KPROF(3) KPROF(3)
NAME
kprof - kernel profiling
SYNOPSIS
bind -a #K /dev
/dev/kpctl
/dev/kpdata
DESCRIPTION
The kprof device provides simple profiling data for the
operating system kernel. The data accumulates by recording
the program counter of the kernel at each `tick' of the sys-
tem clock.
The file kpdata holds the accumulated counts as 4-byte inte-
gers 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 num-
ber 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 presen-
tation.
EXAMPLE
The following rc(1) script runs a test program while profil-
ing the kernel and reports the results.
bind -a '#T' /dev
echo start > /dev/kpctl
runtest
echo stop > /dev/kpctl
kprof /386/9pcdisk /dev/kpdata
SOURCE
/sys/src/9/port/devkprof.c
SEE ALSO
prof(1)
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