Messages in this thread | | | Date | Mon, 3 Mar 2008 15:42:24 +0100 | From | "Michael Kerrisk" <> | Subject | Re: SCHED_IDLE documentation |
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Ingo,
One more thought while we're in this thread. In my recent tests I notice that the magnitude of the effect of nice values has changed quite a lot in recent times. For example, back in 2.6.18, two CPU intensive processes would get the following shares of the CPU over 100 seconds of run time (here, three different examples of nice value settings):
A nice B nice %A %B -20 -10 58.3 41.7 -20 0 89.2 10.8 -20 +19 99.7 0.3
In 2.6.25-rc2, we have:
A nice B nice %A %B -20 -10 90.5 9.5 -20 0 99.0 1.0 -20 +19 100.0 0.0
While I realise that nice values are not intended to guarantee any particular degree of access to the CPU, these wide variations in the effect of the nice value are surprising. (For the 2.6.25-rc2 -20/+19 case, my test shows the low priority process is getting 0.000% of the CPU -- i.e., < one thousandth of a percent. In other words it is in effect being totally starved of the CPU.) Any comments?
Cheers,
Michael
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