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 total ticks the kernel
spent at any one program counter, indexed by their offset
from the minimum kernel text address.
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 '#K' /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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