[libvirt] [PATCH] add flag to enforce hugepage backing of guest RAM

[Marcelo Tosatti]

On Mon, Mar 17, 2014 at 09:39:54AM +0000, Daniel P. Berrange wrote:
> On Fri, Mar 14, 2014 at 06:52:19PM -0300, Marcelo Tosatti wrote:
> > On Tue, Feb 04, 2014 at 11:54:22AM -0500, Marcelo Tosatti wrote:
> > > On Tue, Feb 04, 2014 at 04:42:02PM +0000, Daniel P. Berrange wrote:
> > > > On Tue, Feb 04, 2014 at 11:32:47AM -0500, Marcelo Tosatti wrote:
> > > > > 
> > > > > Add an element named "strict-hugepages" to control whether to 
> > > > > refuse guest initialization in case hugepage allocation cannot 
> > > > > be performed.
> > > > > 
> > > > > Signed-off-by: Marcelo Tosatti <mtosatti at redhat.com>
> > > > > 
> > > > > diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
> > > > > index ff50214..e79f5e6 100644
> > > > > --- a/docs/formatdomain.html.in
> > > > > +++ b/docs/formatdomain.html.in
> > > > > @@ -632,6 +632,9 @@
> > > > >        <dt><code>hugepages</code></dt>
> > > > >        <dd>This tells the hypervisor that the guest should have its memory
> > > > >          allocated using hugepages instead of the normal native page size.</dd>
> > > > > +      <dt><code>strict-hugepages</code></dt>
> > > > > +      <dd>This tells the hypervisor that the guest should refuse to start
> > > > > +          in case of failure to allocate guest memory with hugepages</dd>
> > > > 
> > > > Huh, we already supply the -mem-prealloc command line flag alongside
> > > > the -mem-path flag which should cause QEMU to exit if it cannot allocate
> > > > all memory upfront.
> > 
> > Daniel,
> > 
> > Can we merge this patch please? 
> > 
> > Paolo thinks it belongs to libvirt.
> 
> We recently had a bunch more feature requests around huge page support
> in libvirt, so I think it is preferrable not to merge this currently.
> We need to examine the broader problem to come up with a coherant
> design for the whole problemspace.

There is a number of options implemented in the kernel and qemu that
should be exposed via libvirt to the user.

Can you explain what are the properties to be verified in the coherent
design that you mention which are being ignored in the proposed patchset
?