Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756171Ab1FDKYH (ORCPT ); Sat, 4 Jun 2011 06:24:07 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:32881 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755508Ab1FDKYF (ORCPT ); Sat, 4 Jun 2011 06:24:05 -0400 Date: Sat, 4 Jun 2011 12:23:50 +0200 From: Ingo Molnar To: Vince Weaver Cc: David Ahern , Peter Zijlstra , linux-kernel@vger.kernel.org, paulus@samba.org, acme@redhat.com Subject: Re: [patch] perf - comment /proc/sys/kernel/perf_event_paranoid to be part of user ABI Message-ID: <20110604102350.GC16292@elte.hu> References: <1306246306.18455.36.camel@twins> <20110524194810.GB27634@elte.hu> <4DDC1BB2.4090503@gmail.com> <20110524212925.GL27634@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes 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: 1161 Lines: 31 * Vince Weaver wrote: > On Tue, 24 May 2011, Ingo Molnar wrote: > > > I agree with Vince that as far as shell scripts are concerned, checking > > /proc/sys/kernel/perf_event_paranoid would work best - and it works better than > > having to check the perf syscall. > > > > Vince: mind sending a patch that adds a comment to perf_event_paranoid that > > userspace relies on the existence of that file as a feature check? Having such > > reminders in the code works even better than frequent testing ;-) > > Such a patch is included below. Not sure if this is exactly what you > meant. Yeah, that's exactly what i meant - we don't need more really. Most sysctls are not ABIs (there's no userspace that relies on them) so the general attitude is to change them freely and backtrack if something breaks unexpectedly. We can avoid that by commenting the dependency. 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/