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   pthread_setconcurrency    ( 3 )

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Имя (Name)

pthread_setconcurrency, pthread_getconcurrency - set/get the
       concurrency level

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Синопсис (Synopsis)

#include <pthread.h>

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

       Compile and link with -pthread.

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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.

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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.

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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").

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Версии (Versions)

These functions are available in glibc since version 2.1.

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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()              │               │         │
       └──────────────────────────────────────┴───────────────┴─────────┘

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Стандарты (Conforming to)

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

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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.

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Смотри также (See also)

pthread_attr_setscope(3), pthreads(7)

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