Is nice command a myth? Post: 302333836

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Top Forums UNIX for Advanced & Expert Users Is nice command a myth? Post 302333836 by otheus on Tuesday 14th of July 2009 07:10:14 AM

07-14-2009

Registered User

Quote:

that the operating system corrects the priorities as the processes need cpu

Actually, this is true, but nice priorities still come into play. The longer a process has been running and consuming CPU resources, the lower a priority it gets. The more time it's been in the run queue without having had a chance to execute, the higher priority it gets. These mechanisms are meant to ensure fairness and reduce "starvation". Nice affects starting priorities, and only after a very long runtime, will the nice level for a particular process become irrelevant.

At any rate, task scheduling is OS-dependent. The Linux 2.6 kernel uses something called the Completely Fair Scheduler. From the author, this quote might be relevant:

Quote:

the CFS scheduler has a much stronger handling of nice levels and SCHED_BATCH: both types of workloads should be isolated much more agressively than under the vanilla [ie, than the standard Linux scheduler] scheduler.

otheus

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