performance test

Hi,

I recently ran a performance test on reportlab 3.4.0 py36 and found an
unexpected behavior:

somewhere in between 500 to 600 iterations, which is equivalent to at
most 2055 to 2465 pages of pdf output, the time spent per cycle increases:

10 in 0.67 seconds; per ch_pair:= 0,067
100 in 2.964 seconds; per ch_pair:= 0,029
200 in 7.801 seconds; per ch_pair:= 0,039
400 in 27.064 seconds; per ch_pair:= 0,06016
500 in 44.385 seconds; per ch_pair:= 0,0887
600 in 63.645 seconds; per ch_pair:= 0,1
800 in 120.183 seconds; per ch_pair:= 0,15
1000 in 200.063 seconds; per ch_pair:= 0,2

why is the cycle time increasing, shouldn't this be linear?



want to have a look on the test case?
its at:
https://github.com/skidzo/autobasedoc/blob/master/tests/test_autoreport.py