The following is a description of some common ESXi and VM CPU Performance Issues:
High Ready Time
Ready Time above 10% could indicate CPU contention and might impact the Performance of CPU intensive application. However, some less CPU sensitive application and virtual machines can have much higher values of ready time and still perform satisfactorily.
High CoStop (CSTP) Time
CoStop time indicates that there are more vCPUs than necessary, and that the excess vCPUs make overhead that drags down the performance of the VM. The VM will likely run better with fewer vCPUs. The vCPU(s) with high CoStop is being kept from running while the other, more-idle vCPUs are catching up to the busy one.