pthread_setconcurrency(3) - Linux manual page (original) (raw)

pthreads...ncurrency(3) Library Functions Manual_pthreads...ncurrency_(3)

NAME top

   pthread_setconcurrency, pthread_getconcurrency - set/get the
   concurrency level

LIBRARY top

   POSIX threads library (_libpthread_, _-lpthread_)

SYNOPSIS top

   **#include <pthread.h>**

   **int pthread_setconcurrency(int** _newlevel_**);**
   **int pthread_getconcurrency(**_void_**);**

DESCRIPTION top

   The **pthread_setconcurrency**() function informs the implementation
   of the application's desired concurrency level, specified in
   _newlevel_.  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 _newlevel_ 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.

RETURN VALUE top

   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.

ERRORS top

   **pthread_setconcurrency**() can fail with the following error:

   **EINVAL** _newlevel_ is negative.

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

ATTRIBUTES top

   For an explanation of the terms used in this section, see
   [attributes(7)](../man7/attributes.7.html).
   ┌──────────────────────────────────────┬───────────────┬─────────┐
   │ **Interface** │ **Attribute** │ **Value** │
   ├──────────────────────────────────────┼───────────────┼─────────┤
   │ **pthread_setconcurrency**(),            │ Thread safety │ MT-Safe │
   │ **pthread_getconcurrency**()             │               │         │
   └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS top

   POSIX.1-2008.

HISTORY top

   glibc 2.1.  POSIX.1-2001.

NOTES top

   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.

SEE ALSO top

   [pthread_attr_setscope(3)](../man3/pthread%5Fattr%5Fsetscope.3.html), [pthreads(7)](../man7/pthreads.7.html)

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Linux man-pages 6.10 2024-07-23 pthreads...ncurrency(3)