[libvirt] PING: [RFC] vhost-user + shared memory + NUMA

Pavel Fedin p.fedin at samsung.com
Mon Feb 15 13:38:51 UTC 2016


 Hello! Sorry, but i did not get any answer to the last question. Would it be OK to require <memoryBacking> and implicitly add only
shared mode ?

Kind regards,
Pavel Fedin
Senior Engineer
Samsung Electronics Research center Russia


> -----Original Message-----
> From: libvir-list-bounces at redhat.com [mailto:libvir-list-bounces at redhat.com] On Behalf Of
> Pavel Fedin
> Sent: Thursday, February 11, 2016 5:36 PM
> To: 'Daniel P. Berrange'
> Cc: 'Libvirt'
> Subject: Re: [libvirt] [RFC] vhost-user + shared memory + NUMA
> 
>  Hello!
> 
> > >  Ok, then would it be a good compromise if we require <memoryBacking>, and only
> implicitly
> > add "shared" if we have vhost-user
> > > devices? This way we would not change the way the guest memory is allocated.
> >
> > Adding shared implicitly *will* change the way guest memory is allocated,
> > as it will have to use tmpfs to make it shared.
> 
>  You perhaps didn't get my idea. I meant - we will still need to specify <memoryBacking> with
> huge pages, just no <numa>. Therefore, the memory will be allocated via file backend from
> hugetlbfs. Only mode will be changed implicitly (private -> shared).
> 
> > >  IMHO being able to manually specify "shared" both in <numa> and
> > > in <memoryBacking> would be ambiguous.
> >
> > That's not really any different to what we have already with NUMA.
> > The top level setting would apply as the default, and the NUMA level
> > settings override it if needed.
> 
>  Well, the only little drawback would be necessity to add "shared" by itself. This would
> require additional patching to clients (e. g. openstack).
> 
> Kind regards,
> Pavel Fedin
> Senior Engineer
> Samsung Electronics Research center Russia
> 
> 
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