27b9567d6113422e4fc25d9563ebff80ae8cff9d
[sfrench/samba-autobuild/.git] / docs-xml / manpages / vfs_preopen.8.xml
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">3.6</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>