high ready time for any vm

[ricky73]

I noted "READY time" in performance section of CPU chart (real time/past day/past week/...) of any virtual machine are values between 100 ms and 14000 ms, USAGE cpu of vm  is low and load average of hosts is lower than 0.5, what means?

I saw this behaviour now before I remember ready time under 20-30 ms.

[MattiasN81]

High CPU Ready Time values means thats your VMs is struggling for CPU cycles, this are often a result of CPU over commitment.

For example

If you have one ESXi host with a total of 16 cores and 6 VMs with 4 vCPU each and all of the VMs are requesting CPU you will end up with higher CPU ready times as VMs need to wait for the needed amount of CPU cycles before it can start processing.

If high CPU values actually have an negative impact on you environment depends on the applications running on the VMs.

A VM with twice the vCPU also requires twice the CPU cycles to perform the same type of operation as a VM with just one vCPU

Generally a value of 5% CPU ready times is consider OK but to actually see hoe many percent ready times you have you need to make some calculations, VMware have an excellent KB for that

VMware KB: Converting between CPU summation and CPU % ready values

In the end, never give a VM a bunch of CPUs "just in case of", instead give it CPU when it actually requires it.

[hussainbte]

Here is a small article about %RDY.

http://blogs.totalcaos.com/understanding-rdy-cpu-ready/

Attached is a also a good white paper from VMware on CPU Scheduling

https://www.vmware.com/files/pdf/techpaper/VMware-vSphere-CPU-Sched-Perf.pdf