[libvirt] Problem of host CPU topology parsing

[Osier Yang]

On 2012年05月11日 16:35, Daniel P. Berrange wrote:
> On Fri, May 11, 2012 at 04:21:48PM +0800, Osier Yang wrote:
>> Hi,
>>
>> We have problem of host CPU topology parsing on special
>> platforms (general platforms are fine). E.g.
>>
>> On a AMD machine with 48 CPUs [1] (4 sockets, 6 cores indeed
>> [2]), VIR_NODEINFO_MAXCPUS [3] will always return 24 as the
>> total CPU number.
>
> If it is returning 24, then surely we have the 'nodes' value
> wrong in the virNodeInfo ? It sounds like it should have been
> set to 2  (4 * 6 * 2 =>  48)

     /* nodeinfo->sockets is supposed to be a number of sockets per NUMA 
node,
      * however if NUMA nodes are not composed of whole sockets, we just lie
      * about the number of NUMA nodes and force apps to check 
capabilities XML
      * for the actual NUMA topology.
      */
     if (nodeinfo->sockets % nodeinfo->nodes == 0)
         nodeinfo->sockets /= nodeinfo->nodes;
     else
         nodeinfo->nodes = 1;

Jirka said this was for a fix, but I don't quite understand it,
what does the "nodeinfo.nodes" mean actually? Shouldn't it
be 8 (for the 48 CPUs machine) instead? But then we will be
wrong again with using VIR_NODEINFO_MAXCPUS.

>
>> [3] #define VIR_NODEINFO_MAXCPUS(nodeinfo) ((nodeinfo).nodes*(nodeinfo).sockets*(nodeinfo).cores*(nodeinfo).threads)
>
> Rgeards,
> Daniel