From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751233AbWBWNm7 (ORCPT ); Thu, 23 Feb 2006 08:42:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751235AbWBWNm7 (ORCPT ); Thu, 23 Feb 2006 08:42:59 -0500 Received: from omx2-ext.sgi.com ([192.48.171.19]:9883 "EHLO omx2.sgi.com") by vger.kernel.org with ESMTP id S1751233AbWBWNm6 (ORCPT ); Thu, 23 Feb 2006 08:42:58 -0500 Date: Fri, 24 Feb 2006 00:42:13 +1100 From: David Chinner To: Robin Holt Cc: Andrew Morton , john@johnmccutchan.com, linux-kernel@vger.kernel.org, rml@novell.com, arnd@arndb.de, hch@lst.de Subject: Re: udevd is killing file write performance. Message-ID: <20060223134213.GG1332401@melbourne.sgi.com> References: <20060222134250.GE20786@lnx-holt.americas.sgi.com> <1140626903.13461.5.camel@localhost.localdomain> <20060222175030.GB30556@lnx-holt.americas.sgi.com> <20060222120547.2ae23a16.akpm@osdl.org> <20060223125639.GB25007@lnx-holt.americas.sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060223125639.GB25007@lnx-holt.americas.sgi.com> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 23, 2006 at 06:56:39AM -0600, Robin Holt wrote: > On Wed, Feb 22, 2006 at 12:05:47PM -0800, Andrew Morton wrote: > > Robin Holt wrote: > > > > > > Let me reiterate, I know _VERY_ little about filesystems. Can the > > > dentry->d_lock be changed to a read/write lock? > > > > Well, it could, but I suspect that won't help - the hold times in there > > will be very short so the problem is more likely acquisition frequency. > > > > However it's a bit strange that this function is the bottleneck. If their > > workload is doing large numbers of reads or writes from large numbers of > > processes against the same file then they should be hitting heavy > > contention on other locks, such as i_sem and/or tree_lock and/or lru_lock > > and others. > > > > Can you tell us more about the kernel-visible behaviour of this app? > > I looked at a little more of the output. All I have to go on is a few > back traces generated by kdb of the entire system a few seconds apart. > > In all of the traces, the first chunk of cpus are the only ones doing > writes. I have not counted exactly, but I think it is around 32. There > may be more or less, but that is the feeling (sometimes they are doing > reads as well). Robin, is the app doing direct or buffered I/O? Cheers, Dave. -- Dave Chinner R&D Software Enginner SGI Australian Software Group