This patch reduces lock contention in btree walks. We modify the functions init_ro_wpin, exit_ro_spine and ro_step so that they use dm_bufio_lock_read/dm_bufio_get_unlocked/dm_bufio_unlock_read. If dm_bm_fast_get_block fails, we fallback to normal locking.
When doing tests on pmem and fully provisioned thin volume, it improves thoughput from 286MiB/s to 442MiB/s. fio --ioengine=psync --iodepth=1 --rw=randrw --bs=4k --direct=1 --numjobs=12 --time_based --runtime=10 --group_reporting --name=/dev/vg/thin before: READ: bw=286MiB/s WRITE: bw=286MiB/s after: READ: bw=442MiB/s WRITE: bw=442MiB/s Signed-off-by: Mikulas Patocka <[email protected]> --- drivers/md/persistent-data/dm-block-manager.c | 32 ++++++++++++++++ drivers/md/persistent-data/dm-block-manager.h | 6 +++ drivers/md/persistent-data/dm-btree-internal.h | 2 + drivers/md/persistent-data/dm-btree-spine.c | 39 ++++++++++++++++++-- drivers/md/persistent-data/dm-transaction-manager.c | 17 ++++++++ drivers/md/persistent-data/dm-transaction-manager.h | 6 +++ 6 files changed, 99 insertions(+), 3 deletions(-) Index: linux-2.6/drivers/md/persistent-data/dm-block-manager.c =================================================================== --- linux-2.6.orig/drivers/md/persistent-data/dm-block-manager.c 2022-10-10 11:26:03.000000000 +0200 +++ linux-2.6/drivers/md/persistent-data/dm-block-manager.c 2022-10-10 11:32:20.000000000 +0200 @@ -601,6 +601,38 @@ void dm_bm_unlock(struct dm_block *b) } EXPORT_SYMBOL_GPL(dm_bm_unlock); +void dm_bm_fast_lock(struct dm_block_manager *bm) +{ + dm_bufio_lock_read(bm->bufio); +} + +void dm_bm_fast_unlock(struct dm_block_manager *bm) +{ + dm_bufio_unlock_read(bm->bufio); +} + +int dm_bm_fast_get_block(struct dm_block_manager *bm, + dm_block_t b, struct dm_block_validator *v, + struct dm_block **result) +{ + int r; + struct buffer_aux *aux; + void *p; + + p = dm_bufio_get_unlocked(bm->bufio, b, (struct dm_buffer **) result); + if (IS_ERR(p)) + return PTR_ERR(p); + if (unlikely(!p)) + return -EWOULDBLOCK; + + aux = dm_bufio_get_aux_data(to_buffer(*result)); + r = dm_bm_validate_buffer(bm, to_buffer(*result), aux, v); + if (unlikely(r)) + return r; + + return 0; +} + int dm_bm_flush(struct dm_block_manager *bm) { if (dm_bm_is_read_only(bm)) Index: linux-2.6/drivers/md/persistent-data/dm-block-manager.h =================================================================== --- linux-2.6.orig/drivers/md/persistent-data/dm-block-manager.h 2022-10-10 11:26:03.000000000 +0200 +++ linux-2.6/drivers/md/persistent-data/dm-block-manager.h 2022-10-10 11:31:24.000000000 +0200 @@ -96,6 +96,12 @@ int dm_bm_write_lock_zero(struct dm_bloc void dm_bm_unlock(struct dm_block *b); +void dm_bm_fast_lock(struct dm_block_manager *bm); +void dm_bm_fast_unlock(struct dm_block_manager *bm); +int dm_bm_fast_get_block(struct dm_block_manager *bm, + dm_block_t b, struct dm_block_validator *v, + struct dm_block **result); + /* * It's a common idiom to have a superblock that should be committed last. * Index: linux-2.6/drivers/md/persistent-data/dm-btree-internal.h =================================================================== --- linux-2.6.orig/drivers/md/persistent-data/dm-btree-internal.h 2022-10-10 11:26:03.000000000 +0200 +++ linux-2.6/drivers/md/persistent-data/dm-btree-internal.h 2022-10-10 11:26:03.000000000 +0200 @@ -64,6 +64,8 @@ struct ro_spine { struct dm_btree_info *info; struct dm_block *node; + bool fast_locked; + bool fast_lock_failed; }; void init_ro_spine(struct ro_spine *s, struct dm_btree_info *info); Index: linux-2.6/drivers/md/persistent-data/dm-btree-spine.c =================================================================== --- linux-2.6.orig/drivers/md/persistent-data/dm-btree-spine.c 2022-10-10 11:26:03.000000000 +0200 +++ linux-2.6/drivers/md/persistent-data/dm-btree-spine.c 2022-10-10 11:38:00.000000000 +0200 @@ -118,27 +118,60 @@ void unlock_block(struct dm_btree_info * dm_tm_unlock(info->tm, b); } +static void bn_fast_lock(struct dm_btree_info *info) +{ + dm_tm_fast_lock(info->tm); +} + +static void bn_fast_unlock(struct dm_btree_info *info) +{ + dm_tm_fast_unlock(info->tm); +} + +static int bn_fast_get_block(struct dm_btree_info *info, dm_block_t b, + struct dm_block **result) +{ + return dm_tm_fast_get_block(info->tm, b, &btree_node_validator, result); +} + /*----------------------------------------------------------------*/ void init_ro_spine(struct ro_spine *s, struct dm_btree_info *info) { s->info = info; s->node = NULL; + s->fast_locked = false; + s->fast_lock_failed = false; } void exit_ro_spine(struct ro_spine *s) { - if (s->node) + if (s->fast_locked) + bn_fast_unlock(s->info); + else if (s->node) unlock_block(s->info, s->node); } int ro_step(struct ro_spine *s, dm_block_t new_child) { if (s->node) { - unlock_block(s->info, s->node); + if (unlikely(!s->fast_locked)) + unlock_block(s->info, s->node); s->node = NULL; } - + if (likely(!s->fast_lock_failed)) { + int r; + if (!s->fast_locked) { + bn_fast_lock(s->info); + s->fast_locked = true; + } + r = bn_fast_get_block(s->info, new_child, &s->node); + if (likely(!r)) + return 0; + s->fast_lock_failed = true; + s->fast_locked = false; + bn_fast_unlock(s->info); + } return bn_read_lock(s->info, new_child, &s->node); } Index: linux-2.6/drivers/md/persistent-data/dm-transaction-manager.c =================================================================== --- linux-2.6.orig/drivers/md/persistent-data/dm-transaction-manager.c 2022-10-10 11:26:03.000000000 +0200 +++ linux-2.6/drivers/md/persistent-data/dm-transaction-manager.c 2022-10-10 11:50:50.000000000 +0200 @@ -348,6 +348,23 @@ void dm_tm_unlock(struct dm_transaction_ } EXPORT_SYMBOL_GPL(dm_tm_unlock); +void dm_tm_fast_lock(struct dm_transaction_manager *tm) +{ + dm_bm_fast_lock(tm->is_clone ? tm->real->bm : tm->bm); +} + +void dm_tm_fast_unlock(struct dm_transaction_manager *tm) +{ + dm_bm_fast_unlock(tm->is_clone ? tm->real->bm : tm->bm); +} + +int dm_tm_fast_get_block(struct dm_transaction_manager *tm, dm_block_t b, + struct dm_block_validator *v, + struct dm_block **blk) +{ + return dm_bm_fast_get_block(tm->is_clone ? tm->real->bm : tm->bm, b, v, blk); +} + void dm_tm_inc(struct dm_transaction_manager *tm, dm_block_t b) { /* Index: linux-2.6/drivers/md/persistent-data/dm-transaction-manager.h =================================================================== --- linux-2.6.orig/drivers/md/persistent-data/dm-transaction-manager.h 2022-10-10 11:26:03.000000000 +0200 +++ linux-2.6/drivers/md/persistent-data/dm-transaction-manager.h 2022-10-10 11:30:17.000000000 +0200 @@ -96,6 +96,12 @@ int dm_tm_read_lock(struct dm_transactio void dm_tm_unlock(struct dm_transaction_manager *tm, struct dm_block *b); +void dm_tm_fast_lock(struct dm_transaction_manager *tm); +void dm_tm_fast_unlock(struct dm_transaction_manager *tm); +int dm_tm_fast_get_block(struct dm_transaction_manager *tm, dm_block_t b, + struct dm_block_validator *v, + struct dm_block **blk); + /* * Functions for altering the reference count of a block directly. */ -- dm-devel mailing list [email protected] https://listman.redhat.com/mailman/listinfo/dm-devel
