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From: Keith Busch <keith.busch@intel.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Ming Lei <ming.lei@redhat.com>,
	linux-nvme@lists.infradead.org, Christoph Hellwig <hch@lst.de>,
	Jens Axboe <axboe@fb.com>,
	linux-pci@vger.kernel.org
Subject: Re: [PATCH V2 1/3] PCI/MSI: preference to returning -ENOSPC from pci_alloc_irq_vectors_affinity
Date: Mon, 31 Dec 2018 15:41:02 -0700	[thread overview]
Message-ID: <20181231224102.GA5024@localhost.localdomain> (raw)
In-Reply-To: <20181231220059.GI159477@google.com>

On Mon, Dec 31, 2018 at 04:00:59PM -0600, Bjorn Helgaas wrote:
> On Sat, Dec 29, 2018 at 11:26:48AM +0800, Ming Lei wrote:
> > Users of pci_alloc_irq_vectors_affinity() may try to reduce irq
> > vectors and allocate vectors again in case that -ENOSPC is returned, such
> > as NVMe, so we need to respect the current interface and give preference to
> > -ENOSPC.
> 
> I thought the whole point of the (min_vecs, max_vecs) tuple was to
> avoid this sort of "reduce and try again" iteration in the callers.

The min/max vecs doesn't work correctly when using the irq_affinity
nr_sets because rebalancing the set counts is driver specific. To get
around that, drivers using nr_sets have to set min and max to the same
value and handle the "reduce and try again".

WARNING: multiple messages have this Message-ID (diff)
From: keith.busch@intel.com (Keith Busch)
Subject: [PATCH V2 1/3] PCI/MSI: preference to returning -ENOSPC from pci_alloc_irq_vectors_affinity
Date: Mon, 31 Dec 2018 15:41:02 -0700	[thread overview]
Message-ID: <20181231224102.GA5024@localhost.localdomain> (raw)
In-Reply-To: <20181231220059.GI159477@google.com>

On Mon, Dec 31, 2018@04:00:59PM -0600, Bjorn Helgaas wrote:
> On Sat, Dec 29, 2018@11:26:48AM +0800, Ming Lei wrote:
> > Users of pci_alloc_irq_vectors_affinity() may try to reduce irq
> > vectors and allocate vectors again in case that -ENOSPC is returned, such
> > as NVMe, so we need to respect the current interface and give preference to
> > -ENOSPC.
> 
> I thought the whole point of the (min_vecs, max_vecs) tuple was to
> avoid this sort of "reduce and try again" iteration in the callers.

The min/max vecs doesn't work correctly when using the irq_affinity
nr_sets because rebalancing the set counts is driver specific. To get
around that, drivers using nr_sets have to set min and max to the same
value and handle the "reduce and try again".

  reply	other threads:[~2018-12-31 22:42 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-29  3:26 [PATCH V2 0/3] nvme pci: two fixes on nvme_setup_irqs Ming Lei
2018-12-29  3:26 ` Ming Lei
2018-12-29  3:26 ` [PATCH V2 1/3] PCI/MSI: preference to returning -ENOSPC from pci_alloc_irq_vectors_affinity Ming Lei
2018-12-29  3:26   ` Ming Lei
2018-12-31 22:00   ` Bjorn Helgaas
2018-12-31 22:00     ` Bjorn Helgaas
2018-12-31 22:41     ` Keith Busch [this message]
2018-12-31 22:41       ` Keith Busch
2019-01-01  5:24     ` Ming Lei
2019-01-01  5:24       ` Ming Lei
2019-01-02 21:02       ` Bjorn Helgaas
2019-01-02 21:02         ` Bjorn Helgaas
2019-01-02 22:46         ` Keith Busch
2019-01-02 22:46           ` Keith Busch
2018-12-29  3:26 ` [PATCH V2 2/3] nvme pci: fix nvme_setup_irqs() Ming Lei
2018-12-29  3:26 ` [PATCH V2 3/3] nvme pci: introduce module parameter of 'default_queues' Ming Lei
2018-12-31 21:24   ` Bjorn Helgaas
2019-01-01  5:47     ` Ming Lei
2019-01-02  2:14       ` Shan Hai
     [not found]         ` <20190102073607.GA25590@ming.t460p>
     [not found]           ` <d59007c6-af13-318c-5c9d-438ad7d9149d@oracle.com>
     [not found]             ` <20190102083901.GA26881@ming.t460p>
2019-01-03  2:04               ` Shan Hai
2019-01-02 20:11       ` Bjorn Helgaas
2019-01-03  2:12         ` Ming Lei
2019-01-03  2:52           ` Shan Hai
2019-01-03  3:11             ` Shan Hai
2019-01-03  3:31               ` Ming Lei
2019-01-03  4:36                 ` Shan Hai
2019-01-03 10:34                   ` Ming Lei
2019-01-04  2:53                     ` Shan Hai
2019-01-03  4:51                 ` Shan Hai
2019-01-03  3:21             ` Ming Lei
2019-01-14 13:13 ` [PATCH V2 0/3] nvme pci: two fixes on nvme_setup_irqs John Garry
2019-01-14 13:13   ` John Garry

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