On 14/01/15 20:56, Roman Kagan wrote:
On Tue, Dec 30, 2014 at 01:07:12PM +0300, Denis V. Lunev wrote:
Plain image expansion spends a lot of time to update image file size.
This seriously affects the performance. The following simple test
qemu_img create -f parallels -o cluster_size=64k ./1.hds 64G
qemu_io -n -c "write -P 0x11 0 1024M" ./1.hds
could be improved if the format driver will pre-allocate some space
in the image file with a reasonable chunk.
This patch preallocates 128 Mb using bdrv_write_zeroes, which should
normally use fallocate() call inside. Fallback to older truncate()
could be used as a fallback using image open options thanks to the
previous patch.
The benefit is around 15%.
This patch is final in this series. Block driver has near native
performance now.
Signed-off-by: Denis V. Lunev <d...@openvz.org>
CC: Kevin Wolf <kw...@redhat.com>
CC: Stefan Hajnoczi <stefa...@redhat.com>
---
block/parallels.c | 35 +++++++++++++++++++++++++++++++++--
1 file changed, 33 insertions(+), 2 deletions(-)
diff --git a/block/parallels.c b/block/parallels.c
index 12a9cea..5ec4a0d 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -82,6 +82,7 @@ typedef struct BDRVParallelsState {
int bat_cache_off;
int data_off;
+ int64_t prealloc_off;
This field name confused me. I think "data_end" would fit better.
Otherwise looks good to me.
Roman.
agree
