Anyone using cpuid.coresPerSocket??

[RobBerginNH]

I just tested two different 4 vCPU VMs.

VM #1 = 4 vCPU with the cpuid.coresPerSocket set to 1

VM #2 = 4 vCPU with the cpuid.coresPerSocket set to 2

And VM #2 was 2x faster (scored a 7530) vs. VM#1 (3778).

I get that it doesn't make the physical cores any faster - but it does let a 4 vCPU use 8 cores where the default is 4 vCPU hitting 4 cores. I think for an operating system that limited to 4 CPU's - this would allow for

The VM gets faster (albeit not the physical cores) - and I wanted to know if anyone else was using this with any good results?

My current physical hosts are dual 6-core or quad 10-core so I have plenty of places to let the CPU get more cores.

[GuilhermeStela]

Hi Rob,

     That configuration is very usefull when using a limited OS, like Windows XP for example.

     We use this OS here and found in this configuration a way to "overpass" that limitation when giving more vCPUs to a VM.

Forgetting these specific limitations, the "CoresPerSocket" configuration let you define how much cores you want to "run" inside a unique socket(wich would be physical) and make an early quad core, if configured with 2 CoresPersocket, later becomes a core-two-quad.

And Yes, here we have a huge gain thinking in performance and speed inside guest OS.

Otherwise, if you don't plan early, your environment can become bad for manage.

In these cases, the most important thing you will have to wory about is to your environment.

To the Guest OS, i think you will ever have gain. Take a look at this document, it will explain much better:

http://www.vmware.com/resources/techresources/10059

[RobBerginNH]

I did some testing.

One VM - with 8 vCPU and then changed the cpuid.coresPerSocket from 2, 4 and then 1.

They all used the same CPU - 1900 Mhz - regardless of the configuration.

But how they used the CPU was interesting.

The first wave the 8/2 (which the OS thinks is 4 sockets with 2 cores each) - it was 50% CPU used alot of them I am thinking 16-20 of the hosts LPUs (logical processor units).

This host has 40 cores - and therefore 80 LPUs.

The 2nd wave was 8/4 - (OS thinks its 2 sockets with 4 cores) it was 100% CPU on alot fo the LPU's and appeared to use less - around 8 of them.

The last wave was 8/8 - (OS thinks its 1 socket with 8 cores) it was higher than the 8/2 but not as high as the 8/4 so it makes me think it wanted to use more cores - it appears to have used up all 20 of the cores.

So not sure which option is preferred - maxing out 8 cores or partially maxing out 16-20 cores.

But the danger here is that it can drastically cut down the virtual machine density if its not managed correctly (nods to GuilhermeStela), but it can make a virtual machine faster (2x on a 4 vCPU).

[GuilhermeStela]

Maybe thinking in how you use the Virtual Machine it could be more benefical.

Here we have a lot of users who uses Microsoft Office Excel 2007, wich uses all the processors with its Multi-threading features.

The performance for these users and their activities are awesome, otherwise, some users does not really realize that difference.

I think this question is about how you use, and not how much you can put on it.

Regards.

#####If it helps please point as fair

[GuilhermeStela · Accepted solution]

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