harvey/sys/man/3/kprof

.TH KPROF 3 
.SH NAME
kprof \- kernel profiling
.SH SYNOPSIS
.nf
.B bind -a #K /dev
.sp
.B /dev/kpctl
.B /dev/kpdata
.fi
.SH DESCRIPTION
The
.I 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
system clock.
.PP
The file
.B 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.
.PP
The file
.B kpctl
controls profiling.
Writing the string
.B start
to
.B kpctl
begins profiling;
.B stop
terminates it.  The message
.B startclr
restarts profiling after zeroing the array of counts.
.PP
The program
.I kprof
(see
.IR prof (1))
formats the data for presentation.
.SH EXAMPLE
The following
.IR rc (1)
script runs a test program while profiling the kernel
and reports the results.
.sp
.EX
	bind -a '#K' /dev
	echo start > /dev/kpctl
	runtest
	echo stop > /dev/kpctl
	kprof /386/9pcdisk /dev/kpdata
.EE
.SH SOURCE
.B /sys/src/9/port/devkprof.c
.SH SEE ALSO
.IR prof (1)