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Re: [libvirt] virsh nodeinfo CPU detection questions



On 01/29/2013 02:55 PM, Doug Goldstein wrote:
On Tue, Jan 29, 2013 at 9:52 AM, Scott Sullivan<ssullivan 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 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 host28 ~]#

1.0.1:
[root 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 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 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,

I'm running a RedHat kernel; 2.6.32-220.2.1.el6.x86_64 specifically.

Thanks for the insight of your experiences, very interesting. I find the same that the NUMA info appears detected incorrectly for this processor.


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