From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH] SCSI sym53c8xx_2: bigger transfer limits Date: Wed, 1 Mar 2006 16:54:02 +0100 Message-ID: <20060301155401.GA4816@suse.de> References: <20060301152929.GZ4816@suse.de> <1141227541.3276.26.camel@mulgrave.il.steeleye.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from ns.virtualhost.dk ([195.184.98.160]:2881 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S932414AbWCAPy1 (ORCPT ); Wed, 1 Mar 2006 10:54:27 -0500 Content-Disposition: inline In-Reply-To: <1141227541.3276.26.camel@mulgrave.il.steeleye.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: Kai Makisara , matthew@wil.cx, linux-scsi@vger.kernel.org On Wed, Mar 01 2006, James Bottomley wrote: > On Wed, 2006-03-01 at 16:29 +0100, Jens Axboe wrote: > > Strictly speaking, the clustering bit is unrelated. I seem to recall > > Gerard years ago talking about some sym chips that did not like > > clustering, hence it was disabled. > > Yes, I remember that too ... I've never been able to find out which > chip, though ... the scripts all seem happily coded for variable size sg > segments. > > However, given the new way 2.6 does memory allocations, > ENABLE_CLUSTERING will probably make quite a difference to the size of > the sg list ... since we try to allocate contiguous pages, physical > merging becomes much more of a possibility (I think I last measured it > at around 30% of all SG tables, as opposed to <1% with the old > allocation method). So if we want to enable clustering, it should be done as a separate patch just in case... -- Jens Axboe