Re: [PATCH v6 6/9] isolation: introduce io_queue isolcpus type

Daniel Wagner
2025-05-14T16:08:46Z

On Fri, May 09, 2025 at 10:04:18AM +0800, Ming Lei wrote:
> > io_queue
> > Isolate from IO queue work caused by multiqueue
> > device drivers. Restrict the placement of
> > queues to housekeeping CPUs only, ensuring that
> > all IO work is processed by a housekeeping CPU.
> >
> > Note: When an isolated CPU issues an IO, it is
> > forwarded to a housekeeping CPU. This will
> > trigger a software interrupt on the completion
> > path.
> >
> > Note: It is not possible to offline housekeeping
> > CPUs that serve isolated CPUs.
>
> This patch adds kernel parameter only, but not apply it at all, the above
> words just confuses everyone, so I'd suggest to not expose the kernel
> command line & document until the whole mechanism is supported.

I'll add this doc update as last patch.

> Especially 'irqaffinity=0 isolcpus=io_queue' requires the application
> to offline CPU in order, which has to be documented:
>
> https://lore.kernel.org/all/cc5e44dd-e1dc-4f24-88d9-ce45a8b0794f@flourine.local/

Okay, so you want me to extend the above second note in this case. I'll
give it a go.