1. Compressed oops are enabled by default whenever they are most useful.
2. A 31 GB heap using compressed oops will often outperform slightly larger heaps
that are too big to use compressed oops.
Although the Java heap is the memory region that gets the most attention, the entire footprint
of the JVM is crucial to its performance, particularly in relation to the operating system. The
tools discussed in this chapter allow you to track that footprint over time (and, crucially, to
focus on the committed memory of the JVM rather than the reserved memory).
Certain ways that the JVM uses OS memory—particularly large pages—can also be tuned to
improve performance. Long-running JVMs will almost always benefit by using large pages,
particularly if they have large heaps.