Re: [PATCH RFC] rcu/nocb: Provide default all-CPUs mask for RCU_NOCB_CPU=y

Joel Fernandes
2022-04-14T19:20:35Z

On Mon, Apr 11, 2022 at 08:41:09AM -0700, Paul E. McKenney wrote:
[..]
> > > [4] All CPUs are offloaded at boot, and any CPU can be de-offloaded
> > > and offloaded at runtime. This is the same behavior that
> > > you would currently get with CONFIG_RCU_NOCB_CPU_ALL=n and
> > > rcu_nocbs=0-N.
> >
> > Yes, this is the behavior I intend. So then there would not be a need
> > to pass a mask (and I suspect for a large number of users, it
> > simplifies boot params).
>
> Very good, and from what I can see, this should work for everyone.

Just to clarify, what I am going to do is, if this new option =y, then
rcu_nocbs effectively wont do anything. i.e. All CPUs are offloaded at boot.
Let me know if we are not on the same page about it though. I do feel that is
a sensible choice given =y. If we are on same page, please ignore my comment.

> > > I believe that Steve Rostedt's review would carry weight for ChromeOS,
> > > however, I am suffering a senior moment on the right person for Android.
> >
> > I think for Android, Kalesh Singh is in the kernel team and Tim Murray
> > is the performance lead. They could appropriately represent their RCU
> > needs.
>
> Sounds good! Please collect a Reviewed-by from one or both of them.

Ok.

thanks,

- Joel