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SubjectRe: Does anyone use CONFIG_TINY_PREEMPT_RCU?
On Tue, Nov 13, 2012 at 02:12:27AM +0100, Frederic Weisbecker wrote:
> 2012/11/13 Paul E. McKenney <paulmck@linux.vnet.ibm.com>:
> > Hello!
> >
> > I know of people using TINY_RCU, TREE_RCU, and TREE_PREEMPT_RCU, but I
> > have not heard of anyone using TINY_PREEMPT_RCU for whom TREE_PREEMPT_RCU
> > was not a viable option (in contrast, the people running Linux on
> > tiny-memmory systems typically use TINY_RCU). Of course, if no one
> > really needs it, the proper thing to do is to remove it.
> >
> > So, if you need TINY_PREEMPT_RCU, please let me know. Otherwise, I will
> > remove it, probably in the 3.9 timeframe.
>
> I don't use it personally but if you remove it, does that mean that
> RCU couldn't be preemptible on UP?

It would mean that a kernel built with SMP=n and PREEMPT=y would use
TREE_PREEMPT_RCU rather than the current TINY_PREEMPT_RCU. So it would
work just as well, but use somewhat more memory.

Thanx, Paul



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