Re: [Question] Generic way to retrieve IRQ number of Tx/Rx queue

Daniel Sedlak
2025-01-14T08:32:29Z

On 1/13/25 10:15 PM, Jakub Kicinski wrote:
> On Fri, 10 Jan 2025 10:07:18 +0100 Daniel Sedlak wrote:
>> Hello,
>> I am writing an affinity scheduler in the userspace for network cards's
>> Tx/Rx queues. Is there a generic way to retrieve all IRQ numbers for
>> those queues for each interface?
>>
>> My goal is to get all Tx/Rx queues for a given interface, get the IRQ
>> number of the individual queues, and set an affinity hint for each
>> queue. I have tried to loop over /proc/interrupts to retrieve all queues
>> for an interface in a hope that the last column would contain the
>> interface name however this does not work since the naming is not
>> unified across drivers. My second attempt was to retrieve all registered
>> interrupts by network interface from
>> /sys/class/net/{interface_name}/device/msi_irqs/, but this attempt was
>> also without luck because some drivers request more IRQs than the number
>> of queues (for example i40e driver).
>
> We do have an API for that
> https://docs.kernel.org/next/networking/netlink_spec/netdev.html#napi
> but unfortunately the driver needs to support it, and i40e currently
> doesn't:

Thank you for the link, I somehow missed that part of netlink…

> $ git grep --files-with-matches netif_napi_set_irq
> drivers/net/ethernet/amazon/ena/ena_netdev.c
> drivers/net/ethernet/broadcom/bnxt/bnxt.c
> drivers/net/ethernet/broadcom/tg3.c
> drivers/net/ethernet/google/gve/gve_utils.c
> drivers/net/ethernet/intel/e1000/e1000_main.c
> drivers/net/ethernet/intel/e1000e/netdev.c
> drivers/net/ethernet/intel/ice/ice_lib.c
> drivers/net/ethernet/intel/igc/igc_main.c
> drivers/net/ethernet/mellanox/mlx4/en_cq.c
> drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> drivers/net/ethernet/meta/fbnic/fbnic_txrx.c
>
> Should be easy to add. Let me CC the Intel list in case they already
> have a relevant change queued for i40e..

Thank you for directions, will check Intel's mailing list and poke
around with implementing that.

Daniel