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fadvise
Langue: en
Version: 2008-11-08 (ubuntu - 07/07/09)
Section: 1 (Commandes utilisateur)
NAME
fadvise - File ADVISE: give file advisory informationSYNOPSIS
fadvise [options] file [...]Options: -help - brief help message -man - full documentation -sequential -random -willneed -dontneed -noreuse -normal (default) -offset=n -length=n -verbose -noverbose
OPTIONS
- -help
- Shows usage information and exits.
- -man
- Shows the manual page and exits.
- -offset=n
- Specifies offset for fadvise. Defaults to zero if unspecified.
- -length=n
- Specifies length for fadvise. Defaults to zero if unspecified, i.e. the whole file if offset is also zero.
- -verbose
- Shows incore page info after fadvise.
- -noverbose
- Doesn't show incore page info after fadvise. This is the default.
- -sequential
- Announces the expectation to access the file sequentially.
- -random
- Announces the expectation to access the file randomly.
- -willneed
- Announces the expectation that file content will be needed in the near future.
- -dontneed
- Announces the expectation that file content won't be needed in the near future.
Under Linux 2.6.9, this is known to cause the file content to be evicted from the buffer-cache immediately.
Note that this option first causes an fsync of the file.
- -noreuse
- Announces the expectation that file content won't be reused in the near future.
- -normal
- Announces the expectation to access the file normally. This is the default.
DESCRIPTION
fadvise is a command used to give file advisory information to the operating system.Its ``don't need'' option (fadvise --dontneed) is particularly useful to cause the files' pages (blocks) to be evicted from the buffer-cache.
EXAMPLE
$ fadvise --verbose --dontneed foo.rrd page size: 4096 foo.rrd: no incore pages.
BUGS
-dontneed might be the only really useful option.In verbose mode, you may get an error from mincore such as ``cannot allocate memory'' if the file size is zero.
Some operating systems have posix_fadvise, but it doesn't work. For instance under Linux 2.4, you may see this error:
posix_fadvise: Inappropriate ioctl for device
AUTHOR
Dave Plonka <plonka@cs.wisc.edu>Copyright (C) 2007 Dave Plonka. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
VERSION
This is fadvise $Revision: 1.5 $.SEE ALSO
The fincore command.Contenus ©2006-2024 Benjamin Poulain
Design ©2006-2024 Maxime Vantorre