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"> 4 5<refmeta> 6 <refentrytitle>vfs_readahead</refentrytitle> 7 <manvolnum>8</manvolnum> 8 <refmiscinfo class="source">Samba</refmiscinfo> 9 <refmiscinfo class="manual">System Administration tools</refmiscinfo> 10 <refmiscinfo class="version">3.5</refmiscinfo> 11</refmeta> 12 13 14<refnamediv> 15 <refname>vfs_readahead</refname> 16 <refpurpose>pre-load the kernel buffer cache</refpurpose> 17</refnamediv> 18 19<refsynopsisdiv> 20 <cmdsynopsis> 21 <command>vfs objects = readahead</command> 22 </cmdsynopsis> 23</refsynopsisdiv> 24 25<refsect1> 26 <title>DESCRIPTION</title> 27 28 <para>This VFS module is part of the 29 <citerefentry><refentrytitle>samba</refentrytitle> 30 <manvolnum>7</manvolnum></citerefentry> suite.</para> 31 32 <para>This <command>vfs_readahead</command> VFS module detects 33 read requests at multiples of a given offset (hex 0x80000 by 34 default) and then tells the kernel via either the readahead 35 system call (on Linux) or the posix_fadvise system call to 36 pre-fetch this data into the buffer cache.</para> 37 38 <para>This module is useful for Windows Vista clients reading 39 data using the Windows Explorer program, which asynchronously 40 does multiple file read requests at offset boundaries of 0x80000 41 bytes.</para> 42 43 <para>The offset multiple used is given by the readahead:offset 44 option, which defaults to 0x80000.</para> 45 46 <para>The size of the disk read operations performed 47 by <command>vfs_readahead</command> is determined by the 48 readahead:length option. By default this is set to the 49 same value as the readahead:offset option and if not 50 set explicitly will use the current value of 51 readahead:offset.</para> 52 53 <para>This module is stackable.</para> 54</refsect1> 55 56<refsect1> 57 <title>OPTIONS</title> 58 59 <variablelist> 60 61 <varlistentry> 62 <term>readahead:offset = BYTES</term> 63 <listitem> 64 <para>The offset multiple that causes readahead to be 65 requested of the kernel buffer cache.</para> 66 </listitem> 67 </varlistentry> 68 69 <varlistentry> 70 <term>readahead:length = BYTES</term> 71 <listitem> 72 <para>The number of bytes requested to be 73 read into the kernel buffer cache on each 74 readahead call.</para> 75 </listitem> 76 </varlistentry> 77 78 <para>The following suffixes may be applied to BYTES:</para> 79 <itemizedlist> 80 <listitem><para><command>K</command> - BYTES is a number of kilobytes</para></listitem> 81 <listitem><para><command>M</command> - BYTES is a number of megabytes</para></listitem> 82 <listitem><para><command>G</command> - BYTES is a number of gigabytes</para></listitem> 83 </itemizedlist> 84 85 86 </variablelist> 87</refsect1> 88 89<refsect1> 90 <title>EXAMPLES</title> 91 92<programlisting> 93 <smbconfsection name="[hypothetical]"/> 94 <smbconfoption name="vfs objects">readahead</smbconfoption> 95</programlisting> 96 97</refsect1> 98 99<refsect1> 100 <title>VERSION</title> 101 <para>This man page is correct for version 3.0.25 of the Samba suite. 102 </para> 103</refsect1> 104 105<refsect1> 106 <title>AUTHOR</title> 107 108 <para>The original Samba software and related utilities 109 were created by Andrew Tridgell. Samba is now developed 110 by the Samba Team as an Open Source project similar 111 to the way the Linux kernel is developed.</para> 112 113</refsect1> 114 115</refentry> 116