`make perf` will build, by default, perf.log, but you may also build perf.*;
for example:
$ make perf.1
# make some changes
$ make perf.2
This allows comparing changes easily.
Styled for display to user as the tests are running, but data are written to
perf.out for additional processing.
You can style the perf.out file cleanly using:
$ column -ts\| perf.out