In order to handle 'cairo-perf-trace benchmark', we need to perform the
can_run? test on the directory name as opposed to the individual trace
names. Make it so.
By ensuring that tests take longer than a couple of seconds we eliminate
systematic errors in our measurements. However, we also effectively
eliminate the synchronisation overhead. To compensate, we attempt to
estimate the overhead by reporting the difference between a single
instance and the minimum averaged instance.
This test shows that drawing a 100x100 single-pixel wide box outline is
currently 5 to 16 times slower when using the natural cairo_stroke() as
compared to a rather awkward cairo_fill() of two rectangles.
[ # ] backend-content test-size min(ticks) min(ms) median(ms) stddev. iterations
[ 0] image-rgba box-outline-stroke-100 301321 0.218 0.219 0.39% 5
[ 1] image-rgba box-outline-fill-100 18178 0.013 0.013 0.43% 5
[ 0] xlib-rgba box-outline-stroke-100 379177 0.275 0.276 1.39% 6
[ 1] xlib-rgba box-outline-fill-100 83355 0.060 0.060 0.17% 5
