From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ipmail02.adl2.internode.on.net ([150.101.137.139]:49151 "EHLO ipmail02.adl2.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726086AbfBDXPB (ORCPT ); Mon, 4 Feb 2019 18:15:01 -0500 Date: Tue, 5 Feb 2019 10:13:46 +1100 From: Dave Chinner Subject: Re: [PATCH] xfs: allow disabling xfs tracepoints via Kconfig Message-ID: <20190204231346.GC14116@dastard> References: <20190204212035.9919-1-linux@rasmusvillemoes.dk> <20190204215332.GB14116@dastard> <4d66f2c2-bf5c-be47-9ef1-e581c5901823@rasmusvillemoes.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4d66f2c2-bf5c-be47-9ef1-e581c5901823@rasmusvillemoes.dk> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Rasmus Villemoes Cc: "Darrick J. Wong" , linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org On Mon, Feb 04, 2019 at 11:12:57PM +0100, Rasmus Villemoes wrote: > On 04/02/2019 22.53, Dave Chinner wrote: > > On Mon, Feb 04, 2019 at 10:20:35PM +0100, Rasmus Villemoes wrote: > >> linux/tracepoints.h allows individual subsystems to disable their > >> tracepoints. Add such a knob for xfs. Disabling XFS_TRACEPOINTS > >> reduces the resident size of xfs.ko by about a third, or ~350 KiB. > > > > Ok, now we can't debug typical problems on live production systems > > if tracepoints are turned off on the user/distro kernels. So under > > what circumstances would we ever want to turn off tracepoints on > > XFS? > > I don't expect any mainstream distros to turn it off. But for embedded > systems that use a hand-tuned .config, being able to shave off 100s of K > of the kernel image is quite valuable. However, small embedded systems don't use XFS because of it's size, dependence on 64 bit capability (ie. 64BIT || LBDAF), its CPU and memory overhead in comparison to other filesystems, etc. Increasing kconfig options increases the test matrix (even just the "does this changeset compile" matrix) so these things don't come for free. XFS is firmly focussed on the other end of the scale (big, lots, fast), so I'm not sure that increasing the kconfig combination matrix to cater for really low end embedded systems is really that worthwhile. > Tracing _is_ useful, > also/especially when doing embedded development, which is why "just turn > off CONFIG_TRACING" isn't really an option. Do you have a specific need for this, or is it just "I noticed this, here's a patch"? If you need it and will use it, great, let's add it. But config options that don't ever get used tend to rot.... Cheers, Dave. -- Dave Chinner david@fromorbit.com