linux-kernel - Re: [Bug #11308] tbench regression on each kernel release from 2.6.22 -> 2.6.28

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Message-ID: <alpine.LFD.2.00.0811171147380.18283@nehalem.linux-foundation.org>
Date:	Mon, 17 Nov 2008 11:48:33 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	David Miller <davem@...emloft.net>
cc:	mingo@...e.hu, rjw@...k.pl, linux-kernel@...r.kernel.org,
	kernel-testers@...r.kernel.org, cl@...ux-foundation.org,
	efault@....de, a.p.zijlstra@...llo.nl
Subject: Re: [Bug #11308] tbench regression on each kernel release from 2.6.22
 -&gt; 2.6.28



On Mon, 17 Nov 2008, David Miller wrote:

> From: Ingo Molnar <mingo@...e.hu>
> Date: Mon, 17 Nov 2008 12:01:19 +0100
> 
> > The scheduler's overhead barely even registers on a 16-way x86 system 
> > i'm running tbench on. Here's the NMI profile during 64 threads tbench 
> > on a 16-way x86 box with an v2.6.28-rc5 kernel [config attached]:
> 
> Try a non-NMI profile.
> 
> It's the whole of the try_to_wake_up() path that's the problem.

David, that makes no sense. A NMI profile is going to be a _lot_ more 
accurate than a non-NMI one. Asking somebody to do a clearly inferior 
profile to get "better numbers" is insane.

We've asked _you_ to do NMI profiling, it shouldn't be the other way 
around.

		Linus
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