Do logical processors constitute as pCPU's for calculating pCPU to vCPU ratios?

[kdbinger]

I have been trying to get a solid answer of what constitutes as a pCPU.  In vCenter, if you click on a cluster > summary you get a total of "Processors."  This number, however, is the summation of core count for all the hosts in the clusters.  In the article from zdnet (http://www.zdnet.com/virtual-cpus-the-overprovisioning-penalty-of-vcpu-to-pcpu-ratios-4010025185/) he mentions that logical processors (when hyperthreading is turned on) are to be counted as pCPU's when determining your pCPU to vCPU ratio for CPU Ready Times (or the vm processor scheduler).

Ultimately, this is what I am trying to determine (i.e. what my pCPU to vCPU ratio is).  We have a lot high of CPU Ready Times and I'm trying to determine how much net new hardware (pCPU's) I need to order (please consider that we are already pursing right sizing vm's and do not need information on ready times per se; rather, just trying to get the low down on what constitutes as pCPU's here and/or how the VM scheduler works with logical processors).

Thanks in advance!

[NuggetGTR]

No logical processors do not count as a pCPU when it comes to ratio. pCPU to vCPU ratio is done via physical cores. if you look at a host summery you will see it will have next to CPU cores will have something like 8 CPUs x 2.6 GHz for example not 16 logical ones it has.

When using VMware vCenter Operations manger you can set vCPU to pCPU capacity limits etc and all of those ratio metrics are using Physical Cores.

ESXi does not treat hyper threaded core like normal cores it will intelligently use them when CPU scheduling if it will not impact performance.

[kdbinger]

That is what I had supposed prior to reading the article on zdnet.  For extra credit   could you tell me where in Operations Manager I would find that?

[NuggetGTR]

Haha sure, from the vsphere ui navigate to a cluster or host select Operations Tab -> all metrics. Look for density and it will be under there in a pCPU to vCPU metric. you will have to change the time line to something greater than 24 hours to see the data points.

If you want to set a vCPU to pCPU capacity limit, click on configuration up on the top right select the profile(s) you have setup or use. and under "usage calculation" you can enter the ration you would like. Obviously these same ration metrics are available in the custom ui  also.

Hope it helps

Cheers

[kdbinger]

Not sure what the deal was, I went back in and graphs are present.

Thanks NuggetGTR

[kdbinger · Accepted solution]

To anyone who is still looking for the answer as to whether logical processors constitute as pCPU's when determining the vCPU to pCPU ratios, the definite answer is yes. 

See Scott D. Lowe's document here: https://communities.vmware.com/servlet/JiveServlet/previewBody/21181-102-1-28328/vsphere-oversubscri...

Which also confirms with this zdnet article: http://www.zdnet.com/virtual-cpus-the-overprovisioning-penalty-of-vcpu-to-pcpu-ratios-4010025185/

From an empirical stance, I would agree this is correct as well.  We are able to easily get an 8:1 ratio without any ready time or heavy "workloads."  I have been monitoring this since the original post and have not had any issues and having great density results.