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dm bufio: prepare to intelligently size dm_buffer_cache's buffer_trees 

Add num_locks member to dm_buffer_cache struct and use it rather than
the NR_LOCKS magic value (64).

Next commit will size the dm_buffer_cache's buffer_trees according to
dm_num_hash_locks().

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
This commit is contained in:
Mike Snitzer 2023-03-27 14:09:45 -04:00
parent 0bac3f2f28
commit 36c18b8639
1 changed files with 26 additions and 22 deletions
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48
drivers/md/dm-bufio.c
View File

@ -380,7 +380,6 @@ struct dm_buffer {
*/
#define NR_LOCKS 64
#define LOCKS_MASK (NR_LOCKS - 1)
struct buffer_tree {
struct rw_semaphore lock;
@ -388,37 +387,38 @@ struct buffer_tree {
} ____cacheline_aligned_in_smp;
struct dm_buffer_cache {
struct lru lru[LIST_SIZE];
/*
* We spread entries across multiple trees to reduce contention
* on the locks.
*/
unsigned int num_locks;
struct buffer_tree trees[NR_LOCKS];
struct lru lru[LIST_SIZE];
};
static inline unsigned int cache_index(sector_t block)
static inline unsigned int cache_index(sector_t block, unsigned int num_locks)
{
return block & LOCKS_MASK;
return block & (num_locks - 1);
}
static inline void cache_read_lock(struct dm_buffer_cache *bc, sector_t block)
{
down_read(&bc->trees[cache_index(block)].lock);
down_read(&bc->trees[cache_index(block, bc->num_locks)].lock);
}
static inline void cache_read_unlock(struct dm_buffer_cache *bc, sector_t block)
{
up_read(&bc->trees[cache_index(block)].lock);
up_read(&bc->trees[cache_index(block, bc->num_locks)].lock);
}
static inline void cache_write_lock(struct dm_buffer_cache *bc, sector_t block)
{
down_write(&bc->trees[cache_index(block)].lock);
down_write(&bc->trees[cache_index(block, bc->num_locks)].lock);
}
static inline void cache_write_unlock(struct dm_buffer_cache *bc, sector_t block)
{
up_write(&bc->trees[cache_index(block)].lock);
up_write(&bc->trees[cache_index(block, bc->num_locks)].lock);
}
/*
@ -429,13 +429,15 @@ struct lock_history {
struct dm_buffer_cache *cache;
bool write;
unsigned int previous;
unsigned int no_previous;
};
static void lh_init(struct lock_history *lh, struct dm_buffer_cache *cache, bool write)
{
lh->cache = cache;
lh->write = write;
lh->previous = NR_LOCKS; /* indicates no previous */
lh->no_previous = cache->num_locks;
lh->previous = lh->no_previous;
}
static void __lh_lock(struct lock_history *lh, unsigned int index)
@ -459,9 +461,9 @@ static void __lh_unlock(struct lock_history *lh, unsigned int index)
*/
static void lh_exit(struct lock_history *lh)
{
if (lh->previous != NR_LOCKS) {
if (lh->previous != lh->no_previous) {
__lh_unlock(lh, lh->previous);
lh->previous = NR_LOCKS;
lh->previous = lh->no_previous;
}
}
@ -471,9 +473,9 @@ static void lh_exit(struct lock_history *lh)
*/
static void lh_next(struct lock_history *lh, sector_t b)
{
unsigned int index = cache_index(b);
unsigned int index = cache_index(b, lh->no_previous); /* no_previous is num_locks */
if (lh->previous != NR_LOCKS) {
if (lh->previous != lh->no_previous) {
if (lh->previous != index) {
__lh_unlock(lh, lh->previous);
__lh_lock(lh, index);
@ -500,11 +502,13 @@ static struct dm_buffer *list_to_buffer(struct list_head *l)
return le_to_buffer(le);
}
static void cache_init(struct dm_buffer_cache *bc)
static void cache_init(struct dm_buffer_cache *bc, unsigned int num_locks)
{
unsigned int i;
for (i = 0; i < NR_LOCKS; i++) {
bc->num_locks = num_locks;
for (i = 0; i < bc->num_locks; i++) {
init_rwsem(&bc->trees[i].lock);
bc->trees[i].root = RB_ROOT;
}
@ -517,7 +521,7 @@ static void cache_destroy(struct dm_buffer_cache *bc)
{
unsigned int i;
for (i = 0; i < NR_LOCKS; i++)
for (i = 0; i < bc->num_locks; i++)
WARN_ON_ONCE(!RB_EMPTY_ROOT(&bc->trees[i].root));
lru_destroy(&bc->lru[LIST_CLEAN]);
@ -576,7 +580,7 @@ static struct dm_buffer *cache_get(struct dm_buffer_cache *bc, sector_t block)
struct dm_buffer *b;
cache_read_lock(bc, block);
b = __cache_get(&bc->trees[cache_index(block)].root, block);
b = __cache_get(&bc->trees[cache_index(block, bc->num_locks)].root, block);
if (b) {
lru_reference(&b->lru);
__cache_inc_buffer(b);
@ -650,7 +654,7 @@ static struct dm_buffer *__cache_evict(struct dm_buffer_cache *bc, int list_mode
b = le_to_buffer(le);
/* __evict_pred will have locked the appropriate tree. */
rb_erase(&b->node, &bc->trees[cache_index(b->block)].root);
rb_erase(&b->node, &bc->trees[cache_index(b->block, bc->num_locks)].root);
return b;
}
@ -816,7 +820,7 @@ static bool cache_insert(struct dm_buffer_cache *bc, struct dm_buffer *b)
cache_write_lock(bc, b->block);
BUG_ON(atomic_read(&b->hold_count) != 1);
r = __cache_insert(&bc->trees[cache_index(b->block)].root, b);
r = __cache_insert(&bc->trees[cache_index(b->block, bc->num_locks)].root, b);
if (r)
lru_insert(&bc->lru[b->list_mode], &b->lru);
cache_write_unlock(bc, b->block);
@ -842,7 +846,7 @@ static bool cache_remove(struct dm_buffer_cache *bc, struct dm_buffer *b)
r = false;
} else {
r = true;
rb_erase(&b->node, &bc->trees[cache_index(b->block)].root);
rb_erase(&b->node, &bc->trees[cache_index(b->block, bc->num_locks)].root);
lru_remove(&bc->lru[b->list_mode], &b->lru);
}
@ -911,7 +915,7 @@ static void cache_remove_range(struct dm_buffer_cache *bc,
{
unsigned int i;
for (i = 0; i < NR_LOCKS; i++) {
for (i = 0; i < bc->num_locks; i++) {
down_write(&bc->trees[i].lock);
__remove_range(bc, &bc->trees[i].root, begin, end, pred, release);
up_write(&bc->trees[i].lock);
@ -2432,7 +2436,7 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign
r = -ENOMEM;
goto bad_client;
}
cache_init(&c->cache);
cache_init(&c->cache, NR_LOCKS);
c->bdev = bdev;
c->block_size = block_size;