Gc_stats.Mainval create :
string ->
generation:int ->
commit_offset:Import.int63 ->
before_suffix_start_offset:Import.int63 ->
before_suffix_end_offset:Import.int63 ->
after_suffix_start_offset:Import.int63 ->
tval finalise :
t ->
Stats.Latest_gc.worker ->
after_suffix_end_offset:Import.int63 ->
Stats.Latest_gc.stats