Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266567AbUFQQcx (ORCPT ); Thu, 17 Jun 2004 12:32:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266566AbUFQQcx (ORCPT ); Thu, 17 Jun 2004 12:32:53 -0400 Received: from rtp-iport-1.cisco.com ([64.102.122.148]:10606 "EHLO rtp-iport-1.cisco.com") by vger.kernel.org with ESMTP id S266563AbUFQQch (ORCPT ); Thu, 17 Jun 2004 12:32:37 -0400 X-BrightmailFiltered: true To: James Bottomley Cc: "Salyzyn, Mark" , Christoph Hellwig , Alan Cox , Linux Kernel , SCSI Mailing List Subject: Re: PATCH: Further aacraid work References: <547AF3BD0F3F0B4CBDC379BAC7E4189FD2402C@otce2k03.adaptec.com> <1087484107.2090.42.camel@mulgrave> From: Clay Haapala Organization: Cisco Systems, Inc. SRBU Face: iVBORw0KGgoAAAANSUhEUgAAADAAAAAwBAMAAAClLOS0AAAAHlBMVEXl5ufMrp3a4OLr6ujO lXzChGmsblZzRzjF1+ErFRAz+KIaAAACVElEQVR4nG3TQW/aMBQAYC9IO88dguyWUomqt0DQ do7koO22SXFQb6uE7XIMKrFya+mhPk8D43+79+wMyrp3gnx59nvxMxmNEnIWycgH+U9E55CO rkZJ8hYipbXTdfcvQK/Xy6JF2zqI+qpbjZAszSDG2oXYp0FI5mOqbAeuDtLBdeuO8fNVxkzr E9jklKEgQWsppYYf9v4IE3i/4RiVRPneQTpoXSM8QA7un3QZQ2cl54wXIH7VDwEmrdOiZBgF V5BiLwLM4B3BS0ZpB24d4IvzW+QIc7/JIcAQIadF2eeUzn3FAa6xWFYUotjIRmLB7vEvCC4t VAugpTrC2FleLBm2wVnlAc7Dl2u5L1UozgWCjTxMW+vb4GVVFhWWFSCdKmgDMhaNFoxL3bSH rc/Irn1/RcWlh+UqNgHeNwishJ1L6LCpjdmGz76RmFGyuSwLgLUxJhyUlLA7fHMpeSGVPsFA wqtK4voI8RE+I3DsDpfamSNMpIBTKrF1yIpPMA0AzQPU5gSwCTyC/aEAtX4NM6gLM3CCziBT jRR+StQ/AA8a7AMuwxn0YAmcRKnVGwDRiOcw3uMWlajgAJsAPbw4OIpwrH3/vdq9B7hpl7GD w61A4PxwSqyH9J25gePnYdqhYjjZ5s6QCb3bwvOLJWPBFvCvWVDSthYmcff44IcacOUOt1Yv yGCF1+twuQtQCPjzZIaK/Lrx9+6b7TKEdXTwgz8R+uJv5K1jOcWMnO7NJ3v/QlprnzP1deUe 8j4CpVE82MRj4j5SHGDnfvul8uGwjqNnpf4Ak4pzJDIy3lkAAAAASUVORK5CYII= Date: Thu, 17 Jun 2004 11:32:29 -0500 In-Reply-To: <1087484107.2090.42.camel@mulgrave> (James Bottomley's message of "17 Jun 2004 09:55:03 -0500") Message-ID: User-Agent: Gnus/5.110003 (No Gnus v0.3) XEmacs/21.5 (chayote, linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1839 Lines: 41 On 17 Jun 2004, James Bottomley spake thusly: > On Thu, 2004-06-17 at 09:39, Salyzyn, Mark wrote: >> This would not be such an issue if Linux provided large SG elements >> rather than the fubar descending page order ones they issue today. If >> this could be fixed, I'd not even be interested in the optimization of >> the SG. > > This is hardly a big problem, is it? it only occurs during the first > few moments of system operation. After that, the pages assigned to a > virtual region are pretty much random. > > Fundamentally, sg lists have to operate at the level of the MMU, so > we're stuck with the page size, which is 4k on x86. There's nothing we > can do in SCSI about this. > > Of course, if you're on a platform with an IOMMU then this problem > simply doesn't exist and we can coalesce nicely. > > James Just to see if my understanding is on track ... Today's scatterlists already handle entries with a size greater than MMU pagelength, even on x86, right? We have seen it in iSCSI driver testing, though it is not the usual case. crypto/digests.c:update() function was recently patched to handle the case and properly kmap() the additional memory represented by the sg entry. So, on regular x86 this is a matter of convenience/timing, and the page assignments will tend toward, but not always be, random 1-page entries as the system is used. -- Clay Haapala (chaapala@cisco.com) Cisco Systems SRBU +1 763-398-1056 6450 Wedgwood Rd, Suite 130 Maple Grove MN 55311 PGP: C89240AD Overheard somewhere in Washington D.C.: "Doh! Invaded the wrong country!" - 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/