Each plot depicts memory use during the raco setup -j 1 part of installing main-distribution plus main-distribution-test in minimal Racket.
The X-direction is CPU time. The Y-direction for the black line is memory use sampled at each GC (before and after as separate lines, but you can't usually see distinct lines). Each color vertical line corresponds to a printout from raco setup:
The upward slant in the blue region is not a leak; the “running” phase accumulates cross-reference information across documents.
Using plot.rkt, you can generate graphs from the (unzipped) logs, show in them in a GUI that provides more detail (such as the printouts correcting to the color lines), and compare multiple plots. Use the -h flag of plot.rkt for more information.