Identify CPU contention on a virtual machine in ESXTOP





  • %RUN
  • %READY
  • %CSTP
  • %WAIT
"%RUN"
 The percentage of total scheduled time for the world to run.

"%RDY"
 The percentage of
time the world was ready to run

"%CSTP"
 The percentage of time the world spent in ready, co-deschedule state. This co-deschedule state is only meaningful for SMP VMs. Roughly speaking, ESX CPU scheduler deliberately puts a VCPU in this state, if this VCPU advances much farther than other VCPUs.

"%WAIT"
 The percentage of time the world spent in wait state. This %WAIT is the total wait time. I.e., the world is waiting for some VMKernel resource. This wait time includes I/O wait time, idle time and among other resources. Idle time is presented as %IDLE.


+Q: How do I know CPU resource is under contention?+
+A: %RDY is a main indicator. But, it is not sufficient by itself.+

 +If a "CPU Limit" is set to a VM's resource settings, the VM will be deliberately held from scheduled to a PCPU when it uses up its allocated CPU resource. This may happen even when there is plenty of free CPU cycles. This time deliberately held by scheduler is shown by "%MLMTD", which will be describe next. Note that %RDY includes %MLMTD. For, for CPU contention, we will use "%RDY - %MLMTD". So, if "%RDY - %MLMTD" is high, e.g., larger than 20%, you may experience CPU contention.+

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