VMWare, number of vCPU

I know I am a little slow about this, but I have been experimenting, and yes, my VM's perform better with less vCPU, instead of more, especially when they are not running at a high CPU utilization

So from reading the posts and the documentation, what I am gleaning is that the scheduler is swapping the vCPU'sfrequently, and with less vCPU it basically swaps less often,a nd can obtain a higher performance.

Is this correct.  Can anyone enlighten me as to the 'core' reasons less vCPU seems to improve performance.
Los Angeles1Asked:
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
You server applications need to take advantage of vSMP.

How are you testing, are you using Exchange, SQL that can take advantagebof multiprocessors?

Your findings are correct. This is how vSMP works.

Only allocate more CPUs if your servers applications can take advantage.

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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
less time spent waiting for cpu states.
Aaron TomoskyDirector of Solutions ConsultingCommented:
If you are over allocated more vcpu just makes it worse
Only add vcpu not counting hyperthreading.
It really depends on your boxes and vms how to best set this up. For example, I have a osx vm for Xcode compiling runnin on an Xserve. I gave it 4 vcpu because it can compile multithreaded.
I also have a mailserver that would run at 90% inside the vm with one vcpu which was basically maxing one core of the real CPU. So I gave it two vcpu and now it's running at 30%. Whatever, it's happy. The general rule is as few as possible. Most of my vms are 1vcpu.
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