In JDK-8017163 card set allocator sizing heuristics (that is, initial buffer sizes etc) are reset after freeing them.

Investigate whether it makes sense to not start all over again every time with sizing to avoid some allocations.

Another avenue of investigation should be to see if the existing sizing bounds (i.e. at some point we start doubling the amount of pre-allocated buffers in the arenas, see see G1CardSetConfiguration::mem_object_alloc_options()) could be improved.