Thanks On Mon, Feb 2, 2015 at 4:09 AM, Daniel P. Berrange <berra...@redhat.com> wrote:
> On Sun, Feb 01, 2015 at 03:03:45PM -0700, David Medberry wrote: > > I'll second much of what Rob said: > > API that indicated how many live-migrations (l-m) were going would be > good. > > API that told you what progress (and start time) a given l-m had made > would > > be great. > > API to cancel a given l-m would also be great. I think this is a > preferred > > approach over an auto timeout (it would give us the tools we need to > > implement an auto timeout though.) > > > > I like the idea of trying auto-convergence (and agree it should be flavor > > feature and likely not the default.) I suspect this one needs some > testing. > > It may be fine to automatically do this if it doesn't actually throttle > the > > VM some 90-99% of the time. (Presumably this could also increase the max > > downtime between cutover as well as throttling the vm.) > > For reference the auto-convergance code in QEMU is this commit > > > http://git.qemu.org/?p=qemu.git;a=commit;h=7ca1dfad952d8a8655b32e78623edcc38a51b14a > > If the migration operation is making good progress, it does not have any > impact on the guest. Periodically it checks the data transfer progress and > if the guest has dirtied more than 50% of the pages than were transferred > it'll start throttling. It throttles by simplying preventing the guest > vCPUs from running for a period of time. So the guest will obviously get > a performance drop, but the migration is more likely (but not guaranteed) > to succeed. > > From the QEMU level you can actually enable this on the fly it seems, but > libvirt only lets it be set at startup of migration. > > Regards, > 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 > :| >
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