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authorHeinz Mauelshagen <heinzm@redhat.com>2014-06-05 15:23:09 +0100
committerMike Snitzer <snitzer@redhat.com>2014-06-11 16:48:54 -0400
commitadcc44472bacb227ebc0b1a8876efa5302474338 (patch)
tree594f3024476830cb98887266b282307cc960dd3d /drivers/md
parent11f0431be2f99c574a65c6dfc0ca205511500f29 (diff)
dm bio prison: implement per bucket locking in the dm_bio_prison hash table
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>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm-bio-prison.c66
1 files changed, 39 insertions, 27 deletions
diff --git a/drivers/md/dm-bio-prison.c b/drivers/md/dm-bio-prison.c
index 71434382cb64..f752d12081ff 100644
--- a/drivers/md/dm-bio-prison.c
+++ b/drivers/md/dm-bio-prison.c
@@ -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);