[libvirt] [PATCH V2] Set qemu migration speed unlimited when migrating to file

[Eric Blake]

On 08/04/2011 12:41 PM, Jim Fehlig wrote:
>
> Yeah, I debated about whether to even add this hunk, but was considering
> 'virsh dump --live ...' where the  process still exists and could
> potentially be migrated to another host later.

Oh, I forgot about that.  I guess we do have a case where migration to 
file does not imply the death of the qemu process.

>
>>
>> Meanwhile, it raises independent issues - why do we have a write-only
>> interface in virDomainMigrateSetMaxSpeed?  Shouldn't we also be able
>> to query the speed currently in use, and shouldn't the domain XML
>> track the current migration speed?
>
> AFAICT, qemu doesn't provide a way to query the speed.  The monitor
> would need this addition before we could plumb it in libvirt.

Not necessarily true.  If we track it in the domain xml, then libvirt 
can update that xml any time it makes a change, and set qemu to match 
the xml any time that it is changed or qemu started, and answer queries 
from the xml rather than by querying the monitor.

> How would you like to proceed?

Are you in the mood to add virDomainMigrateGetMaxSpeed and the XML 
change necessary to track it?  If so, then I'd favor tackling that 
first, at which point we'll have answered our questions about what speed 
to restore here.

I would even be okay with pushing this patch first (with the tweak of 
adding a #define for the 32<<20 magic number), if you can get more 
feedback from others agreeing on the points raised here; cleaning things 
up to restore the saved value rather than the default value would be an 
appropriate part of the series adding the ability to track the saved value.

-- 
Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org