RFR (S): 8245087: Use ratios instead of percentages in G1HeapSizingPolicy::expansion_amount

[Kim Barrett]

> On May 18, 2020, at 4:15 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> 
> Hi all,
> 
>  can I have reviews for this change that changes internal calculations to use ratios (i.e. values between 0-1) instead of percentages (0-100)?
> 
> While in this case use of percent or ratios cancels itself out I prefer to use ratios for calculations and if needed percent for displaying.
> 
> There is just no need to scale the ratios we have with 100, apparently done to make the printing code simpler, but I really prefer it the other way.
> 
> In the log message I also unified the code to print the "%" sign without whitespace before (there has been a mix of that).
> 
> Based on 8245086 also out for review.
> 
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8245087
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8245087/webrev
> Testing:
> hs-tier1-5
> 
> Thanks,
>  Thomas

Looks good. 

One tiny nit:
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src/hotspot/share/gc/g1/g1HeapSizingPolicy.cpp
  74     log_trace(gc, ergo, heap)("Can not expand (heap already fully expanded) "

[pre-existing]
s/Can not/Cannot/  -- "Can not" looks weird here.

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