From owner-freebsd-current@FreeBSD.ORG Sun May 16 09:44:23 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 5705316A4CE for ; Sun, 16 May 2004 09:44:23 -0700 (PDT) Received: from pooker.samsco.org (pooker.samsco.org [168.103.85.57]) by mx1.FreeBSD.org (Postfix) with ESMTP id 8946143D39 for ; Sun, 16 May 2004 09:44:22 -0700 (PDT) (envelope-from scottl@freebsd.org) Received: from freebsd.org (junior-wifi.samsco.home [192.168.0.11]) by pooker.samsco.org (8.12.10/8.12.10) with ESMTP id i4GGnZu6097846; Sun, 16 May 2004 10:49:35 -0600 (MDT) (envelope-from scottl@freebsd.org) Message-ID: <40A79A54.3090703@freebsd.org> Date: Sun, 16 May 2004 10:44:04 -0600 From: Scott Long User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.6) Gecko/20040304 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Dan Nelson References: <20040515220258.H920@ganymede.hub.org> <20040515233728.Q30269@ganymede.hub.org> <20040516163039.GE29158@dan.emsphone.com> In-Reply-To: <20040516163039.GE29158@dan.emsphone.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, hits=0.0 required=3.8 tests=none autolearn=no version=2.63 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on pooker.samsco.org cc: freebsd-current@freebsd.org cc: Michael Hamburg Subject: Re: fsck in -current X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 16 May 2004 16:44:23 -0000 Dan Nelson wrote: > In the last episode (May 16), Michael Hamburg said: > >>On May 15, 2004, at 10:41 PM, Marc G. Fournier wrote: >> >>>On Sat, 15 May 2004, Michael Hamburg wrote: >>> >>>>On May 15, 2004, at 9:08 PM, Marc G. Fournier wrote: >>>> >>>>>I'm seriously considering putting 5.x onto my next server, to take >>>>>advantage of, if nothing else, the reduction in the GIANT LOCK >>>>>reliance ... one "concern" I have is how fsck works in 5.x ... >>>>> >>>>>Right now, on 4.x, I have an fsck running that has been going for >>>>>~3hrs now: >>>>> >>>>># date; ps aux | grep fsck >>>>>Sat May 15 22:04:00 ADT 2004 >>>>>root 40 99.0 4.5 185756 185796 p0 R+ 6:55PM 164:01.60 fsck -y /dev/da0s1h >>>>> >>>>>and is in Phase 4 ... >>>>> >>>>>In 5.x, if I'm not mistaken, fsck's are backgrounded on reboot, so >>>>>that the system comes up faster ... but: >>>>> >>>>>a. wouldn't that slow down the fsck itself, since all the >>>>>processes on the machine would be using CPU/memory? >>>> >>>>Yes. You can probably renice it or something, though, and it >>>>wouldn't take that much longer. > > > Fsck takes very little CPU; it's almost all disk I/O, and bgfsck tries > to throttle its load if it thinks that there's too much disk load. > Actually, bgfsck unconditionally inserts a delay into every 8th i/o operation to try to keep from saturating the disks. Unfortunately this isn't terribly sophisticated and it results in bgfsck taking an eternity whether the system is idle, loaded, or reniced. A _really_ nice TODO item for FreeBSD 6.0 would be a real I/O scheduler. There are plenty of papers on it, some even focused on FreeBSD. Any volunteers? Scott