From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: Marvell MV88SX6041 SATA Driver PIO4 Mode Not DMA Date: Fri, 11 Nov 2005 15:29:05 +0100 Message-ID: <20051111142905.GV3699@suse.de> References: <1131648518.26701.247242836@webmail.messagingengine.com> <437471D0.3090404@pobox.com> <20051111121447.GQ3699@suse.de> <4374A4AC.8010007@pobox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from ns.virtualhost.dk ([195.184.98.160]:41308 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S1750786AbVKKO2C (ORCPT ); Fri, 11 Nov 2005 09:28:02 -0500 Content-Disposition: inline In-Reply-To: <4374A4AC.8010007@pobox.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Jeff Garzik Cc: Spencer Tuttle , linux-ide@vger.kernel.org On Fri, Nov 11 2005, Jeff Garzik wrote: > Jens Axboe wrote: > >On Fri, Nov 11 2005, Jeff Garzik wrote: > > > >>Spencer Tuttle wrote: > >> > >>>I have just compiled the new 2.6.14 kernel from the gentoo-sources tree. > >>> > >>>I can access the drives just fine, but it seems really slow. Here is > >>>the dmesg output when I load the kernel module > >> > >>That's expected, since the driver in 2.6.14 only does PIO mode. > >> > >>Try 2.6.14-gitN which supports EDMA. > > > > > >Did you see these as well: > > > >blk_queue_max_hw_segments: set to minimum 1 > > > >Could it be forgetting to set ->sg_tablesize as well? > > [jgarzik@sata linux-2.6]$ grep MV_MAX_SG_CT drivers/scsi/sata_mv.c > MV_MAX_SG_CT = 176, > MV_SG_TBL_SZ = (16 * MV_MAX_SG_CT), > .sg_tablesize = MV_MAX_SG_CT, It was just a guess, clearly someone is calling scsi_alloc_queue() with an sdev->host->sg_tablesize of 0. While that wont make PIO a whole lot faster, it's clearly a bug and would certainly hurt DMA performance. -- Jens Axboe