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

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Message-ID: <20250110093821.4eddeff3@hermes.local>
Date: Fri, 10 Jan 2025 09:38:21 -0800
From: Stephen Hemminger <stephen@...workplumber.org>
To: Daniel Sedlak <daniel@...lak.dev>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [Question] Generic way to retrieve IRQ number of Tx/Rx queue

On Fri, 10 Jan 2025 10:07:18 +0100
Daniel Sedlak <daniel@...lak.dev> 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).
> 
> Thank you for any help or advice
> 
> Daniel
> 

Good luck reinventing irqbalance.

There can be multiple interrupts per queue, or one interrupt can serve multiple queues.