DB_ENV->memp_stat
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#include <db.h>
int
DB_ENV->memp_stat(DB_ENV *env, DB_MPOOL_STAT **gsp,
DB_MPOOL_FSTAT *(*fsp)[], u_int32_t flags);
Description
The DB_ENV->memp_stat function method creates statistical structures and copies
pointers to them into user-specified memory locations. The statistics
include the number of files participating in the pool, the active pages
in the pool, and information about how effective the cache has been.
The flags value must be set to 0 or
the following value:
- DB_STAT_CLEAR
- Reset statistics after returning their values.
Statistical structures are created in allocated memory. If application-specific allocation
routines have been declared (see DB_ENV->set_alloc for more
information), they are used to allocate the memory; otherwise, the
library function malloc(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.
If gsp is non-NULL, the global statistics for the memory pool
mp are copied into the memory location to which it refers. The
global statistics are stored in a structure of type DB_MPOOL_STAT.
The following DB_MPOOL_STAT fields will be filled in:
- size_t st_gbytes;
- Gigabytes of cache (total cache size is st_gbytes + st_bytes).
- size_t st_bytes;
- Bytes of cache (total cache size is st_gbytes + st_bytes).
- u_int32_t st_ncache;
- Number of caches.
- u_int32_t st_regsize;
- Individual cache size.
- u_int32_t st_cache_hit;
- Requested pages found in the cache.
- u_int32_t st_cache_miss;
- Requested pages not found in the cache.
- u_int32_t st_map;
- 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).
- u_int32_t st_page_create;
- Pages created in the cache.
- u_int32_t st_page_in;
- Pages read into the cache.
- u_int32_t st_page_out;
- Pages written from the cache to the backing file.
- u_int32_t st_ro_evict;
- Clean pages forced from the cache.
- u_int32_t st_rw_evict;
- Dirty pages forced from the cache.
- u_int32_t st_hash_buckets;
- Number of hash buckets in buffer hash table.
- u_int32_t st_hash_searches;
- Total number of buffer hash table lookups.
- u_int32_t st_hash_longest;
- The longest chain ever encountered in buffer hash table lookups.
- u_int32_t st_hash_examined;
- Total number of hash elements traversed during hash table lookups.
- u_int32_t st_page_clean;
- Clean pages currently in the cache.
- u_int32_t st_page_dirty;
- Dirty pages currently in the cache.
- u_int32_t st_page_trickle;
- Dirty pages written using the DB_ENV->memp_trickle interface.
- u_int32_t st_region_wait;
- The number of times that a thread of control was forced to wait before
obtaining the region lock.
- u_int32_t st_region_nowait;
- The number of times that a thread of control was able to obtain
the region lock without waiting.
If fsp is non-NULL, a pointer to a NULL-terminated
variable length array of statistics for individual files, in the memory
pool mp, is copied into the memory location to which it refers.
If no individual files currently exist in the memory pool, fsp
will be set to NULL.
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 pool; that is, each element of the array:
- char *file_name;
- The name of the file.
- size_t st_pagesize;
- Page size in bytes.
- u_int32_t st_cache_hit;
- Requested pages found in the cache.
- u_int32_t st_cache_miss;
- Requested pages not found in the cache.
- u_int32_t st_map;
- Requested pages mapped into the process' address space.
- u_int32_t st_page_create;
- Pages created in the cache.
- u_int32_t st_page_in;
- Pages read into the cache.
- u_int32_t st_page_out;
- Pages written from the cache to the backing file.
The DB_ENV->memp_stat function returns a non-zero error value on failure and 0 on success.
Errors
The DB_ENV->memp_stat function may fail and return a non-zero error for the following conditions:
- EINVAL
- An invalid flag value or parameter was specified.
The DB_ENV->memp_stat function may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions.
If a catastrophic error has occurred, the DB_ENV->memp_stat function may fail and return
DB_RUNRECOVERY, in which case all subsequent Berkeley DB calls will fail
in the same way.
See Also
DB_ENV->set_cachesize,
DB_ENV->set_mp_mmapsize,
DB_ENV->memp_fcreate,
DB_MPOOLFILE->close,
DB_MPOOLFILE->get,
DB_MPOOLFILE->open,
DB_MPOOLFILE->put,
DB_MPOOLFILE->set,
DB_MPOOLFILE->sync,
DB_ENV->memp_register,
DB_MPOOLFILE->set_clear_len,
DB_MPOOLFILE->set_fileid,
DB_MPOOLFILE->set_ftype,
DB_MPOOLFILE->set_lsn_offset,
DB_MPOOLFILE->set_pgcookie,
DB_ENV->memp_stat,
DB_ENV->memp_sync,
and
DB_ENV->memp_trickle.
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