Re: [PATCH V2 3/4] nvme-pci: avoid irq allocation retrying via .calc_sets

On Tue, Feb 12, 2019 at 05:04:38AM -0800, Ming Lei wrote:

Currently pre-caculate each set vectors, and this way requires same
'max_vecs' and 'min_vecs' passed to pci_alloc_irq_vectors_affinity(),
then nvme_setup_irqs() has to retry in case of allocation failure.

This usage & interface is a bit awkward because the retry should have
been avoided by providing one reasonable 'min_vecs'.

Implement the callback of .calc_sets, so that pci_alloc_irq_vectors_affinity()
can calculate each set's vector after IRQ vectors is allocated and
before spread IRQ, then NVMe's retry in case of irq allocation failure
can be removed.

Signed-off-by: Ming Lei <redacted>

Thanks, Ming, this whole series looks like a great improvement for
drivers using irq sets.

Minor nit below. Otherwise you may add my review for the whole series
if you spin a v3 for the other minor comments.

Reviewed-by: Keith Busch <redacted>

+static void nvme_calc_irq_sets(struct irq_affinity *affd, int nvecs)
+{
+	struct nvme_dev *dev = affd->priv;
+
+	nvme_calc_io_queues(dev, nvecs);
+
+	affd->set_vectors[HCTX_TYPE_DEFAULT] = dev->io_queues[HCTX_TYPE_DEFAULT];
+	affd->set_vectors[HCTX_TYPE_READ] = dev->io_queues[HCTX_TYPE_READ];
+	affd->nr_sets = HCTX_TYPE_POLL;
+}

The value of HCTX_TYPE_POLL happens to be 2, but that seems more of a
coincidence right now. Can we hard code 2 just in case the value changes?