<?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::memp_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="memp.html" title="Chapter 9. The DbMpoolFile Handle" /> <link rel="prev" href="mempregister.html" title="DbEnv::memp_register()" /> <link rel="next" href="mempstat_print.html" title="DbEnv::memp_stat_print()" /> </head> <body> <div xmlns="" class="navheader"> <div class="libver"> <p>Library Version 11.2.5.3</p> </div> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center">DbEnv::memp_stat()</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="mempregister.html">Prev</a> </td> <th width="60%" align="center">Chapter 9. The DbMpoolFile Handle </th> <td width="20%" align="right"> <a accesskey="n" href="mempstat_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="mempstat"></a>DbEnv::memp_stat()</h2> </div> </div> </div> <pre class="programlisting">#include <db_cxx.h> int DbEnv::memp_stat(DB_MPOOL_STAT **gsp, DB_MPOOL_FSTAT *(*fsp)[], u_int32_t flags); </pre> <p> The <code class="methodname">DbEnv::memp_stat()</code> method returns the memory pool (that is, the buffer cache) subsystem statistics. </p> <p> The <code class="methodname">DbEnv::memp_stat()</code> method creates statistical structures of type <code class="literal">DB_MPOOL_STAT</code> and <code class="literal">DB_MPOOL_FSTAT</code>, and copy pointers to them into user-specified memory locations. The cache statistics are stored in the <code class="literal">DB_MPOOL_STAT</code> structure and the per-file cache statistics are stored the <code class="literal">DB_MPOOL_FSTAT</code> structure. </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> If <span class="bold"><strong>gsp</strong></span> is non-NULL, the global statistics for the cache <span class="bold"><strong>mp</strong></span> are copied into the memory location to which it refers. The following <code class="literal">DB_MPOOL_STAT</code> fields will be filled in: </p> <div class="itemizedlist"> <ul type="disc"> <li> <p> <span class="bold"><strong>u_int32_t st_gbytes;</strong></span> </p> <p> Gigabytes of cache (total cache size is st_gbytes + st_bytes). </p> </li> <li> <p> <span class="bold"><strong>u_int32_t st_bytes;</strong></span> </p> <p> Bytes of cache (total cache size is st_gbytes + st_bytes). </p> </li> <li> <p> <span class="bold"><strong>u_int32_t st_ncache;</strong></span> </p> <p> Number of caches. </p> </li> <li> <p> <span class="bold"><strong>u_int32_t st_max_ncache;</strong></span> </p> <p> Maximum number of caches, as configured with the <a class="xref" href="envset_cache_max.html" title="DbEnv::set_cache_max()">DbEnv::set_cache_max()</a> method. </p> </li> <li> <p> <span class="bold"><strong>roff_t st_regsize;</strong></span> </p> <p> Individual cache size, in bytes. </p> </li> <li> <p> <span class="bold"><strong>size_t st_mmapsize;</strong></span> </p> <p> Maximum memory-mapped file size. </p> </li> <li> <p> <span class="bold"><strong>int st_maxopenfd;</strong></span> </p> <p> Maximum open file descriptors. </p> </li> <li> <p> <span class="bold"><strong>int st_maxwrite;</strong></span> </p> <p> Maximum sequential buffer writes. </p> </li> <li> <p> <span class="bold"><strong>db_timeout_t st_maxwrite_sleep;</strong></span> </p> <p> Microseconds to pause after writing maximum sequential buffers. </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 (there is no available information about whether or not this request caused disk I/O, although examining the application page fault rate may be helpful). </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>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> <li> <p> <span class="bold"><strong>uintmax_t st_ro_evict;</strong></span> </p> <p> Clean pages forced from the cache. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_rw_evict;</strong></span> </p> <p> Dirty pages forced from the cache. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_page_trickle;</strong></span> </p> <p> Dirty pages written using the <a class="xref" href="memptrickle.html" title="DbEnv::memp_trickle()">DbEnv::memp_trickle()</a> method. </p> </li> <li> <p> <span class="bold"><strong>u_int32_t st_pages;</strong></span> </p> <p> Pages in the cache. </p> </li> <li> <p> <span class="bold"><strong>u_int32_t st_page_clean;</strong></span> </p> <p> Clean pages currently in the cache. </p> </li> <li> <p> <span class="bold"><strong>u_int32_t st_page_dirty;</strong></span> </p> <p> Dirty pages currently in the cache. </p> </li> <li> <p> <span class="bold"><strong>u_int32_t st_hash_buckets;</strong></span> </p> <p> Number of hash buckets in buffer hash table. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_hash_examined;</strong></span> </p> <p> Total number of hash elements traversed during hash table lookups. </p> </li> <li> <p> <span class="bold"><strong>u_int32_t st_hash_longest;</strong></span> </p> <p> Longest chain ever encountered in buffer hash table lookups. </p> </li> <li> <p> <span class="bold"><strong>u_int32_t st_hash_mutexes;</strong></span> </p> <p> The number of hash bucket mutexes in the buffer hash table. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_hash_nowait;</strong></span> </p> <p> Number of times that a thread of control was able to obtain a hash bucket lock without waiting. </p> </li> <li> <p> <span class="bold"><strong>u_int32_t st_hash_searches;</strong></span> </p> <p> Total number of buffer hash table lookups. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_hash_wait;</strong></span> </p> <p> Number of times that a thread of control was forced to wait before obtaining a hash bucket lock. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_hash_max_nowait;</strong></span> </p> <p> The number of times a thread of control was able to obtain the hash bucket lock without waiting on the bucket which had the maximum number of times that a thread of control needed to wait. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_hash_max_wait;</strong></span> </p> <p> Maximum number of times any hash bucket lock was waited for by a thread of control. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_region_wait;</strong></span> </p> <p> Number of times that a thread of control was forced to wait before obtaining a cache region mutex. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_region_nowait;</strong></span> </p> <p> Number of times that a thread of control was able to obtain a cache region mutex without waiting. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_mvcc_frozen;</strong></span> </p> <p> Number of buffers frozen. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_mvcc_thawed;</strong></span> </p> <p> Number of buffers thawed. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_mvcc_freed;</strong></span> </p> <p> Number of frozen buffers freed. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_alloc;</strong></span> </p> <p> Number of page allocations. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_alloc_buckets;</strong></span> </p> <p> Number of hash buckets checked during allocation. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_alloc_max_buckets;</strong></span> </p> <p> Maximum number of hash buckets checked during an allocation. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_alloc_pages;</strong></span> </p> <p> Number of pages checked during allocation. </p> </li> <li> <p> <span class="bold"><strong>uintmax_t st_alloc_max_pages;</strong></span> </p> <p> 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">DbEnv::memp_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::memp_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="idp8737464"></a>Parameters</h3> </div> </div> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp8736672"></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="idp8740576"></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="idp8741352"></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="idp8746472"></a>Errors</h3> </div> </div> </div> <p> The <code class="methodname">DbEnv::memp_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="idp8754336"></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="idp8753040"></a>Class</h3> </div> </div> </div> <p> <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>, <a class="link" href="memp.html" title="Chapter 9. The DbMpoolFile Handle">DbMpoolFile</a> </p> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp8726936"></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> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <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">DbEnv::memp_register() </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> DbEnv::memp_stat_print()</td> </tr> </table> </div> </body> </html>