispatch_request; |
| 1251 | } |
| 1252 | |
| 1253 | /* |
| 1254 | * the last batch was a read |
| 1255 | */ |
| 1256 | |
| 1257 | if (writes) { |
| 1258 | dispatch_writes: |
| 1259 | BUG_ON(RB_EMPTY(&ad->sort_list[REQ_ASYNC])); |
| 1260 | |
| 1261 | if (ad->batch_data_dir == REQ_SYNC) { |
| 1262 | ad->changed_batch = 1; |
| 1263 | |
| 1264 | /* |
| 1265 | * new_batch might be 1 when the queue runs out of |
| 1266 | * reads. A subsequent submission of a write might |
| 1267 | * cause a change of batch before the read is finished. |
| 1268 | */ |
| 1269 | ad->new_batch = 0; |
| 1270 | } |
| 1271 | ad->batch_data_dir = REQ_ASYNC; |
| 1272 | ad->current_write_count = ad->write_batch_count; |
| 1273 | ad->write_batch_idled = 0; |
| 1274 | arq = ad->next_arq[ad->batch_data_dir]; |
| 1275 | goto dispatch_request; |
| 1276 | } |
| 1277 | |
| 1278 | BUG(); |
| 1279 | return 0; |
| 1280 | |
| 1281 | dispatch_request: |
| 1282 | /* |
| 1283 | * If a request has expired, service it. |
| 1284 | */ |
| 1285 | |
| 1286 | if (as_fifo_expired(ad, ad->batch_data_dir)) { |
| 1287 | fifo_expired: |
| 1288 | arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next); |
| 1289 | BUG_ON(arq == NULL); |
| 1290 | } |
| 1291 | |
| 1292 | if (ad->changed_batch) { |
| 1293 | WARN_ON(ad->new_batch); |
| 1294 | |
| 1295 | if (ad->nr_dispatched) |
| 1296 | return 0; |
| 1297 | |
| 1298 | if (ad->batch_data_dir == REQ_ASYNC) |
| 1299 | ad->current_batch_expires = jiffies + |
| 1300 | ad->batch_expire[REQ_ASYNC]; |
| 1301 | else |
| 1302 | ad->new_batch = 1; |
| 1303 | |
| 1304 | ad->changed_batch = 0; |
| 1305 | } |
| 1306 | |
| 1307 | /* |
| 1308 | * arq is the selected appropriate request. |
| 1309 | */ |
| 1310 | as_move_to_dispatch(ad, arq); |
| 1311 | |
| 1312 | return 1; |
| 1313 | } |
| 1314 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1315 | /* |
| 1316 | * Add arq to a list behind alias |
| 1317 | */ |
| 1318 | static inline void |
| 1319 | as_add_aliased_request(struct as_data *ad, struct as_rq *arq, struct as_rq *alias) |
| 1320 | { |
| 1321 | struct request *req = arq->request; |
| 1322 | struct list_head *insert = alias->request->queuelist.prev; |
| 1323 | |
| 1324 | /* |
| 1325 | * Transfer list of aliases |
| 1326 | */ |
| 1327 | while (!list_empty(&req->queuelist)) { |
| 1328 | struct request *__rq = list_entry_rq(req->queuelist.next); |
| 1329 | struct as_rq *__arq = RQ_DATA(__rq); |
| 1330 | |
| 1331 | list_move_tail(&__rq->queuelist, &alias->request->queuelist); |
| 1332 | |
| 1333 | WARN_ON(__arq->state != AS_RQ_QUEUED); |
| 1334 | } |
| 1335 | |
| 1336 | /* |
| 1337 | * Another request with the same start sector on the rbtree. |
| 1338 | * Link this request to that sector. They are untangled in |
| 1339 | * as_move_to_dispatch |
| 1340 | */ |
| 1341 | list_add(&arq->request->queuelist, insert); |
| 1342 | |
| 1343 | /* |
| 1344 | * Don't want to have to handle merges. |
| 1345 | */ |
Tejun Heo | 98b1147 | 2005-10-20 16:46:54 +0200 | [diff] [blame] | 1346 | as_del_arq_hash(arq); |
Tejun Heo | 47e627c | 2005-10-29 18:18:42 +0900 | [diff] [blame^] | 1347 | arq->request->flags |= REQ_NOMERGE; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1348 | } |
| 1349 | |
| 1350 | /* |
| 1351 | * add arq to rbtree and fifo |
| 1352 | */ |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 1353 | static void as_add_request(request_queue_t *q, struct request *rq) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1354 | { |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 1355 | struct as_data *ad = q->elevator->elevator_data; |
| 1356 | struct as_rq *arq = RQ_DATA(rq); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1357 | struct as_rq *alias; |
| 1358 | int data_dir; |
| 1359 | |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 1360 | if (arq->state != AS_RQ_PRESCHED) { |
| 1361 | printk("arq->state: %d\n", arq->state); |
| 1362 | WARN_ON(1); |
| 1363 | } |
| 1364 | arq->state = AS_RQ_NEW; |
| 1365 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1366 | if (rq_data_dir(arq->request) == READ |
| 1367 | || current->flags&PF_SYNCWRITE) |
| 1368 | arq->is_sync = 1; |
| 1369 | else |
| 1370 | arq->is_sync = 0; |
| 1371 | data_dir = arq->is_sync; |
| 1372 | |
| 1373 | arq->io_context = as_get_io_context(); |
| 1374 | |
| 1375 | if (arq->io_context) { |
| 1376 | as_update_iohist(ad, arq->io_context->aic, arq->request); |
| 1377 | atomic_inc(&arq->io_context->aic->nr_queued); |
| 1378 | } |
| 1379 | |
| 1380 | alias = as_add_arq_rb(ad, arq); |
| 1381 | if (!alias) { |
| 1382 | /* |
| 1383 | * set expire time (only used for reads) and add to fifo list |
| 1384 | */ |
| 1385 | arq->expires = jiffies + ad->fifo_expire[data_dir]; |
| 1386 | list_add_tail(&arq->fifo, &ad->fifo_list[data_dir]); |
| 1387 | |
Tejun Heo | 98b1147 | 2005-10-20 16:46:54 +0200 | [diff] [blame] | 1388 | if (rq_mergeable(arq->request)) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1389 | as_add_arq_hash(ad, arq); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1390 | as_update_arq(ad, arq); /* keep state machine up to date */ |
| 1391 | |
| 1392 | } else { |
| 1393 | as_add_aliased_request(ad, arq, alias); |
| 1394 | |
| 1395 | /* |
| 1396 | * have we been anticipating this request? |
| 1397 | * or does it come from the same process as the one we are |
| 1398 | * anticipating for? |
| 1399 | */ |
| 1400 | if (ad->antic_status == ANTIC_WAIT_REQ |
| 1401 | || ad->antic_status == ANTIC_WAIT_NEXT) { |
| 1402 | if (as_can_break_anticipation(ad, arq)) |
| 1403 | as_antic_stop(ad); |
| 1404 | } |
| 1405 | } |
| 1406 | |
| 1407 | arq->state = AS_RQ_QUEUED; |
| 1408 | } |
| 1409 | |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 1410 | static void as_activate_request(request_queue_t *q, struct request *rq) |
| 1411 | { |
| 1412 | struct as_rq *arq = RQ_DATA(rq); |
| 1413 | |
| 1414 | WARN_ON(arq->state != AS_RQ_DISPATCHED); |
| 1415 | arq->state = AS_RQ_REMOVED; |
| 1416 | if (arq->io_context && arq->io_context->aic) |
| 1417 | atomic_dec(&arq->io_context->aic->nr_dispatched); |
| 1418 | } |
| 1419 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1420 | static void as_deactivate_request(request_queue_t *q, struct request *rq) |
| 1421 | { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1422 | struct as_rq *arq = RQ_DATA(rq); |
| 1423 | |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 1424 | WARN_ON(arq->state != AS_RQ_REMOVED); |
| 1425 | arq->state = AS_RQ_DISPATCHED; |
| 1426 | if (arq->io_context && arq->io_context->aic) |
| 1427 | atomic_inc(&arq->io_context->aic->nr_dispatched); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1428 | } |
| 1429 | |
| 1430 | /* |
| 1431 | * as_queue_empty tells us if there are requests left in the device. It may |
| 1432 | * not be the case that a driver can get the next request even if the queue |
| 1433 | * is not empty - it is used in the block layer to check for plugging and |
| 1434 | * merging opportunities |
| 1435 | */ |
| 1436 | static int as_queue_empty(request_queue_t *q) |
| 1437 | { |
| 1438 | struct as_data *ad = q->elevator->elevator_data; |
| 1439 | |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 1440 | return list_empty(&ad->fifo_list[REQ_ASYNC]) |
| 1441 | && list_empty(&ad->fifo_list[REQ_SYNC]); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1442 | } |
| 1443 | |
| 1444 | static struct request * |
| 1445 | as_former_request(request_queue_t *q, struct request *rq) |
| 1446 | { |
| 1447 | struct as_rq *arq = RQ_DATA(rq); |
| 1448 | struct rb_node *rbprev = rb_prev(&arq->rb_node); |
| 1449 | struct request *ret = NULL; |
| 1450 | |
| 1451 | if (rbprev) |
| 1452 | ret = rb_entry_arq(rbprev)->request; |
| 1453 | |
| 1454 | return ret; |
| 1455 | } |
| 1456 | |
| 1457 | static struct request * |
| 1458 | as_latter_request(request_queue_t *q, struct request *rq) |
| 1459 | { |
| 1460 | struct as_rq *arq = RQ_DATA(rq); |
| 1461 | struct rb_node *rbnext = rb_next(&arq->rb_node); |
| 1462 | struct request *ret = NULL; |
| 1463 | |
| 1464 | if (rbnext) |
| 1465 | ret = rb_entry_arq(rbnext)->request; |
| 1466 | |
| 1467 | return ret; |
| 1468 | } |
| 1469 | |
| 1470 | static int |
| 1471 | as_merge(request_queue_t *q, struct request **req, struct bio *bio) |
| 1472 | { |
| 1473 | struct as_data *ad = q->elevator->elevator_data; |
| 1474 | sector_t rb_key = bio->bi_sector + bio_sectors(bio); |
| 1475 | struct request *__rq; |
| 1476 | int ret; |
| 1477 | |
| 1478 | /* |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1479 | * see if the merge hash can satisfy a back merge |
| 1480 | */ |
| 1481 | __rq = as_find_arq_hash(ad, bio->bi_sector); |
| 1482 | if (__rq) { |
| 1483 | BUG_ON(__rq->sector + __rq->nr_sectors != bio->bi_sector); |
| 1484 | |
| 1485 | if (elv_rq_merge_ok(__rq, bio)) { |
| 1486 | ret = ELEVATOR_BACK_MERGE; |
| 1487 | goto out; |
| 1488 | } |
| 1489 | } |
| 1490 | |
| 1491 | /* |
| 1492 | * check for front merge |
| 1493 | */ |
| 1494 | __rq = as_find_arq_rb(ad, rb_key, bio_data_dir(bio)); |
| 1495 | if (__rq) { |
| 1496 | BUG_ON(rb_key != rq_rb_key(__rq)); |
| 1497 | |
| 1498 | if (elv_rq_merge_ok(__rq, bio)) { |
| 1499 | ret = ELEVATOR_FRONT_MERGE; |
| 1500 | goto out; |
| 1501 | } |
| 1502 | } |
| 1503 | |
| 1504 | return ELEVATOR_NO_MERGE; |
| 1505 | out: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1506 | if (ret) { |
| 1507 | if (rq_mergeable(__rq)) |
| 1508 | as_hot_arq_hash(ad, RQ_DATA(__rq)); |
| 1509 | } |
| 1510 | *req = __rq; |
| 1511 | return ret; |
| 1512 | } |
| 1513 | |
| 1514 | static void as_merged_request(request_queue_t *q, struct request *req) |
| 1515 | { |
| 1516 | struct as_data *ad = q->elevator->elevator_data; |
| 1517 | struct as_rq *arq = RQ_DATA(req); |
| 1518 | |
| 1519 | /* |
| 1520 | * hash always needs to be repositioned, key is end sector |
| 1521 | */ |
| 1522 | as_del_arq_hash(arq); |
| 1523 | as_add_arq_hash(ad, arq); |
| 1524 | |
| 1525 | /* |
| 1526 | * if the merge was a front merge, we need to reposition request |
| 1527 | */ |
| 1528 | if (rq_rb_key(req) != arq->rb_key) { |
| 1529 | struct as_rq *alias, *next_arq = NULL; |
| 1530 | |
| 1531 | if (ad->next_arq[arq->is_sync] == arq) |
| 1532 | next_arq = as_find_next_arq(ad, arq); |
| 1533 | |
| 1534 | /* |
| 1535 | * Note! We should really be moving any old aliased requests |
| 1536 | * off this request and try to insert them into the rbtree. We |
| 1537 | * currently don't bother. Ditto the next function. |
| 1538 | */ |
| 1539 | as_del_arq_rb(ad, arq); |
| 1540 | if ((alias = as_add_arq_rb(ad, arq)) ) { |
| 1541 | list_del_init(&arq->fifo); |
| 1542 | as_add_aliased_request(ad, arq, alias); |
| 1543 | if (next_arq) |
| 1544 | ad->next_arq[arq->is_sync] = next_arq; |
| 1545 | } |
| 1546 | /* |
| 1547 | * Note! At this stage of this and the next function, our next |
| 1548 | * request may not be optimal - eg the request may have "grown" |
| 1549 | * behind the disk head. We currently don't bother adjusting. |
| 1550 | */ |
| 1551 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1552 | } |
| 1553 | |
| 1554 | static void |
| 1555 | as_merged_requests(request_queue_t *q, struct request *req, |
| 1556 | struct request *next) |
| 1557 | { |
| 1558 | struct as_data *ad = q->elevator->elevator_data; |
| 1559 | struct as_rq *arq = RQ_DATA(req); |
| 1560 | struct as_rq *anext = RQ_DATA(next); |
| 1561 | |
| 1562 | BUG_ON(!arq); |
| 1563 | BUG_ON(!anext); |
| 1564 | |
| 1565 | /* |
| 1566 | * reposition arq (this is the merged request) in hash, and in rbtree |
| 1567 | * in case of a front merge |
| 1568 | */ |
| 1569 | as_del_arq_hash(arq); |
| 1570 | as_add_arq_hash(ad, arq); |
| 1571 | |
| 1572 | if (rq_rb_key(req) != arq->rb_key) { |
| 1573 | struct as_rq *alias, *next_arq = NULL; |
| 1574 | |
| 1575 | if (ad->next_arq[arq->is_sync] == arq) |
| 1576 | next_arq = as_find_next_arq(ad, arq); |
| 1577 | |
| 1578 | as_del_arq_rb(ad, arq); |
| 1579 | if ((alias = as_add_arq_rb(ad, arq)) ) { |
| 1580 | list_del_init(&arq->fifo); |
| 1581 | as_add_aliased_request(ad, arq, alias); |
| 1582 | if (next_arq) |
| 1583 | ad->next_arq[arq->is_sync] = next_arq; |
| 1584 | } |
| 1585 | } |
| 1586 | |
| 1587 | /* |
| 1588 | * if anext expires before arq, assign its expire time to arq |
| 1589 | * and move into anext position (anext will be deleted) in fifo |
| 1590 | */ |
| 1591 | if (!list_empty(&arq->fifo) && !list_empty(&anext->fifo)) { |
| 1592 | if (time_before(anext->expires, arq->expires)) { |
| 1593 | list_move(&arq->fifo, &anext->fifo); |
| 1594 | arq->expires = anext->expires; |
| 1595 | /* |
| 1596 | * Don't copy here but swap, because when anext is |
| 1597 | * removed below, it must contain the unused context |
| 1598 | */ |
| 1599 | swap_io_context(&arq->io_context, &anext->io_context); |
| 1600 | } |
| 1601 | } |
| 1602 | |
| 1603 | /* |
| 1604 | * Transfer list of aliases |
| 1605 | */ |
| 1606 | while (!list_empty(&next->queuelist)) { |
| 1607 | struct request *__rq = list_entry_rq(next->queuelist.next); |
| 1608 | struct as_rq *__arq = RQ_DATA(__rq); |
| 1609 | |
| 1610 | list_move_tail(&__rq->queuelist, &req->queuelist); |
| 1611 | |
| 1612 | WARN_ON(__arq->state != AS_RQ_QUEUED); |
| 1613 | } |
| 1614 | |
| 1615 | /* |
| 1616 | * kill knowledge of next, this one is a goner |
| 1617 | */ |
| 1618 | as_remove_queued_request(q, next); |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 1619 | as_put_io_context(anext); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1620 | |
| 1621 | anext->state = AS_RQ_MERGED; |
| 1622 | } |
| 1623 | |
| 1624 | /* |
| 1625 | * This is executed in a "deferred" process context, by kblockd. It calls the |
| 1626 | * driver's request_fn so the driver can submit that request. |
| 1627 | * |
| 1628 | * IMPORTANT! This guy will reenter the elevator, so set up all queue global |
| 1629 | * state before calling, and don't rely on any state over calls. |
| 1630 | * |
| 1631 | * FIXME! dispatch queue is not a queue at all! |
| 1632 | */ |
| 1633 | static void as_work_handler(void *data) |
| 1634 | { |
| 1635 | struct request_queue *q = data; |
| 1636 | unsigned long flags; |
| 1637 | |
| 1638 | spin_lock_irqsave(q->queue_lock, flags); |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 1639 | if (!as_queue_empty(q)) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1640 | q->request_fn(q); |
| 1641 | spin_unlock_irqrestore(q->queue_lock, flags); |
| 1642 | } |
| 1643 | |
| 1644 | static void as_put_request(request_queue_t *q, struct request *rq) |
| 1645 | { |
| 1646 | struct as_data *ad = q->elevator->elevator_data; |
| 1647 | struct as_rq *arq = RQ_DATA(rq); |
| 1648 | |
| 1649 | if (!arq) { |
| 1650 | WARN_ON(1); |
| 1651 | return; |
| 1652 | } |
| 1653 | |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 1654 | if (unlikely(arq->state != AS_RQ_POSTSCHED && |
| 1655 | arq->state != AS_RQ_PRESCHED && |
| 1656 | arq->state != AS_RQ_MERGED)) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1657 | printk("arq->state %d\n", arq->state); |
| 1658 | WARN_ON(1); |
| 1659 | } |
| 1660 | |
| 1661 | mempool_free(arq, ad->arq_pool); |
| 1662 | rq->elevator_private = NULL; |
| 1663 | } |
| 1664 | |
Jens Axboe | 22e2c50 | 2005-06-27 10:55:12 +0200 | [diff] [blame] | 1665 | static int as_set_request(request_queue_t *q, struct request *rq, |
Al Viro | 8267e26 | 2005-10-21 03:20:53 -0400 | [diff] [blame] | 1666 | struct bio *bio, gfp_t gfp_mask) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1667 | { |
| 1668 | struct as_data *ad = q->elevator->elevator_data; |
| 1669 | struct as_rq *arq = mempool_alloc(ad->arq_pool, gfp_mask); |
| 1670 | |
| 1671 | if (arq) { |
| 1672 | memset(arq, 0, sizeof(*arq)); |
| 1673 | RB_CLEAR(&arq->rb_node); |
| 1674 | arq->request = rq; |
| 1675 | arq->state = AS_RQ_PRESCHED; |
| 1676 | arq->io_context = NULL; |
| 1677 | INIT_LIST_HEAD(&arq->hash); |
| 1678 | arq->on_hash = 0; |
| 1679 | INIT_LIST_HEAD(&arq->fifo); |
| 1680 | rq->elevator_private = arq; |
| 1681 | return 0; |
| 1682 | } |
| 1683 | |
| 1684 | return 1; |
| 1685 | } |
| 1686 | |
Jens Axboe | 22e2c50 | 2005-06-27 10:55:12 +0200 | [diff] [blame] | 1687 | static int as_may_queue(request_queue_t *q, int rw, struct bio *bio) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1688 | { |
| 1689 | int ret = ELV_MQUEUE_MAY; |
| 1690 | struct as_data *ad = q->elevator->elevator_data; |
| 1691 | struct io_context *ioc; |
| 1692 | if (ad->antic_status == ANTIC_WAIT_REQ || |
| 1693 | ad->antic_status == ANTIC_WAIT_NEXT) { |
| 1694 | ioc = as_get_io_context(); |
| 1695 | if (ad->io_context == ioc) |
| 1696 | ret = ELV_MQUEUE_MUST; |
| 1697 | put_io_context(ioc); |
| 1698 | } |
| 1699 | |
| 1700 | return ret; |
| 1701 | } |
| 1702 | |
| 1703 | static void as_exit_queue(elevator_t *e) |
| 1704 | { |
| 1705 | struct as_data *ad = e->elevator_data; |
| 1706 | |
| 1707 | del_timer_sync(&ad->antic_timer); |
| 1708 | kblockd_flush(); |
| 1709 | |
| 1710 | BUG_ON(!list_empty(&ad->fifo_list[REQ_SYNC])); |
| 1711 | BUG_ON(!list_empty(&ad->fifo_list[REQ_ASYNC])); |
| 1712 | |
| 1713 | mempool_destroy(ad->arq_pool); |
| 1714 | put_io_context(ad->io_context); |
| 1715 | kfree(ad->hash); |
| 1716 | kfree(ad); |
| 1717 | } |
| 1718 | |
| 1719 | /* |
| 1720 | * initialize elevator private data (as_data), and alloc a arq for |
| 1721 | * each request on the free lists |
| 1722 | */ |
| 1723 | static int as_init_queue(request_queue_t *q, elevator_t *e) |
| 1724 | { |
| 1725 | struct as_data *ad; |
| 1726 | int i; |
| 1727 | |
| 1728 | if (!arq_pool) |
| 1729 | return -ENOMEM; |
| 1730 | |
Christoph Lameter | 1946089 | 2005-06-23 00:08:19 -0700 | [diff] [blame] | 1731 | ad = kmalloc_node(sizeof(*ad), GFP_KERNEL, q->node); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1732 | if (!ad) |
| 1733 | return -ENOMEM; |
| 1734 | memset(ad, 0, sizeof(*ad)); |
| 1735 | |
| 1736 | ad->q = q; /* Identify what queue the data belongs to */ |
| 1737 | |
Christoph Lameter | 1946089 | 2005-06-23 00:08:19 -0700 | [diff] [blame] | 1738 | ad->hash = kmalloc_node(sizeof(struct list_head)*AS_HASH_ENTRIES, |
| 1739 | GFP_KERNEL, q->node); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1740 | if (!ad->hash) { |
| 1741 | kfree(ad); |
| 1742 | return -ENOMEM; |
| 1743 | } |
| 1744 | |
Christoph Lameter | 1946089 | 2005-06-23 00:08:19 -0700 | [diff] [blame] | 1745 | ad->arq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab, |
| 1746 | mempool_free_slab, arq_pool, q->node); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1747 | if (!ad->arq_pool) { |
| 1748 | kfree(ad->hash); |
| 1749 | kfree(ad); |
| 1750 | return -ENOMEM; |
| 1751 | } |
| 1752 | |
| 1753 | /* anticipatory scheduling helpers */ |
| 1754 | ad->antic_timer.function = as_antic_timeout; |
| 1755 | ad->antic_timer.data = (unsigned long)q; |
| 1756 | init_timer(&ad->antic_timer); |
| 1757 | INIT_WORK(&ad->antic_work, as_work_handler, q); |
| 1758 | |
| 1759 | for (i = 0; i < AS_HASH_ENTRIES; i++) |
| 1760 | INIT_LIST_HEAD(&ad->hash[i]); |
| 1761 | |
| 1762 | INIT_LIST_HEAD(&ad->fifo_list[REQ_SYNC]); |
| 1763 | INIT_LIST_HEAD(&ad->fifo_list[REQ_ASYNC]); |
| 1764 | ad->sort_list[REQ_SYNC] = RB_ROOT; |
| 1765 | ad->sort_list[REQ_ASYNC] = RB_ROOT; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1766 | ad->fifo_expire[REQ_SYNC] = default_read_expire; |
| 1767 | ad->fifo_expire[REQ_ASYNC] = default_write_expire; |
| 1768 | ad->antic_expire = default_antic_expire; |
| 1769 | ad->batch_expire[REQ_SYNC] = default_read_batch_expire; |
| 1770 | ad->batch_expire[REQ_ASYNC] = default_write_batch_expire; |
| 1771 | e->elevator_data = ad; |
| 1772 | |
| 1773 | ad->current_batch_expires = jiffies + ad->batch_expire[REQ_SYNC]; |
| 1774 | ad->write_batch_count = ad->batch_expire[REQ_ASYNC] / 10; |
| 1775 | if (ad->write_batch_count < 2) |
| 1776 | ad->write_batch_count = 2; |
| 1777 | |
| 1778 | return 0; |
| 1779 | } |
| 1780 | |
| 1781 | /* |
| 1782 | * sysfs parts below |
| 1783 | */ |
| 1784 | struct as_fs_entry { |
| 1785 | struct attribute attr; |
| 1786 | ssize_t (*show)(struct as_data *, char *); |
| 1787 | ssize_t (*store)(struct as_data *, const char *, size_t); |
| 1788 | }; |
| 1789 | |
| 1790 | static ssize_t |
| 1791 | as_var_show(unsigned int var, char *page) |
| 1792 | { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1793 | return sprintf(page, "%d\n", var); |
| 1794 | } |
| 1795 | |
| 1796 | static ssize_t |
| 1797 | as_var_store(unsigned long *var, const char *page, size_t count) |
| 1798 | { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1799 | char *p = (char *) page; |
| 1800 | |
Jens Axboe | c9b3ad6 | 2005-07-27 11:43:37 -0700 | [diff] [blame] | 1801 | *var = simple_strtoul(p, &p, 10); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1802 | return count; |
| 1803 | } |
| 1804 | |
| 1805 | static ssize_t as_est_show(struct as_data *ad, char *page) |
| 1806 | { |
| 1807 | int pos = 0; |
| 1808 | |
| 1809 | pos += sprintf(page+pos, "%lu %% exit probability\n", 100*ad->exit_prob/256); |
| 1810 | pos += sprintf(page+pos, "%lu ms new thinktime\n", ad->new_ttime_mean); |
| 1811 | pos += sprintf(page+pos, "%llu sectors new seek distance\n", (unsigned long long)ad->new_seek_mean); |
| 1812 | |
| 1813 | return pos; |
| 1814 | } |
| 1815 | |
| 1816 | #define SHOW_FUNCTION(__FUNC, __VAR) \ |
| 1817 | static ssize_t __FUNC(struct as_data *ad, char *page) \ |
| 1818 | { \ |
| 1819 | return as_var_show(jiffies_to_msecs((__VAR)), (page)); \ |
| 1820 | } |
| 1821 | SHOW_FUNCTION(as_readexpire_show, ad->fifo_expire[REQ_SYNC]); |
| 1822 | SHOW_FUNCTION(as_writeexpire_show, ad->fifo_expire[REQ_ASYNC]); |
| 1823 | SHOW_FUNCTION(as_anticexpire_show, ad->antic_expire); |
| 1824 | SHOW_FUNCTION(as_read_batchexpire_show, ad->batch_expire[REQ_SYNC]); |
| 1825 | SHOW_FUNCTION(as_write_batchexpire_show, ad->batch_expire[REQ_ASYNC]); |
| 1826 | #undef SHOW_FUNCTION |
| 1827 | |
| 1828 | #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \ |
| 1829 | static ssize_t __FUNC(struct as_data *ad, const char *page, size_t count) \ |
| 1830 | { \ |
| 1831 | int ret = as_var_store(__PTR, (page), count); \ |
| 1832 | if (*(__PTR) < (MIN)) \ |
| 1833 | *(__PTR) = (MIN); \ |
| 1834 | else if (*(__PTR) > (MAX)) \ |
| 1835 | *(__PTR) = (MAX); \ |
| 1836 | *(__PTR) = msecs_to_jiffies(*(__PTR)); \ |
| 1837 | return ret; \ |
| 1838 | } |
| 1839 | STORE_FUNCTION(as_readexpire_store, &ad->fifo_expire[REQ_SYNC], 0, INT_MAX); |
| 1840 | STORE_FUNCTION(as_writeexpire_store, &ad->fifo_expire[REQ_ASYNC], 0, INT_MAX); |
| 1841 | STORE_FUNCTION(as_anticexpire_store, &ad->antic_expire, 0, INT_MAX); |
| 1842 | STORE_FUNCTION(as_read_batchexpire_store, |
| 1843 | &ad->batch_expire[REQ_SYNC], 0, INT_MAX); |
| 1844 | STORE_FUNCTION(as_write_batchexpire_store, |
| 1845 | &ad->batch_expire[REQ_ASYNC], 0, INT_MAX); |
| 1846 | #undef STORE_FUNCTION |
| 1847 | |
| 1848 | static struct as_fs_entry as_est_entry = { |
| 1849 | .attr = {.name = "est_time", .mode = S_IRUGO }, |
| 1850 | .show = as_est_show, |
| 1851 | }; |
| 1852 | static struct as_fs_entry as_readexpire_entry = { |
| 1853 | .attr = {.name = "read_expire", .mode = S_IRUGO | S_IWUSR }, |
| 1854 | .show = as_readexpire_show, |
| 1855 | .store = as_readexpire_store, |
| 1856 | }; |
| 1857 | static struct as_fs_entry as_writeexpire_entry = { |
| 1858 | .attr = {.name = "write_expire", .mode = S_IRUGO | S_IWUSR }, |
| 1859 | .show = as_writeexpire_show, |
| 1860 | .store = as_writeexpire_store, |
| 1861 | }; |
| 1862 | static struct as_fs_entry as_anticexpire_entry = { |
| 1863 | .attr = {.name = "antic_expire", .mode = S_IRUGO | S_IWUSR }, |
| 1864 | .show = as_anticexpire_show, |
| 1865 | .store = as_anticexpire_store, |
| 1866 | }; |
| 1867 | static struct as_fs_entry as_read_batchexpire_entry = { |
| 1868 | .attr = {.name = "read_batch_expire", .mode = S_IRUGO | S_IWUSR }, |
| 1869 | .show = as_read_batchexpire_show, |
| 1870 | .store = as_read_batchexpire_store, |
| 1871 | }; |
| 1872 | static struct as_fs_entry as_write_batchexpire_entry = { |
| 1873 | .attr = {.name = "write_batch_expire", .mode = S_IRUGO | S_IWUSR }, |
| 1874 | .show = as_write_batchexpire_show, |
| 1875 | .store = as_write_batchexpire_store, |
| 1876 | }; |
| 1877 | |
| 1878 | static struct attribute *default_attrs[] = { |
| 1879 | &as_est_entry.attr, |
| 1880 | &as_readexpire_entry.attr, |
| 1881 | &as_writeexpire_entry.attr, |
| 1882 | &as_anticexpire_entry.attr, |
| 1883 | &as_read_batchexpire_entry.attr, |
| 1884 | &as_write_batchexpire_entry.attr, |
| 1885 | NULL, |
| 1886 | }; |
| 1887 | |
| 1888 | #define to_as(atr) container_of((atr), struct as_fs_entry, attr) |
| 1889 | |
| 1890 | static ssize_t |
| 1891 | as_attr_show(struct kobject *kobj, struct attribute *attr, char *page) |
| 1892 | { |
| 1893 | elevator_t *e = container_of(kobj, elevator_t, kobj); |
| 1894 | struct as_fs_entry *entry = to_as(attr); |
| 1895 | |
| 1896 | if (!entry->show) |
Dmitry Torokhov | 6c1852a | 2005-04-29 01:26:06 -0500 | [diff] [blame] | 1897 | return -EIO; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1898 | |
| 1899 | return entry->show(e->elevator_data, page); |
| 1900 | } |
| 1901 | |
| 1902 | static ssize_t |
| 1903 | as_attr_store(struct kobject *kobj, struct attribute *attr, |
| 1904 | const char *page, size_t length) |
| 1905 | { |
| 1906 | elevator_t *e = container_of(kobj, elevator_t, kobj); |
| 1907 | struct as_fs_entry *entry = to_as(attr); |
| 1908 | |
| 1909 | if (!entry->store) |
Dmitry Torokhov | 6c1852a | 2005-04-29 01:26:06 -0500 | [diff] [blame] | 1910 | return -EIO; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1911 | |
| 1912 | return entry->store(e->elevator_data, page, length); |
| 1913 | } |
| 1914 | |
| 1915 | static struct sysfs_ops as_sysfs_ops = { |
| 1916 | .show = as_attr_show, |
| 1917 | .store = as_attr_store, |
| 1918 | }; |
| 1919 | |
| 1920 | static struct kobj_type as_ktype = { |
| 1921 | .sysfs_ops = &as_sysfs_ops, |
| 1922 | .default_attrs = default_attrs, |
| 1923 | }; |
| 1924 | |
| 1925 | static struct elevator_type iosched_as = { |
| 1926 | .ops = { |
| 1927 | .elevator_merge_fn = as_merge, |
| 1928 | .elevator_merged_fn = as_merged_request, |
| 1929 | .elevator_merge_req_fn = as_merged_requests, |
Jens Axboe | b4878f2 | 2005-10-20 16:42:29 +0200 | [diff] [blame] | 1930 | .elevator_dispatch_fn = as_dispatch_request, |
| 1931 | .elevator_add_req_fn = as_add_request, |
| 1932 | .elevator_activate_req_fn = as_activate_request, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1933 | .elevator_deactivate_req_fn = as_deactivate_request, |
| 1934 | .elevator_queue_empty_fn = as_queue_empty, |
| 1935 | .elevator_completed_req_fn = as_completed_request, |
| 1936 | .elevator_former_req_fn = as_former_request, |
| 1937 | .elevator_latter_req_fn = as_latter_request, |
| 1938 | .elevator_set_req_fn = as_set_request, |
| 1939 | .elevator_put_req_fn = as_put_request, |
| 1940 | .elevator_may_queue_fn = as_may_queue, |
| 1941 | .elevator_init_fn = as_init_queue, |
| 1942 | .elevator_exit_fn = as_exit_queue, |
| 1943 | }, |
| 1944 | |
| 1945 | .elevator_ktype = &as_ktype, |
| 1946 | .elevator_name = "anticipatory", |
| 1947 | .elevator_owner = THIS_MODULE, |
| 1948 | }; |
| 1949 | |
| 1950 | static int __init as_init(void) |
| 1951 | { |
| 1952 | int ret; |
| 1953 | |
| 1954 | arq_pool = kmem_cache_create("as_arq", sizeof(struct as_rq), |
| 1955 | 0, 0, NULL, NULL); |
| 1956 | if (!arq_pool) |
| 1957 | return -ENOMEM; |
| 1958 | |
| 1959 | ret = elv_register(&iosched_as); |
| 1960 | if (!ret) { |
| 1961 | /* |
| 1962 | * don't allow AS to get unregistered, since we would have |
| 1963 | * to browse all tasks in the system and release their |
| 1964 | * as_io_context first |
| 1965 | */ |
| 1966 | __module_get(THIS_MODULE); |
| 1967 | return 0; |
| 1968 | } |
| 1969 | |
| 1970 | kmem_cache_destroy(arq_pool); |
| 1971 | return ret; |
| 1972 | } |
| 1973 | |
| 1974 | static void __exit as_exit(void) |
| 1975 | { |
| 1976 | kmem_cache_destroy(arq_pool); |
| 1977 | elv_unregister(&iosched_as); |
| 1978 | } |
| 1979 | |
| 1980 | module_init(as_init); |
| 1981 | module_exit(as_exit); |
| 1982 | |
| 1983 | MODULE_AUTHOR("Nick Piggin"); |
| 1984 | MODULE_LICENSE("GPL"); |
| 1985 | MODULE_DESCRIPTION("anticipatory IO scheduler"); |