The default view of esxtop is CPU, there are several useful counters in this view.

GID – group ID

NAME – virtual machine name

NWLD – number of worlds

%USED – percentage physical CPU time accounted to this world

%RUN – percentage of total scheduled time for the world to run

%SYS – percentage of time spend by system services for that world

%WAIT – percentage of time spent by the world in a wait state

%VMWAIT – derivative of %WAIT except it doesn’t include %IDLE

%RDY – percentage of time the world was ready to run

%IDLE – percentage of time the vCPU world is in idle loop

%OVRLP – percentage of time spend by system services on behalf of other worlds

%CSTP – percentage of time the world spend in ready, co-deschedule state (only relevant to SMP VMs)

%MLMTD – percentage of time world was ready to run but was not scheduled because that would violate “CPU limit” settings

%SWPWT – percentage of time the world is waiting for the VMkernel swapping memory

High CPU ready time is a major indicator of CPU performance issues, you may have excessive usage of vSMP or a limit set (check %MLMTD for that). Another metric to check is %CSTP, this will help you determine whether you can decrease the amount of vCPUs for some of the virtual machines which will help with improving scheduling opportunities.

%SYS is usually caused by high IO virtual machine. %SWPWT is usually caused by memory overcommitment.