Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756668AbZD1JZ0 (ORCPT ); Tue, 28 Apr 2009 05:25:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753361AbZD1JZK (ORCPT ); Tue, 28 Apr 2009 05:25:10 -0400 Received: from mail-bw0-f163.google.com ([209.85.218.163]:65053 "EHLO mail-bw0-f163.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753137AbZD1JZJ convert rfc822-to-8bit (ORCPT ); Tue, 28 Apr 2009 05:25:09 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=a7uVuMlSoBxDIY1wCCBo6KuHqLEw3i1sUagANGBddbk8cVe3a2LGyT56F/aKhXHyq9 5h12MWXJTawEY4JinzRxm3gVXs3kBC7owWnxC43KxXA/T90+6dHPKCOV2BVUxIpiHQG0 eqVqhnu+BzbmYtZgefX2rh1E1dHYcNSJnuGL4= MIME-Version: 1.0 In-Reply-To: <84144f020904280219p197d5ceag846ae9a80a76884e@mail.gmail.com> 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> Date: Tue, 28 Apr 2009 12:25:06 +0300 X-Google-Sender-Auth: d7436f7223628c81 Message-ID: <84144f020904280225h490ef682p8973cb1241a1f3ea@mail.gmail.com> Subject: Re: [PATCH 5/5] proc: export more page flags in /proc/kpageflags From: Pekka Enberg To: Ingo Molnar 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" Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1755 Lines: 34 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. Pekka -- 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/