Re: [Xen-devel] [PATCH v4 17/21] libxl: disallow memory relocation when vNUMA is enabled

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2015-01-28 at 22:22 +0000, Wei Liu wrote:
> On Wed, Jan 28, 2015 at 04:41:11PM +0000, Ian Campbell wrote:
> > On Fri, 2015-01-23 at 11:13 +0000, Wei Liu wrote:
> > > Disallow memory relocation when vNUMA is enabled, because relocated
> > > memory ends up off node. Further more, even if we dynamically expand
> > > node coverage in hvmloader, low memory and high memory may reside
> > > in different physical nodes, blindly relocating low memory to high
> > > memory gives us a sub-optimal configuration.
> > 
> > What are the downsides of doing this? Less flexible PCI passthrough/MMIO
> > hole sizing I think? Anything else?
> 
> Yes, PCI passthrough and MMIO hole size are affected, but not to the
> degree that they are unusable.  Going forward like this doesn't make
> thing worse than before I think.

> Memory relocation is already disabled if we're using QEMU upstream.

Is that a shortcoming which might get fixed?

Is this vnuma restriction something which could be fixed in the future?
 
> > Does some user doc somewhere need this adding?
> > 
> > (and now I think of it, the PoD vs. vnuma one too).
> > 
> 
> Maybe release note or xl manpage?

Manpage would be good. Perhaps in some vnuma docs on the wiki too.

> 
> Wei.
> 
> > Ian.



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