Which core is Witch?

[Patonb]

Running a vbox guest OS on my 2p L5639 box. Ideally I want to run the Vbox on the 12 true cores, and let the Windows run the HT Threads. BUT I cannot find, which of the 0->23 are Real and which are the HT ones.

Any help would be fantastic.

 

[TCM]

Data point: Win7 with i7-2600: even numbers are real cores, odd numbers are virtual cores.

You could test with 7zip for example. Run a benchmark on 2 cores and fix it to 0 and 1 and then 0 and 2 and see which is faster.

 

[cactus]

With what I understand with HT there are not "real" cores and "pseudo" cores. Each core is seen as a "full" core to the OS. See section 3.3 of this. This does not mean TCM is wrong. The windows cores 0 and 1 could be the two logical units of physical core 0. This would make sense because the scheduler is aware there are two logical units of each physical core. I havent looked into the windows scheduler but that could mean it keeps tightly coupled threads on a single physical core to limit cache poisoning or it could try to keep each physical core loaded with only a sinle thread.

Also, since you have dual CPUs with local memory, it may be better to keep the VMs on a single CPU thus limiting needs to use a second CPU for accessing memory. I know windows is NUMA aware but I dont know how that translates into VBox and if it is NUMA aware.

So try every other or the first 12 and see if it makes a difference, but I would guess leaving it to the windows CPU scheduler will work out better for you.