Hi Andy
Thanks for your precious time for this and kindly reminding.
On 02/28/2018 11:59 PM, Andy Shevchenko wrote:
> On Wed, Feb 28, 2018 at 5:48 PM, Jianchao Wang
> <jianchao.w.w...@oracle.com> wrote:
>> Currently, adminq and ioq0 share the same irq vector. This is
>> unfair for both amdinq and ioq0.
>> - For adminq, its completion irq has to be bound on cpu0. It
>> just has only one hw queue, it is unreasonable to do this.
>> - For ioq0, when the irq fires for io completion, the adminq irq
>> action on this irq vector will introduce an uncached access on
>> adminq cqe at least, even worse when adminq is busy.
>>
>> To improve this, allocate separate irq vectors for adminq and
>> ioq0, and not set irq affinity for adminq one. If just one irq
>> vector, setup adminq + 1 ioq and let them share it. In addition
>> add new helper interface nvme_ioq_vector to get ioq vector.
>
>> +static inline unsigned int nvme_ioq_vector(struct nvme_dev *dev,
>> + unsigned int qid)
>> +{
>> + /*
>> + * If controller has only legacy or single-message MSI, there will
>> + * be only 1 irq vector. At the moment, we setup adminq + 1 ioq
>> + * and let them share irq vector.
>> + */
>> + return (dev->num_vecs == 1) ? 0 : qid;
>
> Redundant parens.
Yes, but parens make it more clearly
>
>> +}
>
>>
>> for (i = dev->ctrl.queue_count; i <= dev->max_qid; i++) {
>> - /* vector == qid - 1, match nvme_create_queue */
>
>> if (nvme_alloc_queue(dev, i, dev->q_depth,
>> - pci_irq_get_node(to_pci_dev(dev->dev), i - 1))) {
>> + pci_irq_get_node(to_pci_dev(dev->dev),
>> + nvme_ioq_vector(dev, i)))) {
>
> Perhaps better to introduce a temporary variable to make it readable?
yes, indeed.
>
>> ret = -ENOMEM;
>> break;
>> }
>
>> + ret = pci_alloc_irq_vectors_affinity(pdev, 1, (nr_io_queues + 1),
>> + PCI_IRQ_ALL_TYPES | PCI_IRQ_AFFINITY, &affd);
>> + if (ret <= 0)
>> return -EIO;
>> - dev->max_qid = nr_io_queues;
>> -
>> + dev->num_vecs = ret;
>> + dev->max_qid = (ret > 1) ? (ret - 1) : 1;
>
> I don not see how ret can possible be < 1 here.
>
> Thus, the logic looks like this:
> if ret >= 2 => return ret - 1; // Possible variants [1..ret - 1]
> if ret == 1 => return 1;
>
> So, for ret == 1 or ret == 2 we still use 1.
>
> Is it by design?
>
> Can it be written like
>
> dev->max_qid = max(ret - 1, 1);
>
Yes, it looks like more clearly.
Thanks
Jianchao
