From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 17 Jun 2001 15:10:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 17 Jun 2001 15:10:17 -0400 Received: from cpe-24-221-152-185.az.sprintbbd.net ([24.221.152.185]:520 "EHLO Opus.bloom.county") by vger.kernel.org with ESMTP id ; Sun, 17 Jun 2001 15:10:09 -0400 Date: Sun, 17 Jun 2001 12:06:45 -0700 From: Tom Rini To: Jakob ?stergaard , linux-kernel@vger.kernel.org Subject: Re: 2.4 VM & swap question Message-ID: <20010617120645.E11642@opus.bloom.county> In-Reply-To: <20010617104836.B11642@opus.bloom.county> <20010617205835.A12767@unthought.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20010617205835.A12767@unthought.net> User-Agent: Mutt/1.3.18i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jun 17, 2001 at 08:58:35PM +0200, Jakob ?stergaard wrote: > On Sun, Jun 17, 2001 at 10:48:36AM -0700, Tom Rini wrote: > > 'lo all. I've got a question about swap and RAM requirements in 2.4. Now, > > when 2.4.0 was kicked out, the fact that you need swap=2xRAM was mentioned. > > But what I'm wondering is what exactly are the limits on this. Right now > > I've got an x86 box w/ 128ram and currently 256swap. When I had 128, I'd get > > low on ram/swap after some time in X, and doing this seems to 'fix' it, in > > 2.4.4. However, I've also got 2 PPC boxes, both with 256:256 in 2.4. One > > of which never has X up, but lots of other activity, and swap usage seems > > to be about the same as 2.2.x (right now 'free' says i'm ~40MB into swap, > > 18day+ uptime). The other box is a laptop and has X up when it's awake and > > that too doesn't seem to have any problem. So what exactly is the real > > minium swap ammount? > > It completely totally and absolutely depends on the kind of workloads you put > your system under. Well, yes. :) But 2.4.x is much more swap-happy then 2.2.x was. I haven't changed my workload that much but the 256 swap became noticiably needed recently. > There is no simple answer. swap = 2*phys may be reasonable for some desktop > uses, I don't know. But there *is* *no* *simple* *answer*. Yes. The problem is the requirement has seemingly doubled recently. > With the amount of work that's gone into just *understanding* why the VM > behaves as it does (even after the VM rewrite that was done exactly in order to > come up with a VM we could *understand*), it's beyond me how anyone can even > begin to think that one can define a set of simple and exact rules for minimum > or "optimal" (whatever that means) values for swap. Well, it's also been said that the 'need' for 2xswap was fixed by one of the probably-not-yet-in-linus'-tree VM patches. And that it's 'artificial' -- Tom Rini (TR1265) http://gate.crashing.org/~trini/