From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Higdon Subject: Re: [RFC] Make the SCSI mempool allocations variable Date: Tue, 9 Mar 2004 22:21:20 -0800 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <20040310062120.GN148048@sgi.com> References: <1078858977.1756.40.camel@mulgrave> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mtvcafw.SGI.COM ([192.48.171.6]:8743 "EHLO zok.sgi.com") by vger.kernel.org with ESMTP id S262528AbUCJGVs (ORCPT ); Wed, 10 Mar 2004 01:21:48 -0500 Content-Disposition: inline In-Reply-To: <1078858977.1756.40.camel@mulgrave> List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: mpm@waste.org, SCSI Mailing List On Tue, Mar 09, 2004 at 02:02:55PM -0500, James Bottomley wrote: > Based on Jeremy's request to increase max_phys_segments, this is the way > to do it (SCSI_MAX_PHYS_SEGMENTS) is the value that gets set as the > queue's max_phys_segments. > > I have to say that when I tried raising it to 256 and hammering a 10GB > ext2 filesystem, I still didn't generate any >128 segment requests, so > I'm dubious that raising it has any benefit at all, but feel free to try > it and publish the figures. > > I did wonder if lowering it might help improve the memory footprint for > some embedded systems, so I set it up to be lowered as far as 32. > > James Thanks, James! I promise that we will take advantage of this, but it might take a couple of months. As you point out, the filesystem code also has to deliver the larger requests. I'll try a couple of tests with XFS and block device direct I/O. jeremy