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block: do not allocate an iovec per read of a growable/zero_after_eof BDS 

Most reads do not go past the end of the file, and they can use the
input QEMUIOVector instead of creating one.  This removes the
qemu_iovec_* functions from the profile.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Paolo Bonzini 2014-12-17 16:09:59 +01:00 committed by Stefan Hajnoczi
parent fcf5def1ab
commit e012b78cf5
1 changed files with 5 additions and 7 deletions
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12
block.c
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@ -3034,18 +3034,16 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs,
max_nb_sectors = ROUND_UP(MAX(0, total_sectors - sector_num),
align >> BDRV_SECTOR_BITS);
if (max_nb_sectors > 0) {
if (nb_sectors < max_nb_sectors) {
ret = drv->bdrv_co_readv(bs, sector_num, nb_sectors, qiov);
} else if (max_nb_sectors > 0) {
QEMUIOVector local_qiov;
size_t local_sectors;
max_nb_sectors = MIN(max_nb_sectors, SIZE_MAX / BDRV_SECTOR_BITS);
local_sectors = MIN(max_nb_sectors, nb_sectors);
qemu_iovec_init(&local_qiov, qiov->niov);
qemu_iovec_concat(&local_qiov, qiov, 0,
local_sectors * BDRV_SECTOR_SIZE);
max_nb_sectors * BDRV_SECTOR_SIZE);
ret = drv->bdrv_co_readv(bs, sector_num, local_sectors,
ret = drv->bdrv_co_readv(bs, sector_num, max_nb_sectors,
&local_qiov);
qemu_iovec_destroy(&local_qiov);