From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264322AbTLKBdV (ORCPT ); Wed, 10 Dec 2003 20:33:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264303AbTLKBcu (ORCPT ); Wed, 10 Dec 2003 20:32:50 -0500 Received: from nat-pool-bos.redhat.com ([66.187.230.200]:59310 "EHLO chimarrao.boston.redhat.com") by vger.kernel.org with ESMTP id S264281AbTLKBb7 (ORCPT ); Wed, 10 Dec 2003 20:31:59 -0500 Date: Wed, 10 Dec 2003 20:31:40 -0500 (EST) From: Rik van Riel X-X-Sender: riel@chimarrao.boston.redhat.com To: Roger Luethi cc: William Lee Irwin III , Con Kolivas , Chris Vine , , "Martin J. Bligh" Subject: Re: 2.6.0-test9 - poor swap performance on low end machines In-Reply-To: <20031210231729.GC28912@k3.hellgate.ch> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 11 Dec 2003, Roger Luethi wrote: Hmmm, those definitions have changed a little from the OS books I read ;)) > - It is light thrashing when load control has no advantage. This used to be called "no thrashing" ;) > - It is medium thrashing when using load control is a toss-up. Probably > better throughput, but somewhat higher latency. This would be when the system load is so high that decreasing the multiprocessing level would increase system load, but performance would still be within acceptable limits (say, 30% of top performance). > - It is heavy thrashing when load control is a winner in both regards. Heavy thrashing would be "no work gets done by the processes in the system, nobody makes good progress". In that case load control is needed to make the system survive in a useful way. > I just made this up. It neatly resolves all arguments about when load > control is appropriate. Yeah, so it's a circular definition. Sue me. Knowing what your definitions are has definately made it easier for me to understand your previous mails. Still, sticking to the textbook definitions might make it even easier to talk about things, and compare the plans for Linux with what's been done for other OSes. Also, it would make the job of a load control mechanism really easy to define: "Prevent the system from thrashing" -- "Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it." - Brian W. Kernighan