Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932400AbWBALId (ORCPT ); Wed, 1 Feb 2006 06:08:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932419AbWBALId (ORCPT ); Wed, 1 Feb 2006 06:08:33 -0500 Received: from uproxy.gmail.com ([66.249.92.196]:15893 "EHLO uproxy.gmail.com") by vger.kernel.org with ESMTP id S932400AbWBALIc convert rfc822-to-8bit (ORCPT ); Wed, 1 Feb 2006 06:08:32 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=Vm0ujGqf6tDkfnn0ikCx4xY1zCqPwBXm7w4SjeIFiGIVZcb9GGY+RGMk2ogTL+FAG29Z+vQpfFFIEkWZ2kbmus7HBGdpZr6FGHFtlfo8jTVPQIa0isxwkXwIJeJzeI7Oiyr/L//A92AQ+MTvlL6Nj3Nz+3WH8ru/0VKqzuYR3qQ= Message-ID: <58cb370e0602010308o4cde24aeg8d629b1b3d45cdd3@mail.gmail.com> Date: Wed, 1 Feb 2006 12:08:30 +0100 From: Bartlomiej Zolnierkiewicz To: Jeremy Higdon Subject: Re: [patch] SGIIOC4 limit request size Cc: Jes Sorensen , Alan Cox , Linus Torvalds , linux-kernel@vger.kernel.org In-Reply-To: <20060201104913.GA152005@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Content-Disposition: inline References: <58cb370e0602010234p62521a00h6d8920c84cac44d5@mail.gmail.com> <20060201104913.GA152005@sgi.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3788 Lines: 104 On 2/1/06, Jeremy Higdon wrote: > On Wed, Feb 01, 2006 at 11:34:18AM +0100, Bartlomiej Zolnierkiewicz wrote: > > On 01 Feb 2006 03:59:16 -0500, Jes Sorensen wrote: > > > Hi, > > > > Hi, > > > > > 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? > > Actually, it happens with a 16KB page size. > > > 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)? > > I may be misunderstanding something, but it looks to me as though > IOC4_PRD_ENTRIES may be ignored, since ide_init_queue() just uses > PRD_ENTRIES. Fortunately, with a 16KB page size, the arithmetic > works out to the same. In any case, it seems that the 64KB > limit is the problem. Whether that is due to too many s/g entries Indeed, seems that hwif->max_sg_nents is not respected when setting queue ->max_hw_segments and ->max_phys_segments. Does the logic really work the same? Isn't PCI_DMA_BUS_IS_PHYS == 0 for SN2? If so then the code sets ->max_{hw,phys}_segments to IOC4_PRD_ENTRIES/2 which actually shouldn't hurt... > or total byte count I cannot say. I do know that with a 2KB > physical sector size, the minimum size for a s/g entry should be > 2KB, which would mean we're using at most 32 with 127 max sectors -- > well below the 256 that we get from PRD_ENTRIES and IOC4_PRD_ENTRIES. > > We're still looking for root cause of this problem. But with the > default 128KB max request size, we occasionally get timeouts on > DMA commands. I have no big problem with applying patch as it is but I think that it just hides the real problem and/or makes it harder to hit... Bartlomiej > jeremy > > > Cheers. > > Bartlomiej > > > > > Cheers, > > > Jes > > > > > > Avoid requests larger than the number of SG table entries, to avoid > > > DMA timeouts. > > > > > > Signed-off-by: Jes Sorensen > > > > > > ---- > > > > > > drivers/ide/pci/sgiioc4.c | 8 +++++++- > > > 1 files changed, 7 insertions(+), 1 deletion(-) > > > > > > Index: linux-2.6/drivers/ide/pci/sgiioc4.c > > > =================================================================== > > > --- linux-2.6.orig/drivers/ide/pci/sgiioc4.c > > > +++ linux-2.6/drivers/ide/pci/sgiioc4.c > > > @@ -1,5 +1,5 @@ > > > /* > > > - * Copyright (c) 2003 Silicon Graphics, Inc. All Rights Reserved. > > > + * Copyright (C) 2003, 2006 Silicon Graphics, Inc. All Rights Reserved. > > > * > > > * This program is free software; you can redistribute it and/or modify it > > > * under the terms of version 2 of the GNU General Public License > > > @@ -613,6 +613,12 @@ > > > hwif->ide_dma_lostirq = &sgiioc4_ide_dma_lostirq; > > > hwif->ide_dma_timeout = &__ide_dma_timeout; > > > hwif->INB = &sgiioc4_INB; > > > + > > > + /* > > > + * Limit the request size to avoid DMA timeouts when > > > + * requesting more entries than goes in the sg table. > > > + */ > > > + hwif->rqsize = 127; > > > } > > > > > > static int __devinit > - 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/