Messages in this thread | | | Date | Mon, 9 Aug 1999 15:33:15 +0200 (CEST) | From | Ingo Molnar <> | Subject | Re: SMP Scheduling |
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On Mon, 9 Aug 1999, Peter Waltenberg wrote:
> It's not that the process changes CPU's, it's that it's doing it at > regular intervals that I find worrying. > Yes, that could just be coincidence, or it could be a real problem.
no, it's a feature, there is nothing to worry about. Start the CPU-hog with 'nice -n -100 ./cpuhog' and you will see no 'hopping'. The following thing happens in the scenario you tested: _three_ processes are running at once, X, xosview and cpuhog. Since all of them have the same static priority, and X and xosview has much higher 'interactiveness', the scheduler does the right thing when all these three processes are running at once.
I've just tried redirecting xosview to another box (this makes the scheduling scenario 2-process), and there wasnt a single 'CPU-hop' in minutes. I have seen scheduler patches that 'solve' the above xosview phenomemon, but they are in reality just destroying the _correct_ behavior of preempting a CPU-hog with interactive processes. This whole non-issue is btw. a typical case of the 'observer' (xosview and X) intruding into the measured system.
-- mingo
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