From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756351AbZHPWv0 (ORCPT ); Sun, 16 Aug 2009 18:51:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756309AbZHPWvZ (ORCPT ); Sun, 16 Aug 2009 18:51:25 -0400 Received: from rtr.ca ([76.10.145.34]:48435 "EHLO mail.rtr.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756308AbZHPWvX (ORCPT ); Sun, 16 Aug 2009 18:51:23 -0400 Message-ID: <4A888D6B.8020103@rtr.ca> Date: Sun, 16 Aug 2009 18:51:23 -0400 From: Mark Lord Organization: Real-Time Remedies Inc. User-Agent: Thunderbird 2.0.0.22 (X11/20090608) MIME-Version: 1.0 To: Theodore Tso , Roland Dreier , James Bottomley , Arjan van de Ven , Alan Cox , Mark Lord , Chris Worley , Matthew Wilcox , Bryan Donlan , david@lang.hm, Greg Freemyer , Markus Trippelsdorf , Matthew Wilcox , Hugh Dickins , Nitin Gupta , Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org, Linux RAID Subject: Re: Discard support References: <20090814234539.GE27148@parisc-linux.org> <1250341176.4159.2.camel@mulgrave.site> <4A86B69C.7090001@rtr.ca> <1250344518.4159.4.camel@mulgrave.site> <20090816150530.2bae6d1f@lxorguk.ukuu.org.uk> <20090816083434.2ce69859@infradead.org> <1250437927.3856.119.camel@mulgrave.site> <20090816221325.GF17958@mit.edu> In-Reply-To: <20090816221325.GF17958@mit.edu> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Theodore Tso wrote: > On Sun, Aug 16, 2009 at 02:50:40PM -0700, Roland Dreier wrote: >> > Well, yes and no ... a lot of SSDs don't actually implement NCQ, so the >> > impact to them will be less ... although I think enterprise class SSDs >> > do implement NCQ. >> >> Really? Which SSDs don't implement NCQ? > > The Intel X25-M was the first SSD to implement NCQ. The OCZ Core V2 > advertised NCQ with a queue depth of 1, but even that was buggy, so > Linux has a black list for the that SSD: > > http://markmail.org/message/jvjpmcdqjwrmyl4w > > As far as I know, all of the SSD's using the crappy JMicron JMF602 > controllers don't support NCQ in any real way, which would includes > most of the reasonably priced SSD's up until first half of this year. > (The OCZ Summit SSD, which uses the Indilnx controller is an exception > to this statement, but it's more expensive that the JMF602 based > SSD's, although less expensive than the Intel SSD.) > > JMicron is trying to seek redemption with their JMF612 controllers, > which were announced at the end of May of this year, and those > controllers do support NCQ, and are claimed to not to have the > disatrous small write latency problem of their '602 bretheren. I'm > not aware of any products using the JMF612 yet, though. (According to > reports the '612 controllers weren't going to hit mass production > until July, so hopefully later this fall we'll start seeing products > using the new JMicron controller.) .. Great summary, Ted. To add: SSDs based upon the Indilinx controller don't appear to scale beyond an NCQ depth of about 4 or so. Whereas Intel SSDs continue to improve with increased queue depth up to 31 on Linux. Or at least that's what I recall from reading various SSD benchmarks a few weeks ago here. Cheers