From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932337AbWB0URG (ORCPT ); Mon, 27 Feb 2006 15:17:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932339AbWB0URG (ORCPT ); Mon, 27 Feb 2006 15:17:06 -0500 Received: from d36-15-41.home1.cgocable.net ([24.36.15.41]:10931 "EHLO localhost.localdomain") by vger.kernel.org with ESMTP id S932337AbWB0URE (ORCPT ); Mon, 27 Feb 2006 15:17:04 -0500 Subject: Re: udevd is killing file write performance. From: John McCutchan Reply-To: john@johnmccutchan.com To: Nick Piggin Cc: Andrew Morton , holt@sgi.com, linux-kernel@vger.kernel.org, rml@novell.com, arnd@arndb.de, hch@lst.de, Dipankar Sarma In-Reply-To: <4402D039.1050307@yahoo.com.au> References: <20060222134250.GE20786@lnx-holt.americas.sgi.com> <1140626903.13461.5.camel@localhost.localdomain> <20060222175030.GB30556@lnx-holt.americas.sgi.com> <1140648776.1729.5.camel@localhost.localdomain> <20060222151223.5c9061fd.akpm@osdl.org> <1140651662.2985.2.camel@localhost.localdomain> <20060223161425.4388540e.akpm@osdl.org> <20060224054724.GA8593@johnmccutchan.com> <20060223220053.2f7a977e.akpm@osdl.org> <43FEB0BF.6080403@yahoo.com.au> <1140972918.15634.1.camel@localhost.localdomain> <4402D039.1050307@yahoo.com.au> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Mon, 27 Feb 2006 15:17:00 -0500 Message-Id: <1141071420.3735.5.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.4.2.1 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2006-27-02 at 21:11 +1100, Nick Piggin wrote: > John McCutchan wrote: > > On Fri, 2006-24-02 at 18:07 +1100, Nick Piggin wrote: > > >>I saw this problem when testing my lockless pagecache a while back. > >> > >>Attached is a first implementation of what was my idea then of how > >>to solve it... note it is pretty rough and I never got around to doing > >>much testing of it. > >> > >>Basically: moves work out of inotify event time and to inotify attach > >>/detach time while staying out of the core VFS. > > > > > > > > This looks really good. There might be some corner cases but it looks > > like it will solve this problem nicely. > > > > Thanks. You should see I sent a new version which fixes several bugs > and cleans up the code a bit. > Yeah, it looks good. I haven't had time to test it myself but nothing jumps out at as being wrong. I can only say that about the code that touches inotify -- the rest of the VFS someone else will need to comment on. > There might be some areas of potential problems: > - creating and deleting watches on directories with many entries will > take a long time. Is anyone likely to be creating and destroying > these things at a very high frequency? Probably nobody cares except > it might twist some real-time knickers. > That's not a typical inotify usage pattern. Typically a watch is created and left until the directory is deleted, or the application closes. > - concurrent operations in the same watched directory will incur the > same scalability penalty. I think this is basically a non-issue since > the sheer number of events coming out will likely be a bigger problem. > Doctor, it hurts when I do this. > Again, Yeah, I don't think we need to worry. -- John McCutchan