From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752435AbXBYXro (ORCPT ); Sun, 25 Feb 2007 18:47:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751154AbXBYXro (ORCPT ); Sun, 25 Feb 2007 18:47:44 -0500 Received: from mx1.redhat.com ([66.187.233.31]:53064 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751150AbXBYXrn (ORCPT ); Sun, 25 Feb 2007 18:47:43 -0500 Message-ID: <45E21FEC.9060605@redhat.com> Date: Sun, 25 Feb 2007 18:46:52 -0500 From: Rik van Riel Organization: Red Hat, Inc User-Agent: Thunderbird 1.5.0.7 (X11/20061008) MIME-Version: 1.0 To: Lorenzo Allegrucci CC: linux-kernel@vger.kernel.org, Ingo Molnar , Suparna Bhattacharya , Jens Axboe Subject: Re: SMP performance degradation with sysbench References: <1172425476.5489.11.camel@odyssey.lan> In-Reply-To: <1172425476.5489.11.camel@odyssey.lan> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Lorenzo Allegrucci wrote: > Hi lkml, > > according to the test below (sysbench) Linux seems to have scalability > problems beyond 8 client threads: > http://jeffr-tech.livejournal.com/6268.html#cutid1 > http://jeffr-tech.livejournal.com/5705.html > Hardware is an 8-core amd64 system and jeffr seems willing to try more > Linux versions on that machine. > Anyway, is there anyone who can reproduce this? I have reproduced it on a quad core test system. With 4 threads (on 4 cores) I get a high throughput, with approximately 58% user time and 42% system time. With 8 threads (on 4 cores) I get way lower throughput, with 37% user time, 29% system time 35% idle time! The maximum time taken per query also increases from 0.0096s to 0.5273s. Ouch! I don't know if this is MySQL, glibc or Linux kernel, but something strange is going on... -- Politics is the struggle between those who want to make their country the best in the world, and those who believe it already is. Each group calls the other unpatriotic.