Re: [RFC PATCH] Documentation: Add managed interrupts

[Ming Lei]

On Mon, Apr 13, 2026 at 11:53 PM Sebastian Andrzej Siewior
<bigeasy@xxxxxxxxxxxxx> wrote:
>
> On 2026-04-11 20:18:17 [+0800], Ming Lei wrote:
> > > +CPUs listed in the avoided mask remain part of the interrupt’s affinity mask.
> > > +This means that if all non‑isolated CPUs go offline while isolated CPUs remain
> > > +online, the interrupt will be assigned to one of the isolated CPUs.
> >
> > Maybe you can add:
> >
> > In reality it is fine because IO isn't supposed to submit from isolated CPUs.
>
> You can argue both way. And I have some vague memory that block will
> schedule kworker and there was some work to use unbound worker instead
> of _this_ CPU.

It is actually to rule out isolated cpus from hctx->cpu_mask, please see
blk_mq_map_swqueue().

Also unbound worker won't be scheduled on isolated CPU too, if I
remember correctly.

> I just don't know what happens with interrupt and this is
> probably the one thing you can't configure.

Interrupt control is determined by `irq.effective_affinity`, as shown
in your documentation.
Or you may provide more detail about the question.

Thanks,
Ming