From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bartlomiej Zolnierkiewicz Subject: Re: SATA RAID5 speed drop of 100 MB/s Date: Sat, 23 Jun 2007 19:30:57 +0200 Message-ID: <200706231930.57688.bzolnier@gmail.com> References: <20070620224847.GA5488@alinoe.com> <467CC5C5.6040201@garzik.org> <20070623125316.GB26672@alinoe.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from ug-out-1314.google.com ([66.249.92.174]:28198 "EHLO ug-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755834AbXFWRwf (ORCPT ); Sat, 23 Jun 2007 13:52:35 -0400 Received: by ug-out-1314.google.com with SMTP id j3so1019617ugf for ; Sat, 23 Jun 2007 10:52:34 -0700 (PDT) In-Reply-To: <20070623125316.GB26672@alinoe.com> Content-Disposition: inline Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Carlo Wood Cc: Jeff Garzik , Tejun Heo , Manoj Kasichainula , linux-kernel@vger.kernel.org, IDE/ATA development list Hi, On Saturday 23 June 2007, Carlo Wood wrote: > PS I'd like to do extensive testing with Bonnie++ to tune everything > there is to tune. But bonnie likes to write/read files TWICE the amount > of RAM I have. It therefore takes a LOT of time to run one test. Do you > happen to know how I can limit the amount of RAM that the linux kernel > sees to, say 500 MB? That should be enough to run in Single User mode > but allow me to run the tests MUCH faster. (I have dual channel, four > DIMM's of 1 GB each -- 2 GB per Core 2 die. Hopefully the fact that > I have dual channel isn't going to be a problem when limiting the ram > that the kernel sees.) "mem=" kernel parameter limits amount of memory seen by kernel (more info in Documentation/kernel-parameters.txt) You can also limit amount of RAM detected by bonnie++ by using -r parameter but please remember that this will make bonnie++ benchmark combined kernel I/O buffering + filesystem + hard disk performance instead of just filesystem + hard disk performance (as it can happen that some / all data won't ever hit the disk). Bart