path: root/drivers
diff options
authorMikulas Patocka <mpatocka@redhat.com>2013-09-18 19:40:42 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-10-05 07:13:11 -0700
commit0f64fad39c9577f3eaa26b45a9ad774c415c19ff (patch)
treedca9dbd1d23a57ffd79a5e60067e19b538eb19c7 /drivers
parent4541f4e356fe1d9d47165a041f85235e394b0d61 (diff)
dm-snapshot: fix performance degradation due to small hash size
commit 60e356f381954d79088d0455e357db48cfdd6857 upstream. LVM2, since version 2.02.96, creates origin with zero size, then loads the snapshot driver and then loads the origin. Consequently, the snapshot driver sees the origin size zero and sets the hash size to the lower bound 64. Such small hash table causes performance degradation. This patch changes it so that the hash size is determined by the size of snapshot volume, not minimum of origin and snapshot size. It doesn't make sense to set the snapshot size significantly larger than the origin size, so we do not need to take origin size into account when calculating the hash size. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers')
1 files changed, 2 insertions, 3 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index c434e5aab2d..aec57d76db5 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -725,17 +725,16 @@ static int calc_max_buckets(void)
static int init_hash_tables(struct dm_snapshot *s)
- sector_t hash_size, cow_dev_size, origin_dev_size, max_buckets;
+ sector_t hash_size, cow_dev_size, max_buckets;
* Calculate based on the size of the original volume or
* the COW volume...
cow_dev_size = get_dev_size(s->cow->bdev);
- origin_dev_size = get_dev_size(s->origin->bdev);
max_buckets = calc_max_buckets();
- hash_size = min(origin_dev_size, cow_dev_size) >> s->store->chunk_shift;
+ hash_size = cow_dev_size >> s->store->chunk_shift;
hash_size = min(hash_size, max_buckets);
if (hash_size < 64)