Re: [PATCH v9 09/13] isolation: Introduce io_queue isolcpus type

Sebastian Andrzej Siewior
2026-04-02T07:58:14Z

On 2026-04-01 15:05:21 [-0400], Waiman Long wrote:
> > Could we please clarify whether we want to keep it and this
> > additionally or if managed_irq could be used instead. This adds another
> > bit. If networking folks jump in on managed_irqs, would they need to
> > duplicate this with their net sub flag?
>
> Yes, I will very much prefer to reuse an existing HK cpumask like
> managed_irqs for this purpose, if possible, rather than adding another
> cpumask that we need to manage. Note that we are in the process of making
> these housekeeping cpumasks modifiable at run time in the near future.

Now if you want to change it at run time, it would mean to reconfigure
the interrupts, device and so on. Not sure if this useful _or_ if it
would be "easier" to just the tell upper layer (block in case of I/O)
not to perform any request on this CPU. Then we would have an interrupt
on that CPU but it wouldn't do anything.
It would only become a problem if you would have less queues than CPUs
and you would like to migrate things.

> Cheers,
> Longman

Sebastian