> Alexandre Derumier via pve-devel <pve-devel@lists.proxmox.com> hat am
> 04.07.2025 08:44 CEST geschrieben:
> and use it for plugin linked clone
>
> This also enable extended_l2=on, as it's mandatory for backing file
> preallocation.
>
> Preallocation was missing previously, so it should increase performance
> for linked clone now (around x5 in randwrite 4k)
>
> cluster_size is set to 128k, as it reduce qcow2 overhead (reduce disk,
> but also memory needed to cache metadatas)
should we make this configurable?
> l2_extended is not enabled yet on base image, but it could help too
> to reduce overhead without impacting performance
>
> bench on 100G qcow2 file:
>
> fio --filename=/dev/sdb --direct=1 --rw=randwrite --bs=4k --iodepth=32
> --ioengine=libaio --name=test
> fio --filename=/dev/sdb --direct=1 --rw=randread --bs=4k --iodepth=32
> --ioengine=libaio --name=test
>
> base image:
>
> randwrite 4k: prealloc=metadata, l2_extended=off, cluster_size=64k: 20215
> randread 4k: prealloc=metadata, l2_extended=off, cluster_size=64k: 22219
> randwrite 4k: prealloc=metadata, l2_extended=on, cluster_size=64k: 20217
> randread 4k: prealloc=metadata, l2_extended=on, cluster_size=64k: 21742
> randwrite 4k: prealloc=metadata, l2_extended=on, cluster_size=128k: 21599
> randread 4k: prealloc=metadata, l2_extended=on, cluster_size=128k: 22037
>
> clone image with backing file:
>
> randwrite 4k: prealloc=metadata, l2_extended=off, cluster_size=64k: 3912
> randread 4k: prealloc=metadata, l2_extended=off, cluster_size=64k: 21476
> randwrite 4k: prealloc=metadata, l2_extended=on, cluster_size=64k: 20563
> randread 4k: prealloc=metadata, l2_extended=on, cluster_size=64k: 22265
> randwrite 4k: prealloc=metadata, l2_extended=on, cluster_size=128k: 18016
> randread 4k: prealloc=metadata, l2_extended=on, cluster_size=128k: 21611
>
> Signed-off-by: Alexandre Derumier <alexandre.derum...@groupe-cyllene.com>
> ---
> src/PVE/Storage/Common.pm | 17 +++++++++++++----
> src/PVE/Storage/Plugin.pm | 17 +++--------------
> 2 files changed, 16 insertions(+), 18 deletions(-)
>
> diff --git a/src/PVE/Storage/Common.pm b/src/PVE/Storage/Common.pm
> index 29f2e52..78e5320 100644
> --- a/src/PVE/Storage/Common.pm
> +++ b/src/PVE/Storage/Common.pm
> @@ -150,14 +150,23 @@ sub preallocation_cmd_option {
> }
>
> sub qemu_img_create {
> - my ($scfg, $fmt, $size, $path) = @_;
> + my ($scfg, $fmt, $size, $path, $backing_path) = @_;
> +
> + die "size can't be specified if backing file is used" if $size &&
> $backing_path;
should we assert that $backing_path is only used with $fmt eq 'qcow2'?
>
> my $cmd = ['/usr/bin/qemu-img', 'create'];
>
> - my $prealloc_opt = preallocation_cmd_option($scfg, $fmt);
> - push @$cmd, '-o', $prealloc_opt if defined($prealloc_opt);
> + my $options = [];
> +
> + if ($backing_path) {
> + push @$cmd, '-b', $backing_path, '-F', 'qcow2';
and then use $fmt here as well?
> + push @$options, 'extended_l2=on', 'cluster_size=128k';
> + }
>
> - push @$cmd, '-f', $fmt, $path, "${size}K";
> + push @$options, preallocation_cmd_option($scfg, $fmt);
> + push @$cmd, '-o', join(',', @$options) if @$options > 0;
> + push @$cmd, '-f', $fmt, $path;
> + push @$cmd, "${size}K" if $size;
>
> run_command($cmd, errmsg => "unable to create image");
> }
> diff --git a/src/PVE/Storage/Plugin.pm b/src/PVE/Storage/Plugin.pm
> index 80bb077..c35d5e5 100644
> --- a/src/PVE/Storage/Plugin.pm
> +++ b/src/PVE/Storage/Plugin.pm
> @@ -880,20 +880,9 @@ sub clone_image {
> # Note: we use relative paths, so we need to call chdir before qemu-img
> eval {
> local $CWD = $imagedir;
> -
> - my $cmd = [
> - '/usr/bin/qemu-img',
> - 'create',
> - '-b',
> - "../$basevmid/$basename",
> - '-F',
> - $format,
> - '-f',
> - 'qcow2',
> - $path,
> - ];
> -
> - run_command($cmd);
> + PVE::Storage::Common::qemu_img_create(
> + $scfg, $format, undef, $path, "../$basevmid/$basename",
> + );
> };
> my $err = $@;
>
> --
> 2.39.5
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