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, 10 deletions

diff --git a/drivers/md/dm-era-target.c b/drivers/md/dm-era-target.c
index d9ac7372108c..3b748393fca5 100644
--- a/drivers/md/dm-era-target.c
+++ b/drivers/md/dm-era-target.c
@@ -363,28 +363,32 @@ static void ws_unpack(const struct writeset_disk *disk, struct writeset_metadata
 	core->root = le64_to_cpu(disk->root);
 }
 
-static void ws_inc(void *context, const void *value)
+static void ws_inc(void *context, const void *value, unsigned count)
 {
 	struct era_metadata *md = context;
 	struct writeset_disk ws_d;
 	dm_block_t b;
+	unsigned i;
 
-	memcpy(&ws_d, value, sizeof(ws_d));
-	b = le64_to_cpu(ws_d.root);
-
-	dm_tm_inc(md->tm, b);
+	for (i = 0; i < count; i++) {
+		memcpy(&ws_d, value + (i * sizeof(ws_d)), sizeof(ws_d));
+		b = le64_to_cpu(ws_d.root);
+		dm_tm_inc(md->tm, b);
+	}
 }
 
-static void ws_dec(void *context, const void *value)
+static void ws_dec(void *context, const void *value, unsigned count)
 {
 	struct era_metadata *md = context;
 	struct writeset_disk ws_d;
 	dm_block_t b;
+	unsigned i;
 
-	memcpy(&ws_d, value, sizeof(ws_d));
-	b = le64_to_cpu(ws_d.root);
-
-	dm_bitset_del(&md->bitset_info, b);
+	for (i = 0; i < count; i++) {
+		memcpy(&ws_d, value + (i * sizeof(ws_d)), sizeof(ws_d));
+		b = le64_to_cpu(ws_d.root);
+		dm_bitset_del(&md->bitset_info, b);
+	}
 }
 
 static int ws_eq(void *context, const void *value1, const void *value2)