Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756697Ab3ILUnT (ORCPT ); Thu, 12 Sep 2013 16:43:19 -0400 Received: from mail-ea0-f177.google.com ([209.85.215.177]:56702 "EHLO mail-ea0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753590Ab3ILUnR (ORCPT ); Thu, 12 Sep 2013 16:43:17 -0400 Date: Thu, 12 Sep 2013 22:43:13 +0200 From: Ingo Molnar To: Arnaldo Carvalho de Melo Cc: David Ahern , Linus Torvalds , Linux Kernel Mailing List , Peter Zijlstra , Thomas Gleixner , Andrew Morton Subject: Re: [GIT PULL] perf fixes Message-ID: <20130912204313.GA3259@gmail.com> References: <20130912133855.GA23780@gmail.com> <20130912184341.GA11400@ghostprotocols.net> <52321CE4.1080804@gmail.com> <20130912200236.GC11400@ghostprotocols.net> <20130912203116.GD32644@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130912203116.GD32644@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 Content-Length: 2591 Lines: 71 * Ingo Molnar wrote: > Instead of having 20 testcases crammed into a single Makefile: > > comet:~/tip/tools/perf> git grep -w main config/feature-tests.mak > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(int argc, char *argv[]) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > config/feature-tests.mak:int main(void) > > Why not put those into 20x standalone .c files and try to build them as > an explicit make command attempt from within the main Makefile? If the > build fails then the feature flag is set to off, if it succeeds it's > defined. > > That makes feature tests generally easier to debug, easier to understand > and generally easier to extend as well. > > 'Feature test binaries' that are already built will be 'cached' > automatically, and the result of their build attempt will be a quick > success. A successfull 'make' attempt of a target file within a separate, simple Makefile is very, very fast: comet:~/tip/tools/power/x86/turbostat> perf stat --null --sync --repeat 10 make turbostat make: `turbostat' is up to date. make: `turbostat' is up to date. make: `turbostat' is up to date. make: `turbostat' is up to date. make: `turbostat' is up to date. make: `turbostat' is up to date. make: `turbostat' is up to date. make: `turbostat' is up to date. make: `turbostat' is up to date. make: `turbostat' is up to date. Performance counter stats for 'make turbostat' (10 runs): 0.002146182 seconds time elapsed ( +- 0.35% ) That's 2 msecs only. 20 such tests will take less than 50 msecs in the 'cached' case. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/