dm space maps: improve performance with inc/dec on ranges of blocks

When we break sharing on btree nodes we typically need to increment
the reference counts to every value held in the node.  This can
cause a lot of repeated calls to the space maps.  Fix this by changing
the interface to the space map inc/dec methods to take ranges of
adjacent blocks to be operated on.

For installations that are using a lot of snapshots this will reduce
cpu overhead of fundamental operations such as provisioning a new block,
or deleting a snapshot, by as much as 10 times.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 14 insertions, 4 deletions

diff --git a/drivers/md/persistent-data/dm-space-map.h b/drivers/md/persistent-data/dm-space-map.h
index 3e6d1153b7c4..a015cd11f6e9 100644
--- a/drivers/md/persistent-data/dm-space-map.h
+++ b/drivers/md/persistent-data/dm-space-map.h
@@ -46,8 +46,8 @@ struct dm_space_map {
 
 	int (*commit)(struct dm_space_map *sm);
 
-	int (*inc_block)(struct dm_space_map *sm, dm_block_t b);
-	int (*dec_block)(struct dm_space_map *sm, dm_block_t b);
+	int (*inc_blocks)(struct dm_space_map *sm, dm_block_t b, dm_block_t e);
+	int (*dec_blocks)(struct dm_space_map *sm, dm_block_t b, dm_block_t e);
 
 	/*
 	 * new_block will increment the returned block.
@@ -117,14 +117,24 @@ static inline int dm_sm_commit(struct dm_space_map *sm)
 	return sm->commit(sm);
 }
 
+static inline int dm_sm_inc_blocks(struct dm_space_map *sm, dm_block_t b, dm_block_t e)
+{
+	return sm->inc_blocks(sm, b, e);
+}
+
 static inline int dm_sm_inc_block(struct dm_space_map *sm, dm_block_t b)
 {
-	return sm->inc_block(sm, b);
+	return dm_sm_inc_blocks(sm, b, b + 1);
+}
+
+static inline int dm_sm_dec_blocks(struct dm_space_map *sm, dm_block_t b, dm_block_t e)
+{
+	return sm->dec_blocks(sm, b, e);
 }
 
 static inline int dm_sm_dec_block(struct dm_space_map *sm, dm_block_t b)
 {
-	return sm->dec_block(sm, b);
+	return dm_sm_dec_blocks(sm, b, b + 1);
 }
 
 static inline int dm_sm_new_block(struct dm_space_map *sm, dm_block_t *b)