RFR (M): 8233588: Clean up SurvRateGroup

[Kim Barrett]

> On Nov 12, 2019, at 10:23 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> 
> Hi all,
> 
>  can I have some reviews for this change that cleans up the SurvRateGroup class. In particular, while working with it I found that it contains two members that are duplicates of others.
> 
> This removed a few methods, which in turn made some others obsolete.
> 
> Further I tried to improve encapsulation so that not everyone needs to know all details down to SurvRateGroup.
> 
> That's why this change is a bit larger than you'd probably expect, but it contains a significant amount of code deletion! :)
> 
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8233588
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8233588/webrev/
> Testing:
> hs-tier1-5
> 
> Thanks,
>  Thomas

Looks good.

One pre-existing issue:

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src/hotspot/share/gc/g1/g1CollectionSet.cpp
 343     if (r->age_in_surv_rate_group() < 0) {

[pre-existing]

A few lines before we checked r->has_surv_rate_group().  If it doesn't
have one, should we really be checking the age?  Looks like we'd currently
assert if we don't have one.

I think just making this an "else if” with the preceeding “has” check fixes it.

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