From mboxrd@z Thu Jan 1 00:00:00 1970 From: "J. Bruce Fields" Subject: Re: Beagle and logging inotify events Date: Wed, 14 Nov 2007 14:38:05 -0500 Message-ID: <20071114193805.GN14254@fieldses.org> References: <9e4733910711131604k1290d4e1s5ee9808cbb61c2b6@mail.gmail.com> <45578746-916A-4F59-9A92-E7CEEFBC09B0@oracle.com> <9e4733910711140544l3f311868n96d753ce0b70cee5@mail.gmail.com> <473B0908.1060304@oracle.com> <9e4733910711140701q36cc168awbe060ed5537c491e@mail.gmail.com> <473B2329.8000407@oracle.com> <20071114193245.GE3966@webber.adilger.int> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: Chuck Lever , Jon Smirl , linux-fsdevel@vger.kernel.org, Jan Kara Return-path: Received: from mail.fieldses.org ([66.93.2.214]:43752 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761488AbXKNTiI (ORCPT ); Wed, 14 Nov 2007 14:38:08 -0500 Content-Disposition: inline In-Reply-To: <20071114193245.GE3966@webber.adilger.int> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Wed, Nov 14, 2007 at 12:32:45PM -0700, Andreas Dilger wrote: > On Nov 14, 2007 11:32 -0500, Chuck Lever wrote: > > I disagree: we don't need a "bullet-proof" log. We can get a significant > > performance improvement even with a permanent dnotify log implemented in > > user-space. We already have well-defined fallback behavior if such a log > > is missing or incomplete. > > > > The problem with a permanent inotify log is that it can become unmanageably > > enormous, and a performance problem to boot. Recording at that level of > > detail makes it more likely that the logger won't be able to keep up with > > file system activity. > > > > A lightweight solution gets us most of the way there, is simple to > > implement, and doesn't introduce many new issues. As long as it can tell > > us precisely where the holes are, it shouldn't be a problem. > > Jan Kara is working on a patch for ext4 which would store a recursive > timestamp for each directory that gives the latest time that a file in > that directory was modified. ZFS has a similar mechanism by virtue of > doing full-tree updates during COW of all the metadata blocks and storing > the most recent transaction number in each block. I suspect btrfs could > do the same thing easily. > > That would allow recursive-descent filesystem traversal to be much more > efficient because whole chunks of the filesystem tree can be ignored during > scans. The problem is that people may not be happy with the random behavior of hardlinks, right? --b.