test/jdk/java/lang/management/MemoryMXBean/LowMemoryTest2.sh

rev 60538 : imported patch jep387-test.patch

*** 60,69 ****
--- 60,78 ----
  go -noclassgc -XX:MaxMetaspaceSize=32m -XX:+UseSerialGC LowMemoryTest2
  go -noclassgc -XX:MaxMetaspaceSize=32m -XX:+UseParallelGC LowMemoryTest2
  
  # Test class metaspace - might hit MaxMetaspaceSize instead if
  # UseCompressedClassPointers is off or if 32 bit.
+ #
+ # (note: This is very shaky and that shakiness exposes a problem with MemoryMXBean:
+ #
+ #  MemoryMXBean defines "used" "committed" and "max" (see java/lang/management/MemoryUsage.java)
+ #  This abstraction misses a definition for "address space exhausted" which with the new Metaspace (jep387)
+ #  can happen before committed/used hits any trigger. We now commit only on demand and therefore class loaders
+ #  can sit atop of uncommitted address space, denying new loaders address space. In the old Metaspace,
+ #  we would have committed the space right away and therefore the MemoryMXBean "committed" trigger
+ #  would have fired. In the new Metaspace, we don't commit, so the MemoryMXBean does not fire.
  go -noclassgc -XX:MaxMetaspaceSize=16m -XX:CompressedClassSpaceSize=4m LowMemoryTest2
  
  echo ''
  if [ $failures -gt 0 ];
    then echo "$failures test(s) failed";