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I'm trying to understand certain impacts of virtualisation on performance by running benchmarks on VMs. I'm considering ESXi and Hyper-V as the hypervisors. I wanted to know if I can pin a VM to a particular core or set of cores. If possible, I could then pin 2 VMs to the same core and try reading into the effects when there's a memory intensive job running in both

helloworld
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  • Does this answer your question? [Can you help me with my capacity planning?](https://serverfault.com/questions/384686/can-you-help-me-with-my-capacity-planning) – djdomi May 19 '22 at 08:34
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    It does not - he asks for a specific manipulation of the scheduler (pinning 2 vm's to identical cores) so he can study the effects. THis is not the same as asking us to do his capacity planning. – TomTom May 19 '22 at 08:50

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Pinning a VM to a specific set of cores limits the hypervisor's choices when scheduling vCPU cores to pCPUs cores. Pinning several VMs to the same set of cores very much resembles running them on a host with only that number of cores.

On the process level, this has nearly the same impact as running all processes on a single machine. How that interacts with memory-intensive access highly depends on the CPU type and the cache and memory subsystem, especially the cache sizes and the number of usable channels.

Zac67
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