Re: [libvirt] Problem of host CPU topology parsing

On 11.05.2012 10:40, Osier Yang wrote: > 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. Why do you think it will be wrong? My understanding is that VIR_NODEINFO_MAXCPUS just tell the max number of possible cpus not the actual. So if it's over 48 we are safe.

Btw: the code above seems like a hack to me. Michal