Berkeley DB: DB_ENV->mutex_stat
Description: Berkeley DB: An embedded database programmatic toolkit.
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DB_ENV->mutex_stat |

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    #include <db.h>

    int
    DB_ENV->mutex_stat(DB_ENV *env, DB_MUTEX_STAT **statp, u_int32_t flags);

    int
    DB_ENV->mutex_stat_print(DB_ENV *env, u_int32_t flags);

Description: DB_ENV->mutex_stat

The DB_ENV->mutex_stat method returns the mutex subsystem statistics.

The DB_ENV->mutex_stat method creates a statistical structure of type DB_MUTEX_STAT and copies a pointer to it into a user-specified memory location.

Statistical structures are stored 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 standard C library 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.

The following DB_MUTEX_STAT fields will be filled in:

u_int32_t st_mutex_align;

- The mutex alignment, in bytes.

u_int32_t st_mutex_tas_spins;

- The number of times test-and-set mutexes will spin without blocking.

int st_mutex_cnt;

- The total number of mutexes configured.

u_int32_t st_mutex_free;

- The number of mutexes currently available.

u_int32_t st_mutex_inuse;

- The number of mutexes currently in use.

u_int32_t st_mutex_inuse_max;

- The maximum number of mutexes ever in use.

roff_t st_regsize;

- The size of the mutex region, in bytes.

u_int32_t st_region_wait;

- The number of times that a thread of control was forced to wait before obtaining the mutex region mutex.

u_int32_t st_region_nowait;

- The number of times that a thread of control was able to obtain the mutex region mutex without waiting.

The DB_ENV->mutex_stat method may not be called before the DB_ENV->open method is called.

The DB_ENV->mutex_stat method returns a non-zero error value on failure and 0 on success.

Parameters
flags

- The flags parameter must be set to 0 or the following value:
  DB_STAT_CLEAR
  - Reset statistics after returning their values.

statp

- The statp parameter references memory into which a pointer to the allocated statistics structure is copied.

Errors

The DB_ENV->mutex_stat method may fail and return one of the following non-zero errors:

EINVAL

- An invalid flag value or parameter was specified.

Description: DB_ENV->mutex_stat_print

The DB_ENV->mutex_stat_print method displays the mutex subsystem statistical information, as described for the DB_ENV->mutex_stat method. The information is printed to a specified output channel (see the DB_ENV->set_msgfile method for more information), or passed to an application callback function (see the DB_ENV->set_msgcall method for more information).

The DB_ENV->mutex_stat_print method may not be called before the DB_ENV->open method is called.

The DB_ENV->mutex_stat_print method returns a non-zero error value on failure and 0 on success.

Parameters
flags

- The flags parameter must be set to 0 or by bitwise inclusively OR'ing together one or more of the following values:
  DB_STAT_ALL
  - Display all available information.
  DB_STAT_CLEAR
  - Reset statistics after displaying their values.

Class DB_ENV
See Also Database Environments and Related Methods`

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