Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755306AbZD1JE5 (ORCPT ); Tue, 28 Apr 2009 05:04:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752239AbZD1JEs (ORCPT ); Tue, 28 Apr 2009 05:04:48 -0400 Received: from courier.cs.helsinki.fi ([128.214.9.1]:51836 "EHLO mail.cs.helsinki.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752044AbZD1JEr (ORCPT ); Tue, 28 Apr 2009 05:04:47 -0400 Subject: Re: [PATCH 5/5] proc: export more page flags in /proc/kpageflags From: Pekka Enberg To: Andi Kleen Cc: Ingo Molnar , 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" In-Reply-To: <20090428074031.GK27382@one.firstfloor.org> References: <20090428010907.912554629@intel.com> <20090428014920.769723618@intel.com> <20090428065507.GA2024@elte.hu> <20090428074031.GK27382@one.firstfloor.org> Date: Tue, 28 Apr 2009 12:04:44 +0300 Message-Id: <1240909484.1982.16.camel@penberg-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7bit X-Mailer: Evolution 2.24.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1052 Lines: 26 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. 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. 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/