Re: [PATCH v3] doc: Add CPU Isolation documentation

[Sebastian Andrzej Siewior]

On 2026-04-02 11:47:49 [+0200], Frederic Weisbecker wrote:
> nohz_full was introduced in v3.10 in 2013, which means this
> documentation is overdue for 13 years.
> 
> Fortunately Paul wrote a part of the needed documentation a while ago,
> especially concerning nohz_full in Documentation/timers/no_hz.rst and
> also about per-CPU kthreads in
> Documentation/admin-guide/kernel-per-CPU-kthreads.rst
> 
> Introduce a new page that gives an overview of CPU isolation in general.
> 
> Acked-by: Waiman Long <longman@xxxxxxxxxx>
> Reviewed-by: Valentin Schneider <vschneid@xxxxxxxxxx>
> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>

This documents also isolcpus= boot argument. The only thing that this
argument does and runtime can not do is the managed_irq sub argument.
This sub argument is a story of its own and it is of quite limited for
me taste.

However, isolcpus= is marked as deprecated. I suggest to remove the
"Deprecated - use cpusets instead" note as the static configuration is
fine if the system is partitioned once never changed within its
lifetime.
Are there any objections and if so why needs this boot argument be
removed (assuming we have a runtime equivalent knob for managed_irq)?

Sebastian