From owner-freebsd-questions Wed Feb 12 23:18:51 2003 Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 7EB3037B401; Wed, 12 Feb 2003 23:18:50 -0800 (PST) Received: from heron.mail.pas.earthlink.net (heron.mail.pas.earthlink.net [207.217.120.189]) by mx1.FreeBSD.org (Postfix) with ESMTP id AFD7643F93; Wed, 12 Feb 2003 23:18:49 -0800 (PST) (envelope-from tlambert2@mindspring.com) Received: from pool0060.cvx21-bradley.dialup.earthlink.net ([209.179.192.60] helo=mindspring.com) by heron.mail.pas.earthlink.net with asmtp (SSLv3:RC4-MD5:128) (Exim 3.33 #1) id 18jDdn-00054j-00; Wed, 12 Feb 2003 23:18:40 -0800 Message-ID: <3E4B467B.4DCF6D5@mindspring.com> Date: Wed, 12 Feb 2003 23:17:15 -0800 From: Terry Lambert X-Mailer: Mozilla 4.79 [en] (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: David Schultz Cc: Brooks Davis , Darren Pilgrim , Matthew Emmerton , Daxbert , Bill Moran , Heinrich Rebehn , freebsd-questions@FreeBSD.ORG, freebsd-fs@FreeBSD.ORG Subject: Re: Why is there no JFS? References: <3E4A8EF5.1070308@ant.uni-bremen.de> <3E4A9712.8030609@potentialtech.com> <3E4AA331.5040701@ant.uni-bremen.de> <3E4AA734.5040102@potentialtech.com> <045401c2d2db$f9d45c30$0a0aa8c0@dweebsoft.com> <20030212225631.GA10375@HAL9000.homeunix.com> <005801c2d2eb$aa5fae60$1200a8c0@gsicomp.on.ca> <3E4ADDDE.5040208@pantherdragon.org> <3E4B138F.26E32E75@mindspring.com> <20030212210721.A9481@Odin.AC.HMC.Edu> <20030213051952.GA11572@HAL9000.homeunix.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-ELNK-Trace: b1a02af9316fbb217a47c185c03b154d40683398e744b8a4bbafef6825ccc3a32be407111dfa09be3ca473d225a0f487350badd9bab72f9c350badd9bab72f9c Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG David Schultz wrote: > > There's no chicken and egg problem when you're booting off install > > media or for that matter from single user mode. The problem was that > > softupdates means you don't get space back from deleted files immediatly > > so previously / tended to fillup during installworld or installkernel. > > I know some fixes have been implemented in that area, but I'm not sure > > if then mean you can always write to the space occupied by unlinked > > files or just that you have a better chance. > > The problem is effectively fixed in 5.0. Basically, when no space > can be found, the syncer is accelerated to try to speed up frees. > Technically it's possible to run into a livelock, where you keep > freeing space and it keeps getting snatched up before you can grab > it, so you wait forever. So IIRC, there is a point where it just > gives up on finding the space. However, that won't happen with an > install, so the free space problem isn't a reason not to use > softupdates on the root FS. I think the default hasn't been > changed just because nobody has bothered. The easy way to fix this is to insert a new dependency for the completion of the allocation. Basically, this would put in a stall barrier that would cause the outstanding I/O to drain before the new I/O was attempted. All other operations behind the one that caused the stall would b held off, which would avoid the starvation deadlock you describe. Most likely, all this would require some minor code to maintain a running tally of virtual vs. real free block count. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message