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 :|