PTHREAD_SETCONCURRENCY
PTHREAD_SETCONCURRENCY
NAMESYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
VERSIONS
ATTRIBUTES
CONFORMING TO
NOTES
SEE ALSO
COLOPHON
NAME
pthread_setconcurrency, pthread_getconcurrency − set/get the concurrency level
SYNOPSIS
#include <pthread.h>
int
pthread_setconcurrency(int new_level);
int pthread_getconcurrency(void);
Compile and link with −pthread.
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.
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.
ERRORS
pthread_setconcurrency() can fail with the following error:
|
EINVAL |
new_level is negative. |
POSIX.1-2001 also documents an EAGAIN error ("the value specified by new_level would cause a system resource to be exceeded").
VERSIONS
These functions are available in glibc since version 2.1.
ATTRIBUTES
Multithreading
(see pthreads(7))
The pthread_setconcurrency() and
pthread_getconcurrency() functions are
thread-safe.
CONFORMING TO
POSIX.1-2001.
NOTES
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
pthread_attr_setscope(3), pthreads(7)
COLOPHON
This page is part of release 3.69 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at http://www.kernel.org/doc/man−pages/.
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