From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932690Ab1EFVK5 (ORCPT ); Fri, 6 May 2011 17:10:57 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.123]:34550 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932268Ab1EFVK4 (ORCPT ); Fri, 6 May 2011 17:10:56 -0400 X-Authority-Analysis: v=1.1 cv=ZtuXOl23UuD1yoJUTgnZ6i6Z5VPlPhPMWCeUNtN8OGA= c=1 sm=0 a=UZYI7n2t75YA:10 a=5SG0PmZfjMsA:10 a=Q9fys5e9bTEA:10 a=OPBmh+XkhLl+Enan7BmTLg==:17 a=meVymXHHAAAA:8 a=Ev-mm6w7t5DsACkrcGAA:9 a=lFnyZK4mzMqTg_0429kA:7 a=PUjeQqilurYA:10 a=jeBq3FmKZ4MA:10 a=OPBmh+XkhLl+Enan7BmTLg==:117 X-Cloudmark-Score: 0 X-Originating-IP: 67.242.120.143 Subject: Re: Fix powerTOP regression with 2.6.39-rc5 From: Steven Rostedt To: Linus Torvalds Cc: Arjan van de Ven , Ingo Molnar , linux-kernel , Frederic Weisbecker , Peter Zijlstra , Thomas Gleixner In-Reply-To: References: <4DC45537.6070609@linux.intel.com> <1304713252.25414.2532.camel@gandalf.stny.rr.com> Content-Type: text/plain; charset="ISO-8859-15" Date: Fri, 06 May 2011 17:10:55 -0400 Message-ID: <1304716255.25414.2540.camel@gandalf.stny.rr.com> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2011-05-06 at 13:51 -0700, Linus Torvalds wrote: > On Fri, May 6, 2011 at 1:20 PM, Steven Rostedt wrote: > > > > I strongly NACK this! > > Doesn't matter. > > Binary compatibility is more important. > > And if binaries don't use the interface to parse the format (or just > parse it wrongly - see the fairly recent example of adding uuid's to > /proc/self/mountinfo), then it's a regression. > > And regressions get reverted, unless there are security issues or > similar that makes us go "Oh Gods, we really have to break things". Um, this is an internal tracepoint. Does this mean that all internal data inside the kernel that is exported with trace events are locked down? > > I don't understand why this simple logic is so hard for some kernel > developers to understand. Reality matters. Your personal wishes matter > NOT AT ALL. This isn't a personal wish. This brings every advancement that I was planning on making this year to a dead halt. We were really about to restructure the events to make them lighter weight and faster. Also, this isn't the first time this structure has changed. It just happens that something started using it. This field did not even exist until recently. > > If you made an interface that can be used without parsing the > interface description, then we're stuck with the interface. Theory > simply doesn't matter. I never had an interface used this way. It was just by luck. Damn, I should have listened to Peter Zijlstra when he recommended that every boot restructures the data in the format differently. Then this would never have happened. But doing that would have slowed things down tremendously (or remove the ease of TRACE_EVENT). > > You could help fix the tools, and try to avoid the compatibility > issues that way. There aren't that many of them. As I said, I have a library (.so even) that does the parsing for you. If I get powertop to use it, can we hold off on this patch? Note, I'm about to leave to Budapest. I could try to get this done on the trip. -- Steve