Red Hat Bugzilla – Bug 810580
AMD Magny-cours processors have wrong topology
Last modified: 2016-03-23 17:02:35 EDT
Description of problem:
Magny-cours processors with 12 cores per physical socket should be detected as either having one socket and 12 cores, or possibly two sockets with 6 cores each. Instead they are detected as one socket and six cores, so only half the cores are usable by libvirt.
Version-Release number of selected component (if applicable):
0.9.11, 0.9.10, and possibly more after 0.9.4.
Steps to Reproduce:
1. Run virsh capabilities on a host with an AMD Opteron 6174 or similar processor
2. Examine the topology entry
<topology sockets='4' cores='6' threads='1'/>
<topology sockets='4' cores='12' threads='1'/>
There seems to be confusion between the topology reported by numa and the physical topology that's causing the problem. Numa detects 8 sockets with 6 cores each, yet there are four physical sockets with 12 cores. The issue did not exist in libvirt 0.9.4.
Sorry this never received a response. I'm not sure if this was ever fixed since I don't have that system. If you can still reproduce with newer libvirt please reopen this bug and provide /proc/cpuinfo