In an application that is fairly quiescent wrt to allocations, G1 normally keeps or shrinks heap size because gc cpu usage is low.

However, in reality there can be applications which do not allocate, but cause high other (refinement) activity, causing unnecessary heap expansions. It is not obvious that refinement activity is dependent on heap size, so changing heap size based on refinement activity may be unsuitable.

There is also a similar case, when gc activity is high, the pause time goal is exceeded, and expanding the heap can not decrease it, g1 expands further anyway.

Investigate and try to come up with a fix if necessary. May split into multiple issues.