What is CPU READY?

The time a virtual machine waits in the queue in a ready-to-run state before it can be scheduled on a CPU is known as ready time. The ready time should preferably be as low as possible. Virtual machines that are allocated multiple cpus or have high timer interrupts are more frequently seen with high ready time values.

Previously VMware warned about having virtual machines with 5% or higher values, but they now seem to no longer specify such a given value. Whether 5% is ok for a given service depends on the service, but it should preferably be as low as possible.

VMware has a very good paper on this subject here: http://www.vmware.com/pdf/esx3_ready_time.pdf

The Virtual Infrastructure client will only show ready time values as milliseconds so if you want to see it as percent you might want to use esxtop, resxtop (Remote CLI), a third party alternate product or you can calculate the values found there into percent yourself.

Here are some stats from the VMware Remote CLI 3.5U2 appliance as seen from different places. This appliance is based on debian 3.1 and is running with healthy performance and show very low ready values.

Virtual Infrastructure client:



esxtop:


vmktree: