[libvirt] virsh nodeinfo CPU detection questions

[Scott Sullivan]

On 01/29/2013 02:55 PM, Doug Goldstein wrote:
> 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.
>>
>> --
>> libvir-list mailing list
>> libvir-list at redhat.com
>> https://www.redhat.com/mailman/listinfo/libvir-list
>>      
> 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,

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.