Am 18.04.2014 um 14:39 hat Fam Zheng geschrieben: > 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> > --- > 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)));
Are you sure that this is what you wanted to assert? cluster_offset is in bytes, whereas extent->cluster_sectors is in sectors. I think the assertion holds true, but might be weaker than what you intended to assert (that the offset is on a cluster boundary). Kevin > 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 >