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

Waiman Long
2026-04-03T01:55:17Z

On 4/2/26 3:58 AM, Sebastian Andrzej Siewior wrote:
> 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.

I know that it will not be easy. Anyway, I will let this patch reaching
a good compromise and get merged first before thinking about that.

Cheers,
Longman