The design goals of G1 GC

G1 GC was designed to avoid full GC collections. One of the main design goals of G1 was to add predictability and configurability to the duration and distribution of stop-the-world GC pauses.

For instance, with G1 GC, you can specify that the stop-the-world pauses should not be longer than x ms in a y ms time range. A real example of this is by specifying that a stop-the-world pause with a G1 GC should not be more than 8 milliseconds, every 70 seconds. The G1 GC will do its best to meet this performance goal.

However, there could be a mismatch in how you configure these values and the actual pause times with the G1 GC.