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_preopen.8"> 4 5<refmeta> 6 <refentrytitle>vfs_preopen</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<refnamediv> 14 <refname>vfs_preopen</refname> 15 <refpurpose>Hide read latencies for applications reading numbered files</refpurpose> 16</refnamediv> 17 18<refsynopsisdiv> 19 <cmdsynopsis> 20 <command>vfs objects = preopen</command> 21 </cmdsynopsis> 22</refsynopsisdiv> 23 24<refsect1> 25 <title>DESCRIPTION</title> 26 27 <para>This VFS module is part of the 28 <citerefentry><refentrytitle>samba</refentrytitle> 29 <manvolnum>7</manvolnum></citerefentry> suite.</para> 30 31 <para>This module assists applications that want to read numbered 32 files in sequence with very strict latency requirements. One area 33 where this happens in video streaming applications that want to read 34 one file per frame.</para> 35 36 <para>When you use this module, a number of helper processes is 37 started that speculatively open files and read a number of bytes to 38 prime the file system cache, so that later on when the real 39 application's request comes along, no disk access is necessary.</para> 40 41 <para>This module is stackable.</para> 42 43</refsect1> 44 45 46<refsect1> 47 <title>OPTIONS</title> 48 49 <variablelist> 50 51 <varlistentry> 52 <term>preopen:names = /pattern/</term> 53 <listitem> 54 <para> 55 preopen:names specifies the file name pattern which should 56 trigger the preopen helpers to do their work. We assume that 57 the files are numbered incrementally. So if your file names 58 are numbered FRAME00000.frm FRAME00001.frm and so on you would 59 list them as <command>preopen:names=/FRAME*.frm/</command> 60 </para> 61 </listitem> 62 </varlistentry> 63 64 <varlistentry> 65 <term>preopen:num_bytes = BYTES</term> 66 <listitem> 67 <para> 68 Specifies the number of bytes the helpers should speculatively 69 read, defaults to 1. 70 </para> 71 </listitem> 72 </varlistentry> 73 74 <varlistentry> 75 <term>preopen:helpers = NUM-PROCS</term> 76 <listitem> 77 <para> 78 Number of forked helper processes, defaults to 1. 79 </para> 80 </listitem> 81 </varlistentry> 82 83 <varlistentry> 84 <term>preopen:queuelen = NUM-FILES</term> 85 <listitem> 86 <para> 87 Number of files that should be speculatively opened. Defaults 88 to the 10 subsequent files. 89 </para> 90 </listitem> 91 </varlistentry> 92 93 </variablelist> 94</refsect1> 95 96<refsect1> 97 <title>VERSION</title> 98 <para>This man page is correct for version 3.3 of the Samba suite. 99 </para> 100</refsect1> 101 102<refsect1> 103 <title>AUTHOR</title> 104 105 <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> 109 110 <para>The PREOPEN VFS module was created with contributions from 111 Volker Lendecke and the developers at IBM. 112 </para> 113</refsect1> 114 115</refentry> 116