8202466: Test serviceability/tmtools/jstat/GcTest01.java fails: Number of concurrent GC events is 1, but CGCT is 0

[Yasumasa Suenaga]

Hi all,

I've tried to fix 8202466, but I do not yet certain which solution is the best for it.
So I want your opinion for it.

https://bugs.openjdk.java.net/browse/JDK-8202466

David reports serviceability/tmtools/jstat/GcTest01.java failed in Mach5. It seems to appear on OS X only.
He has shared jtreg report, and I found as below:

```
stdout: S0C S1C S0U S1U EC EU OC OU MC MU CCSC CCSU YGC YGCT FGC FGCT CGC CGCT GCT
  0.0 0.0 0.0 0.0 3072.0 0.0 11264.0 2825.6 9472.0 9003.3 1024.0 845.3 26 0.204 3 0.292 1 0.000 0.497
```

YGCT: 0.204
FGCT: 0.292
CGCT: 0.000

  GCT: 0.497

I guess this failure was caused by rounding error because (YGCT + FGCT + CGCT) < GCT.
CGC is 1, so CGC operation might finish in very short time.


GcTest01.java:
   http://hg.openjdk.java.net/jdk/jdk/file/4da7dce7e2bf/test/hotspot/jtreg/serviceability/tmtools/jstat/GcTest01.java#l57

GcCauseTest01.java:
   http://hg.openjdk.java.net/jdk/jdk/file/4da7dce7e2bf/test/hotspot/jtreg/serviceability/tmtools/jstat/GcCauseTest01.java#l53

GcTest01 and GcCauseTest01 are very similar, but GcCauseTest01 passed.
Both tests use GcProvoker::provokeGc() to inflate memory usage. So I wonder why GcTest01 just only failed.
I guess we might encounter similar issue(s) in the future if we get more fast machines.

Hence I think we can take two approaches as below:

   1. Add all tests in serviceability/tmtools/jstat to ProblemList.
   2. Change all JstatGc*Tool to use custom jstat_options - to show raw values in PerfCounters


What do you think?
I can start to work for it if they are OK.


Thanks,

Yasumasa