Ran across a nodemanager that was spending most of its time in GC. Upon examination of the heap most of the memory was going to the map of names in org.apache.hadoop.metrics2.lib.UniqueNames. In this case the map had almost 2 million entries. Looking at a few of the map showed entries like "ContainerResource_container_e01_1459548490386_8560138_01_002020", "ContainerResource_container_e01_1459548490386_2378745_01_000410", etc.
Looks like the ContainerMetrics for each container will cause a unique name to be registered with UniqueNames and the name will never be unregistered.