'\" te
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.TH POSIX_MADVISE 3C "Jul 14, 2008"
.SH NAME
posix_madvise \- memory advisory information
.SH SYNOPSIS
.LP
.nf
#include <sys/mman.h>

\fBint\fR \fBposix_madvise\fR(\fBvoid *\fR\fIaddr\fR, \fBsize_t\fR \fIlen\fR, \fBint\fR \fIadvice\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBposix_madvise()\fR function advises the system on the expected behavior
of the application with respect to the data in the memory starting at address
\fIaddr\fR, and continuing for \fIlen\fR bytes. The system may use this
information to optimize handling of the specified data. The
\fBposix_madvise()\fR function has no effect on the semantics of access to
memory in the specified range, although it may affect the performance of
access.
.sp
.LP
The advice to be applied to the memory range is specified by the \fIadvice\fR
parameter and may be one of the following values:
.sp
.ne 2
.na
\fB\fBPOSIX_MADV_NORMAL\fR\fR
.ad
.RS 25n
Specifies that the application has no advice to give on its behavior with
respect to the specified range. It is the default characteristic if no advice
is given for a range of memory.
.RE

.sp
.ne 2
.na
\fB\fBPOSIX_MADV_SEQUENTIAL\fR\fR
.ad
.RS 25n
Specifies that the application expects to access the specified range
sequentially from lower addresses to higher addresses.
.RE

.sp
.ne 2
.na
\fB\fBPOSIX_MADV_RANDOM\fR\fR
.ad
.RS 25n
Specifies that the application expects to access the specified range in a
random order.
.RE

.sp
.ne 2
.na
\fB\fBPOSIX_MADV_WILLNEED\fR\fR
.ad
.RS 25n
Specifies that the application expects to access the specified range in the
near future.
.RE

.sp
.ne 2
.na
\fB\fBPOSIX_MADV_DONTNEED\fR\fR
.ad
.RS 25n
Specifies that the application expects that it will not access the specified
range in the near future.
.RE

.sp
.LP
These values are defined in \fB<sys/mman.h>\fR
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBposix_madvise()\fR returns zero. Otherwise, an
error number is returned to indicate the error.
.SH ERRORS
.sp
.LP
The \fBposix_madvise()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The value of \fIadvice\fR is invalid.
.RE

.sp
.ne 2
.na
\fB\fBENOMEM\fR\fR
.ad
.RS 10n
Addresses in the range starting at \fIaddr\fR and continuing for \fIlen\fR
bytes are partly or completely outside the range allowed for the address space
of the calling process.
.RE

.sp
.LP
The \fBposix_madvise()\fR function may fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The value of \fIlen\fR is zero.
.RE

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

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Committed
_
MT-Level	MT-Safe
_
Standard	See \fBstandards\fR(5).
.TE

.SH SEE ALSO
.sp
.LP
\fBmmap\fR(2), \fBmadvise\fR(3C), posix_madvise(3C), \fBattributes\fR(5),
\fBstandards\fR(5)