[libvirt] speeding up qemu core dumps
Daniel P. Berrange
berrange at redhat.com
Thu Aug 4 08:07:43 UTC 2011
On Wed, Aug 03, 2011 at 09:42:23PM -0600, Jim Fehlig wrote:
> Eric Blake wrote:
> > On 08/03/2011 08:37 AM, Jim Fehlig wrote:
> >> http://lists.nongnu.org/archive/html/qemu-devel/2011-02/msg01156.html
> >>
> >> I thought there were more discussions on the topic but can only find the
> >> above thread ATM.
> >>
> >> Do folks here have objections to increasing the migration speed prior to
> >> core dump? If not, any suggestions for a value? I set the migration
> >> speed to 1G in doCoreDump() prior to calling qemuMigrationToFile() with
> >> following improvement dumping a 4G guest
> >
> > Why any limit at all? When dumping to file rather than network, I
> > can't think of any justification for a default limit when targetting a
> > local drive (a particular installation may have a reasonable limit,
> > especially if the file involved happens to use a network - think
> > NFS). It seems like it would make sense to override the qemu defaults
> > and go with unlimited speed for faster dump and save operations.
>
> Agreed, 1G was just a test value, but I'm haven't yet figured out how to
> define unlimited. From libvirt json monitor connection I tried
> migrate_set_speed with INT64_MAX, but that was invalid. Using qemu
> monitor directly, I can go as high as INT64_MAX-512
>
> (qemu) migrate_set_speed 9223372036854775295B
> (qemu) migrate_set_speed 9223372036854775296B
> invalid size
>
> Any hints on proper way to set unlimited migration speed?
The code doesn't seem to have a way to set a truely unlimited rate,
but even INT64_MAX / 2 would be more than sufficient for us to max
out the host OS storage throughput
Daniel
--
|: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org -o- http://virt-manager.org :|
|: http://autobuild.org -o- http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
More information about the libvir-list
mailing list