kprof - kernel profiling
bind -a #K /dev
The kprof device provides simple profiling data for the operating sys‐
tem kernel. The data accumulates by recording the program counter of
the kernel at each `tick' of the system clock.
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 ker‐
nel 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.
The following rc(1) script runs a test program while profiling the ker‐
nel and reports the results.
bind -a '#K' /dev
echo start > /dev/kpctl
echo stop > /dev/kpctl
kprof /386/9pcdisk /dev/kpdata