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    SubjectRe: Does anyone use CONFIG_TINY_PREEMPT_RCU?
    On Tue, Nov 13, 2012 at 04:47:20PM -0500, Nick Bowler wrote:
    > On 2012-11-13 13:19 -0800, Paul E. McKenney wrote:
    > > On Tue, Nov 13, 2012 at 12:56:54PM -0500, Nick Bowler wrote:
    > > > On 2012-11-13 09:08 -0800, Paul E. McKenney wrote:
    > > > > Suppose that TREE_PREEMPT_RCU was available for !SMP && PREEMPT builds.
    > > > > Would that work for you?
    > > >
    > > > To be honest I don't really know what the difference is, other than what
    > > > the help text says, which is:
    > > >
    > > > [TINY_PREEMPT_RCU] greatly reduces the memory footprint of RCU.
    > > >
    > > > "Greatly reduced memory footprint" sounds pretty useful...
    > >
    > > OK, so from your viewpoint, the only possible benefit is smaller
    > > memory?
    >
    > Well, I have no idea. If I was given the choice between TREE_PREEMPT_RCU
    > and TINY_PREEMPT_RCU, absent any information not in the description of
    > these options, I would choose TINY. The description suggests that the
    > memory savings come at the expense of SMP support, which sounds like a
    > great tradeoff to make for a UP system.
    >
    > > How much memory does your device have, if I may ask?
    >
    > It's a (pretty old!) desktop. I recently had to upgrade it to two
    > gigabytes due to unbearable thrashing with only one...

    If you have two gigabytes (or even one gigabyte), you won't notice the
    few kilobytes of difference between TINY_PREEMPT_RCU and TREE_PREEMPT_RCU.

    Thanx, Paul



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