[libvirt] [RFC] libvirt support multi-thread compression for live migration

[Jiri Denemark]

On Tue, Jun 02, 2015 at 11:02:27 -0600, Eric Blake wrote:
> On 06/02/2015 07:56 AM, Qiao, Liyong wrote:
> > Hi Eric
> > Thanks for replying the mail, replied in lines.
> > 
> 
> >> +virdomainMigrateGetParameters(virDomainPtr domain,
> >> +                                  int *level,
> >> +                                  int *threads,
> >> +                                  int *dthreads,
> >> +                                  int flags)
> >> +
> > 
> > I'd rather we used virTypedParameters, to make it easier to use the same API to pass ALL future possible tuning parameters, rather than just hard-coding to only the parameters of this one feature.
> > 
> > Okay ,that sound good, but if virTypedParameters can be passed to qemu_driver such as qemu_monitor_json.c qemu_monitor_text.c ?
> 
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> Use existing API for a guide - for example, virDomainSetBlockIoTune
> takes virTypedParamters, as well as defines a specific set of parameters
> that it will understand.

And do we actually need to changed these migration parameters on the fly
when migration is already running. I can imagine we would need to do so
for some parameters but multithreaded compression sounds like something
that needs to be configured when migration starts and there's nothing to
be tuned on the fly. If this is the case, I think we should just add
these new parameters to virDomainMigrate3 instead of requiring another
API to be called to actually configure multithreaded compression.

The separate API makes it a bit harder to repeat migration (which
previously failed) with a different parameters (e.g., without
multithreaded compression).

Jirka