<div dir="ltr">Thanks</div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Feb 2, 2015 at 4:09 AM, Daniel P. Berrange <span dir="ltr"><<a href="mailto:berrange@redhat.com" target="_blank">berrange@redhat.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">On Sun, Feb 01, 2015 at 03:03:45PM -0700, David Medberry wrote:<br>
> I'll second much of what Rob said:<br>
> API that indicated how many live-migrations (l-m) were going would be good.<br>
> API that told you what progress (and start time) a given l-m had made would<br>
> be great.<br>
> API to cancel a given l-m would also be great. I think this is a preferred<br>
> approach over an auto timeout (it would give us the tools we need to<br>
> implement an auto timeout though.)<br>
><br>
> I like the idea of trying auto-convergence (and agree it should be flavor<br>
> feature and likely not the default.) I suspect this one needs some testing.<br>
> It may be fine to automatically do this if it doesn't actually throttle the<br>
> VM some 90-99% of the time. (Presumably this could also increase the max<br>
> downtime between cutover as well as throttling the vm.)<br>
<br>
</span>For reference the auto-convergance code in QEMU is this commit<br>
<br>
<a href="http://git.qemu.org/?p=qemu.git;a=commit;h=7ca1dfad952d8a8655b32e78623edcc38a51b14a" target="_blank">http://git.qemu.org/?p=qemu.git;a=commit;h=7ca1dfad952d8a8655b32e78623edcc38a51b14a</a><br>
<br>
If the migration operation is making good progress, it does not have any<br>
impact on the guest. Periodically it checks the data transfer progress and<br>
if the guest has dirtied more than 50% of the pages than were transferred<br>
it'll start throttling. It throttles by simplying preventing the guest<br>
vCPUs from running for a period of time. So the guest will obviously get<br>
a performance drop, but the migration is more likely (but not guaranteed)<br>
to succeed.<br>
<br>
>From the QEMU level you can actually enable this on the fly it seems, but<br>
libvirt only lets it be set at startup of migration.<br>
<div class="HOEnZb"><div class="h5"><br>
Regards,<br>
Daniel<br>
--<br>
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</div></div></blockquote></div><br></div>