Re: Does anyone use CONFIG_TINY_PREEMPT_RCU?

[Frederic Weisbecker]

2012/11/13 Josh Triplett <josh@xxxxxxxxxxxxxxxx>:
> On Tue, Nov 13, 2012 at 02:12:27AM +0100, Frederic Weisbecker wrote:
>> 2012/11/13 Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>:
>> > 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?
>
> No, it would mean that on UP you could choose between TINY_RCU and
> TREE_PREEMPT_RCU, depending on whether you want tiny or preemptible.

Ok. I thought the TREE version wasn't possible anymore on UP when I
saw some patches that removed optimizations for nr_online_cpus=1.
Hence the confusion.
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