What do we see with G1? Young pauses that are in in 500..1000 ms range. These pauses are likely to be less once we reach steady state and heuristics figure out how much to collect to keep pause times on target. After a while, concurrent GC cycle starts, and continues until almost to the end. (Notice how Young collections overlap with concurrent phases too). It should have been followed by "mixed" collection pauses, but VM had exited before that. These non-steady-state pauses really contributed to the long run times for this one-off job.