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.\" Copyright (c) 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Donn Seeley of BSDI.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\" must display the following acknowledgement:
.\" This product includes software developed by the University of
.\" California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" @(#)profil.2 8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd June 4, 1993
.Dt PROFIL 2
.Os
.Sh NAME
.Nm profil
.Nd control process profiling
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft int
.Fn profil "char *samples" "size_t size" "vm_offset_t offset" "int scale"
.Sh DESCRIPTION
The
.Fn profil
system call enables or disables
program counter profiling of the current process.
If profiling is enabled,
then at every profiling clock tick,
the kernel updates an appropriate count in the
.Fa samples
buffer.
The frequency of the profiling clock is recorded
in the header in the profiling output file.
.Pp
The buffer
.Fa samples
contains
.Fa size
bytes and is divided into
a series of 16-bit bins.
Each bin counts the number of times the program counter
was in a particular address range in the process
when a profiling clock tick occurred while profiling was enabled.
For a given program counter address,
the number of the corresponding bin is given
by the relation:
.Bd -literal -offset indent
[(pc - offset) / 2] * scale / 65536
.Ed
.Pp
The
.Fa offset
argument is the lowest address at which
the kernel takes program counter samples.
The
.Fa scale
argument ranges from 1 to 65536 and
can be used to change the span of the bins.
A scale of 65536 maps each bin to 2 bytes of address range;
a scale of 32768 gives 4 bytes, 16384 gives 8 bytes and so on.
Intermediate values provide approximate intermediate ranges.
A
.Fa scale
value of 0 disables profiling.
.Sh RETURN VALUES
.Rv -std profil
.Sh FILES
.Bl -tag -width /usr/lib/gcrt0.o -compact
.It Pa /usr/lib/gcrt0.o
profiling C run-time startup file
.It Pa gmon.out
conventional name for profiling output file
.El
.Sh ERRORS
The following error may be reported:
.Bl -tag -width Er
.It Bq Er EFAULT
The buffer
.Fa samples
contains an invalid address.
.El
.Sh SEE ALSO
.Xr gprof 1
.Sh HISTORY
The
.Fn profil
function appeared in
.At v7 .
.Sh BUGS
This routine should be named
.Fn profile .
.Pp
The
.Fa samples
argument should really be a vector of type
.Fa "unsigned short" .
.Pp
The format of the gmon.out file is undocumented.
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