source: vendor/3.5.4/docs-xml/manpages-3/vfs_readahead.8.xml

<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE refentry PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc">
<refentry id="vfs_readahead.8">

<refmeta>
        <refentrytitle>vfs_readahead</refentrytitle>
        <manvolnum>8</manvolnum>
        <refmiscinfo class="source">Samba</refmiscinfo>
        <refmiscinfo class="manual">System Administration tools</refmiscinfo>
        <refmiscinfo class="version">3.5</refmiscinfo>
</refmeta>


<refnamediv>
        <refname>vfs_readahead</refname>
        <refpurpose>pre-load the kernel buffer cache</refpurpose>
</refnamediv>

<refsynopsisdiv>
        <cmdsynopsis>
                <command>vfs objects = readahead</command>
        </cmdsynopsis>
</refsynopsisdiv>

<refsect1>
        <title>DESCRIPTION</title>

        <para>This VFS module is part of the
        <citerefentry><refentrytitle>samba</refentrytitle>
        <manvolnum>7</manvolnum></citerefentry> suite.</para>

        <para>This <command>vfs_readahead</command> VFS module detects
        read requests at multiples of a given offset (hex 0x80000 by
        default) and then tells the kernel via either the readahead
        system call (on Linux) or the posix_fadvise system call to
        pre-fetch this data into the buffer cache.</para>

        <para>This module is useful for Windows Vista clients reading
        data using the Windows Explorer program, which asynchronously
        does multiple file read requests at offset boundaries of 0x80000
        bytes.</para>

        <para>The offset multiple used is given by the readahead:offset
        option, which defaults to 0x80000.</para>

        <para>The size of the disk read operations performed
        by <command>vfs_readahead</command> is determined by the
        readahead:length option. By default this is set to the
        same value as the readahead:offset option and if not
        set explicitly will use the current value of
        readahead:offset.</para>

        <para>This module is stackable.</para>
</refsect1>

<refsect1>
        <title>OPTIONS</title>

        <variablelist>

                <varlistentry>
                <term>readahead:offset = BYTES</term>
                <listitem>
                <para>The offset multiple that causes readahead to be
                requested of the kernel buffer cache.</para>
                </listitem>
                </varlistentry>

                <varlistentry>
                <term>readahead:length = BYTES</term>
                <listitem>
                <para>The number of bytes requested to be
                read into the kernel buffer cache on each
                readahead call.</para>
                </listitem>
                </varlistentry>

                <para>The following suffixes may be applied to BYTES:</para>
                <itemizedlist>
                <listitem><para><command>K</command> - BYTES is a number of kilobytes</para></listitem>
                <listitem><para><command>M</command> - BYTES is a number of megabytes</para></listitem>
                <listitem><para><command>G</command> - BYTES is a number of gigabytes</para></listitem>
                </itemizedlist>


        </variablelist>
</refsect1>

<refsect1>
        <title>EXAMPLES</title>

<programlisting>
        <smbconfsection name="[hypothetical]"/>
        <smbconfoption name="vfs objects">readahead</smbconfoption>
</programlisting>

</refsect1>

<refsect1>
        <title>VERSION</title>
        <para>This man page is correct for version 3.0.25 of the Samba suite.
        </para>
</refsect1>

<refsect1>
        <title>AUTHOR</title>

        <para>The original Samba software and related utilities
        were created by Andrew Tridgell. Samba is now developed
        by the Samba Team as an Open Source project similar
        to the way the Linux kernel is developed.</para>

</refsect1>

</refentry>