sched_yield(3)sched_yield(3)NAMEsched_yield - Signals scheduler a willingness to yield to another
thread
SYNOPSIS
#include <pthread.h>
void sched_yield(
void );
LIBRARY
DECthreads POSIX 1003.1c Library (libpthread.so)
STANDARDS
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
IEEE Std 1003.1c-1995, POSIX System Application Program Interface
PARAMETERS
None
DESCRIPTION
This routine forces the running thread to relinquish the processor
until it again becomes the head of its thread list. This routine noti‐
fies the thread scheduler that the current thread is willing to release
its processor to other threads of equivalent or greater scheduling
precedence. (A thread generally will release its processor to a thread
of a greater scheduling precedence without calling this routine.) If
no other threads of equivalent or greater scheduling precedence are
ready to execute, the thread continues.
This routine can allow knowledge of the details of an application to be
used to improve its performance. If a thread does not call sched_yield,
other threads may be given the opportunity to run at arbitrary points
(possibly even when the interrupted thread holds a required resource).
By making strategic calls to sched_yield, other threads can be given
the opportunity to run when the resources are free. This can sometimes
improve performance by reducing contention for the resource.
As a general guideline, consider calling this routine after a thread
has released a resource (such as a mutex) that is heavily contended for
by other threads. This can be especially important if the program is
running on a uniprocessor machine, or if the thread acquires and
releases the resource inside a tight loop.
Use this routine carefully and sparingly, because misuse can cause
unnecessary context switching which will increase overhead and degrade
performance. For example, it is counter-productive for a thread to
yield while it holds a resource that the threads to which it is yield‐
ing will need. Likewise, it is pointless to yield unless there is
likely to be another thread that is ready to run.
RETURN VALUES
None
SEE ALSO
Functions: pthread_attr_setschedparam(3), pthread_setschedparam(3)
Manuals: Guide to DECthreads and Programmer's Guide
sched_yield(3)