[libvirt] virsh nodeinfo CPU detection questions

[Doug Goldstein]

On Tue, Jan 29, 2013 at 9:52 AM, Scott Sullivan <ssullivan at liquidweb.com> wrote:
> I have a machine with four AMD Opteron(TM) 6272 processors:
>
> http://www.amd.com/us/products/server/processors/6000-series-platform/6200/Pages/6200-series-processors.aspx#5
>
> I use 'virsh nodeinfo' to determine the amount of physical CPUs, and CPU
> cores. What values should I be looking at in the output of nodeinfo to
> determine this? With 1.X libvirts the output values have changed from 0.9.4:
>
> 0.9.4:
> [root at host ~]# virsh nodeinfo
> CPU model: x86_64
> CPU(s): 64
> CPU frequency: 2099 MHz
> CPU socket(s): 4
> Core(s) per socket: 8
> Thread(s) per core: 2
> NUMA cell(s): 1
> Memory size: 24713980 kB
> [root at host28 ~]#
>
> 1.0.1:
> [root at host ~]# virsh nodeinfo
> CPU model: x86_64
> CPU(s): 64
> CPU frequency: 2099 MHz
> CPU socket(s): 1
> Core(s) per socket: 8
> Thread(s) per core: 2
> NUMA cell(s): 4
> Memory size: 24713980 KiB
> [root at host28 ~]#
>
> As you can see, the CPU socket and NUMA cells values have changed in these
> two versions, on the same machine. To get the physical CPU count, is it safe
> to assume this?
>
> Numa cell(s) X CPU Socket(s) == physical CPUs present
>
> However, I am not positive what formula I should use to determine the CPU
> core count. On this processor, it has 16 cores. Would that mean I can do
> this?
>
> Core(s) per socket X Thread(s) per core: == CPU cores
>
> Thanks in advance for clarifying.
>
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Scott,

I've got the exact same CPUs (Dell PowerEdge R815). You'll find the
NUMA info is detected node info is detected incorrectly. Oddly we have
different data detected. What kernel are you running?

with libvirt 1.0.1
root at host ~ # virsh nodeinfo
CPU model:           x86_64
CPU(s):              64
CPU frequency:       2100 MHz
CPU socket(s):       1
Core(s) per socket:  64
Thread(s) per core:  1
NUMA cell(s):        1
Memory size:         132013200 KiB

virsh capabilities is a bit "smarter" but still not 100%. It sees 8
NUMA nodes and puts the CPUs in the correct nodes but still detects
the CPU incorrectly.

-- 
Doug Goldstein