Re: arm64: Approach for DT based NUMA and issues

[Dario Faggioli <dario.faggioli@citrix.com>]

[-- Attachment #1.1: Type: text/plain, Size: 1835 bytes --]

On Fri, 2016-12-16 at 09:40 +0000, Julien Grall wrote:
> Hi Vijay,
> On 16/12/2016 07:39, Vijay Kilari wrote:
> > If we drop numa-node-id from memory node generated to dom0, then
> > dom0 will
> > assume all the memory is from node0. So eventually node1 device
> > intialization fails.
> 
> I suggested to drop the property numa-node-id from every node (not
> only 
> memory one). So DOM0 will think it is running a non-NUMA platform.
> 
>  From my knowledge this is working on x86, and I don't understand
> why 
> this would be an issue on ARM. If you think the device may not work, 
> please explain why.
> 
Yes, I confirm that what you said works and any x86 NUMA system I've
seen.

AFAIUI, since Vijay is talking about "devices", the x86 equivalent of
what would be an "IONUMA system", i.e. a platform where I/O devices are
physically attached to more than just one I/O hub, which in turn are
attached to different nodes.
I don't have first hand experience with these systems on the x86 world,
but I'm quite sure they also function with the configuration Julien is
suggesting to use.

Boris did some work to _improve_ the situation (namely, to make it
possible for *Xen* to report to the toolstack, to which NUMA node a
specific device is attached to). But:
 - things were working already before this
 - that does involve Xen and toolstack, while Dom0 remains totally 
   NUMA _unaware_.

And I indeed think that doing what Julien says (i.e., keep dom0 NUMA-
ignorant) is, if possible, best as a first step.

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

[-- Attachment #1.2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 819 bytes --]

[-- Attachment #2: Type: text/plain, Size: 127 bytes --]

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel