From: Christoph Hellwig <hch@infradead.org>
To: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
James Bottomley <james.bottomley@hansenpartnership.com>,
Don Brace <don.brace@microsemi.com>,
linux-scsi@vger.kernel.org, Hannes Reinecke <hare@suse.com>,
Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH] hpsa: scsi-mq support
Date: Fri, 11 Nov 2016 08:35:32 -0800 [thread overview]
Message-ID: <20161111163532.GA14922@infradead.org> (raw)
In-Reply-To: <1478879194-32529-1-git-send-email-hare@suse.de>
On Fri, Nov 11, 2016 at 04:46:34PM +0100, Hannes Reinecke wrote:
> This patch enables full scsi-mq support for the hpsa driver.
> Due to some reports of performance regressions this patch
> also adds a parameter 'use_blk_mq' which can be used to
> disable multiqueue support if required.
This patch looks odd to me. The hardware does not seem to support
multiple submission queues, which makes exposing nr_hw_queues > 1
rather pointless given that the block layer (using blk-mq or the legacy
path) can already steer completions to the submitting cpu.
You also mention there are performance regressions, but don't talk
about any benefits. I also think per-driver module parameters for this
are generally a rather bad idea.
So what exactly are the benefits of this MQ-mode for a single submission
queue device, and what do we need to do to get these without lying about
the number of submission queues?
next prev parent reply other threads:[~2016-11-11 16:35 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-11 15:46 [PATCH] hpsa: scsi-mq support Hannes Reinecke
2016-11-11 16:34 ` kbuild test robot
2016-11-11 16:35 ` Christoph Hellwig [this message]
2016-11-11 18:22 ` Hannes Reinecke
2016-11-12 17:32 ` Christoph Hellwig
2016-11-13 9:44 ` Hannes Reinecke
2016-11-13 11:58 ` Christoph Hellwig
2016-11-14 11:05 ` Kashyap Desai
2016-11-12 18:30 ` Jens Axboe
2016-11-11 16:57 ` kbuild test robot
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