1<!--$Id: mutex_set_align.so,v 10.1 2005/07/20 16:34:00 bostic Exp $--> 2<!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> 3<!--See the file LICENSE for redistribution information.--> 4<html> 5<head> 6<title>Berkeley DB: DB_ENV->mutex_set_align</title> 7<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> 8<meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> 9</head> 10<body bgcolor=white> 11<table width="100%"><tr valign=top> 12<td> 13<b>DB_ENV->mutex_set_align</b> 14</td> 15<td align=right> 16<a href="../api_c/api_core.html"><img src="../images/api.gif" alt="API"></a> 17<a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a></td> 18</tr></table> 19<hr size=1 noshade> 20<tt> 21<b><pre> 22#include <db.h> 23<p> 24int 25DB_ENV->mutex_set_align(DB_ENV *dbenv, u_int32_t align); 26<p> 27int 28DB_ENV->mutex_get_align(DB_ENV *dbenv, u_int32_t *alignp); 29</pre></b> 30<hr size=1 noshade> 31<b>Description: DB_ENV->mutex_set_align</b> 32<p>Set the mutex alignment, in bytes.</p> 33<p>It is sometimes advantageous to align mutexes on specific byte 34boundaries in order to minimize cache line collisions. The 35DB_ENV->mutex_set_align method specifies an alignment for mutexes allocated 36by Berkeley DB.</p> 37<p>The database environment's mutex alignment may also be configured using the 38environment's <a href="../ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file. The syntax of the entry in that 39file is a single line with the string "mutex_set_align", one or more whitespace 40characters, and the mutex alignment in bytes. 41Because the <a href="../ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file is read when the database environment 42is opened, it will silently overrule configuration done before that 43time.</p> 44<p>The DB_ENV->mutex_set_align method configures a database environment, not only operations 45performed using the specified <a href="../api_c/env_class.html">DB_ENV</a> handle.</p> 46<p>The DB_ENV->mutex_set_align method may not be called after the <a href="../api_c/env_open.html">DB_ENV->open</a> method is 47called. 48If the database environment already exists when 49<a href="../api_c/env_open.html">DB_ENV->open</a> is called, the information specified to DB_ENV->mutex_set_align 50will be ignored. 51</p> 52<p>The DB_ENV->mutex_set_align method 53returns a non-zero error value on failure 54and 0 on success. 55</p> 56<b>Parameters</b> <br> 57 <b>align</b><ul compact><li>The <b>align</b> parameter is the mutex alignment, in bytes. The mutex 58alignment must be a power-of-two.</ul> 59<br> 60<br><b>Errors</b> 61<p>The DB_ENV->mutex_set_align method 62may fail and return one of the following non-zero errors:</p> 63<br> 64<b>EINVAL</b><ul compact><li>An 65invalid flag value or parameter was specified.</ul> 66<br> 67<hr size=1 noshade> 68<b>Description: DB_ENV->mutex_get_align</b> 69<p>The DB_ENV->mutex_get_align method returns the mutex alignment, in bytes.</p> 70<p>The DB_ENV->mutex_get_align method may be called at any time during the life of the 71application.</p> 72<p>The DB_ENV->mutex_get_align method 73returns a non-zero error value on failure 74and 0 on success. 75</p> 76<b>Parameters</b> <br> 77 <b>alignp</b><ul compact><li>The DB_ENV->mutex_get_align method returns the 78mutex alignment, in bytes in <b>alignp</b>.</ul> 79<br> 80<hr size=1 noshade> 81<br><b>Class</b> 82<a href="../api_c/env_class.html">DB_ENV</a> 83<br><b>See Also</b> 84<a href="../api_c/env_list.html">Database Environments and Related Methods</a> 85</tt> 86<table width="100%"><tr><td><br></td><td align=right> 87<a href="../api_c/api_core.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a> 88</td></tr></table> 89<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> 90</body> 91</html> 92
