vCPU - Cores vs threads in INTEL CPU

[zeuxprox]

Hi to everybody,

first of all I'm sorry for my English...

My question is simple: if I give "n" cores to a VM in a server with Intel CPU (HT enabled), the "n" cores are REAL "n" cores or they are only "n/2" real cores (=n threads) ?

For example: I create a new VM with 1 socket and 4 cores. These cores are REAL 4 cores or they are only 2 real cores (=4 threads)?

Thanks a lot

 

[wolfgang]

a KVM core is like a thread so if you have 4/8 cores/HT you can make one machine with 8 vcpus.

if you have more vcpus per machine then HT cores Qemu start to emulate cores an your vms get very slow.

if you want real cores you must pin the vcpus to the cpus.

 

[zeuxprox]

a KVM core is like a thread so if you have 4/8 cores/HT you can make one machine with 8 vcpus.

if you have more vcpus per machine then HT cores Qemu start to emulate cores an your vms get very slow.

if you want real cores you must pin the vcpus to the cpus.

OK, but how can I pin vCPU to real cores?

Thank you