From adcc44472bacb227ebc0b1a8876efa5302474338 Mon Sep 17 00:00:00 2001 From: Heinz Mauelshagen Date: Thu, 5 Jun 2014 15:23:09 +0100 Subject: [PATCH] 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 Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer --- drivers/md/dm-bio-prison.c | 66 ++++++++++++++++++++++---------------- 1 file 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); -- 2.20.1