Some applications can be pathological, in which case you are better off setting lower-level flags. For example, Lucene both churns through tons of short-lived

Some applications can be pathological, in which case you are better off setting lower-level flags. For example, Lucene both churns through tons of short-lived strings and tries to maintain caches of large arrays. The memory/gc optimizer handles this very poorly. Between modern Java tending to move caches to unmanaged memory-mapped regions as libraries mature, and the potential of G1 as a concurrent compacting collector, we're on the cusp of not having to worry about any of this anymore.