On Wed, 05/07 11:06, Kevin Wolf wrote: > Am 07.05.2014 um 10:57 hat Fam Zheng geschrieben: > > On Wed, 05/07 10:20, Kevin Wolf wrote: > > > Am 07.05.2014 um 03:45 hat Fam Zheng geschrieben: > > > > On Tue, 05/06 10:32, Fam Zheng wrote: > > > > > 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> > > > > > > > > > > --- > > > > > V2: Fix cluster_offset check. (Kevin) > > > > > > > > > > Signed-off-by: Fam Zheng <f...@redhat.com> > > > > > --- > > > > > block/vmdk.c | 19 ++++++++++++++----- > > > > > 1 file changed, 14 insertions(+), 5 deletions(-) > > > > > > > > > > diff --git a/block/vmdk.c b/block/vmdk.c > > > > > index 06a1f9f..98d2d56 100644 > > > > > --- a/block/vmdk.c > > > > > +++ b/block/vmdk.c > > > > > @@ -1037,6 +1037,7 @@ static int get_cluster_offset(BlockDriverState > > > > > *bs, > > > > > int min_index, i, j; > > > > > uint32_t min_count, *l2_table; > > > > > bool zeroed = false; > > > > > + int64_t ret; > > > > > > > > > > if (m_data) { > > > > > m_data->valid = 0; > > > > > @@ -1110,12 +1111,20 @@ static int > > > > > get_cluster_offset(BlockDriverState *bs, > > > > > } > > > > > > > > > > /* Avoid the L2 tables update for the images that have > > > > > snapshots. */ > > > > > - *cluster_offset = bdrv_getlength(extent->file); > > > > > + ret = bdrv_getlength(extent->file); > > > > > + if (ret < 0 || > > > > > + ret & ((extent->cluster_sectors << BDRV_SECTOR_BITS) - > > > > > 1)) { > > > > > + return VMDK_ERROR; > > > > > + } > > > > > + *cluster_offset = ret; > > > > > 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); > > > > > > > > Hi Stefan, > > > > > > > > By considering a bdrv_write_zeroes as a pre-write, it in general > > > > doubles the > > > > write for the whole image, so it's not a good solution. > > > > > > > > A better way would be removing the bdrv_truncate and require the caller > > > > to do > > > > full cluster write (with a bounce buffer if necessary). > > > > > > Doesn't get_whole_cluster() already ensure that you already write a full > > > cluster to the image file? > > > > That one is actually called get_backing_cluster(), if you look at the code > > it > > has. :) > > Right, it doesn't do anything without a backing file. This is different > from qcow2, whose mechanism I assumed without reading the code in > detail. :-) > > I think it would make sense to rewrite get_whole_cluster() to write the > cluster for both image with a backing file and standalone images; just > that without a backing file it would use memset() to fill the buffer > instead of bdrv_read(). > > Not sure how easy it would be, but it might be an opportunity to also > change it to write only those parts of the cluster that aren't written > to anyway by the cluster. >
I think that shouldn't be hard . I'll make the change and send another patch later. Thanks, Fam