From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932700AbXCUQIu (ORCPT ); Wed, 21 Mar 2007 12:08:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932710AbXCUQIu (ORCPT ); Wed, 21 Mar 2007 12:08:50 -0400 Received: from mx1.redhat.com ([66.187.233.31]:34419 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932700AbXCUQIt (ORCPT ); Wed, 21 Mar 2007 12:08:49 -0400 Message-ID: <4601586E.302@redhat.com> Date: Wed, 21 Mar 2007 12:08:14 -0400 From: Rik van Riel User-Agent: Thunderbird 1.5.0.7 (X11/20061004) MIME-Version: 1.0 To: Nikita Danilov CC: Linux Kernel Mailing List , linux-mm Subject: Re: [RFC][PATCH] split file and anonymous page queues #3 References: <46005B4A.6050307@redhat.com> <17920.61568.770999.626623@gargle.gargle.HOWL> <460115D9.7030806@redhat.com> <17921.7074.900919.784218@gargle.gargle.HOWL> <46011E8F.2000109@redhat.com> <46011EF6.3040704@redhat.com> <17921.20299.7899.527765@gargle.gargle.HOWL> In-Reply-To: <17921.20299.7899.527765@gargle.gargle.HOWL> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Nikita Danilov wrote: > Generally speaking, multi-queue replacement mechanisms were tried in the > past, and they all suffer from the common drawback: once scanning rate > is different for different queues, so is the notion of "hotness", > measured by scanner. As a result multi-queue scanner fails to capture > working set properly. You realize that the current "single" queue in the 2.6 kernel has this problem in a much worse way: when swappiness is low and the kernel does not want to reclaim mapped pages, it will randomly rotate those pages around the list. In addition, the referenced bit on unmapped page cache pages was ignored completely, making it impossible for the VM to separate the page cache working set from transient pages due to streaming IO. I agree that we should put some more negative feedback in place if it turns out we need it. I have refault code ready that can be plugged into this patch, but I don't want to add the overhead of such code if it turns out we do not actually need it. -- All Rights Reversed