On mounted NFS filesystem, ftruncate is much much slower than doing a
zero write. Changing this significantly speeds up cluster allocation.
Comparing by converting a cirros image (296M) to VMDK on an NFS mount
point, over 1Gbe LAN:
$ time qemu-img convert cirros-0.3.1.img /mnt/a.raw -O vmdk
Before:
real 0m26.464s
user 0m0.133s
sys 0m0.527s
After:
real 0m2.120s
user 0m0.080s
sys 0m0.197s
Signed-off-by: Fam Zheng <f...@redhat.com>
---
V2: Fix cluster_offset check. (Kevin)
Signed-off-by: Fam Zheng <f...@redhat.com>
---
block/vmdk.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/block/vmdk.c b/block/vmdk.c
index 06a1f9f..98d2d56 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1037,6 +1037,7 @@ static int get_cluster_offset(BlockDriverState *bs,
int min_index, i, j;
uint32_t min_count, *l2_table;
bool zeroed = false;
+ int64_t ret;
if (m_data) {
m_data->valid = 0;
@@ -1110,12 +1111,20 @@ static int get_cluster_offset(BlockDriverState *bs,
}
/* Avoid the L2 tables update for the images that have snapshots. */
- *cluster_offset = bdrv_getlength(extent->file);
+ ret = bdrv_getlength(extent->file);
+ if (ret < 0 ||
+ ret & ((extent->cluster_sectors << BDRV_SECTOR_BITS) - 1)) {
+ return VMDK_ERROR;
+ }
+ *cluster_offset = ret;
if (!extent->compressed) {
- bdrv_truncate(
- extent->file,
- *cluster_offset + (extent->cluster_sectors << 9)
- );
+ ret = bdrv_write_zeroes(extent->file,
+ *cluster_offset >> BDRV_SECTOR_BITS,
+ extent->cluster_sectors,
+ 0);
+ if (ret) {
+ return VMDK_ERROR;
+ }
}
*cluster_offset >>= 9;
--
1.9.2
