Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932408AbWBAKlg (ORCPT ); Wed, 1 Feb 2006 05:41:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932411AbWBAKlf (ORCPT ); Wed, 1 Feb 2006 05:41:35 -0500 Received: from omx1-ext.sgi.com ([192.48.179.11]:49287 "EHLO omx1.americas.sgi.com") by vger.kernel.org with ESMTP id S932408AbWBAKle (ORCPT ); Wed, 1 Feb 2006 05:41:34 -0500 Message-ID: <43E0904C.1020201@sgi.com> Date: Wed, 01 Feb 2006 11:41:16 +0100 From: Jes Sorensen User-Agent: Mozilla Thunderbird 1.0.7-1.1.fc4 (X11/20050929) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Bartlomiej Zolnierkiewicz CC: Alan Cox , Linus Torvalds , linux-kernel@vger.kernel.org, Jeremy Higdon Subject: Re: [patch] SGIIOC4 limit request size References: <58cb370e0602010234p62521a00h6d8920c84cac44d5@mail.gmail.com> In-Reply-To: <58cb370e0602010234p62521a00h6d8920c84cac44d5@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1321 Lines: 34 Bartlomiej Zolnierkiewicz wrote: > On 01 Feb 2006 03:59:16 -0500, Jes Sorensen wrote: >>This one takes care of a problem with the SGI IOC4 driver where it >>hits DMA problems if the request grows too large. > > > Does this happen only for CONFIG_IA64_PAGE_SIZE_4KB=y > or CONFIG_IA64_PAGE_SIZE_8KB=y? > > from sgiioc4.c: > > /* Each Physical Region Descriptor Entry size is 16 bytes (2 * 64 bits) */ > /* IOC4 has only 1 IDE channel */ > #define IOC4_PRD_BYTES 16 > #define IOC4_PRD_ENTRIES (PAGE_SIZE /(4*IOC4_PRD_BYTES)) > > As limiting request size to 127 sectors punishes performance > wouldn't it be better to define IOC4_PRD_ENTRIES to 256 > if this is possible (would need 4 pages for PAGE_SIZE=4096 > and 2 for PAGE_SIZE=8192)? This happens with the default page size which is 16KB, ie. IOC4_PRD_ENTRIES=256, the problem is not due to the request going beyond the number of PRD_ENTRIES. I haven't tried with smaller page sizes but I would assume the problem would be the same. Even with this patch performance seems very reasonable. Jes - 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/