From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752501AbWCGMeO (ORCPT ); Tue, 7 Mar 2006 07:34:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752502AbWCGMeO (ORCPT ); Tue, 7 Mar 2006 07:34:14 -0500 Received: from nproxy.gmail.com ([64.233.182.202]:60061 "EHLO nproxy.gmail.com") by vger.kernel.org with ESMTP id S1752501AbWCGMeN convert rfc822-to-8bit (ORCPT ); Tue, 7 Mar 2006 07:34:13 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:to:subject:mime-version:content-type:content-transfer-encoding:content-disposition; b=ReTG243nTIKMpI7UNGtUWbbpkOFYh9DXM9X54K6J83CyXttwGGV3vhYK9iTNbzAQqy6ZyY5STyDQtPnXZRVQ6BMsLYnpXtiiR9VQKWCE1Cv8ELEY1Z06p1M/0j+hj0NGUIGGMlKMZg7R6rphYTFsTh3oC4+NGyVNbttW35PCMp4= Message-ID: Date: Tue, 7 Mar 2006 21:34:11 +0900 From: "Magnus Damm" To: "Linux Kernel Mailing List" Subject: SMP and 101% cpu max? MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi guys, I'm doing some memory related hacking, and part of that is testing the current behaviour of the Linux VM. This testing involves running some simple tests (building the linux kernel is one of the tests) while varying the amount of RAM available to the kernel. I've tested memory configurations of 64MB, 128MB and 256MB on a Dual PIII machine. The tested kernel is 2.6.16-rc5, and user space is based on debian-3.1. I run 5 tests per memory configuration, and the machine is rebooted between each test. Problem: With 128MB and 256MB configurations, a majority of the tests never make it over 101% CPU usage when I run "make -j 2 bzImage", building a allnoconfig kernel. With 64MB memory, everything seems to be working as expected. Also, running "make bzImage" works as expected too. Results for "make bzImage": # time: real user sys, cpu: percentage, ram: KB, swap: KB time: 229.261 211.6 18.18, cpu: 100, ram: 256716, swap: 125944 time: 229.621 211.45 17.51, cpu: 100, ram: 256716, swap: 125944 time: 229.698 212.11 17.68, cpu: 100, ram: 256716, swap: 125944 time: 230.711 211.89 17.86, cpu: 100, ram: 256716, swap: 125944 time: 232.219 210.55 18.5, cpu: 99, ram: 256716, swap: 125944 time: 233.203 213.34 17.79, cpu: 99, ram: 126876, swap: 125944 time: 233.371 213.82 17.15, cpu: 99, ram: 126876, swap: 125944 time: 234.18 213.43 17.92, cpu: 99, ram: 126876, swap: 125944 time: 234.315 213.11 17.92, cpu: 99, ram: 126876, swap: 125944 time: 235.334 215.06 17.22, cpu: 99, ram: 126876, swap: 125944 time: 241.159 222.82 15.38, cpu: 99, ram: 61956, swap: 125944 time: 241.299 222.39 15.34, cpu: 99, ram: 61956, swap: 125944 time: 241.475 223.16 15.38, cpu: 99, ram: 61956, swap: 125944 time: 241.955 223.24 15.66, cpu: 99, ram: 61956, swap: 125944 time: 242.099 222.92 15.98, cpu: 99, ram: 61956, swap: 125944 Results for "make -j 2 bzImage": # time: real user sys, cpu: percentage, ram: KB, swap: KB time: 124.336 220.03 18.98, cpu: 192, ram: 126876, swap: 125944 time: 124.547 217.57 19.15, cpu: 190, ram: 256716, swap: 125944 time: 125.162 218.35 19.51, cpu: 190, ram: 256716, swap: 125944 time: 132.488 228.71 17.1, cpu: 186, ram: 61956, swap: 125944 time: 132.502 230.93 16.26, cpu: 187, ram: 61956, swap: 125944 time: 132.634 230.55 16.42, cpu: 186, ram: 61956, swap: 125944 time: 132.643 229.89 17.63, cpu: 187, ram: 61956, swap: 125944 time: 133.2 230.09 16.28, cpu: 185, ram: 61956, swap: 125944 time: 227.371 211.45 17.36, cpu: 101, ram: 256716, swap: 125944 time: 227.898 211.93 17.3, cpu: 101, ram: 256716, swap: 125944 time: 228.071 212.21 17.15, cpu: 101, ram: 256716, swap: 125944 time: 228.788 212.46 17.88, cpu: 101, ram: 126876, swap: 125944 time: 229.223 214.14 16.46, cpu: 101, ram: 126876, swap: 125944 time: 229.255 213.56 17.19, cpu: 101, ram: 126876, swap: 125944 time: 230.296 214.25 17.44, cpu: 101, ram: 126876, swap: 125944 Any ideas what is causing this? Is it a memory subsystem issue, or cpu scheduling? Thanks, / magnus