Re: [Qemu-devel] [v3 12/13] migration: Add command to set migration parameter

[Eric Blake]

On 01/23/2015 06:48 AM, Dr. David Alan Gilbert wrote:
> * Liang Li (address@hidden) wrote:
>> Add the qmp and hmp commands to tune the parameters used in live
>> migration.
> 
> If I understand correctly on the destination side we need to set the number of
> decompression threads very early on an incoming migration - I'm not
> clear how early that needs to be - especially if you're using fd: so it's
> not waiting for a connect ?
> 
> Eric: How would libvirt do that?

Libvirt does some handshaking before starting migration.  The source
would advertise that "I'm capable of threaded migration; and plan to use
X send and Y receive threads"; the destination would either reply that
threads are unsupported or set the receive thread count at that point,
then the source would know if it can enable threads and set the send
thread count, before letting migration start.  I don't see any problems
with the current design of starting things up.

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

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