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

[Dulloor <dulloor@gmail.com>]

On Wed, Apr 7, 2010 at 10:52 AM, Cui, Dexuan <dexuan.cui@intel.com> wrote:
> Andre Przywara 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
> I also have the same feeling. :-)
>
>> 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?
>> 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'd like to have Nitin's patch: http://old.nabble.com/Host-Numa-informtion-in-dom0-td27379527.html.

As I mentioned in earlier mail, I wanted to have all the desired node
information (size, free memory,
node_to_cpu masks, distances) in a single place. Also, I somewhat
dislike the existing interface for two reasons :
1) having to pass pointers to arrays (like cpu_to_node_arr), when all
we need are simple cpu-bitmasks, for which we already have the
xenctl_cpumap structure.
2) placeholders for (controversial ?) parameters like cpu_to_socket,
which we surely don't need. The existing interface is overloaded with
information we don't need for our use.

>
>>  From a design point of view I would avoid exporting so many host
>> machine information to Dom0 unless we really need it.
> Agree. I think we should have a fundamental and brief API to export the necessary info.
With the XENMEM_numa_op, I was shooting for such a fundamental and
(equally importantly) brief API.

However, I don't have a very strong preference and I can construct the
information from Nitin's patch too, if you think that one sub-command
is such a lot of duplication. Please let me know.

>
> Thanks,
> -- Dexuan