Sorting an already sorted list in Erlang

sorting.sh

% ./erlperf \
  'runner(Unsorted) -> lists:sort(Unsorted).' \
   --init_runner '[{rand:uniform(), I} || I <- lists:seq(1,500)].' \
   'runner(Sorted) -> lists:sort(Sorted).' \
   --init_runner 'lists:sort([{rand:uniform(), I} || I <- lists:seq(1,500)]).'
Code                                              ||        QPS       Time     Rel
runner(Sorted) -> lists:sort(Sorted).              1      69223   14446 ns    100%
runner(Unsorted) -> lists:sort(Unsorted).          1       7158     140 us     10%


% ./erlperf \
    'runner(Unsorted) -> lists:sort(Unsorted).' \
    --init_runner '[{rand:uniform(), I} || I <- lists:seq(1,1000)].' \
    'runner(Sorted) -> lists:sort(Sorted).' \
    --init_runner 'lists:sort([{rand:uniform(), I} || I <- lists:seq(1,1000)]).'
Code                                              ||        QPS       Time     Rel
runner(Sorted) -> lists:sort(Sorted).              1      30532   32752 ns    100%
runner(Unsorted) -> lists:sort(Unsorted).          1       2995     334 us      9%