From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Chinner Subject: Re: The VFS hot tracking debacle Date: Sun, 20 Jul 2014 10:02:28 +1000 Message-ID: <20140720000228.GK4453@dastard> References: <1383745544-391-1-git-send-email-zwu.kernel@gmail.com> <2831755.nuyKSN0E6B@merkaba> <20140717215248.GD20518@dastard> <5288000.xmdEPgGx6M@merkaba> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Daniel Poelzleithner , linux-fsdevel@vger.kernel.org To: Martin Steigerwald Return-path: Received: from ipmail04.adl6.internode.on.net ([150.101.137.141]:12390 "EHLO ipmail04.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756143AbaGTACx (ORCPT ); Sat, 19 Jul 2014 20:02:53 -0400 Content-Disposition: inline In-Reply-To: <5288000.xmdEPgGx6M@merkaba> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Fri, Jul 18, 2014 at 10:25:23AM +0200, Martin Steigerwald wrote: > Am Freitag, 18. Juli 2014, 07:52:48 schrieb Dave Chinner: > > On Thu, Jul 17, 2014 at 11:34:49PM +0200, Martin Steigerwald wrote: > > > Am Donnerstag, 17. Juli 2014, 19:35:53 schrieb Daniel Poelzleithner: > > > > Zhi Yong Wu gmail.com> writes: > > > > > Ping ^ 7 > > > > > > > > I'm following this patch now for quite some time and I have to say that > > > > this thread+patch is one of the most disappointing experiences I had > > > > with kernel development. > > > > > > > > I can't understand why such a patch is simply ignored from the > > > > maintainers > > > > of the subsystem, no comment, no review, no checkin. > > > > > > I always wanted to try this one out, but never got around doing it. > > > > > > I really like the general approach of it to put the general stuff into VFS > > > and only the special stuff into filesystems like BTRFS. > > > > And that's the core issue here: there are no applications that use > > the information. i.e. it's a solution looking for a problem. > > > > I spent a lot of time reviewing and helping on this, and I made > > repeated suggestions that applications like xfs_fsr could make use > > of the information to do optimised file layout during > > defragmentation, but nothing like that has ever been implemented. > > > > So, really, until there is an application that actually demonstrates > > the usefulness of the specific information that is tracked and > > exported, we can't verify that the code as it stands is actually > > useful. We can verify that the code doesn't have problems, but we > > can't verify whether it is fit for purpose because it currently has > > no purpose.... > > So this needs an example implementation for one filesystem? > > I thought there is one for BTRFS. The tracking of the "hot data" was implemented for both btrfs and XFS. There isn't a *consumer* of that data, however, and that's the missing piece of the picture. Cheers, Dave. -- Dave Chinner david@fromorbit.com