From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753492AbXDCHZg (ORCPT ); Tue, 3 Apr 2007 03:25:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753493AbXDCHZg (ORCPT ); Tue, 3 Apr 2007 03:25:36 -0400 Received: from bay0-omc1-s18.bay0.hotmail.com ([65.54.246.90]:65159 "EHLO bay0-omc1-s18.bay0.hotmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753492AbXDCHZf (ORCPT ); Tue, 3 Apr 2007 03:25:35 -0400 X-Greylist: delayed 845 seconds by postgrey-1.27 at vger.kernel.org; Tue, 03 Apr 2007 03:25:35 EDT Message-ID: X-Originating-IP: [88.114.147.249] X-Originating-Email: [paapaa125@hotmail.com] From: "Paa Paa" To: linux-kernel@vger.kernel.org Subject: Lower HD transfer rate with NCQ enabled? Date: Tue, 03 Apr 2007 07:11:28 +0000 Mime-Version: 1.0 Content-Type: text/plain; format=flowed X-OriginalArrivalTime: 03 Apr 2007 07:11:29.0956 (UTC) FILETIME=[4D4EC640:01C775BF] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org I'm using Linux 2.6.20.4. I noticed that I get lower SATA hard drive throughput with 2.6.20.4 than with 2.6.19. The reason was that 2.6.20 enables NCQ by defauly (queue_depth = 31/32 instead of 0/32). Transfer rate was measured using "hdparm -t": With NCQ (queue_depth == 31): 50MB/s. Without NCQ (queue_depth == 0): 60MB/s. 20% difference is quite a lot. This is with Intel ICH8R controller and Western Digital WD1600YS hard disk in AHCI mode. I also used the next command to cat-copy a biggish (540MB) file and time it: rm temp && sync && time sh -c 'cat quite_big_file > temp && sync' Here I noticed no differences at all with and without NCQ. The times (real time) were basically the same in many successive runs. Around 19s. Q: What conclusion can I make on "hdparm -t" results or can I make any conclusions? Do I really have lower performance with NCQ or not? If I do, is this because of my HD or because of kernel? Best regards, Paapaa _________________________________________________________________ Express yourself instantly with MSN Messenger! Download today it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/