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

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Message-ID: <adf7c053-ffde-4df8-bc24-99740906410d@sedlak.dev>
Date: Tue, 14 Jan 2025 09:32:26 +0100
From: Daniel Sedlak <daniel@...lak.dev>
To: Jakub Kicinski <kuba@...nel.org>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
 intel-wired-lan@...ts.osuosl.org
Subject: Re: [Question] Generic way to retrieve IRQ number of Tx/Rx queue



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