On Mon, 24 Jun 2019 10:36:55 +0100
Daniel P. Berrangé <berra...@redhat.com> wrote:
> On Mon, Jun 24, 2019 at 10:17:33AM +0200, Markus Armbruster wrote:
> > Igor Mammedov <imamm...@redhat.com> writes:
> >
> > > Fallback might affect guest or worse whole host performance
> > > or functionality if backing file were used to share guest RAM
> > > with another process.
> > >
> > > Patch deprecates fallback so that we could remove it in future
> > > and ensure that QEMU will provide expected behavior and fail if
> > > it can't use user provided backing file.
> > >
> > > Signed-off-by: Igor Mammedov <imamm...@redhat.com>
> > > ---
> > > PS:
> > > Patch is written on top of
> > > [PATCH v4 0/3] numa: deprecate '-numa node, mem' and default memory
> > > distribution
> > > to avoid conflicts in qemu-deprecated.texi
> > >
> > > numa.c | 4 ++--
> > > qemu-deprecated.texi | 8 ++++++++
> > > 2 files changed, 10 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/numa.c b/numa.c
> > > index 91a29138a2..53d67b8ad9 100644
> > > --- a/numa.c
> > > +++ b/numa.c
> > > @@ -494,8 +494,8 @@ static void
> > > allocate_system_memory_nonnuma(MemoryRegion *mr, Object *owner,
> > > if (mem_prealloc) {
> > > exit(1);
> > > }
> > > - error_report("falling back to regular RAM allocation.");
> > > -
> > > + warn_report("falling back to regular RAM allocation. "
> > > + "Fallback to RAM allocation is deprecated.");
> >
> > Can we give the user clues on how to avoid the deprecated fallback?
>
> There's nothing a user can do aside from ensuring they have sufficient
> free memory before launching QEMU to satisfy the huge pag request.
>
> Probably just needs changing to do.
>
> "This is deprecated, future QEMU releases will exit when
> huge pages cannot be allocated"
Also it could be that users might use other than hugepages backing
storage, that's why I completely left concrete advice out from
suggestion.
User should know what he/she is doing when providing mem-path,
if user supplies mis-configured path QEMU will print error
from memory-backend-file if/when allocation fails.
> Regards,
> Daniel
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