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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-15 19:40:15 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-15 19:40:15 +0000 |
commit | 399644e47874bff147afb19c89228901ac39340e (patch) | |
tree | 1c4c0b733f4c16b5783b41bebb19194a9ef62ad1 /man3/posix_madvise.3 | |
parent | Initial commit. (diff) | |
download | manpages-399644e47874bff147afb19c89228901ac39340e.tar.xz manpages-399644e47874bff147afb19c89228901ac39340e.zip |
Adding upstream version 6.05.01.upstream/6.05.01
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'man3/posix_madvise.3')
-rw-r--r-- | man3/posix_madvise.3 | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/man3/posix_madvise.3 b/man3/posix_madvise.3 new file mode 100644 index 0000000..25ab37d --- /dev/null +++ b/man3/posix_madvise.3 @@ -0,0 +1,112 @@ +.\" Copyright (C) 2015 Michael Kerrisk <mtk.manpages@gmail.com> +.\" +.\" SPDX-License-Identifier: GPL-2.0-or-later +.\" +.TH posix_madvise 3 2023-03-30 "Linux man-pages 6.05.01" +.SH NAME +posix_madvise \- give advice about patterns of memory usage +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B #include <sys/mman.h> +.PP +.BI "int posix_madvise(void " addr [. len "], size_t " len ", int " advice ); +.fi +.PP +.RS -4 +Feature Test Macro Requirements for glibc (see +.BR feature_test_macros (7)): +.RE +.PP +.BR posix_madvise (): +.nf + _POSIX_C_SOURCE >= 200112L +.fi +.SH DESCRIPTION +The +.BR posix_madvise () +function allows an application to advise the system about its expected +patterns of usage of memory in the address range starting at +.I addr +and continuing for +.I len +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 +.BR posix_madvise () +shall not affect the semantics of access to memory in the specified range. +.PP +The +.I advice +argument is one of the following: +.TP +.B POSIX_MADV_NORMAL +The application has no special advice regarding its memory usage patterns +for the specified address range. +This is the default behavior. +.TP +.B 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. +.TP +.B POSIX_MADV_RANDOM +The application expects to access the specified address range randomly. +Thus, read ahead may be less useful than normally. +.TP +.B POSIX_MADV_WILLNEED +The application expects to access the specified address range +in the near future. +Thus, read ahead may be beneficial. +.TP +.B POSIX_MADV_DONTNEED +The application expects that it will not access the specified address range +in the near future. +.SH RETURN VALUE +On success, +.BR posix_madvise () +returns 0. +On failure, it returns a positive error number. +.SH ERRORS +.TP +.B EINVAL +.I addr +is not a multiple of the system page size or +.I len +is negative. +.TP +.B EINVAL +.I advice +is invalid. +.TP +.B ENOMEM +Addresses in the specified range are partially or completely outside +the caller's address space. +.SH VERSIONS +POSIX.1 permits an implementation to generate an error if +.I len +is 0. +On Linux, specifying +.I len +as 0 is permitted (as a successful no-op). +.PP +In glibc, this function is implemented using +.BR madvise (2). +However, since glibc 2.6, +.B POSIX_MADV_DONTNEED +is treated as a no-op, because the corresponding +.BR madvise (2) +value, +.BR MADV_DONTNEED , +has destructive semantics. +.SH STANDARDS +POSIX.1-2008. +.SH HISTORY +glibc 2.2. +POSIX.1-2001. +.SH SEE ALSO +.BR madvise (2), +.BR posix_fadvise (2) |