Re: [PATCH 03/11] [XEN] NUMA guest tools interface

[Dulloor <dulloor@gmail.com>]

On Wed, Apr 7, 2010 at 8:13 AM, Andre Przywara <andre.przywara@amd.com> wrote:
> Dulloor wrote:
>>
>> The patch adds hypercall interfaces to get/set the virtual numa layout
>> for a domain.
>
> I don't see the need for introducing this many new interfaces. I couldn't
> find a reference for the nodemap information (mfn_to_nid) to be actually
> used somewhere, is there any missing part or was it just for the sake of
> completeness?
The nodemap information is right now a place holder. The part is used in the
implementation of enlightened ballooning, which is essential for NUMA
guests that
could increase/decrease/exchange memory reservations. I will spin out
a refreshed
patch for this in a couple of days.

> Beside that, cpu_to_node is already in physinfo, and via xc_availheap (which
> takes a node parameter) you can query the amount of free memory per node. I
> think that is all we need to know about the host's NUMA topology, but
> correct me if I am wrong.
> (OK, the distance information is missing...)
I wanted to have all the desired node information (size, free memory,
node_to_cpu masks, distances) in a single place. But, I could have
constructed this without adding a new interface too.

> From a design point of view I would avoid exporting so many host machine
> information to Dom0 unless we really need it.
I agree. I am exporting only the information that is essential and
which makes design sense.

>
> Regards,
> Andre.
>
> --
> Andre Przywara
> AMD-Operating System Research Center (OSRC), Dresden, Germany
> Tel: +49 351 448-3567-12
>
>