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Subject: Re: 2.6.17-rc6-rt1
From: Mike Galbraith <efault@gmx.de>
To: tglx@linutronix.de
Cc: =?ISO-8859-1?Q?S=E9bastien_Dugu=E9?= <sebastien.dugue@bull.net>,
       Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org,
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Date: Fri, 09 Jun 2006 15:42:38 +0200
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On Fri, 2006-06-09 at 15:11 +0200, Thomas Gleixner wrote:
> On Fri, 2006-06-09 at 14:57 +0200, Sébastien Dugué wrote:
> > All the round trips under strace are in the 2ms range.
> > 
> >   How on earth can it be that stracing the ping gives better
> > performance???
> 
> Was busy fixing a scheduling while atomic bug. I just verified that I
> have the same weird behaviour. I'm looking into it.

I downloaded and patched a ping.c to do a user triggered latency trace
around recvfrom() of a ping -c 1 127.0.0.1 running SCHED_RR.  We
schedule away at 25us, do aaaall kinds of interesting stuff, and come
back at 42234us.  If you want the trace, holler.  It's 51k bzipped.

	-Mike