Upps. Ok This is because the host has 1 cpu with 6 core, each of 2599MHz. Because I assigned 1 cpu to the guest, it consumed fully those cpu resources...
"If the guest is maxing at 100% that is an OS limitation not the host limitation. "
I think not. If a guest is maxing at 100% it shows that the guest wants more, so the limiting factor is the host.
thank you for helping