.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
-.\"
+.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date. The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
-.\"
+.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.I start
and with size
.I length
-bytes. It allows an application to tell the kernel how it expects to use
+bytes.
+It allows an application to tell the kernel how it expects to use
some mapped or shared memory areas, so that the kernel can choose
appropriate read-ahead and caching techniques.
-This call does not influence the semantics of the application
+This call does not influence the semantics of the application
(except in the case of
.BR MADV_DONTNEED ),
but
-may influence its performance. The kernel is free to ignore the advice.
+may influence its performance.
+The kernel is free to ignore the advice.
.LP
-The advice is indicated in the
+The advice is indicated in the
.I advice
parameter which can be
.TP
.B MADV_NORMAL
-No special treatment. This is the default.
+No special treatment.
+This is the default.
.TP
.B MADV_RANDOM
Expect page references in random order.
.TP
.BR MADV_REMOVE " (Since Linux 2.6.16)"
Free up a given range of pages
-and its associated backing store.
+and its associated backing store.
Currently,
.\" 2.6.18-rc5
-only shmfs/tmpfs supports this; other filesystems return -ENOSYS.
-.\" Databases want to use this feature to drop a section of their
-.\" bufferpool (shared memory segments) - without writing back to
-.\" disk/swap space. This feature is also useful for supporting
+only shmfs/tmpfs supports this; other filesystems return -ENOSYS.
+.\" Databases want to use this feature to drop a section of their
+.\" bufferpool (shared memory segments) - without writing back to
+.\" disk/swap space. This feature is also useful for supporting
.\" hot-plug memory on UML.
.TP
.BR MADV_DONTFORK " (Since Linux 2.6.16)"
(Such page relocations cause problems for hardware that
DMAs into the page(s).)
.\" [PATCH] madvise MADV_DONTFORK/MADV_DOFORK
-.\" Currently, copy-on-write may change the physical address of
-.\" a page even if the user requested that the page is pinned in
-.\" memory (either by mlock or by get_user_pages). This happens
-.\" if the process forks meanwhile, and the parent writes to that
-.\" page. As a result, the page is orphaned: in case of
-.\" get_user_pages, the application will never see any data hardware
-.\" DMA's into this page after the COW. In case of mlock'd memory,
+.\" Currently, copy-on-write may change the physical address of
+.\" a page even if the user requested that the page is pinned in
+.\" memory (either by mlock or by get_user_pages). This happens
+.\" if the process forks meanwhile, and the parent writes to that
+.\" page. As a result, the page is orphaned: in case of
+.\" get_user_pages, the application will never see any data hardware
+.\" DMA's into this page after the COW. In case of mlock'd memory,
.\" the parent is not getting the realtime/security benefits of mlock.
-.\"
-.\" In particular, this affects the Infiniband modules which do DMA from
+.\"
+.\" In particular, this affects the Infiniband modules which do DMA from
.\" and into user pages all the time.
-.\"
-.\" This patch adds madvise options to control whether memory range is
-.\" inherited across fork. Useful e.g. for when hardware is doing DMA
-.\" from/into these pages. Could also be useful to an application
-.\" wanting to speed up its forks by cutting large areas out of
+.\"
+.\" This patch adds madvise options to control whether memory range is
+.\" inherited across fork. Useful e.g. for when hardware is doing DMA
+.\" from/into these pages. Could also be useful to an application
+.\" wanting to speed up its forks by cutting large areas out of
.\" consideration.
.TP
.BR MADV_DOFORK " (Since Linux 2.6.16)"
restoring the default behaviour, whereby a mapping is inherited across
.BR fork (2).
.SH "RETURN VALUE"
-On success
+On success
.BR madvise ()
-returns zero. On error, it returns \-1 and
+returns zero.
+On error, it returns \-1 and
.I errno
is set appropriately.
.SH ERRORS
The map exists, but the area maps something that isn't a file.
.TP
.B EINVAL
-The value
+The value
.IR len
is negative,
.\" .I len
.\" is zero,
.I start
is not page-aligned,
-.I advice
+.I advice
is not a valid value, or the application is attempting
to release locked or shared pages (with MADV_DONTNEED).
.TP
.I start
be page-aligned, and allows
.I length
-to be zero. If there are some parts of the specified address range
+to be zero.
+If there are some parts of the specified address range
that are not mapped, the Linux version of
.BR madvise ()
-ignores them and applies the call to the rest (but returns
+ignores them and applies the call to the rest (but returns
.B ENOMEM
from the system call, as it should).
.SH HISTORY
POSIX.1-2001 describes
.BR posix_madvise ()
with constants POSIX_MADV_NORMAL, etc.,
-with a behaviour close to that described here.
+with a behaviour close to that described here.
There is a similar
.BR posix_fadvise ()
for file access.
projects / thirdparty / man-pages.git / blobdiff