From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753147AbXCXWMz (ORCPT ); Sat, 24 Mar 2007 18:12:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932319AbXCXWMz (ORCPT ); Sat, 24 Mar 2007 18:12:55 -0400 Received: from shawidc-mo1.cg.shawcable.net ([24.71.223.10]:55059 "EHLO pd4mo3so.prod.shaw.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753100AbXCXWMy (ORCPT ); Sat, 24 Mar 2007 18:12:54 -0400 Date: Sat, 24 Mar 2007 16:11:21 -0600 From: Robert Hancock Subject: Re: Why is NCQ enabled by default by libata? (2.6.20) In-reply-to: To: Justin Piszcz Cc: linux-kernel@vger.kernel.org Message-id: <4605A209.9050808@shaw.ca> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7bit References: User-Agent: Thunderbird 1.5.0.10 (Windows/20070221) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Justin Piszcz wrote: > Without NCQ, performance is MUCH better on almost every operation, with > the exception of 2-3 items. > > /usr/sbin/bonnie++ -d /x/bonnie -s 7952 -m p34 -n 16:100000:16:64 > > run.txt; > > # Average of 3 runs with NCQ on for Quad Raptor ADFD 150 RAID 5 Software > RAID: > p34-ncq-on,7952M,43916.3,96.6667,151943,28.6667,75794.3,18.6667,48991.3,99,181687,24,558.033,0.333333,16:100000:16/64,867.667,9,29972.7,98.3333,2801.67,16,890.667,9.33333,27743,94.3333,2115.33,15.6667 > > # Average of 3 runs with NCQ off for Quad Raptor ADFD 150 RAID 5 > Software RAID: > p34-ncq-off,7952M,42470,97.3333,200409,36.3333,90240.3,22.6667,48656,99,198853,27,546.467,0,16:100000:16/64,972.333,10,21833,72.3333,3697,21,995,10.6667,27901.7,95.6667,2681,20.6667 > > > http://home.comcast.net/~jpiszcz/ncq_vs_noncq/results.html > > In general, for networking, etc, the kernel chooses 'optimized' > defaults, therefore, I was curious why is NCQ enabled by default? Normally NCQ is faster, though it depends on the drive firmware. It's also possible that software RAID is a case where there are negative interactions. -- Robert Hancock Saskatoon, SK, Canada To email, remove "nospam" from hancockr@nospamshaw.ca Home Page: http://www.roberthancock.com/