linux-kernel - Re: High scheduler wake up times

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Message-ID: <20100130155640.62ce3104@infradead.org>
Date:	Sat, 30 Jan 2010 15:56:40 -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 17:45:51 -0600
Shawn Bohrer <shawn.bohrer@...il.com> wrote:

> Hello,
> 
> Currently we have a workload that depends on around 50 processes that
> wake up 1000 times a second do a small amount of work and go back to
> sleep.  This works great on RHEL 5 (2.6.18-164.6.1.el5), but on recent
> kernels we are unable to achieve 1000 iterations per second.  Using
> the simple test application below on RHEL 5 2.6.18-164.6.1.el5 I can
> run 500 of these processes on and still achieve 999.99 iterations per
> second.  Running just 10 of these processes on the same machine with
> 2.6.32.6 produces results like:
> 
> ...
> Iterations Per Sec: 905.659667
> Iterations Per Sec: 805.099068
> Iterations Per Sec: 925.195578
> Iterations Per Sec: 759.310773
> Iterations Per Sec: 702.849261
> Iterations Per Sec: 782.157292
> Iterations Per Sec: 917.138031
> Iterations Per Sec: 834.770391
> Iterations Per Sec: 850.543755
> ...
> 
> I've tried playing with some of the cfs tunables in /proc/sys/kernel/
> without success.  Are there any suggestions on how to achieve the
> results we are looking for using a recent kernel?

I'll play a bit, but I wonder idly what kind of machine this is on ?
(number and types of cpus)
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