hyper-threadinghyper-v
My processor has 4 physical cores.
Maximum of 8 virtual cores per core. Does the following applies:
if hyper threading is enabled than 4x 2 = 8 logical cores. Which means 8 x 8 = 64 maximum virtual cores
if hyper threading is not enabled than it's 4 x 8 = 32 maximum virtual cores.
Or is it always 4×8=32 virtual cores?
In response to your second question:
So if I say, here Mr.VM take 1 core, will it take 1 of the 4 'cores' or 1 of 2 the physical cores?
There is an option when you create the VM and also after you have created it, in the settings panel under Processors in which you specify whether you want to use both processors, or the cores per processor.
Edit by Asker:
This proves that it does indeed take from a pool of the total cores available that includes hyper threaded cores because when I selected 8-cores it gave a warning, but when I selected 4-cores it did not.
The answer: Hyper threaded cores are included in the available cores to be given to the VM.
In my case, I don't have the ability to use that many cores or processors, but with your CPU, you should be able to do so.
Based on the benchmark done by Kristian Wedberg I would say you should use all logical cores you have.
Also I did my own benchmark using same CPU (i7, 4 CPU with HT) which confirmed performance boost for multi-threaded applications. If guest PC (Win. 8.1 x64) used all 8 cores, then host PC (Ubuntu x64) also used all 8 cores.
I compared also performance in single-threaded applications. In both cases I measured same values so there is no penalty using more than physical (but up to logical) number of CPUs.
Here you can see that 1 CPU full load in guest PC will result to 1 CPU load in host PC.
Best Answer
Hi there are some few basics which help you to understand:
1. The more physical cores you have, better will be the performance
2. Logical cores in a single physical processor helps the processor to multitask but not better as compare to having a dedicated physical processor
3. Hyper threading is a process to achieve multi core performance in a single physical core
4. Hyper threading does not multiply logical cores, their implementation is already fixed by manufacturer
5. Hyper threading allows the CPU load to distribute in the cores and if more distribution required, then divide the load within a physical core with different technologies like time slicing, round robin etc
So if your CPU is having 4 physical cores with maximum of 8 logical/virtual cores per core then is will always be 4x8 = 32 cores
Hope this will help you. :-)