Currently the code for sampling the rset sizes of the incremental collection set is way too complicated.
The iteration state and the aggregate and final values of the sampled rset sizes are all stored in the YoungList class for no good reason.
Suggested fix is to move the iteration and aggregation to G1YoungRemSetSamplingThread::sample_young_list_rs_lengths and instead of storing the final value of the samples sizes passing them as an explicit parameter to the policy:
g1p->revise_young_list_target_length_if_necessary(sampled_rs_lengths);