cfq-iosched.c revision b706f64281b24d8b1fdc8ae883700131d365c412
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@kernel.dk> 8 */ 9#include <linux/module.h> 10#include <linux/blkdev.h> 11#include <linux/elevator.h> 12#include <linux/rbtree.h> 13#include <linux/ioprio.h> 14#include <linux/blktrace_api.h> 15 16/* 17 * tunables 18 */ 19/* max queue in one round of service */ 20static const int cfq_quantum = 4; 21static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 }; 22/* maximum backwards seek, in KiB */ 23static const int cfq_back_max = 16 * 1024; 24/* penalty of a backwards seek */ 25static const int cfq_back_penalty = 2; 26static const int cfq_slice_sync = HZ / 10; 27static int cfq_slice_async = HZ / 25; 28static const int cfq_slice_async_rq = 2; 29static int cfq_slice_idle = HZ / 125; 30 31/* 32 * offset from end of service tree 33 */ 34#define CFQ_IDLE_DELAY (HZ / 5) 35 36/* 37 * below this threshold, we consider thinktime immediate 38 */ 39#define CFQ_MIN_TT (2) 40 41#define CFQ_SLICE_SCALE (5) 42#define CFQ_HW_QUEUE_MIN (5) 43 44#define RQ_CIC(rq) \ 45 ((struct cfq_io_context *) (rq)->elevator_private) 46#define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2) 47 48static struct kmem_cache *cfq_pool; 49static struct kmem_cache *cfq_ioc_pool; 50 51static DEFINE_PER_CPU(unsigned long, ioc_count); 52static struct completion *ioc_gone; 53static DEFINE_SPINLOCK(ioc_gone_lock); 54 55#define CFQ_PRIO_LISTS IOPRIO_BE_NR 56#define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE) 57#define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT) 58 59#define sample_valid(samples) ((samples) > 80) 60 61/* 62 * Most of our rbtree usage is for sorting with min extraction, so 63 * if we cache the leftmost node we don't have to walk down the tree 64 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should 65 * move this into the elevator for the rq sorting as well. 66 */ 67struct cfq_rb_root { 68 struct rb_root rb; 69 struct rb_node *left; 70}; 71#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, } 72 73/* 74 * Per process-grouping structure 75 */ 76struct cfq_queue { 77 /* reference count */ 78 atomic_t ref; 79 /* various state flags, see below */ 80 unsigned int flags; 81 /* parent cfq_data */ 82 struct cfq_data *cfqd; 83 /* service_tree member */ 84 struct rb_node rb_node; 85 /* service_tree key */ 86 unsigned long rb_key; 87 /* prio tree member */ 88 struct rb_node p_node; 89 /* prio tree root we belong to, if any */ 90 struct rb_root *p_root; 91 /* sorted list of pending requests */ 92 struct rb_root sort_list; 93 /* if fifo isn't expired, next request to serve */ 94 struct request *next_rq; 95 /* requests queued in sort_list */ 96 int queued[2]; 97 /* currently allocated requests */ 98 int allocated[2]; 99 /* fifo list of requests in sort_list */ 100 struct list_head fifo; 101 102 unsigned long slice_end; 103 long slice_resid; 104 unsigned int slice_dispatch; 105 106 /* pending metadata requests */ 107 int meta_pending; 108 /* number of requests that are on the dispatch list or inside driver */ 109 int dispatched; 110 111 /* io prio of this group */ 112 unsigned short ioprio, org_ioprio; 113 unsigned short ioprio_class, org_ioprio_class; 114 115 pid_t pid; 116}; 117 118/* 119 * Per block device queue structure 120 */ 121struct cfq_data { 122 struct request_queue *queue; 123 124 /* 125 * rr list of queues with requests and the count of them 126 */ 127 struct cfq_rb_root service_tree; 128 129 /* 130 * Each priority tree is sorted by next_request position. These 131 * trees are used when determining if two or more queues are 132 * interleaving requests (see cfq_close_cooperator). 133 */ 134 struct rb_root prio_trees[CFQ_PRIO_LISTS]; 135 136 unsigned int busy_queues; 137 /* 138 * Used to track any pending rt requests so we can pre-empt current 139 * non-RT cfqq in service when this value is non-zero. 140 */ 141 unsigned int busy_rt_queues; 142 143 int rq_in_driver; 144 int sync_flight; 145 146 /* 147 * queue-depth detection 148 */ 149 int rq_queued; 150 int hw_tag; 151 int hw_tag_samples; 152 int rq_in_driver_peak; 153 154 /* 155 * idle window management 156 */ 157 struct timer_list idle_slice_timer; 158 struct work_struct unplug_work; 159 160 struct cfq_queue *active_queue; 161 struct cfq_io_context *active_cic; 162 163 /* 164 * async queue for each priority case 165 */ 166 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR]; 167 struct cfq_queue *async_idle_cfqq; 168 169 sector_t last_position; 170 171 /* 172 * tunables, see top of file 173 */ 174 unsigned int cfq_quantum; 175 unsigned int cfq_fifo_expire[2]; 176 unsigned int cfq_back_penalty; 177 unsigned int cfq_back_max; 178 unsigned int cfq_slice[2]; 179 unsigned int cfq_slice_async_rq; 180 unsigned int cfq_slice_idle; 181 182 struct list_head cic_list; 183 184 /* 185 * Fallback dummy cfqq for extreme OOM conditions 186 */ 187 struct cfq_queue oom_cfqq; 188}; 189 190enum cfqq_state_flags { 191 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */ 192 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */ 193 CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */ 194 CFQ_CFQQ_FLAG_must_alloc, /* must be allowed rq alloc */ 195 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */ 196 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */ 197 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */ 198 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */ 199 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */ 200 CFQ_CFQQ_FLAG_sync, /* synchronous queue */ 201 CFQ_CFQQ_FLAG_coop, /* has done a coop jump of the queue */ 202}; 203 204#define CFQ_CFQQ_FNS(name) \ 205static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \ 206{ \ 207 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \ 208} \ 209static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \ 210{ \ 211 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \ 212} \ 213static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \ 214{ \ 215 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \ 216} 217 218CFQ_CFQQ_FNS(on_rr); 219CFQ_CFQQ_FNS(wait_request); 220CFQ_CFQQ_FNS(must_dispatch); 221CFQ_CFQQ_FNS(must_alloc); 222CFQ_CFQQ_FNS(must_alloc_slice); 223CFQ_CFQQ_FNS(fifo_expire); 224CFQ_CFQQ_FNS(idle_window); 225CFQ_CFQQ_FNS(prio_changed); 226CFQ_CFQQ_FNS(slice_new); 227CFQ_CFQQ_FNS(sync); 228CFQ_CFQQ_FNS(coop); 229#undef CFQ_CFQQ_FNS 230 231#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \ 232 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args) 233#define cfq_log(cfqd, fmt, args...) \ 234 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args) 235 236static void cfq_dispatch_insert(struct request_queue *, struct request *); 237static struct cfq_queue *cfq_get_queue(struct cfq_data *, int, 238 struct io_context *, gfp_t); 239static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *, 240 struct io_context *); 241 242static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic, 243 int is_sync) 244{ 245 return cic->cfqq[!!is_sync]; 246} 247 248static inline void cic_set_cfqq(struct cfq_io_context *cic, 249 struct cfq_queue *cfqq, int is_sync) 250{ 251 cic->cfqq[!!is_sync] = cfqq; 252} 253 254/* 255 * We regard a request as SYNC, if it's either a read or has the SYNC bit 256 * set (in which case it could also be direct WRITE). 257 */ 258static inline int cfq_bio_sync(struct bio *bio) 259{ 260 if (bio_data_dir(bio) == READ || bio_sync(bio)) 261 return 1; 262 263 return 0; 264} 265 266/* 267 * scheduler run of queue, if there are requests pending and no one in the 268 * driver that will restart queueing 269 */ 270static inline void cfq_schedule_dispatch(struct cfq_data *cfqd) 271{ 272 if (cfqd->busy_queues) { 273 cfq_log(cfqd, "schedule dispatch"); 274 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work); 275 } 276} 277 278static int cfq_queue_empty(struct request_queue *q) 279{ 280 struct cfq_data *cfqd = q->elevator->elevator_data; 281 282 return !cfqd->busy_queues; 283} 284 285/* 286 * Scale schedule slice based on io priority. Use the sync time slice only 287 * if a queue is marked sync and has sync io queued. A sync queue with async 288 * io only, should not get full sync slice length. 289 */ 290static inline int cfq_prio_slice(struct cfq_data *cfqd, int sync, 291 unsigned short prio) 292{ 293 const int base_slice = cfqd->cfq_slice[sync]; 294 295 WARN_ON(prio >= IOPRIO_BE_NR); 296 297 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio)); 298} 299 300static inline int 301cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 302{ 303 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio); 304} 305 306static inline void 307cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 308{ 309 cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies; 310 cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies); 311} 312 313/* 314 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end 315 * isn't valid until the first request from the dispatch is activated 316 * and the slice time set. 317 */ 318static inline int cfq_slice_used(struct cfq_queue *cfqq) 319{ 320 if (cfq_cfqq_slice_new(cfqq)) 321 return 0; 322 if (time_before(jiffies, cfqq->slice_end)) 323 return 0; 324 325 return 1; 326} 327 328/* 329 * Lifted from AS - choose which of rq1 and rq2 that is best served now. 330 * We choose the request that is closest to the head right now. Distance 331 * behind the head is penalized and only allowed to a certain extent. 332 */ 333static struct request * 334cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2) 335{ 336 sector_t last, s1, s2, d1 = 0, d2 = 0; 337 unsigned long back_max; 338#define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */ 339#define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */ 340 unsigned wrap = 0; /* bit mask: requests behind the disk head? */ 341 342 if (rq1 == NULL || rq1 == rq2) 343 return rq2; 344 if (rq2 == NULL) 345 return rq1; 346 347 if (rq_is_sync(rq1) && !rq_is_sync(rq2)) 348 return rq1; 349 else if (rq_is_sync(rq2) && !rq_is_sync(rq1)) 350 return rq2; 351 if (rq_is_meta(rq1) && !rq_is_meta(rq2)) 352 return rq1; 353 else if (rq_is_meta(rq2) && !rq_is_meta(rq1)) 354 return rq2; 355 356 s1 = blk_rq_pos(rq1); 357 s2 = blk_rq_pos(rq2); 358 359 last = cfqd->last_position; 360 361 /* 362 * by definition, 1KiB is 2 sectors 363 */ 364 back_max = cfqd->cfq_back_max * 2; 365 366 /* 367 * Strict one way elevator _except_ in the case where we allow 368 * short backward seeks which are biased as twice the cost of a 369 * similar forward seek. 370 */ 371 if (s1 >= last) 372 d1 = s1 - last; 373 else if (s1 + back_max >= last) 374 d1 = (last - s1) * cfqd->cfq_back_penalty; 375 else 376 wrap |= CFQ_RQ1_WRAP; 377 378 if (s2 >= last) 379 d2 = s2 - last; 380 else if (s2 + back_max >= last) 381 d2 = (last - s2) * cfqd->cfq_back_penalty; 382 else 383 wrap |= CFQ_RQ2_WRAP; 384 385 /* Found required data */ 386 387 /* 388 * By doing switch() on the bit mask "wrap" we avoid having to 389 * check two variables for all permutations: --> faster! 390 */ 391 switch (wrap) { 392 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */ 393 if (d1 < d2) 394 return rq1; 395 else if (d2 < d1) 396 return rq2; 397 else { 398 if (s1 >= s2) 399 return rq1; 400 else 401 return rq2; 402 } 403 404 case CFQ_RQ2_WRAP: 405 return rq1; 406 case CFQ_RQ1_WRAP: 407 return rq2; 408 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */ 409 default: 410 /* 411 * Since both rqs are wrapped, 412 * start with the one that's further behind head 413 * (--> only *one* back seek required), 414 * since back seek takes more time than forward. 415 */ 416 if (s1 <= s2) 417 return rq1; 418 else 419 return rq2; 420 } 421} 422 423/* 424 * The below is leftmost cache rbtree addon 425 */ 426static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root) 427{ 428 if (!root->left) 429 root->left = rb_first(&root->rb); 430 431 if (root->left) 432 return rb_entry(root->left, struct cfq_queue, rb_node); 433 434 return NULL; 435} 436 437static void rb_erase_init(struct rb_node *n, struct rb_root *root) 438{ 439 rb_erase(n, root); 440 RB_CLEAR_NODE(n); 441} 442 443static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root) 444{ 445 if (root->left == n) 446 root->left = NULL; 447 rb_erase_init(n, &root->rb); 448} 449 450/* 451 * would be nice to take fifo expire time into account as well 452 */ 453static struct request * 454cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq, 455 struct request *last) 456{ 457 struct rb_node *rbnext = rb_next(&last->rb_node); 458 struct rb_node *rbprev = rb_prev(&last->rb_node); 459 struct request *next = NULL, *prev = NULL; 460 461 BUG_ON(RB_EMPTY_NODE(&last->rb_node)); 462 463 if (rbprev) 464 prev = rb_entry_rq(rbprev); 465 466 if (rbnext) 467 next = rb_entry_rq(rbnext); 468 else { 469 rbnext = rb_first(&cfqq->sort_list); 470 if (rbnext && rbnext != &last->rb_node) 471 next = rb_entry_rq(rbnext); 472 } 473 474 return cfq_choose_req(cfqd, next, prev); 475} 476 477static unsigned long cfq_slice_offset(struct cfq_data *cfqd, 478 struct cfq_queue *cfqq) 479{ 480 /* 481 * just an approximation, should be ok. 482 */ 483 return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) - 484 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio)); 485} 486 487/* 488 * The cfqd->service_tree holds all pending cfq_queue's that have 489 * requests waiting to be processed. It is sorted in the order that 490 * we will service the queues. 491 */ 492static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, 493 int add_front) 494{ 495 struct rb_node **p, *parent; 496 struct cfq_queue *__cfqq; 497 unsigned long rb_key; 498 int left; 499 500 if (cfq_class_idle(cfqq)) { 501 rb_key = CFQ_IDLE_DELAY; 502 parent = rb_last(&cfqd->service_tree.rb); 503 if (parent && parent != &cfqq->rb_node) { 504 __cfqq = rb_entry(parent, struct cfq_queue, rb_node); 505 rb_key += __cfqq->rb_key; 506 } else 507 rb_key += jiffies; 508 } else if (!add_front) { 509 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies; 510 rb_key += cfqq->slice_resid; 511 cfqq->slice_resid = 0; 512 } else 513 rb_key = 0; 514 515 if (!RB_EMPTY_NODE(&cfqq->rb_node)) { 516 /* 517 * same position, nothing more to do 518 */ 519 if (rb_key == cfqq->rb_key) 520 return; 521 522 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree); 523 } 524 525 left = 1; 526 parent = NULL; 527 p = &cfqd->service_tree.rb.rb_node; 528 while (*p) { 529 struct rb_node **n; 530 531 parent = *p; 532 __cfqq = rb_entry(parent, struct cfq_queue, rb_node); 533 534 /* 535 * sort RT queues first, we always want to give 536 * preference to them. IDLE queues goes to the back. 537 * after that, sort on the next service time. 538 */ 539 if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq)) 540 n = &(*p)->rb_left; 541 else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq)) 542 n = &(*p)->rb_right; 543 else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq)) 544 n = &(*p)->rb_left; 545 else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq)) 546 n = &(*p)->rb_right; 547 else if (rb_key < __cfqq->rb_key) 548 n = &(*p)->rb_left; 549 else 550 n = &(*p)->rb_right; 551 552 if (n == &(*p)->rb_right) 553 left = 0; 554 555 p = n; 556 } 557 558 if (left) 559 cfqd->service_tree.left = &cfqq->rb_node; 560 561 cfqq->rb_key = rb_key; 562 rb_link_node(&cfqq->rb_node, parent, p); 563 rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb); 564} 565 566static struct cfq_queue * 567cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root, 568 sector_t sector, struct rb_node **ret_parent, 569 struct rb_node ***rb_link) 570{ 571 struct rb_node **p, *parent; 572 struct cfq_queue *cfqq = NULL; 573 574 parent = NULL; 575 p = &root->rb_node; 576 while (*p) { 577 struct rb_node **n; 578 579 parent = *p; 580 cfqq = rb_entry(parent, struct cfq_queue, p_node); 581 582 /* 583 * Sort strictly based on sector. Smallest to the left, 584 * largest to the right. 585 */ 586 if (sector > blk_rq_pos(cfqq->next_rq)) 587 n = &(*p)->rb_right; 588 else if (sector < blk_rq_pos(cfqq->next_rq)) 589 n = &(*p)->rb_left; 590 else 591 break; 592 p = n; 593 cfqq = NULL; 594 } 595 596 *ret_parent = parent; 597 if (rb_link) 598 *rb_link = p; 599 return cfqq; 600} 601 602static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq) 603{ 604 struct rb_node **p, *parent; 605 struct cfq_queue *__cfqq; 606 607 if (cfqq->p_root) { 608 rb_erase(&cfqq->p_node, cfqq->p_root); 609 cfqq->p_root = NULL; 610 } 611 612 if (cfq_class_idle(cfqq)) 613 return; 614 if (!cfqq->next_rq) 615 return; 616 617 cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio]; 618 __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root, 619 blk_rq_pos(cfqq->next_rq), &parent, &p); 620 if (!__cfqq) { 621 rb_link_node(&cfqq->p_node, parent, p); 622 rb_insert_color(&cfqq->p_node, cfqq->p_root); 623 } else 624 cfqq->p_root = NULL; 625} 626 627/* 628 * Update cfqq's position in the service tree. 629 */ 630static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq) 631{ 632 /* 633 * Resorting requires the cfqq to be on the RR list already. 634 */ 635 if (cfq_cfqq_on_rr(cfqq)) { 636 cfq_service_tree_add(cfqd, cfqq, 0); 637 cfq_prio_tree_add(cfqd, cfqq); 638 } 639} 640 641/* 642 * add to busy list of queues for service, trying to be fair in ordering 643 * the pending list according to last request service 644 */ 645static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) 646{ 647 cfq_log_cfqq(cfqd, cfqq, "add_to_rr"); 648 BUG_ON(cfq_cfqq_on_rr(cfqq)); 649 cfq_mark_cfqq_on_rr(cfqq); 650 cfqd->busy_queues++; 651 if (cfq_class_rt(cfqq)) 652 cfqd->busy_rt_queues++; 653 654 cfq_resort_rr_list(cfqd, cfqq); 655} 656 657/* 658 * Called when the cfqq no longer has requests pending, remove it from 659 * the service tree. 660 */ 661static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) 662{ 663 cfq_log_cfqq(cfqd, cfqq, "del_from_rr"); 664 BUG_ON(!cfq_cfqq_on_rr(cfqq)); 665 cfq_clear_cfqq_on_rr(cfqq); 666 667 if (!RB_EMPTY_NODE(&cfqq->rb_node)) 668 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree); 669 if (cfqq->p_root) { 670 rb_erase(&cfqq->p_node, cfqq->p_root); 671 cfqq->p_root = NULL; 672 } 673 674 BUG_ON(!cfqd->busy_queues); 675 cfqd->busy_queues--; 676 if (cfq_class_rt(cfqq)) 677 cfqd->busy_rt_queues--; 678} 679 680/* 681 * rb tree support functions 682 */ 683static void cfq_del_rq_rb(struct request *rq) 684{ 685 struct cfq_queue *cfqq = RQ_CFQQ(rq); 686 struct cfq_data *cfqd = cfqq->cfqd; 687 const int sync = rq_is_sync(rq); 688 689 BUG_ON(!cfqq->queued[sync]); 690 cfqq->queued[sync]--; 691 692 elv_rb_del(&cfqq->sort_list, rq); 693 694 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) 695 cfq_del_cfqq_rr(cfqd, cfqq); 696} 697 698static void cfq_add_rq_rb(struct request *rq) 699{ 700 struct cfq_queue *cfqq = RQ_CFQQ(rq); 701 struct cfq_data *cfqd = cfqq->cfqd; 702 struct request *__alias, *prev; 703 704 cfqq->queued[rq_is_sync(rq)]++; 705 706 /* 707 * looks a little odd, but the first insert might return an alias. 708 * if that happens, put the alias on the dispatch list 709 */ 710 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL) 711 cfq_dispatch_insert(cfqd->queue, __alias); 712 713 if (!cfq_cfqq_on_rr(cfqq)) 714 cfq_add_cfqq_rr(cfqd, cfqq); 715 716 /* 717 * check if this request is a better next-serve candidate 718 */ 719 prev = cfqq->next_rq; 720 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq); 721 722 /* 723 * adjust priority tree position, if ->next_rq changes 724 */ 725 if (prev != cfqq->next_rq) 726 cfq_prio_tree_add(cfqd, cfqq); 727 728 BUG_ON(!cfqq->next_rq); 729} 730 731static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq) 732{ 733 elv_rb_del(&cfqq->sort_list, rq); 734 cfqq->queued[rq_is_sync(rq)]--; 735 cfq_add_rq_rb(rq); 736} 737 738static struct request * 739cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio) 740{ 741 struct task_struct *tsk = current; 742 struct cfq_io_context *cic; 743 struct cfq_queue *cfqq; 744 745 cic = cfq_cic_lookup(cfqd, tsk->io_context); 746 if (!cic) 747 return NULL; 748 749 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); 750 if (cfqq) { 751 sector_t sector = bio->bi_sector + bio_sectors(bio); 752 753 return elv_rb_find(&cfqq->sort_list, sector); 754 } 755 756 return NULL; 757} 758 759static void cfq_activate_request(struct request_queue *q, struct request *rq) 760{ 761 struct cfq_data *cfqd = q->elevator->elevator_data; 762 763 cfqd->rq_in_driver++; 764 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d", 765 cfqd->rq_in_driver); 766 767 cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq); 768} 769 770static void cfq_deactivate_request(struct request_queue *q, struct request *rq) 771{ 772 struct cfq_data *cfqd = q->elevator->elevator_data; 773 774 WARN_ON(!cfqd->rq_in_driver); 775 cfqd->rq_in_driver--; 776 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d", 777 cfqd->rq_in_driver); 778} 779 780static void cfq_remove_request(struct request *rq) 781{ 782 struct cfq_queue *cfqq = RQ_CFQQ(rq); 783 784 if (cfqq->next_rq == rq) 785 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq); 786 787 list_del_init(&rq->queuelist); 788 cfq_del_rq_rb(rq); 789 790 cfqq->cfqd->rq_queued--; 791 if (rq_is_meta(rq)) { 792 WARN_ON(!cfqq->meta_pending); 793 cfqq->meta_pending--; 794 } 795} 796 797static int cfq_merge(struct request_queue *q, struct request **req, 798 struct bio *bio) 799{ 800 struct cfq_data *cfqd = q->elevator->elevator_data; 801 struct request *__rq; 802 803 __rq = cfq_find_rq_fmerge(cfqd, bio); 804 if (__rq && elv_rq_merge_ok(__rq, bio)) { 805 *req = __rq; 806 return ELEVATOR_FRONT_MERGE; 807 } 808 809 return ELEVATOR_NO_MERGE; 810} 811 812static void cfq_merged_request(struct request_queue *q, struct request *req, 813 int type) 814{ 815 if (type == ELEVATOR_FRONT_MERGE) { 816 struct cfq_queue *cfqq = RQ_CFQQ(req); 817 818 cfq_reposition_rq_rb(cfqq, req); 819 } 820} 821 822static void 823cfq_merged_requests(struct request_queue *q, struct request *rq, 824 struct request *next) 825{ 826 /* 827 * reposition in fifo if next is older than rq 828 */ 829 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && 830 time_before(next->start_time, rq->start_time)) 831 list_move(&rq->queuelist, &next->queuelist); 832 833 cfq_remove_request(next); 834} 835 836static int cfq_allow_merge(struct request_queue *q, struct request *rq, 837 struct bio *bio) 838{ 839 struct cfq_data *cfqd = q->elevator->elevator_data; 840 struct cfq_io_context *cic; 841 struct cfq_queue *cfqq; 842 843 /* 844 * Disallow merge of a sync bio into an async request. 845 */ 846 if (cfq_bio_sync(bio) && !rq_is_sync(rq)) 847 return 0; 848 849 /* 850 * Lookup the cfqq that this bio will be queued with. Allow 851 * merge only if rq is queued there. 852 */ 853 cic = cfq_cic_lookup(cfqd, current->io_context); 854 if (!cic) 855 return 0; 856 857 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); 858 if (cfqq == RQ_CFQQ(rq)) 859 return 1; 860 861 return 0; 862} 863 864static void __cfq_set_active_queue(struct cfq_data *cfqd, 865 struct cfq_queue *cfqq) 866{ 867 if (cfqq) { 868 cfq_log_cfqq(cfqd, cfqq, "set_active"); 869 cfqq->slice_end = 0; 870 cfqq->slice_dispatch = 0; 871 872 cfq_clear_cfqq_wait_request(cfqq); 873 cfq_clear_cfqq_must_dispatch(cfqq); 874 cfq_clear_cfqq_must_alloc_slice(cfqq); 875 cfq_clear_cfqq_fifo_expire(cfqq); 876 cfq_mark_cfqq_slice_new(cfqq); 877 878 del_timer(&cfqd->idle_slice_timer); 879 } 880 881 cfqd->active_queue = cfqq; 882} 883 884/* 885 * current cfqq expired its slice (or was too idle), select new one 886 */ 887static void 888__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, 889 int timed_out) 890{ 891 cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out); 892 893 if (cfq_cfqq_wait_request(cfqq)) 894 del_timer(&cfqd->idle_slice_timer); 895 896 cfq_clear_cfqq_wait_request(cfqq); 897 898 /* 899 * store what was left of this slice, if the queue idled/timed out 900 */ 901 if (timed_out && !cfq_cfqq_slice_new(cfqq)) { 902 cfqq->slice_resid = cfqq->slice_end - jiffies; 903 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid); 904 } 905 906 cfq_resort_rr_list(cfqd, cfqq); 907 908 if (cfqq == cfqd->active_queue) 909 cfqd->active_queue = NULL; 910 911 if (cfqd->active_cic) { 912 put_io_context(cfqd->active_cic->ioc); 913 cfqd->active_cic = NULL; 914 } 915} 916 917static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out) 918{ 919 struct cfq_queue *cfqq = cfqd->active_queue; 920 921 if (cfqq) 922 __cfq_slice_expired(cfqd, cfqq, timed_out); 923} 924 925/* 926 * Get next queue for service. Unless we have a queue preemption, 927 * we'll simply select the first cfqq in the service tree. 928 */ 929static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd) 930{ 931 if (RB_EMPTY_ROOT(&cfqd->service_tree.rb)) 932 return NULL; 933 934 return cfq_rb_first(&cfqd->service_tree); 935} 936 937/* 938 * Get and set a new active queue for service. 939 */ 940static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd, 941 struct cfq_queue *cfqq) 942{ 943 if (!cfqq) { 944 cfqq = cfq_get_next_queue(cfqd); 945 if (cfqq) 946 cfq_clear_cfqq_coop(cfqq); 947 } 948 949 __cfq_set_active_queue(cfqd, cfqq); 950 return cfqq; 951} 952 953static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd, 954 struct request *rq) 955{ 956 if (blk_rq_pos(rq) >= cfqd->last_position) 957 return blk_rq_pos(rq) - cfqd->last_position; 958 else 959 return cfqd->last_position - blk_rq_pos(rq); 960} 961 962#define CIC_SEEK_THR 8 * 1024 963#define CIC_SEEKY(cic) ((cic)->seek_mean > CIC_SEEK_THR) 964 965static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq) 966{ 967 struct cfq_io_context *cic = cfqd->active_cic; 968 sector_t sdist = cic->seek_mean; 969 970 if (!sample_valid(cic->seek_samples)) 971 sdist = CIC_SEEK_THR; 972 973 return cfq_dist_from_last(cfqd, rq) <= sdist; 974} 975 976static struct cfq_queue *cfqq_close(struct cfq_data *cfqd, 977 struct cfq_queue *cur_cfqq) 978{ 979 struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio]; 980 struct rb_node *parent, *node; 981 struct cfq_queue *__cfqq; 982 sector_t sector = cfqd->last_position; 983 984 if (RB_EMPTY_ROOT(root)) 985 return NULL; 986 987 /* 988 * First, if we find a request starting at the end of the last 989 * request, choose it. 990 */ 991 __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL); 992 if (__cfqq) 993 return __cfqq; 994 995 /* 996 * If the exact sector wasn't found, the parent of the NULL leaf 997 * will contain the closest sector. 998 */ 999 __cfqq = rb_entry(parent, struct cfq_queue, p_node); 1000 if (cfq_rq_close(cfqd, __cfqq->next_rq)) 1001 return __cfqq; 1002 1003 if (blk_rq_pos(__cfqq->next_rq) < sector) 1004 node = rb_next(&__cfqq->p_node); 1005 else 1006 node = rb_prev(&__cfqq->p_node); 1007 if (!node) 1008 return NULL; 1009 1010 __cfqq = rb_entry(node, struct cfq_queue, p_node); 1011 if (cfq_rq_close(cfqd, __cfqq->next_rq)) 1012 return __cfqq; 1013 1014 return NULL; 1015} 1016 1017/* 1018 * cfqd - obvious 1019 * cur_cfqq - passed in so that we don't decide that the current queue is 1020 * closely cooperating with itself. 1021 * 1022 * So, basically we're assuming that that cur_cfqq has dispatched at least 1023 * one request, and that cfqd->last_position reflects a position on the disk 1024 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid 1025 * assumption. 1026 */ 1027static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd, 1028 struct cfq_queue *cur_cfqq, 1029 int probe) 1030{ 1031 struct cfq_queue *cfqq; 1032 1033 /* 1034 * A valid cfq_io_context is necessary to compare requests against 1035 * the seek_mean of the current cfqq. 1036 */ 1037 if (!cfqd->active_cic) 1038 return NULL; 1039 1040 /* 1041 * We should notice if some of the queues are cooperating, eg 1042 * working closely on the same area of the disk. In that case, 1043 * we can group them together and don't waste time idling. 1044 */ 1045 cfqq = cfqq_close(cfqd, cur_cfqq); 1046 if (!cfqq) 1047 return NULL; 1048 1049 if (cfq_cfqq_coop(cfqq)) 1050 return NULL; 1051 1052 if (!probe) 1053 cfq_mark_cfqq_coop(cfqq); 1054 return cfqq; 1055} 1056 1057static void cfq_arm_slice_timer(struct cfq_data *cfqd) 1058{ 1059 struct cfq_queue *cfqq = cfqd->active_queue; 1060 struct cfq_io_context *cic; 1061 unsigned long sl; 1062 1063 /* 1064 * SSD device without seek penalty, disable idling. But only do so 1065 * for devices that support queuing, otherwise we still have a problem 1066 * with sync vs async workloads. 1067 */ 1068 if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag) 1069 return; 1070 1071 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list)); 1072 WARN_ON(cfq_cfqq_slice_new(cfqq)); 1073 1074 /* 1075 * idle is disabled, either manually or by past process history 1076 */ 1077 if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq)) 1078 return; 1079 1080 /* 1081 * still requests with the driver, don't idle 1082 */ 1083 if (cfqd->rq_in_driver) 1084 return; 1085 1086 /* 1087 * task has exited, don't wait 1088 */ 1089 cic = cfqd->active_cic; 1090 if (!cic || !atomic_read(&cic->ioc->nr_tasks)) 1091 return; 1092 1093 cfq_mark_cfqq_wait_request(cfqq); 1094 1095 /* 1096 * we don't want to idle for seeks, but we do want to allow 1097 * fair distribution of slice time for a process doing back-to-back 1098 * seeks. so allow a little bit of time for him to submit a new rq 1099 */ 1100 sl = cfqd->cfq_slice_idle; 1101 if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic)) 1102 sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT)); 1103 1104 mod_timer(&cfqd->idle_slice_timer, jiffies + sl); 1105 cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl); 1106} 1107 1108/* 1109 * Move request from internal lists to the request queue dispatch list. 1110 */ 1111static void cfq_dispatch_insert(struct request_queue *q, struct request *rq) 1112{ 1113 struct cfq_data *cfqd = q->elevator->elevator_data; 1114 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1115 1116 cfq_log_cfqq(cfqd, cfqq, "dispatch_insert"); 1117 1118 cfq_remove_request(rq); 1119 cfqq->dispatched++; 1120 elv_dispatch_sort(q, rq); 1121 1122 if (cfq_cfqq_sync(cfqq)) 1123 cfqd->sync_flight++; 1124} 1125 1126/* 1127 * return expired entry, or NULL to just start from scratch in rbtree 1128 */ 1129static struct request *cfq_check_fifo(struct cfq_queue *cfqq) 1130{ 1131 struct cfq_data *cfqd = cfqq->cfqd; 1132 struct request *rq; 1133 int fifo; 1134 1135 if (cfq_cfqq_fifo_expire(cfqq)) 1136 return NULL; 1137 1138 cfq_mark_cfqq_fifo_expire(cfqq); 1139 1140 if (list_empty(&cfqq->fifo)) 1141 return NULL; 1142 1143 fifo = cfq_cfqq_sync(cfqq); 1144 rq = rq_entry_fifo(cfqq->fifo.next); 1145 1146 if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) 1147 rq = NULL; 1148 1149 cfq_log_cfqq(cfqd, cfqq, "fifo=%p", rq); 1150 return rq; 1151} 1152 1153static inline int 1154cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1155{ 1156 const int base_rq = cfqd->cfq_slice_async_rq; 1157 1158 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR); 1159 1160 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio)); 1161} 1162 1163/* 1164 * Select a queue for service. If we have a current active queue, 1165 * check whether to continue servicing it, or retrieve and set a new one. 1166 */ 1167static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd) 1168{ 1169 struct cfq_queue *cfqq, *new_cfqq = NULL; 1170 1171 cfqq = cfqd->active_queue; 1172 if (!cfqq) 1173 goto new_queue; 1174 1175 /* 1176 * The active queue has run out of time, expire it and select new. 1177 */ 1178 if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) 1179 goto expire; 1180 1181 /* 1182 * If we have a RT cfqq waiting, then we pre-empt the current non-rt 1183 * cfqq. 1184 */ 1185 if (!cfq_class_rt(cfqq) && cfqd->busy_rt_queues) { 1186 /* 1187 * We simulate this as cfqq timed out so that it gets to bank 1188 * the remaining of its time slice. 1189 */ 1190 cfq_log_cfqq(cfqd, cfqq, "preempt"); 1191 cfq_slice_expired(cfqd, 1); 1192 goto new_queue; 1193 } 1194 1195 /* 1196 * The active queue has requests and isn't expired, allow it to 1197 * dispatch. 1198 */ 1199 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) 1200 goto keep_queue; 1201 1202 /* 1203 * If another queue has a request waiting within our mean seek 1204 * distance, let it run. The expire code will check for close 1205 * cooperators and put the close queue at the front of the service 1206 * tree. 1207 */ 1208 new_cfqq = cfq_close_cooperator(cfqd, cfqq, 0); 1209 if (new_cfqq) 1210 goto expire; 1211 1212 /* 1213 * No requests pending. If the active queue still has requests in 1214 * flight or is idling for a new request, allow either of these 1215 * conditions to happen (or time out) before selecting a new queue. 1216 */ 1217 if (timer_pending(&cfqd->idle_slice_timer) || 1218 (cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) { 1219 cfqq = NULL; 1220 goto keep_queue; 1221 } 1222 1223expire: 1224 cfq_slice_expired(cfqd, 0); 1225new_queue: 1226 cfqq = cfq_set_active_queue(cfqd, new_cfqq); 1227keep_queue: 1228 return cfqq; 1229} 1230 1231static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq) 1232{ 1233 int dispatched = 0; 1234 1235 while (cfqq->next_rq) { 1236 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq); 1237 dispatched++; 1238 } 1239 1240 BUG_ON(!list_empty(&cfqq->fifo)); 1241 return dispatched; 1242} 1243 1244/* 1245 * Drain our current requests. Used for barriers and when switching 1246 * io schedulers on-the-fly. 1247 */ 1248static int cfq_forced_dispatch(struct cfq_data *cfqd) 1249{ 1250 struct cfq_queue *cfqq; 1251 int dispatched = 0; 1252 1253 while ((cfqq = cfq_rb_first(&cfqd->service_tree)) != NULL) 1254 dispatched += __cfq_forced_dispatch_cfqq(cfqq); 1255 1256 cfq_slice_expired(cfqd, 0); 1257 1258 BUG_ON(cfqd->busy_queues); 1259 1260 cfq_log(cfqd, "forced_dispatch=%d", dispatched); 1261 return dispatched; 1262} 1263 1264/* 1265 * Dispatch a request from cfqq, moving them to the request queue 1266 * dispatch list. 1267 */ 1268static void cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1269{ 1270 struct request *rq; 1271 1272 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list)); 1273 1274 /* 1275 * follow expired path, else get first next available 1276 */ 1277 rq = cfq_check_fifo(cfqq); 1278 if (!rq) 1279 rq = cfqq->next_rq; 1280 1281 /* 1282 * insert request into driver dispatch list 1283 */ 1284 cfq_dispatch_insert(cfqd->queue, rq); 1285 1286 if (!cfqd->active_cic) { 1287 struct cfq_io_context *cic = RQ_CIC(rq); 1288 1289 atomic_long_inc(&cic->ioc->refcount); 1290 cfqd->active_cic = cic; 1291 } 1292} 1293 1294/* 1295 * Find the cfqq that we need to service and move a request from that to the 1296 * dispatch list 1297 */ 1298static int cfq_dispatch_requests(struct request_queue *q, int force) 1299{ 1300 struct cfq_data *cfqd = q->elevator->elevator_data; 1301 struct cfq_queue *cfqq; 1302 unsigned int max_dispatch; 1303 1304 if (!cfqd->busy_queues) 1305 return 0; 1306 1307 if (unlikely(force)) 1308 return cfq_forced_dispatch(cfqd); 1309 1310 cfqq = cfq_select_queue(cfqd); 1311 if (!cfqq) 1312 return 0; 1313 1314 /* 1315 * If this is an async queue and we have sync IO in flight, let it wait 1316 */ 1317 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq)) 1318 return 0; 1319 1320 max_dispatch = cfqd->cfq_quantum; 1321 if (cfq_class_idle(cfqq)) 1322 max_dispatch = 1; 1323 1324 /* 1325 * Does this cfqq already have too much IO in flight? 1326 */ 1327 if (cfqq->dispatched >= max_dispatch) { 1328 /* 1329 * idle queue must always only have a single IO in flight 1330 */ 1331 if (cfq_class_idle(cfqq)) 1332 return 0; 1333 1334 /* 1335 * We have other queues, don't allow more IO from this one 1336 */ 1337 if (cfqd->busy_queues > 1) 1338 return 0; 1339 1340 /* 1341 * we are the only queue, allow up to 4 times of 'quantum' 1342 */ 1343 if (cfqq->dispatched >= 4 * max_dispatch) 1344 return 0; 1345 } 1346 1347 /* 1348 * Dispatch a request from this cfqq 1349 */ 1350 cfq_dispatch_request(cfqd, cfqq); 1351 cfqq->slice_dispatch++; 1352 cfq_clear_cfqq_must_dispatch(cfqq); 1353 1354 /* 1355 * expire an async queue immediately if it has used up its slice. idle 1356 * queue always expire after 1 dispatch round. 1357 */ 1358 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) && 1359 cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) || 1360 cfq_class_idle(cfqq))) { 1361 cfqq->slice_end = jiffies + 1; 1362 cfq_slice_expired(cfqd, 0); 1363 } 1364 1365 cfq_log(cfqd, "dispatched a request"); 1366 return 1; 1367} 1368 1369/* 1370 * task holds one reference to the queue, dropped when task exits. each rq 1371 * in-flight on this queue also holds a reference, dropped when rq is freed. 1372 * 1373 * queue lock must be held here. 1374 */ 1375static void cfq_put_queue(struct cfq_queue *cfqq) 1376{ 1377 struct cfq_data *cfqd = cfqq->cfqd; 1378 1379 BUG_ON(atomic_read(&cfqq->ref) <= 0); 1380 1381 if (!atomic_dec_and_test(&cfqq->ref)) 1382 return; 1383 1384 cfq_log_cfqq(cfqd, cfqq, "put_queue"); 1385 BUG_ON(rb_first(&cfqq->sort_list)); 1386 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]); 1387 BUG_ON(cfq_cfqq_on_rr(cfqq)); 1388 1389 if (unlikely(cfqd->active_queue == cfqq)) { 1390 __cfq_slice_expired(cfqd, cfqq, 0); 1391 cfq_schedule_dispatch(cfqd); 1392 } 1393 1394 kmem_cache_free(cfq_pool, cfqq); 1395} 1396 1397/* 1398 * Must always be called with the rcu_read_lock() held 1399 */ 1400static void 1401__call_for_each_cic(struct io_context *ioc, 1402 void (*func)(struct io_context *, struct cfq_io_context *)) 1403{ 1404 struct cfq_io_context *cic; 1405 struct hlist_node *n; 1406 1407 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list) 1408 func(ioc, cic); 1409} 1410 1411/* 1412 * Call func for each cic attached to this ioc. 1413 */ 1414static void 1415call_for_each_cic(struct io_context *ioc, 1416 void (*func)(struct io_context *, struct cfq_io_context *)) 1417{ 1418 rcu_read_lock(); 1419 __call_for_each_cic(ioc, func); 1420 rcu_read_unlock(); 1421} 1422 1423static void cfq_cic_free_rcu(struct rcu_head *head) 1424{ 1425 struct cfq_io_context *cic; 1426 1427 cic = container_of(head, struct cfq_io_context, rcu_head); 1428 1429 kmem_cache_free(cfq_ioc_pool, cic); 1430 elv_ioc_count_dec(ioc_count); 1431 1432 if (ioc_gone) { 1433 /* 1434 * CFQ scheduler is exiting, grab exit lock and check 1435 * the pending io context count. If it hits zero, 1436 * complete ioc_gone and set it back to NULL 1437 */ 1438 spin_lock(&ioc_gone_lock); 1439 if (ioc_gone && !elv_ioc_count_read(ioc_count)) { 1440 complete(ioc_gone); 1441 ioc_gone = NULL; 1442 } 1443 spin_unlock(&ioc_gone_lock); 1444 } 1445} 1446 1447static void cfq_cic_free(struct cfq_io_context *cic) 1448{ 1449 call_rcu(&cic->rcu_head, cfq_cic_free_rcu); 1450} 1451 1452static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic) 1453{ 1454 unsigned long flags; 1455 1456 BUG_ON(!cic->dead_key); 1457 1458 spin_lock_irqsave(&ioc->lock, flags); 1459 radix_tree_delete(&ioc->radix_root, cic->dead_key); 1460 hlist_del_rcu(&cic->cic_list); 1461 spin_unlock_irqrestore(&ioc->lock, flags); 1462 1463 cfq_cic_free(cic); 1464} 1465 1466/* 1467 * Must be called with rcu_read_lock() held or preemption otherwise disabled. 1468 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(), 1469 * and ->trim() which is called with the task lock held 1470 */ 1471static void cfq_free_io_context(struct io_context *ioc) 1472{ 1473 /* 1474 * ioc->refcount is zero here, or we are called from elv_unregister(), 1475 * so no more cic's are allowed to be linked into this ioc. So it 1476 * should be ok to iterate over the known list, we will see all cic's 1477 * since no new ones are added. 1478 */ 1479 __call_for_each_cic(ioc, cic_free_func); 1480} 1481 1482static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1483{ 1484 if (unlikely(cfqq == cfqd->active_queue)) { 1485 __cfq_slice_expired(cfqd, cfqq, 0); 1486 cfq_schedule_dispatch(cfqd); 1487 } 1488 1489 cfq_put_queue(cfqq); 1490} 1491 1492static void __cfq_exit_single_io_context(struct cfq_data *cfqd, 1493 struct cfq_io_context *cic) 1494{ 1495 struct io_context *ioc = cic->ioc; 1496 1497 list_del_init(&cic->queue_list); 1498 1499 /* 1500 * Make sure key == NULL is seen for dead queues 1501 */ 1502 smp_wmb(); 1503 cic->dead_key = (unsigned long) cic->key; 1504 cic->key = NULL; 1505 1506 if (ioc->ioc_data == cic) 1507 rcu_assign_pointer(ioc->ioc_data, NULL); 1508 1509 if (cic->cfqq[BLK_RW_ASYNC]) { 1510 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]); 1511 cic->cfqq[BLK_RW_ASYNC] = NULL; 1512 } 1513 1514 if (cic->cfqq[BLK_RW_SYNC]) { 1515 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]); 1516 cic->cfqq[BLK_RW_SYNC] = NULL; 1517 } 1518} 1519 1520static void cfq_exit_single_io_context(struct io_context *ioc, 1521 struct cfq_io_context *cic) 1522{ 1523 struct cfq_data *cfqd = cic->key; 1524 1525 if (cfqd) { 1526 struct request_queue *q = cfqd->queue; 1527 unsigned long flags; 1528 1529 spin_lock_irqsave(q->queue_lock, flags); 1530 1531 /* 1532 * Ensure we get a fresh copy of the ->key to prevent 1533 * race between exiting task and queue 1534 */ 1535 smp_read_barrier_depends(); 1536 if (cic->key) 1537 __cfq_exit_single_io_context(cfqd, cic); 1538 1539 spin_unlock_irqrestore(q->queue_lock, flags); 1540 } 1541} 1542 1543/* 1544 * The process that ioc belongs to has exited, we need to clean up 1545 * and put the internal structures we have that belongs to that process. 1546 */ 1547static void cfq_exit_io_context(struct io_context *ioc) 1548{ 1549 call_for_each_cic(ioc, cfq_exit_single_io_context); 1550} 1551 1552static struct cfq_io_context * 1553cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 1554{ 1555 struct cfq_io_context *cic; 1556 1557 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO, 1558 cfqd->queue->node); 1559 if (cic) { 1560 cic->last_end_request = jiffies; 1561 INIT_LIST_HEAD(&cic->queue_list); 1562 INIT_HLIST_NODE(&cic->cic_list); 1563 cic->dtor = cfq_free_io_context; 1564 cic->exit = cfq_exit_io_context; 1565 elv_ioc_count_inc(ioc_count); 1566 } 1567 1568 return cic; 1569} 1570 1571static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc) 1572{ 1573 struct task_struct *tsk = current; 1574 int ioprio_class; 1575 1576 if (!cfq_cfqq_prio_changed(cfqq)) 1577 return; 1578 1579 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio); 1580 switch (ioprio_class) { 1581 default: 1582 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class); 1583 case IOPRIO_CLASS_NONE: 1584 /* 1585 * no prio set, inherit CPU scheduling settings 1586 */ 1587 cfqq->ioprio = task_nice_ioprio(tsk); 1588 cfqq->ioprio_class = task_nice_ioclass(tsk); 1589 break; 1590 case IOPRIO_CLASS_RT: 1591 cfqq->ioprio = task_ioprio(ioc); 1592 cfqq->ioprio_class = IOPRIO_CLASS_RT; 1593 break; 1594 case IOPRIO_CLASS_BE: 1595 cfqq->ioprio = task_ioprio(ioc); 1596 cfqq->ioprio_class = IOPRIO_CLASS_BE; 1597 break; 1598 case IOPRIO_CLASS_IDLE: 1599 cfqq->ioprio_class = IOPRIO_CLASS_IDLE; 1600 cfqq->ioprio = 7; 1601 cfq_clear_cfqq_idle_window(cfqq); 1602 break; 1603 } 1604 1605 /* 1606 * keep track of original prio settings in case we have to temporarily 1607 * elevate the priority of this queue 1608 */ 1609 cfqq->org_ioprio = cfqq->ioprio; 1610 cfqq->org_ioprio_class = cfqq->ioprio_class; 1611 cfq_clear_cfqq_prio_changed(cfqq); 1612} 1613 1614static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic) 1615{ 1616 struct cfq_data *cfqd = cic->key; 1617 struct cfq_queue *cfqq; 1618 unsigned long flags; 1619 1620 if (unlikely(!cfqd)) 1621 return; 1622 1623 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 1624 1625 cfqq = cic->cfqq[BLK_RW_ASYNC]; 1626 if (cfqq) { 1627 struct cfq_queue *new_cfqq; 1628 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc, 1629 GFP_ATOMIC); 1630 if (new_cfqq) { 1631 cic->cfqq[BLK_RW_ASYNC] = new_cfqq; 1632 cfq_put_queue(cfqq); 1633 } 1634 } 1635 1636 cfqq = cic->cfqq[BLK_RW_SYNC]; 1637 if (cfqq) 1638 cfq_mark_cfqq_prio_changed(cfqq); 1639 1640 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 1641} 1642 1643static void cfq_ioc_set_ioprio(struct io_context *ioc) 1644{ 1645 call_for_each_cic(ioc, changed_ioprio); 1646 ioc->ioprio_changed = 0; 1647} 1648 1649static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1650 pid_t pid, int is_sync) 1651{ 1652 RB_CLEAR_NODE(&cfqq->rb_node); 1653 RB_CLEAR_NODE(&cfqq->p_node); 1654 INIT_LIST_HEAD(&cfqq->fifo); 1655 1656 atomic_set(&cfqq->ref, 0); 1657 cfqq->cfqd = cfqd; 1658 1659 cfq_mark_cfqq_prio_changed(cfqq); 1660 1661 if (is_sync) { 1662 if (!cfq_class_idle(cfqq)) 1663 cfq_mark_cfqq_idle_window(cfqq); 1664 cfq_mark_cfqq_sync(cfqq); 1665 } 1666 cfqq->pid = pid; 1667} 1668 1669static struct cfq_queue * 1670cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync, 1671 struct io_context *ioc, gfp_t gfp_mask) 1672{ 1673 struct cfq_queue *cfqq, *new_cfqq = NULL; 1674 struct cfq_io_context *cic; 1675 1676retry: 1677 cic = cfq_cic_lookup(cfqd, ioc); 1678 /* cic always exists here */ 1679 cfqq = cic_to_cfqq(cic, is_sync); 1680 1681 /* 1682 * Always try a new alloc if we fell back to the OOM cfqq 1683 * originally, since it should just be a temporary situation. 1684 */ 1685 if (!cfqq || cfqq == &cfqd->oom_cfqq) { 1686 cfqq = NULL; 1687 if (new_cfqq) { 1688 cfqq = new_cfqq; 1689 new_cfqq = NULL; 1690 } else if (gfp_mask & __GFP_WAIT) { 1691 spin_unlock_irq(cfqd->queue->queue_lock); 1692 new_cfqq = kmem_cache_alloc_node(cfq_pool, 1693 gfp_mask | __GFP_ZERO, 1694 cfqd->queue->node); 1695 spin_lock_irq(cfqd->queue->queue_lock); 1696 if (new_cfqq) 1697 goto retry; 1698 } else { 1699 cfqq = kmem_cache_alloc_node(cfq_pool, 1700 gfp_mask | __GFP_ZERO, 1701 cfqd->queue->node); 1702 } 1703 1704 if (cfqq) { 1705 cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync); 1706 cfq_init_prio_data(cfqq, ioc); 1707 cfq_log_cfqq(cfqd, cfqq, "alloced"); 1708 } else 1709 cfqq = &cfqd->oom_cfqq; 1710 } 1711 1712 if (new_cfqq) 1713 kmem_cache_free(cfq_pool, new_cfqq); 1714 1715 return cfqq; 1716} 1717 1718static struct cfq_queue ** 1719cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio) 1720{ 1721 switch (ioprio_class) { 1722 case IOPRIO_CLASS_RT: 1723 return &cfqd->async_cfqq[0][ioprio]; 1724 case IOPRIO_CLASS_BE: 1725 return &cfqd->async_cfqq[1][ioprio]; 1726 case IOPRIO_CLASS_IDLE: 1727 return &cfqd->async_idle_cfqq; 1728 default: 1729 BUG(); 1730 } 1731} 1732 1733static struct cfq_queue * 1734cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc, 1735 gfp_t gfp_mask) 1736{ 1737 const int ioprio = task_ioprio(ioc); 1738 const int ioprio_class = task_ioprio_class(ioc); 1739 struct cfq_queue **async_cfqq = NULL; 1740 struct cfq_queue *cfqq = NULL; 1741 1742 if (!is_sync) { 1743 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio); 1744 cfqq = *async_cfqq; 1745 } 1746 1747 if (!cfqq) 1748 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask); 1749 1750 /* 1751 * pin the queue now that it's allocated, scheduler exit will prune it 1752 */ 1753 if (!is_sync && !(*async_cfqq)) { 1754 atomic_inc(&cfqq->ref); 1755 *async_cfqq = cfqq; 1756 } 1757 1758 atomic_inc(&cfqq->ref); 1759 return cfqq; 1760} 1761 1762/* 1763 * We drop cfq io contexts lazily, so we may find a dead one. 1764 */ 1765static void 1766cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc, 1767 struct cfq_io_context *cic) 1768{ 1769 unsigned long flags; 1770 1771 WARN_ON(!list_empty(&cic->queue_list)); 1772 1773 spin_lock_irqsave(&ioc->lock, flags); 1774 1775 BUG_ON(ioc->ioc_data == cic); 1776 1777 radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd); 1778 hlist_del_rcu(&cic->cic_list); 1779 spin_unlock_irqrestore(&ioc->lock, flags); 1780 1781 cfq_cic_free(cic); 1782} 1783 1784static struct cfq_io_context * 1785cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc) 1786{ 1787 struct cfq_io_context *cic; 1788 unsigned long flags; 1789 void *k; 1790 1791 if (unlikely(!ioc)) 1792 return NULL; 1793 1794 rcu_read_lock(); 1795 1796 /* 1797 * we maintain a last-hit cache, to avoid browsing over the tree 1798 */ 1799 cic = rcu_dereference(ioc->ioc_data); 1800 if (cic && cic->key == cfqd) { 1801 rcu_read_unlock(); 1802 return cic; 1803 } 1804 1805 do { 1806 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd); 1807 rcu_read_unlock(); 1808 if (!cic) 1809 break; 1810 /* ->key must be copied to avoid race with cfq_exit_queue() */ 1811 k = cic->key; 1812 if (unlikely(!k)) { 1813 cfq_drop_dead_cic(cfqd, ioc, cic); 1814 rcu_read_lock(); 1815 continue; 1816 } 1817 1818 spin_lock_irqsave(&ioc->lock, flags); 1819 rcu_assign_pointer(ioc->ioc_data, cic); 1820 spin_unlock_irqrestore(&ioc->lock, flags); 1821 break; 1822 } while (1); 1823 1824 return cic; 1825} 1826 1827/* 1828 * Add cic into ioc, using cfqd as the search key. This enables us to lookup 1829 * the process specific cfq io context when entered from the block layer. 1830 * Also adds the cic to a per-cfqd list, used when this queue is removed. 1831 */ 1832static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc, 1833 struct cfq_io_context *cic, gfp_t gfp_mask) 1834{ 1835 unsigned long flags; 1836 int ret; 1837 1838 ret = radix_tree_preload(gfp_mask); 1839 if (!ret) { 1840 cic->ioc = ioc; 1841 cic->key = cfqd; 1842 1843 spin_lock_irqsave(&ioc->lock, flags); 1844 ret = radix_tree_insert(&ioc->radix_root, 1845 (unsigned long) cfqd, cic); 1846 if (!ret) 1847 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list); 1848 spin_unlock_irqrestore(&ioc->lock, flags); 1849 1850 radix_tree_preload_end(); 1851 1852 if (!ret) { 1853 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 1854 list_add(&cic->queue_list, &cfqd->cic_list); 1855 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 1856 } 1857 } 1858 1859 if (ret) 1860 printk(KERN_ERR "cfq: cic link failed!\n"); 1861 1862 return ret; 1863} 1864 1865/* 1866 * Setup general io context and cfq io context. There can be several cfq 1867 * io contexts per general io context, if this process is doing io to more 1868 * than one device managed by cfq. 1869 */ 1870static struct cfq_io_context * 1871cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 1872{ 1873 struct io_context *ioc = NULL; 1874 struct cfq_io_context *cic; 1875 1876 might_sleep_if(gfp_mask & __GFP_WAIT); 1877 1878 ioc = get_io_context(gfp_mask, cfqd->queue->node); 1879 if (!ioc) 1880 return NULL; 1881 1882 cic = cfq_cic_lookup(cfqd, ioc); 1883 if (cic) 1884 goto out; 1885 1886 cic = cfq_alloc_io_context(cfqd, gfp_mask); 1887 if (cic == NULL) 1888 goto err; 1889 1890 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask)) 1891 goto err_free; 1892 1893out: 1894 smp_read_barrier_depends(); 1895 if (unlikely(ioc->ioprio_changed)) 1896 cfq_ioc_set_ioprio(ioc); 1897 1898 return cic; 1899err_free: 1900 cfq_cic_free(cic); 1901err: 1902 put_io_context(ioc); 1903 return NULL; 1904} 1905 1906static void 1907cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic) 1908{ 1909 unsigned long elapsed = jiffies - cic->last_end_request; 1910 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle); 1911 1912 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8; 1913 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8; 1914 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples; 1915} 1916 1917static void 1918cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic, 1919 struct request *rq) 1920{ 1921 sector_t sdist; 1922 u64 total; 1923 1924 if (!cic->last_request_pos) 1925 sdist = 0; 1926 else if (cic->last_request_pos < blk_rq_pos(rq)) 1927 sdist = blk_rq_pos(rq) - cic->last_request_pos; 1928 else 1929 sdist = cic->last_request_pos - blk_rq_pos(rq); 1930 1931 /* 1932 * Don't allow the seek distance to get too large from the 1933 * odd fragment, pagein, etc 1934 */ 1935 if (cic->seek_samples <= 60) /* second&third seek */ 1936 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024); 1937 else 1938 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64); 1939 1940 cic->seek_samples = (7*cic->seek_samples + 256) / 8; 1941 cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8; 1942 total = cic->seek_total + (cic->seek_samples/2); 1943 do_div(total, cic->seek_samples); 1944 cic->seek_mean = (sector_t)total; 1945} 1946 1947/* 1948 * Disable idle window if the process thinks too long or seeks so much that 1949 * it doesn't matter 1950 */ 1951static void 1952cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1953 struct cfq_io_context *cic) 1954{ 1955 int old_idle, enable_idle; 1956 1957 /* 1958 * Don't idle for async or idle io prio class 1959 */ 1960 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq)) 1961 return; 1962 1963 enable_idle = old_idle = cfq_cfqq_idle_window(cfqq); 1964 1965 if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle || 1966 (cfqd->hw_tag && CIC_SEEKY(cic))) 1967 enable_idle = 0; 1968 else if (sample_valid(cic->ttime_samples)) { 1969 if (cic->ttime_mean > cfqd->cfq_slice_idle) 1970 enable_idle = 0; 1971 else 1972 enable_idle = 1; 1973 } 1974 1975 if (old_idle != enable_idle) { 1976 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle); 1977 if (enable_idle) 1978 cfq_mark_cfqq_idle_window(cfqq); 1979 else 1980 cfq_clear_cfqq_idle_window(cfqq); 1981 } 1982} 1983 1984/* 1985 * Check if new_cfqq should preempt the currently active queue. Return 0 for 1986 * no or if we aren't sure, a 1 will cause a preempt. 1987 */ 1988static int 1989cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, 1990 struct request *rq) 1991{ 1992 struct cfq_queue *cfqq; 1993 1994 cfqq = cfqd->active_queue; 1995 if (!cfqq) 1996 return 0; 1997 1998 if (cfq_slice_used(cfqq)) 1999 return 1; 2000 2001 if (cfq_class_idle(new_cfqq)) 2002 return 0; 2003 2004 if (cfq_class_idle(cfqq)) 2005 return 1; 2006 2007 /* 2008 * if the new request is sync, but the currently running queue is 2009 * not, let the sync request have priority. 2010 */ 2011 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq)) 2012 return 1; 2013 2014 /* 2015 * So both queues are sync. Let the new request get disk time if 2016 * it's a metadata request and the current queue is doing regular IO. 2017 */ 2018 if (rq_is_meta(rq) && !cfqq->meta_pending) 2019 return 1; 2020 2021 /* 2022 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice. 2023 */ 2024 if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq)) 2025 return 1; 2026 2027 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq)) 2028 return 0; 2029 2030 /* 2031 * if this request is as-good as one we would expect from the 2032 * current cfqq, let it preempt 2033 */ 2034 if (cfq_rq_close(cfqd, rq)) 2035 return 1; 2036 2037 return 0; 2038} 2039 2040/* 2041 * cfqq preempts the active queue. if we allowed preempt with no slice left, 2042 * let it have half of its nominal slice. 2043 */ 2044static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) 2045{ 2046 cfq_log_cfqq(cfqd, cfqq, "preempt"); 2047 cfq_slice_expired(cfqd, 1); 2048 2049 /* 2050 * Put the new queue at the front of the of the current list, 2051 * so we know that it will be selected next. 2052 */ 2053 BUG_ON(!cfq_cfqq_on_rr(cfqq)); 2054 2055 cfq_service_tree_add(cfqd, cfqq, 1); 2056 2057 cfqq->slice_end = 0; 2058 cfq_mark_cfqq_slice_new(cfqq); 2059} 2060 2061/* 2062 * Called when a new fs request (rq) is added (to cfqq). Check if there's 2063 * something we should do about it 2064 */ 2065static void 2066cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq, 2067 struct request *rq) 2068{ 2069 struct cfq_io_context *cic = RQ_CIC(rq); 2070 2071 cfqd->rq_queued++; 2072 if (rq_is_meta(rq)) 2073 cfqq->meta_pending++; 2074 2075 cfq_update_io_thinktime(cfqd, cic); 2076 cfq_update_io_seektime(cfqd, cic, rq); 2077 cfq_update_idle_window(cfqd, cfqq, cic); 2078 2079 cic->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq); 2080 2081 if (cfqq == cfqd->active_queue) { 2082 /* 2083 * Remember that we saw a request from this process, but 2084 * don't start queuing just yet. Otherwise we risk seeing lots 2085 * of tiny requests, because we disrupt the normal plugging 2086 * and merging. If the request is already larger than a single 2087 * page, let it rip immediately. For that case we assume that 2088 * merging is already done. Ditto for a busy system that 2089 * has other work pending, don't risk delaying until the 2090 * idle timer unplug to continue working. 2091 */ 2092 if (cfq_cfqq_wait_request(cfqq)) { 2093 if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE || 2094 cfqd->busy_queues > 1) { 2095 del_timer(&cfqd->idle_slice_timer); 2096 __blk_run_queue(cfqd->queue); 2097 } 2098 cfq_mark_cfqq_must_dispatch(cfqq); 2099 } 2100 } else if (cfq_should_preempt(cfqd, cfqq, rq)) { 2101 /* 2102 * not the active queue - expire current slice if it is 2103 * idle and has expired it's mean thinktime or this new queue 2104 * has some old slice time left and is of higher priority or 2105 * this new queue is RT and the current one is BE 2106 */ 2107 cfq_preempt_queue(cfqd, cfqq); 2108 __blk_run_queue(cfqd->queue); 2109 } 2110} 2111 2112static void cfq_insert_request(struct request_queue *q, struct request *rq) 2113{ 2114 struct cfq_data *cfqd = q->elevator->elevator_data; 2115 struct cfq_queue *cfqq = RQ_CFQQ(rq); 2116 2117 cfq_log_cfqq(cfqd, cfqq, "insert_request"); 2118 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc); 2119 2120 cfq_add_rq_rb(rq); 2121 2122 list_add_tail(&rq->queuelist, &cfqq->fifo); 2123 2124 cfq_rq_enqueued(cfqd, cfqq, rq); 2125} 2126 2127/* 2128 * Update hw_tag based on peak queue depth over 50 samples under 2129 * sufficient load. 2130 */ 2131static void cfq_update_hw_tag(struct cfq_data *cfqd) 2132{ 2133 if (cfqd->rq_in_driver > cfqd->rq_in_driver_peak) 2134 cfqd->rq_in_driver_peak = cfqd->rq_in_driver; 2135 2136 if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN && 2137 cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN) 2138 return; 2139 2140 if (cfqd->hw_tag_samples++ < 50) 2141 return; 2142 2143 if (cfqd->rq_in_driver_peak >= CFQ_HW_QUEUE_MIN) 2144 cfqd->hw_tag = 1; 2145 else 2146 cfqd->hw_tag = 0; 2147 2148 cfqd->hw_tag_samples = 0; 2149 cfqd->rq_in_driver_peak = 0; 2150} 2151 2152static void cfq_completed_request(struct request_queue *q, struct request *rq) 2153{ 2154 struct cfq_queue *cfqq = RQ_CFQQ(rq); 2155 struct cfq_data *cfqd = cfqq->cfqd; 2156 const int sync = rq_is_sync(rq); 2157 unsigned long now; 2158 2159 now = jiffies; 2160 cfq_log_cfqq(cfqd, cfqq, "complete"); 2161 2162 cfq_update_hw_tag(cfqd); 2163 2164 WARN_ON(!cfqd->rq_in_driver); 2165 WARN_ON(!cfqq->dispatched); 2166 cfqd->rq_in_driver--; 2167 cfqq->dispatched--; 2168 2169 if (cfq_cfqq_sync(cfqq)) 2170 cfqd->sync_flight--; 2171 2172 if (sync) 2173 RQ_CIC(rq)->last_end_request = now; 2174 2175 /* 2176 * If this is the active queue, check if it needs to be expired, 2177 * or if we want to idle in case it has no pending requests. 2178 */ 2179 if (cfqd->active_queue == cfqq) { 2180 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list); 2181 2182 if (cfq_cfqq_slice_new(cfqq)) { 2183 cfq_set_prio_slice(cfqd, cfqq); 2184 cfq_clear_cfqq_slice_new(cfqq); 2185 } 2186 /* 2187 * If there are no requests waiting in this queue, and 2188 * there are other queues ready to issue requests, AND 2189 * those other queues are issuing requests within our 2190 * mean seek distance, give them a chance to run instead 2191 * of idling. 2192 */ 2193 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq)) 2194 cfq_slice_expired(cfqd, 1); 2195 else if (cfqq_empty && !cfq_close_cooperator(cfqd, cfqq, 1) && 2196 sync && !rq_noidle(rq)) 2197 cfq_arm_slice_timer(cfqd); 2198 } 2199 2200 if (!cfqd->rq_in_driver) 2201 cfq_schedule_dispatch(cfqd); 2202} 2203 2204/* 2205 * we temporarily boost lower priority queues if they are holding fs exclusive 2206 * resources. they are boosted to normal prio (CLASS_BE/4) 2207 */ 2208static void cfq_prio_boost(struct cfq_queue *cfqq) 2209{ 2210 if (has_fs_excl()) { 2211 /* 2212 * boost idle prio on transactions that would lock out other 2213 * users of the filesystem 2214 */ 2215 if (cfq_class_idle(cfqq)) 2216 cfqq->ioprio_class = IOPRIO_CLASS_BE; 2217 if (cfqq->ioprio > IOPRIO_NORM) 2218 cfqq->ioprio = IOPRIO_NORM; 2219 } else { 2220 /* 2221 * check if we need to unboost the queue 2222 */ 2223 if (cfqq->ioprio_class != cfqq->org_ioprio_class) 2224 cfqq->ioprio_class = cfqq->org_ioprio_class; 2225 if (cfqq->ioprio != cfqq->org_ioprio) 2226 cfqq->ioprio = cfqq->org_ioprio; 2227 } 2228} 2229 2230static inline int __cfq_may_queue(struct cfq_queue *cfqq) 2231{ 2232 if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) && 2233 !cfq_cfqq_must_alloc_slice(cfqq)) { 2234 cfq_mark_cfqq_must_alloc_slice(cfqq); 2235 return ELV_MQUEUE_MUST; 2236 } 2237 2238 return ELV_MQUEUE_MAY; 2239} 2240 2241static int cfq_may_queue(struct request_queue *q, int rw) 2242{ 2243 struct cfq_data *cfqd = q->elevator->elevator_data; 2244 struct task_struct *tsk = current; 2245 struct cfq_io_context *cic; 2246 struct cfq_queue *cfqq; 2247 2248 /* 2249 * don't force setup of a queue from here, as a call to may_queue 2250 * does not necessarily imply that a request actually will be queued. 2251 * so just lookup a possibly existing queue, or return 'may queue' 2252 * if that fails 2253 */ 2254 cic = cfq_cic_lookup(cfqd, tsk->io_context); 2255 if (!cic) 2256 return ELV_MQUEUE_MAY; 2257 2258 cfqq = cic_to_cfqq(cic, rw_is_sync(rw)); 2259 if (cfqq) { 2260 cfq_init_prio_data(cfqq, cic->ioc); 2261 cfq_prio_boost(cfqq); 2262 2263 return __cfq_may_queue(cfqq); 2264 } 2265 2266 return ELV_MQUEUE_MAY; 2267} 2268 2269/* 2270 * queue lock held here 2271 */ 2272static void cfq_put_request(struct request *rq) 2273{ 2274 struct cfq_queue *cfqq = RQ_CFQQ(rq); 2275 2276 if (cfqq) { 2277 const int rw = rq_data_dir(rq); 2278 2279 BUG_ON(!cfqq->allocated[rw]); 2280 cfqq->allocated[rw]--; 2281 2282 put_io_context(RQ_CIC(rq)->ioc); 2283 2284 rq->elevator_private = NULL; 2285 rq->elevator_private2 = NULL; 2286 2287 cfq_put_queue(cfqq); 2288 } 2289} 2290 2291/* 2292 * Allocate cfq data structures associated with this request. 2293 */ 2294static int 2295cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) 2296{ 2297 struct cfq_data *cfqd = q->elevator->elevator_data; 2298 struct cfq_io_context *cic; 2299 const int rw = rq_data_dir(rq); 2300 const int is_sync = rq_is_sync(rq); 2301 struct cfq_queue *cfqq; 2302 unsigned long flags; 2303 2304 might_sleep_if(gfp_mask & __GFP_WAIT); 2305 2306 cic = cfq_get_io_context(cfqd, gfp_mask); 2307 2308 spin_lock_irqsave(q->queue_lock, flags); 2309 2310 if (!cic) 2311 goto queue_fail; 2312 2313 cfqq = cic_to_cfqq(cic, is_sync); 2314 if (!cfqq) { 2315 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask); 2316 cic_set_cfqq(cic, cfqq, is_sync); 2317 } 2318 2319 cfqq->allocated[rw]++; 2320 cfq_clear_cfqq_must_alloc(cfqq); 2321 atomic_inc(&cfqq->ref); 2322 2323 spin_unlock_irqrestore(q->queue_lock, flags); 2324 2325 rq->elevator_private = cic; 2326 rq->elevator_private2 = cfqq; 2327 return 0; 2328 2329queue_fail: 2330 if (cic) 2331 put_io_context(cic->ioc); 2332 2333 cfq_schedule_dispatch(cfqd); 2334 spin_unlock_irqrestore(q->queue_lock, flags); 2335 cfq_log(cfqd, "set_request fail"); 2336 return 1; 2337} 2338 2339static void cfq_kick_queue(struct work_struct *work) 2340{ 2341 struct cfq_data *cfqd = 2342 container_of(work, struct cfq_data, unplug_work); 2343 struct request_queue *q = cfqd->queue; 2344 2345 spin_lock_irq(q->queue_lock); 2346 __blk_run_queue(cfqd->queue); 2347 spin_unlock_irq(q->queue_lock); 2348} 2349 2350/* 2351 * Timer running if the active_queue is currently idling inside its time slice 2352 */ 2353static void cfq_idle_slice_timer(unsigned long data) 2354{ 2355 struct cfq_data *cfqd = (struct cfq_data *) data; 2356 struct cfq_queue *cfqq; 2357 unsigned long flags; 2358 int timed_out = 1; 2359 2360 cfq_log(cfqd, "idle timer fired"); 2361 2362 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 2363 2364 cfqq = cfqd->active_queue; 2365 if (cfqq) { 2366 timed_out = 0; 2367 2368 /* 2369 * We saw a request before the queue expired, let it through 2370 */ 2371 if (cfq_cfqq_must_dispatch(cfqq)) 2372 goto out_kick; 2373 2374 /* 2375 * expired 2376 */ 2377 if (cfq_slice_used(cfqq)) 2378 goto expire; 2379 2380 /* 2381 * only expire and reinvoke request handler, if there are 2382 * other queues with pending requests 2383 */ 2384 if (!cfqd->busy_queues) 2385 goto out_cont; 2386 2387 /* 2388 * not expired and it has a request pending, let it dispatch 2389 */ 2390 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) 2391 goto out_kick; 2392 } 2393expire: 2394 cfq_slice_expired(cfqd, timed_out); 2395out_kick: 2396 cfq_schedule_dispatch(cfqd); 2397out_cont: 2398 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 2399} 2400 2401static void cfq_shutdown_timer_wq(struct cfq_data *cfqd) 2402{ 2403 del_timer_sync(&cfqd->idle_slice_timer); 2404 cancel_work_sync(&cfqd->unplug_work); 2405} 2406 2407static void cfq_put_async_queues(struct cfq_data *cfqd) 2408{ 2409 int i; 2410 2411 for (i = 0; i < IOPRIO_BE_NR; i++) { 2412 if (cfqd->async_cfqq[0][i]) 2413 cfq_put_queue(cfqd->async_cfqq[0][i]); 2414 if (cfqd->async_cfqq[1][i]) 2415 cfq_put_queue(cfqd->async_cfqq[1][i]); 2416 } 2417 2418 if (cfqd->async_idle_cfqq) 2419 cfq_put_queue(cfqd->async_idle_cfqq); 2420} 2421 2422static void cfq_exit_queue(struct elevator_queue *e) 2423{ 2424 struct cfq_data *cfqd = e->elevator_data; 2425 struct request_queue *q = cfqd->queue; 2426 2427 cfq_shutdown_timer_wq(cfqd); 2428 2429 spin_lock_irq(q->queue_lock); 2430 2431 if (cfqd->active_queue) 2432 __cfq_slice_expired(cfqd, cfqd->active_queue, 0); 2433 2434 while (!list_empty(&cfqd->cic_list)) { 2435 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next, 2436 struct cfq_io_context, 2437 queue_list); 2438 2439 __cfq_exit_single_io_context(cfqd, cic); 2440 } 2441 2442 cfq_put_async_queues(cfqd); 2443 2444 spin_unlock_irq(q->queue_lock); 2445 2446 cfq_shutdown_timer_wq(cfqd); 2447 2448 kfree(cfqd); 2449} 2450 2451static void *cfq_init_queue(struct request_queue *q) 2452{ 2453 struct cfq_data *cfqd; 2454 int i; 2455 2456 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node); 2457 if (!cfqd) 2458 return NULL; 2459 2460 cfqd->service_tree = CFQ_RB_ROOT; 2461 2462 /* 2463 * Not strictly needed (since RB_ROOT just clears the node and we 2464 * zeroed cfqd on alloc), but better be safe in case someone decides 2465 * to add magic to the rb code 2466 */ 2467 for (i = 0; i < CFQ_PRIO_LISTS; i++) 2468 cfqd->prio_trees[i] = RB_ROOT; 2469 2470 /* 2471 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues. 2472 * Grab a permanent reference to it, so that the normal code flow 2473 * will not attempt to free it. 2474 */ 2475 cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0); 2476 atomic_inc(&cfqd->oom_cfqq.ref); 2477 2478 INIT_LIST_HEAD(&cfqd->cic_list); 2479 2480 cfqd->queue = q; 2481 2482 init_timer(&cfqd->idle_slice_timer); 2483 cfqd->idle_slice_timer.function = cfq_idle_slice_timer; 2484 cfqd->idle_slice_timer.data = (unsigned long) cfqd; 2485 2486 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue); 2487 2488 cfqd->cfq_quantum = cfq_quantum; 2489 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0]; 2490 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1]; 2491 cfqd->cfq_back_max = cfq_back_max; 2492 cfqd->cfq_back_penalty = cfq_back_penalty; 2493 cfqd->cfq_slice[0] = cfq_slice_async; 2494 cfqd->cfq_slice[1] = cfq_slice_sync; 2495 cfqd->cfq_slice_async_rq = cfq_slice_async_rq; 2496 cfqd->cfq_slice_idle = cfq_slice_idle; 2497 cfqd->hw_tag = 1; 2498 2499 return cfqd; 2500} 2501 2502static void cfq_slab_kill(void) 2503{ 2504 /* 2505 * Caller already ensured that pending RCU callbacks are completed, 2506 * so we should have no busy allocations at this point. 2507 */ 2508 if (cfq_pool) 2509 kmem_cache_destroy(cfq_pool); 2510 if (cfq_ioc_pool) 2511 kmem_cache_destroy(cfq_ioc_pool); 2512} 2513 2514static int __init cfq_slab_setup(void) 2515{ 2516 cfq_pool = KMEM_CACHE(cfq_queue, 0); 2517 if (!cfq_pool) 2518 goto fail; 2519 2520 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0); 2521 if (!cfq_ioc_pool) 2522 goto fail; 2523 2524 return 0; 2525fail: 2526 cfq_slab_kill(); 2527 return -ENOMEM; 2528} 2529 2530/* 2531 * sysfs parts below --> 2532 */ 2533static ssize_t 2534cfq_var_show(unsigned int var, char *page) 2535{ 2536 return sprintf(page, "%d\n", var); 2537} 2538 2539static ssize_t 2540cfq_var_store(unsigned int *var, const char *page, size_t count) 2541{ 2542 char *p = (char *) page; 2543 2544 *var = simple_strtoul(p, &p, 10); 2545 return count; 2546} 2547 2548#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ 2549static ssize_t __FUNC(struct elevator_queue *e, char *page) \ 2550{ \ 2551 struct cfq_data *cfqd = e->elevator_data; \ 2552 unsigned int __data = __VAR; \ 2553 if (__CONV) \ 2554 __data = jiffies_to_msecs(__data); \ 2555 return cfq_var_show(__data, (page)); \ 2556} 2557SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0); 2558SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1); 2559SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1); 2560SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0); 2561SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0); 2562SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1); 2563SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1); 2564SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1); 2565SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0); 2566#undef SHOW_FUNCTION 2567 2568#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ 2569static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ 2570{ \ 2571 struct cfq_data *cfqd = e->elevator_data; \ 2572 unsigned int __data; \ 2573 int ret = cfq_var_store(&__data, (page), count); \ 2574 if (__data < (MIN)) \ 2575 __data = (MIN); \ 2576 else if (__data > (MAX)) \ 2577 __data = (MAX); \ 2578 if (__CONV) \ 2579 *(__PTR) = msecs_to_jiffies(__data); \ 2580 else \ 2581 *(__PTR) = __data; \ 2582 return ret; \ 2583} 2584STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0); 2585STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, 2586 UINT_MAX, 1); 2587STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, 2588 UINT_MAX, 1); 2589STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0); 2590STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, 2591 UINT_MAX, 0); 2592STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1); 2593STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1); 2594STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1); 2595STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, 2596 UINT_MAX, 0); 2597#undef STORE_FUNCTION 2598 2599#define CFQ_ATTR(name) \ 2600 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store) 2601 2602static struct elv_fs_entry cfq_attrs[] = { 2603 CFQ_ATTR(quantum), 2604 CFQ_ATTR(fifo_expire_sync), 2605 CFQ_ATTR(fifo_expire_async), 2606 CFQ_ATTR(back_seek_max), 2607 CFQ_ATTR(back_seek_penalty), 2608 CFQ_ATTR(slice_sync), 2609 CFQ_ATTR(slice_async), 2610 CFQ_ATTR(slice_async_rq), 2611 CFQ_ATTR(slice_idle), 2612 __ATTR_NULL 2613}; 2614 2615static struct elevator_type iosched_cfq = { 2616 .ops = { 2617 .elevator_merge_fn = cfq_merge, 2618 .elevator_merged_fn = cfq_merged_request, 2619 .elevator_merge_req_fn = cfq_merged_requests, 2620 .elevator_allow_merge_fn = cfq_allow_merge, 2621 .elevator_dispatch_fn = cfq_dispatch_requests, 2622 .elevator_add_req_fn = cfq_insert_request, 2623 .elevator_activate_req_fn = cfq_activate_request, 2624 .elevator_deactivate_req_fn = cfq_deactivate_request, 2625 .elevator_queue_empty_fn = cfq_queue_empty, 2626 .elevator_completed_req_fn = cfq_completed_request, 2627 .elevator_former_req_fn = elv_rb_former_request, 2628 .elevator_latter_req_fn = elv_rb_latter_request, 2629 .elevator_set_req_fn = cfq_set_request, 2630 .elevator_put_req_fn = cfq_put_request, 2631 .elevator_may_queue_fn = cfq_may_queue, 2632 .elevator_init_fn = cfq_init_queue, 2633 .elevator_exit_fn = cfq_exit_queue, 2634 .trim = cfq_free_io_context, 2635 }, 2636 .elevator_attrs = cfq_attrs, 2637 .elevator_name = "cfq", 2638 .elevator_owner = THIS_MODULE, 2639}; 2640 2641static int __init cfq_init(void) 2642{ 2643 /* 2644 * could be 0 on HZ < 1000 setups 2645 */ 2646 if (!cfq_slice_async) 2647 cfq_slice_async = 1; 2648 if (!cfq_slice_idle) 2649 cfq_slice_idle = 1; 2650 2651 if (cfq_slab_setup()) 2652 return -ENOMEM; 2653 2654 elv_register(&iosched_cfq); 2655 2656 return 0; 2657} 2658 2659static void __exit cfq_exit(void) 2660{ 2661 DECLARE_COMPLETION_ONSTACK(all_gone); 2662 elv_unregister(&iosched_cfq); 2663 ioc_gone = &all_gone; 2664 /* ioc_gone's update must be visible before reading ioc_count */ 2665 smp_wmb(); 2666 2667 /* 2668 * this also protects us from entering cfq_slab_kill() with 2669 * pending RCU callbacks 2670 */ 2671 if (elv_ioc_count_read(ioc_count)) 2672 wait_for_completion(&all_gone); 2673 cfq_slab_kill(); 2674} 2675 2676module_init(cfq_init); 2677module_exit(cfq_exit); 2678 2679MODULE_AUTHOR("Jens Axboe"); 2680MODULE_LICENSE("GPL"); 2681MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler"); 2682