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24 KiB
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>DB_ENV->memp_stat()</title>
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<link rel="stylesheet" href="apiReference.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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<link rel="start" href="index.html" title="Berkeley DB C API Reference" />
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<link rel="up" href="memp.html" title="Chapter 8. The DB_MPOOLFILE Handle" />
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<link rel="prev" href="mempregister.html" title="DB_ENV->memp_register()" />
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<link rel="next" href="mempstat_print.html" title="DB_ENV->memp_stat_print()" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 11.2.5.3</p>
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</div>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">DB_ENV->memp_stat()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="mempregister.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 8.
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The DB_MPOOLFILE Handle
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="mempstat_print.html">Next</a></td>
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</tr>
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</table>
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<hr />
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||
</div>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="mempstat"></a>DB_ENV->memp_stat()</h2>
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</div>
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</div>
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</div>
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<pre class="programlisting">#include <db.h>
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int
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DB_ENV->memp_stat(DB_ENV *env, DB_MPOOL_STAT **gsp,
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DB_MPOOL_FSTAT *(*fsp)[], u_int32_t flags); </pre>
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<p>
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The <code class="methodname">DB_ENV->memp_stat()</code> method returns the memory pool (that is, the
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buffer cache) subsystem statistics.
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</p>
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<p>
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The <code class="methodname">DB_ENV->memp_stat()</code> method creates statistical structures of
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type <code class="literal">DB_MPOOL_STAT</code> and <code class="literal">DB_MPOOL_FSTAT</code>, and copy
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pointers to them into user-specified memory locations. The cache statistics are stored in
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the <code class="literal">DB_MPOOL_STAT</code> structure and the per-file cache statistics are stored
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the <code class="literal">DB_MPOOL_FSTAT</code> structure.
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</p>
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<p>
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Statistical structures are stored in allocated memory. If
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application-specific allocation routines have been declared (see
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<a class="xref" href="envset_alloc.html" title="DB_ENV->set_alloc()">DB_ENV->set_alloc()</a>
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for more information), they are used to allocate the memory;
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otherwise, the standard C library <span class="bold"><strong>malloc</strong></span>(3) is used. The caller is responsible
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for deallocating the memory. To deallocate the memory, free the
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memory reference; references inside the returned memory need not be
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individually freed.
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</p>
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<p>
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If <span class="bold"><strong>gsp</strong></span> is non-NULL, the global
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statistics for the cache <span class="bold"><strong>mp</strong></span> are
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copied into the memory location to which it refers. The following
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<code class="literal">DB_MPOOL_STAT</code> fields will be filled in:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_gbytes;</strong></span>
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</p>
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<p>
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Gigabytes of cache (total cache size is st_gbytes + st_bytes).
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_bytes;</strong></span>
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</p>
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<p>
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Bytes of cache (total cache size is st_gbytes + st_bytes).
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_ncache;</strong></span>
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</p>
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<p>
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Number of caches.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_max_ncache;</strong></span>
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</p>
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<p>
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Maximum number of caches, as configured with the
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<a class="xref" href="envset_cache_max.html" title="DB_ENV->set_cache_max()">DB_ENV->set_cache_max()</a>
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method.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>roff_t st_regsize;</strong></span>
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</p>
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<p>
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Individual cache size, in bytes.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>size_t st_mmapsize;</strong></span>
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</p>
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<p>
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||
Maximum memory-mapped file size.
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||
</p>
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||
</li>
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<li>
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||
<p>
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||
<span class="bold"><strong>int st_maxopenfd;</strong></span>
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</p>
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||
<p>
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||
Maximum open file descriptors.
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</p>
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</li>
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<li>
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||
<p>
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||
<span class="bold"><strong>int st_maxwrite;</strong></span>
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||
</p>
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||
<p>
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Maximum sequential buffer writes.
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</p>
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</li>
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<li>
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<p>
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||
<span class="bold"><strong>db_timeout_t st_maxwrite_sleep;</strong></span>
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</p>
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<p>
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Microseconds to pause after writing maximum sequential buffers.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_map;</strong></span>
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</p>
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<p>
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Requested pages mapped into the process' address space (there is no
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available information about whether or not this request caused disk
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I/O, although examining the application page fault rate may be
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helpful).
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_cache_hit;</strong></span>
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</p>
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<p>
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Requested pages found in the cache.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_cache_miss;</strong></span>
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</p>
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<p>
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Requested pages not found in the cache.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_page_create;</strong></span>
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</p>
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<p>
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Pages created in the cache.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_page_in;</strong></span>
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</p>
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<p>
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Pages read into the cache.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_page_out;</strong></span>
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</p>
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<p>
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Pages written from the cache to the backing file.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_ro_evict;</strong></span>
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</p>
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<p>
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Clean pages forced from the cache.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_rw_evict;</strong></span>
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</p>
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<p>
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Dirty pages forced from the cache.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_page_trickle;</strong></span>
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</p>
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<p>
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Dirty pages written using the
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<a class="xref" href="memptrickle.html" title="DB_ENV->memp_trickle()">DB_ENV->memp_trickle()</a>
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method.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_pages;</strong></span>
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</p>
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<p>
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Pages in the cache.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_page_clean;</strong></span>
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</p>
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<p>
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Clean pages currently in the cache.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_page_dirty;</strong></span>
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</p>
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<p>
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Dirty pages currently in the cache.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_hash_buckets;</strong></span>
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</p>
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<p>
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Number of hash buckets in buffer hash table.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_hash_examined;</strong></span>
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</p>
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<p>
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Total number of hash elements traversed during hash table lookups.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_hash_longest;</strong></span>
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</p>
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<p>
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Longest chain ever encountered in buffer hash table lookups.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_hash_mutexes;</strong></span>
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</p>
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<p>
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The number of hash bucket mutexes in the buffer hash table.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_hash_nowait;</strong></span>
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</p>
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<p>
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Number of times that a thread of control was able to obtain a hash
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bucket lock without waiting.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>u_int32_t st_hash_searches;</strong></span>
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</p>
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<p>
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Total number of buffer hash table lookups.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_hash_wait;</strong></span>
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</p>
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<p>
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Number of times that a thread of control was forced to wait before
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obtaining a hash bucket lock.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_hash_max_nowait;</strong></span>
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</p>
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<p>
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The number of times a thread of control was able to obtain the hash
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bucket lock without waiting on the bucket which had the maximum number
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||
of times that a thread of control needed to wait.
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</p>
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||
</li>
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||
<li>
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<p>
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<span class="bold"><strong>uintmax_t st_hash_max_wait;</strong></span>
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||
</p>
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<p>
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Maximum number of times any hash bucket lock was waited for by a
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thread of control.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_region_wait;</strong></span>
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</p>
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<p>
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Number of times that a thread of control was forced to wait before
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obtaining a cache region mutex.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_region_nowait;</strong></span>
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</p>
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<p>
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Number of times that a thread of control was able to obtain a cache
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region mutex without waiting.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_mvcc_frozen;</strong></span>
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</p>
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<p>
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Number of buffers frozen.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_mvcc_thawed;</strong></span>
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</p>
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<p>
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Number of buffers thawed.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>uintmax_t st_mvcc_freed;</strong></span>
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</p>
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<p>
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Number of frozen buffers freed.
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</p>
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||
</li>
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<li>
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<p>
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||
<span class="bold"><strong>uintmax_t st_alloc;</strong></span>
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||
</p>
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<p>
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||
Number of page allocations.
|
||
</p>
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||
</li>
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||
<li>
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||
<p>
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||
<span class="bold"><strong>uintmax_t st_alloc_buckets;</strong></span>
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||
</p>
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||
<p>
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Number of hash buckets checked during allocation.
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||
</p>
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</li>
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||
<li>
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||
<p>
|
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<span class="bold"><strong>uintmax_t st_alloc_max_buckets;</strong></span>
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||
</p>
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<p>
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Maximum number of hash buckets checked during an allocation.
|
||
</p>
|
||
</li>
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||
<li>
|
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<p>
|
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<span class="bold"><strong>uintmax_t st_alloc_pages;</strong></span>
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</p>
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<p>
|
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Number of pages checked during allocation.
|
||
</p>
|
||
</li>
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<li>
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<p>
|
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<span class="bold"><strong>uintmax_t st_alloc_max_pages;</strong></span>
|
||
</p>
|
||
<p>
|
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Maximum number of pages checked during an allocation.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
<span class="bold"><strong>uintmax_t st_io_wait;</strong></span>
|
||
</p>
|
||
<p>
|
||
Number of operations blocked waiting for I/O to complete.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
<span class="bold"><strong>uintmax_t st_sync_interrupted;</strong></span>
|
||
</p>
|
||
<p>
|
||
Number of mpool sync operations interrupted.
|
||
</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<p>
|
||
If <span class="bold"><strong>fsp</strong></span> is non-NULL, a pointer to a
|
||
NULL-terminated variable length array of statistics for individual
|
||
files, in the cache <span class="bold"><strong>mp</strong></span>, is copied
|
||
into the memory location to which it refers. If no individual files
|
||
currently exist in the cache, <span class="bold"><strong>fsp</strong></span>
|
||
will be set to NULL.
|
||
</p>
|
||
<p>
|
||
The per-file statistics are stored in structures of type <code class="literal">DB_MPOOL_FSTAT</code>.
|
||
The following <code class="literal">DB_MPOOL_FSTAT</code> fields will be filled in for each file in
|
||
the cache; that is, each element of the array:
|
||
</p>
|
||
<div class="itemizedlist">
|
||
<ul type="disc">
|
||
<li>
|
||
<p>
|
||
<span class="bold"><strong>char * file_name;</strong></span>
|
||
</p>
|
||
<p>
|
||
The name of the file.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
<span class="bold"><strong>size_t st_pagesize;</strong></span>
|
||
</p>
|
||
<p>
|
||
Page size in bytes.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
<span class="bold"><strong>uintmax_t st_cache_hit;</strong></span>
|
||
</p>
|
||
<p>
|
||
Requested pages found in the cache.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
<span class="bold"><strong>uintmax_t st_cache_miss;</strong></span>
|
||
</p>
|
||
<p>
|
||
Requested pages not found in the cache.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
<span class="bold"><strong>u_int32_t st_map;</strong></span>
|
||
</p>
|
||
<p>
|
||
Requested pages mapped into the process' address space.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
<span class="bold"><strong>uintmax_t st_page_create;</strong></span>
|
||
</p>
|
||
<p>
|
||
Pages created in the cache.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
<span class="bold"><strong>uintmax_t st_page_in;</strong></span>
|
||
</p>
|
||
<p>
|
||
Pages read into the cache.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
<span class="bold"><strong>uintmax_t st_page_out;</strong></span>
|
||
</p>
|
||
<p>
|
||
Pages written from the cache to the backing file.
|
||
</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<p>
|
||
The <code class="methodname">DB_ENV->memp_stat()</code> method may not be called before the
|
||
<a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a> method is called.
|
||
</p>
|
||
<p>
|
||
The <code class="methodname">DB_ENV->memp_stat()</code> <span>
|
||
<span>
|
||
method returns a non-zero error value on failure and 0 on success.
|
||
</span>
|
||
|
||
</span>
|
||
</p>
|
||
<div class="sect2" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h3 class="title"><a id="idp61252072"></a>Parameters</h3>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect3" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h4 class="title"><a id="idp61227096"></a>gsp</h4>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>
|
||
The <span class="bold"><strong>gsp</strong></span> parameter references memory
|
||
into which a pointer to the allocated global statistics structure is
|
||
copied.
|
||
</p>
|
||
</div>
|
||
<div class="sect3" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h4 class="title"><a id="idp61255296"></a>fsp</h4>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>
|
||
The <span class="bold"><strong>fsp</strong></span> parameter references memory
|
||
into which a pointer to the allocated per-file statistics structures
|
||
is copied.
|
||
</p>
|
||
</div>
|
||
<div class="sect3" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h4 class="title"><a id="idp61256024"></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><a id="mempstat_DB_STAT_CLEAR"></a>
|
||
<code class="literal">DB_STAT_CLEAR</code>
|
||
</p>
|
||
<p>
|
||
Reset statistics after returning their values.
|
||
</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h3 class="title"><a id="idp61260936"></a>Errors</h3>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>
|
||
The <code class="methodname">DB_ENV->memp_stat()</code> <span>
|
||
<span>
|
||
method may fail and 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="idp61265528"></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="idp61264232"></a>Class</h3>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>
|
||
<a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a>, <a class="link" href="memp.html" title="Chapter 8. The DB_MPOOLFILE Handle">DB_MPOOLFILE</a>
|
||
</p>
|
||
</div>
|
||
<div class="sect2" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h3 class="title"><a id="idp61256896"></a>See Also</h3>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>
|
||
<a class="xref" href="memp.html#memplist" title="Memory Pools and Related Methods">Memory Pools and Related Methods</a>
|
||
</p>
|
||
</div>
|
||
</div>
|
||
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|
||
<hr />
|
||
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||
<td width="40%" align="left"><a accesskey="p" href="mempregister.html">Prev</a> </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="u" href="memp.html">Up</a>
|
||
</td>
|
||
<td width="40%" align="right"> <a accesskey="n" href="mempstat_print.html">Next</a></td>
|
||
</tr>
|
||
<tr>
|
||
<td width="40%" align="left" valign="top">DB_ENV->memp_register() </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="h" href="index.html">Home</a>
|
||
</td>
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||
<td width="40%" align="right" valign="top"> DB_ENV->memp_stat_print()</td>
|
||
</tr>
|
||
</table>
|
||
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|
||
</body>
|
||
</html>
|