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block: Change bdrv_commit to handle multiple sectors at once 

bdrv_commit copies the image to its backing file sector by sector, which
is (surprise!) relatively slow. Let's take a larger buffer and handle more
sectors at once if possible.

With a 1G qcow2 file, this brought the time bdrv_commit takes down from
5:06 min to 1:14 min for me.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2010-07-16 17:17:01 +02:00
parent 5933e8a96a
commit 8a4266144e
1 changed files with 19 additions and 18 deletions
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37
block.c
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@ -739,14 +739,16 @@ int bdrv_check(BlockDriverState *bs, BdrvCheckResult *res)
return bs->drv->bdrv_check(bs, res);
}
#define COMMIT_BUF_SECTORS 2048
/* commit COW file into the raw image */
int bdrv_commit(BlockDriverState *bs)
{
BlockDriver *drv = bs->drv;
int64_t i, total_sectors;
int n, j, ro, open_flags;
int64_t sector, total_sectors;
int n, ro, open_flags;
int ret = 0, rw_ret = 0;
unsigned char sector[BDRV_SECTOR_SIZE];
uint8_t *buf;
char filename[1024];
BlockDriverState *bs_rw, *bs_ro;
@ -789,22 +791,20 @@ int bdrv_commit(BlockDriverState *bs)
}
total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
for (i = 0; i < total_sectors;) {
if (drv->bdrv_is_allocated(bs, i, 65536, &n)) {
for(j = 0; j < n; j++) {
if (bdrv_read(bs, i, sector, 1) != 0) {
ret = -EIO;
goto ro_cleanup;
}
buf = qemu_malloc(COMMIT_BUF_SECTORS * BDRV_SECTOR_SIZE);
if (bdrv_write(bs->backing_hd, i, sector, 1) != 0) {
ret = -EIO;
goto ro_cleanup;
}
i++;
}
} else {
i += n;
for (sector = 0; sector < total_sectors; sector += n) {
if (drv->bdrv_is_allocated(bs, sector, COMMIT_BUF_SECTORS, &n)) {
if (bdrv_read(bs, sector, buf, n) != 0) {
ret = -EIO;
goto ro_cleanup;
}
if (bdrv_write(bs->backing_hd, sector, buf, n) != 0) {
ret = -EIO;
goto ro_cleanup;
}
}
}
@ -821,6 +821,7 @@ int bdrv_commit(BlockDriverState *bs)
bdrv_flush(bs->backing_hd);
ro_cleanup:
qemu_free(buf);
if (ro) {
/* re-open as RO */