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RonRosenkoetter
Contributor
Contributor

Hyperthreading - 16 vCPU VMs on a 16-core host

We're looking at virtualizing some of our larger servers... servers with 16 cores... But our host servers only have 16 cores as well (but with hyperthreading enabled)

Can we get two 16 vCPUs VMs on a 16-core host without tons of CPU contention?  Both will be running fairly hard at times (hopefully not at the same time).

I know these VMs will tread all over each other if they both have high CPU at the same time... but I'm worried they may even cause problems for each other when one is running low CPU and one is running high CPU just because of the scheduling issues with 16 vCPUs.

Anyone have any experience with this?

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weinstein5
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Immortal

Just to be clear when you say your hosts have 16 cores but HT is enabled - are you seeing 32 LCPUs or you have 16 LCPUs with HT enabled (i.e. 8 physical cores)

If it is 16 cores total you almost certainly be gauranteeded to have CPU conention - if its is 32 then you will see if contention I am sure if both workloads peak at the same time -

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RonRosenkoetter
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32 LCPUs,  16 physical cores (2 sockets with 8 cores each)

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weinstein5
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Immortal

IMO if these are the only two VMs running on this host and do not consume CPU resources at the same you should see minimal contention -

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