Say I have 8 core physical CPU system which supports hyperthreading which is mapped to 16 vCPU. Is it possible to configure increase or decrease the vCPU to 24 vCPU or 12 vCPU or this setting/configuration comes with system that can not be changed?
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The VCPU is a refection of hardware and can not be changed/optimused to give better results. It comprises of the number of cores (x2 for hyperthreading). It may be possible to create an emulator whic shows more cores, but it will be significantly slower - because its emulating.
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You said
It may be possible to create an emulator which shows more cores, but it will be significantly slowerDo you mean it will just show more cores for display purpose but actual will be same ? Mar 7, 2019 at 1:51 -
(In practice) you can't change the actual number of cores a system has in software. Think of each core as a CPU (which is what it is). In bygone times, if you wanted a faster system, you got a system with more then 1 CPU. As limits were reached, chip makers started putting multiple CPUs in a single chip - which is what a core is. Hyperthreading is a very cut down version of this. If you describe a more specific case/requirement/goal, I can provide a more specific answer. Unfortunately I don't mean "it will just show more cores for display purposes but actually be the same"...– davidgoMar 7, 2019 at 1:58
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It will be slower because it will have a lot more overhead by pretending to be something it isn't and can't be.– davidgoMar 7, 2019 at 1:58
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looks like I was not clear in my question. My question is If have 1 physical CPU, with hyper threading is it possible to map it to more than 2 virtual CPU or it will always be 2x of physical CPU ? Mar 7, 2019 at 2:18
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You can only map it to 2 VCPU. Note that you can run multiple VMs and allocate up to 2 CPUs to each in this instance, whereby oversubscribing CPU on V's– davidgoMar 7, 2019 at 2:53