From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752732AbZIZPBH (ORCPT ); Sat, 26 Sep 2009 11:01:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752345AbZIZPBG (ORCPT ); Sat, 26 Sep 2009 11:01:06 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:38280 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752161AbZIZPBE (ORCPT ); Sat, 26 Sep 2009 11:01:04 -0400 Date: Sat, 26 Sep 2009 17:01:03 +0200 From: Ingo Molnar To: Eric Dumazet Cc: Ulrich Drepper , Peter Zijlstra , Fr??d??ric Weisbecker , linux kernel , linux-perf-users@vger.kernel.org Subject: Re: [PATCH] perf tools: Dont use openat() Message-ID: <20090926150103.GB30071@elte.hu> References: <4ABB6EB7.7000002@gmail.com> <20090924131250.GA15132@elte.hu> <4ABB767D.6080004@gmail.com> <4ABBDF77.3090106@redhat.com> <4ABBE9B7.1050505@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4ABBE9B7.1050505@gmail.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 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 * Eric Dumazet wrote: > Ulrich Drepper a ??crit : > > -----BEGIN PGP SIGNED MESSAGE----- > > Hash: SHA1 > > > > Eric Dumazet wrote: > >>> We can certainly remove that reliance - wanna send a patch for it? > > > > Come on, the silliness has to stop. The kernel must be recent and to > > use it adequately the C library also must be recent. And "recent" is > > not even correct anymore: the functions are available for more then two > > years. Removing the use of the modern interfaces makes everything > > slower and might even re-introduce race conditions my patch fixed. > > > > First time I ear that C library *must* be recent. This was never > mentionned in Documentation/Changes, "Minimal Requirements" > > "perf list" can be 100x slower, and even racy, I dont mind. At all. > > $ time perf list >/dev/null 2>/dev/null > > real 0m0.001s > user 0m0.000s > sys 0m0.001s Yep, doesnt look problematic from a performance POV. > With openat(), I cannot use "perf" on machines I can only change > kernel, since changing glibc is too risky for legacy apps. I could use > static and private glibc, but last time I tried this I lost few hours > and failed. Yeah, we generally dont want to force an upgrade of other components if possible. The fact that you ran into it in a pre -rc1 kernel means that there's a thousand others out there who will run into similar problems. Ingo