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Message-ID: <alpine.DEB.1.10.0904171629470.26593@qirst.com> Date: Fri, 17 Apr 2009 16:34:47 -0400 (EDT) From: Christoph Lameter <cl@...ux.com> To: Peter Zijlstra <peterz@...radead.org> cc: Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org Subject: Re: Scheduler regression: Too frequent timer interrupts(?) On Fri, 17 Apr 2009, Peter Zijlstra wrote: > > often must occur in parallel on multiple cores. Processing is delayed if > > any of the cores encounters a delay due to OS noise. > > So you have hard deadlines in the order of us? Are these SCHED_FIFO > tasks or SCHED_OTHER? SCHED_FIFO has the effect of removing all the involuntary context switches but it does not effect the other interrutions. > Your Xeon is a core2 class machine and should have relatively stable > TSC, however its also a dual socket, which I think defeats the > stable-ness. > What clocksource do you have? > > cat /sys/devices/system/clocksource/clocksource0/current_clocksource cat /sys/devices/system/clocksource/clocksource0/current_clocksource tsc > Also, looking over the rest of the scheduler tick code, I can't really > see what would be so expensive. The expensiveness may be fine if we can limit the number of occurences. Maybe the histograms for those releases give more insight. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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