From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 13/14] scsi: add support for a blk-mq based I/O path. Date: Tue, 19 Aug 2014 18:06:25 +0200 Message-ID: <20140819160625.GA29770@lst.de> References: <1405678393-11497-1-git-send-email-hch@lst.de> <1405678393-11497-14-git-send-email-hch@lst.de> <885d029677826efe0cfe3803411cbdba@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from verein.lst.de ([213.95.11.211]:57559 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752097AbaHSQG3 (ORCPT ); Tue, 19 Aug 2014 12:06:29 -0400 Content-Disposition: inline In-Reply-To: <885d029677826efe0cfe3803411cbdba@mail.gmail.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Kashyap Desai Cc: Christoph Hellwig , James Bottomley , linux-scsi@vger.kernel.org, Jens Axboe , Bart Van Assche , Mike Christie , "Martin K. Petersen" , Robert Elliott , Webb Scales , linux-kernel@vger.kernel.org On Tue, Aug 19, 2014 at 03:51:42AM +0530, Kashyap Desai wrote: > I read this comment and find that very few drivers are using this > cmd_list. I think if we remove this cmd_list, performance will scale as I > am seeing major contention in this lock. > Just thought to ping you to see if this is known limitation for now or any > plan to change this lock in near future ? Removing the lock entirely and pushing the list into the two drivers using it is on my TODO list. Bart actually suggested keeping the code in the SCSI core and having a flag to enabled. Given that I'm too busy to get my full version done in time, it might be a good idea if someone picks up Barts idea. Can you send me a patch to add a enable_cmd_list flag to the host template and only enable it for aacraid and dpt_i2o?