Re: [Qemu-devel] [PATCH 2/2] migration: Dynamic cpu throttling for auto-converge

[Eric Blake <eblake@redhat.com>]

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On 06/02/2015 08:37 AM, Jason J. Herne wrote:
>>
>> Well, one thing you can do is add a parameter with a name starting
>> with x-
>> which means it's not a fixed interface (so things like libvirt wont
>> use it).
>> And the reason I was interested in seeing the information was otherwise
>> we don't really have any way of knowing how well the code is working;
>> is it already throttling down more and more?
>>
> 
> Fair point. Can we add a qmp/hmp command like "info x-cpu-throttle"? Or a
> new line in "info migrate" output, "x-throttle-ration:  1.0" perhaps?
> Would this mess up libvirt's parsing of the hmp/qmp data?

Libvirt doesn't parse HMP data, and when parsing QMP data it gracefully
ignores any fields it doesn't recognize (especially fields beginning
with 'x-') (and if not, that's a bug to be fixed in libvirt).  The QMP
protocol even documents that clients MUST be prepared for new keys to
appear in output.  So this proposal should not cause any grief.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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