Current issue is that this is triggering the "mark IC as something
being inside", which trips up the bjit's "overwrite the last few
bytes of the previous block, assuming that they are just a jump".

create 100M ints and free them periodically
timing for refcounting:
free them every 100 ints: 2.79s
free them every 10k ints: 6.660s

gc now runs, though it can't free everything