Re: [PATCH v3 0/9] block: cheaper zero handling in backup and commit

[Eric Blake <eblake@redhat.com>]

On Mon, Oct 05, 2026 at 10:59:11AM +0200, Denis V. Lunev wrote:
> On 9/29/26 17:51, Denis V. Lunev wrote:
> > This email originated from an IP that might not be authorized by the domain it was sent from.
> > Do not click links or open attachments unless it is an email you expected to receive.
> > Backup and commit re-query the source block status for every task and
> > size a task by the copy buffer, so a long run of zeroes turns into a
> > crowd of small write-zeroes requests. This series reuses what the
> > up-front scan already learned and lets one write-zeroes task cover a
> > whole run.
> >
> > Backup of a 16G qcow2 image holding 1G of data, the rest never
> > allocated, sync=full to a raw target on ext4:
> >
> >                tasks    time
> >     before     16384    1.6s
> >     after       1088    1.0s
> >
> > Such an image is the normal case rather than a corner one: a guest with
> > discard enabled on a disk which is mostly free leaves exactly this
> > shape behind.

> ping

It looks like this series is fully reviewed; I also took a look at it
and didn't spot anything to add. I plan on queueing into a pull
request shortly.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization:  qemu.org | libguestfs.org