Background (cont.)

Placing related functions together reduces working set size.
Performance benefits:
reduces memory consumption
improves load times
improves cache performance

Typically "code coverage" is relatively low for big programs:
gcc compiling haifa-sched.c (8764 lines):
976 / 3004 functions were called
798596 / 1790348 (44%) of the code was executed

Functions tend to be spread out