RFR: 8226797: serviceability/tmtools/jstat/GcCapacityTest.java fails with Exception: java.lang.RuntimeException: OGCMN > OGCMX (min generation capacity > max generation capacity)

[Stefan Karlsson]

Hi all,

Please review this patch to fix a problem with unintialized values in 
our generation counters.

https://cr.openjdk.java.net/~stefank/8226797/webrev.01/
https://bugs.openjdk.java.net/browse/JDK-8226797

The jstat values NGCMN and OGCMN both return uninitialized values.

I stumbled upon this while creating a patch to remove the GenerationSpec 
class.

GenerationSpec::_min_size is never initialized, and then used to create 
the generations:

     case Generation::DefNew:
       return new DefNewGeneration(rs, _init_size, _min_size, _max_size);

     case Generation::MarkSweepCompact:
       return new TenuredGeneration(rs, _init_size, _min_size, 
_max_size, remset);

That in turn uses it to initialize the perf counters:
DefNewGeneration::DefNewGeneration(ReservedSpace rs,
                                    size_t initial_size,
                                    size_t min_size,
                                    size_t max_size,
                                    const char* policy)
...
   _gen_counters = new GenerationCounters("new", 0, 3,
       min_size, max_size, &_virtual_space);

I'm setting the value to _init_size, because it reflects how MinNewSize 
and MinOldSize relates to NewSize and OldSize.

Thanks,
StefanK