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[Qemu-devel] [PATCH] vmdk: Optimize cluster allocation
From: |
Fam Zheng |
Subject: |
[Qemu-devel] [PATCH] vmdk: Optimize cluster allocation |
Date: |
Fri, 18 Apr 2014 20:39:00 +0800 |
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 <address@hidden>
---
block/vmdk.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/block/vmdk.c b/block/vmdk.c
index b69988d..b829265 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1036,6 +1036,7 @@ static int get_cluster_offset(BlockDriverState *bs,
int min_index, i, j;
uint32_t min_count, *l2_table;
bool zeroed = false;
+ int ret;
if (m_data) {
m_data->valid = 0;
@@ -1110,11 +1111,15 @@ static int get_cluster_offset(BlockDriverState *bs,
/* Avoid the L2 tables update for the images that have snapshots. */
*cluster_offset = bdrv_getlength(extent->file);
+ assert(0 == (*cluster_offset & (extent->cluster_sectors - 1)));
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
- [Qemu-devel] [PATCH] vmdk: Optimize cluster allocation,
Fam Zheng <=