Merge tag 'nfsd-6.4-2' of git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux
[platform/kernel/linux-starfive.git] / block / kyber-iosched.c
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         /*
161          * Async request percentage, converted to per-word depth for
162          * sbitmap_get_shallow().
163          */
164         unsigned int async_depth;
165
166         struct kyber_cpu_latency __percpu *cpu_latency;
167
168         /* Timer for stats aggregation and adjusting domain tokens. */
169         struct timer_list timer;
170
171         unsigned int latency_buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS];
172
173         unsigned long latency_timeout[KYBER_OTHER];
174
175         int domain_p99[KYBER_OTHER];
176
177         /* Target latencies in nanoseconds. */
178         u64 latency_targets[KYBER_OTHER];
179 };
180
181 struct kyber_hctx_data {
182         spinlock_t lock;
183         struct list_head rqs[KYBER_NUM_DOMAINS];
184         unsigned int cur_domain;
185         unsigned int batching;
186         struct kyber_ctx_queue *kcqs;
187         struct sbitmap kcq_map[KYBER_NUM_DOMAINS];
188         struct sbq_wait domain_wait[KYBER_NUM_DOMAINS];
189         struct sbq_wait_state *domain_ws[KYBER_NUM_DOMAINS];
190         atomic_t wait_index[KYBER_NUM_DOMAINS];
191 };
192
193 static int kyber_domain_wake(wait_queue_entry_t *wait, unsigned mode, int flags,
194                              void *key);
195
196 static unsigned int kyber_sched_domain(blk_opf_t opf)
197 {
198         switch (opf & REQ_OP_MASK) {
199         case REQ_OP_READ:
200                 return KYBER_READ;
201         case REQ_OP_WRITE:
202                 return KYBER_WRITE;
203         case REQ_OP_DISCARD:
204                 return KYBER_DISCARD;
205         default:
206                 return KYBER_OTHER;
207         }
208 }
209
210 static void flush_latency_buckets(struct kyber_queue_data *kqd,
211                                   struct kyber_cpu_latency *cpu_latency,
212                                   unsigned int sched_domain, unsigned int type)
213 {
214         unsigned int *buckets = kqd->latency_buckets[sched_domain][type];
215         atomic_t *cpu_buckets = cpu_latency->buckets[sched_domain][type];
216         unsigned int bucket;
217
218         for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++)
219                 buckets[bucket] += atomic_xchg(&cpu_buckets[bucket], 0);
220 }
221
222 /*
223  * Calculate the histogram bucket with the given percentile rank, or -1 if there
224  * aren't enough samples yet.
225  */
226 static int calculate_percentile(struct kyber_queue_data *kqd,
227                                 unsigned int sched_domain, unsigned int type,
228                                 unsigned int percentile)
229 {
230         unsigned int *buckets = kqd->latency_buckets[sched_domain][type];
231         unsigned int bucket, samples = 0, percentile_samples;
232
233         for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++)
234                 samples += buckets[bucket];
235
236         if (!samples)
237                 return -1;
238
239         /*
240          * We do the calculation once we have 500 samples or one second passes
241          * since the first sample was recorded, whichever comes first.
242          */
243         if (!kqd->latency_timeout[sched_domain])
244                 kqd->latency_timeout[sched_domain] = max(jiffies + HZ, 1UL);
245         if (samples < 500 &&
246             time_is_after_jiffies(kqd->latency_timeout[sched_domain])) {
247                 return -1;
248         }
249         kqd->latency_timeout[sched_domain] = 0;
250
251         percentile_samples = DIV_ROUND_UP(samples * percentile, 100);
252         for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS - 1; bucket++) {
253                 if (buckets[bucket] >= percentile_samples)
254                         break;
255                 percentile_samples -= buckets[bucket];
256         }
257         memset(buckets, 0, sizeof(kqd->latency_buckets[sched_domain][type]));
258
259         trace_kyber_latency(kqd->dev, kyber_domain_names[sched_domain],
260                             kyber_latency_type_names[type], percentile,
261                             bucket + 1, 1 << KYBER_LATENCY_SHIFT, samples);
262
263         return bucket;
264 }
265
266 static void kyber_resize_domain(struct kyber_queue_data *kqd,
267                                 unsigned int sched_domain, unsigned int depth)
268 {
269         depth = clamp(depth, 1U, kyber_depth[sched_domain]);
270         if (depth != kqd->domain_tokens[sched_domain].sb.depth) {
271                 sbitmap_queue_resize(&kqd->domain_tokens[sched_domain], depth);
272                 trace_kyber_adjust(kqd->dev, kyber_domain_names[sched_domain],
273                                    depth);
274         }
275 }
276
277 static void kyber_timer_fn(struct timer_list *t)
278 {
279         struct kyber_queue_data *kqd = from_timer(kqd, t, timer);
280         unsigned int sched_domain;
281         int cpu;
282         bool bad = false;
283
284         /* Sum all of the per-cpu latency histograms. */
285         for_each_online_cpu(cpu) {
286                 struct kyber_cpu_latency *cpu_latency;
287
288                 cpu_latency = per_cpu_ptr(kqd->cpu_latency, cpu);
289                 for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
290                         flush_latency_buckets(kqd, cpu_latency, sched_domain,
291                                               KYBER_TOTAL_LATENCY);
292                         flush_latency_buckets(kqd, cpu_latency, sched_domain,
293                                               KYBER_IO_LATENCY);
294                 }
295         }
296
297         /*
298          * Check if any domains have a high I/O latency, which might indicate
299          * congestion in the device. Note that we use the p90; we don't want to
300          * be too sensitive to outliers here.
301          */
302         for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
303                 int p90;
304
305                 p90 = calculate_percentile(kqd, sched_domain, KYBER_IO_LATENCY,
306                                            90);
307                 if (p90 >= KYBER_GOOD_BUCKETS)
308                         bad = true;
309         }
310
311         /*
312          * Adjust the scheduling domain depths. If we determined that there was
313          * congestion, we throttle all domains with good latencies. Either way,
314          * we ease up on throttling domains with bad latencies.
315          */
316         for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
317                 unsigned int orig_depth, depth;
318                 int p99;
319
320                 p99 = calculate_percentile(kqd, sched_domain,
321                                            KYBER_TOTAL_LATENCY, 99);
322                 /*
323                  * This is kind of subtle: different domains will not
324                  * necessarily have enough samples to calculate the latency
325                  * percentiles during the same window, so we have to remember
326                  * the p99 for the next time we observe congestion; once we do,
327                  * we don't want to throttle again until we get more data, so we
328                  * reset it to -1.
329                  */
330                 if (bad) {
331                         if (p99 < 0)
332                                 p99 = kqd->domain_p99[sched_domain];
333                         kqd->domain_p99[sched_domain] = -1;
334                 } else if (p99 >= 0) {
335                         kqd->domain_p99[sched_domain] = p99;
336                 }
337                 if (p99 < 0)
338                         continue;
339
340                 /*
341                  * If this domain has bad latency, throttle less. Otherwise,
342                  * throttle more iff we determined that there is congestion.
343                  *
344                  * The new depth is scaled linearly with the p99 latency vs the
345                  * latency target. E.g., if the p99 is 3/4 of the target, then
346                  * we throttle down to 3/4 of the current depth, and if the p99
347                  * is 2x the target, then we double the depth.
348                  */
349                 if (bad || p99 >= KYBER_GOOD_BUCKETS) {
350                         orig_depth = kqd->domain_tokens[sched_domain].sb.depth;
351                         depth = (orig_depth * (p99 + 1)) >> KYBER_LATENCY_SHIFT;
352                         kyber_resize_domain(kqd, sched_domain, depth);
353                 }
354         }
355 }
356
357 static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q)
358 {
359         struct kyber_queue_data *kqd;
360         int ret = -ENOMEM;
361         int i;
362
363         kqd = kzalloc_node(sizeof(*kqd), GFP_KERNEL, q->node);
364         if (!kqd)
365                 goto err;
366
367         kqd->q = q;
368         kqd->dev = disk_devt(q->disk);
369
370         kqd->cpu_latency = alloc_percpu_gfp(struct kyber_cpu_latency,
371                                             GFP_KERNEL | __GFP_ZERO);
372         if (!kqd->cpu_latency)
373                 goto err_kqd;
374
375         timer_setup(&kqd->timer, kyber_timer_fn, 0);
376
377         for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
378                 WARN_ON(!kyber_depth[i]);
379                 WARN_ON(!kyber_batch_size[i]);
380                 ret = sbitmap_queue_init_node(&kqd->domain_tokens[i],
381                                               kyber_depth[i], -1, false,
382                                               GFP_KERNEL, q->node);
383                 if (ret) {
384                         while (--i >= 0)
385                                 sbitmap_queue_free(&kqd->domain_tokens[i]);
386                         goto err_buckets;
387                 }
388         }
389
390         for (i = 0; i < KYBER_OTHER; i++) {
391                 kqd->domain_p99[i] = -1;
392                 kqd->latency_targets[i] = kyber_latency_targets[i];
393         }
394
395         return kqd;
396
397 err_buckets:
398         free_percpu(kqd->cpu_latency);
399 err_kqd:
400         kfree(kqd);
401 err:
402         return ERR_PTR(ret);
403 }
404
405 static int kyber_init_sched(struct request_queue *q, struct elevator_type *e)
406 {
407         struct kyber_queue_data *kqd;
408         struct elevator_queue *eq;
409
410         eq = elevator_alloc(q, e);
411         if (!eq)
412                 return -ENOMEM;
413
414         kqd = kyber_queue_data_alloc(q);
415         if (IS_ERR(kqd)) {
416                 kobject_put(&eq->kobj);
417                 return PTR_ERR(kqd);
418         }
419
420         blk_stat_enable_accounting(q);
421
422         blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q);
423
424         eq->elevator_data = kqd;
425         q->elevator = eq;
426
427         return 0;
428 }
429
430 static void kyber_exit_sched(struct elevator_queue *e)
431 {
432         struct kyber_queue_data *kqd = e->elevator_data;
433         int i;
434
435         timer_shutdown_sync(&kqd->timer);
436         blk_stat_disable_accounting(kqd->q);
437
438         for (i = 0; i < KYBER_NUM_DOMAINS; i++)
439                 sbitmap_queue_free(&kqd->domain_tokens[i]);
440         free_percpu(kqd->cpu_latency);
441         kfree(kqd);
442 }
443
444 static void kyber_ctx_queue_init(struct kyber_ctx_queue *kcq)
445 {
446         unsigned int i;
447
448         spin_lock_init(&kcq->lock);
449         for (i = 0; i < KYBER_NUM_DOMAINS; i++)
450                 INIT_LIST_HEAD(&kcq->rq_list[i]);
451 }
452
453 static void kyber_depth_updated(struct blk_mq_hw_ctx *hctx)
454 {
455         struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;
456         struct blk_mq_tags *tags = hctx->sched_tags;
457         unsigned int shift = tags->bitmap_tags.sb.shift;
458
459         kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;
460
461         sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, kqd->async_depth);
462 }
463
464 static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
465 {
466         struct kyber_hctx_data *khd;
467         int i;
468
469         khd = kmalloc_node(sizeof(*khd), GFP_KERNEL, hctx->numa_node);
470         if (!khd)
471                 return -ENOMEM;
472
473         khd->kcqs = kmalloc_array_node(hctx->nr_ctx,
474                                        sizeof(struct kyber_ctx_queue),
475                                        GFP_KERNEL, hctx->numa_node);
476         if (!khd->kcqs)
477                 goto err_khd;
478
479         for (i = 0; i < hctx->nr_ctx; i++)
480                 kyber_ctx_queue_init(&khd->kcqs[i]);
481
482         for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
483                 if (sbitmap_init_node(&khd->kcq_map[i], hctx->nr_ctx,
484                                       ilog2(8), GFP_KERNEL, hctx->numa_node,
485                                       false, false)) {
486                         while (--i >= 0)
487                                 sbitmap_free(&khd->kcq_map[i]);
488                         goto err_kcqs;
489                 }
490         }
491
492         spin_lock_init(&khd->lock);
493
494         for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
495                 INIT_LIST_HEAD(&khd->rqs[i]);
496                 khd->domain_wait[i].sbq = NULL;
497                 init_waitqueue_func_entry(&khd->domain_wait[i].wait,
498                                           kyber_domain_wake);
499                 khd->domain_wait[i].wait.private = hctx;
500                 INIT_LIST_HEAD(&khd->domain_wait[i].wait.entry);
501                 atomic_set(&khd->wait_index[i], 0);
502         }
503
504         khd->cur_domain = 0;
505         khd->batching = 0;
506
507         hctx->sched_data = khd;
508         kyber_depth_updated(hctx);
509
510         return 0;
511
512 err_kcqs:
513         kfree(khd->kcqs);
514 err_khd:
515         kfree(khd);
516         return -ENOMEM;
517 }
518
519 static void kyber_exit_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
520 {
521         struct kyber_hctx_data *khd = hctx->sched_data;
522         int i;
523
524         for (i = 0; i < KYBER_NUM_DOMAINS; i++)
525                 sbitmap_free(&khd->kcq_map[i]);
526         kfree(khd->kcqs);
527         kfree(hctx->sched_data);
528 }
529
530 static int rq_get_domain_token(struct request *rq)
531 {
532         return (long)rq->elv.priv[0];
533 }
534
535 static void rq_set_domain_token(struct request *rq, int token)
536 {
537         rq->elv.priv[0] = (void *)(long)token;
538 }
539
540 static void rq_clear_domain_token(struct kyber_queue_data *kqd,
541                                   struct request *rq)
542 {
543         unsigned int sched_domain;
544         int nr;
545
546         nr = rq_get_domain_token(rq);
547         if (nr != -1) {
548                 sched_domain = kyber_sched_domain(rq->cmd_flags);
549                 sbitmap_queue_clear(&kqd->domain_tokens[sched_domain], nr,
550                                     rq->mq_ctx->cpu);
551         }
552 }
553
554 static void kyber_limit_depth(blk_opf_t opf, struct blk_mq_alloc_data *data)
555 {
556         /*
557          * We use the scheduler tags as per-hardware queue queueing tokens.
558          * Async requests can be limited at this stage.
559          */
560         if (!op_is_sync(opf)) {
561                 struct kyber_queue_data *kqd = data->q->elevator->elevator_data;
562
563                 data->shallow_depth = kqd->async_depth;
564         }
565 }
566
567 static bool kyber_bio_merge(struct request_queue *q, struct bio *bio,
568                 unsigned int nr_segs)
569 {
570         struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
571         struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, bio->bi_opf, ctx);
572         struct kyber_hctx_data *khd = hctx->sched_data;
573         struct kyber_ctx_queue *kcq = &khd->kcqs[ctx->index_hw[hctx->type]];
574         unsigned int sched_domain = kyber_sched_domain(bio->bi_opf);
575         struct list_head *rq_list = &kcq->rq_list[sched_domain];
576         bool merged;
577
578         spin_lock(&kcq->lock);
579         merged = blk_bio_list_merge(hctx->queue, rq_list, bio, nr_segs);
580         spin_unlock(&kcq->lock);
581
582         return merged;
583 }
584
585 static void kyber_prepare_request(struct request *rq)
586 {
587         rq_set_domain_token(rq, -1);
588 }
589
590 static void kyber_insert_requests(struct blk_mq_hw_ctx *hctx,
591                                   struct list_head *rq_list,
592                                   blk_insert_t flags)
593 {
594         struct kyber_hctx_data *khd = hctx->sched_data;
595         struct request *rq, *next;
596
597         list_for_each_entry_safe(rq, next, rq_list, queuelist) {
598                 unsigned int sched_domain = kyber_sched_domain(rq->cmd_flags);
599                 struct kyber_ctx_queue *kcq = &khd->kcqs[rq->mq_ctx->index_hw[hctx->type]];
600                 struct list_head *head = &kcq->rq_list[sched_domain];
601
602                 spin_lock(&kcq->lock);
603                 trace_block_rq_insert(rq);
604                 if (flags & BLK_MQ_INSERT_AT_HEAD)
605                         list_move(&rq->queuelist, head);
606                 else
607                         list_move_tail(&rq->queuelist, head);
608                 sbitmap_set_bit(&khd->kcq_map[sched_domain],
609                                 rq->mq_ctx->index_hw[hctx->type]);
610                 spin_unlock(&kcq->lock);
611         }
612 }
613
614 static void kyber_finish_request(struct request *rq)
615 {
616         struct kyber_queue_data *kqd = rq->q->elevator->elevator_data;
617
618         rq_clear_domain_token(kqd, rq);
619 }
620
621 static void add_latency_sample(struct kyber_cpu_latency *cpu_latency,
622                                unsigned int sched_domain, unsigned int type,
623                                u64 target, u64 latency)
624 {
625         unsigned int bucket;
626         u64 divisor;
627
628         if (latency > 0) {
629                 divisor = max_t(u64, target >> KYBER_LATENCY_SHIFT, 1);
630                 bucket = min_t(unsigned int, div64_u64(latency - 1, divisor),
631                                KYBER_LATENCY_BUCKETS - 1);
632         } else {
633                 bucket = 0;
634         }
635
636         atomic_inc(&cpu_latency->buckets[sched_domain][type][bucket]);
637 }
638
639 static void kyber_completed_request(struct request *rq, u64 now)
640 {
641         struct kyber_queue_data *kqd = rq->q->elevator->elevator_data;
642         struct kyber_cpu_latency *cpu_latency;
643         unsigned int sched_domain;
644         u64 target;
645
646         sched_domain = kyber_sched_domain(rq->cmd_flags);
647         if (sched_domain == KYBER_OTHER)
648                 return;
649
650         cpu_latency = get_cpu_ptr(kqd->cpu_latency);
651         target = kqd->latency_targets[sched_domain];
652         add_latency_sample(cpu_latency, sched_domain, KYBER_TOTAL_LATENCY,
653                            target, now - rq->start_time_ns);
654         add_latency_sample(cpu_latency, sched_domain, KYBER_IO_LATENCY, target,
655                            now - rq->io_start_time_ns);
656         put_cpu_ptr(kqd->cpu_latency);
657
658         timer_reduce(&kqd->timer, jiffies + HZ / 10);
659 }
660
661 struct flush_kcq_data {
662         struct kyber_hctx_data *khd;
663         unsigned int sched_domain;
664         struct list_head *list;
665 };
666
667 static bool flush_busy_kcq(struct sbitmap *sb, unsigned int bitnr, void *data)
668 {
669         struct flush_kcq_data *flush_data = data;
670         struct kyber_ctx_queue *kcq = &flush_data->khd->kcqs[bitnr];
671
672         spin_lock(&kcq->lock);
673         list_splice_tail_init(&kcq->rq_list[flush_data->sched_domain],
674                               flush_data->list);
675         sbitmap_clear_bit(sb, bitnr);
676         spin_unlock(&kcq->lock);
677
678         return true;
679 }
680
681 static void kyber_flush_busy_kcqs(struct kyber_hctx_data *khd,
682                                   unsigned int sched_domain,
683                                   struct list_head *list)
684 {
685         struct flush_kcq_data data = {
686                 .khd = khd,
687                 .sched_domain = sched_domain,
688                 .list = list,
689         };
690
691         sbitmap_for_each_set(&khd->kcq_map[sched_domain],
692                              flush_busy_kcq, &data);
693 }
694
695 static int kyber_domain_wake(wait_queue_entry_t *wqe, unsigned mode, int flags,
696                              void *key)
697 {
698         struct blk_mq_hw_ctx *hctx = READ_ONCE(wqe->private);
699         struct sbq_wait *wait = container_of(wqe, struct sbq_wait, wait);
700
701         sbitmap_del_wait_queue(wait);
702         blk_mq_run_hw_queue(hctx, true);
703         return 1;
704 }
705
706 static int kyber_get_domain_token(struct kyber_queue_data *kqd,
707                                   struct kyber_hctx_data *khd,
708                                   struct blk_mq_hw_ctx *hctx)
709 {
710         unsigned int sched_domain = khd->cur_domain;
711         struct sbitmap_queue *domain_tokens = &kqd->domain_tokens[sched_domain];
712         struct sbq_wait *wait = &khd->domain_wait[sched_domain];
713         struct sbq_wait_state *ws;
714         int nr;
715
716         nr = __sbitmap_queue_get(domain_tokens);
717
718         /*
719          * If we failed to get a domain token, make sure the hardware queue is
720          * run when one becomes available. Note that this is serialized on
721          * khd->lock, but we still need to be careful about the waker.
722          */
723         if (nr < 0 && list_empty_careful(&wait->wait.entry)) {
724                 ws = sbq_wait_ptr(domain_tokens,
725                                   &khd->wait_index[sched_domain]);
726                 khd->domain_ws[sched_domain] = ws;
727                 sbitmap_add_wait_queue(domain_tokens, ws, wait);
728
729                 /*
730                  * Try again in case a token was freed before we got on the wait
731                  * queue.
732                  */
733                 nr = __sbitmap_queue_get(domain_tokens);
734         }
735
736         /*
737          * If we got a token while we were on the wait queue, remove ourselves
738          * from the wait queue to ensure that all wake ups make forward
739          * progress. It's possible that the waker already deleted the entry
740          * between the !list_empty_careful() check and us grabbing the lock, but
741          * list_del_init() is okay with that.
742          */
743         if (nr >= 0 && !list_empty_careful(&wait->wait.entry)) {
744                 ws = khd->domain_ws[sched_domain];
745                 spin_lock_irq(&ws->wait.lock);
746                 sbitmap_del_wait_queue(wait);
747                 spin_unlock_irq(&ws->wait.lock);
748         }
749
750         return nr;
751 }
752
753 static struct request *
754 kyber_dispatch_cur_domain(struct kyber_queue_data *kqd,
755                           struct kyber_hctx_data *khd,
756                           struct blk_mq_hw_ctx *hctx)
757 {
758         struct list_head *rqs;
759         struct request *rq;
760         int nr;
761
762         rqs = &khd->rqs[khd->cur_domain];
763
764         /*
765          * If we already have a flushed request, then we just need to get a
766          * token for it. Otherwise, if there are pending requests in the kcqs,
767          * flush the kcqs, but only if we can get a token. If not, we should
768          * leave the requests in the kcqs so that they can be merged. Note that
769          * khd->lock serializes the flushes, so if we observed any bit set in
770          * the kcq_map, we will always get a request.
771          */
772         rq = list_first_entry_or_null(rqs, struct request, queuelist);
773         if (rq) {
774                 nr = kyber_get_domain_token(kqd, khd, hctx);
775                 if (nr >= 0) {
776                         khd->batching++;
777                         rq_set_domain_token(rq, nr);
778                         list_del_init(&rq->queuelist);
779                         return rq;
780                 } else {
781                         trace_kyber_throttled(kqd->dev,
782                                               kyber_domain_names[khd->cur_domain]);
783                 }
784         } else if (sbitmap_any_bit_set(&khd->kcq_map[khd->cur_domain])) {
785                 nr = kyber_get_domain_token(kqd, khd, hctx);
786                 if (nr >= 0) {
787                         kyber_flush_busy_kcqs(khd, khd->cur_domain, rqs);
788                         rq = list_first_entry(rqs, struct request, queuelist);
789                         khd->batching++;
790                         rq_set_domain_token(rq, nr);
791                         list_del_init(&rq->queuelist);
792                         return rq;
793                 } else {
794                         trace_kyber_throttled(kqd->dev,
795                                               kyber_domain_names[khd->cur_domain]);
796                 }
797         }
798
799         /* There were either no pending requests or no tokens. */
800         return NULL;
801 }
802
803 static struct request *kyber_dispatch_request(struct blk_mq_hw_ctx *hctx)
804 {
805         struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;
806         struct kyber_hctx_data *khd = hctx->sched_data;
807         struct request *rq;
808         int i;
809
810         spin_lock(&khd->lock);
811
812         /*
813          * First, if we are still entitled to batch, try to dispatch a request
814          * from the batch.
815          */
816         if (khd->batching < kyber_batch_size[khd->cur_domain]) {
817                 rq = kyber_dispatch_cur_domain(kqd, khd, hctx);
818                 if (rq)
819                         goto out;
820         }
821
822         /*
823          * Either,
824          * 1. We were no longer entitled to a batch.
825          * 2. The domain we were batching didn't have any requests.
826          * 3. The domain we were batching was out of tokens.
827          *
828          * Start another batch. Note that this wraps back around to the original
829          * domain if no other domains have requests or tokens.
830          */
831         khd->batching = 0;
832         for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
833                 if (khd->cur_domain == KYBER_NUM_DOMAINS - 1)
834                         khd->cur_domain = 0;
835                 else
836                         khd->cur_domain++;
837
838                 rq = kyber_dispatch_cur_domain(kqd, khd, hctx);
839                 if (rq)
840                         goto out;
841         }
842
843         rq = NULL;
844 out:
845         spin_unlock(&khd->lock);
846         return rq;
847 }
848
849 static bool kyber_has_work(struct blk_mq_hw_ctx *hctx)
850 {
851         struct kyber_hctx_data *khd = hctx->sched_data;
852         int i;
853
854         for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
855                 if (!list_empty_careful(&khd->rqs[i]) ||
856                     sbitmap_any_bit_set(&khd->kcq_map[i]))
857                         return true;
858         }
859
860         return false;
861 }
862
863 #define KYBER_LAT_SHOW_STORE(domain, name)                              \
864 static ssize_t kyber_##name##_lat_show(struct elevator_queue *e,        \
865                                        char *page)                      \
866 {                                                                       \
867         struct kyber_queue_data *kqd = e->elevator_data;                \
868                                                                         \
869         return sprintf(page, "%llu\n", kqd->latency_targets[domain]);   \
870 }                                                                       \
871                                                                         \
872 static ssize_t kyber_##name##_lat_store(struct elevator_queue *e,       \
873                                         const char *page, size_t count) \
874 {                                                                       \
875         struct kyber_queue_data *kqd = e->elevator_data;                \
876         unsigned long long nsec;                                        \
877         int ret;                                                        \
878                                                                         \
879         ret = kstrtoull(page, 10, &nsec);                               \
880         if (ret)                                                        \
881                 return ret;                                             \
882                                                                         \
883         kqd->latency_targets[domain] = nsec;                            \
884                                                                         \
885         return count;                                                   \
886 }
887 KYBER_LAT_SHOW_STORE(KYBER_READ, read);
888 KYBER_LAT_SHOW_STORE(KYBER_WRITE, write);
889 #undef KYBER_LAT_SHOW_STORE
890
891 #define KYBER_LAT_ATTR(op) __ATTR(op##_lat_nsec, 0644, kyber_##op##_lat_show, kyber_##op##_lat_store)
892 static struct elv_fs_entry kyber_sched_attrs[] = {
893         KYBER_LAT_ATTR(read),
894         KYBER_LAT_ATTR(write),
895         __ATTR_NULL
896 };
897 #undef KYBER_LAT_ATTR
898
899 #ifdef CONFIG_BLK_DEBUG_FS
900 #define KYBER_DEBUGFS_DOMAIN_ATTRS(domain, name)                        \
901 static int kyber_##name##_tokens_show(void *data, struct seq_file *m)   \
902 {                                                                       \
903         struct request_queue *q = data;                                 \
904         struct kyber_queue_data *kqd = q->elevator->elevator_data;      \
905                                                                         \
906         sbitmap_queue_show(&kqd->domain_tokens[domain], m);             \
907         return 0;                                                       \
908 }                                                                       \
909                                                                         \
910 static void *kyber_##name##_rqs_start(struct seq_file *m, loff_t *pos)  \
911         __acquires(&khd->lock)                                          \
912 {                                                                       \
913         struct blk_mq_hw_ctx *hctx = m->private;                        \
914         struct kyber_hctx_data *khd = hctx->sched_data;                 \
915                                                                         \
916         spin_lock(&khd->lock);                                          \
917         return seq_list_start(&khd->rqs[domain], *pos);                 \
918 }                                                                       \
919                                                                         \
920 static void *kyber_##name##_rqs_next(struct seq_file *m, void *v,       \
921                                      loff_t *pos)                       \
922 {                                                                       \
923         struct blk_mq_hw_ctx *hctx = m->private;                        \
924         struct kyber_hctx_data *khd = hctx->sched_data;                 \
925                                                                         \
926         return seq_list_next(v, &khd->rqs[domain], pos);                \
927 }                                                                       \
928                                                                         \
929 static void kyber_##name##_rqs_stop(struct seq_file *m, void *v)        \
930         __releases(&khd->lock)                                          \
931 {                                                                       \
932         struct blk_mq_hw_ctx *hctx = m->private;                        \
933         struct kyber_hctx_data *khd = hctx->sched_data;                 \
934                                                                         \
935         spin_unlock(&khd->lock);                                        \
936 }                                                                       \
937                                                                         \
938 static const struct seq_operations kyber_##name##_rqs_seq_ops = {       \
939         .start  = kyber_##name##_rqs_start,                             \
940         .next   = kyber_##name##_rqs_next,                              \
941         .stop   = kyber_##name##_rqs_stop,                              \
942         .show   = blk_mq_debugfs_rq_show,                               \
943 };                                                                      \
944                                                                         \
945 static int kyber_##name##_waiting_show(void *data, struct seq_file *m)  \
946 {                                                                       \
947         struct blk_mq_hw_ctx *hctx = data;                              \
948         struct kyber_hctx_data *khd = hctx->sched_data;                 \
949         wait_queue_entry_t *wait = &khd->domain_wait[domain].wait;      \
950                                                                         \
951         seq_printf(m, "%d\n", !list_empty_careful(&wait->entry));       \
952         return 0;                                                       \
953 }
954 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_READ, read)
955 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_WRITE, write)
956 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_DISCARD, discard)
957 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_OTHER, other)
958 #undef KYBER_DEBUGFS_DOMAIN_ATTRS
959
960 static int kyber_async_depth_show(void *data, struct seq_file *m)
961 {
962         struct request_queue *q = data;
963         struct kyber_queue_data *kqd = q->elevator->elevator_data;
964
965         seq_printf(m, "%u\n", kqd->async_depth);
966         return 0;
967 }
968
969 static int kyber_cur_domain_show(void *data, struct seq_file *m)
970 {
971         struct blk_mq_hw_ctx *hctx = data;
972         struct kyber_hctx_data *khd = hctx->sched_data;
973
974         seq_printf(m, "%s\n", kyber_domain_names[khd->cur_domain]);
975         return 0;
976 }
977
978 static int kyber_batching_show(void *data, struct seq_file *m)
979 {
980         struct blk_mq_hw_ctx *hctx = data;
981         struct kyber_hctx_data *khd = hctx->sched_data;
982
983         seq_printf(m, "%u\n", khd->batching);
984         return 0;
985 }
986
987 #define KYBER_QUEUE_DOMAIN_ATTRS(name)  \
988         {#name "_tokens", 0400, kyber_##name##_tokens_show}
989 static const struct blk_mq_debugfs_attr kyber_queue_debugfs_attrs[] = {
990         KYBER_QUEUE_DOMAIN_ATTRS(read),
991         KYBER_QUEUE_DOMAIN_ATTRS(write),
992         KYBER_QUEUE_DOMAIN_ATTRS(discard),
993         KYBER_QUEUE_DOMAIN_ATTRS(other),
994         {"async_depth", 0400, kyber_async_depth_show},
995         {},
996 };
997 #undef KYBER_QUEUE_DOMAIN_ATTRS
998
999 #define KYBER_HCTX_DOMAIN_ATTRS(name)                                   \
1000         {#name "_rqs", 0400, .seq_ops = &kyber_##name##_rqs_seq_ops},   \
1001         {#name "_waiting", 0400, kyber_##name##_waiting_show}
1002 static const struct blk_mq_debugfs_attr kyber_hctx_debugfs_attrs[] = {
1003         KYBER_HCTX_DOMAIN_ATTRS(read),
1004         KYBER_HCTX_DOMAIN_ATTRS(write),
1005         KYBER_HCTX_DOMAIN_ATTRS(discard),
1006         KYBER_HCTX_DOMAIN_ATTRS(other),
1007         {"cur_domain", 0400, kyber_cur_domain_show},
1008         {"batching", 0400, kyber_batching_show},
1009         {},
1010 };
1011 #undef KYBER_HCTX_DOMAIN_ATTRS
1012 #endif
1013
1014 static struct elevator_type kyber_sched = {
1015         .ops = {
1016                 .init_sched = kyber_init_sched,
1017                 .exit_sched = kyber_exit_sched,
1018                 .init_hctx = kyber_init_hctx,
1019                 .exit_hctx = kyber_exit_hctx,
1020                 .limit_depth = kyber_limit_depth,
1021                 .bio_merge = kyber_bio_merge,
1022                 .prepare_request = kyber_prepare_request,
1023                 .insert_requests = kyber_insert_requests,
1024                 .finish_request = kyber_finish_request,
1025                 .requeue_request = kyber_finish_request,
1026                 .completed_request = kyber_completed_request,
1027                 .dispatch_request = kyber_dispatch_request,
1028                 .has_work = kyber_has_work,
1029                 .depth_updated = kyber_depth_updated,
1030         },
1031 #ifdef CONFIG_BLK_DEBUG_FS
1032         .queue_debugfs_attrs = kyber_queue_debugfs_attrs,
1033         .hctx_debugfs_attrs = kyber_hctx_debugfs_attrs,
1034 #endif
1035         .elevator_attrs = kyber_sched_attrs,
1036         .elevator_name = "kyber",
1037         .elevator_owner = THIS_MODULE,
1038 };
1039
1040 static int __init kyber_init(void)
1041 {
1042         return elv_register(&kyber_sched);
1043 }
1044
1045 static void __exit kyber_exit(void)
1046 {
1047         elv_unregister(&kyber_sched);
1048 }
1049
1050 module_init(kyber_init);
1051 module_exit(kyber_exit);
1052
1053 MODULE_AUTHOR("Omar Sandoval");
1054 MODULE_LICENSE("GPL");
1055 MODULE_DESCRIPTION("Kyber I/O scheduler");