From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934351AbXC2Vrk (ORCPT ); Thu, 29 Mar 2007 17:47:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934354AbXC2Vrk (ORCPT ); Thu, 29 Mar 2007 17:47:40 -0400 Received: from mail1.webmaster.com ([216.152.64.169]:2046 "EHLO mail1.webmaster.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934351AbXC2Vrj (ORCPT ); Thu, 29 Mar 2007 17:47:39 -0400 From: "David Schwartz" To: "Linux-Kernel@Vger. Kernel. Org" Subject: RE: Why is NCQ enabled by default by libata? (2.6.20) Date: Thu, 29 Mar 2007 14:47:20 -0700 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.6604 (9.0.2911.0) Importance: Normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 In-Reply-To: <460BF73C.5070707@cfl.rr.com> X-Authenticated-Sender: joelkatz@webmaster.com X-Spam-Processed: mail1.webmaster.com, Thu, 29 Mar 2007 14:47:32 -0800 (not processed: message from trusted or authenticated source) X-MDRemoteIP: 206.171.168.138 X-Return-Path: davids@webmaster.com X-MDaemon-Deliver-To: linux-kernel@vger.kernel.org Reply-To: davids@webmaster.com X-MDAV-Processed: mail1.webmaster.com, Thu, 29 Mar 2007 14:47:32 -0800 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > But when writing, what is the difference between queuing multiple tagged > writes, and sending down multiple untagged cached writes that complete > immediately and actually hit the disk later? Either way the host keeps > sending writes to the disk until it's buffers are full, and the disk is > constantly trying to commit those buffers to the media in the most > optimal order. Which sounds faster to you: 1) "Do A, B, C, and D." "Okay, I've finished A, B, C, and B." or 2) "Do A." "Okay." "Do B." "Okay." "Do C." "Okay." "Do D." "Okay." The first looks a bit more efficient to me. DS