Re: [Xen-devel] [PATCH v2 12/16] libxl: get and set soft affinity

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On ven, 2013-11-15 at 12:02 +0000, George Dunlap wrote:
> On 14/11/13 16:25, Ian Jackson wrote:
> > Maybe it is a bug that it doesn't do anything.  I think it depends how
> > we expect people to use this.  If a caller sets the hard affinities
> > and then changes the cpupool, are they supposed to always then set the
> > hard affinities again to a new suitable value ?
> 
> Well in fact, as far as I can tell, it *does* do something.  When moving 
> a vcpu to a new pool, it unconditionally calls 
> cpumask_setall(v->cpu_affinity) for each vcpu, which will effectively 
> erase the hard affinity. (xen/common/schedule.c:sched_move_domain()).
> 
> And, when unplugging cpus, if it unplugs the last cpu a vcpu can run on, 
> it also resets the affinity to "all".
> 
Right. But this all happens in hypervisor level and, personally, I think
it's just fine.

The point here is how we should behave and what kind of interface we
should have/add at the libxl level. My opinion here is that, while it is
ok to have calls that deals with both hard and soft affinity together,
we should leave cpupool alone, as it is too different of both a concept
and of an interface.

Thanks and Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
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Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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