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Message-ID: <20100131102846.4d1e18aa@infradead.org> Date: Sun, 31 Jan 2010 10:28:46 -0800 From: Arjan van de Ven <arjan@...radead.org> To: Shawn Bohrer <shawn.bohrer@...il.com> Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org> Subject: Re: High scheduler wake up times On Sat, 30 Jan 2010 21:47:18 -0600 Shawn Bohrer <shawn.bohrer@...il.com> wrote: > > Of course that patch makes my situation worse, which was my point. We > are depending on the _current_ epoll_wait() implementation which calls > schedule_timeout(1). > You do agree that the current epoll_wait() > implementation sleeps less than 1 msec with HZ == 1000 correct? I agree with your hypothesis, but I wouldn't call the behavior correct ;-) First of all, jiffies based timeouts are supposed to round *up*, not down, and second.. it should really be just 1 msec. > With the old kernel I can run 500 of these processes, and I'm hoping > that I'm simply missing the knob I need to tweak to achieve similar > performance on a recent kernel. can you run powertop during your workload? maybe you're getting hit by some C state exit latencies tilting the rounding over the top just too many times... -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org -- 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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