Re: [libvirt] Problem of host CPU topology parsing

On 2012年05月11日 17:01, Jiri Denemark wrote: >On Fri, May 11, 2012 at 10:47:06 +0200, Michal Privoznik wrote: >>On 11.05.2012 10:40, Osier Yang wrote: >>> /* 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. > >Not really, the macro should count exactly the number of CPUs available to >host, otherwise lots of other issues (incl. backward compatibility) appear. It >is just a badly named macro that should never exist but we can't do anything >with it since it is our public API. > >>Btw: the code above seems like a hack to me. > >Yes, it is a hack but it's unfortunately required because we can't change the >macro. > >Anyway, I agree with Daniel that the bug most likely lies somewhere in the >code that populates nodeinfo structure. > >Jirka In /proc/cpuinfo: <snip> cpu cores : 12 </snip> However, there are only 6 core IDs, as showed in http://fpaste.org/mtoA/. And we parse the core_id file of each CPU as: core = parse_core(cpu); if (!CPU_ISSET(core, &core_mask)) { CPU_SET(core, &core_mask); nodeinfo->cores++; } and thus get only 6 cores. Don't known how 12 in /proc/cpuinfo is figured out. But could it be a clue?