From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263678AbTDGWFf (for ); Mon, 7 Apr 2003 18:05:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263690AbTDGWFf (for ); Mon, 7 Apr 2003 18:05:35 -0400 Received: from [12.47.58.221] ([12.47.58.221]:19527 "EHLO pao-ex01.pao.digeo.com") by vger.kernel.org with ESMTP id S263678AbTDGWFe (for ); Mon, 7 Apr 2003 18:05:34 -0400 Date: Mon, 7 Apr 2003 14:15:51 -0700 From: Andrew Morton To: Badari Pulavarty Cc: linux-kernel@vger.kernel.org Subject: Re: More Testing with 4000 disks Message-Id: <20030407141551.5900e44f.akpm@digeo.com> In-Reply-To: <200304071454.49849.pbadari@us.ibm.com> References: <200304071454.49849.pbadari@us.ibm.com> X-Mailer: Sylpheed version 0.8.10 (GTK+ 1.2.10; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 07 Apr 2003 22:17:04.0098 (UTC) FILETIME=[6B1D2420:01C2FD53] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Badari Pulavarty wrote: > > Hi, > > Here is more on testing with simulated 4000 disks. > > I mounted 4000 simulated (scsi_debug) disks. But > when I tried to do IO on 200 of them (just reads), > system is 100% busy. Here are the vmstat, > 10-sec profile output and sysrq-t output. > > I am wondering why 100% sys ? > This doesn't make sense. You're showing 50% CPU time in schedule(), yet the (undescribed) machine is doing only 11k context switches/sec. How come? What context switch rate and profile were you getting when performing IO against a large number of real disks?