NAME
SYNOPSIS
OPTIONS
DESCRIPTION
EXAMPLE
BUGS
AUTHOR
VERSION
SEE ALSO

NAME

fadvise - File ADVISE: give file advisory information

SYNOPSIS

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 $.