On Fri, Feb 08, 2019 at 11:03:34 -0200, Daniel Henrique Barboza wrote: > Some devices creates empty (= cpu-less) NUMA nodes to host > its memory. This results in topologies where the following > sanity rule does not apply as is: > > nodes * sockets * cores * threads = total_cpus > > As a result, a call to 'virsh nodeinfo' will return the default > value (1) to nodes, sockets and threads, while cores defaults > to the total_cpus value. For example, in a Power9 host that has > 160 total cpus, 4 cpu-less NUMA nodes, 2 populated NUMA nodes, > 1 socket per populated node, 20 cores per socket and 4 threads > per socket: > > $ virsh nodeinfo > CPU model: ppc64le > CPU(s): 160 > CPU frequency: 3783 MHz > CPU socket(s): 1 > Core(s) per socket: 160 > Thread(s) per core: 1 > NUMA cell(s): 1 > Memory size: 535981376 KiB > > This patch adjusts virHostCPUGetInfoPopulateLinux to count the > cpu-less NUMA nodes and discard them in the sanity rule, changing > it to: > > (nodes - empty_nodes) * sockets * cores * threads = total_cpus > > And with this new rule, virsh nodeinfo will return the > appropriate info for those topologies, without changing the > behavior for any other scenario it was previously working. > > This is the resulting output of nodeinfo after this patch in the > same Power9 host mentioned above: > > $ virsh nodeinfo > CPU model: ppc64le > CPU(s): 160 > CPU frequency: 3783 MHz > CPU socket(s): 1 > Core(s) per socket: 20 > Thread(s) per core: 4 > NUMA cell(s): 6 > Memory size: 535981376 KiB This change would break backward compatibility as we have the following public macro in libvirt-host.h: # define VIR_NODEINFO_MAXCPUS(nodeinfo) \ ((nodeinfo).nodes*(nodeinfo).sockets*(nodeinfo).cores*(nodeinfo).threads) Anyway, the virNodeInfo structure is just not flexible enough to deal with all possible topologies and users are advised to look at the host capabilities XML to get a proper view of the host CPU topology. Jirka
