diff options
Diffstat (limited to 'drivers/md/dm-cache-policy-mq.c')
| -rw-r--r-- | drivers/md/dm-cache-policy-mq.c | 1473 |
1 files changed, 0 insertions, 1473 deletions
diff --git a/drivers/md/dm-cache-policy-mq.c b/drivers/md/dm-cache-policy-mq.c deleted file mode 100644 index ddb26980cd66..000000000000 --- a/drivers/md/dm-cache-policy-mq.c +++ /dev/null @@ -1,1473 +0,0 @@ -/* - * Copyright (C) 2012 Red Hat. All rights reserved. - * - * This file is released under the GPL. - */ - -#include "dm-cache-policy.h" -#include "dm.h" - -#include <linux/hash.h> -#include <linux/jiffies.h> -#include <linux/module.h> -#include <linux/mutex.h> -#include <linux/slab.h> -#include <linux/vmalloc.h> - -#define DM_MSG_PREFIX "cache-policy-mq" - -static struct kmem_cache *mq_entry_cache; - -/*----------------------------------------------------------------*/ - -static unsigned next_power(unsigned n, unsigned min) -{ - return roundup_pow_of_two(max(n, min)); -} - -/*----------------------------------------------------------------*/ - -/* - * Large, sequential ios are probably better left on the origin device since - * spindles tend to have good bandwidth. - * - * The io_tracker tries to spot when the io is in one of these sequential - * modes. - * - * Two thresholds to switch between random and sequential io mode are defaulting - * as follows and can be adjusted via the constructor and message interfaces. - */ -#define RANDOM_THRESHOLD_DEFAULT 4 -#define SEQUENTIAL_THRESHOLD_DEFAULT 512 - -enum io_pattern { - PATTERN_SEQUENTIAL, - PATTERN_RANDOM -}; - -struct io_tracker { - enum io_pattern pattern; - - unsigned nr_seq_samples; - unsigned nr_rand_samples; - unsigned thresholds[2]; - - dm_oblock_t last_end_oblock; -}; - -static void iot_init(struct io_tracker *t, - int sequential_threshold, int random_threshold) -{ - t->pattern = PATTERN_RANDOM; - t->nr_seq_samples = 0; - t->nr_rand_samples = 0; - t->last_end_oblock = 0; - t->thresholds[PATTERN_RANDOM] = random_threshold; - t->thresholds[PATTERN_SEQUENTIAL] = sequential_threshold; -} - -static enum io_pattern iot_pattern(struct io_tracker *t) -{ - return t->pattern; -} - -static void iot_update_stats(struct io_tracker *t, struct bio *bio) -{ - if (bio->bi_iter.bi_sector == from_oblock(t->last_end_oblock) + 1) - t->nr_seq_samples++; - else { - /* - * Just one non-sequential IO is enough to reset the - * counters. - */ - if (t->nr_seq_samples) { - t->nr_seq_samples = 0; - t->nr_rand_samples = 0; - } - - t->nr_rand_samples++; - } - - t->last_end_oblock = to_oblock(bio_end_sector(bio) - 1); -} - -static void iot_check_for_pattern_switch(struct io_tracker *t) -{ - switch (t->pattern) { - case PATTERN_SEQUENTIAL: - if (t->nr_rand_samples >= t->thresholds[PATTERN_RANDOM]) { - t->pattern = PATTERN_RANDOM; - t->nr_seq_samples = t->nr_rand_samples = 0; - } - break; - - case PATTERN_RANDOM: - if (t->nr_seq_samples >= t->thresholds[PATTERN_SEQUENTIAL]) { - t->pattern = PATTERN_SEQUENTIAL; - t->nr_seq_samples = t->nr_rand_samples = 0; - } - break; - } -} - -static void iot_examine_bio(struct io_tracker *t, struct bio *bio) -{ - iot_update_stats(t, bio); - iot_check_for_pattern_switch(t); -} - -/*----------------------------------------------------------------*/ - - -/* - * This queue is divided up into different levels. Allowing us to push - * entries to the back of any of the levels. Think of it as a partially - * sorted queue. - */ -#define NR_QUEUE_LEVELS 16u -#define NR_SENTINELS NR_QUEUE_LEVELS * 3 - -#define WRITEBACK_PERIOD HZ - -struct queue { - unsigned nr_elts; - bool current_writeback_sentinels; - unsigned long next_writeback; - struct list_head qs[NR_QUEUE_LEVELS]; - struct list_head sentinels[NR_SENTINELS]; -}; - -static void queue_init(struct queue *q) -{ - unsigned i; - - q->nr_elts = 0; - q->current_writeback_sentinels = false; - q->next_writeback = 0; - for (i = 0; i < NR_QUEUE_LEVELS; i++) { - INIT_LIST_HEAD(q->qs + i); - INIT_LIST_HEAD(q->sentinels + i); - INIT_LIST_HEAD(q->sentinels + NR_QUEUE_LEVELS + i); - INIT_LIST_HEAD(q->sentinels + (2 * NR_QUEUE_LEVELS) + i); - } -} - -static unsigned queue_size(struct queue *q) -{ - return q->nr_elts; -} - -static bool queue_empty(struct queue *q) -{ - return q->nr_elts == 0; -} - -/* - * Insert an entry to the back of the given level. - */ -static void queue_push(struct queue *q, unsigned level, struct list_head *elt) -{ - q->nr_elts++; - list_add_tail(elt, q->qs + level); -} - -static void queue_remove(struct queue *q, struct list_head *elt) -{ - q->nr_elts--; - list_del(elt); -} - -static bool is_sentinel(struct queue *q, struct list_head *h) -{ - return (h >= q->sentinels) && (h < (q->sentinels + NR_SENTINELS)); -} - -/* - * Gives us the oldest entry of the lowest popoulated level. If the first - * level is emptied then we shift down one level. - */ -static struct list_head *queue_peek(struct queue *q) -{ - unsigned level; - struct list_head *h; - - for (level = 0; level < NR_QUEUE_LEVELS; level++) - list_for_each(h, q->qs + level) - if (!is_sentinel(q, h)) - return h; - - return NULL; -} - -static struct list_head *queue_pop(struct queue *q) -{ - struct list_head *r = queue_peek(q); - - if (r) { - q->nr_elts--; - list_del(r); - } - - return r; -} - -/* - * Pops an entry from a level that is not past a sentinel. - */ -static struct list_head *queue_pop_old(struct queue *q) -{ - unsigned level; - struct list_head *h; - - for (level = 0; level < NR_QUEUE_LEVELS; level++) - list_for_each(h, q->qs + level) { - if (is_sentinel(q, h)) - break; - - q->nr_elts--; - list_del(h); - return h; - } - - return NULL; -} - -static struct list_head *list_pop(struct list_head *lh) -{ - struct list_head *r = lh->next; - - BUG_ON(!r); - list_del_init(r); - - return r; -} - -static struct list_head *writeback_sentinel(struct queue *q, unsigned level) -{ - if (q->current_writeback_sentinels) - return q->sentinels + NR_QUEUE_LEVELS + level; - else - return q->sentinels + 2 * NR_QUEUE_LEVELS + level; -} - -static void queue_update_writeback_sentinels(struct queue *q) -{ - unsigned i; - struct list_head *h; - - if (time_after(jiffies, q->next_writeback)) { - for (i = 0; i < NR_QUEUE_LEVELS; i++) { - h = writeback_sentinel(q, i); - list_del(h); - list_add_tail(h, q->qs + i); - } - - q->next_writeback = jiffies + WRITEBACK_PERIOD; - q->current_writeback_sentinels = !q->current_writeback_sentinels; - } -} - -/* - * Sometimes we want to iterate through entries that have been pushed since - * a certain event. We use sentinel entries on the queues to delimit these - * 'tick' events. - */ -static void queue_tick(struct queue *q) -{ - unsigned i; - - for (i = 0; i < NR_QUEUE_LEVELS; i++) { - list_del(q->sentinels + i); - list_add_tail(q->sentinels + i, q->qs + i); - } -} - -typedef void (*iter_fn)(struct list_head *, void *); -static void queue_iterate_tick(struct queue *q, iter_fn fn, void *context) -{ - unsigned i; - struct list_head *h; - - for (i = 0; i < NR_QUEUE_LEVELS; i++) { - list_for_each_prev(h, q->qs + i) { - if (is_sentinel(q, h)) - break; - - fn(h, context); - } - } -} - -/*----------------------------------------------------------------*/ - -/* - * Describes a cache entry. Used in both the cache and the pre_cache. - */ -struct entry { - struct hlist_node hlist; - struct list_head list; - dm_oblock_t oblock; - - /* - * FIXME: pack these better - */ - bool dirty:1; - unsigned hit_count; -}; - -/* - * Rather than storing the cblock in an entry, we allocate all entries in - * an array, and infer the cblock from the entry position. - * - * Free entries are linked together into a list. - */ -struct entry_pool { - struct entry *entries, *entries_end; - struct list_head free; - unsigned nr_allocated; -}; - -static int epool_init(struct entry_pool *ep, unsigned nr_entries) -{ - unsigned i; - - ep->entries = vzalloc(sizeof(struct entry) * nr_entries); - if (!ep->entries) - return -ENOMEM; - - ep->entries_end = ep->entries + nr_entries; - - INIT_LIST_HEAD(&ep->free); - for (i = 0; i < nr_entries; i++) - list_add(&ep->entries[i].list, &ep->free); - - ep->nr_allocated = 0; - - return 0; -} - -static void epool_exit(struct entry_pool *ep) -{ - vfree(ep->entries); -} - -static struct entry *alloc_entry(struct entry_pool *ep) -{ - struct entry *e; - - if (list_empty(&ep->free)) - return NULL; - - e = list_entry(list_pop(&ep->free), struct entry, list); - INIT_LIST_HEAD(&e->list); - INIT_HLIST_NODE(&e->hlist); - ep->nr_allocated++; - - return e; -} - -/* - * This assumes the cblock hasn't already been allocated. - */ -static struct entry *alloc_particular_entry(struct entry_pool *ep, dm_cblock_t cblock) -{ - struct entry *e = ep->entries + from_cblock(cblock); - - list_del_init(&e->list); - INIT_HLIST_NODE(&e->hlist); - ep->nr_allocated++; - - return e; -} - -static void free_entry(struct entry_pool *ep, struct entry *e) -{ - BUG_ON(!ep->nr_allocated); - ep->nr_allocated--; - INIT_HLIST_NODE(&e->hlist); - list_add(&e->list, &ep->free); -} - -/* - * Returns NULL if the entry is free. - */ -static struct entry *epool_find(struct entry_pool *ep, dm_cblock_t cblock) -{ - struct entry *e = ep->entries + from_cblock(cblock); - return !hlist_unhashed(&e->hlist) ? e : NULL; -} - -static bool epool_empty(struct entry_pool *ep) -{ - return list_empty(&ep->free); -} - -static bool in_pool(struct entry_pool *ep, struct entry *e) -{ - return e >= ep->entries && e < ep->entries_end; -} - -static dm_cblock_t infer_cblock(struct entry_pool *ep, struct entry *e) -{ - return to_cblock(e - ep->entries); -} - -/*----------------------------------------------------------------*/ - -struct mq_policy { - struct dm_cache_policy policy; - - /* protects everything */ - struct mutex lock; - dm_cblock_t cache_size; - struct io_tracker tracker; - - /* - * Entries come from two pools, one of pre-cache entries, and one - * for the cache proper. - */ - struct entry_pool pre_cache_pool; - struct entry_pool cache_pool; - - /* - * We maintain three queues of entries. The cache proper, - * consisting of a clean and dirty queue, contains the currently - * active mappings. Whereas the pre_cache tracks blocks that - * are being hit frequently and potential candidates for promotion - * to the cache. - */ - struct queue pre_cache; - struct queue cache_clean; - struct queue cache_dirty; - - /* - * Keeps track of time, incremented by the core. We use this to - * avoid attributing multiple hits within the same tick. - * - * Access to tick_protected should be done with the spin lock held. - * It's copied to tick at the start of the map function (within the - * mutex). - */ - spinlock_t tick_lock; - unsigned tick_protected; - unsigned tick; - - /* - * A count of the number of times the map function has been called - * and found an entry in the pre_cache or cache. Currently used to - * calculate the generation. - */ - unsigned hit_count; - - /* - * A generation is a longish period that is used to trigger some - * book keeping effects. eg, decrementing hit counts on entries. - * This is needed to allow the cache to evolve as io patterns - * change. - */ - unsigned generation; - unsigned generation_period; /* in lookups (will probably change) */ - - unsigned discard_promote_adjustment; - unsigned read_promote_adjustment; - unsigned write_promote_adjustment; - - /* - * The hash table allows us to quickly find an entry by origin - * block. Both pre_cache and cache entries are in here. - */ - unsigned nr_buckets; - dm_block_t hash_bits; - struct hlist_head *table; -}; - -#define DEFAULT_DISCARD_PROMOTE_ADJUSTMENT 1 -#define DEFAULT_READ_PROMOTE_ADJUSTMENT 4 -#define DEFAULT_WRITE_PROMOTE_ADJUSTMENT 8 -#define DISCOURAGE_DEMOTING_DIRTY_THRESHOLD 128 - -/*----------------------------------------------------------------*/ - -/* - * Simple hash table implementation. Should replace with the standard hash - * table that's making its way upstream. - */ -static void hash_insert(struct mq_policy *mq, struct entry *e) -{ - unsigned h = hash_64(from_oblock(e->oblock), mq->hash_bits); - - hlist_add_head(&e->hlist, mq->table + h); -} - -static struct entry *hash_lookup(struct mq_policy *mq, dm_oblock_t oblock) -{ - unsigned h = hash_64(from_oblock(oblock), mq->hash_bits); - struct hlist_head *bucket = mq->table + h; - struct entry *e; - - hlist_for_each_entry(e, bucket, hlist) - if (e->oblock == oblock) { - hlist_del(&e->hlist); - hlist_add_head(&e->hlist, bucket); - return e; - } - - return NULL; -} - -static void hash_remove(struct entry *e) -{ - hlist_del(&e->hlist); -} - -/*----------------------------------------------------------------*/ - -static bool any_free_cblocks(struct mq_policy *mq) -{ - return !epool_empty(&mq->cache_pool); -} - -static bool any_clean_cblocks(struct mq_policy *mq) -{ - return !queue_empty(&mq->cache_clean); -} - -/*----------------------------------------------------------------*/ - -/* - * Now we get to the meat of the policy. This section deals with deciding - * when to to add entries to the pre_cache and cache, and move between - * them. - */ - -/* - * The queue level is based on the log2 of the hit count. - */ -static unsigned queue_level(struct entry *e) -{ - return min((unsigned) ilog2(e->hit_count), NR_QUEUE_LEVELS - 1u); -} - -static bool in_cache(struct mq_policy *mq, struct entry *e) -{ - return in_pool(&mq->cache_pool, e); -} - -/* - * 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); - 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"); |