From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964844AbXDCJSP (ORCPT ); Tue, 3 Apr 2007 05:18:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964868AbXDCJSP (ORCPT ); Tue, 3 Apr 2007 05:18:15 -0400 Received: from smtp102.mail.mud.yahoo.com ([209.191.85.212]:43263 "HELO smtp102.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S964844AbXDCJSO (ORCPT ); Tue, 3 Apr 2007 05:18:14 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:X-YMail-OSG:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=aOOrKUihvkDDN5re0cGW6gHKsahjjASgSVycWSK060pFYjKbt7gsP3onvFpcR8e8bO9XCQOtBjiIv4Zw+6q/SZabmoZFpOpCzUsoaiwzEt5AgmY3nYYiNHwpE+6DnJkxOEQk2yGNwvm3H0p12m33aou4IxHGxownoR/rBE3SohU= ; X-YMail-OSG: FkXarZMVM1npAusbZB1RIVd6YX03YsGnFAhoSx7.0eRk3XGfel33ge_ZNDBLewnxNU87zGqYbA-- Message-ID: <46121BCF.50401@yahoo.com.au> Date: Tue, 03 Apr 2007 19:18:07 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Paa Paa CC: linux-kernel@vger.kernel.org Subject: Re: Lower HD transfer rate with NCQ enabled? References: In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Paa Paa wrote: > 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? What IO scheduler are you using? If AS or CFQ, could you try with deadline? -- SUSE Labs, Novell Inc.