Re: [Xen-devel] [PATCH] libxl: Make 'xl vcpu-set' work properly on overcommited hosts.

[Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>]

On 09.05.2013 00:39, Konrad Rzeszutek Wilk wrote:
> > > > > Well, overcommit comes in mind. Say you migrate to a 4PCPU box and you
> > > > > have 12VCPUs, then you decide to go down to 4, then back to 16 before
> > > > > migrating it to some other box. Can't do.
> > > > You could do it *after* the migration back to a 16 way box n stead of
> > > > before though, which is most likely when you would actually want to do
> > > > it...
> > > I am kind of lost. Are we arguing for this being a bug or whether there is
> > > justification for putting in Xen 4.3?
> > The former needs deciding before the latter.
> >
> > I'm not convinced that the current xl behaviour of refusing to
> > overcommit VCPUs on a host isn't the right one for the majority of use
> > cases. Obviously the silently refusing bit is a bug which should be
> > fixed.
> >
> > I don't buy that this is a "regression compared to Xend". It's certainly
> > a difference from how xend behaved but it seems on the whole to be a
> > positive one (i.e. xend was wrong).
> CC-ing Juergen here as he added this in.
I surely didn't mean to disable overcommitting. So I'm fine with your patch
to do the cpumap allocation with maxvcpus.


Juergen

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Juergen Gross                 Principal Developer Operating Systems
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