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

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.