Professional Multicore Programming: Design and Implementation for C++ Developers

Name

NAME

pthread_getconcurrency, pthread_setconcurrency — get and set the level of concurrency

SYNOPSIS

XSI #include <pthread.h>

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

DESCRIPTION

Unbound threads in a process may or may not be required to be simultaneously active. By default, the threads implementation ensures that a sufficient number of threads are active so that the process can continue to make progress. While this conserves system resources, it may not produce the most effective level of concurrency.

The pthread_setconcurrency() function allows an application to inform the threads implementation of its desired concurrency level, new_level. The actual level of concurrency provided by the implementation as a result of this function call is unspecified.

If new_level is zero, it causes the implementation to maintain the concurrency level at its discretion as if pthread_setconcurrency() had never been called.

The pthread_getconcurrency() function shall return the value set by a previous call to the pthread_setconcurrency() function. If the pthread_setconcurrency() function was not previously called, this function shall return zero to indicate that the implementation is maintaining the concurrency level.

A call to pthread_setconcurrency() shall inform the implementation of its desired concurrency level. The implementation shall use this as a hint, not a requirement.

If an implementation does not support multiplexing of user threads on top of several kernel-scheduled ...