Saxon

Saxon maintains a cache of "converter" objects for converting/casting values from type A to type B: if the same conversion is performed repeatedly, this avoids complex navigation of the type hierarchy to decide what to do. The cache is an LRU cache held in ThreadLocal. Because the converter objects contain a reference to a Configuration, in the case where many Configuration objects are created they can end up not being garbage collected. The fact that the cache is LRU should avoid this in theory, but in practice it seems the number of ThreadLocal objects on the heap can greatly exceed the number of threads, leading to a large number of Configuration objects, and their associated resources such as the namePool and TypeHierarchy, being locked down in memory.