From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: AIM7 40% regression with 2.6.26-rc1 Date: Wed, 7 May 2008 11:27:21 -0700 (PDT) Message-ID: References: <20080506120934.GH19219@parisc-linux.org> <20080506162332.GI19219@parisc-linux.org> <20080506102153.5484c6ac.akpm@linux-foundation.org> <20080507163811.GY19219@parisc-linux.org> <20080507172246.GA13262@elte.hu> <20080507174900.GB13591@elte.hu> <20080507181714.GA14980@elte.hu> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Matthew Wilcox , Andrew Morton , "J. Bruce Fields" , "Zhang, Yanmin" , LKML , Alexander Viro , linux-fsdevel@vger.kernel.org To: Ingo Molnar Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:55338 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1765614AbYEGS1n (ORCPT ); Wed, 7 May 2008 14:27:43 -0400 In-Reply-To: <20080507181714.GA14980@elte.hu> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Wed, 7 May 2008, Ingo Molnar wrote: > > [ this patch should in fact be a bit worse, because there's two more > atomics in the fastpath - the fastpath atomics of the old semaphore > code. ] Well, it doesn't have the irq stuff, which is also pretty costly. Also, it doesn't nest the accesses the same way (with the counts being *inside* the spinlock and serialized against each other), so I'm not 100% sure you'd get the same behaviour. But yes, it certainly has the potential to show the same slowdown. But it's not a very good patch, since not showing it doesn't really prove much. Linus