From owner-freebsd-arch@FreeBSD.ORG Fri May 27 12:07:44 2005 Return-Path: X-Original-To: freebsd-arch@freebsd.org Delivered-To: freebsd-arch@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 38EF016A41C for ; Fri, 27 May 2005 12:07:44 +0000 (GMT) (envelope-from kensmith@cse.Buffalo.EDU) Received: from opus.cse.buffalo.edu (opus.cse.Buffalo.EDU [128.205.32.4]) by mx1.FreeBSD.org (Postfix) with ESMTP id DEDD643D49 for ; Fri, 27 May 2005 12:07:43 +0000 (GMT) (envelope-from kensmith@cse.Buffalo.EDU) Received: from opus.cse.buffalo.edu (opus.cse.buffalo.edu [128.205.32.4]) by opus.cse.buffalo.edu (8.13.3/8.12.10) with ESMTP id j4RC7ZpW088600; Fri, 27 May 2005 08:07:42 -0400 (EDT) From: Ken Smith To: Marc Olzheim In-Reply-To: <20050527091750.GB91258@stack.nl> References: <1117139065.82793.20.camel@opus.cse.buffalo.edu> <20050527091750.GB91258@stack.nl> Content-Type: text/plain Organization: U. Buffalo CSE Department Date: Fri, 27 May 2005 08:07:35 -0400 Message-Id: <1117195655.88498.9.camel@opus.cse.buffalo.edu> Mime-Version: 1.0 X-Mailer: Evolution 2.2.2 FreeBSD GNOME Team Port Content-Transfer-Encoding: 7bit Cc: freebsd-arch@freebsd.org Subject: Re: Modifying file access time upon exec... X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 27 May 2005 12:07:44 -0000 On Fri, 2005-05-27 at 11:17 +0200, Marc Olzheim wrote: > On Thu, May 26, 2005 at 04:24:25PM -0400, Ken Smith wrote: > > Any thoughts before I commit it? The patch itself is pretty small. But > > given the sections of code it's mucking with combined with it adding a > > little 'nit' filesystem implementers should be aware of I wanted to run > > it by as many clueful eyes as possible before doing the final commit. > > Has this been run through some kind of real world performance test ? I > can imagine for instance /bin/sh's vnode is being updated a lot... Would > it be eligible to a becoming a mount option ? Bruce did some benchmarking and this approach seemed to be the minimal hit on performance of the options we have. The other things that got tested were things like "fake reads". The whole issue started when the exec mechanisms were shifted away from doing file reads in favor of a more mmap based mechanism for starting the executables. >From his tests the hit seemed minimal. The noatime mount option seems to be the most appropriate thing to use for turning it off, and in that case the only cost involved with this addition is the check in exec to see if the file is coming from a filesystem that's either noatime or readonly. > I don't see any real problems with it, but perhaps people running > executables over NFS filesystems that cannot be mounted with noatime > might have an issue, like netbooting diskless machines... I'm not sure why you say NFS filesystems can't be mounted with noatime. -- Ken Smith - From there to here, from here to | kensmith@cse.buffalo.edu there, funny things are everywhere. | - Theodore Geisel |