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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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posix_madvise(3) Library Functions Manual posix_madvise(3)
posix_madvise - give advice about patterns of memory usage
Standard C library (libc, -lc)
#include <sys/mman.h>
int posix_madvise(size_t size;
void addr[size], size_t size, int advice);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
posix_madvise():
_POSIX_C_SOURCE >= 200112L
The posix_madvise() function allows an application to advise the
system about its expected patterns of usage of memory in the
address range starting at addr and continuing for size bytes. The
system is free to use this advice in order to improve the
performance of memory accesses (or to ignore the advice
altogether), but calling posix_madvise() shall not affect the
semantics of access to memory in the specified range.
The advice argument is one of the following:
POSIX_MADV_NORMAL
The application has no special advice regarding its memory
usage patterns for the specified address range. This is
the default behavior.
POSIX_MADV_SEQUENTIAL
The application expects to access the specified address
range sequentially, running from lower addresses to higher
addresses. Hence, pages in this region can be aggressively
read ahead, and may be freed soon after they are accessed.
POSIX_MADV_RANDOM
The application expects to access the specified address
range randomly. Thus, read ahead may be less useful than
normally.
POSIX_MADV_WILLNEED
The application expects to access the specified address
range in the near future. Thus, read ahead may be
beneficial.
POSIX_MADV_DONTNEED
The application expects that it will not access the
specified address range in the near future.
On success, posix_madvise() returns 0. On failure, it returns a
positive error number.
EINVAL addr is not a multiple of the system page size or size is
negative.
EINVAL advice is invalid.
ENOMEM Addresses in the specified range are partially or
completely outside the caller's address space.
POSIX.1 permits an implementation to generate an error if size is
0. On Linux, specifying size as 0 is permitted (as a successful
no-op).
In glibc, this function is implemented using madvise(2). However,
since glibc 2.6, POSIX_MADV_DONTNEED is treated as a no-op,
because the corresponding madvise(2) value, MADV_DONTNEED, has
destructive semantics.
POSIX.1-2008.
glibc 2.2. POSIX.1-2001.
madvise(2), posix_fadvise(2)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-06-28 posix_madvise(3)
Pages that refer to this page: madvise(2), mincore(2), posix_fadvise(2)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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