Re: [PATCH V3 4/5] nvme-pci: avoid irq allocation retrying via .calc_sets

Bjorn Helgaas
2019-02-13T15:13:44Z

On Wed, Feb 13, 2019 at 06:50:40PM +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.

s/pre-caculate/precalculate/
My usual "set vectors" question as on other patches.

> 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.

s/irq/IRQ/

> Reviewed-by: Keith Busch <keith.busch@intel.com>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
> drivers/nvme/host/pci.c | 62 +++++++++++++------------------------------------
> 1 file changed, 16 insertions(+), 46 deletions(-)
>
> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index 0086bdf80ea1..8c51252a897e 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -2078,14 +2078,25 @@ static void nvme_calc_io_queues(struct nvme_dev *dev, unsigned int irq_queues)
> }
> }
>
> +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 = 2;
> +}
> +
> static int nvme_setup_irqs(struct nvme_dev *dev, unsigned int nr_io_queues)
> {
> struct pci_dev *pdev = to_pci_dev(dev->dev);
> struct irq_affinity affd = {
> .pre_vectors = 1,
> - .nr_sets = 2,
> + .calc_sets = nvme_calc_irq_sets,
> + .priv = dev,
> };
> - int *irq_sets = affd.set_vectors;
> int result = 0;
> unsigned int irq_queues, this_p_queues;
>
> @@ -2102,50 +2113,8 @@ static int nvme_setup_irqs(struct nvme_dev *dev, unsigned int nr_io_queues)
> }
> dev->io_queues[HCTX_TYPE_POLL] = this_p_queues;
>
> - /*
> - * For irq sets, we have to ask for minvec == maxvec. This passes
> - * any reduction back to us, so we can adjust our queue counts and
> - * IRQ vector needs.
> - */
> - do {
> - nvme_calc_io_queues(dev, irq_queues);
> - irq_sets[0] = dev->io_queues[HCTX_TYPE_DEFAULT];
> - irq_sets[1] = dev->io_queues[HCTX_TYPE_READ];
> - if (!irq_sets[1])
> - affd.nr_sets = 1;
> -
> - /*
> - * If we got a failure and we're down to asking for just
> - * 1 + 1 queues, just ask for a single vector. We'll share
> - * that between the single IO queue and the admin queue.
> - * Otherwise, we assign one independent vector to admin queue.
> - */
> - if (irq_queues > 1)
> - irq_queues = irq_sets[0] + irq_sets[1] + 1;
> -
> - result = pci_alloc_irq_vectors_affinity(pdev, irq_queues,
> - irq_queues,
> - PCI_IRQ_ALL_TYPES | PCI_IRQ_AFFINITY, &affd);
> -
> - /*
> - * Need to reduce our vec counts. If we get ENOSPC, the
> - * platform should support mulitple vecs, we just need
> - * to decrease our ask. If we get EINVAL, the platform
> - * likely does not. Back down to ask for just one vector.
> - */
> - if (result == -ENOSPC) {
> - irq_queues--;
> - if (!irq_queues)
> - return result;
> - continue;
> - } else if (result == -EINVAL) {
> - irq_queues = 1;
> - continue;
> - } else if (result <= 0)
> - return -EIO;
> - break;
> - } while (1);
> -
> + result = pci_alloc_irq_vectors_affinity(pdev, 1, irq_queues,
> + PCI_IRQ_ALL_TYPES | PCI_IRQ_AFFINITY, &affd);
> return result;
> }
>
> @@ -3021,6 +2990,7 @@ static struct pci_driver nvme_driver = {
>
> static int __init nvme_init(void)
> {
> + BUILD_BUG_ON(2 > IRQ_MAX_SETS);

"IRQ_MAX_SETS < 2" would read more naturally; is there a reason to have it
reversed?

> return pci_register_driver(&nvme_driver);
> }
>
> --
> 2.9.5
>