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dm bio prison: implement per bucket locking in the dm_bio_prison hash table

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Split the single per bio-prison lock by using per bucket locking.  Per
bucket locking benefits both dm-thin and dm-cache targets by reducing
bio-prison lock contention.

Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Heinz Mauelshagen 2014-06-05 15:23:09 +01:00 committed by Mike Snitzer
parent 11f0431be2
commit adcc44472b
1 changed files with 39 additions and 27 deletions
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66
drivers/md/dm-bio-prison.c
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@ -14,13 +14,17 @@
/*----------------------------------------------------------------*/
struct dm_bio_prison {
struct bucket {
spinlock_t lock;
struct hlist_head cells;
};
struct dm_bio_prison {
mempool_t *cell_pool;
unsigned nr_buckets;
unsigned hash_mask;
struct hlist_head *cells;
struct bucket *buckets;
};
/*----------------------------------------------------------------*/
@ -40,6 +44,12 @@ static uint32_t calc_nr_buckets(unsigned nr_cells)
static struct kmem_cache *_cell_cache;
static void init_bucket(struct bucket *b)
{
spin_lock_init(&b->lock);
INIT_HLIST_HEAD(&b->cells);
}
/*
* @nr_cells should be the number of cells you want in use _concurrently_.
* Don't confuse it with the number of distinct keys.
@ -49,13 +59,12 @@ struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells)
unsigned i;
uint32_t nr_buckets = calc_nr_buckets(nr_cells);
size_t len = sizeof(struct dm_bio_prison) +
(sizeof(struct hlist_head) * nr_buckets);
(sizeof(struct bucket) * nr_buckets);
struct dm_bio_prison *prison = kmalloc(len, GFP_KERNEL);
if (!prison)
return NULL;
spin_lock_init(&prison->lock);
prison->cell_pool = mempool_create_slab_pool(nr_cells, _cell_cache);
if (!prison->cell_pool) {
kfree(prison);
@ -64,9 +73,9 @@ struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells)
prison->nr_buckets = nr_buckets;
prison->hash_mask = nr_buckets - 1;
prison->cells = (struct hlist_head *) (prison + 1);
prison->buckets = (struct bucket *) (prison + 1);
for (i = 0; i < nr_buckets; i++)
INIT_HLIST_HEAD(prison->cells + i);
init_bucket(prison->buckets + i);
return prison;
}
@ -107,40 +116,44 @@ static int keys_equal(struct dm_cell_key *lhs, struct dm_cell_key *rhs)
(lhs->block == rhs->block);
}
static struct dm_bio_prison_cell *__search_bucket(struct hlist_head *bucket,
static struct bucket *get_bucket(struct dm_bio_prison *prison,
struct dm_cell_key *key)
{
return prison->buckets + hash_key(prison, key);
}
static struct dm_bio_prison_cell *__search_bucket(struct bucket *b,
struct dm_cell_key *key)
{
struct dm_bio_prison_cell *cell;
hlist_for_each_entry(cell, bucket, list)
hlist_for_each_entry(cell, &b->cells, list)
if (keys_equal(&cell->key, key))
return cell;
return NULL;
}
static void __setup_new_cell(struct dm_bio_prison *prison,
static void __setup_new_cell(struct bucket *b,
struct dm_cell_key *key,
struct bio *holder,
uint32_t hash,
struct dm_bio_prison_cell *cell)
{
memcpy(&cell->key, key, sizeof(cell->key));
cell->holder = holder;
bio_list_init(&cell->bios);
hlist_add_head(&cell->list, prison->cells + hash);
hlist_add_head(&cell->list, &b->cells);
}
static int __bio_detain(struct dm_bio_prison *prison,
static int __bio_detain(struct bucket *b,
struct dm_cell_key *key,
struct bio *inmate,
struct dm_bio_prison_cell *cell_prealloc,
struct dm_bio_prison_cell **cell_result)
{
uint32_t hash = hash_key(prison, key);
struct dm_bio_prison_cell *cell;
cell = __search_bucket(prison->cells + hash, key);
cell = __search_bucket(b, key);
if (cell) {
if (inmate)
bio_list_add(&cell->bios, inmate);
@ -148,7 +161,7 @@ static int __bio_detain(struct dm_bio_prison *prison,
return 1;
}
__setup_new_cell(prison, key, inmate, hash, cell_prealloc);
__setup_new_cell(b, key, inmate, cell_prealloc);
*cell_result = cell_prealloc;
return 0;
}
@ -161,10 +174,11 @@ static int bio_detain(struct dm_bio_prison *prison,
{
int r;
unsigned long flags;
struct bucket *b = get_bucket(prison, key);
spin_lock_irqsave(&prison->lock, flags);
r = __bio_detain(prison, key, inmate, cell_prealloc, cell_result);
spin_unlock_irqrestore(&prison->lock, flags);
spin_lock_irqsave(&b->lock, flags);
r = __bio_detain(b, key, inmate, cell_prealloc, cell_result);
spin_unlock_irqrestore(&b->lock, flags);
return r;
}
@ -208,10 +222,11 @@ void dm_cell_release(struct dm_bio_prison *prison,
struct bio_list *bios)
{
unsigned long flags;
struct bucket *b = get_bucket(prison, &cell->key);
spin_lock_irqsave(&prison->lock, flags);
spin_lock_irqsave(&b->lock, flags);
__cell_release(cell, bios);
spin_unlock_irqrestore(&prison->lock, flags);
spin_unlock_irqrestore(&b->lock, flags);
}
EXPORT_SYMBOL_GPL(dm_cell_release);
@ -230,10 +245,11 @@ void dm_cell_release_no_holder(struct dm_bio_prison *prison,
struct bio_list *inmates)
{
unsigned long flags;
struct bucket *b = get_bucket(prison, &cell->key);
spin_lock_irqsave(&prison->lock, flags);
spin_lock_irqsave(&b->lock, flags);
__cell_release_no_holder(cell, inmates);
spin_unlock_irqrestore(&prison->lock, flags);
spin_unlock_irqrestore(&b->lock, flags);
}
EXPORT_SYMBOL_GPL(dm_cell_release_no_holder);
@ -242,13 +258,9 @@ void dm_cell_error(struct dm_bio_prison *prison,
{
struct bio_list bios;
struct bio *bio;
unsigned long flags;
bio_list_init(&bios);
spin_lock_irqsave(&prison->lock, flags);
__cell_release(cell, &bios);
spin_unlock_irqrestore(&prison->lock, flags);
dm_cell_release(prison, cell, &bios);
while ((bio = bio_list_pop(&bios)))
bio_endio(bio, error);