From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bartlomiej Zolnierkiewicz Subject: Re: [PATCH V13 00/10] mmc: Add Command Queue support Date: Thu, 16 Nov 2017 10:46:40 +0100 Message-ID: <1716036.6EalJ2kXtr@amdc3058> References: <1509715220-31885-1-git-send-email-adrian.hunter@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-reply-to: <1509715220-31885-1-git-send-email-adrian.hunter@intel.com> Sender: linux-block-owner@vger.kernel.org To: Adrian Hunter Cc: Ulf Hansson , linux-mmc , linux-block , linux-kernel , Bough Chen , Alex Lemberg , Mateusz Nowak , Yuliy Izrailov , Jaehoon Chung , Dong Aisheng , Das Asutosh , Zhangfei Gao , Sahitya Tummala , Harjani Ritesh , Venu Byravarasu , Linus Walleij , Shawn Lin , Christoph Hellwig List-Id: linux-mmc@vger.kernel.org On Friday, November 03, 2017 03:20:10 PM Adrian Hunter wrote: > Hi > > Here is V13 of the hardware command queue patches without the software > command queue patches, now using blk-mq and now with blk-mq support for > non-CQE I/O. > > HW CMDQ offers 25% - 50% better random multi-threaded I/O. I see a slight > 2% drop in sequential read speed but no change to sequential write. > > Non-CQE blk-mq showed a 3% decrease in sequential read performance. This > seemed to be coming from the inferior latency of running work items compared > with a dedicated thread. Hacking blk-mq workqueue to be unbound reduced the > performance degradation from 3% to 1%. > > While we should look at changing blk-mq to give better workqueue performance, > a bigger gain is likely to be made by adding a new host API to enable the > next already-prepared request to be issued directly from within ->done() > callback of the current request. Tested-by: Bartlomiej Zolnierkiewicz [ for non-CQE changes ] Best regards, -- Bartlomiej Zolnierkiewicz Samsung R&D Institute Poland Samsung Electronics