fadvise(1)

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 $.

SEE ALSO

The fincore command.

perl v5.10.0 2008-11-08 FADVISE(1)