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

From	Dan Streetman <ddstreet@ieee.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] nvme: use the correct msix vector for each queue
Date	2016-12-07 23:50 +0100
Message-ID	<sLTcd-6aD-23@gated-at.bofh.it> (permalink)
References	<sLSzw-5Ru-9@gated-at.bofh.it> <sLT2x-63V-11@gated-at.bofh.it> <sLT2x-63V-13@gated-at.bofh.it> <sLT2x-63V-9@gated-at.bofh.it>
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On Wed, Dec 7, 2016 at 5:49 PM, Keith Busch <keith.busch@intel.com> wrote:
> 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@intel.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?

that's intentional?  Ok then.  That's extremely non-obvious.

Is there a reason you want to share the interrupt between the queues?

Thread

[PATCH] nvme: use the correct msix vector for each queue Dan Streetman <ddstreet@ieee.org> - 2016-12-07 23:10 +0100
  Re: [PATCH] nvme: use the correct msix vector for each queue Keith Busch <keith.busch@intel.com> - 2016-12-07 23:40 +0100
    Re: [PATCH] nvme: use the correct msix vector for each queue Christoph Hellwig <hch@infradead.org> - 2016-12-07 23:50 +0100
      Re: [PATCH] nvme: use the correct msix vector for each queue Dan Streetman <ddstreet@ieee.org> - 2016-12-08 00:00 +0100
    Re: [PATCH] nvme: use the correct msix vector for each queue Dan Streetman <ddstreet@ieee.org> - 2016-12-07 23:50 +0100
      Re: [PATCH] nvme: use the correct msix vector for each queue Keith Busch <keith.busch@intel.com> - 2016-12-08 00:00 +0100
  Re: [PATCH] nvme: use the correct msix vector for each queue Keith Busch <keith.busch@intel.com> - 2016-12-07 23:40 +0100
    Re: [PATCH] nvme: use the correct msix vector for each queue Dan Streetman <ddstreet@ieee.org> - 2016-12-07 23:40 +0100

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