cfq-iosched.c revision 334e94de9bea353156abd6f2242d3cc4a24562b0
1/* 2 * CFQ, or complete fairness queueing, disk scheduler. 3 * 4 * Based on ideas from a previously unfinished io 5 * scheduler (round robin per-process disk scheduling) and Andrea Arcangeli. 6 * 7 * Copyright (C) 2003 Jens Axboe <axboe@suse.de> 8 */ 9#include <linux/kernel.h> 10#include <linux/fs.h> 11#include <linux/blkdev.h> 12#include <linux/elevator.h> 13#include <linux/bio.h> 14#include <linux/config.h> 15#include <linux/module.h> 16#include <linux/slab.h> 17#include <linux/init.h> 18#include <linux/compiler.h> 19#include <linux/hash.h> 20#include <linux/rbtree.h> 21#include <linux/mempool.h> 22#include <linux/ioprio.h> 23#include <linux/writeback.h> 24 25/* 26 * tunables 27 */ 28static const int cfq_quantum = 4; /* max queue in one round of service */ 29static const int cfq_queued = 8; /* minimum rq allocate limit per-queue*/ 30static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 }; 31static const int cfq_back_max = 16 * 1024; /* maximum backwards seek, in KiB */ 32static const int cfq_back_penalty = 2; /* penalty of a backwards seek */ 33 34static const int cfq_slice_sync = HZ / 10; 35static int cfq_slice_async = HZ / 25; 36static const int cfq_slice_async_rq = 2; 37static int cfq_slice_idle = HZ / 100; 38 39#define CFQ_IDLE_GRACE (HZ / 10) 40#define CFQ_SLICE_SCALE (5) 41 42#define CFQ_KEY_ASYNC (0) 43#define CFQ_KEY_ANY (0xffff) 44 45/* 46 * disable queueing at the driver/hardware level 47 */ 48static const int cfq_max_depth = 2; 49 50static DEFINE_RWLOCK(cfq_exit_lock); 51 52/* 53 * for the hash of cfqq inside the cfqd 54 */ 55#define CFQ_QHASH_SHIFT 6 56#define CFQ_QHASH_ENTRIES (1 << CFQ_QHASH_SHIFT) 57#define list_entry_qhash(entry) hlist_entry((entry), struct cfq_queue, cfq_hash) 58 59/* 60 * for the hash of crq inside the cfqq 61 */ 62#define CFQ_MHASH_SHIFT 6 63#define CFQ_MHASH_BLOCK(sec) ((sec) >> 3) 64#define CFQ_MHASH_ENTRIES (1 << CFQ_MHASH_SHIFT) 65#define CFQ_MHASH_FN(sec) hash_long(CFQ_MHASH_BLOCK(sec), CFQ_MHASH_SHIFT) 66#define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors) 67#define list_entry_hash(ptr) hlist_entry((ptr), struct cfq_rq, hash) 68 69#define list_entry_cfqq(ptr) list_entry((ptr), struct cfq_queue, cfq_list) 70#define list_entry_fifo(ptr) list_entry((ptr), struct request, queuelist) 71 72#define RQ_DATA(rq) (rq)->elevator_private 73 74/* 75 * rb-tree defines 76 */ 77#define RB_NONE (2) 78#define RB_EMPTY(node) ((node)->rb_node == NULL) 79#define RB_CLEAR_COLOR(node) (node)->rb_color = RB_NONE 80#define RB_CLEAR(node) do { \ 81 (node)->rb_parent = NULL; \ 82 RB_CLEAR_COLOR((node)); \ 83 (node)->rb_right = NULL; \ 84 (node)->rb_left = NULL; \ 85} while (0) 86#define RB_CLEAR_ROOT(root) ((root)->rb_node = NULL) 87#define rb_entry_crq(node) rb_entry((node), struct cfq_rq, rb_node) 88#define rq_rb_key(rq) (rq)->sector 89 90static kmem_cache_t *crq_pool; 91static kmem_cache_t *cfq_pool; 92static kmem_cache_t *cfq_ioc_pool; 93 94static atomic_t ioc_count = ATOMIC_INIT(0); 95static struct completion *ioc_gone; 96 97#define CFQ_PRIO_LISTS IOPRIO_BE_NR 98#define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE) 99#define cfq_class_be(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_BE) 100#define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT) 101 102#define ASYNC (0) 103#define SYNC (1) 104 105#define cfq_cfqq_dispatched(cfqq) \ 106 ((cfqq)->on_dispatch[ASYNC] + (cfqq)->on_dispatch[SYNC]) 107 108#define cfq_cfqq_class_sync(cfqq) ((cfqq)->key != CFQ_KEY_ASYNC) 109 110#define cfq_cfqq_sync(cfqq) \ 111 (cfq_cfqq_class_sync(cfqq) || (cfqq)->on_dispatch[SYNC]) 112 113/* 114 * Per block device queue structure 115 */ 116struct cfq_data { 117 atomic_t ref; 118 request_queue_t *queue; 119 120 /* 121 * rr list of queues with requests and the count of them 122 */ 123 struct list_head rr_list[CFQ_PRIO_LISTS]; 124 struct list_head busy_rr; 125 struct list_head cur_rr; 126 struct list_head idle_rr; 127 unsigned int busy_queues; 128 129 /* 130 * non-ordered list of empty cfqq's 131 */ 132 struct list_head empty_list; 133 134 /* 135 * cfqq lookup hash 136 */ 137 struct hlist_head *cfq_hash; 138 139 /* 140 * global crq hash for all queues 141 */ 142 struct hlist_head *crq_hash; 143 144 unsigned int max_queued; 145 146 mempool_t *crq_pool; 147 148 int rq_in_driver; 149 150 /* 151 * schedule slice state info 152 */ 153 /* 154 * idle window management 155 */ 156 struct timer_list idle_slice_timer; 157 struct work_struct unplug_work; 158 159 struct cfq_queue *active_queue; 160 struct cfq_io_context *active_cic; 161 int cur_prio, cur_end_prio; 162 unsigned int dispatch_slice; 163 164 struct timer_list idle_class_timer; 165 166 sector_t last_sector; 167 unsigned long last_end_request; 168 169 unsigned int rq_starved; 170 171 /* 172 * tunables, see top of file 173 */ 174 unsigned int cfq_quantum; 175 unsigned int cfq_queued; 176 unsigned int cfq_fifo_expire[2]; 177 unsigned int cfq_back_penalty; 178 unsigned int cfq_back_max; 179 unsigned int cfq_slice[2]; 180 unsigned int cfq_slice_async_rq; 181 unsigned int cfq_slice_idle; 182 unsigned int cfq_max_depth; 183 184 struct list_head cic_list; 185}; 186 187/* 188 * Per process-grouping structure 189 */ 190struct cfq_queue { 191 /* reference count */ 192 atomic_t ref; 193 /* parent cfq_data */ 194 struct cfq_data *cfqd; 195 /* cfqq lookup hash */ 196 struct hlist_node cfq_hash; 197 /* hash key */ 198 unsigned int key; 199 /* on either rr or empty list of cfqd */ 200 struct list_head cfq_list; 201 /* sorted list of pending requests */ 202 struct rb_root sort_list; 203 /* if fifo isn't expired, next request to serve */ 204 struct cfq_rq *next_crq; 205 /* requests queued in sort_list */ 206 int queued[2]; 207 /* currently allocated requests */ 208 int allocated[2]; 209 /* fifo list of requests in sort_list */ 210 struct list_head fifo; 211 212 unsigned long slice_start; 213 unsigned long slice_end; 214 unsigned long slice_left; 215 unsigned long service_last; 216 217 /* number of requests that are on the dispatch list */ 218 int on_dispatch[2]; 219 220 /* io prio of this group */ 221 unsigned short ioprio, org_ioprio; 222 unsigned short ioprio_class, org_ioprio_class; 223 224 /* various state flags, see below */ 225 unsigned int flags; 226}; 227 228struct cfq_rq { 229 struct rb_node rb_node; 230 sector_t rb_key; 231 struct request *request; 232 struct hlist_node hash; 233 234 struct cfq_queue *cfq_queue; 235 struct cfq_io_context *io_context; 236 237 unsigned int crq_flags; 238}; 239 240enum cfqq_state_flags { 241 CFQ_CFQQ_FLAG_on_rr = 0, 242 CFQ_CFQQ_FLAG_wait_request, 243 CFQ_CFQQ_FLAG_must_alloc, 244 CFQ_CFQQ_FLAG_must_alloc_slice, 245 CFQ_CFQQ_FLAG_must_dispatch, 246 CFQ_CFQQ_FLAG_fifo_expire, 247 CFQ_CFQQ_FLAG_idle_window, 248 CFQ_CFQQ_FLAG_prio_changed, 249}; 250 251#define CFQ_CFQQ_FNS(name) \ 252static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \ 253{ \ 254 cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name); \ 255} \ 256static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \ 257{ \ 258 cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \ 259} \ 260static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \ 261{ \ 262 return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \ 263} 264 265CFQ_CFQQ_FNS(on_rr); 266CFQ_CFQQ_FNS(wait_request); 267CFQ_CFQQ_FNS(must_alloc); 268CFQ_CFQQ_FNS(must_alloc_slice); 269CFQ_CFQQ_FNS(must_dispatch); 270CFQ_CFQQ_FNS(fifo_expire); 271CFQ_CFQQ_FNS(idle_window); 272CFQ_CFQQ_FNS(prio_changed); 273#undef CFQ_CFQQ_FNS 274 275enum cfq_rq_state_flags { 276 CFQ_CRQ_FLAG_is_sync = 0, 277}; 278 279#define CFQ_CRQ_FNS(name) \ 280static inline void cfq_mark_crq_##name(struct cfq_rq *crq) \ 281{ \ 282 crq->crq_flags |= (1 << CFQ_CRQ_FLAG_##name); \ 283} \ 284static inline void cfq_clear_crq_##name(struct cfq_rq *crq) \ 285{ \ 286 crq->crq_flags &= ~(1 << CFQ_CRQ_FLAG_##name); \ 287} \ 288static inline int cfq_crq_##name(const struct cfq_rq *crq) \ 289{ \ 290 return (crq->crq_flags & (1 << CFQ_CRQ_FLAG_##name)) != 0; \ 291} 292 293CFQ_CRQ_FNS(is_sync); 294#undef CFQ_CRQ_FNS 295 296static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsigned short); 297static void cfq_dispatch_insert(request_queue_t *, struct cfq_rq *); 298static void cfq_put_cfqd(struct cfq_data *cfqd); 299 300#define process_sync(tsk) ((tsk)->flags & PF_SYNCWRITE) 301 302/* 303 * lots of deadline iosched dupes, can be abstracted later... 304 */ 305static inline void cfq_del_crq_hash(struct cfq_rq *crq) 306{ 307 hlist_del_init(&crq->hash); 308} 309 310static inline void cfq_add_crq_hash(struct cfq_data *cfqd, struct cfq_rq *crq) 311{ 312 const int hash_idx = CFQ_MHASH_FN(rq_hash_key(crq->request)); 313 314 hlist_add_head(&crq->hash, &cfqd->crq_hash[hash_idx]); 315} 316 317static struct request *cfq_find_rq_hash(struct cfq_data *cfqd, sector_t offset) 318{ 319 struct hlist_head *hash_list = &cfqd->crq_hash[CFQ_MHASH_FN(offset)]; 320 struct hlist_node *entry, *next; 321 322 hlist_for_each_safe(entry, next, hash_list) { 323 struct cfq_rq *crq = list_entry_hash(entry); 324 struct request *__rq = crq->request; 325 326 if (!rq_mergeable(__rq)) { 327 cfq_del_crq_hash(crq); 328 continue; 329 } 330 331 if (rq_hash_key(__rq) == offset) 332 return __rq; 333 } 334 335 return NULL; 336} 337 338/* 339 * scheduler run of queue, if there are requests pending and no one in the 340 * driver that will restart queueing 341 */ 342static inline void cfq_schedule_dispatch(struct cfq_data *cfqd) 343{ 344 if (cfqd->busy_queues) 345 kblockd_schedule_work(&cfqd->unplug_work); 346} 347 348static int cfq_queue_empty(request_queue_t *q) 349{ 350 struct cfq_data *cfqd = q->elevator->elevator_data; 351 352 return !cfqd->busy_queues; 353} 354 355/* 356 * Lifted from AS - choose which of crq1 and crq2 that is best served now. 357 * We choose the request that is closest to the head right now. Distance 358 * behind the head are penalized and only allowed to a certain extent. 359 */ 360static struct cfq_rq * 361cfq_choose_req(struct cfq_data *cfqd, struct cfq_rq *crq1, struct cfq_rq *crq2) 362{ 363 sector_t last, s1, s2, d1 = 0, d2 = 0; 364 int r1_wrap = 0, r2_wrap = 0; /* requests are behind the disk head */ 365 unsigned long back_max; 366 367 if (crq1 == NULL || crq1 == crq2) 368 return crq2; 369 if (crq2 == NULL) 370 return crq1; 371 372 if (cfq_crq_is_sync(crq1) && !cfq_crq_is_sync(crq2)) 373 return crq1; 374 else if (cfq_crq_is_sync(crq2) && !cfq_crq_is_sync(crq1)) 375 return crq2; 376 377 s1 = crq1->request->sector; 378 s2 = crq2->request->sector; 379 380 last = cfqd->last_sector; 381 382 /* 383 * by definition, 1KiB is 2 sectors 384 */ 385 back_max = cfqd->cfq_back_max * 2; 386 387 /* 388 * Strict one way elevator _except_ in the case where we allow 389 * short backward seeks which are biased as twice the cost of a 390 * similar forward seek. 391 */ 392 if (s1 >= last) 393 d1 = s1 - last; 394 else if (s1 + back_max >= last) 395 d1 = (last - s1) * cfqd->cfq_back_penalty; 396 else 397 r1_wrap = 1; 398 399 if (s2 >= last) 400 d2 = s2 - last; 401 else if (s2 + back_max >= last) 402 d2 = (last - s2) * cfqd->cfq_back_penalty; 403 else 404 r2_wrap = 1; 405 406 /* Found required data */ 407 if (!r1_wrap && r2_wrap) 408 return crq1; 409 else if (!r2_wrap && r1_wrap) 410 return crq2; 411 else if (r1_wrap && r2_wrap) { 412 /* both behind the head */ 413 if (s1 <= s2) 414 return crq1; 415 else 416 return crq2; 417 } 418 419 /* Both requests in front of the head */ 420 if (d1 < d2) 421 return crq1; 422 else if (d2 < d1) 423 return crq2; 424 else { 425 if (s1 >= s2) 426 return crq1; 427 else 428 return crq2; 429 } 430} 431 432/* 433 * would be nice to take fifo expire time into account as well 434 */ 435static struct cfq_rq * 436cfq_find_next_crq(struct cfq_data *cfqd, struct cfq_queue *cfqq, 437 struct cfq_rq *last) 438{ 439 struct cfq_rq *crq_next = NULL, *crq_prev = NULL; 440 struct rb_node *rbnext, *rbprev; 441 442 if (!(rbnext = rb_next(&last->rb_node))) { 443 rbnext = rb_first(&cfqq->sort_list); 444 if (rbnext == &last->rb_node) 445 rbnext = NULL; 446 } 447 448 rbprev = rb_prev(&last->rb_node); 449 450 if (rbprev) 451 crq_prev = rb_entry_crq(rbprev); 452 if (rbnext) 453 crq_next = rb_entry_crq(rbnext); 454 455 return cfq_choose_req(cfqd, crq_next, crq_prev); 456} 457 458static void cfq_update_next_crq(struct cfq_rq *crq) 459{ 460 struct cfq_queue *cfqq = crq->cfq_queue; 461 462 if (cfqq->next_crq == crq) 463 cfqq->next_crq = cfq_find_next_crq(cfqq->cfqd, cfqq, crq); 464} 465 466static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted) 467{ 468 struct cfq_data *cfqd = cfqq->cfqd; 469 struct list_head *list, *entry; 470 471 BUG_ON(!cfq_cfqq_on_rr(cfqq)); 472 473 list_del(&cfqq->cfq_list); 474 475 if (cfq_class_rt(cfqq)) 476 list = &cfqd->cur_rr; 477 else if (cfq_class_idle(cfqq)) 478 list = &cfqd->idle_rr; 479 else { 480 /* 481 * if cfqq has requests in flight, don't allow it to be 482 * found in cfq_set_active_queue before it has finished them. 483 * this is done to increase fairness between a process that 484 * has lots of io pending vs one that only generates one 485 * sporadically or synchronously 486 */ 487 if (cfq_cfqq_dispatched(cfqq)) 488 list = &cfqd->busy_rr; 489 else 490 list = &cfqd->rr_list[cfqq->ioprio]; 491 } 492 493 /* 494 * if queue was preempted, just add to front to be fair. busy_rr 495 * isn't sorted. 496 */ 497 if (preempted || list == &cfqd->busy_rr) { 498 list_add(&cfqq->cfq_list, list); 499 return; 500 } 501 502 /* 503 * sort by when queue was last serviced 504 */ 505 entry = list; 506 while ((entry = entry->prev) != list) { 507 struct cfq_queue *__cfqq = list_entry_cfqq(entry); 508 509 if (!__cfqq->service_last) 510 break; 511 if (time_before(__cfqq->service_last, cfqq->service_last)) 512 break; 513 } 514 515 list_add(&cfqq->cfq_list, entry); 516} 517 518/* 519 * add to busy list of queues for service, trying to be fair in ordering 520 * the pending list according to last request service 521 */ 522static inline void 523cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) 524{ 525 BUG_ON(cfq_cfqq_on_rr(cfqq)); 526 cfq_mark_cfqq_on_rr(cfqq); 527 cfqd->busy_queues++; 528 529 cfq_resort_rr_list(cfqq, 0); 530} 531 532static inline void 533cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) 534{ 535 BUG_ON(!cfq_cfqq_on_rr(cfqq)); 536 cfq_clear_cfqq_on_rr(cfqq); 537 list_move(&cfqq->cfq_list, &cfqd->empty_list); 538 539 BUG_ON(!cfqd->busy_queues); 540 cfqd->busy_queues--; 541} 542 543/* 544 * rb tree support functions 545 */ 546static inline void cfq_del_crq_rb(struct cfq_rq *crq) 547{ 548 struct cfq_queue *cfqq = crq->cfq_queue; 549 struct cfq_data *cfqd = cfqq->cfqd; 550 const int sync = cfq_crq_is_sync(crq); 551 552 BUG_ON(!cfqq->queued[sync]); 553 cfqq->queued[sync]--; 554 555 cfq_update_next_crq(crq); 556 557 rb_erase(&crq->rb_node, &cfqq->sort_list); 558 RB_CLEAR_COLOR(&crq->rb_node); 559 560 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY(&cfqq->sort_list)) 561 cfq_del_cfqq_rr(cfqd, cfqq); 562} 563 564static struct cfq_rq * 565__cfq_add_crq_rb(struct cfq_rq *crq) 566{ 567 struct rb_node **p = &crq->cfq_queue->sort_list.rb_node; 568 struct rb_node *parent = NULL; 569 struct cfq_rq *__crq; 570 571 while (*p) { 572 parent = *p; 573 __crq = rb_entry_crq(parent); 574 575 if (crq->rb_key < __crq->rb_key) 576 p = &(*p)->rb_left; 577 else if (crq->rb_key > __crq->rb_key) 578 p = &(*p)->rb_right; 579 else 580 return __crq; 581 } 582 583 rb_link_node(&crq->rb_node, parent, p); 584 return NULL; 585} 586 587static void cfq_add_crq_rb(struct cfq_rq *crq) 588{ 589 struct cfq_queue *cfqq = crq->cfq_queue; 590 struct cfq_data *cfqd = cfqq->cfqd; 591 struct request *rq = crq->request; 592 struct cfq_rq *__alias; 593 594 crq->rb_key = rq_rb_key(rq); 595 cfqq->queued[cfq_crq_is_sync(crq)]++; 596 597 /* 598 * looks a little odd, but the first insert might return an alias. 599 * if that happens, put the alias on the dispatch list 600 */ 601 while ((__alias = __cfq_add_crq_rb(crq)) != NULL) 602 cfq_dispatch_insert(cfqd->queue, __alias); 603 604 rb_insert_color(&crq->rb_node, &cfqq->sort_list); 605 606 if (!cfq_cfqq_on_rr(cfqq)) 607 cfq_add_cfqq_rr(cfqd, cfqq); 608 609 /* 610 * check if this request is a better next-serve candidate 611 */ 612 cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq); 613} 614 615static inline void 616cfq_reposition_crq_rb(struct cfq_queue *cfqq, struct cfq_rq *crq) 617{ 618 rb_erase(&crq->rb_node, &cfqq->sort_list); 619 cfqq->queued[cfq_crq_is_sync(crq)]--; 620 621 cfq_add_crq_rb(crq); 622} 623 624static struct request *cfq_find_rq_rb(struct cfq_data *cfqd, sector_t sector) 625 626{ 627 struct cfq_queue *cfqq = cfq_find_cfq_hash(cfqd, current->pid, CFQ_KEY_ANY); 628 struct rb_node *n; 629 630 if (!cfqq) 631 goto out; 632 633 n = cfqq->sort_list.rb_node; 634 while (n) { 635 struct cfq_rq *crq = rb_entry_crq(n); 636 637 if (sector < crq->rb_key) 638 n = n->rb_left; 639 else if (sector > crq->rb_key) 640 n = n->rb_right; 641 else 642 return crq->request; 643 } 644 645out: 646 return NULL; 647} 648 649static void cfq_activate_request(request_queue_t *q, struct request *rq) 650{ 651 struct cfq_data *cfqd = q->elevator->elevator_data; 652 653 cfqd->rq_in_driver++; 654} 655 656static void cfq_deactivate_request(request_queue_t *q, struct request *rq) 657{ 658 struct cfq_data *cfqd = q->elevator->elevator_data; 659 660 WARN_ON(!cfqd->rq_in_driver); 661 cfqd->rq_in_driver--; 662} 663 664static void cfq_remove_request(struct request *rq) 665{ 666 struct cfq_rq *crq = RQ_DATA(rq); 667 668 list_del_init(&rq->queuelist); 669 cfq_del_crq_rb(crq); 670 cfq_del_crq_hash(crq); 671} 672 673static int 674cfq_merge(request_queue_t *q, struct request **req, struct bio *bio) 675{ 676 struct cfq_data *cfqd = q->elevator->elevator_data; 677 struct request *__rq; 678 int ret; 679 680 __rq = cfq_find_rq_hash(cfqd, bio->bi_sector); 681 if (__rq && elv_rq_merge_ok(__rq, bio)) { 682 ret = ELEVATOR_BACK_MERGE; 683 goto out; 684 } 685 686 __rq = cfq_find_rq_rb(cfqd, bio->bi_sector + bio_sectors(bio)); 687 if (__rq && elv_rq_merge_ok(__rq, bio)) { 688 ret = ELEVATOR_FRONT_MERGE; 689 goto out; 690 } 691 692 return ELEVATOR_NO_MERGE; 693out: 694 *req = __rq; 695 return ret; 696} 697 698static void cfq_merged_request(request_queue_t *q, struct request *req) 699{ 700 struct cfq_data *cfqd = q->elevator->elevator_data; 701 struct cfq_rq *crq = RQ_DATA(req); 702 703 cfq_del_crq_hash(crq); 704 cfq_add_crq_hash(cfqd, crq); 705 706 if (rq_rb_key(req) != crq->rb_key) { 707 struct cfq_queue *cfqq = crq->cfq_queue; 708 709 cfq_update_next_crq(crq); 710 cfq_reposition_crq_rb(cfqq, crq); 711 } 712} 713 714static void 715cfq_merged_requests(request_queue_t *q, struct request *rq, 716 struct request *next) 717{ 718 cfq_merged_request(q, rq); 719 720 /* 721 * reposition in fifo if next is older than rq 722 */ 723 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && 724 time_before(next->start_time, rq->start_time)) 725 list_move(&rq->queuelist, &next->queuelist); 726 727 cfq_remove_request(next); 728} 729 730static inline void 731__cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) 732{ 733 if (cfqq) { 734 /* 735 * stop potential idle class queues waiting service 736 */ 737 del_timer(&cfqd->idle_class_timer); 738 739 cfqq->slice_start = jiffies; 740 cfqq->slice_end = 0; 741 cfqq->slice_left = 0; 742 cfq_clear_cfqq_must_alloc_slice(cfqq); 743 cfq_clear_cfqq_fifo_expire(cfqq); 744 } 745 746 cfqd->active_queue = cfqq; 747} 748 749/* 750 * current cfqq expired its slice (or was too idle), select new one 751 */ 752static void 753__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, 754 int preempted) 755{ 756 unsigned long now = jiffies; 757 758 if (cfq_cfqq_wait_request(cfqq)) 759 del_timer(&cfqd->idle_slice_timer); 760 761 if (!preempted && !cfq_cfqq_dispatched(cfqq)) { 762 cfqq->service_last = now; 763 cfq_schedule_dispatch(cfqd); 764 } 765 766 cfq_clear_cfqq_must_dispatch(cfqq); 767 cfq_clear_cfqq_wait_request(cfqq); 768 769 /* 770 * store what was left of this slice, if the queue idled out 771 * or was preempted 772 */ 773 if (time_after(cfqq->slice_end, now)) 774 cfqq->slice_left = cfqq->slice_end - now; 775 else 776 cfqq->slice_left = 0; 777 778 if (cfq_cfqq_on_rr(cfqq)) 779 cfq_resort_rr_list(cfqq, preempted); 780 781 if (cfqq == cfqd->active_queue) 782 cfqd->active_queue = NULL; 783 784 if (cfqd->active_cic) { 785 put_io_context(cfqd->active_cic->ioc); 786 cfqd->active_cic = NULL; 787 } 788 789 cfqd->dispatch_slice = 0; 790} 791 792static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted) 793{ 794 struct cfq_queue *cfqq = cfqd->active_queue; 795 796 if (cfqq) 797 __cfq_slice_expired(cfqd, cfqq, preempted); 798} 799 800/* 801 * 0 802 * 0,1 803 * 0,1,2 804 * 0,1,2,3 805 * 0,1,2,3,4 806 * 0,1,2,3,4,5 807 * 0,1,2,3,4,5,6 808 * 0,1,2,3,4,5,6,7 809 */ 810static int cfq_get_next_prio_level(struct cfq_data *cfqd) 811{ 812 int prio, wrap; 813 814 prio = -1; 815 wrap = 0; 816 do { 817 int p; 818 819 for (p = cfqd->cur_prio; p <= cfqd->cur_end_prio; p++) { 820 if (!list_empty(&cfqd->rr_list[p])) { 821 prio = p; 822 break; 823 } 824 } 825 826 if (prio != -1) 827 break; 828 cfqd->cur_prio = 0; 829 if (++cfqd->cur_end_prio == CFQ_PRIO_LISTS) { 830 cfqd->cur_end_prio = 0; 831 if (wrap) 832 break; 833 wrap = 1; 834 } 835 } while (1); 836 837 if (unlikely(prio == -1)) 838 return -1; 839 840 BUG_ON(prio >= CFQ_PRIO_LISTS); 841 842 list_splice_init(&cfqd->rr_list[prio], &cfqd->cur_rr); 843 844 cfqd->cur_prio = prio + 1; 845 if (cfqd->cur_prio > cfqd->cur_end_prio) { 846 cfqd->cur_end_prio = cfqd->cur_prio; 847 cfqd->cur_prio = 0; 848 } 849 if (cfqd->cur_end_prio == CFQ_PRIO_LISTS) { 850 cfqd->cur_prio = 0; 851 cfqd->cur_end_prio = 0; 852 } 853 854 return prio; 855} 856 857static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd) 858{ 859 struct cfq_queue *cfqq = NULL; 860 861 /* 862 * if current list is non-empty, grab first entry. if it is empty, 863 * get next prio level and grab first entry then if any are spliced 864 */ 865 if (!list_empty(&cfqd->cur_rr) || cfq_get_next_prio_level(cfqd) != -1) 866 cfqq = list_entry_cfqq(cfqd->cur_rr.next); 867 868 /* 869 * if we have idle queues and no rt or be queues had pending 870 * requests, either allow immediate service if the grace period 871 * has passed or arm the idle grace timer 872 */ 873 if (!cfqq && !list_empty(&cfqd->idle_rr)) { 874 unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE; 875 876 if (time_after_eq(jiffies, end)) 877 cfqq = list_entry_cfqq(cfqd->idle_rr.next); 878 else 879 mod_timer(&cfqd->idle_class_timer, end); 880 } 881 882 __cfq_set_active_queue(cfqd, cfqq); 883 return cfqq; 884} 885 886static int cfq_arm_slice_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq) 887 888{ 889 unsigned long sl; 890 891 WARN_ON(!RB_EMPTY(&cfqq->sort_list)); 892 WARN_ON(cfqq != cfqd->active_queue); 893 894 /* 895 * idle is disabled, either manually or by past process history 896 */ 897 if (!cfqd->cfq_slice_idle) 898 return 0; 899 if (!cfq_cfqq_idle_window(cfqq)) 900 return 0; 901 /* 902 * task has exited, don't wait 903 */ 904 if (cfqd->active_cic && !cfqd->active_cic->ioc->task) 905 return 0; 906 907 cfq_mark_cfqq_must_dispatch(cfqq); 908 cfq_mark_cfqq_wait_request(cfqq); 909 910 sl = min(cfqq->slice_end - 1, (unsigned long) cfqd->cfq_slice_idle); 911 mod_timer(&cfqd->idle_slice_timer, jiffies + sl); 912 return 1; 913} 914 915static void cfq_dispatch_insert(request_queue_t *q, struct cfq_rq *crq) 916{ 917 struct cfq_data *cfqd = q->elevator->elevator_data; 918 struct cfq_queue *cfqq = crq->cfq_queue; 919 920 cfqq->next_crq = cfq_find_next_crq(cfqd, cfqq, crq); 921 cfq_remove_request(crq->request); 922 cfqq->on_dispatch[cfq_crq_is_sync(crq)]++; 923 elv_dispatch_sort(q, crq->request); 924} 925 926/* 927 * return expired entry, or NULL to just start from scratch in rbtree 928 */ 929static inline struct cfq_rq *cfq_check_fifo(struct cfq_queue *cfqq) 930{ 931 struct cfq_data *cfqd = cfqq->cfqd; 932 struct request *rq; 933 struct cfq_rq *crq; 934 935 if (cfq_cfqq_fifo_expire(cfqq)) 936 return NULL; 937 938 if (!list_empty(&cfqq->fifo)) { 939 int fifo = cfq_cfqq_class_sync(cfqq); 940 941 crq = RQ_DATA(list_entry_fifo(cfqq->fifo.next)); 942 rq = crq->request; 943 if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) { 944 cfq_mark_cfqq_fifo_expire(cfqq); 945 return crq; 946 } 947 } 948 949 return NULL; 950} 951 952/* 953 * Scale schedule slice based on io priority. Use the sync time slice only 954 * if a queue is marked sync and has sync io queued. A sync queue with async 955 * io only, should not get full sync slice length. 956 */ 957static inline int 958cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 959{ 960 const int base_slice = cfqd->cfq_slice[cfq_cfqq_sync(cfqq)]; 961 962 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR); 963 964 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - cfqq->ioprio)); 965} 966 967static inline void 968cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 969{ 970 cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies; 971} 972 973static inline int 974cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq) 975{ 976 const int base_rq = cfqd->cfq_slice_async_rq; 977 978 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR); 979 980 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio)); 981} 982 983/* 984 * get next queue for service 985 */ 986static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd) 987{ 988 unsigned long now = jiffies; 989 struct cfq_queue *cfqq; 990 991 cfqq = cfqd->active_queue; 992 if (!cfqq) 993 goto new_queue; 994 995 /* 996 * slice has expired 997 */ 998 if (!cfq_cfqq_must_dispatch(cfqq) && time_after(now, cfqq->slice_end)) 999 goto expire; 1000 1001 /* 1002 * if queue has requests, dispatch one. if not, check if 1003 * enough slice is left to wait for one 1004 */ 1005 if (!RB_EMPTY(&cfqq->sort_list)) 1006 goto keep_queue; 1007 else if (cfq_cfqq_class_sync(cfqq) && 1008 time_before(now, cfqq->slice_end)) { 1009 if (cfq_arm_slice_timer(cfqd, cfqq)) 1010 return NULL; 1011 } 1012 1013expire: 1014 cfq_slice_expired(cfqd, 0); 1015new_queue: 1016 cfqq = cfq_set_active_queue(cfqd); 1017keep_queue: 1018 return cfqq; 1019} 1020 1021static int 1022__cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1023 int max_dispatch) 1024{ 1025 int dispatched = 0; 1026 1027 BUG_ON(RB_EMPTY(&cfqq->sort_list)); 1028 1029 do { 1030 struct cfq_rq *crq; 1031 1032 /* 1033 * follow expired path, else get first next available 1034 */ 1035 if ((crq = cfq_check_fifo(cfqq)) == NULL) 1036 crq = cfqq->next_crq; 1037 1038 /* 1039 * finally, insert request into driver dispatch list 1040 */ 1041 cfq_dispatch_insert(cfqd->queue, crq); 1042 1043 cfqd->dispatch_slice++; 1044 dispatched++; 1045 1046 if (!cfqd->active_cic) { 1047 atomic_inc(&crq->io_context->ioc->refcount); 1048 cfqd->active_cic = crq->io_context; 1049 } 1050 1051 if (RB_EMPTY(&cfqq->sort_list)) 1052 break; 1053 1054 } while (dispatched < max_dispatch); 1055 1056 /* 1057 * if slice end isn't set yet, set it. if at least one request was 1058 * sync, use the sync time slice value 1059 */ 1060 if (!cfqq->slice_end) 1061 cfq_set_prio_slice(cfqd, cfqq); 1062 1063 /* 1064 * expire an async queue immediately if it has used up its slice. idle 1065 * queue always expire after 1 dispatch round. 1066 */ 1067 if ((!cfq_cfqq_sync(cfqq) && 1068 cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) || 1069 cfq_class_idle(cfqq)) 1070 cfq_slice_expired(cfqd, 0); 1071 1072 return dispatched; 1073} 1074 1075static int 1076cfq_forced_dispatch_cfqqs(struct list_head *list) 1077{ 1078 int dispatched = 0; 1079 struct cfq_queue *cfqq, *next; 1080 struct cfq_rq *crq; 1081 1082 list_for_each_entry_safe(cfqq, next, list, cfq_list) { 1083 while ((crq = cfqq->next_crq)) { 1084 cfq_dispatch_insert(cfqq->cfqd->queue, crq); 1085 dispatched++; 1086 } 1087 BUG_ON(!list_empty(&cfqq->fifo)); 1088 } 1089 return dispatched; 1090} 1091 1092static int 1093cfq_forced_dispatch(struct cfq_data *cfqd) 1094{ 1095 int i, dispatched = 0; 1096 1097 for (i = 0; i < CFQ_PRIO_LISTS; i++) 1098 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->rr_list[i]); 1099 1100 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->busy_rr); 1101 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr); 1102 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->idle_rr); 1103 1104 cfq_slice_expired(cfqd, 0); 1105 1106 BUG_ON(cfqd->busy_queues); 1107 1108 return dispatched; 1109} 1110 1111static int 1112cfq_dispatch_requests(request_queue_t *q, int force) 1113{ 1114 struct cfq_data *cfqd = q->elevator->elevator_data; 1115 struct cfq_queue *cfqq; 1116 1117 if (!cfqd->busy_queues) 1118 return 0; 1119 1120 if (unlikely(force)) 1121 return cfq_forced_dispatch(cfqd); 1122 1123 cfqq = cfq_select_queue(cfqd); 1124 if (cfqq) { 1125 int max_dispatch; 1126 1127 /* 1128 * if idle window is disabled, allow queue buildup 1129 */ 1130 if (!cfq_cfqq_idle_window(cfqq) && 1131 cfqd->rq_in_driver >= cfqd->cfq_max_depth) 1132 return 0; 1133 1134 cfq_clear_cfqq_must_dispatch(cfqq); 1135 cfq_clear_cfqq_wait_request(cfqq); 1136 del_timer(&cfqd->idle_slice_timer); 1137 1138 max_dispatch = cfqd->cfq_quantum; 1139 if (cfq_class_idle(cfqq)) 1140 max_dispatch = 1; 1141 1142 return __cfq_dispatch_requests(cfqd, cfqq, max_dispatch); 1143 } 1144 1145 return 0; 1146} 1147 1148/* 1149 * task holds one reference to the queue, dropped when task exits. each crq 1150 * in-flight on this queue also holds a reference, dropped when crq is freed. 1151 * 1152 * queue lock must be held here. 1153 */ 1154static void cfq_put_queue(struct cfq_queue *cfqq) 1155{ 1156 struct cfq_data *cfqd = cfqq->cfqd; 1157 1158 BUG_ON(atomic_read(&cfqq->ref) <= 0); 1159 1160 if (!atomic_dec_and_test(&cfqq->ref)) 1161 return; 1162 1163 BUG_ON(rb_first(&cfqq->sort_list)); 1164 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]); 1165 BUG_ON(cfq_cfqq_on_rr(cfqq)); 1166 1167 if (unlikely(cfqd->active_queue == cfqq)) 1168 __cfq_slice_expired(cfqd, cfqq, 0); 1169 1170 cfq_put_cfqd(cfqq->cfqd); 1171 1172 /* 1173 * it's on the empty list and still hashed 1174 */ 1175 list_del(&cfqq->cfq_list); 1176 hlist_del(&cfqq->cfq_hash); 1177 kmem_cache_free(cfq_pool, cfqq); 1178} 1179 1180static inline struct cfq_queue * 1181__cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned int prio, 1182 const int hashval) 1183{ 1184 struct hlist_head *hash_list = &cfqd->cfq_hash[hashval]; 1185 struct hlist_node *entry, *next; 1186 1187 hlist_for_each_safe(entry, next, hash_list) { 1188 struct cfq_queue *__cfqq = list_entry_qhash(entry); 1189 const unsigned short __p = IOPRIO_PRIO_VALUE(__cfqq->org_ioprio_class, __cfqq->org_ioprio); 1190 1191 if (__cfqq->key == key && (__p == prio || prio == CFQ_KEY_ANY)) 1192 return __cfqq; 1193 } 1194 1195 return NULL; 1196} 1197 1198static struct cfq_queue * 1199cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned short prio) 1200{ 1201 return __cfq_find_cfq_hash(cfqd, key, prio, hash_long(key, CFQ_QHASH_SHIFT)); 1202} 1203 1204static void cfq_free_io_context(struct cfq_io_context *cic) 1205{ 1206 struct cfq_io_context *__cic; 1207 struct list_head *entry, *next; 1208 int freed = 1; 1209 1210 list_for_each_safe(entry, next, &cic->list) { 1211 __cic = list_entry(entry, struct cfq_io_context, list); 1212 kmem_cache_free(cfq_ioc_pool, __cic); 1213 freed++; 1214 } 1215 1216 kmem_cache_free(cfq_ioc_pool, cic); 1217 if (atomic_sub_and_test(freed, &ioc_count) && ioc_gone) 1218 complete(ioc_gone); 1219} 1220 1221static void cfq_trim(struct io_context *ioc) 1222{ 1223 ioc->set_ioprio = NULL; 1224 if (ioc->cic) 1225 cfq_free_io_context(ioc->cic); 1226} 1227 1228/* 1229 * Called with interrupts disabled 1230 */ 1231static void cfq_exit_single_io_context(struct cfq_io_context *cic) 1232{ 1233 struct cfq_data *cfqd = cic->key; 1234 request_queue_t *q; 1235 1236 if (!cfqd) 1237 return; 1238 1239 q = cfqd->queue; 1240 1241 WARN_ON(!irqs_disabled()); 1242 1243 spin_lock(q->queue_lock); 1244 1245 if (cic->cfqq[ASYNC]) { 1246 if (unlikely(cic->cfqq[ASYNC] == cfqd->active_queue)) 1247 __cfq_slice_expired(cfqd, cic->cfqq[ASYNC], 0); 1248 cfq_put_queue(cic->cfqq[ASYNC]); 1249 cic->cfqq[ASYNC] = NULL; 1250 } 1251 1252 if (cic->cfqq[SYNC]) { 1253 if (unlikely(cic->cfqq[SYNC] == cfqd->active_queue)) 1254 __cfq_slice_expired(cfqd, cic->cfqq[SYNC], 0); 1255 cfq_put_queue(cic->cfqq[SYNC]); 1256 cic->cfqq[SYNC] = NULL; 1257 } 1258 1259 cic->key = NULL; 1260 list_del_init(&cic->queue_list); 1261 spin_unlock(q->queue_lock); 1262} 1263 1264/* 1265 * Another task may update the task cic list, if it is doing a queue lookup 1266 * on its behalf. cfq_cic_lock excludes such concurrent updates 1267 */ 1268static void cfq_exit_io_context(struct cfq_io_context *cic) 1269{ 1270 struct cfq_io_context *__cic; 1271 struct list_head *entry; 1272 unsigned long flags; 1273 1274 local_irq_save(flags); 1275 1276 /* 1277 * put the reference this task is holding to the various queues 1278 */ 1279 read_lock(&cfq_exit_lock); 1280 list_for_each(entry, &cic->list) { 1281 __cic = list_entry(entry, struct cfq_io_context, list); 1282 cfq_exit_single_io_context(__cic); 1283 } 1284 1285 cfq_exit_single_io_context(cic); 1286 read_unlock(&cfq_exit_lock); 1287 local_irq_restore(flags); 1288} 1289 1290static struct cfq_io_context * 1291cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 1292{ 1293 struct cfq_io_context *cic = kmem_cache_alloc(cfq_ioc_pool, gfp_mask); 1294 1295 if (cic) { 1296 INIT_LIST_HEAD(&cic->list); 1297 cic->cfqq[ASYNC] = NULL; 1298 cic->cfqq[SYNC] = NULL; 1299 cic->key = NULL; 1300 cic->last_end_request = jiffies; 1301 cic->ttime_total = 0; 1302 cic->ttime_samples = 0; 1303 cic->ttime_mean = 0; 1304 cic->dtor = cfq_free_io_context; 1305 cic->exit = cfq_exit_io_context; 1306 INIT_LIST_HEAD(&cic->queue_list); 1307 atomic_inc(&ioc_count); 1308 } 1309 1310 return cic; 1311} 1312 1313static void cfq_init_prio_data(struct cfq_queue *cfqq) 1314{ 1315 struct task_struct *tsk = current; 1316 int ioprio_class; 1317 1318 if (!cfq_cfqq_prio_changed(cfqq)) 1319 return; 1320 1321 ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio); 1322 switch (ioprio_class) { 1323 default: 1324 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class); 1325 case IOPRIO_CLASS_NONE: 1326 /* 1327 * no prio set, place us in the middle of the BE classes 1328 */ 1329 cfqq->ioprio = task_nice_ioprio(tsk); 1330 cfqq->ioprio_class = IOPRIO_CLASS_BE; 1331 break; 1332 case IOPRIO_CLASS_RT: 1333 cfqq->ioprio = task_ioprio(tsk); 1334 cfqq->ioprio_class = IOPRIO_CLASS_RT; 1335 break; 1336 case IOPRIO_CLASS_BE: 1337 cfqq->ioprio = task_ioprio(tsk); 1338 cfqq->ioprio_class = IOPRIO_CLASS_BE; 1339 break; 1340 case IOPRIO_CLASS_IDLE: 1341 cfqq->ioprio_class = IOPRIO_CLASS_IDLE; 1342 cfqq->ioprio = 7; 1343 cfq_clear_cfqq_idle_window(cfqq); 1344 break; 1345 } 1346 1347 /* 1348 * keep track of original prio settings in case we have to temporarily 1349 * elevate the priority of this queue 1350 */ 1351 cfqq->org_ioprio = cfqq->ioprio; 1352 cfqq->org_ioprio_class = cfqq->ioprio_class; 1353 1354 if (cfq_cfqq_on_rr(cfqq)) 1355 cfq_resort_rr_list(cfqq, 0); 1356 1357 cfq_clear_cfqq_prio_changed(cfqq); 1358} 1359 1360static inline void changed_ioprio(struct cfq_io_context *cic) 1361{ 1362 struct cfq_data *cfqd = cic->key; 1363 struct cfq_queue *cfqq; 1364 if (cfqd) { 1365 spin_lock(cfqd->queue->queue_lock); 1366 cfqq = cic->cfqq[ASYNC]; 1367 if (cfqq) { 1368 cfq_mark_cfqq_prio_changed(cfqq); 1369 cfq_init_prio_data(cfqq); 1370 } 1371 cfqq = cic->cfqq[SYNC]; 1372 if (cfqq) { 1373 cfq_mark_cfqq_prio_changed(cfqq); 1374 cfq_init_prio_data(cfqq); 1375 } 1376 spin_unlock(cfqd->queue->queue_lock); 1377 } 1378} 1379 1380/* 1381 * callback from sys_ioprio_set, irqs are disabled 1382 */ 1383static int cfq_ioc_set_ioprio(struct io_context *ioc, unsigned int ioprio) 1384{ 1385 struct cfq_io_context *cic; 1386 1387 write_lock(&cfq_exit_lock); 1388 1389 cic = ioc->cic; 1390 1391 changed_ioprio(cic); 1392 1393 list_for_each_entry(cic, &cic->list, list) 1394 changed_ioprio(cic); 1395 1396 write_unlock(&cfq_exit_lock); 1397 1398 return 0; 1399} 1400 1401static struct cfq_queue * 1402cfq_get_queue(struct cfq_data *cfqd, unsigned int key, unsigned short ioprio, 1403 gfp_t gfp_mask) 1404{ 1405 const int hashval = hash_long(key, CFQ_QHASH_SHIFT); 1406 struct cfq_queue *cfqq, *new_cfqq = NULL; 1407 1408retry: 1409 cfqq = __cfq_find_cfq_hash(cfqd, key, ioprio, hashval); 1410 1411 if (!cfqq) { 1412 if (new_cfqq) { 1413 cfqq = new_cfqq; 1414 new_cfqq = NULL; 1415 } else if (gfp_mask & __GFP_WAIT) { 1416 spin_unlock_irq(cfqd->queue->queue_lock); 1417 new_cfqq = kmem_cache_alloc(cfq_pool, gfp_mask); 1418 spin_lock_irq(cfqd->queue->queue_lock); 1419 goto retry; 1420 } else { 1421 cfqq = kmem_cache_alloc(cfq_pool, gfp_mask); 1422 if (!cfqq) 1423 goto out; 1424 } 1425 1426 memset(cfqq, 0, sizeof(*cfqq)); 1427 1428 INIT_HLIST_NODE(&cfqq->cfq_hash); 1429 INIT_LIST_HEAD(&cfqq->cfq_list); 1430 RB_CLEAR_ROOT(&cfqq->sort_list); 1431 INIT_LIST_HEAD(&cfqq->fifo); 1432 1433 cfqq->key = key; 1434 hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]); 1435 atomic_set(&cfqq->ref, 0); 1436 cfqq->cfqd = cfqd; 1437 atomic_inc(&cfqd->ref); 1438 cfqq->service_last = 0; 1439 /* 1440 * set ->slice_left to allow preemption for a new process 1441 */ 1442 cfqq->slice_left = 2 * cfqd->cfq_slice_idle; 1443 cfq_mark_cfqq_idle_window(cfqq); 1444 cfq_mark_cfqq_prio_changed(cfqq); 1445 cfq_init_prio_data(cfqq); 1446 } 1447 1448 if (new_cfqq) 1449 kmem_cache_free(cfq_pool, new_cfqq); 1450 1451 atomic_inc(&cfqq->ref); 1452out: 1453 WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq); 1454 return cfqq; 1455} 1456 1457/* 1458 * Setup general io context and cfq io context. There can be several cfq 1459 * io contexts per general io context, if this process is doing io to more 1460 * than one device managed by cfq. Note that caller is holding a reference to 1461 * cfqq, so we don't need to worry about it disappearing 1462 */ 1463static struct cfq_io_context * 1464cfq_get_io_context(struct cfq_data *cfqd, pid_t pid, gfp_t gfp_mask) 1465{ 1466 struct io_context *ioc = NULL; 1467 struct cfq_io_context *cic; 1468 1469 might_sleep_if(gfp_mask & __GFP_WAIT); 1470 1471 ioc = get_io_context(gfp_mask); 1472 if (!ioc) 1473 return NULL; 1474 1475restart: 1476 if ((cic = ioc->cic) == NULL) { 1477 cic = cfq_alloc_io_context(cfqd, gfp_mask); 1478 1479 if (cic == NULL) 1480 goto err; 1481 1482 /* 1483 * manually increment generic io_context usage count, it 1484 * cannot go away since we are already holding one ref to it 1485 */ 1486 cic->ioc = ioc; 1487 cic->key = cfqd; 1488 read_lock(&cfq_exit_lock); 1489 ioc->set_ioprio = cfq_ioc_set_ioprio; 1490 ioc->cic = cic; 1491 list_add(&cic->queue_list, &cfqd->cic_list); 1492 read_unlock(&cfq_exit_lock); 1493 } else { 1494 struct cfq_io_context *__cic; 1495 1496 /* 1497 * the first cic on the list is actually the head itself 1498 */ 1499 if (cic->key == cfqd) 1500 goto out; 1501 1502 if (unlikely(!cic->key)) { 1503 read_lock(&cfq_exit_lock); 1504 if (list_empty(&cic->list)) 1505 ioc->cic = NULL; 1506 else 1507 ioc->cic = list_entry(cic->list.next, 1508 struct cfq_io_context, 1509 list); 1510 read_unlock(&cfq_exit_lock); 1511 kmem_cache_free(cfq_ioc_pool, cic); 1512 atomic_dec(&ioc_count); 1513 goto restart; 1514 } 1515 1516 /* 1517 * cic exists, check if we already are there. linear search 1518 * should be ok here, the list will usually not be more than 1519 * 1 or a few entries long 1520 */ 1521 list_for_each_entry(__cic, &cic->list, list) { 1522 /* 1523 * this process is already holding a reference to 1524 * this queue, so no need to get one more 1525 */ 1526 if (__cic->key == cfqd) { 1527 cic = __cic; 1528 goto out; 1529 } 1530 if (unlikely(!__cic->key)) { 1531 read_lock(&cfq_exit_lock); 1532 list_del(&__cic->list); 1533 read_unlock(&cfq_exit_lock); 1534 kmem_cache_free(cfq_ioc_pool, __cic); 1535 atomic_dec(&ioc_count); 1536 goto restart; 1537 } 1538 } 1539 1540 /* 1541 * nope, process doesn't have a cic assoicated with this 1542 * cfqq yet. get a new one and add to list 1543 */ 1544 __cic = cfq_alloc_io_context(cfqd, gfp_mask); 1545 if (__cic == NULL) 1546 goto err; 1547 1548 __cic->ioc = ioc; 1549 __cic->key = cfqd; 1550 read_lock(&cfq_exit_lock); 1551 list_add(&__cic->list, &cic->list); 1552 list_add(&__cic->queue_list, &cfqd->cic_list); 1553 read_unlock(&cfq_exit_lock); 1554 cic = __cic; 1555 } 1556 1557out: 1558 return cic; 1559err: 1560 put_io_context(ioc); 1561 return NULL; 1562} 1563 1564static void 1565cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic) 1566{ 1567 unsigned long elapsed, ttime; 1568 1569 /* 1570 * if this context already has stuff queued, thinktime is from 1571 * last queue not last end 1572 */ 1573#if 0 1574 if (time_after(cic->last_end_request, cic->last_queue)) 1575 elapsed = jiffies - cic->last_end_request; 1576 else 1577 elapsed = jiffies - cic->last_queue; 1578#else 1579 elapsed = jiffies - cic->last_end_request; 1580#endif 1581 1582 ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle); 1583 1584 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8; 1585 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8; 1586 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples; 1587} 1588 1589#define sample_valid(samples) ((samples) > 80) 1590 1591/* 1592 * Disable idle window if the process thinks too long or seeks so much that 1593 * it doesn't matter 1594 */ 1595static void 1596cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1597 struct cfq_io_context *cic) 1598{ 1599 int enable_idle = cfq_cfqq_idle_window(cfqq); 1600 1601 if (!cic->ioc->task || !cfqd->cfq_slice_idle) 1602 enable_idle = 0; 1603 else if (sample_valid(cic->ttime_samples)) { 1604 if (cic->ttime_mean > cfqd->cfq_slice_idle) 1605 enable_idle = 0; 1606 else 1607 enable_idle = 1; 1608 } 1609 1610 if (enable_idle) 1611 cfq_mark_cfqq_idle_window(cfqq); 1612 else 1613 cfq_clear_cfqq_idle_window(cfqq); 1614} 1615 1616 1617/* 1618 * Check if new_cfqq should preempt the currently active queue. Return 0 for 1619 * no or if we aren't sure, a 1 will cause a preempt. 1620 */ 1621static int 1622cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, 1623 struct cfq_rq *crq) 1624{ 1625 struct cfq_queue *cfqq = cfqd->active_queue; 1626 1627 if (cfq_class_idle(new_cfqq)) 1628 return 0; 1629 1630 if (!cfqq) 1631 return 1; 1632 1633 if (cfq_class_idle(cfqq)) 1634 return 1; 1635 if (!cfq_cfqq_wait_request(new_cfqq)) 1636 return 0; 1637 /* 1638 * if it doesn't have slice left, forget it 1639 */ 1640 if (new_cfqq->slice_left < cfqd->cfq_slice_idle) 1641 return 0; 1642 if (cfq_crq_is_sync(crq) && !cfq_cfqq_sync(cfqq)) 1643 return 1; 1644 1645 return 0; 1646} 1647 1648/* 1649 * cfqq preempts the active queue. if we allowed preempt with no slice left, 1650 * let it have half of its nominal slice. 1651 */ 1652static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1653{ 1654 struct cfq_queue *__cfqq, *next; 1655 1656 list_for_each_entry_safe(__cfqq, next, &cfqd->cur_rr, cfq_list) 1657 cfq_resort_rr_list(__cfqq, 1); 1658 1659 if (!cfqq->slice_left) 1660 cfqq->slice_left = cfq_prio_to_slice(cfqd, cfqq) / 2; 1661 1662 cfqq->slice_end = cfqq->slice_left + jiffies; 1663 __cfq_slice_expired(cfqd, cfqq, 1); 1664 __cfq_set_active_queue(cfqd, cfqq); 1665} 1666 1667/* 1668 * should really be a ll_rw_blk.c helper 1669 */ 1670static void cfq_start_queueing(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1671{ 1672 request_queue_t *q = cfqd->queue; 1673 1674 if (!blk_queue_plugged(q)) 1675 q->request_fn(q); 1676 else 1677 __generic_unplug_device(q); 1678} 1679 1680/* 1681 * Called when a new fs request (crq) is added (to cfqq). Check if there's 1682 * something we should do about it 1683 */ 1684static void 1685cfq_crq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1686 struct cfq_rq *crq) 1687{ 1688 struct cfq_io_context *cic; 1689 1690 cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq); 1691 1692 /* 1693 * we never wait for an async request and we don't allow preemption 1694 * of an async request. so just return early 1695 */ 1696 if (!cfq_crq_is_sync(crq)) 1697 return; 1698 1699 cic = crq->io_context; 1700 1701 cfq_update_io_thinktime(cfqd, cic); 1702 cfq_update_idle_window(cfqd, cfqq, cic); 1703 1704 cic->last_queue = jiffies; 1705 1706 if (cfqq == cfqd->active_queue) { 1707 /* 1708 * if we are waiting for a request for this queue, let it rip 1709 * immediately and flag that we must not expire this queue 1710 * just now 1711 */ 1712 if (cfq_cfqq_wait_request(cfqq)) { 1713 cfq_mark_cfqq_must_dispatch(cfqq); 1714 del_timer(&cfqd->idle_slice_timer); 1715 cfq_start_queueing(cfqd, cfqq); 1716 } 1717 } else if (cfq_should_preempt(cfqd, cfqq, crq)) { 1718 /* 1719 * not the active queue - expire current slice if it is 1720 * idle and has expired it's mean thinktime or this new queue 1721 * has some old slice time left and is of higher priority 1722 */ 1723 cfq_preempt_queue(cfqd, cfqq); 1724 cfq_mark_cfqq_must_dispatch(cfqq); 1725 cfq_start_queueing(cfqd, cfqq); 1726 } 1727} 1728 1729static void cfq_insert_request(request_queue_t *q, struct request *rq) 1730{ 1731 struct cfq_data *cfqd = q->elevator->elevator_data; 1732 struct cfq_rq *crq = RQ_DATA(rq); 1733 struct cfq_queue *cfqq = crq->cfq_queue; 1734 1735 cfq_init_prio_data(cfqq); 1736 1737 cfq_add_crq_rb(crq); 1738 1739 list_add_tail(&rq->queuelist, &cfqq->fifo); 1740 1741 if (rq_mergeable(rq)) 1742 cfq_add_crq_hash(cfqd, crq); 1743 1744 cfq_crq_enqueued(cfqd, cfqq, crq); 1745} 1746 1747static void cfq_completed_request(request_queue_t *q, struct request *rq) 1748{ 1749 struct cfq_rq *crq = RQ_DATA(rq); 1750 struct cfq_queue *cfqq = crq->cfq_queue; 1751 struct cfq_data *cfqd = cfqq->cfqd; 1752 const int sync = cfq_crq_is_sync(crq); 1753 unsigned long now; 1754 1755 now = jiffies; 1756 1757 WARN_ON(!cfqd->rq_in_driver); 1758 WARN_ON(!cfqq->on_dispatch[sync]); 1759 cfqd->rq_in_driver--; 1760 cfqq->on_dispatch[sync]--; 1761 1762 if (!cfq_class_idle(cfqq)) 1763 cfqd->last_end_request = now; 1764 1765 if (!cfq_cfqq_dispatched(cfqq)) { 1766 if (cfq_cfqq_on_rr(cfqq)) { 1767 cfqq->service_last = now; 1768 cfq_resort_rr_list(cfqq, 0); 1769 } 1770 cfq_schedule_dispatch(cfqd); 1771 } 1772 1773 if (cfq_crq_is_sync(crq)) 1774 crq->io_context->last_end_request = now; 1775} 1776 1777static struct request * 1778cfq_former_request(request_queue_t *q, struct request *rq) 1779{ 1780 struct cfq_rq *crq = RQ_DATA(rq); 1781 struct rb_node *rbprev = rb_prev(&crq->rb_node); 1782 1783 if (rbprev) 1784 return rb_entry_crq(rbprev)->request; 1785 1786 return NULL; 1787} 1788 1789static struct request * 1790cfq_latter_request(request_queue_t *q, struct request *rq) 1791{ 1792 struct cfq_rq *crq = RQ_DATA(rq); 1793 struct rb_node *rbnext = rb_next(&crq->rb_node); 1794 1795 if (rbnext) 1796 return rb_entry_crq(rbnext)->request; 1797 1798 return NULL; 1799} 1800 1801/* 1802 * we temporarily boost lower priority queues if they are holding fs exclusive 1803 * resources. they are boosted to normal prio (CLASS_BE/4) 1804 */ 1805static void cfq_prio_boost(struct cfq_queue *cfqq) 1806{ 1807 const int ioprio_class = cfqq->ioprio_class; 1808 const int ioprio = cfqq->ioprio; 1809 1810 if (has_fs_excl()) { 1811 /* 1812 * boost idle prio on transactions that would lock out other 1813 * users of the filesystem 1814 */ 1815 if (cfq_class_idle(cfqq)) 1816 cfqq->ioprio_class = IOPRIO_CLASS_BE; 1817 if (cfqq->ioprio > IOPRIO_NORM) 1818 cfqq->ioprio = IOPRIO_NORM; 1819 } else { 1820 /* 1821 * check if we need to unboost the queue 1822 */ 1823 if (cfqq->ioprio_class != cfqq->org_ioprio_class) 1824 cfqq->ioprio_class = cfqq->org_ioprio_class; 1825 if (cfqq->ioprio != cfqq->org_ioprio) 1826 cfqq->ioprio = cfqq->org_ioprio; 1827 } 1828 1829 /* 1830 * refile between round-robin lists if we moved the priority class 1831 */ 1832 if ((ioprio_class != cfqq->ioprio_class || ioprio != cfqq->ioprio) && 1833 cfq_cfqq_on_rr(cfqq)) 1834 cfq_resort_rr_list(cfqq, 0); 1835} 1836 1837static inline pid_t cfq_queue_pid(struct task_struct *task, int rw) 1838{ 1839 if (rw == READ || process_sync(task)) 1840 return task->pid; 1841 1842 return CFQ_KEY_ASYNC; 1843} 1844 1845static inline int 1846__cfq_may_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1847 struct task_struct *task, int rw) 1848{ 1849#if 1 1850 if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) && 1851 !cfq_cfqq_must_alloc_slice(cfqq)) { 1852 cfq_mark_cfqq_must_alloc_slice(cfqq); 1853 return ELV_MQUEUE_MUST; 1854 } 1855 1856 return ELV_MQUEUE_MAY; 1857#else 1858 if (!cfqq || task->flags & PF_MEMALLOC) 1859 return ELV_MQUEUE_MAY; 1860 if (!cfqq->allocated[rw] || cfq_cfqq_must_alloc(cfqq)) { 1861 if (cfq_cfqq_wait_request(cfqq)) 1862 return ELV_MQUEUE_MUST; 1863 1864 /* 1865 * only allow 1 ELV_MQUEUE_MUST per slice, otherwise we 1866 * can quickly flood the queue with writes from a single task 1867 */ 1868 if (rw == READ || !cfq_cfqq_must_alloc_slice(cfqq)) { 1869 cfq_mark_cfqq_must_alloc_slice(cfqq); 1870 return ELV_MQUEUE_MUST; 1871 } 1872 1873 return ELV_MQUEUE_MAY; 1874 } 1875 if (cfq_class_idle(cfqq)) 1876 return ELV_MQUEUE_NO; 1877 if (cfqq->allocated[rw] >= cfqd->max_queued) { 1878 struct io_context *ioc = get_io_context(GFP_ATOMIC); 1879 int ret = ELV_MQUEUE_NO; 1880 1881 if (ioc && ioc->nr_batch_requests) 1882 ret = ELV_MQUEUE_MAY; 1883 1884 put_io_context(ioc); 1885 return ret; 1886 } 1887 1888 return ELV_MQUEUE_MAY; 1889#endif 1890} 1891 1892static int cfq_may_queue(request_queue_t *q, int rw, struct bio *bio) 1893{ 1894 struct cfq_data *cfqd = q->elevator->elevator_data; 1895 struct task_struct *tsk = current; 1896 struct cfq_queue *cfqq; 1897 1898 /* 1899 * don't force setup of a queue from here, as a call to may_queue 1900 * does not necessarily imply that a request actually will be queued. 1901 * so just lookup a possibly existing queue, or return 'may queue' 1902 * if that fails 1903 */ 1904 cfqq = cfq_find_cfq_hash(cfqd, cfq_queue_pid(tsk, rw), tsk->ioprio); 1905 if (cfqq) { 1906 cfq_init_prio_data(cfqq); 1907 cfq_prio_boost(cfqq); 1908 1909 return __cfq_may_queue(cfqd, cfqq, tsk, rw); 1910 } 1911 1912 return ELV_MQUEUE_MAY; 1913} 1914 1915static void cfq_check_waiters(request_queue_t *q, struct cfq_queue *cfqq) 1916{ 1917 struct cfq_data *cfqd = q->elevator->elevator_data; 1918 struct request_list *rl = &q->rq; 1919 1920 if (cfqq->allocated[READ] <= cfqd->max_queued || cfqd->rq_starved) { 1921 smp_mb(); 1922 if (waitqueue_active(&rl->wait[READ])) 1923 wake_up(&rl->wait[READ]); 1924 } 1925 1926 if (cfqq->allocated[WRITE] <= cfqd->max_queued || cfqd->rq_starved) { 1927 smp_mb(); 1928 if (waitqueue_active(&rl->wait[WRITE])) 1929 wake_up(&rl->wait[WRITE]); 1930 } 1931} 1932 1933/* 1934 * queue lock held here 1935 */ 1936static void cfq_put_request(request_queue_t *q, struct request *rq) 1937{ 1938 struct cfq_data *cfqd = q->elevator->elevator_data; 1939 struct cfq_rq *crq = RQ_DATA(rq); 1940 1941 if (crq) { 1942 struct cfq_queue *cfqq = crq->cfq_queue; 1943 const int rw = rq_data_dir(rq); 1944 1945 BUG_ON(!cfqq->allocated[rw]); 1946 cfqq->allocated[rw]--; 1947 1948 put_io_context(crq->io_context->ioc); 1949 1950 mempool_free(crq, cfqd->crq_pool); 1951 rq->elevator_private = NULL; 1952 1953 cfq_check_waiters(q, cfqq); 1954 cfq_put_queue(cfqq); 1955 } 1956} 1957 1958/* 1959 * Allocate cfq data structures associated with this request. 1960 */ 1961static int 1962cfq_set_request(request_queue_t *q, struct request *rq, struct bio *bio, 1963 gfp_t gfp_mask) 1964{ 1965 struct cfq_data *cfqd = q->elevator->elevator_data; 1966 struct task_struct *tsk = current; 1967 struct cfq_io_context *cic; 1968 const int rw = rq_data_dir(rq); 1969 pid_t key = cfq_queue_pid(tsk, rw); 1970 struct cfq_queue *cfqq; 1971 struct cfq_rq *crq; 1972 unsigned long flags; 1973 int is_sync = key != CFQ_KEY_ASYNC; 1974 1975 might_sleep_if(gfp_mask & __GFP_WAIT); 1976 1977 cic = cfq_get_io_context(cfqd, key, gfp_mask); 1978 1979 spin_lock_irqsave(q->queue_lock, flags); 1980 1981 if (!cic) 1982 goto queue_fail; 1983 1984 if (!cic->cfqq[is_sync]) { 1985 cfqq = cfq_get_queue(cfqd, key, tsk->ioprio, gfp_mask); 1986 if (!cfqq) 1987 goto queue_fail; 1988 1989 cic->cfqq[is_sync] = cfqq; 1990 } else 1991 cfqq = cic->cfqq[is_sync]; 1992 1993 cfqq->allocated[rw]++; 1994 cfq_clear_cfqq_must_alloc(cfqq); 1995 cfqd->rq_starved = 0; 1996 atomic_inc(&cfqq->ref); 1997 spin_unlock_irqrestore(q->queue_lock, flags); 1998 1999 crq = mempool_alloc(cfqd->crq_pool, gfp_mask); 2000 if (crq) { 2001 RB_CLEAR(&crq->rb_node); 2002 crq->rb_key = 0; 2003 crq->request = rq; 2004 INIT_HLIST_NODE(&crq->hash); 2005 crq->cfq_queue = cfqq; 2006 crq->io_context = cic; 2007 2008 if (is_sync) 2009 cfq_mark_crq_is_sync(crq); 2010 else 2011 cfq_clear_crq_is_sync(crq); 2012 2013 rq->elevator_private = crq; 2014 return 0; 2015 } 2016 2017 spin_lock_irqsave(q->queue_lock, flags); 2018 cfqq->allocated[rw]--; 2019 if (!(cfqq->allocated[0] + cfqq->allocated[1])) 2020 cfq_mark_cfqq_must_alloc(cfqq); 2021 cfq_put_queue(cfqq); 2022queue_fail: 2023 if (cic) 2024 put_io_context(cic->ioc); 2025 /* 2026 * mark us rq allocation starved. we need to kickstart the process 2027 * ourselves if there are no pending requests that can do it for us. 2028 * that would be an extremely rare OOM situation 2029 */ 2030 cfqd->rq_starved = 1; 2031 cfq_schedule_dispatch(cfqd); 2032 spin_unlock_irqrestore(q->queue_lock, flags); 2033 return 1; 2034} 2035 2036static void cfq_kick_queue(void *data) 2037{ 2038 request_queue_t *q = data; 2039 struct cfq_data *cfqd = q->elevator->elevator_data; 2040 unsigned long flags; 2041 2042 spin_lock_irqsave(q->queue_lock, flags); 2043 2044 if (cfqd->rq_starved) { 2045 struct request_list *rl = &q->rq; 2046 2047 /* 2048 * we aren't guaranteed to get a request after this, but we 2049 * have to be opportunistic 2050 */ 2051 smp_mb(); 2052 if (waitqueue_active(&rl->wait[READ])) 2053 wake_up(&rl->wait[READ]); 2054 if (waitqueue_active(&rl->wait[WRITE])) 2055 wake_up(&rl->wait[WRITE]); 2056 } 2057 2058 blk_remove_plug(q); 2059 q->request_fn(q); 2060 spin_unlock_irqrestore(q->queue_lock, flags); 2061} 2062 2063/* 2064 * Timer running if the active_queue is currently idling inside its time slice 2065 */ 2066static void cfq_idle_slice_timer(unsigned long data) 2067{ 2068 struct cfq_data *cfqd = (struct cfq_data *) data; 2069 struct cfq_queue *cfqq; 2070 unsigned long flags; 2071 2072 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 2073 2074 if ((cfqq = cfqd->active_queue) != NULL) { 2075 unsigned long now = jiffies; 2076 2077 /* 2078 * expired 2079 */ 2080 if (time_after(now, cfqq->slice_end)) 2081 goto expire; 2082 2083 /* 2084 * only expire and reinvoke request handler, if there are 2085 * other queues with pending requests 2086 */ 2087 if (!cfqd->busy_queues) { 2088 cfqd->idle_slice_timer.expires = min(now + cfqd->cfq_slice_idle, cfqq->slice_end); 2089 add_timer(&cfqd->idle_slice_timer); 2090 goto out_cont; 2091 } 2092 2093 /* 2094 * not expired and it has a request pending, let it dispatch 2095 */ 2096 if (!RB_EMPTY(&cfqq->sort_list)) { 2097 cfq_mark_cfqq_must_dispatch(cfqq); 2098 goto out_kick; 2099 } 2100 } 2101expire: 2102 cfq_slice_expired(cfqd, 0); 2103out_kick: 2104 cfq_schedule_dispatch(cfqd); 2105out_cont: 2106 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 2107} 2108 2109/* 2110 * Timer running if an idle class queue is waiting for service 2111 */ 2112static void cfq_idle_class_timer(unsigned long data) 2113{ 2114 struct cfq_data *cfqd = (struct cfq_data *) data; 2115 unsigned long flags, end; 2116 2117 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 2118 2119 /* 2120 * race with a non-idle queue, reset timer 2121 */ 2122 end = cfqd->last_end_request + CFQ_IDLE_GRACE; 2123 if (!time_after_eq(jiffies, end)) { 2124 cfqd->idle_class_timer.expires = end; 2125 add_timer(&cfqd->idle_class_timer); 2126 } else 2127 cfq_schedule_dispatch(cfqd); 2128 2129 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 2130} 2131 2132static void cfq_shutdown_timer_wq(struct cfq_data *cfqd) 2133{ 2134 del_timer_sync(&cfqd->idle_slice_timer); 2135 del_timer_sync(&cfqd->idle_class_timer); 2136 blk_sync_queue(cfqd->queue); 2137} 2138 2139static void cfq_put_cfqd(struct cfq_data *cfqd) 2140{ 2141 if (!atomic_dec_and_test(&cfqd->ref)) 2142 return; 2143 2144 cfq_shutdown_timer_wq(cfqd); 2145 2146 mempool_destroy(cfqd->crq_pool); 2147 kfree(cfqd->crq_hash); 2148 kfree(cfqd->cfq_hash); 2149 kfree(cfqd); 2150} 2151 2152static void cfq_exit_queue(elevator_t *e) 2153{ 2154 struct cfq_data *cfqd = e->elevator_data; 2155 request_queue_t *q = cfqd->queue; 2156 2157 cfq_shutdown_timer_wq(cfqd); 2158 write_lock(&cfq_exit_lock); 2159 spin_lock_irq(q->queue_lock); 2160 if (cfqd->active_queue) 2161 __cfq_slice_expired(cfqd, cfqd->active_queue, 0); 2162 while(!list_empty(&cfqd->cic_list)) { 2163 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next, 2164 struct cfq_io_context, 2165 queue_list); 2166 if (cic->cfqq[ASYNC]) { 2167 cfq_put_queue(cic->cfqq[ASYNC]); 2168 cic->cfqq[ASYNC] = NULL; 2169 } 2170 if (cic->cfqq[SYNC]) { 2171 cfq_put_queue(cic->cfqq[SYNC]); 2172 cic->cfqq[SYNC] = NULL; 2173 } 2174 cic->key = NULL; 2175 list_del_init(&cic->queue_list); 2176 } 2177 spin_unlock_irq(q->queue_lock); 2178 write_unlock(&cfq_exit_lock); 2179 cfq_put_cfqd(cfqd); 2180} 2181 2182static int cfq_init_queue(request_queue_t *q, elevator_t *e) 2183{ 2184 struct cfq_data *cfqd; 2185 int i; 2186 2187 cfqd = kmalloc(sizeof(*cfqd), GFP_KERNEL); 2188 if (!cfqd) 2189 return -ENOMEM; 2190 2191 memset(cfqd, 0, sizeof(*cfqd)); 2192 2193 for (i = 0; i < CFQ_PRIO_LISTS; i++) 2194 INIT_LIST_HEAD(&cfqd->rr_list[i]); 2195 2196 INIT_LIST_HEAD(&cfqd->busy_rr); 2197 INIT_LIST_HEAD(&cfqd->cur_rr); 2198 INIT_LIST_HEAD(&cfqd->idle_rr); 2199 INIT_LIST_HEAD(&cfqd->empty_list); 2200 INIT_LIST_HEAD(&cfqd->cic_list); 2201 2202 cfqd->crq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_MHASH_ENTRIES, GFP_KERNEL); 2203 if (!cfqd->crq_hash) 2204 goto out_crqhash; 2205 2206 cfqd->cfq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL); 2207 if (!cfqd->cfq_hash) 2208 goto out_cfqhash; 2209 2210 cfqd->crq_pool = mempool_create(BLKDEV_MIN_RQ, mempool_alloc_slab, mempool_free_slab, crq_pool); 2211 if (!cfqd->crq_pool) 2212 goto out_crqpool; 2213 2214 for (i = 0; i < CFQ_MHASH_ENTRIES; i++) 2215 INIT_HLIST_HEAD(&cfqd->crq_hash[i]); 2216 for (i = 0; i < CFQ_QHASH_ENTRIES; i++) 2217 INIT_HLIST_HEAD(&cfqd->cfq_hash[i]); 2218 2219 e->elevator_data = cfqd; 2220 2221 cfqd->queue = q; 2222 2223 cfqd->max_queued = q->nr_requests / 4; 2224 q->nr_batching = cfq_queued; 2225 2226 init_timer(&cfqd->idle_slice_timer); 2227 cfqd->idle_slice_timer.function = cfq_idle_slice_timer; 2228 cfqd->idle_slice_timer.data = (unsigned long) cfqd; 2229 2230 init_timer(&cfqd->idle_class_timer); 2231 cfqd->idle_class_timer.function = cfq_idle_class_timer; 2232 cfqd->idle_class_timer.data = (unsigned long) cfqd; 2233 2234 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue, q); 2235 2236 atomic_set(&cfqd->ref, 1); 2237 2238 cfqd->cfq_queued = cfq_queued; 2239 cfqd->cfq_quantum = cfq_quantum; 2240 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0]; 2241 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1]; 2242 cfqd->cfq_back_max = cfq_back_max; 2243 cfqd->cfq_back_penalty = cfq_back_penalty; 2244 cfqd->cfq_slice[0] = cfq_slice_async; 2245 cfqd->cfq_slice[1] = cfq_slice_sync; 2246 cfqd->cfq_slice_async_rq = cfq_slice_async_rq; 2247 cfqd->cfq_slice_idle = cfq_slice_idle; 2248 cfqd->cfq_max_depth = cfq_max_depth; 2249 2250 return 0; 2251out_crqpool: 2252 kfree(cfqd->cfq_hash); 2253out_cfqhash: 2254 kfree(cfqd->crq_hash); 2255out_crqhash: 2256 kfree(cfqd); 2257 return -ENOMEM; 2258} 2259 2260static void cfq_slab_kill(void) 2261{ 2262 if (crq_pool) 2263 kmem_cache_destroy(crq_pool); 2264 if (cfq_pool) 2265 kmem_cache_destroy(cfq_pool); 2266 if (cfq_ioc_pool) 2267 kmem_cache_destroy(cfq_ioc_pool); 2268} 2269 2270static int __init cfq_slab_setup(void) 2271{ 2272 crq_pool = kmem_cache_create("crq_pool", sizeof(struct cfq_rq), 0, 0, 2273 NULL, NULL); 2274 if (!crq_pool) 2275 goto fail; 2276 2277 cfq_pool = kmem_cache_create("cfq_pool", sizeof(struct cfq_queue), 0, 0, 2278 NULL, NULL); 2279 if (!cfq_pool) 2280 goto fail; 2281 2282 cfq_ioc_pool = kmem_cache_create("cfq_ioc_pool", 2283 sizeof(struct cfq_io_context), 0, 0, NULL, NULL); 2284 if (!cfq_ioc_pool) 2285 goto fail; 2286 2287 return 0; 2288fail: 2289 cfq_slab_kill(); 2290 return -ENOMEM; 2291} 2292 2293/* 2294 * sysfs parts below --> 2295 */ 2296struct cfq_fs_entry { 2297 struct attribute attr; 2298 ssize_t (*show)(struct cfq_data *, char *); 2299 ssize_t (*store)(struct cfq_data *, const char *, size_t); 2300}; 2301 2302static ssize_t 2303cfq_var_show(unsigned int var, char *page) 2304{ 2305 return sprintf(page, "%d\n", var); 2306} 2307 2308static ssize_t 2309cfq_var_store(unsigned int *var, const char *page, size_t count) 2310{ 2311 char *p = (char *) page; 2312 2313 *var = simple_strtoul(p, &p, 10); 2314 return count; 2315} 2316 2317#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ 2318static ssize_t __FUNC(struct cfq_data *cfqd, char *page) \ 2319{ \ 2320 unsigned int __data = __VAR; \ 2321 if (__CONV) \ 2322 __data = jiffies_to_msecs(__data); \ 2323 return cfq_var_show(__data, (page)); \ 2324} 2325SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0); 2326SHOW_FUNCTION(cfq_queued_show, cfqd->cfq_queued, 0); 2327SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1); 2328SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1); 2329SHOW_FUNCTION(cfq_back_max_show, cfqd->cfq_back_max, 0); 2330SHOW_FUNCTION(cfq_back_penalty_show, cfqd->cfq_back_penalty, 0); 2331SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1); 2332SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1); 2333SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1); 2334SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0); 2335SHOW_FUNCTION(cfq_max_depth_show, cfqd->cfq_max_depth, 0); 2336#undef SHOW_FUNCTION 2337 2338#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ 2339static ssize_t __FUNC(struct cfq_data *cfqd, const char *page, size_t count) \ 2340{ \ 2341 unsigned int __data; \ 2342 int ret = cfq_var_store(&__data, (page), count); \ 2343 if (__data < (MIN)) \ 2344 __data = (MIN); \ 2345 else if (__data > (MAX)) \ 2346 __data = (MAX); \ 2347 if (__CONV) \ 2348 *(__PTR) = msecs_to_jiffies(__data); \ 2349 else \ 2350 *(__PTR) = __data; \ 2351 return ret; \ 2352} 2353STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0); 2354STORE_FUNCTION(cfq_queued_store, &cfqd->cfq_queued, 1, UINT_MAX, 0); 2355STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1); 2356STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1); 2357STORE_FUNCTION(cfq_back_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0); 2358STORE_FUNCTION(cfq_back_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0); 2359STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1); 2360STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1); 2361STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1); 2362STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0); 2363STORE_FUNCTION(cfq_max_depth_store, &cfqd->cfq_max_depth, 1, UINT_MAX, 0); 2364#undef STORE_FUNCTION 2365 2366static struct cfq_fs_entry cfq_quantum_entry = { 2367 .attr = {.name = "quantum", .mode = S_IRUGO | S_IWUSR }, 2368 .show = cfq_quantum_show, 2369 .store = cfq_quantum_store, 2370}; 2371static struct cfq_fs_entry cfq_queued_entry = { 2372 .attr = {.name = "queued", .mode = S_IRUGO | S_IWUSR }, 2373 .show = cfq_queued_show, 2374 .store = cfq_queued_store, 2375}; 2376static struct cfq_fs_entry cfq_fifo_expire_sync_entry = { 2377 .attr = {.name = "fifo_expire_sync", .mode = S_IRUGO | S_IWUSR }, 2378 .show = cfq_fifo_expire_sync_show, 2379 .store = cfq_fifo_expire_sync_store, 2380}; 2381static struct cfq_fs_entry cfq_fifo_expire_async_entry = { 2382 .attr = {.name = "fifo_expire_async", .mode = S_IRUGO | S_IWUSR }, 2383 .show = cfq_fifo_expire_async_show, 2384 .store = cfq_fifo_expire_async_store, 2385}; 2386static struct cfq_fs_entry cfq_back_max_entry = { 2387 .attr = {.name = "back_seek_max", .mode = S_IRUGO | S_IWUSR }, 2388 .show = cfq_back_max_show, 2389 .store = cfq_back_max_store, 2390}; 2391static struct cfq_fs_entry cfq_back_penalty_entry = { 2392 .attr = {.name = "back_seek_penalty", .mode = S_IRUGO | S_IWUSR }, 2393 .show = cfq_back_penalty_show, 2394 .store = cfq_back_penalty_store, 2395}; 2396static struct cfq_fs_entry cfq_slice_sync_entry = { 2397 .attr = {.name = "slice_sync", .mode = S_IRUGO | S_IWUSR }, 2398 .show = cfq_slice_sync_show, 2399 .store = cfq_slice_sync_store, 2400}; 2401static struct cfq_fs_entry cfq_slice_async_entry = { 2402 .attr = {.name = "slice_async", .mode = S_IRUGO | S_IWUSR }, 2403 .show = cfq_slice_async_show, 2404 .store = cfq_slice_async_store, 2405}; 2406static struct cfq_fs_entry cfq_slice_async_rq_entry = { 2407 .attr = {.name = "slice_async_rq", .mode = S_IRUGO | S_IWUSR }, 2408 .show = cfq_slice_async_rq_show, 2409 .store = cfq_slice_async_rq_store, 2410}; 2411static struct cfq_fs_entry cfq_slice_idle_entry = { 2412 .attr = {.name = "slice_idle", .mode = S_IRUGO | S_IWUSR }, 2413 .show = cfq_slice_idle_show, 2414 .store = cfq_slice_idle_store, 2415}; 2416static struct cfq_fs_entry cfq_max_depth_entry = { 2417 .attr = {.name = "max_depth", .mode = S_IRUGO | S_IWUSR }, 2418 .show = cfq_max_depth_show, 2419 .store = cfq_max_depth_store, 2420}; 2421 2422static struct attribute *default_attrs[] = { 2423 &cfq_quantum_entry.attr, 2424 &cfq_queued_entry.attr, 2425 &cfq_fifo_expire_sync_entry.attr, 2426 &cfq_fifo_expire_async_entry.attr, 2427 &cfq_back_max_entry.attr, 2428 &cfq_back_penalty_entry.attr, 2429 &cfq_slice_sync_entry.attr, 2430 &cfq_slice_async_entry.attr, 2431 &cfq_slice_async_rq_entry.attr, 2432 &cfq_slice_idle_entry.attr, 2433 &cfq_max_depth_entry.attr, 2434 NULL, 2435}; 2436 2437#define to_cfq(atr) container_of((atr), struct cfq_fs_entry, attr) 2438 2439static ssize_t 2440cfq_attr_show(struct kobject *kobj, struct attribute *attr, char *page) 2441{ 2442 elevator_t *e = container_of(kobj, elevator_t, kobj); 2443 struct cfq_fs_entry *entry = to_cfq(attr); 2444 2445 if (!entry->show) 2446 return -EIO; 2447 2448 return entry->show(e->elevator_data, page); 2449} 2450 2451static ssize_t 2452cfq_attr_store(struct kobject *kobj, struct attribute *attr, 2453 const char *page, size_t length) 2454{ 2455 elevator_t *e = container_of(kobj, elevator_t, kobj); 2456 struct cfq_fs_entry *entry = to_cfq(attr); 2457 2458 if (!entry->store) 2459 return -EIO; 2460 2461 return entry->store(e->elevator_data, page, length); 2462} 2463 2464static struct sysfs_ops cfq_sysfs_ops = { 2465 .show = cfq_attr_show, 2466 .store = cfq_attr_store, 2467}; 2468 2469static struct kobj_type cfq_ktype = { 2470 .sysfs_ops = &cfq_sysfs_ops, 2471 .default_attrs = default_attrs, 2472}; 2473 2474static struct elevator_type iosched_cfq = { 2475 .ops = { 2476 .elevator_merge_fn = cfq_merge, 2477 .elevator_merged_fn = cfq_merged_request, 2478 .elevator_merge_req_fn = cfq_merged_requests, 2479 .elevator_dispatch_fn = cfq_dispatch_requests, 2480 .elevator_add_req_fn = cfq_insert_request, 2481 .elevator_activate_req_fn = cfq_activate_request, 2482 .elevator_deactivate_req_fn = cfq_deactivate_request, 2483 .elevator_queue_empty_fn = cfq_queue_empty, 2484 .elevator_completed_req_fn = cfq_completed_request, 2485 .elevator_former_req_fn = cfq_former_request, 2486 .elevator_latter_req_fn = cfq_latter_request, 2487 .elevator_set_req_fn = cfq_set_request, 2488 .elevator_put_req_fn = cfq_put_request, 2489 .elevator_may_queue_fn = cfq_may_queue, 2490 .elevator_init_fn = cfq_init_queue, 2491 .elevator_exit_fn = cfq_exit_queue, 2492 .trim = cfq_trim, 2493 }, 2494 .elevator_ktype = &cfq_ktype, 2495 .elevator_name = "cfq", 2496 .elevator_owner = THIS_MODULE, 2497}; 2498 2499static int __init cfq_init(void) 2500{ 2501 int ret; 2502 2503 /* 2504 * could be 0 on HZ < 1000 setups 2505 */ 2506 if (!cfq_slice_async) 2507 cfq_slice_async = 1; 2508 if (!cfq_slice_idle) 2509 cfq_slice_idle = 1; 2510 2511 if (cfq_slab_setup()) 2512 return -ENOMEM; 2513 2514 ret = elv_register(&iosched_cfq); 2515 if (ret) 2516 cfq_slab_kill(); 2517 2518 return ret; 2519} 2520 2521static void __exit cfq_exit(void) 2522{ 2523 DECLARE_COMPLETION(all_gone); 2524 elv_unregister(&iosched_cfq); 2525 ioc_gone = &all_gone; 2526 barrier(); 2527 if (atomic_read(&ioc_count)) 2528 complete(ioc_gone); 2529 synchronize_rcu(); 2530 cfq_slab_kill(); 2531} 2532 2533module_init(cfq_init); 2534module_exit(cfq_exit); 2535 2536MODULE_AUTHOR("Jens Axboe"); 2537MODULE_LICENSE("GPL"); 2538MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler"); 2539