From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Moyer Subject: Re: New driver mtipx2xx submission Date: Tue, 28 Jun 2011 11:18:43 -0400 Message-ID: References: <22A973199D2C2F46933448F6E7990A300204F2BC@ntxboimbx31.micron.com> <20110428230605.78c55c70@lxorguk.ukuu.org.uk> <22A973199D2C2F46933448F6E7990A300204F728@ntxboimbx31.micron.com> <20110502184206.25907c5e@lxorguk.ukuu.org.uk> <22A973199D2C2F46933448F6E7990A300214B0D6@ntxboimbx31.micron.com> <20110511202013.075b07cc@lxorguk.ukuu.org.uk> <4DD722DB.8030303@micron.com> <22A973199D2C2F46933448F6E7990A300239EA77@ntxboimbx31.micron.com> <20110601212129.11534c55@lxorguk.ukuu.org.uk> <4DF80ADE.8020206@micron.com> <22A973199D2C2F46933448F6E7990A3002697E77@ntxboimbx31.micron.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mx1.redhat.com ([209.132.183.28]:9803 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758544Ab1F1PS6 (ORCPT ); Tue, 28 Jun 2011 11:18:58 -0400 In-Reply-To: <22A973199D2C2F46933448F6E7990A3002697E77@ntxboimbx31.micron.com> (Asai Thambi Samymuthu Pattrayasamy's message of "Mon, 27 Jun 2011 17:38:48 -0600") Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: "Asai Thambi Samymuthu Pattrayasamy (asamymuthupa) [CONTRACTOR]" Cc: Alan Cox , linux-ide@vger.kernel.org "Asai Thambi Samymuthu Pattrayasamy (asamymuthupa) [CONTRACTOR]" writes: >> 2.6.39 introduced the on-stack plugging work from Jens, the intent of >> which is to reduce queue lock contention. It would be great if you >> could run with that kernel and noop to see if we make up some of the >> performance gap (which looks to be just north of 10%). >> >> Asai, thanks for running these tests and providing all of this data! >> >> -Jeff > > At least with noop and deadline for ahci driver, now queue lock is not > the top offender. With the new change in plugging, seems noop and > deadline are spending more time in processing I/O similar to Micron > block driver. > > With the current test results with 2.6.39.1 (new optimization for > plugging) and application queue depth of 32, > * Micron block driver exhibits 43% better IOPS than ahci driver > with noop > * Micron block driver slightly better in CPU utilization. > > With application queue depth of 256, Micron block driver is able to > leverage the device capability, and hence performance increases more > than 225%. > >>From the perf report, I would have guessed that the CPU utilization for the ahci test case would have been lower than the Micron block driver. Odd, I wonder what I'm missing. Asai, did you notice if any of the CPUs was completely pegged during testing with ahci? You're using a NUMA box, right? I also wonder what the irq distribution looked like, and whether rq_affinity is hurting performance for the ahci case. Also, does the Micron driver do any sort of interrupt coalescing that maybe the ahci driver isn't doing? Anywho, a 40% difference is pretty significant (though NUMA can have that sort of impact). Alan, what do you think? I was never clear on how exactly the ahci driver would handle a queue depth larger than 32 (if it can't, then clearly we'd need a block driver for this hardware). Cheers, Jeff