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<!--$Id: mutex_stat.so,v 10.2 2005/11/08 11:43:55 mjc Exp $-->
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<title>Berkeley DB: DB_ENV->mutex_stat</title>
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<h3>DB_ENV->mutex_stat</h3>
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<h3><pre>
#include <db.h>
<p>
int
DB_ENV->mutex_stat(DB_ENV *env, DB_MUTEX_STAT **statp, u_int32_t flags);
<p>
int
DB_ENV->mutex_stat_print(DB_ENV *env, u_int32_t flags);
</pre></h3>
<hr size=1 noshade>
<h3>Description: DB_ENV->mutex_stat</h3>
<p>The DB_ENV->mutex_stat method returns the mutex subsystem statistics.</p>
<p>The DB_ENV->mutex_stat method creates a statistical structure of type
DB_MUTEX_STAT 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 href="../api_c/env_set_alloc.html">DB_ENV->set_alloc</a> for more
information), they are used to allocate the memory; otherwise, the
standard C library <b>malloc</b>(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 DB_MUTEX_STAT fields will be filled in:</p>
<dl compact>
<dt>u_int32_t st_mutex_align;<dd>The mutex alignment, in bytes.
<dt>u_int32_t st_mutex_tas_spins;<dd>The number of times test-and-set mutexes will spin without blocking.
<dt>int st_mutex_cnt;<dd>The total number of mutexes configured.
<dt>u_int32_t st_mutex_free;<dd>The number of mutexes currently available.
<dt>u_int32_t st_mutex_inuse;<dd>The number of mutexes currently in use.
<dt>u_int32_t st_mutex_inuse_max;<dd>The maximum number of mutexes ever in use.
<dt>roff_t st_regsize;<dd>The size of the mutex region, in bytes.
<dt>u_int32_t st_region_wait;<dd>The number of times that a thread of control was forced to wait before
obtaining the mutex region mutex.
<dt>u_int32_t st_region_nowait;<dd>The number of times that a thread of control was able to obtain
the mutex region mutex without waiting.
</dl>
<p>The DB_ENV->mutex_stat method
returns a non-zero error value on failure
and 0 on success.
</p>
<h3>Parameters</h3>
<dl compact>
<dt><b>flags</b><dd>The <b>flags</b> parameter must be set to 0 or
the following value:
<dl compact>
<dt><a name="DB_STAT_CLEAR">DB_STAT_CLEAR</a><dd>Reset statistics after returning their values.
</dl>
<dt><b>statp</b><dd>The <b>statp</b> parameter references memory into which
a pointer to the allocated statistics structure is copied.
</dl>
<h3>Errors</h3>
<p>The DB_ENV->mutex_stat method
may fail and return one of the following non-zero errors:</p>
<dl compact>
<dt>EINVAL<dd>An
invalid flag value or parameter was specified.
</dl>
<hr size=1 noshade>
<h3>Description: DB_ENV->mutex_stat_print</h3>
<p>The DB_ENV->mutex_stat_print method displays the
mutex subsystem statistical information, as described for the DB_ENV->mutex_stat method.
The information is printed to a specified output channel (see the
<a href="../api_c/env_set_msgfile.html">DB_ENV->set_msgfile</a> method for more information), or passed to an
application callback function (see the <a href="../api_c/env_set_msgcall.html">DB_ENV->set_msgcall</a> method for
more information).</p>
<p>The DB_ENV->mutex_stat_print method may not be called before the <a href="../api_c/env_open.html">DB_ENV->open</a> method has
been called.</p>
<p>The DB_ENV->mutex_stat_print method
returns a non-zero error value on failure
and 0 on success.
</p>
<h3>Parameters</h3>
<dl compact>
<dt><b>flags</b><dd>The <b>flags</b> parameter must be set to 0 or
the following value:
<dl compact>
<dt><a name="DB_STAT_ALL">DB_STAT_ALL</a><dd>Display all available information.
</dl>
</dl>
<hr size=1 noshade>
<h3>Class</h3>
<a href="../api_c/env_class.html">DB_ENV</a>
<h3>See Also</h3>
<a href="../api_c/env_list.html">Database Environments and Related Methods</a>
</tt>
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