RFR: 8252093: formula used to calculate decaying variance in numberSeq

[Kim Barrett]

> On Aug 26, 2020, at 9:59 AM, Albert Yang <albert.m.yang at oracle.com> wrote:
> 
> Hi,
> 
> I am sending this to both runtime-dev and gc-dev, since the changed code lives in runtime, but it's used by GC.
> 
> https://bugs.openjdk.java.net/browse/JDK-8252093
> http://cr.openjdk.java.net/~ayang/webrevs/8252093/webrev.1/
> 
> Both the code and the literature use `alpha`, but its meaning is actually inverted. I could include this refactoring in later revision if people feel that it's desirable.
> 
> Tested: tier1 (locally) and tier1-3 (mach5)
> 
> -- 
> /Albert

Nice find.  Looks good.

I wonder if this has any noticeable performance effect.
For G1 it affects many/all policy-based predictions, since it affects the G1Predictions::predict function.