"-Xgcpolicy:optthruput is a single generation parallel non-concurrent GC with optional compaction targeted at GC throughput; -Xgcpolicy:gencon is a parallel and concurrent 2-generation GC with concurrent collection in both generations; metronome is an incremental parallel GC with an upper bound on GC pause time; -Xgcpolicy:balanced is like optthruput but reduces the max pause time by doing smaller partial GCs where possible."