From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756764Ab3ILUTE (ORCPT ); Thu, 12 Sep 2013 16:19:04 -0400 Received: from mail-ea0-f169.google.com ([209.85.215.169]:57294 "EHLO mail-ea0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756729Ab3ILUS6 (ORCPT ); Thu, 12 Sep 2013 16:18:58 -0400 Date: Thu, 12 Sep 2013 22:18:55 +0200 From: Ingo Molnar To: David Ahern Cc: Arnaldo Carvalho de Melo , Linus Torvalds , Linux Kernel Mailing List , Peter Zijlstra , Thomas Gleixner , Andrew Morton Subject: Re: [GIT PULL] perf fixes Message-ID: <20130912201855.GC32644@gmail.com> References: <20130912133855.GA23780@gmail.com> <20130912184341.GA11400@ghostprotocols.net> <52321CE4.1080804@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <52321CE4.1080804@gmail.com> 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 * David Ahern wrote: > On 9/12/13 11:43 AM, Arnaldo Carvalho de Melo wrote: > > Its something that annoys me as well, but not so much as to make me > > figure out how to make those be done only if some source file changed. > > Jiri and I have both taken stabs at a config-based build rather than > probing. Just need to finish it. Mind outlining the approach you are thinking about? Firstly, please don't even think about autotools. (Just forget it exists.) Secondly, the way perf tries to build by auto-detecting the build environment and auto-disabling bits it cannot build just yet is pretty powerful. The core bits will build on just about any system, and our fallbacks are really good. The result is that perf will build on just about any random system, without the user having to install any dependency. It would be really sad to lose that aspect. What I think would work best is what I outlined in the previous mail: to cache successful feature test results and only re-do unsuccessful tests: those are the ones that are expected to turn into successful tests in the future, once the missing dependencies are installed. Since most tests succeed even on a sparsely installed system, this trick alone will speed up the checks big time. Furthermore, this method would encourage people to install the dependencies - and perf developers, who do many repeat builds after trivial one-file changes, will typically have all dependencies installed anyway, so for them such a caching feature would result in totally cached feature tests and very fast build times. Thanks, Ingo