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

stefan.johansson at oracle.com stefan.johansson at oracle.com
Thu Aug 27 15:23:46 UTC 2020

Hi Albert,

On 2020-08-26 15:59, Albert Yang 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/
Looks good, nice to have the comment as reference. As Kim, I wonder if 
this will cause any visible change because of changed predictions. Have 
you run any benchmarks and compared scores as well as GC-behavior?

> 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.
Is there a good reason for keeping it inverted, I see that we have a few 
places where we specify an alpha when creating the seq, so I guess there 
are a few places to change. Otherwise maybe adding a comment to the 
defined default might be helpful.


> Tested: tier1 (locally) and tier1-3 (mach5)

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