From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261606AbUE0GCo (ORCPT ); Thu, 27 May 2004 02:02:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261610AbUE0GCo (ORCPT ); Thu, 27 May 2004 02:02:44 -0400 Received: from smtp104.mail.sc5.yahoo.com ([66.163.169.223]:49274 "HELO smtp104.mail.sc5.yahoo.com") by vger.kernel.org with SMTP id S261606AbUE0GCl (ORCPT ); Thu, 27 May 2004 02:02:41 -0400 Message-ID: <40B5847E.90604@yahoo.com.au> Date: Thu, 27 May 2004 16:02:38 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.6) Gecko/20040401 Debian/1.6-4 X-Accept-Language: en MIME-Version: 1.0 To: Tom Felker CC: Matthias Schniedermeyer , linux-kernel@vger.kernel.org Subject: Re: why swap at all? References: <40B47D4C.6050206@yahoo.com.au> <20040526123740.GA14584@citd.de> <200405270014.10096.tcfelker@mtco.com> In-Reply-To: <200405270014.10096.tcfelker@mtco.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Tom Felker wrote: > On Wednesday 26 May 2004 7:37 am, Matthias Schniedermeyer wrote: > > >>program to kernel: "i read ONCE though this file caching not useful". > > > Very true. The system is based on the assumption that just-used pages are > more useful that older pages, and it slows when this isn't true. We need > ways to tell the kernel whether the assumption holds. > A streaming flag is great, but we usually do OK without it. There is a "used once" heuristic that often gets it right as far as I know. Basically, new pages that are only used once put almost zero pressure on the rest of the memory. It has a few corner cases where it breaks down. Hopefully they can be improved...