Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753976Ab3DLJe3 (ORCPT ); Fri, 12 Apr 2013 05:34:29 -0400 Received: from cantor2.suse.de ([195.135.220.15]:59922 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751982Ab3DLJe2 (ORCPT ); Fri, 12 Apr 2013 05:34:28 -0400 Date: Fri, 12 Apr 2013 10:34:20 +0100 From: Mel Gorman To: Ric Mason Cc: Will Huck , Rik van Riel , Johannes Weiner , Linux-MM , Jiri Slaby , Valdis Kletnieks , Zlatko Calusic , dormando , Satoru Moriya , Michal Hocko , LKML Subject: Re: [PATCH 01/10] mm: vmscan: Limit the number of pages kswapd reclaims at each priority Message-ID: <20130412093420.GG11656@suse.de> References: <1363525456-10448-1-git-send-email-mgorman@suse.de> <1363525456-10448-2-git-send-email-mgorman@suse.de> <20130321155705.GA27848@cmpxchg.org> <514BA04D.2090002@gmail.com> <514BD56F.6050709@redhat.com> <5166510E.2050709@gmail.com> <51679FAE.7090504@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <51679FAE.7090504@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2042 Lines: 39 On Fri, Apr 12, 2013 at 01:46:22PM +0800, Ric Mason wrote: > Ping Rik, I also want to know the answer. ;-) This question, like a *lot* of list traffic recently, is a "how long is a piece of string" with hints that it is an important question but really is just going to waste a developers time because the question lacks any relevant meaning. The Inter-Reference Distance (IRD) is mentioned as a problem but gives no context as to why it is perceived as a problem. IRD is the distance in time or events between two references of the same page and is a function of the workload and an arbitrary page, not the page reclaim algorithm. A page algorithm may take IRD into account but IRD is not and cannot be a "problem" so the question framing is already confusing. Furthermore, the upsides and downsides of any given page reclaim algorithm are complex but in most cases are discussed in the academic pages describing them. People who are interested need to research and read these papers and then see how it might apply to the algorithm implemented in Linux or alternatively investigate what important workloads Linux treats badly and addressing the problem. The result of such research (and patches) is then a relevant discussion. This question asks what the "downside" is versus anonymous pages. To me the question lacks any meaning because how can a page reclaim algorithm "against" anonymous pages? As the question lacks meaning, answering it is impossible and it is effectively asking a developer to write a small paper to try and discover the meaning of the question before then answering it. I do not speak for Rik but I at least am ignoring most of these questions because there is not enough time in the day already. Pings are not likely to change my opinion. -- Mel Gorman SUSE Labs -- 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/