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![Yi Zhang](/assets/img/avatar_default.png)
When creating dm-cache with the default policy, it will call
request_module("dm-cache-default") to register the default policy.
But the "dm-cache-default" alias was left referring to the MQ policy.
Fix this by moving the module alias to SMQ.
Fixes: bccab6a0
(dm cache: switch the "default" cache replacement policy from mq to smq)
Signed-off-by: Yi Zhang <yizhan@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
1473 lines
33 KiB
C
1473 lines
33 KiB
C
/*
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* Copyright (C) 2012 Red Hat. All rights reserved.
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*
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* This file is released under the GPL.
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*/
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#include "dm-cache-policy.h"
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#include "dm.h"
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#include <linux/hash.h>
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#include <linux/jiffies.h>
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#include <linux/module.h>
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#include <linux/mutex.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#define DM_MSG_PREFIX "cache-policy-mq"
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static struct kmem_cache *mq_entry_cache;
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/*----------------------------------------------------------------*/
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static unsigned next_power(unsigned n, unsigned min)
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{
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return roundup_pow_of_two(max(n, min));
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}
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/*----------------------------------------------------------------*/
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/*
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* Large, sequential ios are probably better left on the origin device since
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* spindles tend to have good bandwidth.
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*
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* The io_tracker tries to spot when the io is in one of these sequential
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* modes.
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*
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* Two thresholds to switch between random and sequential io mode are defaulting
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* as follows and can be adjusted via the constructor and message interfaces.
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*/
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#define RANDOM_THRESHOLD_DEFAULT 4
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#define SEQUENTIAL_THRESHOLD_DEFAULT 512
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enum io_pattern {
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PATTERN_SEQUENTIAL,
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PATTERN_RANDOM
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};
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struct io_tracker {
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enum io_pattern pattern;
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unsigned nr_seq_samples;
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unsigned nr_rand_samples;
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unsigned thresholds[2];
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dm_oblock_t last_end_oblock;
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};
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static void iot_init(struct io_tracker *t,
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int sequential_threshold, int random_threshold)
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{
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t->pattern = PATTERN_RANDOM;
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t->nr_seq_samples = 0;
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t->nr_rand_samples = 0;
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t->last_end_oblock = 0;
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t->thresholds[PATTERN_RANDOM] = random_threshold;
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t->thresholds[PATTERN_SEQUENTIAL] = sequential_threshold;
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}
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static enum io_pattern iot_pattern(struct io_tracker *t)
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{
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return t->pattern;
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}
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static void iot_update_stats(struct io_tracker *t, struct bio *bio)
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{
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if (bio->bi_iter.bi_sector == from_oblock(t->last_end_oblock) + 1)
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t->nr_seq_samples++;
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else {
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/*
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* Just one non-sequential IO is enough to reset the
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* counters.
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*/
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if (t->nr_seq_samples) {
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t->nr_seq_samples = 0;
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t->nr_rand_samples = 0;
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}
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t->nr_rand_samples++;
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}
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t->last_end_oblock = to_oblock(bio_end_sector(bio) - 1);
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}
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static void iot_check_for_pattern_switch(struct io_tracker *t)
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{
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switch (t->pattern) {
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case PATTERN_SEQUENTIAL:
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if (t->nr_rand_samples >= t->thresholds[PATTERN_RANDOM]) {
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t->pattern = PATTERN_RANDOM;
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t->nr_seq_samples = t->nr_rand_samples = 0;
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}
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break;
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case PATTERN_RANDOM:
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if (t->nr_seq_samples >= t->thresholds[PATTERN_SEQUENTIAL]) {
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t->pattern = PATTERN_SEQUENTIAL;
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t->nr_seq_samples = t->nr_rand_samples = 0;
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}
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break;
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}
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}
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static void iot_examine_bio(struct io_tracker *t, struct bio *bio)
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{
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iot_update_stats(t, bio);
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iot_check_for_pattern_switch(t);
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}
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/*----------------------------------------------------------------*/
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/*
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* This queue is divided up into different levels. Allowing us to push
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* entries to the back of any of the levels. Think of it as a partially
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* sorted queue.
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*/
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#define NR_QUEUE_LEVELS 16u
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#define NR_SENTINELS NR_QUEUE_LEVELS * 3
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#define WRITEBACK_PERIOD HZ
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struct queue {
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unsigned nr_elts;
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bool current_writeback_sentinels;
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unsigned long next_writeback;
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struct list_head qs[NR_QUEUE_LEVELS];
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struct list_head sentinels[NR_SENTINELS];
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};
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static void queue_init(struct queue *q)
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{
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unsigned i;
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q->nr_elts = 0;
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q->current_writeback_sentinels = false;
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q->next_writeback = 0;
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for (i = 0; i < NR_QUEUE_LEVELS; i++) {
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INIT_LIST_HEAD(q->qs + i);
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INIT_LIST_HEAD(q->sentinels + i);
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INIT_LIST_HEAD(q->sentinels + NR_QUEUE_LEVELS + i);
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INIT_LIST_HEAD(q->sentinels + (2 * NR_QUEUE_LEVELS) + i);
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}
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}
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static unsigned queue_size(struct queue *q)
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{
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return q->nr_elts;
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}
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static bool queue_empty(struct queue *q)
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{
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return q->nr_elts == 0;
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}
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/*
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* Insert an entry to the back of the given level.
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*/
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static void queue_push(struct queue *q, unsigned level, struct list_head *elt)
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{
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q->nr_elts++;
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list_add_tail(elt, q->qs + level);
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}
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static void queue_remove(struct queue *q, struct list_head *elt)
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{
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q->nr_elts--;
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list_del(elt);
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}
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static bool is_sentinel(struct queue *q, struct list_head *h)
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{
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return (h >= q->sentinels) && (h < (q->sentinels + NR_SENTINELS));
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}
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/*
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* Gives us the oldest entry of the lowest popoulated level. If the first
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* level is emptied then we shift down one level.
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*/
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static struct list_head *queue_peek(struct queue *q)
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{
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unsigned level;
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struct list_head *h;
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for (level = 0; level < NR_QUEUE_LEVELS; level++)
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list_for_each(h, q->qs + level)
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if (!is_sentinel(q, h))
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return h;
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return NULL;
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}
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static struct list_head *queue_pop(struct queue *q)
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{
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struct list_head *r = queue_peek(q);
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if (r) {
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q->nr_elts--;
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list_del(r);
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}
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return r;
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}
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/*
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* Pops an entry from a level that is not past a sentinel.
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*/
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static struct list_head *queue_pop_old(struct queue *q)
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{
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unsigned level;
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struct list_head *h;
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for (level = 0; level < NR_QUEUE_LEVELS; level++)
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list_for_each(h, q->qs + level) {
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if (is_sentinel(q, h))
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break;
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q->nr_elts--;
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list_del(h);
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return h;
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}
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return NULL;
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}
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static struct list_head *list_pop(struct list_head *lh)
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{
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struct list_head *r = lh->next;
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BUG_ON(!r);
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list_del_init(r);
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return r;
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}
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static struct list_head *writeback_sentinel(struct queue *q, unsigned level)
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{
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if (q->current_writeback_sentinels)
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return q->sentinels + NR_QUEUE_LEVELS + level;
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else
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return q->sentinels + 2 * NR_QUEUE_LEVELS + level;
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}
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static void queue_update_writeback_sentinels(struct queue *q)
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{
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unsigned i;
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struct list_head *h;
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if (time_after(jiffies, q->next_writeback)) {
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for (i = 0; i < NR_QUEUE_LEVELS; i++) {
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h = writeback_sentinel(q, i);
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list_del(h);
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list_add_tail(h, q->qs + i);
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}
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q->next_writeback = jiffies + WRITEBACK_PERIOD;
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q->current_writeback_sentinels = !q->current_writeback_sentinels;
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}
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}
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/*
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* Sometimes we want to iterate through entries that have been pushed since
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* a certain event. We use sentinel entries on the queues to delimit these
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* 'tick' events.
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*/
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static void queue_tick(struct queue *q)
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{
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unsigned i;
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for (i = 0; i < NR_QUEUE_LEVELS; i++) {
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list_del(q->sentinels + i);
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list_add_tail(q->sentinels + i, q->qs + i);
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}
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}
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typedef void (*iter_fn)(struct list_head *, void *);
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static void queue_iterate_tick(struct queue *q, iter_fn fn, void *context)
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{
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unsigned i;
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struct list_head *h;
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for (i = 0; i < NR_QUEUE_LEVELS; i++) {
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list_for_each_prev(h, q->qs + i) {
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if (is_sentinel(q, h))
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break;
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fn(h, context);
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}
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}
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}
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/*----------------------------------------------------------------*/
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/*
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* Describes a cache entry. Used in both the cache and the pre_cache.
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*/
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struct entry {
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struct hlist_node hlist;
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struct list_head list;
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dm_oblock_t oblock;
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/*
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* FIXME: pack these better
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*/
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bool dirty:1;
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unsigned hit_count;
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};
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/*
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* Rather than storing the cblock in an entry, we allocate all entries in
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* an array, and infer the cblock from the entry position.
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*
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* Free entries are linked together into a list.
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*/
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struct entry_pool {
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struct entry *entries, *entries_end;
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struct list_head free;
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unsigned nr_allocated;
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};
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static int epool_init(struct entry_pool *ep, unsigned nr_entries)
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{
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unsigned i;
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ep->entries = vzalloc(sizeof(struct entry) * nr_entries);
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if (!ep->entries)
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return -ENOMEM;
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ep->entries_end = ep->entries + nr_entries;
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INIT_LIST_HEAD(&ep->free);
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for (i = 0; i < nr_entries; i++)
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list_add(&ep->entries[i].list, &ep->free);
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ep->nr_allocated = 0;
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return 0;
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}
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static void epool_exit(struct entry_pool *ep)
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{
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vfree(ep->entries);
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}
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static struct entry *alloc_entry(struct entry_pool *ep)
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{
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struct entry *e;
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if (list_empty(&ep->free))
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return NULL;
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e = list_entry(list_pop(&ep->free), struct entry, list);
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INIT_LIST_HEAD(&e->list);
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INIT_HLIST_NODE(&e->hlist);
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ep->nr_allocated++;
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return e;
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}
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/*
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* This assumes the cblock hasn't already been allocated.
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*/
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static struct entry *alloc_particular_entry(struct entry_pool *ep, dm_cblock_t cblock)
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{
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struct entry *e = ep->entries + from_cblock(cblock);
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list_del_init(&e->list);
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INIT_HLIST_NODE(&e->hlist);
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ep->nr_allocated++;
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return e;
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}
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static void free_entry(struct entry_pool *ep, struct entry *e)
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{
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BUG_ON(!ep->nr_allocated);
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ep->nr_allocated--;
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INIT_HLIST_NODE(&e->hlist);
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list_add(&e->list, &ep->free);
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}
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/*
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* Returns NULL if the entry is free.
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*/
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static struct entry *epool_find(struct entry_pool *ep, dm_cblock_t cblock)
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{
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struct entry *e = ep->entries + from_cblock(cblock);
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return !hlist_unhashed(&e->hlist) ? e : NULL;
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}
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static bool epool_empty(struct entry_pool *ep)
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{
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return list_empty(&ep->free);
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}
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static bool in_pool(struct entry_pool *ep, struct entry *e)
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{
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return e >= ep->entries && e < ep->entries_end;
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}
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static dm_cblock_t infer_cblock(struct entry_pool *ep, struct entry *e)
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{
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return to_cblock(e - ep->entries);
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}
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/*----------------------------------------------------------------*/
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struct mq_policy {
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struct dm_cache_policy policy;
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/* protects everything */
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struct mutex lock;
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dm_cblock_t cache_size;
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struct io_tracker tracker;
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/*
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* Entries come from two pools, one of pre-cache entries, and one
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* for the cache proper.
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*/
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struct entry_pool pre_cache_pool;
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struct entry_pool cache_pool;
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/*
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* We maintain three queues of entries. The cache proper,
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* consisting of a clean and dirty queue, contains the currently
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* active mappings. Whereas the pre_cache tracks blocks that
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* are being hit frequently and potential candidates for promotion
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* to the cache.
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*/
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struct queue pre_cache;
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struct queue cache_clean;
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struct queue cache_dirty;
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/*
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* Keeps track of time, incremented by the core. We use this to
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* avoid attributing multiple hits within the same tick.
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*
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* Access to tick_protected should be done with the spin lock held.
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* It's copied to tick at the start of the map function (within the
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* mutex).
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*/
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spinlock_t tick_lock;
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unsigned tick_protected;
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unsigned tick;
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/*
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* A count of the number of times the map function has been called
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* and found an entry in the pre_cache or cache. Currently used to
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* calculate the generation.
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*/
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unsigned hit_count;
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/*
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* A generation is a longish period that is used to trigger some
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* book keeping effects. eg, decrementing hit counts on entries.
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* This is needed to allow the cache to evolve as io patterns
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* change.
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*/
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unsigned generation;
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unsigned generation_period; /* in lookups (will probably change) */
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|
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unsigned discard_promote_adjustment;
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unsigned read_promote_adjustment;
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unsigned write_promote_adjustment;
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|
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/*
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* The hash table allows us to quickly find an entry by origin
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* block. Both pre_cache and cache entries are in here.
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*/
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unsigned nr_buckets;
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dm_block_t hash_bits;
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struct hlist_head *table;
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};
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|
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#define DEFAULT_DISCARD_PROMOTE_ADJUSTMENT 1
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#define DEFAULT_READ_PROMOTE_ADJUSTMENT 4
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#define DEFAULT_WRITE_PROMOTE_ADJUSTMENT 8
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#define DISCOURAGE_DEMOTING_DIRTY_THRESHOLD 128
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|
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/*----------------------------------------------------------------*/
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|
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/*
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* Simple hash table implementation. Should replace with the standard hash
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* table that's making its way upstream.
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*/
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static void hash_insert(struct mq_policy *mq, struct entry *e)
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{
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unsigned h = hash_64(from_oblock(e->oblock), mq->hash_bits);
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|
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hlist_add_head(&e->hlist, mq->table + h);
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}
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|
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static struct entry *hash_lookup(struct mq_policy *mq, dm_oblock_t oblock)
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{
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unsigned h = hash_64(from_oblock(oblock), mq->hash_bits);
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struct hlist_head *bucket = mq->table + h;
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struct entry *e;
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|
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hlist_for_each_entry(e, bucket, hlist)
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if (e->oblock == oblock) {
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hlist_del(&e->hlist);
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hlist_add_head(&e->hlist, bucket);
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return e;
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}
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|
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return NULL;
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}
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|
|
static void hash_remove(struct entry *e)
|
|
{
|
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hlist_del(&e->hlist);
|
|
}
|
|
|
|
/*----------------------------------------------------------------*/
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|
|
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static bool any_free_cblocks(struct mq_policy *mq)
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|
{
|
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return !epool_empty(&mq->cache_pool);
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}
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|
|
static bool any_clean_cblocks(struct mq_policy *mq)
|
|
{
|
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return !queue_empty(&mq->cache_clean);
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}
|
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|
|
/*----------------------------------------------------------------*/
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|
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/*
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* Now we get to the meat of the policy. This section deals with deciding
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* when to to add entries to the pre_cache and cache, and move between
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* them.
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*/
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|
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/*
|
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* The queue level is based on the log2 of the hit count.
|
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*/
|
|
static unsigned queue_level(struct entry *e)
|
|
{
|
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return min((unsigned) ilog2(e->hit_count), NR_QUEUE_LEVELS - 1u);
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}
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|
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static bool in_cache(struct mq_policy *mq, struct entry *e)
|
|
{
|
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return in_pool(&mq->cache_pool, e);
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}
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|
|
/*
|
|
* Inserts the entry into the pre_cache or the cache. Ensures the cache
|
|
* block is marked as allocated if necc. Inserts into the hash table.
|
|
* Sets the tick which records when the entry was last moved about.
|
|
*/
|
|
static void push(struct mq_policy *mq, struct entry *e)
|
|
{
|
|
hash_insert(mq, e);
|
|
|
|
if (in_cache(mq, e))
|
|
queue_push(e->dirty ? &mq->cache_dirty : &mq->cache_clean,
|
|
queue_level(e), &e->list);
|
|
else
|
|
queue_push(&mq->pre_cache, queue_level(e), &e->list);
|
|
}
|
|
|
|
/*
|
|
* Removes an entry from pre_cache or cache. Removes from the hash table.
|
|
*/
|
|
static void del(struct mq_policy *mq, struct entry *e)
|
|
{
|
|
if (in_cache(mq, e))
|
|
queue_remove(e->dirty ? &mq->cache_dirty : &mq->cache_clean, &e->list);
|
|
else
|
|
queue_remove(&mq->pre_cache, &e->list);
|
|
|
|
hash_remove(e);
|
|
}
|
|
|
|
/*
|
|
* Like del, except it removes the first entry in the queue (ie. the least
|
|
* recently used).
|
|
*/
|
|
static struct entry *pop(struct mq_policy *mq, struct queue *q)
|
|
{
|
|
struct entry *e;
|
|
struct list_head *h = queue_pop(q);
|
|
|
|
if (!h)
|
|
return NULL;
|
|
|
|
e = container_of(h, struct entry, list);
|
|
hash_remove(e);
|
|
|
|
return e;
|
|
}
|
|
|
|
static struct entry *pop_old(struct mq_policy *mq, struct queue *q)
|
|
{
|
|
struct entry *e;
|
|
struct list_head *h = queue_pop_old(q);
|
|
|
|
if (!h)
|
|
return NULL;
|
|
|
|
e = container_of(h, struct entry, list);
|
|
hash_remove(e);
|
|
|
|
return e;
|
|
}
|
|
|
|
static struct entry *peek(struct queue *q)
|
|
{
|
|
struct list_head *h = queue_peek(q);
|
|
return h ? container_of(h, struct entry, list) : NULL;
|
|
}
|
|
|
|
/*
|
|
* The promotion threshold is adjusted every generation. As are the counts
|
|
* of the entries.
|
|
*
|
|
* At the moment the threshold is taken by averaging the hit counts of some
|
|
* of the entries in the cache (the first 20 entries across all levels in
|
|
* ascending order, giving preference to the clean entries at each level).
|
|
*
|
|
* We can be much cleverer than this though. For example, each promotion
|
|
* could bump up the threshold helping to prevent churn. Much more to do
|
|
* here.
|
|
*/
|
|
|
|
#define MAX_TO_AVERAGE 20
|
|
|
|
static void check_generation(struct mq_policy *mq)
|
|
{
|
|
unsigned total = 0, nr = 0, count = 0, level;
|
|
struct list_head *head;
|
|
struct entry *e;
|
|
|
|
if ((mq->hit_count >= mq->generation_period) && (epool_empty(&mq->cache_pool))) {
|
|
mq->hit_count = 0;
|
|
mq->generation++;
|
|
|
|
for (level = 0; level < NR_QUEUE_LEVELS && count < MAX_TO_AVERAGE; level++) {
|
|
head = mq->cache_clean.qs + level;
|
|
list_for_each_entry(e, head, list) {
|
|
nr++;
|
|
total += e->hit_count;
|
|
|
|
if (++count >= MAX_TO_AVERAGE)
|
|
break;
|
|
}
|
|
|
|
head = mq->cache_dirty.qs + level;
|
|
list_for_each_entry(e, head, list) {
|
|
nr++;
|
|
total += e->hit_count;
|
|
|
|
if (++count >= MAX_TO_AVERAGE)
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Whenever we use an entry we bump up it's hit counter, and push it to the
|
|
* back to it's current level.
|
|
*/
|
|
static void requeue(struct mq_policy *mq, struct entry *e)
|
|
{
|
|
check_generation(mq);
|
|
del(mq, e);
|
|
push(mq, e);
|
|
}
|
|
|
|
/*
|
|
* Demote the least recently used entry from the cache to the pre_cache.
|
|
* Returns the new cache entry to use, and the old origin block it was
|
|
* mapped to.
|
|
*
|
|
* We drop the hit count on the demoted entry back to 1 to stop it bouncing
|
|
* straight back into the cache if it's subsequently hit. There are
|
|
* various options here, and more experimentation would be good:
|
|
*
|
|
* - just forget about the demoted entry completely (ie. don't insert it
|
|
into the pre_cache).
|
|
* - divide the hit count rather that setting to some hard coded value.
|
|
* - set the hit count to a hard coded value other than 1, eg, is it better
|
|
* if it goes in at level 2?
|
|
*/
|
|
static int demote_cblock(struct mq_policy *mq,
|
|
struct policy_locker *locker, dm_oblock_t *oblock)
|
|
{
|
|
struct entry *demoted = peek(&mq->cache_clean);
|
|
|
|
if (!demoted)
|
|
/*
|
|
* We could get a block from mq->cache_dirty, but that
|
|
* would add extra latency to the triggering bio as it
|
|
* waits for the writeback. Better to not promote this
|
|
* time and hope there's a clean block next time this block
|
|
* is hit.
|
|
*/
|
|
return -ENOSPC;
|
|
|
|
if (locker->fn(locker, demoted->oblock))
|
|
/*
|
|
* We couldn't lock the demoted block.
|
|
*/
|
|
return -EBUSY;
|
|
|
|
del(mq, demoted);
|
|
*oblock = demoted->oblock;
|
|
free_entry(&mq->cache_pool, demoted);
|
|
|
|
/*
|
|
* We used to put the demoted block into the pre-cache, but I think
|
|
* it's simpler to just let it work it's way up from zero again.
|
|
* Stops blocks flickering in and out of the cache.
|
|
*/
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Entries in the pre_cache whose hit count passes the promotion
|
|
* threshold move to the cache proper. Working out the correct
|
|
* value for the promotion_threshold is crucial to this policy.
|
|
*/
|
|
static unsigned promote_threshold(struct mq_policy *mq)
|
|
{
|
|
struct entry *e;
|
|
|
|
if (any_free_cblocks(mq))
|
|
return 0;
|
|
|
|
e = peek(&mq->cache_clean);
|
|
if (e)
|
|
return e->hit_count;
|
|
|
|
e = peek(&mq->cache_dirty);
|
|
if (e)
|
|
return e->hit_count + DISCOURAGE_DEMOTING_DIRTY_THRESHOLD;
|
|
|
|
/* This should never happen */
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* We modify the basic promotion_threshold depending on the specific io.
|
|
*
|
|
* If the origin block has been discarded then there's no cost to copy it
|
|
* to the cache.
|
|
*
|
|
* We bias towards reads, since they can be demoted at no cost if they
|
|
* haven't been dirtied.
|
|
*/
|
|
static unsigned adjusted_promote_threshold(struct mq_policy *mq,
|
|
bool discarded_oblock, int data_dir)
|
|
{
|
|
if (data_dir == READ)
|
|
return promote_threshold(mq) + mq->read_promote_adjustment;
|
|
|
|
if (discarded_oblock && (any_free_cblocks(mq) || any_clean_cblocks(mq))) {
|
|
/*
|
|
* We don't need to do any copying at all, so give this a
|
|
* very low threshold.
|
|
*/
|
|
return mq->discard_promote_adjustment;
|
|
}
|
|
|
|
return promote_threshold(mq) + mq->write_promote_adjustment;
|
|
}
|
|
|
|
static bool should_promote(struct mq_policy *mq, struct entry *e,
|
|
bool discarded_oblock, int data_dir)
|
|
{
|
|
return e->hit_count >=
|
|
adjusted_promote_threshold(mq, discarded_oblock, data_dir);
|
|
}
|
|
|
|
static int cache_entry_found(struct mq_policy *mq,
|
|
struct entry *e,
|
|
struct policy_result *result)
|
|
{
|
|
requeue(mq, e);
|
|
|
|
if (in_cache(mq, e)) {
|
|
result->op = POLICY_HIT;
|
|
result->cblock = infer_cblock(&mq->cache_pool, e);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Moves an entry from the pre_cache to the cache. The main work is
|
|
* finding which cache block to use.
|
|
*/
|
|
static int pre_cache_to_cache(struct mq_policy *mq, struct entry *e,
|
|
struct policy_locker *locker,
|
|
struct policy_result *result)
|
|
{
|
|
int r;
|
|
struct entry *new_e;
|
|
|
|
/* Ensure there's a free cblock in the cache */
|
|
if (epool_empty(&mq->cache_pool)) {
|
|
result->op = POLICY_REPLACE;
|
|
r = demote_cblock(mq, locker, &result->old_oblock);
|
|
if (r) {
|
|
result->op = POLICY_MISS;
|
|
return 0;
|
|
}
|
|
|
|
} else
|
|
result->op = POLICY_NEW;
|
|
|
|
new_e = alloc_entry(&mq->cache_pool);
|
|
BUG_ON(!new_e);
|
|
|
|
new_e->oblock = e->oblock;
|
|
new_e->dirty = false;
|
|
new_e->hit_count = e->hit_count;
|
|
|
|
del(mq, e);
|
|
free_entry(&mq->pre_cache_pool, e);
|
|
push(mq, new_e);
|
|
|
|
result->cblock = infer_cblock(&mq->cache_pool, new_e);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int pre_cache_entry_found(struct mq_policy *mq, struct entry *e,
|
|
bool can_migrate, bool discarded_oblock,
|
|
int data_dir, struct policy_locker *locker,
|
|
struct policy_result *result)
|
|
{
|
|
int r = 0;
|
|
|
|
if (!should_promote(mq, e, discarded_oblock, data_dir)) {
|
|
requeue(mq, e);
|
|
result->op = POLICY_MISS;
|
|
|
|
} else if (!can_migrate)
|
|
r = -EWOULDBLOCK;
|
|
|
|
else {
|
|
requeue(mq, e);
|
|
r = pre_cache_to_cache(mq, e, locker, result);
|
|
}
|
|
|
|
return r;
|
|
}
|
|
|
|
static void insert_in_pre_cache(struct mq_policy *mq,
|
|
dm_oblock_t oblock)
|
|
{
|
|
struct entry *e = alloc_entry(&mq->pre_cache_pool);
|
|
|
|
if (!e)
|
|
/*
|
|
* There's no spare entry structure, so we grab the least
|
|
* used one from the pre_cache.
|
|
*/
|
|
e = pop(mq, &mq->pre_cache);
|
|
|
|
if (unlikely(!e)) {
|
|
DMWARN("couldn't pop from pre cache");
|
|
return;
|
|
}
|
|
|
|
e->dirty = false;
|
|
e->oblock = oblock;
|
|
e->hit_count = 1;
|
|
push(mq, e);
|
|
}
|
|
|
|
static void insert_in_cache(struct mq_policy *mq, dm_oblock_t oblock,
|
|
struct policy_locker *locker,
|
|
struct policy_result *result)
|
|
{
|
|
int r;
|
|
struct entry *e;
|
|
|
|
if (epool_empty(&mq->cache_pool)) {
|
|
result->op = POLICY_REPLACE;
|
|
r = demote_cblock(mq, locker, &result->old_oblock);
|
|
if (unlikely(r)) {
|
|
result->op = POLICY_MISS;
|
|
insert_in_pre_cache(mq, oblock);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* This will always succeed, since we've just demoted.
|
|
*/
|
|
e = alloc_entry(&mq->cache_pool);
|
|
BUG_ON(!e);
|
|
|
|
} else {
|
|
e = alloc_entry(&mq->cache_pool);
|
|
result->op = POLICY_NEW;
|
|
}
|
|
|
|
e->oblock = oblock;
|
|
e->dirty = false;
|
|
e->hit_count = 1;
|
|
push(mq, e);
|
|
|
|
result->cblock = infer_cblock(&mq->cache_pool, e);
|
|
}
|
|
|
|
static int no_entry_found(struct mq_policy *mq, dm_oblock_t oblock,
|
|
bool can_migrate, bool discarded_oblock,
|
|
int data_dir, struct policy_locker *locker,
|
|
struct policy_result *result)
|
|
{
|
|
if (adjusted_promote_threshold(mq, discarded_oblock, data_dir) <= 1) {
|
|
if (can_migrate)
|
|
insert_in_cache(mq, oblock, locker, result);
|
|
else
|
|
return -EWOULDBLOCK;
|
|
} else {
|
|
insert_in_pre_cache(mq, oblock);
|
|
result->op = POLICY_MISS;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Looks the oblock up in the hash table, then decides whether to put in
|
|
* pre_cache, or cache etc.
|
|
*/
|
|
static int map(struct mq_policy *mq, dm_oblock_t oblock,
|
|
bool can_migrate, bool discarded_oblock,
|
|
int data_dir, struct policy_locker *locker,
|
|
struct policy_result *result)
|
|
{
|
|
int r = 0;
|
|
struct entry *e = hash_lookup(mq, oblock);
|
|
|
|
if (e && in_cache(mq, e))
|
|
r = cache_entry_found(mq, e, result);
|
|
|
|
else if (mq->tracker.thresholds[PATTERN_SEQUENTIAL] &&
|
|
iot_pattern(&mq->tracker) == PATTERN_SEQUENTIAL)
|
|
result->op = POLICY_MISS;
|
|
|
|
else if (e)
|
|
r = pre_cache_entry_found(mq, e, can_migrate, discarded_oblock,
|
|
data_dir, locker, result);
|
|
|
|
else
|
|
r = no_entry_found(mq, oblock, can_migrate, discarded_oblock,
|
|
data_dir, locker, result);
|
|
|
|
if (r == -EWOULDBLOCK)
|
|
result->op = POLICY_MISS;
|
|
|
|
return r;
|
|
}
|
|
|
|
/*----------------------------------------------------------------*/
|
|
|
|
/*
|
|
* Public interface, via the policy struct. See dm-cache-policy.h for a
|
|
* description of these.
|
|
*/
|
|
|
|
static struct mq_policy *to_mq_policy(struct dm_cache_policy *p)
|
|
{
|
|
return container_of(p, struct mq_policy, policy);
|
|
}
|
|
|
|
static void mq_destroy(struct dm_cache_policy *p)
|
|
{
|
|
struct mq_policy *mq = to_mq_policy(p);
|
|
|
|
vfree(mq->table);
|
|
epool_exit(&mq->cache_pool);
|
|
epool_exit(&mq->pre_cache_pool);
|
|
kfree(mq);
|
|
}
|
|
|
|
static void update_pre_cache_hits(struct list_head *h, void *context)
|
|
{
|
|
struct entry *e = container_of(h, struct entry, list);
|
|
e->hit_count++;
|
|
}
|
|
|
|
static void update_cache_hits(struct list_head *h, void *context)
|
|
{
|
|
struct mq_policy *mq = context;
|
|
struct entry *e = container_of(h, struct entry, list);
|
|
e->hit_count++;
|
|
mq->hit_count++;
|
|
}
|
|
|
|
static void copy_tick(struct mq_policy *mq)
|
|
{
|
|
unsigned long flags, tick;
|
|
|
|
spin_lock_irqsave(&mq->tick_lock, flags);
|
|
tick = mq->tick_protected;
|
|
if (tick != mq->tick) {
|
|
queue_iterate_tick(&mq->pre_cache, update_pre_cache_hits, mq);
|
|
queue_iterate_tick(&mq->cache_dirty, update_cache_hits, mq);
|
|
queue_iterate_tick(&mq->cache_clean, update_cache_hits, mq);
|
|
mq->tick = tick;
|
|
}
|
|
|
|
queue_tick(&mq->pre_cache);
|
|
queue_tick(&mq->cache_dirty);
|
|
queue_tick(&mq->cache_clean);
|
|
queue_update_writeback_sentinels(&mq->cache_dirty);
|
|
spin_unlock_irqrestore(&mq->tick_lock, flags);
|
|
}
|
|
|
|
static int mq_map(struct dm_cache_policy *p, dm_oblock_t oblock,
|
|
bool can_block, bool can_migrate, bool discarded_oblock,
|
|
struct bio *bio, struct policy_locker *locker,
|
|
struct policy_result *result)
|
|
{
|
|
int r;
|
|
struct mq_policy *mq = to_mq_policy(p);
|
|
|
|
result->op = POLICY_MISS;
|
|
|
|
if (can_block)
|
|
mutex_lock(&mq->lock);
|
|
else if (!mutex_trylock(&mq->lock))
|
|
return -EWOULDBLOCK;
|
|
|
|
copy_tick(mq);
|
|
|
|
iot_examine_bio(&mq->tracker, bio);
|
|
r = map(mq, oblock, can_migrate, discarded_oblock,
|
|
bio_data_dir(bio), locker, result);
|
|
|
|
mutex_unlock(&mq->lock);
|
|
|
|
return r;
|
|
}
|
|
|
|
static int mq_lookup(struct dm_cache_policy *p, dm_oblock_t oblock, dm_cblock_t *cblock)
|
|
{
|
|
int r;
|
|
struct mq_policy *mq = to_mq_policy(p);
|
|
struct entry *e;
|
|
|
|
if (!mutex_trylock(&mq->lock))
|
|
return -EWOULDBLOCK;
|
|
|
|
e = hash_lookup(mq, oblock);
|
|
if (e && in_cache(mq, e)) {
|
|
*cblock = infer_cblock(&mq->cache_pool, e);
|
|
r = 0;
|
|
} else
|
|
r = -ENOENT;
|
|
|
|
mutex_unlock(&mq->lock);
|
|
|
|
return r;
|
|
}
|
|
|
|
static void __mq_set_clear_dirty(struct mq_policy *mq, dm_oblock_t oblock, bool set)
|
|
{
|
|
struct entry *e;
|
|
|
|
e = hash_lookup(mq, oblock);
|
|
BUG_ON(!e || !in_cache(mq, e));
|
|
|
|
del(mq, e);
|
|
e->dirty = set;
|
|
push(mq, e);
|
|
}
|
|
|
|
static void mq_set_dirty(struct dm_cache_policy *p, dm_oblock_t oblock)
|
|
{
|
|
struct mq_policy *mq = to_mq_policy(p);
|
|
|
|
mutex_lock(&mq->lock);
|
|
__mq_set_clear_dirty(mq, oblock, true);
|
|
mutex_unlock(&mq->lock);
|
|
}
|
|
|
|
static void mq_clear_dirty(struct dm_cache_policy *p, dm_oblock_t oblock)
|
|
{
|
|
struct mq_policy *mq = to_mq_policy(p);
|
|
|
|
mutex_lock(&mq->lock);
|
|
__mq_set_clear_dirty(mq, oblock, false);
|
|
mutex_unlock(&mq->lock);
|
|
}
|
|
|
|
static int mq_load_mapping(struct dm_cache_policy *p,
|
|
dm_oblock_t oblock, dm_cblock_t cblock,
|
|
uint32_t hint, bool hint_valid)
|
|
{
|
|
struct mq_policy *mq = to_mq_policy(p);
|
|
struct entry *e;
|
|
|
|
e = alloc_particular_entry(&mq->cache_pool, cblock);
|
|
e->oblock = oblock;
|
|
e->dirty = false; /* this gets corrected in a minute */
|
|
e->hit_count = hint_valid ? hint : 1;
|
|
push(mq, e);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int mq_save_hints(struct mq_policy *mq, struct queue *q,
|
|
policy_walk_fn fn, void *context)
|
|
{
|
|
int r;
|
|
unsigned level;
|
|
struct list_head *h;
|
|
struct entry *e;
|
|
|
|
for (level = 0; level < NR_QUEUE_LEVELS; level++)
|
|
list_for_each(h, q->qs + level) {
|
|
if (is_sentinel(q, h))
|
|
continue;
|
|
|
|
e = container_of(h, struct entry, list);
|
|
r = fn(context, infer_cblock(&mq->cache_pool, e),
|
|
e->oblock, e->hit_count);
|
|
if (r)
|
|
return r;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int mq_walk_mappings(struct dm_cache_policy *p, policy_walk_fn fn,
|
|
void *context)
|
|
{
|
|
struct mq_policy *mq = to_mq_policy(p);
|
|
int r = 0;
|
|
|
|
mutex_lock(&mq->lock);
|
|
|
|
r = mq_save_hints(mq, &mq->cache_clean, fn, context);
|
|
if (!r)
|
|
r = mq_save_hints(mq, &mq->cache_dirty, fn, context);
|
|
|
|
mutex_unlock(&mq->lock);
|
|
|
|
return r;
|
|
}
|
|
|
|
static void __remove_mapping(struct mq_policy *mq, dm_oblock_t oblock)
|
|
{
|
|
struct entry *e;
|
|
|
|
e = hash_lookup(mq, oblock);
|
|
BUG_ON(!e || !in_cache(mq, e));
|
|
|
|
del(mq, e);
|
|
free_entry(&mq->cache_pool, e);
|
|
}
|
|
|
|
static void mq_remove_mapping(struct dm_cache_policy *p, dm_oblock_t oblock)
|
|
{
|
|
struct mq_policy *mq = to_mq_policy(p);
|
|
|
|
mutex_lock(&mq->lock);
|
|
__remove_mapping(mq, oblock);
|
|
mutex_unlock(&mq->lock);
|
|
}
|
|
|
|
static int __remove_cblock(struct mq_policy *mq, dm_cblock_t cblock)
|
|
{
|
|
struct entry *e = epool_find(&mq->cache_pool, cblock);
|
|
|
|
if (!e)
|
|
return -ENODATA;
|
|
|
|
del(mq, e);
|
|
free_entry(&mq->cache_pool, e);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int mq_remove_cblock(struct dm_cache_policy *p, dm_cblock_t cblock)
|
|
{
|
|
int r;
|
|
struct mq_policy *mq = to_mq_policy(p);
|
|
|
|
mutex_lock(&mq->lock);
|
|
r = __remove_cblock(mq, cblock);
|
|
mutex_unlock(&mq->lock);
|
|
|
|
return r;
|
|
}
|
|
|
|
#define CLEAN_TARGET_PERCENTAGE 25
|
|
|
|
static bool clean_target_met(struct mq_policy *mq)
|
|
{
|
|
/*
|
|
* Cache entries may not be populated. So we're cannot rely on the
|
|
* size of the clean queue.
|
|
*/
|
|
unsigned nr_clean = from_cblock(mq->cache_size) - queue_size(&mq->cache_dirty);
|
|
unsigned target = from_cblock(mq->cache_size) * CLEAN_TARGET_PERCENTAGE / 100;
|
|
|
|
return nr_clean >= target;
|
|
}
|
|
|
|
static int __mq_writeback_work(struct mq_policy *mq, dm_oblock_t *oblock,
|
|
dm_cblock_t *cblock)
|
|
{
|
|
struct entry *e = pop_old(mq, &mq->cache_dirty);
|
|
|
|
if (!e && !clean_target_met(mq))
|
|
e = pop(mq, &mq->cache_dirty);
|
|
|
|
if (!e)
|
|
return -ENODATA;
|
|
|
|
*oblock = e->oblock;
|
|
*cblock = infer_cblock(&mq->cache_pool, e);
|
|
e->dirty = false;
|
|
push(mq, e);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int mq_writeback_work(struct dm_cache_policy *p, dm_oblock_t *oblock,
|
|
dm_cblock_t *cblock, bool critical_only)
|
|
{
|
|
int r;
|
|
struct mq_policy *mq = to_mq_policy(p);
|
|
|
|
mutex_lock(&mq->lock);
|
|
r = __mq_writeback_work(mq, oblock, cblock);
|
|
mutex_unlock(&mq->lock);
|
|
|
|
return r;
|
|
}
|
|
|
|
static void __force_mapping(struct mq_policy *mq,
|
|
dm_oblock_t current_oblock, dm_oblock_t new_oblock)
|
|
{
|
|
struct entry *e = hash_lookup(mq, current_oblock);
|
|
|
|
if (e && in_cache(mq, e)) {
|
|
del(mq, e);
|
|
e->oblock = new_oblock;
|
|
e->dirty = true;
|
|
push(mq, e);
|
|
}
|
|
}
|
|
|
|
static void mq_force_mapping(struct dm_cache_policy *p,
|
|
dm_oblock_t current_oblock, dm_oblock_t new_oblock)
|
|
{
|
|
struct mq_policy *mq = to_mq_policy(p);
|
|
|
|
mutex_lock(&mq->lock);
|
|
__force_mapping(mq, current_oblock, new_oblock);
|
|
mutex_unlock(&mq->lock);
|
|
}
|
|
|
|
static dm_cblock_t mq_residency(struct dm_cache_policy *p)
|
|
{
|
|
dm_cblock_t r;
|
|
struct mq_policy *mq = to_mq_policy(p);
|
|
|
|
mutex_lock(&mq->lock);
|
|
r = to_cblock(mq->cache_pool.nr_allocated);
|
|
mutex_unlock(&mq->lock);
|
|
|
|
return r;
|
|
}
|
|
|
|
static void mq_tick(struct dm_cache_policy *p, bool can_block)
|
|
{
|
|
struct mq_policy *mq = to_mq_policy(p);
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&mq->tick_lock, flags);
|
|
mq->tick_protected++;
|
|
spin_unlock_irqrestore(&mq->tick_lock, flags);
|
|
|
|
if (can_block) {
|
|
mutex_lock(&mq->lock);
|
|
copy_tick(mq);
|
|
mutex_unlock(&mq->lock);
|
|
}
|
|
}
|
|
|
|
static int mq_set_config_value(struct dm_cache_policy *p,
|
|
const char *key, const char *value)
|
|
{
|
|
struct mq_policy *mq = to_mq_policy(p);
|
|
unsigned long tmp;
|
|
|
|
if (kstrtoul(value, 10, &tmp))
|
|
return -EINVAL;
|
|
|
|
if (!strcasecmp(key, "random_threshold")) {
|
|
mq->tracker.thresholds[PATTERN_RANDOM] = tmp;
|
|
|
|
} else if (!strcasecmp(key, "sequential_threshold")) {
|
|
mq->tracker.thresholds[PATTERN_SEQUENTIAL] = tmp;
|
|
|
|
} else if (!strcasecmp(key, "discard_promote_adjustment"))
|
|
mq->discard_promote_adjustment = tmp;
|
|
|
|
else if (!strcasecmp(key, "read_promote_adjustment"))
|
|
mq->read_promote_adjustment = tmp;
|
|
|
|
else if (!strcasecmp(key, "write_promote_adjustment"))
|
|
mq->write_promote_adjustment = tmp;
|
|
|
|
else
|
|
return -EINVAL;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int mq_emit_config_values(struct dm_cache_policy *p, char *result,
|
|
unsigned maxlen, ssize_t *sz_ptr)
|
|
{
|
|
ssize_t sz = *sz_ptr;
|
|
struct mq_policy *mq = to_mq_policy(p);
|
|
|
|
DMEMIT("10 random_threshold %u "
|
|
"sequential_threshold %u "
|
|
"discard_promote_adjustment %u "
|
|
"read_promote_adjustment %u "
|
|
"write_promote_adjustment %u ",
|
|
mq->tracker.thresholds[PATTERN_RANDOM],
|
|
mq->tracker.thresholds[PATTERN_SEQUENTIAL],
|
|
mq->discard_promote_adjustment,
|
|
mq->read_promote_adjustment,
|
|
mq->write_promote_adjustment);
|
|
|
|
*sz_ptr = sz;
|
|
return 0;
|
|
}
|
|
|
|
/* Init the policy plugin interface function pointers. */
|
|
static void init_policy_functions(struct mq_policy *mq)
|
|
{
|
|
mq->policy.destroy = mq_destroy;
|
|
mq->policy.map = mq_map;
|
|
mq->policy.lookup = mq_lookup;
|
|
mq->policy.set_dirty = mq_set_dirty;
|
|
mq->policy.clear_dirty = mq_clear_dirty;
|
|
mq->policy.load_mapping = mq_load_mapping;
|
|
mq->policy.walk_mappings = mq_walk_mappings;
|
|
mq->policy.remove_mapping = mq_remove_mapping;
|
|
mq->policy.remove_cblock = mq_remove_cblock;
|
|
mq->policy.writeback_work = mq_writeback_work;
|
|
mq->policy.force_mapping = mq_force_mapping;
|
|
mq->policy.residency = mq_residency;
|
|
mq->policy.tick = mq_tick;
|
|
mq->policy.emit_config_values = mq_emit_config_values;
|
|
mq->policy.set_config_value = mq_set_config_value;
|
|
}
|
|
|
|
static struct dm_cache_policy *mq_create(dm_cblock_t cache_size,
|
|
sector_t origin_size,
|
|
sector_t cache_block_size)
|
|
{
|
|
struct mq_policy *mq = kzalloc(sizeof(*mq), GFP_KERNEL);
|
|
|
|
if (!mq)
|
|
return NULL;
|
|
|
|
init_policy_functions(mq);
|
|
iot_init(&mq->tracker, SEQUENTIAL_THRESHOLD_DEFAULT, RANDOM_THRESHOLD_DEFAULT);
|
|
mq->cache_size = cache_size;
|
|
|
|
if (epool_init(&mq->pre_cache_pool, from_cblock(cache_size))) {
|
|
DMERR("couldn't initialize pool of pre-cache entries");
|
|
goto bad_pre_cache_init;
|
|
}
|
|
|
|
if (epool_init(&mq->cache_pool, from_cblock(cache_size))) {
|
|
DMERR("couldn't initialize pool of cache entries");
|
|
goto bad_cache_init;
|
|
}
|
|
|
|
mq->tick_protected = 0;
|
|
mq->tick = 0;
|
|
mq->hit_count = 0;
|
|
mq->generation = 0;
|
|
mq->discard_promote_adjustment = DEFAULT_DISCARD_PROMOTE_ADJUSTMENT;
|
|
mq->read_promote_adjustment = DEFAULT_READ_PROMOTE_ADJUSTMENT;
|
|
mq->write_promote_adjustment = DEFAULT_WRITE_PROMOTE_ADJUSTMENT;
|
|
mutex_init(&mq->lock);
|
|
spin_lock_init(&mq->tick_lock);
|
|
|
|
queue_init(&mq->pre_cache);
|
|
queue_init(&mq->cache_clean);
|
|
queue_init(&mq->cache_dirty);
|
|
|
|
mq->generation_period = max((unsigned) from_cblock(cache_size), 1024U);
|
|
|
|
mq->nr_buckets = next_power(from_cblock(cache_size) / 2, 16);
|
|
mq->hash_bits = ffs(mq->nr_buckets) - 1;
|
|
mq->table = vzalloc(sizeof(*mq->table) * mq->nr_buckets);
|
|
if (!mq->table)
|
|
goto bad_alloc_table;
|
|
|
|
return &mq->policy;
|
|
|
|
bad_alloc_table:
|
|
epool_exit(&mq->cache_pool);
|
|
bad_cache_init:
|
|
epool_exit(&mq->pre_cache_pool);
|
|
bad_pre_cache_init:
|
|
kfree(mq);
|
|
|
|
return NULL;
|
|
}
|
|
|
|
/*----------------------------------------------------------------*/
|
|
|
|
static struct dm_cache_policy_type mq_policy_type = {
|
|
.name = "mq",
|
|
.version = {1, 4, 0},
|
|
.hint_size = 4,
|
|
.owner = THIS_MODULE,
|
|
.create = mq_create
|
|
};
|
|
|
|
static int __init mq_init(void)
|
|
{
|
|
int r;
|
|
|
|
mq_entry_cache = kmem_cache_create("dm_mq_policy_cache_entry",
|
|
sizeof(struct entry),
|
|
__alignof__(struct entry),
|
|
0, NULL);
|
|
if (!mq_entry_cache)
|
|
return -ENOMEM;
|
|
|
|
r = dm_cache_policy_register(&mq_policy_type);
|
|
if (r) {
|
|
DMERR("register failed %d", r);
|
|
kmem_cache_destroy(mq_entry_cache);
|
|
return -ENOMEM;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void __exit mq_exit(void)
|
|
{
|
|
dm_cache_policy_unregister(&mq_policy_type);
|
|
|
|
kmem_cache_destroy(mq_entry_cache);
|
|
}
|
|
|
|
module_init(mq_init);
|
|
module_exit(mq_exit);
|
|
|
|
MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_DESCRIPTION("mq cache policy");
|