From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH 1/2] libata: switch to using block layer tagging support Date: Thu, 21 May 2009 13:27:41 -0400 Message-ID: <4A158F0D.2090505@garzik.org> References: <20090520065942.GD11363@kernel.dk> <20090520070038.GE11363@kernel.dk> <1242845440.2881.74.camel@localhost.localdomain> <4A1452E9.7000204@garzik.org> <4A145458.5080302@garzik.org> <4A155AA5.3080704@rtr.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from srv5.dvmed.net ([207.36.208.214]:59415 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753545AbZEUR1s (ORCPT ); Thu, 21 May 2009 13:27:48 -0400 In-Reply-To: <4A155AA5.3080704@rtr.ca> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Mark Lord Cc: Gwendal Grignou , James Bottomley , Grant Grundler , Jens Axboe , linux-ide@vger.kernel.org, htejun@gmail.com Mark Lord wrote: > Gwendal Grignou wrote: >> Jeff, you're right, I made some mistakes: >> - Reading SiI3132 doc again, it only supports 32 command per port, so >> the tags must be share among all the drives behind the same port. >> But other chipset does support up to 128 commands per port. >> - Jens' patch is working when all disks support NCQ. Only when we have >> a mix of drives with or without NCQ we have a problem. > .. > > Along those lines, the newer Marvell chipsets support up to 128 commands > per host port. > > I seem to recall that the Pacific Digital Qstor chip > can manage an insane number of commands -- something like > 32 per device per PM port [eg. (15 * 32) in total per host port]. > > Seems to be a widespread kind of thing for non-legacy chipsets. > Someday we really ought to beef up libata to allow host-chipset queuing > of non-NCQ commands, too. SAS+SATA chips do not necessarily have per-port limits at all, even. The limit may instead be a host-wide command queue size limit, rather than a per-port limit. Jeff