Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964841AbVLGBS5 (ORCPT ); Tue, 6 Dec 2005 20:18:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965038AbVLGBS5 (ORCPT ); Tue, 6 Dec 2005 20:18:57 -0500 Received: from ns.ustc.edu.cn ([202.38.64.1]:2025 "EHLO mx1.ustc.edu.cn") by vger.kernel.org with ESMTP id S964841AbVLGBS5 (ORCPT ); Tue, 6 Dec 2005 20:18:57 -0500 Date: Wed, 7 Dec 2005 09:42:35 +0800 From: Wu Fengguang To: Nikita Danilov Cc: Andrew Morton , Linux Kernel Mailing List Subject: Re: [PATCH 01/16] mm: delayed page activation Message-ID: <20051207014235.GA5186@mail.ustc.edu.cn> Mail-Followup-To: Wu Fengguang , Nikita Danilov , Andrew Morton , Linux Kernel Mailing List References: <20051203071444.260068000@localhost.localdomain> <20051203071609.755741000@localhost.localdomain> <17298.56560.78408.693927@gargle.gargle.HOWL> <20051204134818.GA4305@mail.ustc.edu.cn> <17299.1331.368159.374754@gargle.gargle.HOWL> <20051205014842.GA5103@mail.ustc.edu.cn> <17301.53377.614777.913013@gargle.gargle.HOWL> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <17301.53377.614777.913013@gargle.gargle.HOWL> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2446 Lines: 51 On Tue, Dec 06, 2005 at 08:55:13PM +0300, Nikita Danilov wrote: > Wu Fengguang writes: > > On Sun, Dec 04, 2005 at 06:03:15PM +0300, Nikita Danilov wrote: > > > > inter-reference distance, and therefore should be better protected(if ignore > > > > possible read-ahead effects). If we move re-accessed pages immediately into > > > > active_list, we are pushing them closer to danger of eviction. > > > > > > Huh? Pages in the active list are closer to the eviction? If it is > > > really so, then CLOCK-pro hijacks the meaning of active list in a very > > > unintuitive way. In the current MM active list is supposed to contain > > > hot pages that will be evicted last. > > > > The page is going to active list anyway. So its remaining lifetime in inactive > > list is killed by the early move. > > But this change increased lifetimes of _all_ pages, so this is Yes, it also increased the lifetimes by meaningful values: first re-accessed pages are prolonged more lifetime. Immediately removing them from inactive_list is basicly doing MRU eviction. > irrelevant. Consequently, it has a chance of increasing scanning > activity, because there will be more referenced pages at the cold tail > of the inactive list. Delayed activation increased scanning activity, while immediate activation increased the locking activity. Early profiling data on a 2 CPU Xeon box showed that the delayed activation acctually cost less time. > And --again-- this erases information about relative order of > references, and this is important. In the past, several VM modifications > (like split inactive_clean and inactive_dirty lists) were tried that had > various advantages over current scanner, but maintained weaker LRU, and > they all were found to degrade horribly under certain easy triggerable > conditions. Yeah, the patch does need more testing. It has been in -ck tree for a while, and there's no negative report about it. Andrew, and anyone in the lkml, do you feel ok to test it in -mm tree? It is there because some readahead code test the PG_actvation bit explicitly. If the answer is 'not for now', I'll strip it out from the readahead patchset in the next version. Thanks, Wu - 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/