cfq-iosched.c revision 3a9a3f6cc55418dd1525e636dccbbe13c394f652
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 ASYNC (0) 60#define SYNC (1) 61 62#define sample_valid(samples) ((samples) > 80) 63 64/* 65 * Most of our rbtree usage is for sorting with min extraction, so 66 * if we cache the leftmost node we don't have to walk down the tree 67 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should 68 * move this into the elevator for the rq sorting as well. 69 */ 70struct cfq_rb_root { 71 struct rb_root rb; 72 struct rb_node *left; 73}; 74#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, } 75 76/* 77 * Per block device queue structure 78 */ 79struct cfq_data { 80 struct request_queue *queue; 81 82 /* 83 * rr list of queues with requests and the count of them 84 */ 85 struct cfq_rb_root service_tree; 86 unsigned int busy_queues; 87 /* 88 * Used to track any pending rt requests so we can pre-empt current 89 * non-RT cfqq in service when this value is non-zero. 90 */ 91 unsigned int busy_rt_queues; 92 93 int rq_in_driver; 94 int sync_flight; 95 96 /* 97 * queue-depth detection 98 */ 99 int rq_queued; 100 int hw_tag; 101 int hw_tag_samples; 102 int rq_in_driver_peak; 103 104 /* 105 * idle window management 106 */ 107 struct timer_list idle_slice_timer; 108 struct work_struct unplug_work; 109 110 struct cfq_queue *active_queue; 111 struct cfq_io_context *active_cic; 112 113 /* 114 * async queue for each priority case 115 */ 116 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR]; 117 struct cfq_queue *async_idle_cfqq; 118 119 sector_t last_position; 120 unsigned long last_end_request; 121 122 /* 123 * tunables, see top of file 124 */ 125 unsigned int cfq_quantum; 126 unsigned int cfq_fifo_expire[2]; 127 unsigned int cfq_back_penalty; 128 unsigned int cfq_back_max; 129 unsigned int cfq_slice[2]; 130 unsigned int cfq_slice_async_rq; 131 unsigned int cfq_slice_idle; 132 133 struct list_head cic_list; 134}; 135 136/* 137 * Per process-grouping structure 138 */ 139struct cfq_queue { 140 /* reference count */ 141 atomic_t ref; 142 /* various state flags, see below */ 143 unsigned int flags; 144 /* parent cfq_data */ 145 struct cfq_data *cfqd; 146 /* service_tree member */ 147 struct rb_node rb_node; 148 /* service_tree key */ 149 unsigned long rb_key; 150 /* sorted list of pending requests */ 151 struct rb_root sort_list; 152 /* if fifo isn't expired, next request to serve */ 153 struct request *next_rq; 154 /* requests queued in sort_list */ 155 int queued[2]; 156 /* currently allocated requests */ 157 int allocated[2]; 158 /* fifo list of requests in sort_list */ 159 struct list_head fifo; 160 161 unsigned long slice_end; 162 long slice_resid; 163 164 /* pending metadata requests */ 165 int meta_pending; 166 /* number of requests that are on the dispatch list or inside driver */ 167 int dispatched; 168 169 /* io prio of this group */ 170 unsigned short ioprio, org_ioprio; 171 unsigned short ioprio_class, org_ioprio_class; 172 173 pid_t pid; 174}; 175 176enum cfqq_state_flags { 177 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */ 178 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */ 179 CFQ_CFQQ_FLAG_must_alloc, /* must be allowed rq alloc */ 180 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */ 181 CFQ_CFQQ_FLAG_must_dispatch, /* must dispatch, even if expired */ 182 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */ 183 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */ 184 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */ 185 CFQ_CFQQ_FLAG_queue_new, /* queue never been serviced */ 186 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */ 187 CFQ_CFQQ_FLAG_sync, /* synchronous queue */ 188}; 189 190#define CFQ_CFQQ_FNS(name) \ 191static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \ 192{ \ 193 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \ 194} \ 195static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \ 196{ \ 197 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \ 198} \ 199static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \ 200{ \ 201 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \ 202} 203 204CFQ_CFQQ_FNS(on_rr); 205CFQ_CFQQ_FNS(wait_request); 206CFQ_CFQQ_FNS(must_alloc); 207CFQ_CFQQ_FNS(must_alloc_slice); 208CFQ_CFQQ_FNS(must_dispatch); 209CFQ_CFQQ_FNS(fifo_expire); 210CFQ_CFQQ_FNS(idle_window); 211CFQ_CFQQ_FNS(prio_changed); 212CFQ_CFQQ_FNS(queue_new); 213CFQ_CFQQ_FNS(slice_new); 214CFQ_CFQQ_FNS(sync); 215#undef CFQ_CFQQ_FNS 216 217#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \ 218 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args) 219#define cfq_log(cfqd, fmt, args...) \ 220 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args) 221 222static void cfq_dispatch_insert(struct request_queue *, struct request *); 223static struct cfq_queue *cfq_get_queue(struct cfq_data *, int, 224 struct io_context *, gfp_t); 225static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *, 226 struct io_context *); 227 228static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic, 229 int is_sync) 230{ 231 return cic->cfqq[!!is_sync]; 232} 233 234static inline void cic_set_cfqq(struct cfq_io_context *cic, 235 struct cfq_queue *cfqq, int is_sync) 236{ 237 cic->cfqq[!!is_sync] = cfqq; 238} 239 240/* 241 * We regard a request as SYNC, if it's either a read or has the SYNC bit 242 * set (in which case it could also be direct WRITE). 243 */ 244static inline int cfq_bio_sync(struct bio *bio) 245{ 246 if (bio_data_dir(bio) == READ || bio_sync(bio)) 247 return 1; 248 249 return 0; 250} 251 252/* 253 * scheduler run of queue, if there are requests pending and no one in the 254 * driver that will restart queueing 255 */ 256static inline void cfq_schedule_dispatch(struct cfq_data *cfqd) 257{ 258 if (cfqd->busy_queues) { 259 cfq_log(cfqd, "schedule dispatch"); 260 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work); 261 } 262} 263 264static int cfq_queue_empty(struct request_queue *q) 265{ 266 struct cfq_data *cfqd = q->elevator->elevator_data; 267 268 return !cfqd->busy_queues; 269} 270 271/* 272 * Scale schedule slice based on io priority. Use the sync time slice only 273 * if a queue is marked sync and has sync io queued. A sync queue with async 274 * io only, should not get full sync slice length. 275 */ 276static inline int cfq_prio_slice(struct cfq_data *cfqd, int sync, 277 unsigned short prio) 278{ 279 const int base_slice = cfqd->cfq_slice[sync]; 280 281 WARN_ON(prio >= IOPRIO_BE_NR); 282 283 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio)); 284} 285 286static inline int 287cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 288{ 289 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio); 290} 291 292static inline void 293cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 294{ 295 cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies; 296 cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies); 297} 298 299/* 300 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end 301 * isn't valid until the first request from the dispatch is activated 302 * and the slice time set. 303 */ 304static inline int cfq_slice_used(struct cfq_queue *cfqq) 305{ 306 if (cfq_cfqq_slice_new(cfqq)) 307 return 0; 308 if (time_before(jiffies, cfqq->slice_end)) 309 return 0; 310 311 return 1; 312} 313 314/* 315 * Lifted from AS - choose which of rq1 and rq2 that is best served now. 316 * We choose the request that is closest to the head right now. Distance 317 * behind the head is penalized and only allowed to a certain extent. 318 */ 319static struct request * 320cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2) 321{ 322 sector_t last, s1, s2, d1 = 0, d2 = 0; 323 unsigned long back_max; 324#define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */ 325#define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */ 326 unsigned wrap = 0; /* bit mask: requests behind the disk head? */ 327 328 if (rq1 == NULL || rq1 == rq2) 329 return rq2; 330 if (rq2 == NULL) 331 return rq1; 332 333 if (rq_is_sync(rq1) && !rq_is_sync(rq2)) 334 return rq1; 335 else if (rq_is_sync(rq2) && !rq_is_sync(rq1)) 336 return rq2; 337 if (rq_is_meta(rq1) && !rq_is_meta(rq2)) 338 return rq1; 339 else if (rq_is_meta(rq2) && !rq_is_meta(rq1)) 340 return rq2; 341 342 s1 = rq1->sector; 343 s2 = rq2->sector; 344 345 last = cfqd->last_position; 346 347 /* 348 * by definition, 1KiB is 2 sectors 349 */ 350 back_max = cfqd->cfq_back_max * 2; 351 352 /* 353 * Strict one way elevator _except_ in the case where we allow 354 * short backward seeks which are biased as twice the cost of a 355 * similar forward seek. 356 */ 357 if (s1 >= last) 358 d1 = s1 - last; 359 else if (s1 + back_max >= last) 360 d1 = (last - s1) * cfqd->cfq_back_penalty; 361 else 362 wrap |= CFQ_RQ1_WRAP; 363 364 if (s2 >= last) 365 d2 = s2 - last; 366 else if (s2 + back_max >= last) 367 d2 = (last - s2) * cfqd->cfq_back_penalty; 368 else 369 wrap |= CFQ_RQ2_WRAP; 370 371 /* Found required data */ 372 373 /* 374 * By doing switch() on the bit mask "wrap" we avoid having to 375 * check two variables for all permutations: --> faster! 376 */ 377 switch (wrap) { 378 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */ 379 if (d1 < d2) 380 return rq1; 381 else if (d2 < d1) 382 return rq2; 383 else { 384 if (s1 >= s2) 385 return rq1; 386 else 387 return rq2; 388 } 389 390 case CFQ_RQ2_WRAP: 391 return rq1; 392 case CFQ_RQ1_WRAP: 393 return rq2; 394 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */ 395 default: 396 /* 397 * Since both rqs are wrapped, 398 * start with the one that's further behind head 399 * (--> only *one* back seek required), 400 * since back seek takes more time than forward. 401 */ 402 if (s1 <= s2) 403 return rq1; 404 else 405 return rq2; 406 } 407} 408 409/* 410 * The below is leftmost cache rbtree addon 411 */ 412static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root) 413{ 414 if (!root->left) 415 root->left = rb_first(&root->rb); 416 417 if (root->left) 418 return rb_entry(root->left, struct cfq_queue, rb_node); 419 420 return NULL; 421} 422 423static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root) 424{ 425 if (root->left == n) 426 root->left = NULL; 427 428 rb_erase(n, &root->rb); 429 RB_CLEAR_NODE(n); 430} 431 432/* 433 * would be nice to take fifo expire time into account as well 434 */ 435static struct request * 436cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq, 437 struct request *last) 438{ 439 struct rb_node *rbnext = rb_next(&last->rb_node); 440 struct rb_node *rbprev = rb_prev(&last->rb_node); 441 struct request *next = NULL, *prev = NULL; 442 443 BUG_ON(RB_EMPTY_NODE(&last->rb_node)); 444 445 if (rbprev) 446 prev = rb_entry_rq(rbprev); 447 448 if (rbnext) 449 next = rb_entry_rq(rbnext); 450 else { 451 rbnext = rb_first(&cfqq->sort_list); 452 if (rbnext && rbnext != &last->rb_node) 453 next = rb_entry_rq(rbnext); 454 } 455 456 return cfq_choose_req(cfqd, next, prev); 457} 458 459static unsigned long cfq_slice_offset(struct cfq_data *cfqd, 460 struct cfq_queue *cfqq) 461{ 462 /* 463 * just an approximation, should be ok. 464 */ 465 return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) - 466 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio)); 467} 468 469/* 470 * The cfqd->service_tree holds all pending cfq_queue's that have 471 * requests waiting to be processed. It is sorted in the order that 472 * we will service the queues. 473 */ 474static void cfq_service_tree_add(struct cfq_data *cfqd, 475 struct cfq_queue *cfqq, int add_front) 476{ 477 struct rb_node **p, *parent; 478 struct cfq_queue *__cfqq; 479 unsigned long rb_key; 480 int left; 481 482 if (cfq_class_idle(cfqq)) { 483 rb_key = CFQ_IDLE_DELAY; 484 parent = rb_last(&cfqd->service_tree.rb); 485 if (parent && parent != &cfqq->rb_node) { 486 __cfqq = rb_entry(parent, struct cfq_queue, rb_node); 487 rb_key += __cfqq->rb_key; 488 } else 489 rb_key += jiffies; 490 } else if (!add_front) { 491 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies; 492 rb_key += cfqq->slice_resid; 493 cfqq->slice_resid = 0; 494 } else 495 rb_key = 0; 496 497 if (!RB_EMPTY_NODE(&cfqq->rb_node)) { 498 /* 499 * same position, nothing more to do 500 */ 501 if (rb_key == cfqq->rb_key) 502 return; 503 504 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree); 505 } 506 507 left = 1; 508 parent = NULL; 509 p = &cfqd->service_tree.rb.rb_node; 510 while (*p) { 511 struct rb_node **n; 512 513 parent = *p; 514 __cfqq = rb_entry(parent, struct cfq_queue, rb_node); 515 516 /* 517 * sort RT queues first, we always want to give 518 * preference to them. IDLE queues goes to the back. 519 * after that, sort on the next service time. 520 */ 521 if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq)) 522 n = &(*p)->rb_left; 523 else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq)) 524 n = &(*p)->rb_right; 525 else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq)) 526 n = &(*p)->rb_left; 527 else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq)) 528 n = &(*p)->rb_right; 529 else if (rb_key < __cfqq->rb_key) 530 n = &(*p)->rb_left; 531 else 532 n = &(*p)->rb_right; 533 534 if (n == &(*p)->rb_right) 535 left = 0; 536 537 p = n; 538 } 539 540 if (left) 541 cfqd->service_tree.left = &cfqq->rb_node; 542 543 cfqq->rb_key = rb_key; 544 rb_link_node(&cfqq->rb_node, parent, p); 545 rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb); 546} 547 548/* 549 * Update cfqq's position in the service tree. 550 */ 551static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq) 552{ 553 /* 554 * Resorting requires the cfqq to be on the RR list already. 555 */ 556 if (cfq_cfqq_on_rr(cfqq)) 557 cfq_service_tree_add(cfqd, cfqq, 0); 558} 559 560/* 561 * add to busy list of queues for service, trying to be fair in ordering 562 * the pending list according to last request service 563 */ 564static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) 565{ 566 cfq_log_cfqq(cfqd, cfqq, "add_to_rr"); 567 BUG_ON(cfq_cfqq_on_rr(cfqq)); 568 cfq_mark_cfqq_on_rr(cfqq); 569 cfqd->busy_queues++; 570 if (cfq_class_rt(cfqq)) 571 cfqd->busy_rt_queues++; 572 573 cfq_resort_rr_list(cfqd, cfqq); 574} 575 576/* 577 * Called when the cfqq no longer has requests pending, remove it from 578 * the service tree. 579 */ 580static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) 581{ 582 cfq_log_cfqq(cfqd, cfqq, "del_from_rr"); 583 BUG_ON(!cfq_cfqq_on_rr(cfqq)); 584 cfq_clear_cfqq_on_rr(cfqq); 585 586 if (!RB_EMPTY_NODE(&cfqq->rb_node)) 587 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree); 588 589 BUG_ON(!cfqd->busy_queues); 590 cfqd->busy_queues--; 591 if (cfq_class_rt(cfqq)) 592 cfqd->busy_rt_queues--; 593} 594 595/* 596 * rb tree support functions 597 */ 598static void cfq_del_rq_rb(struct request *rq) 599{ 600 struct cfq_queue *cfqq = RQ_CFQQ(rq); 601 struct cfq_data *cfqd = cfqq->cfqd; 602 const int sync = rq_is_sync(rq); 603 604 BUG_ON(!cfqq->queued[sync]); 605 cfqq->queued[sync]--; 606 607 elv_rb_del(&cfqq->sort_list, rq); 608 609 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) 610 cfq_del_cfqq_rr(cfqd, cfqq); 611} 612 613static void cfq_add_rq_rb(struct request *rq) 614{ 615 struct cfq_queue *cfqq = RQ_CFQQ(rq); 616 struct cfq_data *cfqd = cfqq->cfqd; 617 struct request *__alias; 618 619 cfqq->queued[rq_is_sync(rq)]++; 620 621 /* 622 * looks a little odd, but the first insert might return an alias. 623 * if that happens, put the alias on the dispatch list 624 */ 625 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL) 626 cfq_dispatch_insert(cfqd->queue, __alias); 627 628 if (!cfq_cfqq_on_rr(cfqq)) 629 cfq_add_cfqq_rr(cfqd, cfqq); 630 631 /* 632 * check if this request is a better next-serve candidate 633 */ 634 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq); 635 BUG_ON(!cfqq->next_rq); 636} 637 638static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq) 639{ 640 elv_rb_del(&cfqq->sort_list, rq); 641 cfqq->queued[rq_is_sync(rq)]--; 642 cfq_add_rq_rb(rq); 643} 644 645static struct request * 646cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio) 647{ 648 struct task_struct *tsk = current; 649 struct cfq_io_context *cic; 650 struct cfq_queue *cfqq; 651 652 cic = cfq_cic_lookup(cfqd, tsk->io_context); 653 if (!cic) 654 return NULL; 655 656 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); 657 if (cfqq) { 658 sector_t sector = bio->bi_sector + bio_sectors(bio); 659 660 return elv_rb_find(&cfqq->sort_list, sector); 661 } 662 663 return NULL; 664} 665 666static void cfq_activate_request(struct request_queue *q, struct request *rq) 667{ 668 struct cfq_data *cfqd = q->elevator->elevator_data; 669 670 cfqd->rq_in_driver++; 671 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d", 672 cfqd->rq_in_driver); 673 674 cfqd->last_position = rq->hard_sector + rq->hard_nr_sectors; 675} 676 677static void cfq_deactivate_request(struct request_queue *q, struct request *rq) 678{ 679 struct cfq_data *cfqd = q->elevator->elevator_data; 680 681 WARN_ON(!cfqd->rq_in_driver); 682 cfqd->rq_in_driver--; 683 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d", 684 cfqd->rq_in_driver); 685} 686 687static void cfq_remove_request(struct request *rq) 688{ 689 struct cfq_queue *cfqq = RQ_CFQQ(rq); 690 691 if (cfqq->next_rq == rq) 692 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq); 693 694 list_del_init(&rq->queuelist); 695 cfq_del_rq_rb(rq); 696 697 cfqq->cfqd->rq_queued--; 698 if (rq_is_meta(rq)) { 699 WARN_ON(!cfqq->meta_pending); 700 cfqq->meta_pending--; 701 } 702} 703 704static int cfq_merge(struct request_queue *q, struct request **req, 705 struct bio *bio) 706{ 707 struct cfq_data *cfqd = q->elevator->elevator_data; 708 struct request *__rq; 709 710 __rq = cfq_find_rq_fmerge(cfqd, bio); 711 if (__rq && elv_rq_merge_ok(__rq, bio)) { 712 *req = __rq; 713 return ELEVATOR_FRONT_MERGE; 714 } 715 716 return ELEVATOR_NO_MERGE; 717} 718 719static void cfq_merged_request(struct request_queue *q, struct request *req, 720 int type) 721{ 722 if (type == ELEVATOR_FRONT_MERGE) { 723 struct cfq_queue *cfqq = RQ_CFQQ(req); 724 725 cfq_reposition_rq_rb(cfqq, req); 726 } 727} 728 729static void 730cfq_merged_requests(struct request_queue *q, struct request *rq, 731 struct request *next) 732{ 733 /* 734 * reposition in fifo if next is older than rq 735 */ 736 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && 737 time_before(next->start_time, rq->start_time)) 738 list_move(&rq->queuelist, &next->queuelist); 739 740 cfq_remove_request(next); 741} 742 743static int cfq_allow_merge(struct request_queue *q, struct request *rq, 744 struct bio *bio) 745{ 746 struct cfq_data *cfqd = q->elevator->elevator_data; 747 struct cfq_io_context *cic; 748 struct cfq_queue *cfqq; 749 750 /* 751 * Disallow merge of a sync bio into an async request. 752 */ 753 if (cfq_bio_sync(bio) && !rq_is_sync(rq)) 754 return 0; 755 756 /* 757 * Lookup the cfqq that this bio will be queued with. Allow 758 * merge only if rq is queued there. 759 */ 760 cic = cfq_cic_lookup(cfqd, current->io_context); 761 if (!cic) 762 return 0; 763 764 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); 765 if (cfqq == RQ_CFQQ(rq)) 766 return 1; 767 768 return 0; 769} 770 771static void __cfq_set_active_queue(struct cfq_data *cfqd, 772 struct cfq_queue *cfqq) 773{ 774 if (cfqq) { 775 cfq_log_cfqq(cfqd, cfqq, "set_active"); 776 cfqq->slice_end = 0; 777 cfq_clear_cfqq_must_alloc_slice(cfqq); 778 cfq_clear_cfqq_fifo_expire(cfqq); 779 cfq_mark_cfqq_slice_new(cfqq); 780 cfq_clear_cfqq_queue_new(cfqq); 781 } 782 783 cfqd->active_queue = cfqq; 784} 785 786/* 787 * current cfqq expired its slice (or was too idle), select new one 788 */ 789static void 790__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, 791 int timed_out) 792{ 793 cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out); 794 795 if (cfq_cfqq_wait_request(cfqq)) 796 del_timer(&cfqd->idle_slice_timer); 797 798 cfq_clear_cfqq_must_dispatch(cfqq); 799 cfq_clear_cfqq_wait_request(cfqq); 800 801 /* 802 * store what was left of this slice, if the queue idled/timed out 803 */ 804 if (timed_out && !cfq_cfqq_slice_new(cfqq)) { 805 cfqq->slice_resid = cfqq->slice_end - jiffies; 806 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid); 807 } 808 809 cfq_resort_rr_list(cfqd, cfqq); 810 811 if (cfqq == cfqd->active_queue) 812 cfqd->active_queue = NULL; 813 814 if (cfqd->active_cic) { 815 put_io_context(cfqd->active_cic->ioc); 816 cfqd->active_cic = NULL; 817 } 818} 819 820static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out) 821{ 822 struct cfq_queue *cfqq = cfqd->active_queue; 823 824 if (cfqq) 825 __cfq_slice_expired(cfqd, cfqq, timed_out); 826} 827 828/* 829 * Get next queue for service. Unless we have a queue preemption, 830 * we'll simply select the first cfqq in the service tree. 831 */ 832static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd) 833{ 834 if (RB_EMPTY_ROOT(&cfqd->service_tree.rb)) 835 return NULL; 836 837 return cfq_rb_first(&cfqd->service_tree); 838} 839 840/* 841 * Get and set a new active queue for service. 842 */ 843static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd) 844{ 845 struct cfq_queue *cfqq; 846 847 cfqq = cfq_get_next_queue(cfqd); 848 __cfq_set_active_queue(cfqd, cfqq); 849 return cfqq; 850} 851 852static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd, 853 struct request *rq) 854{ 855 if (rq->sector >= cfqd->last_position) 856 return rq->sector - cfqd->last_position; 857 else 858 return cfqd->last_position - rq->sector; 859} 860 861static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq) 862{ 863 struct cfq_io_context *cic = cfqd->active_cic; 864 865 if (!sample_valid(cic->seek_samples)) 866 return 0; 867 868 return cfq_dist_from_last(cfqd, rq) <= cic->seek_mean; 869} 870 871static int cfq_close_cooperator(struct cfq_data *cfq_data, 872 struct cfq_queue *cfqq) 873{ 874 /* 875 * We should notice if some of the queues are cooperating, eg 876 * working closely on the same area of the disk. In that case, 877 * we can group them together and don't waste time idling. 878 */ 879 return 0; 880} 881 882#define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024)) 883 884static void cfq_arm_slice_timer(struct cfq_data *cfqd) 885{ 886 struct cfq_queue *cfqq = cfqd->active_queue; 887 struct cfq_io_context *cic; 888 unsigned long sl; 889 890 /* 891 * SSD device without seek penalty, disable idling. But only do so 892 * for devices that support queuing, otherwise we still have a problem 893 * with sync vs async workloads. 894 */ 895 if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag) 896 return; 897 898 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list)); 899 WARN_ON(cfq_cfqq_slice_new(cfqq)); 900 901 /* 902 * idle is disabled, either manually or by past process history 903 */ 904 if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq)) 905 return; 906 907 /* 908 * still requests with the driver, don't idle 909 */ 910 if (cfqd->rq_in_driver) 911 return; 912 913 /* 914 * task has exited, don't wait 915 */ 916 cic = cfqd->active_cic; 917 if (!cic || !atomic_read(&cic->ioc->nr_tasks)) 918 return; 919 920 /* 921 * See if this prio level has a good candidate 922 */ 923 if (cfq_close_cooperator(cfqd, cfqq) && 924 (sample_valid(cic->ttime_samples) && cic->ttime_mean > 2)) 925 return; 926 927 cfq_mark_cfqq_must_dispatch(cfqq); 928 cfq_mark_cfqq_wait_request(cfqq); 929 930 /* 931 * we don't want to idle for seeks, but we do want to allow 932 * fair distribution of slice time for a process doing back-to-back 933 * seeks. so allow a little bit of time for him to submit a new rq 934 */ 935 sl = cfqd->cfq_slice_idle; 936 if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic)) 937 sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT)); 938 939 mod_timer(&cfqd->idle_slice_timer, jiffies + sl); 940 cfq_log(cfqd, "arm_idle: %lu", sl); 941} 942 943/* 944 * Move request from internal lists to the request queue dispatch list. 945 */ 946static void cfq_dispatch_insert(struct request_queue *q, struct request *rq) 947{ 948 struct cfq_data *cfqd = q->elevator->elevator_data; 949 struct cfq_queue *cfqq = RQ_CFQQ(rq); 950 951 cfq_log_cfqq(cfqd, cfqq, "dispatch_insert"); 952 953 cfq_remove_request(rq); 954 cfqq->dispatched++; 955 elv_dispatch_sort(q, rq); 956 957 if (cfq_cfqq_sync(cfqq)) 958 cfqd->sync_flight++; 959} 960 961/* 962 * return expired entry, or NULL to just start from scratch in rbtree 963 */ 964static struct request *cfq_check_fifo(struct cfq_queue *cfqq) 965{ 966 struct cfq_data *cfqd = cfqq->cfqd; 967 struct request *rq; 968 int fifo; 969 970 if (cfq_cfqq_fifo_expire(cfqq)) 971 return NULL; 972 973 cfq_mark_cfqq_fifo_expire(cfqq); 974 975 if (list_empty(&cfqq->fifo)) 976 return NULL; 977 978 fifo = cfq_cfqq_sync(cfqq); 979 rq = rq_entry_fifo(cfqq->fifo.next); 980 981 if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) 982 rq = NULL; 983 984 cfq_log_cfqq(cfqd, cfqq, "fifo=%p", rq); 985 return rq; 986} 987 988static inline int 989cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq) 990{ 991 const int base_rq = cfqd->cfq_slice_async_rq; 992 993 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR); 994 995 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio)); 996} 997 998/* 999 * Select a queue for service. If we have a current active queue, 1000 * check whether to continue servicing it, or retrieve and set a new one. 1001 */ 1002static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd) 1003{ 1004 struct cfq_queue *cfqq; 1005 1006 cfqq = cfqd->active_queue; 1007 if (!cfqq) 1008 goto new_queue; 1009 1010 /* 1011 * The active queue has run out of time, expire it and select new. 1012 */ 1013 if (cfq_slice_used(cfqq)) 1014 goto expire; 1015 1016 /* 1017 * If we have a RT cfqq waiting, then we pre-empt the current non-rt 1018 * cfqq. 1019 */ 1020 if (!cfq_class_rt(cfqq) && cfqd->busy_rt_queues) { 1021 /* 1022 * We simulate this as cfqq timed out so that it gets to bank 1023 * the remaining of its time slice. 1024 */ 1025 cfq_log_cfqq(cfqd, cfqq, "preempt"); 1026 cfq_slice_expired(cfqd, 1); 1027 goto new_queue; 1028 } 1029 1030 /* 1031 * The active queue has requests and isn't expired, allow it to 1032 * dispatch. 1033 */ 1034 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) 1035 goto keep_queue; 1036 1037 /* 1038 * No requests pending. If the active queue still has requests in 1039 * flight or is idling for a new request, allow either of these 1040 * conditions to happen (or time out) before selecting a new queue. 1041 */ 1042 if (timer_pending(&cfqd->idle_slice_timer) || 1043 (cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) { 1044 cfqq = NULL; 1045 goto keep_queue; 1046 } 1047 1048expire: 1049 cfq_slice_expired(cfqd, 0); 1050new_queue: 1051 cfqq = cfq_set_active_queue(cfqd); 1052keep_queue: 1053 return cfqq; 1054} 1055 1056/* 1057 * Dispatch some requests from cfqq, moving them to the request queue 1058 * dispatch list. 1059 */ 1060static int 1061__cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1062 int max_dispatch) 1063{ 1064 int dispatched = 0; 1065 1066 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list)); 1067 1068 do { 1069 struct request *rq; 1070 1071 /* 1072 * follow expired path, else get first next available 1073 */ 1074 rq = cfq_check_fifo(cfqq); 1075 if (rq == NULL) 1076 rq = cfqq->next_rq; 1077 1078 /* 1079 * finally, insert request into driver dispatch list 1080 */ 1081 cfq_dispatch_insert(cfqd->queue, rq); 1082 1083 dispatched++; 1084 1085 if (!cfqd->active_cic) { 1086 atomic_inc(&RQ_CIC(rq)->ioc->refcount); 1087 cfqd->active_cic = RQ_CIC(rq); 1088 } 1089 1090 if (RB_EMPTY_ROOT(&cfqq->sort_list)) 1091 break; 1092 1093 /* 1094 * If there is a non-empty RT cfqq waiting for current 1095 * cfqq's timeslice to complete, pre-empt this cfqq 1096 */ 1097 if (!cfq_class_rt(cfqq) && cfqd->busy_rt_queues) 1098 break; 1099 1100 } while (dispatched < max_dispatch); 1101 1102 /* 1103 * expire an async queue immediately if it has used up its slice. idle 1104 * queue always expire after 1 dispatch round. 1105 */ 1106 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) && 1107 dispatched >= cfq_prio_to_maxrq(cfqd, cfqq)) || 1108 cfq_class_idle(cfqq))) { 1109 cfqq->slice_end = jiffies + 1; 1110 cfq_slice_expired(cfqd, 0); 1111 } 1112 1113 return dispatched; 1114} 1115 1116static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq) 1117{ 1118 int dispatched = 0; 1119 1120 while (cfqq->next_rq) { 1121 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq); 1122 dispatched++; 1123 } 1124 1125 BUG_ON(!list_empty(&cfqq->fifo)); 1126 return dispatched; 1127} 1128 1129/* 1130 * Drain our current requests. Used for barriers and when switching 1131 * io schedulers on-the-fly. 1132 */ 1133static int cfq_forced_dispatch(struct cfq_data *cfqd) 1134{ 1135 struct cfq_queue *cfqq; 1136 int dispatched = 0; 1137 1138 while ((cfqq = cfq_rb_first(&cfqd->service_tree)) != NULL) 1139 dispatched += __cfq_forced_dispatch_cfqq(cfqq); 1140 1141 cfq_slice_expired(cfqd, 0); 1142 1143 BUG_ON(cfqd->busy_queues); 1144 1145 cfq_log(cfqd, "forced_dispatch=%d\n", dispatched); 1146 return dispatched; 1147} 1148 1149static int cfq_dispatch_requests(struct request_queue *q, int force) 1150{ 1151 struct cfq_data *cfqd = q->elevator->elevator_data; 1152 struct cfq_queue *cfqq; 1153 int dispatched; 1154 1155 if (!cfqd->busy_queues) 1156 return 0; 1157 1158 if (unlikely(force)) 1159 return cfq_forced_dispatch(cfqd); 1160 1161 dispatched = 0; 1162 while ((cfqq = cfq_select_queue(cfqd)) != NULL) { 1163 int max_dispatch; 1164 1165 max_dispatch = cfqd->cfq_quantum; 1166 if (cfq_class_idle(cfqq)) 1167 max_dispatch = 1; 1168 1169 if (cfqq->dispatched >= max_dispatch && cfqd->busy_queues > 1) 1170 break; 1171 1172 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq)) 1173 break; 1174 1175 cfq_clear_cfqq_must_dispatch(cfqq); 1176 cfq_clear_cfqq_wait_request(cfqq); 1177 del_timer(&cfqd->idle_slice_timer); 1178 1179 dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch); 1180 } 1181 1182 cfq_log(cfqd, "dispatched=%d", dispatched); 1183 return dispatched; 1184} 1185 1186/* 1187 * task holds one reference to the queue, dropped when task exits. each rq 1188 * in-flight on this queue also holds a reference, dropped when rq is freed. 1189 * 1190 * queue lock must be held here. 1191 */ 1192static void cfq_put_queue(struct cfq_queue *cfqq) 1193{ 1194 struct cfq_data *cfqd = cfqq->cfqd; 1195 1196 BUG_ON(atomic_read(&cfqq->ref) <= 0); 1197 1198 if (!atomic_dec_and_test(&cfqq->ref)) 1199 return; 1200 1201 cfq_log_cfqq(cfqd, cfqq, "put_queue"); 1202 BUG_ON(rb_first(&cfqq->sort_list)); 1203 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]); 1204 BUG_ON(cfq_cfqq_on_rr(cfqq)); 1205 1206 if (unlikely(cfqd->active_queue == cfqq)) { 1207 __cfq_slice_expired(cfqd, cfqq, 0); 1208 cfq_schedule_dispatch(cfqd); 1209 } 1210 1211 kmem_cache_free(cfq_pool, cfqq); 1212} 1213 1214/* 1215 * Must always be called with the rcu_read_lock() held 1216 */ 1217static void 1218__call_for_each_cic(struct io_context *ioc, 1219 void (*func)(struct io_context *, struct cfq_io_context *)) 1220{ 1221 struct cfq_io_context *cic; 1222 struct hlist_node *n; 1223 1224 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list) 1225 func(ioc, cic); 1226} 1227 1228/* 1229 * Call func for each cic attached to this ioc. 1230 */ 1231static void 1232call_for_each_cic(struct io_context *ioc, 1233 void (*func)(struct io_context *, struct cfq_io_context *)) 1234{ 1235 rcu_read_lock(); 1236 __call_for_each_cic(ioc, func); 1237 rcu_read_unlock(); 1238} 1239 1240static void cfq_cic_free_rcu(struct rcu_head *head) 1241{ 1242 struct cfq_io_context *cic; 1243 1244 cic = container_of(head, struct cfq_io_context, rcu_head); 1245 1246 kmem_cache_free(cfq_ioc_pool, cic); 1247 elv_ioc_count_dec(ioc_count); 1248 1249 if (ioc_gone) { 1250 /* 1251 * CFQ scheduler is exiting, grab exit lock and check 1252 * the pending io context count. If it hits zero, 1253 * complete ioc_gone and set it back to NULL 1254 */ 1255 spin_lock(&ioc_gone_lock); 1256 if (ioc_gone && !elv_ioc_count_read(ioc_count)) { 1257 complete(ioc_gone); 1258 ioc_gone = NULL; 1259 } 1260 spin_unlock(&ioc_gone_lock); 1261 } 1262} 1263 1264static void cfq_cic_free(struct cfq_io_context *cic) 1265{ 1266 call_rcu(&cic->rcu_head, cfq_cic_free_rcu); 1267} 1268 1269static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic) 1270{ 1271 unsigned long flags; 1272 1273 BUG_ON(!cic->dead_key); 1274 1275 spin_lock_irqsave(&ioc->lock, flags); 1276 radix_tree_delete(&ioc->radix_root, cic->dead_key); 1277 hlist_del_rcu(&cic->cic_list); 1278 spin_unlock_irqrestore(&ioc->lock, flags); 1279 1280 cfq_cic_free(cic); 1281} 1282 1283/* 1284 * Must be called with rcu_read_lock() held or preemption otherwise disabled. 1285 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(), 1286 * and ->trim() which is called with the task lock held 1287 */ 1288static void cfq_free_io_context(struct io_context *ioc) 1289{ 1290 /* 1291 * ioc->refcount is zero here, or we are called from elv_unregister(), 1292 * so no more cic's are allowed to be linked into this ioc. So it 1293 * should be ok to iterate over the known list, we will see all cic's 1294 * since no new ones are added. 1295 */ 1296 __call_for_each_cic(ioc, cic_free_func); 1297} 1298 1299static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1300{ 1301 if (unlikely(cfqq == cfqd->active_queue)) { 1302 __cfq_slice_expired(cfqd, cfqq, 0); 1303 cfq_schedule_dispatch(cfqd); 1304 } 1305 1306 cfq_put_queue(cfqq); 1307} 1308 1309static void __cfq_exit_single_io_context(struct cfq_data *cfqd, 1310 struct cfq_io_context *cic) 1311{ 1312 struct io_context *ioc = cic->ioc; 1313 1314 list_del_init(&cic->queue_list); 1315 1316 /* 1317 * Make sure key == NULL is seen for dead queues 1318 */ 1319 smp_wmb(); 1320 cic->dead_key = (unsigned long) cic->key; 1321 cic->key = NULL; 1322 1323 if (ioc->ioc_data == cic) 1324 rcu_assign_pointer(ioc->ioc_data, NULL); 1325 1326 if (cic->cfqq[ASYNC]) { 1327 cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]); 1328 cic->cfqq[ASYNC] = NULL; 1329 } 1330 1331 if (cic->cfqq[SYNC]) { 1332 cfq_exit_cfqq(cfqd, cic->cfqq[SYNC]); 1333 cic->cfqq[SYNC] = NULL; 1334 } 1335} 1336 1337static void cfq_exit_single_io_context(struct io_context *ioc, 1338 struct cfq_io_context *cic) 1339{ 1340 struct cfq_data *cfqd = cic->key; 1341 1342 if (cfqd) { 1343 struct request_queue *q = cfqd->queue; 1344 unsigned long flags; 1345 1346 spin_lock_irqsave(q->queue_lock, flags); 1347 1348 /* 1349 * Ensure we get a fresh copy of the ->key to prevent 1350 * race between exiting task and queue 1351 */ 1352 smp_read_barrier_depends(); 1353 if (cic->key) 1354 __cfq_exit_single_io_context(cfqd, cic); 1355 1356 spin_unlock_irqrestore(q->queue_lock, flags); 1357 } 1358} 1359 1360/* 1361 * The process that ioc belongs to has exited, we need to clean up 1362 * and put the internal structures we have that belongs to that process. 1363 */ 1364static void cfq_exit_io_context(struct io_context *ioc) 1365{ 1366 call_for_each_cic(ioc, cfq_exit_single_io_context); 1367} 1368 1369static struct cfq_io_context * 1370cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 1371{ 1372 struct cfq_io_context *cic; 1373 1374 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO, 1375 cfqd->queue->node); 1376 if (cic) { 1377 cic->last_end_request = jiffies; 1378 INIT_LIST_HEAD(&cic->queue_list); 1379 INIT_HLIST_NODE(&cic->cic_list); 1380 cic->dtor = cfq_free_io_context; 1381 cic->exit = cfq_exit_io_context; 1382 elv_ioc_count_inc(ioc_count); 1383 } 1384 1385 return cic; 1386} 1387 1388static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc) 1389{ 1390 struct task_struct *tsk = current; 1391 int ioprio_class; 1392 1393 if (!cfq_cfqq_prio_changed(cfqq)) 1394 return; 1395 1396 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio); 1397 switch (ioprio_class) { 1398 default: 1399 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class); 1400 case IOPRIO_CLASS_NONE: 1401 /* 1402 * no prio set, inherit CPU scheduling settings 1403 */ 1404 cfqq->ioprio = task_nice_ioprio(tsk); 1405 cfqq->ioprio_class = task_nice_ioclass(tsk); 1406 break; 1407 case IOPRIO_CLASS_RT: 1408 cfqq->ioprio = task_ioprio(ioc); 1409 cfqq->ioprio_class = IOPRIO_CLASS_RT; 1410 break; 1411 case IOPRIO_CLASS_BE: 1412 cfqq->ioprio = task_ioprio(ioc); 1413 cfqq->ioprio_class = IOPRIO_CLASS_BE; 1414 break; 1415 case IOPRIO_CLASS_IDLE: 1416 cfqq->ioprio_class = IOPRIO_CLASS_IDLE; 1417 cfqq->ioprio = 7; 1418 cfq_clear_cfqq_idle_window(cfqq); 1419 break; 1420 } 1421 1422 /* 1423 * keep track of original prio settings in case we have to temporarily 1424 * elevate the priority of this queue 1425 */ 1426 cfqq->org_ioprio = cfqq->ioprio; 1427 cfqq->org_ioprio_class = cfqq->ioprio_class; 1428 cfq_clear_cfqq_prio_changed(cfqq); 1429} 1430 1431static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic) 1432{ 1433 struct cfq_data *cfqd = cic->key; 1434 struct cfq_queue *cfqq; 1435 unsigned long flags; 1436 1437 if (unlikely(!cfqd)) 1438 return; 1439 1440 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 1441 1442 cfqq = cic->cfqq[ASYNC]; 1443 if (cfqq) { 1444 struct cfq_queue *new_cfqq; 1445 new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc, GFP_ATOMIC); 1446 if (new_cfqq) { 1447 cic->cfqq[ASYNC] = new_cfqq; 1448 cfq_put_queue(cfqq); 1449 } 1450 } 1451 1452 cfqq = cic->cfqq[SYNC]; 1453 if (cfqq) 1454 cfq_mark_cfqq_prio_changed(cfqq); 1455 1456 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 1457} 1458 1459static void cfq_ioc_set_ioprio(struct io_context *ioc) 1460{ 1461 call_for_each_cic(ioc, changed_ioprio); 1462 ioc->ioprio_changed = 0; 1463} 1464 1465static struct cfq_queue * 1466cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync, 1467 struct io_context *ioc, gfp_t gfp_mask) 1468{ 1469 struct cfq_queue *cfqq, *new_cfqq = NULL; 1470 struct cfq_io_context *cic; 1471 1472retry: 1473 cic = cfq_cic_lookup(cfqd, ioc); 1474 /* cic always exists here */ 1475 cfqq = cic_to_cfqq(cic, is_sync); 1476 1477 if (!cfqq) { 1478 if (new_cfqq) { 1479 cfqq = new_cfqq; 1480 new_cfqq = NULL; 1481 } else if (gfp_mask & __GFP_WAIT) { 1482 /* 1483 * Inform the allocator of the fact that we will 1484 * just repeat this allocation if it fails, to allow 1485 * the allocator to do whatever it needs to attempt to 1486 * free memory. 1487 */ 1488 spin_unlock_irq(cfqd->queue->queue_lock); 1489 new_cfqq = kmem_cache_alloc_node(cfq_pool, 1490 gfp_mask | __GFP_NOFAIL | __GFP_ZERO, 1491 cfqd->queue->node); 1492 spin_lock_irq(cfqd->queue->queue_lock); 1493 goto retry; 1494 } else { 1495 cfqq = kmem_cache_alloc_node(cfq_pool, 1496 gfp_mask | __GFP_ZERO, 1497 cfqd->queue->node); 1498 if (!cfqq) 1499 goto out; 1500 } 1501 1502 RB_CLEAR_NODE(&cfqq->rb_node); 1503 INIT_LIST_HEAD(&cfqq->fifo); 1504 1505 atomic_set(&cfqq->ref, 0); 1506 cfqq->cfqd = cfqd; 1507 1508 cfq_mark_cfqq_prio_changed(cfqq); 1509 cfq_mark_cfqq_queue_new(cfqq); 1510 1511 cfq_init_prio_data(cfqq, ioc); 1512 1513 if (is_sync) { 1514 if (!cfq_class_idle(cfqq)) 1515 cfq_mark_cfqq_idle_window(cfqq); 1516 cfq_mark_cfqq_sync(cfqq); 1517 } 1518 cfqq->pid = current->pid; 1519 cfq_log_cfqq(cfqd, cfqq, "alloced"); 1520 } 1521 1522 if (new_cfqq) 1523 kmem_cache_free(cfq_pool, new_cfqq); 1524 1525out: 1526 WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq); 1527 return cfqq; 1528} 1529 1530static struct cfq_queue ** 1531cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio) 1532{ 1533 switch (ioprio_class) { 1534 case IOPRIO_CLASS_RT: 1535 return &cfqd->async_cfqq[0][ioprio]; 1536 case IOPRIO_CLASS_BE: 1537 return &cfqd->async_cfqq[1][ioprio]; 1538 case IOPRIO_CLASS_IDLE: 1539 return &cfqd->async_idle_cfqq; 1540 default: 1541 BUG(); 1542 } 1543} 1544 1545static struct cfq_queue * 1546cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc, 1547 gfp_t gfp_mask) 1548{ 1549 const int ioprio = task_ioprio(ioc); 1550 const int ioprio_class = task_ioprio_class(ioc); 1551 struct cfq_queue **async_cfqq = NULL; 1552 struct cfq_queue *cfqq = NULL; 1553 1554 if (!is_sync) { 1555 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio); 1556 cfqq = *async_cfqq; 1557 } 1558 1559 if (!cfqq) { 1560 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask); 1561 if (!cfqq) 1562 return NULL; 1563 } 1564 1565 /* 1566 * pin the queue now that it's allocated, scheduler exit will prune it 1567 */ 1568 if (!is_sync && !(*async_cfqq)) { 1569 atomic_inc(&cfqq->ref); 1570 *async_cfqq = cfqq; 1571 } 1572 1573 atomic_inc(&cfqq->ref); 1574 return cfqq; 1575} 1576 1577/* 1578 * We drop cfq io contexts lazily, so we may find a dead one. 1579 */ 1580static void 1581cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc, 1582 struct cfq_io_context *cic) 1583{ 1584 unsigned long flags; 1585 1586 WARN_ON(!list_empty(&cic->queue_list)); 1587 1588 spin_lock_irqsave(&ioc->lock, flags); 1589 1590 BUG_ON(ioc->ioc_data == cic); 1591 1592 radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd); 1593 hlist_del_rcu(&cic->cic_list); 1594 spin_unlock_irqrestore(&ioc->lock, flags); 1595 1596 cfq_cic_free(cic); 1597} 1598 1599static struct cfq_io_context * 1600cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc) 1601{ 1602 struct cfq_io_context *cic; 1603 unsigned long flags; 1604 void *k; 1605 1606 if (unlikely(!ioc)) 1607 return NULL; 1608 1609 rcu_read_lock(); 1610 1611 /* 1612 * we maintain a last-hit cache, to avoid browsing over the tree 1613 */ 1614 cic = rcu_dereference(ioc->ioc_data); 1615 if (cic && cic->key == cfqd) { 1616 rcu_read_unlock(); 1617 return cic; 1618 } 1619 1620 do { 1621 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd); 1622 rcu_read_unlock(); 1623 if (!cic) 1624 break; 1625 /* ->key must be copied to avoid race with cfq_exit_queue() */ 1626 k = cic->key; 1627 if (unlikely(!k)) { 1628 cfq_drop_dead_cic(cfqd, ioc, cic); 1629 rcu_read_lock(); 1630 continue; 1631 } 1632 1633 spin_lock_irqsave(&ioc->lock, flags); 1634 rcu_assign_pointer(ioc->ioc_data, cic); 1635 spin_unlock_irqrestore(&ioc->lock, flags); 1636 break; 1637 } while (1); 1638 1639 return cic; 1640} 1641 1642/* 1643 * Add cic into ioc, using cfqd as the search key. This enables us to lookup 1644 * the process specific cfq io context when entered from the block layer. 1645 * Also adds the cic to a per-cfqd list, used when this queue is removed. 1646 */ 1647static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc, 1648 struct cfq_io_context *cic, gfp_t gfp_mask) 1649{ 1650 unsigned long flags; 1651 int ret; 1652 1653 ret = radix_tree_preload(gfp_mask); 1654 if (!ret) { 1655 cic->ioc = ioc; 1656 cic->key = cfqd; 1657 1658 spin_lock_irqsave(&ioc->lock, flags); 1659 ret = radix_tree_insert(&ioc->radix_root, 1660 (unsigned long) cfqd, cic); 1661 if (!ret) 1662 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list); 1663 spin_unlock_irqrestore(&ioc->lock, flags); 1664 1665 radix_tree_preload_end(); 1666 1667 if (!ret) { 1668 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 1669 list_add(&cic->queue_list, &cfqd->cic_list); 1670 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 1671 } 1672 } 1673 1674 if (ret) 1675 printk(KERN_ERR "cfq: cic link failed!\n"); 1676 1677 return ret; 1678} 1679 1680/* 1681 * Setup general io context and cfq io context. There can be several cfq 1682 * io contexts per general io context, if this process is doing io to more 1683 * than one device managed by cfq. 1684 */ 1685static struct cfq_io_context * 1686cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 1687{ 1688 struct io_context *ioc = NULL; 1689 struct cfq_io_context *cic; 1690 1691 might_sleep_if(gfp_mask & __GFP_WAIT); 1692 1693 ioc = get_io_context(gfp_mask, cfqd->queue->node); 1694 if (!ioc) 1695 return NULL; 1696 1697 cic = cfq_cic_lookup(cfqd, ioc); 1698 if (cic) 1699 goto out; 1700 1701 cic = cfq_alloc_io_context(cfqd, gfp_mask); 1702 if (cic == NULL) 1703 goto err; 1704 1705 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask)) 1706 goto err_free; 1707 1708out: 1709 smp_read_barrier_depends(); 1710 if (unlikely(ioc->ioprio_changed)) 1711 cfq_ioc_set_ioprio(ioc); 1712 1713 return cic; 1714err_free: 1715 cfq_cic_free(cic); 1716err: 1717 put_io_context(ioc); 1718 return NULL; 1719} 1720 1721static void 1722cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic) 1723{ 1724 unsigned long elapsed = jiffies - cic->last_end_request; 1725 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle); 1726 1727 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8; 1728 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8; 1729 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples; 1730} 1731 1732static void 1733cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic, 1734 struct request *rq) 1735{ 1736 sector_t sdist; 1737 u64 total; 1738 1739 if (cic->last_request_pos < rq->sector) 1740 sdist = rq->sector - cic->last_request_pos; 1741 else 1742 sdist = cic->last_request_pos - rq->sector; 1743 1744 /* 1745 * Don't allow the seek distance to get too large from the 1746 * odd fragment, pagein, etc 1747 */ 1748 if (cic->seek_samples <= 60) /* second&third seek */ 1749 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024); 1750 else 1751 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64); 1752 1753 cic->seek_samples = (7*cic->seek_samples + 256) / 8; 1754 cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8; 1755 total = cic->seek_total + (cic->seek_samples/2); 1756 do_div(total, cic->seek_samples); 1757 cic->seek_mean = (sector_t)total; 1758} 1759 1760/* 1761 * Disable idle window if the process thinks too long or seeks so much that 1762 * it doesn't matter 1763 */ 1764static void 1765cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1766 struct cfq_io_context *cic) 1767{ 1768 int old_idle, enable_idle; 1769 1770 /* 1771 * Don't idle for async or idle io prio class 1772 */ 1773 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq)) 1774 return; 1775 1776 enable_idle = old_idle = cfq_cfqq_idle_window(cfqq); 1777 1778 if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle || 1779 (cfqd->hw_tag && CIC_SEEKY(cic))) 1780 enable_idle = 0; 1781 else if (sample_valid(cic->ttime_samples)) { 1782 if (cic->ttime_mean > cfqd->cfq_slice_idle) 1783 enable_idle = 0; 1784 else 1785 enable_idle = 1; 1786 } 1787 1788 if (old_idle != enable_idle) { 1789 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle); 1790 if (enable_idle) 1791 cfq_mark_cfqq_idle_window(cfqq); 1792 else 1793 cfq_clear_cfqq_idle_window(cfqq); 1794 } 1795} 1796 1797/* 1798 * Check if new_cfqq should preempt the currently active queue. Return 0 for 1799 * no or if we aren't sure, a 1 will cause a preempt. 1800 */ 1801static int 1802cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, 1803 struct request *rq) 1804{ 1805 struct cfq_queue *cfqq; 1806 1807 cfqq = cfqd->active_queue; 1808 if (!cfqq) 1809 return 0; 1810 1811 if (cfq_slice_used(cfqq)) 1812 return 1; 1813 1814 if (cfq_class_idle(new_cfqq)) 1815 return 0; 1816 1817 if (cfq_class_idle(cfqq)) 1818 return 1; 1819 1820 /* 1821 * if the new request is sync, but the currently running queue is 1822 * not, let the sync request have priority. 1823 */ 1824 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq)) 1825 return 1; 1826 1827 /* 1828 * So both queues are sync. Let the new request get disk time if 1829 * it's a metadata request and the current queue is doing regular IO. 1830 */ 1831 if (rq_is_meta(rq) && !cfqq->meta_pending) 1832 return 1; 1833 1834 /* 1835 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice. 1836 */ 1837 if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq)) 1838 return 1; 1839 1840 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq)) 1841 return 0; 1842 1843 /* 1844 * if this request is as-good as one we would expect from the 1845 * current cfqq, let it preempt 1846 */ 1847 if (cfq_rq_close(cfqd, rq)) 1848 return 1; 1849 1850 return 0; 1851} 1852 1853/* 1854 * cfqq preempts the active queue. if we allowed preempt with no slice left, 1855 * let it have half of its nominal slice. 1856 */ 1857static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1858{ 1859 cfq_log_cfqq(cfqd, cfqq, "preempt"); 1860 cfq_slice_expired(cfqd, 1); 1861 1862 /* 1863 * Put the new queue at the front of the of the current list, 1864 * so we know that it will be selected next. 1865 */ 1866 BUG_ON(!cfq_cfqq_on_rr(cfqq)); 1867 1868 cfq_service_tree_add(cfqd, cfqq, 1); 1869 1870 cfqq->slice_end = 0; 1871 cfq_mark_cfqq_slice_new(cfqq); 1872} 1873 1874/* 1875 * Called when a new fs request (rq) is added (to cfqq). Check if there's 1876 * something we should do about it 1877 */ 1878static void 1879cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1880 struct request *rq) 1881{ 1882 struct cfq_io_context *cic = RQ_CIC(rq); 1883 1884 cfqd->rq_queued++; 1885 if (rq_is_meta(rq)) 1886 cfqq->meta_pending++; 1887 1888 cfq_update_io_thinktime(cfqd, cic); 1889 cfq_update_io_seektime(cfqd, cic, rq); 1890 cfq_update_idle_window(cfqd, cfqq, cic); 1891 1892 cic->last_request_pos = rq->sector + rq->nr_sectors; 1893 1894 if (cfqq == cfqd->active_queue) { 1895 /* 1896 * if we are waiting for a request for this queue, let it rip 1897 * immediately and flag that we must not expire this queue 1898 * just now 1899 */ 1900 if (cfq_cfqq_wait_request(cfqq)) { 1901 cfq_mark_cfqq_must_dispatch(cfqq); 1902 del_timer(&cfqd->idle_slice_timer); 1903 blk_start_queueing(cfqd->queue); 1904 } 1905 } else if (cfq_should_preempt(cfqd, cfqq, rq)) { 1906 /* 1907 * not the active queue - expire current slice if it is 1908 * idle and has expired it's mean thinktime or this new queue 1909 * has some old slice time left and is of higher priority or 1910 * this new queue is RT and the current one is BE 1911 */ 1912 cfq_preempt_queue(cfqd, cfqq); 1913 cfq_mark_cfqq_must_dispatch(cfqq); 1914 blk_start_queueing(cfqd->queue); 1915 } 1916} 1917 1918static void cfq_insert_request(struct request_queue *q, struct request *rq) 1919{ 1920 struct cfq_data *cfqd = q->elevator->elevator_data; 1921 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1922 1923 cfq_log_cfqq(cfqd, cfqq, "insert_request"); 1924 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc); 1925 1926 cfq_add_rq_rb(rq); 1927 1928 list_add_tail(&rq->queuelist, &cfqq->fifo); 1929 1930 cfq_rq_enqueued(cfqd, cfqq, rq); 1931} 1932 1933/* 1934 * Update hw_tag based on peak queue depth over 50 samples under 1935 * sufficient load. 1936 */ 1937static void cfq_update_hw_tag(struct cfq_data *cfqd) 1938{ 1939 if (cfqd->rq_in_driver > cfqd->rq_in_driver_peak) 1940 cfqd->rq_in_driver_peak = cfqd->rq_in_driver; 1941 1942 if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN && 1943 cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN) 1944 return; 1945 1946 if (cfqd->hw_tag_samples++ < 50) 1947 return; 1948 1949 if (cfqd->rq_in_driver_peak >= CFQ_HW_QUEUE_MIN) 1950 cfqd->hw_tag = 1; 1951 else 1952 cfqd->hw_tag = 0; 1953 1954 cfqd->hw_tag_samples = 0; 1955 cfqd->rq_in_driver_peak = 0; 1956} 1957 1958static void cfq_completed_request(struct request_queue *q, struct request *rq) 1959{ 1960 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1961 struct cfq_data *cfqd = cfqq->cfqd; 1962 const int sync = rq_is_sync(rq); 1963 unsigned long now; 1964 1965 now = jiffies; 1966 cfq_log_cfqq(cfqd, cfqq, "complete"); 1967 1968 cfq_update_hw_tag(cfqd); 1969 1970 WARN_ON(!cfqd->rq_in_driver); 1971 WARN_ON(!cfqq->dispatched); 1972 cfqd->rq_in_driver--; 1973 cfqq->dispatched--; 1974 1975 if (cfq_cfqq_sync(cfqq)) 1976 cfqd->sync_flight--; 1977 1978 if (!cfq_class_idle(cfqq)) 1979 cfqd->last_end_request = now; 1980 1981 if (sync) 1982 RQ_CIC(rq)->last_end_request = now; 1983 1984 /* 1985 * If this is the active queue, check if it needs to be expired, 1986 * or if we want to idle in case it has no pending requests. 1987 */ 1988 if (cfqd->active_queue == cfqq) { 1989 if (cfq_cfqq_slice_new(cfqq)) { 1990 cfq_set_prio_slice(cfqd, cfqq); 1991 cfq_clear_cfqq_slice_new(cfqq); 1992 } 1993 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq)) 1994 cfq_slice_expired(cfqd, 1); 1995 else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list)) 1996 cfq_arm_slice_timer(cfqd); 1997 } 1998 1999 if (!cfqd->rq_in_driver) 2000 cfq_schedule_dispatch(cfqd); 2001} 2002 2003/* 2004 * we temporarily boost lower priority queues if they are holding fs exclusive 2005 * resources. they are boosted to normal prio (CLASS_BE/4) 2006 */ 2007static void cfq_prio_boost(struct cfq_queue *cfqq) 2008{ 2009 if (has_fs_excl()) { 2010 /* 2011 * boost idle prio on transactions that would lock out other 2012 * users of the filesystem 2013 */ 2014 if (cfq_class_idle(cfqq)) 2015 cfqq->ioprio_class = IOPRIO_CLASS_BE; 2016 if (cfqq->ioprio > IOPRIO_NORM) 2017 cfqq->ioprio = IOPRIO_NORM; 2018 } else { 2019 /* 2020 * check if we need to unboost the queue 2021 */ 2022 if (cfqq->ioprio_class != cfqq->org_ioprio_class) 2023 cfqq->ioprio_class = cfqq->org_ioprio_class; 2024 if (cfqq->ioprio != cfqq->org_ioprio) 2025 cfqq->ioprio = cfqq->org_ioprio; 2026 } 2027} 2028 2029static inline int __cfq_may_queue(struct cfq_queue *cfqq) 2030{ 2031 if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) && 2032 !cfq_cfqq_must_alloc_slice(cfqq)) { 2033 cfq_mark_cfqq_must_alloc_slice(cfqq); 2034 return ELV_MQUEUE_MUST; 2035 } 2036 2037 return ELV_MQUEUE_MAY; 2038} 2039 2040static int cfq_may_queue(struct request_queue *q, int rw) 2041{ 2042 struct cfq_data *cfqd = q->elevator->elevator_data; 2043 struct task_struct *tsk = current; 2044 struct cfq_io_context *cic; 2045 struct cfq_queue *cfqq; 2046 2047 /* 2048 * don't force setup of a queue from here, as a call to may_queue 2049 * does not necessarily imply that a request actually will be queued. 2050 * so just lookup a possibly existing queue, or return 'may queue' 2051 * if that fails 2052 */ 2053 cic = cfq_cic_lookup(cfqd, tsk->io_context); 2054 if (!cic) 2055 return ELV_MQUEUE_MAY; 2056 2057 cfqq = cic_to_cfqq(cic, rw & REQ_RW_SYNC); 2058 if (cfqq) { 2059 cfq_init_prio_data(cfqq, cic->ioc); 2060 cfq_prio_boost(cfqq); 2061 2062 return __cfq_may_queue(cfqq); 2063 } 2064 2065 return ELV_MQUEUE_MAY; 2066} 2067 2068/* 2069 * queue lock held here 2070 */ 2071static void cfq_put_request(struct request *rq) 2072{ 2073 struct cfq_queue *cfqq = RQ_CFQQ(rq); 2074 2075 if (cfqq) { 2076 const int rw = rq_data_dir(rq); 2077 2078 BUG_ON(!cfqq->allocated[rw]); 2079 cfqq->allocated[rw]--; 2080 2081 put_io_context(RQ_CIC(rq)->ioc); 2082 2083 rq->elevator_private = NULL; 2084 rq->elevator_private2 = NULL; 2085 2086 cfq_put_queue(cfqq); 2087 } 2088} 2089 2090/* 2091 * Allocate cfq data structures associated with this request. 2092 */ 2093static int 2094cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) 2095{ 2096 struct cfq_data *cfqd = q->elevator->elevator_data; 2097 struct cfq_io_context *cic; 2098 const int rw = rq_data_dir(rq); 2099 const int is_sync = rq_is_sync(rq); 2100 struct cfq_queue *cfqq; 2101 unsigned long flags; 2102 2103 might_sleep_if(gfp_mask & __GFP_WAIT); 2104 2105 cic = cfq_get_io_context(cfqd, gfp_mask); 2106 2107 spin_lock_irqsave(q->queue_lock, flags); 2108 2109 if (!cic) 2110 goto queue_fail; 2111 2112 cfqq = cic_to_cfqq(cic, is_sync); 2113 if (!cfqq) { 2114 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask); 2115 2116 if (!cfqq) 2117 goto queue_fail; 2118 2119 cic_set_cfqq(cic, cfqq, is_sync); 2120 } 2121 2122 cfqq->allocated[rw]++; 2123 cfq_clear_cfqq_must_alloc(cfqq); 2124 atomic_inc(&cfqq->ref); 2125 2126 spin_unlock_irqrestore(q->queue_lock, flags); 2127 2128 rq->elevator_private = cic; 2129 rq->elevator_private2 = cfqq; 2130 return 0; 2131 2132queue_fail: 2133 if (cic) 2134 put_io_context(cic->ioc); 2135 2136 cfq_schedule_dispatch(cfqd); 2137 spin_unlock_irqrestore(q->queue_lock, flags); 2138 cfq_log(cfqd, "set_request fail"); 2139 return 1; 2140} 2141 2142static void cfq_kick_queue(struct work_struct *work) 2143{ 2144 struct cfq_data *cfqd = 2145 container_of(work, struct cfq_data, unplug_work); 2146 struct request_queue *q = cfqd->queue; 2147 unsigned long flags; 2148 2149 spin_lock_irqsave(q->queue_lock, flags); 2150 blk_start_queueing(q); 2151 spin_unlock_irqrestore(q->queue_lock, flags); 2152} 2153 2154/* 2155 * Timer running if the active_queue is currently idling inside its time slice 2156 */ 2157static void cfq_idle_slice_timer(unsigned long data) 2158{ 2159 struct cfq_data *cfqd = (struct cfq_data *) data; 2160 struct cfq_queue *cfqq; 2161 unsigned long flags; 2162 int timed_out = 1; 2163 2164 cfq_log(cfqd, "idle timer fired"); 2165 2166 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 2167 2168 cfqq = cfqd->active_queue; 2169 if (cfqq) { 2170 timed_out = 0; 2171 2172 /* 2173 * expired 2174 */ 2175 if (cfq_slice_used(cfqq)) 2176 goto expire; 2177 2178 /* 2179 * only expire and reinvoke request handler, if there are 2180 * other queues with pending requests 2181 */ 2182 if (!cfqd->busy_queues) 2183 goto out_cont; 2184 2185 /* 2186 * not expired and it has a request pending, let it dispatch 2187 */ 2188 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) { 2189 cfq_mark_cfqq_must_dispatch(cfqq); 2190 goto out_kick; 2191 } 2192 } 2193expire: 2194 cfq_slice_expired(cfqd, timed_out); 2195out_kick: 2196 cfq_schedule_dispatch(cfqd); 2197out_cont: 2198 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 2199} 2200 2201static void cfq_shutdown_timer_wq(struct cfq_data *cfqd) 2202{ 2203 del_timer_sync(&cfqd->idle_slice_timer); 2204 cancel_work_sync(&cfqd->unplug_work); 2205} 2206 2207static void cfq_put_async_queues(struct cfq_data *cfqd) 2208{ 2209 int i; 2210 2211 for (i = 0; i < IOPRIO_BE_NR; i++) { 2212 if (cfqd->async_cfqq[0][i]) 2213 cfq_put_queue(cfqd->async_cfqq[0][i]); 2214 if (cfqd->async_cfqq[1][i]) 2215 cfq_put_queue(cfqd->async_cfqq[1][i]); 2216 } 2217 2218 if (cfqd->async_idle_cfqq) 2219 cfq_put_queue(cfqd->async_idle_cfqq); 2220} 2221 2222static void cfq_exit_queue(struct elevator_queue *e) 2223{ 2224 struct cfq_data *cfqd = e->elevator_data; 2225 struct request_queue *q = cfqd->queue; 2226 2227 cfq_shutdown_timer_wq(cfqd); 2228 2229 spin_lock_irq(q->queue_lock); 2230 2231 if (cfqd->active_queue) 2232 __cfq_slice_expired(cfqd, cfqd->active_queue, 0); 2233 2234 while (!list_empty(&cfqd->cic_list)) { 2235 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next, 2236 struct cfq_io_context, 2237 queue_list); 2238 2239 __cfq_exit_single_io_context(cfqd, cic); 2240 } 2241 2242 cfq_put_async_queues(cfqd); 2243 2244 spin_unlock_irq(q->queue_lock); 2245 2246 cfq_shutdown_timer_wq(cfqd); 2247 2248 kfree(cfqd); 2249} 2250 2251static void *cfq_init_queue(struct request_queue *q) 2252{ 2253 struct cfq_data *cfqd; 2254 2255 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node); 2256 if (!cfqd) 2257 return NULL; 2258 2259 cfqd->service_tree = CFQ_RB_ROOT; 2260 INIT_LIST_HEAD(&cfqd->cic_list); 2261 2262 cfqd->queue = q; 2263 2264 init_timer(&cfqd->idle_slice_timer); 2265 cfqd->idle_slice_timer.function = cfq_idle_slice_timer; 2266 cfqd->idle_slice_timer.data = (unsigned long) cfqd; 2267 2268 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue); 2269 2270 cfqd->last_end_request = jiffies; 2271 cfqd->cfq_quantum = cfq_quantum; 2272 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0]; 2273 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1]; 2274 cfqd->cfq_back_max = cfq_back_max; 2275 cfqd->cfq_back_penalty = cfq_back_penalty; 2276 cfqd->cfq_slice[0] = cfq_slice_async; 2277 cfqd->cfq_slice[1] = cfq_slice_sync; 2278 cfqd->cfq_slice_async_rq = cfq_slice_async_rq; 2279 cfqd->cfq_slice_idle = cfq_slice_idle; 2280 cfqd->hw_tag = 1; 2281 2282 return cfqd; 2283} 2284 2285static void cfq_slab_kill(void) 2286{ 2287 /* 2288 * Caller already ensured that pending RCU callbacks are completed, 2289 * so we should have no busy allocations at this point. 2290 */ 2291 if (cfq_pool) 2292 kmem_cache_destroy(cfq_pool); 2293 if (cfq_ioc_pool) 2294 kmem_cache_destroy(cfq_ioc_pool); 2295} 2296 2297static int __init cfq_slab_setup(void) 2298{ 2299 cfq_pool = KMEM_CACHE(cfq_queue, 0); 2300 if (!cfq_pool) 2301 goto fail; 2302 2303 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0); 2304 if (!cfq_ioc_pool) 2305 goto fail; 2306 2307 return 0; 2308fail: 2309 cfq_slab_kill(); 2310 return -ENOMEM; 2311} 2312 2313/* 2314 * sysfs parts below --> 2315 */ 2316static ssize_t 2317cfq_var_show(unsigned int var, char *page) 2318{ 2319 return sprintf(page, "%d\n", var); 2320} 2321 2322static ssize_t 2323cfq_var_store(unsigned int *var, const char *page, size_t count) 2324{ 2325 char *p = (char *) page; 2326 2327 *var = simple_strtoul(p, &p, 10); 2328 return count; 2329} 2330 2331#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ 2332static ssize_t __FUNC(struct elevator_queue *e, char *page) \ 2333{ \ 2334 struct cfq_data *cfqd = e->elevator_data; \ 2335 unsigned int __data = __VAR; \ 2336 if (__CONV) \ 2337 __data = jiffies_to_msecs(__data); \ 2338 return cfq_var_show(__data, (page)); \ 2339} 2340SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0); 2341SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1); 2342SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1); 2343SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0); 2344SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0); 2345SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1); 2346SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1); 2347SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1); 2348SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0); 2349#undef SHOW_FUNCTION 2350 2351#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ 2352static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ 2353{ \ 2354 struct cfq_data *cfqd = e->elevator_data; \ 2355 unsigned int __data; \ 2356 int ret = cfq_var_store(&__data, (page), count); \ 2357 if (__data < (MIN)) \ 2358 __data = (MIN); \ 2359 else if (__data > (MAX)) \ 2360 __data = (MAX); \ 2361 if (__CONV) \ 2362 *(__PTR) = msecs_to_jiffies(__data); \ 2363 else \ 2364 *(__PTR) = __data; \ 2365 return ret; \ 2366} 2367STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0); 2368STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, 2369 UINT_MAX, 1); 2370STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, 2371 UINT_MAX, 1); 2372STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0); 2373STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, 2374 UINT_MAX, 0); 2375STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1); 2376STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1); 2377STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1); 2378STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, 2379 UINT_MAX, 0); 2380#undef STORE_FUNCTION 2381 2382#define CFQ_ATTR(name) \ 2383 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store) 2384 2385static struct elv_fs_entry cfq_attrs[] = { 2386 CFQ_ATTR(quantum), 2387 CFQ_ATTR(fifo_expire_sync), 2388 CFQ_ATTR(fifo_expire_async), 2389 CFQ_ATTR(back_seek_max), 2390 CFQ_ATTR(back_seek_penalty), 2391 CFQ_ATTR(slice_sync), 2392 CFQ_ATTR(slice_async), 2393 CFQ_ATTR(slice_async_rq), 2394 CFQ_ATTR(slice_idle), 2395 __ATTR_NULL 2396}; 2397 2398static struct elevator_type iosched_cfq = { 2399 .ops = { 2400 .elevator_merge_fn = cfq_merge, 2401 .elevator_merged_fn = cfq_merged_request, 2402 .elevator_merge_req_fn = cfq_merged_requests, 2403 .elevator_allow_merge_fn = cfq_allow_merge, 2404 .elevator_dispatch_fn = cfq_dispatch_requests, 2405 .elevator_add_req_fn = cfq_insert_request, 2406 .elevator_activate_req_fn = cfq_activate_request, 2407 .elevator_deactivate_req_fn = cfq_deactivate_request, 2408 .elevator_queue_empty_fn = cfq_queue_empty, 2409 .elevator_completed_req_fn = cfq_completed_request, 2410 .elevator_former_req_fn = elv_rb_former_request, 2411 .elevator_latter_req_fn = elv_rb_latter_request, 2412 .elevator_set_req_fn = cfq_set_request, 2413 .elevator_put_req_fn = cfq_put_request, 2414 .elevator_may_queue_fn = cfq_may_queue, 2415 .elevator_init_fn = cfq_init_queue, 2416 .elevator_exit_fn = cfq_exit_queue, 2417 .trim = cfq_free_io_context, 2418 }, 2419 .elevator_attrs = cfq_attrs, 2420 .elevator_name = "cfq", 2421 .elevator_owner = THIS_MODULE, 2422}; 2423 2424static int __init cfq_init(void) 2425{ 2426 /* 2427 * could be 0 on HZ < 1000 setups 2428 */ 2429 if (!cfq_slice_async) 2430 cfq_slice_async = 1; 2431 if (!cfq_slice_idle) 2432 cfq_slice_idle = 1; 2433 2434 if (cfq_slab_setup()) 2435 return -ENOMEM; 2436 2437 elv_register(&iosched_cfq); 2438 2439 return 0; 2440} 2441 2442static void __exit cfq_exit(void) 2443{ 2444 DECLARE_COMPLETION_ONSTACK(all_gone); 2445 elv_unregister(&iosched_cfq); 2446 ioc_gone = &all_gone; 2447 /* ioc_gone's update must be visible before reading ioc_count */ 2448 smp_wmb(); 2449 2450 /* 2451 * this also protects us from entering cfq_slab_kill() with 2452 * pending RCU callbacks 2453 */ 2454 if (elv_ioc_count_read(ioc_count)) 2455 wait_for_completion(&all_gone); 2456 cfq_slab_kill(); 2457} 2458 2459module_init(cfq_init); 2460module_exit(cfq_exit); 2461 2462MODULE_AUTHOR("Jens Axboe"); 2463MODULE_LICENSE("GPL"); 2464MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler"); 2465