linux-kernel - Re: [PATCH 11/13] blk-mq: allow the driver to pass in an affinity mask

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Message-ID: <20160712064238.GA26968@agordeev.lab.eng.brq.redhat.com>
Date:	Tue, 12 Jul 2016 08:42:39 +0200
From:	Alexander Gordeev <agordeev@...hat.com>
To:	Christoph Hellwig <hch@....de>
Cc:	tglx@...utronix.de, axboe@...com, linux-block@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-nvme@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 11/13] blk-mq: allow the driver to pass in an affinity
 mask

On Sun, Jul 10, 2016 at 05:41:44AM +0200, Christoph Hellwig wrote:
> On Mon, Jul 04, 2016 at 11:35:28AM +0200, Alexander Gordeev wrote:
> > > mq_map is initialized to zero already, so we don't really need the
> > > assignment for queue 0.  The reason why this check exists is because
> > > we start with queue = -1 and we never want to assignment -1 to mq_map.
> > 
> > Would this read better then?
> > 
> > 	int queue = 0;
> > 
> > 	...
> > 
> > 	/* If cpus are offline, map them to first hctx */
> > 	for_each_online_cpu(cpu) {
> > 		set->mq_map[cpu] = queue;
> > 		if (cpumask_test_cpu(cpu, affinity_mask))
> > 			queue++;
> 
> It would read better, but I don't think it's actually correct.
> We'd still assign the 'old' queue to the cpu that is set in the affinity
> mask.

To be honest, I fail to see a functional difference, but it is just
a nit anyway.