On Fri, May 11, 2012 at 05:42:34PM +0800, Osier Yang wrote: > 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? Ahhh. The AMD 12 "core" CPUs are in fact a pair of 6 core CPUs with 2 NUMA nodes in the CPU itself. http://frankdenneman.nl/2011/01/amd-magny-cours-and-esx/ "Instead of developing one CPU with 12 cores, the Magny Cours is actually two 6 core “Bulldozer” CPUs combined in to one package." So we need to take account of this when calculating the NUMA nodes Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list