Date: Mon, 17 Nov 2008 11:52:58 -0800 (PST)
Message-Id: <20081117.115258.227376348.davem@davemloft.net>
To: torvalds@linux-foundation.org
Cc: mingo@elte.hu, rjw@sisk.pl, linux-kernel@vger.kernel.org,
       kernel-testers@vger.kernel.org, cl@linux-foundation.org, efault@gmx.de,
       a.p.zijlstra@chello.nl
Subject: Re: [Bug #11308] tbench regression on each kernel release from
 2.6.22 -&gt; 2.6.28
From: David Miller <davem@davemloft.net>
In-Reply-To: <alpine.LFD.2.00.0811171147380.18283@nehalem.linux-foundation.org>
References: <20081117110119.GL28786@elte.hu>
	<20081117.112157.146825192.davem@davemloft.net>
	<alpine.LFD.2.00.0811171147380.18283@nehalem.linux-foundation.org>
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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Mon, 17 Nov 2008 11:48:33 -0800 (PST)

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

I wasn't able to on these systems, so instead I did cycle level
evaluation of the parts that have to run with interrupts disabled.

And as a result I found that wake_up() is now 4 times slower than it
was in 2.6.22, I even analyzed this for every single kernel release
till now.

It could be a sparc specific issue, because the call chain is deeper
and we eat a lot more register window spills onto the stack.
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