<!--$Id: memp_stat.so,v 10.72 2007/09/21 20:06:03 bostic Exp $--> <!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> <!--See the file LICENSE for redistribution information.--> <html> <head> <title>Berkeley DB: DbEnv::memp_stat</title> <meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> <meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> </head> <body bgcolor=white> <table width="100%"><tr valign=top> <td> <b>DbEnv::memp_stat</b> </td> <td align=right> <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></td> </tr></table> <hr size=1 noshade> <tt> <b><pre> #include <db_cxx.h> <p> int DbEnv::memp_stat(DB_MPOOL_STAT **gsp, DB_MPOOL_FSTAT *(*fsp)[], u_int32_t flags); <p> int DbEnv::memp_stat_print(u_int32_t flags); </pre></b> <hr size=1 noshade> <b>Description: DbEnv::memp_stat</b> <p>The DbEnv::memp_stat method returns the memory pool (that is, the buffer cache) subsystem statistics.</p> <p>The DbEnv::memp_stat method creates statistical structures of type DB_MPOOL_STAT and DB_MPOOL_FSTAT, and copy pointers to them into user-specified memory locations. The cache statistics are stored in the DB_MPOOL_STAT structure and the per-file cache statistics are stored the DB_MPOOL_FSTAT structure.</p> <p>Statistical structures are stored in allocated memory. If application-specific allocation routines have been declared (see <a href="../api_cxx/env_set_alloc.html">DbEnv::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>If <b>gsp</b> is non-NULL, the global statistics for the cache <b>mp</b> are copied into the memory location to which it refers. The following DB_MPOOL_STAT fields will be filled in:</p> <br> <b>size_t st_gbytes;</b><ul compact><li>Gigabytes of cache (total cache size is st_gbytes + st_bytes).</ul> <b>size_t st_bytes;</b><ul compact><li>Bytes of cache (total cache size is st_gbytes + st_bytes).</ul> <b>u_int32_t st_ncache;</b><ul compact><li>Number of caches.</ul> <b>u_int32_t st_max_ncache;</b><ul compact><li>Maximum number of caches, as configured with the <a href="../api_cxx/env_set_cache_max.html">DbEnv::set_cache_max</a> method.</ul> <b>roff_t st_regsize;</b><ul compact><li>Individual cache size, in bytes.</ul> <b>size_t st_mmapsize;</b><ul compact><li>Maximum memory-mapped file size.</ul> <b>int st_maxopenfd;</b><ul compact><li>Maximum open file descriptors.</ul> <b>int st_maxwrite;</b><ul compact><li>Maximum sequential buffer writes.</ul> <b>db_timeout_t st_maxwrite_sleep;</b><ul compact><li>Microseconds to pause after writing maximum sequential buffers.</ul> <b>u_int32_t st_map;</b><ul compact><li>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).</ul> <b>u_int32_t st_cache_hit;</b><ul compact><li>Requested pages found in the cache.</ul> <b>u_int32_t st_cache_miss;</b><ul compact><li>Requested pages not found in the cache.</ul> <b>u_int32_t st_page_create;</b><ul compact><li>Pages created in the cache.</ul> <b>u_int32_t st_page_in;</b><ul compact><li>Pages read into the cache.</ul> <b>u_int32_t st_page_out;</b><ul compact><li>Pages written from the cache to the backing file.</ul> <b>u_int32_t st_ro_evict;</b><ul compact><li>Clean pages forced from the cache.</ul> <b>u_int32_t st_rw_evict;</b><ul compact><li>Dirty pages forced from the cache.</ul> <b>u_int32_t st_page_trickle;</b><ul compact><li>Dirty pages written using the <a href="../api_cxx/memp_trickle.html">DbEnv::memp_trickle</a> method.</ul> <b>u_int32_t st_pages;</b><ul compact><li>Pages in the cache.</ul> <b>u_int32_t st_page_clean;</b><ul compact><li>Clean pages currently in the cache.</ul> <b>u_int32_t st_page_dirty;</b><ul compact><li>Dirty pages currently in the cache.</ul> <b>u_int32_t st_hash_buckets;</b><ul compact><li>Number of hash buckets in buffer hash table.</ul> <b>u_int32_t st_hash_searches;</b><ul compact><li>Total number of buffer hash table lookups.</ul> <b>u_int32_t st_hash_longest;</b><ul compact><li>Longest chain ever encountered in buffer hash table lookups.</ul> <b>u_int32_t st_hash_examined;</b><ul compact><li>Total number of hash elements traversed during hash table lookups.</ul> <b>u_int32_t st_hash_nowait;</b><ul compact><li>Number of times that a thread of control was able to obtain a hash bucket lock without waiting.</ul> <b>u_int32_t st_hash_wait;</b><ul compact><li>Number of times that a thread of control was forced to wait before obtaining a hash bucket lock.</ul> <b>u_int32_t st_hash_max_nowait;</b><ul compact><li>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.</ul> <b>u_int32_t st_hash_max_wait;</b><ul compact><li>Maximum number of times any hash bucket lock was waited for by a thread of control.</ul> <b>u_int32_t st_region_wait;</b><ul compact><li>Number of times that a thread of control was forced to wait before obtaining a cache region mutex.</ul> <b>u_int32_t st_region_nowait;</b><ul compact><li>Number of times that a thread of control was able to obtain a cache region mutex without waiting.</ul> <b>u_int32_t st_mvcc_frozen;</b><ul compact><li>Number of buffers frozen.</ul> <b>u_int32_t st_mvcc_thawed;</b><ul compact><li>Number of buffers thawed.</ul> <b>u_int32_t st_mvcc_freed;</b><ul compact><li>Number of frozen buffers freed.</ul> <b>u_int32_t st_alloc;</b><ul compact><li>Number of page allocations.</ul> <b>u_int32_t st_alloc_buckets;</b><ul compact><li>Number of hash buckets checked during allocation.</ul> <b>u_int32_t st_alloc_max_buckets;</b><ul compact><li>Maximum number of hash buckets checked during an allocation.</ul> <b>u_int32_t st_alloc_pages;</b><ul compact><li>Number of pages checked during allocation.</ul> <b>u_int32_t st_alloc_max_pages;</b><ul compact><li>Maximum number of pages checked during an allocation.</ul> <b>u_int32_t st_io_wait;</b><ul compact><li>Number of operations blocked waiting for I/O to complete.</ul> <br> <p>If <b>fsp</b> is non-NULL, a pointer to a NULL-terminated variable length array of statistics for individual files, in the cache <b>mp</b>, is copied into the memory location to which it refers. If no individual files currently exist in the cache, <b>fsp</b> will be set to NULL.</p> <p>The per-file statistics are stored in structures of type DB_MPOOL_FSTAT. The following DB_MPOOL_FSTAT fields will be filled in for each file in the cache; that is, each element of the array:</p> <br> <b>char * file_name;</b><ul compact><li>The name of the file.</ul> <b>size_t st_pagesize;</b><ul compact><li>Page size in bytes.</ul> <b>u_int32_t st_cache_hit;</b><ul compact><li>Requested pages found in the cache.</ul> <b>u_int32_t st_cache_miss;</b><ul compact><li>Requested pages not found in the cache.</ul> <b>u_int32_t st_map;</b><ul compact><li>Requested pages mapped into the process' address space.</ul> <b>u_int32_t st_page_create;</b><ul compact><li>Pages created in the cache.</ul> <b>u_int32_t st_page_in;</b><ul compact><li>Pages read into the cache.</ul> <b>u_int32_t st_page_out;</b><ul compact><li>Pages written from the cache to the backing file.</ul> <br> <p>The DbEnv::memp_stat method may not be called before the <a href="../api_cxx/env_open.html">DbEnv::open</a> method is called.</p> <p>The DbEnv::memp_stat 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. </p> <b>Parameters</b> <br> <b>flags</b><ul compact><li>The <b>flags</b> parameter must be set to 0 or the following value: <br> <b><a name="DB_STAT_CLEAR">DB_STAT_CLEAR</a></b><ul compact><li>Reset statistics after returning their values.</ul> <br></ul> <b>fsp</b><ul compact><li>The <b>fsp</b> parameter references memory into which a pointer to the allocated per-file statistics structures is copied.</ul> <b>gsp</b><ul compact><li>The <b>gsp</b> parameter references memory into which a pointer to the allocated global statistics structure is copied.</ul> <br> <br><b>Errors</b> <p>The DbEnv::memp_stat method may fail and throw <a href="../api_cxx/except_class.html">DbException</a>, encapsulating one of the following non-zero errors, or return one of the following non-zero errors:</p> <br> <b>EINVAL</b><ul compact><li>An invalid flag value or parameter was specified.</ul> <br> <hr size=1 noshade> <b>Description: DbEnv::memp_stat_print</b> <p>The DbEnv::memp_stat_print method displays the memory pool subsystem statistical information, as described for the DbEnv::memp_stat method. The information is printed to a specified output channel (see the <a href="../api_cxx/env_set_msgfile.html">DbEnv::set_msgfile</a> method for more information), or passed to an application callback function (see the <a href="../api_cxx/env_set_msgcall.html">DbEnv::set_msgcall</a> method for more information).</p> <p>The DbEnv::memp_stat_print method may not be called before the <a href="../api_cxx/env_open.html">DbEnv::open</a> method is called.</p> <p>The DbEnv::memp_stat_print 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. </p> <b>Parameters</b> <br> <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 or more of the following values: <br> <b><a name="DB_STAT_ALL">DB_STAT_ALL</a></b><ul compact><li>Display all available information.</ul> <b><a name="DB_STAT_CLEAR">DB_STAT_CLEAR</a></b><ul compact><li>Reset statistics after displaying their values.</ul> <b><a name="DB_STAT_MEMP_HASH">DB_STAT_MEMP_HASH</a></b><ul compact><li>Display the buffers with hash chains.</ul> <br></ul> <br> <hr size=1 noshade> <br><b>Class</b> <a href="../api_cxx/env_class.html">DbEnv</a>, <a href="../api_cxx/mempfile_class.html">DbMpoolFile</a> <br><b>See Also</b> <a href="../api_cxx/memp_list.html">Memory Pools and Related Methods</a> </tt> <table width="100%"><tr><td><br></td><td align=right> <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> </td></tr></table> <p><font size=1>Copyright (c) 1996,2008 Oracle. 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