RFR 8038822: java/lang/management/MemoryMXBean/LowMemoryTest2.sh still fails with OutOfMemoryError: Metaspace

[Mattias Tobiasson]

Hi,
This test sometimes fails with OutOfMemory. It fails rarely, I have not been able to reproduce it.

The test keeps loading new classes until MemoryMXBean.getUsageThresholdCount() > 0.
UsageThresholdCount is only updated during a GC. My guess is that the test loads classes
too fast so we run out of memory before the flag is set.

This fix will force a GC when used memory is above the threshold.
That should update the UsageThresholdCount immediately.
I have also added more logging if the test fails again.

changes:
1. Force a GC if memory usage is above threshold.
2. Split the big check pools loop into sub functions.
3. "pools" list only contains the relevant pools,
instead of keeping all pools and filter them each loop.  

webrev: http://cr.openjdk.java.net/~ykantser/8038822/webrev.00
bug: https://bugs.openjdk.java.net/browse/JDK-8038822

Mattias