Mastering KVM Virtualization

CPU tuning

I would like to reiterate that vCPUs are POSIX threads in the KVM host. You can allocate vCPUs for guest systems according to your needs. However, to get the maximum or optimal performance, it is always better to allocate required virtual CPUs for each guest based on the expected load of the guest operating system. There is nothing wrong with allocating more than is needed; however, it may cause scaling issues in future, when considering the host system as a single unit serving all configured guests.

There is also a misconception that the number of vCPUs defined by all of the guest systems should be less than the total number of CPUs available in the HOST system. To expand further on this thought, if the total number of CPUs available ...