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From: Ming Lei <ming.lei@redhat.com>
To: Keith Busch <keith.busch@intel.com>
Cc: Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
	Sagi Grimberg <sagi@grimberg.me>,
	linux-nvme@lists.infradead.org,
	Bjorn Helgaas <helgaas@kernel.org>,
	linux-pci@vger.kernel.org
Subject: Re: [PATCHv2 2/4] nvme-pci: Distribute io queue types after creation
Date: Sun, 6 Jan 2019 10:56:45 +0800	[thread overview]
Message-ID: <20190106025643.GB20802@ming.t460p> (raw)
In-Reply-To: <20190104155324.GA12342@localhost.localdomain>

On Fri, Jan 04, 2019 at 08:53:24AM -0700, Keith Busch wrote:
> On Fri, Jan 04, 2019 at 03:21:07PM +0800, Ming Lei wrote:
> > Thinking about the patch further: after pci_alloc_irq_vectors_affinity()
> > is returned, queue number for non-polled queues can't be changed at will,
> > because we have to make sure to spread all CPUs on each queue type, and
> > the mapping has been fixed by pci_alloc_irq_vectors_affinity() already.
> > 
> > So looks the approach in this patch may be wrong.
> 
> That's a bit of a problem, and not a new one. We always had to allocate
> vectors before creating IRQ driven CQ's, but the vector affinity is
> created before we know if the queue-pair can be created. Should the
> queue creation fail, there may be CPUs that don't have a queue.
> 
> Does this mean the pci msi API is wrong? It seems like we'd need to
> initially allocate vectors without PCI_IRQ_AFFINITY, then have the
> kernel set affinity only after completing the queue-pair setup.

I think this kind of API style(two stages) is more clean, and
error-immune.

- pci_alloc_irq_vectors() is only for allocating irq vectors
- pci_set_irq_vectors_affnity() is for spreading affinity at will


Thanks,
Ming

  parent reply	other threads:[~2019-01-06  2:56 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-03 22:50 [PATCHv2 0/4] NVMe IRQ sets fixups Keith Busch
2019-01-03 22:50 ` [PATCHv2 1/4] nvme-pci: Set tagset nr_maps just once Keith Busch
2019-01-04  1:46   ` Ming Lei
2019-01-03 22:50 ` [PATCHv2 2/4] nvme-pci: Distribute io queue types after creation Keith Busch
2019-01-04  2:31   ` Ming Lei
2019-01-04  7:21     ` Ming Lei
2019-01-04 15:53       ` Keith Busch
2019-01-04 18:17         ` Christoph Hellwig
2019-01-04 18:35           ` Keith Busch
2019-01-06  2:56         ` Ming Lei [this message]
2019-01-03 22:50 ` [PATCHv2 3/4] PCI/MSI: Handle vector reduce and retry Keith Busch
2019-01-04  2:45   ` Ming Lei
2019-01-04 22:35   ` Bjorn Helgaas
2019-01-04 22:56     ` Keith Busch
2019-01-03 22:50 ` [PATCHv2 4/4] nvme-pci: Use PCI to handle IRQ " Keith Busch
2019-01-04  2:41   ` Ming Lei
2019-01-04 18:19   ` Christoph Hellwig
2019-01-04 18:33     ` Keith Busch

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