1<?xml version="1.0" encoding="UTF-8" standalone="no"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml"> 4 <head> 5 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> 6 <title>DB_ENV->mutex_set_align()</title> 7 <link rel="stylesheet" href="apiReference.css" type="text/css" /> 8 <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> 9 <link rel="start" href="index.html" title="Berkeley DB C API Reference" /> 10 <link rel="up" href="mutex.html" title="Chapter 9. Mutex Methods" /> 11 <link rel="prev" href="mutexlock.html" title="DB_ENV->mutex_lock()" /> 12 <link rel="next" href="mutexset_increment.html" title="DB_ENV->mutex_set_increment()" /> 13 </head> 14 <body> 15 <div class="navheader"> 16 <table width="100%" summary="Navigation header"> 17 <tr> 18 <th colspan="3" align="center">DB_ENV->mutex_set_align()</th> 19 </tr> 20 <tr> 21 <td width="20%" align="left"><a accesskey="p" href="mutexlock.html">Prev</a> </td> 22 <th width="60%" align="center">Chapter 9. 23 Mutex Methods 24 </th> 25 <td width="20%" align="right"> <a accesskey="n" href="mutexset_increment.html">Next</a></td> 26 </tr> 27 </table> 28 <hr /> 29 </div> 30 <div class="sect1" lang="en" xml:lang="en"> 31 <div class="titlepage"> 32 <div> 33 <div> 34 <h2 class="title" style="clear: both"><a id="mutexset_align"></a>DB_ENV->mutex_set_align()</h2> 35 </div> 36 </div> 37 </div> 38 <pre class="programlisting">#include <db.h> 39 40int 41DB_ENV->mutex_set_align(DB_ENV *dbenv, u_int32_t align); </pre> 42 <p> 43 Set the mutex alignment, in bytes. 44 </p> 45 <p> 46 It is sometimes advantageous to align mutexes on specific byte 47 boundaries in order to minimize cache line collisions. The 48 <code class="methodname">DB_ENV->mutex_set_align()</code> method specifies an alignment for mutexes 49 allocated by Berkeley DB. 50 </p> 51 <p> 52 The database environment's mutex alignment may also be configured 53 using the environment's <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file. The 54 syntax of the entry in that file is a single line with the string 55 "mutex_set_align", one or more whitespace characters, and the mutex 56 alignment in bytes. Because the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file is 57 read when the database environment is opened, it will silently 58 overrule configuration done before that time. 59 </p> 60 <p> 61 The <code class="methodname">DB_ENV->mutex_set_align()</code> method configures a database 62 environment, not only operations performed using the specified 63 <a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a> handle. 64 </p> 65 <p> 66 The <code class="methodname">DB_ENV->mutex_set_align()</code> method may not be called after the 67 <a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a> method is 68 called. If the database environment already exists when 69 <a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a> is called, the 70 information specified to <code class="methodname">DB_ENV->mutex_set_align()</code> will be ignored. 71 </p> 72 <p> 73 The <code class="methodname">DB_ENV->mutex_set_align()</code> <span> 74 <span> 75 method returns a non-zero error value on failure and 0 on success. 76 </span> 77 78 </span> 79 </p> 80 <div class="sect2" lang="en" xml:lang="en"> 81 <div class="titlepage"> 82 <div> 83 <div> 84 <h3 class="title"><a id="id1694350"></a>Parameters</h3> 85 </div> 86 </div> 87 </div> 88 <div class="sect3" lang="en" xml:lang="en"> 89 <div class="titlepage"> 90 <div> 91 <div> 92 <h4 class="title"><a id="id1694355"></a>align</h4> 93 </div> 94 </div> 95 </div> 96 <p> 97 The <span class="bold"><strong>align</strong></span> parameter is the mutex 98 alignment, in bytes. The mutex alignment must be a power-of-two. 99 </p> 100 </div> 101 </div> 102 <div class="sect2" lang="en" xml:lang="en"> 103 <div class="titlepage"> 104 <div> 105 <div> 106 <h3 class="title"><a id="id1694501"></a>Errors</h3> 107 </div> 108 </div> 109 </div> 110 <p> 111 The <code class="methodname">DB_ENV->mutex_set_align()</code> <span> 112 <span> 113 method may fail and return one of the following non-zero errors: 114 </span> 115 116 </span> 117 </p> 118 <div class="sect3" lang="en" xml:lang="en"> 119 <div class="titlepage"> 120 <div> 121 <div> 122 <h4 class="title"><a id="id1694443"></a>EINVAL</h4> 123 </div> 124 </div> 125 </div> 126 <p> 127 If the method was called after <a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a> 128 was called; or if an invalid flag value or parameter was specified. 129 </p> 130 </div> 131 </div> 132 <div class="sect2" lang="en" xml:lang="en"> 133 <div class="titlepage"> 134 <div> 135 <div> 136 <h3 class="title"><a id="id1694433"></a>Class</h3> 137 </div> 138 </div> 139 </div> 140 <p> 141 <a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a> 142 </p> 143 </div> 144 <div class="sect2" lang="en" xml:lang="en"> 145 <div class="titlepage"> 146 <div> 147 <div> 148 <h3 class="title"><a id="id1694307"></a>See Also</h3> 149 </div> 150 </div> 151 </div> 152 <p> 153 <a class="xref" href="mutex.html#mutexlist" title="Mutex Methods">Mutex Methods</a> 154 </p> 155 </div> 156 </div> 157 <div class="navfooter"> 158 <hr /> 159 <table width="100%" summary="Navigation footer"> 160 <tr> 161 <td width="40%" align="left"><a accesskey="p" href="mutexlock.html">Prev</a> </td> 162 <td width="20%" align="center"> 163 <a accesskey="u" href="mutex.html">Up</a> 164 </td> 165 <td width="40%" align="right"> <a accesskey="n" href="mutexset_increment.html">Next</a></td> 166 </tr> 167 <tr> 168 <td width="40%" align="left" valign="top">DB_ENV->mutex_lock() </td> 169 <td width="20%" align="center"> 170 <a accesskey="h" href="index.html">Home</a> 171 </td> 172 <td width="40%" align="right" valign="top"> DB_ENV->mutex_set_increment()</td> 173 </tr> 174 </table> 175 </div> 176 </body> 177</html> 178