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Date: Tue, 4 Jan 2011 16:16:56 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Chris Mason <chris.mason@oracle.com>,
        Frank Rowand <frank.rowand@am.sony.com>,
        Thomas Gleixner <tglx@linutronix.de>, Mike Galbraith <efault@gmx.de>,
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        Jens Axboe <axboe@kernel.dk>, Yong Zhang <yong.zhang0@gmail.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH 00/18] sched: Reduce runqueue lock contention -v4
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References: <20110104145929.772813816@chello.nl>
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* Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:

> Latest version of the scary patches...

Just to make it easier for others to see the rationale behind this series, see the 
numbers and limitations listed below.

	Ingo

------------------------->
As measured using: http://oss.oracle.com/~mason/sembench.c

$ echo 4096 32000 64 128 > /proc/sys/kernel/sem
$ ./sembench -t 2048 -w 1900 -o 0

unpatched: run time 30 seconds 639476 worker burns per second
patched:   run time 30 seconds 847526 worker burns per second

Still need to sort out all the races marked XXX (non-trivial), and its
x86 only for the moment.