According to my notes from when I first put that together -XX:+UseParNewGC is automatically implied by +UseConcMarkSweepGC, for which my source was this very ol

According to my notes from when I first put that together -XX:+UseParNewGC is automatically implied by +UseConcMarkSweepGC, for which my source was this very old web page about a very old jvm version (again, dark art): http://cybergav.in/2010/01/11/tuning-hotspot-jvm-1-4-2-with-cms-low-pause-garbage-collector/ http://cybergav.in/2010/01/11/tuning-hotspot-jvm-1-4-2-with-... Also, more concretely, this is the most frequent type of entry in my gc log: http://pastie.org/pastes/7142036/text?key=dkwvlvaaysk63rcajbp2na http://pastie.org/pastes/7142036/text?key=dkwvlvaaysk63rcajb... I (perhaps wrongly?) interpret the ParNew there to imply that's the young gen collector in use.