]>
Commit | Line | Data |
---|---|---|
aee69d78 PV |
1 | /* |
2 | * Budget Fair Queueing (BFQ) I/O scheduler. | |
3 | * | |
4 | * Based on ideas and code from CFQ: | |
5 | * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk> | |
6 | * | |
7 | * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it> | |
8 | * Paolo Valente <paolo.valente@unimore.it> | |
9 | * | |
10 | * Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it> | |
11 | * Arianna Avanzini <avanzini@google.com> | |
12 | * | |
13 | * Copyright (C) 2017 Paolo Valente <paolo.valente@linaro.org> | |
14 | * | |
15 | * This program is free software; you can redistribute it and/or | |
16 | * modify it under the terms of the GNU General Public License as | |
17 | * published by the Free Software Foundation; either version 2 of the | |
18 | * License, or (at your option) any later version. | |
19 | * | |
20 | * This program is distributed in the hope that it will be useful, | |
21 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
22 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
23 | * General Public License for more details. | |
24 | * | |
25 | * BFQ is a proportional-share I/O scheduler, with some extra | |
26 | * low-latency capabilities. BFQ also supports full hierarchical | |
27 | * scheduling through cgroups. Next paragraphs provide an introduction | |
28 | * on BFQ inner workings. Details on BFQ benefits, usage and | |
29 | * limitations can be found in Documentation/block/bfq-iosched.txt. | |
30 | * | |
31 | * BFQ is a proportional-share storage-I/O scheduling algorithm based | |
32 | * on the slice-by-slice service scheme of CFQ. But BFQ assigns | |
33 | * budgets, measured in number of sectors, to processes instead of | |
34 | * time slices. The device is not granted to the in-service process | |
35 | * for a given time slice, but until it has exhausted its assigned | |
36 | * budget. This change from the time to the service domain enables BFQ | |
37 | * to distribute the device throughput among processes as desired, | |
38 | * without any distortion due to throughput fluctuations, or to device | |
39 | * internal queueing. BFQ uses an ad hoc internal scheduler, called | |
40 | * B-WF2Q+, to schedule processes according to their budgets. More | |
41 | * precisely, BFQ schedules queues associated with processes. Each | |
42 | * process/queue is assigned a user-configurable weight, and B-WF2Q+ | |
43 | * guarantees that each queue receives a fraction of the throughput | |
44 | * proportional to its weight. Thanks to the accurate policy of | |
45 | * B-WF2Q+, BFQ can afford to assign high budgets to I/O-bound | |
46 | * processes issuing sequential requests (to boost the throughput), | |
47 | * and yet guarantee a low latency to interactive and soft real-time | |
48 | * applications. | |
49 | * | |
50 | * In particular, to provide these low-latency guarantees, BFQ | |
51 | * explicitly privileges the I/O of two classes of time-sensitive | |
52 | * applications: interactive and soft real-time. This feature enables | |
53 | * BFQ to provide applications in these classes with a very low | |
54 | * latency. Finally, BFQ also features additional heuristics for | |
55 | * preserving both a low latency and a high throughput on NCQ-capable, | |
56 | * rotational or flash-based devices, and to get the job done quickly | |
57 | * for applications consisting in many I/O-bound processes. | |
58 | * | |
59 | * BFQ is described in [1], where also a reference to the initial, more | |
60 | * theoretical paper on BFQ can be found. The interested reader can find | |
61 | * in the latter paper full details on the main algorithm, as well as | |
62 | * formulas of the guarantees and formal proofs of all the properties. | |
63 | * With respect to the version of BFQ presented in these papers, this | |
64 | * implementation adds a few more heuristics, such as the one that | |
65 | * guarantees a low latency to soft real-time applications, and a | |
66 | * hierarchical extension based on H-WF2Q+. | |
67 | * | |
68 | * B-WF2Q+ is based on WF2Q+, which is described in [2], together with | |
69 | * H-WF2Q+, while the augmented tree used here to implement B-WF2Q+ | |
70 | * with O(log N) complexity derives from the one introduced with EEVDF | |
71 | * in [3]. | |
72 | * | |
73 | * [1] P. Valente, A. Avanzini, "Evolution of the BFQ Storage I/O | |
74 | * Scheduler", Proceedings of the First Workshop on Mobile System | |
75 | * Technologies (MST-2015), May 2015. | |
76 | * http://algogroup.unimore.it/people/paolo/disk_sched/mst-2015.pdf | |
77 | * | |
78 | * [2] Jon C.R. Bennett and H. Zhang, "Hierarchical Packet Fair Queueing | |
79 | * Algorithms", IEEE/ACM Transactions on Networking, 5(5):675-689, | |
80 | * Oct 1997. | |
81 | * | |
82 | * http://www.cs.cmu.edu/~hzhang/papers/TON-97-Oct.ps.gz | |
83 | * | |
84 | * [3] I. Stoica and H. Abdel-Wahab, "Earliest Eligible Virtual Deadline | |
85 | * First: A Flexible and Accurate Mechanism for Proportional Share | |
86 | * Resource Allocation", technical report. | |
87 | * | |
88 | * http://www.cs.berkeley.edu/~istoica/papers/eevdf-tr-95.pdf | |
89 | */ | |
90 | #include <linux/module.h> | |
91 | #include <linux/slab.h> | |
92 | #include <linux/blkdev.h> | |
93 | #include <linux/elevator.h> | |
94 | #include <linux/ktime.h> | |
95 | #include <linux/rbtree.h> | |
96 | #include <linux/ioprio.h> | |
97 | #include <linux/sbitmap.h> | |
98 | #include <linux/delay.h> | |
99 | ||
100 | #include "blk.h" | |
101 | #include "blk-mq.h" | |
102 | #include "blk-mq-tag.h" | |
103 | #include "blk-mq-sched.h" | |
104 | #include <linux/blktrace_api.h> | |
105 | #include <linux/hrtimer.h> | |
106 | #include <linux/blk-cgroup.h> | |
107 | ||
108 | #define BFQ_IOPRIO_CLASSES 3 | |
109 | #define BFQ_CL_IDLE_TIMEOUT (HZ/5) | |
110 | ||
111 | #define BFQ_MIN_WEIGHT 1 | |
112 | #define BFQ_MAX_WEIGHT 1000 | |
113 | #define BFQ_WEIGHT_CONVERSION_COEFF 10 | |
114 | ||
115 | #define BFQ_DEFAULT_QUEUE_IOPRIO 4 | |
116 | ||
117 | #define BFQ_DEFAULT_GRP_WEIGHT 10 | |
118 | #define BFQ_DEFAULT_GRP_IOPRIO 0 | |
119 | #define BFQ_DEFAULT_GRP_CLASS IOPRIO_CLASS_BE | |
120 | ||
121 | struct bfq_entity; | |
122 | ||
123 | /** | |
124 | * struct bfq_service_tree - per ioprio_class service tree. | |
125 | * | |
126 | * Each service tree represents a B-WF2Q+ scheduler on its own. Each | |
127 | * ioprio_class has its own independent scheduler, and so its own | |
128 | * bfq_service_tree. All the fields are protected by the queue lock | |
129 | * of the containing bfqd. | |
130 | */ | |
131 | struct bfq_service_tree { | |
132 | /* tree for active entities (i.e., those backlogged) */ | |
133 | struct rb_root active; | |
134 | /* tree for idle entities (i.e., not backlogged, with V <= F_i)*/ | |
135 | struct rb_root idle; | |
136 | ||
137 | /* idle entity with minimum F_i */ | |
138 | struct bfq_entity *first_idle; | |
139 | /* idle entity with maximum F_i */ | |
140 | struct bfq_entity *last_idle; | |
141 | ||
142 | /* scheduler virtual time */ | |
143 | u64 vtime; | |
144 | /* scheduler weight sum; active and idle entities contribute to it */ | |
145 | unsigned long wsum; | |
146 | }; | |
147 | ||
148 | /** | |
149 | * struct bfq_sched_data - multi-class scheduler. | |
150 | * | |
151 | * bfq_sched_data is the basic scheduler queue. It supports three | |
152 | * ioprio_classes, and can be used either as a toplevel queue or as | |
153 | * an intermediate queue on a hierarchical setup. | |
154 | * @next_in_service points to the active entity of the sched_data | |
155 | * service trees that will be scheduled next. | |
156 | * | |
157 | * The supported ioprio_classes are the same as in CFQ, in descending | |
158 | * priority order, IOPRIO_CLASS_RT, IOPRIO_CLASS_BE, IOPRIO_CLASS_IDLE. | |
159 | * Requests from higher priority queues are served before all the | |
160 | * requests from lower priority queues; among requests of the same | |
161 | * queue requests are served according to B-WF2Q+. | |
162 | * All the fields are protected by the queue lock of the containing bfqd. | |
163 | */ | |
164 | struct bfq_sched_data { | |
165 | /* entity in service */ | |
166 | struct bfq_entity *in_service_entity; | |
167 | /* head-of-the-line entity in the scheduler */ | |
168 | struct bfq_entity *next_in_service; | |
169 | /* array of service trees, one per ioprio_class */ | |
170 | struct bfq_service_tree service_tree[BFQ_IOPRIO_CLASSES]; | |
171 | }; | |
172 | ||
173 | /** | |
174 | * struct bfq_entity - schedulable entity. | |
175 | * | |
176 | * A bfq_entity is used to represent a bfq_queue (leaf node in the upper | |
177 | * level scheduler). Each entity belongs to the sched_data of the parent | |
178 | * group hierarchy. Non-leaf entities have also their own sched_data, | |
179 | * stored in @my_sched_data. | |
180 | * | |
181 | * Each entity stores independently its priority values; this would | |
182 | * allow different weights on different devices, but this | |
183 | * functionality is not exported to userspace by now. Priorities and | |
184 | * weights are updated lazily, first storing the new values into the | |
185 | * new_* fields, then setting the @prio_changed flag. As soon as | |
186 | * there is a transition in the entity state that allows the priority | |
187 | * update to take place the effective and the requested priority | |
188 | * values are synchronized. | |
189 | * | |
190 | * The weight value is calculated from the ioprio to export the same | |
191 | * interface as CFQ. When dealing with ``well-behaved'' queues (i.e., | |
192 | * queues that do not spend too much time to consume their budget | |
193 | * and have true sequential behavior, and when there are no external | |
194 | * factors breaking anticipation) the relative weights at each level | |
195 | * of the hierarchy should be guaranteed. All the fields are | |
196 | * protected by the queue lock of the containing bfqd. | |
197 | */ | |
198 | struct bfq_entity { | |
199 | /* service_tree member */ | |
200 | struct rb_node rb_node; | |
201 | ||
202 | /* | |
203 | * flag, true if the entity is on a tree (either the active or | |
204 | * the idle one of its service_tree). | |
205 | */ | |
206 | int on_st; | |
207 | ||
208 | /* B-WF2Q+ start and finish timestamps [sectors/weight] */ | |
209 | u64 start, finish; | |
210 | ||
211 | /* tree the entity is enqueued into; %NULL if not on a tree */ | |
212 | struct rb_root *tree; | |
213 | ||
214 | /* | |
215 | * minimum start time of the (active) subtree rooted at this | |
216 | * entity; used for O(log N) lookups into active trees | |
217 | */ | |
218 | u64 min_start; | |
219 | ||
220 | /* amount of service received during the last service slot */ | |
221 | int service; | |
222 | ||
223 | /* budget, used also to calculate F_i: F_i = S_i + @budget / @weight */ | |
224 | int budget; | |
225 | ||
226 | /* weight of the queue */ | |
227 | int weight; | |
228 | /* next weight if a change is in progress */ | |
229 | int new_weight; | |
230 | ||
231 | /* original weight, used to implement weight boosting */ | |
232 | int orig_weight; | |
233 | ||
234 | /* parent entity, for hierarchical scheduling */ | |
235 | struct bfq_entity *parent; | |
236 | ||
237 | /* | |
238 | * For non-leaf nodes in the hierarchy, the associated | |
239 | * scheduler queue, %NULL on leaf nodes. | |
240 | */ | |
241 | struct bfq_sched_data *my_sched_data; | |
242 | /* the scheduler queue this entity belongs to */ | |
243 | struct bfq_sched_data *sched_data; | |
244 | ||
245 | /* flag, set to request a weight, ioprio or ioprio_class change */ | |
246 | int prio_changed; | |
247 | }; | |
248 | ||
249 | /** | |
250 | * struct bfq_ttime - per process thinktime stats. | |
251 | */ | |
252 | struct bfq_ttime { | |
253 | /* completion time of the last request */ | |
254 | u64 last_end_request; | |
255 | ||
256 | /* total process thinktime */ | |
257 | u64 ttime_total; | |
258 | /* number of thinktime samples */ | |
259 | unsigned long ttime_samples; | |
260 | /* average process thinktime */ | |
261 | u64 ttime_mean; | |
262 | }; | |
263 | ||
264 | /** | |
265 | * struct bfq_queue - leaf schedulable entity. | |
266 | * | |
267 | * A bfq_queue is a leaf request queue; it can be associated with an | |
268 | * io_context or more, if it is async. | |
269 | */ | |
270 | struct bfq_queue { | |
271 | /* reference counter */ | |
272 | int ref; | |
273 | /* parent bfq_data */ | |
274 | struct bfq_data *bfqd; | |
275 | ||
276 | /* current ioprio and ioprio class */ | |
277 | unsigned short ioprio, ioprio_class; | |
278 | /* next ioprio and ioprio class if a change is in progress */ | |
279 | unsigned short new_ioprio, new_ioprio_class; | |
280 | ||
281 | /* sorted list of pending requests */ | |
282 | struct rb_root sort_list; | |
283 | /* if fifo isn't expired, next request to serve */ | |
284 | struct request *next_rq; | |
285 | /* number of sync and async requests queued */ | |
286 | int queued[2]; | |
287 | /* number of requests currently allocated */ | |
288 | int allocated; | |
289 | /* number of pending metadata requests */ | |
290 | int meta_pending; | |
291 | /* fifo list of requests in sort_list */ | |
292 | struct list_head fifo; | |
293 | ||
294 | /* entity representing this queue in the scheduler */ | |
295 | struct bfq_entity entity; | |
296 | ||
297 | /* maximum budget allowed from the feedback mechanism */ | |
298 | int max_budget; | |
299 | /* budget expiration (in jiffies) */ | |
300 | unsigned long budget_timeout; | |
301 | ||
302 | /* number of requests on the dispatch list or inside driver */ | |
303 | int dispatched; | |
304 | ||
305 | /* status flags */ | |
306 | unsigned long flags; | |
307 | ||
308 | /* node for active/idle bfqq list inside parent bfqd */ | |
309 | struct list_head bfqq_list; | |
310 | ||
311 | /* associated @bfq_ttime struct */ | |
312 | struct bfq_ttime ttime; | |
313 | ||
314 | /* bit vector: a 1 for each seeky requests in history */ | |
315 | u32 seek_history; | |
316 | /* position of the last request enqueued */ | |
317 | sector_t last_request_pos; | |
318 | ||
319 | /* Number of consecutive pairs of request completion and | |
320 | * arrival, such that the queue becomes idle after the | |
321 | * completion, but the next request arrives within an idle | |
322 | * time slice; used only if the queue's IO_bound flag has been | |
323 | * cleared. | |
324 | */ | |
325 | unsigned int requests_within_timer; | |
326 | ||
327 | /* pid of the process owning the queue, used for logging purposes */ | |
328 | pid_t pid; | |
329 | }; | |
330 | ||
331 | /** | |
332 | * struct bfq_io_cq - per (request_queue, io_context) structure. | |
333 | */ | |
334 | struct bfq_io_cq { | |
335 | /* associated io_cq structure */ | |
336 | struct io_cq icq; /* must be the first member */ | |
337 | /* array of two process queues, the sync and the async */ | |
338 | struct bfq_queue *bfqq[2]; | |
339 | /* per (request_queue, blkcg) ioprio */ | |
340 | int ioprio; | |
341 | }; | |
342 | ||
343 | /** | |
344 | * struct bfq_data - per-device data structure. | |
345 | * | |
346 | * All the fields are protected by @lock. | |
347 | */ | |
348 | struct bfq_data { | |
349 | /* device request queue */ | |
350 | struct request_queue *queue; | |
351 | /* dispatch queue */ | |
352 | struct list_head dispatch; | |
353 | ||
354 | /* root @bfq_sched_data for the device */ | |
355 | struct bfq_sched_data sched_data; | |
356 | ||
357 | /* | |
358 | * Number of bfq_queues containing requests (including the | |
359 | * queue in service, even if it is idling). | |
360 | */ | |
361 | int busy_queues; | |
362 | /* number of queued requests */ | |
363 | int queued; | |
364 | /* number of requests dispatched and waiting for completion */ | |
365 | int rq_in_driver; | |
366 | ||
367 | /* | |
368 | * Maximum number of requests in driver in the last | |
369 | * @hw_tag_samples completed requests. | |
370 | */ | |
371 | int max_rq_in_driver; | |
372 | /* number of samples used to calculate hw_tag */ | |
373 | int hw_tag_samples; | |
374 | /* flag set to one if the driver is showing a queueing behavior */ | |
375 | int hw_tag; | |
376 | ||
377 | /* number of budgets assigned */ | |
378 | int budgets_assigned; | |
379 | ||
380 | /* | |
381 | * Timer set when idling (waiting) for the next request from | |
382 | * the queue in service. | |
383 | */ | |
384 | struct hrtimer idle_slice_timer; | |
385 | ||
386 | /* bfq_queue in service */ | |
387 | struct bfq_queue *in_service_queue; | |
388 | /* bfq_io_cq (bic) associated with the @in_service_queue */ | |
389 | struct bfq_io_cq *in_service_bic; | |
390 | ||
391 | /* on-disk position of the last served request */ | |
392 | sector_t last_position; | |
393 | ||
394 | /* beginning of the last budget */ | |
395 | ktime_t last_budget_start; | |
396 | /* beginning of the last idle slice */ | |
397 | ktime_t last_idling_start; | |
398 | /* number of samples used to calculate @peak_rate */ | |
399 | int peak_rate_samples; | |
400 | /* | |
401 | * Peak read/write rate, observed during the service of a | |
402 | * budget [BFQ_RATE_SHIFT * sectors/usec]. The value is | |
403 | * left-shifted by BFQ_RATE_SHIFT to increase precision in | |
404 | * fixed-point calculations. | |
405 | */ | |
406 | u64 peak_rate; | |
407 | /* maximum budget allotted to a bfq_queue before rescheduling */ | |
408 | int bfq_max_budget; | |
409 | ||
410 | /* list of all the bfq_queues active on the device */ | |
411 | struct list_head active_list; | |
412 | /* list of all the bfq_queues idle on the device */ | |
413 | struct list_head idle_list; | |
414 | ||
415 | /* | |
416 | * Timeout for async/sync requests; when it fires, requests | |
417 | * are served in fifo order. | |
418 | */ | |
419 | u64 bfq_fifo_expire[2]; | |
420 | /* weight of backward seeks wrt forward ones */ | |
421 | unsigned int bfq_back_penalty; | |
422 | /* maximum allowed backward seek */ | |
423 | unsigned int bfq_back_max; | |
424 | /* maximum idling time */ | |
425 | u32 bfq_slice_idle; | |
426 | /* last time CLASS_IDLE was served */ | |
427 | u64 bfq_class_idle_last_service; | |
428 | ||
429 | /* user-configured max budget value (0 for auto-tuning) */ | |
430 | int bfq_user_max_budget; | |
431 | /* | |
432 | * Timeout for bfq_queues to consume their budget; used to | |
433 | * prevent seeky queues from imposing long latencies to | |
434 | * sequential or quasi-sequential ones (this also implies that | |
435 | * seeky queues cannot receive guarantees in the service | |
436 | * domain; after a timeout they are charged for the time they | |
437 | * have been in service, to preserve fairness among them, but | |
438 | * without service-domain guarantees). | |
439 | */ | |
440 | unsigned int bfq_timeout; | |
441 | ||
442 | /* | |
443 | * Number of consecutive requests that must be issued within | |
444 | * the idle time slice to set again idling to a queue which | |
445 | * was marked as non-I/O-bound (see the definition of the | |
446 | * IO_bound flag for further details). | |
447 | */ | |
448 | unsigned int bfq_requests_within_timer; | |
449 | ||
450 | /* | |
451 | * Force device idling whenever needed to provide accurate | |
452 | * service guarantees, without caring about throughput | |
453 | * issues. CAVEAT: this may even increase latencies, in case | |
454 | * of useless idling for processes that did stop doing I/O. | |
455 | */ | |
456 | bool strict_guarantees; | |
457 | ||
458 | /* fallback dummy bfqq for extreme OOM conditions */ | |
459 | struct bfq_queue oom_bfqq; | |
460 | ||
461 | spinlock_t lock; | |
462 | ||
463 | /* | |
464 | * bic associated with the task issuing current bio for | |
465 | * merging. This and the next field are used as a support to | |
466 | * be able to perform the bic lookup, needed by bio-merge | |
467 | * functions, before the scheduler lock is taken, and thus | |
468 | * avoid taking the request-queue lock while the scheduler | |
469 | * lock is being held. | |
470 | */ | |
471 | struct bfq_io_cq *bio_bic; | |
472 | /* bfqq associated with the task issuing current bio for merging */ | |
473 | struct bfq_queue *bio_bfqq; | |
474 | }; | |
475 | ||
476 | enum bfqq_state_flags { | |
477 | BFQQF_busy = 0, /* has requests or is in service */ | |
478 | BFQQF_wait_request, /* waiting for a request */ | |
479 | BFQQF_non_blocking_wait_rq, /* | |
480 | * waiting for a request | |
481 | * without idling the device | |
482 | */ | |
483 | BFQQF_fifo_expire, /* FIFO checked in this slice */ | |
484 | BFQQF_idle_window, /* slice idling enabled */ | |
485 | BFQQF_sync, /* synchronous queue */ | |
486 | BFQQF_budget_new, /* no completion with this budget */ | |
487 | BFQQF_IO_bound, /* | |
488 | * bfqq has timed-out at least once | |
489 | * having consumed at most 2/10 of | |
490 | * its budget | |
491 | */ | |
492 | }; | |
493 | ||
494 | #define BFQ_BFQQ_FNS(name) \ | |
495 | static void bfq_mark_bfqq_##name(struct bfq_queue *bfqq) \ | |
496 | { \ | |
497 | __set_bit(BFQQF_##name, &(bfqq)->flags); \ | |
498 | } \ | |
499 | static void bfq_clear_bfqq_##name(struct bfq_queue *bfqq) \ | |
500 | { \ | |
501 | __clear_bit(BFQQF_##name, &(bfqq)->flags); \ | |
502 | } \ | |
503 | static int bfq_bfqq_##name(const struct bfq_queue *bfqq) \ | |
504 | { \ | |
505 | return test_bit(BFQQF_##name, &(bfqq)->flags); \ | |
506 | } | |
507 | ||
508 | BFQ_BFQQ_FNS(busy); | |
509 | BFQ_BFQQ_FNS(wait_request); | |
510 | BFQ_BFQQ_FNS(non_blocking_wait_rq); | |
511 | BFQ_BFQQ_FNS(fifo_expire); | |
512 | BFQ_BFQQ_FNS(idle_window); | |
513 | BFQ_BFQQ_FNS(sync); | |
514 | BFQ_BFQQ_FNS(budget_new); | |
515 | BFQ_BFQQ_FNS(IO_bound); | |
516 | #undef BFQ_BFQQ_FNS | |
517 | ||
518 | /* Logging facilities. */ | |
519 | #define bfq_log_bfqq(bfqd, bfqq, fmt, args...) \ | |
520 | blk_add_trace_msg((bfqd)->queue, "bfq%d " fmt, (bfqq)->pid, ##args) | |
521 | ||
522 | #define bfq_log(bfqd, fmt, args...) \ | |
523 | blk_add_trace_msg((bfqd)->queue, "bfq " fmt, ##args) | |
524 | ||
525 | /* Expiration reasons. */ | |
526 | enum bfqq_expiration { | |
527 | BFQQE_TOO_IDLE = 0, /* | |
528 | * queue has been idling for | |
529 | * too long | |
530 | */ | |
531 | BFQQE_BUDGET_TIMEOUT, /* budget took too long to be used */ | |
532 | BFQQE_BUDGET_EXHAUSTED, /* budget consumed */ | |
533 | BFQQE_NO_MORE_REQUESTS, /* the queue has no more requests */ | |
534 | BFQQE_PREEMPTED /* preemption in progress */ | |
535 | }; | |
536 | ||
537 | static struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity); | |
538 | ||
539 | static struct bfq_service_tree * | |
540 | bfq_entity_service_tree(struct bfq_entity *entity) | |
541 | { | |
542 | struct bfq_sched_data *sched_data = entity->sched_data; | |
543 | struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); | |
544 | unsigned int idx = bfqq ? bfqq->ioprio_class - 1 : | |
545 | BFQ_DEFAULT_GRP_CLASS - 1; | |
546 | ||
547 | return sched_data->service_tree + idx; | |
548 | } | |
549 | ||
550 | static struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, bool is_sync) | |
551 | { | |
552 | return bic->bfqq[is_sync]; | |
553 | } | |
554 | ||
555 | static void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq, | |
556 | bool is_sync) | |
557 | { | |
558 | bic->bfqq[is_sync] = bfqq; | |
559 | } | |
560 | ||
561 | static struct bfq_data *bic_to_bfqd(struct bfq_io_cq *bic) | |
562 | { | |
563 | return bic->icq.q->elevator->elevator_data; | |
564 | } | |
565 | ||
566 | static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio); | |
567 | static void bfq_put_queue(struct bfq_queue *bfqq); | |
568 | static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd, | |
569 | struct bio *bio, bool is_sync, | |
570 | struct bfq_io_cq *bic); | |
571 | static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq); | |
572 | ||
573 | /* | |
574 | * Array of async queues for all the processes, one queue | |
575 | * per ioprio value per ioprio_class. | |
576 | */ | |
577 | struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR]; | |
578 | /* Async queue for the idle class (ioprio is ignored) */ | |
579 | struct bfq_queue *async_idle_bfqq; | |
580 | ||
581 | /* Expiration time of sync (0) and async (1) requests, in ns. */ | |
582 | static const u64 bfq_fifo_expire[2] = { NSEC_PER_SEC / 4, NSEC_PER_SEC / 8 }; | |
583 | ||
584 | /* Maximum backwards seek (magic number lifted from CFQ), in KiB. */ | |
585 | static const int bfq_back_max = 16 * 1024; | |
586 | ||
587 | /* Penalty of a backwards seek, in number of sectors. */ | |
588 | static const int bfq_back_penalty = 2; | |
589 | ||
590 | /* Idling period duration, in ns. */ | |
591 | static u64 bfq_slice_idle = NSEC_PER_SEC / 125; | |
592 | ||
593 | /* Minimum number of assigned budgets for which stats are safe to compute. */ | |
594 | static const int bfq_stats_min_budgets = 194; | |
595 | ||
596 | /* Default maximum budget values, in sectors and number of requests. */ | |
597 | static const int bfq_default_max_budget = 16 * 1024; | |
598 | ||
599 | /* Default timeout values, in jiffies, approximating CFQ defaults. */ | |
600 | static const int bfq_timeout = HZ / 8; | |
601 | ||
602 | static struct kmem_cache *bfq_pool; | |
603 | ||
604 | /* Below this threshold (in ms), we consider thinktime immediate. */ | |
605 | #define BFQ_MIN_TT (2 * NSEC_PER_MSEC) | |
606 | ||
607 | /* hw_tag detection: parallel requests threshold and min samples needed. */ | |
608 | #define BFQ_HW_QUEUE_THRESHOLD 4 | |
609 | #define BFQ_HW_QUEUE_SAMPLES 32 | |
610 | ||
611 | #define BFQQ_SEEK_THR (sector_t)(8 * 100) | |
612 | #define BFQQ_SECT_THR_NONROT (sector_t)(2 * 32) | |
613 | #define BFQQ_CLOSE_THR (sector_t)(8 * 1024) | |
614 | #define BFQQ_SEEKY(bfqq) (hweight32(bfqq->seek_history) > 32/8) | |
615 | ||
616 | /* Budget feedback step. */ | |
617 | #define BFQ_BUDGET_STEP 128 | |
618 | ||
619 | /* Min samples used for peak rate estimation (for autotuning). */ | |
620 | #define BFQ_PEAK_RATE_SAMPLES 32 | |
621 | ||
622 | /* Shift used for peak rate fixed precision calculations. */ | |
623 | #define BFQ_RATE_SHIFT 16 | |
624 | ||
625 | #define BFQ_SERVICE_TREE_INIT ((struct bfq_service_tree) \ | |
626 | { RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 }) | |
627 | ||
628 | #define RQ_BIC(rq) ((struct bfq_io_cq *) (rq)->elv.priv[0]) | |
629 | #define RQ_BFQQ(rq) ((rq)->elv.priv[1]) | |
630 | ||
631 | /** | |
632 | * icq_to_bic - convert iocontext queue structure to bfq_io_cq. | |
633 | * @icq: the iocontext queue. | |
634 | */ | |
635 | static struct bfq_io_cq *icq_to_bic(struct io_cq *icq) | |
636 | { | |
637 | /* bic->icq is the first member, %NULL will convert to %NULL */ | |
638 | return container_of(icq, struct bfq_io_cq, icq); | |
639 | } | |
640 | ||
641 | /** | |
642 | * bfq_bic_lookup - search into @ioc a bic associated to @bfqd. | |
643 | * @bfqd: the lookup key. | |
644 | * @ioc: the io_context of the process doing I/O. | |
645 | * @q: the request queue. | |
646 | */ | |
647 | static struct bfq_io_cq *bfq_bic_lookup(struct bfq_data *bfqd, | |
648 | struct io_context *ioc, | |
649 | struct request_queue *q) | |
650 | { | |
651 | if (ioc) { | |
652 | unsigned long flags; | |
653 | struct bfq_io_cq *icq; | |
654 | ||
655 | spin_lock_irqsave(q->queue_lock, flags); | |
656 | icq = icq_to_bic(ioc_lookup_icq(ioc, q)); | |
657 | spin_unlock_irqrestore(q->queue_lock, flags); | |
658 | ||
659 | return icq; | |
660 | } | |
661 | ||
662 | return NULL; | |
663 | } | |
664 | ||
665 | /* | |
666 | * Next two macros are just fake loops for the moment. They will | |
667 | * become true loops in the cgroups-enabled variant of the code. Such | |
668 | * a variant, in its turn, will be introduced by next commit. | |
669 | */ | |
670 | #define for_each_entity(entity) \ | |
671 | for (; entity ; entity = NULL) | |
672 | ||
673 | #define for_each_entity_safe(entity, parent) \ | |
674 | for (parent = NULL; entity ; entity = parent) | |
675 | ||
676 | static int bfq_update_next_in_service(struct bfq_sched_data *sd) | |
677 | { | |
678 | return 0; | |
679 | } | |
680 | ||
681 | static void bfq_check_next_in_service(struct bfq_sched_data *sd, | |
682 | struct bfq_entity *entity) | |
683 | { | |
684 | } | |
685 | ||
686 | static void bfq_update_budget(struct bfq_entity *next_in_service) | |
687 | { | |
688 | } | |
689 | ||
690 | /* | |
691 | * Shift for timestamp calculations. This actually limits the maximum | |
692 | * service allowed in one timestamp delta (small shift values increase it), | |
693 | * the maximum total weight that can be used for the queues in the system | |
694 | * (big shift values increase it), and the period of virtual time | |
695 | * wraparounds. | |
696 | */ | |
697 | #define WFQ_SERVICE_SHIFT 22 | |
698 | ||
699 | /** | |
700 | * bfq_gt - compare two timestamps. | |
701 | * @a: first ts. | |
702 | * @b: second ts. | |
703 | * | |
704 | * Return @a > @b, dealing with wrapping correctly. | |
705 | */ | |
706 | static int bfq_gt(u64 a, u64 b) | |
707 | { | |
708 | return (s64)(a - b) > 0; | |
709 | } | |
710 | ||
711 | static struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity) | |
712 | { | |
713 | struct bfq_queue *bfqq = NULL; | |
714 | ||
715 | if (!entity->my_sched_data) | |
716 | bfqq = container_of(entity, struct bfq_queue, entity); | |
717 | ||
718 | return bfqq; | |
719 | } | |
720 | ||
721 | ||
722 | /** | |
723 | * bfq_delta - map service into the virtual time domain. | |
724 | * @service: amount of service. | |
725 | * @weight: scale factor (weight of an entity or weight sum). | |
726 | */ | |
727 | static u64 bfq_delta(unsigned long service, unsigned long weight) | |
728 | { | |
729 | u64 d = (u64)service << WFQ_SERVICE_SHIFT; | |
730 | ||
731 | do_div(d, weight); | |
732 | return d; | |
733 | } | |
734 | ||
735 | /** | |
736 | * bfq_calc_finish - assign the finish time to an entity. | |
737 | * @entity: the entity to act upon. | |
738 | * @service: the service to be charged to the entity. | |
739 | */ | |
740 | static void bfq_calc_finish(struct bfq_entity *entity, unsigned long service) | |
741 | { | |
742 | struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); | |
743 | ||
744 | entity->finish = entity->start + | |
745 | bfq_delta(service, entity->weight); | |
746 | ||
747 | if (bfqq) { | |
748 | bfq_log_bfqq(bfqq->bfqd, bfqq, | |
749 | "calc_finish: serv %lu, w %d", | |
750 | service, entity->weight); | |
751 | bfq_log_bfqq(bfqq->bfqd, bfqq, | |
752 | "calc_finish: start %llu, finish %llu, delta %llu", | |
753 | entity->start, entity->finish, | |
754 | bfq_delta(service, entity->weight)); | |
755 | } | |
756 | } | |
757 | ||
758 | /** | |
759 | * bfq_entity_of - get an entity from a node. | |
760 | * @node: the node field of the entity. | |
761 | * | |
762 | * Convert a node pointer to the relative entity. This is used only | |
763 | * to simplify the logic of some functions and not as the generic | |
764 | * conversion mechanism because, e.g., in the tree walking functions, | |
765 | * the check for a %NULL value would be redundant. | |
766 | */ | |
767 | static struct bfq_entity *bfq_entity_of(struct rb_node *node) | |
768 | { | |
769 | struct bfq_entity *entity = NULL; | |
770 | ||
771 | if (node) | |
772 | entity = rb_entry(node, struct bfq_entity, rb_node); | |
773 | ||
774 | return entity; | |
775 | } | |
776 | ||
777 | /** | |
778 | * bfq_extract - remove an entity from a tree. | |
779 | * @root: the tree root. | |
780 | * @entity: the entity to remove. | |
781 | */ | |
782 | static void bfq_extract(struct rb_root *root, struct bfq_entity *entity) | |
783 | { | |
784 | entity->tree = NULL; | |
785 | rb_erase(&entity->rb_node, root); | |
786 | } | |
787 | ||
788 | /** | |
789 | * bfq_idle_extract - extract an entity from the idle tree. | |
790 | * @st: the service tree of the owning @entity. | |
791 | * @entity: the entity being removed. | |
792 | */ | |
793 | static void bfq_idle_extract(struct bfq_service_tree *st, | |
794 | struct bfq_entity *entity) | |
795 | { | |
796 | struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); | |
797 | struct rb_node *next; | |
798 | ||
799 | if (entity == st->first_idle) { | |
800 | next = rb_next(&entity->rb_node); | |
801 | st->first_idle = bfq_entity_of(next); | |
802 | } | |
803 | ||
804 | if (entity == st->last_idle) { | |
805 | next = rb_prev(&entity->rb_node); | |
806 | st->last_idle = bfq_entity_of(next); | |
807 | } | |
808 | ||
809 | bfq_extract(&st->idle, entity); | |
810 | ||
811 | if (bfqq) | |
812 | list_del(&bfqq->bfqq_list); | |
813 | } | |
814 | ||
815 | /** | |
816 | * bfq_insert - generic tree insertion. | |
817 | * @root: tree root. | |
818 | * @entity: entity to insert. | |
819 | * | |
820 | * This is used for the idle and the active tree, since they are both | |
821 | * ordered by finish time. | |
822 | */ | |
823 | static void bfq_insert(struct rb_root *root, struct bfq_entity *entity) | |
824 | { | |
825 | struct bfq_entity *entry; | |
826 | struct rb_node **node = &root->rb_node; | |
827 | struct rb_node *parent = NULL; | |
828 | ||
829 | while (*node) { | |
830 | parent = *node; | |
831 | entry = rb_entry(parent, struct bfq_entity, rb_node); | |
832 | ||
833 | if (bfq_gt(entry->finish, entity->finish)) | |
834 | node = &parent->rb_left; | |
835 | else | |
836 | node = &parent->rb_right; | |
837 | } | |
838 | ||
839 | rb_link_node(&entity->rb_node, parent, node); | |
840 | rb_insert_color(&entity->rb_node, root); | |
841 | ||
842 | entity->tree = root; | |
843 | } | |
844 | ||
845 | /** | |
846 | * bfq_update_min - update the min_start field of a entity. | |
847 | * @entity: the entity to update. | |
848 | * @node: one of its children. | |
849 | * | |
850 | * This function is called when @entity may store an invalid value for | |
851 | * min_start due to updates to the active tree. The function assumes | |
852 | * that the subtree rooted at @node (which may be its left or its right | |
853 | * child) has a valid min_start value. | |
854 | */ | |
855 | static void bfq_update_min(struct bfq_entity *entity, struct rb_node *node) | |
856 | { | |
857 | struct bfq_entity *child; | |
858 | ||
859 | if (node) { | |
860 | child = rb_entry(node, struct bfq_entity, rb_node); | |
861 | if (bfq_gt(entity->min_start, child->min_start)) | |
862 | entity->min_start = child->min_start; | |
863 | } | |
864 | } | |
865 | ||
866 | /** | |
867 | * bfq_update_active_node - recalculate min_start. | |
868 | * @node: the node to update. | |
869 | * | |
870 | * @node may have changed position or one of its children may have moved, | |
871 | * this function updates its min_start value. The left and right subtrees | |
872 | * are assumed to hold a correct min_start value. | |
873 | */ | |
874 | static void bfq_update_active_node(struct rb_node *node) | |
875 | { | |
876 | struct bfq_entity *entity = rb_entry(node, struct bfq_entity, rb_node); | |
877 | ||
878 | entity->min_start = entity->start; | |
879 | bfq_update_min(entity, node->rb_right); | |
880 | bfq_update_min(entity, node->rb_left); | |
881 | } | |
882 | ||
883 | /** | |
884 | * bfq_update_active_tree - update min_start for the whole active tree. | |
885 | * @node: the starting node. | |
886 | * | |
887 | * @node must be the deepest modified node after an update. This function | |
888 | * updates its min_start using the values held by its children, assuming | |
889 | * that they did not change, and then updates all the nodes that may have | |
890 | * changed in the path to the root. The only nodes that may have changed | |
891 | * are the ones in the path or their siblings. | |
892 | */ | |
893 | static void bfq_update_active_tree(struct rb_node *node) | |
894 | { | |
895 | struct rb_node *parent; | |
896 | ||
897 | up: | |
898 | bfq_update_active_node(node); | |
899 | ||
900 | parent = rb_parent(node); | |
901 | if (!parent) | |
902 | return; | |
903 | ||
904 | if (node == parent->rb_left && parent->rb_right) | |
905 | bfq_update_active_node(parent->rb_right); | |
906 | else if (parent->rb_left) | |
907 | bfq_update_active_node(parent->rb_left); | |
908 | ||
909 | node = parent; | |
910 | goto up; | |
911 | } | |
912 | ||
913 | /** | |
914 | * bfq_active_insert - insert an entity in the active tree of its | |
915 | * group/device. | |
916 | * @st: the service tree of the entity. | |
917 | * @entity: the entity being inserted. | |
918 | * | |
919 | * The active tree is ordered by finish time, but an extra key is kept | |
920 | * per each node, containing the minimum value for the start times of | |
921 | * its children (and the node itself), so it's possible to search for | |
922 | * the eligible node with the lowest finish time in logarithmic time. | |
923 | */ | |
924 | static void bfq_active_insert(struct bfq_service_tree *st, | |
925 | struct bfq_entity *entity) | |
926 | { | |
927 | struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); | |
928 | struct rb_node *node = &entity->rb_node; | |
929 | ||
930 | bfq_insert(&st->active, entity); | |
931 | ||
932 | if (node->rb_left) | |
933 | node = node->rb_left; | |
934 | else if (node->rb_right) | |
935 | node = node->rb_right; | |
936 | ||
937 | bfq_update_active_tree(node); | |
938 | ||
939 | if (bfqq) | |
940 | list_add(&bfqq->bfqq_list, &bfqq->bfqd->active_list); | |
941 | } | |
942 | ||
943 | /** | |
944 | * bfq_ioprio_to_weight - calc a weight from an ioprio. | |
945 | * @ioprio: the ioprio value to convert. | |
946 | */ | |
947 | static unsigned short bfq_ioprio_to_weight(int ioprio) | |
948 | { | |
949 | return (IOPRIO_BE_NR - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF; | |
950 | } | |
951 | ||
952 | /** | |
953 | * bfq_weight_to_ioprio - calc an ioprio from a weight. | |
954 | * @weight: the weight value to convert. | |
955 | * | |
956 | * To preserve as much as possible the old only-ioprio user interface, | |
957 | * 0 is used as an escape ioprio value for weights (numerically) equal or | |
958 | * larger than IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF. | |
959 | */ | |
960 | static unsigned short bfq_weight_to_ioprio(int weight) | |
961 | { | |
962 | return max_t(int, 0, | |
963 | IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF - weight); | |
964 | } | |
965 | ||
966 | static void bfq_get_entity(struct bfq_entity *entity) | |
967 | { | |
968 | struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); | |
969 | ||
970 | if (bfqq) { | |
971 | bfqq->ref++; | |
972 | bfq_log_bfqq(bfqq->bfqd, bfqq, "get_entity: %p %d", | |
973 | bfqq, bfqq->ref); | |
974 | } | |
975 | } | |
976 | ||
977 | /** | |
978 | * bfq_find_deepest - find the deepest node that an extraction can modify. | |
979 | * @node: the node being removed. | |
980 | * | |
981 | * Do the first step of an extraction in an rb tree, looking for the | |
982 | * node that will replace @node, and returning the deepest node that | |
983 | * the following modifications to the tree can touch. If @node is the | |
984 | * last node in the tree return %NULL. | |
985 | */ | |
986 | static struct rb_node *bfq_find_deepest(struct rb_node *node) | |
987 | { | |
988 | struct rb_node *deepest; | |
989 | ||
990 | if (!node->rb_right && !node->rb_left) | |
991 | deepest = rb_parent(node); | |
992 | else if (!node->rb_right) | |
993 | deepest = node->rb_left; | |
994 | else if (!node->rb_left) | |
995 | deepest = node->rb_right; | |
996 | else { | |
997 | deepest = rb_next(node); | |
998 | if (deepest->rb_right) | |
999 | deepest = deepest->rb_right; | |
1000 | else if (rb_parent(deepest) != node) | |
1001 | deepest = rb_parent(deepest); | |
1002 | } | |
1003 | ||
1004 | return deepest; | |
1005 | } | |
1006 | ||
1007 | /** | |
1008 | * bfq_active_extract - remove an entity from the active tree. | |
1009 | * @st: the service_tree containing the tree. | |
1010 | * @entity: the entity being removed. | |
1011 | */ | |
1012 | static void bfq_active_extract(struct bfq_service_tree *st, | |
1013 | struct bfq_entity *entity) | |
1014 | { | |
1015 | struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); | |
1016 | struct rb_node *node; | |
1017 | ||
1018 | node = bfq_find_deepest(&entity->rb_node); | |
1019 | bfq_extract(&st->active, entity); | |
1020 | ||
1021 | if (node) | |
1022 | bfq_update_active_tree(node); | |
1023 | ||
1024 | if (bfqq) | |
1025 | list_del(&bfqq->bfqq_list); | |
1026 | } | |
1027 | ||
1028 | /** | |
1029 | * bfq_idle_insert - insert an entity into the idle tree. | |
1030 | * @st: the service tree containing the tree. | |
1031 | * @entity: the entity to insert. | |
1032 | */ | |
1033 | static void bfq_idle_insert(struct bfq_service_tree *st, | |
1034 | struct bfq_entity *entity) | |
1035 | { | |
1036 | struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); | |
1037 | struct bfq_entity *first_idle = st->first_idle; | |
1038 | struct bfq_entity *last_idle = st->last_idle; | |
1039 | ||
1040 | if (!first_idle || bfq_gt(first_idle->finish, entity->finish)) | |
1041 | st->first_idle = entity; | |
1042 | if (!last_idle || bfq_gt(entity->finish, last_idle->finish)) | |
1043 | st->last_idle = entity; | |
1044 | ||
1045 | bfq_insert(&st->idle, entity); | |
1046 | ||
1047 | if (bfqq) | |
1048 | list_add(&bfqq->bfqq_list, &bfqq->bfqd->idle_list); | |
1049 | } | |
1050 | ||
1051 | /** | |
1052 | * bfq_forget_entity - do not consider entity any longer for scheduling | |
1053 | * @st: the service tree. | |
1054 | * @entity: the entity being removed. | |
1055 | * @is_in_service: true if entity is currently the in-service entity. | |
1056 | * | |
1057 | * Forget everything about @entity. In addition, if entity represents | |
1058 | * a queue, and the latter is not in service, then release the service | |
1059 | * reference to the queue (the one taken through bfq_get_entity). In | |
1060 | * fact, in this case, there is really no more service reference to | |
1061 | * the queue, as the latter is also outside any service tree. If, | |
1062 | * instead, the queue is in service, then __bfq_bfqd_reset_in_service | |
1063 | * will take care of putting the reference when the queue finally | |
1064 | * stops being served. | |
1065 | */ | |
1066 | static void bfq_forget_entity(struct bfq_service_tree *st, | |
1067 | struct bfq_entity *entity, | |
1068 | bool is_in_service) | |
1069 | { | |
1070 | struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); | |
1071 | ||
1072 | entity->on_st = 0; | |
1073 | st->wsum -= entity->weight; | |
1074 | if (bfqq && !is_in_service) | |
1075 | bfq_put_queue(bfqq); | |
1076 | } | |
1077 | ||
1078 | /** | |
1079 | * bfq_put_idle_entity - release the idle tree ref of an entity. | |
1080 | * @st: service tree for the entity. | |
1081 | * @entity: the entity being released. | |
1082 | */ | |
1083 | static void bfq_put_idle_entity(struct bfq_service_tree *st, | |
1084 | struct bfq_entity *entity) | |
1085 | { | |
1086 | bfq_idle_extract(st, entity); | |
1087 | bfq_forget_entity(st, entity, | |
1088 | entity == entity->sched_data->in_service_entity); | |
1089 | } | |
1090 | ||
1091 | /** | |
1092 | * bfq_forget_idle - update the idle tree if necessary. | |
1093 | * @st: the service tree to act upon. | |
1094 | * | |
1095 | * To preserve the global O(log N) complexity we only remove one entry here; | |
1096 | * as the idle tree will not grow indefinitely this can be done safely. | |
1097 | */ | |
1098 | static void bfq_forget_idle(struct bfq_service_tree *st) | |
1099 | { | |
1100 | struct bfq_entity *first_idle = st->first_idle; | |
1101 | struct bfq_entity *last_idle = st->last_idle; | |
1102 | ||
1103 | if (RB_EMPTY_ROOT(&st->active) && last_idle && | |
1104 | !bfq_gt(last_idle->finish, st->vtime)) { | |
1105 | /* | |
1106 | * Forget the whole idle tree, increasing the vtime past | |
1107 | * the last finish time of idle entities. | |
1108 | */ | |
1109 | st->vtime = last_idle->finish; | |
1110 | } | |
1111 | ||
1112 | if (first_idle && !bfq_gt(first_idle->finish, st->vtime)) | |
1113 | bfq_put_idle_entity(st, first_idle); | |
1114 | } | |
1115 | ||
1116 | static struct bfq_service_tree * | |
1117 | __bfq_entity_update_weight_prio(struct bfq_service_tree *old_st, | |
1118 | struct bfq_entity *entity) | |
1119 | { | |
1120 | struct bfq_service_tree *new_st = old_st; | |
1121 | ||
1122 | if (entity->prio_changed) { | |
1123 | struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); | |
1124 | unsigned short prev_weight, new_weight; | |
1125 | struct bfq_data *bfqd = NULL; | |
1126 | ||
1127 | if (bfqq) | |
1128 | bfqd = bfqq->bfqd; | |
1129 | ||
1130 | old_st->wsum -= entity->weight; | |
1131 | ||
1132 | if (entity->new_weight != entity->orig_weight) { | |
1133 | if (entity->new_weight < BFQ_MIN_WEIGHT || | |
1134 | entity->new_weight > BFQ_MAX_WEIGHT) { | |
1135 | pr_crit("update_weight_prio: new_weight %d\n", | |
1136 | entity->new_weight); | |
1137 | if (entity->new_weight < BFQ_MIN_WEIGHT) | |
1138 | entity->new_weight = BFQ_MIN_WEIGHT; | |
1139 | else | |
1140 | entity->new_weight = BFQ_MAX_WEIGHT; | |
1141 | } | |
1142 | entity->orig_weight = entity->new_weight; | |
1143 | if (bfqq) | |
1144 | bfqq->ioprio = | |
1145 | bfq_weight_to_ioprio(entity->orig_weight); | |
1146 | } | |
1147 | ||
1148 | if (bfqq) | |
1149 | bfqq->ioprio_class = bfqq->new_ioprio_class; | |
1150 | entity->prio_changed = 0; | |
1151 | ||
1152 | /* | |
1153 | * NOTE: here we may be changing the weight too early, | |
1154 | * this will cause unfairness. The correct approach | |
1155 | * would have required additional complexity to defer | |
1156 | * weight changes to the proper time instants (i.e., | |
1157 | * when entity->finish <= old_st->vtime). | |
1158 | */ | |
1159 | new_st = bfq_entity_service_tree(entity); | |
1160 | ||
1161 | prev_weight = entity->weight; | |
1162 | new_weight = entity->orig_weight; | |
1163 | entity->weight = new_weight; | |
1164 | ||
1165 | new_st->wsum += entity->weight; | |
1166 | ||
1167 | if (new_st != old_st) | |
1168 | entity->start = new_st->vtime; | |
1169 | } | |
1170 | ||
1171 | return new_st; | |
1172 | } | |
1173 | ||
1174 | /** | |
1175 | * bfq_bfqq_served - update the scheduler status after selection for | |
1176 | * service. | |
1177 | * @bfqq: the queue being served. | |
1178 | * @served: bytes to transfer. | |
1179 | * | |
1180 | * NOTE: this can be optimized, as the timestamps of upper level entities | |
1181 | * are synchronized every time a new bfqq is selected for service. By now, | |
1182 | * we keep it to better check consistency. | |
1183 | */ | |
1184 | static void bfq_bfqq_served(struct bfq_queue *bfqq, int served) | |
1185 | { | |
1186 | struct bfq_entity *entity = &bfqq->entity; | |
1187 | struct bfq_service_tree *st; | |
1188 | ||
1189 | for_each_entity(entity) { | |
1190 | st = bfq_entity_service_tree(entity); | |
1191 | ||
1192 | entity->service += served; | |
1193 | ||
1194 | st->vtime += bfq_delta(served, st->wsum); | |
1195 | bfq_forget_idle(st); | |
1196 | } | |
1197 | bfq_log_bfqq(bfqq->bfqd, bfqq, "bfqq_served %d secs", served); | |
1198 | } | |
1199 | ||
1200 | /** | |
1201 | * bfq_bfqq_charge_full_budget - set the service to the entity budget. | |
1202 | * @bfqq: the queue that needs a service update. | |
1203 | * | |
1204 | * When it's not possible to be fair in the service domain, because | |
1205 | * a queue is not consuming its budget fast enough (the meaning of | |
1206 | * fast depends on the timeout parameter), we charge it a full | |
1207 | * budget. In this way we should obtain a sort of time-domain | |
1208 | * fairness among all the seeky/slow queues. | |
1209 | */ | |
1210 | static void bfq_bfqq_charge_full_budget(struct bfq_queue *bfqq) | |
1211 | { | |
1212 | struct bfq_entity *entity = &bfqq->entity; | |
1213 | ||
1214 | bfq_log_bfqq(bfqq->bfqd, bfqq, "charge_full_budget"); | |
1215 | ||
1216 | bfq_bfqq_served(bfqq, entity->budget - entity->service); | |
1217 | } | |
1218 | ||
1219 | /** | |
1220 | * __bfq_activate_entity - activate an entity. | |
1221 | * @entity: the entity being activated. | |
1222 | * @non_blocking_wait_rq: true if this entity was waiting for a request | |
1223 | * | |
1224 | * Called whenever an entity is activated, i.e., it is not active and one | |
1225 | * of its children receives a new request, or has to be reactivated due to | |
1226 | * budget exhaustion. It uses the current budget of the entity (and the | |
1227 | * service received if @entity is active) of the queue to calculate its | |
1228 | * timestamps. | |
1229 | */ | |
1230 | static void __bfq_activate_entity(struct bfq_entity *entity, | |
1231 | bool non_blocking_wait_rq) | |
1232 | { | |
1233 | struct bfq_sched_data *sd = entity->sched_data; | |
1234 | struct bfq_service_tree *st = bfq_entity_service_tree(entity); | |
1235 | bool backshifted = false; | |
1236 | ||
1237 | if (entity == sd->in_service_entity) { | |
1238 | /* | |
1239 | * If we are requeueing the current entity we have | |
1240 | * to take care of not charging to it service it has | |
1241 | * not received. | |
1242 | */ | |
1243 | bfq_calc_finish(entity, entity->service); | |
1244 | entity->start = entity->finish; | |
1245 | sd->in_service_entity = NULL; | |
1246 | } else if (entity->tree == &st->active) { | |
1247 | /* | |
1248 | * Requeueing an entity due to a change of some | |
1249 | * next_in_service entity below it. We reuse the | |
1250 | * old start time. | |
1251 | */ | |
1252 | bfq_active_extract(st, entity); | |
1253 | } else { | |
1254 | unsigned long long min_vstart; | |
1255 | ||
1256 | /* See comments on bfq_fqq_update_budg_for_activation */ | |
1257 | if (non_blocking_wait_rq && bfq_gt(st->vtime, entity->finish)) { | |
1258 | backshifted = true; | |
1259 | min_vstart = entity->finish; | |
1260 | } else | |
1261 | min_vstart = st->vtime; | |
1262 | ||
1263 | if (entity->tree == &st->idle) { | |
1264 | /* | |
1265 | * Must be on the idle tree, bfq_idle_extract() will | |
1266 | * check for that. | |
1267 | */ | |
1268 | bfq_idle_extract(st, entity); | |
1269 | entity->start = bfq_gt(min_vstart, entity->finish) ? | |
1270 | min_vstart : entity->finish; | |
1271 | } else { | |
1272 | /* | |
1273 | * The finish time of the entity may be invalid, and | |
1274 | * it is in the past for sure, otherwise the queue | |
1275 | * would have been on the idle tree. | |
1276 | */ | |
1277 | entity->start = min_vstart; | |
1278 | st->wsum += entity->weight; | |
1279 | /* | |
1280 | * entity is about to be inserted into a service tree, | |
1281 | * and then set in service: get a reference to make | |
1282 | * sure entity does not disappear until it is no | |
1283 | * longer in service or scheduled for service. | |
1284 | */ | |
1285 | bfq_get_entity(entity); | |
1286 | ||
1287 | entity->on_st = 1; | |
1288 | } | |
1289 | } | |
1290 | ||
1291 | st = __bfq_entity_update_weight_prio(st, entity); | |
1292 | bfq_calc_finish(entity, entity->budget); | |
1293 | ||
1294 | /* | |
1295 | * If some queues enjoy backshifting for a while, then their | |
1296 | * (virtual) finish timestamps may happen to become lower and | |
1297 | * lower than the system virtual time. In particular, if | |
1298 | * these queues often happen to be idle for short time | |
1299 | * periods, and during such time periods other queues with | |
1300 | * higher timestamps happen to be busy, then the backshifted | |
1301 | * timestamps of the former queues can become much lower than | |
1302 | * the system virtual time. In fact, to serve the queues with | |
1303 | * higher timestamps while the ones with lower timestamps are | |
1304 | * idle, the system virtual time may be pushed-up to much | |
1305 | * higher values than the finish timestamps of the idle | |
1306 | * queues. As a consequence, the finish timestamps of all new | |
1307 | * or newly activated queues may end up being much larger than | |
1308 | * those of lucky queues with backshifted timestamps. The | |
1309 | * latter queues may then monopolize the device for a lot of | |
1310 | * time. This would simply break service guarantees. | |
1311 | * | |
1312 | * To reduce this problem, push up a little bit the | |
1313 | * backshifted timestamps of the queue associated with this | |
1314 | * entity (only a queue can happen to have the backshifted | |
1315 | * flag set): just enough to let the finish timestamp of the | |
1316 | * queue be equal to the current value of the system virtual | |
1317 | * time. This may introduce a little unfairness among queues | |
1318 | * with backshifted timestamps, but it does not break | |
1319 | * worst-case fairness guarantees. | |
1320 | */ | |
1321 | if (backshifted && bfq_gt(st->vtime, entity->finish)) { | |
1322 | unsigned long delta = st->vtime - entity->finish; | |
1323 | ||
1324 | entity->start += delta; | |
1325 | entity->finish += delta; | |
1326 | } | |
1327 | ||
1328 | bfq_active_insert(st, entity); | |
1329 | } | |
1330 | ||
1331 | /** | |
1332 | * bfq_activate_entity - activate an entity and its ancestors if necessary. | |
1333 | * @entity: the entity to activate. | |
1334 | * @non_blocking_wait_rq: true if this entity was waiting for a request | |
1335 | * | |
1336 | * Activate @entity and all the entities on the path from it to the root. | |
1337 | */ | |
1338 | static void bfq_activate_entity(struct bfq_entity *entity, | |
1339 | bool non_blocking_wait_rq) | |
1340 | { | |
1341 | struct bfq_sched_data *sd; | |
1342 | ||
1343 | for_each_entity(entity) { | |
1344 | __bfq_activate_entity(entity, non_blocking_wait_rq); | |
1345 | ||
1346 | sd = entity->sched_data; | |
1347 | if (!bfq_update_next_in_service(sd)) | |
1348 | /* | |
1349 | * No need to propagate the activation to the | |
1350 | * upper entities, as they will be updated when | |
1351 | * the in-service entity is rescheduled. | |
1352 | */ | |
1353 | break; | |
1354 | } | |
1355 | } | |
1356 | ||
1357 | /** | |
1358 | * __bfq_deactivate_entity - deactivate an entity from its service tree. | |
1359 | * @entity: the entity to deactivate. | |
1360 | * @requeue: if false, the entity will not be put into the idle tree. | |
1361 | * | |
1362 | * Deactivate an entity, independently from its previous state. If the | |
1363 | * entity was not on a service tree just return, otherwise if it is on | |
1364 | * any scheduler tree, extract it from that tree, and if necessary | |
1365 | * and if the caller did not specify @requeue, put it on the idle tree. | |
1366 | * | |
1367 | * Return %1 if the caller should update the entity hierarchy, i.e., | |
1368 | * if the entity was in service or if it was the next_in_service for | |
1369 | * its sched_data; return %0 otherwise. | |
1370 | */ | |
1371 | static int __bfq_deactivate_entity(struct bfq_entity *entity, int requeue) | |
1372 | { | |
1373 | struct bfq_sched_data *sd = entity->sched_data; | |
1374 | struct bfq_service_tree *st = bfq_entity_service_tree(entity); | |
1375 | int is_in_service = entity == sd->in_service_entity; | |
1376 | int ret = 0; | |
1377 | ||
1378 | if (!entity->on_st) | |
1379 | return 0; | |
1380 | ||
1381 | if (is_in_service) { | |
1382 | bfq_calc_finish(entity, entity->service); | |
1383 | sd->in_service_entity = NULL; | |
1384 | } else if (entity->tree == &st->active) | |
1385 | bfq_active_extract(st, entity); | |
1386 | else if (entity->tree == &st->idle) | |
1387 | bfq_idle_extract(st, entity); | |
1388 | ||
1389 | if (is_in_service || sd->next_in_service == entity) | |
1390 | ret = bfq_update_next_in_service(sd); | |
1391 | ||
1392 | if (!requeue || !bfq_gt(entity->finish, st->vtime)) | |
1393 | bfq_forget_entity(st, entity, is_in_service); | |
1394 | else | |
1395 | bfq_idle_insert(st, entity); | |
1396 | ||
1397 | return ret; | |
1398 | } | |
1399 | ||
1400 | /** | |
1401 | * bfq_deactivate_entity - deactivate an entity. | |
1402 | * @entity: the entity to deactivate. | |
1403 | * @requeue: true if the entity can be put on the idle tree | |
1404 | */ | |
1405 | static void bfq_deactivate_entity(struct bfq_entity *entity, int requeue) | |
1406 | { | |
1407 | struct bfq_sched_data *sd; | |
1408 | struct bfq_entity *parent = NULL; | |
1409 | ||
1410 | for_each_entity_safe(entity, parent) { | |
1411 | sd = entity->sched_data; | |
1412 | ||
1413 | if (!__bfq_deactivate_entity(entity, requeue)) | |
1414 | /* | |
1415 | * The parent entity is still backlogged, and | |
1416 | * we don't need to update it as it is still | |
1417 | * in service. | |
1418 | */ | |
1419 | break; | |
1420 | ||
1421 | if (sd->next_in_service) | |
1422 | /* | |
1423 | * The parent entity is still backlogged and | |
1424 | * the budgets on the path towards the root | |
1425 | * need to be updated. | |
1426 | */ | |
1427 | goto update; | |
1428 | ||
1429 | /* | |
1430 | * If we get here, then the parent is no more backlogged and | |
1431 | * we want to propagate the deactivation upwards. | |
1432 | */ | |
1433 | requeue = 1; | |
1434 | } | |
1435 | ||
1436 | return; | |
1437 | ||
1438 | update: | |
1439 | entity = parent; | |
1440 | for_each_entity(entity) { | |
1441 | __bfq_activate_entity(entity, false); | |
1442 | ||
1443 | sd = entity->sched_data; | |
1444 | if (!bfq_update_next_in_service(sd)) | |
1445 | break; | |
1446 | } | |
1447 | } | |
1448 | ||
1449 | /** | |
1450 | * bfq_update_vtime - update vtime if necessary. | |
1451 | * @st: the service tree to act upon. | |
1452 | * | |
1453 | * If necessary update the service tree vtime to have at least one | |
1454 | * eligible entity, skipping to its start time. Assumes that the | |
1455 | * active tree of the device is not empty. | |
1456 | * | |
1457 | * NOTE: this hierarchical implementation updates vtimes quite often, | |
1458 | * we may end up with reactivated processes getting timestamps after a | |
1459 | * vtime skip done because we needed a ->first_active entity on some | |
1460 | * intermediate node. | |
1461 | */ | |
1462 | static void bfq_update_vtime(struct bfq_service_tree *st) | |
1463 | { | |
1464 | struct bfq_entity *entry; | |
1465 | struct rb_node *node = st->active.rb_node; | |
1466 | ||
1467 | entry = rb_entry(node, struct bfq_entity, rb_node); | |
1468 | if (bfq_gt(entry->min_start, st->vtime)) { | |
1469 | st->vtime = entry->min_start; | |
1470 | bfq_forget_idle(st); | |
1471 | } | |
1472 | } | |
1473 | ||
1474 | /** | |
1475 | * bfq_first_active_entity - find the eligible entity with | |
1476 | * the smallest finish time | |
1477 | * @st: the service tree to select from. | |
1478 | * | |
1479 | * This function searches the first schedulable entity, starting from the | |
1480 | * root of the tree and going on the left every time on this side there is | |
1481 | * a subtree with at least one eligible (start >= vtime) entity. The path on | |
1482 | * the right is followed only if a) the left subtree contains no eligible | |
1483 | * entities and b) no eligible entity has been found yet. | |
1484 | */ | |
1485 | static struct bfq_entity *bfq_first_active_entity(struct bfq_service_tree *st) | |
1486 | { | |
1487 | struct bfq_entity *entry, *first = NULL; | |
1488 | struct rb_node *node = st->active.rb_node; | |
1489 | ||
1490 | while (node) { | |
1491 | entry = rb_entry(node, struct bfq_entity, rb_node); | |
1492 | left: | |
1493 | if (!bfq_gt(entry->start, st->vtime)) | |
1494 | first = entry; | |
1495 | ||
1496 | if (node->rb_left) { | |
1497 | entry = rb_entry(node->rb_left, | |
1498 | struct bfq_entity, rb_node); | |
1499 | if (!bfq_gt(entry->min_start, st->vtime)) { | |
1500 | node = node->rb_left; | |
1501 | goto left; | |
1502 | } | |
1503 | } | |
1504 | if (first) | |
1505 | break; | |
1506 | node = node->rb_right; | |
1507 | } | |
1508 | ||
1509 | return first; | |
1510 | } | |
1511 | ||
1512 | /** | |
1513 | * __bfq_lookup_next_entity - return the first eligible entity in @st. | |
1514 | * @st: the service tree. | |
1515 | * | |
1516 | * Update the virtual time in @st and return the first eligible entity | |
1517 | * it contains. | |
1518 | */ | |
1519 | static struct bfq_entity *__bfq_lookup_next_entity(struct bfq_service_tree *st, | |
1520 | bool force) | |
1521 | { | |
1522 | struct bfq_entity *entity, *new_next_in_service = NULL; | |
1523 | ||
1524 | if (RB_EMPTY_ROOT(&st->active)) | |
1525 | return NULL; | |
1526 | ||
1527 | bfq_update_vtime(st); | |
1528 | entity = bfq_first_active_entity(st); | |
1529 | ||
1530 | /* | |
1531 | * If the chosen entity does not match with the sched_data's | |
1532 | * next_in_service and we are forcedly serving the IDLE priority | |
1533 | * class tree, bubble up budget update. | |
1534 | */ | |
1535 | if (unlikely(force && entity != entity->sched_data->next_in_service)) { | |
1536 | new_next_in_service = entity; | |
1537 | for_each_entity(new_next_in_service) | |
1538 | bfq_update_budget(new_next_in_service); | |
1539 | } | |
1540 | ||
1541 | return entity; | |
1542 | } | |
1543 | ||
1544 | /** | |
1545 | * bfq_lookup_next_entity - return the first eligible entity in @sd. | |
1546 | * @sd: the sched_data. | |
1547 | * @extract: if true the returned entity will be also extracted from @sd. | |
1548 | * | |
1549 | * NOTE: since we cache the next_in_service entity at each level of the | |
1550 | * hierarchy, the complexity of the lookup can be decreased with | |
1551 | * absolutely no effort just returning the cached next_in_service value; | |
1552 | * we prefer to do full lookups to test the consistency of the data | |
1553 | * structures. | |
1554 | */ | |
1555 | static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd, | |
1556 | int extract, | |
1557 | struct bfq_data *bfqd) | |
1558 | { | |
1559 | struct bfq_service_tree *st = sd->service_tree; | |
1560 | struct bfq_entity *entity; | |
1561 | int i = 0; | |
1562 | ||
1563 | /* | |
1564 | * Choose from idle class, if needed to guarantee a minimum | |
1565 | * bandwidth to this class. This should also mitigate | |
1566 | * priority-inversion problems in case a low priority task is | |
1567 | * holding file system resources. | |
1568 | */ | |
1569 | if (bfqd && | |
1570 | jiffies - bfqd->bfq_class_idle_last_service > | |
1571 | BFQ_CL_IDLE_TIMEOUT) { | |
1572 | entity = __bfq_lookup_next_entity(st + BFQ_IOPRIO_CLASSES - 1, | |
1573 | true); | |
1574 | if (entity) { | |
1575 | i = BFQ_IOPRIO_CLASSES - 1; | |
1576 | bfqd->bfq_class_idle_last_service = jiffies; | |
1577 | sd->next_in_service = entity; | |
1578 | } | |
1579 | } | |
1580 | for (; i < BFQ_IOPRIO_CLASSES; i++) { | |
1581 | entity = __bfq_lookup_next_entity(st + i, false); | |
1582 | if (entity) { | |
1583 | if (extract) { | |
1584 | bfq_check_next_in_service(sd, entity); | |
1585 | bfq_active_extract(st + i, entity); | |
1586 | sd->in_service_entity = entity; | |
1587 | sd->next_in_service = NULL; | |
1588 | } | |
1589 | break; | |
1590 | } | |
1591 | } | |
1592 | ||
1593 | return entity; | |
1594 | } | |
1595 | ||
1596 | static bool next_queue_may_preempt(struct bfq_data *bfqd) | |
1597 | { | |
1598 | struct bfq_sched_data *sd = &bfqd->sched_data; | |
1599 | ||
1600 | return sd->next_in_service != sd->in_service_entity; | |
1601 | } | |
1602 | ||
1603 | ||
1604 | /* | |
1605 | * Get next queue for service. | |
1606 | */ | |
1607 | static struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd) | |
1608 | { | |
1609 | struct bfq_entity *entity = NULL; | |
1610 | struct bfq_sched_data *sd; | |
1611 | struct bfq_queue *bfqq; | |
1612 | ||
1613 | if (bfqd->busy_queues == 0) | |
1614 | return NULL; | |
1615 | ||
1616 | sd = &bfqd->sched_data; | |
1617 | for (; sd ; sd = entity->my_sched_data) { | |
1618 | entity = bfq_lookup_next_entity(sd, 1, bfqd); | |
1619 | entity->service = 0; | |
1620 | } | |
1621 | ||
1622 | bfqq = bfq_entity_to_bfqq(entity); | |
1623 | ||
1624 | return bfqq; | |
1625 | } | |
1626 | ||
1627 | static void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd) | |
1628 | { | |
1629 | struct bfq_queue *in_serv_bfqq = bfqd->in_service_queue; | |
1630 | struct bfq_entity *in_serv_entity = &in_serv_bfqq->entity; | |
1631 | ||
1632 | if (bfqd->in_service_bic) { | |
1633 | put_io_context(bfqd->in_service_bic->icq.ioc); | |
1634 | bfqd->in_service_bic = NULL; | |
1635 | } | |
1636 | ||
1637 | bfq_clear_bfqq_wait_request(in_serv_bfqq); | |
1638 | hrtimer_try_to_cancel(&bfqd->idle_slice_timer); | |
1639 | bfqd->in_service_queue = NULL; | |
1640 | ||
1641 | /* | |
1642 | * in_serv_entity is no longer in service, so, if it is in no | |
1643 | * service tree either, then release the service reference to | |
1644 | * the queue it represents (taken with bfq_get_entity). | |
1645 | */ | |
1646 | if (!in_serv_entity->on_st) | |
1647 | bfq_put_queue(in_serv_bfqq); | |
1648 | } | |
1649 | ||
1650 | static void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, | |
1651 | int requeue) | |
1652 | { | |
1653 | struct bfq_entity *entity = &bfqq->entity; | |
1654 | ||
1655 | bfq_deactivate_entity(entity, requeue); | |
1656 | } | |
1657 | ||
1658 | static void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq) | |
1659 | { | |
1660 | struct bfq_entity *entity = &bfqq->entity; | |
1661 | ||
1662 | bfq_activate_entity(entity, bfq_bfqq_non_blocking_wait_rq(bfqq)); | |
1663 | bfq_clear_bfqq_non_blocking_wait_rq(bfqq); | |
1664 | } | |
1665 | ||
1666 | /* | |
1667 | * Called when the bfqq no longer has requests pending, remove it from | |
1668 | * the service tree. | |
1669 | */ | |
1670 | static void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq, | |
1671 | int requeue) | |
1672 | { | |
1673 | bfq_log_bfqq(bfqd, bfqq, "del from busy"); | |
1674 | ||
1675 | bfq_clear_bfqq_busy(bfqq); | |
1676 | ||
1677 | bfqd->busy_queues--; | |
1678 | ||
1679 | bfq_deactivate_bfqq(bfqd, bfqq, requeue); | |
1680 | } | |
1681 | ||
1682 | /* | |
1683 | * Called when an inactive queue receives a new request. | |
1684 | */ | |
1685 | static void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq) | |
1686 | { | |
1687 | bfq_log_bfqq(bfqd, bfqq, "add to busy"); | |
1688 | ||
1689 | bfq_activate_bfqq(bfqd, bfqq); | |
1690 | ||
1691 | bfq_mark_bfqq_busy(bfqq); | |
1692 | bfqd->busy_queues++; | |
1693 | } | |
1694 | ||
1695 | static void bfq_init_entity(struct bfq_entity *entity) | |
1696 | { | |
1697 | struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); | |
1698 | ||
1699 | entity->weight = entity->new_weight; | |
1700 | entity->orig_weight = entity->new_weight; | |
1701 | ||
1702 | bfqq->ioprio = bfqq->new_ioprio; | |
1703 | bfqq->ioprio_class = bfqq->new_ioprio_class; | |
1704 | ||
1705 | entity->sched_data = &bfqq->bfqd->sched_data; | |
1706 | } | |
1707 | ||
1708 | #define bfq_class_idle(bfqq) ((bfqq)->ioprio_class == IOPRIO_CLASS_IDLE) | |
1709 | #define bfq_class_rt(bfqq) ((bfqq)->ioprio_class == IOPRIO_CLASS_RT) | |
1710 | ||
1711 | #define bfq_sample_valid(samples) ((samples) > 80) | |
1712 | ||
1713 | /* | |
1714 | * Scheduler run of queue, if there are requests pending and no one in the | |
1715 | * driver that will restart queueing. | |
1716 | */ | |
1717 | static void bfq_schedule_dispatch(struct bfq_data *bfqd) | |
1718 | { | |
1719 | if (bfqd->queued != 0) { | |
1720 | bfq_log(bfqd, "schedule dispatch"); | |
1721 | blk_mq_run_hw_queues(bfqd->queue, true); | |
1722 | } | |
1723 | } | |
1724 | ||
1725 | /* | |
1726 | * Lifted from AS - choose which of rq1 and rq2 that is best served now. | |
1727 | * We choose the request that is closesr to the head right now. Distance | |
1728 | * behind the head is penalized and only allowed to a certain extent. | |
1729 | */ | |
1730 | static struct request *bfq_choose_req(struct bfq_data *bfqd, | |
1731 | struct request *rq1, | |
1732 | struct request *rq2, | |
1733 | sector_t last) | |
1734 | { | |
1735 | sector_t s1, s2, d1 = 0, d2 = 0; | |
1736 | unsigned long back_max; | |
1737 | #define BFQ_RQ1_WRAP 0x01 /* request 1 wraps */ | |
1738 | #define BFQ_RQ2_WRAP 0x02 /* request 2 wraps */ | |
1739 | unsigned int wrap = 0; /* bit mask: requests behind the disk head? */ | |
1740 | ||
1741 | if (!rq1 || rq1 == rq2) | |
1742 | return rq2; | |
1743 | if (!rq2) | |
1744 | return rq1; | |
1745 | ||
1746 | if (rq_is_sync(rq1) && !rq_is_sync(rq2)) | |
1747 | return rq1; | |
1748 | else if (rq_is_sync(rq2) && !rq_is_sync(rq1)) | |
1749 | return rq2; | |
1750 | if ((rq1->cmd_flags & REQ_META) && !(rq2->cmd_flags & REQ_META)) | |
1751 | return rq1; | |
1752 | else if ((rq2->cmd_flags & REQ_META) && !(rq1->cmd_flags & REQ_META)) | |
1753 | return rq2; | |
1754 | ||
1755 | s1 = blk_rq_pos(rq1); | |
1756 | s2 = blk_rq_pos(rq2); | |
1757 | ||
1758 | /* | |
1759 | * By definition, 1KiB is 2 sectors. | |
1760 | */ | |
1761 | back_max = bfqd->bfq_back_max * 2; | |
1762 | ||
1763 | /* | |
1764 | * Strict one way elevator _except_ in the case where we allow | |
1765 | * short backward seeks which are biased as twice the cost of a | |
1766 | * similar forward seek. | |
1767 | */ | |
1768 | if (s1 >= last) | |
1769 | d1 = s1 - last; | |
1770 | else if (s1 + back_max >= last) | |
1771 | d1 = (last - s1) * bfqd->bfq_back_penalty; | |
1772 | else | |
1773 | wrap |= BFQ_RQ1_WRAP; | |
1774 | ||
1775 | if (s2 >= last) | |
1776 | d2 = s2 - last; | |
1777 | else if (s2 + back_max >= last) | |
1778 | d2 = (last - s2) * bfqd->bfq_back_penalty; | |
1779 | else | |
1780 | wrap |= BFQ_RQ2_WRAP; | |
1781 | ||
1782 | /* Found required data */ | |
1783 | ||
1784 | /* | |
1785 | * By doing switch() on the bit mask "wrap" we avoid having to | |
1786 | * check two variables for all permutations: --> faster! | |
1787 | */ | |
1788 | switch (wrap) { | |
1789 | case 0: /* common case for CFQ: rq1 and rq2 not wrapped */ | |
1790 | if (d1 < d2) | |
1791 | return rq1; | |
1792 | else if (d2 < d1) | |
1793 | return rq2; | |
1794 | ||
1795 | if (s1 >= s2) | |
1796 | return rq1; | |
1797 | else | |
1798 | return rq2; | |
1799 | ||
1800 | case BFQ_RQ2_WRAP: | |
1801 | return rq1; | |
1802 | case BFQ_RQ1_WRAP: | |
1803 | return rq2; | |
1804 | case BFQ_RQ1_WRAP|BFQ_RQ2_WRAP: /* both rqs wrapped */ | |
1805 | default: | |
1806 | /* | |
1807 | * Since both rqs are wrapped, | |
1808 | * start with the one that's further behind head | |
1809 | * (--> only *one* back seek required), | |
1810 | * since back seek takes more time than forward. | |
1811 | */ | |
1812 | if (s1 <= s2) | |
1813 | return rq1; | |
1814 | else | |
1815 | return rq2; | |
1816 | } | |
1817 | } | |
1818 | ||
1819 | /* | |
1820 | * Return expired entry, or NULL to just start from scratch in rbtree. | |
1821 | */ | |
1822 | static struct request *bfq_check_fifo(struct bfq_queue *bfqq, | |
1823 | struct request *last) | |
1824 | { | |
1825 | struct request *rq; | |
1826 | ||
1827 | if (bfq_bfqq_fifo_expire(bfqq)) | |
1828 | return NULL; | |
1829 | ||
1830 | bfq_mark_bfqq_fifo_expire(bfqq); | |
1831 | ||
1832 | rq = rq_entry_fifo(bfqq->fifo.next); | |
1833 | ||
1834 | if (rq == last || ktime_get_ns() < rq->fifo_time) | |
1835 | return NULL; | |
1836 | ||
1837 | bfq_log_bfqq(bfqq->bfqd, bfqq, "check_fifo: returned %p", rq); | |
1838 | return rq; | |
1839 | } | |
1840 | ||
1841 | static struct request *bfq_find_next_rq(struct bfq_data *bfqd, | |
1842 | struct bfq_queue *bfqq, | |
1843 | struct request *last) | |
1844 | { | |
1845 | struct rb_node *rbnext = rb_next(&last->rb_node); | |
1846 | struct rb_node *rbprev = rb_prev(&last->rb_node); | |
1847 | struct request *next, *prev = NULL; | |
1848 | ||
1849 | /* Follow expired path, else get first next available. */ | |
1850 | next = bfq_check_fifo(bfqq, last); | |
1851 | if (next) | |
1852 | return next; | |
1853 | ||
1854 | if (rbprev) | |
1855 | prev = rb_entry_rq(rbprev); | |
1856 | ||
1857 | if (rbnext) | |
1858 | next = rb_entry_rq(rbnext); | |
1859 | else { | |
1860 | rbnext = rb_first(&bfqq->sort_list); | |
1861 | if (rbnext && rbnext != &last->rb_node) | |
1862 | next = rb_entry_rq(rbnext); | |
1863 | } | |
1864 | ||
1865 | return bfq_choose_req(bfqd, next, prev, blk_rq_pos(last)); | |
1866 | } | |
1867 | ||
1868 | static unsigned long bfq_serv_to_charge(struct request *rq, | |
1869 | struct bfq_queue *bfqq) | |
1870 | { | |
1871 | return blk_rq_sectors(rq); | |
1872 | } | |
1873 | ||
1874 | /** | |
1875 | * bfq_updated_next_req - update the queue after a new next_rq selection. | |
1876 | * @bfqd: the device data the queue belongs to. | |
1877 | * @bfqq: the queue to update. | |
1878 | * | |
1879 | * If the first request of a queue changes we make sure that the queue | |
1880 | * has enough budget to serve at least its first request (if the | |
1881 | * request has grown). We do this because if the queue has not enough | |
1882 | * budget for its first request, it has to go through two dispatch | |
1883 | * rounds to actually get it dispatched. | |
1884 | */ | |
1885 | static void bfq_updated_next_req(struct bfq_data *bfqd, | |
1886 | struct bfq_queue *bfqq) | |
1887 | { | |
1888 | struct bfq_entity *entity = &bfqq->entity; | |
1889 | struct request *next_rq = bfqq->next_rq; | |
1890 | unsigned long new_budget; | |
1891 | ||
1892 | if (!next_rq) | |
1893 | return; | |
1894 | ||
1895 | if (bfqq == bfqd->in_service_queue) | |
1896 | /* | |
1897 | * In order not to break guarantees, budgets cannot be | |
1898 | * changed after an entity has been selected. | |
1899 | */ | |
1900 | return; | |
1901 | ||
1902 | new_budget = max_t(unsigned long, bfqq->max_budget, | |
1903 | bfq_serv_to_charge(next_rq, bfqq)); | |
1904 | if (entity->budget != new_budget) { | |
1905 | entity->budget = new_budget; | |
1906 | bfq_log_bfqq(bfqd, bfqq, "updated next rq: new budget %lu", | |
1907 | new_budget); | |
1908 | bfq_activate_bfqq(bfqd, bfqq); | |
1909 | } | |
1910 | } | |
1911 | ||
1912 | static int bfq_bfqq_budget_left(struct bfq_queue *bfqq) | |
1913 | { | |
1914 | struct bfq_entity *entity = &bfqq->entity; | |
1915 | ||
1916 | return entity->budget - entity->service; | |
1917 | } | |
1918 | ||
1919 | /* | |
1920 | * If enough samples have been computed, return the current max budget | |
1921 | * stored in bfqd, which is dynamically updated according to the | |
1922 | * estimated disk peak rate; otherwise return the default max budget | |
1923 | */ | |
1924 | static int bfq_max_budget(struct bfq_data *bfqd) | |
1925 | { | |
1926 | if (bfqd->budgets_assigned < bfq_stats_min_budgets) | |
1927 | return bfq_default_max_budget; | |
1928 | else | |
1929 | return bfqd->bfq_max_budget; | |
1930 | } | |
1931 | ||
1932 | /* | |
1933 | * Return min budget, which is a fraction of the current or default | |
1934 | * max budget (trying with 1/32) | |
1935 | */ | |
1936 | static int bfq_min_budget(struct bfq_data *bfqd) | |
1937 | { | |
1938 | if (bfqd->budgets_assigned < bfq_stats_min_budgets) | |
1939 | return bfq_default_max_budget / 32; | |
1940 | else | |
1941 | return bfqd->bfq_max_budget / 32; | |
1942 | } | |
1943 | ||
1944 | static void bfq_bfqq_expire(struct bfq_data *bfqd, | |
1945 | struct bfq_queue *bfqq, | |
1946 | bool compensate, | |
1947 | enum bfqq_expiration reason); | |
1948 | ||
1949 | /* | |
1950 | * The next function, invoked after the input queue bfqq switches from | |
1951 | * idle to busy, updates the budget of bfqq. The function also tells | |
1952 | * whether the in-service queue should be expired, by returning | |
1953 | * true. The purpose of expiring the in-service queue is to give bfqq | |
1954 | * the chance to possibly preempt the in-service queue, and the reason | |
1955 | * for preempting the in-service queue is to achieve the following | |
1956 | * goal: guarantee to bfqq its reserved bandwidth even if bfqq has | |
1957 | * expired because it has remained idle. | |
1958 | * | |
1959 | * In particular, bfqq may have expired for one of the following two | |
1960 | * reasons: | |
1961 | * | |
1962 | * - BFQQE_NO_MORE_REQUESTS bfqq did not enjoy any device idling | |
1963 | * and did not make it to issue a new request before its last | |
1964 | * request was served; | |
1965 | * | |
1966 | * - BFQQE_TOO_IDLE bfqq did enjoy device idling, but did not issue | |
1967 | * a new request before the expiration of the idling-time. | |
1968 | * | |
1969 | * Even if bfqq has expired for one of the above reasons, the process | |
1970 | * associated with the queue may be however issuing requests greedily, | |
1971 | * and thus be sensitive to the bandwidth it receives (bfqq may have | |
1972 | * remained idle for other reasons: CPU high load, bfqq not enjoying | |
1973 | * idling, I/O throttling somewhere in the path from the process to | |
1974 | * the I/O scheduler, ...). But if, after every expiration for one of | |
1975 | * the above two reasons, bfqq has to wait for the service of at least | |
1976 | * one full budget of another queue before being served again, then | |
1977 | * bfqq is likely to get a much lower bandwidth or resource time than | |
1978 | * its reserved ones. To address this issue, two countermeasures need | |
1979 | * to be taken. | |
1980 | * | |
1981 | * First, the budget and the timestamps of bfqq need to be updated in | |
1982 | * a special way on bfqq reactivation: they need to be updated as if | |
1983 | * bfqq did not remain idle and did not expire. In fact, if they are | |
1984 | * computed as if bfqq expired and remained idle until reactivation, | |
1985 | * then the process associated with bfqq is treated as if, instead of | |
1986 | * being greedy, it stopped issuing requests when bfqq remained idle, | |
1987 | * and restarts issuing requests only on this reactivation. In other | |
1988 | * words, the scheduler does not help the process recover the "service | |
1989 | * hole" between bfqq expiration and reactivation. As a consequence, | |
1990 | * the process receives a lower bandwidth than its reserved one. In | |
1991 | * contrast, to recover this hole, the budget must be updated as if | |
1992 | * bfqq was not expired at all before this reactivation, i.e., it must | |
1993 | * be set to the value of the remaining budget when bfqq was | |
1994 | * expired. Along the same line, timestamps need to be assigned the | |
1995 | * value they had the last time bfqq was selected for service, i.e., | |
1996 | * before last expiration. Thus timestamps need to be back-shifted | |
1997 | * with respect to their normal computation (see [1] for more details | |
1998 | * on this tricky aspect). | |
1999 | * | |
2000 | * Secondly, to allow the process to recover the hole, the in-service | |
2001 | * queue must be expired too, to give bfqq the chance to preempt it | |
2002 | * immediately. In fact, if bfqq has to wait for a full budget of the | |
2003 | * in-service queue to be completed, then it may become impossible to | |
2004 | * let the process recover the hole, even if the back-shifted | |
2005 | * timestamps of bfqq are lower than those of the in-service queue. If | |
2006 | * this happens for most or all of the holes, then the process may not | |
2007 | * receive its reserved bandwidth. In this respect, it is worth noting | |
2008 | * that, being the service of outstanding requests unpreemptible, a | |
2009 | * little fraction of the holes may however be unrecoverable, thereby | |
2010 | * causing a little loss of bandwidth. | |
2011 | * | |
2012 | * The last important point is detecting whether bfqq does need this | |
2013 | * bandwidth recovery. In this respect, the next function deems the | |
2014 | * process associated with bfqq greedy, and thus allows it to recover | |
2015 | * the hole, if: 1) the process is waiting for the arrival of a new | |
2016 | * request (which implies that bfqq expired for one of the above two | |
2017 | * reasons), and 2) such a request has arrived soon. The first | |
2018 | * condition is controlled through the flag non_blocking_wait_rq, | |
2019 | * while the second through the flag arrived_in_time. If both | |
2020 | * conditions hold, then the function computes the budget in the | |
2021 | * above-described special way, and signals that the in-service queue | |
2022 | * should be expired. Timestamp back-shifting is done later in | |
2023 | * __bfq_activate_entity. | |
2024 | */ | |
2025 | static bool bfq_bfqq_update_budg_for_activation(struct bfq_data *bfqd, | |
2026 | struct bfq_queue *bfqq, | |
2027 | bool arrived_in_time) | |
2028 | { | |
2029 | struct bfq_entity *entity = &bfqq->entity; | |
2030 | ||
2031 | if (bfq_bfqq_non_blocking_wait_rq(bfqq) && arrived_in_time) { | |
2032 | /* | |
2033 | * We do not clear the flag non_blocking_wait_rq here, as | |
2034 | * the latter is used in bfq_activate_bfqq to signal | |
2035 | * that timestamps need to be back-shifted (and is | |
2036 | * cleared right after). | |
2037 | */ | |
2038 | ||
2039 | /* | |
2040 | * In next assignment we rely on that either | |
2041 | * entity->service or entity->budget are not updated | |
2042 | * on expiration if bfqq is empty (see | |
2043 | * __bfq_bfqq_recalc_budget). Thus both quantities | |
2044 | * remain unchanged after such an expiration, and the | |
2045 | * following statement therefore assigns to | |
2046 | * entity->budget the remaining budget on such an | |
2047 | * expiration. For clarity, entity->service is not | |
2048 | * updated on expiration in any case, and, in normal | |
2049 | * operation, is reset only when bfqq is selected for | |
2050 | * service (see bfq_get_next_queue). | |
2051 | */ | |
2052 | entity->budget = min_t(unsigned long, | |
2053 | bfq_bfqq_budget_left(bfqq), | |
2054 | bfqq->max_budget); | |
2055 | ||
2056 | return true; | |
2057 | } | |
2058 | ||
2059 | entity->budget = max_t(unsigned long, bfqq->max_budget, | |
2060 | bfq_serv_to_charge(bfqq->next_rq, bfqq)); | |
2061 | bfq_clear_bfqq_non_blocking_wait_rq(bfqq); | |
2062 | return false; | |
2063 | } | |
2064 | ||
2065 | static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, | |
2066 | struct bfq_queue *bfqq, | |
2067 | struct request *rq) | |
2068 | { | |
2069 | bool bfqq_wants_to_preempt, | |
2070 | /* | |
2071 | * See the comments on | |
2072 | * bfq_bfqq_update_budg_for_activation for | |
2073 | * details on the usage of the next variable. | |
2074 | */ | |
2075 | arrived_in_time = ktime_get_ns() <= | |
2076 | bfqq->ttime.last_end_request + | |
2077 | bfqd->bfq_slice_idle * 3; | |
2078 | ||
2079 | /* | |
2080 | * Update budget and check whether bfqq may want to preempt | |
2081 | * the in-service queue. | |
2082 | */ | |
2083 | bfqq_wants_to_preempt = | |
2084 | bfq_bfqq_update_budg_for_activation(bfqd, bfqq, | |
2085 | arrived_in_time); | |
2086 | ||
2087 | if (!bfq_bfqq_IO_bound(bfqq)) { | |
2088 | if (arrived_in_time) { | |
2089 | bfqq->requests_within_timer++; | |
2090 | if (bfqq->requests_within_timer >= | |
2091 | bfqd->bfq_requests_within_timer) | |
2092 | bfq_mark_bfqq_IO_bound(bfqq); | |
2093 | } else | |
2094 | bfqq->requests_within_timer = 0; | |
2095 | } | |
2096 | ||
2097 | bfq_add_bfqq_busy(bfqd, bfqq); | |
2098 | ||
2099 | /* | |
2100 | * Expire in-service queue only if preemption may be needed | |
2101 | * for guarantees. In this respect, the function | |
2102 | * next_queue_may_preempt just checks a simple, necessary | |
2103 | * condition, and not a sufficient condition based on | |
2104 | * timestamps. In fact, for the latter condition to be | |
2105 | * evaluated, timestamps would need first to be updated, and | |
2106 | * this operation is quite costly (see the comments on the | |
2107 | * function bfq_bfqq_update_budg_for_activation). | |
2108 | */ | |
2109 | if (bfqd->in_service_queue && bfqq_wants_to_preempt && | |
2110 | next_queue_may_preempt(bfqd)) | |
2111 | bfq_bfqq_expire(bfqd, bfqd->in_service_queue, | |
2112 | false, BFQQE_PREEMPTED); | |
2113 | } | |
2114 | ||
2115 | static void bfq_add_request(struct request *rq) | |
2116 | { | |
2117 | struct bfq_queue *bfqq = RQ_BFQQ(rq); | |
2118 | struct bfq_data *bfqd = bfqq->bfqd; | |
2119 | struct request *next_rq, *prev; | |
2120 | ||
2121 | bfq_log_bfqq(bfqd, bfqq, "add_request %d", rq_is_sync(rq)); | |
2122 | bfqq->queued[rq_is_sync(rq)]++; | |
2123 | bfqd->queued++; | |
2124 | ||
2125 | elv_rb_add(&bfqq->sort_list, rq); | |
2126 | ||
2127 | /* | |
2128 | * Check if this request is a better next-serve candidate. | |
2129 | */ | |
2130 | prev = bfqq->next_rq; | |
2131 | next_rq = bfq_choose_req(bfqd, bfqq->next_rq, rq, bfqd->last_position); | |
2132 | bfqq->next_rq = next_rq; | |
2133 | ||
2134 | if (!bfq_bfqq_busy(bfqq)) /* switching to busy ... */ | |
2135 | bfq_bfqq_handle_idle_busy_switch(bfqd, bfqq, rq); | |
2136 | else if (prev != bfqq->next_rq) | |
2137 | bfq_updated_next_req(bfqd, bfqq); | |
2138 | } | |
2139 | ||
2140 | static struct request *bfq_find_rq_fmerge(struct bfq_data *bfqd, | |
2141 | struct bio *bio, | |
2142 | struct request_queue *q) | |
2143 | { | |
2144 | struct bfq_queue *bfqq = bfqd->bio_bfqq; | |
2145 | ||
2146 | ||
2147 | if (bfqq) | |
2148 | return elv_rb_find(&bfqq->sort_list, bio_end_sector(bio)); | |
2149 | ||
2150 | return NULL; | |
2151 | } | |
2152 | ||
2153 | #if 0 /* Still not clear if we can do without next two functions */ | |
2154 | static void bfq_activate_request(struct request_queue *q, struct request *rq) | |
2155 | { | |
2156 | struct bfq_data *bfqd = q->elevator->elevator_data; | |
2157 | ||
2158 | bfqd->rq_in_driver++; | |
2159 | bfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq); | |
2160 | bfq_log(bfqd, "activate_request: new bfqd->last_position %llu", | |
2161 | (unsigned long long)bfqd->last_position); | |
2162 | } | |
2163 | ||
2164 | static void bfq_deactivate_request(struct request_queue *q, struct request *rq) | |
2165 | { | |
2166 | struct bfq_data *bfqd = q->elevator->elevator_data; | |
2167 | ||
2168 | bfqd->rq_in_driver--; | |
2169 | } | |
2170 | #endif | |
2171 | ||
2172 | static void bfq_remove_request(struct request_queue *q, | |
2173 | struct request *rq) | |
2174 | { | |
2175 | struct bfq_queue *bfqq = RQ_BFQQ(rq); | |
2176 | struct bfq_data *bfqd = bfqq->bfqd; | |
2177 | const int sync = rq_is_sync(rq); | |
2178 | ||
2179 | if (bfqq->next_rq == rq) { | |
2180 | bfqq->next_rq = bfq_find_next_rq(bfqd, bfqq, rq); | |
2181 | bfq_updated_next_req(bfqd, bfqq); | |
2182 | } | |
2183 | ||
2184 | if (rq->queuelist.prev != &rq->queuelist) | |
2185 | list_del_init(&rq->queuelist); | |
2186 | bfqq->queued[sync]--; | |
2187 | bfqd->queued--; | |
2188 | elv_rb_del(&bfqq->sort_list, rq); | |
2189 | ||
2190 | elv_rqhash_del(q, rq); | |
2191 | if (q->last_merge == rq) | |
2192 | q->last_merge = NULL; | |
2193 | ||
2194 | if (RB_EMPTY_ROOT(&bfqq->sort_list)) { | |
2195 | bfqq->next_rq = NULL; | |
2196 | ||
2197 | if (bfq_bfqq_busy(bfqq) && bfqq != bfqd->in_service_queue) { | |
2198 | bfq_del_bfqq_busy(bfqd, bfqq, 1); | |
2199 | /* | |
2200 | * bfqq emptied. In normal operation, when | |
2201 | * bfqq is empty, bfqq->entity.service and | |
2202 | * bfqq->entity.budget must contain, | |
2203 | * respectively, the service received and the | |
2204 | * budget used last time bfqq emptied. These | |
2205 | * facts do not hold in this case, as at least | |
2206 | * this last removal occurred while bfqq is | |
2207 | * not in service. To avoid inconsistencies, | |
2208 | * reset both bfqq->entity.service and | |
2209 | * bfqq->entity.budget, if bfqq has still a | |
2210 | * process that may issue I/O requests to it. | |
2211 | */ | |
2212 | bfqq->entity.budget = bfqq->entity.service = 0; | |
2213 | } | |
2214 | } | |
2215 | ||
2216 | if (rq->cmd_flags & REQ_META) | |
2217 | bfqq->meta_pending--; | |
2218 | } | |
2219 | ||
2220 | static bool bfq_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio) | |
2221 | { | |
2222 | struct request_queue *q = hctx->queue; | |
2223 | struct bfq_data *bfqd = q->elevator->elevator_data; | |
2224 | struct request *free = NULL; | |
2225 | /* | |
2226 | * bfq_bic_lookup grabs the queue_lock: invoke it now and | |
2227 | * store its return value for later use, to avoid nesting | |
2228 | * queue_lock inside the bfqd->lock. We assume that the bic | |
2229 | * returned by bfq_bic_lookup does not go away before | |
2230 | * bfqd->lock is taken. | |
2231 | */ | |
2232 | struct bfq_io_cq *bic = bfq_bic_lookup(bfqd, current->io_context, q); | |
2233 | bool ret; | |
2234 | ||
2235 | spin_lock_irq(&bfqd->lock); | |
2236 | ||
2237 | if (bic) | |
2238 | bfqd->bio_bfqq = bic_to_bfqq(bic, op_is_sync(bio->bi_opf)); | |
2239 | else | |
2240 | bfqd->bio_bfqq = NULL; | |
2241 | bfqd->bio_bic = bic; | |
2242 | ||
2243 | ret = blk_mq_sched_try_merge(q, bio, &free); | |
2244 | ||
2245 | if (free) | |
2246 | blk_mq_free_request(free); | |
2247 | spin_unlock_irq(&bfqd->lock); | |
2248 | ||
2249 | return ret; | |
2250 | } | |
2251 | ||
2252 | static int bfq_request_merge(struct request_queue *q, struct request **req, | |
2253 | struct bio *bio) | |
2254 | { | |
2255 | struct bfq_data *bfqd = q->elevator->elevator_data; | |
2256 | struct request *__rq; | |
2257 | ||
2258 | __rq = bfq_find_rq_fmerge(bfqd, bio, q); | |
2259 | if (__rq && elv_bio_merge_ok(__rq, bio)) { | |
2260 | *req = __rq; | |
2261 | return ELEVATOR_FRONT_MERGE; | |
2262 | } | |
2263 | ||
2264 | return ELEVATOR_NO_MERGE; | |
2265 | } | |
2266 | ||
2267 | static void bfq_request_merged(struct request_queue *q, struct request *req, | |
2268 | enum elv_merge type) | |
2269 | { | |
2270 | if (type == ELEVATOR_FRONT_MERGE && | |
2271 | rb_prev(&req->rb_node) && | |
2272 | blk_rq_pos(req) < | |
2273 | blk_rq_pos(container_of(rb_prev(&req->rb_node), | |
2274 | struct request, rb_node))) { | |
2275 | struct bfq_queue *bfqq = RQ_BFQQ(req); | |
2276 | struct bfq_data *bfqd = bfqq->bfqd; | |
2277 | struct request *prev, *next_rq; | |
2278 | ||
2279 | /* Reposition request in its sort_list */ | |
2280 | elv_rb_del(&bfqq->sort_list, req); | |
2281 | elv_rb_add(&bfqq->sort_list, req); | |
2282 | ||
2283 | /* Choose next request to be served for bfqq */ | |
2284 | prev = bfqq->next_rq; | |
2285 | next_rq = bfq_choose_req(bfqd, bfqq->next_rq, req, | |
2286 | bfqd->last_position); | |
2287 | bfqq->next_rq = next_rq; | |
2288 | /* | |
2289 | * If next_rq changes, update the queue's budget to fit | |
2290 | * the new request. | |
2291 | */ | |
2292 | if (prev != bfqq->next_rq) | |
2293 | bfq_updated_next_req(bfqd, bfqq); | |
2294 | } | |
2295 | } | |
2296 | ||
2297 | static void bfq_requests_merged(struct request_queue *q, struct request *rq, | |
2298 | struct request *next) | |
2299 | { | |
2300 | struct bfq_queue *bfqq = RQ_BFQQ(rq), *next_bfqq = RQ_BFQQ(next); | |
2301 | ||
2302 | if (!RB_EMPTY_NODE(&rq->rb_node)) | |
2303 | return; | |
2304 | spin_lock_irq(&bfqq->bfqd->lock); | |
2305 | ||
2306 | /* | |
2307 | * If next and rq belong to the same bfq_queue and next is older | |
2308 | * than rq, then reposition rq in the fifo (by substituting next | |
2309 | * with rq). Otherwise, if next and rq belong to different | |
2310 | * bfq_queues, never reposition rq: in fact, we would have to | |
2311 | * reposition it with respect to next's position in its own fifo, | |
2312 | * which would most certainly be too expensive with respect to | |
2313 | * the benefits. | |
2314 | */ | |
2315 | if (bfqq == next_bfqq && | |
2316 | !list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && | |
2317 | next->fifo_time < rq->fifo_time) { | |
2318 | list_del_init(&rq->queuelist); | |
2319 | list_replace_init(&next->queuelist, &rq->queuelist); | |
2320 | rq->fifo_time = next->fifo_time; | |
2321 | } | |
2322 | ||
2323 | if (bfqq->next_rq == next) | |
2324 | bfqq->next_rq = rq; | |
2325 | ||
2326 | bfq_remove_request(q, next); | |
2327 | ||
2328 | spin_unlock_irq(&bfqq->bfqd->lock); | |
2329 | } | |
2330 | ||
2331 | static bool bfq_allow_bio_merge(struct request_queue *q, struct request *rq, | |
2332 | struct bio *bio) | |
2333 | { | |
2334 | struct bfq_data *bfqd = q->elevator->elevator_data; | |
2335 | bool is_sync = op_is_sync(bio->bi_opf); | |
2336 | struct bfq_queue *bfqq = bfqd->bio_bfqq; | |
2337 | ||
2338 | /* | |
2339 | * Disallow merge of a sync bio into an async request. | |
2340 | */ | |
2341 | if (is_sync && !rq_is_sync(rq)) | |
2342 | return false; | |
2343 | ||
2344 | /* | |
2345 | * Lookup the bfqq that this bio will be queued with. Allow | |
2346 | * merge only if rq is queued there. | |
2347 | */ | |
2348 | if (!bfqq) | |
2349 | return false; | |
2350 | ||
2351 | return bfqq == RQ_BFQQ(rq); | |
2352 | } | |
2353 | ||
2354 | static void __bfq_set_in_service_queue(struct bfq_data *bfqd, | |
2355 | struct bfq_queue *bfqq) | |
2356 | { | |
2357 | if (bfqq) { | |
2358 | bfq_mark_bfqq_budget_new(bfqq); | |
2359 | bfq_clear_bfqq_fifo_expire(bfqq); | |
2360 | ||
2361 | bfqd->budgets_assigned = (bfqd->budgets_assigned * 7 + 256) / 8; | |
2362 | ||
2363 | bfq_log_bfqq(bfqd, bfqq, | |
2364 | "set_in_service_queue, cur-budget = %d", | |
2365 | bfqq->entity.budget); | |
2366 | } | |
2367 | ||
2368 | bfqd->in_service_queue = bfqq; | |
2369 | } | |
2370 | ||
2371 | /* | |
2372 | * Get and set a new queue for service. | |
2373 | */ | |
2374 | static struct bfq_queue *bfq_set_in_service_queue(struct bfq_data *bfqd) | |
2375 | { | |
2376 | struct bfq_queue *bfqq = bfq_get_next_queue(bfqd); | |
2377 | ||
2378 | __bfq_set_in_service_queue(bfqd, bfqq); | |
2379 | return bfqq; | |
2380 | } | |
2381 | ||
2382 | /* | |
2383 | * bfq_default_budget - return the default budget for @bfqq on @bfqd. | |
2384 | * @bfqd: the device descriptor. | |
2385 | * @bfqq: the queue to consider. | |
2386 | * | |
2387 | * We use 3/4 of the @bfqd maximum budget as the default value | |
2388 | * for the max_budget field of the queues. This lets the feedback | |
2389 | * mechanism to start from some middle ground, then the behavior | |
2390 | * of the process will drive the heuristics towards high values, if | |
2391 | * it behaves as a greedy sequential reader, or towards small values | |
2392 | * if it shows a more intermittent behavior. | |
2393 | */ | |
2394 | static unsigned long bfq_default_budget(struct bfq_data *bfqd, | |
2395 | struct bfq_queue *bfqq) | |
2396 | { | |
2397 | unsigned long budget; | |
2398 | ||
2399 | /* | |
2400 | * When we need an estimate of the peak rate we need to avoid | |
2401 | * to give budgets that are too short due to previous | |
2402 | * measurements. So, in the first 10 assignments use a | |
2403 | * ``safe'' budget value. For such first assignment the value | |
2404 | * of bfqd->budgets_assigned happens to be lower than 194. | |
2405 | * See __bfq_set_in_service_queue for the formula by which | |
2406 | * this field is computed. | |
2407 | */ | |
2408 | if (bfqd->budgets_assigned < 194 && bfqd->bfq_user_max_budget == 0) | |
2409 | budget = bfq_default_max_budget; | |
2410 | else | |
2411 | budget = bfqd->bfq_max_budget; | |
2412 | ||
2413 | return budget - budget / 4; | |
2414 | } | |
2415 | ||
2416 | static void bfq_arm_slice_timer(struct bfq_data *bfqd) | |
2417 | { | |
2418 | struct bfq_queue *bfqq = bfqd->in_service_queue; | |
2419 | struct bfq_io_cq *bic; | |
2420 | u32 sl; | |
2421 | ||
2422 | /* Processes have exited, don't wait. */ | |
2423 | bic = bfqd->in_service_bic; | |
2424 | if (!bic || atomic_read(&bic->icq.ioc->active_ref) == 0) | |
2425 | return; | |
2426 | ||
2427 | bfq_mark_bfqq_wait_request(bfqq); | |
2428 | ||
2429 | /* | |
2430 | * We don't want to idle for seeks, but we do want to allow | |
2431 | * fair distribution of slice time for a process doing back-to-back | |
2432 | * seeks. So allow a little bit of time for him to submit a new rq. | |
2433 | */ | |
2434 | sl = bfqd->bfq_slice_idle; | |
2435 | /* | |
2436 | * Grant only minimum idle time if the queue is seeky. | |
2437 | */ | |
2438 | if (BFQQ_SEEKY(bfqq)) | |
2439 | sl = min_t(u64, sl, BFQ_MIN_TT); | |
2440 | ||
2441 | bfqd->last_idling_start = ktime_get(); | |
2442 | hrtimer_start(&bfqd->idle_slice_timer, ns_to_ktime(sl), | |
2443 | HRTIMER_MODE_REL); | |
2444 | } | |
2445 | ||
2446 | /* | |
2447 | * Set the maximum time for the in-service queue to consume its | |
2448 | * budget. This prevents seeky processes from lowering the disk | |
2449 | * throughput (always guaranteed with a time slice scheme as in CFQ). | |
2450 | */ | |
2451 | static void bfq_set_budget_timeout(struct bfq_data *bfqd) | |
2452 | { | |
2453 | struct bfq_queue *bfqq = bfqd->in_service_queue; | |
2454 | unsigned int timeout_coeff = bfqq->entity.weight / | |
2455 | bfqq->entity.orig_weight; | |
2456 | ||
2457 | bfqd->last_budget_start = ktime_get(); | |
2458 | ||
2459 | bfq_clear_bfqq_budget_new(bfqq); | |
2460 | bfqq->budget_timeout = jiffies + | |
2461 | bfqd->bfq_timeout * timeout_coeff; | |
2462 | ||
2463 | bfq_log_bfqq(bfqd, bfqq, "set budget_timeout %u", | |
2464 | jiffies_to_msecs(bfqd->bfq_timeout * timeout_coeff)); | |
2465 | } | |
2466 | ||
2467 | /* | |
2468 | * Remove request from internal lists. | |
2469 | */ | |
2470 | static void bfq_dispatch_remove(struct request_queue *q, struct request *rq) | |
2471 | { | |
2472 | struct bfq_queue *bfqq = RQ_BFQQ(rq); | |
2473 | ||
2474 | /* | |
2475 | * For consistency, the next instruction should have been | |
2476 | * executed after removing the request from the queue and | |
2477 | * dispatching it. We execute instead this instruction before | |
2478 | * bfq_remove_request() (and hence introduce a temporary | |
2479 | * inconsistency), for efficiency. In fact, should this | |
2480 | * dispatch occur for a non in-service bfqq, this anticipated | |
2481 | * increment prevents two counters related to bfqq->dispatched | |
2482 | * from risking to be, first, uselessly decremented, and then | |
2483 | * incremented again when the (new) value of bfqq->dispatched | |
2484 | * happens to be taken into account. | |
2485 | */ | |
2486 | bfqq->dispatched++; | |
2487 | ||
2488 | bfq_remove_request(q, rq); | |
2489 | } | |
2490 | ||
2491 | static void __bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq) | |
2492 | { | |
2493 | __bfq_bfqd_reset_in_service(bfqd); | |
2494 | ||
2495 | if (RB_EMPTY_ROOT(&bfqq->sort_list)) | |
2496 | bfq_del_bfqq_busy(bfqd, bfqq, 1); | |
2497 | else | |
2498 | bfq_activate_bfqq(bfqd, bfqq); | |
2499 | } | |
2500 | ||
2501 | /** | |
2502 | * __bfq_bfqq_recalc_budget - try to adapt the budget to the @bfqq behavior. | |
2503 | * @bfqd: device data. | |
2504 | * @bfqq: queue to update. | |
2505 | * @reason: reason for expiration. | |
2506 | * | |
2507 | * Handle the feedback on @bfqq budget at queue expiration. | |
2508 | * See the body for detailed comments. | |
2509 | */ | |
2510 | static void __bfq_bfqq_recalc_budget(struct bfq_data *bfqd, | |
2511 | struct bfq_queue *bfqq, | |
2512 | enum bfqq_expiration reason) | |
2513 | { | |
2514 | struct request *next_rq; | |
2515 | int budget, min_budget; | |
2516 | ||
2517 | budget = bfqq->max_budget; | |
2518 | min_budget = bfq_min_budget(bfqd); | |
2519 | ||
2520 | bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last budg %d, budg left %d", | |
2521 | bfqq->entity.budget, bfq_bfqq_budget_left(bfqq)); | |
2522 | bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last max_budg %d, min budg %d", | |
2523 | budget, bfq_min_budget(bfqd)); | |
2524 | bfq_log_bfqq(bfqd, bfqq, "recalc_budg: sync %d, seeky %d", | |
2525 | bfq_bfqq_sync(bfqq), BFQQ_SEEKY(bfqd->in_service_queue)); | |
2526 | ||
2527 | if (bfq_bfqq_sync(bfqq)) { | |
2528 | switch (reason) { | |
2529 | /* | |
2530 | * Caveat: in all the following cases we trade latency | |
2531 | * for throughput. | |
2532 | */ | |
2533 | case BFQQE_TOO_IDLE: | |
2534 | if (budget > min_budget + BFQ_BUDGET_STEP) | |
2535 | budget -= BFQ_BUDGET_STEP; | |
2536 | else | |
2537 | budget = min_budget; | |
2538 | break; | |
2539 | case BFQQE_BUDGET_TIMEOUT: | |
2540 | budget = bfq_default_budget(bfqd, bfqq); | |
2541 | break; | |
2542 | case BFQQE_BUDGET_EXHAUSTED: | |
2543 | /* | |
2544 | * The process still has backlog, and did not | |
2545 | * let either the budget timeout or the disk | |
2546 | * idling timeout expire. Hence it is not | |
2547 | * seeky, has a short thinktime and may be | |
2548 | * happy with a higher budget too. So | |
2549 | * definitely increase the budget of this good | |
2550 | * candidate to boost the disk throughput. | |
2551 | */ | |
2552 | budget = min(budget + 8 * BFQ_BUDGET_STEP, | |
2553 | bfqd->bfq_max_budget); | |
2554 | break; | |
2555 | case BFQQE_NO_MORE_REQUESTS: | |
2556 | /* | |
2557 | * For queues that expire for this reason, it | |
2558 | * is particularly important to keep the | |
2559 | * budget close to the actual service they | |
2560 | * need. Doing so reduces the timestamp | |
2561 | * misalignment problem described in the | |
2562 | * comments in the body of | |
2563 | * __bfq_activate_entity. In fact, suppose | |
2564 | * that a queue systematically expires for | |
2565 | * BFQQE_NO_MORE_REQUESTS and presents a | |
2566 | * new request in time to enjoy timestamp | |
2567 | * back-shifting. The larger the budget of the | |
2568 | * queue is with respect to the service the | |
2569 | * queue actually requests in each service | |
2570 | * slot, the more times the queue can be | |
2571 | * reactivated with the same virtual finish | |
2572 | * time. It follows that, even if this finish | |
2573 | * time is pushed to the system virtual time | |
2574 | * to reduce the consequent timestamp | |
2575 | * misalignment, the queue unjustly enjoys for | |
2576 | * many re-activations a lower finish time | |
2577 | * than all newly activated queues. | |
2578 | * | |
2579 | * The service needed by bfqq is measured | |
2580 | * quite precisely by bfqq->entity.service. | |
2581 | * Since bfqq does not enjoy device idling, | |
2582 | * bfqq->entity.service is equal to the number | |
2583 | * of sectors that the process associated with | |
2584 | * bfqq requested to read/write before waiting | |
2585 | * for request completions, or blocking for | |
2586 | * other reasons. | |
2587 | */ | |
2588 | budget = max_t(int, bfqq->entity.service, min_budget); | |
2589 | break; | |
2590 | default: | |
2591 | return; | |
2592 | } | |
2593 | } else { | |
2594 | /* | |
2595 | * Async queues get always the maximum possible | |
2596 | * budget, as for them we do not care about latency | |
2597 | * (in addition, their ability to dispatch is limited | |
2598 | * by the charging factor). | |
2599 | */ | |
2600 | budget = bfqd->bfq_max_budget; | |
2601 | } | |
2602 | ||
2603 | bfqq->max_budget = budget; | |
2604 | ||
2605 | if (bfqd->budgets_assigned >= bfq_stats_min_budgets && | |
2606 | !bfqd->bfq_user_max_budget) | |
2607 | bfqq->max_budget = min(bfqq->max_budget, bfqd->bfq_max_budget); | |
2608 | ||
2609 | /* | |
2610 | * If there is still backlog, then assign a new budget, making | |
2611 | * sure that it is large enough for the next request. Since | |
2612 | * the finish time of bfqq must be kept in sync with the | |
2613 | * budget, be sure to call __bfq_bfqq_expire() *after* this | |
2614 | * update. | |
2615 | * | |
2616 | * If there is no backlog, then no need to update the budget; | |
2617 | * it will be updated on the arrival of a new request. | |
2618 | */ | |
2619 | next_rq = bfqq->next_rq; | |
2620 | if (next_rq) | |
2621 | bfqq->entity.budget = max_t(unsigned long, bfqq->max_budget, | |
2622 | bfq_serv_to_charge(next_rq, bfqq)); | |
2623 | ||
2624 | bfq_log_bfqq(bfqd, bfqq, "head sect: %u, new budget %d", | |
2625 | next_rq ? blk_rq_sectors(next_rq) : 0, | |
2626 | bfqq->entity.budget); | |
2627 | } | |
2628 | ||
2629 | static unsigned long bfq_calc_max_budget(u64 peak_rate, u64 timeout) | |
2630 | { | |
2631 | unsigned long max_budget; | |
2632 | ||
2633 | /* | |
2634 | * The max_budget calculated when autotuning is equal to the | |
2635 | * amount of sectors transferred in timeout at the estimated | |
2636 | * peak rate. To get this value, peak_rate is, first, | |
2637 | * multiplied by 1000, because timeout is measured in ms, | |
2638 | * while peak_rate is measured in sectors/usecs. Then the | |
2639 | * result of this multiplication is right-shifted by | |
2640 | * BFQ_RATE_SHIFT, because peak_rate is equal to the value of | |
2641 | * the peak rate left-shifted by BFQ_RATE_SHIFT. | |
2642 | */ | |
2643 | max_budget = (unsigned long)(peak_rate * 1000 * | |
2644 | timeout >> BFQ_RATE_SHIFT); | |
2645 | ||
2646 | return max_budget; | |
2647 | } | |
2648 | ||
2649 | /* | |
2650 | * In addition to updating the peak rate, checks whether the process | |
2651 | * is "slow", and returns 1 if so. This slow flag is used, in addition | |
2652 | * to the budget timeout, to reduce the amount of service provided to | |
2653 | * seeky processes, and hence reduce their chances to lower the | |
2654 | * throughput. See the code for more details. | |
2655 | */ | |
2656 | static bool bfq_update_peak_rate(struct bfq_data *bfqd, struct bfq_queue *bfqq, | |
2657 | bool compensate) | |
2658 | { | |
2659 | u64 bw, usecs, expected, timeout; | |
2660 | ktime_t delta; | |
2661 | int update = 0; | |
2662 | ||
2663 | if (!bfq_bfqq_sync(bfqq) || bfq_bfqq_budget_new(bfqq)) | |
2664 | return false; | |
2665 | ||
2666 | if (compensate) | |
2667 | delta = bfqd->last_idling_start; | |
2668 | else | |
2669 | delta = ktime_get(); | |
2670 | delta = ktime_sub(delta, bfqd->last_budget_start); | |
2671 | usecs = ktime_to_us(delta); | |
2672 | ||
2673 | /* don't use too short time intervals */ | |
2674 | if (usecs < 1000) | |
2675 | return false; | |
2676 | ||
2677 | /* | |
2678 | * Calculate the bandwidth for the last slice. We use a 64 bit | |
2679 | * value to store the peak rate, in sectors per usec in fixed | |
2680 | * point math. We do so to have enough precision in the estimate | |
2681 | * and to avoid overflows. | |
2682 | */ | |
2683 | bw = (u64)bfqq->entity.service << BFQ_RATE_SHIFT; | |
2684 | do_div(bw, (unsigned long)usecs); | |
2685 | ||
2686 | timeout = jiffies_to_msecs(bfqd->bfq_timeout); | |
2687 | ||
2688 | /* | |
2689 | * Use only long (> 20ms) intervals to filter out spikes for | |
2690 | * the peak rate estimation. | |
2691 | */ | |
2692 | if (usecs > 20000) { | |
2693 | if (bw > bfqd->peak_rate) { | |
2694 | bfqd->peak_rate = bw; | |
2695 | update = 1; | |
2696 | bfq_log(bfqd, "new peak_rate=%llu", bw); | |
2697 | } | |
2698 | ||
2699 | update |= bfqd->peak_rate_samples == BFQ_PEAK_RATE_SAMPLES - 1; | |
2700 | ||
2701 | if (bfqd->peak_rate_samples < BFQ_PEAK_RATE_SAMPLES) | |
2702 | bfqd->peak_rate_samples++; | |
2703 | ||
2704 | if (bfqd->peak_rate_samples == BFQ_PEAK_RATE_SAMPLES && | |
2705 | update && bfqd->bfq_user_max_budget == 0) { | |
2706 | bfqd->bfq_max_budget = | |
2707 | bfq_calc_max_budget(bfqd->peak_rate, | |
2708 | timeout); | |
2709 | bfq_log(bfqd, "new max_budget=%d", | |
2710 | bfqd->bfq_max_budget); | |
2711 | } | |
2712 | } | |
2713 | ||
2714 | /* | |
2715 | * A process is considered ``slow'' (i.e., seeky, so that we | |
2716 | * cannot treat it fairly in the service domain, as it would | |
2717 | * slow down too much the other processes) if, when a slice | |
2718 | * ends for whatever reason, it has received service at a | |
2719 | * rate that would not be high enough to complete the budget | |
2720 | * before the budget timeout expiration. | |
2721 | */ | |
2722 | expected = bw * 1000 * timeout >> BFQ_RATE_SHIFT; | |
2723 | ||
2724 | /* | |
2725 | * Caveat: processes doing IO in the slower disk zones will | |
2726 | * tend to be slow(er) even if not seeky. And the estimated | |
2727 | * peak rate will actually be an average over the disk | |
2728 | * surface. Hence, to not be too harsh with unlucky processes, | |
2729 | * we keep a budget/3 margin of safety before declaring a | |
2730 | * process slow. | |
2731 | */ | |
2732 | return expected > (4 * bfqq->entity.budget) / 3; | |
2733 | } | |
2734 | ||
2735 | /* | |
2736 | * Return the farthest past time instant according to jiffies | |
2737 | * macros. | |
2738 | */ | |
2739 | static unsigned long bfq_smallest_from_now(void) | |
2740 | { | |
2741 | return jiffies - MAX_JIFFY_OFFSET; | |
2742 | } | |
2743 | ||
2744 | /** | |
2745 | * bfq_bfqq_expire - expire a queue. | |
2746 | * @bfqd: device owning the queue. | |
2747 | * @bfqq: the queue to expire. | |
2748 | * @compensate: if true, compensate for the time spent idling. | |
2749 | * @reason: the reason causing the expiration. | |
2750 | * | |
2751 | * | |
2752 | * If the process associated with the queue is slow (i.e., seeky), or | |
2753 | * in case of budget timeout, or, finally, if it is async, we | |
2754 | * artificially charge it an entire budget (independently of the | |
2755 | * actual service it received). As a consequence, the queue will get | |
2756 | * higher timestamps than the correct ones upon reactivation, and | |
2757 | * hence it will be rescheduled as if it had received more service | |
2758 | * than what it actually received. In the end, this class of processes | |
2759 | * will receive less service in proportion to how slowly they consume | |
2760 | * their budgets (and hence how seriously they tend to lower the | |
2761 | * throughput). | |
2762 | * | |
2763 | * In contrast, when a queue expires because it has been idling for | |
2764 | * too much or because it exhausted its budget, we do not touch the | |
2765 | * amount of service it has received. Hence when the queue will be | |
2766 | * reactivated and its timestamps updated, the latter will be in sync | |
2767 | * with the actual service received by the queue until expiration. | |
2768 | * | |
2769 | * Charging a full budget to the first type of queues and the exact | |
2770 | * service to the others has the effect of using the WF2Q+ policy to | |
2771 | * schedule the former on a timeslice basis, without violating the | |
2772 | * service domain guarantees of the latter. | |
2773 | */ | |
2774 | static void bfq_bfqq_expire(struct bfq_data *bfqd, | |
2775 | struct bfq_queue *bfqq, | |
2776 | bool compensate, | |
2777 | enum bfqq_expiration reason) | |
2778 | { | |
2779 | bool slow; | |
2780 | int ref; | |
2781 | ||
2782 | /* | |
2783 | * Update device peak rate for autotuning and check whether the | |
2784 | * process is slow (see bfq_update_peak_rate). | |
2785 | */ | |
2786 | slow = bfq_update_peak_rate(bfqd, bfqq, compensate); | |
2787 | ||
2788 | /* | |
2789 | * As above explained, 'punish' slow (i.e., seeky), timed-out | |
2790 | * and async queues, to favor sequential sync workloads. | |
2791 | */ | |
2792 | if (slow || reason == BFQQE_BUDGET_TIMEOUT) | |
2793 | bfq_bfqq_charge_full_budget(bfqq); | |
2794 | ||
2795 | if (reason == BFQQE_TOO_IDLE && | |
2796 | bfqq->entity.service <= 2 * bfqq->entity.budget / 10) | |
2797 | bfq_clear_bfqq_IO_bound(bfqq); | |
2798 | ||
2799 | bfq_log_bfqq(bfqd, bfqq, | |
2800 | "expire (%d, slow %d, num_disp %d, idle_win %d)", reason, | |
2801 | slow, bfqq->dispatched, bfq_bfqq_idle_window(bfqq)); | |
2802 | ||
2803 | /* | |
2804 | * Increase, decrease or leave budget unchanged according to | |
2805 | * reason. | |
2806 | */ | |
2807 | __bfq_bfqq_recalc_budget(bfqd, bfqq, reason); | |
2808 | ref = bfqq->ref; | |
2809 | __bfq_bfqq_expire(bfqd, bfqq); | |
2810 | ||
2811 | /* mark bfqq as waiting a request only if a bic still points to it */ | |
2812 | if (ref > 1 && !bfq_bfqq_busy(bfqq) && | |
2813 | reason != BFQQE_BUDGET_TIMEOUT && | |
2814 | reason != BFQQE_BUDGET_EXHAUSTED) | |
2815 | bfq_mark_bfqq_non_blocking_wait_rq(bfqq); | |
2816 | } | |
2817 | ||
2818 | /* | |
2819 | * Budget timeout is not implemented through a dedicated timer, but | |
2820 | * just checked on request arrivals and completions, as well as on | |
2821 | * idle timer expirations. | |
2822 | */ | |
2823 | static bool bfq_bfqq_budget_timeout(struct bfq_queue *bfqq) | |
2824 | { | |
2825 | if (bfq_bfqq_budget_new(bfqq) || | |
2826 | time_is_after_jiffies(bfqq->budget_timeout)) | |
2827 | return false; | |
2828 | return true; | |
2829 | } | |
2830 | ||
2831 | /* | |
2832 | * If we expire a queue that is actively waiting (i.e., with the | |
2833 | * device idled) for the arrival of a new request, then we may incur | |
2834 | * the timestamp misalignment problem described in the body of the | |
2835 | * function __bfq_activate_entity. Hence we return true only if this | |
2836 | * condition does not hold, or if the queue is slow enough to deserve | |
2837 | * only to be kicked off for preserving a high throughput. | |
2838 | */ | |
2839 | static bool bfq_may_expire_for_budg_timeout(struct bfq_queue *bfqq) | |
2840 | { | |
2841 | bfq_log_bfqq(bfqq->bfqd, bfqq, | |
2842 | "may_budget_timeout: wait_request %d left %d timeout %d", | |
2843 | bfq_bfqq_wait_request(bfqq), | |
2844 | bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3, | |
2845 | bfq_bfqq_budget_timeout(bfqq)); | |
2846 | ||
2847 | return (!bfq_bfqq_wait_request(bfqq) || | |
2848 | bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3) | |
2849 | && | |
2850 | bfq_bfqq_budget_timeout(bfqq); | |
2851 | } | |
2852 | ||
2853 | /* | |
2854 | * For a queue that becomes empty, device idling is allowed only if | |
2855 | * this function returns true for the queue. And this function returns | |
2856 | * true only if idling is beneficial for throughput. | |
2857 | */ | |
2858 | static bool bfq_bfqq_may_idle(struct bfq_queue *bfqq) | |
2859 | { | |
2860 | struct bfq_data *bfqd = bfqq->bfqd; | |
2861 | bool idling_boosts_thr; | |
2862 | ||
2863 | if (bfqd->strict_guarantees) | |
2864 | return true; | |
2865 | ||
2866 | /* | |
2867 | * The value of the next variable is computed considering that | |
2868 | * idling is usually beneficial for the throughput if: | |
2869 | * (a) the device is not NCQ-capable, or | |
2870 | * (b) regardless of the presence of NCQ, the request pattern | |
2871 | * for bfqq is I/O-bound (possible throughput losses | |
2872 | * caused by granting idling to seeky queues are mitigated | |
2873 | * by the fact that, in all scenarios where boosting | |
2874 | * throughput is the best thing to do, i.e., in all | |
2875 | * symmetric scenarios, only a minimal idle time is | |
2876 | * allowed to seeky queues). | |
2877 | */ | |
2878 | idling_boosts_thr = !bfqd->hw_tag || bfq_bfqq_IO_bound(bfqq); | |
2879 | ||
2880 | /* | |
2881 | * We have now the components we need to compute the return | |
2882 | * value of the function, which is true only if both the | |
2883 | * following conditions hold: | |
2884 | * 1) bfqq is sync, because idling make sense only for sync queues; | |
2885 | * 2) idling boosts the throughput. | |
2886 | */ | |
2887 | return bfq_bfqq_sync(bfqq) && idling_boosts_thr; | |
2888 | } | |
2889 | ||
2890 | /* | |
2891 | * If the in-service queue is empty but the function bfq_bfqq_may_idle | |
2892 | * returns true, then: | |
2893 | * 1) the queue must remain in service and cannot be expired, and | |
2894 | * 2) the device must be idled to wait for the possible arrival of a new | |
2895 | * request for the queue. | |
2896 | * See the comments on the function bfq_bfqq_may_idle for the reasons | |
2897 | * why performing device idling is the best choice to boost the throughput | |
2898 | * and preserve service guarantees when bfq_bfqq_may_idle itself | |
2899 | * returns true. | |
2900 | */ | |
2901 | static bool bfq_bfqq_must_idle(struct bfq_queue *bfqq) | |
2902 | { | |
2903 | struct bfq_data *bfqd = bfqq->bfqd; | |
2904 | ||
2905 | return RB_EMPTY_ROOT(&bfqq->sort_list) && bfqd->bfq_slice_idle != 0 && | |
2906 | bfq_bfqq_may_idle(bfqq); | |
2907 | } | |
2908 | ||
2909 | /* | |
2910 | * Select a queue for service. If we have a current queue in service, | |
2911 | * check whether to continue servicing it, or retrieve and set a new one. | |
2912 | */ | |
2913 | static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd) | |
2914 | { | |
2915 | struct bfq_queue *bfqq; | |
2916 | struct request *next_rq; | |
2917 | enum bfqq_expiration reason = BFQQE_BUDGET_TIMEOUT; | |
2918 | ||
2919 | bfqq = bfqd->in_service_queue; | |
2920 | if (!bfqq) | |
2921 | goto new_queue; | |
2922 | ||
2923 | bfq_log_bfqq(bfqd, bfqq, "select_queue: already in-service queue"); | |
2924 | ||
2925 | if (bfq_may_expire_for_budg_timeout(bfqq) && | |
2926 | !bfq_bfqq_wait_request(bfqq) && | |
2927 | !bfq_bfqq_must_idle(bfqq)) | |
2928 | goto expire; | |
2929 | ||
2930 | check_queue: | |
2931 | /* | |
2932 | * This loop is rarely executed more than once. Even when it | |
2933 | * happens, it is much more convenient to re-execute this loop | |
2934 | * than to return NULL and trigger a new dispatch to get a | |
2935 | * request served. | |
2936 | */ | |
2937 | next_rq = bfqq->next_rq; | |
2938 | /* | |
2939 | * If bfqq has requests queued and it has enough budget left to | |
2940 | * serve them, keep the queue, otherwise expire it. | |
2941 | */ | |
2942 | if (next_rq) { | |
2943 | if (bfq_serv_to_charge(next_rq, bfqq) > | |
2944 | bfq_bfqq_budget_left(bfqq)) { | |
2945 | /* | |
2946 | * Expire the queue for budget exhaustion, | |
2947 | * which makes sure that the next budget is | |
2948 | * enough to serve the next request, even if | |
2949 | * it comes from the fifo expired path. | |
2950 | */ | |
2951 | reason = BFQQE_BUDGET_EXHAUSTED; | |
2952 | goto expire; | |
2953 | } else { | |
2954 | /* | |
2955 | * The idle timer may be pending because we may | |
2956 | * not disable disk idling even when a new request | |
2957 | * arrives. | |
2958 | */ | |
2959 | if (bfq_bfqq_wait_request(bfqq)) { | |
2960 | /* | |
2961 | * If we get here: 1) at least a new request | |
2962 | * has arrived but we have not disabled the | |
2963 | * timer because the request was too small, | |
2964 | * 2) then the block layer has unplugged | |
2965 | * the device, causing the dispatch to be | |
2966 | * invoked. | |
2967 | * | |
2968 | * Since the device is unplugged, now the | |
2969 | * requests are probably large enough to | |
2970 | * provide a reasonable throughput. | |
2971 | * So we disable idling. | |
2972 | */ | |
2973 | bfq_clear_bfqq_wait_request(bfqq); | |
2974 | hrtimer_try_to_cancel(&bfqd->idle_slice_timer); | |
2975 | } | |
2976 | goto keep_queue; | |
2977 | } | |
2978 | } | |
2979 | ||
2980 | /* | |
2981 | * No requests pending. However, if the in-service queue is idling | |
2982 | * for a new request, or has requests waiting for a completion and | |
2983 | * may idle after their completion, then keep it anyway. | |
2984 | */ | |
2985 | if (bfq_bfqq_wait_request(bfqq) || | |
2986 | (bfqq->dispatched != 0 && bfq_bfqq_may_idle(bfqq))) { | |
2987 | bfqq = NULL; | |
2988 | goto keep_queue; | |
2989 | } | |
2990 | ||
2991 | reason = BFQQE_NO_MORE_REQUESTS; | |
2992 | expire: | |
2993 | bfq_bfqq_expire(bfqd, bfqq, false, reason); | |
2994 | new_queue: | |
2995 | bfqq = bfq_set_in_service_queue(bfqd); | |
2996 | if (bfqq) { | |
2997 | bfq_log_bfqq(bfqd, bfqq, "select_queue: checking new queue"); | |
2998 | goto check_queue; | |
2999 | } | |
3000 | keep_queue: | |
3001 | if (bfqq) | |
3002 | bfq_log_bfqq(bfqd, bfqq, "select_queue: returned this queue"); | |
3003 | else | |
3004 | bfq_log(bfqd, "select_queue: no queue returned"); | |
3005 | ||
3006 | return bfqq; | |
3007 | } | |
3008 | ||
3009 | /* | |
3010 | * Dispatch next request from bfqq. | |
3011 | */ | |
3012 | static struct request *bfq_dispatch_rq_from_bfqq(struct bfq_data *bfqd, | |
3013 | struct bfq_queue *bfqq) | |
3014 | { | |
3015 | struct request *rq = bfqq->next_rq; | |
3016 | unsigned long service_to_charge; | |
3017 | ||
3018 | service_to_charge = bfq_serv_to_charge(rq, bfqq); | |
3019 | ||
3020 | bfq_bfqq_served(bfqq, service_to_charge); | |
3021 | ||
3022 | bfq_dispatch_remove(bfqd->queue, rq); | |
3023 | ||
3024 | if (!bfqd->in_service_bic) { | |
3025 | atomic_long_inc(&RQ_BIC(rq)->icq.ioc->refcount); | |
3026 | bfqd->in_service_bic = RQ_BIC(rq); | |
3027 | } | |
3028 | ||
3029 | /* | |
3030 | * Expire bfqq, pretending that its budget expired, if bfqq | |
3031 | * belongs to CLASS_IDLE and other queues are waiting for | |
3032 | * service. | |
3033 | */ | |
3034 | if (bfqd->busy_queues > 1 && bfq_class_idle(bfqq)) | |
3035 | goto expire; | |
3036 | ||
3037 | return rq; | |
3038 | ||
3039 | expire: | |
3040 | bfq_bfqq_expire(bfqd, bfqq, false, BFQQE_BUDGET_EXHAUSTED); | |
3041 | return rq; | |
3042 | } | |
3043 | ||
3044 | static bool bfq_has_work(struct blk_mq_hw_ctx *hctx) | |
3045 | { | |
3046 | struct bfq_data *bfqd = hctx->queue->elevator->elevator_data; | |
3047 | ||
3048 | /* | |
3049 | * Avoiding lock: a race on bfqd->busy_queues should cause at | |
3050 | * most a call to dispatch for nothing | |
3051 | */ | |
3052 | return !list_empty_careful(&bfqd->dispatch) || | |
3053 | bfqd->busy_queues > 0; | |
3054 | } | |
3055 | ||
3056 | static struct request *__bfq_dispatch_request(struct blk_mq_hw_ctx *hctx) | |
3057 | { | |
3058 | struct bfq_data *bfqd = hctx->queue->elevator->elevator_data; | |
3059 | struct request *rq = NULL; | |
3060 | struct bfq_queue *bfqq = NULL; | |
3061 | ||
3062 | if (!list_empty(&bfqd->dispatch)) { | |
3063 | rq = list_first_entry(&bfqd->dispatch, struct request, | |
3064 | queuelist); | |
3065 | list_del_init(&rq->queuelist); | |
3066 | ||
3067 | bfqq = RQ_BFQQ(rq); | |
3068 | ||
3069 | if (bfqq) { | |
3070 | /* | |
3071 | * Increment counters here, because this | |
3072 | * dispatch does not follow the standard | |
3073 | * dispatch flow (where counters are | |
3074 | * incremented) | |
3075 | */ | |
3076 | bfqq->dispatched++; | |
3077 | ||
3078 | goto inc_in_driver_start_rq; | |
3079 | } | |
3080 | ||
3081 | /* | |
3082 | * We exploit the put_rq_private hook to decrement | |
3083 | * rq_in_driver, but put_rq_private will not be | |
3084 | * invoked on this request. So, to avoid unbalance, | |
3085 | * just start this request, without incrementing | |
3086 | * rq_in_driver. As a negative consequence, | |
3087 | * rq_in_driver is deceptively lower than it should be | |
3088 | * while this request is in service. This may cause | |
3089 | * bfq_schedule_dispatch to be invoked uselessly. | |
3090 | * | |
3091 | * As for implementing an exact solution, the | |
3092 | * put_request hook, if defined, is probably invoked | |
3093 | * also on this request. So, by exploiting this hook, | |
3094 | * we could 1) increment rq_in_driver here, and 2) | |
3095 | * decrement it in put_request. Such a solution would | |
3096 | * let the value of the counter be always accurate, | |
3097 | * but it would entail using an extra interface | |
3098 | * function. This cost seems higher than the benefit, | |
3099 | * being the frequency of non-elevator-private | |
3100 | * requests very low. | |
3101 | */ | |
3102 | goto start_rq; | |
3103 | } | |
3104 | ||
3105 | bfq_log(bfqd, "dispatch requests: %d busy queues", bfqd->busy_queues); | |
3106 | ||
3107 | if (bfqd->busy_queues == 0) | |
3108 | goto exit; | |
3109 | ||
3110 | /* | |
3111 | * Force device to serve one request at a time if | |
3112 | * strict_guarantees is true. Forcing this service scheme is | |
3113 | * currently the ONLY way to guarantee that the request | |
3114 | * service order enforced by the scheduler is respected by a | |
3115 | * queueing device. Otherwise the device is free even to make | |
3116 | * some unlucky request wait for as long as the device | |
3117 | * wishes. | |
3118 | * | |
3119 | * Of course, serving one request at at time may cause loss of | |
3120 | * throughput. | |
3121 | */ | |
3122 | if (bfqd->strict_guarantees && bfqd->rq_in_driver > 0) | |
3123 | goto exit; | |
3124 | ||
3125 | bfqq = bfq_select_queue(bfqd); | |
3126 | if (!bfqq) | |
3127 | goto exit; | |
3128 | ||
3129 | rq = bfq_dispatch_rq_from_bfqq(bfqd, bfqq); | |
3130 | ||
3131 | if (rq) { | |
3132 | inc_in_driver_start_rq: | |
3133 | bfqd->rq_in_driver++; | |
3134 | start_rq: | |
3135 | rq->rq_flags |= RQF_STARTED; | |
3136 | } | |
3137 | exit: | |
3138 | return rq; | |
3139 | } | |
3140 | ||
3141 | static struct request *bfq_dispatch_request(struct blk_mq_hw_ctx *hctx) | |
3142 | { | |
3143 | struct bfq_data *bfqd = hctx->queue->elevator->elevator_data; | |
3144 | struct request *rq; | |
3145 | ||
3146 | spin_lock_irq(&bfqd->lock); | |
3147 | rq = __bfq_dispatch_request(hctx); | |
3148 | spin_unlock_irq(&bfqd->lock); | |
3149 | ||
3150 | return rq; | |
3151 | } | |
3152 | ||
3153 | /* | |
3154 | * Task holds one reference to the queue, dropped when task exits. Each rq | |
3155 | * in-flight on this queue also holds a reference, dropped when rq is freed. | |
3156 | * | |
3157 | * Scheduler lock must be held here. Recall not to use bfqq after calling | |
3158 | * this function on it. | |
3159 | */ | |
3160 | static void bfq_put_queue(struct bfq_queue *bfqq) | |
3161 | { | |
3162 | if (bfqq->bfqd) | |
3163 | bfq_log_bfqq(bfqq->bfqd, bfqq, "put_queue: %p %d", | |
3164 | bfqq, bfqq->ref); | |
3165 | ||
3166 | bfqq->ref--; | |
3167 | if (bfqq->ref) | |
3168 | return; | |
3169 | ||
3170 | kmem_cache_free(bfq_pool, bfqq); | |
3171 | } | |
3172 | ||
3173 | static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq) | |
3174 | { | |
3175 | if (bfqq == bfqd->in_service_queue) { | |
3176 | __bfq_bfqq_expire(bfqd, bfqq); | |
3177 | bfq_schedule_dispatch(bfqd); | |
3178 | } | |
3179 | ||
3180 | bfq_log_bfqq(bfqd, bfqq, "exit_bfqq: %p, %d", bfqq, bfqq->ref); | |
3181 | ||
3182 | bfq_put_queue(bfqq); /* release process reference */ | |
3183 | } | |
3184 | ||
3185 | static void bfq_exit_icq_bfqq(struct bfq_io_cq *bic, bool is_sync) | |
3186 | { | |
3187 | struct bfq_queue *bfqq = bic_to_bfqq(bic, is_sync); | |
3188 | struct bfq_data *bfqd; | |
3189 | ||
3190 | if (bfqq) | |
3191 | bfqd = bfqq->bfqd; /* NULL if scheduler already exited */ | |
3192 | ||
3193 | if (bfqq && bfqd) { | |
3194 | unsigned long flags; | |
3195 | ||
3196 | spin_lock_irqsave(&bfqd->lock, flags); | |
3197 | bfq_exit_bfqq(bfqd, bfqq); | |
3198 | bic_set_bfqq(bic, NULL, is_sync); | |
3199 | spin_unlock_irq(&bfqd->lock); | |
3200 | } | |
3201 | } | |
3202 | ||
3203 | static void bfq_exit_icq(struct io_cq *icq) | |
3204 | { | |
3205 | struct bfq_io_cq *bic = icq_to_bic(icq); | |
3206 | ||
3207 | bfq_exit_icq_bfqq(bic, true); | |
3208 | bfq_exit_icq_bfqq(bic, false); | |
3209 | } | |
3210 | ||
3211 | /* | |
3212 | * Update the entity prio values; note that the new values will not | |
3213 | * be used until the next (re)activation. | |
3214 | */ | |
3215 | static void | |
3216 | bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic) | |
3217 | { | |
3218 | struct task_struct *tsk = current; | |
3219 | int ioprio_class; | |
3220 | struct bfq_data *bfqd = bfqq->bfqd; | |
3221 | ||
3222 | if (!bfqd) | |
3223 | return; | |
3224 | ||
3225 | ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio); | |
3226 | switch (ioprio_class) { | |
3227 | default: | |
3228 | dev_err(bfqq->bfqd->queue->backing_dev_info->dev, | |
3229 | "bfq: bad prio class %d\n", ioprio_class); | |
3230 | case IOPRIO_CLASS_NONE: | |
3231 | /* | |
3232 | * No prio set, inherit CPU scheduling settings. | |
3233 | */ | |
3234 | bfqq->new_ioprio = task_nice_ioprio(tsk); | |
3235 | bfqq->new_ioprio_class = task_nice_ioclass(tsk); | |
3236 | break; | |
3237 | case IOPRIO_CLASS_RT: | |
3238 | bfqq->new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio); | |
3239 | bfqq->new_ioprio_class = IOPRIO_CLASS_RT; | |
3240 | break; | |
3241 | case IOPRIO_CLASS_BE: | |
3242 | bfqq->new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio); | |
3243 | bfqq->new_ioprio_class = IOPRIO_CLASS_BE; | |
3244 | break; | |
3245 | case IOPRIO_CLASS_IDLE: | |
3246 | bfqq->new_ioprio_class = IOPRIO_CLASS_IDLE; | |
3247 | bfqq->new_ioprio = 7; | |
3248 | bfq_clear_bfqq_idle_window(bfqq); | |
3249 | break; | |
3250 | } | |
3251 | ||
3252 | if (bfqq->new_ioprio >= IOPRIO_BE_NR) { | |
3253 | pr_crit("bfq_set_next_ioprio_data: new_ioprio %d\n", | |
3254 | bfqq->new_ioprio); | |
3255 | bfqq->new_ioprio = IOPRIO_BE_NR; | |
3256 | } | |
3257 | ||
3258 | bfqq->entity.new_weight = bfq_ioprio_to_weight(bfqq->new_ioprio); | |
3259 | bfqq->entity.prio_changed = 1; | |
3260 | } | |
3261 | ||
3262 | static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio) | |
3263 | { | |
3264 | struct bfq_data *bfqd = bic_to_bfqd(bic); | |
3265 | struct bfq_queue *bfqq; | |
3266 | int ioprio = bic->icq.ioc->ioprio; | |
3267 | ||
3268 | /* | |
3269 | * This condition may trigger on a newly created bic, be sure to | |
3270 | * drop the lock before returning. | |
3271 | */ | |
3272 | if (unlikely(!bfqd) || likely(bic->ioprio == ioprio)) | |
3273 | return; | |
3274 | ||
3275 | bic->ioprio = ioprio; | |
3276 | ||
3277 | bfqq = bic_to_bfqq(bic, false); | |
3278 | if (bfqq) { | |
3279 | /* release process reference on this queue */ | |
3280 | bfq_put_queue(bfqq); | |
3281 | bfqq = bfq_get_queue(bfqd, bio, BLK_RW_ASYNC, bic); | |
3282 | bic_set_bfqq(bic, bfqq, false); | |
3283 | } | |
3284 | ||
3285 | bfqq = bic_to_bfqq(bic, true); | |
3286 | if (bfqq) | |
3287 | bfq_set_next_ioprio_data(bfqq, bic); | |
3288 | } | |
3289 | ||
3290 | static void bfq_init_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, | |
3291 | struct bfq_io_cq *bic, pid_t pid, int is_sync) | |
3292 | { | |
3293 | RB_CLEAR_NODE(&bfqq->entity.rb_node); | |
3294 | INIT_LIST_HEAD(&bfqq->fifo); | |
3295 | ||
3296 | bfqq->ref = 0; | |
3297 | bfqq->bfqd = bfqd; | |
3298 | ||
3299 | if (bic) | |
3300 | bfq_set_next_ioprio_data(bfqq, bic); | |
3301 | ||
3302 | if (is_sync) { | |
3303 | if (!bfq_class_idle(bfqq)) | |
3304 | bfq_mark_bfqq_idle_window(bfqq); | |
3305 | bfq_mark_bfqq_sync(bfqq); | |
3306 | } else | |
3307 | bfq_clear_bfqq_sync(bfqq); | |
3308 | ||
3309 | /* set end request to minus infinity from now */ | |
3310 | bfqq->ttime.last_end_request = ktime_get_ns() + 1; | |
3311 | ||
3312 | bfq_mark_bfqq_IO_bound(bfqq); | |
3313 | ||
3314 | bfqq->pid = pid; | |
3315 | ||
3316 | /* Tentative initial value to trade off between thr and lat */ | |
3317 | bfqq->max_budget = bfq_default_budget(bfqd, bfqq); | |
3318 | bfqq->budget_timeout = bfq_smallest_from_now(); | |
3319 | bfqq->pid = pid; | |
3320 | ||
3321 | /* first request is almost certainly seeky */ | |
3322 | bfqq->seek_history = 1; | |
3323 | } | |
3324 | ||
3325 | static struct bfq_queue **bfq_async_queue_prio(struct bfq_data *bfqd, | |
3326 | int ioprio_class, int ioprio) | |
3327 | { | |
3328 | switch (ioprio_class) { | |
3329 | case IOPRIO_CLASS_RT: | |
3330 | return &async_bfqq[0][ioprio]; | |
3331 | case IOPRIO_CLASS_NONE: | |
3332 | ioprio = IOPRIO_NORM; | |
3333 | /* fall through */ | |
3334 | case IOPRIO_CLASS_BE: | |
3335 | return &async_bfqq[1][ioprio]; | |
3336 | case IOPRIO_CLASS_IDLE: | |
3337 | return &async_idle_bfqq; | |
3338 | default: | |
3339 | return NULL; | |
3340 | } | |
3341 | } | |
3342 | ||
3343 | static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd, | |
3344 | struct bio *bio, bool is_sync, | |
3345 | struct bfq_io_cq *bic) | |
3346 | { | |
3347 | const int ioprio = IOPRIO_PRIO_DATA(bic->ioprio); | |
3348 | const int ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio); | |
3349 | struct bfq_queue **async_bfqq = NULL; | |
3350 | struct bfq_queue *bfqq; | |
3351 | ||
3352 | rcu_read_lock(); | |
3353 | ||
3354 | if (!is_sync) { | |
3355 | async_bfqq = bfq_async_queue_prio(bfqd, ioprio_class, | |
3356 | ioprio); | |
3357 | bfqq = *async_bfqq; | |
3358 | if (bfqq) | |
3359 | goto out; | |
3360 | } | |
3361 | ||
3362 | bfqq = kmem_cache_alloc_node(bfq_pool, | |
3363 | GFP_NOWAIT | __GFP_ZERO | __GFP_NOWARN, | |
3364 | bfqd->queue->node); | |
3365 | ||
3366 | if (bfqq) { | |
3367 | bfq_init_bfqq(bfqd, bfqq, bic, current->pid, | |
3368 | is_sync); | |
3369 | bfq_init_entity(&bfqq->entity); | |
3370 | bfq_log_bfqq(bfqd, bfqq, "allocated"); | |
3371 | } else { | |
3372 | bfqq = &bfqd->oom_bfqq; | |
3373 | bfq_log_bfqq(bfqd, bfqq, "using oom bfqq"); | |
3374 | goto out; | |
3375 | } | |
3376 | ||
3377 | /* | |
3378 | * Pin the queue now that it's allocated, scheduler exit will | |
3379 | * prune it. | |
3380 | */ | |
3381 | if (async_bfqq) { | |
3382 | bfqq->ref++; | |
3383 | bfq_log_bfqq(bfqd, bfqq, | |
3384 | "get_queue, bfqq not in async: %p, %d", | |
3385 | bfqq, bfqq->ref); | |
3386 | *async_bfqq = bfqq; | |
3387 | } | |
3388 | ||
3389 | out: | |
3390 | bfqq->ref++; /* get a process reference to this queue */ | |
3391 | bfq_log_bfqq(bfqd, bfqq, "get_queue, at end: %p, %d", bfqq, bfqq->ref); | |
3392 | rcu_read_unlock(); | |
3393 | return bfqq; | |
3394 | } | |
3395 | ||
3396 | static void bfq_update_io_thinktime(struct bfq_data *bfqd, | |
3397 | struct bfq_queue *bfqq) | |
3398 | { | |
3399 | struct bfq_ttime *ttime = &bfqq->ttime; | |
3400 | u64 elapsed = ktime_get_ns() - bfqq->ttime.last_end_request; | |
3401 | ||
3402 | elapsed = min_t(u64, elapsed, 2ULL * bfqd->bfq_slice_idle); | |
3403 | ||
3404 | ttime->ttime_samples = (7*bfqq->ttime.ttime_samples + 256) / 8; | |
3405 | ttime->ttime_total = div_u64(7*ttime->ttime_total + 256*elapsed, 8); | |
3406 | ttime->ttime_mean = div64_ul(ttime->ttime_total + 128, | |
3407 | ttime->ttime_samples); | |
3408 | } | |
3409 | ||
3410 | static void | |
3411 | bfq_update_io_seektime(struct bfq_data *bfqd, struct bfq_queue *bfqq, | |
3412 | struct request *rq) | |
3413 | { | |
3414 | sector_t sdist = 0; | |
3415 | ||
3416 | if (bfqq->last_request_pos) { | |
3417 | if (bfqq->last_request_pos < blk_rq_pos(rq)) | |
3418 | sdist = blk_rq_pos(rq) - bfqq->last_request_pos; | |
3419 | else | |
3420 | sdist = bfqq->last_request_pos - blk_rq_pos(rq); | |
3421 | } | |
3422 | ||
3423 | bfqq->seek_history <<= 1; | |
3424 | bfqq->seek_history |= sdist > BFQQ_SEEK_THR && | |
3425 | (!blk_queue_nonrot(bfqd->queue) || | |
3426 | blk_rq_sectors(rq) < BFQQ_SECT_THR_NONROT); | |
3427 | } | |
3428 | ||
3429 | /* | |
3430 | * Disable idle window if the process thinks too long or seeks so much that | |
3431 | * it doesn't matter. | |
3432 | */ | |
3433 | static void bfq_update_idle_window(struct bfq_data *bfqd, | |
3434 | struct bfq_queue *bfqq, | |
3435 | struct bfq_io_cq *bic) | |
3436 | { | |
3437 | int enable_idle; | |
3438 | ||
3439 | /* Don't idle for async or idle io prio class. */ | |
3440 | if (!bfq_bfqq_sync(bfqq) || bfq_class_idle(bfqq)) | |
3441 | return; | |
3442 | ||
3443 | enable_idle = bfq_bfqq_idle_window(bfqq); | |
3444 | ||
3445 | if (atomic_read(&bic->icq.ioc->active_ref) == 0 || | |
3446 | bfqd->bfq_slice_idle == 0 || | |
3447 | (bfqd->hw_tag && BFQQ_SEEKY(bfqq))) | |
3448 | enable_idle = 0; | |
3449 | else if (bfq_sample_valid(bfqq->ttime.ttime_samples)) { | |
3450 | if (bfqq->ttime.ttime_mean > bfqd->bfq_slice_idle) | |
3451 | enable_idle = 0; | |
3452 | else | |
3453 | enable_idle = 1; | |
3454 | } | |
3455 | bfq_log_bfqq(bfqd, bfqq, "update_idle_window: enable_idle %d", | |
3456 | enable_idle); | |
3457 | ||
3458 | if (enable_idle) | |
3459 | bfq_mark_bfqq_idle_window(bfqq); | |
3460 | else | |
3461 | bfq_clear_bfqq_idle_window(bfqq); | |
3462 | } | |
3463 | ||
3464 | /* | |
3465 | * Called when a new fs request (rq) is added to bfqq. Check if there's | |
3466 | * something we should do about it. | |
3467 | */ | |
3468 | static void bfq_rq_enqueued(struct bfq_data *bfqd, struct bfq_queue *bfqq, | |
3469 | struct request *rq) | |
3470 | { | |
3471 | struct bfq_io_cq *bic = RQ_BIC(rq); | |
3472 | ||
3473 | if (rq->cmd_flags & REQ_META) | |
3474 | bfqq->meta_pending++; | |
3475 | ||
3476 | bfq_update_io_thinktime(bfqd, bfqq); | |
3477 | bfq_update_io_seektime(bfqd, bfqq, rq); | |
3478 | if (bfqq->entity.service > bfq_max_budget(bfqd) / 8 || | |
3479 | !BFQQ_SEEKY(bfqq)) | |
3480 | bfq_update_idle_window(bfqd, bfqq, bic); | |
3481 | ||
3482 | bfq_log_bfqq(bfqd, bfqq, | |
3483 | "rq_enqueued: idle_window=%d (seeky %d)", | |
3484 | bfq_bfqq_idle_window(bfqq), BFQQ_SEEKY(bfqq)); | |
3485 | ||
3486 | bfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq); | |
3487 | ||
3488 | if (bfqq == bfqd->in_service_queue && bfq_bfqq_wait_request(bfqq)) { | |
3489 | bool small_req = bfqq->queued[rq_is_sync(rq)] == 1 && | |
3490 | blk_rq_sectors(rq) < 32; | |
3491 | bool budget_timeout = bfq_bfqq_budget_timeout(bfqq); | |
3492 | ||
3493 | /* | |
3494 | * There is just this request queued: if the request | |
3495 | * is small and the queue is not to be expired, then | |
3496 | * just exit. | |
3497 | * | |
3498 | * In this way, if the device is being idled to wait | |
3499 | * for a new request from the in-service queue, we | |
3500 | * avoid unplugging the device and committing the | |
3501 | * device to serve just a small request. On the | |
3502 | * contrary, we wait for the block layer to decide | |
3503 | * when to unplug the device: hopefully, new requests | |
3504 | * will be merged to this one quickly, then the device | |
3505 | * will be unplugged and larger requests will be | |
3506 | * dispatched. | |
3507 | */ | |
3508 | if (small_req && !budget_timeout) | |
3509 | return; | |
3510 | ||
3511 | /* | |
3512 | * A large enough request arrived, or the queue is to | |
3513 | * be expired: in both cases disk idling is to be | |
3514 | * stopped, so clear wait_request flag and reset | |
3515 | * timer. | |
3516 | */ | |
3517 | bfq_clear_bfqq_wait_request(bfqq); | |
3518 | hrtimer_try_to_cancel(&bfqd->idle_slice_timer); | |
3519 | ||
3520 | /* | |
3521 | * The queue is not empty, because a new request just | |
3522 | * arrived. Hence we can safely expire the queue, in | |
3523 | * case of budget timeout, without risking that the | |
3524 | * timestamps of the queue are not updated correctly. | |
3525 | * See [1] for more details. | |
3526 | */ | |
3527 | if (budget_timeout) | |
3528 | bfq_bfqq_expire(bfqd, bfqq, false, | |
3529 | BFQQE_BUDGET_TIMEOUT); | |
3530 | } | |
3531 | } | |
3532 | ||
3533 | static void __bfq_insert_request(struct bfq_data *bfqd, struct request *rq) | |
3534 | { | |
3535 | struct bfq_queue *bfqq = RQ_BFQQ(rq); | |
3536 | ||
3537 | bfq_add_request(rq); | |
3538 | ||
3539 | rq->fifo_time = ktime_get_ns() + bfqd->bfq_fifo_expire[rq_is_sync(rq)]; | |
3540 | list_add_tail(&rq->queuelist, &bfqq->fifo); | |
3541 | ||
3542 | bfq_rq_enqueued(bfqd, bfqq, rq); | |
3543 | } | |
3544 | ||
3545 | static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, | |
3546 | bool at_head) | |
3547 | { | |
3548 | struct request_queue *q = hctx->queue; | |
3549 | struct bfq_data *bfqd = q->elevator->elevator_data; | |
3550 | ||
3551 | spin_lock_irq(&bfqd->lock); | |
3552 | if (blk_mq_sched_try_insert_merge(q, rq)) { | |
3553 | spin_unlock_irq(&bfqd->lock); | |
3554 | return; | |
3555 | } | |
3556 | ||
3557 | spin_unlock_irq(&bfqd->lock); | |
3558 | ||
3559 | blk_mq_sched_request_inserted(rq); | |
3560 | ||
3561 | spin_lock_irq(&bfqd->lock); | |
3562 | if (at_head || blk_rq_is_passthrough(rq)) { | |
3563 | if (at_head) | |
3564 | list_add(&rq->queuelist, &bfqd->dispatch); | |
3565 | else | |
3566 | list_add_tail(&rq->queuelist, &bfqd->dispatch); | |
3567 | } else { | |
3568 | __bfq_insert_request(bfqd, rq); | |
3569 | ||
3570 | if (rq_mergeable(rq)) { | |
3571 | elv_rqhash_add(q, rq); | |
3572 | if (!q->last_merge) | |
3573 | q->last_merge = rq; | |
3574 | } | |
3575 | } | |
3576 | ||
3577 | spin_unlock_irq(&bfqd->lock); | |
3578 | } | |
3579 | ||
3580 | static void bfq_insert_requests(struct blk_mq_hw_ctx *hctx, | |
3581 | struct list_head *list, bool at_head) | |
3582 | { | |
3583 | while (!list_empty(list)) { | |
3584 | struct request *rq; | |
3585 | ||
3586 | rq = list_first_entry(list, struct request, queuelist); | |
3587 | list_del_init(&rq->queuelist); | |
3588 | bfq_insert_request(hctx, rq, at_head); | |
3589 | } | |
3590 | } | |
3591 | ||
3592 | static void bfq_update_hw_tag(struct bfq_data *bfqd) | |
3593 | { | |
3594 | bfqd->max_rq_in_driver = max_t(int, bfqd->max_rq_in_driver, | |
3595 | bfqd->rq_in_driver); | |
3596 | ||
3597 | if (bfqd->hw_tag == 1) | |
3598 | return; | |
3599 | ||
3600 | /* | |
3601 | * This sample is valid if the number of outstanding requests | |
3602 | * is large enough to allow a queueing behavior. Note that the | |
3603 | * sum is not exact, as it's not taking into account deactivated | |
3604 | * requests. | |
3605 | */ | |
3606 | if (bfqd->rq_in_driver + bfqd->queued < BFQ_HW_QUEUE_THRESHOLD) | |
3607 | return; | |
3608 | ||
3609 | if (bfqd->hw_tag_samples++ < BFQ_HW_QUEUE_SAMPLES) | |
3610 | return; | |
3611 | ||
3612 | bfqd->hw_tag = bfqd->max_rq_in_driver > BFQ_HW_QUEUE_THRESHOLD; | |
3613 | bfqd->max_rq_in_driver = 0; | |
3614 | bfqd->hw_tag_samples = 0; | |
3615 | } | |
3616 | ||
3617 | static void bfq_completed_request(struct bfq_queue *bfqq, struct bfq_data *bfqd) | |
3618 | { | |
3619 | bfq_update_hw_tag(bfqd); | |
3620 | ||
3621 | bfqd->rq_in_driver--; | |
3622 | bfqq->dispatched--; | |
3623 | ||
3624 | bfqq->ttime.last_end_request = ktime_get_ns(); | |
3625 | ||
3626 | /* | |
3627 | * If this is the in-service queue, check if it needs to be expired, | |
3628 | * or if we want to idle in case it has no pending requests. | |
3629 | */ | |
3630 | if (bfqd->in_service_queue == bfqq) { | |
3631 | if (bfq_bfqq_budget_new(bfqq)) | |
3632 | bfq_set_budget_timeout(bfqd); | |
3633 | ||
3634 | if (bfq_bfqq_must_idle(bfqq)) { | |
3635 | bfq_arm_slice_timer(bfqd); | |
3636 | return; | |
3637 | } else if (bfq_may_expire_for_budg_timeout(bfqq)) | |
3638 | bfq_bfqq_expire(bfqd, bfqq, false, | |
3639 | BFQQE_BUDGET_TIMEOUT); | |
3640 | else if (RB_EMPTY_ROOT(&bfqq->sort_list) && | |
3641 | (bfqq->dispatched == 0 || | |
3642 | !bfq_bfqq_may_idle(bfqq))) | |
3643 | bfq_bfqq_expire(bfqd, bfqq, false, | |
3644 | BFQQE_NO_MORE_REQUESTS); | |
3645 | } | |
3646 | } | |
3647 | ||
3648 | static void bfq_put_rq_priv_body(struct bfq_queue *bfqq) | |
3649 | { | |
3650 | bfqq->allocated--; | |
3651 | ||
3652 | bfq_put_queue(bfqq); | |
3653 | } | |
3654 | ||
3655 | static void bfq_put_rq_private(struct request_queue *q, struct request *rq) | |
3656 | { | |
3657 | struct bfq_queue *bfqq = RQ_BFQQ(rq); | |
3658 | struct bfq_data *bfqd = bfqq->bfqd; | |
3659 | ||
3660 | ||
3661 | if (likely(rq->rq_flags & RQF_STARTED)) { | |
3662 | unsigned long flags; | |
3663 | ||
3664 | spin_lock_irqsave(&bfqd->lock, flags); | |
3665 | ||
3666 | bfq_completed_request(bfqq, bfqd); | |
3667 | bfq_put_rq_priv_body(bfqq); | |
3668 | ||
3669 | spin_unlock_irqrestore(&bfqd->lock, flags); | |
3670 | } else { | |
3671 | /* | |
3672 | * Request rq may be still/already in the scheduler, | |
3673 | * in which case we need to remove it. And we cannot | |
3674 | * defer such a check and removal, to avoid | |
3675 | * inconsistencies in the time interval from the end | |
3676 | * of this function to the start of the deferred work. | |
3677 | * This situation seems to occur only in process | |
3678 | * context, as a consequence of a merge. In the | |
3679 | * current version of the code, this implies that the | |
3680 | * lock is held. | |
3681 | */ | |
3682 | ||
3683 | if (!RB_EMPTY_NODE(&rq->rb_node)) | |
3684 | bfq_remove_request(q, rq); | |
3685 | bfq_put_rq_priv_body(bfqq); | |
3686 | } | |
3687 | ||
3688 | rq->elv.priv[0] = NULL; | |
3689 | rq->elv.priv[1] = NULL; | |
3690 | } | |
3691 | ||
3692 | /* | |
3693 | * Allocate bfq data structures associated with this request. | |
3694 | */ | |
3695 | static int bfq_get_rq_private(struct request_queue *q, struct request *rq, | |
3696 | struct bio *bio) | |
3697 | { | |
3698 | struct bfq_data *bfqd = q->elevator->elevator_data; | |
3699 | struct bfq_io_cq *bic = icq_to_bic(rq->elv.icq); | |
3700 | const int is_sync = rq_is_sync(rq); | |
3701 | struct bfq_queue *bfqq; | |
3702 | ||
3703 | spin_lock_irq(&bfqd->lock); | |
3704 | ||
3705 | bfq_check_ioprio_change(bic, bio); | |
3706 | ||
3707 | if (!bic) | |
3708 | goto queue_fail; | |
3709 | ||
3710 | bfqq = bic_to_bfqq(bic, is_sync); | |
3711 | if (!bfqq || bfqq == &bfqd->oom_bfqq) { | |
3712 | if (bfqq) | |
3713 | bfq_put_queue(bfqq); | |
3714 | bfqq = bfq_get_queue(bfqd, bio, is_sync, bic); | |
3715 | bic_set_bfqq(bic, bfqq, is_sync); | |
3716 | } | |
3717 | ||
3718 | bfqq->allocated++; | |
3719 | bfqq->ref++; | |
3720 | bfq_log_bfqq(bfqd, bfqq, "get_request %p: bfqq %p, %d", | |
3721 | rq, bfqq, bfqq->ref); | |
3722 | ||
3723 | rq->elv.priv[0] = bic; | |
3724 | rq->elv.priv[1] = bfqq; | |
3725 | ||
3726 | spin_unlock_irq(&bfqd->lock); | |
3727 | ||
3728 | return 0; | |
3729 | ||
3730 | queue_fail: | |
3731 | spin_unlock_irq(&bfqd->lock); | |
3732 | ||
3733 | return 1; | |
3734 | } | |
3735 | ||
3736 | static void bfq_idle_slice_timer_body(struct bfq_queue *bfqq) | |
3737 | { | |
3738 | struct bfq_data *bfqd = bfqq->bfqd; | |
3739 | enum bfqq_expiration reason; | |
3740 | unsigned long flags; | |
3741 | ||
3742 | spin_lock_irqsave(&bfqd->lock, flags); | |
3743 | bfq_clear_bfqq_wait_request(bfqq); | |
3744 | ||
3745 | if (bfqq != bfqd->in_service_queue) { | |
3746 | spin_unlock_irqrestore(&bfqd->lock, flags); | |
3747 | return; | |
3748 | } | |
3749 | ||
3750 | if (bfq_bfqq_budget_timeout(bfqq)) | |
3751 | /* | |
3752 | * Also here the queue can be safely expired | |
3753 | * for budget timeout without wasting | |
3754 | * guarantees | |
3755 | */ | |
3756 | reason = BFQQE_BUDGET_TIMEOUT; | |
3757 | else if (bfqq->queued[0] == 0 && bfqq->queued[1] == 0) | |
3758 | /* | |
3759 | * The queue may not be empty upon timer expiration, | |
3760 | * because we may not disable the timer when the | |
3761 | * first request of the in-service queue arrives | |
3762 | * during disk idling. | |
3763 | */ | |
3764 | reason = BFQQE_TOO_IDLE; | |
3765 | else | |
3766 | goto schedule_dispatch; | |
3767 | ||
3768 | bfq_bfqq_expire(bfqd, bfqq, true, reason); | |
3769 | ||
3770 | schedule_dispatch: | |
3771 | spin_unlock_irqrestore(&bfqd->lock, flags); | |
3772 | bfq_schedule_dispatch(bfqd); | |
3773 | } | |
3774 | ||
3775 | /* | |
3776 | * Handler of the expiration of the timer running if the in-service queue | |
3777 | * is idling inside its time slice. | |
3778 | */ | |
3779 | static enum hrtimer_restart bfq_idle_slice_timer(struct hrtimer *timer) | |
3780 | { | |
3781 | struct bfq_data *bfqd = container_of(timer, struct bfq_data, | |
3782 | idle_slice_timer); | |
3783 | struct bfq_queue *bfqq = bfqd->in_service_queue; | |
3784 | ||
3785 | /* | |
3786 | * Theoretical race here: the in-service queue can be NULL or | |
3787 | * different from the queue that was idling if a new request | |
3788 | * arrives for the current queue and there is a full dispatch | |
3789 | * cycle that changes the in-service queue. This can hardly | |
3790 | * happen, but in the worst case we just expire a queue too | |
3791 | * early. | |
3792 | */ | |
3793 | if (bfqq) | |
3794 | bfq_idle_slice_timer_body(bfqq); | |
3795 | ||
3796 | return HRTIMER_NORESTART; | |
3797 | } | |
3798 | ||
3799 | static void __bfq_put_async_bfqq(struct bfq_data *bfqd, | |
3800 | struct bfq_queue **bfqq_ptr) | |
3801 | { | |
3802 | struct bfq_queue *bfqq = *bfqq_ptr; | |
3803 | ||
3804 | bfq_log(bfqd, "put_async_bfqq: %p", bfqq); | |
3805 | if (bfqq) { | |
3806 | bfq_log_bfqq(bfqd, bfqq, "put_async_bfqq: putting %p, %d", | |
3807 | bfqq, bfqq->ref); | |
3808 | bfq_put_queue(bfqq); | |
3809 | *bfqq_ptr = NULL; | |
3810 | } | |
3811 | } | |
3812 | ||
3813 | /* | |
3814 | * Release the extra reference of the async queues as the device | |
3815 | * goes away. | |
3816 | */ | |
3817 | static void bfq_put_async_queues(struct bfq_data *bfqd) | |
3818 | { | |
3819 | int i, j; | |
3820 | ||
3821 | for (i = 0; i < 2; i++) | |
3822 | for (j = 0; j < IOPRIO_BE_NR; j++) | |
3823 | __bfq_put_async_bfqq(bfqd, &async_bfqq[i][j]); | |
3824 | ||
3825 | __bfq_put_async_bfqq(bfqd, &async_idle_bfqq); | |
3826 | } | |
3827 | ||
3828 | static void bfq_exit_queue(struct elevator_queue *e) | |
3829 | { | |
3830 | struct bfq_data *bfqd = e->elevator_data; | |
3831 | struct bfq_queue *bfqq, *n; | |
3832 | ||
3833 | hrtimer_cancel(&bfqd->idle_slice_timer); | |
3834 | ||
3835 | spin_lock_irq(&bfqd->lock); | |
3836 | list_for_each_entry_safe(bfqq, n, &bfqd->idle_list, bfqq_list) | |
3837 | bfq_deactivate_bfqq(bfqd, bfqq, false); | |
3838 | bfq_put_async_queues(bfqd); | |
3839 | spin_unlock_irq(&bfqd->lock); | |
3840 | ||
3841 | hrtimer_cancel(&bfqd->idle_slice_timer); | |
3842 | ||
3843 | kfree(bfqd); | |
3844 | } | |
3845 | ||
3846 | static int bfq_init_queue(struct request_queue *q, struct elevator_type *e) | |
3847 | { | |
3848 | struct bfq_data *bfqd; | |
3849 | struct elevator_queue *eq; | |
3850 | int i; | |
3851 | ||
3852 | eq = elevator_alloc(q, e); | |
3853 | if (!eq) | |
3854 | return -ENOMEM; | |
3855 | ||
3856 | bfqd = kzalloc_node(sizeof(*bfqd), GFP_KERNEL, q->node); | |
3857 | if (!bfqd) { | |
3858 | kobject_put(&eq->kobj); | |
3859 | return -ENOMEM; | |
3860 | } | |
3861 | eq->elevator_data = bfqd; | |
3862 | ||
3863 | /* | |
3864 | * Our fallback bfqq if bfq_find_alloc_queue() runs into OOM issues. | |
3865 | * Grab a permanent reference to it, so that the normal code flow | |
3866 | * will not attempt to free it. | |
3867 | */ | |
3868 | bfq_init_bfqq(bfqd, &bfqd->oom_bfqq, NULL, 1, 0); | |
3869 | bfqd->oom_bfqq.ref++; | |
3870 | bfqd->oom_bfqq.new_ioprio = BFQ_DEFAULT_QUEUE_IOPRIO; | |
3871 | bfqd->oom_bfqq.new_ioprio_class = IOPRIO_CLASS_BE; | |
3872 | bfqd->oom_bfqq.entity.new_weight = | |
3873 | bfq_ioprio_to_weight(bfqd->oom_bfqq.new_ioprio); | |
3874 | /* | |
3875 | * Trigger weight initialization, according to ioprio, at the | |
3876 | * oom_bfqq's first activation. The oom_bfqq's ioprio and ioprio | |
3877 | * class won't be changed any more. | |
3878 | */ | |
3879 | bfqd->oom_bfqq.entity.prio_changed = 1; | |
3880 | ||
3881 | bfqd->queue = q; | |
3882 | ||
3883 | for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) | |
3884 | bfqd->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT; | |
3885 | ||
3886 | hrtimer_init(&bfqd->idle_slice_timer, CLOCK_MONOTONIC, | |
3887 | HRTIMER_MODE_REL); | |
3888 | bfqd->idle_slice_timer.function = bfq_idle_slice_timer; | |
3889 | ||
3890 | INIT_LIST_HEAD(&bfqd->active_list); | |
3891 | INIT_LIST_HEAD(&bfqd->idle_list); | |
3892 | ||
3893 | bfqd->hw_tag = -1; | |
3894 | ||
3895 | bfqd->bfq_max_budget = bfq_default_max_budget; | |
3896 | ||
3897 | bfqd->bfq_fifo_expire[0] = bfq_fifo_expire[0]; | |
3898 | bfqd->bfq_fifo_expire[1] = bfq_fifo_expire[1]; | |
3899 | bfqd->bfq_back_max = bfq_back_max; | |
3900 | bfqd->bfq_back_penalty = bfq_back_penalty; | |
3901 | bfqd->bfq_slice_idle = bfq_slice_idle; | |
3902 | bfqd->bfq_class_idle_last_service = 0; | |
3903 | bfqd->bfq_timeout = bfq_timeout; | |
3904 | ||
3905 | bfqd->bfq_requests_within_timer = 120; | |
3906 | ||
3907 | spin_lock_init(&bfqd->lock); | |
3908 | INIT_LIST_HEAD(&bfqd->dispatch); | |
3909 | ||
3910 | q->elevator = eq; | |
3911 | ||
3912 | return 0; | |
3913 | } | |
3914 | ||
3915 | static void bfq_slab_kill(void) | |
3916 | { | |
3917 | kmem_cache_destroy(bfq_pool); | |
3918 | } | |
3919 | ||
3920 | static int __init bfq_slab_setup(void) | |
3921 | { | |
3922 | bfq_pool = KMEM_CACHE(bfq_queue, 0); | |
3923 | if (!bfq_pool) | |
3924 | return -ENOMEM; | |
3925 | return 0; | |
3926 | } | |
3927 | ||
3928 | static ssize_t bfq_var_show(unsigned int var, char *page) | |
3929 | { | |
3930 | return sprintf(page, "%u\n", var); | |
3931 | } | |
3932 | ||
3933 | static ssize_t bfq_var_store(unsigned long *var, const char *page, | |
3934 | size_t count) | |
3935 | { | |
3936 | unsigned long new_val; | |
3937 | int ret = kstrtoul(page, 10, &new_val); | |
3938 | ||
3939 | if (ret == 0) | |
3940 | *var = new_val; | |
3941 | ||
3942 | return count; | |
3943 | } | |
3944 | ||
3945 | #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ | |
3946 | static ssize_t __FUNC(struct elevator_queue *e, char *page) \ | |
3947 | { \ | |
3948 | struct bfq_data *bfqd = e->elevator_data; \ | |
3949 | u64 __data = __VAR; \ | |
3950 | if (__CONV == 1) \ | |
3951 | __data = jiffies_to_msecs(__data); \ | |
3952 | else if (__CONV == 2) \ | |
3953 | __data = div_u64(__data, NSEC_PER_MSEC); \ | |
3954 | return bfq_var_show(__data, (page)); \ | |
3955 | } | |
3956 | SHOW_FUNCTION(bfq_fifo_expire_sync_show, bfqd->bfq_fifo_expire[1], 2); | |
3957 | SHOW_FUNCTION(bfq_fifo_expire_async_show, bfqd->bfq_fifo_expire[0], 2); | |
3958 | SHOW_FUNCTION(bfq_back_seek_max_show, bfqd->bfq_back_max, 0); | |
3959 | SHOW_FUNCTION(bfq_back_seek_penalty_show, bfqd->bfq_back_penalty, 0); | |
3960 | SHOW_FUNCTION(bfq_slice_idle_show, bfqd->bfq_slice_idle, 2); | |
3961 | SHOW_FUNCTION(bfq_max_budget_show, bfqd->bfq_user_max_budget, 0); | |
3962 | SHOW_FUNCTION(bfq_timeout_sync_show, bfqd->bfq_timeout, 1); | |
3963 | SHOW_FUNCTION(bfq_strict_guarantees_show, bfqd->strict_guarantees, 0); | |
3964 | #undef SHOW_FUNCTION | |
3965 | ||
3966 | #define USEC_SHOW_FUNCTION(__FUNC, __VAR) \ | |
3967 | static ssize_t __FUNC(struct elevator_queue *e, char *page) \ | |
3968 | { \ | |
3969 | struct bfq_data *bfqd = e->elevator_data; \ | |
3970 | u64 __data = __VAR; \ | |
3971 | __data = div_u64(__data, NSEC_PER_USEC); \ | |
3972 | return bfq_var_show(__data, (page)); \ | |
3973 | } | |
3974 | USEC_SHOW_FUNCTION(bfq_slice_idle_us_show, bfqd->bfq_slice_idle); | |
3975 | #undef USEC_SHOW_FUNCTION | |
3976 | ||
3977 | #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ | |
3978 | static ssize_t \ | |
3979 | __FUNC(struct elevator_queue *e, const char *page, size_t count) \ | |
3980 | { \ | |
3981 | struct bfq_data *bfqd = e->elevator_data; \ | |
3982 | unsigned long uninitialized_var(__data); \ | |
3983 | int ret = bfq_var_store(&__data, (page), count); \ | |
3984 | if (__data < (MIN)) \ | |
3985 | __data = (MIN); \ | |
3986 | else if (__data > (MAX)) \ | |
3987 | __data = (MAX); \ | |
3988 | if (__CONV == 1) \ | |
3989 | *(__PTR) = msecs_to_jiffies(__data); \ | |
3990 | else if (__CONV == 2) \ | |
3991 | *(__PTR) = (u64)__data * NSEC_PER_MSEC; \ | |
3992 | else \ | |
3993 | *(__PTR) = __data; \ | |
3994 | return ret; \ | |
3995 | } | |
3996 | STORE_FUNCTION(bfq_fifo_expire_sync_store, &bfqd->bfq_fifo_expire[1], 1, | |
3997 | INT_MAX, 2); | |
3998 | STORE_FUNCTION(bfq_fifo_expire_async_store, &bfqd->bfq_fifo_expire[0], 1, | |
3999 | INT_MAX, 2); | |
4000 | STORE_FUNCTION(bfq_back_seek_max_store, &bfqd->bfq_back_max, 0, INT_MAX, 0); | |
4001 | STORE_FUNCTION(bfq_back_seek_penalty_store, &bfqd->bfq_back_penalty, 1, | |
4002 | INT_MAX, 0); | |
4003 | STORE_FUNCTION(bfq_slice_idle_store, &bfqd->bfq_slice_idle, 0, INT_MAX, 2); | |
4004 | #undef STORE_FUNCTION | |
4005 | ||
4006 | #define USEC_STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \ | |
4007 | static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count)\ | |
4008 | { \ | |
4009 | struct bfq_data *bfqd = e->elevator_data; \ | |
4010 | unsigned long uninitialized_var(__data); \ | |
4011 | int ret = bfq_var_store(&__data, (page), count); \ | |
4012 | if (__data < (MIN)) \ | |
4013 | __data = (MIN); \ | |
4014 | else if (__data > (MAX)) \ | |
4015 | __data = (MAX); \ | |
4016 | *(__PTR) = (u64)__data * NSEC_PER_USEC; \ | |
4017 | return ret; \ | |
4018 | } | |
4019 | USEC_STORE_FUNCTION(bfq_slice_idle_us_store, &bfqd->bfq_slice_idle, 0, | |
4020 | UINT_MAX); | |
4021 | #undef USEC_STORE_FUNCTION | |
4022 | ||
4023 | static unsigned long bfq_estimated_max_budget(struct bfq_data *bfqd) | |
4024 | { | |
4025 | u64 timeout = jiffies_to_msecs(bfqd->bfq_timeout); | |
4026 | ||
4027 | if (bfqd->peak_rate_samples >= BFQ_PEAK_RATE_SAMPLES) | |
4028 | return bfq_calc_max_budget(bfqd->peak_rate, timeout); | |
4029 | else | |
4030 | return bfq_default_max_budget; | |
4031 | } | |
4032 | ||
4033 | static ssize_t bfq_max_budget_store(struct elevator_queue *e, | |
4034 | const char *page, size_t count) | |
4035 | { | |
4036 | struct bfq_data *bfqd = e->elevator_data; | |
4037 | unsigned long uninitialized_var(__data); | |
4038 | int ret = bfq_var_store(&__data, (page), count); | |
4039 | ||
4040 | if (__data == 0) | |
4041 | bfqd->bfq_max_budget = bfq_estimated_max_budget(bfqd); | |
4042 | else { | |
4043 | if (__data > INT_MAX) | |
4044 | __data = INT_MAX; | |
4045 | bfqd->bfq_max_budget = __data; | |
4046 | } | |
4047 | ||
4048 | bfqd->bfq_user_max_budget = __data; | |
4049 | ||
4050 | return ret; | |
4051 | } | |
4052 | ||
4053 | /* | |
4054 | * Leaving this name to preserve name compatibility with cfq | |
4055 | * parameters, but this timeout is used for both sync and async. | |
4056 | */ | |
4057 | static ssize_t bfq_timeout_sync_store(struct elevator_queue *e, | |
4058 | const char *page, size_t count) | |
4059 | { | |
4060 | struct bfq_data *bfqd = e->elevator_data; | |
4061 | unsigned long uninitialized_var(__data); | |
4062 | int ret = bfq_var_store(&__data, (page), count); | |
4063 | ||
4064 | if (__data < 1) | |
4065 | __data = 1; | |
4066 | else if (__data > INT_MAX) | |
4067 | __data = INT_MAX; | |
4068 | ||
4069 | bfqd->bfq_timeout = msecs_to_jiffies(__data); | |
4070 | if (bfqd->bfq_user_max_budget == 0) | |
4071 | bfqd->bfq_max_budget = bfq_estimated_max_budget(bfqd); | |
4072 | ||
4073 | return ret; | |
4074 | } | |
4075 | ||
4076 | static ssize_t bfq_strict_guarantees_store(struct elevator_queue *e, | |
4077 | const char *page, size_t count) | |
4078 | { | |
4079 | struct bfq_data *bfqd = e->elevator_data; | |
4080 | unsigned long uninitialized_var(__data); | |
4081 | int ret = bfq_var_store(&__data, (page), count); | |
4082 | ||
4083 | if (__data > 1) | |
4084 | __data = 1; | |
4085 | if (!bfqd->strict_guarantees && __data == 1 | |
4086 | && bfqd->bfq_slice_idle < 8 * NSEC_PER_MSEC) | |
4087 | bfqd->bfq_slice_idle = 8 * NSEC_PER_MSEC; | |
4088 | ||
4089 | bfqd->strict_guarantees = __data; | |
4090 | ||
4091 | return ret; | |
4092 | } | |
4093 | ||
4094 | #define BFQ_ATTR(name) \ | |
4095 | __ATTR(name, 0644, bfq_##name##_show, bfq_##name##_store) | |
4096 | ||
4097 | static struct elv_fs_entry bfq_attrs[] = { | |
4098 | BFQ_ATTR(fifo_expire_sync), | |
4099 | BFQ_ATTR(fifo_expire_async), | |
4100 | BFQ_ATTR(back_seek_max), | |
4101 | BFQ_ATTR(back_seek_penalty), | |
4102 | BFQ_ATTR(slice_idle), | |
4103 | BFQ_ATTR(slice_idle_us), | |
4104 | BFQ_ATTR(max_budget), | |
4105 | BFQ_ATTR(timeout_sync), | |
4106 | BFQ_ATTR(strict_guarantees), | |
4107 | __ATTR_NULL | |
4108 | }; | |
4109 | ||
4110 | static struct elevator_type iosched_bfq_mq = { | |
4111 | .ops.mq = { | |
4112 | .get_rq_priv = bfq_get_rq_private, | |
4113 | .put_rq_priv = bfq_put_rq_private, | |
4114 | .exit_icq = bfq_exit_icq, | |
4115 | .insert_requests = bfq_insert_requests, | |
4116 | .dispatch_request = bfq_dispatch_request, | |
4117 | .next_request = elv_rb_latter_request, | |
4118 | .former_request = elv_rb_former_request, | |
4119 | .allow_merge = bfq_allow_bio_merge, | |
4120 | .bio_merge = bfq_bio_merge, | |
4121 | .request_merge = bfq_request_merge, | |
4122 | .requests_merged = bfq_requests_merged, | |
4123 | .request_merged = bfq_request_merged, | |
4124 | .has_work = bfq_has_work, | |
4125 | .init_sched = bfq_init_queue, | |
4126 | .exit_sched = bfq_exit_queue, | |
4127 | }, | |
4128 | ||
4129 | .uses_mq = true, | |
4130 | .icq_size = sizeof(struct bfq_io_cq), | |
4131 | .icq_align = __alignof__(struct bfq_io_cq), | |
4132 | .elevator_attrs = bfq_attrs, | |
4133 | .elevator_name = "bfq", | |
4134 | .elevator_owner = THIS_MODULE, | |
4135 | }; | |
4136 | ||
4137 | static int __init bfq_init(void) | |
4138 | { | |
4139 | int ret; | |
4140 | ||
4141 | ret = -ENOMEM; | |
4142 | if (bfq_slab_setup()) | |
4143 | goto err_pol_unreg; | |
4144 | ||
4145 | ret = elv_register(&iosched_bfq_mq); | |
4146 | if (ret) | |
4147 | goto err_pol_unreg; | |
4148 | ||
4149 | return 0; | |
4150 | ||
4151 | err_pol_unreg: | |
4152 | return ret; | |
4153 | } | |
4154 | ||
4155 | static void __exit bfq_exit(void) | |
4156 | { | |
4157 | elv_unregister(&iosched_bfq_mq); | |
4158 | bfq_slab_kill(); | |
4159 | } | |
4160 | ||
4161 | module_init(bfq_init); | |
4162 | module_exit(bfq_exit); | |
4163 | ||
4164 | MODULE_AUTHOR("Paolo Valente"); | |
4165 | MODULE_LICENSE("GPL"); | |
4166 | MODULE_DESCRIPTION("MQ Budget Fair Queueing I/O Scheduler"); |