The file kpdata holds the accumulated counts as 4-byte integers in big-endian byte order. The size of the file depends on the size of kernel text. The first count holds the total number of clock ticks during profiling; the second the number of ticks that occurred while the kernel was running. The rest each hold the number of ticks the kernel program counter was within the corresponding 8-byte range of kernel text, starting from the base of kernel text.

The file kpctl controls profiling. Writing the string start to kpctl begins profiling; stop terminates it. The message startclr restarts profiling after zeroing the array of counts.

The program kprof (see prof(1)) formats the data for presentation.