Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753550AbbGJIfg (ORCPT ); Fri, 10 Jul 2015 04:35:36 -0400 Received: from mail-wi0-f181.google.com ([209.85.212.181]:37988 "EHLO mail-wi0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752487AbbGJIf3 (ORCPT ); Fri, 10 Jul 2015 04:35:29 -0400 Date: Fri, 10 Jul 2015 10:35:23 +0200 From: Ingo Molnar To: Peter Zijlstra Cc: Adrian Hunter , Arnaldo Carvalho de Melo , Andy Lutomirski , Vince Weaver , Thomas Gleixner , "H. Peter Anvin" , linux-kernel@vger.kernel.org, Jiri Olsa , Stephane Eranian , Borislav Petkov , Alexander Shishkin , Andi Kleen Subject: Re: [RFC PATCH] perf: Provide status of known PMUs Message-ID: <20150710083523.GA11445@gmail.com> References: <1436428080-3098-1-git-send-email-adrian.hunter@intel.com> <20150709085022.GB2859@worktop.programming.kicks-ass.net> <20150709092656.GA13336@gmail.com> <20150709115948.GS19282@twins.programming.kicks-ass.net> <20150709123205.GA9496@gmail.com> <20150709124257.GU19282@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150709124257.GU19282@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2203 Lines: 51 * Peter Zijlstra wrote: > On Thu, Jul 09, 2015 at 02:32:05PM +0200, Ingo Molnar wrote: > > > > perf record error: The 'bts' PMU is not available, because the CPU does not support it > > This one makes sense. > > > perf record error: The 'bts' PMU is not available, because this architecture does not support it > > perf record error: The 'bts' PMU is not available, because its driver is not built into the kernel > > > > Because if it's the wrong architecture or CPU, I look for a box with the right > > one, if it's simply the kernel not having the necessary PMU driver then I'll boot > > a kernel with it enabled. > > These not so much; why won't a generic: "Unknown PMU, check arch/kernel" do? Yeah, I mean why not make the user's job harder if we can? We really don't want to solve this problem technically and we _really_ want tooling to be fundamentally unhelpful, right? ;-) I realize that the 'Error: there was a bug, aborting' style of sado-masochistic error messages are the current Linux tooling status quo, which opaque error feedback comes from an early technological mistake of Unix system calls screwing up error handling, and I also see that after decades of abuse people are showing signs of the Stockholm Syndrome related to this problem, but it _really_ does not have to be so ... Whenever we can we should change such bad patterns. > The thing is, I hate that hard-coded list, its pain I don't need. Absolutely! I pointed this out during review as well. It does not impact the core concept though: we should have a single numeric error, and free form error strings provided by the place that first triggers some problem. That should be both programmatically easy to handle and maximally informative to the users. At least half of a tool's usability comes not from how it behaves when it works, but how it behaves when it does not. (SystemD, I'm looking at you.) 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/