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Re: [Xen-devel] RFC: vNUMA project



On Wed, Nov 12, 2014 at 09:35:01AM +0000, Jan Beulich wrote:
> >>> On 11.11.14 at 19:03, <david.vrabel@xxxxxxxxxx> wrote:
> > On 11/11/14 17:36, Wei Liu wrote:
> >> Option #1 requires less modification to guest, because guest won't
> >> need to switch to new hypercall. It's unclear at this point if a guest
> >> asks to populate a gpfn that doesn't belong to any vnode, what Xen
> >> should do about it. Should it be permissive or strict? 
> > 
> > There are XENMEMF flags to request exact node or not  -- leave it up to
> > the balloon driver.  The Linux balloon driver could try exact on all
> > nodes before falling back to permissive or just always try inexact.
> > 
> > Perhaps a XENMEMF_vnode bit to indicate the node is virtual?
> 
> Yes. The only bad thing here is that we don't currently check in the
> hypervisor that unknown bits are zero, i.e. code using the new flag
> will need to have a separate means to find out whether the bit is
> supported. Not a big deal of course.
> 

If this new bit is set and domain has vnuma, then it's valid
(supported); otherwise it's not.

To not break existing guests, we can fall back to non-vnuma hinted
allocation when the new bit is set and vnuma is not available.

Wei.

> Jan

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