Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759945AbZFYH2X (ORCPT ); Thu, 25 Jun 2009 03:28:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752828AbZFYH2P (ORCPT ); Thu, 25 Jun 2009 03:28:15 -0400 Received: from stz-softwaretechnik.de ([217.160.223.211]:3005 "EHLO stlx01.stz-softwaretechnik.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752449AbZFYH2P (ORCPT ); Thu, 25 Jun 2009 03:28:15 -0400 Date: Thu, 25 Jun 2009 09:27:54 +0200 From: Ralf Gross To: Al Boldi Cc: linux-kernel@vger.kernel.org, fengguang.wu@intel.com Subject: Re: io-scheduler tuning for better read/write ratio Message-ID: <20090625072754.GC16642@p15145560.pureserver.info> References: <4A37CB2A.6010209@davidnewall.com> <20090624072554.GA16642@p15145560.pureserver.info> <200906241057.41227.a1426z@gawab.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200906241057.41227.a1426z@gawab.com> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2083 Lines: 108 Al Boldi schrieb: > Ralf Gross wrote: > > The main problem is with bacula. It reads/writes from/to two > > spoolfiles on the same device. > > > > I get the same behavior with 2 dd processes, one reading from disk, one > > writing to it. > > > > Here's the output from dstat (5 sec intervall). > > > > --dsk/md1-- > > _read _writ > > 26M 95M > > 31M 96M > > 20M 85M > > 31M 108M > > 28M 89M > > 24M 95M > > 26M 79M > > 32M 115M > > 50M 74M > > 129M 15k > > 147M 1638B > > 147M 0 > > 147M 0 > > 113M 0 > > > > > > At the end I stopped the dd process that is writing to the device, so you > > can see that the md device is capable of reading with >120 MB/s. > > > > I did this with these two commands. > > > > dd if=/dev/zero of=test bs=1MB > > dd if=/dev/md1 of=/dev/null bs=1M > > Try changing /proc/sys/vm/dirty_ratio = 1 $cat /proc/sys/vm/dirty_ratio 1 $dstat -D md1 -d 5 --dsk/md1-- _read _writ 18M 18M 0 0 820k 101M 18M 113M 26M 73M 26M 110M 32M 100M 19M 111M 13M 117M 13M 142M 32M 88M 26M 99M 38M 58M No change. Even setting dirty_ratio to 100 didn't show any difference. With the cfq scheduler and slice_idle = 24 (trial and error) I get better results. Itried this before, but the overall throughput was a bit lower than with deadline. It seems that I can not tune deadline to get the samet behaviour. --dsk/md1-- _read _writ 18M 18M 25M 77M 51M 65M 51M 47M 62M 45M 53M 28M 45M 43M 46M 47M 47M 42M 51M 41M 38M 51M 51M 40M 45M 40M 58M 42M 69M 41M 72M 42M 122M 0 141M 340k --dsk/md1-- _read _writ 139M 562k 136M 0 141M 13k 64M 0 1638B 104M 0 110M 0 122M 0 104M 0 108M The last numbers are for reading/writing only. Ralf -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/