Import translated manuals from JM CVS Repository.

[linuxjm/jm.git] / manual / LDP_man-pages / draft / man2 / posix_fadvise.2

.\" Hey Emacs! This file is -*- nroff -*- source.
.\"
.\" Copyright 2003 Abhijit Menon-Sen <ams@wiw.org>
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" 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.\" manual page may be incorrect or out-of-date.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
.\" the use of the information contained herein.  The author(s) may not
.\" 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.
.\"
.\" 2005-04-08 mtk, noted kernel version and added BUGS
.\"
.\" Japanese Version Copyright (c) 2004-2007 Yuichi SATO
.\"         all rights reserved.
.\" Translated Sun Jun 20 16:23:17 JST 2004
.\"         by Yuichi SATO <ysato444@yahoo.co.jp>, LDP v1.66
.\" Updated & Modified Fri Apr 22 03:05:51 JST 2005 by Yuichi SATO, LDP v2.02
.\" Updated & Modified Thu Jan  4 23:55:18 JST 2007 by Yuichi SATO, LDP v2.43
.\"
.TH POSIX_FADVISE 2 2003-02-14 "Linux" "Linux Programmer's Manual"
.\"O .SH NAME
.SH ̾Á°
.\"O posix_fadvise \- predeclare an access pattern for file data
posix_fadvise \- ¥Õ¥¡¥¤¥ë¥Ç¡¼¥¿¤Î¥¢¥¯¥»¥¹¥Ñ¥¿¡¼¥ó¤ò¤¢¤é¤«¤¸¤áÀë¸À¤¹¤ë
.\"O .SH SYNOPSIS
.SH ½ñ¼°
.nf
.B #define _XOPEN_SOURCE 600
.B #include <fcntl.h>
.sp
.BI "int posix_fadvise(int " fd ", off_t " offset ", off_t " len \
", int " advice ");"
.fi
.\"O .SH DESCRIPTION
.SH ÀâÌÀ
.\"O Programs can use
.\"O .BR posix_fadvise ()
.\"O to announce an intention to access
.\"O file data in a specific pattern in the future, thus allowing the kernel
.\"O to perform appropriate optimizations.
¥×¥í¥°¥é¥à¤Ï¡¢¾­ÍèÆÃÄê¤Î¥Ñ¥¿¡¼¥ó¤Ç¥Õ¥¡¥¤¥ë¥Ç¡¼¥¿¤Ë
¥¢¥¯¥»¥¹¤¹¤ë°Õ»×¤òÅÁ¤¨¤ë¤¿¤á¤Ë
.BR posix_fadvise ()
¤ò»È¤¦¤³¤È¤¬¤Ç¤­¤ë¡£
¤³¤ì¤Ë¤è¤ê¡¢¥«¡¼¥Í¥ë¤¬Å¬ÀڤʺÇŬ²½¤ò¼Â¹Ô¤¹¤ë¤³¤È¤¬²Äǽ¤Ë¤Ê¤ë¡£

.\"O The \fIadvice\fP applies to a (not necessarily existent) region starting
.\"O at \fIoffset\fP and extending for \fIlen\fP bytes (or until the end of
.\"O the file if \fIlen\fP is 0) within the file referred to by \fIfd\fP.
.\"O The advice is not binding; it merely constitutes an expectation on behalf of
.\"O the application.
\fIadvice\fP ¤Ï  \fIfd\fP ¤¬»²¾È¤·¤Æ¤¤¤ë¥Õ¥¡¥¤¥ë¤Î
\fIoffset\fP ¤«¤é»Ï¤Þ¤ë \fIlen\fP ¥Ð¥¤¥È¤ÎÈÏ°ÏÆâ
(\fIlen\fP ¤¬ 0 ¤Î¾ì¹ç¤Ï¥Õ¥¡¥¤¥ë¤Î½ª¤ê¤Þ¤Ç) ¤Î
(ɬ¤º¤·¤â¸ºß¤·¤Ê¤¤) Îΰè¤ËŬÍѤµ¤ì¤ë¡£
¥¢¥É¥Ð¥¤¥¹¤ÏµÁ̳¤Å¤±¤Ç¤Ï¤Ê¤¤¡£
¥¢¥É¥Ð¥¤¥¹¤Ïñ¤Ë¥¢¥×¥ê¥±¡¼¥·¥ç¥ó¤Î¤¿¤á¤Ë²ÄǽÀ­¤ò¹½À®¤¹¤ë¤À¤±¤Ç¤¢¤ë¡£

.\"O Permissible values for \fIadvice\fP include:
\fIadvice\fP ¤Ëµö¤µ¤ì¤ëÃͤˤϡ¢°Ê²¼¤Î¤â¤Î¤¬´Þ¤Þ¤ì¤ë:
.TP
.B POSIX_FADV_NORMAL
.\"O Indicates that the application has no advice to give about its access
.\"O pattern for the specified data.
.\"O If no advice is given for an open file,
.\"O this is the default assumption.
»ØÄꤵ¤ì¤¿¥Ç¡¼¥¿¤Î¥¢¥¯¥»¥¹¥Ñ¥¿¡¼¥ó¤ò»Ø¼¨¤¹¤ë¥¢¥É¥Ð¥¤¥¹¤ò
¥¢¥×¥ê¥±¡¼¥·¥ç¥ó¤¬²¿¤â»ý¤Ã¤Æ¤¤¤Ê¤¤¤³¤È¤ò¼¨¤¹¡£
¥ª¡¼¥×¥ó¤µ¤ì¤¿¥Õ¥¡¥¤¥ë¤Ë¥¢¥É¥Ð¥¤¥¹¤¬»ØÄꤵ¤ì¤Ê¤¤¾ì¹ç¡¢
¤³¤ì¤¬¥Ç¥Õ¥©¥ë¥È¤Ç²¾Äꤵ¤ì¤ë¡£
.TP
.B POSIX_FADV_SEQUENTIAL
.\"O The application expects to access the specified data sequentially (with
.\"O lower offsets read before higher ones).
¥¢¥×¥ê¥±¡¼¥·¥ç¥ó¤Ï»ØÄꤵ¤ì¤¿¥Ç¡¼¥¿¤¬¥·¡¼¥±¥ó¥·¥ã¥ë¤Ë
(Â礭¤Ê¥ª¥Õ¥»¥Ã¥È¤ÎÁ°¤Ë¾®¤µ¤Ê¥ª¥Õ¥»¥Ã¥È¤Î¥Ç¡¼¥¿¤òÆɤà¤è¤¦¤Ë)
¥¢¥¯¥»¥¹¤µ¤ì¤ë¤³¤È¤ò´üÂÔ¤¹¤ë¡£
.TP
.B POSIX_FADV_RANDOM
.\"O The specified data will be accessed in random order.
»ØÄꤵ¤ì¤¿¥Ç¡¼¥¿¤¬¥é¥ó¥À¥à¤Ê½çÈ֤ǥ¢¥¯¥»¥¹¤µ¤ì¤ë¡£
.TP
.B POSIX_FADV_NOREUSE
.\"O The specified data will be accessed only once.
»ØÄꤵ¤ì¤¿¥Ç¡¼¥¿¤Ï 1 ÅÙ¤·¤«¥¢¥¯¥»¥¹¤µ¤ì¤Ê¤¤¡£
.TP
.B POSIX_FADV_WILLNEED
.\"O The specified data will be accessed in the near future.
»ØÄꤵ¤ì¤¿¥Ç¡¼¥¿¤Ï¶á¤¤¾­Í襢¥¯¥»¥¹¤µ¤ì¤ë¡£
.TP
.B POSIX_FADV_DONTNEED
.\"O The specified data will not be accessed in the near future.
»ØÄꤵ¤ì¤¿¥Ç¡¼¥¿¤Ï¶á¤¤¾­Í襢¥¯¥»¥¹¤µ¤ì¤Ê¤¤¡£
.\"O .SH "RETURN VALUE"
.SH ÊÖ¤êÃÍ
.\"O On success, zero is returned.
.\"O On error, an error number is returned.
À®¸ù¤·¤¿¾ì¹ç¤Ï 0 ¤¬ÊÖ¤µ¤ì¤ë¡£
¼ºÇÔ¤·¤¿¾ì¹ç¤Ï¥¨¥é¡¼Èֹ椬ÊÖ¤µ¤ì¤ë¡£
.\"O .SH ERRORS
.SH ¥¨¥é¡¼
.TP
.B EBADF
.\"O The \fIfd\fP argument was not a valid file descriptor.
\fIfd\fP °ú¤­¿ô¤¬Í­¸ú¤Ê¥Õ¥¡¥¤¥ë¥Ç¥£¥¹¥¯¥ê¥×¥¿¤Ç¤Ê¤¤¡£
.TP
.B EINVAL
.\"O An invalid value was specified for \fIadvice\fP.
̵¸ú¤ÊÃͤ¬ \fIadvice\fP ¤Ë»ØÄꤵ¤ì¤¿¡£
.TP
.B ESPIPE
.\"O returns EINVAL in this case.)
.\"O The specified file descriptor refers to a pipe or FIFO.
.\"O (Linux actually
.\"O returns
.\"O .B EINVAL
.\"O in this case.)
»ØÄꤵ¤ì¤¿¥Õ¥¡¥¤¥ë¥Ç¥£¥¹¥¯¥ê¥×¥¿¤¬¥Ñ¥¤¥×¤Þ¤¿¤Ï FIFO ¤ò»²¾È¤·¤Æ¤¤¤ë
(¤³¤Î¾ì¹ç¡¢Linux ¤Ï¼ÂºÝ¤Ë¤Ï
.B EINVAL
¤òÊÖ¤¹)¡£
.\"O .SH VERSIONS
.SH ¥Ð¡¼¥¸¥ç¥ó
.\"O .BR posix_fadvise ()
.\"O appeared in kernel 2.5.60.
.\"O .\" Actually as fadvise64() -- MTK
.\"O Glibc support has been provided since version 2.2.
.BR posix_fadvise ()
¤Ï¥«¡¼¥Í¥ë 2.5.60 ¤ÇÅо줷¤¿¡£
.\" ¼ÂºÝ¤Ë¤Ï fadvise64() ¤È¤·¤ÆÅо줷¤¿¡£-- MTK
glibc ¤Ç¤Î¥µ¥Ý¡¼¥È¤Ï glibc ¥Ð¡¼¥¸¥ç¥ó 2.2 °Ê¹ß¤Ç¹Ô¤ï¤ì¤Æ¤¤¤ë¡£
.\"O .SH "CONFORMING TO"
.SH ½àµò
POSIX.1-2001.
.\"O Note that the type of the
.\"O .I len
.\"O argument was changed from
.\"O .I size_t
.\"O to
.\"O .I off_t
.\"O in POSIX.1-2003 TC1.
.I len
°ú¤­¿ô¤Î·¿¤¬ POSIX.1-2003 TC1 ¤Ë¤ª¤¤¤Æ
.I size_t
¤«¤é
.I off_t
¤ËÊѹ¹¤µ¤ì¤¿ÅÀ¤ËÃí°Õ¤¹¤ë¤³¤È¡£
.\"O .SH NOTES
.\"O Under Linux, \fBPOSIX_FADV_NORMAL\fP sets the readahead window to the
.\"O default size for the backing device; \fBPOSIX_FADV_SEQUENTIAL\fP doubles
.\"O this size, and \fBPOSIX_FADV_RANDOM\fP disables file readahead entirely.
.SH Ãí°Õ
Linux ¤Ç¤Ï¡¢\fBPOSIX_FADV_NORMAL\fP ¤Ï¥Ð¥Ã¥­¥ó¥°¥Ç¥Ð¥¤¥¹¤Î
¥Ç¥Õ¥©¥ë¥È¥µ¥¤¥º¤ËÀèÆÉ¤ß (readahead) ¥¦¥¤¥ó¥É¥¦¤òÀßÄꤹ¤ë¡£
\fBPOSIX_FADV_SEQUENTIAL\fP ¤Ï¤³¤Î¥µ¥¤¥º¤ò 2 Çܤ·¡¢
\fBPOSIX_FADV_RANDOM\fP ¤ÏÀèÆɤߤòÁ´¤¯Ìµ¸ú¤Ë¤¹¤ë¡£
.\"O These changes affect the entire file, not just the specified region
.\"O (but other open file handles to the same file are unaffected).
¤³¤ì¤é¤ÎÊѹ¹¤Ï¥Õ¥¡¥¤¥ëÁ´ÂΤ˱ƶÁ¤·¡¢»ØÄꤵ¤ì¤¿Îΰè¤Î¤ß¤Ë±Æ¶Á¤¹¤ë¤ï¤±¤Ç¤Ï¤Ê¤¤
(¤·¤«¤·Æ±¤¸¥Õ¥¡¥¤¥ë¤ËÂФ¹¤ë¾¤Î¥ª¡¼¥×¥ó¥Õ¥¡¥¤¥ë¥Ï¥ó¥É¥ë¤Ï±Æ¶Á¤ò¼õ¤±¤Ê¤¤)¡£

.\"O \fBPOSIX_FADV_WILLNEED\fP initiates a
.\"O nonblocking read of the specified region into the page cache.
.\"O The amount of data read may be decreased by the kernel depending
.\"O on virtual memory load.
.\"O (A few megabytes will usually be fully satisfied,
.\"O and more is rarely useful.)
\fBPOSIX_FADV_WILLNEED\fP ¤Ï¡¢
¥Ú¡¼¥¸¥­¥ã¥Ã¥·¥å¤Ë»ØÄêÎΰè¤Î¥Ö¥í¥Ã¥¯¤µ¤ì¤Ê¤¤Æɤ߹þ¤ß¤ò³«»Ï¤¹¤ë¡£
Æɤ߹þ¤Þ¤ì¤ë¥Ç¡¼¥¿¤ÎÁíÎ̤ϡ¢
²¾ÁÛ¥á¥â¥ê¤ÎÉé²Ù¤Ë°Í¤Ã¤Æ¥«¡¼¥Í¥ë¤¬¸º¤é¤¹¤«¤â¤·¤ì¤Ê¤¤
(¿ô¥á¥¬¥Ð¥¤¥È¤Ç¤¢¤ì¤ÐÄ̾ï¤ÏÁ´¤¯½½Ê¬¤Ç¤¢¤ê¡¢
¤½¤ì¤è¤ê¿¤¯¤Æ¤â¤á¤Ã¤¿¤ËÌò¤ËΩ¤¿¤Ê¤¤)¡£

.\"O In kernels before 2.6.18, \fBPOSIX_FADV_NOREUSE\fP had the
.\"O same semantics as \fBPOSIX_FADV_WILLNEED\fP.
.\"O This was probably a bug; since kernel 2.6.18, this flag is a no-op.
2.6.18 ¤è¤êÁ°¤Î¥«¡¼¥Í¥ë¤Ç¤Ï¡¢\fBPOSIX_FADV_NOREUSE\fP ¤Ï
\fBPOSIX_FADV_WILLNEED\fP ¤ÈƱ¤¸°ÕÌ£¤Ç¤¢¤Ã¤¿¡£
¤³¤ì¤Ï¿ʬ¥Ð¥°¤Ç¤¢¤Ã¤¿¡£
¥«¡¼¥Í¥ë 2.6.18 °Ê¹ß¤Ç¤Ï¡¢¤³¤Î¥Õ¥é¥°¤Ï²¿¤â¹Ô¤ï¤Ê¤¤¡£

.\"O \fBPOSIX_FADV_DONTNEED\fP attempts to free cached pages associated with
.\"O the specified region.
.\"O This is useful, for example, while streaming large
.\"O files.
.\"O A program may periodically request the kernel to free cached data
.\"O that has already been used, so that more useful cached pages are not
.\"O discarded instead.
\fBPOSIX_FADV_DONTNEED\fP ¤Ï»ØÄꤵ¤ì¤¿Îΰè¤Ë´ØÏ¢ÉÕ¤±¤é¤ì¤¿
¥­¥ã¥Ã¥·¥å¥Ú¡¼¥¸¤ò²òÊü¤·¤è¤¦¤È¤¹¤ë¡£
Î㤨¤Ð¡¢¤³¤ì¤ÏÂ礭¤Ê¥Õ¥¡¥¤¥ë¤ò¥¹¥È¥ê¡¼¥ß¥ó¥°¤¹¤ë¤È¤­¤ËÌòΩ¤Ä¡£
¥×¥í¥°¥é¥à¤Ï¡¢»ÈÍѺѤߤΥ­¥ã¥Ã¥·¥å¤µ¤ì¤¿¥Ç¡¼¥¿¤ò²òÊü¤¹¤ë¤è¤¦¤Ë¡¢
Äê´üŪ¤Ë¥«¡¼¥Í¥ë¤ËÍ׵᤹¤ë¤«¤â¤·¤ì¤Ê¤¤¡£
¤½¤¦¤¹¤ë¤³¤È¤Ë¤è¤ê¡¢¤µ¤é¤ËÍ­¸ú¤Ê¥­¥ã¥Ã¥·¥å¤µ¤ì¤¿¥Ú¡¼¥¸¤¬¡¢
Âå¤ï¤ê¤ËÇË´þ¤µ¤ì¤ë¤³¤È¤Ï¤Ê¤¤¡£

.\"O Pages that have not yet been written out will be unaffected, so if the
.\"O application wishes to guarantee that pages will be released, it should
.\"O call
.\"O .BR fsync (2)
.\"O or
.\"O .BR fdatasync (2)
.\"O first.
¤Þ¤À½ñ¤­½Ð¤µ¤ì¤Æ¤¤¤Ê¤¤¥Ú¡¼¥¸¤Ï±Æ¶Á¤ò¼õ¤±¤Ê¤¤¤Î¤Ç¡¢
¤½¤Î¥Ú¡¼¥¸¤Î²òÊü¤¬Êݾڤµ¤ì¤ë¤³¤È¤ò¥¢¥×¥ê¥±¡¼¥·¥ç¥ó¤¬Ë¾¤ó¤Ç¤¤¤ë¤Ê¤é¡¢
ºÇ½é¤Ë
.BR fsync (2)
¤Þ¤¿¤Ï
.BR fdatasync (2)
¤ò¸Æ¤Ö¤Ù¤­¤Ç¤¢¤ë¡£
.\"O .SH BUGS
.SH ¥Ð¥°
.\"O In kernels before 2.6.6, if
.\"O .I len
.\"O was specified as 0, then this was interpreted literally as "zero bytes",
.\"O rather than as meaning "all bytes through to the end of the file".
2.6.6 ¤è¤êÁ°¤Î¥«¡¼¥Í¥ë¤Ç¤Ï¡¢
.I len
¤Ë 0 ¤¬»ØÄꤵ¤ì¤¿¾ì¹ç¡¢
¡Ö¥Õ¥¡¥¤¥ë¤Î½ª¤ê¤Þ¤Ç¤ÎÁ´¤Æ¤Î¥Ð¥¤¥È¡×¤È¤¤¤¦°ÕÌ£¤Ç¤Ï¤Ê¤¯¡¢
ʸ»úÄ̤ê¡Ö0 ¥Ð¥¤¥È¡×¤È¤·¤Æ²ò¼á¤µ¤ì¤Æ¤¤¤¿¡£
.\"O .SH "SEE ALSO"
.SH ´ØÏ¢¹àÌÜ
.BR readahead (2),
.BR posix_fallocate (3),
.BR posix_madvise (3),
.\" FIXME . Write a posix_fadvise(3) page.
.BR feature_test_macros (7)