RFR (S): 8177764: Humongous Reclaimed log output may be confusing

[Thomas Schatzl]

Hi all,

  can I have reviews for this following small change (plus accompanying
test case) that fixes log output for the "Humongous Reclaimed" message.

In particular, the value next to it showed the number of reclaimed
regions, while the previous related messages show the number of
reclaimed objects.

This resulted in log output where the value of "Humongous Reclaimed" is
larger than the number of candidates. E.g.:

[267.722s][debug][gc,phases ] GC(486) Humongous Register: 0.1ms 
[267.722s][trace][gc,phases ] GC(486) Humongous Total: 73 
[267.722s][trace][gc,phases ] GC(486) Humongous Candidate: 73 
[...] 
[267.722s][debug][gc,phases ] GC(486) Humongous Reclaim: 1.4ms 
[267.722s][trace][gc,phases ] GC(486) Humongous Reclaimed: 221 

This change makes "Humongous Reclaimed" to also report the number of
reclaimed objects. There is still a gc+heap=info message at every GC
that shows the number of reclaimed regions (as before/after
difference). 

E.g.:

[90.145s][info ][gc,heap        ] GC(13) Humongous regions: 150->13

I think this information is sufficient to avoid the need for another
log message.

CR:
https://bugs.openjdk.java.net/browse/JDK-8177764
Webrev:
http://cr.openjdk.java.net/~tschatzl/8177764/webrev/
Testing:
jprt, test case failing without patch, succeeding now

Thanks,
  Thomas