1<!--$Id: mutex_stat.so,v 10.4 2007/09/21 20:06:03 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: DbEnv::mutex_stat</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>DbEnv::mutex_stat</b> 14</td> 15<td align=right> 16<a href="../api_cxx/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_cxx.h> 23<p> 24int 25DbEnv::mutex_stat(DB_MUTEX_STAT **statp, u_int32_t flags); 26<p> 27int 28DbEnv::mutex_stat_print(u_int32_t flags); 29</pre></b> 30<hr size=1 noshade> 31<b>Description: DbEnv::mutex_stat</b> 32<p>The DbEnv::mutex_stat method returns the mutex subsystem statistics.</p> 33<p>The DbEnv::mutex_stat method creates a statistical structure of type 34DB_MUTEX_STAT and copies a pointer to it into a user-specified memory 35location.</p> 36<p>Statistical structures are stored in allocated memory. If application-specific allocation 37routines have been declared (see <a href="../api_cxx/env_set_alloc.html">DbEnv::set_alloc</a> for more 38information), they are used to allocate the memory; otherwise, the 39standard C library <b>malloc</b>(3) is used. The caller is 40responsible for deallocating the memory. To deallocate the memory, free 41the memory reference; references inside the returned memory need not be 42individually freed.</p> 43<p>The following DB_MUTEX_STAT fields will be filled in:</p> 44<br> 45<b>u_int32_t st_mutex_align;</b><ul compact><li>The mutex alignment, in bytes.</ul> 46<b>u_int32_t st_mutex_tas_spins;</b><ul compact><li>The number of times test-and-set mutexes will spin without blocking.</ul> 47<b>int st_mutex_cnt;</b><ul compact><li>The total number of mutexes configured.</ul> 48<b>u_int32_t st_mutex_free;</b><ul compact><li>The number of mutexes currently available.</ul> 49<b>u_int32_t st_mutex_inuse;</b><ul compact><li>The number of mutexes currently in use.</ul> 50<b>u_int32_t st_mutex_inuse_max;</b><ul compact><li>The maximum number of mutexes ever in use.</ul> 51<b>roff_t st_regsize;</b><ul compact><li>The size of the mutex region, in bytes.</ul> 52<b>u_int32_t st_region_wait;</b><ul compact><li>The number of times that a thread of control was forced to wait before 53obtaining the mutex region mutex.</ul> 54<b>u_int32_t st_region_nowait;</b><ul compact><li>The number of times that a thread of control was able to obtain 55the mutex region mutex without waiting.</ul> 56<br> 57<p>The DbEnv::mutex_stat method may not be called before the <a href="../api_cxx/env_open.html">DbEnv::open</a> method is called.</p> 58<p>The DbEnv::mutex_stat method 59either returns a non-zero error value 60or throws an exception that encapsulates a non-zero error value on 61failure, and returns 0 on success. 62</p> 63<b>Parameters</b> <br> 64 <b>flags</b><ul compact><li>The <b>flags</b> parameter must be set to 0 or 65the following value: 66<br> 67<b><a name="DB_STAT_CLEAR">DB_STAT_CLEAR</a></b><ul compact><li>Reset statistics after returning their values.</ul> 68<br></ul> 69 <b>statp</b><ul compact><li>The <b>statp</b> parameter references memory into which 70a pointer to the allocated statistics structure is copied.</ul> 71<br> 72<br><b>Errors</b> 73<p>The DbEnv::mutex_stat method 74may fail and throw 75<a href="../api_cxx/except_class.html">DbException</a>, 76encapsulating one of the following non-zero errors, or return one of 77the following non-zero errors:</p> 78<br> 79<b>EINVAL</b><ul compact><li>An 80invalid flag value or parameter was specified.</ul> 81<br> 82<hr size=1 noshade> 83<b>Description: DbEnv::mutex_stat_print</b> 84<p>The DbEnv::mutex_stat_print method displays the 85mutex subsystem statistical information, as described for the DbEnv::mutex_stat method. 86The information is printed to a specified output channel (see the 87<a href="../api_cxx/env_set_msgfile.html">DbEnv::set_msgfile</a> method for more information), or passed to an 88application callback function (see the <a href="../api_cxx/env_set_msgcall.html">DbEnv::set_msgcall</a> method for 89more information).</p> 90<p>The DbEnv::mutex_stat_print method may not be called before the <a href="../api_cxx/env_open.html">DbEnv::open</a> method is called.</p> 91<p>The DbEnv::mutex_stat_print method 92either returns a non-zero error value 93or throws an exception that encapsulates a non-zero error value on 94failure, and returns 0 on success. 95</p> 96<b>Parameters</b> <br> 97 <b>flags</b><ul compact><li>The <b>flags</b> parameter must be set to 0 or by bitwise inclusively <b>OR</b>'ing together one 98or more of the following values: 99<br> 100<b><a name="DB_STAT_ALL">DB_STAT_ALL</a></b><ul compact><li>Display all available information.</ul> 101<b><a name="DB_STAT_CLEAR">DB_STAT_CLEAR</a></b><ul compact><li>Reset statistics after displaying their values.</ul> 102<br></ul> 103<br> 104<hr size=1 noshade> 105<br><b>Class</b> 106<a href="../api_cxx/env_class.html">DbEnv</a> 107<br><b>See Also</b> 108<a href="../api_cxx/env_list.html">Database Environments and Related Methods</a> 109</tt> 110<table width="100%"><tr><td><br></td><td align=right> 111<a href="../api_cxx/api_core.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a> 112</td></tr></table> 113<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> 114</body> 115</html> 116
