From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: Re: [Lsf] [LSF/MM TOPIC] block-mq issues with FC Date: Fri, 8 Apr 2016 10:26:49 -0700 Message-ID: <5707E9D9.70504@sandisk.com> References: <57079616.4000202@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-bn1on0073.outbound.protection.outlook.com ([157.56.110.73]:1632 "EHLO na01-bn1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754523AbcDHR0y (ORCPT ); Fri, 8 Apr 2016 13:26:54 -0400 In-Reply-To: <57079616.4000202@suse.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Hannes Reinecke , "lsf@lists.linux-foundation.org" Cc: "linux-block@vger.kernel.org" , Jens Axboe , Christoph Hellwig , SCSI Mailing List On 04/08/2016 04:29 AM, Hannes Reinecke wrote: > I'd like to propose a topic on block-mq issues with FC. > During my performance testing using block/scsi-mq with FC I've hit > several issues I'd like to discuss: > > - timeout handling: > Out of necessity the status of any timed out command is undefined. > So to be absolutely safe HBAs will be using extended timeouts here > (eg 70secs for lpfc). During that time we _could_ signal I/O timeout > to the upper layers, but then the tag will be reused, despite the > HBA still having a reference to it. > I'd like to discuss how this could be solved best with blk-mq. > > - Adaption on other HBAs to multiqueue: > The current block-mq design assumes symmetric send and receive > queues (in effect queue pairs). Any hardware _not_ providing this > (like qla2xxx) can not be easily converted to scsi-mq. I'd like to > discuss how one could approach converting these drivers. Hello Hannes, Without commenting on the specifics of the above proposal, I'm interested in a further discussion of how to improve multiqueue support for FC drivers. Bart.