linux-kernel - Modifying isolcpus, nohz_full, and rcu

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Date:   Thu, 7 Dec 2023 10:07:13 -0500
From:   Gianfranco Dutka <gianfranco.dutka@...sta.com>
To:     linux-kernel@...r.kernel.org
Cc:     vincent.guittot@...aro.com
Subject: Modifying isolcpus, nohz_full, and rcu_nocb kernel parameters at
 runtime

Good afternoon maintainers and subscribers to the lkml, 

I'm a bit new to kernel development but I had a question with respect to the kernel parameters: isolcpus, nohz_full, and rcu_nocbs. 

Basically the question is this, am I able to modify the three parameters I mentioned above at runtime after the kernel has already started/booted? Doing some reading online it seems that it’s not possible but I wanted to double check with the maintainers if there wasn’t some sort of change in the works that might make it possible. If not, what would be required to make the change after boot-time through some kind of patch or something like that? Would that be something that might be valuable upstream?

At the moment we are running an application that might see some benefit from being able to isolate cpus on the fly without having to reboot everything every time we want to modify the parameters mentioned above. 

Thanks, 
Gianfranco