1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * The Kyber I/O scheduler. Controls latency by throttling queue depths using
4 * scalable techniques.
5 *
6 * Copyright (C) 2017 Facebook
7 */
8
9 #include <linux/kernel.h>
10 #include <linux/blkdev.h>
11 #include <linux/module.h>
12 #include <linux/sbitmap.h>
13
14 #include <trace/events/block.h>
15
16 #include "elevator.h"
17 #include "blk.h"
18 #include "blk-mq.h"
19 #include "blk-mq-debugfs.h"
20 #include "blk-mq-sched.h"
21
22 #define CREATE_TRACE_POINTS
23 #include <trace/events/kyber.h>
24
25 /*
26 * Scheduling domains: the device is divided into multiple domains based on the
27 * request type.
28 */
29 enum {
30 KYBER_READ,
31 KYBER_WRITE,
32 KYBER_DISCARD,
33 KYBER_OTHER,
34 KYBER_NUM_DOMAINS,
35 };
36
37 static const char *kyber_domain_names[] = {
38 [KYBER_READ] = "READ",
39 [KYBER_WRITE] = "WRITE",
40 [KYBER_DISCARD] = "DISCARD",
41 [KYBER_OTHER] = "OTHER",
42 };
43
44 enum {
45 /*
46 * In order to prevent starvation of synchronous requests by a flood of
47 * asynchronous requests, we reserve 25% of requests for synchronous
48 * operations.
49 */
50 KYBER_ASYNC_PERCENT = 75,
51 };
52
53 /*
54 * Maximum device-wide depth for each scheduling domain.
55 *
56 * Even for fast devices with lots of tags like NVMe, you can saturate the
57 * device with only a fraction of the maximum possible queue depth. So, we cap
58 * these to a reasonable value.
59 */
60 static const unsigned int kyber_depth[] = {
61 [KYBER_READ] = 256,
62 [KYBER_WRITE] = 128,
63 [KYBER_DISCARD] = 64,
64 [KYBER_OTHER] = 16,
65 };
66
67 /*
68 * Default latency targets for each scheduling domain.
69 */
70 static const u64 kyber_latency_targets[] = {
71 [KYBER_READ] = 2ULL * NSEC_PER_MSEC,
72 [KYBER_WRITE] = 10ULL * NSEC_PER_MSEC,
73 [KYBER_DISCARD] = 5ULL * NSEC_PER_SEC,
74 };
75
76 /*
77 * Batch size (number of requests we'll dispatch in a row) for each scheduling
78 * domain.
79 */
80 static const unsigned int kyber_batch_size[] = {
81 [KYBER_READ] = 16,
82 [KYBER_WRITE] = 8,
83 [KYBER_DISCARD] = 1,
84 [KYBER_OTHER] = 1,
85 };
86
87 /*
88 * Requests latencies are recorded in a histogram with buckets defined relative
89 * to the target latency:
90 *
91 * <= 1/4 * target latency
92 * <= 1/2 * target latency
93 * <= 3/4 * target latency
94 * <= target latency
95 * <= 1 1/4 * target latency
96 * <= 1 1/2 * target latency
97 * <= 1 3/4 * target latency
98 * > 1 3/4 * target latency
99 */
100 enum {
101 /*
102 * The width of the latency histogram buckets is
103 * 1 / (1 << KYBER_LATENCY_SHIFT) * target latency.
104 */
105 KYBER_LATENCY_SHIFT = 2,
106 /*
107 * The first (1 << KYBER_LATENCY_SHIFT) buckets are <= target latency,
108 * thus, "good".
109 */
110 KYBER_GOOD_BUCKETS = 1 << KYBER_LATENCY_SHIFT,
111 /* There are also (1 << KYBER_LATENCY_SHIFT) "bad" buckets. */
112 KYBER_LATENCY_BUCKETS = 2 << KYBER_LATENCY_SHIFT,
113 };
114
115 /*
116 * We measure both the total latency and the I/O latency (i.e., latency after
117 * submitting to the device).
118 */
119 enum {
120 KYBER_TOTAL_LATENCY,
121 KYBER_IO_LATENCY,
122 };
123
124 static const char *kyber_latency_type_names[] = {
125 [KYBER_TOTAL_LATENCY] = "total",
126 [KYBER_IO_LATENCY] = "I/O",
127 };
128
129 /*
130 * Per-cpu latency histograms: total latency and I/O latency for each scheduling
131 * domain except for KYBER_OTHER.
132 */
133 struct kyber_cpu_latency {
134 atomic_t buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS];
135 };
136
137 /*
138 * There is a same mapping between ctx & hctx and kcq & khd,
139 * we use request->mq_ctx->index_hw to index the kcq in khd.
140 */
141 struct kyber_ctx_queue {
142 /*
143 * Used to ensure operations on rq_list and kcq_map to be an atmoic one.
144 * Also protect the rqs on rq_list when merge.
145 */
146 spinlock_t lock;
147 struct list_head rq_list[KYBER_NUM_DOMAINS];
148 } ____cacheline_aligned_in_smp;
149
150 struct kyber_queue_data {
151 struct request_queue *q;
152 dev_t dev;
153
154 /*
155 * Each scheduling domain has a limited number of in-flight requests
156 * device-wide, limited by these tokens.
157 */
158 struct sbitmap_queue domain_tokens[KYBER_NUM_DOMAINS];
159
160 /* Number of allowed async requests. */
161 unsigned int async_depth;
162
163 struct kyber_cpu_latency __percpu *cpu_latency;
164
165 /* Timer for stats aggregation and adjusting domain tokens. */
166 struct timer_list timer;
167
168 unsigned int latency_buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS];
169
170 unsigned long latency_timeout[KYBER_OTHER];
171
172 int domain_p99[KYBER_OTHER];
173
174 /* Target latencies in nanoseconds. */
175 u64 latency_targets[KYBER_OTHER];
176 };
177
178 struct kyber_hctx_data {
179 spinlock_t lock;
180 struct list_head rqs[KYBER_NUM_DOMAINS];
181 unsigned int cur_domain;
182 unsigned int batching;
183 struct kyber_ctx_queue *kcqs;
184 struct sbitmap kcq_map[KYBER_NUM_DOMAINS];
185 struct sbq_wait domain_wait[KYBER_NUM_DOMAINS];
186 struct sbq_wait_state *domain_ws[KYBER_NUM_DOMAINS];
187 atomic_t wait_index[KYBER_NUM_DOMAINS];
188 };
189
190 static int kyber_domain_wake(wait_queue_entry_t *wait, unsigned mode, int flags,
191 void *key);
192
kyber_sched_domain(blk_opf_t opf)193 static unsigned int kyber_sched_domain(blk_opf_t opf)
194 {
195 switch (opf & REQ_OP_MASK) {
196 case REQ_OP_READ:
197 return KYBER_READ;
198 case REQ_OP_WRITE:
199 return KYBER_WRITE;
200 case REQ_OP_DISCARD:
201 return KYBER_DISCARD;
202 default:
203 return KYBER_OTHER;
204 }
205 }
206
flush_latency_buckets(struct kyber_queue_data * kqd,struct kyber_cpu_latency * cpu_latency,unsigned int sched_domain,unsigned int type)207 static void flush_latency_buckets(struct kyber_queue_data *kqd,
208 struct kyber_cpu_latency *cpu_latency,
209 unsigned int sched_domain, unsigned int type)
210 {
211 unsigned int *buckets = kqd->latency_buckets[sched_domain][type];
212 atomic_t *cpu_buckets = cpu_latency->buckets[sched_domain][type];
213 unsigned int bucket;
214
215 for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++)
216 buckets[bucket] += atomic_xchg(&cpu_buckets[bucket], 0);
217 }
218
219 /*
220 * Calculate the histogram bucket with the given percentile rank, or -1 if there
221 * aren't enough samples yet.
222 */
calculate_percentile(struct kyber_queue_data * kqd,unsigned int sched_domain,unsigned int type,unsigned int percentile)223 static int calculate_percentile(struct kyber_queue_data *kqd,
224 unsigned int sched_domain, unsigned int type,
225 unsigned int percentile)
226 {
227 unsigned int *buckets = kqd->latency_buckets[sched_domain][type];
228 unsigned int bucket, samples = 0, percentile_samples;
229
230 for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++)
231 samples += buckets[bucket];
232
233 if (!samples)
234 return -1;
235
236 /*
237 * We do the calculation once we have 500 samples or one second passes
238 * since the first sample was recorded, whichever comes first.
239 */
240 if (!kqd->latency_timeout[sched_domain])
241 kqd->latency_timeout[sched_domain] = max(jiffies + HZ, 1UL);
242 if (samples < 500 &&
243 time_is_after_jiffies(kqd->latency_timeout[sched_domain])) {
244 return -1;
245 }
246 kqd->latency_timeout[sched_domain] = 0;
247
248 percentile_samples = DIV_ROUND_UP(samples * percentile, 100);
249 for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS - 1; bucket++) {
250 if (buckets[bucket] >= percentile_samples)
251 break;
252 percentile_samples -= buckets[bucket];
253 }
254 memset(buckets, 0, sizeof(kqd->latency_buckets[sched_domain][type]));
255
256 trace_kyber_latency(kqd->dev, kyber_domain_names[sched_domain],
257 kyber_latency_type_names[type], percentile,
258 bucket + 1, 1 << KYBER_LATENCY_SHIFT, samples);
259
260 return bucket;
261 }
262
kyber_resize_domain(struct kyber_queue_data * kqd,unsigned int sched_domain,unsigned int depth)263 static void kyber_resize_domain(struct kyber_queue_data *kqd,
264 unsigned int sched_domain, unsigned int depth)
265 {
266 depth = clamp(depth, 1U, kyber_depth[sched_domain]);
267 if (depth != kqd->domain_tokens[sched_domain].sb.depth) {
268 sbitmap_queue_resize(&kqd->domain_tokens[sched_domain], depth);
269 trace_kyber_adjust(kqd->dev, kyber_domain_names[sched_domain],
270 depth);
271 }
272 }
273
kyber_timer_fn(struct timer_list * t)274 static void kyber_timer_fn(struct timer_list *t)
275 {
276 struct kyber_queue_data *kqd = timer_container_of(kqd, t, timer);
277 unsigned int sched_domain;
278 int cpu;
279 bool bad = false;
280
281 /* Sum all of the per-cpu latency histograms. */
282 for_each_online_cpu(cpu) {
283 struct kyber_cpu_latency *cpu_latency;
284
285 cpu_latency = per_cpu_ptr(kqd->cpu_latency, cpu);
286 for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
287 flush_latency_buckets(kqd, cpu_latency, sched_domain,
288 KYBER_TOTAL_LATENCY);
289 flush_latency_buckets(kqd, cpu_latency, sched_domain,
290 KYBER_IO_LATENCY);
291 }
292 }
293
294 /*
295 * Check if any domains have a high I/O latency, which might indicate
296 * congestion in the device. Note that we use the p90; we don't want to
297 * be too sensitive to outliers here.
298 */
299 for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
300 int p90;
301
302 p90 = calculate_percentile(kqd, sched_domain, KYBER_IO_LATENCY,
303 90);
304 if (p90 >= KYBER_GOOD_BUCKETS)
305 bad = true;
306 }
307
308 /*
309 * Adjust the scheduling domain depths. If we determined that there was
310 * congestion, we throttle all domains with good latencies. Either way,
311 * we ease up on throttling domains with bad latencies.
312 */
313 for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
314 unsigned int orig_depth, depth;
315 int p99;
316
317 p99 = calculate_percentile(kqd, sched_domain,
318 KYBER_TOTAL_LATENCY, 99);
319 /*
320 * This is kind of subtle: different domains will not
321 * necessarily have enough samples to calculate the latency
322 * percentiles during the same window, so we have to remember
323 * the p99 for the next time we observe congestion; once we do,
324 * we don't want to throttle again until we get more data, so we
325 * reset it to -1.
326 */
327 if (bad) {
328 if (p99 < 0)
329 p99 = kqd->domain_p99[sched_domain];
330 kqd->domain_p99[sched_domain] = -1;
331 } else if (p99 >= 0) {
332 kqd->domain_p99[sched_domain] = p99;
333 }
334 if (p99 < 0)
335 continue;
336
337 /*
338 * If this domain has bad latency, throttle less. Otherwise,
339 * throttle more iff we determined that there is congestion.
340 *
341 * The new depth is scaled linearly with the p99 latency vs the
342 * latency target. E.g., if the p99 is 3/4 of the target, then
343 * we throttle down to 3/4 of the current depth, and if the p99
344 * is 2x the target, then we double the depth.
345 */
346 if (bad || p99 >= KYBER_GOOD_BUCKETS) {
347 orig_depth = kqd->domain_tokens[sched_domain].sb.depth;
348 depth = (orig_depth * (p99 + 1)) >> KYBER_LATENCY_SHIFT;
349 kyber_resize_domain(kqd, sched_domain, depth);
350 }
351 }
352 }
353
kyber_queue_data_alloc(struct request_queue * q)354 static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q)
355 {
356 struct kyber_queue_data *kqd;
357 int ret = -ENOMEM;
358 int i;
359
360 kqd = kzalloc_node(sizeof(*kqd), GFP_KERNEL, q->node);
361 if (!kqd)
362 goto err;
363
364 kqd->q = q;
365 kqd->dev = disk_devt(q->disk);
366
367 kqd->cpu_latency = alloc_percpu_gfp(struct kyber_cpu_latency,
368 GFP_KERNEL | __GFP_ZERO);
369 if (!kqd->cpu_latency)
370 goto err_kqd;
371
372 timer_setup(&kqd->timer, kyber_timer_fn, 0);
373
374 for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
375 WARN_ON(!kyber_depth[i]);
376 WARN_ON(!kyber_batch_size[i]);
377 ret = sbitmap_queue_init_node(&kqd->domain_tokens[i],
378 kyber_depth[i], -1, false,
379 GFP_KERNEL, q->node);
380 if (ret) {
381 while (--i >= 0)
382 sbitmap_queue_free(&kqd->domain_tokens[i]);
383 goto err_buckets;
384 }
385 }
386
387 for (i = 0; i < KYBER_OTHER; i++) {
388 kqd->domain_p99[i] = -1;
389 kqd->latency_targets[i] = kyber_latency_targets[i];
390 }
391
392 return kqd;
393
394 err_buckets:
395 free_percpu(kqd->cpu_latency);
396 err_kqd:
397 kfree(kqd);
398 err:
399 return ERR_PTR(ret);
400 }
401
kyber_init_sched(struct request_queue * q,struct elevator_queue * eq)402 static int kyber_init_sched(struct request_queue *q, struct elevator_queue *eq)
403 {
404 struct kyber_queue_data *kqd;
405
406 kqd = kyber_queue_data_alloc(q);
407 if (IS_ERR(kqd))
408 return PTR_ERR(kqd);
409
410 blk_stat_enable_accounting(q);
411
412 blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q);
413
414 eq->elevator_data = kqd;
415 q->elevator = eq;
416
417 return 0;
418 }
419
kyber_exit_sched(struct elevator_queue * e)420 static void kyber_exit_sched(struct elevator_queue *e)
421 {
422 struct kyber_queue_data *kqd = e->elevator_data;
423 int i;
424
425 timer_shutdown_sync(&kqd->timer);
426 blk_stat_disable_accounting(kqd->q);
427
428 for (i = 0; i < KYBER_NUM_DOMAINS; i++)
429 sbitmap_queue_free(&kqd->domain_tokens[i]);
430 free_percpu(kqd->cpu_latency);
431 kfree(kqd);
432 }
433
kyber_ctx_queue_init(struct kyber_ctx_queue * kcq)434 static void kyber_ctx_queue_init(struct kyber_ctx_queue *kcq)
435 {
436 unsigned int i;
437
438 spin_lock_init(&kcq->lock);
439 for (i = 0; i < KYBER_NUM_DOMAINS; i++)
440 INIT_LIST_HEAD(&kcq->rq_list[i]);
441 }
442
kyber_depth_updated(struct blk_mq_hw_ctx * hctx)443 static void kyber_depth_updated(struct blk_mq_hw_ctx *hctx)
444 {
445 struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;
446 struct blk_mq_tags *tags = hctx->sched_tags;
447
448 kqd->async_depth = hctx->queue->nr_requests * KYBER_ASYNC_PERCENT / 100U;
449 sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, kqd->async_depth);
450 }
451
kyber_init_hctx(struct blk_mq_hw_ctx * hctx,unsigned int hctx_idx)452 static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
453 {
454 struct kyber_hctx_data *khd;
455 int i;
456
457 khd = kmalloc_node(sizeof(*khd), GFP_KERNEL, hctx->numa_node);
458 if (!khd)
459 return -ENOMEM;
460
461 khd->kcqs = kmalloc_array_node(hctx->nr_ctx,
462 sizeof(struct kyber_ctx_queue),
463 GFP_KERNEL, hctx->numa_node);
464 if (!khd->kcqs)
465 goto err_khd;
466
467 for (i = 0; i < hctx->nr_ctx; i++)
468 kyber_ctx_queue_init(&khd->kcqs[i]);
469
470 for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
471 if (sbitmap_init_node(&khd->kcq_map[i], hctx->nr_ctx,
472 ilog2(8), GFP_KERNEL, hctx->numa_node,
473 false, false)) {
474 while (--i >= 0)
475 sbitmap_free(&khd->kcq_map[i]);
476 goto err_kcqs;
477 }
478 }
479
480 spin_lock_init(&khd->lock);
481
482 for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
483 INIT_LIST_HEAD(&khd->rqs[i]);
484 khd->domain_wait[i].sbq = NULL;
485 init_waitqueue_func_entry(&khd->domain_wait[i].wait,
486 kyber_domain_wake);
487 khd->domain_wait[i].wait.private = hctx;
488 INIT_LIST_HEAD(&khd->domain_wait[i].wait.entry);
489 atomic_set(&khd->wait_index[i], 0);
490 }
491
492 khd->cur_domain = 0;
493 khd->batching = 0;
494
495 hctx->sched_data = khd;
496 kyber_depth_updated(hctx);
497
498 return 0;
499
500 err_kcqs:
501 kfree(khd->kcqs);
502 err_khd:
503 kfree(khd);
504 return -ENOMEM;
505 }
506
kyber_exit_hctx(struct blk_mq_hw_ctx * hctx,unsigned int hctx_idx)507 static void kyber_exit_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
508 {
509 struct kyber_hctx_data *khd = hctx->sched_data;
510 int i;
511
512 for (i = 0; i < KYBER_NUM_DOMAINS; i++)
513 sbitmap_free(&khd->kcq_map[i]);
514 kfree(khd->kcqs);
515 kfree(hctx->sched_data);
516 }
517
rq_get_domain_token(struct request * rq)518 static int rq_get_domain_token(struct request *rq)
519 {
520 return (long)rq->elv.priv[0];
521 }
522
rq_set_domain_token(struct request * rq,int token)523 static void rq_set_domain_token(struct request *rq, int token)
524 {
525 rq->elv.priv[0] = (void *)(long)token;
526 }
527
rq_clear_domain_token(struct kyber_queue_data * kqd,struct request * rq)528 static void rq_clear_domain_token(struct kyber_queue_data *kqd,
529 struct request *rq)
530 {
531 unsigned int sched_domain;
532 int nr;
533
534 nr = rq_get_domain_token(rq);
535 if (nr != -1) {
536 sched_domain = kyber_sched_domain(rq->cmd_flags);
537 sbitmap_queue_clear(&kqd->domain_tokens[sched_domain], nr,
538 rq->mq_ctx->cpu);
539 }
540 }
541
kyber_limit_depth(blk_opf_t opf,struct blk_mq_alloc_data * data)542 static void kyber_limit_depth(blk_opf_t opf, struct blk_mq_alloc_data *data)
543 {
544 /*
545 * We use the scheduler tags as per-hardware queue queueing tokens.
546 * Async requests can be limited at this stage.
547 */
548 if (!op_is_sync(opf)) {
549 struct kyber_queue_data *kqd = data->q->elevator->elevator_data;
550
551 data->shallow_depth = kqd->async_depth;
552 }
553 }
554
kyber_bio_merge(struct request_queue * q,struct bio * bio,unsigned int nr_segs)555 static bool kyber_bio_merge(struct request_queue *q, struct bio *bio,
556 unsigned int nr_segs)
557 {
558 struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
559 struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(bio->bi_opf, ctx);
560 struct kyber_hctx_data *khd = hctx->sched_data;
561 struct kyber_ctx_queue *kcq = &khd->kcqs[ctx->index_hw[hctx->type]];
562 unsigned int sched_domain = kyber_sched_domain(bio->bi_opf);
563 struct list_head *rq_list = &kcq->rq_list[sched_domain];
564 bool merged;
565
566 spin_lock(&kcq->lock);
567 merged = blk_bio_list_merge(hctx->queue, rq_list, bio, nr_segs);
568 spin_unlock(&kcq->lock);
569
570 return merged;
571 }
572
kyber_prepare_request(struct request * rq)573 static void kyber_prepare_request(struct request *rq)
574 {
575 rq_set_domain_token(rq, -1);
576 }
577
kyber_insert_requests(struct blk_mq_hw_ctx * hctx,struct list_head * rq_list,blk_insert_t flags)578 static void kyber_insert_requests(struct blk_mq_hw_ctx *hctx,
579 struct list_head *rq_list,
580 blk_insert_t flags)
581 {
582 struct kyber_hctx_data *khd = hctx->sched_data;
583 struct request *rq, *next;
584
585 list_for_each_entry_safe(rq, next, rq_list, queuelist) {
586 unsigned int sched_domain = kyber_sched_domain(rq->cmd_flags);
587 struct kyber_ctx_queue *kcq = &khd->kcqs[rq->mq_ctx->index_hw[hctx->type]];
588 struct list_head *head = &kcq->rq_list[sched_domain];
589
590 spin_lock(&kcq->lock);
591 trace_block_rq_insert(rq);
592 if (flags & BLK_MQ_INSERT_AT_HEAD)
593 list_move(&rq->queuelist, head);
594 else
595 list_move_tail(&rq->queuelist, head);
596 sbitmap_set_bit(&khd->kcq_map[sched_domain],
597 rq->mq_ctx->index_hw[hctx->type]);
598 spin_unlock(&kcq->lock);
599 }
600 }
601
kyber_finish_request(struct request * rq)602 static void kyber_finish_request(struct request *rq)
603 {
604 struct kyber_queue_data *kqd = rq->q->elevator->elevator_data;
605
606 rq_clear_domain_token(kqd, rq);
607 }
608
add_latency_sample(struct kyber_cpu_latency * cpu_latency,unsigned int sched_domain,unsigned int type,u64 target,u64 latency)609 static void add_latency_sample(struct kyber_cpu_latency *cpu_latency,
610 unsigned int sched_domain, unsigned int type,
611 u64 target, u64 latency)
612 {
613 unsigned int bucket;
614 u64 divisor;
615
616 if (latency > 0) {
617 divisor = max_t(u64, target >> KYBER_LATENCY_SHIFT, 1);
618 bucket = min_t(unsigned int, div64_u64(latency - 1, divisor),
619 KYBER_LATENCY_BUCKETS - 1);
620 } else {
621 bucket = 0;
622 }
623
624 atomic_inc(&cpu_latency->buckets[sched_domain][type][bucket]);
625 }
626
kyber_completed_request(struct request * rq,u64 now)627 static void kyber_completed_request(struct request *rq, u64 now)
628 {
629 struct kyber_queue_data *kqd = rq->q->elevator->elevator_data;
630 struct kyber_cpu_latency *cpu_latency;
631 unsigned int sched_domain;
632 u64 target;
633
634 sched_domain = kyber_sched_domain(rq->cmd_flags);
635 if (sched_domain == KYBER_OTHER)
636 return;
637
638 cpu_latency = get_cpu_ptr(kqd->cpu_latency);
639 target = kqd->latency_targets[sched_domain];
640 add_latency_sample(cpu_latency, sched_domain, KYBER_TOTAL_LATENCY,
641 target, now - rq->start_time_ns);
642 add_latency_sample(cpu_latency, sched_domain, KYBER_IO_LATENCY, target,
643 now - rq->io_start_time_ns);
644 put_cpu_ptr(kqd->cpu_latency);
645
646 timer_reduce(&kqd->timer, jiffies + HZ / 10);
647 }
648
649 struct flush_kcq_data {
650 struct kyber_hctx_data *khd;
651 unsigned int sched_domain;
652 struct list_head *list;
653 };
654
flush_busy_kcq(struct sbitmap * sb,unsigned int bitnr,void * data)655 static bool flush_busy_kcq(struct sbitmap *sb, unsigned int bitnr, void *data)
656 {
657 struct flush_kcq_data *flush_data = data;
658 struct kyber_ctx_queue *kcq = &flush_data->khd->kcqs[bitnr];
659
660 spin_lock(&kcq->lock);
661 list_splice_tail_init(&kcq->rq_list[flush_data->sched_domain],
662 flush_data->list);
663 sbitmap_clear_bit(sb, bitnr);
664 spin_unlock(&kcq->lock);
665
666 return true;
667 }
668
kyber_flush_busy_kcqs(struct kyber_hctx_data * khd,unsigned int sched_domain,struct list_head * list)669 static void kyber_flush_busy_kcqs(struct kyber_hctx_data *khd,
670 unsigned int sched_domain,
671 struct list_head *list)
672 {
673 struct flush_kcq_data data = {
674 .khd = khd,
675 .sched_domain = sched_domain,
676 .list = list,
677 };
678
679 sbitmap_for_each_set(&khd->kcq_map[sched_domain],
680 flush_busy_kcq, &data);
681 }
682
kyber_domain_wake(wait_queue_entry_t * wqe,unsigned mode,int flags,void * key)683 static int kyber_domain_wake(wait_queue_entry_t *wqe, unsigned mode, int flags,
684 void *key)
685 {
686 struct blk_mq_hw_ctx *hctx = READ_ONCE(wqe->private);
687 struct sbq_wait *wait = container_of(wqe, struct sbq_wait, wait);
688
689 sbitmap_del_wait_queue(wait);
690 blk_mq_run_hw_queue(hctx, true);
691 return 1;
692 }
693
kyber_get_domain_token(struct kyber_queue_data * kqd,struct kyber_hctx_data * khd,struct blk_mq_hw_ctx * hctx)694 static int kyber_get_domain_token(struct kyber_queue_data *kqd,
695 struct kyber_hctx_data *khd,
696 struct blk_mq_hw_ctx *hctx)
697 {
698 unsigned int sched_domain = khd->cur_domain;
699 struct sbitmap_queue *domain_tokens = &kqd->domain_tokens[sched_domain];
700 struct sbq_wait *wait = &khd->domain_wait[sched_domain];
701 struct sbq_wait_state *ws;
702 int nr;
703
704 nr = __sbitmap_queue_get(domain_tokens);
705
706 /*
707 * If we failed to get a domain token, make sure the hardware queue is
708 * run when one becomes available. Note that this is serialized on
709 * khd->lock, but we still need to be careful about the waker.
710 */
711 if (nr < 0 && list_empty_careful(&wait->wait.entry)) {
712 ws = sbq_wait_ptr(domain_tokens,
713 &khd->wait_index[sched_domain]);
714 khd->domain_ws[sched_domain] = ws;
715 sbitmap_add_wait_queue(domain_tokens, ws, wait);
716
717 /*
718 * Try again in case a token was freed before we got on the wait
719 * queue.
720 */
721 nr = __sbitmap_queue_get(domain_tokens);
722 }
723
724 /*
725 * If we got a token while we were on the wait queue, remove ourselves
726 * from the wait queue to ensure that all wake ups make forward
727 * progress. It's possible that the waker already deleted the entry
728 * between the !list_empty_careful() check and us grabbing the lock, but
729 * list_del_init() is okay with that.
730 */
731 if (nr >= 0 && !list_empty_careful(&wait->wait.entry)) {
732 ws = khd->domain_ws[sched_domain];
733 spin_lock_irq(&ws->wait.lock);
734 sbitmap_del_wait_queue(wait);
735 spin_unlock_irq(&ws->wait.lock);
736 }
737
738 return nr;
739 }
740
741 static struct request *
kyber_dispatch_cur_domain(struct kyber_queue_data * kqd,struct kyber_hctx_data * khd,struct blk_mq_hw_ctx * hctx)742 kyber_dispatch_cur_domain(struct kyber_queue_data *kqd,
743 struct kyber_hctx_data *khd,
744 struct blk_mq_hw_ctx *hctx)
745 {
746 struct list_head *rqs;
747 struct request *rq;
748 int nr;
749
750 rqs = &khd->rqs[khd->cur_domain];
751
752 /*
753 * If we already have a flushed request, then we just need to get a
754 * token for it. Otherwise, if there are pending requests in the kcqs,
755 * flush the kcqs, but only if we can get a token. If not, we should
756 * leave the requests in the kcqs so that they can be merged. Note that
757 * khd->lock serializes the flushes, so if we observed any bit set in
758 * the kcq_map, we will always get a request.
759 */
760 rq = list_first_entry_or_null(rqs, struct request, queuelist);
761 if (rq) {
762 nr = kyber_get_domain_token(kqd, khd, hctx);
763 if (nr >= 0) {
764 khd->batching++;
765 rq_set_domain_token(rq, nr);
766 list_del_init(&rq->queuelist);
767 return rq;
768 } else {
769 trace_kyber_throttled(kqd->dev,
770 kyber_domain_names[khd->cur_domain]);
771 }
772 } else if (sbitmap_any_bit_set(&khd->kcq_map[khd->cur_domain])) {
773 nr = kyber_get_domain_token(kqd, khd, hctx);
774 if (nr >= 0) {
775 kyber_flush_busy_kcqs(khd, khd->cur_domain, rqs);
776 rq = list_first_entry(rqs, struct request, queuelist);
777 khd->batching++;
778 rq_set_domain_token(rq, nr);
779 list_del_init(&rq->queuelist);
780 return rq;
781 } else {
782 trace_kyber_throttled(kqd->dev,
783 kyber_domain_names[khd->cur_domain]);
784 }
785 }
786
787 /* There were either no pending requests or no tokens. */
788 return NULL;
789 }
790
kyber_dispatch_request(struct blk_mq_hw_ctx * hctx)791 static struct request *kyber_dispatch_request(struct blk_mq_hw_ctx *hctx)
792 {
793 struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;
794 struct kyber_hctx_data *khd = hctx->sched_data;
795 struct request *rq;
796 int i;
797
798 spin_lock(&khd->lock);
799
800 /*
801 * First, if we are still entitled to batch, try to dispatch a request
802 * from the batch.
803 */
804 if (khd->batching < kyber_batch_size[khd->cur_domain]) {
805 rq = kyber_dispatch_cur_domain(kqd, khd, hctx);
806 if (rq)
807 goto out;
808 }
809
810 /*
811 * Either,
812 * 1. We were no longer entitled to a batch.
813 * 2. The domain we were batching didn't have any requests.
814 * 3. The domain we were batching was out of tokens.
815 *
816 * Start another batch. Note that this wraps back around to the original
817 * domain if no other domains have requests or tokens.
818 */
819 khd->batching = 0;
820 for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
821 if (khd->cur_domain == KYBER_NUM_DOMAINS - 1)
822 khd->cur_domain = 0;
823 else
824 khd->cur_domain++;
825
826 rq = kyber_dispatch_cur_domain(kqd, khd, hctx);
827 if (rq)
828 goto out;
829 }
830
831 rq = NULL;
832 out:
833 spin_unlock(&khd->lock);
834 return rq;
835 }
836
kyber_has_work(struct blk_mq_hw_ctx * hctx)837 static bool kyber_has_work(struct blk_mq_hw_ctx *hctx)
838 {
839 struct kyber_hctx_data *khd = hctx->sched_data;
840 int i;
841
842 for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
843 if (!list_empty_careful(&khd->rqs[i]) ||
844 sbitmap_any_bit_set(&khd->kcq_map[i]))
845 return true;
846 }
847
848 return false;
849 }
850
851 #define KYBER_LAT_SHOW_STORE(domain, name) \
852 static ssize_t kyber_##name##_lat_show(struct elevator_queue *e, \
853 char *page) \
854 { \
855 struct kyber_queue_data *kqd = e->elevator_data; \
856 \
857 return sprintf(page, "%llu\n", kqd->latency_targets[domain]); \
858 } \
859 \
860 static ssize_t kyber_##name##_lat_store(struct elevator_queue *e, \
861 const char *page, size_t count) \
862 { \
863 struct kyber_queue_data *kqd = e->elevator_data; \
864 unsigned long long nsec; \
865 int ret; \
866 \
867 ret = kstrtoull(page, 10, &nsec); \
868 if (ret) \
869 return ret; \
870 \
871 kqd->latency_targets[domain] = nsec; \
872 \
873 return count; \
874 }
875 KYBER_LAT_SHOW_STORE(KYBER_READ, read);
876 KYBER_LAT_SHOW_STORE(KYBER_WRITE, write);
877 #undef KYBER_LAT_SHOW_STORE
878
879 #define KYBER_LAT_ATTR(op) __ATTR(op##_lat_nsec, 0644, kyber_##op##_lat_show, kyber_##op##_lat_store)
880 static const struct elv_fs_entry kyber_sched_attrs[] = {
881 KYBER_LAT_ATTR(read),
882 KYBER_LAT_ATTR(write),
883 __ATTR_NULL
884 };
885 #undef KYBER_LAT_ATTR
886
887 #ifdef CONFIG_BLK_DEBUG_FS
888 #define KYBER_DEBUGFS_DOMAIN_ATTRS(domain, name) \
889 static int kyber_##name##_tokens_show(void *data, struct seq_file *m) \
890 { \
891 struct request_queue *q = data; \
892 struct kyber_queue_data *kqd = q->elevator->elevator_data; \
893 \
894 sbitmap_queue_show(&kqd->domain_tokens[domain], m); \
895 return 0; \
896 } \
897 \
898 static void *kyber_##name##_rqs_start(struct seq_file *m, loff_t *pos) \
899 __acquires(&khd->lock) \
900 { \
901 struct blk_mq_hw_ctx *hctx = m->private; \
902 struct kyber_hctx_data *khd = hctx->sched_data; \
903 \
904 spin_lock(&khd->lock); \
905 return seq_list_start(&khd->rqs[domain], *pos); \
906 } \
907 \
908 static void *kyber_##name##_rqs_next(struct seq_file *m, void *v, \
909 loff_t *pos) \
910 { \
911 struct blk_mq_hw_ctx *hctx = m->private; \
912 struct kyber_hctx_data *khd = hctx->sched_data; \
913 \
914 return seq_list_next(v, &khd->rqs[domain], pos); \
915 } \
916 \
917 static void kyber_##name##_rqs_stop(struct seq_file *m, void *v) \
918 __releases(&khd->lock) \
919 { \
920 struct blk_mq_hw_ctx *hctx = m->private; \
921 struct kyber_hctx_data *khd = hctx->sched_data; \
922 \
923 spin_unlock(&khd->lock); \
924 } \
925 \
926 static const struct seq_operations kyber_##name##_rqs_seq_ops = { \
927 .start = kyber_##name##_rqs_start, \
928 .next = kyber_##name##_rqs_next, \
929 .stop = kyber_##name##_rqs_stop, \
930 .show = blk_mq_debugfs_rq_show, \
931 }; \
932 \
933 static int kyber_##name##_waiting_show(void *data, struct seq_file *m) \
934 { \
935 struct blk_mq_hw_ctx *hctx = data; \
936 struct kyber_hctx_data *khd = hctx->sched_data; \
937 wait_queue_entry_t *wait = &khd->domain_wait[domain].wait; \
938 \
939 seq_printf(m, "%d\n", !list_empty_careful(&wait->entry)); \
940 return 0; \
941 }
KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_READ,read)942 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_READ, read)
943 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_WRITE, write)
944 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_DISCARD, discard)
945 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_OTHER, other)
946 #undef KYBER_DEBUGFS_DOMAIN_ATTRS
947
948 static int kyber_async_depth_show(void *data, struct seq_file *m)
949 {
950 struct request_queue *q = data;
951 struct kyber_queue_data *kqd = q->elevator->elevator_data;
952
953 seq_printf(m, "%u\n", kqd->async_depth);
954 return 0;
955 }
956
kyber_cur_domain_show(void * data,struct seq_file * m)957 static int kyber_cur_domain_show(void *data, struct seq_file *m)
958 {
959 struct blk_mq_hw_ctx *hctx = data;
960 struct kyber_hctx_data *khd = hctx->sched_data;
961
962 seq_printf(m, "%s\n", kyber_domain_names[khd->cur_domain]);
963 return 0;
964 }
965
kyber_batching_show(void * data,struct seq_file * m)966 static int kyber_batching_show(void *data, struct seq_file *m)
967 {
968 struct blk_mq_hw_ctx *hctx = data;
969 struct kyber_hctx_data *khd = hctx->sched_data;
970
971 seq_printf(m, "%u\n", khd->batching);
972 return 0;
973 }
974
975 #define KYBER_QUEUE_DOMAIN_ATTRS(name) \
976 {#name "_tokens", 0400, kyber_##name##_tokens_show}
977 static const struct blk_mq_debugfs_attr kyber_queue_debugfs_attrs[] = {
978 KYBER_QUEUE_DOMAIN_ATTRS(read),
979 KYBER_QUEUE_DOMAIN_ATTRS(write),
980 KYBER_QUEUE_DOMAIN_ATTRS(discard),
981 KYBER_QUEUE_DOMAIN_ATTRS(other),
982 {"async_depth", 0400, kyber_async_depth_show},
983 {},
984 };
985 #undef KYBER_QUEUE_DOMAIN_ATTRS
986
987 #define KYBER_HCTX_DOMAIN_ATTRS(name) \
988 {#name "_rqs", 0400, .seq_ops = &kyber_##name##_rqs_seq_ops}, \
989 {#name "_waiting", 0400, kyber_##name##_waiting_show}
990 static const struct blk_mq_debugfs_attr kyber_hctx_debugfs_attrs[] = {
991 KYBER_HCTX_DOMAIN_ATTRS(read),
992 KYBER_HCTX_DOMAIN_ATTRS(write),
993 KYBER_HCTX_DOMAIN_ATTRS(discard),
994 KYBER_HCTX_DOMAIN_ATTRS(other),
995 {"cur_domain", 0400, kyber_cur_domain_show},
996 {"batching", 0400, kyber_batching_show},
997 {},
998 };
999 #undef KYBER_HCTX_DOMAIN_ATTRS
1000 #endif
1001
1002 static struct elevator_type kyber_sched = {
1003 .ops = {
1004 .init_sched = kyber_init_sched,
1005 .exit_sched = kyber_exit_sched,
1006 .init_hctx = kyber_init_hctx,
1007 .exit_hctx = kyber_exit_hctx,
1008 .limit_depth = kyber_limit_depth,
1009 .bio_merge = kyber_bio_merge,
1010 .prepare_request = kyber_prepare_request,
1011 .insert_requests = kyber_insert_requests,
1012 .finish_request = kyber_finish_request,
1013 .requeue_request = kyber_finish_request,
1014 .completed_request = kyber_completed_request,
1015 .dispatch_request = kyber_dispatch_request,
1016 .has_work = kyber_has_work,
1017 .depth_updated = kyber_depth_updated,
1018 },
1019 #ifdef CONFIG_BLK_DEBUG_FS
1020 .queue_debugfs_attrs = kyber_queue_debugfs_attrs,
1021 .hctx_debugfs_attrs = kyber_hctx_debugfs_attrs,
1022 #endif
1023 .elevator_attrs = kyber_sched_attrs,
1024 .elevator_name = "kyber",
1025 .elevator_owner = THIS_MODULE,
1026 };
1027
kyber_init(void)1028 static int __init kyber_init(void)
1029 {
1030 return elv_register(&kyber_sched);
1031 }
1032
kyber_exit(void)1033 static void __exit kyber_exit(void)
1034 {
1035 elv_unregister(&kyber_sched);
1036 }
1037
1038 module_init(kyber_init);
1039 module_exit(kyber_exit);
1040
1041 MODULE_AUTHOR("Omar Sandoval");
1042 MODULE_LICENSE("GPL");
1043 MODULE_DESCRIPTION("Kyber I/O scheduler");
1044