I see lots of CPU's that run sub-2GHz but feature up to 1 GHz more turbo boost. I know it's a single threaded boost, meaning only 1 core is boosted. How much can Proxmox take advantage of that? Is there logic as which VM gets the boost? If a core is boosted, does it also boost Hyperthreading, meaning 2 vCPU"s would run boosted? How does it work?
Does Turbo Boost help much?
- Thread starter jaytee129
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I know that one to be true. Regarding your other related questions: Proxmox is "just Linux" under the hood.
The performance for a VMs vCPUs mostly comes down to how Qemu/KVM handles that.
When you assign a virtual CPU to a VM it is not automatically assigned to a physical CPU core (though KVM implements this via core-pinning) but rather the process gets the appropriate resources given via the Linux scheduler. However, this is intransparent for the VM which means it simply sees 1, 2, 4, or how many vCPUs you set in the settings.
With your base system having more processing power at its disposal, this should also increase your VM performance accordingly.
In short, Chris Thorpe's answer in the first link below answers it very succinctly:
Here's a serverfault forum post discussing this exact topic and here is a great visualization which might clear up some more of your questions.
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Thank you. That helps. Is the boost tied to Physical CPU 1 only, which I could pin to a VM, or will the boost occur with whatever pCPU is first to ask for it, so I couldn't pin it to a VM and it would not easily predictable to know which VM gets it?
After skimming some more threads online (e.g. this one) and the Overview Information for Intel® Turbo Boost Technology a performance increase will only happen if your system isn't utilized at capacity anyway, as TurboBoost simply tries to use unused resources. E.g. it will increase the clock speed for certain cores if the CPU as a whole is not at maximum specified power consumption, is still cool enough, etc...
From what I've gathered, you therefore also cannot really tell which CPU core in particular is turboboosted at the moment, at most you could make an educated guess if one core is utilized particularly heavily.
TurboBoost, as far as I understand, shines when a process needs a lot of computing power, but only uses a single core and leaves the rest of the system idle. These unused resources are then directed to this sole core to make it run faster (with some efficiency penalty, of course).
As the Linux Kernel scheduler handles the KVM (sub)processes, it should automatically split up workloads across different cores anyway. Therefore using the CPU resources much more ideally, right from the start. In this case TurboBoost will most likely not kick in, as it wouldn't make that much sense anyway.
From what I've gathered, you therefore also cannot really tell which CPU core in particular is turboboosted at the moment, at most you could make an educated guess if one core is utilized particularly heavily.
TurboBoost, as far as I understand, shines when a process needs a lot of computing power, but only uses a single core and leaves the rest of the system idle. These unused resources are then directed to this sole core to make it run faster (with some efficiency penalty, of course).
As the Linux Kernel scheduler handles the KVM (sub)processes, it should automatically split up workloads across different cores anyway. Therefore using the CPU resources much more ideally, right from the start. In this case TurboBoost will most likely not kick in, as it wouldn't make that much sense anyway.