Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods

[Christopher Lameter]

On Wed, 19 Jul 2017, Paul E. McKenney wrote:

> > Do we have any problem if we skip RCU idle enter/exit under a fast idle scenario?
> > My understanding is, if tick is not stopped, then we don't need inform RCU in
> > idle path, it can be informed in irq exit.
>
> Indeed, the problem arises when the tick is stopped.

Well is there a boundary when you would want the notification calls? I
would think that even an idle period of a couple of seconds does not
necessarily require a callback to rcu. Had some brokenness here where RCU
calls did not occur for hours or so. At some point the system ran out of
memory but thats far off.