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Description of SRMTIDLE

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From Brian Wade, IBM:

This tool sets the value of the CP dispatcher's "test-idle" timer.

CP sometimes uses the test-idle timer to hold an unrunnable virtual machine in the dispatch list for a small amount of time after the virtual machine becomes unrunnable, in case the virtual machine becomes runnable again very soon.

Holding a virtual machine in the dispatch list tends to protect its working set. CP will not steal page frames as aggressively from a virtual machine in the dispatch list as it will from a virtual machine in the dormant or eligible lists. Thus such protection sometimes pays off.

On an unmodified VM system, the test-idle timer is set to 300 milliseconds. For some workloads, especially some storage-constrained Linux or TPF guest workloads, we are sometimes finding that a smaller test-idle value might be more appropriate.

See the exec prologue for syntax and invocation information.

Note: This tool is provided as-is and is for use by experienced VM system programmers interested in determining the effect of a test-idle timer change on their specific environment. IBM makes no warranty, express or implied, about how such a change will affect any given workload or environment. The person using this tool will need to use his judgement and expertise to determine whether changing the test-idle timer value is appropriate for his situation.