From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755028Ab3IMJqE (ORCPT ); Fri, 13 Sep 2013 05:46:04 -0400 Received: from mail-ea0-f170.google.com ([209.85.215.170]:43733 "EHLO mail-ea0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753772Ab3IMJp7 (ORCPT ); Fri, 13 Sep 2013 05:45:59 -0400 Date: Fri, 13 Sep 2013 11:45:55 +0200 From: Ingo Molnar To: Jean Pihet Cc: David Ahern , Arnaldo Carvalho de Melo , Linus Torvalds , Linux Kernel Mailing List , Peter Zijlstra , Thomas Gleixner , Andrew Morton Subject: Re: [GIT PULL] perf fixes Message-ID: <20130913094555.GA11611@gmail.com> References: <20130912184341.GA11400@ghostprotocols.net> <52321CE4.1080804@gmail.com> <20130912201855.GC32644@gmail.com> <20130912203831.GD11400@ghostprotocols.net> <20130912204618.GA3262@gmail.com> <52322D81.5090708@gmail.com> <20130912211846.GA7890@gmail.com> <52323BE4.5080100@gmail.com> <20130913050927.GA8634@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Jean Pihet wrote: > Hi, > > On 13 September 2013 07:09, Ingo Molnar wrote: > > > > * David Ahern wrote: > > > >> > By default a simple 'make' should build perf to the maximum extent > >> > possible, with no other input required from the user - with warnings > >> > displayed as package install suggestions. > >> > >> By default there is no config. Autoprobing generates a first one or a > >> user can specify a defconfig. > > > > This could work if there's not two but three states for individual > > features: > > > > - autoprobe > > - on > > - off > > > > and if autoprobe, if a system feature has been probed successfully, > > automatically turned 'autoprobe' entries into 'on'. > > > > That would give us the best of all worlds - autodetection, configurability > > and caching: > > > > - initial user types 'make' and gets a .config that has almost all > > entries 'on', a few 'autoprobe'. > > > > - once the user installs a dependency, the corresponding .config entry > > turns into 'on'. > > > > - the regular user or developers would have libraries that turn all > > entries in the .config to 'on'. > > > > - if a user is genuinely uninterested in a feature, he can mark it 'off', > > which would then stay off permanently. This could also be used by > > embedded/specialized builds. > > > > - other specialized users, like distro builds, could use a .config with > > all entries 'on' and could enforce the presence of all dependencies for > > a successful build. [We could add 'make allyesconfig' to help that.] > > Is there a way to detect the presence of a dependency and _also_ check > its version? Some new features are depending on a recent version of a > library, e.g. dwarf unwinding depends on libunwind >= 1.1 (cf. > http://www.spinics.net/lists/kernel/msg1598951.html). Yeah, see the testcases in tools/perf/config/feature-tests.mak, they typically include the latest library API usages, which will fail on older versions. That kind of 'does it actually work?' test is a lot more robust than explicit version checks, and combined with caching it should be fast and parallelizable as well. (One of the problems of the current simple implementation of the feature tests is that they are 20 serial tests with no parallelization.) Thanks, Ingo