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   pthread_setconcurrency    ( 3 )

установить / получить уровень параллелизма (set/get the concurrency level)

Имя (Name)

pthread_setconcurrency, pthread_getconcurrency - set/get the
       concurrency level

Синопсис (Synopsis)

#include <pthread.h>

int pthread_setconcurrency(int new_level); int pthread_getconcurrency(void);

Compile and link with -pthread.


Описание (Description)

The pthread_setconcurrency() function informs the implementation
       of the application's desired concurrency level, specified in
       new_level.  The implementation takes this only as a hint: POSIX.1
       does not specify the level of concurrency that should be provided
       as a result of calling pthread_setconcurrency().

Specifying new_level as 0 instructs the implementation to manage the concurrency level as it deems appropriate.

pthread_getconcurrency() returns the current value of the concurrency level for this process.


Возвращаемое значение (Return value)

On success, pthread_setconcurrency() returns 0; on error, it
       returns a nonzero error number.

pthread_getconcurrency() always succeeds, returning the concurrency level set by a previous call to pthread_setconcurrency(), or 0, if pthread_setconcurrency() has not previously been called.


Ошибки (Error)

pthread_setconcurrency() can fail with the following error:

EINVAL new_level is negative.

POSIX.1 also documents an EAGAIN error ("the value specified by new_level would cause a system resource to be exceeded").


Версии (Versions)

These functions are available in glibc since version 2.1.

Атрибуты (Attributes)

For an explanation of the terms used in this section, see
       attributes(7).

┌──────────────────────────────────────┬───────────────┬─────────┐ │Interface Attribute Value │ ├──────────────────────────────────────┼───────────────┼─────────┤ │pthread_setconcurrency(), │ Thread safety │ MT-Safe │ │pthread_getconcurrency() │ │ │ └──────────────────────────────────────┴───────────────┴─────────┘


Стандарты (Conforming to)

POSIX.1-2001, POSIX.1-2008.

Примечание (Note)

The default concurrency level is 0.

Concurrency levels are meaningful only for M:N threading implementations, where at any moment a subset of a process's set of user-level threads may be bound to a smaller number of kernel- scheduling entities. Setting the concurrency level allows the application to give the system a hint as to the number of kernel- scheduling entities that should be provided for efficient execution of the application.

Both LinuxThreads and NPTL are 1:1 threading implementations, so setting the concurrency level has no meaning. In other words, on Linux these functions merely exist for compatibility with other systems, and they have no effect on the execution of a program.


Смотри также (See also)

pthread_attr_setscope(3), pthreads(7)