cfq-iosched.c revision c265a7f41706cee20508de5b4a919214cfd7a11b
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 43#define RQ_CIC(rq) \ 44 ((struct cfq_io_context *) (rq)->elevator_private) 45#define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2) 46 47static struct kmem_cache *cfq_pool; 48static struct kmem_cache *cfq_ioc_pool; 49 50static DEFINE_PER_CPU(unsigned long, ioc_count); 51static struct completion *ioc_gone; 52static DEFINE_SPINLOCK(ioc_gone_lock); 53 54#define CFQ_PRIO_LISTS IOPRIO_BE_NR 55#define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE) 56#define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT) 57 58#define ASYNC (0) 59#define SYNC (1) 60 61#define sample_valid(samples) ((samples) > 80) 62 63/* 64 * Most of our rbtree usage is for sorting with min extraction, so 65 * if we cache the leftmost node we don't have to walk down the tree 66 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should 67 * move this into the elevator for the rq sorting as well. 68 */ 69struct cfq_rb_root { 70 struct rb_root rb; 71 struct rb_node *left; 72}; 73#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, } 74 75/* 76 * Per block device queue structure 77 */ 78struct cfq_data { 79 struct request_queue *queue; 80 81 /* 82 * rr list of queues with requests and the count of them 83 */ 84 struct cfq_rb_root service_tree; 85 unsigned int busy_queues; 86 87 int rq_in_driver; 88 int sync_flight; 89 int hw_tag; 90 91 /* 92 * idle window management 93 */ 94 struct timer_list idle_slice_timer; 95 struct work_struct unplug_work; 96 97 struct cfq_queue *active_queue; 98 struct cfq_io_context *active_cic; 99 100 /* 101 * async queue for each priority case 102 */ 103 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR]; 104 struct cfq_queue *async_idle_cfqq; 105 106 sector_t last_position; 107 unsigned long last_end_request; 108 109 /* 110 * tunables, see top of file 111 */ 112 unsigned int cfq_quantum; 113 unsigned int cfq_fifo_expire[2]; 114 unsigned int cfq_back_penalty; 115 unsigned int cfq_back_max; 116 unsigned int cfq_slice[2]; 117 unsigned int cfq_slice_async_rq; 118 unsigned int cfq_slice_idle; 119 120 struct list_head cic_list; 121}; 122 123/* 124 * Per process-grouping structure 125 */ 126struct cfq_queue { 127 /* reference count */ 128 atomic_t ref; 129 /* various state flags, see below */ 130 unsigned int flags; 131 /* parent cfq_data */ 132 struct cfq_data *cfqd; 133 /* service_tree member */ 134 struct rb_node rb_node; 135 /* service_tree key */ 136 unsigned long rb_key; 137 /* sorted list of pending requests */ 138 struct rb_root sort_list; 139 /* if fifo isn't expired, next request to serve */ 140 struct request *next_rq; 141 /* requests queued in sort_list */ 142 int queued[2]; 143 /* currently allocated requests */ 144 int allocated[2]; 145 /* fifo list of requests in sort_list */ 146 struct list_head fifo; 147 148 unsigned long slice_end; 149 long slice_resid; 150 151 /* pending metadata requests */ 152 int meta_pending; 153 /* number of requests that are on the dispatch list or inside driver */ 154 int dispatched; 155 156 /* io prio of this group */ 157 unsigned short ioprio, org_ioprio; 158 unsigned short ioprio_class, org_ioprio_class; 159 160 pid_t pid; 161}; 162 163enum cfqq_state_flags { 164 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */ 165 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */ 166 CFQ_CFQQ_FLAG_must_alloc, /* must be allowed rq alloc */ 167 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */ 168 CFQ_CFQQ_FLAG_must_dispatch, /* must dispatch, even if expired */ 169 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */ 170 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */ 171 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */ 172 CFQ_CFQQ_FLAG_queue_new, /* queue never been serviced */ 173 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */ 174 CFQ_CFQQ_FLAG_sync, /* synchronous queue */ 175}; 176 177#define CFQ_CFQQ_FNS(name) \ 178static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \ 179{ \ 180 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \ 181} \ 182static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \ 183{ \ 184 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \ 185} \ 186static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \ 187{ \ 188 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \ 189} 190 191CFQ_CFQQ_FNS(on_rr); 192CFQ_CFQQ_FNS(wait_request); 193CFQ_CFQQ_FNS(must_alloc); 194CFQ_CFQQ_FNS(must_alloc_slice); 195CFQ_CFQQ_FNS(must_dispatch); 196CFQ_CFQQ_FNS(fifo_expire); 197CFQ_CFQQ_FNS(idle_window); 198CFQ_CFQQ_FNS(prio_changed); 199CFQ_CFQQ_FNS(queue_new); 200CFQ_CFQQ_FNS(slice_new); 201CFQ_CFQQ_FNS(sync); 202#undef CFQ_CFQQ_FNS 203 204#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \ 205 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args) 206#define cfq_log(cfqd, fmt, args...) \ 207 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args) 208 209static void cfq_dispatch_insert(struct request_queue *, struct request *); 210static struct cfq_queue *cfq_get_queue(struct cfq_data *, int, 211 struct io_context *, gfp_t); 212static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *, 213 struct io_context *); 214 215static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic, 216 int is_sync) 217{ 218 return cic->cfqq[!!is_sync]; 219} 220 221static inline void cic_set_cfqq(struct cfq_io_context *cic, 222 struct cfq_queue *cfqq, int is_sync) 223{ 224 cic->cfqq[!!is_sync] = cfqq; 225} 226 227/* 228 * We regard a request as SYNC, if it's either a read or has the SYNC bit 229 * set (in which case it could also be direct WRITE). 230 */ 231static inline int cfq_bio_sync(struct bio *bio) 232{ 233 if (bio_data_dir(bio) == READ || bio_sync(bio)) 234 return 1; 235 236 return 0; 237} 238 239/* 240 * scheduler run of queue, if there are requests pending and no one in the 241 * driver that will restart queueing 242 */ 243static inline void cfq_schedule_dispatch(struct cfq_data *cfqd) 244{ 245 if (cfqd->busy_queues) { 246 cfq_log(cfqd, "schedule dispatch"); 247 kblockd_schedule_work(&cfqd->unplug_work); 248 } 249} 250 251static int cfq_queue_empty(struct request_queue *q) 252{ 253 struct cfq_data *cfqd = q->elevator->elevator_data; 254 255 return !cfqd->busy_queues; 256} 257 258/* 259 * Scale schedule slice based on io priority. Use the sync time slice only 260 * if a queue is marked sync and has sync io queued. A sync queue with async 261 * io only, should not get full sync slice length. 262 */ 263static inline int cfq_prio_slice(struct cfq_data *cfqd, int sync, 264 unsigned short prio) 265{ 266 const int base_slice = cfqd->cfq_slice[sync]; 267 268 WARN_ON(prio >= IOPRIO_BE_NR); 269 270 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio)); 271} 272 273static inline int 274cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 275{ 276 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio); 277} 278 279static inline void 280cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 281{ 282 cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies; 283 cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies); 284} 285 286/* 287 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end 288 * isn't valid until the first request from the dispatch is activated 289 * and the slice time set. 290 */ 291static inline int cfq_slice_used(struct cfq_queue *cfqq) 292{ 293 if (cfq_cfqq_slice_new(cfqq)) 294 return 0; 295 if (time_before(jiffies, cfqq->slice_end)) 296 return 0; 297 298 return 1; 299} 300 301/* 302 * Lifted from AS - choose which of rq1 and rq2 that is best served now. 303 * We choose the request that is closest to the head right now. Distance 304 * behind the head is penalized and only allowed to a certain extent. 305 */ 306static struct request * 307cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2) 308{ 309 sector_t last, s1, s2, d1 = 0, d2 = 0; 310 unsigned long back_max; 311#define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */ 312#define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */ 313 unsigned wrap = 0; /* bit mask: requests behind the disk head? */ 314 315 if (rq1 == NULL || rq1 == rq2) 316 return rq2; 317 if (rq2 == NULL) 318 return rq1; 319 320 if (rq_is_sync(rq1) && !rq_is_sync(rq2)) 321 return rq1; 322 else if (rq_is_sync(rq2) && !rq_is_sync(rq1)) 323 return rq2; 324 if (rq_is_meta(rq1) && !rq_is_meta(rq2)) 325 return rq1; 326 else if (rq_is_meta(rq2) && !rq_is_meta(rq1)) 327 return rq2; 328 329 s1 = rq1->sector; 330 s2 = rq2->sector; 331 332 last = cfqd->last_position; 333 334 /* 335 * by definition, 1KiB is 2 sectors 336 */ 337 back_max = cfqd->cfq_back_max * 2; 338 339 /* 340 * Strict one way elevator _except_ in the case where we allow 341 * short backward seeks which are biased as twice the cost of a 342 * similar forward seek. 343 */ 344 if (s1 >= last) 345 d1 = s1 - last; 346 else if (s1 + back_max >= last) 347 d1 = (last - s1) * cfqd->cfq_back_penalty; 348 else 349 wrap |= CFQ_RQ1_WRAP; 350 351 if (s2 >= last) 352 d2 = s2 - last; 353 else if (s2 + back_max >= last) 354 d2 = (last - s2) * cfqd->cfq_back_penalty; 355 else 356 wrap |= CFQ_RQ2_WRAP; 357 358 /* Found required data */ 359 360 /* 361 * By doing switch() on the bit mask "wrap" we avoid having to 362 * check two variables for all permutations: --> faster! 363 */ 364 switch (wrap) { 365 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */ 366 if (d1 < d2) 367 return rq1; 368 else if (d2 < d1) 369 return rq2; 370 else { 371 if (s1 >= s2) 372 return rq1; 373 else 374 return rq2; 375 } 376 377 case CFQ_RQ2_WRAP: 378 return rq1; 379 case CFQ_RQ1_WRAP: 380 return rq2; 381 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */ 382 default: 383 /* 384 * Since both rqs are wrapped, 385 * start with the one that's further behind head 386 * (--> only *one* back seek required), 387 * since back seek takes more time than forward. 388 */ 389 if (s1 <= s2) 390 return rq1; 391 else 392 return rq2; 393 } 394} 395 396/* 397 * The below is leftmost cache rbtree addon 398 */ 399static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root) 400{ 401 if (!root->left) 402 root->left = rb_first(&root->rb); 403 404 if (root->left) 405 return rb_entry(root->left, struct cfq_queue, rb_node); 406 407 return NULL; 408} 409 410static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root) 411{ 412 if (root->left == n) 413 root->left = NULL; 414 415 rb_erase(n, &root->rb); 416 RB_CLEAR_NODE(n); 417} 418 419/* 420 * would be nice to take fifo expire time into account as well 421 */ 422static struct request * 423cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq, 424 struct request *last) 425{ 426 struct rb_node *rbnext = rb_next(&last->rb_node); 427 struct rb_node *rbprev = rb_prev(&last->rb_node); 428 struct request *next = NULL, *prev = NULL; 429 430 BUG_ON(RB_EMPTY_NODE(&last->rb_node)); 431 432 if (rbprev) 433 prev = rb_entry_rq(rbprev); 434 435 if (rbnext) 436 next = rb_entry_rq(rbnext); 437 else { 438 rbnext = rb_first(&cfqq->sort_list); 439 if (rbnext && rbnext != &last->rb_node) 440 next = rb_entry_rq(rbnext); 441 } 442 443 return cfq_choose_req(cfqd, next, prev); 444} 445 446static unsigned long cfq_slice_offset(struct cfq_data *cfqd, 447 struct cfq_queue *cfqq) 448{ 449 /* 450 * just an approximation, should be ok. 451 */ 452 return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) - 453 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio)); 454} 455 456/* 457 * The cfqd->service_tree holds all pending cfq_queue's that have 458 * requests waiting to be processed. It is sorted in the order that 459 * we will service the queues. 460 */ 461static void cfq_service_tree_add(struct cfq_data *cfqd, 462 struct cfq_queue *cfqq, int add_front) 463{ 464 struct rb_node **p, *parent; 465 struct cfq_queue *__cfqq; 466 unsigned long rb_key; 467 int left; 468 469 if (cfq_class_idle(cfqq)) { 470 rb_key = CFQ_IDLE_DELAY; 471 parent = rb_last(&cfqd->service_tree.rb); 472 if (parent && parent != &cfqq->rb_node) { 473 __cfqq = rb_entry(parent, struct cfq_queue, rb_node); 474 rb_key += __cfqq->rb_key; 475 } else 476 rb_key += jiffies; 477 } else if (!add_front) { 478 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies; 479 rb_key += cfqq->slice_resid; 480 cfqq->slice_resid = 0; 481 } else 482 rb_key = 0; 483 484 if (!RB_EMPTY_NODE(&cfqq->rb_node)) { 485 /* 486 * same position, nothing more to do 487 */ 488 if (rb_key == cfqq->rb_key) 489 return; 490 491 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree); 492 } 493 494 left = 1; 495 parent = NULL; 496 p = &cfqd->service_tree.rb.rb_node; 497 while (*p) { 498 struct rb_node **n; 499 500 parent = *p; 501 __cfqq = rb_entry(parent, struct cfq_queue, rb_node); 502 503 /* 504 * sort RT queues first, we always want to give 505 * preference to them. IDLE queues goes to the back. 506 * after that, sort on the next service time. 507 */ 508 if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq)) 509 n = &(*p)->rb_left; 510 else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq)) 511 n = &(*p)->rb_right; 512 else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq)) 513 n = &(*p)->rb_left; 514 else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq)) 515 n = &(*p)->rb_right; 516 else if (rb_key < __cfqq->rb_key) 517 n = &(*p)->rb_left; 518 else 519 n = &(*p)->rb_right; 520 521 if (n == &(*p)->rb_right) 522 left = 0; 523 524 p = n; 525 } 526 527 if (left) 528 cfqd->service_tree.left = &cfqq->rb_node; 529 530 cfqq->rb_key = rb_key; 531 rb_link_node(&cfqq->rb_node, parent, p); 532 rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb); 533} 534 535/* 536 * Update cfqq's position in the service tree. 537 */ 538static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq) 539{ 540 /* 541 * Resorting requires the cfqq to be on the RR list already. 542 */ 543 if (cfq_cfqq_on_rr(cfqq)) 544 cfq_service_tree_add(cfqd, cfqq, 0); 545} 546 547/* 548 * add to busy list of queues for service, trying to be fair in ordering 549 * the pending list according to last request service 550 */ 551static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) 552{ 553 cfq_log_cfqq(cfqd, cfqq, "add_to_rr"); 554 BUG_ON(cfq_cfqq_on_rr(cfqq)); 555 cfq_mark_cfqq_on_rr(cfqq); 556 cfqd->busy_queues++; 557 558 cfq_resort_rr_list(cfqd, cfqq); 559} 560 561/* 562 * Called when the cfqq no longer has requests pending, remove it from 563 * the service tree. 564 */ 565static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) 566{ 567 cfq_log_cfqq(cfqd, cfqq, "del_from_rr"); 568 BUG_ON(!cfq_cfqq_on_rr(cfqq)); 569 cfq_clear_cfqq_on_rr(cfqq); 570 571 if (!RB_EMPTY_NODE(&cfqq->rb_node)) 572 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree); 573 574 BUG_ON(!cfqd->busy_queues); 575 cfqd->busy_queues--; 576} 577 578/* 579 * rb tree support functions 580 */ 581static void cfq_del_rq_rb(struct request *rq) 582{ 583 struct cfq_queue *cfqq = RQ_CFQQ(rq); 584 struct cfq_data *cfqd = cfqq->cfqd; 585 const int sync = rq_is_sync(rq); 586 587 BUG_ON(!cfqq->queued[sync]); 588 cfqq->queued[sync]--; 589 590 elv_rb_del(&cfqq->sort_list, rq); 591 592 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) 593 cfq_del_cfqq_rr(cfqd, cfqq); 594} 595 596static void cfq_add_rq_rb(struct request *rq) 597{ 598 struct cfq_queue *cfqq = RQ_CFQQ(rq); 599 struct cfq_data *cfqd = cfqq->cfqd; 600 struct request *__alias; 601 602 cfqq->queued[rq_is_sync(rq)]++; 603 604 /* 605 * looks a little odd, but the first insert might return an alias. 606 * if that happens, put the alias on the dispatch list 607 */ 608 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL) 609 cfq_dispatch_insert(cfqd->queue, __alias); 610 611 if (!cfq_cfqq_on_rr(cfqq)) 612 cfq_add_cfqq_rr(cfqd, cfqq); 613 614 /* 615 * check if this request is a better next-serve candidate 616 */ 617 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq); 618 BUG_ON(!cfqq->next_rq); 619} 620 621static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq) 622{ 623 elv_rb_del(&cfqq->sort_list, rq); 624 cfqq->queued[rq_is_sync(rq)]--; 625 cfq_add_rq_rb(rq); 626} 627 628static struct request * 629cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio) 630{ 631 struct task_struct *tsk = current; 632 struct cfq_io_context *cic; 633 struct cfq_queue *cfqq; 634 635 cic = cfq_cic_lookup(cfqd, tsk->io_context); 636 if (!cic) 637 return NULL; 638 639 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); 640 if (cfqq) { 641 sector_t sector = bio->bi_sector + bio_sectors(bio); 642 643 return elv_rb_find(&cfqq->sort_list, sector); 644 } 645 646 return NULL; 647} 648 649static void cfq_activate_request(struct request_queue *q, struct request *rq) 650{ 651 struct cfq_data *cfqd = q->elevator->elevator_data; 652 653 cfqd->rq_in_driver++; 654 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d", 655 cfqd->rq_in_driver); 656 657 /* 658 * If the depth is larger 1, it really could be queueing. But lets 659 * make the mark a little higher - idling could still be good for 660 * low queueing, and a low queueing number could also just indicate 661 * a SCSI mid layer like behaviour where limit+1 is often seen. 662 */ 663 if (!cfqd->hw_tag && cfqd->rq_in_driver > 4) 664 cfqd->hw_tag = 1; 665 666 cfqd->last_position = rq->hard_sector + rq->hard_nr_sectors; 667} 668 669static void cfq_deactivate_request(struct request_queue *q, struct request *rq) 670{ 671 struct cfq_data *cfqd = q->elevator->elevator_data; 672 673 WARN_ON(!cfqd->rq_in_driver); 674 cfqd->rq_in_driver--; 675 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d", 676 cfqd->rq_in_driver); 677} 678 679static void cfq_remove_request(struct request *rq) 680{ 681 struct cfq_queue *cfqq = RQ_CFQQ(rq); 682 683 if (cfqq->next_rq == rq) 684 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq); 685 686 list_del_init(&rq->queuelist); 687 cfq_del_rq_rb(rq); 688 689 if (rq_is_meta(rq)) { 690 WARN_ON(!cfqq->meta_pending); 691 cfqq->meta_pending--; 692 } 693} 694 695static int cfq_merge(struct request_queue *q, struct request **req, 696 struct bio *bio) 697{ 698 struct cfq_data *cfqd = q->elevator->elevator_data; 699 struct request *__rq; 700 701 __rq = cfq_find_rq_fmerge(cfqd, bio); 702 if (__rq && elv_rq_merge_ok(__rq, bio)) { 703 *req = __rq; 704 return ELEVATOR_FRONT_MERGE; 705 } 706 707 return ELEVATOR_NO_MERGE; 708} 709 710static void cfq_merged_request(struct request_queue *q, struct request *req, 711 int type) 712{ 713 if (type == ELEVATOR_FRONT_MERGE) { 714 struct cfq_queue *cfqq = RQ_CFQQ(req); 715 716 cfq_reposition_rq_rb(cfqq, req); 717 } 718} 719 720static void 721cfq_merged_requests(struct request_queue *q, struct request *rq, 722 struct request *next) 723{ 724 /* 725 * reposition in fifo if next is older than rq 726 */ 727 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && 728 time_before(next->start_time, rq->start_time)) 729 list_move(&rq->queuelist, &next->queuelist); 730 731 cfq_remove_request(next); 732} 733 734static int cfq_allow_merge(struct request_queue *q, struct request *rq, 735 struct bio *bio) 736{ 737 struct cfq_data *cfqd = q->elevator->elevator_data; 738 struct cfq_io_context *cic; 739 struct cfq_queue *cfqq; 740 741 /* 742 * Disallow merge of a sync bio into an async request. 743 */ 744 if (cfq_bio_sync(bio) && !rq_is_sync(rq)) 745 return 0; 746 747 /* 748 * Lookup the cfqq that this bio will be queued with. Allow 749 * merge only if rq is queued there. 750 */ 751 cic = cfq_cic_lookup(cfqd, current->io_context); 752 if (!cic) 753 return 0; 754 755 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); 756 if (cfqq == RQ_CFQQ(rq)) 757 return 1; 758 759 return 0; 760} 761 762static void __cfq_set_active_queue(struct cfq_data *cfqd, 763 struct cfq_queue *cfqq) 764{ 765 if (cfqq) { 766 cfq_log_cfqq(cfqd, cfqq, "set_active"); 767 cfqq->slice_end = 0; 768 cfq_clear_cfqq_must_alloc_slice(cfqq); 769 cfq_clear_cfqq_fifo_expire(cfqq); 770 cfq_mark_cfqq_slice_new(cfqq); 771 cfq_clear_cfqq_queue_new(cfqq); 772 } 773 774 cfqd->active_queue = cfqq; 775} 776 777/* 778 * current cfqq expired its slice (or was too idle), select new one 779 */ 780static void 781__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, 782 int timed_out) 783{ 784 cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out); 785 786 if (cfq_cfqq_wait_request(cfqq)) 787 del_timer(&cfqd->idle_slice_timer); 788 789 cfq_clear_cfqq_must_dispatch(cfqq); 790 cfq_clear_cfqq_wait_request(cfqq); 791 792 /* 793 * store what was left of this slice, if the queue idled/timed out 794 */ 795 if (timed_out && !cfq_cfqq_slice_new(cfqq)) { 796 cfqq->slice_resid = cfqq->slice_end - jiffies; 797 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid); 798 } 799 800 cfq_resort_rr_list(cfqd, cfqq); 801 802 if (cfqq == cfqd->active_queue) 803 cfqd->active_queue = NULL; 804 805 if (cfqd->active_cic) { 806 put_io_context(cfqd->active_cic->ioc); 807 cfqd->active_cic = NULL; 808 } 809} 810 811static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out) 812{ 813 struct cfq_queue *cfqq = cfqd->active_queue; 814 815 if (cfqq) 816 __cfq_slice_expired(cfqd, cfqq, timed_out); 817} 818 819/* 820 * Get next queue for service. Unless we have a queue preemption, 821 * we'll simply select the first cfqq in the service tree. 822 */ 823static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd) 824{ 825 if (RB_EMPTY_ROOT(&cfqd->service_tree.rb)) 826 return NULL; 827 828 return cfq_rb_first(&cfqd->service_tree); 829} 830 831/* 832 * Get and set a new active queue for service. 833 */ 834static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd) 835{ 836 struct cfq_queue *cfqq; 837 838 cfqq = cfq_get_next_queue(cfqd); 839 __cfq_set_active_queue(cfqd, cfqq); 840 return cfqq; 841} 842 843static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd, 844 struct request *rq) 845{ 846 if (rq->sector >= cfqd->last_position) 847 return rq->sector - cfqd->last_position; 848 else 849 return cfqd->last_position - rq->sector; 850} 851 852static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq) 853{ 854 struct cfq_io_context *cic = cfqd->active_cic; 855 856 if (!sample_valid(cic->seek_samples)) 857 return 0; 858 859 return cfq_dist_from_last(cfqd, rq) <= cic->seek_mean; 860} 861 862static int cfq_close_cooperator(struct cfq_data *cfq_data, 863 struct cfq_queue *cfqq) 864{ 865 /* 866 * We should notice if some of the queues are cooperating, eg 867 * working closely on the same area of the disk. In that case, 868 * we can group them together and don't waste time idling. 869 */ 870 return 0; 871} 872 873#define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024)) 874 875static void cfq_arm_slice_timer(struct cfq_data *cfqd) 876{ 877 struct cfq_queue *cfqq = cfqd->active_queue; 878 struct cfq_io_context *cic; 879 unsigned long sl; 880 881 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list)); 882 WARN_ON(cfq_cfqq_slice_new(cfqq)); 883 884 /* 885 * idle is disabled, either manually or by past process history 886 */ 887 if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq)) 888 return; 889 890 /* 891 * still requests with the driver, don't idle 892 */ 893 if (cfqd->rq_in_driver) 894 return; 895 896 /* 897 * task has exited, don't wait 898 */ 899 cic = cfqd->active_cic; 900 if (!cic || !atomic_read(&cic->ioc->nr_tasks)) 901 return; 902 903 /* 904 * See if this prio level has a good candidate 905 */ 906 if (cfq_close_cooperator(cfqd, cfqq) && 907 (sample_valid(cic->ttime_samples) && cic->ttime_mean > 2)) 908 return; 909 910 cfq_mark_cfqq_must_dispatch(cfqq); 911 cfq_mark_cfqq_wait_request(cfqq); 912 913 /* 914 * we don't want to idle for seeks, but we do want to allow 915 * fair distribution of slice time for a process doing back-to-back 916 * seeks. so allow a little bit of time for him to submit a new rq 917 */ 918 sl = cfqd->cfq_slice_idle; 919 if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic)) 920 sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT)); 921 922 mod_timer(&cfqd->idle_slice_timer, jiffies + sl); 923 cfq_log(cfqd, "arm_idle: %lu", sl); 924} 925 926/* 927 * Move request from internal lists to the request queue dispatch list. 928 */ 929static void cfq_dispatch_insert(struct request_queue *q, struct request *rq) 930{ 931 struct cfq_data *cfqd = q->elevator->elevator_data; 932 struct cfq_queue *cfqq = RQ_CFQQ(rq); 933 934 cfq_log_cfqq(cfqd, cfqq, "dispatch_insert"); 935 936 cfq_remove_request(rq); 937 cfqq->dispatched++; 938 elv_dispatch_sort(q, rq); 939 940 if (cfq_cfqq_sync(cfqq)) 941 cfqd->sync_flight++; 942} 943 944/* 945 * return expired entry, or NULL to just start from scratch in rbtree 946 */ 947static struct request *cfq_check_fifo(struct cfq_queue *cfqq) 948{ 949 struct cfq_data *cfqd = cfqq->cfqd; 950 struct request *rq; 951 int fifo; 952 953 if (cfq_cfqq_fifo_expire(cfqq)) 954 return NULL; 955 956 cfq_mark_cfqq_fifo_expire(cfqq); 957 958 if (list_empty(&cfqq->fifo)) 959 return NULL; 960 961 fifo = cfq_cfqq_sync(cfqq); 962 rq = rq_entry_fifo(cfqq->fifo.next); 963 964 if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) 965 rq = NULL; 966 967 cfq_log_cfqq(cfqd, cfqq, "fifo=%p", rq); 968 return rq; 969} 970 971static inline int 972cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq) 973{ 974 const int base_rq = cfqd->cfq_slice_async_rq; 975 976 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR); 977 978 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio)); 979} 980 981/* 982 * Select a queue for service. If we have a current active queue, 983 * check whether to continue servicing it, or retrieve and set a new one. 984 */ 985static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd) 986{ 987 struct cfq_queue *cfqq; 988 989 cfqq = cfqd->active_queue; 990 if (!cfqq) 991 goto new_queue; 992 993 /* 994 * The active queue has run out of time, expire it and select new. 995 */ 996 if (cfq_slice_used(cfqq)) 997 goto expire; 998 999 /* 1000 * The active queue has requests and isn't expired, allow it to 1001 * dispatch. 1002 */ 1003 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) 1004 goto keep_queue; 1005 1006 /* 1007 * No requests pending. If the active queue still has requests in 1008 * flight or is idling for a new request, allow either of these 1009 * conditions to happen (or time out) before selecting a new queue. 1010 */ 1011 if (timer_pending(&cfqd->idle_slice_timer) || 1012 (cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) { 1013 cfqq = NULL; 1014 goto keep_queue; 1015 } 1016 1017expire: 1018 cfq_slice_expired(cfqd, 0); 1019new_queue: 1020 cfqq = cfq_set_active_queue(cfqd); 1021keep_queue: 1022 return cfqq; 1023} 1024 1025/* 1026 * Dispatch some requests from cfqq, moving them to the request queue 1027 * dispatch list. 1028 */ 1029static int 1030__cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1031 int max_dispatch) 1032{ 1033 int dispatched = 0; 1034 1035 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list)); 1036 1037 do { 1038 struct request *rq; 1039 1040 /* 1041 * follow expired path, else get first next available 1042 */ 1043 rq = cfq_check_fifo(cfqq); 1044 if (rq == NULL) 1045 rq = cfqq->next_rq; 1046 1047 /* 1048 * finally, insert request into driver dispatch list 1049 */ 1050 cfq_dispatch_insert(cfqd->queue, rq); 1051 1052 dispatched++; 1053 1054 if (!cfqd->active_cic) { 1055 atomic_inc(&RQ_CIC(rq)->ioc->refcount); 1056 cfqd->active_cic = RQ_CIC(rq); 1057 } 1058 1059 if (RB_EMPTY_ROOT(&cfqq->sort_list)) 1060 break; 1061 1062 } while (dispatched < max_dispatch); 1063 1064 /* 1065 * expire an async queue immediately if it has used up its slice. idle 1066 * queue always expire after 1 dispatch round. 1067 */ 1068 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) && 1069 dispatched >= cfq_prio_to_maxrq(cfqd, cfqq)) || 1070 cfq_class_idle(cfqq))) { 1071 cfqq->slice_end = jiffies + 1; 1072 cfq_slice_expired(cfqd, 0); 1073 } 1074 1075 return dispatched; 1076} 1077 1078static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq) 1079{ 1080 int dispatched = 0; 1081 1082 while (cfqq->next_rq) { 1083 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq); 1084 dispatched++; 1085 } 1086 1087 BUG_ON(!list_empty(&cfqq->fifo)); 1088 return dispatched; 1089} 1090 1091/* 1092 * Drain our current requests. Used for barriers and when switching 1093 * io schedulers on-the-fly. 1094 */ 1095static int cfq_forced_dispatch(struct cfq_data *cfqd) 1096{ 1097 struct cfq_queue *cfqq; 1098 int dispatched = 0; 1099 1100 while ((cfqq = cfq_rb_first(&cfqd->service_tree)) != NULL) 1101 dispatched += __cfq_forced_dispatch_cfqq(cfqq); 1102 1103 cfq_slice_expired(cfqd, 0); 1104 1105 BUG_ON(cfqd->busy_queues); 1106 1107 cfq_log(cfqd, "forced_dispatch=%d\n", dispatched); 1108 return dispatched; 1109} 1110 1111static int cfq_dispatch_requests(struct request_queue *q, int force) 1112{ 1113 struct cfq_data *cfqd = q->elevator->elevator_data; 1114 struct cfq_queue *cfqq; 1115 int dispatched; 1116 1117 if (!cfqd->busy_queues) 1118 return 0; 1119 1120 if (unlikely(force)) 1121 return cfq_forced_dispatch(cfqd); 1122 1123 dispatched = 0; 1124 while ((cfqq = cfq_select_queue(cfqd)) != NULL) { 1125 int max_dispatch; 1126 1127 max_dispatch = cfqd->cfq_quantum; 1128 if (cfq_class_idle(cfqq)) 1129 max_dispatch = 1; 1130 1131 if (cfqq->dispatched >= max_dispatch) { 1132 if (cfqd->busy_queues > 1) 1133 break; 1134 if (cfqq->dispatched >= 4 * max_dispatch) 1135 break; 1136 } 1137 1138 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq)) 1139 break; 1140 1141 cfq_clear_cfqq_must_dispatch(cfqq); 1142 cfq_clear_cfqq_wait_request(cfqq); 1143 del_timer(&cfqd->idle_slice_timer); 1144 1145 dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch); 1146 } 1147 1148 cfq_log(cfqd, "dispatched=%d", dispatched); 1149 return dispatched; 1150} 1151 1152/* 1153 * task holds one reference to the queue, dropped when task exits. each rq 1154 * in-flight on this queue also holds a reference, dropped when rq is freed. 1155 * 1156 * queue lock must be held here. 1157 */ 1158static void cfq_put_queue(struct cfq_queue *cfqq) 1159{ 1160 struct cfq_data *cfqd = cfqq->cfqd; 1161 1162 BUG_ON(atomic_read(&cfqq->ref) <= 0); 1163 1164 if (!atomic_dec_and_test(&cfqq->ref)) 1165 return; 1166 1167 cfq_log_cfqq(cfqd, cfqq, "put_queue"); 1168 BUG_ON(rb_first(&cfqq->sort_list)); 1169 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]); 1170 BUG_ON(cfq_cfqq_on_rr(cfqq)); 1171 1172 if (unlikely(cfqd->active_queue == cfqq)) { 1173 __cfq_slice_expired(cfqd, cfqq, 0); 1174 cfq_schedule_dispatch(cfqd); 1175 } 1176 1177 kmem_cache_free(cfq_pool, cfqq); 1178} 1179 1180/* 1181 * Must always be called with the rcu_read_lock() held 1182 */ 1183static void 1184__call_for_each_cic(struct io_context *ioc, 1185 void (*func)(struct io_context *, struct cfq_io_context *)) 1186{ 1187 struct cfq_io_context *cic; 1188 struct hlist_node *n; 1189 1190 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list) 1191 func(ioc, cic); 1192} 1193 1194/* 1195 * Call func for each cic attached to this ioc. 1196 */ 1197static void 1198call_for_each_cic(struct io_context *ioc, 1199 void (*func)(struct io_context *, struct cfq_io_context *)) 1200{ 1201 rcu_read_lock(); 1202 __call_for_each_cic(ioc, func); 1203 rcu_read_unlock(); 1204} 1205 1206static void cfq_cic_free_rcu(struct rcu_head *head) 1207{ 1208 struct cfq_io_context *cic; 1209 1210 cic = container_of(head, struct cfq_io_context, rcu_head); 1211 1212 kmem_cache_free(cfq_ioc_pool, cic); 1213 elv_ioc_count_dec(ioc_count); 1214 1215 if (ioc_gone) { 1216 /* 1217 * CFQ scheduler is exiting, grab exit lock and check 1218 * the pending io context count. If it hits zero, 1219 * complete ioc_gone and set it back to NULL 1220 */ 1221 spin_lock(&ioc_gone_lock); 1222 if (ioc_gone && !elv_ioc_count_read(ioc_count)) { 1223 complete(ioc_gone); 1224 ioc_gone = NULL; 1225 } 1226 spin_unlock(&ioc_gone_lock); 1227 } 1228} 1229 1230static void cfq_cic_free(struct cfq_io_context *cic) 1231{ 1232 call_rcu(&cic->rcu_head, cfq_cic_free_rcu); 1233} 1234 1235static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic) 1236{ 1237 unsigned long flags; 1238 1239 BUG_ON(!cic->dead_key); 1240 1241 spin_lock_irqsave(&ioc->lock, flags); 1242 radix_tree_delete(&ioc->radix_root, cic->dead_key); 1243 hlist_del_rcu(&cic->cic_list); 1244 spin_unlock_irqrestore(&ioc->lock, flags); 1245 1246 cfq_cic_free(cic); 1247} 1248 1249/* 1250 * Must be called with rcu_read_lock() held or preemption otherwise disabled. 1251 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(), 1252 * and ->trim() which is called with the task lock held 1253 */ 1254static void cfq_free_io_context(struct io_context *ioc) 1255{ 1256 /* 1257 * ioc->refcount is zero here, or we are called from elv_unregister(), 1258 * so no more cic's are allowed to be linked into this ioc. So it 1259 * should be ok to iterate over the known list, we will see all cic's 1260 * since no new ones are added. 1261 */ 1262 __call_for_each_cic(ioc, cic_free_func); 1263} 1264 1265static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1266{ 1267 if (unlikely(cfqq == cfqd->active_queue)) { 1268 __cfq_slice_expired(cfqd, cfqq, 0); 1269 cfq_schedule_dispatch(cfqd); 1270 } 1271 1272 cfq_put_queue(cfqq); 1273} 1274 1275static void __cfq_exit_single_io_context(struct cfq_data *cfqd, 1276 struct cfq_io_context *cic) 1277{ 1278 struct io_context *ioc = cic->ioc; 1279 1280 list_del_init(&cic->queue_list); 1281 1282 /* 1283 * Make sure key == NULL is seen for dead queues 1284 */ 1285 smp_wmb(); 1286 cic->dead_key = (unsigned long) cic->key; 1287 cic->key = NULL; 1288 1289 if (ioc->ioc_data == cic) 1290 rcu_assign_pointer(ioc->ioc_data, NULL); 1291 1292 if (cic->cfqq[ASYNC]) { 1293 cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]); 1294 cic->cfqq[ASYNC] = NULL; 1295 } 1296 1297 if (cic->cfqq[SYNC]) { 1298 cfq_exit_cfqq(cfqd, cic->cfqq[SYNC]); 1299 cic->cfqq[SYNC] = NULL; 1300 } 1301} 1302 1303static void cfq_exit_single_io_context(struct io_context *ioc, 1304 struct cfq_io_context *cic) 1305{ 1306 struct cfq_data *cfqd = cic->key; 1307 1308 if (cfqd) { 1309 struct request_queue *q = cfqd->queue; 1310 unsigned long flags; 1311 1312 spin_lock_irqsave(q->queue_lock, flags); 1313 __cfq_exit_single_io_context(cfqd, cic); 1314 spin_unlock_irqrestore(q->queue_lock, flags); 1315 } 1316} 1317 1318/* 1319 * The process that ioc belongs to has exited, we need to clean up 1320 * and put the internal structures we have that belongs to that process. 1321 */ 1322static void cfq_exit_io_context(struct io_context *ioc) 1323{ 1324 call_for_each_cic(ioc, cfq_exit_single_io_context); 1325} 1326 1327static struct cfq_io_context * 1328cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 1329{ 1330 struct cfq_io_context *cic; 1331 1332 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO, 1333 cfqd->queue->node); 1334 if (cic) { 1335 cic->last_end_request = jiffies; 1336 INIT_LIST_HEAD(&cic->queue_list); 1337 INIT_HLIST_NODE(&cic->cic_list); 1338 cic->dtor = cfq_free_io_context; 1339 cic->exit = cfq_exit_io_context; 1340 elv_ioc_count_inc(ioc_count); 1341 } 1342 1343 return cic; 1344} 1345 1346static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc) 1347{ 1348 struct task_struct *tsk = current; 1349 int ioprio_class; 1350 1351 if (!cfq_cfqq_prio_changed(cfqq)) 1352 return; 1353 1354 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio); 1355 switch (ioprio_class) { 1356 default: 1357 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class); 1358 case IOPRIO_CLASS_NONE: 1359 /* 1360 * no prio set, inherit CPU scheduling settings 1361 */ 1362 cfqq->ioprio = task_nice_ioprio(tsk); 1363 cfqq->ioprio_class = task_nice_ioclass(tsk); 1364 break; 1365 case IOPRIO_CLASS_RT: 1366 cfqq->ioprio = task_ioprio(ioc); 1367 cfqq->ioprio_class = IOPRIO_CLASS_RT; 1368 break; 1369 case IOPRIO_CLASS_BE: 1370 cfqq->ioprio = task_ioprio(ioc); 1371 cfqq->ioprio_class = IOPRIO_CLASS_BE; 1372 break; 1373 case IOPRIO_CLASS_IDLE: 1374 cfqq->ioprio_class = IOPRIO_CLASS_IDLE; 1375 cfqq->ioprio = 7; 1376 cfq_clear_cfqq_idle_window(cfqq); 1377 break; 1378 } 1379 1380 /* 1381 * keep track of original prio settings in case we have to temporarily 1382 * elevate the priority of this queue 1383 */ 1384 cfqq->org_ioprio = cfqq->ioprio; 1385 cfqq->org_ioprio_class = cfqq->ioprio_class; 1386 cfq_clear_cfqq_prio_changed(cfqq); 1387} 1388 1389static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic) 1390{ 1391 struct cfq_data *cfqd = cic->key; 1392 struct cfq_queue *cfqq; 1393 unsigned long flags; 1394 1395 if (unlikely(!cfqd)) 1396 return; 1397 1398 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 1399 1400 cfqq = cic->cfqq[ASYNC]; 1401 if (cfqq) { 1402 struct cfq_queue *new_cfqq; 1403 new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc, GFP_ATOMIC); 1404 if (new_cfqq) { 1405 cic->cfqq[ASYNC] = new_cfqq; 1406 cfq_put_queue(cfqq); 1407 } 1408 } 1409 1410 cfqq = cic->cfqq[SYNC]; 1411 if (cfqq) 1412 cfq_mark_cfqq_prio_changed(cfqq); 1413 1414 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 1415} 1416 1417static void cfq_ioc_set_ioprio(struct io_context *ioc) 1418{ 1419 call_for_each_cic(ioc, changed_ioprio); 1420 ioc->ioprio_changed = 0; 1421} 1422 1423static struct cfq_queue * 1424cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync, 1425 struct io_context *ioc, gfp_t gfp_mask) 1426{ 1427 struct cfq_queue *cfqq, *new_cfqq = NULL; 1428 struct cfq_io_context *cic; 1429 1430retry: 1431 cic = cfq_cic_lookup(cfqd, ioc); 1432 /* cic always exists here */ 1433 cfqq = cic_to_cfqq(cic, is_sync); 1434 1435 if (!cfqq) { 1436 if (new_cfqq) { 1437 cfqq = new_cfqq; 1438 new_cfqq = NULL; 1439 } else if (gfp_mask & __GFP_WAIT) { 1440 /* 1441 * Inform the allocator of the fact that we will 1442 * just repeat this allocation if it fails, to allow 1443 * the allocator to do whatever it needs to attempt to 1444 * free memory. 1445 */ 1446 spin_unlock_irq(cfqd->queue->queue_lock); 1447 new_cfqq = kmem_cache_alloc_node(cfq_pool, 1448 gfp_mask | __GFP_NOFAIL | __GFP_ZERO, 1449 cfqd->queue->node); 1450 spin_lock_irq(cfqd->queue->queue_lock); 1451 goto retry; 1452 } else { 1453 cfqq = kmem_cache_alloc_node(cfq_pool, 1454 gfp_mask | __GFP_ZERO, 1455 cfqd->queue->node); 1456 if (!cfqq) 1457 goto out; 1458 } 1459 1460 RB_CLEAR_NODE(&cfqq->rb_node); 1461 INIT_LIST_HEAD(&cfqq->fifo); 1462 1463 atomic_set(&cfqq->ref, 0); 1464 cfqq->cfqd = cfqd; 1465 1466 cfq_mark_cfqq_prio_changed(cfqq); 1467 cfq_mark_cfqq_queue_new(cfqq); 1468 1469 cfq_init_prio_data(cfqq, ioc); 1470 1471 if (is_sync) { 1472 if (!cfq_class_idle(cfqq)) 1473 cfq_mark_cfqq_idle_window(cfqq); 1474 cfq_mark_cfqq_sync(cfqq); 1475 } 1476 cfqq->pid = current->pid; 1477 cfq_log_cfqq(cfqd, cfqq, "alloced"); 1478 } 1479 1480 if (new_cfqq) 1481 kmem_cache_free(cfq_pool, new_cfqq); 1482 1483out: 1484 WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq); 1485 return cfqq; 1486} 1487 1488static struct cfq_queue ** 1489cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio) 1490{ 1491 switch (ioprio_class) { 1492 case IOPRIO_CLASS_RT: 1493 return &cfqd->async_cfqq[0][ioprio]; 1494 case IOPRIO_CLASS_BE: 1495 return &cfqd->async_cfqq[1][ioprio]; 1496 case IOPRIO_CLASS_IDLE: 1497 return &cfqd->async_idle_cfqq; 1498 default: 1499 BUG(); 1500 } 1501} 1502 1503static struct cfq_queue * 1504cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc, 1505 gfp_t gfp_mask) 1506{ 1507 const int ioprio = task_ioprio(ioc); 1508 const int ioprio_class = task_ioprio_class(ioc); 1509 struct cfq_queue **async_cfqq = NULL; 1510 struct cfq_queue *cfqq = NULL; 1511 1512 if (!is_sync) { 1513 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio); 1514 cfqq = *async_cfqq; 1515 } 1516 1517 if (!cfqq) { 1518 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask); 1519 if (!cfqq) 1520 return NULL; 1521 } 1522 1523 /* 1524 * pin the queue now that it's allocated, scheduler exit will prune it 1525 */ 1526 if (!is_sync && !(*async_cfqq)) { 1527 atomic_inc(&cfqq->ref); 1528 *async_cfqq = cfqq; 1529 } 1530 1531 atomic_inc(&cfqq->ref); 1532 return cfqq; 1533} 1534 1535/* 1536 * We drop cfq io contexts lazily, so we may find a dead one. 1537 */ 1538static void 1539cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc, 1540 struct cfq_io_context *cic) 1541{ 1542 unsigned long flags; 1543 1544 WARN_ON(!list_empty(&cic->queue_list)); 1545 1546 spin_lock_irqsave(&ioc->lock, flags); 1547 1548 BUG_ON(ioc->ioc_data == cic); 1549 1550 radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd); 1551 hlist_del_rcu(&cic->cic_list); 1552 spin_unlock_irqrestore(&ioc->lock, flags); 1553 1554 cfq_cic_free(cic); 1555} 1556 1557static struct cfq_io_context * 1558cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc) 1559{ 1560 struct cfq_io_context *cic; 1561 unsigned long flags; 1562 void *k; 1563 1564 if (unlikely(!ioc)) 1565 return NULL; 1566 1567 rcu_read_lock(); 1568 1569 /* 1570 * we maintain a last-hit cache, to avoid browsing over the tree 1571 */ 1572 cic = rcu_dereference(ioc->ioc_data); 1573 if (cic && cic->key == cfqd) { 1574 rcu_read_unlock(); 1575 return cic; 1576 } 1577 1578 do { 1579 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd); 1580 rcu_read_unlock(); 1581 if (!cic) 1582 break; 1583 /* ->key must be copied to avoid race with cfq_exit_queue() */ 1584 k = cic->key; 1585 if (unlikely(!k)) { 1586 cfq_drop_dead_cic(cfqd, ioc, cic); 1587 rcu_read_lock(); 1588 continue; 1589 } 1590 1591 spin_lock_irqsave(&ioc->lock, flags); 1592 rcu_assign_pointer(ioc->ioc_data, cic); 1593 spin_unlock_irqrestore(&ioc->lock, flags); 1594 break; 1595 } while (1); 1596 1597 return cic; 1598} 1599 1600/* 1601 * Add cic into ioc, using cfqd as the search key. This enables us to lookup 1602 * the process specific cfq io context when entered from the block layer. 1603 * Also adds the cic to a per-cfqd list, used when this queue is removed. 1604 */ 1605static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc, 1606 struct cfq_io_context *cic, gfp_t gfp_mask) 1607{ 1608 unsigned long flags; 1609 int ret; 1610 1611 ret = radix_tree_preload(gfp_mask); 1612 if (!ret) { 1613 cic->ioc = ioc; 1614 cic->key = cfqd; 1615 1616 spin_lock_irqsave(&ioc->lock, flags); 1617 ret = radix_tree_insert(&ioc->radix_root, 1618 (unsigned long) cfqd, cic); 1619 if (!ret) 1620 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list); 1621 spin_unlock_irqrestore(&ioc->lock, flags); 1622 1623 radix_tree_preload_end(); 1624 1625 if (!ret) { 1626 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 1627 list_add(&cic->queue_list, &cfqd->cic_list); 1628 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 1629 } 1630 } 1631 1632 if (ret) 1633 printk(KERN_ERR "cfq: cic link failed!\n"); 1634 1635 return ret; 1636} 1637 1638/* 1639 * Setup general io context and cfq io context. There can be several cfq 1640 * io contexts per general io context, if this process is doing io to more 1641 * than one device managed by cfq. 1642 */ 1643static struct cfq_io_context * 1644cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 1645{ 1646 struct io_context *ioc = NULL; 1647 struct cfq_io_context *cic; 1648 1649 might_sleep_if(gfp_mask & __GFP_WAIT); 1650 1651 ioc = get_io_context(gfp_mask, cfqd->queue->node); 1652 if (!ioc) 1653 return NULL; 1654 1655 cic = cfq_cic_lookup(cfqd, ioc); 1656 if (cic) 1657 goto out; 1658 1659 cic = cfq_alloc_io_context(cfqd, gfp_mask); 1660 if (cic == NULL) 1661 goto err; 1662 1663 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask)) 1664 goto err_free; 1665 1666out: 1667 smp_read_barrier_depends(); 1668 if (unlikely(ioc->ioprio_changed)) 1669 cfq_ioc_set_ioprio(ioc); 1670 1671 return cic; 1672err_free: 1673 cfq_cic_free(cic); 1674err: 1675 put_io_context(ioc); 1676 return NULL; 1677} 1678 1679static void 1680cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic) 1681{ 1682 unsigned long elapsed = jiffies - cic->last_end_request; 1683 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle); 1684 1685 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8; 1686 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8; 1687 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples; 1688} 1689 1690static void 1691cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic, 1692 struct request *rq) 1693{ 1694 sector_t sdist; 1695 u64 total; 1696 1697 if (cic->last_request_pos < rq->sector) 1698 sdist = rq->sector - cic->last_request_pos; 1699 else 1700 sdist = cic->last_request_pos - rq->sector; 1701 1702 /* 1703 * Don't allow the seek distance to get too large from the 1704 * odd fragment, pagein, etc 1705 */ 1706 if (cic->seek_samples <= 60) /* second&third seek */ 1707 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024); 1708 else 1709 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64); 1710 1711 cic->seek_samples = (7*cic->seek_samples + 256) / 8; 1712 cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8; 1713 total = cic->seek_total + (cic->seek_samples/2); 1714 do_div(total, cic->seek_samples); 1715 cic->seek_mean = (sector_t)total; 1716} 1717 1718/* 1719 * Disable idle window if the process thinks too long or seeks so much that 1720 * it doesn't matter 1721 */ 1722static void 1723cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1724 struct cfq_io_context *cic) 1725{ 1726 int old_idle, enable_idle; 1727 1728 /* 1729 * Don't idle for async or idle io prio class 1730 */ 1731 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq)) 1732 return; 1733 1734 enable_idle = old_idle = cfq_cfqq_idle_window(cfqq); 1735 1736 if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle || 1737 (cfqd->hw_tag && CIC_SEEKY(cic))) 1738 enable_idle = 0; 1739 else if (sample_valid(cic->ttime_samples)) { 1740 if (cic->ttime_mean > cfqd->cfq_slice_idle) 1741 enable_idle = 0; 1742 else 1743 enable_idle = 1; 1744 } 1745 1746 if (old_idle != enable_idle) { 1747 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle); 1748 if (enable_idle) 1749 cfq_mark_cfqq_idle_window(cfqq); 1750 else 1751 cfq_clear_cfqq_idle_window(cfqq); 1752 } 1753} 1754 1755/* 1756 * Check if new_cfqq should preempt the currently active queue. Return 0 for 1757 * no or if we aren't sure, a 1 will cause a preempt. 1758 */ 1759static int 1760cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, 1761 struct request *rq) 1762{ 1763 struct cfq_queue *cfqq; 1764 1765 cfqq = cfqd->active_queue; 1766 if (!cfqq) 1767 return 0; 1768 1769 if (cfq_slice_used(cfqq)) 1770 return 1; 1771 1772 if (cfq_class_idle(new_cfqq)) 1773 return 0; 1774 1775 if (cfq_class_idle(cfqq)) 1776 return 1; 1777 1778 /* 1779 * if the new request is sync, but the currently running queue is 1780 * not, let the sync request have priority. 1781 */ 1782 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq)) 1783 return 1; 1784 1785 /* 1786 * So both queues are sync. Let the new request get disk time if 1787 * it's a metadata request and the current queue is doing regular IO. 1788 */ 1789 if (rq_is_meta(rq) && !cfqq->meta_pending) 1790 return 1; 1791 1792 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq)) 1793 return 0; 1794 1795 /* 1796 * if this request is as-good as one we would expect from the 1797 * current cfqq, let it preempt 1798 */ 1799 if (cfq_rq_close(cfqd, rq)) 1800 return 1; 1801 1802 return 0; 1803} 1804 1805/* 1806 * cfqq preempts the active queue. if we allowed preempt with no slice left, 1807 * let it have half of its nominal slice. 1808 */ 1809static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1810{ 1811 cfq_log_cfqq(cfqd, cfqq, "preempt"); 1812 cfq_slice_expired(cfqd, 1); 1813 1814 /* 1815 * Put the new queue at the front of the of the current list, 1816 * so we know that it will be selected next. 1817 */ 1818 BUG_ON(!cfq_cfqq_on_rr(cfqq)); 1819 1820 cfq_service_tree_add(cfqd, cfqq, 1); 1821 1822 cfqq->slice_end = 0; 1823 cfq_mark_cfqq_slice_new(cfqq); 1824} 1825 1826/* 1827 * Called when a new fs request (rq) is added (to cfqq). Check if there's 1828 * something we should do about it 1829 */ 1830static void 1831cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1832 struct request *rq) 1833{ 1834 struct cfq_io_context *cic = RQ_CIC(rq); 1835 1836 if (rq_is_meta(rq)) 1837 cfqq->meta_pending++; 1838 1839 cfq_update_io_thinktime(cfqd, cic); 1840 cfq_update_io_seektime(cfqd, cic, rq); 1841 cfq_update_idle_window(cfqd, cfqq, cic); 1842 1843 cic->last_request_pos = rq->sector + rq->nr_sectors; 1844 1845 if (cfqq == cfqd->active_queue) { 1846 /* 1847 * if we are waiting for a request for this queue, let it rip 1848 * immediately and flag that we must not expire this queue 1849 * just now 1850 */ 1851 if (cfq_cfqq_wait_request(cfqq)) { 1852 cfq_mark_cfqq_must_dispatch(cfqq); 1853 del_timer(&cfqd->idle_slice_timer); 1854 blk_start_queueing(cfqd->queue); 1855 } 1856 } else if (cfq_should_preempt(cfqd, cfqq, rq)) { 1857 /* 1858 * not the active queue - expire current slice if it is 1859 * idle and has expired it's mean thinktime or this new queue 1860 * has some old slice time left and is of higher priority 1861 */ 1862 cfq_preempt_queue(cfqd, cfqq); 1863 cfq_mark_cfqq_must_dispatch(cfqq); 1864 blk_start_queueing(cfqd->queue); 1865 } 1866} 1867 1868static void cfq_insert_request(struct request_queue *q, struct request *rq) 1869{ 1870 struct cfq_data *cfqd = q->elevator->elevator_data; 1871 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1872 1873 cfq_log_cfqq(cfqd, cfqq, "insert_request"); 1874 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc); 1875 1876 cfq_add_rq_rb(rq); 1877 1878 list_add_tail(&rq->queuelist, &cfqq->fifo); 1879 1880 cfq_rq_enqueued(cfqd, cfqq, rq); 1881} 1882 1883static void cfq_completed_request(struct request_queue *q, struct request *rq) 1884{ 1885 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1886 struct cfq_data *cfqd = cfqq->cfqd; 1887 const int sync = rq_is_sync(rq); 1888 unsigned long now; 1889 1890 now = jiffies; 1891 cfq_log_cfqq(cfqd, cfqq, "complete"); 1892 1893 WARN_ON(!cfqd->rq_in_driver); 1894 WARN_ON(!cfqq->dispatched); 1895 cfqd->rq_in_driver--; 1896 cfqq->dispatched--; 1897 1898 if (cfq_cfqq_sync(cfqq)) 1899 cfqd->sync_flight--; 1900 1901 if (!cfq_class_idle(cfqq)) 1902 cfqd->last_end_request = now; 1903 1904 if (sync) 1905 RQ_CIC(rq)->last_end_request = now; 1906 1907 /* 1908 * If this is the active queue, check if it needs to be expired, 1909 * or if we want to idle in case it has no pending requests. 1910 */ 1911 if (cfqd->active_queue == cfqq) { 1912 if (cfq_cfqq_slice_new(cfqq)) { 1913 cfq_set_prio_slice(cfqd, cfqq); 1914 cfq_clear_cfqq_slice_new(cfqq); 1915 } 1916 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq)) 1917 cfq_slice_expired(cfqd, 1); 1918 else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list)) 1919 cfq_arm_slice_timer(cfqd); 1920 } 1921 1922 if (!cfqd->rq_in_driver) 1923 cfq_schedule_dispatch(cfqd); 1924} 1925 1926/* 1927 * we temporarily boost lower priority queues if they are holding fs exclusive 1928 * resources. they are boosted to normal prio (CLASS_BE/4) 1929 */ 1930static void cfq_prio_boost(struct cfq_queue *cfqq) 1931{ 1932 if (has_fs_excl()) { 1933 /* 1934 * boost idle prio on transactions that would lock out other 1935 * users of the filesystem 1936 */ 1937 if (cfq_class_idle(cfqq)) 1938 cfqq->ioprio_class = IOPRIO_CLASS_BE; 1939 if (cfqq->ioprio > IOPRIO_NORM) 1940 cfqq->ioprio = IOPRIO_NORM; 1941 } else { 1942 /* 1943 * check if we need to unboost the queue 1944 */ 1945 if (cfqq->ioprio_class != cfqq->org_ioprio_class) 1946 cfqq->ioprio_class = cfqq->org_ioprio_class; 1947 if (cfqq->ioprio != cfqq->org_ioprio) 1948 cfqq->ioprio = cfqq->org_ioprio; 1949 } 1950} 1951 1952static inline int __cfq_may_queue(struct cfq_queue *cfqq) 1953{ 1954 if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) && 1955 !cfq_cfqq_must_alloc_slice(cfqq)) { 1956 cfq_mark_cfqq_must_alloc_slice(cfqq); 1957 return ELV_MQUEUE_MUST; 1958 } 1959 1960 return ELV_MQUEUE_MAY; 1961} 1962 1963static int cfq_may_queue(struct request_queue *q, int rw) 1964{ 1965 struct cfq_data *cfqd = q->elevator->elevator_data; 1966 struct task_struct *tsk = current; 1967 struct cfq_io_context *cic; 1968 struct cfq_queue *cfqq; 1969 1970 /* 1971 * don't force setup of a queue from here, as a call to may_queue 1972 * does not necessarily imply that a request actually will be queued. 1973 * so just lookup a possibly existing queue, or return 'may queue' 1974 * if that fails 1975 */ 1976 cic = cfq_cic_lookup(cfqd, tsk->io_context); 1977 if (!cic) 1978 return ELV_MQUEUE_MAY; 1979 1980 cfqq = cic_to_cfqq(cic, rw & REQ_RW_SYNC); 1981 if (cfqq) { 1982 cfq_init_prio_data(cfqq, cic->ioc); 1983 cfq_prio_boost(cfqq); 1984 1985 return __cfq_may_queue(cfqq); 1986 } 1987 1988 return ELV_MQUEUE_MAY; 1989} 1990 1991/* 1992 * queue lock held here 1993 */ 1994static void cfq_put_request(struct request *rq) 1995{ 1996 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1997 1998 if (cfqq) { 1999 const int rw = rq_data_dir(rq); 2000 2001 BUG_ON(!cfqq->allocated[rw]); 2002 cfqq->allocated[rw]--; 2003 2004 put_io_context(RQ_CIC(rq)->ioc); 2005 2006 rq->elevator_private = NULL; 2007 rq->elevator_private2 = NULL; 2008 2009 cfq_put_queue(cfqq); 2010 } 2011} 2012 2013/* 2014 * Allocate cfq data structures associated with this request. 2015 */ 2016static int 2017cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) 2018{ 2019 struct cfq_data *cfqd = q->elevator->elevator_data; 2020 struct cfq_io_context *cic; 2021 const int rw = rq_data_dir(rq); 2022 const int is_sync = rq_is_sync(rq); 2023 struct cfq_queue *cfqq; 2024 unsigned long flags; 2025 2026 might_sleep_if(gfp_mask & __GFP_WAIT); 2027 2028 cic = cfq_get_io_context(cfqd, gfp_mask); 2029 2030 spin_lock_irqsave(q->queue_lock, flags); 2031 2032 if (!cic) 2033 goto queue_fail; 2034 2035 cfqq = cic_to_cfqq(cic, is_sync); 2036 if (!cfqq) { 2037 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask); 2038 2039 if (!cfqq) 2040 goto queue_fail; 2041 2042 cic_set_cfqq(cic, cfqq, is_sync); 2043 } 2044 2045 cfqq->allocated[rw]++; 2046 cfq_clear_cfqq_must_alloc(cfqq); 2047 atomic_inc(&cfqq->ref); 2048 2049 spin_unlock_irqrestore(q->queue_lock, flags); 2050 2051 rq->elevator_private = cic; 2052 rq->elevator_private2 = cfqq; 2053 return 0; 2054 2055queue_fail: 2056 if (cic) 2057 put_io_context(cic->ioc); 2058 2059 cfq_schedule_dispatch(cfqd); 2060 spin_unlock_irqrestore(q->queue_lock, flags); 2061 cfq_log(cfqd, "set_request fail"); 2062 return 1; 2063} 2064 2065static void cfq_kick_queue(struct work_struct *work) 2066{ 2067 struct cfq_data *cfqd = 2068 container_of(work, struct cfq_data, unplug_work); 2069 struct request_queue *q = cfqd->queue; 2070 unsigned long flags; 2071 2072 spin_lock_irqsave(q->queue_lock, flags); 2073 blk_start_queueing(q); 2074 spin_unlock_irqrestore(q->queue_lock, flags); 2075} 2076 2077/* 2078 * Timer running if the active_queue is currently idling inside its time slice 2079 */ 2080static void cfq_idle_slice_timer(unsigned long data) 2081{ 2082 struct cfq_data *cfqd = (struct cfq_data *) data; 2083 struct cfq_queue *cfqq; 2084 unsigned long flags; 2085 int timed_out = 1; 2086 2087 cfq_log(cfqd, "idle timer fired"); 2088 2089 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 2090 2091 cfqq = cfqd->active_queue; 2092 if (cfqq) { 2093 timed_out = 0; 2094 2095 /* 2096 * expired 2097 */ 2098 if (cfq_slice_used(cfqq)) 2099 goto expire; 2100 2101 /* 2102 * only expire and reinvoke request handler, if there are 2103 * other queues with pending requests 2104 */ 2105 if (!cfqd->busy_queues) 2106 goto out_cont; 2107 2108 /* 2109 * not expired and it has a request pending, let it dispatch 2110 */ 2111 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) { 2112 cfq_mark_cfqq_must_dispatch(cfqq); 2113 goto out_kick; 2114 } 2115 } 2116expire: 2117 cfq_slice_expired(cfqd, timed_out); 2118out_kick: 2119 cfq_schedule_dispatch(cfqd); 2120out_cont: 2121 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 2122} 2123 2124static void cfq_shutdown_timer_wq(struct cfq_data *cfqd) 2125{ 2126 del_timer_sync(&cfqd->idle_slice_timer); 2127 kblockd_flush_work(&cfqd->unplug_work); 2128} 2129 2130static void cfq_put_async_queues(struct cfq_data *cfqd) 2131{ 2132 int i; 2133 2134 for (i = 0; i < IOPRIO_BE_NR; i++) { 2135 if (cfqd->async_cfqq[0][i]) 2136 cfq_put_queue(cfqd->async_cfqq[0][i]); 2137 if (cfqd->async_cfqq[1][i]) 2138 cfq_put_queue(cfqd->async_cfqq[1][i]); 2139 } 2140 2141 if (cfqd->async_idle_cfqq) 2142 cfq_put_queue(cfqd->async_idle_cfqq); 2143} 2144 2145static void cfq_exit_queue(elevator_t *e) 2146{ 2147 struct cfq_data *cfqd = e->elevator_data; 2148 struct request_queue *q = cfqd->queue; 2149 2150 cfq_shutdown_timer_wq(cfqd); 2151 2152 spin_lock_irq(q->queue_lock); 2153 2154 if (cfqd->active_queue) 2155 __cfq_slice_expired(cfqd, cfqd->active_queue, 0); 2156 2157 while (!list_empty(&cfqd->cic_list)) { 2158 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next, 2159 struct cfq_io_context, 2160 queue_list); 2161 2162 __cfq_exit_single_io_context(cfqd, cic); 2163 } 2164 2165 cfq_put_async_queues(cfqd); 2166 2167 spin_unlock_irq(q->queue_lock); 2168 2169 cfq_shutdown_timer_wq(cfqd); 2170 2171 kfree(cfqd); 2172} 2173 2174static void *cfq_init_queue(struct request_queue *q) 2175{ 2176 struct cfq_data *cfqd; 2177 2178 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node); 2179 if (!cfqd) 2180 return NULL; 2181 2182 cfqd->service_tree = CFQ_RB_ROOT; 2183 INIT_LIST_HEAD(&cfqd->cic_list); 2184 2185 cfqd->queue = q; 2186 2187 init_timer(&cfqd->idle_slice_timer); 2188 cfqd->idle_slice_timer.function = cfq_idle_slice_timer; 2189 cfqd->idle_slice_timer.data = (unsigned long) cfqd; 2190 2191 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue); 2192 2193 cfqd->last_end_request = jiffies; 2194 cfqd->cfq_quantum = cfq_quantum; 2195 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0]; 2196 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1]; 2197 cfqd->cfq_back_max = cfq_back_max; 2198 cfqd->cfq_back_penalty = cfq_back_penalty; 2199 cfqd->cfq_slice[0] = cfq_slice_async; 2200 cfqd->cfq_slice[1] = cfq_slice_sync; 2201 cfqd->cfq_slice_async_rq = cfq_slice_async_rq; 2202 cfqd->cfq_slice_idle = cfq_slice_idle; 2203 2204 return cfqd; 2205} 2206 2207static void cfq_slab_kill(void) 2208{ 2209 /* 2210 * Caller already ensured that pending RCU callbacks are completed, 2211 * so we should have no busy allocations at this point. 2212 */ 2213 if (cfq_pool) 2214 kmem_cache_destroy(cfq_pool); 2215 if (cfq_ioc_pool) 2216 kmem_cache_destroy(cfq_ioc_pool); 2217} 2218 2219static int __init cfq_slab_setup(void) 2220{ 2221 cfq_pool = KMEM_CACHE(cfq_queue, 0); 2222 if (!cfq_pool) 2223 goto fail; 2224 2225 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0); 2226 if (!cfq_ioc_pool) 2227 goto fail; 2228 2229 return 0; 2230fail: 2231 cfq_slab_kill(); 2232 return -ENOMEM; 2233} 2234 2235/* 2236 * sysfs parts below --> 2237 */ 2238static ssize_t 2239cfq_var_show(unsigned int var, char *page) 2240{ 2241 return sprintf(page, "%d\n", var); 2242} 2243 2244static ssize_t 2245cfq_var_store(unsigned int *var, const char *page, size_t count) 2246{ 2247 char *p = (char *) page; 2248 2249 *var = simple_strtoul(p, &p, 10); 2250 return count; 2251} 2252 2253#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ 2254static ssize_t __FUNC(elevator_t *e, char *page) \ 2255{ \ 2256 struct cfq_data *cfqd = e->elevator_data; \ 2257 unsigned int __data = __VAR; \ 2258 if (__CONV) \ 2259 __data = jiffies_to_msecs(__data); \ 2260 return cfq_var_show(__data, (page)); \ 2261} 2262SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0); 2263SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1); 2264SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1); 2265SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0); 2266SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0); 2267SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1); 2268SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1); 2269SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1); 2270SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0); 2271#undef SHOW_FUNCTION 2272 2273#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ 2274static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \ 2275{ \ 2276 struct cfq_data *cfqd = e->elevator_data; \ 2277 unsigned int __data; \ 2278 int ret = cfq_var_store(&__data, (page), count); \ 2279 if (__data < (MIN)) \ 2280 __data = (MIN); \ 2281 else if (__data > (MAX)) \ 2282 __data = (MAX); \ 2283 if (__CONV) \ 2284 *(__PTR) = msecs_to_jiffies(__data); \ 2285 else \ 2286 *(__PTR) = __data; \ 2287 return ret; \ 2288} 2289STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0); 2290STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, 2291 UINT_MAX, 1); 2292STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, 2293 UINT_MAX, 1); 2294STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0); 2295STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, 2296 UINT_MAX, 0); 2297STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1); 2298STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1); 2299STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1); 2300STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, 2301 UINT_MAX, 0); 2302#undef STORE_FUNCTION 2303 2304#define CFQ_ATTR(name) \ 2305 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store) 2306 2307static struct elv_fs_entry cfq_attrs[] = { 2308 CFQ_ATTR(quantum), 2309 CFQ_ATTR(fifo_expire_sync), 2310 CFQ_ATTR(fifo_expire_async), 2311 CFQ_ATTR(back_seek_max), 2312 CFQ_ATTR(back_seek_penalty), 2313 CFQ_ATTR(slice_sync), 2314 CFQ_ATTR(slice_async), 2315 CFQ_ATTR(slice_async_rq), 2316 CFQ_ATTR(slice_idle), 2317 __ATTR_NULL 2318}; 2319 2320static struct elevator_type iosched_cfq = { 2321 .ops = { 2322 .elevator_merge_fn = cfq_merge, 2323 .elevator_merged_fn = cfq_merged_request, 2324 .elevator_merge_req_fn = cfq_merged_requests, 2325 .elevator_allow_merge_fn = cfq_allow_merge, 2326 .elevator_dispatch_fn = cfq_dispatch_requests, 2327 .elevator_add_req_fn = cfq_insert_request, 2328 .elevator_activate_req_fn = cfq_activate_request, 2329 .elevator_deactivate_req_fn = cfq_deactivate_request, 2330 .elevator_queue_empty_fn = cfq_queue_empty, 2331 .elevator_completed_req_fn = cfq_completed_request, 2332 .elevator_former_req_fn = elv_rb_former_request, 2333 .elevator_latter_req_fn = elv_rb_latter_request, 2334 .elevator_set_req_fn = cfq_set_request, 2335 .elevator_put_req_fn = cfq_put_request, 2336 .elevator_may_queue_fn = cfq_may_queue, 2337 .elevator_init_fn = cfq_init_queue, 2338 .elevator_exit_fn = cfq_exit_queue, 2339 .trim = cfq_free_io_context, 2340 }, 2341 .elevator_attrs = cfq_attrs, 2342 .elevator_name = "cfq", 2343 .elevator_owner = THIS_MODULE, 2344}; 2345 2346static int __init cfq_init(void) 2347{ 2348 /* 2349 * could be 0 on HZ < 1000 setups 2350 */ 2351 if (!cfq_slice_async) 2352 cfq_slice_async = 1; 2353 if (!cfq_slice_idle) 2354 cfq_slice_idle = 1; 2355 2356 if (cfq_slab_setup()) 2357 return -ENOMEM; 2358 2359 elv_register(&iosched_cfq); 2360 2361 return 0; 2362} 2363 2364static void __exit cfq_exit(void) 2365{ 2366 DECLARE_COMPLETION_ONSTACK(all_gone); 2367 elv_unregister(&iosched_cfq); 2368 ioc_gone = &all_gone; 2369 /* ioc_gone's update must be visible before reading ioc_count */ 2370 smp_wmb(); 2371 2372 /* 2373 * this also protects us from entering cfq_slab_kill() with 2374 * pending RCU callbacks 2375 */ 2376 if (elv_ioc_count_read(ioc_count)) 2377 wait_for_completion(&all_gone); 2378 cfq_slab_kill(); 2379} 2380 2381module_init(cfq_init); 2382module_exit(cfq_exit); 2383 2384MODULE_AUTHOR("Jens Axboe"); 2385MODULE_LICENSE("GPL"); 2386MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler"); 2387