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

[Daniel P. Berrange]

On Tue, Apr 08, 2014 at 03:06:13PM -0300, Marcelo Tosatti wrote:
> On Mon, Mar 17, 2014 at 09:39:54AM +0000, Daniel P. Berrange wrote:
> > 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

Libvirt needs to be able to report huge pages available per NUMA node,
to report how many of the pages are free, what size they are. Also need
to consider how we tell QEMU to use hugepages from specific host NUMA
nodes when launching guests, possibly also mapping those to specific
guest NUMA nodes. With NUMA there's more policy considerations if
enough hugepages aren't available, do we fallback to non-hugepages on
the same numa node, or to hugepages frorm a different numa node. I
don't believe we're going to be able to solve all this in libvirt alone
and so I think we're going to need improve QEMU command line args for
setting up hugepages

Regards,
Daniel
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