Re: [PATCH v16 0/9] blk: honor isolcpus configuration

[Aaron Tomlin]

On Thu, Oct 15, 2026 at 01:22:35PM +0200, Daniel Wagner wrote:
> On Thu, Sep 10, 2026 at 12:42:28PM -0400, Aaron Tomlin wrote:
> > Maintainer guidance requested
> > =============================
> > 
> > We would appreciate guidance from Frederic Weisbecker regarding preference
> > on this front:
> >         1.  Do you prefer keeping "managed_irq_strict" as an explicit
> >             opt-in (as implemented in this series) to preserve historical
> >             behaviour for existing users of "managed_irq"?
> > 
> >         2.  Or would you prefer upgrading the semantics of "managed_irq"
> >             directly in place without introducing a new parameter, on the
> >             grounds that the legacy post-allocation behaviour is already
> >             broken for modern multiqueue hardware?
> 
> During Plumbers we had several discussions on this series. This is what I
> remember we discussed and decided:
> 
>   - The current managed_irq behavior doesn't match the other flags of isolcpus.
> 
>   - Instead of introducing managed_irq_strict, it's better to change the
>     existing managed_irq to follow the strict interpretation.

Hi Daniel,

Indeed. This was the common consensus.

>   - The main existing user of the current managed_irq mapping is
>     RH with OpenShift. After discussing with Juri, it doesn't look like
>     it is a real blocker to change to the strict interpretation.

Excellent.

>   - If there are complaints about the managed irq behavior change, it's
>     better to introduce a different flag for this. Though there have been
>     many discussions and proposals on how to deal with isolation during the
>     conference, and the general mood was that the placement of resources
>     should be done during runtime. Thus it is likely that the old behaviour
>     is not necessary at all if runtime configuration is possible.
> 
> Hope this helps to move forward with this series,
> Daniel

That makes total sense, and I agree with the direction. I will prepare v17
with these updates:
    -   Upgrade "isolcpus=managed_irq" directly to enforce strict
        pre-allocation queue and interrupt isolation.

    -   Drop "managed_irq_strict"

    -   Update the documentation in kernel-parameters.txt accordingly.


Kind regards,
-- 
Aaron Tomlin