Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757791Ab0GNUqR (ORCPT ); Wed, 14 Jul 2010 16:46:17 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:57576 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757778Ab0GNUqE (ORCPT ); Wed, 14 Jul 2010 16:46:04 -0400 Date: Wed, 14 Jul 2010 22:45:31 +0200 From: Ingo Molnar To: Arnaldo Carvalho de Melo Cc: Steven Rostedt , Srikar Dronamraju , Peter Zijlstra , Randy Dunlap , Linus Torvalds , Christoph Hellwig , Masami Hiramatsu , Oleg Nesterov , Mark Wielaard , Mathieu Desnoyers , LKML , Naren A Devaiah , Jim Keniston , Frederic Weisbecker , "Frank Ch. Eigler" , Ananth N Mavinakayanahalli , Andrew Morton , "Paul E. McKenney" Subject: Re: [PATCHv9 2.6.35-rc4-tip 10/13] perf: Re-Add make_absolute_path Message-ID: <20100714204531.GA14474@elte.hu> References: <20100712103214.27491.15142.sendpatchset@localhost6.localdomain6> <20100712103412.27491.18737.sendpatchset@localhost6.localdomain6> <20100712140023.GC25238@ghostprotocols.net> <1278945036.1537.189.camel@gandalf.stny.rr.com> <20100712161239.GF25238@ghostprotocols.net> <1279075767.4190.1.camel@localhost> <20100714162332.GA4000@ghostprotocols.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100714162332.GA4000@ghostprotocols.net> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -1.9 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.9 required=5.9 tests=BAYES_00,FS_TIP_DDD autolearn=no SpamAssassin version=3.2.5 0.1 FS_TIP_DDD Phrase: subject = tip ddd -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2503 Lines: 54 * Arnaldo Carvalho de Melo wrote: > Em Tue, Jul 13, 2010 at 10:49:27PM -0400, Steven Rostedt escreveu: > > On Mon, 2010-07-12 at 13:12 -0300, Arnaldo Carvalho de Melo wrote: > > > Em Mon, Jul 12, 2010 at 10:30:36AM -0400, Steven Rostedt escreveu: > > > > Well, I prefer to follow the kernel way of doing things, i.e. to > > > propagate as much as possible up the callchain the error return value, > > > so that the apps can handle it in any way they prefer, i.e. die() calls > > > in tools/perf/builtin-foo.c are okayish, but not on tools/perf/util/. > > > Ah, yes, die is a bit strong. And I have been starting to avoid them > > too. Although, when malloc fails, it's almost certain that the app will > > die soon anyway ;-) > > The interesting thing is that years ago, when modules were being introduced > in the kernel and panic() calls for things like out of memory conditions > were being removed, some people made the same comments, 'if that happens, > you're doomed anyway!' :-) > > I can see things like trying to load a huge perf.data file in the TUI > interface failing and the user just being warned about it and going on with > life loading some other file, etc. > > Certainly it is interesting to try to apply as much as possible of the > mindset (and fear of criticism) present when coding for the kernel when one > codes for userland. Yeah, and especially for perf the absolutely most important quality is reliability. It's not just an app - it's a measurement tool. People rely on it to reject or apply patches, on a daily basis. perf must be very reliable and very dependable (and i'm happy that we managed to achieve that goal so far :), and if it fails it should be apparent that it failed and that results should not be relied on. With other tools that are statistical i've sometimes seen a special type of dangerous attitude of: "hey, it's just a sample, no biggie if it's lost, it's just statistical anyway, lost in the noise" - but that's really a slippery slope leading to a sloppy tool we cannot depend on 110%. Just like physicists or engineers want to be able to trust their measurement instruments, do we want kernel hackers to be able to trust the results of perf. 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/