From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756302AbZD1JQZ (ORCPT ); Tue, 28 Apr 2009 05:16:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755636AbZD1JQE (ORCPT ); Tue, 28 Apr 2009 05:16:04 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:53219 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755716AbZD1JQC (ORCPT ); Tue, 28 Apr 2009 05:16:02 -0400 Date: Tue, 28 Apr 2009 11:15:08 +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: <20090428091508.GA21085@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1240909484.1982.16.camel@penberg-laptop> 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 * Pekka Enberg wrote: > Hi Andi, > > 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 > > > > I think because it has zero fast path overhead and can be used > > any time without enabling anything special. ( 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. ) > Yes, zero overhead is important for certain things (like > CONFIG_SLUB_STATS, for example). However, putting slab allocator > specific checks in fs/proc looks pretty fragile to me. It would be > nice to have this under the "kmemtrace umbrella" so that there's > just one place that needs to be fixed up when allocators change. > > Also, while you probably don't want to use tracepoints for this > kind of instrumentation, you might want to look into reusing the > ftrace reporting bits. Exactly - we have a tracing and statistics framework for a reason. Ingo From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with ESMTP id 529486B004D for ; Tue, 28 Apr 2009 05:15:16 -0400 (EDT) Date: Tue, 28 Apr 2009 11:15:08 +0200 From: Ingo Molnar Subject: Re: [PATCH 5/5] proc: export more page flags in /proc/kpageflags Message-ID: <20090428091508.GA21085@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1240909484.1982.16.camel@penberg-laptop> Sender: owner-linux-mm@kvack.org 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" List-ID: * Pekka Enberg wrote: > Hi Andi, > > 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 > > > > I think because it has zero fast path overhead and can be used > > any time without enabling anything special. ( 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. ) > Yes, zero overhead is important for certain things (like > CONFIG_SLUB_STATS, for example). However, putting slab allocator > specific checks in fs/proc looks pretty fragile to me. It would be > nice to have this under the "kmemtrace umbrella" so that there's > just one place that needs to be fixed up when allocators change. > > Also, while you probably don't want to use tracepoints for this > kind of instrumentation, you might want to look into reusing the > ftrace reporting bits. Exactly - we have a tracing and statistics framework for a reason. Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org