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Message-ID: <20071110001103.GD16250@vmware.com> Date: Fri, 9 Nov 2007 16:11:03 -0800 From: Micah Dowty <micah@...are.com> To: Cyrus Massoumi <cyrusm@....net> Cc: linux-kernel@...r.kernel.org Subject: Re: High priority tasks break SMP balancer? On Sat, Nov 10, 2007 at 12:56:07AM +0100, Cyrus Massoumi wrote: > I tried your program on my machine (C2D, 2.6.17, O(1) scheduler). > > Both CPUs are 100% busy all the time. Each busy-looping thread is running > on its own CPU. I've been watching top output for 10 minutes, the spreading > is stable and the threads don't bounce at all. As I said, YMMV. I haven't been able to find a single set of parameters for the demo program which cause the problem to occur 100% of the time on all systems. In general, boosting the MAINTHREAD_PRIORITY even more and increasing the WAKE_HZ should exaggerate the problem. These parameters reproduce the problem very reliably on my system: #define NUM_BUSY_THREADS 2 #define MAINTHREAD_PRIORITY -20 #define MAINTHREAD_WAKE_HZ 1024 #define MAINTHREAD_LOAD_PERCENT 5 #define MAINTHREAD_LOAD_CYCLES 2 It's also possible this problem doesn't occur on 2.6.17. I have only tested this example on 2.6.23.1 and 2.6.20 so far. Thanks, --Micah - 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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