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PTHREAD_SETCONCURRENCY(3) Linux Programmer's Manual PTHREAD_SETCONCURRENCY(3)
pthread_setconcurrency, pthread_getconcurrency - set/get the concurrency level
#include <pthread.h>
int pthread_setconcurrency(int new_level);
int pthread_getconcurrency(void);
Compile and link with -pthread.
The pthread_setconcurrency() function informs the implementation of the
application's desired concurrency level, specified in new_level. The
implementation only takes this 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.
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.
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").
These functions are available in glibc since version 2.1.
POSIX.1-2001.
The default concurrency level is 0.
Concurrency levels are only meaningful 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.
pthread_attr_setscope(3), pthreads(7)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
Linux 2009-04-10 PTHREAD_SETCONCURRENCY(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface