Rastertime
How much of a frame a routine uses, measured in scanlines and made visible by changing the border colour while the code runs.
On a PAL C64 the VIC-II draws 312 lines per frame at 63 cycles per line: 19,656 cycles before the next frame is due. The simplest profiler ever devised is to write a colour to the border register $D020 when a routine starts and restore it when it ends. The coloured band in the border shows exactly how many lines the code consumed.
Demo coders and musicians treat rastertime as currency: a music player taking three lines beats one taking ten, because the rest goes to effects. Badlines and sprites steal cycles and make the band ragged. The stripes were sometimes left in shipped games and demos by accident and are now a well-known developer fingerprint.