Time to time (not often, but quite regularly) the test gc/memory/Nio_PageAlignDirectMemory fails:

Exception in thread "main" gc.memory.Nio.Nio$Fault: Allocating direct memory should not eat the heap! Heap dumped to heapDump.hprof file.
  at gc.memory.Nio.Nio.checkHeapIsNotAffected(Nio.java:138)
  at gc.memory.Nio.Nio.run(Nio.java:52)
  at gc.memory.Nio.Nio.main(Nio.java:28)


The test is executed with: -XX:MaxDirectMemorySize=25m -Dsun.nio.PageAlignDirectMemory=true flags. It allocates all available direct buffer (25m) and heap is not growing.

But heap grows and test fails dumping heap.

Let's start with assumption that this is test issue.