Re: [RFC PATCH] Documentation: Add managed interrupts

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On 2026-04-13 11:45:33 [+0100], Valentin Schneider wrote:
> On 01/04/26 13:02, Sebastian Andrzej Siewior wrote:
> > One more point: Given that isolcpus= is marked deprecated as of commit
> >    b0d40d2b22fe4 ("sched/isolation: Document isolcpus= boot parameter flags, mark it deprecated")
> >
> > and the 'managed_irq' is evaluated at device's probe time it would
> > require additional callbacks to re-evaluate the situation. Probably for
> > 'io_queue', too. Does is make sense or should we simply drop the
> > "deprecation" notice and allowing using it long term?
> 
> AIUI the deprecation notice is more for isolcpus=domain, i.e. the scheduler
> part, but it's still relevant for e.g. managed_irq. FWIW Openshift uses:
> 
>   isolcpus=managed_irq,<cpulist>
>   nohz_full=<cpulist>
> 
> and cpusets for dynamically isolating CPUs from the scheduler.

For the managed_irq you could argue that this could also use some
runtime configuration at which point isolcpus= would have a runtime
counterpart and could be removed.
After going through all this I concluded that it makes hardly sense
since you would require callbacks in every driver using it or other
magic "to reconfigure" but it already makes little sense using it.

Either way, I don't see anything wrong with using isolcpus=domain if you
have a static setup and need/ want reconfigure at runtime.

Sebastian