linux-kernel - Re: [PATCH] nvme: use the correct msix vector for each queue

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Date:   Wed, 7 Dec 2016 17:49:42 -0500
From:   Keith Busch <keith.busch@...el.com>
To:     Dan Streetman <ddstreet@...e.org>
Cc:     Jens Axboe <axboe@...com>, linux-nvme@...ts.infradead.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Dan Streetman <dan.streetman@...onical.com>
Subject: Re: [PATCH] nvme: use the correct msix vector for each queue

On Wed, Dec 07, 2016 at 05:36:00PM -0500, Dan Streetman wrote:
> On Wed, Dec 7, 2016 at 5:44 PM, Keith Busch <keith.busch@...el.com> wrote:
> > pci_alloc_irq_vectors doesn't know you intend to make the first
> > vector special, so it's going to come up with a CPU affinity from
> > blk_mq_pci_map_queues that clashes with what you've programmed in the
> > IO completion queues.
> 
> I don't follow.  You're saying you mean to share cq_vector 0 between
> the admin queue and io queue 1?

I'm just saying that blk-mq's hctx mapping will end up choosing a queue
who's vector is mapped to a different CPU, and we don't want that.

We are currently sharing the first IO queue's interrupt vector with
the admin queue's on purpose. Are you saying there's something wrong
with that?