From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: Re: A question about NCQ Date: Wed, 17 May 2006 14:04:27 +1000 Message-ID: <446AA0CB.60208@yahoo.com.au> References: <1147773689.7273.88.camel@forrest26.sh.intel.com> <4469AE21.6000304@gmail.com> <1147832470.7273.112.camel@forrest26.sh.intel.com> <446A8C78.2000607@gmail.com> <1147836269.7273.127.camel@forrest26.sh.intel.com> <446A9E65.9040608@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Received: from smtp102.mail.mud.yahoo.com ([209.191.85.212]:45188 "HELO smtp102.mail.mud.yahoo.com") by vger.kernel.org with SMTP id S1751209AbWEQEEb (ORCPT ); Wed, 17 May 2006 00:04:31 -0400 In-Reply-To: <446A9E65.9040608@gmail.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tejun Heo Cc: "zhao, forrest" , linux-ide@vger.kernel.org, Jens Axboe Tejun Heo wrote: > >Anyways, anticipatory rules, great. I don't know why NCQ is showing >worse performance w/ AS, but I'm pretty sure it's something which can be >fixed. Jens, Nick, any ideas? > Thanks for the numbers, interesting. Anticipatory basically tries pretty hard to control disk command queues because they can result in starvation... not exactly sure why it is _worse_ with NCQ than without, maybe the drive isn't too smart or there is a bad interaction with AS. I don't see any trivial bugs in AS that would cause this, but there may be one... It's unfortunate that we don't have a grand unified IO scheduler that does everything well (except perhaps noop functionality). It is something I guess Jens and I (or maybe someone completely different) should get together with and try to make progress on one day. -- Send instant messages to your online friends http://au.messenger.yahoo.com