1/*
2 * Copyright (C) 2015 Red Hat. All rights reserved.
3 *
4 * This file is released under the GPL.
5 */
6
7#include "dm-cache-background-tracker.h"
8#include "dm-cache-policy-internal.h"
9#include "dm-cache-policy.h"
10#include "dm.h"
11
12#include <linux/hash.h>
13#include <linux/jiffies.h>
14#include <linux/module.h>
15#include <linux/mutex.h>
16#include <linux/vmalloc.h>
17#include <linux/math64.h>
18
19#define DM_MSG_PREFIX "cache-policy-smq"
20
21/*----------------------------------------------------------------*/
22
23/*
24 * Safe division functions that return zero on divide by zero.
25 */
26static unsigned safe_div(unsigned n, unsigned d)
27{
28 return d ? n / d : 0u;
29}
30
31static unsigned safe_mod(unsigned n, unsigned d)
32{
33 return d ? n % d : 0u;
34}
35
36/*----------------------------------------------------------------*/
37
38struct entry {
39 unsigned hash_next:28;
40 unsigned prev:28;
41 unsigned next:28;
42 unsigned level:6;
43 bool dirty:1;
44 bool allocated:1;
45 bool sentinel:1;
46 bool pending_work:1;
47
48 dm_oblock_t oblock;
49};
50
51/*----------------------------------------------------------------*/
52
53#define INDEXER_NULL ((1u << 28u) - 1u)
54
55/*
56 * An entry_space manages a set of entries that we use for the queues.
57 * The clean and dirty queues share entries, so this object is separate
58 * from the queue itself.
59 */
60struct entry_space {
61 struct entry *begin;
62 struct entry *end;
63};
64
65static int space_init(struct entry_space *es, unsigned nr_entries)
66{
67 if (!nr_entries) {
68 es->begin = es->end = NULL;
69 return 0;
70 }
71
72 es->begin = vzalloc(array_size(nr_entries, sizeof(struct entry)));
73 if (!es->begin)
74 return -ENOMEM;
75
76 es->end = es->begin + nr_entries;
77 return 0;
78}
79
80static void space_exit(struct entry_space *es)
81{
82 vfree(es->begin);
83}
84
85static struct entry *__get_entry(struct entry_space *es, unsigned block)
86{
87 struct entry *e;
88
89 e = es->begin + block;
90 BUG_ON(e >= es->end);
91
92 return e;
93}
94
95static unsigned to_index(struct entry_space *es, struct entry *e)
96{
97 BUG_ON(e < es->begin || e >= es->end);
98 return e - es->begin;
99}
100
101static struct entry *to_entry(struct entry_space *es, unsigned block)
102{
103 if (block == INDEXER_NULL)
104 return NULL;
105
106 return __get_entry(es, block);
107}
108
109/*----------------------------------------------------------------*/
110
111struct ilist {
112 unsigned nr_elts; /* excluding sentinel entries */
113 unsigned head, tail;
114};
115
116static void l_init(struct ilist *l)
117{
118 l->nr_elts = 0;
119 l->head = l->tail = INDEXER_NULL;
120}
121
122static struct entry *l_head(struct entry_space *es, struct ilist *l)
123{
124 return to_entry(es, l->head);
125}
126
127static struct entry *l_tail(struct entry_space *es, struct ilist *l)
128{
129 return to_entry(es, l->tail);
130}
131
132static struct entry *l_next(struct entry_space *es, struct entry *e)
133{
134 return to_entry(es, e->next);
135}
136
137static struct entry *l_prev(struct entry_space *es, struct entry *e)
138{
139 return to_entry(es, e->prev);
140}
141
142static bool l_empty(struct ilist *l)
143{
144 return l->head == INDEXER_NULL;
145}
146
147static void l_add_head(struct entry_space *es, struct ilist *l, struct entry *e)
148{
149 struct entry *head = l_head(es, l);
150
151 e->next = l->head;
152 e->prev = INDEXER_NULL;
153
154 if (head)
155 head->prev = l->head = to_index(es, e);
156 else
157 l->head = l->tail = to_index(es, e);
158
159 if (!e->sentinel)
160 l->nr_elts++;
161}
162
163static void l_add_tail(struct entry_space *es, struct ilist *l, struct entry *e)
164{
165 struct entry *tail = l_tail(es, l);
166
167 e->next = INDEXER_NULL;
168 e->prev = l->tail;
169
170 if (tail)
171 tail->next = l->tail = to_index(es, e);
172 else
173 l->head = l->tail = to_index(es, e);
174
175 if (!e->sentinel)
176 l->nr_elts++;
177}
178
179static void l_add_before(struct entry_space *es, struct ilist *l,
180 struct entry *old, struct entry *e)
181{
182 struct entry *prev = l_prev(es, old);
183
184 if (!prev)
185 l_add_head(es, l, e);
186
187 else {
188 e->prev = old->prev;
189 e->next = to_index(es, old);
190 prev->next = old->prev = to_index(es, e);
191
192 if (!e->sentinel)
193 l->nr_elts++;
194 }
195}
196
197static void l_del(struct entry_space *es, struct ilist *l, struct entry *e)
198{
199 struct entry *prev = l_prev(es, e);
200 struct entry *next = l_next(es, e);
201
202 if (prev)
203 prev->next = e->next;
204 else
205 l->head = e->next;
206
207 if (next)
208 next->prev = e->prev;
209 else
210 l->tail = e->prev;
211
212 if (!e->sentinel)
213 l->nr_elts--;
214}
215
216static struct entry *l_pop_head(struct entry_space *es, struct ilist *l)
217{
218 struct entry *e;
219
220 for (e = l_head(es, l); e; e = l_next(es, e))
221 if (!e->sentinel) {
222 l_del(es, l, e);
223 return e;
224 }
225
226 return NULL;
227}
228
229static struct entry *l_pop_tail(struct entry_space *es, struct ilist *l)
230{
231 struct entry *e;
232
233 for (e = l_tail(es, l); e; e = l_prev(es, e))
234 if (!e->sentinel) {
235 l_del(es, l, e);
236 return e;
237 }
238
239 return NULL;
240}
241
242/*----------------------------------------------------------------*/
243
244/*
245 * The stochastic-multi-queue is a set of lru lists stacked into levels.
246 * Entries are moved up levels when they are used, which loosely orders the
247 * most accessed entries in the top levels and least in the bottom. This
248 * structure is *much* better than a single lru list.
249 */
250#define MAX_LEVELS 64u
251
252struct queue {
253 struct entry_space *es;
254
255 unsigned nr_elts;
256 unsigned nr_levels;
257 struct ilist qs[MAX_LEVELS];
258
259 /*
260 * We maintain a count of the number of entries we would like in each
261 * level.
262 */
263 unsigned last_target_nr_elts;
264 unsigned nr_top_levels;
265 unsigned nr_in_top_levels;
266 unsigned target_count[MAX_LEVELS];
267};
268
269static void q_init(struct queue *q, struct entry_space *es, unsigned nr_levels)
270{
271 unsigned i;
272
273 q->es = es;
274 q->nr_elts = 0;
275 q->nr_levels = nr_levels;
276
277 for (i = 0; i < q->nr_levels; i++) {
278 l_init(q->qs + i);
279 q->target_count[i] = 0u;
280 }
281
282 q->last_target_nr_elts = 0u;
283 q->nr_top_levels = 0u;
284 q->nr_in_top_levels = 0u;
285}
286
287static unsigned q_size(struct queue *q)
288{
289 return q->nr_elts;
290}
291
292/*
293 * Insert an entry to the back of the given level.
294 */
295static void q_push(struct queue *q, struct entry *e)
296{
297 BUG_ON(e->pending_work);
298
299 if (!e->sentinel)
300 q->nr_elts++;
301
302 l_add_tail(q->es, q->qs + e->level, e);
303}
304
305static void q_push_front(struct queue *q, struct entry *e)
306{
307 BUG_ON(e->pending_work);
308
309 if (!e->sentinel)
310 q->nr_elts++;
311
312 l_add_head(q->es, q->qs + e->level, e);
313}
314
315static void q_push_before(struct queue *q, struct entry *old, struct entry *e)
316{
317 BUG_ON(e->pending_work);
318
319 if (!e->sentinel)
320 q->nr_elts++;
321
322 l_add_before(q->es, q->qs + e->level, old, e);
323}
324
325static void q_del(struct queue *q, struct entry *e)
326{
327 l_del(q->es, q->qs + e->level, e);
328 if (!e->sentinel)
329 q->nr_elts--;
330}
331
332/*
333 * Return the oldest entry of the lowest populated level.
334 */
335static struct entry *q_peek(struct queue *q, unsigned max_level, bool can_cross_sentinel)
336{
337 unsigned level;
338 struct entry *e;
339
340 max_level = min(max_level, q->nr_levels);
341
342 for (level = 0; level < max_level; level++)
343 for (e = l_head(q->es, q->qs + level); e; e = l_next(q->es, e)) {
344 if (e->sentinel) {
345 if (can_cross_sentinel)
346 continue;
347 else
348 break;
349 }
350
351 return e;
352 }
353
354 return NULL;
355}
356
357static struct entry *q_pop(struct queue *q)
358{
359 struct entry *e = q_peek(q, q->nr_levels, true);
360
361 if (e)
362 q_del(q, e);
363
364 return e;
365}
366
367/*
368 * This function assumes there is a non-sentinel entry to pop. It's only
369 * used by redistribute, so we know this is true. It also doesn't adjust
370 * the q->nr_elts count.
371 */
372static struct entry *__redist_pop_from(struct queue *q, unsigned level)
373{
374 struct entry *e;
375
376 for (; level < q->nr_levels; level++)
377 for (e = l_head(q->es, q->qs + level); e; e = l_next(q->es, e))
378 if (!e->sentinel) {
379 l_del(q->es, q->qs + e->level, e);
380 return e;
381 }
382
383 return NULL;
384}
385
386static void q_set_targets_subrange_(struct queue *q, unsigned nr_elts, unsigned lbegin, unsigned lend)
387{
388 unsigned level, nr_levels, entries_per_level, remainder;
389
390 BUG_ON(lbegin > lend);
391 BUG_ON(lend > q->nr_levels);
392 nr_levels = lend - lbegin;
393 entries_per_level = safe_div(nr_elts, nr_levels);
394 remainder = safe_mod(nr_elts, nr_levels);
395
396 for (level = lbegin; level < lend; level++)
397 q->target_count[level] =
398 (level < (lbegin + remainder)) ? entries_per_level + 1u : entries_per_level;
399}
400
401/*
402 * Typically we have fewer elements in the top few levels which allows us
403 * to adjust the promote threshold nicely.
404 */
405static void q_set_targets(struct queue *q)
406{
407 if (q->last_target_nr_elts == q->nr_elts)
408 return;
409
410 q->last_target_nr_elts = q->nr_elts;
411
412 if (q->nr_top_levels > q->nr_levels)
413 q_set_targets_subrange_(q, q->nr_elts, 0, q->nr_levels);
414
415 else {
416 q_set_targets_subrange_(q, q->nr_in_top_levels,
417 q->nr_levels - q->nr_top_levels, q->nr_levels);
418
419 if (q->nr_in_top_levels < q->nr_elts)
420 q_set_targets_subrange_(q, q->nr_elts - q->nr_in_top_levels,
421 0, q->nr_levels - q->nr_top_levels);
422 else
423 q_set_targets_subrange_(q, 0, 0, q->nr_levels - q->nr_top_levels);
424 }
425}
426
427static void q_redistribute(struct queue *q)
428{
429 unsigned target, level;
430 struct ilist *l, *l_above;
431 struct entry *e;
432
433 q_set_targets(q);
434
435 for (level = 0u; level < q->nr_levels - 1u; level++) {
436 l = q->qs + level;
437 target = q->target_count[level];
438
439 /*
440 * Pull down some entries from the level above.
441 */
442 while (l->nr_elts < target) {
443 e = __redist_pop_from(q, level + 1u);
444 if (!e) {
445 /* bug in nr_elts */
446 break;
447 }
448
449 e->level = level;
450 l_add_tail(q->es, l, e);
451 }
452
453 /*
454 * Push some entries up.
455 */
456 l_above = q->qs + level + 1u;
457 while (l->nr_elts > target) {
458 e = l_pop_tail(q->es, l);
459
460 if (!e)
461 /* bug in nr_elts */
462 break;
463
464 e->level = level + 1u;
465 l_add_tail(q->es, l_above, e);
466 }
467 }
468}
469
470static void q_requeue(struct queue *q, struct entry *e, unsigned extra_levels,
471 struct entry *s1, struct entry *s2)
472{
473 struct entry *de;
474 unsigned sentinels_passed = 0;
475 unsigned new_level = min(q->nr_levels - 1u, e->level + extra_levels);
476
477 /* try and find an entry to swap with */
478 if (extra_levels && (e->level < q->nr_levels - 1u)) {
479 for (de = l_head(q->es, q->qs + new_level); de && de->sentinel; de = l_next(q->es, de))
480 sentinels_passed++;
481
482 if (de) {
483 q_del(q, de);
484 de->level = e->level;
485 if (s1) {
486 switch (sentinels_passed) {
487 case 0:
488 q_push_before(q, s1, de);
489 break;
490
491 case 1:
492 q_push_before(q, s2, de);
493 break;
494
495 default:
496 q_push(q, de);
497 }
498 } else
499 q_push(q, de);
500 }
501 }
502
503 q_del(q, e);
504 e->level = new_level;
505 q_push(q, e);
506}
507
508/*----------------------------------------------------------------*/
509
510#define FP_SHIFT 8
511#define SIXTEENTH (1u << (FP_SHIFT - 4u))
512#define EIGHTH (1u << (FP_SHIFT - 3u))
513
514struct stats {
515 unsigned hit_threshold;
516 unsigned hits;
517 unsigned misses;
518};
519
520enum performance {
521 Q_POOR,
522 Q_FAIR,
523 Q_WELL
524};
525
526static void stats_init(struct stats *s, unsigned nr_levels)
527{
528 s->hit_threshold = (nr_levels * 3u) / 4u;
529 s->hits = 0u;
530 s->misses = 0u;
531}
532
533static void stats_reset(struct stats *s)
534{
535 s->hits = s->misses = 0u;
536}
537
538static void stats_level_accessed(struct stats *s, unsigned level)
539{
540 if (level >= s->hit_threshold)
541 s->hits++;
542 else
543 s->misses++;
544}
545
546static void stats_miss(struct stats *s)
547{
548 s->misses++;
549}
550
551/*
552 * There are times when we don't have any confidence in the hotspot queue.
553 * Such as when a fresh cache is created and the blocks have been spread
554 * out across the levels, or if an io load changes. We detect this by
555 * seeing how often a lookup is in the top levels of the hotspot queue.
556 */
557static enum performance stats_assess(struct stats *s)
558{
559 unsigned confidence = safe_div(s->hits << FP_SHIFT, s->hits + s->misses);
560
561 if (confidence < SIXTEENTH)
562 return Q_POOR;
563
564 else if (confidence < EIGHTH)
565 return Q_FAIR;
566
567 else
568 return Q_WELL;
569}
570
571/*----------------------------------------------------------------*/
572
573struct smq_hash_table {
574 struct entry_space *es;
575 unsigned long long hash_bits;
576 unsigned *buckets;
577};
578
579/*
580 * All cache entries are stored in a chained hash table. To save space we
581 * use indexing again, and only store indexes to the next entry.
582 */
583static int h_init(struct smq_hash_table *ht, struct entry_space *es, unsigned nr_entries)
584{
585 unsigned i, nr_buckets;
586
587 ht->es = es;
588 nr_buckets = roundup_pow_of_two(max(nr_entries / 4u, 16u));
589 ht->hash_bits = __ffs(nr_buckets);
590
591 ht->buckets = vmalloc(array_size(nr_buckets, sizeof(*ht->buckets)));
592 if (!ht->buckets)
593 return -ENOMEM;
594
595 for (i = 0; i < nr_buckets; i++)
596 ht->buckets[i] = INDEXER_NULL;
597
598 return 0;
599}
600
601static void h_exit(struct smq_hash_table *ht)
602{
603 vfree(ht->buckets);
604}
605
606static struct entry *h_head(struct smq_hash_table *ht, unsigned bucket)
607{
608 return to_entry(ht->es, ht->buckets[bucket]);
609}
610
611static struct entry *h_next(struct smq_hash_table *ht, struct entry *e)
612{
613 return to_entry(ht->es, e->hash_next);
614}
615
616static void __h_insert(struct smq_hash_table *ht, unsigned bucket, struct entry *e)
617{
618 e->hash_next = ht->buckets[bucket];
619 ht->buckets[bucket] = to_index(ht->es, e);
620}
621
622static void h_insert(struct smq_hash_table *ht, struct entry *e)
623{
624 unsigned h = hash_64(from_oblock(e->oblock), ht->hash_bits);
625 __h_insert(ht, h, e);
626}
627
628static struct entry *__h_lookup(struct smq_hash_table *ht, unsigned h, dm_oblock_t oblock,
629 struct entry **prev)
630{
631 struct entry *e;
632
633 *prev = NULL;
634 for (e = h_head(ht, h); e; e = h_next(ht, e)) {
635 if (e->oblock == oblock)
636 return e;
637
638 *prev = e;
639 }
640
641 return NULL;
642}
643
644static void __h_unlink(struct smq_hash_table *ht, unsigned h,
645 struct entry *e, struct entry *prev)
646{
647 if (prev)
648 prev->hash_next = e->hash_next;
649 else
650 ht->buckets[h] = e->hash_next;
651}
652
653/*
654 * Also moves each entry to the front of the bucket.
655 */
656static struct entry *h_lookup(struct smq_hash_table *ht, dm_oblock_t oblock)
657{
658 struct entry *e, *prev;
659 unsigned h = hash_64(from_oblock(oblock), ht->hash_bits);
660
661 e = __h_lookup(ht, h, oblock, &prev);
662 if (e && prev) {
663 /*
664 * Move to the front because this entry is likely
665 * to be hit again.
666 */
667 __h_unlink(ht, h, e, prev);
668 __h_insert(ht, h, e);
669 }
670
671 return e;
672}
673
674static void h_remove(struct smq_hash_table *ht, struct entry *e)
675{
676 unsigned h = hash_64(from_oblock(e->oblock), ht->hash_bits);
677 struct entry *prev;
678
679 /*
680 * The down side of using a singly linked list is we have to
681 * iterate the bucket to remove an item.
682 */
683 e = __h_lookup(ht, h, e->oblock, &prev);
684 if (e)
685 __h_unlink(ht, h, e, prev);
686}
687
688/*----------------------------------------------------------------*/
689
690struct entry_alloc {
691 struct entry_space *es;
692 unsigned begin;
693
694 unsigned nr_allocated;
695 struct ilist free;
696};
697
698static void init_allocator(struct entry_alloc *ea, struct entry_space *es,
699 unsigned begin, unsigned end)
700{
701 unsigned i;
702
703 ea->es = es;
704 ea->nr_allocated = 0u;
705 ea->begin = begin;
706
707 l_init(&ea->free);
708 for (i = begin; i != end; i++)
709 l_add_tail(ea->es, &ea->free, __get_entry(ea->es, i));
710}
711
712static void init_entry(struct entry *e)
713{
714 /*
715 * We can't memset because that would clear the hotspot and
716 * sentinel bits which remain constant.
717 */
718 e->hash_next = INDEXER_NULL;
719 e->next = INDEXER_NULL;
720 e->prev = INDEXER_NULL;
721 e->level = 0u;
722 e->dirty = true; /* FIXME: audit */
723 e->allocated = true;
724 e->sentinel = false;
725 e->pending_work = false;
726}
727
728static struct entry *alloc_entry(struct entry_alloc *ea)
729{
730 struct entry *e;
731
732 if (l_empty(&ea->free))
733 return NULL;
734
735 e = l_pop_head(ea->es, &ea->free);
736 init_entry(e);
737 ea->nr_allocated++;
738
739 return e;
740}
741
742/*
743 * This assumes the cblock hasn't already been allocated.
744 */
745static struct entry *alloc_particular_entry(struct entry_alloc *ea, unsigned i)
746{
747 struct entry *e = __get_entry(ea->es, ea->begin + i);
748
749 BUG_ON(e->allocated);
750
751 l_del(ea->es, &ea->free, e);
752 init_entry(e);
753 ea->nr_allocated++;
754
755 return e;
756}
757
758static void free_entry(struct entry_alloc *ea, struct entry *e)
759{
760 BUG_ON(!ea->nr_allocated);
761 BUG_ON(!e->allocated);
762
763 ea->nr_allocated--;
764 e->allocated = false;
765 l_add_tail(ea->es, &ea->free, e);
766}
767
768static bool allocator_empty(struct entry_alloc *ea)
769{
770 return l_empty(&ea->free);
771}
772
773static unsigned get_index(struct entry_alloc *ea, struct entry *e)
774{
775 return to_index(ea->es, e) - ea->begin;
776}
777
778static struct entry *get_entry(struct entry_alloc *ea, unsigned index)
779{
780 return __get_entry(ea->es, ea->begin + index);
781}
782
783/*----------------------------------------------------------------*/
784
785#define NR_HOTSPOT_LEVELS 64u
786#define NR_CACHE_LEVELS 64u
787
788#define WRITEBACK_PERIOD (10ul * HZ)
789#define DEMOTE_PERIOD (60ul * HZ)
790
791#define HOTSPOT_UPDATE_PERIOD (HZ)
792#define CACHE_UPDATE_PERIOD (60ul * HZ)
793
794struct smq_policy {
795 struct dm_cache_policy policy;
796
797 /* protects everything */
798 spinlock_t lock;
799 dm_cblock_t cache_size;
800 sector_t cache_block_size;
801
802 sector_t hotspot_block_size;
803 unsigned nr_hotspot_blocks;
804 unsigned cache_blocks_per_hotspot_block;
805 unsigned hotspot_level_jump;
806
807 struct entry_space es;
808 struct entry_alloc writeback_sentinel_alloc;
809 struct entry_alloc demote_sentinel_alloc;
810 struct entry_alloc hotspot_alloc;
811 struct entry_alloc cache_alloc;
812
813 unsigned long *hotspot_hit_bits;
814 unsigned long *cache_hit_bits;
815
816 /*
817 * We maintain three queues of entries. The cache proper,
818 * consisting of a clean and dirty queue, containing the currently
819 * active mappings. The hotspot queue uses a larger block size to
820 * track blocks that are being hit frequently and potential
821 * candidates for promotion to the cache.
822 */
823 struct queue hotspot;
824 struct queue clean;
825 struct queue dirty;
826
827 struct stats hotspot_stats;
828 struct stats cache_stats;
829
830 /*
831 * Keeps track of time, incremented by the core. We use this to
832 * avoid attributing multiple hits within the same tick.
833 */
834 unsigned tick;
835
836 /*
837 * The hash tables allows us to quickly find an entry by origin
838 * block.
839 */
840 struct smq_hash_table table;
841 struct smq_hash_table hotspot_table;
842
843 bool current_writeback_sentinels;
844 unsigned long next_writeback_period;
845
846 bool current_demote_sentinels;
847 unsigned long next_demote_period;
848
849 unsigned write_promote_level;
850 unsigned read_promote_level;
851
852 unsigned long next_hotspot_period;
853 unsigned long next_cache_period;
854
855 struct background_tracker *bg_work;
856
857 bool migrations_allowed;
858};
859
860/*----------------------------------------------------------------*/
861
862static struct entry *get_sentinel(struct entry_alloc *ea, unsigned level, bool which)
863{
864 return get_entry(ea, which ? level : NR_CACHE_LEVELS + level);
865}
866
867static struct entry *writeback_sentinel(struct smq_policy *mq, unsigned level)
868{
869 return get_sentinel(&mq->writeback_sentinel_alloc, level, mq->current_writeback_sentinels);
870}
871
872static struct entry *demote_sentinel(struct smq_policy *mq, unsigned level)
873{
874 return get_sentinel(&mq->demote_sentinel_alloc, level, mq->current_demote_sentinels);
875}
876
877static void __update_writeback_sentinels(struct smq_policy *mq)
878{
879 unsigned level;
880 struct queue *q = &mq->dirty;
881 struct entry *sentinel;
882
883 for (level = 0; level < q->nr_levels; level++) {
884 sentinel = writeback_sentinel(mq, level);
885 q_del(q, sentinel);
886 q_push(q, sentinel);
887 }
888}
889
890static void __update_demote_sentinels(struct smq_policy *mq)
891{
892 unsigned level;
893 struct queue *q = &mq->clean;
894 struct entry *sentinel;
895
896 for (level = 0; level < q->nr_levels; level++) {
897 sentinel = demote_sentinel(mq, level);
898 q_del(q, sentinel);
899 q_push(q, sentinel);
900 }
901}
902
903static void update_sentinels(struct smq_policy *mq)
904{
905 if (time_after(jiffies, mq->next_writeback_period)) {
906 mq->next_writeback_period = jiffies + WRITEBACK_PERIOD;
907 mq->current_writeback_sentinels = !mq->current_writeback_sentinels;
908 __update_writeback_sentinels(mq);
909 }
910
911 if (time_after(jiffies, mq->next_demote_period)) {
912 mq->next_demote_period = jiffies + DEMOTE_PERIOD;
913 mq->current_demote_sentinels = !mq->current_demote_sentinels;
914 __update_demote_sentinels(mq);
915 }
916}
917
918static void __sentinels_init(struct smq_policy *mq)
919{
920 unsigned level;
921 struct entry *sentinel;
922
923 for (level = 0; level < NR_CACHE_LEVELS; level++) {
924 sentinel = writeback_sentinel(mq, level);
925 sentinel->level = level;
926 q_push(&mq->dirty, sentinel);
927
928 sentinel = demote_sentinel(mq, level);
929 sentinel->level = level;
930 q_push(&mq->clean, sentinel);
931 }
932}
933
934static void sentinels_init(struct smq_policy *mq)
935{
936 mq->next_writeback_period = jiffies + WRITEBACK_PERIOD;
937 mq->next_demote_period = jiffies + DEMOTE_PERIOD;
938
939 mq->current_writeback_sentinels = false;
940 mq->current_demote_sentinels = false;
941 __sentinels_init(mq);
942
943 mq->current_writeback_sentinels = !mq->current_writeback_sentinels;
944 mq->current_demote_sentinels = !mq->current_demote_sentinels;
945 __sentinels_init(mq);
946}
947
948/*----------------------------------------------------------------*/
949
950static void del_queue(struct smq_policy *mq, struct entry *e)
951{
952 q_del(e->dirty ? &mq->dirty : &mq->clean, e);
953}
954
955static void push_queue(struct smq_policy *mq, struct entry *e)
956{
957 if (e->dirty)
958 q_push(&mq->dirty, e);
959 else
960 q_push(&mq->clean, e);
961}
962
963// !h, !q, a -> h, q, a
964static void push(struct smq_policy *mq, struct entry *e)
965{
966 h_insert(&mq->table, e);
967 if (!e->pending_work)
968 push_queue(mq, e);
969}
970
971static void push_queue_front(struct smq_policy *mq, struct entry *e)
972{
973 if (e->dirty)
974 q_push_front(&mq->dirty, e);
975 else
976 q_push_front(&mq->clean, e);
977}
978
979static void push_front(struct smq_policy *mq, struct entry *e)
980{
981 h_insert(&mq->table, e);
982 if (!e->pending_work)
983 push_queue_front(mq, e);
984}
985
986static dm_cblock_t infer_cblock(struct smq_policy *mq, struct entry *e)
987{
988 return to_cblock(get_index(&mq->cache_alloc, e));
989}
990
991static void requeue(struct smq_policy *mq, struct entry *e)
992{
993 /*
994 * Pending work has temporarily been taken out of the queues.
995 */
996 if (e->pending_work)
997 return;
998
999 if (!test_and_set_bit(from_cblock(infer_cblock(mq, e)), mq->cache_hit_bits)) {
1000 if (!e->dirty) {
1001 q_requeue(&mq->clean, e, 1u, NULL, NULL);
1002 return;
1003 }
1004
1005 q_requeue(&mq->dirty, e, 1u,
1006 get_sentinel(&mq->writeback_sentinel_alloc, e->level, !mq->current_writeback_sentinels),
1007 get_sentinel(&mq->writeback_sentinel_alloc, e->level, mq->current_writeback_sentinels));
1008 }
1009}
1010
1011static unsigned default_promote_level(struct smq_policy *mq)
1012{
1013 /*
1014 * The promote level depends on the current performance of the
1015 * cache.
1016 *
1017 * If the cache is performing badly, then we can't afford
1018 * to promote much without causing performance to drop below that
1019 * of the origin device.
1020 *
1021 * If the cache is performing well, then we don't need to promote
1022 * much. If it isn't broken, don't fix it.
1023 *
1024 * If the cache is middling then we promote more.
1025 *
1026 * This scheme reminds me of a graph of entropy vs probability of a
1027 * binary variable.
1028 */
1029 static unsigned table[] = {1, 1, 1, 2, 4, 6, 7, 8, 7, 6, 4, 4, 3, 3, 2, 2, 1};
1030
1031 unsigned hits = mq->cache_stats.hits;
1032 unsigned misses = mq->cache_stats.misses;
1033 unsigned index = safe_div(hits << 4u, hits + misses);
1034 return table[index];
1035}
1036
1037static void update_promote_levels(struct smq_policy *mq)
1038{
1039 /*
1040 * If there are unused cache entries then we want to be really
1041 * eager to promote.
1042 */
1043 unsigned threshold_level = allocator_empty(&mq->cache_alloc) ?
1044 default_promote_level(mq) : (NR_HOTSPOT_LEVELS / 2u);
1045
1046 threshold_level = max(threshold_level, NR_HOTSPOT_LEVELS);
1047
1048 /*
1049 * If the hotspot queue is performing badly then we have little
1050 * confidence that we know which blocks to promote. So we cut down
1051 * the amount of promotions.
1052 */
1053 switch (stats_assess(&mq->hotspot_stats)) {
1054 case Q_POOR:
1055 threshold_level /= 4u;
1056 break;
1057
1058 case Q_FAIR:
1059 threshold_level /= 2u;
1060 break;
1061
1062 case Q_WELL:
1063 break;
1064 }
1065
1066 mq->read_promote_level = NR_HOTSPOT_LEVELS - threshold_level;
1067 mq->write_promote_level = (NR_HOTSPOT_LEVELS - threshold_level);
1068}
1069
1070/*
1071 * If the hotspot queue is performing badly, then we try and move entries
1072 * around more quickly.
1073 */
1074static void update_level_jump(struct smq_policy *mq)
1075{
1076 switch (stats_assess(&mq->hotspot_stats)) {
1077 case Q_POOR:
1078 mq->hotspot_level_jump = 4u;
1079 break;
1080
1081 case Q_FAIR:
1082 mq->hotspot_level_jump = 2u;
1083 break;
1084
1085 case Q_WELL:
1086 mq->hotspot_level_jump = 1u;
1087 break;
1088 }
1089}
1090
1091static void end_hotspot_period(struct smq_policy *mq)
1092{
1093 clear_bitset(mq->hotspot_hit_bits, mq->nr_hotspot_blocks);
1094 update_promote_levels(mq);
1095
1096 if (time_after(jiffies, mq->next_hotspot_period)) {
1097 update_level_jump(mq);
1098 q_redistribute(&mq->hotspot);
1099 stats_reset(&mq->hotspot_stats);
1100 mq->next_hotspot_period = jiffies + HOTSPOT_UPDATE_PERIOD;
1101 }
1102}
1103
1104static void end_cache_period(struct smq_policy *mq)
1105{
1106 if (time_after(jiffies, mq->next_cache_period)) {
1107 clear_bitset(mq->cache_hit_bits, from_cblock(mq->cache_size));
1108
1109 q_redistribute(&mq->dirty);
1110 q_redistribute(&mq->clean);
1111 stats_reset(&mq->cache_stats);
1112
1113 mq->next_cache_period = jiffies + CACHE_UPDATE_PERIOD;
1114 }
1115}
1116
1117/*----------------------------------------------------------------*/
1118
1119/*
1120 * Targets are given as a percentage.
1121 */
1122#define CLEAN_TARGET 25u
1123#define FREE_TARGET 25u
1124
1125static unsigned percent_to_target(struct smq_policy *mq, unsigned p)
1126{
1127 return from_cblock(mq->cache_size) * p / 100u;
1128}
1129
1130static bool clean_target_met(struct smq_policy *mq, bool idle)
1131{
1132 /*
1133 * Cache entries may not be populated. So we cannot rely on the
1134 * size of the clean queue.
1135 */
1136 if (idle) {
1137 /*
1138 * We'd like to clean everything.
1139 */
1140 return q_size(&mq->dirty) == 0u;
1141 }
1142
1143 /*
1144 * If we're busy we don't worry about cleaning at all.
1145 */
1146 return true;
1147}
1148
1149static bool free_target_met(struct smq_policy *mq)
1150{
1151 unsigned nr_free;
1152
1153 nr_free = from_cblock(mq->cache_size) - mq->cache_alloc.nr_allocated;
1154 return (nr_free + btracker_nr_demotions_queued(mq->bg_work)) >=
1155 percent_to_target(mq, FREE_TARGET);
1156}
1157
1158/*----------------------------------------------------------------*/
1159
1160static void mark_pending(struct smq_policy *mq, struct entry *e)
1161{
1162 BUG_ON(e->sentinel);
1163 BUG_ON(!e->allocated);
1164 BUG_ON(e->pending_work);
1165 e->pending_work = true;
1166}
1167
1168static void clear_pending(struct smq_policy *mq, struct entry *e)
1169{
1170 BUG_ON(!e->pending_work);
1171 e->pending_work = false;
1172}
1173
1174static void queue_writeback(struct smq_policy *mq, bool idle)
1175{
1176 int r;
1177 struct policy_work work;
1178 struct entry *e;
1179
1180 e = q_peek(&mq->dirty, mq->dirty.nr_levels, idle);
1181 if (e) {
1182 mark_pending(mq, e);
1183 q_del(&mq->dirty, e);
1184
1185 work.op = POLICY_WRITEBACK;
1186 work.oblock = e->oblock;
1187 work.cblock = infer_cblock(mq, e);
1188
1189 r = btracker_queue(mq->bg_work, &work, NULL);
1190 if (r) {
1191 clear_pending(mq, e);
1192 q_push_front(&mq->dirty, e);
1193 }
1194 }
1195}
1196
1197static void queue_demotion(struct smq_policy *mq)
1198{
1199 int r;
1200 struct policy_work work;
1201 struct entry *e;
1202
1203 if (WARN_ON_ONCE(!mq->migrations_allowed))
1204 return;
1205
1206 e = q_peek(&mq->clean, mq->clean.nr_levels / 2, true);
1207 if (!e) {
1208 if (!clean_target_met(mq, true))
1209 queue_writeback(mq, false);
1210 return;
1211 }
1212
1213 mark_pending(mq, e);
1214 q_del(&mq->clean, e);
1215
1216 work.op = POLICY_DEMOTE;
1217 work.oblock = e->oblock;
1218 work.cblock = infer_cblock(mq, e);
1219 r = btracker_queue(mq->bg_work, &work, NULL);
1220 if (r) {
1221 clear_pending(mq, e);
1222 q_push_front(&mq->clean, e);
1223 }
1224}
1225
1226static void queue_promotion(struct smq_policy *mq, dm_oblock_t oblock,
1227 struct policy_work **workp)
1228{
1229 int r;
1230 struct entry *e;
1231 struct policy_work work;
1232
1233 if (!mq->migrations_allowed)
1234 return;
1235
1236 if (allocator_empty(&mq->cache_alloc)) {
1237 /*
1238 * We always claim to be 'idle' to ensure some demotions happen
1239 * with continuous loads.
1240 */
1241 if (!free_target_met(mq))
1242 queue_demotion(mq);
1243 return;
1244 }
1245
1246 if (btracker_promotion_already_present(mq->bg_work, oblock))
1247 return;
1248
1249 /*
1250 * We allocate the entry now to reserve the cblock. If the
1251 * background work is aborted we must remember to free it.
1252 */
1253 e = alloc_entry(&mq->cache_alloc);
1254 BUG_ON(!e);
1255 e->pending_work = true;
1256 work.op = POLICY_PROMOTE;
1257 work.oblock = oblock;
1258 work.cblock = infer_cblock(mq, e);
1259 r = btracker_queue(mq->bg_work, &work, workp);
1260 if (r)
1261 free_entry(&mq->cache_alloc, e);
1262}
1263
1264/*----------------------------------------------------------------*/
1265
1266enum promote_result {
1267 PROMOTE_NOT,
1268 PROMOTE_TEMPORARY,
1269 PROMOTE_PERMANENT
1270};
1271
1272/*
1273 * Converts a boolean into a promote result.
1274 */
1275static enum promote_result maybe_promote(bool promote)
1276{
1277 return promote ? PROMOTE_PERMANENT : PROMOTE_NOT;
1278}
1279
1280static enum promote_result should_promote(struct smq_policy *mq, struct entry *hs_e,
1281 int data_dir, bool fast_promote)
1282{
1283 if (data_dir == WRITE) {
1284 if (!allocator_empty(&mq->cache_alloc) && fast_promote)
1285 return PROMOTE_TEMPORARY;
1286
1287 return maybe_promote(hs_e->level >= mq->write_promote_level);
1288 } else
1289 return maybe_promote(hs_e->level >= mq->read_promote_level);
1290}
1291
1292static dm_oblock_t to_hblock(struct smq_policy *mq, dm_oblock_t b)
1293{
1294 sector_t r = from_oblock(b);
1295 (void) sector_div(r, mq->cache_blocks_per_hotspot_block);
1296 return to_oblock(r);
1297}
1298
1299static struct entry *update_hotspot_queue(struct smq_policy *mq, dm_oblock_t b)
1300{
1301 unsigned hi;
1302 dm_oblock_t hb = to_hblock(mq, b);
1303 struct entry *e = h_lookup(&mq->hotspot_table, hb);
1304
1305 if (e) {
1306 stats_level_accessed(&mq->hotspot_stats, e->level);
1307
1308 hi = get_index(&mq->hotspot_alloc, e);
1309 q_requeue(&mq->hotspot, e,
1310 test_and_set_bit(hi, mq->hotspot_hit_bits) ?
1311 0u : mq->hotspot_level_jump,
1312 NULL, NULL);
1313
1314 } else {
1315 stats_miss(&mq->hotspot_stats);
1316
1317 e = alloc_entry(&mq->hotspot_alloc);
1318 if (!e) {
1319 e = q_pop(&mq->hotspot);
1320 if (e) {
1321 h_remove(&mq->hotspot_table, e);
1322 hi = get_index(&mq->hotspot_alloc, e);
1323 clear_bit(hi, mq->hotspot_hit_bits);
1324 }
1325
1326 }
1327
1328 if (e) {
1329 e->oblock = hb;
1330 q_push(&mq->hotspot, e);
1331 h_insert(&mq->hotspot_table, e);
1332 }
1333 }
1334
1335 return e;
1336}
1337
1338/*----------------------------------------------------------------*/
1339
1340/*
1341 * Public interface, via the policy struct. See dm-cache-policy.h for a
1342 * description of these.
1343 */
1344
1345static struct smq_policy *to_smq_policy(struct dm_cache_policy *p)
1346{
1347 return container_of(p, struct smq_policy, policy);
1348}
1349
1350static void smq_destroy(struct dm_cache_policy *p)
1351{
1352 struct smq_policy *mq = to_smq_policy(p);
1353
1354 btracker_destroy(mq->bg_work);
1355 h_exit(&mq->hotspot_table);
1356 h_exit(&mq->table);
1357 free_bitset(mq->hotspot_hit_bits);
1358 free_bitset(mq->cache_hit_bits);
1359 space_exit(&mq->es);
1360 kfree(mq);
1361}
1362
1363/*----------------------------------------------------------------*/
1364
1365static int __lookup(struct smq_policy *mq, dm_oblock_t oblock, dm_cblock_t *cblock,
1366 int data_dir, bool fast_copy,
1367 struct policy_work **work, bool *background_work)
1368{
1369 struct entry *e, *hs_e;
1370 enum promote_result pr;
1371
1372 *background_work = false;
1373
1374 e = h_lookup(&mq->table, oblock);
1375 if (e) {
1376 stats_level_accessed(&mq->cache_stats, e->level);
1377
1378 requeue(mq, e);
1379 *cblock = infer_cblock(mq, e);
1380 return 0;
1381
1382 } else {
1383 stats_miss(&mq->cache_stats);
1384
1385 /*
1386 * The hotspot queue only gets updated with misses.
1387 */
1388 hs_e = update_hotspot_queue(mq, oblock);
1389
1390 pr = should_promote(mq, hs_e, data_dir, fast_copy);
1391 if (pr != PROMOTE_NOT) {
1392 queue_promotion(mq, oblock, work);
1393 *background_work = true;
1394 }
1395
1396 return -ENOENT;
1397 }
1398}
1399
1400static int smq_lookup(struct dm_cache_policy *p, dm_oblock_t oblock, dm_cblock_t *cblock,
1401 int data_dir, bool fast_copy,
1402 bool *background_work)
1403{
1404 int r;
1405 unsigned long flags;
1406 struct smq_policy *mq = to_smq_policy(p);
1407
1408 spin_lock_irqsave(&mq->lock, flags);
1409 r = __lookup(mq, oblock, cblock,
1410 data_dir, fast_copy,
1411 NULL, background_work);
1412 spin_unlock_irqrestore(&mq->lock, flags);
1413
1414 return r;
1415}
1416
1417static int smq_lookup_with_work(struct dm_cache_policy *p,
1418 dm_oblock_t oblock, dm_cblock_t *cblock,
1419 int data_dir, bool fast_copy,
1420 struct policy_work **work)
1421{
1422 int r;
1423 bool background_queued;
1424 unsigned long flags;
1425 struct smq_policy *mq = to_smq_policy(p);
1426
1427 spin_lock_irqsave(&mq->lock, flags);
1428 r = __lookup(mq, oblock, cblock, data_dir, fast_copy, work, &background_queued);
1429 spin_unlock_irqrestore(&mq->lock, flags);
1430
1431 return r;
1432}
1433
1434static int smq_get_background_work(struct dm_cache_policy *p, bool idle,
1435 struct policy_work **result)
1436{
1437 int r;
1438 unsigned long flags;
1439 struct smq_policy *mq = to_smq_policy(p);
1440
1441 spin_lock_irqsave(&mq->lock, flags);
1442 r = btracker_issue(mq->bg_work, result);
1443 if (r == -ENODATA) {
1444 if (!clean_target_met(mq, idle)) {
1445 queue_writeback(mq, idle);
1446 r = btracker_issue(mq->bg_work, result);
1447 }
1448 }
1449 spin_unlock_irqrestore(&mq->lock, flags);
1450
1451 return r;
1452}
1453
1454/*
1455 * We need to clear any pending work flags that have been set, and in the
1456 * case of promotion free the entry for the destination cblock.
1457 */
1458static void __complete_background_work(struct smq_policy *mq,
1459 struct policy_work *work,
1460 bool success)
1461{
1462 struct entry *e = get_entry(&mq->cache_alloc,
1463 from_cblock(work->cblock));
1464
1465 switch (work->op) {
1466 case POLICY_PROMOTE:
1467 // !h, !q, a
1468 clear_pending(mq, e);
1469 if (success) {
1470 e->oblock = work->oblock;
1471 e->level = NR_CACHE_LEVELS - 1;
1472 push(mq, e);
1473 // h, q, a
1474 } else {
1475 free_entry(&mq->cache_alloc, e);
1476 // !h, !q, !a
1477 }
1478 break;
1479
1480 case POLICY_DEMOTE:
1481 // h, !q, a
1482 if (success) {
1483 h_remove(&mq->table, e);
1484 free_entry(&mq->cache_alloc, e);
1485 // !h, !q, !a
1486 } else {
1487 clear_pending(mq, e);
1488 push_queue(mq, e);
1489 // h, q, a
1490 }
1491 break;
1492
1493 case POLICY_WRITEBACK:
1494 // h, !q, a
1495 clear_pending(mq, e);
1496 push_queue(mq, e);
1497 // h, q, a
1498 break;
1499 }
1500
1501 btracker_complete(mq->bg_work, work);
1502}
1503
1504static void smq_complete_background_work(struct dm_cache_policy *p,
1505 struct policy_work *work,
1506 bool success)
1507{
1508 unsigned long flags;
1509 struct smq_policy *mq = to_smq_policy(p);
1510
1511 spin_lock_irqsave(&mq->lock, flags);
1512 __complete_background_work(mq, work, success);
1513 spin_unlock_irqrestore(&mq->lock, flags);
1514}
1515
1516// in_hash(oblock) -> in_hash(oblock)
1517static void __smq_set_clear_dirty(struct smq_policy *mq, dm_cblock_t cblock, bool set)
1518{
1519 struct entry *e = get_entry(&mq->cache_alloc, from_cblock(cblock));
1520
1521 if (e->pending_work)
1522 e->dirty = set;
1523 else {
1524 del_queue(mq, e);
1525 e->dirty = set;
1526 push_queue(mq, e);
1527 }
1528}
1529
1530static void smq_set_dirty(struct dm_cache_policy *p, dm_cblock_t cblock)
1531{
1532 unsigned long flags;
1533 struct smq_policy *mq = to_smq_policy(p);
1534
1535 spin_lock_irqsave(&mq->lock, flags);
1536 __smq_set_clear_dirty(mq, cblock, true);
1537 spin_unlock_irqrestore(&mq->lock, flags);
1538}
1539
1540static void smq_clear_dirty(struct dm_cache_policy *p, dm_cblock_t cblock)
1541{
1542 struct smq_policy *mq = to_smq_policy(p);
1543 unsigned long flags;
1544
1545 spin_lock_irqsave(&mq->lock, flags);
1546 __smq_set_clear_dirty(mq, cblock, false);
1547 spin_unlock_irqrestore(&mq->lock, flags);
1548}
1549
1550static unsigned random_level(dm_cblock_t cblock)
1551{
1552 return hash_32(from_cblock(cblock), 9) & (NR_CACHE_LEVELS - 1);
1553}
1554
1555static int smq_load_mapping(struct dm_cache_policy *p,
1556 dm_oblock_t oblock, dm_cblock_t cblock,
1557 bool dirty, uint32_t hint, bool hint_valid)
1558{
1559 struct smq_policy *mq = to_smq_policy(p);
1560 struct entry *e;
1561
1562 e = alloc_particular_entry(&mq->cache_alloc, from_cblock(cblock));
1563 e->oblock = oblock;
1564 e->dirty = dirty;
1565 e->level = hint_valid ? min(hint, NR_CACHE_LEVELS - 1) : random_level(cblock);
1566 e->pending_work = false;
1567
1568 /*
1569 * When we load mappings we push ahead of both sentinels in order to
1570 * allow demotions and cleaning to occur immediately.
1571 */
1572 push_front(mq, e);
1573
1574 return 0;
1575}
1576
1577static int smq_invalidate_mapping(struct dm_cache_policy *p, dm_cblock_t cblock)
1578{
1579 struct smq_policy *mq = to_smq_policy(p);
1580 struct entry *e = get_entry(&mq->cache_alloc, from_cblock(cblock));
1581
1582 if (!e->allocated)
1583 return -ENODATA;
1584
1585 // FIXME: what if this block has pending background work?
1586 del_queue(mq, e);
1587 h_remove(&mq->table, e);
1588 free_entry(&mq->cache_alloc, e);
1589 return 0;
1590}
1591
1592static uint32_t smq_get_hint(struct dm_cache_policy *p, dm_cblock_t cblock)
1593{
1594 struct smq_policy *mq = to_smq_policy(p);
1595 struct entry *e = get_entry(&mq->cache_alloc, from_cblock(cblock));
1596
1597 if (!e->allocated)
1598 return 0;
1599
1600 return e->level;
1601}
1602
1603static dm_cblock_t smq_residency(struct dm_cache_policy *p)
1604{
1605 dm_cblock_t r;
1606 unsigned long flags;
1607 struct smq_policy *mq = to_smq_policy(p);
1608
1609 spin_lock_irqsave(&mq->lock, flags);
1610 r = to_cblock(mq->cache_alloc.nr_allocated);
1611 spin_unlock_irqrestore(&mq->lock, flags);
1612
1613 return r;
1614}
1615
1616static void smq_tick(struct dm_cache_policy *p, bool can_block)
1617{
1618 struct smq_policy *mq = to_smq_policy(p);
1619 unsigned long flags;
1620
1621 spin_lock_irqsave(&mq->lock, flags);
1622 mq->tick++;
1623 update_sentinels(mq);
1624 end_hotspot_period(mq);
1625 end_cache_period(mq);
1626 spin_unlock_irqrestore(&mq->lock, flags);
1627}
1628
1629static void smq_allow_migrations(struct dm_cache_policy *p, bool allow)
1630{
1631 struct smq_policy *mq = to_smq_policy(p);
1632 mq->migrations_allowed = allow;
1633}
1634
1635/*
1636 * smq has no config values, but the old mq policy did. To avoid breaking
1637 * software we continue to accept these configurables for the mq policy,
1638 * but they have no effect.
1639 */
1640static int mq_set_config_value(struct dm_cache_policy *p,
1641 const char *key, const char *value)
1642{
1643 unsigned long tmp;
1644
1645 if (kstrtoul(value, 10, &tmp))
1646 return -EINVAL;
1647
1648 if (!strcasecmp(key, "random_threshold") ||
1649 !strcasecmp(key, "sequential_threshold") ||
1650 !strcasecmp(key, "discard_promote_adjustment") ||
1651 !strcasecmp(key, "read_promote_adjustment") ||
1652 !strcasecmp(key, "write_promote_adjustment")) {
1653 DMWARN("tunable '%s' no longer has any effect, mq policy is now an alias for smq", key);
1654 return 0;
1655 }
1656
1657 return -EINVAL;
1658}
1659
1660static int mq_emit_config_values(struct dm_cache_policy *p, char *result,
1661 unsigned maxlen, ssize_t *sz_ptr)
1662{
1663 ssize_t sz = *sz_ptr;
1664
1665 DMEMIT("10 random_threshold 0 "
1666 "sequential_threshold 0 "
1667 "discard_promote_adjustment 0 "
1668 "read_promote_adjustment 0 "
1669 "write_promote_adjustment 0 ");
1670
1671 *sz_ptr = sz;
1672 return 0;
1673}
1674
1675/* Init the policy plugin interface function pointers. */
1676static void init_policy_functions(struct smq_policy *mq, bool mimic_mq)
1677{
1678 mq->policy.destroy = smq_destroy;
1679 mq->policy.lookup = smq_lookup;
1680 mq->policy.lookup_with_work = smq_lookup_with_work;
1681 mq->policy.get_background_work = smq_get_background_work;
1682 mq->policy.complete_background_work = smq_complete_background_work;
1683 mq->policy.set_dirty = smq_set_dirty;
1684 mq->policy.clear_dirty = smq_clear_dirty;
1685 mq->policy.load_mapping = smq_load_mapping;
1686 mq->policy.invalidate_mapping = smq_invalidate_mapping;
1687 mq->policy.get_hint = smq_get_hint;
1688 mq->policy.residency = smq_residency;
1689 mq->policy.tick = smq_tick;
1690 mq->policy.allow_migrations = smq_allow_migrations;
1691
1692 if (mimic_mq) {
1693 mq->policy.set_config_value = mq_set_config_value;
1694 mq->policy.emit_config_values = mq_emit_config_values;
1695 }
1696}
1697
1698static bool too_many_hotspot_blocks(sector_t origin_size,
1699 sector_t hotspot_block_size,
1700 unsigned nr_hotspot_blocks)
1701{
1702 return (hotspot_block_size * nr_hotspot_blocks) > origin_size;
1703}
1704
1705static void calc_hotspot_params(sector_t origin_size,
1706 sector_t cache_block_size,
1707 unsigned nr_cache_blocks,
1708 sector_t *hotspot_block_size,
1709 unsigned *nr_hotspot_blocks)
1710{
1711 *hotspot_block_size = cache_block_size * 16u;
1712 *nr_hotspot_blocks = max(nr_cache_blocks / 4u, 1024u);
1713
1714 while ((*hotspot_block_size > cache_block_size) &&
1715 too_many_hotspot_blocks(origin_size, *hotspot_block_size, *nr_hotspot_blocks))
1716 *hotspot_block_size /= 2u;
1717}
1718
1719static struct dm_cache_policy *__smq_create(dm_cblock_t cache_size,
1720 sector_t origin_size,
1721 sector_t cache_block_size,
1722 bool mimic_mq,
1723 bool migrations_allowed)
1724{
1725 unsigned i;
1726 unsigned nr_sentinels_per_queue = 2u * NR_CACHE_LEVELS;
1727 unsigned total_sentinels = 2u * nr_sentinels_per_queue;
1728 struct smq_policy *mq = kzalloc(sizeof(*mq), GFP_KERNEL);
1729
1730 if (!mq)
1731 return NULL;
1732
1733 init_policy_functions(mq, mimic_mq);
1734 mq->cache_size = cache_size;
1735 mq->cache_block_size = cache_block_size;
1736
1737 calc_hotspot_params(origin_size, cache_block_size, from_cblock(cache_size),
1738 &mq->hotspot_block_size, &mq->nr_hotspot_blocks);
1739
1740 mq->cache_blocks_per_hotspot_block = div64_u64(mq->hotspot_block_size, mq->cache_block_size);
1741 mq->hotspot_level_jump = 1u;
1742 if (space_init(&mq->es, total_sentinels + mq->nr_hotspot_blocks + from_cblock(cache_size))) {
1743 DMERR("couldn't initialize entry space");
1744 goto bad_pool_init;
1745 }
1746
1747 init_allocator(&mq->writeback_sentinel_alloc, &mq->es, 0, nr_sentinels_per_queue);
1748 for (i = 0; i < nr_sentinels_per_queue; i++)
1749 get_entry(&mq->writeback_sentinel_alloc, i)->sentinel = true;
1750
1751 init_allocator(&mq->demote_sentinel_alloc, &mq->es, nr_sentinels_per_queue, total_sentinels);
1752 for (i = 0; i < nr_sentinels_per_queue; i++)
1753 get_entry(&mq->demote_sentinel_alloc, i)->sentinel = true;
1754
1755 init_allocator(&mq->hotspot_alloc, &mq->es, total_sentinels,
1756 total_sentinels + mq->nr_hotspot_blocks);
1757
1758 init_allocator(&mq->cache_alloc, &mq->es,
1759 total_sentinels + mq->nr_hotspot_blocks,
1760 total_sentinels + mq->nr_hotspot_blocks + from_cblock(cache_size));
1761
1762 mq->hotspot_hit_bits = alloc_bitset(mq->nr_hotspot_blocks);
1763 if (!mq->hotspot_hit_bits) {
1764 DMERR("couldn't allocate hotspot hit bitset");
1765 goto bad_hotspot_hit_bits;
1766 }
1767 clear_bitset(mq->hotspot_hit_bits, mq->nr_hotspot_blocks);
1768
1769 if (from_cblock(cache_size)) {
1770 mq->cache_hit_bits = alloc_bitset(from_cblock(cache_size));
1771 if (!mq->cache_hit_bits) {
1772 DMERR("couldn't allocate cache hit bitset");
1773 goto bad_cache_hit_bits;
1774 }
1775 clear_bitset(mq->cache_hit_bits, from_cblock(mq->cache_size));
1776 } else
1777 mq->cache_hit_bits = NULL;
1778
1779 mq->tick = 0;
1780 spin_lock_init(&mq->lock);
1781
1782 q_init(&mq->hotspot, &mq->es, NR_HOTSPOT_LEVELS);
1783 mq->hotspot.nr_top_levels = 8;
1784 mq->hotspot.nr_in_top_levels = min(mq->nr_hotspot_blocks / NR_HOTSPOT_LEVELS,
1785 from_cblock(mq->cache_size) / mq->cache_blocks_per_hotspot_block);
1786
1787 q_init(&mq->clean, &mq->es, NR_CACHE_LEVELS);
1788 q_init(&mq->dirty, &mq->es, NR_CACHE_LEVELS);
1789
1790 stats_init(&mq->hotspot_stats, NR_HOTSPOT_LEVELS);
1791 stats_init(&mq->cache_stats, NR_CACHE_LEVELS);
1792
1793 if (h_init(&mq->table, &mq->es, from_cblock(cache_size)))
1794 goto bad_alloc_table;
1795
1796 if (h_init(&mq->hotspot_table, &mq->es, mq->nr_hotspot_blocks))
1797 goto bad_alloc_hotspot_table;
1798
1799 sentinels_init(mq);
1800 mq->write_promote_level = mq->read_promote_level = NR_HOTSPOT_LEVELS;
1801
1802 mq->next_hotspot_period = jiffies;
1803 mq->next_cache_period = jiffies;
1804
1805 mq->bg_work = btracker_create(4096); /* FIXME: hard coded value */
1806 if (!mq->bg_work)
1807 goto bad_btracker;
1808
1809 mq->migrations_allowed = migrations_allowed;
1810
1811 return &mq->policy;
1812
1813bad_btracker:
1814 h_exit(&mq->hotspot_table);
1815bad_alloc_hotspot_table:
1816 h_exit(&mq->table);
1817bad_alloc_table:
1818 free_bitset(mq->cache_hit_bits);
1819bad_cache_hit_bits:
1820 free_bitset(mq->hotspot_hit_bits);
1821bad_hotspot_hit_bits:
1822 space_exit(&mq->es);
1823bad_pool_init:
1824 kfree(mq);
1825
1826 return NULL;
1827}
1828
1829static struct dm_cache_policy *smq_create(dm_cblock_t cache_size,
1830 sector_t origin_size,
1831 sector_t cache_block_size)
1832{
1833 return __smq_create(cache_size, origin_size, cache_block_size, false, true);
1834}
1835
1836static struct dm_cache_policy *mq_create(dm_cblock_t cache_size,
1837 sector_t origin_size,
1838 sector_t cache_block_size)
1839{
1840 return __smq_create(cache_size, origin_size, cache_block_size, true, true);
1841}
1842
1843static struct dm_cache_policy *cleaner_create(dm_cblock_t cache_size,
1844 sector_t origin_size,
1845 sector_t cache_block_size)
1846{
1847 return __smq_create(cache_size, origin_size, cache_block_size, false, false);
1848}
1849
1850/*----------------------------------------------------------------*/
1851
1852static struct dm_cache_policy_type smq_policy_type = {
1853 .name = "smq",
1854 .version = {2, 0, 0},
1855 .hint_size = 4,
1856 .owner = THIS_MODULE,
1857 .create = smq_create
1858};
1859
1860static struct dm_cache_policy_type mq_policy_type = {
1861 .name = "mq",
1862 .version = {2, 0, 0},
1863 .hint_size = 4,
1864 .owner = THIS_MODULE,
1865 .create = mq_create,
1866};
1867
1868static struct dm_cache_policy_type cleaner_policy_type = {
1869 .name = "cleaner",
1870 .version = {2, 0, 0},
1871 .hint_size = 4,
1872 .owner = THIS_MODULE,
1873 .create = cleaner_create,
1874};
1875
1876static struct dm_cache_policy_type default_policy_type = {
1877 .name = "default",
1878 .version = {2, 0, 0},
1879 .hint_size = 4,
1880 .owner = THIS_MODULE,
1881 .create = smq_create,
1882 .real = &smq_policy_type
1883};
1884
1885static int __init smq_init(void)
1886{
1887 int r;
1888
1889 r = dm_cache_policy_register(&smq_policy_type);
1890 if (r) {
1891 DMERR("register failed %d", r);
1892 return -ENOMEM;
1893 }
1894
1895 r = dm_cache_policy_register(&mq_policy_type);
1896 if (r) {
1897 DMERR("register failed (as mq) %d", r);
1898 goto out_mq;
1899 }
1900
1901 r = dm_cache_policy_register(&cleaner_policy_type);
1902 if (r) {
1903 DMERR("register failed (as cleaner) %d", r);
1904 goto out_cleaner;
1905 }
1906
1907 r = dm_cache_policy_register(&default_policy_type);
1908 if (r) {
1909 DMERR("register failed (as default) %d", r);
1910 goto out_default;
1911 }
1912
1913 return 0;
1914
1915out_default:
1916 dm_cache_policy_unregister(&cleaner_policy_type);
1917out_cleaner:
1918 dm_cache_policy_unregister(&mq_policy_type);
1919out_mq:
1920 dm_cache_policy_unregister(&smq_policy_type);
1921
1922 return -ENOMEM;
1923}
1924
1925static void __exit smq_exit(void)
1926{
1927 dm_cache_policy_unregister(&cleaner_policy_type);
1928 dm_cache_policy_unregister(&smq_policy_type);
1929 dm_cache_policy_unregister(&mq_policy_type);
1930 dm_cache_policy_unregister(&default_policy_type);
1931}
1932
1933module_init(smq_init);
1934module_exit(smq_exit);
1935
1936MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
1937MODULE_LICENSE("GPL");
1938MODULE_DESCRIPTION("smq cache policy");
1939
1940MODULE_ALIAS("dm-cache-default");
1941MODULE_ALIAS("dm-cache-mq");
1942MODULE_ALIAS("dm-cache-cleaner");
1943