From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH] speed up SATA Date: Sun, 28 Mar 2004 19:40:13 +0200 Sender: linux-ide-owner@vger.kernel.org Message-ID: <20040328174013.GJ24370@suse.de> References: <4066021A.20308@pobox.com> <40661049.1050004@yahoo.com.au> <406611CA.3050804@pobox.com> <406616EE.80301@pobox.com> <4066191E.4040702@yahoo.com.au> <40662108.40705@pobox.com> <20040328135124.GA32597@mail.shareable.org> <40670A36.3000005@pobox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from ns.virtualhost.dk ([195.184.98.160]:46532 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S262272AbUC1RkV (ORCPT ); Sun, 28 Mar 2004 12:40:21 -0500 Content-Disposition: inline In-Reply-To: <40670A36.3000005@pobox.com> List-Id: linux-ide@vger.kernel.org To: Jeff Garzik Cc: Jamie Lokier , Nick Piggin , linux-ide@vger.kernel.org, Linux Kernel , Andrew Morton On Sun, Mar 28 2004, Jeff Garzik wrote: > Jamie Lokier wrote: > >Jeff Garzik wrote: > > > >>TCQ-on-write for ATA disks is yummy because you don't really know what > >>the heck the ATA disk is writing at the present time. By the time the > >>Linux disk scheduler gets around to deciding it has a nicely merged and > >>scheduled set of requests, it may be totally wrong for the disk's IO > >>scheduler. TCQ gives the disk a lot more power when the disk integrates > >>writes into its internal IO scheduling. > > > > > >Does TCQ-on-write allow you to do ordered write commits, as with barriers, > >but without needing full cache flushes, and still get good performance? > > Nope, TCQ is just a bunch of commands rather than one. There are no > special barrier indicators you can pass down with a command. What would be nice (and I seem to recall that Andre also pushed for this) would be the FUA bit doubling as an ordered tag indicator when using TCQ. It's one of those things that keep ATA squarely outside of the big machine uses. That other OS had a differing opinion of what to do with that, so... -- Jens Axboe