Optimal number of CPU cores for a VM

[thepratikbhagat]

Hi,

I have the below configuration:

Mac:

OS: El Capitan

Processor: 2.5 Ghz Interl Core i7 (8 core)

Memory: 16 Gb 1600 MHz DDR3

Graphics: Intel Iris Pro 1536 Mb

VM Ware Professional 8.5.3

Guest OS: Windows 7 64 Bit

When I configured this VM, I had allocated 4 Gb RAM and 1 CPU core to the guest OS. While running the VM, I noticed that the Mac makes a lot of noise and heats up a lot. After suspending the VM, that problem does not occur. So, I went ahead and increased the number of cores allocated to 4. The problem still persists but the amount of noise and heating has reduces a little.

I am new to such a setup and I was wondering on how to achieve and equilibrium between the performance of the guest OS and the Mac heating up.

What will happen if I assign all 8 cores to the guest OS ? will it negatively affect the Mac or will it be able to distribute work better and take the load off of 1 or 4 cores ?

The requirement for my guest OS is pretty minimal, it do not aim to perform heavy tasks there, all I need is to run 3 GUI based tools to connect to a database, which is not that heavy.

Hope to see some suggestions, thank you.

[ColoradoMarmot]

No individual VM should have more than N-1 physical cores (not virtual ones).  I'm not aware of any Mac that offers 8 cores, so I think you're counting both.

On a Macbook Pro with a 4-core CPU, 2 is the most that you can safely set without starting to starve the host for CPU cycles.

Look inside the VM to see what's running.  Often antivirus is configured to run a periodic scan, or system restore is enabled, both of which can cause CPU spikes.

[thepratikbhagat]

Hi dlhotka,

Thanks for your reply. I get what you are saying, and yes I think I counted the threads and not the cores of my CPU. I have stopped the anti-virus real time scan and system restore.

If you review the attachments, there are no CPU spikes, but the usage stays above 50%.

Any thoughts on why this is so, and how can i curb it ? let me know if more information is needed.

And once again, thanks for your inputs.

[wila]

Hi,

Most likely that's windows updates chewing up your CPU cores, happens on physical hosts as well.

You need to run a few windows patches to cure that.

See:

Re: Can anyone suggest a fix for Windows 7 updates failing?

for details.

--

Wil