From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: Some NCQ numbers... Date: Wed, 04 Jul 2007 10:19:55 +0900 Message-ID: <468AF5BB.10005@gmail.com> References: <468392CE.6010206@msgid.tls.msk.ru> <468A06A0.1020802@gmail.com> <468AB1A7.9010201@msgid.tls.msk.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from nz-out-0506.google.com ([64.233.162.230]:51612 "EHLO nz-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755632AbXGDBUA (ORCPT ); Tue, 3 Jul 2007 21:20:00 -0400 Received: by nz-out-0506.google.com with SMTP id s18so1418942nze for ; Tue, 03 Jul 2007 18:20:00 -0700 (PDT) In-Reply-To: <468AB1A7.9010201@msgid.tls.msk.ru> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Michael Tokarev Cc: Kernel Mailing List , linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org Hello, Michael Tokarev wrote: > Well. It looks like the results does not depend on the > elevator. Originally I tried with deadline, and just > re-ran the test with noop (hence the long delay with > the answer) - changing linux elevator changes almost > nothing in the results - modulo some random "fluctuations". I see. Thanks for testing. > In any case, NCQ - at least in this drive - just does > not work. Linux with its I/O elevator may help to > speed things up a bit, but the disk does nothing in > this area. NCQ doesn't slow things down either - it > just does not work. > > The same's for ST3250620NS "enterprise" drives. > > By the way, Seagate announced Barracuda ES 2 series > (in range 500..1200Gb if memory serves) - maybe with > those, NCQ will work better? No one would know without testing. > Or maybe it's libata which does not implement NCQ > "properly"? (As I shown before, with almost all > ol'good SCSI drives TCQ helps alot - up to 2x the > difference and more - with multiple I/O threads) Well, what the driver does is minimal. It just passes through all the commands to the harddrive. After all, NCQ/TCQ gives the harddrive more responsibility regarding request scheduling. -- tejun