linux-kernel - Re: [PATCH] rcu/nocb: Add an option to ON/OFF an offloading from RT context

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Message-ID: <Ynpxm46hEg0+G82g@linutronix.de>
Date:   Tue, 10 May 2022 16:07:23 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     "Uladzislau Rezki (Sony)" <urezki@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, RCU <rcu@...r.kernel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Neeraj Upadhyay <neeraj.iitr10@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...y.com>
Subject: Re: [PATCH] rcu/nocb: Add an option to ON/OFF an offloading from RT
 context

On 2022-05-05 12:09:15 [-0700], Paul E. McKenney wrote:
> All good points!
> 
> Some questions and comments below.
> 
> Adding Sebastian on CC for his perspective.

Thank you.
I may missing things, I tried to digest the thread…

In my understanding: The boosting option is used to allow a SCHED_OTHER
task within a RCU section to allow to leave the RCU section while tasks
with higher priority occupy the CPU.
As far as the RCU callbacks are concerned, I'm not aware that it would
be beneficial to run them with an elevated priority. On SMP systems,
there is the suggestion to have a housekeeping CPU and to offload the
RCU callbacks to this CPU and no to bother the CPU with the RT workload.

> 						Thanx, Paul

Sebastian