RFR: 8027423: Parallel compact GC class unloading measurement includes symbol and string table time

[Stefan Karlsson]

Hi all,

Please review this patch to get more detailed phase measurements of the 
unloading phases of the parallel and serial collectors. It mimics the 
way CMS reports the unloading phase. G1 parallelizes the unloading 
phase, so it is slightly different.

http://cr.openjdk.java.net/~stefank/8027423/webrev.00/
https://bugs.openjdk.java.net/browse/JDK-8027423

Example of the output that you get with -Xlog:gc=debug:
[2.257s][debug][gc] GC(45) Class Unloading (2.256s, 2.257s) 1.669ms
[2.258s][debug][gc] GC(45) Scrub String Table (2.257s, 2.258s) 0.412ms
[2.259s][debug][gc] GC(45) Scrub Symbol Table (2.258s, 2.259s) 1.027ms
[2.292s][info ][gc] GC(45) Pause Full (System.gc()) 80M->2M(98M) 
(2.248s, 2.292s) 44.631ms

Thanks,
StefanK