1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * buffered writeback throttling. loosely based on CoDel. We can't drop |
4 | * packets for IO scheduling, so the logic is something like this: |
5 | * |
6 | * - Monitor latencies in a defined window of time. |
7 | * - If the minimum latency in the above window exceeds some target, increment |
8 | * scaling step and scale down queue depth by a factor of 2x. The monitoring |
9 | * window is then shrunk to 100 / sqrt(scaling step + 1). |
10 | * - For any window where we don't have solid data on what the latencies |
11 | * look like, retain status quo. |
12 | * - If latencies look good, decrement scaling step. |
13 | * - If we're only doing writes, allow the scaling step to go negative. This |
14 | * will temporarily boost write performance, snapping back to a stable |
15 | * scaling step of 0 if reads show up or the heavy writers finish. Unlike |
16 | * positive scaling steps where we shrink the monitoring window, a negative |
17 | * scaling step retains the default step==0 window size. |
18 | * |
19 | * Copyright (C) 2016 Jens Axboe |
20 | * |
21 | */ |
22 | #include <linux/kernel.h> |
23 | #include <linux/blk_types.h> |
24 | #include <linux/slab.h> |
25 | #include <linux/backing-dev.h> |
26 | #include <linux/swap.h> |
27 | |
28 | #include "blk-stat.h" |
29 | #include "blk-wbt.h" |
30 | #include "blk-rq-qos.h" |
31 | #include "elevator.h" |
32 | #include "blk.h" |
33 | |
34 | #define CREATE_TRACE_POINTS |
35 | #include <trace/events/wbt.h> |
36 | |
37 | enum wbt_flags { |
38 | WBT_TRACKED = 1, /* write, tracked for throttling */ |
39 | WBT_READ = 2, /* read */ |
40 | WBT_KSWAPD = 4, /* write, from kswapd */ |
41 | WBT_DISCARD = 8, /* discard */ |
42 | |
43 | WBT_NR_BITS = 4, /* number of bits */ |
44 | }; |
45 | |
46 | enum { |
47 | WBT_RWQ_BG = 0, |
48 | WBT_RWQ_KSWAPD, |
49 | WBT_RWQ_DISCARD, |
50 | WBT_NUM_RWQ, |
51 | }; |
52 | |
53 | /* |
54 | * If current state is WBT_STATE_ON/OFF_DEFAULT, it can be covered to any other |
55 | * state, if current state is WBT_STATE_ON/OFF_MANUAL, it can only be covered |
56 | * to WBT_STATE_OFF/ON_MANUAL. |
57 | */ |
58 | enum { |
59 | WBT_STATE_ON_DEFAULT = 1, /* on by default */ |
60 | WBT_STATE_ON_MANUAL = 2, /* on manually by sysfs */ |
61 | WBT_STATE_OFF_DEFAULT = 3, /* off by default */ |
62 | WBT_STATE_OFF_MANUAL = 4, /* off manually by sysfs */ |
63 | }; |
64 | |
65 | struct rq_wb { |
66 | /* |
67 | * Settings that govern how we throttle |
68 | */ |
69 | unsigned int wb_background; /* background writeback */ |
70 | unsigned int wb_normal; /* normal writeback */ |
71 | |
72 | short enable_state; /* WBT_STATE_* */ |
73 | |
74 | /* |
75 | * Number of consecutive periods where we don't have enough |
76 | * information to make a firm scale up/down decision. |
77 | */ |
78 | unsigned int unknown_cnt; |
79 | |
80 | u64 win_nsec; /* default window size */ |
81 | u64 cur_win_nsec; /* current window size */ |
82 | |
83 | struct blk_stat_callback *cb; |
84 | |
85 | u64 sync_issue; |
86 | void *sync_cookie; |
87 | |
88 | unsigned long last_issue; /* last non-throttled issue */ |
89 | unsigned long last_comp; /* last non-throttled comp */ |
90 | unsigned long min_lat_nsec; |
91 | struct rq_qos rqos; |
92 | struct rq_wait rq_wait[WBT_NUM_RWQ]; |
93 | struct rq_depth rq_depth; |
94 | }; |
95 | |
96 | static inline struct rq_wb *RQWB(struct rq_qos *rqos) |
97 | { |
98 | return container_of(rqos, struct rq_wb, rqos); |
99 | } |
100 | |
101 | static inline void wbt_clear_state(struct request *rq) |
102 | { |
103 | rq->wbt_flags = 0; |
104 | } |
105 | |
106 | static inline enum wbt_flags wbt_flags(struct request *rq) |
107 | { |
108 | return rq->wbt_flags; |
109 | } |
110 | |
111 | static inline bool wbt_is_tracked(struct request *rq) |
112 | { |
113 | return rq->wbt_flags & WBT_TRACKED; |
114 | } |
115 | |
116 | static inline bool wbt_is_read(struct request *rq) |
117 | { |
118 | return rq->wbt_flags & WBT_READ; |
119 | } |
120 | |
121 | enum { |
122 | /* |
123 | * Default setting, we'll scale up (to 75% of QD max) or down (min 1) |
124 | * from here depending on device stats |
125 | */ |
126 | RWB_DEF_DEPTH = 16, |
127 | |
128 | /* |
129 | * 100msec window |
130 | */ |
131 | RWB_WINDOW_NSEC = 100 * 1000 * 1000ULL, |
132 | |
133 | /* |
134 | * Disregard stats, if we don't meet this minimum |
135 | */ |
136 | RWB_MIN_WRITE_SAMPLES = 3, |
137 | |
138 | /* |
139 | * If we have this number of consecutive windows with not enough |
140 | * information to scale up or down, scale up. |
141 | */ |
142 | RWB_UNKNOWN_BUMP = 5, |
143 | }; |
144 | |
145 | static inline bool rwb_enabled(struct rq_wb *rwb) |
146 | { |
147 | return rwb && rwb->enable_state != WBT_STATE_OFF_DEFAULT && |
148 | rwb->enable_state != WBT_STATE_OFF_MANUAL; |
149 | } |
150 | |
151 | static void wb_timestamp(struct rq_wb *rwb, unsigned long *var) |
152 | { |
153 | if (rwb_enabled(rwb)) { |
154 | const unsigned long cur = jiffies; |
155 | |
156 | if (cur != *var) |
157 | *var = cur; |
158 | } |
159 | } |
160 | |
161 | /* |
162 | * If a task was rate throttled in balance_dirty_pages() within the last |
163 | * second or so, use that to indicate a higher cleaning rate. |
164 | */ |
165 | static bool wb_recent_wait(struct rq_wb *rwb) |
166 | { |
167 | struct backing_dev_info *bdi = rwb->rqos.disk->bdi; |
168 | |
169 | return time_before(jiffies, bdi->last_bdp_sleep + HZ); |
170 | } |
171 | |
172 | static inline struct rq_wait *get_rq_wait(struct rq_wb *rwb, |
173 | enum wbt_flags wb_acct) |
174 | { |
175 | if (wb_acct & WBT_KSWAPD) |
176 | return &rwb->rq_wait[WBT_RWQ_KSWAPD]; |
177 | else if (wb_acct & WBT_DISCARD) |
178 | return &rwb->rq_wait[WBT_RWQ_DISCARD]; |
179 | |
180 | return &rwb->rq_wait[WBT_RWQ_BG]; |
181 | } |
182 | |
183 | static void rwb_wake_all(struct rq_wb *rwb) |
184 | { |
185 | int i; |
186 | |
187 | for (i = 0; i < WBT_NUM_RWQ; i++) { |
188 | struct rq_wait *rqw = &rwb->rq_wait[i]; |
189 | |
190 | if (wq_has_sleeper(wq_head: &rqw->wait)) |
191 | wake_up_all(&rqw->wait); |
192 | } |
193 | } |
194 | |
195 | static void wbt_rqw_done(struct rq_wb *rwb, struct rq_wait *rqw, |
196 | enum wbt_flags wb_acct) |
197 | { |
198 | int inflight, limit; |
199 | |
200 | inflight = atomic_dec_return(v: &rqw->inflight); |
201 | |
202 | /* |
203 | * For discards, our limit is always the background. For writes, if |
204 | * the device does write back caching, drop further down before we |
205 | * wake people up. |
206 | */ |
207 | if (wb_acct & WBT_DISCARD) |
208 | limit = rwb->wb_background; |
209 | else if (test_bit(QUEUE_FLAG_WC, &rwb->rqos.disk->queue->queue_flags) && |
210 | !wb_recent_wait(rwb)) |
211 | limit = 0; |
212 | else |
213 | limit = rwb->wb_normal; |
214 | |
215 | /* |
216 | * Don't wake anyone up if we are above the normal limit. |
217 | */ |
218 | if (inflight && inflight >= limit) |
219 | return; |
220 | |
221 | if (wq_has_sleeper(wq_head: &rqw->wait)) { |
222 | int diff = limit - inflight; |
223 | |
224 | if (!inflight || diff >= rwb->wb_background / 2) |
225 | wake_up_all(&rqw->wait); |
226 | } |
227 | } |
228 | |
229 | static void __wbt_done(struct rq_qos *rqos, enum wbt_flags wb_acct) |
230 | { |
231 | struct rq_wb *rwb = RQWB(rqos); |
232 | struct rq_wait *rqw; |
233 | |
234 | if (!(wb_acct & WBT_TRACKED)) |
235 | return; |
236 | |
237 | rqw = get_rq_wait(rwb, wb_acct); |
238 | wbt_rqw_done(rwb, rqw, wb_acct); |
239 | } |
240 | |
241 | /* |
242 | * Called on completion of a request. Note that it's also called when |
243 | * a request is merged, when the request gets freed. |
244 | */ |
245 | static void wbt_done(struct rq_qos *rqos, struct request *rq) |
246 | { |
247 | struct rq_wb *rwb = RQWB(rqos); |
248 | |
249 | if (!wbt_is_tracked(rq)) { |
250 | if (rwb->sync_cookie == rq) { |
251 | rwb->sync_issue = 0; |
252 | rwb->sync_cookie = NULL; |
253 | } |
254 | |
255 | if (wbt_is_read(rq)) |
256 | wb_timestamp(rwb, var: &rwb->last_comp); |
257 | } else { |
258 | WARN_ON_ONCE(rq == rwb->sync_cookie); |
259 | __wbt_done(rqos, wb_acct: wbt_flags(rq)); |
260 | } |
261 | wbt_clear_state(rq); |
262 | } |
263 | |
264 | static inline bool stat_sample_valid(struct blk_rq_stat *stat) |
265 | { |
266 | /* |
267 | * We need at least one read sample, and a minimum of |
268 | * RWB_MIN_WRITE_SAMPLES. We require some write samples to know |
269 | * that it's writes impacting us, and not just some sole read on |
270 | * a device that is in a lower power state. |
271 | */ |
272 | return (stat[READ].nr_samples >= 1 && |
273 | stat[WRITE].nr_samples >= RWB_MIN_WRITE_SAMPLES); |
274 | } |
275 | |
276 | static u64 rwb_sync_issue_lat(struct rq_wb *rwb) |
277 | { |
278 | u64 issue = READ_ONCE(rwb->sync_issue); |
279 | |
280 | if (!issue || !rwb->sync_cookie) |
281 | return 0; |
282 | |
283 | return blk_time_get_ns() - issue; |
284 | } |
285 | |
286 | static inline unsigned int wbt_inflight(struct rq_wb *rwb) |
287 | { |
288 | unsigned int i, ret = 0; |
289 | |
290 | for (i = 0; i < WBT_NUM_RWQ; i++) |
291 | ret += atomic_read(v: &rwb->rq_wait[i].inflight); |
292 | |
293 | return ret; |
294 | } |
295 | |
296 | enum { |
297 | LAT_OK = 1, |
298 | LAT_UNKNOWN, |
299 | LAT_UNKNOWN_WRITES, |
300 | LAT_EXCEEDED, |
301 | }; |
302 | |
303 | static int latency_exceeded(struct rq_wb *rwb, struct blk_rq_stat *stat) |
304 | { |
305 | struct backing_dev_info *bdi = rwb->rqos.disk->bdi; |
306 | struct rq_depth *rqd = &rwb->rq_depth; |
307 | u64 thislat; |
308 | |
309 | /* |
310 | * If our stored sync issue exceeds the window size, or it |
311 | * exceeds our min target AND we haven't logged any entries, |
312 | * flag the latency as exceeded. wbt works off completion latencies, |
313 | * but for a flooded device, a single sync IO can take a long time |
314 | * to complete after being issued. If this time exceeds our |
315 | * monitoring window AND we didn't see any other completions in that |
316 | * window, then count that sync IO as a violation of the latency. |
317 | */ |
318 | thislat = rwb_sync_issue_lat(rwb); |
319 | if (thislat > rwb->cur_win_nsec || |
320 | (thislat > rwb->min_lat_nsec && !stat[READ].nr_samples)) { |
321 | trace_wbt_lat(bdi, lat: thislat); |
322 | return LAT_EXCEEDED; |
323 | } |
324 | |
325 | /* |
326 | * No read/write mix, if stat isn't valid |
327 | */ |
328 | if (!stat_sample_valid(stat)) { |
329 | /* |
330 | * If we had writes in this stat window and the window is |
331 | * current, we're only doing writes. If a task recently |
332 | * waited or still has writes in flights, consider us doing |
333 | * just writes as well. |
334 | */ |
335 | if (stat[WRITE].nr_samples || wb_recent_wait(rwb) || |
336 | wbt_inflight(rwb)) |
337 | return LAT_UNKNOWN_WRITES; |
338 | return LAT_UNKNOWN; |
339 | } |
340 | |
341 | /* |
342 | * If the 'min' latency exceeds our target, step down. |
343 | */ |
344 | if (stat[READ].min > rwb->min_lat_nsec) { |
345 | trace_wbt_lat(bdi, lat: stat[READ].min); |
346 | trace_wbt_stat(bdi, stat); |
347 | return LAT_EXCEEDED; |
348 | } |
349 | |
350 | if (rqd->scale_step) |
351 | trace_wbt_stat(bdi, stat); |
352 | |
353 | return LAT_OK; |
354 | } |
355 | |
356 | static void rwb_trace_step(struct rq_wb *rwb, const char *msg) |
357 | { |
358 | struct backing_dev_info *bdi = rwb->rqos.disk->bdi; |
359 | struct rq_depth *rqd = &rwb->rq_depth; |
360 | |
361 | trace_wbt_step(bdi, msg, step: rqd->scale_step, window: rwb->cur_win_nsec, |
362 | bg: rwb->wb_background, normal: rwb->wb_normal, max: rqd->max_depth); |
363 | } |
364 | |
365 | static void calc_wb_limits(struct rq_wb *rwb) |
366 | { |
367 | if (rwb->min_lat_nsec == 0) { |
368 | rwb->wb_normal = rwb->wb_background = 0; |
369 | } else if (rwb->rq_depth.max_depth <= 2) { |
370 | rwb->wb_normal = rwb->rq_depth.max_depth; |
371 | rwb->wb_background = 1; |
372 | } else { |
373 | rwb->wb_normal = (rwb->rq_depth.max_depth + 1) / 2; |
374 | rwb->wb_background = (rwb->rq_depth.max_depth + 3) / 4; |
375 | } |
376 | } |
377 | |
378 | static void scale_up(struct rq_wb *rwb) |
379 | { |
380 | if (!rq_depth_scale_up(rqd: &rwb->rq_depth)) |
381 | return; |
382 | calc_wb_limits(rwb); |
383 | rwb->unknown_cnt = 0; |
384 | rwb_wake_all(rwb); |
385 | rwb_trace_step(rwb, tracepoint_string("scale up" )); |
386 | } |
387 | |
388 | static void scale_down(struct rq_wb *rwb, bool hard_throttle) |
389 | { |
390 | if (!rq_depth_scale_down(rqd: &rwb->rq_depth, hard_throttle)) |
391 | return; |
392 | calc_wb_limits(rwb); |
393 | rwb->unknown_cnt = 0; |
394 | rwb_trace_step(rwb, tracepoint_string("scale down" )); |
395 | } |
396 | |
397 | static void rwb_arm_timer(struct rq_wb *rwb) |
398 | { |
399 | struct rq_depth *rqd = &rwb->rq_depth; |
400 | |
401 | if (rqd->scale_step > 0) { |
402 | /* |
403 | * We should speed this up, using some variant of a fast |
404 | * integer inverse square root calculation. Since we only do |
405 | * this for every window expiration, it's not a huge deal, |
406 | * though. |
407 | */ |
408 | rwb->cur_win_nsec = div_u64(dividend: rwb->win_nsec << 4, |
409 | divisor: int_sqrt((rqd->scale_step + 1) << 8)); |
410 | } else { |
411 | /* |
412 | * For step < 0, we don't want to increase/decrease the |
413 | * window size. |
414 | */ |
415 | rwb->cur_win_nsec = rwb->win_nsec; |
416 | } |
417 | |
418 | blk_stat_activate_nsecs(cb: rwb->cb, nsecs: rwb->cur_win_nsec); |
419 | } |
420 | |
421 | static void wb_timer_fn(struct blk_stat_callback *cb) |
422 | { |
423 | struct rq_wb *rwb = cb->data; |
424 | struct rq_depth *rqd = &rwb->rq_depth; |
425 | unsigned int inflight = wbt_inflight(rwb); |
426 | int status; |
427 | |
428 | if (!rwb->rqos.disk) |
429 | return; |
430 | |
431 | status = latency_exceeded(rwb, stat: cb->stat); |
432 | |
433 | trace_wbt_timer(bdi: rwb->rqos.disk->bdi, status, step: rqd->scale_step, inflight); |
434 | |
435 | /* |
436 | * If we exceeded the latency target, step down. If we did not, |
437 | * step one level up. If we don't know enough to say either exceeded |
438 | * or ok, then don't do anything. |
439 | */ |
440 | switch (status) { |
441 | case LAT_EXCEEDED: |
442 | scale_down(rwb, hard_throttle: true); |
443 | break; |
444 | case LAT_OK: |
445 | scale_up(rwb); |
446 | break; |
447 | case LAT_UNKNOWN_WRITES: |
448 | /* |
449 | * We started a the center step, but don't have a valid |
450 | * read/write sample, but we do have writes going on. |
451 | * Allow step to go negative, to increase write perf. |
452 | */ |
453 | scale_up(rwb); |
454 | break; |
455 | case LAT_UNKNOWN: |
456 | if (++rwb->unknown_cnt < RWB_UNKNOWN_BUMP) |
457 | break; |
458 | /* |
459 | * We get here when previously scaled reduced depth, and we |
460 | * currently don't have a valid read/write sample. For that |
461 | * case, slowly return to center state (step == 0). |
462 | */ |
463 | if (rqd->scale_step > 0) |
464 | scale_up(rwb); |
465 | else if (rqd->scale_step < 0) |
466 | scale_down(rwb, hard_throttle: false); |
467 | break; |
468 | default: |
469 | break; |
470 | } |
471 | |
472 | /* |
473 | * Re-arm timer, if we have IO in flight |
474 | */ |
475 | if (rqd->scale_step || inflight) |
476 | rwb_arm_timer(rwb); |
477 | } |
478 | |
479 | static void wbt_update_limits(struct rq_wb *rwb) |
480 | { |
481 | struct rq_depth *rqd = &rwb->rq_depth; |
482 | |
483 | rqd->scale_step = 0; |
484 | rqd->scaled_max = false; |
485 | |
486 | rq_depth_calc_max_depth(rqd); |
487 | calc_wb_limits(rwb); |
488 | |
489 | rwb_wake_all(rwb); |
490 | } |
491 | |
492 | bool wbt_disabled(struct request_queue *q) |
493 | { |
494 | struct rq_qos *rqos = wbt_rq_qos(q); |
495 | |
496 | return !rqos || !rwb_enabled(rwb: RQWB(rqos)); |
497 | } |
498 | |
499 | u64 wbt_get_min_lat(struct request_queue *q) |
500 | { |
501 | struct rq_qos *rqos = wbt_rq_qos(q); |
502 | if (!rqos) |
503 | return 0; |
504 | return RQWB(rqos)->min_lat_nsec; |
505 | } |
506 | |
507 | void wbt_set_min_lat(struct request_queue *q, u64 val) |
508 | { |
509 | struct rq_qos *rqos = wbt_rq_qos(q); |
510 | if (!rqos) |
511 | return; |
512 | |
513 | RQWB(rqos)->min_lat_nsec = val; |
514 | if (val) |
515 | RQWB(rqos)->enable_state = WBT_STATE_ON_MANUAL; |
516 | else |
517 | RQWB(rqos)->enable_state = WBT_STATE_OFF_MANUAL; |
518 | |
519 | wbt_update_limits(rwb: RQWB(rqos)); |
520 | } |
521 | |
522 | |
523 | static bool close_io(struct rq_wb *rwb) |
524 | { |
525 | const unsigned long now = jiffies; |
526 | |
527 | return time_before(now, rwb->last_issue + HZ / 10) || |
528 | time_before(now, rwb->last_comp + HZ / 10); |
529 | } |
530 | |
531 | #define REQ_HIPRIO (REQ_SYNC | REQ_META | REQ_PRIO) |
532 | |
533 | static inline unsigned int get_limit(struct rq_wb *rwb, blk_opf_t opf) |
534 | { |
535 | unsigned int limit; |
536 | |
537 | if ((opf & REQ_OP_MASK) == REQ_OP_DISCARD) |
538 | return rwb->wb_background; |
539 | |
540 | /* |
541 | * At this point we know it's a buffered write. If this is |
542 | * kswapd trying to free memory, or REQ_SYNC is set, then |
543 | * it's WB_SYNC_ALL writeback, and we'll use the max limit for |
544 | * that. If the write is marked as a background write, then use |
545 | * the idle limit, or go to normal if we haven't had competing |
546 | * IO for a bit. |
547 | */ |
548 | if ((opf & REQ_HIPRIO) || wb_recent_wait(rwb) || current_is_kswapd()) |
549 | limit = rwb->rq_depth.max_depth; |
550 | else if ((opf & REQ_BACKGROUND) || close_io(rwb)) { |
551 | /* |
552 | * If less than 100ms since we completed unrelated IO, |
553 | * limit us to half the depth for background writeback. |
554 | */ |
555 | limit = rwb->wb_background; |
556 | } else |
557 | limit = rwb->wb_normal; |
558 | |
559 | return limit; |
560 | } |
561 | |
562 | struct wbt_wait_data { |
563 | struct rq_wb *rwb; |
564 | enum wbt_flags wb_acct; |
565 | blk_opf_t opf; |
566 | }; |
567 | |
568 | static bool wbt_inflight_cb(struct rq_wait *rqw, void *private_data) |
569 | { |
570 | struct wbt_wait_data *data = private_data; |
571 | return rq_wait_inc_below(rq_wait: rqw, limit: get_limit(rwb: data->rwb, opf: data->opf)); |
572 | } |
573 | |
574 | static void wbt_cleanup_cb(struct rq_wait *rqw, void *private_data) |
575 | { |
576 | struct wbt_wait_data *data = private_data; |
577 | wbt_rqw_done(rwb: data->rwb, rqw, wb_acct: data->wb_acct); |
578 | } |
579 | |
580 | /* |
581 | * Block if we will exceed our limit, or if we are currently waiting for |
582 | * the timer to kick off queuing again. |
583 | */ |
584 | static void __wbt_wait(struct rq_wb *rwb, enum wbt_flags wb_acct, |
585 | blk_opf_t opf) |
586 | { |
587 | struct rq_wait *rqw = get_rq_wait(rwb, wb_acct); |
588 | struct wbt_wait_data data = { |
589 | .rwb = rwb, |
590 | .wb_acct = wb_acct, |
591 | .opf = opf, |
592 | }; |
593 | |
594 | rq_qos_wait(rqw, private_data: &data, acquire_inflight_cb: wbt_inflight_cb, cleanup_cb: wbt_cleanup_cb); |
595 | } |
596 | |
597 | static inline bool wbt_should_throttle(struct bio *bio) |
598 | { |
599 | switch (bio_op(bio)) { |
600 | case REQ_OP_WRITE: |
601 | /* |
602 | * Don't throttle WRITE_ODIRECT |
603 | */ |
604 | if ((bio->bi_opf & (REQ_SYNC | REQ_IDLE)) == |
605 | (REQ_SYNC | REQ_IDLE)) |
606 | return false; |
607 | fallthrough; |
608 | case REQ_OP_DISCARD: |
609 | return true; |
610 | default: |
611 | return false; |
612 | } |
613 | } |
614 | |
615 | static enum wbt_flags bio_to_wbt_flags(struct rq_wb *rwb, struct bio *bio) |
616 | { |
617 | enum wbt_flags flags = 0; |
618 | |
619 | if (!rwb_enabled(rwb)) |
620 | return 0; |
621 | |
622 | if (bio_op(bio) == REQ_OP_READ) { |
623 | flags = WBT_READ; |
624 | } else if (wbt_should_throttle(bio)) { |
625 | if (current_is_kswapd()) |
626 | flags |= WBT_KSWAPD; |
627 | if (bio_op(bio) == REQ_OP_DISCARD) |
628 | flags |= WBT_DISCARD; |
629 | flags |= WBT_TRACKED; |
630 | } |
631 | return flags; |
632 | } |
633 | |
634 | static void wbt_cleanup(struct rq_qos *rqos, struct bio *bio) |
635 | { |
636 | struct rq_wb *rwb = RQWB(rqos); |
637 | enum wbt_flags flags = bio_to_wbt_flags(rwb, bio); |
638 | __wbt_done(rqos, wb_acct: flags); |
639 | } |
640 | |
641 | /* |
642 | * May sleep, if we have exceeded the writeback limits. Caller can pass |
643 | * in an irq held spinlock, if it holds one when calling this function. |
644 | * If we do sleep, we'll release and re-grab it. |
645 | */ |
646 | static void wbt_wait(struct rq_qos *rqos, struct bio *bio) |
647 | { |
648 | struct rq_wb *rwb = RQWB(rqos); |
649 | enum wbt_flags flags; |
650 | |
651 | flags = bio_to_wbt_flags(rwb, bio); |
652 | if (!(flags & WBT_TRACKED)) { |
653 | if (flags & WBT_READ) |
654 | wb_timestamp(rwb, var: &rwb->last_issue); |
655 | return; |
656 | } |
657 | |
658 | __wbt_wait(rwb, wb_acct: flags, opf: bio->bi_opf); |
659 | |
660 | if (!blk_stat_is_active(cb: rwb->cb)) |
661 | rwb_arm_timer(rwb); |
662 | } |
663 | |
664 | static void wbt_track(struct rq_qos *rqos, struct request *rq, struct bio *bio) |
665 | { |
666 | struct rq_wb *rwb = RQWB(rqos); |
667 | rq->wbt_flags |= bio_to_wbt_flags(rwb, bio); |
668 | } |
669 | |
670 | static void wbt_issue(struct rq_qos *rqos, struct request *rq) |
671 | { |
672 | struct rq_wb *rwb = RQWB(rqos); |
673 | |
674 | if (!rwb_enabled(rwb)) |
675 | return; |
676 | |
677 | /* |
678 | * Track sync issue, in case it takes a long time to complete. Allows us |
679 | * to react quicker, if a sync IO takes a long time to complete. Note |
680 | * that this is just a hint. The request can go away when it completes, |
681 | * so it's important we never dereference it. We only use the address to |
682 | * compare with, which is why we store the sync_issue time locally. |
683 | */ |
684 | if (wbt_is_read(rq) && !rwb->sync_issue) { |
685 | rwb->sync_cookie = rq; |
686 | rwb->sync_issue = rq->io_start_time_ns; |
687 | } |
688 | } |
689 | |
690 | static void wbt_requeue(struct rq_qos *rqos, struct request *rq) |
691 | { |
692 | struct rq_wb *rwb = RQWB(rqos); |
693 | if (!rwb_enabled(rwb)) |
694 | return; |
695 | if (rq == rwb->sync_cookie) { |
696 | rwb->sync_issue = 0; |
697 | rwb->sync_cookie = NULL; |
698 | } |
699 | } |
700 | |
701 | /* |
702 | * Enable wbt if defaults are configured that way |
703 | */ |
704 | void wbt_enable_default(struct gendisk *disk) |
705 | { |
706 | struct request_queue *q = disk->queue; |
707 | struct rq_qos *rqos; |
708 | bool enable = IS_ENABLED(CONFIG_BLK_WBT_MQ); |
709 | |
710 | if (q->elevator && |
711 | test_bit(ELEVATOR_FLAG_DISABLE_WBT, &q->elevator->flags)) |
712 | enable = false; |
713 | |
714 | /* Throttling already enabled? */ |
715 | rqos = wbt_rq_qos(q); |
716 | if (rqos) { |
717 | if (enable && RQWB(rqos)->enable_state == WBT_STATE_OFF_DEFAULT) |
718 | RQWB(rqos)->enable_state = WBT_STATE_ON_DEFAULT; |
719 | return; |
720 | } |
721 | |
722 | /* Queue not registered? Maybe shutting down... */ |
723 | if (!blk_queue_registered(q)) |
724 | return; |
725 | |
726 | if (queue_is_mq(q) && enable) |
727 | wbt_init(disk); |
728 | } |
729 | EXPORT_SYMBOL_GPL(wbt_enable_default); |
730 | |
731 | u64 wbt_default_latency_nsec(struct request_queue *q) |
732 | { |
733 | /* |
734 | * We default to 2msec for non-rotational storage, and 75msec |
735 | * for rotational storage. |
736 | */ |
737 | if (blk_queue_nonrot(q)) |
738 | return 2000000ULL; |
739 | else |
740 | return 75000000ULL; |
741 | } |
742 | |
743 | static int wbt_data_dir(const struct request *rq) |
744 | { |
745 | const enum req_op op = req_op(req: rq); |
746 | |
747 | if (op == REQ_OP_READ) |
748 | return READ; |
749 | else if (op_is_write(op)) |
750 | return WRITE; |
751 | |
752 | /* don't account */ |
753 | return -1; |
754 | } |
755 | |
756 | static void wbt_queue_depth_changed(struct rq_qos *rqos) |
757 | { |
758 | RQWB(rqos)->rq_depth.queue_depth = blk_queue_depth(q: rqos->disk->queue); |
759 | wbt_update_limits(rwb: RQWB(rqos)); |
760 | } |
761 | |
762 | static void wbt_exit(struct rq_qos *rqos) |
763 | { |
764 | struct rq_wb *rwb = RQWB(rqos); |
765 | |
766 | blk_stat_remove_callback(q: rqos->disk->queue, cb: rwb->cb); |
767 | blk_stat_free_callback(cb: rwb->cb); |
768 | kfree(objp: rwb); |
769 | } |
770 | |
771 | /* |
772 | * Disable wbt, if enabled by default. |
773 | */ |
774 | void wbt_disable_default(struct gendisk *disk) |
775 | { |
776 | struct rq_qos *rqos = wbt_rq_qos(q: disk->queue); |
777 | struct rq_wb *rwb; |
778 | if (!rqos) |
779 | return; |
780 | rwb = RQWB(rqos); |
781 | if (rwb->enable_state == WBT_STATE_ON_DEFAULT) { |
782 | blk_stat_deactivate(cb: rwb->cb); |
783 | rwb->enable_state = WBT_STATE_OFF_DEFAULT; |
784 | } |
785 | } |
786 | EXPORT_SYMBOL_GPL(wbt_disable_default); |
787 | |
788 | #ifdef CONFIG_BLK_DEBUG_FS |
789 | static int wbt_curr_win_nsec_show(void *data, struct seq_file *m) |
790 | { |
791 | struct rq_qos *rqos = data; |
792 | struct rq_wb *rwb = RQWB(rqos); |
793 | |
794 | seq_printf(m, fmt: "%llu\n" , rwb->cur_win_nsec); |
795 | return 0; |
796 | } |
797 | |
798 | static int wbt_enabled_show(void *data, struct seq_file *m) |
799 | { |
800 | struct rq_qos *rqos = data; |
801 | struct rq_wb *rwb = RQWB(rqos); |
802 | |
803 | seq_printf(m, fmt: "%d\n" , rwb->enable_state); |
804 | return 0; |
805 | } |
806 | |
807 | static int wbt_id_show(void *data, struct seq_file *m) |
808 | { |
809 | struct rq_qos *rqos = data; |
810 | |
811 | seq_printf(m, fmt: "%u\n" , rqos->id); |
812 | return 0; |
813 | } |
814 | |
815 | static int wbt_inflight_show(void *data, struct seq_file *m) |
816 | { |
817 | struct rq_qos *rqos = data; |
818 | struct rq_wb *rwb = RQWB(rqos); |
819 | int i; |
820 | |
821 | for (i = 0; i < WBT_NUM_RWQ; i++) |
822 | seq_printf(m, fmt: "%d: inflight %d\n" , i, |
823 | atomic_read(v: &rwb->rq_wait[i].inflight)); |
824 | return 0; |
825 | } |
826 | |
827 | static int wbt_min_lat_nsec_show(void *data, struct seq_file *m) |
828 | { |
829 | struct rq_qos *rqos = data; |
830 | struct rq_wb *rwb = RQWB(rqos); |
831 | |
832 | seq_printf(m, fmt: "%lu\n" , rwb->min_lat_nsec); |
833 | return 0; |
834 | } |
835 | |
836 | static int wbt_unknown_cnt_show(void *data, struct seq_file *m) |
837 | { |
838 | struct rq_qos *rqos = data; |
839 | struct rq_wb *rwb = RQWB(rqos); |
840 | |
841 | seq_printf(m, fmt: "%u\n" , rwb->unknown_cnt); |
842 | return 0; |
843 | } |
844 | |
845 | static int wbt_normal_show(void *data, struct seq_file *m) |
846 | { |
847 | struct rq_qos *rqos = data; |
848 | struct rq_wb *rwb = RQWB(rqos); |
849 | |
850 | seq_printf(m, fmt: "%u\n" , rwb->wb_normal); |
851 | return 0; |
852 | } |
853 | |
854 | static int wbt_background_show(void *data, struct seq_file *m) |
855 | { |
856 | struct rq_qos *rqos = data; |
857 | struct rq_wb *rwb = RQWB(rqos); |
858 | |
859 | seq_printf(m, fmt: "%u\n" , rwb->wb_background); |
860 | return 0; |
861 | } |
862 | |
863 | static const struct blk_mq_debugfs_attr wbt_debugfs_attrs[] = { |
864 | {"curr_win_nsec" , 0400, wbt_curr_win_nsec_show}, |
865 | {"enabled" , 0400, wbt_enabled_show}, |
866 | {"id" , 0400, wbt_id_show}, |
867 | {"inflight" , 0400, wbt_inflight_show}, |
868 | {"min_lat_nsec" , 0400, wbt_min_lat_nsec_show}, |
869 | {"unknown_cnt" , 0400, wbt_unknown_cnt_show}, |
870 | {"wb_normal" , 0400, wbt_normal_show}, |
871 | {"wb_background" , 0400, wbt_background_show}, |
872 | {}, |
873 | }; |
874 | #endif |
875 | |
876 | static const struct rq_qos_ops wbt_rqos_ops = { |
877 | .throttle = wbt_wait, |
878 | .issue = wbt_issue, |
879 | .track = wbt_track, |
880 | .requeue = wbt_requeue, |
881 | .done = wbt_done, |
882 | .cleanup = wbt_cleanup, |
883 | .queue_depth_changed = wbt_queue_depth_changed, |
884 | .exit = wbt_exit, |
885 | #ifdef CONFIG_BLK_DEBUG_FS |
886 | .debugfs_attrs = wbt_debugfs_attrs, |
887 | #endif |
888 | }; |
889 | |
890 | int wbt_init(struct gendisk *disk) |
891 | { |
892 | struct request_queue *q = disk->queue; |
893 | struct rq_wb *rwb; |
894 | int i; |
895 | int ret; |
896 | |
897 | rwb = kzalloc(size: sizeof(*rwb), GFP_KERNEL); |
898 | if (!rwb) |
899 | return -ENOMEM; |
900 | |
901 | rwb->cb = blk_stat_alloc_callback(timer_fn: wb_timer_fn, bucket_fn: wbt_data_dir, buckets: 2, data: rwb); |
902 | if (!rwb->cb) { |
903 | kfree(objp: rwb); |
904 | return -ENOMEM; |
905 | } |
906 | |
907 | for (i = 0; i < WBT_NUM_RWQ; i++) |
908 | rq_wait_init(rq_wait: &rwb->rq_wait[i]); |
909 | |
910 | rwb->last_comp = rwb->last_issue = jiffies; |
911 | rwb->win_nsec = RWB_WINDOW_NSEC; |
912 | rwb->enable_state = WBT_STATE_ON_DEFAULT; |
913 | rwb->rq_depth.default_depth = RWB_DEF_DEPTH; |
914 | rwb->min_lat_nsec = wbt_default_latency_nsec(q); |
915 | rwb->rq_depth.queue_depth = blk_queue_depth(q); |
916 | wbt_update_limits(rwb); |
917 | |
918 | /* |
919 | * Assign rwb and add the stats callback. |
920 | */ |
921 | mutex_lock(&q->rq_qos_mutex); |
922 | ret = rq_qos_add(rqos: &rwb->rqos, disk, id: RQ_QOS_WBT, ops: &wbt_rqos_ops); |
923 | mutex_unlock(lock: &q->rq_qos_mutex); |
924 | if (ret) |
925 | goto err_free; |
926 | |
927 | blk_stat_add_callback(q, cb: rwb->cb); |
928 | |
929 | return 0; |
930 | |
931 | err_free: |
932 | blk_stat_free_callback(cb: rwb->cb); |
933 | kfree(objp: rwb); |
934 | return ret; |
935 | |
936 | } |
937 | |