[libvirt] [PATCH] add flag to enforce hugepage backing of guest RAM
Daniel P. Berrange
berrange at redhat.com
Wed Feb 5 09:49:53 UTC 2014
On Tue, Feb 04, 2014 at 03:04:11PM -0700, Eric Blake wrote:
> On 02/04/2014 02:57 PM, Marcelo Tosatti wrote:
> >
> >> So perhaps we do need some "policy" attribute on the <hugepages/>
> >> element to indicate desired behaviour here.
> >
> > What about the following new element under <hugepages/> ?
> >
> > enforce_hugepage_size=integer
>
> Which feels a bit redundant (we're already under the <hugepages>
> element, after all). Maybe:
>
> <hugepages>
> <size strict='yes' unit='G'>1</size>
> </hugepages>
>
> where strict could be no if we are giving a hint but don't care if the
> hint cannot be honored (default yes if omitted), and where unit + value
> allows the user to input the size in a sensible unit (on output, we'd
> probably want to use unit='k' and spell out 1048576, for similarity with
> all our other memory interfaces that output in k for back-compat reasons).
I don't think strict=yes|no is neccessarily the best. Per my previous
mail in this thread there are at least 3 possible policies that could
be implemented.
- Require memory size multiple of hugepage size
- Round memory size upto multiple of huge page size
- Fill in with smaller huge pages
So I'd say policy="round|exact|bestfit" even if QEMU doesn't decide
to actually implement all 3 possible policies, we at least futureproof
ourselves by not using a boolean.
Regards,
Daniel
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