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Date: Wed, 7 May 2008 19:25:42 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox <matthew@wil.cx>, Andrew Morton <akpm@linux-foundation.org>,
       "J. Bruce Fields" <bfields@citi.umich.edu>,
       "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>,
       LKML <linux-kernel@vger.kernel.org>,
       Alexander Viro <viro@ftp.linux.org.uk>, linux-fsdevel@vger.kernel.org
Subject: Re: AIM7 40% regression with 2.6.26-rc1
Message-ID: <20080507172542.GA13389@elte.hu>
References: <1210052904.3453.30.camel@ymzhang> <20080506114449.GC32591@elte.hu> <20080506120934.GH19219@parisc-linux.org> <20080506162332.GI19219@parisc-linux.org> <20080506102153.5484c6ac.akpm@linux-foundation.org> <20080507163811.GY19219@parisc-linux.org> <alpine.LFD.1.10.0805070948250.3024@woody.linux-foundation.org> <alpine.LFD.1.10.0805070956060.3024@woody.linux-foundation.org> <20080507172246.GA13262@elte.hu>
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* Ingo Molnar <mingo@elte.hu> wrote:

> There's far more normal mutex fastpath use during an AIM7 run than any 
> BKL use. So if it's due to any direct fastpath overhead and the 
> resulting widening of the window for the real slowdown, we should see 
> a severe slowdown on AIM7 with CONFIG_MUTEX_DEBUG=y. Agreed?

my own guesstimate about AIM7 performance impact resulting out of 
CONFIG_MUTEX_DEBUG=y: performance overhead will not be measurable, or 
will at most be in the sub-1% range. But i've been badly wrong before :)

	Ingo