'\" te
.\"  Copyright (c) 1998, Sun Microsystems, Inc.  All Rights Reserved
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.TH pcsample 2 "10 Mar 1998" "SunOS 5.11" "System Calls"
.SH NAME
pcsample \- program execution time profile
.SH SYNOPSIS
.LP
.nf
#include <pcsample.h>

\fBlong\fR \fBpcsample\fR(\fBuintptr_t\fR \fIsamples[]\fR, \fBlong\fR \fInsamples\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBpcsample()\fR function provides CPU-use statistics by profiling the
amount of \fBCPU\fR time expended by a program.
.sp
.LP
For profiling dynamically-linked programs and 64-bit programs, it is superior
to the \fBprofil\fR(2) function, which assumes that the entire program is
contained in a small, contiguous segment of the address space, divides this
segment into "bins", and on each clock tick increments the counter in the bin
where the program is currently executing. With shared libraries creating
discontinuous program segments spread throughout the address space, and with
64-bit address spaces so large that the size of "bins" would be measured in
megabytes, the \fBprofil()\fR function is of limited value.
.sp
.LP
The \fBpcsample()\fR function is passed an array \fIsamples\fR containing
\fInsamples\fR pointer-sized elements. During program execution, the kernel
samples the program counter of the process, storing unadulterated values in the
array on each clock tick. The kernel stops writing to the array when it is
full, which occurs after \fInsamples\fR / \fBHZ\fR seconds of process virtual
time. The \fBHZ\fR value is obtained by invoking the call
\fBsysconf(_SC_CLK_TCK)\fR. See \fBsysconf\fR(3C).
.sp
.LP
The sampling can be stopped by a subsequent call to \fBpcsample()\fR with the
\fInsamples\fR argument set to 0.  Like \fBprofil()\fR, sampling continues
across a call to \fBfork\fR(2), but is disabled by a call to one of the
\fBexec\fR family of functions (see \fBexec\fR(2)). It is also disabled if an
update of the \fIsamples\fR\fB[\|]\fR array causes a memory fault.
.SH RETURN VALUES
.sp
.LP
The \fBpcsample()\fR function always returns \fB0\fR the first time it is
called.  On subsequent calls, it returns the number of samples that were stored
during the previous invocation. If \fInsamples\fR is invalid, it returns
\fB\(mi1\fR and sets \fBerrno\fR to indicate the error.
.SH ERRORS
.sp
.LP
The \fBpcsample()\fR function will fail if:
.sp
.ne 2
.mk
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
.rt  
The value of \fInsamples\fR is not valid.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
MT-LevelAsync-Signal-Safe
_
Interface StabilityStable
.TE

.SH SEE ALSO
.sp
.LP
\fBexec\fR(2), \fBfork\fR(2), \fBprofil\fR(2), \fBsysconf\fR(3C),
\fBattributes\fR(5)