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From: Hannes Reinecke <hare@suse.de>
To: lsf@lists.linux-foundation.org
Cc: SCSI Mailing List <linux-scsi@vger.kernel.org>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>
Subject: [LSF/MM TOPIC] block-mq issues with FC
Date: Fri, 8 Apr 2016 13:29:26 +0200	[thread overview]
Message-ID: <57079616.4000202@suse.de> (raw)

Hi all,

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.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
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             reply	other threads:[~2016-04-08 11:29 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-08 11:29 Hannes Reinecke [this message]
2016-04-08 15:11 ` [LSF/MM TOPIC] block-mq issues with FC James Bottomley
2016-04-08 15:51   ` [Lsf] " Ewan D. Milne
2016-04-08 16:06     ` James Bottomley
2016-04-08 17:26 ` Bart Van Assche
2016-04-08 17:40 ` Matthew Wilcox
2016-04-08 18:00   ` James Bottomley
2016-04-08 18:08     ` Christoph Hellwig
2016-04-08 18:24       ` James Bottomley
2016-04-08 18:06   ` Keith Busch
2016-04-12 19:16     ` Jens Axboe
2016-04-08 18:14   ` Bart Van Assche
2016-04-08 19:22   ` Waskiewicz, PJ
2016-04-10 19:02   ` Sagi Grimberg
2016-04-12 19:04     ` Quinn Tran
2016-04-08 18:13 ` Christoph Hellwig

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