From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 68795C282CB for ; Mon, 4 Feb 2019 23:15:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 365A72081B for ; Mon, 4 Feb 2019 23:15:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726969AbfBDXPB (ORCPT ); Mon, 4 Feb 2019 18:15:01 -0500 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 Received: from ppp59-167-129-252.static.internode.on.net (HELO dastard) ([59.167.129.252]) by ipmail02.adl2.internode.on.net with ESMTP; 05 Feb 2019 09:43:46 +1030 Received: from dave by dastard with local (Exim 4.80) (envelope-from ) id 1gqnQw-0000Ul-Bx; Tue, 05 Feb 2019 10:13:46 +1100 Date: Tue, 5 Feb 2019 10:13:46 +1100 From: Dave Chinner To: Rasmus Villemoes Cc: "Darrick J. Wong" , linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org 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> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: 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