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We have been provided with 1 virtualized Windows VM machine with 24 2.8 Ghz processors.

I want to check whether all 24 cores on the VM are actually mapped to 24 dedicated physical CPU cores.

I want to ensure that the data center folks haven't for example got a 24 (or more) physical core machine out of which they have assigned the same 24 cores to multiple VMs, thereby effectively sharing the cores with multiple VMs.

I'm assuming that if the above is done by the data center folks to save on costs then I will loose on CPU performance. Is there anyway to check and verify this on the VM?

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I am not sure you can do this reliably with only access to the VM guest (Just like we can't prove we are living in a simulation). One way to get a good part of the way there might be to spin up multiple instances of 95 *one per core) and monitor performance and clockspeed over a fair time. If its a Linux based system, the load should remain constant [on a system that is purely CPU bound] - it it is quite variable the CPU is oversubscribed.

I'm sure there are more then a couple of gothas but some confounding things/things to be aware of -

  • When you get 24 cores you are often getting 24 Virtual Cores - which is actually 12 cores and 12 threads.

  • It is possible your system has been provisioned and nothing else on this machine - nothing to stop the provider from changing this later.

  • It may be worth advising what the cores are described as, and who the provider is - there maybe "shortcut answers" to your question.

  • While I'm sure it is possible, I'd be surprised if your provider is pinning specific cores to specific CPU's.

  • While CPU's are important, they are not the only thing that can be oversubscribed. I'd be more worried about oversubscribing memory and potentially very worried about how disk IOPS are handled.

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  • The machine will go into production next month. So is there a script that I run keep running for 24*7 for a few days to check the CPU capability. It's a windows machine.
    – variable
    Nov 11, 2023 at 9:20
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    Cant help on Windows.
    – davidgo
    Nov 11, 2023 at 18:39

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