Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757566AbZD1JhQ (ORCPT ); Tue, 28 Apr 2009 05:37:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755035AbZD1JhB (ORCPT ); Tue, 28 Apr 2009 05:37:01 -0400 Received: from mga14.intel.com ([143.182.124.37]:56543 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755015AbZD1JhA (ORCPT ); Tue, 28 Apr 2009 05:37:00 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.40,259,1239001200"; d="scan'208";a="136710493" Date: Tue, 28 Apr 2009 17:36:08 +0800 From: Wu Fengguang To: Pekka Enberg Cc: Ingo Molnar , Andi Kleen , Steven Rostedt , =?utf-8?B?RnLDqWTDqXJpYw==?= 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: <20090428093608.GA21168@localhost> 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=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <84144f020904280225h490ef682p8973cb1241a1f3ea@mail.gmail.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1980 Lines: 39 On Tue, Apr 28, 2009 at 05:25:06PM +0800, Pekka Enberg wrote: > On Tue, 2009-04-28 at 09:40 +0200, Andi Kleen wrote: > >>> > > I think i have to NAK this kind of ad-hoc instrumentation of kernel > >>> > > internals and statistics until we clear up why such instrumentation > > * Pekka Enberg wrote: > >>> > I think because it has zero fast path overhead and can be used > >>> > any time without enabling anything special. > > > > On Tue, Apr 28, 2009 at 12:15 PM, Ingo Molnar wrote: > >> ( That's a dubious claim in any case - tracepoints are very cheap. > >>  And they could be made even cheaper and such efforts would benefit > >>  all the tracepoint users so it's a prime focus of interest. > >>  Andi is a SystemTap proponent, right? I saw him oppose pretty much > >>  everything built-in kernel tracing related. I consider that a > >>  pretty extreme position. ) > > On Tue, Apr 28, 2009 at 12:19 PM, 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. Exactly - kmemtrace is the tool I looked for when hunting down the page flags of the leaked ring buffer memory :-) Thanks, Fengguang -- 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/