<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>DbEnv::mutex_stat()</title> <link rel="stylesheet" href="apiReference.css" type="text/css" /> <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> <link rel="start" href="index.html" title="Berkeley DB C++ API Reference" /> <link rel="up" href="mutex.html" title="Chapter 10. Mutex Methods" /> <link rel="prev" href="mutexset_tas_spins.html" title="DbEnv::mutex_set_tas_spins()" /> <link rel="next" href="mutexstat_print.html" title="DbEnv::mutex_stat_print()" /> </head> <body> <div class="navheader"> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center">DbEnv::mutex_stat()</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="mutexset_tas_spins.html">Prev</a> </td> <th width="60%" align="center">Chapter 10. Mutex Methods </th> <td width="20%" align="right"> <a accesskey="n" href="mutexstat_print.html">Next</a></td> </tr> </table> <hr /> </div> <div class="sect1" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h2 class="title" style="clear: both"><a id="mutexstat"></a>DbEnv::mutex_stat()</h2> </div> </div> </div> <pre class="programlisting">#include <db_cxx.h> int DbEnv::mutex_stat(DB_MUTEX_STAT **statp, u_int32_t flags); </pre> <p> The <code class="methodname">DbEnv::mutex_stat()</code> method returns the mutex subsystem statistics. </p> <p> The <code class="methodname">DbEnv::mutex_stat()</code> method creates a statistical structure of type <code class="literal">DB_MUTEX_STAT</code> and copies a pointer to it into a user-specified memory location. </p> <p> Statistical structures are stored in allocated memory. If application-specific allocation routines have been declared (see <a class="xref" href="envset_alloc.html" title="DbEnv::set_alloc()">DbEnv::set_alloc()</a> for more information), they are used to allocate the memory; otherwise, the standard C library <span class="bold"><strong>malloc</strong></span>(3) is used. The caller is responsible for deallocating the memory. To deallocate the memory, free the memory reference; references inside the returned memory need not be individually freed. </p> <p> The following <code class="literal">DB_MUTEX_STAT</code> fields will be filled in: </p> <div class="itemizedlist"> <ul type="disc"> <li> <p> <span class="bold"><strong>u_int32_t st_mutex_align;</strong></span> </p> <p> The mutex alignment, in bytes. </p> </li> <li> <p> <span class="bold"><strong>u_int32_t st_mutex_tas_spins;</strong></span> </p> <p> The number of times test-and-set mutexes will spin without blocking. </p> </li> <li> <p> <span class="bold"><strong>int st_mutex_cnt;</strong></span> </p> <p> The total number of mutexes configured. </p> </li> <li> <p> <span class="bold"><strong>u_int32_t st_mutex_free;</strong></span> </p> <p> The number of mutexes currently available. </p> </li> <li> <p> <span class="bold"><strong>u_int32_t st_mutex_inuse;</strong></span> </p> <p> The number of mutexes currently in use. </p> </li> <li> <p> <span class="bold"><strong>u_int32_t st_mutex_inuse_max;</strong></span> </p> <p> The maximum number of mutexes ever in use. </p> </li> <li> <p> <span class="bold"><strong>roff_t st_regsize;</strong></span> </p> <p> The size of the mutex region, in bytes. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_region_wait;</strong></span> </p> <p> The number of times that a thread of control was forced to wait before obtaining the mutex region mutex. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_region_nowait;</strong></span> </p> <p> The number of times that a thread of control was able to obtain the mutex region mutex without waiting. </p> </li> </ul> </div> <p> The <code class="methodname">DbEnv::mutex_stat()</code> method may not be called before the <a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> method is called. </p> <p> The <code class="methodname">DbEnv::mutex_stat()</code> <span> <span> method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success. </span> </span> </p> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="id1700000"></a>Parameters</h3> </div> </div> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="id1700081"></a>flags</h4> </div> </div> </div> <p> The <span class="bold"><strong>flags</strong></span> parameter must be set to 0 or the following value: </p> <div class="itemizedlist"> <ul type="disc"> <li> <p> <code class="literal">DB_STAT_CLEAR</code> </p> <p> Reset statistics after returning their values. </p> </li> </ul> </div> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="id1700176"></a>statp</h4> </div> </div> </div> <p> The <span class="bold"><strong>statp</strong></span> parameter references memory into which a pointer to the allocated statistics structure is copied. </p> </div> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="id1700313"></a>Errors</h3> </div> </div> </div> <p> The <code class="methodname">DbEnv::mutex_stat()</code> <span> <span> method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a> exception, encapsulating one of the following non-zero errors, or return one of the following non-zero errors: </span> </span> </p> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="id1700240"></a>EINVAL</h4> </div> </div> </div> <p> An invalid flag value or parameter was specified. </p> </div> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="id1699883"></a>Class</h3> </div> </div> </div> <p> <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> </p> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="id1699855"></a>See Also</h3> </div> </div> </div> <p> <a class="xref" href="mutex.html#mutexlist" title="Mutex Methods">Mutex Methods</a> </p> </div> </div> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"><a accesskey="p" href="mutexset_tas_spins.html">Prev</a> </td> <td width="20%" align="center"> <a accesskey="u" href="mutex.html">Up</a> </td> <td width="40%" align="right"> <a accesskey="n" href="mutexstat_print.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">DbEnv::mutex_set_tas_spins() </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> DbEnv::mutex_stat_print()</td> </tr> </table> </div> </body> </html>