Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262009AbUC1AJU (ORCPT ); Sat, 27 Mar 2004 19:09:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262006AbUC1AJT (ORCPT ); Sat, 27 Mar 2004 19:09:19 -0500 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:29109 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id S261990AbUC1AI7 (ORCPT ); Sat, 27 Mar 2004 19:08:59 -0500 Message-ID: <4066178C.5020605@pobox.com> Date: Sat, 27 Mar 2004 19:08:44 -0500 From: Jeff Garzik User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030703 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Bartlomiej Zolnierkiewicz CC: Stefan Smietanowski , linux-ide@vger.kernel.org, Linux Kernel , Andrew Morton Subject: Re: [PATCH] speed up SATA References: <4066021A.20308@pobox.com> <40660FEC.8080703@pobox.com> <406610EA.4010607@pobox.com> <200403280113.58555.bzolnier@elka.pw.edu.pl> In-Reply-To: <200403280113.58555.bzolnier@elka.pw.edu.pl> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1324 Lines: 36 Bartlomiej Zolnierkiewicz wrote: > On Sunday 28 of March 2004 00:40, Jeff Garzik wrote: > >>Jeff Garzik wrote: >> >>>That's the main limitation on request size right now... libata limits >>>S/G table entries to 128[1], so a perfectly aligned, fully merged >> >> ... >> >>[1] because even though the block layer properly splits on segment >>boundaries, pci_map_sg() may violate those boundaries (James B and >>others are working on fixing this). So... for right now the driver >>must check the s/g entry boundaries after DMA mapping, and split them >>(again) if necessary. IDE does this in ide_build_dmatable(). > > > You are right but small clarification is needed: code in ide_build_dmatable() > predates segment boundary support in block layer (IDE never relied on it). Agreed... I'm saying it's still needed. When the iommu layer knows about the boundaries it should respect, that code can be removed from libata and drivers/ide, IMO... But also double-check and make sure IDE driver supports the worst case, by limiting to 128 PRD entries, not 256. Jeff - 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/