Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757585AbZD1J4c (ORCPT ); Tue, 28 Apr 2009 05:56:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753086AbZD1J4V (ORCPT ); Tue, 28 Apr 2009 05:56:21 -0400 Received: from mga14.intel.com ([143.182.124.37]:57046 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751693AbZD1J4U (ORCPT ); Tue, 28 Apr 2009 05:56:20 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.40,259,1239001200"; d="scan'208";a="136715327" Date: Tue, 28 Apr 2009 17:55:51 +0800 From: Wu Fengguang To: Ingo Molnar Cc: KOSAKI Motohiro , Pekka Enberg , Andi Kleen , Steven Rostedt , =?utf-8?B?RnLpppjpp7tpYw==?= Weisbecker , Larry Woodman , Peter Zijlstra , Eduard - Gabriel Munteanu , Andrew Morton , LKML , Matt Mackall , Alexey Dobriyan , "linux-mm@kvack.org" Subject: Re: [PATCH 5/5] proc: export more page flags in /proc/kpageflags Message-ID: <20090428095551.GB21168@localhost> References: <84144f020904280219p197d5ceag846ae9a80a76884e@mail.gmail.com> <20090428092918.GC21085@elte.hu> <20090428183237.EBDE.A69D9226@jp.fujitsu.com> <20090428093833.GE21085@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090428093833.GE21085@elte.hu> 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: 2340 Lines: 57 On Tue, Apr 28, 2009 at 05:38:33PM +0800, Ingo Molnar wrote: > > * KOSAKI Motohiro wrote: > > > > > > > * 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. > > > > > > My point is that the allocation patterns can be derived from dynamic > > > events. We can build a map of everything if we know all the events > > > that led up to it. Doing: > > > > > > echo 3 > /proc/sys/vm/drop_caches > > > > > > will clear 99% of the memory allocations, so we can build a new map > > > from scratch just about anytime. (and if boot allocations are > > > interesting they can be traced too) > > > > > > _And_ via this angle we'll also have access to the dynamic events, > > > in a different 'view' of the same tracepoints - which is obviously > > > very useful for different purposes. > > > > I am one of most strongly want guys to MM tracepoint. but No, many > > cunstomer never permit to use drop_caches. > > See my other mail i just sent: it would be a natural extension of > tracing to also dump all current object state when tracing is turned > on. That way no drop_caches is needed at all. I can understand the merits here - I also did readahead tracing/accounting in _one_ piece of code. Very handy. The readahead traces are now raw printks - converting to the ftrace framework would be a big win. But. It's still not a fit-all solution. Imagine when full data _since_ booting is required, but the user cannot afford a reboot. > But it has to be expressed in one framework that cares about the > totality of the kernel - not just these splintered bits of > instrumentation and pieces of statistics. Though minded to push the kpageflags interface, I totally agree the above fine principle and discipline :-) 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/