Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262476AbUC1U6q (ORCPT ); Sun, 28 Mar 2004 15:58:46 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262465AbUC1U6q (ORCPT ); Sun, 28 Mar 2004 15:58:46 -0500 Received: from 80-169-17-66.mesanetworks.net ([66.17.169.80]:34481 "EHLO mail.bounceswoosh.org") by vger.kernel.org with ESMTP id S262424AbUC1U6j (ORCPT ); Sun, 28 Mar 2004 15:58:39 -0500 Date: Sun, 28 Mar 2004 13:59:17 -0700 From: "Eric D. Mudama" To: Nick Piggin , "Eric D. Mudama" , Jeff Garzik , linux-ide@vger.kernel.org, Linux Kernel , Andrew Morton Subject: Re: [PATCH] speed up SATA Message-ID: <20040328205917.GF6405@bounceswoosh.org> Mail-Followup-To: Nick Piggin , "Eric D. Mudama" , Jeff Garzik , linux-ide@vger.kernel.org, Linux Kernel , Andrew Morton References: <4066021A.20308@pobox.com> <40661049.1050004@yahoo.com.au> <20040328044029.GB1984@bounceswoosh.org> <40667734.8090203@yahoo.com.au> <20040328203357.GB6405@bounceswoosh.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20040328203357.GB6405@bounceswoosh.org> User-Agent: Mutt/1.5.5.1+cvs20040105i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1188 Lines: 28 Er, forgot about the queue depth of only 2... Even in that case, you'll more than likely still get better throughput with a single 32-MB command... If you send a pair of queued commands down, and the 2nd one is chosen, there's no reason that the first one won't get starved until the very end of the request, which would have bad latency on that command. Even worse, would be it getting force-promoted in the middle of the rest of the 32MB chunk due to an approaching internal timeout, and therefore interrupting a 31-MB sequential read to do a 1MB read. However, most of this is silly... 32 1MB requests will be way faster than 32,000 1LBA requests, etc... in general, bigger requests = better throughput for all but a few specific workloads that I can think of off the top of my head. (lots of simultaneous stream workloads with very low latency requirements per-stream, for example) -- Eric D. Mudama edmudama@mail.bounceswoosh.org - 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/