User sunweiei provided the following jmap output in 0.96 deployment:
Heap consumption by Interns$CacheWith2Keys$2 could be due to calls to Interns.info() in DynamicMetricsRegistry.
This scenario would arise when large number of regions are tracked through metrics2.
Interns class doesn't provide API to remove entries in its internal Map.
Meaning, DynamicMetricsRegistry#clearMetrics() is unable to reclaim that part of heap.