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Date: Wed, 19 Jul 2017 10:03:22 -0500 (CDT)
From: Christopher Lameter <cl@linux.com>
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To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
cc: "Li, Aubrey" <aubrey.li@linux.intel.com>,
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Subject: Re: [RFC PATCH v1 00/11] Create fast idle path for short idle
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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.