1 <?xml version="1.0" encoding="iso-8859-1"?>
2 <!DOCTYPE refentry PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc">
3 <refentry id="vfs_readahead.8">
6 <refentrytitle>vfs_readahead</refentrytitle>
7 <manvolnum>8</manvolnum>
12 <refname>vfs_readahead</refname>
13 <refpurpose>pre-load the kernel buffer cache</refpurpose>
18 <command>vfs objects = readahead</command>
23 <title>DESCRIPTION</title>
25 <para>This VFS module is part of the
26 <citerefentry><refentrytitle>samba</refentrytitle>
27 <manvolnum>7</manvolnum></citerefentry> suite.</para>
29 <para>This <command>vfs_readahead</command> VFS module detects
30 read requests at multiples of a given offset (hex 0x80000 by
31 default) and then tells the kernel via either the readahead
32 system call (on Linux) or the posix_fadvise system call to
33 pre-fetch this data into the buffer cache.</para>
35 <para>This module is useful for Windows Vista clients reading
36 data using the Windows Explorer program, which asynchronously
37 does multiple file read requests at offset boundaries of 0x80000
40 <para>The offset multiple used is given by the readahead:offset
41 option, which defaults to 0x80000.</para>
43 <para>The size of the disk read operations performed
44 by <command>vfs_readahead</command> is determined by the
45 readahead:length option. By default this is set to the
46 same value as the readahead:offset option and if not
47 set explicitly will use the current value of
48 readahead:offset.</para>
50 <para>This module is stackable.</para>
54 <title>OPTIONS</title>
59 <term>readahead:offset = BYTES</term>
61 <para>The offset multiple that causes readahead to be
62 requested of the kernel buffer cache.</para>
67 <term>readahead:length = BYTES</term>
69 <para>The number of bytes requested to be
70 read into the kernel buffer cache on each
71 readahead call.</para>
75 <para>The following suffixes may be applied to BYTES:</para>
77 <listitem><para><command>K</command> - BYTES is a number of kilobytes</para></listitem>
78 <listitem><para><command>M</command> - BYTES is a number of megabytes</para></listitem>
79 <listitem><para><command>G</command> - BYTES is a number of gigabytes</para></listitem>
87 <title>EXAMPLES</title>
90 <smbconfsection name="[hypothetical]"/>
91 <smbconfoption name="vfs objects">readahead</smbconfoption>
97 <title>VERSION</title>
98 <para>This man page is correct for version 3.0.25 of the Samba suite.
103 <title>AUTHOR</title>
105 <para>The original Samba software and related utilities
106 were created by Andrew Tridgell. Samba is now developed
107 by the Samba Team as an Open Source project similar
108 to the way the Linux kernel is developed.</para>