Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760304AbZD1Sh3 (ORCPT ); Tue, 28 Apr 2009 14:37:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753246AbZD1ShM (ORCPT ); Tue, 28 Apr 2009 14:37:12 -0400 Received: from waste.org ([66.93.16.53]:48883 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753367AbZD1ShK (ORCPT ); Tue, 28 Apr 2009 14:37:10 -0400 Subject: Re: [PATCH 5/5] proc: export more page flags in /proc/kpageflags From: Matt Mackall To: Tony Luck Cc: Wu Fengguang , Ingo Molnar , Steven Rostedt , =?ISO-8859-1?Q?Fr=E9d=E9ric?= Weisbecker , Larry Woodman , Peter Zijlstra , Pekka Enberg , Eduard - Gabriel Munteanu , Andrew Morton , LKML , KOSAKI Motohiro , Andi Kleen , Alexey Dobriyan , "linux-mm@kvack.org" In-Reply-To: <12c511ca0904281111r10f37a5coe5a2750f4dbfbcda@mail.gmail.com> References: <20090428010907.912554629@intel.com> <20090428014920.769723618@intel.com> <20090428065507.GA2024@elte.hu> <20090428083320.GB17038@localhost> <12c511ca0904281111r10f37a5coe5a2750f4dbfbcda@mail.gmail.com> Content-Type: text/plain Date: Tue, 28 Apr 2009 13:34:31 -0500 Message-Id: <1240943671.938.575.camel@calx> Mime-Version: 1.0 X-Mailer: Evolution 2.24.5 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1250 Lines: 34 On Tue, 2009-04-28 at 11:11 -0700, Tony Luck wrote: > On Tue, Apr 28, 2009 at 1:33 AM, Wu Fengguang wrote: > > 1) FAST > > > > It takes merely 0.2s to scan 4GB pages: > > > > ./page-types 0.02s user 0.20s system 99% cpu 0.216 total > > OK on a tiny system ... but sounds painful on a big > server. 0.2s for 4G scales up to 3 minutes 25 seconds > on a 4TB system (4TB systems were being sold two > years ago ... so by now the high end will have moved > up to 8TB or perhaps 16TB). > > Would the resulting output be anything but noise on > a big system (a *lot* of pages can change state in > 3 minutes)? Bah. The rate of change is proportional to #cpus, not #pages. Assuming you've got 1024 processors, you could run the scan in parallel in .2 seconds still. It won't be an atomic snapshot, obviously. But stopping the whole machine on a system that size is probably not what you want anyway. -- http://selenic.com : development and support for Mercurial and Linux -- 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/