<!--$Id: memp_stat.so,v 10.71 2007/07/06 00:22:53 mjc Exp $--> <!--Copyright (c) 1997,2007 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> <h3>DbEnv::memp_stat</h3> </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> <h3><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></h3> <hr size=1 noshade> <h3>Description: DbEnv::memp_stat</h3> <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> <dl compact> <dt>size_t st_gbytes;<dd>Gigabytes of cache (total cache size is st_gbytes + st_bytes). <dt>size_t st_bytes;<dd>Bytes of cache (total cache size is st_gbytes + st_bytes). <dt>u_int32_t st_ncache;<dd>Number of caches. <dt>u_int32_t st_max_ncache;<dd>Maximum number of caches, as configured with the <a href="../api_cxx/env_set_cache_max.html">DbEnv::set_cache_max</a> method. <dt>roff_t st_regsize;<dd>Individual cache size, in bytes. <dt>size_t st_mmapsize;<dd>Maximum memory-mapped file size. <dt>int st_maxopenfd;<dd>Maximum open file descriptors. <dt>int st_maxwrite;<dd>Maximum sequential buffer writes. <dt>db_timeout_t st_maxwrite_sleep;<dd>Microseconds to pause after writing maximum sequential buffers. <dt>u_int32_t st_map;<dd>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). <dt>u_int32_t st_cache_hit;<dd>Requested pages found in the cache. <dt>u_int32_t st_cache_miss;<dd>Requested pages not found in the cache. <dt>u_int32_t st_page_create;<dd>Pages created in the cache. <dt>u_int32_t st_page_in;<dd>Pages read into the cache. <dt>u_int32_t st_page_out;<dd>Pages written from the cache to the backing file. <dt>u_int32_t st_ro_evict;<dd>Clean pages forced from the cache. <dt>u_int32_t st_rw_evict;<dd>Dirty pages forced from the cache. <dt>u_int32_t st_page_trickle;<dd>Dirty pages written using the <a href="../api_cxx/memp_trickle.html">DbEnv::memp_trickle</a> method. <dt>u_int32_t st_pages;<dd>Pages in the cache. <dt>u_int32_t st_page_clean;<dd>Clean pages currently in the cache. <dt>u_int32_t st_page_dirty;<dd>Dirty pages currently in the cache. <dt>u_int32_t st_hash_buckets;<dd>Number of hash buckets in buffer hash table. <dt>u_int32_t st_hash_searches;<dd>Total number of buffer hash table lookups. <dt>u_int32_t st_hash_longest;<dd>Longest chain ever encountered in buffer hash table lookups. <dt>u_int32_t st_hash_examined;<dd>Total number of hash elements traversed during hash table lookups. <dt>u_int32_t st_hash_nowait;<dd>Number of times that a thread of control was able to obtain a hash bucket lock without waiting. <dt>u_int32_t st_hash_wait;<dd>Number of times that a thread of control was forced to wait before obtaining a hash bucket lock. <dt>u_int32_t st_hash_max_nowait;<dd>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. <dt>u_int32_t st_hash_max_wait;<dd>Maximum number of times any hash bucket lock was waited for by a thread of control. <dt>u_int32_t st_region_wait;<dd>Number of times that a thread of control was forced to wait before obtaining a cache region mutex. <dt>u_int32_t st_region_nowait;<dd>Number of times that a thread of control was able to obtain a cache region mutex without waiting. <dt>u_int32_t st_mvcc_frozen;<dd>Number of buffers frozen. <dt>u_int32_t st_mvcc_thawed;<dd>Number of buffers thawed. <dt>u_int32_t st_mvcc_freed;<dd>Number of frozen buffers freed. <dt>u_int32_t st_alloc;<dd>Number of page allocations. <dt>u_int32_t st_alloc_buckets;<dd>Number of hash buckets checked during allocation. <dt>u_int32_t st_alloc_max_buckets;<dd>Maximum number of hash buckets checked during an allocation. <dt>u_int32_t st_alloc_pages;<dd>Number of pages checked during allocation. <dt>u_int32_t st_alloc_max_pages;<dd>Maximum number of pages checked during an allocation. <dt>u_int32_t st_io_wait;<dd>Number of operations blocked waiting for I/O to complete. </dl> <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> <dl compact> <dt>char * file_name;<dd>The name of the file. <dt>size_t st_pagesize;<dd>Page size in bytes. <dt>u_int32_t st_cache_hit;<dd>Requested pages found in the cache. <dt>u_int32_t st_cache_miss;<dd>Requested pages not found in the cache. <dt>u_int32_t st_map;<dd>Requested pages mapped into the process' address space. <dt>u_int32_t st_page_create;<dd>Pages created in the cache. <dt>u_int32_t st_page_in;<dd>Pages read into the cache. <dt>u_int32_t st_page_out;<dd>Pages written from the cache to the backing file. </dl> <p>The DbEnv::memp_stat method may not be called before the <a href="../api_cxx/env_open.html">DbEnv::open</a> method has been 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> <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>fsp</b><dd>The <b>fsp</b> parameter references memory into which a pointer to the allocated per-file statistics structures is copied. <dt><b>gsp</b><dd>The <b>gsp</b> parameter references memory into which a pointer to the allocated global statistics structure is copied. </dl> <h3>Errors</h3> <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> <dl compact> <dt>EINVAL<dd>An invalid flag value or parameter was specified. </dl> <hr size=1 noshade> <h3>Description: DbEnv::memp_stat_print</h3> <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 has been 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> <h3>Parameters</h3> <dl compact> <dt><b>flags</b><dd>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: <dl compact> <dt><a name="DB_STAT_ALL">DB_STAT_ALL</a><dd>Display all available information. <dt><a name="DB_STAT_CLEAR">DB_STAT_CLEAR</a><dd>Reset statistics after displaying their values. <dt><a name="DB_STAT_MEMP_HASH">DB_STAT_MEMP_HASH</a><dd>Display the buffers with hash chains. </dl> </dl> <hr size=1 noshade> <h3>Class</h3> <a href="../api_cxx/env_class.html">DbEnv</a>, <a href="../api_cxx/mempfile_class.html">DbMpoolFile</a> <h3>See Also</h3> <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) 1996,2007 Oracle. 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