From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756027AbYEGQin (ORCPT ); Wed, 7 May 2008 12:38:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752007AbYEGQia (ORCPT ); Wed, 7 May 2008 12:38:30 -0400 Received: from palinux.external.hp.com ([192.25.206.14]:46438 "EHLO mail.parisc-linux.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751975AbYEGQi3 (ORCPT ); Wed, 7 May 2008 12:38:29 -0400 Date: Wed, 7 May 2008 10:38:12 -0600 From: Matthew Wilcox To: Andrew Morton Cc: Ingo Molnar , "J. Bruce Fields" , "Zhang, Yanmin" , LKML , Alexander Viro , Linus Torvalds , linux-fsdevel@vger.kernel.org Subject: Re: AIM7 40% regression with 2.6.26-rc1 Message-ID: <20080507163811.GY19219@parisc-linux.org> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080506102153.5484c6ac.akpm@linux-foundation.org> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 06, 2008 at 10:21:53AM -0700, Andrew Morton wrote: > up() seems to be doing wake-one, FIFO which is nice. Did the > implementation which we just removed also do that? Was it perhaps > accidentally doing LIFO or something like that? If heavily contended, it could do this. up() would increment sem->count and cal __up() which would call wake_up() down() would decrement sem->count. The unlucky task woken by __up would lose the race and go back to sleep. -- Intel are signing my paycheques ... these opinions are still mine "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step."