Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757890AbZD1Jhm (ORCPT ); Tue, 28 Apr 2009 05:37:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754293AbZD1Jhc (ORCPT ); Tue, 28 Apr 2009 05:37:32 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:40854 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754035AbZD1Jhb (ORCPT ); Tue, 28 Apr 2009 05:37:31 -0400 Date: Tue, 28 Apr 2009 11:36:21 +0200 From: Ingo Molnar To: Pekka Enberg Cc: Andi Kleen , Wu Fengguang , Steven Rostedt , =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker , Larry Woodman , Peter Zijlstra , Eduard - Gabriel Munteanu , Andrew Morton , LKML , KOSAKI Motohiro , Matt Mackall , Alexey Dobriyan , "linux-mm@kvack.org" Subject: Re: [PATCH 5/5] proc: export more page flags in /proc/kpageflags Message-ID: <20090428093621.GD21085@elte.hu> References: <20090428010907.912554629@intel.com> <20090428014920.769723618@intel.com> <20090428065507.GA2024@elte.hu> <20090428074031.GK27382@one.firstfloor.org> <1240909484.1982.16.camel@penberg-laptop> <20090428091508.GA21085@elte.hu> <84144f020904280219p197d5ceag846ae9a80a76884e@mail.gmail.com> <84144f020904280225h490ef682p8973cb1241a1f3ea@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <84144f020904280225h490ef682p8973cb1241a1f3ea@mail.gmail.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean 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=3.2.3 -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 Content-Length: 1806 Lines: 50 * Pekka Enberg wrote: > > I have no idea how expensive tracepoints are but I suspect they > > don't make too much sense for this particular scenario. After > > all, kmemtrace is mainly interested in _allocation patterns_ > > whereas this patch seems to be more interested in "memory > > layout" type of things. > > That said, I do foresee a need to be able to turn on more detailed > tracing after you've identified problematic areas from kpageflags > type of overview report. And for that, you almost certainly want > kmemtrace/tracepoints style solution with pid/function/whatever > regexp matching ftrace already provides. yes. My point is that by having the latter, we pretty much have the former as well! I 'integrate' traces all the time to get summary counts. This series of dynamic events: allocation page count up page count up page count down page count up page count up page count up page count up integrates into: "page count is 6". Note that "integration" can be done wholly in the kernel too, without going to the overhead of streaming all dynamic events to user-space, just to summarize data into counts, in-kernel. That is what the ftrace statistics framework and various ftrace plugins are about. Also, it might make sense to extend the framework with a series of 'get current object state' events when tracing is turned on. A special case of _that_ would in essence be what the /proc hack does now - just expressed in a much more generic, and a much more usable form. 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/