Your CPU is NOT Starving!

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I often hear claims of CPU Starvation:

Me: "How have you met this conclusion?"

Client: "There are 'CPU Starvation' messages in the SystemOut.log."

Me: "Does the CPU monitor report high CPU?"

Client: "No."

Me: "Do the end users report slowness when using the application?"

Client: "No."

Me: "Is this a virtual environment?"

More often the answer to the last question is "Yes".  In this case it is important to check the virtual environment host for inadequate CPU settings.  In any case, virtual or not, it is best to get the whole picture.  CPU Starvation messages rarely have anything to do with CPU.  Typically we find the problem in a long GC (Garbage Collection) cycle (with differing underlying cause), not enough system resources allocated for all of the processes on the system (RAM) or another higher priority process running (scheduled task, system backup, virus scan, etc.).

There are documents that provide this explanation:

IBM HMGR0152W: CPU Starvation detected messages in SystemOut.log

and

Help! My CPU is starved. What do I feed it? (IBM Business Process Management Products Support Blog)

So if you see "CPU Starvation" messages in the SystemOut.log, please be sure to check the overall system for resources and other running tasks before assuming the problem is an actual CPU problem.

...and if you still feel that there is something eating the CPU, then collect a set of performance Mustgather data during the time of the problem.  IBM Support can then help to pinpoint the area of contention:

IBM MustGather: Performance, hang, or high CPU issues on Windows

IBM MustGather: Performance, hang, or high CPU issues with WebSphere Application Server on Linux

IBM MustGather: Performance, hang, or high CPU issues with WebSphere Application Server on AIX

IBM MustGather: Performance, hang, or high CPU issues on Solaris

IBM MustGather: Performance, Hang, or High CPU Issues on HP-UX