From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262905AbTDVECb (ORCPT ); Tue, 22 Apr 2003 00:02:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262908AbTDVECb (ORCPT ); Tue, 22 Apr 2003 00:02:31 -0400 Received: from franka.aracnet.com ([216.99.193.44]:45503 "EHLO franka.aracnet.com") by vger.kernel.org with ESMTP id S262905AbTDVECa (ORCPT ); Tue, 22 Apr 2003 00:02:30 -0400 Date: Mon, 21 Apr 2003 21:14:33 -0700 From: "Martin J. Bligh" To: Andrew Morton cc: linux-kernel@vger.kernel.org Subject: Re: 67-mjb2 vs 68-mjb1 (sdet degredation) Message-ID: <149880000.1050984872@[10.10.2.4]> In-Reply-To: <20030421205231.4392aaa7.akpm@digeo.com> References: <1425480000.1050959528@flay> <20030421144631.4987db46.akpm@digeo.com><147950000.1050981750@[10.10.2.4]> <20030421205231.4392aaa7.akpm@digeo.com> X-Mailer: Mulberry/2.2.1 (Linux/x86) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org >> > Here's a backout patch. Does it fix it up? >> >> Yeah, that fixes it. Ho hum ... I wonder if we can find something that >> works well for both cases? I guess the options would be: >> >> 1. Some way to make the rwlock mechanism itself faster. >> 2. Try to fix the contention itself somehow for this instance. > > You're using PIII's, which don't mind the additional buslocked operation. > P4's hate it. We'd need to retest on big P4 and other architectures to > decide. OK, I can try do get someone to test on big x440s (P4 Xeon). > I suspect the spinlock is better that the rwlock overall - having multiple > CPUs looking up things in the same address_space is relatively uncommon. > Having one CPU looking things up in one address space is very common, and > that's the thing which the s/rwlock/spinlock/ speeds up. Yeah, wasn't really complaining - I think the spinlock is the right thing to do ... I just wanted to nail down what caused it, and be sure it was deliberate. Looks like it is, so that all seems OK. Thanks for the help ;-) M.