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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/slab.h> | |
11 | #include <linux/blkdev.h> | |
12 | #include <linux/elevator.h> | |
13 | #include <linux/jiffies.h> | |
14 | #include <linux/rbtree.h> | |
15 | #include <linux/ioprio.h> | |
16 | #include <linux/blktrace_api.h> | |
17 | #include "cfq.h" | |
18 | ||
19 | /* | |
20 | * tunables | |
21 | */ | |
22 | /* max queue in one round of service */ | |
23 | static const int cfq_quantum = 8; | |
24 | static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 }; | |
25 | /* maximum backwards seek, in KiB */ | |
26 | static const int cfq_back_max = 16 * 1024; | |
27 | /* penalty of a backwards seek */ | |
28 | static const int cfq_back_penalty = 2; | |
29 | static const int cfq_slice_sync = HZ / 10; | |
30 | static int cfq_slice_async = HZ / 25; | |
31 | static const int cfq_slice_async_rq = 2; | |
32 | static int cfq_slice_idle = HZ / 125; | |
33 | static int cfq_group_idle = HZ / 125; | |
34 | static const int cfq_target_latency = HZ * 3/10; /* 300 ms */ | |
35 | static const int cfq_hist_divisor = 4; | |
36 | ||
37 | /* | |
38 | * offset from end of service tree | |
39 | */ | |
40 | #define CFQ_IDLE_DELAY (HZ / 5) | |
41 | ||
42 | /* | |
43 | * below this threshold, we consider thinktime immediate | |
44 | */ | |
45 | #define CFQ_MIN_TT (2) | |
46 | ||
47 | #define CFQ_SLICE_SCALE (5) | |
48 | #define CFQ_HW_QUEUE_MIN (5) | |
49 | #define CFQ_SERVICE_SHIFT 12 | |
50 | ||
51 | #define CFQQ_SEEK_THR (sector_t)(8 * 100) | |
52 | #define CFQQ_CLOSE_THR (sector_t)(8 * 1024) | |
53 | #define CFQQ_SECT_THR_NONROT (sector_t)(2 * 32) | |
54 | #define CFQQ_SEEKY(cfqq) (hweight32(cfqq->seek_history) > 32/8) | |
55 | ||
56 | #define RQ_CIC(rq) \ | |
57 | ((struct cfq_io_context *) (rq)->elevator_private[0]) | |
58 | #define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private[1]) | |
59 | #define RQ_CFQG(rq) (struct cfq_group *) ((rq)->elevator_private[2]) | |
60 | ||
61 | static struct kmem_cache *cfq_pool; | |
62 | static struct kmem_cache *cfq_ioc_pool; | |
63 | ||
64 | static DEFINE_PER_CPU(unsigned long, cfq_ioc_count); | |
65 | static struct completion *ioc_gone; | |
66 | static DEFINE_SPINLOCK(ioc_gone_lock); | |
67 | ||
68 | static DEFINE_SPINLOCK(cic_index_lock); | |
69 | static DEFINE_IDA(cic_index_ida); | |
70 | ||
71 | #define CFQ_PRIO_LISTS IOPRIO_BE_NR | |
72 | #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE) | |
73 | #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT) | |
74 | ||
75 | #define sample_valid(samples) ((samples) > 80) | |
76 | #define rb_entry_cfqg(node) rb_entry((node), struct cfq_group, rb_node) | |
77 | ||
78 | /* | |
79 | * Most of our rbtree usage is for sorting with min extraction, so | |
80 | * if we cache the leftmost node we don't have to walk down the tree | |
81 | * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should | |
82 | * move this into the elevator for the rq sorting as well. | |
83 | */ | |
84 | struct cfq_rb_root { | |
85 | struct rb_root rb; | |
86 | struct rb_node *left; | |
87 | unsigned count; | |
88 | unsigned total_weight; | |
89 | u64 min_vdisktime; | |
90 | struct cfq_ttime ttime; | |
91 | }; | |
92 | #define CFQ_RB_ROOT (struct cfq_rb_root) { .rb = RB_ROOT, \ | |
93 | .ttime = {.last_end_request = jiffies,},} | |
94 | ||
95 | /* | |
96 | * Per process-grouping structure | |
97 | */ | |
98 | struct cfq_queue { | |
99 | /* reference count */ | |
100 | int ref; | |
101 | /* various state flags, see below */ | |
102 | unsigned int flags; | |
103 | /* parent cfq_data */ | |
104 | struct cfq_data *cfqd; | |
105 | /* service_tree member */ | |
106 | struct rb_node rb_node; | |
107 | /* service_tree key */ | |
108 | unsigned long rb_key; | |
109 | /* prio tree member */ | |
110 | struct rb_node p_node; | |
111 | /* prio tree root we belong to, if any */ | |
112 | struct rb_root *p_root; | |
113 | /* sorted list of pending requests */ | |
114 | struct rb_root sort_list; | |
115 | /* if fifo isn't expired, next request to serve */ | |
116 | struct request *next_rq; | |
117 | /* requests queued in sort_list */ | |
118 | int queued[2]; | |
119 | /* currently allocated requests */ | |
120 | int allocated[2]; | |
121 | /* fifo list of requests in sort_list */ | |
122 | struct list_head fifo; | |
123 | ||
124 | /* time when queue got scheduled in to dispatch first request. */ | |
125 | unsigned long dispatch_start; | |
126 | unsigned int allocated_slice; | |
127 | unsigned int slice_dispatch; | |
128 | /* time when first request from queue completed and slice started. */ | |
129 | unsigned long slice_start; | |
130 | unsigned long slice_end; | |
131 | long slice_resid; | |
132 | ||
133 | /* number of requests that are on the dispatch list or inside driver */ | |
134 | int dispatched; | |
135 | ||
136 | /* io prio of this group */ | |
137 | unsigned short ioprio, org_ioprio; | |
138 | unsigned short ioprio_class; | |
139 | ||
140 | pid_t pid; | |
141 | ||
142 | u32 seek_history; | |
143 | sector_t last_request_pos; | |
144 | ||
145 | struct cfq_rb_root *service_tree; | |
146 | struct cfq_queue *new_cfqq; | |
147 | struct cfq_group *cfqg; | |
148 | /* Number of sectors dispatched from queue in single dispatch round */ | |
149 | unsigned long nr_sectors; | |
150 | }; | |
151 | ||
152 | /* | |
153 | * First index in the service_trees. | |
154 | * IDLE is handled separately, so it has negative index | |
155 | */ | |
156 | enum wl_prio_t { | |
157 | BE_WORKLOAD = 0, | |
158 | RT_WORKLOAD = 1, | |
159 | IDLE_WORKLOAD = 2, | |
160 | CFQ_PRIO_NR, | |
161 | }; | |
162 | ||
163 | /* | |
164 | * Second index in the service_trees. | |
165 | */ | |
166 | enum wl_type_t { | |
167 | ASYNC_WORKLOAD = 0, | |
168 | SYNC_NOIDLE_WORKLOAD = 1, | |
169 | SYNC_WORKLOAD = 2 | |
170 | }; | |
171 | ||
172 | /* This is per cgroup per device grouping structure */ | |
173 | struct cfq_group { | |
174 | /* group service_tree member */ | |
175 | struct rb_node rb_node; | |
176 | ||
177 | /* group service_tree key */ | |
178 | u64 vdisktime; | |
179 | unsigned int weight; | |
180 | unsigned int new_weight; | |
181 | bool needs_update; | |
182 | ||
183 | /* number of cfqq currently on this group */ | |
184 | int nr_cfqq; | |
185 | ||
186 | /* | |
187 | * Per group busy queues average. Useful for workload slice calc. We | |
188 | * create the array for each prio class but at run time it is used | |
189 | * only for RT and BE class and slot for IDLE class remains unused. | |
190 | * This is primarily done to avoid confusion and a gcc warning. | |
191 | */ | |
192 | unsigned int busy_queues_avg[CFQ_PRIO_NR]; | |
193 | /* | |
194 | * rr lists of queues with requests. We maintain service trees for | |
195 | * RT and BE classes. These trees are subdivided in subclasses | |
196 | * of SYNC, SYNC_NOIDLE and ASYNC based on workload type. For IDLE | |
197 | * class there is no subclassification and all the cfq queues go on | |
198 | * a single tree service_tree_idle. | |
199 | * Counts are embedded in the cfq_rb_root | |
200 | */ | |
201 | struct cfq_rb_root service_trees[2][3]; | |
202 | struct cfq_rb_root service_tree_idle; | |
203 | ||
204 | unsigned long saved_workload_slice; | |
205 | enum wl_type_t saved_workload; | |
206 | enum wl_prio_t saved_serving_prio; | |
207 | struct blkio_group blkg; | |
208 | #ifdef CONFIG_CFQ_GROUP_IOSCHED | |
209 | struct hlist_node cfqd_node; | |
210 | int ref; | |
211 | #endif | |
212 | /* number of requests that are on the dispatch list or inside driver */ | |
213 | int dispatched; | |
214 | }; | |
215 | ||
216 | /* | |
217 | * Per block device queue structure | |
218 | */ | |
219 | struct cfq_data { | |
220 | struct request_queue *queue; | |
221 | /* Root service tree for cfq_groups */ | |
222 | struct cfq_rb_root grp_service_tree; | |
223 | struct cfq_group root_group; | |
224 | ||
225 | /* | |
226 | * The priority currently being served | |
227 | */ | |
228 | enum wl_prio_t serving_prio; | |
229 | enum wl_type_t serving_type; | |
230 | unsigned long workload_expires; | |
231 | struct cfq_group *serving_group; | |
232 | ||
233 | /* | |
234 | * Each priority tree is sorted by next_request position. These | |
235 | * trees are used when determining if two or more queues are | |
236 | * interleaving requests (see cfq_close_cooperator). | |
237 | */ | |
238 | struct rb_root prio_trees[CFQ_PRIO_LISTS]; | |
239 | ||
240 | unsigned int busy_queues; | |
241 | unsigned int busy_sync_queues; | |
242 | ||
243 | int rq_in_driver; | |
244 | int rq_in_flight[2]; | |
245 | ||
246 | /* | |
247 | * queue-depth detection | |
248 | */ | |
249 | int rq_queued; | |
250 | int hw_tag; | |
251 | /* | |
252 | * hw_tag can be | |
253 | * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection) | |
254 | * 1 => NCQ is present (hw_tag_est_depth is the estimated max depth) | |
255 | * 0 => no NCQ | |
256 | */ | |
257 | int hw_tag_est_depth; | |
258 | unsigned int hw_tag_samples; | |
259 | ||
260 | /* | |
261 | * idle window management | |
262 | */ | |
263 | struct timer_list idle_slice_timer; | |
264 | struct work_struct unplug_work; | |
265 | ||
266 | struct cfq_queue *active_queue; | |
267 | struct cfq_io_context *active_cic; | |
268 | ||
269 | /* | |
270 | * async queue for each priority case | |
271 | */ | |
272 | struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR]; | |
273 | struct cfq_queue *async_idle_cfqq; | |
274 | ||
275 | sector_t last_position; | |
276 | ||
277 | /* | |
278 | * tunables, see top of file | |
279 | */ | |
280 | unsigned int cfq_quantum; | |
281 | unsigned int cfq_fifo_expire[2]; | |
282 | unsigned int cfq_back_penalty; | |
283 | unsigned int cfq_back_max; | |
284 | unsigned int cfq_slice[2]; | |
285 | unsigned int cfq_slice_async_rq; | |
286 | unsigned int cfq_slice_idle; | |
287 | unsigned int cfq_group_idle; | |
288 | unsigned int cfq_latency; | |
289 | ||
290 | unsigned int cic_index; | |
291 | struct list_head cic_list; | |
292 | ||
293 | /* | |
294 | * Fallback dummy cfqq for extreme OOM conditions | |
295 | */ | |
296 | struct cfq_queue oom_cfqq; | |
297 | ||
298 | unsigned long last_delayed_sync; | |
299 | ||
300 | /* List of cfq groups being managed on this device*/ | |
301 | struct hlist_head cfqg_list; | |
302 | ||
303 | /* Number of groups which are on blkcg->blkg_list */ | |
304 | unsigned int nr_blkcg_linked_grps; | |
305 | }; | |
306 | ||
307 | static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd); | |
308 | ||
309 | static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg, | |
310 | enum wl_prio_t prio, | |
311 | enum wl_type_t type) | |
312 | { | |
313 | if (!cfqg) | |
314 | return NULL; | |
315 | ||
316 | if (prio == IDLE_WORKLOAD) | |
317 | return &cfqg->service_tree_idle; | |
318 | ||
319 | return &cfqg->service_trees[prio][type]; | |
320 | } | |
321 | ||
322 | enum cfqq_state_flags { | |
323 | CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */ | |
324 | CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */ | |
325 | CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */ | |
326 | CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */ | |
327 | CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */ | |
328 | CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */ | |
329 | CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */ | |
330 | CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */ | |
331 | CFQ_CFQQ_FLAG_sync, /* synchronous queue */ | |
332 | CFQ_CFQQ_FLAG_coop, /* cfqq is shared */ | |
333 | CFQ_CFQQ_FLAG_split_coop, /* shared cfqq will be splitted */ | |
334 | CFQ_CFQQ_FLAG_deep, /* sync cfqq experienced large depth */ | |
335 | CFQ_CFQQ_FLAG_wait_busy, /* Waiting for next request */ | |
336 | }; | |
337 | ||
338 | #define CFQ_CFQQ_FNS(name) \ | |
339 | static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \ | |
340 | { \ | |
341 | (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \ | |
342 | } \ | |
343 | static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \ | |
344 | { \ | |
345 | (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \ | |
346 | } \ | |
347 | static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \ | |
348 | { \ | |
349 | return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \ | |
350 | } | |
351 | ||
352 | CFQ_CFQQ_FNS(on_rr); | |
353 | CFQ_CFQQ_FNS(wait_request); | |
354 | CFQ_CFQQ_FNS(must_dispatch); | |
355 | CFQ_CFQQ_FNS(must_alloc_slice); | |
356 | CFQ_CFQQ_FNS(fifo_expire); | |
357 | CFQ_CFQQ_FNS(idle_window); | |
358 | CFQ_CFQQ_FNS(prio_changed); | |
359 | CFQ_CFQQ_FNS(slice_new); | |
360 | CFQ_CFQQ_FNS(sync); | |
361 | CFQ_CFQQ_FNS(coop); | |
362 | CFQ_CFQQ_FNS(split_coop); | |
363 | CFQ_CFQQ_FNS(deep); | |
364 | CFQ_CFQQ_FNS(wait_busy); | |
365 | #undef CFQ_CFQQ_FNS | |
366 | ||
367 | #ifdef CONFIG_CFQ_GROUP_IOSCHED | |
368 | #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \ | |
369 | blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \ | |
370 | cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \ | |
371 | blkg_path(&(cfqq)->cfqg->blkg), ##args) | |
372 | ||
373 | #define cfq_log_cfqg(cfqd, cfqg, fmt, args...) \ | |
374 | blk_add_trace_msg((cfqd)->queue, "%s " fmt, \ | |
375 | blkg_path(&(cfqg)->blkg), ##args) \ | |
376 | ||
377 | #else | |
378 | #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \ | |
379 | blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args) | |
380 | #define cfq_log_cfqg(cfqd, cfqg, fmt, args...) do {} while (0) | |
381 | #endif | |
382 | #define cfq_log(cfqd, fmt, args...) \ | |
383 | blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args) | |
384 | ||
385 | /* Traverses through cfq group service trees */ | |
386 | #define for_each_cfqg_st(cfqg, i, j, st) \ | |
387 | for (i = 0; i <= IDLE_WORKLOAD; i++) \ | |
388 | for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\ | |
389 | : &cfqg->service_tree_idle; \ | |
390 | (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \ | |
391 | (i == IDLE_WORKLOAD && j == 0); \ | |
392 | j++, st = i < IDLE_WORKLOAD ? \ | |
393 | &cfqg->service_trees[i][j]: NULL) \ | |
394 | ||
395 | static inline bool cfq_io_thinktime_big(struct cfq_data *cfqd, | |
396 | struct cfq_ttime *ttime, bool group_idle) | |
397 | { | |
398 | unsigned long slice; | |
399 | if (!sample_valid(ttime->ttime_samples)) | |
400 | return false; | |
401 | if (group_idle) | |
402 | slice = cfqd->cfq_group_idle; | |
403 | else | |
404 | slice = cfqd->cfq_slice_idle; | |
405 | return ttime->ttime_mean > slice; | |
406 | } | |
407 | ||
408 | static inline bool iops_mode(struct cfq_data *cfqd) | |
409 | { | |
410 | /* | |
411 | * If we are not idling on queues and it is a NCQ drive, parallel | |
412 | * execution of requests is on and measuring time is not possible | |
413 | * in most of the cases until and unless we drive shallower queue | |
414 | * depths and that becomes a performance bottleneck. In such cases | |
415 | * switch to start providing fairness in terms of number of IOs. | |
416 | */ | |
417 | if (!cfqd->cfq_slice_idle && cfqd->hw_tag) | |
418 | return true; | |
419 | else | |
420 | return false; | |
421 | } | |
422 | ||
423 | static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq) | |
424 | { | |
425 | if (cfq_class_idle(cfqq)) | |
426 | return IDLE_WORKLOAD; | |
427 | if (cfq_class_rt(cfqq)) | |
428 | return RT_WORKLOAD; | |
429 | return BE_WORKLOAD; | |
430 | } | |
431 | ||
432 | ||
433 | static enum wl_type_t cfqq_type(struct cfq_queue *cfqq) | |
434 | { | |
435 | if (!cfq_cfqq_sync(cfqq)) | |
436 | return ASYNC_WORKLOAD; | |
437 | if (!cfq_cfqq_idle_window(cfqq)) | |
438 | return SYNC_NOIDLE_WORKLOAD; | |
439 | return SYNC_WORKLOAD; | |
440 | } | |
441 | ||
442 | static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl, | |
443 | struct cfq_data *cfqd, | |
444 | struct cfq_group *cfqg) | |
445 | { | |
446 | if (wl == IDLE_WORKLOAD) | |
447 | return cfqg->service_tree_idle.count; | |
448 | ||
449 | return cfqg->service_trees[wl][ASYNC_WORKLOAD].count | |
450 | + cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count | |
451 | + cfqg->service_trees[wl][SYNC_WORKLOAD].count; | |
452 | } | |
453 | ||
454 | static inline int cfqg_busy_async_queues(struct cfq_data *cfqd, | |
455 | struct cfq_group *cfqg) | |
456 | { | |
457 | return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count | |
458 | + cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count; | |
459 | } | |
460 | ||
461 | static void cfq_dispatch_insert(struct request_queue *, struct request *); | |
462 | static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool, | |
463 | struct io_context *, gfp_t); | |
464 | static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *, | |
465 | struct io_context *); | |
466 | ||
467 | static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic, | |
468 | bool is_sync) | |
469 | { | |
470 | return cic->cfqq[is_sync]; | |
471 | } | |
472 | ||
473 | static inline void cic_set_cfqq(struct cfq_io_context *cic, | |
474 | struct cfq_queue *cfqq, bool is_sync) | |
475 | { | |
476 | cic->cfqq[is_sync] = cfqq; | |
477 | } | |
478 | ||
479 | #define CIC_DEAD_KEY 1ul | |
480 | #define CIC_DEAD_INDEX_SHIFT 1 | |
481 | ||
482 | static inline void *cfqd_dead_key(struct cfq_data *cfqd) | |
483 | { | |
484 | return (void *)(cfqd->cic_index << CIC_DEAD_INDEX_SHIFT | CIC_DEAD_KEY); | |
485 | } | |
486 | ||
487 | static inline struct cfq_data *cic_to_cfqd(struct cfq_io_context *cic) | |
488 | { | |
489 | struct cfq_data *cfqd = cic->key; | |
490 | ||
491 | if (unlikely((unsigned long) cfqd & CIC_DEAD_KEY)) | |
492 | return NULL; | |
493 | ||
494 | return cfqd; | |
495 | } | |
496 | ||
497 | /* | |
498 | * We regard a request as SYNC, if it's either a read or has the SYNC bit | |
499 | * set (in which case it could also be direct WRITE). | |
500 | */ | |
501 | static inline bool cfq_bio_sync(struct bio *bio) | |
502 | { | |
503 | return bio_data_dir(bio) == READ || (bio->bi_rw & REQ_SYNC); | |
504 | } | |
505 | ||
506 | /* | |
507 | * scheduler run of queue, if there are requests pending and no one in the | |
508 | * driver that will restart queueing | |
509 | */ | |
510 | static inline void cfq_schedule_dispatch(struct cfq_data *cfqd) | |
511 | { | |
512 | if (cfqd->busy_queues) { | |
513 | cfq_log(cfqd, "schedule dispatch"); | |
514 | kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work); | |
515 | } | |
516 | } | |
517 | ||
518 | /* | |
519 | * Scale schedule slice based on io priority. Use the sync time slice only | |
520 | * if a queue is marked sync and has sync io queued. A sync queue with async | |
521 | * io only, should not get full sync slice length. | |
522 | */ | |
523 | static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync, | |
524 | unsigned short prio) | |
525 | { | |
526 | const int base_slice = cfqd->cfq_slice[sync]; | |
527 | ||
528 | WARN_ON(prio >= IOPRIO_BE_NR); | |
529 | ||
530 | return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio)); | |
531 | } | |
532 | ||
533 | static inline int | |
534 | cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) | |
535 | { | |
536 | return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio); | |
537 | } | |
538 | ||
539 | static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg) | |
540 | { | |
541 | u64 d = delta << CFQ_SERVICE_SHIFT; | |
542 | ||
543 | d = d * BLKIO_WEIGHT_DEFAULT; | |
544 | do_div(d, cfqg->weight); | |
545 | return d; | |
546 | } | |
547 | ||
548 | static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime) | |
549 | { | |
550 | s64 delta = (s64)(vdisktime - min_vdisktime); | |
551 | if (delta > 0) | |
552 | min_vdisktime = vdisktime; | |
553 | ||
554 | return min_vdisktime; | |
555 | } | |
556 | ||
557 | static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime) | |
558 | { | |
559 | s64 delta = (s64)(vdisktime - min_vdisktime); | |
560 | if (delta < 0) | |
561 | min_vdisktime = vdisktime; | |
562 | ||
563 | return min_vdisktime; | |
564 | } | |
565 | ||
566 | static void update_min_vdisktime(struct cfq_rb_root *st) | |
567 | { | |
568 | struct cfq_group *cfqg; | |
569 | ||
570 | if (st->left) { | |
571 | cfqg = rb_entry_cfqg(st->left); | |
572 | st->min_vdisktime = max_vdisktime(st->min_vdisktime, | |
573 | cfqg->vdisktime); | |
574 | } | |
575 | } | |
576 | ||
577 | /* | |
578 | * get averaged number of queues of RT/BE priority. | |
579 | * average is updated, with a formula that gives more weight to higher numbers, | |
580 | * to quickly follows sudden increases and decrease slowly | |
581 | */ | |
582 | ||
583 | static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd, | |
584 | struct cfq_group *cfqg, bool rt) | |
585 | { | |
586 | unsigned min_q, max_q; | |
587 | unsigned mult = cfq_hist_divisor - 1; | |
588 | unsigned round = cfq_hist_divisor / 2; | |
589 | unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg); | |
590 | ||
591 | min_q = min(cfqg->busy_queues_avg[rt], busy); | |
592 | max_q = max(cfqg->busy_queues_avg[rt], busy); | |
593 | cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) / | |
594 | cfq_hist_divisor; | |
595 | return cfqg->busy_queues_avg[rt]; | |
596 | } | |
597 | ||
598 | static inline unsigned | |
599 | cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg) | |
600 | { | |
601 | struct cfq_rb_root *st = &cfqd->grp_service_tree; | |
602 | ||
603 | return cfq_target_latency * cfqg->weight / st->total_weight; | |
604 | } | |
605 | ||
606 | static inline unsigned | |
607 | cfq_scaled_cfqq_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) | |
608 | { | |
609 | unsigned slice = cfq_prio_to_slice(cfqd, cfqq); | |
610 | if (cfqd->cfq_latency) { | |
611 | /* | |
612 | * interested queues (we consider only the ones with the same | |
613 | * priority class in the cfq group) | |
614 | */ | |
615 | unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg, | |
616 | cfq_class_rt(cfqq)); | |
617 | unsigned sync_slice = cfqd->cfq_slice[1]; | |
618 | unsigned expect_latency = sync_slice * iq; | |
619 | unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg); | |
620 | ||
621 | if (expect_latency > group_slice) { | |
622 | unsigned base_low_slice = 2 * cfqd->cfq_slice_idle; | |
623 | /* scale low_slice according to IO priority | |
624 | * and sync vs async */ | |
625 | unsigned low_slice = | |
626 | min(slice, base_low_slice * slice / sync_slice); | |
627 | /* the adapted slice value is scaled to fit all iqs | |
628 | * into the target latency */ | |
629 | slice = max(slice * group_slice / expect_latency, | |
630 | low_slice); | |
631 | } | |
632 | } | |
633 | return slice; | |
634 | } | |
635 | ||
636 | static inline void | |
637 | cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) | |
638 | { | |
639 | unsigned slice = cfq_scaled_cfqq_slice(cfqd, cfqq); | |
640 | ||
641 | cfqq->slice_start = jiffies; | |
642 | cfqq->slice_end = jiffies + slice; | |
643 | cfqq->allocated_slice = slice; | |
644 | cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies); | |
645 | } | |
646 | ||
647 | /* | |
648 | * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end | |
649 | * isn't valid until the first request from the dispatch is activated | |
650 | * and the slice time set. | |
651 | */ | |
652 | static inline bool cfq_slice_used(struct cfq_queue *cfqq) | |
653 | { | |
654 | if (cfq_cfqq_slice_new(cfqq)) | |
655 | return false; | |
656 | if (time_before(jiffies, cfqq->slice_end)) | |
657 | return false; | |
658 | ||
659 | return true; | |
660 | } | |
661 | ||
662 | /* | |
663 | * Lifted from AS - choose which of rq1 and rq2 that is best served now. | |
664 | * We choose the request that is closest to the head right now. Distance | |
665 | * behind the head is penalized and only allowed to a certain extent. | |
666 | */ | |
667 | static struct request * | |
668 | cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last) | |
669 | { | |
670 | sector_t s1, s2, d1 = 0, d2 = 0; | |
671 | unsigned long back_max; | |
672 | #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */ | |
673 | #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */ | |
674 | unsigned wrap = 0; /* bit mask: requests behind the disk head? */ | |
675 | ||
676 | if (rq1 == NULL || rq1 == rq2) | |
677 | return rq2; | |
678 | if (rq2 == NULL) | |
679 | return rq1; | |
680 | ||
681 | if (rq_is_sync(rq1) != rq_is_sync(rq2)) | |
682 | return rq_is_sync(rq1) ? rq1 : rq2; | |
683 | ||
684 | s1 = blk_rq_pos(rq1); | |
685 | s2 = blk_rq_pos(rq2); | |
686 | ||
687 | /* | |
688 | * by definition, 1KiB is 2 sectors | |
689 | */ | |
690 | back_max = cfqd->cfq_back_max * 2; | |
691 | ||
692 | /* | |
693 | * Strict one way elevator _except_ in the case where we allow | |
694 | * short backward seeks which are biased as twice the cost of a | |
695 | * similar forward seek. | |
696 | */ | |
697 | if (s1 >= last) | |
698 | d1 = s1 - last; | |
699 | else if (s1 + back_max >= last) | |
700 | d1 = (last - s1) * cfqd->cfq_back_penalty; | |
701 | else | |
702 | wrap |= CFQ_RQ1_WRAP; | |
703 | ||
704 | if (s2 >= last) | |
705 | d2 = s2 - last; | |
706 | else if (s2 + back_max >= last) | |
707 | d2 = (last - s2) * cfqd->cfq_back_penalty; | |
708 | else | |
709 | wrap |= CFQ_RQ2_WRAP; | |
710 | ||
711 | /* Found required data */ | |
712 | ||
713 | /* | |
714 | * By doing switch() on the bit mask "wrap" we avoid having to | |
715 | * check two variables for all permutations: --> faster! | |
716 | */ | |
717 | switch (wrap) { | |
718 | case 0: /* common case for CFQ: rq1 and rq2 not wrapped */ | |
719 | if (d1 < d2) | |
720 | return rq1; | |
721 | else if (d2 < d1) | |
722 | return rq2; | |
723 | else { | |
724 | if (s1 >= s2) | |
725 | return rq1; | |
726 | else | |
727 | return rq2; | |
728 | } | |
729 | ||
730 | case CFQ_RQ2_WRAP: | |
731 | return rq1; | |
732 | case CFQ_RQ1_WRAP: | |
733 | return rq2; | |
734 | case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */ | |
735 | default: | |
736 | /* | |
737 | * Since both rqs are wrapped, | |
738 | * start with the one that's further behind head | |
739 | * (--> only *one* back seek required), | |
740 | * since back seek takes more time than forward. | |
741 | */ | |
742 | if (s1 <= s2) | |
743 | return rq1; | |
744 | else | |
745 | return rq2; | |
746 | } | |
747 | } | |
748 | ||
749 | /* | |
750 | * The below is leftmost cache rbtree addon | |
751 | */ | |
752 | static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root) | |
753 | { | |
754 | /* Service tree is empty */ | |
755 | if (!root->count) | |
756 | return NULL; | |
757 | ||
758 | if (!root->left) | |
759 | root->left = rb_first(&root->rb); | |
760 | ||
761 | if (root->left) | |
762 | return rb_entry(root->left, struct cfq_queue, rb_node); | |
763 | ||
764 | return NULL; | |
765 | } | |
766 | ||
767 | static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root) | |
768 | { | |
769 | if (!root->left) | |
770 | root->left = rb_first(&root->rb); | |
771 | ||
772 | if (root->left) | |
773 | return rb_entry_cfqg(root->left); | |
774 | ||
775 | return NULL; | |
776 | } | |
777 | ||
778 | static void rb_erase_init(struct rb_node *n, struct rb_root *root) | |
779 | { | |
780 | rb_erase(n, root); | |
781 | RB_CLEAR_NODE(n); | |
782 | } | |
783 | ||
784 | static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root) | |
785 | { | |
786 | if (root->left == n) | |
787 | root->left = NULL; | |
788 | rb_erase_init(n, &root->rb); | |
789 | --root->count; | |
790 | } | |
791 | ||
792 | /* | |
793 | * would be nice to take fifo expire time into account as well | |
794 | */ | |
795 | static struct request * | |
796 | cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq, | |
797 | struct request *last) | |
798 | { | |
799 | struct rb_node *rbnext = rb_next(&last->rb_node); | |
800 | struct rb_node *rbprev = rb_prev(&last->rb_node); | |
801 | struct request *next = NULL, *prev = NULL; | |
802 | ||
803 | BUG_ON(RB_EMPTY_NODE(&last->rb_node)); | |
804 | ||
805 | if (rbprev) | |
806 | prev = rb_entry_rq(rbprev); | |
807 | ||
808 | if (rbnext) | |
809 | next = rb_entry_rq(rbnext); | |
810 | else { | |
811 | rbnext = rb_first(&cfqq->sort_list); | |
812 | if (rbnext && rbnext != &last->rb_node) | |
813 | next = rb_entry_rq(rbnext); | |
814 | } | |
815 | ||
816 | return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last)); | |
817 | } | |
818 | ||
819 | static unsigned long cfq_slice_offset(struct cfq_data *cfqd, | |
820 | struct cfq_queue *cfqq) | |
821 | { | |
822 | /* | |
823 | * just an approximation, should be ok. | |
824 | */ | |
825 | return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) - | |
826 | cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio)); | |
827 | } | |
828 | ||
829 | static inline s64 | |
830 | cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg) | |
831 | { | |
832 | return cfqg->vdisktime - st->min_vdisktime; | |
833 | } | |
834 | ||
835 | static void | |
836 | __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg) | |
837 | { | |
838 | struct rb_node **node = &st->rb.rb_node; | |
839 | struct rb_node *parent = NULL; | |
840 | struct cfq_group *__cfqg; | |
841 | s64 key = cfqg_key(st, cfqg); | |
842 | int left = 1; | |
843 | ||
844 | while (*node != NULL) { | |
845 | parent = *node; | |
846 | __cfqg = rb_entry_cfqg(parent); | |
847 | ||
848 | if (key < cfqg_key(st, __cfqg)) | |
849 | node = &parent->rb_left; | |
850 | else { | |
851 | node = &parent->rb_right; | |
852 | left = 0; | |
853 | } | |
854 | } | |
855 | ||
856 | if (left) | |
857 | st->left = &cfqg->rb_node; | |
858 | ||
859 | rb_link_node(&cfqg->rb_node, parent, node); | |
860 | rb_insert_color(&cfqg->rb_node, &st->rb); | |
861 | } | |
862 | ||
863 | static void | |
864 | cfq_update_group_weight(struct cfq_group *cfqg) | |
865 | { | |
866 | BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node)); | |
867 | if (cfqg->needs_update) { | |
868 | cfqg->weight = cfqg->new_weight; | |
869 | cfqg->needs_update = false; | |
870 | } | |
871 | } | |
872 | ||
873 | static void | |
874 | cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg) | |
875 | { | |
876 | BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node)); | |
877 | ||
878 | cfq_update_group_weight(cfqg); | |
879 | __cfq_group_service_tree_add(st, cfqg); | |
880 | st->total_weight += cfqg->weight; | |
881 | } | |
882 | ||
883 | static void | |
884 | cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg) | |
885 | { | |
886 | struct cfq_rb_root *st = &cfqd->grp_service_tree; | |
887 | struct cfq_group *__cfqg; | |
888 | struct rb_node *n; | |
889 | ||
890 | cfqg->nr_cfqq++; | |
891 | if (!RB_EMPTY_NODE(&cfqg->rb_node)) | |
892 | return; | |
893 | ||
894 | /* | |
895 | * Currently put the group at the end. Later implement something | |
896 | * so that groups get lesser vtime based on their weights, so that | |
897 | * if group does not loose all if it was not continuously backlogged. | |
898 | */ | |
899 | n = rb_last(&st->rb); | |
900 | if (n) { | |
901 | __cfqg = rb_entry_cfqg(n); | |
902 | cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY; | |
903 | } else | |
904 | cfqg->vdisktime = st->min_vdisktime; | |
905 | cfq_group_service_tree_add(st, cfqg); | |
906 | } | |
907 | ||
908 | static void | |
909 | cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg) | |
910 | { | |
911 | st->total_weight -= cfqg->weight; | |
912 | if (!RB_EMPTY_NODE(&cfqg->rb_node)) | |
913 | cfq_rb_erase(&cfqg->rb_node, st); | |
914 | } | |
915 | ||
916 | static void | |
917 | cfq_group_notify_queue_del(struct cfq_data *cfqd, struct cfq_group *cfqg) | |
918 | { | |
919 | struct cfq_rb_root *st = &cfqd->grp_service_tree; | |
920 | ||
921 | BUG_ON(cfqg->nr_cfqq < 1); | |
922 | cfqg->nr_cfqq--; | |
923 | ||
924 | /* If there are other cfq queues under this group, don't delete it */ | |
925 | if (cfqg->nr_cfqq) | |
926 | return; | |
927 | ||
928 | cfq_log_cfqg(cfqd, cfqg, "del_from_rr group"); | |
929 | cfq_group_service_tree_del(st, cfqg); | |
930 | cfqg->saved_workload_slice = 0; | |
931 | cfq_blkiocg_update_dequeue_stats(&cfqg->blkg, 1); | |
932 | } | |
933 | ||
934 | static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq, | |
935 | unsigned int *unaccounted_time) | |
936 | { | |
937 | unsigned int slice_used; | |
938 | ||
939 | /* | |
940 | * Queue got expired before even a single request completed or | |
941 | * got expired immediately after first request completion. | |
942 | */ | |
943 | if (!cfqq->slice_start || cfqq->slice_start == jiffies) { | |
944 | /* | |
945 | * Also charge the seek time incurred to the group, otherwise | |
946 | * if there are mutiple queues in the group, each can dispatch | |
947 | * a single request on seeky media and cause lots of seek time | |
948 | * and group will never know it. | |
949 | */ | |
950 | slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start), | |
951 | 1); | |
952 | } else { | |
953 | slice_used = jiffies - cfqq->slice_start; | |
954 | if (slice_used > cfqq->allocated_slice) { | |
955 | *unaccounted_time = slice_used - cfqq->allocated_slice; | |
956 | slice_used = cfqq->allocated_slice; | |
957 | } | |
958 | if (time_after(cfqq->slice_start, cfqq->dispatch_start)) | |
959 | *unaccounted_time += cfqq->slice_start - | |
960 | cfqq->dispatch_start; | |
961 | } | |
962 | ||
963 | return slice_used; | |
964 | } | |
965 | ||
966 | static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg, | |
967 | struct cfq_queue *cfqq) | |
968 | { | |
969 | struct cfq_rb_root *st = &cfqd->grp_service_tree; | |
970 | unsigned int used_sl, charge, unaccounted_sl = 0; | |
971 | int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg) | |
972 | - cfqg->service_tree_idle.count; | |
973 | ||
974 | BUG_ON(nr_sync < 0); | |
975 | used_sl = charge = cfq_cfqq_slice_usage(cfqq, &unaccounted_sl); | |
976 | ||
977 | if (iops_mode(cfqd)) | |
978 | charge = cfqq->slice_dispatch; | |
979 | else if (!cfq_cfqq_sync(cfqq) && !nr_sync) | |
980 | charge = cfqq->allocated_slice; | |
981 | ||
982 | /* Can't update vdisktime while group is on service tree */ | |
983 | cfq_group_service_tree_del(st, cfqg); | |
984 | cfqg->vdisktime += cfq_scale_slice(charge, cfqg); | |
985 | /* If a new weight was requested, update now, off tree */ | |
986 | cfq_group_service_tree_add(st, cfqg); | |
987 | ||
988 | /* This group is being expired. Save the context */ | |
989 | if (time_after(cfqd->workload_expires, jiffies)) { | |
990 | cfqg->saved_workload_slice = cfqd->workload_expires | |
991 | - jiffies; | |
992 | cfqg->saved_workload = cfqd->serving_type; | |
993 | cfqg->saved_serving_prio = cfqd->serving_prio; | |
994 | } else | |
995 | cfqg->saved_workload_slice = 0; | |
996 | ||
997 | cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime, | |
998 | st->min_vdisktime); | |
999 | cfq_log_cfqq(cfqq->cfqd, cfqq, | |
1000 | "sl_used=%u disp=%u charge=%u iops=%u sect=%lu", | |
1001 | used_sl, cfqq->slice_dispatch, charge, | |
1002 | iops_mode(cfqd), cfqq->nr_sectors); | |
1003 | cfq_blkiocg_update_timeslice_used(&cfqg->blkg, used_sl, | |
1004 | unaccounted_sl); | |
1005 | cfq_blkiocg_set_start_empty_time(&cfqg->blkg); | |
1006 | } | |
1007 | ||
1008 | #ifdef CONFIG_CFQ_GROUP_IOSCHED | |
1009 | static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg) | |
1010 | { | |
1011 | if (blkg) | |
1012 | return container_of(blkg, struct cfq_group, blkg); | |
1013 | return NULL; | |
1014 | } | |
1015 | ||
1016 | static void cfq_update_blkio_group_weight(void *key, struct blkio_group *blkg, | |
1017 | unsigned int weight) | |
1018 | { | |
1019 | struct cfq_group *cfqg = cfqg_of_blkg(blkg); | |
1020 | cfqg->new_weight = weight; | |
1021 | cfqg->needs_update = true; | |
1022 | } | |
1023 | ||
1024 | static void cfq_init_add_cfqg_lists(struct cfq_data *cfqd, | |
1025 | struct cfq_group *cfqg, struct blkio_cgroup *blkcg) | |
1026 | { | |
1027 | struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info; | |
1028 | unsigned int major, minor; | |
1029 | ||
1030 | /* | |
1031 | * Add group onto cgroup list. It might happen that bdi->dev is | |
1032 | * not initialized yet. Initialize this new group without major | |
1033 | * and minor info and this info will be filled in once a new thread | |
1034 | * comes for IO. | |
1035 | */ | |
1036 | if (bdi->dev) { | |
1037 | sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor); | |
1038 | cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, | |
1039 | (void *)cfqd, MKDEV(major, minor)); | |
1040 | } else | |
1041 | cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, | |
1042 | (void *)cfqd, 0); | |
1043 | ||
1044 | cfqd->nr_blkcg_linked_grps++; | |
1045 | cfqg->weight = blkcg_get_weight(blkcg, cfqg->blkg.dev); | |
1046 | ||
1047 | /* Add group on cfqd list */ | |
1048 | hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list); | |
1049 | } | |
1050 | ||
1051 | /* | |
1052 | * Should be called from sleepable context. No request queue lock as per | |
1053 | * cpu stats are allocated dynamically and alloc_percpu needs to be called | |
1054 | * from sleepable context. | |
1055 | */ | |
1056 | static struct cfq_group * cfq_alloc_cfqg(struct cfq_data *cfqd) | |
1057 | { | |
1058 | struct cfq_group *cfqg = NULL; | |
1059 | int i, j, ret; | |
1060 | struct cfq_rb_root *st; | |
1061 | ||
1062 | cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node); | |
1063 | if (!cfqg) | |
1064 | return NULL; | |
1065 | ||
1066 | for_each_cfqg_st(cfqg, i, j, st) | |
1067 | *st = CFQ_RB_ROOT; | |
1068 | RB_CLEAR_NODE(&cfqg->rb_node); | |
1069 | ||
1070 | /* | |
1071 | * Take the initial reference that will be released on destroy | |
1072 | * This can be thought of a joint reference by cgroup and | |
1073 | * elevator which will be dropped by either elevator exit | |
1074 | * or cgroup deletion path depending on who is exiting first. | |
1075 | */ | |
1076 | cfqg->ref = 1; | |
1077 | ||
1078 | ret = blkio_alloc_blkg_stats(&cfqg->blkg); | |
1079 | if (ret) { | |
1080 | kfree(cfqg); | |
1081 | return NULL; | |
1082 | } | |
1083 | ||
1084 | return cfqg; | |
1085 | } | |
1086 | ||
1087 | static struct cfq_group * | |
1088 | cfq_find_cfqg(struct cfq_data *cfqd, struct blkio_cgroup *blkcg) | |
1089 | { | |
1090 | struct cfq_group *cfqg = NULL; | |
1091 | void *key = cfqd; | |
1092 | struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info; | |
1093 | unsigned int major, minor; | |
1094 | ||
1095 | /* | |
1096 | * This is the common case when there are no blkio cgroups. | |
1097 | * Avoid lookup in this case | |
1098 | */ | |
1099 | if (blkcg == &blkio_root_cgroup) | |
1100 | cfqg = &cfqd->root_group; | |
1101 | else | |
1102 | cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key)); | |
1103 | ||
1104 | if (cfqg && !cfqg->blkg.dev && bdi->dev && dev_name(bdi->dev)) { | |
1105 | sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor); | |
1106 | cfqg->blkg.dev = MKDEV(major, minor); | |
1107 | } | |
1108 | ||
1109 | return cfqg; | |
1110 | } | |
1111 | ||
1112 | /* | |
1113 | * Search for the cfq group current task belongs to. request_queue lock must | |
1114 | * be held. | |
1115 | */ | |
1116 | static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd) | |
1117 | { | |
1118 | struct blkio_cgroup *blkcg; | |
1119 | struct cfq_group *cfqg = NULL, *__cfqg = NULL; | |
1120 | struct request_queue *q = cfqd->queue; | |
1121 | ||
1122 | rcu_read_lock(); | |
1123 | blkcg = task_blkio_cgroup(current); | |
1124 | cfqg = cfq_find_cfqg(cfqd, blkcg); | |
1125 | if (cfqg) { | |
1126 | rcu_read_unlock(); | |
1127 | return cfqg; | |
1128 | } | |
1129 | ||
1130 | /* | |
1131 | * Need to allocate a group. Allocation of group also needs allocation | |
1132 | * of per cpu stats which in-turn takes a mutex() and can block. Hence | |
1133 | * we need to drop rcu lock and queue_lock before we call alloc. | |
1134 | * | |
1135 | * Not taking any queue reference here and assuming that queue is | |
1136 | * around by the time we return. CFQ queue allocation code does | |
1137 | * the same. It might be racy though. | |
1138 | */ | |
1139 | ||
1140 | rcu_read_unlock(); | |
1141 | spin_unlock_irq(q->queue_lock); | |
1142 | ||
1143 | cfqg = cfq_alloc_cfqg(cfqd); | |
1144 | ||
1145 | spin_lock_irq(q->queue_lock); | |
1146 | ||
1147 | rcu_read_lock(); | |
1148 | blkcg = task_blkio_cgroup(current); | |
1149 | ||
1150 | /* | |
1151 | * If some other thread already allocated the group while we were | |
1152 | * not holding queue lock, free up the group | |
1153 | */ | |
1154 | __cfqg = cfq_find_cfqg(cfqd, blkcg); | |
1155 | ||
1156 | if (__cfqg) { | |
1157 | kfree(cfqg); | |
1158 | rcu_read_unlock(); | |
1159 | return __cfqg; | |
1160 | } | |
1161 | ||
1162 | if (!cfqg) | |
1163 | cfqg = &cfqd->root_group; | |
1164 | ||
1165 | cfq_init_add_cfqg_lists(cfqd, cfqg, blkcg); | |
1166 | rcu_read_unlock(); | |
1167 | return cfqg; | |
1168 | } | |
1169 | ||
1170 | static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg) | |
1171 | { | |
1172 | cfqg->ref++; | |
1173 | return cfqg; | |
1174 | } | |
1175 | ||
1176 | static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) | |
1177 | { | |
1178 | /* Currently, all async queues are mapped to root group */ | |
1179 | if (!cfq_cfqq_sync(cfqq)) | |
1180 | cfqg = &cfqq->cfqd->root_group; | |
1181 | ||
1182 | cfqq->cfqg = cfqg; | |
1183 | /* cfqq reference on cfqg */ | |
1184 | cfqq->cfqg->ref++; | |
1185 | } | |
1186 | ||
1187 | static void cfq_put_cfqg(struct cfq_group *cfqg) | |
1188 | { | |
1189 | struct cfq_rb_root *st; | |
1190 | int i, j; | |
1191 | ||
1192 | BUG_ON(cfqg->ref <= 0); | |
1193 | cfqg->ref--; | |
1194 | if (cfqg->ref) | |
1195 | return; | |
1196 | for_each_cfqg_st(cfqg, i, j, st) | |
1197 | BUG_ON(!RB_EMPTY_ROOT(&st->rb)); | |
1198 | free_percpu(cfqg->blkg.stats_cpu); | |
1199 | kfree(cfqg); | |
1200 | } | |
1201 | ||
1202 | static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg) | |
1203 | { | |
1204 | /* Something wrong if we are trying to remove same group twice */ | |
1205 | BUG_ON(hlist_unhashed(&cfqg->cfqd_node)); | |
1206 | ||
1207 | hlist_del_init(&cfqg->cfqd_node); | |
1208 | ||
1209 | /* | |
1210 | * Put the reference taken at the time of creation so that when all | |
1211 | * queues are gone, group can be destroyed. | |
1212 | */ | |
1213 | cfq_put_cfqg(cfqg); | |
1214 | } | |
1215 | ||
1216 | static void cfq_release_cfq_groups(struct cfq_data *cfqd) | |
1217 | { | |
1218 | struct hlist_node *pos, *n; | |
1219 | struct cfq_group *cfqg; | |
1220 | ||
1221 | hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) { | |
1222 | /* | |
1223 | * If cgroup removal path got to blk_group first and removed | |
1224 | * it from cgroup list, then it will take care of destroying | |
1225 | * cfqg also. | |
1226 | */ | |
1227 | if (!cfq_blkiocg_del_blkio_group(&cfqg->blkg)) | |
1228 | cfq_destroy_cfqg(cfqd, cfqg); | |
1229 | } | |
1230 | } | |
1231 | ||
1232 | /* | |
1233 | * Blk cgroup controller notification saying that blkio_group object is being | |
1234 | * delinked as associated cgroup object is going away. That also means that | |
1235 | * no new IO will come in this group. So get rid of this group as soon as | |
1236 | * any pending IO in the group is finished. | |
1237 | * | |
1238 | * This function is called under rcu_read_lock(). key is the rcu protected | |
1239 | * pointer. That means "key" is a valid cfq_data pointer as long as we are rcu | |
1240 | * read lock. | |
1241 | * | |
1242 | * "key" was fetched from blkio_group under blkio_cgroup->lock. That means | |
1243 | * it should not be NULL as even if elevator was exiting, cgroup deltion | |
1244 | * path got to it first. | |
1245 | */ | |
1246 | static void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg) | |
1247 | { | |
1248 | unsigned long flags; | |
1249 | struct cfq_data *cfqd = key; | |
1250 | ||
1251 | spin_lock_irqsave(cfqd->queue->queue_lock, flags); | |
1252 | cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg)); | |
1253 | spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); | |
1254 | } | |
1255 | ||
1256 | #else /* GROUP_IOSCHED */ | |
1257 | static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd) | |
1258 | { | |
1259 | return &cfqd->root_group; | |
1260 | } | |
1261 | ||
1262 | static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg) | |
1263 | { | |
1264 | return cfqg; | |
1265 | } | |
1266 | ||
1267 | static inline void | |
1268 | cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) { | |
1269 | cfqq->cfqg = cfqg; | |
1270 | } | |
1271 | ||
1272 | static void cfq_release_cfq_groups(struct cfq_data *cfqd) {} | |
1273 | static inline void cfq_put_cfqg(struct cfq_group *cfqg) {} | |
1274 | ||
1275 | #endif /* GROUP_IOSCHED */ | |
1276 | ||
1277 | /* | |
1278 | * The cfqd->service_trees holds all pending cfq_queue's that have | |
1279 | * requests waiting to be processed. It is sorted in the order that | |
1280 | * we will service the queues. | |
1281 | */ | |
1282 | static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, | |
1283 | bool add_front) | |
1284 | { | |
1285 | struct rb_node **p, *parent; | |
1286 | struct cfq_queue *__cfqq; | |
1287 | unsigned long rb_key; | |
1288 | struct cfq_rb_root *service_tree; | |
1289 | int left; | |
1290 | int new_cfqq = 1; | |
1291 | ||
1292 | service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq), | |
1293 | cfqq_type(cfqq)); | |
1294 | if (cfq_class_idle(cfqq)) { | |
1295 | rb_key = CFQ_IDLE_DELAY; | |
1296 | parent = rb_last(&service_tree->rb); | |
1297 | if (parent && parent != &cfqq->rb_node) { | |
1298 | __cfqq = rb_entry(parent, struct cfq_queue, rb_node); | |
1299 | rb_key += __cfqq->rb_key; | |
1300 | } else | |
1301 | rb_key += jiffies; | |
1302 | } else if (!add_front) { | |
1303 | /* | |
1304 | * Get our rb key offset. Subtract any residual slice | |
1305 | * value carried from last service. A negative resid | |
1306 | * count indicates slice overrun, and this should position | |
1307 | * the next service time further away in the tree. | |
1308 | */ | |
1309 | rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies; | |
1310 | rb_key -= cfqq->slice_resid; | |
1311 | cfqq->slice_resid = 0; | |
1312 | } else { | |
1313 | rb_key = -HZ; | |
1314 | __cfqq = cfq_rb_first(service_tree); | |
1315 | rb_key += __cfqq ? __cfqq->rb_key : jiffies; | |
1316 | } | |
1317 | ||
1318 | if (!RB_EMPTY_NODE(&cfqq->rb_node)) { | |
1319 | new_cfqq = 0; | |
1320 | /* | |
1321 | * same position, nothing more to do | |
1322 | */ | |
1323 | if (rb_key == cfqq->rb_key && | |
1324 | cfqq->service_tree == service_tree) | |
1325 | return; | |
1326 | ||
1327 | cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree); | |
1328 | cfqq->service_tree = NULL; | |
1329 | } | |
1330 | ||
1331 | left = 1; | |
1332 | parent = NULL; | |
1333 | cfqq->service_tree = service_tree; | |
1334 | p = &service_tree->rb.rb_node; | |
1335 | while (*p) { | |
1336 | struct rb_node **n; | |
1337 | ||
1338 | parent = *p; | |
1339 | __cfqq = rb_entry(parent, struct cfq_queue, rb_node); | |
1340 | ||
1341 | /* | |
1342 | * sort by key, that represents service time. | |
1343 | */ | |
1344 | if (time_before(rb_key, __cfqq->rb_key)) | |
1345 | n = &(*p)->rb_left; | |
1346 | else { | |
1347 | n = &(*p)->rb_right; | |
1348 | left = 0; | |
1349 | } | |
1350 | ||
1351 | p = n; | |
1352 | } | |
1353 | ||
1354 | if (left) | |
1355 | service_tree->left = &cfqq->rb_node; | |
1356 | ||
1357 | cfqq->rb_key = rb_key; | |
1358 | rb_link_node(&cfqq->rb_node, parent, p); | |
1359 | rb_insert_color(&cfqq->rb_node, &service_tree->rb); | |
1360 | service_tree->count++; | |
1361 | if (add_front || !new_cfqq) | |
1362 | return; | |
1363 | cfq_group_notify_queue_add(cfqd, cfqq->cfqg); | |
1364 | } | |
1365 | ||
1366 | static struct cfq_queue * | |
1367 | cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root, | |
1368 | sector_t sector, struct rb_node **ret_parent, | |
1369 | struct rb_node ***rb_link) | |
1370 | { | |
1371 | struct rb_node **p, *parent; | |
1372 | struct cfq_queue *cfqq = NULL; | |
1373 | ||
1374 | parent = NULL; | |
1375 | p = &root->rb_node; | |
1376 | while (*p) { | |
1377 | struct rb_node **n; | |
1378 | ||
1379 | parent = *p; | |
1380 | cfqq = rb_entry(parent, struct cfq_queue, p_node); | |
1381 | ||
1382 | /* | |
1383 | * Sort strictly based on sector. Smallest to the left, | |
1384 | * largest to the right. | |
1385 | */ | |
1386 | if (sector > blk_rq_pos(cfqq->next_rq)) | |
1387 | n = &(*p)->rb_right; | |
1388 | else if (sector < blk_rq_pos(cfqq->next_rq)) | |
1389 | n = &(*p)->rb_left; | |
1390 | else | |
1391 | break; | |
1392 | p = n; | |
1393 | cfqq = NULL; | |
1394 | } | |
1395 | ||
1396 | *ret_parent = parent; | |
1397 | if (rb_link) | |
1398 | *rb_link = p; | |
1399 | return cfqq; | |
1400 | } | |
1401 | ||
1402 | static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq) | |
1403 | { | |
1404 | struct rb_node **p, *parent; | |
1405 | struct cfq_queue *__cfqq; | |
1406 | ||
1407 | if (cfqq->p_root) { | |
1408 | rb_erase(&cfqq->p_node, cfqq->p_root); | |
1409 | cfqq->p_root = NULL; | |
1410 | } | |
1411 | ||
1412 | if (cfq_class_idle(cfqq)) | |
1413 | return; | |
1414 | if (!cfqq->next_rq) | |
1415 | return; | |
1416 | ||
1417 | cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio]; | |
1418 | __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root, | |
1419 | blk_rq_pos(cfqq->next_rq), &parent, &p); | |
1420 | if (!__cfqq) { | |
1421 | rb_link_node(&cfqq->p_node, parent, p); | |
1422 | rb_insert_color(&cfqq->p_node, cfqq->p_root); | |
1423 | } else | |
1424 | cfqq->p_root = NULL; | |
1425 | } | |
1426 | ||
1427 | /* | |
1428 | * Update cfqq's position in the service tree. | |
1429 | */ | |
1430 | static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq) | |
1431 | { | |
1432 | /* | |
1433 | * Resorting requires the cfqq to be on the RR list already. | |
1434 | */ | |
1435 | if (cfq_cfqq_on_rr(cfqq)) { | |
1436 | cfq_service_tree_add(cfqd, cfqq, 0); | |
1437 | cfq_prio_tree_add(cfqd, cfqq); | |
1438 | } | |
1439 | } | |
1440 | ||
1441 | /* | |
1442 | * add to busy list of queues for service, trying to be fair in ordering | |
1443 | * the pending list according to last request service | |
1444 | */ | |
1445 | static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) | |
1446 | { | |
1447 | cfq_log_cfqq(cfqd, cfqq, "add_to_rr"); | |
1448 | BUG_ON(cfq_cfqq_on_rr(cfqq)); | |
1449 | cfq_mark_cfqq_on_rr(cfqq); | |
1450 | cfqd->busy_queues++; | |
1451 | if (cfq_cfqq_sync(cfqq)) | |
1452 | cfqd->busy_sync_queues++; | |
1453 | ||
1454 | cfq_resort_rr_list(cfqd, cfqq); | |
1455 | } | |
1456 | ||
1457 | /* | |
1458 | * Called when the cfqq no longer has requests pending, remove it from | |
1459 | * the service tree. | |
1460 | */ | |
1461 | static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) | |
1462 | { | |
1463 | cfq_log_cfqq(cfqd, cfqq, "del_from_rr"); | |
1464 | BUG_ON(!cfq_cfqq_on_rr(cfqq)); | |
1465 | cfq_clear_cfqq_on_rr(cfqq); | |
1466 | ||
1467 | if (!RB_EMPTY_NODE(&cfqq->rb_node)) { | |
1468 | cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree); | |
1469 | cfqq->service_tree = NULL; | |
1470 | } | |
1471 | if (cfqq->p_root) { | |
1472 | rb_erase(&cfqq->p_node, cfqq->p_root); | |
1473 | cfqq->p_root = NULL; | |
1474 | } | |
1475 | ||
1476 | cfq_group_notify_queue_del(cfqd, cfqq->cfqg); | |
1477 | BUG_ON(!cfqd->busy_queues); | |
1478 | cfqd->busy_queues--; | |
1479 | if (cfq_cfqq_sync(cfqq)) | |
1480 | cfqd->busy_sync_queues--; | |
1481 | } | |
1482 | ||
1483 | /* | |
1484 | * rb tree support functions | |
1485 | */ | |
1486 | static void cfq_del_rq_rb(struct request *rq) | |
1487 | { | |
1488 | struct cfq_queue *cfqq = RQ_CFQQ(rq); | |
1489 | const int sync = rq_is_sync(rq); | |
1490 | ||
1491 | BUG_ON(!cfqq->queued[sync]); | |
1492 | cfqq->queued[sync]--; | |
1493 | ||
1494 | elv_rb_del(&cfqq->sort_list, rq); | |
1495 | ||
1496 | if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) { | |
1497 | /* | |
1498 | * Queue will be deleted from service tree when we actually | |
1499 | * expire it later. Right now just remove it from prio tree | |
1500 | * as it is empty. | |
1501 | */ | |
1502 | if (cfqq->p_root) { | |
1503 | rb_erase(&cfqq->p_node, cfqq->p_root); | |
1504 | cfqq->p_root = NULL; | |
1505 | } | |
1506 | } | |
1507 | } | |
1508 | ||
1509 | static void cfq_add_rq_rb(struct request *rq) | |
1510 | { | |
1511 | struct cfq_queue *cfqq = RQ_CFQQ(rq); | |
1512 | struct cfq_data *cfqd = cfqq->cfqd; | |
1513 | struct request *prev; | |
1514 | ||
1515 | cfqq->queued[rq_is_sync(rq)]++; | |
1516 | ||
1517 | elv_rb_add(&cfqq->sort_list, rq); | |
1518 | ||
1519 | if (!cfq_cfqq_on_rr(cfqq)) | |
1520 | cfq_add_cfqq_rr(cfqd, cfqq); | |
1521 | ||
1522 | /* | |
1523 | * check if this request is a better next-serve candidate | |
1524 | */ | |
1525 | prev = cfqq->next_rq; | |
1526 | cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position); | |
1527 | ||
1528 | /* | |
1529 | * adjust priority tree position, if ->next_rq changes | |
1530 | */ | |
1531 | if (prev != cfqq->next_rq) | |
1532 | cfq_prio_tree_add(cfqd, cfqq); | |
1533 | ||
1534 | BUG_ON(!cfqq->next_rq); | |
1535 | } | |
1536 | ||
1537 | static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq) | |
1538 | { | |
1539 | elv_rb_del(&cfqq->sort_list, rq); | |
1540 | cfqq->queued[rq_is_sync(rq)]--; | |
1541 | cfq_blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg, | |
1542 | rq_data_dir(rq), rq_is_sync(rq)); | |
1543 | cfq_add_rq_rb(rq); | |
1544 | cfq_blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg, | |
1545 | &cfqq->cfqd->serving_group->blkg, rq_data_dir(rq), | |
1546 | rq_is_sync(rq)); | |
1547 | } | |
1548 | ||
1549 | static struct request * | |
1550 | cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio) | |
1551 | { | |
1552 | struct task_struct *tsk = current; | |
1553 | struct cfq_io_context *cic; | |
1554 | struct cfq_queue *cfqq; | |
1555 | ||
1556 | cic = cfq_cic_lookup(cfqd, tsk->io_context); | |
1557 | if (!cic) | |
1558 | return NULL; | |
1559 | ||
1560 | cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); | |
1561 | if (cfqq) { | |
1562 | sector_t sector = bio->bi_sector + bio_sectors(bio); | |
1563 | ||
1564 | return elv_rb_find(&cfqq->sort_list, sector); | |
1565 | } | |
1566 | ||
1567 | return NULL; | |
1568 | } | |
1569 | ||
1570 | static void cfq_activate_request(struct request_queue *q, struct request *rq) | |
1571 | { | |
1572 | struct cfq_data *cfqd = q->elevator->elevator_data; | |
1573 | ||
1574 | cfqd->rq_in_driver++; | |
1575 | cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d", | |
1576 | cfqd->rq_in_driver); | |
1577 | ||
1578 | cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq); | |
1579 | } | |
1580 | ||
1581 | static void cfq_deactivate_request(struct request_queue *q, struct request *rq) | |
1582 | { | |
1583 | struct cfq_data *cfqd = q->elevator->elevator_data; | |
1584 | ||
1585 | WARN_ON(!cfqd->rq_in_driver); | |
1586 | cfqd->rq_in_driver--; | |
1587 | cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d", | |
1588 | cfqd->rq_in_driver); | |
1589 | } | |
1590 | ||
1591 | static void cfq_remove_request(struct request *rq) | |
1592 | { | |
1593 | struct cfq_queue *cfqq = RQ_CFQQ(rq); | |
1594 | ||
1595 | if (cfqq->next_rq == rq) | |
1596 | cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq); | |
1597 | ||
1598 | list_del_init(&rq->queuelist); | |
1599 | cfq_del_rq_rb(rq); | |
1600 | ||
1601 | cfqq->cfqd->rq_queued--; | |
1602 | cfq_blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg, | |
1603 | rq_data_dir(rq), rq_is_sync(rq)); | |
1604 | } | |
1605 | ||
1606 | static int cfq_merge(struct request_queue *q, struct request **req, | |
1607 | struct bio *bio) | |
1608 | { | |
1609 | struct cfq_data *cfqd = q->elevator->elevator_data; | |
1610 | struct request *__rq; | |
1611 | ||
1612 | __rq = cfq_find_rq_fmerge(cfqd, bio); | |
1613 | if (__rq && elv_rq_merge_ok(__rq, bio)) { | |
1614 | *req = __rq; | |
1615 | return ELEVATOR_FRONT_MERGE; | |
1616 | } | |
1617 | ||
1618 | return ELEVATOR_NO_MERGE; | |
1619 | } | |
1620 | ||
1621 | static void cfq_merged_request(struct request_queue *q, struct request *req, | |
1622 | int type) | |
1623 | { | |
1624 | if (type == ELEVATOR_FRONT_MERGE) { | |
1625 | struct cfq_queue *cfqq = RQ_CFQQ(req); | |
1626 | ||
1627 | cfq_reposition_rq_rb(cfqq, req); | |
1628 | } | |
1629 | } | |
1630 | ||
1631 | static void cfq_bio_merged(struct request_queue *q, struct request *req, | |
1632 | struct bio *bio) | |
1633 | { | |
1634 | cfq_blkiocg_update_io_merged_stats(&(RQ_CFQG(req))->blkg, | |
1635 | bio_data_dir(bio), cfq_bio_sync(bio)); | |
1636 | } | |
1637 | ||
1638 | static void | |
1639 | cfq_merged_requests(struct request_queue *q, struct request *rq, | |
1640 | struct request *next) | |
1641 | { | |
1642 | struct cfq_queue *cfqq = RQ_CFQQ(rq); | |
1643 | /* | |
1644 | * reposition in fifo if next is older than rq | |
1645 | */ | |
1646 | if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && | |
1647 | time_before(rq_fifo_time(next), rq_fifo_time(rq))) { | |
1648 | list_move(&rq->queuelist, &next->queuelist); | |
1649 | rq_set_fifo_time(rq, rq_fifo_time(next)); | |
1650 | } | |
1651 | ||
1652 | if (cfqq->next_rq == next) | |
1653 | cfqq->next_rq = rq; | |
1654 | cfq_remove_request(next); | |
1655 | cfq_blkiocg_update_io_merged_stats(&(RQ_CFQG(rq))->blkg, | |
1656 | rq_data_dir(next), rq_is_sync(next)); | |
1657 | } | |
1658 | ||
1659 | static int cfq_allow_merge(struct request_queue *q, struct request *rq, | |
1660 | struct bio *bio) | |
1661 | { | |
1662 | struct cfq_data *cfqd = q->elevator->elevator_data; | |
1663 | struct cfq_io_context *cic; | |
1664 | struct cfq_queue *cfqq; | |
1665 | ||
1666 | /* | |
1667 | * Disallow merge of a sync bio into an async request. | |
1668 | */ | |
1669 | if (cfq_bio_sync(bio) && !rq_is_sync(rq)) | |
1670 | return false; | |
1671 | ||
1672 | /* | |
1673 | * Lookup the cfqq that this bio will be queued with. Allow | |
1674 | * merge only if rq is queued there. | |
1675 | */ | |
1676 | cic = cfq_cic_lookup(cfqd, current->io_context); | |
1677 | if (!cic) | |
1678 | return false; | |
1679 | ||
1680 | cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); | |
1681 | return cfqq == RQ_CFQQ(rq); | |
1682 | } | |
1683 | ||
1684 | static inline void cfq_del_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq) | |
1685 | { | |
1686 | del_timer(&cfqd->idle_slice_timer); | |
1687 | cfq_blkiocg_update_idle_time_stats(&cfqq->cfqg->blkg); | |
1688 | } | |
1689 | ||
1690 | static void __cfq_set_active_queue(struct cfq_data *cfqd, | |
1691 | struct cfq_queue *cfqq) | |
1692 | { | |
1693 | if (cfqq) { | |
1694 | cfq_log_cfqq(cfqd, cfqq, "set_active wl_prio:%d wl_type:%d", | |
1695 | cfqd->serving_prio, cfqd->serving_type); | |
1696 | cfq_blkiocg_update_avg_queue_size_stats(&cfqq->cfqg->blkg); | |
1697 | cfqq->slice_start = 0; | |
1698 | cfqq->dispatch_start = jiffies; | |
1699 | cfqq->allocated_slice = 0; | |
1700 | cfqq->slice_end = 0; | |
1701 | cfqq->slice_dispatch = 0; | |
1702 | cfqq->nr_sectors = 0; | |
1703 | ||
1704 | cfq_clear_cfqq_wait_request(cfqq); | |
1705 | cfq_clear_cfqq_must_dispatch(cfqq); | |
1706 | cfq_clear_cfqq_must_alloc_slice(cfqq); | |
1707 | cfq_clear_cfqq_fifo_expire(cfqq); | |
1708 | cfq_mark_cfqq_slice_new(cfqq); | |
1709 | ||
1710 | cfq_del_timer(cfqd, cfqq); | |
1711 | } | |
1712 | ||
1713 | cfqd->active_queue = cfqq; | |
1714 | } | |
1715 | ||
1716 | /* | |
1717 | * current cfqq expired its slice (or was too idle), select new one | |
1718 | */ | |
1719 | static void | |
1720 | __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, | |
1721 | bool timed_out) | |
1722 | { | |
1723 | cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out); | |
1724 | ||
1725 | if (cfq_cfqq_wait_request(cfqq)) | |
1726 | cfq_del_timer(cfqd, cfqq); | |
1727 | ||
1728 | cfq_clear_cfqq_wait_request(cfqq); | |
1729 | cfq_clear_cfqq_wait_busy(cfqq); | |
1730 | ||
1731 | /* | |
1732 | * If this cfqq is shared between multiple processes, check to | |
1733 | * make sure that those processes are still issuing I/Os within | |
1734 | * the mean seek distance. If not, it may be time to break the | |
1735 | * queues apart again. | |
1736 | */ | |
1737 | if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq)) | |
1738 | cfq_mark_cfqq_split_coop(cfqq); | |
1739 | ||
1740 | /* | |
1741 | * store what was left of this slice, if the queue idled/timed out | |
1742 | */ | |
1743 | if (timed_out) { | |
1744 | if (cfq_cfqq_slice_new(cfqq)) | |
1745 | cfqq->slice_resid = cfq_scaled_cfqq_slice(cfqd, cfqq); | |
1746 | else | |
1747 | cfqq->slice_resid = cfqq->slice_end - jiffies; | |
1748 | cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid); | |
1749 | } | |
1750 | ||
1751 | cfq_group_served(cfqd, cfqq->cfqg, cfqq); | |
1752 | ||
1753 | if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) | |
1754 | cfq_del_cfqq_rr(cfqd, cfqq); | |
1755 | ||
1756 | cfq_resort_rr_list(cfqd, cfqq); | |
1757 | ||
1758 | if (cfqq == cfqd->active_queue) | |
1759 | cfqd->active_queue = NULL; | |
1760 | ||
1761 | if (cfqd->active_cic) { | |
1762 | put_io_context(cfqd->active_cic->ioc); | |
1763 | cfqd->active_cic = NULL; | |
1764 | } | |
1765 | } | |
1766 | ||
1767 | static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out) | |
1768 | { | |
1769 | struct cfq_queue *cfqq = cfqd->active_queue; | |
1770 | ||
1771 | if (cfqq) | |
1772 | __cfq_slice_expired(cfqd, cfqq, timed_out); | |
1773 | } | |
1774 | ||
1775 | /* | |
1776 | * Get next queue for service. Unless we have a queue preemption, | |
1777 | * we'll simply select the first cfqq in the service tree. | |
1778 | */ | |
1779 | static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd) | |
1780 | { | |
1781 | struct cfq_rb_root *service_tree = | |
1782 | service_tree_for(cfqd->serving_group, cfqd->serving_prio, | |
1783 | cfqd->serving_type); | |
1784 | ||
1785 | if (!cfqd->rq_queued) | |
1786 | return NULL; | |
1787 | ||
1788 | /* There is nothing to dispatch */ | |
1789 | if (!service_tree) | |
1790 | return NULL; | |
1791 | if (RB_EMPTY_ROOT(&service_tree->rb)) | |
1792 | return NULL; | |
1793 | return cfq_rb_first(service_tree); | |
1794 | } | |
1795 | ||
1796 | static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd) | |
1797 | { | |
1798 | struct cfq_group *cfqg; | |
1799 | struct cfq_queue *cfqq; | |
1800 | int i, j; | |
1801 | struct cfq_rb_root *st; | |
1802 | ||
1803 | if (!cfqd->rq_queued) | |
1804 | return NULL; | |
1805 | ||
1806 | cfqg = cfq_get_next_cfqg(cfqd); | |
1807 | if (!cfqg) | |
1808 | return NULL; | |
1809 | ||
1810 | for_each_cfqg_st(cfqg, i, j, st) | |
1811 | if ((cfqq = cfq_rb_first(st)) != NULL) | |
1812 | return cfqq; | |
1813 | return NULL; | |
1814 | } | |
1815 | ||
1816 | /* | |
1817 | * Get and set a new active queue for service. | |
1818 | */ | |
1819 | static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd, | |
1820 | struct cfq_queue *cfqq) | |
1821 | { | |
1822 | if (!cfqq) | |
1823 | cfqq = cfq_get_next_queue(cfqd); | |
1824 | ||
1825 | __cfq_set_active_queue(cfqd, cfqq); | |
1826 | return cfqq; | |
1827 | } | |
1828 | ||
1829 | static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd, | |
1830 | struct request *rq) | |
1831 | { | |
1832 | if (blk_rq_pos(rq) >= cfqd->last_position) | |
1833 | return blk_rq_pos(rq) - cfqd->last_position; | |
1834 | else | |
1835 | return cfqd->last_position - blk_rq_pos(rq); | |
1836 | } | |
1837 | ||
1838 | static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq, | |
1839 | struct request *rq) | |
1840 | { | |
1841 | return cfq_dist_from_last(cfqd, rq) <= CFQQ_CLOSE_THR; | |
1842 | } | |
1843 | ||
1844 | static struct cfq_queue *cfqq_close(struct cfq_data *cfqd, | |
1845 | struct cfq_queue *cur_cfqq) | |
1846 | { | |
1847 | struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio]; | |
1848 | struct rb_node *parent, *node; | |
1849 | struct cfq_queue *__cfqq; | |
1850 | sector_t sector = cfqd->last_position; | |
1851 | ||
1852 | if (RB_EMPTY_ROOT(root)) | |
1853 | return NULL; | |
1854 | ||
1855 | /* | |
1856 | * First, if we find a request starting at the end of the last | |
1857 | * request, choose it. | |
1858 | */ | |
1859 | __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL); | |
1860 | if (__cfqq) | |
1861 | return __cfqq; | |
1862 | ||
1863 | /* | |
1864 | * If the exact sector wasn't found, the parent of the NULL leaf | |
1865 | * will contain the closest sector. | |
1866 | */ | |
1867 | __cfqq = rb_entry(parent, struct cfq_queue, p_node); | |
1868 | if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq)) | |
1869 | return __cfqq; | |
1870 | ||
1871 | if (blk_rq_pos(__cfqq->next_rq) < sector) | |
1872 | node = rb_next(&__cfqq->p_node); | |
1873 | else | |
1874 | node = rb_prev(&__cfqq->p_node); | |
1875 | if (!node) | |
1876 | return NULL; | |
1877 | ||
1878 | __cfqq = rb_entry(node, struct cfq_queue, p_node); | |
1879 | if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq)) | |
1880 | return __cfqq; | |
1881 | ||
1882 | return NULL; | |
1883 | } | |
1884 | ||
1885 | /* | |
1886 | * cfqd - obvious | |
1887 | * cur_cfqq - passed in so that we don't decide that the current queue is | |
1888 | * closely cooperating with itself. | |
1889 | * | |
1890 | * So, basically we're assuming that that cur_cfqq has dispatched at least | |
1891 | * one request, and that cfqd->last_position reflects a position on the disk | |
1892 | * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid | |
1893 | * assumption. | |
1894 | */ | |
1895 | static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd, | |
1896 | struct cfq_queue *cur_cfqq) | |
1897 | { | |
1898 | struct cfq_queue *cfqq; | |
1899 | ||
1900 | if (cfq_class_idle(cur_cfqq)) | |
1901 | return NULL; | |
1902 | if (!cfq_cfqq_sync(cur_cfqq)) | |
1903 | return NULL; | |
1904 | if (CFQQ_SEEKY(cur_cfqq)) | |
1905 | return NULL; | |
1906 | ||
1907 | /* | |
1908 | * Don't search priority tree if it's the only queue in the group. | |
1909 | */ | |
1910 | if (cur_cfqq->cfqg->nr_cfqq == 1) | |
1911 | return NULL; | |
1912 | ||
1913 | /* | |
1914 | * We should notice if some of the queues are cooperating, eg | |
1915 | * working closely on the same area of the disk. In that case, | |
1916 | * we can group them together and don't waste time idling. | |
1917 | */ | |
1918 | cfqq = cfqq_close(cfqd, cur_cfqq); | |
1919 | if (!cfqq) | |
1920 | return NULL; | |
1921 | ||
1922 | /* If new queue belongs to different cfq_group, don't choose it */ | |
1923 | if (cur_cfqq->cfqg != cfqq->cfqg) | |
1924 | return NULL; | |
1925 | ||
1926 | /* | |
1927 | * It only makes sense to merge sync queues. | |
1928 | */ | |
1929 | if (!cfq_cfqq_sync(cfqq)) | |
1930 | return NULL; | |
1931 | if (CFQQ_SEEKY(cfqq)) | |
1932 | return NULL; | |
1933 | ||
1934 | /* | |
1935 | * Do not merge queues of different priority classes | |
1936 | */ | |
1937 | if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq)) | |
1938 | return NULL; | |
1939 | ||
1940 | return cfqq; | |
1941 | } | |
1942 | ||
1943 | /* | |
1944 | * Determine whether we should enforce idle window for this queue. | |
1945 | */ | |
1946 | ||
1947 | static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq) | |
1948 | { | |
1949 | enum wl_prio_t prio = cfqq_prio(cfqq); | |
1950 | struct cfq_rb_root *service_tree = cfqq->service_tree; | |
1951 | ||
1952 | BUG_ON(!service_tree); | |
1953 | BUG_ON(!service_tree->count); | |
1954 | ||
1955 | if (!cfqd->cfq_slice_idle) | |
1956 | return false; | |
1957 | ||
1958 | /* We never do for idle class queues. */ | |
1959 | if (prio == IDLE_WORKLOAD) | |
1960 | return false; | |
1961 | ||
1962 | /* We do for queues that were marked with idle window flag. */ | |
1963 | if (cfq_cfqq_idle_window(cfqq) && | |
1964 | !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)) | |
1965 | return true; | |
1966 | ||
1967 | /* | |
1968 | * Otherwise, we do only if they are the last ones | |
1969 | * in their service tree. | |
1970 | */ | |
1971 | if (service_tree->count == 1 && cfq_cfqq_sync(cfqq) && | |
1972 | !cfq_io_thinktime_big(cfqd, &service_tree->ttime, false)) | |
1973 | return true; | |
1974 | cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d", | |
1975 | service_tree->count); | |
1976 | return false; | |
1977 | } | |
1978 | ||
1979 | static void cfq_arm_slice_timer(struct cfq_data *cfqd) | |
1980 | { | |
1981 | struct cfq_queue *cfqq = cfqd->active_queue; | |
1982 | struct cfq_io_context *cic; | |
1983 | unsigned long sl, group_idle = 0; | |
1984 | ||
1985 | /* | |
1986 | * SSD device without seek penalty, disable idling. But only do so | |
1987 | * for devices that support queuing, otherwise we still have a problem | |
1988 | * with sync vs async workloads. | |
1989 | */ | |
1990 | if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag) | |
1991 | return; | |
1992 | ||
1993 | WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list)); | |
1994 | WARN_ON(cfq_cfqq_slice_new(cfqq)); | |
1995 | ||
1996 | /* | |
1997 | * idle is disabled, either manually or by past process history | |
1998 | */ | |
1999 | if (!cfq_should_idle(cfqd, cfqq)) { | |
2000 | /* no queue idling. Check for group idling */ | |
2001 | if (cfqd->cfq_group_idle) | |
2002 | group_idle = cfqd->cfq_group_idle; | |
2003 | else | |
2004 | return; | |
2005 | } | |
2006 | ||
2007 | /* | |
2008 | * still active requests from this queue, don't idle | |
2009 | */ | |
2010 | if (cfqq->dispatched) | |
2011 | return; | |
2012 | ||
2013 | /* | |
2014 | * task has exited, don't wait | |
2015 | */ | |
2016 | cic = cfqd->active_cic; | |
2017 | if (!cic || !atomic_read(&cic->ioc->nr_tasks)) | |
2018 | return; | |
2019 | ||
2020 | /* | |
2021 | * If our average think time is larger than the remaining time | |
2022 | * slice, then don't idle. This avoids overrunning the allotted | |
2023 | * time slice. | |
2024 | */ | |
2025 | if (sample_valid(cic->ttime.ttime_samples) && | |
2026 | (cfqq->slice_end - jiffies < cic->ttime.ttime_mean)) { | |
2027 | cfq_log_cfqq(cfqd, cfqq, "Not idling. think_time:%lu", | |
2028 | cic->ttime.ttime_mean); | |
2029 | return; | |
2030 | } | |
2031 | ||
2032 | /* There are other queues in the group, don't do group idle */ | |
2033 | if (group_idle && cfqq->cfqg->nr_cfqq > 1) | |
2034 | return; | |
2035 | ||
2036 | cfq_mark_cfqq_wait_request(cfqq); | |
2037 | ||
2038 | if (group_idle) | |
2039 | sl = cfqd->cfq_group_idle; | |
2040 | else | |
2041 | sl = cfqd->cfq_slice_idle; | |
2042 | ||
2043 | mod_timer(&cfqd->idle_slice_timer, jiffies + sl); | |
2044 | cfq_blkiocg_update_set_idle_time_stats(&cfqq->cfqg->blkg); | |
2045 | cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu group_idle: %d", sl, | |
2046 | group_idle ? 1 : 0); | |
2047 | } | |
2048 | ||
2049 | /* | |
2050 | * Move request from internal lists to the request queue dispatch list. | |
2051 | */ | |
2052 | static void cfq_dispatch_insert(struct request_queue *q, struct request *rq) | |
2053 | { | |
2054 | struct cfq_data *cfqd = q->elevator->elevator_data; | |
2055 | struct cfq_queue *cfqq = RQ_CFQQ(rq); | |
2056 | ||
2057 | cfq_log_cfqq(cfqd, cfqq, "dispatch_insert"); | |
2058 | ||
2059 | cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq); | |
2060 | cfq_remove_request(rq); | |
2061 | cfqq->dispatched++; | |
2062 | (RQ_CFQG(rq))->dispatched++; | |
2063 | elv_dispatch_sort(q, rq); | |
2064 | ||
2065 | cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++; | |
2066 | cfqq->nr_sectors += blk_rq_sectors(rq); | |
2067 | cfq_blkiocg_update_dispatch_stats(&cfqq->cfqg->blkg, blk_rq_bytes(rq), | |
2068 | rq_data_dir(rq), rq_is_sync(rq)); | |
2069 | } | |
2070 | ||
2071 | /* | |
2072 | * return expired entry, or NULL to just start from scratch in rbtree | |
2073 | */ | |
2074 | static struct request *cfq_check_fifo(struct cfq_queue *cfqq) | |
2075 | { | |
2076 | struct request *rq = NULL; | |
2077 | ||
2078 | if (cfq_cfqq_fifo_expire(cfqq)) | |
2079 | return NULL; | |
2080 | ||
2081 | cfq_mark_cfqq_fifo_expire(cfqq); | |
2082 | ||
2083 | if (list_empty(&cfqq->fifo)) | |
2084 | return NULL; | |
2085 | ||
2086 | rq = rq_entry_fifo(cfqq->fifo.next); | |
2087 | if (time_before(jiffies, rq_fifo_time(rq))) | |
2088 | rq = NULL; | |
2089 | ||
2090 | cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq); | |
2091 | return rq; | |
2092 | } | |
2093 | ||
2094 | static inline int | |
2095 | cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq) | |
2096 | { | |
2097 | const int base_rq = cfqd->cfq_slice_async_rq; | |
2098 | ||
2099 | WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR); | |
2100 | ||
2101 | return 2 * base_rq * (IOPRIO_BE_NR - cfqq->ioprio); | |
2102 | } | |
2103 | ||
2104 | /* | |
2105 | * Must be called with the queue_lock held. | |
2106 | */ | |
2107 | static int cfqq_process_refs(struct cfq_queue *cfqq) | |
2108 | { | |
2109 | int process_refs, io_refs; | |
2110 | ||
2111 | io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE]; | |
2112 | process_refs = cfqq->ref - io_refs; | |
2113 | BUG_ON(process_refs < 0); | |
2114 | return process_refs; | |
2115 | } | |
2116 | ||
2117 | static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq) | |
2118 | { | |
2119 | int process_refs, new_process_refs; | |
2120 | struct cfq_queue *__cfqq; | |
2121 | ||
2122 | /* | |
2123 | * If there are no process references on the new_cfqq, then it is | |
2124 | * unsafe to follow the ->new_cfqq chain as other cfqq's in the | |
2125 | * chain may have dropped their last reference (not just their | |
2126 | * last process reference). | |
2127 | */ | |
2128 | if (!cfqq_process_refs(new_cfqq)) | |
2129 | return; | |
2130 | ||
2131 | /* Avoid a circular list and skip interim queue merges */ | |
2132 | while ((__cfqq = new_cfqq->new_cfqq)) { | |
2133 | if (__cfqq == cfqq) | |
2134 | return; | |
2135 | new_cfqq = __cfqq; | |
2136 | } | |
2137 | ||
2138 | process_refs = cfqq_process_refs(cfqq); | |
2139 | new_process_refs = cfqq_process_refs(new_cfqq); | |
2140 | /* | |
2141 | * If the process for the cfqq has gone away, there is no | |
2142 | * sense in merging the queues. | |
2143 | */ | |
2144 | if (process_refs == 0 || new_process_refs == 0) | |
2145 | return; | |
2146 | ||
2147 | /* | |
2148 | * Merge in the direction of the lesser amount of work. | |
2149 | */ | |
2150 | if (new_process_refs >= process_refs) { | |
2151 | cfqq->new_cfqq = new_cfqq; | |
2152 | new_cfqq->ref += process_refs; | |
2153 | } else { | |
2154 | new_cfqq->new_cfqq = cfqq; | |
2155 | cfqq->ref += new_process_refs; | |
2156 | } | |
2157 | } | |
2158 | ||
2159 | static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd, | |
2160 | struct cfq_group *cfqg, enum wl_prio_t prio) | |
2161 | { | |
2162 | struct cfq_queue *queue; | |
2163 | int i; | |
2164 | bool key_valid = false; | |
2165 | unsigned long lowest_key = 0; | |
2166 | enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD; | |
2167 | ||
2168 | for (i = 0; i <= SYNC_WORKLOAD; ++i) { | |
2169 | /* select the one with lowest rb_key */ | |
2170 | queue = cfq_rb_first(service_tree_for(cfqg, prio, i)); | |
2171 | if (queue && | |
2172 | (!key_valid || time_before(queue->rb_key, lowest_key))) { | |
2173 | lowest_key = queue->rb_key; | |
2174 | cur_best = i; | |
2175 | key_valid = true; | |
2176 | } | |
2177 | } | |
2178 | ||
2179 | return cur_best; | |
2180 | } | |
2181 | ||
2182 | static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg) | |
2183 | { | |
2184 | unsigned slice; | |
2185 | unsigned count; | |
2186 | struct cfq_rb_root *st; | |
2187 | unsigned group_slice; | |
2188 | enum wl_prio_t original_prio = cfqd->serving_prio; | |
2189 | ||
2190 | /* Choose next priority. RT > BE > IDLE */ | |
2191 | if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg)) | |
2192 | cfqd->serving_prio = RT_WORKLOAD; | |
2193 | else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg)) | |
2194 | cfqd->serving_prio = BE_WORKLOAD; | |
2195 | else { | |
2196 | cfqd->serving_prio = IDLE_WORKLOAD; | |
2197 | cfqd->workload_expires = jiffies + 1; | |
2198 | return; | |
2199 | } | |
2200 | ||
2201 | if (original_prio != cfqd->serving_prio) | |
2202 | goto new_workload; | |
2203 | ||
2204 | /* | |
2205 | * For RT and BE, we have to choose also the type | |
2206 | * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload | |
2207 | * expiration time | |
2208 | */ | |
2209 | st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type); | |
2210 | count = st->count; | |
2211 | ||
2212 | /* | |
2213 | * check workload expiration, and that we still have other queues ready | |
2214 | */ | |
2215 | if (count && !time_after(jiffies, cfqd->workload_expires)) | |
2216 | return; | |
2217 | ||
2218 | new_workload: | |
2219 | /* otherwise select new workload type */ | |
2220 | cfqd->serving_type = | |
2221 | cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio); | |
2222 | st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type); | |
2223 | count = st->count; | |
2224 | ||
2225 | /* | |
2226 | * the workload slice is computed as a fraction of target latency | |
2227 | * proportional to the number of queues in that workload, over | |
2228 | * all the queues in the same priority class | |
2229 | */ | |
2230 | group_slice = cfq_group_slice(cfqd, cfqg); | |
2231 | ||
2232 | slice = group_slice * count / | |
2233 | max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio], | |
2234 | cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg)); | |
2235 | ||
2236 | if (cfqd->serving_type == ASYNC_WORKLOAD) { | |
2237 | unsigned int tmp; | |
2238 | ||
2239 | /* | |
2240 | * Async queues are currently system wide. Just taking | |
2241 | * proportion of queues with-in same group will lead to higher | |
2242 | * async ratio system wide as generally root group is going | |
2243 | * to have higher weight. A more accurate thing would be to | |
2244 | * calculate system wide asnc/sync ratio. | |
2245 | */ | |
2246 | tmp = cfq_target_latency * cfqg_busy_async_queues(cfqd, cfqg); | |
2247 | tmp = tmp/cfqd->busy_queues; | |
2248 | slice = min_t(unsigned, slice, tmp); | |
2249 | ||
2250 | /* async workload slice is scaled down according to | |
2251 | * the sync/async slice ratio. */ | |
2252 | slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1]; | |
2253 | } else | |
2254 | /* sync workload slice is at least 2 * cfq_slice_idle */ | |
2255 | slice = max(slice, 2 * cfqd->cfq_slice_idle); | |
2256 | ||
2257 | slice = max_t(unsigned, slice, CFQ_MIN_TT); | |
2258 | cfq_log(cfqd, "workload slice:%d", slice); | |
2259 | cfqd->workload_expires = jiffies + slice; | |
2260 | } | |
2261 | ||
2262 | static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd) | |
2263 | { | |
2264 | struct cfq_rb_root *st = &cfqd->grp_service_tree; | |
2265 | struct cfq_group *cfqg; | |
2266 | ||
2267 | if (RB_EMPTY_ROOT(&st->rb)) | |
2268 | return NULL; | |
2269 | cfqg = cfq_rb_first_group(st); | |
2270 | update_min_vdisktime(st); | |
2271 | return cfqg; | |
2272 | } | |
2273 | ||
2274 | static void cfq_choose_cfqg(struct cfq_data *cfqd) | |
2275 | { | |
2276 | struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd); | |
2277 | ||
2278 | cfqd->serving_group = cfqg; | |
2279 | ||
2280 | /* Restore the workload type data */ | |
2281 | if (cfqg->saved_workload_slice) { | |
2282 | cfqd->workload_expires = jiffies + cfqg->saved_workload_slice; | |
2283 | cfqd->serving_type = cfqg->saved_workload; | |
2284 | cfqd->serving_prio = cfqg->saved_serving_prio; | |
2285 | } else | |
2286 | cfqd->workload_expires = jiffies - 1; | |
2287 | ||
2288 | choose_service_tree(cfqd, cfqg); | |
2289 | } | |
2290 | ||
2291 | /* | |
2292 | * Select a queue for service. If we have a current active queue, | |
2293 | * check whether to continue servicing it, or retrieve and set a new one. | |
2294 | */ | |
2295 | static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd) | |
2296 | { | |
2297 | struct cfq_queue *cfqq, *new_cfqq = NULL; | |
2298 | ||
2299 | cfqq = cfqd->active_queue; | |
2300 | if (!cfqq) | |
2301 | goto new_queue; | |
2302 | ||
2303 | if (!cfqd->rq_queued) | |
2304 | return NULL; | |
2305 | ||
2306 | /* | |
2307 | * We were waiting for group to get backlogged. Expire the queue | |
2308 | */ | |
2309 | if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list)) | |
2310 | goto expire; | |
2311 | ||
2312 | /* | |
2313 | * The active queue has run out of time, expire it and select new. | |
2314 | */ | |
2315 | if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) { | |
2316 | /* | |
2317 | * If slice had not expired at the completion of last request | |
2318 | * we might not have turned on wait_busy flag. Don't expire | |
2319 | * the queue yet. Allow the group to get backlogged. | |
2320 | * | |
2321 | * The very fact that we have used the slice, that means we | |
2322 | * have been idling all along on this queue and it should be | |
2323 | * ok to wait for this request to complete. | |
2324 | */ | |
2325 | if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list) | |
2326 | && cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) { | |
2327 | cfqq = NULL; | |
2328 | goto keep_queue; | |
2329 | } else | |
2330 | goto check_group_idle; | |
2331 | } | |
2332 | ||
2333 | /* | |
2334 | * The active queue has requests and isn't expired, allow it to | |
2335 | * dispatch. | |
2336 | */ | |
2337 | if (!RB_EMPTY_ROOT(&cfqq->sort_list)) | |
2338 | goto keep_queue; | |
2339 | ||
2340 | /* | |
2341 | * If another queue has a request waiting within our mean seek | |
2342 | * distance, let it run. The expire code will check for close | |
2343 | * cooperators and put the close queue at the front of the service | |
2344 | * tree. If possible, merge the expiring queue with the new cfqq. | |
2345 | */ | |
2346 | new_cfqq = cfq_close_cooperator(cfqd, cfqq); | |
2347 | if (new_cfqq) { | |
2348 | if (!cfqq->new_cfqq) | |
2349 | cfq_setup_merge(cfqq, new_cfqq); | |
2350 | goto expire; | |
2351 | } | |
2352 | ||
2353 | /* | |
2354 | * No requests pending. If the active queue still has requests in | |
2355 | * flight or is idling for a new request, allow either of these | |
2356 | * conditions to happen (or time out) before selecting a new queue. | |
2357 | */ | |
2358 | if (timer_pending(&cfqd->idle_slice_timer)) { | |
2359 | cfqq = NULL; | |
2360 | goto keep_queue; | |
2361 | } | |
2362 | ||
2363 | /* | |
2364 | * This is a deep seek queue, but the device is much faster than | |
2365 | * the queue can deliver, don't idle | |
2366 | **/ | |
2367 | if (CFQQ_SEEKY(cfqq) && cfq_cfqq_idle_window(cfqq) && | |
2368 | (cfq_cfqq_slice_new(cfqq) || | |
2369 | (cfqq->slice_end - jiffies > jiffies - cfqq->slice_start))) { | |
2370 | cfq_clear_cfqq_deep(cfqq); | |
2371 | cfq_clear_cfqq_idle_window(cfqq); | |
2372 | } | |
2373 | ||
2374 | if (cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) { | |
2375 | cfqq = NULL; | |
2376 | goto keep_queue; | |
2377 | } | |
2378 | ||
2379 | /* | |
2380 | * If group idle is enabled and there are requests dispatched from | |
2381 | * this group, wait for requests to complete. | |
2382 | */ | |
2383 | check_group_idle: | |
2384 | if (cfqd->cfq_group_idle && cfqq->cfqg->nr_cfqq == 1 | |
2385 | && cfqq->cfqg->dispatched) { | |
2386 | cfqq = NULL; | |
2387 | goto keep_queue; | |
2388 | } | |
2389 | ||
2390 | expire: | |
2391 | cfq_slice_expired(cfqd, 0); | |
2392 | new_queue: | |
2393 | /* | |
2394 | * Current queue expired. Check if we have to switch to a new | |
2395 | * service tree | |
2396 | */ | |
2397 | if (!new_cfqq) | |
2398 | cfq_choose_cfqg(cfqd); | |
2399 | ||
2400 | cfqq = cfq_set_active_queue(cfqd, new_cfqq); | |
2401 | keep_queue: | |
2402 | return cfqq; | |
2403 | } | |
2404 | ||
2405 | static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq) | |
2406 | { | |
2407 | int dispatched = 0; | |
2408 | ||
2409 | while (cfqq->next_rq) { | |
2410 | cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq); | |
2411 | dispatched++; | |
2412 | } | |
2413 | ||
2414 | BUG_ON(!list_empty(&cfqq->fifo)); | |
2415 | ||
2416 | /* By default cfqq is not expired if it is empty. Do it explicitly */ | |
2417 | __cfq_slice_expired(cfqq->cfqd, cfqq, 0); | |
2418 | return dispatched; | |
2419 | } | |
2420 | ||
2421 | /* | |
2422 | * Drain our current requests. Used for barriers and when switching | |
2423 | * io schedulers on-the-fly. | |
2424 | */ | |
2425 | static int cfq_forced_dispatch(struct cfq_data *cfqd) | |
2426 | { | |
2427 | struct cfq_queue *cfqq; | |
2428 | int dispatched = 0; | |
2429 | ||
2430 | /* Expire the timeslice of the current active queue first */ | |
2431 | cfq_slice_expired(cfqd, 0); | |
2432 | while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL) { | |
2433 | __cfq_set_active_queue(cfqd, cfqq); | |
2434 | dispatched += __cfq_forced_dispatch_cfqq(cfqq); | |
2435 | } | |
2436 | ||
2437 | BUG_ON(cfqd->busy_queues); | |
2438 | ||
2439 | cfq_log(cfqd, "forced_dispatch=%d", dispatched); | |
2440 | return dispatched; | |
2441 | } | |
2442 | ||
2443 | static inline bool cfq_slice_used_soon(struct cfq_data *cfqd, | |
2444 | struct cfq_queue *cfqq) | |
2445 | { | |
2446 | /* the queue hasn't finished any request, can't estimate */ | |
2447 | if (cfq_cfqq_slice_new(cfqq)) | |
2448 | return true; | |
2449 | if (time_after(jiffies + cfqd->cfq_slice_idle * cfqq->dispatched, | |
2450 | cfqq->slice_end)) | |
2451 | return true; | |
2452 | ||
2453 | return false; | |
2454 | } | |
2455 | ||
2456 | static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq) | |
2457 | { | |
2458 | unsigned int max_dispatch; | |
2459 | ||
2460 | /* | |
2461 | * Drain async requests before we start sync IO | |
2462 | */ | |
2463 | if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_flight[BLK_RW_ASYNC]) | |
2464 | return false; | |
2465 | ||
2466 | /* | |
2467 | * If this is an async queue and we have sync IO in flight, let it wait | |
2468 | */ | |
2469 | if (cfqd->rq_in_flight[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq)) | |
2470 | return false; | |
2471 | ||
2472 | max_dispatch = max_t(unsigned int, cfqd->cfq_quantum / 2, 1); | |
2473 | if (cfq_class_idle(cfqq)) | |
2474 | max_dispatch = 1; | |
2475 | ||
2476 | /* | |
2477 | * Does this cfqq already have too much IO in flight? | |
2478 | */ | |
2479 | if (cfqq->dispatched >= max_dispatch) { | |
2480 | bool promote_sync = false; | |
2481 | /* | |
2482 | * idle queue must always only have a single IO in flight | |
2483 | */ | |
2484 | if (cfq_class_idle(cfqq)) | |
2485 | return false; | |
2486 | ||
2487 | /* | |
2488 | * If there is only one sync queue | |
2489 | * we can ignore async queue here and give the sync | |
2490 | * queue no dispatch limit. The reason is a sync queue can | |
2491 | * preempt async queue, limiting the sync queue doesn't make | |
2492 | * sense. This is useful for aiostress test. | |
2493 | */ | |
2494 | if (cfq_cfqq_sync(cfqq) && cfqd->busy_sync_queues == 1) | |
2495 | promote_sync = true; | |
2496 | ||
2497 | /* | |
2498 | * We have other queues, don't allow more IO from this one | |
2499 | */ | |
2500 | if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq) && | |
2501 | !promote_sync) | |
2502 | return false; | |
2503 | ||
2504 | /* | |
2505 | * Sole queue user, no limit | |
2506 | */ | |
2507 | if (cfqd->busy_queues == 1 || promote_sync) | |
2508 | max_dispatch = -1; | |
2509 | else | |
2510 | /* | |
2511 | * Normally we start throttling cfqq when cfq_quantum/2 | |
2512 | * requests have been dispatched. But we can drive | |
2513 | * deeper queue depths at the beginning of slice | |
2514 | * subjected to upper limit of cfq_quantum. | |
2515 | * */ | |
2516 | max_dispatch = cfqd->cfq_quantum; | |
2517 | } | |
2518 | ||
2519 | /* | |
2520 | * Async queues must wait a bit before being allowed dispatch. | |
2521 | * We also ramp up the dispatch depth gradually for async IO, | |
2522 | * based on the last sync IO we serviced | |
2523 | */ | |
2524 | if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) { | |
2525 | unsigned long last_sync = jiffies - cfqd->last_delayed_sync; | |
2526 | unsigned int depth; | |
2527 | ||
2528 | depth = last_sync / cfqd->cfq_slice[1]; | |
2529 | if (!depth && !cfqq->dispatched) | |
2530 | depth = 1; | |
2531 | if (depth < max_dispatch) | |
2532 | max_dispatch = depth; | |
2533 | } | |
2534 | ||
2535 | /* | |
2536 | * If we're below the current max, allow a dispatch | |
2537 | */ | |
2538 | return cfqq->dispatched < max_dispatch; | |
2539 | } | |
2540 | ||
2541 | /* | |
2542 | * Dispatch a request from cfqq, moving them to the request queue | |
2543 | * dispatch list. | |
2544 | */ | |
2545 | static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq) | |
2546 | { | |
2547 | struct request *rq; | |
2548 | ||
2549 | BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list)); | |
2550 | ||
2551 | if (!cfq_may_dispatch(cfqd, cfqq)) | |
2552 | return false; | |
2553 | ||
2554 | /* | |
2555 | * follow expired path, else get first next available | |
2556 | */ | |
2557 | rq = cfq_check_fifo(cfqq); | |
2558 | if (!rq) | |
2559 | rq = cfqq->next_rq; | |
2560 | ||
2561 | /* | |
2562 | * insert request into driver dispatch list | |
2563 | */ | |
2564 | cfq_dispatch_insert(cfqd->queue, rq); | |
2565 | ||
2566 | if (!cfqd->active_cic) { | |
2567 | struct cfq_io_context *cic = RQ_CIC(rq); | |
2568 | ||
2569 | atomic_long_inc(&cic->ioc->refcount); | |
2570 | cfqd->active_cic = cic; | |
2571 | } | |
2572 | ||
2573 | return true; | |
2574 | } | |
2575 | ||
2576 | /* | |
2577 | * Find the cfqq that we need to service and move a request from that to the | |
2578 | * dispatch list | |
2579 | */ | |
2580 | static int cfq_dispatch_requests(struct request_queue *q, int force) | |
2581 | { | |
2582 | struct cfq_data *cfqd = q->elevator->elevator_data; | |
2583 | struct cfq_queue *cfqq; | |
2584 | ||
2585 | if (!cfqd->busy_queues) | |
2586 | return 0; | |
2587 | ||
2588 | if (unlikely(force)) | |
2589 | return cfq_forced_dispatch(cfqd); | |
2590 | ||
2591 | cfqq = cfq_select_queue(cfqd); | |
2592 | if (!cfqq) | |
2593 | return 0; | |
2594 | ||
2595 | /* | |
2596 | * Dispatch a request from this cfqq, if it is allowed | |
2597 | */ | |
2598 | if (!cfq_dispatch_request(cfqd, cfqq)) | |
2599 | return 0; | |
2600 | ||
2601 | cfqq->slice_dispatch++; | |
2602 | cfq_clear_cfqq_must_dispatch(cfqq); | |
2603 | ||
2604 | /* | |
2605 | * expire an async queue immediately if it has used up its slice. idle | |
2606 | * queue always expire after 1 dispatch round. | |
2607 | */ | |
2608 | if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) && | |
2609 | cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) || | |
2610 | cfq_class_idle(cfqq))) { | |
2611 | cfqq->slice_end = jiffies + 1; | |
2612 | cfq_slice_expired(cfqd, 0); | |
2613 | } | |
2614 | ||
2615 | cfq_log_cfqq(cfqd, cfqq, "dispatched a request"); | |
2616 | return 1; | |
2617 | } | |
2618 | ||
2619 | /* | |
2620 | * task holds one reference to the queue, dropped when task exits. each rq | |
2621 | * in-flight on this queue also holds a reference, dropped when rq is freed. | |
2622 | * | |
2623 | * Each cfq queue took a reference on the parent group. Drop it now. | |
2624 | * queue lock must be held here. | |
2625 | */ | |
2626 | static void cfq_put_queue(struct cfq_queue *cfqq) | |
2627 | { | |
2628 | struct cfq_data *cfqd = cfqq->cfqd; | |
2629 | struct cfq_group *cfqg; | |
2630 | ||
2631 | BUG_ON(cfqq->ref <= 0); | |
2632 | ||
2633 | cfqq->ref--; | |
2634 | if (cfqq->ref) | |
2635 | return; | |
2636 | ||
2637 | cfq_log_cfqq(cfqd, cfqq, "put_queue"); | |
2638 | BUG_ON(rb_first(&cfqq->sort_list)); | |
2639 | BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]); | |
2640 | cfqg = cfqq->cfqg; | |
2641 | ||
2642 | if (unlikely(cfqd->active_queue == cfqq)) { | |
2643 | __cfq_slice_expired(cfqd, cfqq, 0); | |
2644 | cfq_schedule_dispatch(cfqd); | |
2645 | } | |
2646 | ||
2647 | BUG_ON(cfq_cfqq_on_rr(cfqq)); | |
2648 | kmem_cache_free(cfq_pool, cfqq); | |
2649 | cfq_put_cfqg(cfqg); | |
2650 | } | |
2651 | ||
2652 | /* | |
2653 | * Call func for each cic attached to this ioc. | |
2654 | */ | |
2655 | static void | |
2656 | call_for_each_cic(struct io_context *ioc, | |
2657 | void (*func)(struct io_context *, struct cfq_io_context *)) | |
2658 | { | |
2659 | struct cfq_io_context *cic; | |
2660 | struct hlist_node *n; | |
2661 | ||
2662 | rcu_read_lock(); | |
2663 | ||
2664 | hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list) | |
2665 | func(ioc, cic); | |
2666 | ||
2667 | rcu_read_unlock(); | |
2668 | } | |
2669 | ||
2670 | static void cfq_cic_free_rcu(struct rcu_head *head) | |
2671 | { | |
2672 | struct cfq_io_context *cic; | |
2673 | ||
2674 | cic = container_of(head, struct cfq_io_context, rcu_head); | |
2675 | ||
2676 | kmem_cache_free(cfq_ioc_pool, cic); | |
2677 | elv_ioc_count_dec(cfq_ioc_count); | |
2678 | ||
2679 | if (ioc_gone) { | |
2680 | /* | |
2681 | * CFQ scheduler is exiting, grab exit lock and check | |
2682 | * the pending io context count. If it hits zero, | |
2683 | * complete ioc_gone and set it back to NULL | |
2684 | */ | |
2685 | spin_lock(&ioc_gone_lock); | |
2686 | if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) { | |
2687 | complete(ioc_gone); | |
2688 | ioc_gone = NULL; | |
2689 | } | |
2690 | spin_unlock(&ioc_gone_lock); | |
2691 | } | |
2692 | } | |
2693 | ||
2694 | static void cfq_cic_free(struct cfq_io_context *cic) | |
2695 | { | |
2696 | call_rcu(&cic->rcu_head, cfq_cic_free_rcu); | |
2697 | } | |
2698 | ||
2699 | static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic) | |
2700 | { | |
2701 | unsigned long flags; | |
2702 | unsigned long dead_key = (unsigned long) cic->key; | |
2703 | ||
2704 | BUG_ON(!(dead_key & CIC_DEAD_KEY)); | |
2705 | ||
2706 | spin_lock_irqsave(&ioc->lock, flags); | |
2707 | radix_tree_delete(&ioc->radix_root, dead_key >> CIC_DEAD_INDEX_SHIFT); | |
2708 | hlist_del_rcu(&cic->cic_list); | |
2709 | spin_unlock_irqrestore(&ioc->lock, flags); | |
2710 | ||
2711 | cfq_cic_free(cic); | |
2712 | } | |
2713 | ||
2714 | /* | |
2715 | * Must be called with rcu_read_lock() held or preemption otherwise disabled. | |
2716 | * Only two callers of this - ->dtor() which is called with the rcu_read_lock(), | |
2717 | * and ->trim() which is called with the task lock held | |
2718 | */ | |
2719 | static void cfq_free_io_context(struct io_context *ioc) | |
2720 | { | |
2721 | /* | |
2722 | * ioc->refcount is zero here, or we are called from elv_unregister(), | |
2723 | * so no more cic's are allowed to be linked into this ioc. So it | |
2724 | * should be ok to iterate over the known list, we will see all cic's | |
2725 | * since no new ones are added. | |
2726 | */ | |
2727 | call_for_each_cic(ioc, cic_free_func); | |
2728 | } | |
2729 | ||
2730 | static void cfq_put_cooperator(struct cfq_queue *cfqq) | |
2731 | { | |
2732 | struct cfq_queue *__cfqq, *next; | |
2733 | ||
2734 | /* | |
2735 | * If this queue was scheduled to merge with another queue, be | |
2736 | * sure to drop the reference taken on that queue (and others in | |
2737 | * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs. | |
2738 | */ | |
2739 | __cfqq = cfqq->new_cfqq; | |
2740 | while (__cfqq) { | |
2741 | if (__cfqq == cfqq) { | |
2742 | WARN(1, "cfqq->new_cfqq loop detected\n"); | |
2743 | break; | |
2744 | } | |
2745 | next = __cfqq->new_cfqq; | |
2746 | cfq_put_queue(__cfqq); | |
2747 | __cfqq = next; | |
2748 | } | |
2749 | } | |
2750 | ||
2751 | static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq) | |
2752 | { | |
2753 | if (unlikely(cfqq == cfqd->active_queue)) { | |
2754 | __cfq_slice_expired(cfqd, cfqq, 0); | |
2755 | cfq_schedule_dispatch(cfqd); | |
2756 | } | |
2757 | ||
2758 | cfq_put_cooperator(cfqq); | |
2759 | ||
2760 | cfq_put_queue(cfqq); | |
2761 | } | |
2762 | ||
2763 | static void __cfq_exit_single_io_context(struct cfq_data *cfqd, | |
2764 | struct cfq_io_context *cic) | |
2765 | { | |
2766 | struct io_context *ioc = cic->ioc; | |
2767 | ||
2768 | list_del_init(&cic->queue_list); | |
2769 | ||
2770 | /* | |
2771 | * Make sure dead mark is seen for dead queues | |
2772 | */ | |
2773 | smp_wmb(); | |
2774 | cic->key = cfqd_dead_key(cfqd); | |
2775 | ||
2776 | rcu_read_lock(); | |
2777 | if (rcu_dereference(ioc->ioc_data) == cic) { | |
2778 | rcu_read_unlock(); | |
2779 | spin_lock(&ioc->lock); | |
2780 | rcu_assign_pointer(ioc->ioc_data, NULL); | |
2781 | spin_unlock(&ioc->lock); | |
2782 | } else | |
2783 | rcu_read_unlock(); | |
2784 | ||
2785 | if (cic->cfqq[BLK_RW_ASYNC]) { | |
2786 | cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]); | |
2787 | cic->cfqq[BLK_RW_ASYNC] = NULL; | |
2788 | } | |
2789 | ||
2790 | if (cic->cfqq[BLK_RW_SYNC]) { | |
2791 | cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]); | |
2792 | cic->cfqq[BLK_RW_SYNC] = NULL; | |
2793 | } | |
2794 | } | |
2795 | ||
2796 | static void cfq_exit_single_io_context(struct io_context *ioc, | |
2797 | struct cfq_io_context *cic) | |
2798 | { | |
2799 | struct cfq_data *cfqd = cic_to_cfqd(cic); | |
2800 | ||
2801 | if (cfqd) { | |
2802 | struct request_queue *q = cfqd->queue; | |
2803 | unsigned long flags; | |
2804 | ||
2805 | spin_lock_irqsave(q->queue_lock, flags); | |
2806 | ||
2807 | /* | |
2808 | * Ensure we get a fresh copy of the ->key to prevent | |
2809 | * race between exiting task and queue | |
2810 | */ | |
2811 | smp_read_barrier_depends(); | |
2812 | if (cic->key == cfqd) | |
2813 | __cfq_exit_single_io_context(cfqd, cic); | |
2814 | ||
2815 | spin_unlock_irqrestore(q->queue_lock, flags); | |
2816 | } | |
2817 | } | |
2818 | ||
2819 | /* | |
2820 | * The process that ioc belongs to has exited, we need to clean up | |
2821 | * and put the internal structures we have that belongs to that process. | |
2822 | */ | |
2823 | static void cfq_exit_io_context(struct io_context *ioc) | |
2824 | { | |
2825 | call_for_each_cic(ioc, cfq_exit_single_io_context); | |
2826 | } | |
2827 | ||
2828 | static struct cfq_io_context * | |
2829 | cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) | |
2830 | { | |
2831 | struct cfq_io_context *cic; | |
2832 | ||
2833 | cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO, | |
2834 | cfqd->queue->node); | |
2835 | if (cic) { | |
2836 | cic->ttime.last_end_request = jiffies; | |
2837 | INIT_LIST_HEAD(&cic->queue_list); | |
2838 | INIT_HLIST_NODE(&cic->cic_list); | |
2839 | cic->dtor = cfq_free_io_context; | |
2840 | cic->exit = cfq_exit_io_context; | |
2841 | elv_ioc_count_inc(cfq_ioc_count); | |
2842 | } | |
2843 | ||
2844 | return cic; | |
2845 | } | |
2846 | ||
2847 | static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc) | |
2848 | { | |
2849 | struct task_struct *tsk = current; | |
2850 | int ioprio_class; | |
2851 | ||
2852 | if (!cfq_cfqq_prio_changed(cfqq)) | |
2853 | return; | |
2854 | ||
2855 | ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio); | |
2856 | switch (ioprio_class) { | |
2857 | default: | |
2858 | printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class); | |
2859 | case IOPRIO_CLASS_NONE: | |
2860 | /* | |
2861 | * no prio set, inherit CPU scheduling settings | |
2862 | */ | |
2863 | cfqq->ioprio = task_nice_ioprio(tsk); | |
2864 | cfqq->ioprio_class = task_nice_ioclass(tsk); | |
2865 | break; | |
2866 | case IOPRIO_CLASS_RT: | |
2867 | cfqq->ioprio = task_ioprio(ioc); | |
2868 | cfqq->ioprio_class = IOPRIO_CLASS_RT; | |
2869 | break; | |
2870 | case IOPRIO_CLASS_BE: | |
2871 | cfqq->ioprio = task_ioprio(ioc); | |
2872 | cfqq->ioprio_class = IOPRIO_CLASS_BE; | |
2873 | break; | |
2874 | case IOPRIO_CLASS_IDLE: | |
2875 | cfqq->ioprio_class = IOPRIO_CLASS_IDLE; | |
2876 | cfqq->ioprio = 7; | |
2877 | cfq_clear_cfqq_idle_window(cfqq); | |
2878 | break; | |
2879 | } | |
2880 | ||
2881 | /* | |
2882 | * keep track of original prio settings in case we have to temporarily | |
2883 | * elevate the priority of this queue | |
2884 | */ | |
2885 | cfqq->org_ioprio = cfqq->ioprio; | |
2886 | cfq_clear_cfqq_prio_changed(cfqq); | |
2887 | } | |
2888 | ||
2889 | static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic) | |
2890 | { | |
2891 | struct cfq_data *cfqd = cic_to_cfqd(cic); | |
2892 | struct cfq_queue *cfqq; | |
2893 | unsigned long flags; | |
2894 | ||
2895 | if (unlikely(!cfqd)) | |
2896 | return; | |
2897 | ||
2898 | spin_lock_irqsave(cfqd->queue->queue_lock, flags); | |
2899 | ||
2900 | cfqq = cic->cfqq[BLK_RW_ASYNC]; | |
2901 | if (cfqq) { | |
2902 | struct cfq_queue *new_cfqq; | |
2903 | new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc, | |
2904 | GFP_ATOMIC); | |
2905 | if (new_cfqq) { | |
2906 | cic->cfqq[BLK_RW_ASYNC] = new_cfqq; | |
2907 | cfq_put_queue(cfqq); | |
2908 | } | |
2909 | } | |
2910 | ||
2911 | cfqq = cic->cfqq[BLK_RW_SYNC]; | |
2912 | if (cfqq) | |
2913 | cfq_mark_cfqq_prio_changed(cfqq); | |
2914 | ||
2915 | spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); | |
2916 | } | |
2917 | ||
2918 | static void cfq_ioc_set_ioprio(struct io_context *ioc) | |
2919 | { | |
2920 | call_for_each_cic(ioc, changed_ioprio); | |
2921 | ioc->ioprio_changed = 0; | |
2922 | } | |
2923 | ||
2924 | static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq, | |
2925 | pid_t pid, bool is_sync) | |
2926 | { | |
2927 | RB_CLEAR_NODE(&cfqq->rb_node); | |
2928 | RB_CLEAR_NODE(&cfqq->p_node); | |
2929 | INIT_LIST_HEAD(&cfqq->fifo); | |
2930 | ||
2931 | cfqq->ref = 0; | |
2932 | cfqq->cfqd = cfqd; | |
2933 | ||
2934 | cfq_mark_cfqq_prio_changed(cfqq); | |
2935 | ||
2936 | if (is_sync) { | |
2937 | if (!cfq_class_idle(cfqq)) | |
2938 | cfq_mark_cfqq_idle_window(cfqq); | |
2939 | cfq_mark_cfqq_sync(cfqq); | |
2940 | } | |
2941 | cfqq->pid = pid; | |
2942 | } | |
2943 | ||
2944 | #ifdef CONFIG_CFQ_GROUP_IOSCHED | |
2945 | static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic) | |
2946 | { | |
2947 | struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1); | |
2948 | struct cfq_data *cfqd = cic_to_cfqd(cic); | |
2949 | unsigned long flags; | |
2950 | struct request_queue *q; | |
2951 | ||
2952 | if (unlikely(!cfqd)) | |
2953 | return; | |
2954 | ||
2955 | q = cfqd->queue; | |
2956 | ||
2957 | spin_lock_irqsave(q->queue_lock, flags); | |
2958 | ||
2959 | if (sync_cfqq) { | |
2960 | /* | |
2961 | * Drop reference to sync queue. A new sync queue will be | |
2962 | * assigned in new group upon arrival of a fresh request. | |
2963 | */ | |
2964 | cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup"); | |
2965 | cic_set_cfqq(cic, NULL, 1); | |
2966 | cfq_put_queue(sync_cfqq); | |
2967 | } | |
2968 | ||
2969 | spin_unlock_irqrestore(q->queue_lock, flags); | |
2970 | } | |
2971 | ||
2972 | static void cfq_ioc_set_cgroup(struct io_context *ioc) | |
2973 | { | |
2974 | call_for_each_cic(ioc, changed_cgroup); | |
2975 | ioc->cgroup_changed = 0; | |
2976 | } | |
2977 | #endif /* CONFIG_CFQ_GROUP_IOSCHED */ | |
2978 | ||
2979 | static struct cfq_queue * | |
2980 | cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, | |
2981 | struct io_context *ioc, gfp_t gfp_mask) | |
2982 | { | |
2983 | struct cfq_queue *cfqq, *new_cfqq = NULL; | |
2984 | struct cfq_io_context *cic; | |
2985 | struct cfq_group *cfqg; | |
2986 | ||
2987 | retry: | |
2988 | cfqg = cfq_get_cfqg(cfqd); | |
2989 | cic = cfq_cic_lookup(cfqd, ioc); | |
2990 | /* cic always exists here */ | |
2991 | cfqq = cic_to_cfqq(cic, is_sync); | |
2992 | ||
2993 | /* | |
2994 | * Always try a new alloc if we fell back to the OOM cfqq | |
2995 | * originally, since it should just be a temporary situation. | |
2996 | */ | |
2997 | if (!cfqq || cfqq == &cfqd->oom_cfqq) { | |
2998 | cfqq = NULL; | |
2999 | if (new_cfqq) { | |
3000 | cfqq = new_cfqq; | |
3001 | new_cfqq = NULL; | |
3002 | } else if (gfp_mask & __GFP_WAIT) { | |
3003 | spin_unlock_irq(cfqd->queue->queue_lock); | |
3004 | new_cfqq = kmem_cache_alloc_node(cfq_pool, | |
3005 | gfp_mask | __GFP_ZERO, | |
3006 | cfqd->queue->node); | |
3007 | spin_lock_irq(cfqd->queue->queue_lock); | |
3008 | if (new_cfqq) | |
3009 | goto retry; | |
3010 | } else { | |
3011 | cfqq = kmem_cache_alloc_node(cfq_pool, | |
3012 | gfp_mask | __GFP_ZERO, | |
3013 | cfqd->queue->node); | |
3014 | } | |
3015 | ||
3016 | if (cfqq) { | |
3017 | cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync); | |
3018 | cfq_init_prio_data(cfqq, ioc); | |
3019 | cfq_link_cfqq_cfqg(cfqq, cfqg); | |
3020 | cfq_log_cfqq(cfqd, cfqq, "alloced"); | |
3021 | } else | |
3022 | cfqq = &cfqd->oom_cfqq; | |
3023 | } | |
3024 | ||
3025 | if (new_cfqq) | |
3026 | kmem_cache_free(cfq_pool, new_cfqq); | |
3027 | ||
3028 | return cfqq; | |
3029 | } | |
3030 | ||
3031 | static struct cfq_queue ** | |
3032 | cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio) | |
3033 | { | |
3034 | switch (ioprio_class) { | |
3035 | case IOPRIO_CLASS_RT: | |
3036 | return &cfqd->async_cfqq[0][ioprio]; | |
3037 | case IOPRIO_CLASS_BE: | |
3038 | return &cfqd->async_cfqq[1][ioprio]; | |
3039 | case IOPRIO_CLASS_IDLE: | |
3040 | return &cfqd->async_idle_cfqq; | |
3041 | default: | |
3042 | BUG(); | |
3043 | } | |
3044 | } | |
3045 | ||
3046 | static struct cfq_queue * | |
3047 | cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc, | |
3048 | gfp_t gfp_mask) | |
3049 | { | |
3050 | const int ioprio = task_ioprio(ioc); | |
3051 | const int ioprio_class = task_ioprio_class(ioc); | |
3052 | struct cfq_queue **async_cfqq = NULL; | |
3053 | struct cfq_queue *cfqq = NULL; | |
3054 | ||
3055 | if (!is_sync) { | |
3056 | async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio); | |
3057 | cfqq = *async_cfqq; | |
3058 | } | |
3059 | ||
3060 | if (!cfqq) | |
3061 | cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask); | |
3062 | ||
3063 | /* | |
3064 | * pin the queue now that it's allocated, scheduler exit will prune it | |
3065 | */ | |
3066 | if (!is_sync && !(*async_cfqq)) { | |
3067 | cfqq->ref++; | |
3068 | *async_cfqq = cfqq; | |
3069 | } | |
3070 | ||
3071 | cfqq->ref++; | |
3072 | return cfqq; | |
3073 | } | |
3074 | ||
3075 | /* | |
3076 | * We drop cfq io contexts lazily, so we may find a dead one. | |
3077 | */ | |
3078 | static void | |
3079 | cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc, | |
3080 | struct cfq_io_context *cic) | |
3081 | { | |
3082 | unsigned long flags; | |
3083 | ||
3084 | WARN_ON(!list_empty(&cic->queue_list)); | |
3085 | BUG_ON(cic->key != cfqd_dead_key(cfqd)); | |
3086 | ||
3087 | spin_lock_irqsave(&ioc->lock, flags); | |
3088 | ||
3089 | BUG_ON(rcu_dereference_check(ioc->ioc_data, | |
3090 | lockdep_is_held(&ioc->lock)) == cic); | |
3091 | ||
3092 | radix_tree_delete(&ioc->radix_root, cfqd->cic_index); | |
3093 | hlist_del_rcu(&cic->cic_list); | |
3094 | spin_unlock_irqrestore(&ioc->lock, flags); | |
3095 | ||
3096 | cfq_cic_free(cic); | |
3097 | } | |
3098 | ||
3099 | static struct cfq_io_context * | |
3100 | cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc) | |
3101 | { | |
3102 | struct cfq_io_context *cic; | |
3103 | unsigned long flags; | |
3104 | ||
3105 | if (unlikely(!ioc)) | |
3106 | return NULL; | |
3107 | ||
3108 | rcu_read_lock(); | |
3109 | ||
3110 | /* | |
3111 | * we maintain a last-hit cache, to avoid browsing over the tree | |
3112 | */ | |
3113 | cic = rcu_dereference(ioc->ioc_data); | |
3114 | if (cic && cic->key == cfqd) { | |
3115 | rcu_read_unlock(); | |
3116 | return cic; | |
3117 | } | |
3118 | ||
3119 | do { | |
3120 | cic = radix_tree_lookup(&ioc->radix_root, cfqd->cic_index); | |
3121 | rcu_read_unlock(); | |
3122 | if (!cic) | |
3123 | break; | |
3124 | if (unlikely(cic->key != cfqd)) { | |
3125 | cfq_drop_dead_cic(cfqd, ioc, cic); | |
3126 | rcu_read_lock(); | |
3127 | continue; | |
3128 | } | |
3129 | ||
3130 | spin_lock_irqsave(&ioc->lock, flags); | |
3131 | rcu_assign_pointer(ioc->ioc_data, cic); | |
3132 | spin_unlock_irqrestore(&ioc->lock, flags); | |
3133 | break; | |
3134 | } while (1); | |
3135 | ||
3136 | return cic; | |
3137 | } | |
3138 | ||
3139 | /* | |
3140 | * Add cic into ioc, using cfqd as the search key. This enables us to lookup | |
3141 | * the process specific cfq io context when entered from the block layer. | |
3142 | * Also adds the cic to a per-cfqd list, used when this queue is removed. | |
3143 | */ | |
3144 | static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc, | |
3145 | struct cfq_io_context *cic, gfp_t gfp_mask) | |
3146 | { | |
3147 | unsigned long flags; | |
3148 | int ret; | |
3149 | ||
3150 | ret = radix_tree_preload(gfp_mask); | |
3151 | if (!ret) { | |
3152 | cic->ioc = ioc; | |
3153 | cic->key = cfqd; | |
3154 | ||
3155 | spin_lock_irqsave(&ioc->lock, flags); | |
3156 | ret = radix_tree_insert(&ioc->radix_root, | |
3157 | cfqd->cic_index, cic); | |
3158 | if (!ret) | |
3159 | hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list); | |
3160 | spin_unlock_irqrestore(&ioc->lock, flags); | |
3161 | ||
3162 | radix_tree_preload_end(); | |
3163 | ||
3164 | if (!ret) { | |
3165 | spin_lock_irqsave(cfqd->queue->queue_lock, flags); | |
3166 | list_add(&cic->queue_list, &cfqd->cic_list); | |
3167 | spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); | |
3168 | } | |
3169 | } | |
3170 | ||
3171 | if (ret) | |
3172 | printk(KERN_ERR "cfq: cic link failed!\n"); | |
3173 | ||
3174 | return ret; | |
3175 | } | |
3176 | ||
3177 | /* | |
3178 | * Setup general io context and cfq io context. There can be several cfq | |
3179 | * io contexts per general io context, if this process is doing io to more | |
3180 | * than one device managed by cfq. | |
3181 | */ | |
3182 | static struct cfq_io_context * | |
3183 | cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) | |
3184 | { | |
3185 | struct io_context *ioc = NULL; | |
3186 | struct cfq_io_context *cic; | |
3187 | ||
3188 | might_sleep_if(gfp_mask & __GFP_WAIT); | |
3189 | ||
3190 | ioc = get_io_context(gfp_mask, cfqd->queue->node); | |
3191 | if (!ioc) | |
3192 | return NULL; | |
3193 | ||
3194 | cic = cfq_cic_lookup(cfqd, ioc); | |
3195 | if (cic) | |
3196 | goto out; | |
3197 | ||
3198 | cic = cfq_alloc_io_context(cfqd, gfp_mask); | |
3199 | if (cic == NULL) | |
3200 | goto err; | |
3201 | ||
3202 | if (cfq_cic_link(cfqd, ioc, cic, gfp_mask)) | |
3203 | goto err_free; | |
3204 | ||
3205 | out: | |
3206 | smp_read_barrier_depends(); | |
3207 | if (unlikely(ioc->ioprio_changed)) | |
3208 | cfq_ioc_set_ioprio(ioc); | |
3209 | ||
3210 | #ifdef CONFIG_CFQ_GROUP_IOSCHED | |
3211 | if (unlikely(ioc->cgroup_changed)) | |
3212 | cfq_ioc_set_cgroup(ioc); | |
3213 | #endif | |
3214 | return cic; | |
3215 | err_free: | |
3216 | cfq_cic_free(cic); | |
3217 | err: | |
3218 | put_io_context(ioc); | |
3219 | return NULL; | |
3220 | } | |
3221 | ||
3222 | static void | |
3223 | __cfq_update_io_thinktime(struct cfq_ttime *ttime, unsigned long slice_idle) | |
3224 | { | |
3225 | unsigned long elapsed = jiffies - ttime->last_end_request; | |
3226 | elapsed = min(elapsed, 2UL * slice_idle); | |
3227 | ||
3228 | ttime->ttime_samples = (7*ttime->ttime_samples + 256) / 8; | |
3229 | ttime->ttime_total = (7*ttime->ttime_total + 256*elapsed) / 8; | |
3230 | ttime->ttime_mean = (ttime->ttime_total + 128) / ttime->ttime_samples; | |
3231 | } | |
3232 | ||
3233 | static void | |
3234 | cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_queue *cfqq, | |
3235 | struct cfq_io_context *cic) | |
3236 | { | |
3237 | if (cfq_cfqq_sync(cfqq)) { | |
3238 | __cfq_update_io_thinktime(&cic->ttime, cfqd->cfq_slice_idle); | |
3239 | __cfq_update_io_thinktime(&cfqq->service_tree->ttime, | |
3240 | cfqd->cfq_slice_idle); | |
3241 | } | |
3242 | } | |
3243 | ||
3244 | static void | |
3245 | cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq, | |
3246 | struct request *rq) | |
3247 | { | |
3248 | sector_t sdist = 0; | |
3249 | sector_t n_sec = blk_rq_sectors(rq); | |
3250 | if (cfqq->last_request_pos) { | |
3251 | if (cfqq->last_request_pos < blk_rq_pos(rq)) | |
3252 | sdist = blk_rq_pos(rq) - cfqq->last_request_pos; | |
3253 | else | |
3254 | sdist = cfqq->last_request_pos - blk_rq_pos(rq); | |
3255 | } | |
3256 | ||
3257 | cfqq->seek_history <<= 1; | |
3258 | if (blk_queue_nonrot(cfqd->queue)) | |
3259 | cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT); | |
3260 | else | |
3261 | cfqq->seek_history |= (sdist > CFQQ_SEEK_THR); | |
3262 | } | |
3263 | ||
3264 | /* | |
3265 | * Disable idle window if the process thinks too long or seeks so much that | |
3266 | * it doesn't matter | |
3267 | */ | |
3268 | static void | |
3269 | cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, | |
3270 | struct cfq_io_context *cic) | |
3271 | { | |
3272 | int old_idle, enable_idle; | |
3273 | ||
3274 | /* | |
3275 | * Don't idle for async or idle io prio class | |
3276 | */ | |
3277 | if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq)) | |
3278 | return; | |
3279 | ||
3280 | enable_idle = old_idle = cfq_cfqq_idle_window(cfqq); | |
3281 | ||
3282 | if (cfqq->queued[0] + cfqq->queued[1] >= 4) | |
3283 | cfq_mark_cfqq_deep(cfqq); | |
3284 | ||
3285 | if (cfqq->next_rq && (cfqq->next_rq->cmd_flags & REQ_NOIDLE)) | |
3286 | enable_idle = 0; | |
3287 | else if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle || | |
3288 | (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq))) | |
3289 | enable_idle = 0; | |
3290 | else if (sample_valid(cic->ttime.ttime_samples)) { | |
3291 | if (cic->ttime.ttime_mean > cfqd->cfq_slice_idle) | |
3292 | enable_idle = 0; | |
3293 | else | |
3294 | enable_idle = 1; | |
3295 | } | |
3296 | ||
3297 | if (old_idle != enable_idle) { | |
3298 | cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle); | |
3299 | if (enable_idle) | |
3300 | cfq_mark_cfqq_idle_window(cfqq); | |
3301 | else | |
3302 | cfq_clear_cfqq_idle_window(cfqq); | |
3303 | } | |
3304 | } | |
3305 | ||
3306 | /* | |
3307 | * Check if new_cfqq should preempt the currently active queue. Return 0 for | |
3308 | * no or if we aren't sure, a 1 will cause a preempt. | |
3309 | */ | |
3310 | static bool | |
3311 | cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, | |
3312 | struct request *rq) | |
3313 | { | |
3314 | struct cfq_queue *cfqq; | |
3315 | ||
3316 | cfqq = cfqd->active_queue; | |
3317 | if (!cfqq) | |
3318 | return false; | |
3319 | ||
3320 | if (cfq_class_idle(new_cfqq)) | |
3321 | return false; | |
3322 | ||
3323 | if (cfq_class_idle(cfqq)) | |
3324 | return true; | |
3325 | ||
3326 | /* | |
3327 | * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice. | |
3328 | */ | |
3329 | if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq)) | |
3330 | return false; | |
3331 | ||
3332 | /* | |
3333 | * if the new request is sync, but the currently running queue is | |
3334 | * not, let the sync request have priority. | |
3335 | */ | |
3336 | if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq)) | |
3337 | return true; | |
3338 | ||
3339 | if (new_cfqq->cfqg != cfqq->cfqg) | |
3340 | return false; | |
3341 | ||
3342 | if (cfq_slice_used(cfqq)) | |
3343 | return true; | |
3344 | ||
3345 | /* Allow preemption only if we are idling on sync-noidle tree */ | |
3346 | if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD && | |
3347 | cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD && | |
3348 | new_cfqq->service_tree->count == 2 && | |
3349 | RB_EMPTY_ROOT(&cfqq->sort_list)) | |
3350 | return true; | |
3351 | ||
3352 | /* | |
3353 | * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice. | |
3354 | */ | |
3355 | if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq)) | |
3356 | return true; | |
3357 | ||
3358 | /* An idle queue should not be idle now for some reason */ | |
3359 | if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq)) | |
3360 | return true; | |
3361 | ||
3362 | if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq)) | |
3363 | return false; | |
3364 | ||
3365 | /* | |
3366 | * if this request is as-good as one we would expect from the | |
3367 | * current cfqq, let it preempt | |
3368 | */ | |
3369 | if (cfq_rq_close(cfqd, cfqq, rq)) | |
3370 | return true; | |
3371 | ||
3372 | return false; | |
3373 | } | |
3374 | ||
3375 | /* | |
3376 | * cfqq preempts the active queue. if we allowed preempt with no slice left, | |
3377 | * let it have half of its nominal slice. | |
3378 | */ | |
3379 | static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) | |
3380 | { | |
3381 | struct cfq_queue *old_cfqq = cfqd->active_queue; | |
3382 | ||
3383 | cfq_log_cfqq(cfqd, cfqq, "preempt"); | |
3384 | cfq_slice_expired(cfqd, 1); | |
3385 | ||
3386 | /* | |
3387 | * workload type is changed, don't save slice, otherwise preempt | |
3388 | * doesn't happen | |
3389 | */ | |
3390 | if (cfqq_type(old_cfqq) != cfqq_type(cfqq)) | |
3391 | cfqq->cfqg->saved_workload_slice = 0; | |
3392 | ||
3393 | /* | |
3394 | * Put the new queue at the front of the of the current list, | |
3395 | * so we know that it will be selected next. | |
3396 | */ | |
3397 | BUG_ON(!cfq_cfqq_on_rr(cfqq)); | |
3398 | ||
3399 | cfq_service_tree_add(cfqd, cfqq, 1); | |
3400 | ||
3401 | cfqq->slice_end = 0; | |
3402 | cfq_mark_cfqq_slice_new(cfqq); | |
3403 | } | |
3404 | ||
3405 | /* | |
3406 | * Called when a new fs request (rq) is added (to cfqq). Check if there's | |
3407 | * something we should do about it | |
3408 | */ | |
3409 | static void | |
3410 | cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq, | |
3411 | struct request *rq) | |
3412 | { | |
3413 | struct cfq_io_context *cic = RQ_CIC(rq); | |
3414 | ||
3415 | cfqd->rq_queued++; | |
3416 | ||
3417 | cfq_update_io_thinktime(cfqd, cfqq, cic); | |
3418 | cfq_update_io_seektime(cfqd, cfqq, rq); | |
3419 | cfq_update_idle_window(cfqd, cfqq, cic); | |
3420 | ||
3421 | cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq); | |
3422 | ||
3423 | if (cfqq == cfqd->active_queue) { | |
3424 | /* | |
3425 | * Remember that we saw a request from this process, but | |
3426 | * don't start queuing just yet. Otherwise we risk seeing lots | |
3427 | * of tiny requests, because we disrupt the normal plugging | |
3428 | * and merging. If the request is already larger than a single | |
3429 | * page, let it rip immediately. For that case we assume that | |
3430 | * merging is already done. Ditto for a busy system that | |
3431 | * has other work pending, don't risk delaying until the | |
3432 | * idle timer unplug to continue working. | |
3433 | */ | |
3434 | if (cfq_cfqq_wait_request(cfqq)) { | |
3435 | if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE || | |
3436 | cfqd->busy_queues > 1) { | |
3437 | cfq_del_timer(cfqd, cfqq); | |
3438 | cfq_clear_cfqq_wait_request(cfqq); | |
3439 | __blk_run_queue(cfqd->queue); | |
3440 | } else { | |
3441 | cfq_blkiocg_update_idle_time_stats( | |
3442 | &cfqq->cfqg->blkg); | |
3443 | cfq_mark_cfqq_must_dispatch(cfqq); | |
3444 | } | |
3445 | } | |
3446 | } else if (cfq_should_preempt(cfqd, cfqq, rq)) { | |
3447 | /* | |
3448 | * not the active queue - expire current slice if it is | |
3449 | * idle and has expired it's mean thinktime or this new queue | |
3450 | * has some old slice time left and is of higher priority or | |
3451 | * this new queue is RT and the current one is BE | |
3452 | */ | |
3453 | cfq_preempt_queue(cfqd, cfqq); | |
3454 | __blk_run_queue(cfqd->queue); | |
3455 | } | |
3456 | } | |
3457 | ||
3458 | static void cfq_insert_request(struct request_queue *q, struct request *rq) | |
3459 | { | |
3460 | struct cfq_data *cfqd = q->elevator->elevator_data; | |
3461 | struct cfq_queue *cfqq = RQ_CFQQ(rq); | |
3462 | ||
3463 | cfq_log_cfqq(cfqd, cfqq, "insert_request"); | |
3464 | cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc); | |
3465 | ||
3466 | rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]); | |
3467 | list_add_tail(&rq->queuelist, &cfqq->fifo); | |
3468 | cfq_add_rq_rb(rq); | |
3469 | cfq_blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg, | |
3470 | &cfqd->serving_group->blkg, rq_data_dir(rq), | |
3471 | rq_is_sync(rq)); | |
3472 | cfq_rq_enqueued(cfqd, cfqq, rq); | |
3473 | } | |
3474 | ||
3475 | /* | |
3476 | * Update hw_tag based on peak queue depth over 50 samples under | |
3477 | * sufficient load. | |
3478 | */ | |
3479 | static void cfq_update_hw_tag(struct cfq_data *cfqd) | |
3480 | { | |
3481 | struct cfq_queue *cfqq = cfqd->active_queue; | |
3482 | ||
3483 | if (cfqd->rq_in_driver > cfqd->hw_tag_est_depth) | |
3484 | cfqd->hw_tag_est_depth = cfqd->rq_in_driver; | |
3485 | ||
3486 | if (cfqd->hw_tag == 1) | |
3487 | return; | |
3488 | ||
3489 | if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN && | |
3490 | cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN) | |
3491 | return; | |
3492 | ||
3493 | /* | |
3494 | * If active queue hasn't enough requests and can idle, cfq might not | |
3495 | * dispatch sufficient requests to hardware. Don't zero hw_tag in this | |
3496 | * case | |
3497 | */ | |
3498 | if (cfqq && cfq_cfqq_idle_window(cfqq) && | |
3499 | cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] < | |
3500 | CFQ_HW_QUEUE_MIN && cfqd->rq_in_driver < CFQ_HW_QUEUE_MIN) | |
3501 | return; | |
3502 | ||
3503 | if (cfqd->hw_tag_samples++ < 50) | |
3504 | return; | |
3505 | ||
3506 | if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN) | |
3507 | cfqd->hw_tag = 1; | |
3508 | else | |
3509 | cfqd->hw_tag = 0; | |
3510 | } | |
3511 | ||
3512 | static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq) | |
3513 | { | |
3514 | struct cfq_io_context *cic = cfqd->active_cic; | |
3515 | ||
3516 | /* If the queue already has requests, don't wait */ | |
3517 | if (!RB_EMPTY_ROOT(&cfqq->sort_list)) | |
3518 | return false; | |
3519 | ||
3520 | /* If there are other queues in the group, don't wait */ | |
3521 | if (cfqq->cfqg->nr_cfqq > 1) | |
3522 | return false; | |
3523 | ||
3524 | if (cfq_slice_used(cfqq)) | |
3525 | return true; | |
3526 | ||
3527 | /* if slice left is less than think time, wait busy */ | |
3528 | if (cic && sample_valid(cic->ttime.ttime_samples) | |
3529 | && (cfqq->slice_end - jiffies < cic->ttime.ttime_mean)) | |
3530 | return true; | |
3531 | ||
3532 | /* | |
3533 | * If think times is less than a jiffy than ttime_mean=0 and above | |
3534 | * will not be true. It might happen that slice has not expired yet | |
3535 | * but will expire soon (4-5 ns) during select_queue(). To cover the | |
3536 | * case where think time is less than a jiffy, mark the queue wait | |
3537 | * busy if only 1 jiffy is left in the slice. | |
3538 | */ | |
3539 | if (cfqq->slice_end - jiffies == 1) | |
3540 | return true; | |
3541 | ||
3542 | return false; | |
3543 | } | |
3544 | ||
3545 | static void cfq_completed_request(struct request_queue *q, struct request *rq) | |
3546 | { | |
3547 | struct cfq_queue *cfqq = RQ_CFQQ(rq); | |
3548 | struct cfq_data *cfqd = cfqq->cfqd; | |
3549 | const int sync = rq_is_sync(rq); | |
3550 | unsigned long now; | |
3551 | ||
3552 | now = jiffies; | |
3553 | cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d", | |
3554 | !!(rq->cmd_flags & REQ_NOIDLE)); | |
3555 | ||
3556 | cfq_update_hw_tag(cfqd); | |
3557 | ||
3558 | WARN_ON(!cfqd->rq_in_driver); | |
3559 | WARN_ON(!cfqq->dispatched); | |
3560 | cfqd->rq_in_driver--; | |
3561 | cfqq->dispatched--; | |
3562 | (RQ_CFQG(rq))->dispatched--; | |
3563 | cfq_blkiocg_update_completion_stats(&cfqq->cfqg->blkg, | |
3564 | rq_start_time_ns(rq), rq_io_start_time_ns(rq), | |
3565 | rq_data_dir(rq), rq_is_sync(rq)); | |
3566 | ||
3567 | cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--; | |
3568 | ||
3569 | if (sync) { | |
3570 | struct cfq_rb_root *service_tree; | |
3571 | ||
3572 | RQ_CIC(rq)->ttime.last_end_request = now; | |
3573 | ||
3574 | if (cfq_cfqq_on_rr(cfqq)) | |
3575 | service_tree = cfqq->service_tree; | |
3576 | else | |
3577 | service_tree = service_tree_for(cfqq->cfqg, | |
3578 | cfqq_prio(cfqq), cfqq_type(cfqq)); | |
3579 | service_tree->ttime.last_end_request = now; | |
3580 | if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now)) | |
3581 | cfqd->last_delayed_sync = now; | |
3582 | } | |
3583 | ||
3584 | /* | |
3585 | * If this is the active queue, check if it needs to be expired, | |
3586 | * or if we want to idle in case it has no pending requests. | |
3587 | */ | |
3588 | if (cfqd->active_queue == cfqq) { | |
3589 | const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list); | |
3590 | ||
3591 | if (cfq_cfqq_slice_new(cfqq)) { | |
3592 | cfq_set_prio_slice(cfqd, cfqq); | |
3593 | cfq_clear_cfqq_slice_new(cfqq); | |
3594 | } | |
3595 | ||
3596 | /* | |
3597 | * Should we wait for next request to come in before we expire | |
3598 | * the queue. | |
3599 | */ | |
3600 | if (cfq_should_wait_busy(cfqd, cfqq)) { | |
3601 | unsigned long extend_sl = cfqd->cfq_slice_idle; | |
3602 | if (!cfqd->cfq_slice_idle) | |
3603 | extend_sl = cfqd->cfq_group_idle; | |
3604 | cfqq->slice_end = jiffies + extend_sl; | |
3605 | cfq_mark_cfqq_wait_busy(cfqq); | |
3606 | cfq_log_cfqq(cfqd, cfqq, "will busy wait"); | |
3607 | } | |
3608 | ||
3609 | /* | |
3610 | * Idling is not enabled on: | |
3611 | * - expired queues | |
3612 | * - idle-priority queues | |
3613 | * - async queues | |
3614 | * - queues with still some requests queued | |
3615 | * - when there is a close cooperator | |
3616 | */ | |
3617 | if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq)) | |
3618 | cfq_slice_expired(cfqd, 1); | |
3619 | else if (sync && cfqq_empty && | |
3620 | !cfq_close_cooperator(cfqd, cfqq)) { | |
3621 | cfq_arm_slice_timer(cfqd); | |
3622 | } | |
3623 | } | |
3624 | ||
3625 | if (!cfqd->rq_in_driver) | |
3626 | cfq_schedule_dispatch(cfqd); | |
3627 | } | |
3628 | ||
3629 | static inline int __cfq_may_queue(struct cfq_queue *cfqq) | |
3630 | { | |
3631 | if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) { | |
3632 | cfq_mark_cfqq_must_alloc_slice(cfqq); | |
3633 | return ELV_MQUEUE_MUST; | |
3634 | } | |
3635 | ||
3636 | return ELV_MQUEUE_MAY; | |
3637 | } | |
3638 | ||
3639 | static int cfq_may_queue(struct request_queue *q, int rw) | |
3640 | { | |
3641 | struct cfq_data *cfqd = q->elevator->elevator_data; | |
3642 | struct task_struct *tsk = current; | |
3643 | struct cfq_io_context *cic; | |
3644 | struct cfq_queue *cfqq; | |
3645 | ||
3646 | /* | |
3647 | * don't force setup of a queue from here, as a call to may_queue | |
3648 | * does not necessarily imply that a request actually will be queued. | |
3649 | * so just lookup a possibly existing queue, or return 'may queue' | |
3650 | * if that fails | |
3651 | */ | |
3652 | cic = cfq_cic_lookup(cfqd, tsk->io_context); | |
3653 | if (!cic) | |
3654 | return ELV_MQUEUE_MAY; | |
3655 | ||
3656 | cfqq = cic_to_cfqq(cic, rw_is_sync(rw)); | |
3657 | if (cfqq) { | |
3658 | cfq_init_prio_data(cfqq, cic->ioc); | |
3659 | ||
3660 | return __cfq_may_queue(cfqq); | |
3661 | } | |
3662 | ||
3663 | return ELV_MQUEUE_MAY; | |
3664 | } | |
3665 | ||
3666 | /* | |
3667 | * queue lock held here | |
3668 | */ | |
3669 | static void cfq_put_request(struct request *rq) | |
3670 | { | |
3671 | struct cfq_queue *cfqq = RQ_CFQQ(rq); | |
3672 | ||
3673 | if (cfqq) { | |
3674 | const int rw = rq_data_dir(rq); | |
3675 | ||
3676 | BUG_ON(!cfqq->allocated[rw]); | |
3677 | cfqq->allocated[rw]--; | |
3678 | ||
3679 | put_io_context(RQ_CIC(rq)->ioc); | |
3680 | ||
3681 | rq->elevator_private[0] = NULL; | |
3682 | rq->elevator_private[1] = NULL; | |
3683 | ||
3684 | /* Put down rq reference on cfqg */ | |
3685 | cfq_put_cfqg(RQ_CFQG(rq)); | |
3686 | rq->elevator_private[2] = NULL; | |
3687 | ||
3688 | cfq_put_queue(cfqq); | |
3689 | } | |
3690 | } | |
3691 | ||
3692 | static struct cfq_queue * | |
3693 | cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic, | |
3694 | struct cfq_queue *cfqq) | |
3695 | { | |
3696 | cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq); | |
3697 | cic_set_cfqq(cic, cfqq->new_cfqq, 1); | |
3698 | cfq_mark_cfqq_coop(cfqq->new_cfqq); | |
3699 | cfq_put_queue(cfqq); | |
3700 | return cic_to_cfqq(cic, 1); | |
3701 | } | |
3702 | ||
3703 | /* | |
3704 | * Returns NULL if a new cfqq should be allocated, or the old cfqq if this | |
3705 | * was the last process referring to said cfqq. | |
3706 | */ | |
3707 | static struct cfq_queue * | |
3708 | split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq) | |
3709 | { | |
3710 | if (cfqq_process_refs(cfqq) == 1) { | |
3711 | cfqq->pid = current->pid; | |
3712 | cfq_clear_cfqq_coop(cfqq); | |
3713 | cfq_clear_cfqq_split_coop(cfqq); | |
3714 | return cfqq; | |
3715 | } | |
3716 | ||
3717 | cic_set_cfqq(cic, NULL, 1); | |
3718 | ||
3719 | cfq_put_cooperator(cfqq); | |
3720 | ||
3721 | cfq_put_queue(cfqq); | |
3722 | return NULL; | |
3723 | } | |
3724 | /* | |
3725 | * Allocate cfq data structures associated with this request. | |
3726 | */ | |
3727 | static int | |
3728 | cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) | |
3729 | { | |
3730 | struct cfq_data *cfqd = q->elevator->elevator_data; | |
3731 | struct cfq_io_context *cic; | |
3732 | const int rw = rq_data_dir(rq); | |
3733 | const bool is_sync = rq_is_sync(rq); | |
3734 | struct cfq_queue *cfqq; | |
3735 | unsigned long flags; | |
3736 | ||
3737 | might_sleep_if(gfp_mask & __GFP_WAIT); | |
3738 | ||
3739 | cic = cfq_get_io_context(cfqd, gfp_mask); | |
3740 | ||
3741 | spin_lock_irqsave(q->queue_lock, flags); | |
3742 | ||
3743 | if (!cic) | |
3744 | goto queue_fail; | |
3745 | ||
3746 | new_queue: | |
3747 | cfqq = cic_to_cfqq(cic, is_sync); | |
3748 | if (!cfqq || cfqq == &cfqd->oom_cfqq) { | |
3749 | cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask); | |
3750 | cic_set_cfqq(cic, cfqq, is_sync); | |
3751 | } else { | |
3752 | /* | |
3753 | * If the queue was seeky for too long, break it apart. | |
3754 | */ | |
3755 | if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) { | |
3756 | cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq"); | |
3757 | cfqq = split_cfqq(cic, cfqq); | |
3758 | if (!cfqq) | |
3759 | goto new_queue; | |
3760 | } | |
3761 | ||
3762 | /* | |
3763 | * Check to see if this queue is scheduled to merge with | |
3764 | * another, closely cooperating queue. The merging of | |
3765 | * queues happens here as it must be done in process context. | |
3766 | * The reference on new_cfqq was taken in merge_cfqqs. | |
3767 | */ | |
3768 | if (cfqq->new_cfqq) | |
3769 | cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq); | |
3770 | } | |
3771 | ||
3772 | cfqq->allocated[rw]++; | |
3773 | ||
3774 | cfqq->ref++; | |
3775 | rq->elevator_private[0] = cic; | |
3776 | rq->elevator_private[1] = cfqq; | |
3777 | rq->elevator_private[2] = cfq_ref_get_cfqg(cfqq->cfqg); | |
3778 | spin_unlock_irqrestore(q->queue_lock, flags); | |
3779 | return 0; | |
3780 | ||
3781 | queue_fail: | |
3782 | cfq_schedule_dispatch(cfqd); | |
3783 | spin_unlock_irqrestore(q->queue_lock, flags); | |
3784 | cfq_log(cfqd, "set_request fail"); | |
3785 | return 1; | |
3786 | } | |
3787 | ||
3788 | static void cfq_kick_queue(struct work_struct *work) | |
3789 | { | |
3790 | struct cfq_data *cfqd = | |
3791 | container_of(work, struct cfq_data, unplug_work); | |
3792 | struct request_queue *q = cfqd->queue; | |
3793 | ||
3794 | spin_lock_irq(q->queue_lock); | |
3795 | __blk_run_queue(cfqd->queue); | |
3796 | spin_unlock_irq(q->queue_lock); | |
3797 | } | |
3798 | ||
3799 | /* | |
3800 | * Timer running if the active_queue is currently idling inside its time slice | |
3801 | */ | |
3802 | static void cfq_idle_slice_timer(unsigned long data) | |
3803 | { | |
3804 | struct cfq_data *cfqd = (struct cfq_data *) data; | |
3805 | struct cfq_queue *cfqq; | |
3806 | unsigned long flags; | |
3807 | int timed_out = 1; | |
3808 | ||
3809 | cfq_log(cfqd, "idle timer fired"); | |
3810 | ||
3811 | spin_lock_irqsave(cfqd->queue->queue_lock, flags); | |
3812 | ||
3813 | cfqq = cfqd->active_queue; | |
3814 | if (cfqq) { | |
3815 | timed_out = 0; | |
3816 | ||
3817 | /* | |
3818 | * We saw a request before the queue expired, let it through | |
3819 | */ | |
3820 | if (cfq_cfqq_must_dispatch(cfqq)) | |
3821 | goto out_kick; | |
3822 | ||
3823 | /* | |
3824 | * expired | |
3825 | */ | |
3826 | if (cfq_slice_used(cfqq)) | |
3827 | goto expire; | |
3828 | ||
3829 | /* | |
3830 | * only expire and reinvoke request handler, if there are | |
3831 | * other queues with pending requests | |
3832 | */ | |
3833 | if (!cfqd->busy_queues) | |
3834 | goto out_cont; | |
3835 | ||
3836 | /* | |
3837 | * not expired and it has a request pending, let it dispatch | |
3838 | */ | |
3839 | if (!RB_EMPTY_ROOT(&cfqq->sort_list)) | |
3840 | goto out_kick; | |
3841 | ||
3842 | /* | |
3843 | * Queue depth flag is reset only when the idle didn't succeed | |
3844 | */ | |
3845 | cfq_clear_cfqq_deep(cfqq); | |
3846 | } | |
3847 | expire: | |
3848 | cfq_slice_expired(cfqd, timed_out); | |
3849 | out_kick: | |
3850 | cfq_schedule_dispatch(cfqd); | |
3851 | out_cont: | |
3852 | spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); | |
3853 | } | |
3854 | ||
3855 | static void cfq_shutdown_timer_wq(struct cfq_data *cfqd) | |
3856 | { | |
3857 | del_timer_sync(&cfqd->idle_slice_timer); | |
3858 | cancel_work_sync(&cfqd->unplug_work); | |
3859 | } | |
3860 | ||
3861 | static void cfq_put_async_queues(struct cfq_data *cfqd) | |
3862 | { | |
3863 | int i; | |
3864 | ||
3865 | for (i = 0; i < IOPRIO_BE_NR; i++) { | |
3866 | if (cfqd->async_cfqq[0][i]) | |
3867 | cfq_put_queue(cfqd->async_cfqq[0][i]); | |
3868 | if (cfqd->async_cfqq[1][i]) | |
3869 | cfq_put_queue(cfqd->async_cfqq[1][i]); | |
3870 | } | |
3871 | ||
3872 | if (cfqd->async_idle_cfqq) | |
3873 | cfq_put_queue(cfqd->async_idle_cfqq); | |
3874 | } | |
3875 | ||
3876 | static void cfq_exit_queue(struct elevator_queue *e) | |
3877 | { | |
3878 | struct cfq_data *cfqd = e->elevator_data; | |
3879 | struct request_queue *q = cfqd->queue; | |
3880 | bool wait = false; | |
3881 | ||
3882 | cfq_shutdown_timer_wq(cfqd); | |
3883 | ||
3884 | spin_lock_irq(q->queue_lock); | |
3885 | ||
3886 | if (cfqd->active_queue) | |
3887 | __cfq_slice_expired(cfqd, cfqd->active_queue, 0); | |
3888 | ||
3889 | while (!list_empty(&cfqd->cic_list)) { | |
3890 | struct cfq_io_context *cic = list_entry(cfqd->cic_list.next, | |
3891 | struct cfq_io_context, | |
3892 | queue_list); | |
3893 | ||
3894 | __cfq_exit_single_io_context(cfqd, cic); | |
3895 | } | |
3896 | ||
3897 | cfq_put_async_queues(cfqd); | |
3898 | cfq_release_cfq_groups(cfqd); | |
3899 | ||
3900 | /* | |
3901 | * If there are groups which we could not unlink from blkcg list, | |
3902 | * wait for a rcu period for them to be freed. | |
3903 | */ | |
3904 | if (cfqd->nr_blkcg_linked_grps) | |
3905 | wait = true; | |
3906 | ||
3907 | spin_unlock_irq(q->queue_lock); | |
3908 | ||
3909 | cfq_shutdown_timer_wq(cfqd); | |
3910 | ||
3911 | spin_lock(&cic_index_lock); | |
3912 | ida_remove(&cic_index_ida, cfqd->cic_index); | |
3913 | spin_unlock(&cic_index_lock); | |
3914 | ||
3915 | /* | |
3916 | * Wait for cfqg->blkg->key accessors to exit their grace periods. | |
3917 | * Do this wait only if there are other unlinked groups out | |
3918 | * there. This can happen if cgroup deletion path claimed the | |
3919 | * responsibility of cleaning up a group before queue cleanup code | |
3920 | * get to the group. | |
3921 | * | |
3922 | * Do not call synchronize_rcu() unconditionally as there are drivers | |
3923 | * which create/delete request queue hundreds of times during scan/boot | |
3924 | * and synchronize_rcu() can take significant time and slow down boot. | |
3925 | */ | |
3926 | if (wait) | |
3927 | synchronize_rcu(); | |
3928 | ||
3929 | #ifdef CONFIG_CFQ_GROUP_IOSCHED | |
3930 | /* Free up per cpu stats for root group */ | |
3931 | free_percpu(cfqd->root_group.blkg.stats_cpu); | |
3932 | #endif | |
3933 | kfree(cfqd); | |
3934 | } | |
3935 | ||
3936 | static int cfq_alloc_cic_index(void) | |
3937 | { | |
3938 | int index, error; | |
3939 | ||
3940 | do { | |
3941 | if (!ida_pre_get(&cic_index_ida, GFP_KERNEL)) | |
3942 | return -ENOMEM; | |
3943 | ||
3944 | spin_lock(&cic_index_lock); | |
3945 | error = ida_get_new(&cic_index_ida, &index); | |
3946 | spin_unlock(&cic_index_lock); | |
3947 | if (error && error != -EAGAIN) | |
3948 | return error; | |
3949 | } while (error); | |
3950 | ||
3951 | return index; | |
3952 | } | |
3953 | ||
3954 | static void *cfq_init_queue(struct request_queue *q) | |
3955 | { | |
3956 | struct cfq_data *cfqd; | |
3957 | int i, j; | |
3958 | struct cfq_group *cfqg; | |
3959 | struct cfq_rb_root *st; | |
3960 | ||
3961 | i = cfq_alloc_cic_index(); | |
3962 | if (i < 0) | |
3963 | return NULL; | |
3964 | ||
3965 | cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node); | |
3966 | if (!cfqd) { | |
3967 | spin_lock(&cic_index_lock); | |
3968 | ida_remove(&cic_index_ida, i); | |
3969 | spin_unlock(&cic_index_lock); | |
3970 | return NULL; | |
3971 | } | |
3972 | ||
3973 | /* | |
3974 | * Don't need take queue_lock in the routine, since we are | |
3975 | * initializing the ioscheduler, and nobody is using cfqd | |
3976 | */ | |
3977 | cfqd->cic_index = i; | |
3978 | ||
3979 | /* Init root service tree */ | |
3980 | cfqd->grp_service_tree = CFQ_RB_ROOT; | |
3981 | ||
3982 | /* Init root group */ | |
3983 | cfqg = &cfqd->root_group; | |
3984 | for_each_cfqg_st(cfqg, i, j, st) | |
3985 | *st = CFQ_RB_ROOT; | |
3986 | RB_CLEAR_NODE(&cfqg->rb_node); | |
3987 | ||
3988 | /* Give preference to root group over other groups */ | |
3989 | cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT; | |
3990 | ||
3991 | #ifdef CONFIG_CFQ_GROUP_IOSCHED | |
3992 | /* | |
3993 | * Set root group reference to 2. One reference will be dropped when | |
3994 | * all groups on cfqd->cfqg_list are being deleted during queue exit. | |
3995 | * Other reference will remain there as we don't want to delete this | |
3996 | * group as it is statically allocated and gets destroyed when | |
3997 | * throtl_data goes away. | |
3998 | */ | |
3999 | cfqg->ref = 2; | |
4000 | ||
4001 | if (blkio_alloc_blkg_stats(&cfqg->blkg)) { | |
4002 | kfree(cfqg); | |
4003 | kfree(cfqd); | |
4004 | return NULL; | |
4005 | } | |
4006 | ||
4007 | rcu_read_lock(); | |
4008 | ||
4009 | cfq_blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, | |
4010 | (void *)cfqd, 0); | |
4011 | rcu_read_unlock(); | |
4012 | cfqd->nr_blkcg_linked_grps++; | |
4013 | ||
4014 | /* Add group on cfqd->cfqg_list */ | |
4015 | hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list); | |
4016 | #endif | |
4017 | /* | |
4018 | * Not strictly needed (since RB_ROOT just clears the node and we | |
4019 | * zeroed cfqd on alloc), but better be safe in case someone decides | |
4020 | * to add magic to the rb code | |
4021 | */ | |
4022 | for (i = 0; i < CFQ_PRIO_LISTS; i++) | |
4023 | cfqd->prio_trees[i] = RB_ROOT; | |
4024 | ||
4025 | /* | |
4026 | * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues. | |
4027 | * Grab a permanent reference to it, so that the normal code flow | |
4028 | * will not attempt to free it. | |
4029 | */ | |
4030 | cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0); | |
4031 | cfqd->oom_cfqq.ref++; | |
4032 | cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group); | |
4033 | ||
4034 | INIT_LIST_HEAD(&cfqd->cic_list); | |
4035 | ||
4036 | cfqd->queue = q; | |
4037 | ||
4038 | init_timer(&cfqd->idle_slice_timer); | |
4039 | cfqd->idle_slice_timer.function = cfq_idle_slice_timer; | |
4040 | cfqd->idle_slice_timer.data = (unsigned long) cfqd; | |
4041 | ||
4042 | INIT_WORK(&cfqd->unplug_work, cfq_kick_queue); | |
4043 | ||
4044 | cfqd->cfq_quantum = cfq_quantum; | |
4045 | cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0]; | |
4046 | cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1]; | |
4047 | cfqd->cfq_back_max = cfq_back_max; | |
4048 | cfqd->cfq_back_penalty = cfq_back_penalty; | |
4049 | cfqd->cfq_slice[0] = cfq_slice_async; | |
4050 | cfqd->cfq_slice[1] = cfq_slice_sync; | |
4051 | cfqd->cfq_slice_async_rq = cfq_slice_async_rq; | |
4052 | cfqd->cfq_slice_idle = cfq_slice_idle; | |
4053 | cfqd->cfq_group_idle = cfq_group_idle; | |
4054 | cfqd->cfq_latency = 1; | |
4055 | cfqd->hw_tag = -1; | |
4056 | /* | |
4057 | * we optimistically start assuming sync ops weren't delayed in last | |
4058 | * second, in order to have larger depth for async operations. | |
4059 | */ | |
4060 | cfqd->last_delayed_sync = jiffies - HZ; | |
4061 | return cfqd; | |
4062 | } | |
4063 | ||
4064 | static void cfq_slab_kill(void) | |
4065 | { | |
4066 | /* | |
4067 | * Caller already ensured that pending RCU callbacks are completed, | |
4068 | * so we should have no busy allocations at this point. | |
4069 | */ | |
4070 | if (cfq_pool) | |
4071 | kmem_cache_destroy(cfq_pool); | |
4072 | if (cfq_ioc_pool) | |
4073 | kmem_cache_destroy(cfq_ioc_pool); | |
4074 | } | |
4075 | ||
4076 | static int __init cfq_slab_setup(void) | |
4077 | { | |
4078 | cfq_pool = KMEM_CACHE(cfq_queue, 0); | |
4079 | if (!cfq_pool) | |
4080 | goto fail; | |
4081 | ||
4082 | cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0); | |
4083 | if (!cfq_ioc_pool) | |
4084 | goto fail; | |
4085 | ||
4086 | return 0; | |
4087 | fail: | |
4088 | cfq_slab_kill(); | |
4089 | return -ENOMEM; | |
4090 | } | |
4091 | ||
4092 | /* | |
4093 | * sysfs parts below --> | |
4094 | */ | |
4095 | static ssize_t | |
4096 | cfq_var_show(unsigned int var, char *page) | |
4097 | { | |
4098 | return sprintf(page, "%d\n", var); | |
4099 | } | |
4100 | ||
4101 | static ssize_t | |
4102 | cfq_var_store(unsigned int *var, const char *page, size_t count) | |
4103 | { | |
4104 | char *p = (char *) page; | |
4105 | ||
4106 | *var = simple_strtoul(p, &p, 10); | |
4107 | return count; | |
4108 | } | |
4109 | ||
4110 | #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ | |
4111 | static ssize_t __FUNC(struct elevator_queue *e, char *page) \ | |
4112 | { \ | |
4113 | struct cfq_data *cfqd = e->elevator_data; \ | |
4114 | unsigned int __data = __VAR; \ | |
4115 | if (__CONV) \ | |
4116 | __data = jiffies_to_msecs(__data); \ | |
4117 | return cfq_var_show(__data, (page)); \ | |
4118 | } | |
4119 | SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0); | |
4120 | SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1); | |
4121 | SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1); | |
4122 | SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0); | |
4123 | SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0); | |
4124 | SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1); | |
4125 | SHOW_FUNCTION(cfq_group_idle_show, cfqd->cfq_group_idle, 1); | |
4126 | SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1); | |
4127 | SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1); | |
4128 | SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0); | |
4129 | SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0); | |
4130 | #undef SHOW_FUNCTION | |
4131 | ||
4132 | #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ | |
4133 | static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ | |
4134 | { \ | |
4135 | struct cfq_data *cfqd = e->elevator_data; \ | |
4136 | unsigned int __data; \ | |
4137 | int ret = cfq_var_store(&__data, (page), count); \ | |
4138 | if (__data < (MIN)) \ | |
4139 | __data = (MIN); \ | |
4140 | else if (__data > (MAX)) \ | |
4141 | __data = (MAX); \ | |
4142 | if (__CONV) \ | |
4143 | *(__PTR) = msecs_to_jiffies(__data); \ | |
4144 | else \ | |
4145 | *(__PTR) = __data; \ | |
4146 | return ret; \ | |
4147 | } | |
4148 | STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0); | |
4149 | STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, | |
4150 | UINT_MAX, 1); | |
4151 | STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, | |
4152 | UINT_MAX, 1); | |
4153 | STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0); | |
4154 | STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, | |
4155 | UINT_MAX, 0); | |
4156 | STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1); | |
4157 | STORE_FUNCTION(cfq_group_idle_store, &cfqd->cfq_group_idle, 0, UINT_MAX, 1); | |
4158 | STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1); | |
4159 | STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1); | |
4160 | STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, | |
4161 | UINT_MAX, 0); | |
4162 | STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0); | |
4163 | #undef STORE_FUNCTION | |
4164 | ||
4165 | #define CFQ_ATTR(name) \ | |
4166 | __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store) | |
4167 | ||
4168 | static struct elv_fs_entry cfq_attrs[] = { | |
4169 | CFQ_ATTR(quantum), | |
4170 | CFQ_ATTR(fifo_expire_sync), | |
4171 | CFQ_ATTR(fifo_expire_async), | |
4172 | CFQ_ATTR(back_seek_max), | |
4173 | CFQ_ATTR(back_seek_penalty), | |
4174 | CFQ_ATTR(slice_sync), | |
4175 | CFQ_ATTR(slice_async), | |
4176 | CFQ_ATTR(slice_async_rq), | |
4177 | CFQ_ATTR(slice_idle), | |
4178 | CFQ_ATTR(group_idle), | |
4179 | CFQ_ATTR(low_latency), | |
4180 | __ATTR_NULL | |
4181 | }; | |
4182 | ||
4183 | static struct elevator_type iosched_cfq = { | |
4184 | .ops = { | |
4185 | .elevator_merge_fn = cfq_merge, | |
4186 | .elevator_merged_fn = cfq_merged_request, | |
4187 | .elevator_merge_req_fn = cfq_merged_requests, | |
4188 | .elevator_allow_merge_fn = cfq_allow_merge, | |
4189 | .elevator_bio_merged_fn = cfq_bio_merged, | |
4190 | .elevator_dispatch_fn = cfq_dispatch_requests, | |
4191 | .elevator_add_req_fn = cfq_insert_request, | |
4192 | .elevator_activate_req_fn = cfq_activate_request, | |
4193 | .elevator_deactivate_req_fn = cfq_deactivate_request, | |
4194 | .elevator_completed_req_fn = cfq_completed_request, | |
4195 | .elevator_former_req_fn = elv_rb_former_request, | |
4196 | .elevator_latter_req_fn = elv_rb_latter_request, | |
4197 | .elevator_set_req_fn = cfq_set_request, | |
4198 | .elevator_put_req_fn = cfq_put_request, | |
4199 | .elevator_may_queue_fn = cfq_may_queue, | |
4200 | .elevator_init_fn = cfq_init_queue, | |
4201 | .elevator_exit_fn = cfq_exit_queue, | |
4202 | .trim = cfq_free_io_context, | |
4203 | }, | |
4204 | .elevator_attrs = cfq_attrs, | |
4205 | .elevator_name = "cfq", | |
4206 | .elevator_owner = THIS_MODULE, | |
4207 | }; | |
4208 | ||
4209 | #ifdef CONFIG_CFQ_GROUP_IOSCHED | |
4210 | static struct blkio_policy_type blkio_policy_cfq = { | |
4211 | .ops = { | |
4212 | .blkio_unlink_group_fn = cfq_unlink_blkio_group, | |
4213 | .blkio_update_group_weight_fn = cfq_update_blkio_group_weight, | |
4214 | }, | |
4215 | .plid = BLKIO_POLICY_PROP, | |
4216 | }; | |
4217 | #else | |
4218 | static struct blkio_policy_type blkio_policy_cfq; | |
4219 | #endif | |
4220 | ||
4221 | static int __init cfq_init(void) | |
4222 | { | |
4223 | /* | |
4224 | * could be 0 on HZ < 1000 setups | |
4225 | */ | |
4226 | if (!cfq_slice_async) | |
4227 | cfq_slice_async = 1; | |
4228 | if (!cfq_slice_idle) | |
4229 | cfq_slice_idle = 1; | |
4230 | ||
4231 | #ifdef CONFIG_CFQ_GROUP_IOSCHED | |
4232 | if (!cfq_group_idle) | |
4233 | cfq_group_idle = 1; | |
4234 | #else | |
4235 | cfq_group_idle = 0; | |
4236 | #endif | |
4237 | if (cfq_slab_setup()) | |
4238 | return -ENOMEM; | |
4239 | ||
4240 | elv_register(&iosched_cfq); | |
4241 | blkio_policy_register(&blkio_policy_cfq); | |
4242 | ||
4243 | return 0; | |
4244 | } | |
4245 | ||
4246 | static void __exit cfq_exit(void) | |
4247 | { | |
4248 | DECLARE_COMPLETION_ONSTACK(all_gone); | |
4249 | blkio_policy_unregister(&blkio_policy_cfq); | |
4250 | elv_unregister(&iosched_cfq); | |
4251 | ioc_gone = &all_gone; | |
4252 | /* ioc_gone's update must be visible before reading ioc_count */ | |
4253 | smp_wmb(); | |
4254 | ||
4255 | /* | |
4256 | * this also protects us from entering cfq_slab_kill() with | |
4257 | * pending RCU callbacks | |
4258 | */ | |
4259 | if (elv_ioc_count_read(cfq_ioc_count)) | |
4260 | wait_for_completion(&all_gone); | |
4261 | ida_destroy(&cic_index_ida); | |
4262 | cfq_slab_kill(); | |
4263 | } | |
4264 | ||
4265 | module_init(cfq_init); | |
4266 | module_exit(cfq_exit); | |
4267 | ||
4268 | MODULE_AUTHOR("Jens Axboe"); | |
4269 | MODULE_LICENSE("GPL"); | |
4270 | MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler"); |