From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964965AbVHaVQl (ORCPT ); Wed, 31 Aug 2005 17:16:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964968AbVHaVQk (ORCPT ); Wed, 31 Aug 2005 17:16:40 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:16017 "EHLO ZenIV.linux.org.uk") by vger.kernel.org with ESMTP id S964966AbVHaVQj (ORCPT ); Wed, 31 Aug 2005 17:16:39 -0400 Date: Wed, 31 Aug 2005 22:16:50 +0100 From: "Dr. David Alan Gilbert" To: Holger Kiehl Cc: linux-raid , linux-kernel Subject: Re: Where is the performance bottleneck? Message-ID: <20050831211650.GD24383@gallifrey> References: <20050829202529.GA32214@midnight.suse.cz> <20050831071126.GA7502@midnight.ucw.cz> <20050831072644.GF4018@suse.de> <20050831120714.GT4018@suse.de> <20050831142413.GB24383@gallifrey> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.1i X-Chocolate: 70 percent or better cocoa solids preferably X-Operating-System: Linux/2.6.11-1.14_FC3smp (i686) X-Uptime: 22:12:25 up 139 days, 20:43, 46 users, load average: 0.01, 0.01, 0.00 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Holger Kiehl (Holger.Kiehl@dwd.de) wrote: > There is however one difference, here I had set > /sys/block/sd?/queue/nr_requests to 4096. Well from that it looks like none of the queues get about 255 (hmm that's a round number....) > avg-cpu: %user %nice %sys %iowait %idle > 0.10 0.00 21.85 58.55 19.50 Fair amount of system time. > Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s > avgrq-sz avgqu-sz await svctm %util > sdf 11314.90 0.00 365.10 0.00 93440.00 0.00 46720.00 0.00 > 255.93 1.92 5.26 2.74 99.98 > sdg 7973.20 0.00 257.20 0.00 65843.20 0.00 32921.60 0.00 > 256.00 1.94 7.53 3.89 100.01 There seems to be quite a spread of read performance accross the drives (pretty consistent accross the run); what makes sdg so much slower than sdf (which seems to be the slowest and fastest drives respectively). I guess if everyone was running at sdf's speed you would be pretty happy. If you physically swap f and g does the performance follow the drive or the letter? Dave -- -----Open up your eyes, open up your mind, open up your code ------- / Dr. David Alan Gilbert | Running GNU/Linux on Alpha,68K| Happy \ \ gro.gilbert @ treblig.org | MIPS,x86,ARM,SPARC,PPC & HPPA | In Hex / \ _________________________|_____ http://www.treblig.org |_______/