Re: [PATCH v4 00/14] Implement call_rcu_lazy() and miscellaneous fixes

From: Paul E. McKenney
Date: Tue Aug 30 2022 - 07:47:19 EST


On Tue, Aug 30, 2022 at 12:50:02PM +0200, Frederic Weisbecker wrote:
> On Mon, Aug 29, 2022 at 01:31:31PM -0700, Paul E. McKenney wrote:

[ . . . ]

> > Another test would be to look at which callbacks are being invoked
> > on each grace period. We have to have a substantial number of grace
> > periods having all lazy callbacks before call_rcu_lazy() has any chance
> > of helping. This would need to happen on a server platform because
> > Android and ChromeOS data might or might not carry over.
>
> Also that yes.

What would be the best way to collect that data?

Please keep in mind that unless/until we have some clear empirical
indication that call_rcu_lazy() really would help the world of systems
running without rcu_nocbs, moving the call_rcu_lazy() implementation
from the bypass list to cblist does nothing but increase risk to system
that get no benef from call_rcu_lazy().

Thanx, Paul