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Re: [Xen-devel][PATCH]pcpu tuples [was Re: [Xen-devel] Xen 3.4.1 NUMA su

To: Dulloor <dulloor@xxxxxxxxx>
Subject: Re: [Xen-devel][PATCH]pcpu tuples [was Re: [Xen-devel] Xen 3.4.1 NUMA support]
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 17 Nov 2009 07:21:51 +0000
Cc: Andre Przywara <andre.przywara@xxxxxxx>, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>, Papagiannis Anastasios <apapag@xxxxxxxxxxxx>
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Thread-topic: [Xen-devel][PATCH]pcpu tuples [was Re: [Xen-devel] Xen 3.4.1 NUMA support]
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I think this is good. However, the socket and node ids can be fairly
arbitrary small numbers -- we need a way for the admin to find out the
topology and 'addresses' of physical cpus via xm. Perhaps a new 'xm
cpu-list' command to basically dump the pcpu_tuple information in ascending
order of node, then socket, then core, then thread, with one row per cpu:
 node socket core thread xen-cpu-id

More info could be added beyond these five pieces of information, as we
later see fit.

An alternative would be to rename the socket/node identifiers in
pyxc_physinfo, or even in Xen itself, to achieve contiguity. However I think
a cpu-list command would still be useful, and it's easy to implement.

 -- Keir

On 17/11/2009 06:56, "Dulloor" <dulloor@xxxxxxxxx> wrote:

> Attached is a patch to construct pcpu tuples of the form
> (node.socket.core.thread), and (currently)used by xm vcpu-pin utility.
> -dulloor
> On Fri, Nov 13, 2009 at 11:02 AM, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
> wrote:
>> On 13/11/2009 15:40, "Ian Pratt" <Ian.Pratt@xxxxxxxxxxxxx> wrote:
>>>> Even better would be to have pCPUs addressable and listable explicitly as
>>>> dotted tuples. That can be implemented entirely within the toolstack, and
>>>> could even allow wildcarding of tuple components to efficiently express
>>>> cpumasks.
>>> Yes, I'd certainly like to see the toolstack support dotted tuple notation.
>>> However, I just don't trust the toolstack to get this right unless xen has
>>> already set it up nicely for it with a sensible enumeration and defined
>>> sockets-per-node, cores-per-socket and threads-per-core parameters. Xen
>>> should
>>> provide a clean interface to the toolstack in this respect.
>> Xen provides a topology-interrogation hypercall which should suffice for
>> tools to build up a {node,socket,core,thread}<->cpuid mapping table.
>>  -- Keir
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