156 lines
6.5 KiB
HTML
156 lines
6.5 KiB
HTML
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
|
|||
|
|
<HTML>
|
|||
|
|
<HEAD>
|
|||
|
|
<META HTTP-EQUIV="CONTENT-TYPE" CONTENT="text/html; charset=utf-8">
|
|||
|
|
<TITLE>"PTHREAD_GETCONCURRENCY"(P) manual page</TITLE>
|
|||
|
|
<META NAME="GENERATOR" CONTENT="OpenOffice.org 1.1.3 (Linux)">
|
|||
|
|
<META NAME="CREATED" CONTENT="20050505;19162600">
|
|||
|
|
<META NAME="CHANGED" CONTENT="20050505;19223800">
|
|||
|
|
<!-- manual page source format generated by PolyglotMan v3.2, -->
|
|||
|
|
<!-- available at http://polyglotman.sourceforge.net/ -->
|
|||
|
|
</HEAD>
|
|||
|
|
<BODY LANG="en-GB" BGCOLOR="#ffffff" DIR="LTR">
|
|||
|
|
<H4>POSIX Threads for Windows – REFERENCE - <A HREF="http://sources.redhat.com/pthreads-win32">Pthreads-w32</A></H4>
|
|||
|
|
<P><A HREF="index.html">Reference Index</A></P>
|
|||
|
|
<P><A HREF="#toc">Table of Contents</A></P>
|
|||
|
|
<H2><A HREF="#toc0" NAME="sect0">Name</A></H2>
|
|||
|
|
<P>pthread_getconcurrency, pthread_setconcurrency - get and set the
|
|||
|
|
level of concurrency
|
|||
|
|
</P>
|
|||
|
|
<H2><A HREF="#toc1" NAME="sect1">Synopsis</A></H2>
|
|||
|
|
<P><B>#include <pthread.h> </B>
|
|||
|
|
</P>
|
|||
|
|
<P><B>int pthread_getconcurrency(void);</B> <BR><B>int
|
|||
|
|
pthread_setconcurrency(int</B> <I>new_level</I><B>); </B>
|
|||
|
|
</P>
|
|||
|
|
<H2><A HREF="#toc2" NAME="sect2">Description</A></H2>
|
|||
|
|
<P>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.
|
|||
|
|
</P>
|
|||
|
|
<P>The <B>pthread_setconcurrency</B> function allows an application
|
|||
|
|
to inform the threads implementation of its desired concurrency
|
|||
|
|
level, <I>new_level</I>. The actual level of concurrency provided by
|
|||
|
|
the implementation as a result of this function call is unspecified.
|
|||
|
|
</P>
|
|||
|
|
<P>If <I>new_level</I> is zero, it causes the implementation to
|
|||
|
|
maintain the concurrency level at its discretion as if
|
|||
|
|
<B>pthread_setconcurrency</B> had never been called.
|
|||
|
|
</P>
|
|||
|
|
<P>The <B>pthread_getconcurrency</B> function shall return the value
|
|||
|
|
set by a previous call to the <B>pthread_setconcurrency</B> function.
|
|||
|
|
If the <B>pthread_setconcurrency</B> function was not previously
|
|||
|
|
called, this function shall return zero to indicate that the
|
|||
|
|
implementation is maintaining the concurrency level.
|
|||
|
|
</P>
|
|||
|
|
<P>A call to <B>pthread_setconcurrency</B> shall inform the
|
|||
|
|
implementation of its desired concurrency level. The implementation
|
|||
|
|
shall use this as a hint, not a requirement.
|
|||
|
|
</P>
|
|||
|
|
<P>If an implementation does not support multiplexing of user threads
|
|||
|
|
on top of several kernel-scheduled entities, the
|
|||
|
|
<B>pthread_setconcurrency</B> and <B>pthread_getconcurrency</B>
|
|||
|
|
functions are provided for source code compatibility but they shall
|
|||
|
|
have no effect when called. To maintain the function semantics, the
|
|||
|
|
<I>new_level</I> parameter is saved when <B>pthread_setconcurrency</B>
|
|||
|
|
is called so that a subsequent call to <B>pthread_getconcurrency</B>
|
|||
|
|
shall return the same value.
|
|||
|
|
</P>
|
|||
|
|
<P><B>Pthreads-w32</B> provides these routines for source code
|
|||
|
|
compatibility only, as described in the previous paragraph.</P>
|
|||
|
|
<H2><A HREF="#toc3" NAME="sect3">Return Value</A></H2>
|
|||
|
|
<P>If successful, the <B>pthread_setconcurrency</B> function shall
|
|||
|
|
return zero; otherwise, an error number shall be returned to indicate
|
|||
|
|
the error.
|
|||
|
|
</P>
|
|||
|
|
<P>The <B>pthread_getconcurrency</B> function shall always return the
|
|||
|
|
concurrency level set by a previous call to <B>pthread_setconcurrency</B>
|
|||
|
|
. If the <B>pthread_setconcurrency</B> function has never been
|
|||
|
|
called, <B>pthread_getconcurrency</B> shall return zero.
|
|||
|
|
</P>
|
|||
|
|
<H2><A HREF="#toc4" NAME="sect4">Errors</A></H2>
|
|||
|
|
<P>The <B>pthread_setconcurrency</B> function shall fail if:
|
|||
|
|
</P>
|
|||
|
|
<DL>
|
|||
|
|
<DT><B>EINVAL</B>
|
|||
|
|
</DT><DD>
|
|||
|
|
The value specified by <I>new_level</I> is negative.
|
|||
|
|
</DD><DT>
|
|||
|
|
<B>EAGAIN</B>
|
|||
|
|
</DT><DD STYLE="margin-bottom: 0.5cm">
|
|||
|
|
The value specific by <I>new_level</I> would cause a system resource
|
|||
|
|
to be exceeded.
|
|||
|
|
</DD></DL>
|
|||
|
|
<P>
|
|||
|
|
These functions shall not return an error code of [EINTR].
|
|||
|
|
</P>
|
|||
|
|
<P><I>The following sections are informative.</I>
|
|||
|
|
</P>
|
|||
|
|
<H2><A HREF="#toc5" NAME="sect5">Examples</A></H2>
|
|||
|
|
<P>None.
|
|||
|
|
</P>
|
|||
|
|
<H2><A HREF="#toc6" NAME="sect6">Application Usage</A></H2>
|
|||
|
|
<P>Use of these functions changes the state of the underlying
|
|||
|
|
concurrency upon which the application depends. Library developers
|
|||
|
|
are advised to not use the <B>pthread_getconcurrency</B> and
|
|||
|
|
<B>pthread_setconcurrency</B> functions since their use may conflict
|
|||
|
|
with an applications use of these functions.
|
|||
|
|
</P>
|
|||
|
|
<H2><A HREF="#toc7" NAME="sect7">Rationale</A></H2>
|
|||
|
|
<P>None.
|
|||
|
|
</P>
|
|||
|
|
<H2><A HREF="#toc8" NAME="sect8">Future Directions</A></H2>
|
|||
|
|
<P>None.
|
|||
|
|
</P>
|
|||
|
|
<H2><A HREF="#toc9" NAME="sect9">See Also</A></H2>
|
|||
|
|
<P>The Base Definitions volume of IEEE Std 1003.1-2001,
|
|||
|
|
<I><pthread.h></I>
|
|||
|
|
</P>
|
|||
|
|
<H2><A HREF="#toc10" NAME="sect10">Copyright</A></H2>
|
|||
|
|
<P>Portions of this text are reprinted and reproduced in electronic
|
|||
|
|
form from IEEE Std 1003.1, 2003 Edition, Standard for Information
|
|||
|
|
Technology -- Portable Operating System Interface (POSIX), The Open
|
|||
|
|
Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the
|
|||
|
|
Institute of Electrical and Electronics Engineers, Inc and The Open
|
|||
|
|
Group. In the event of any discrepancy between this version and the
|
|||
|
|
original IEEE and The Open Group Standard, the original IEEE and The
|
|||
|
|
Open Group Standard is the referee document. The original Standard
|
|||
|
|
can be obtained online at <A HREF="http://www.opengroup.org/unix/online.html">http://www.opengroup.org/unix/online.html</A>
|
|||
|
|
.
|
|||
|
|
</P>
|
|||
|
|
<P>Modified by Ross Johnson for use with <A HREF="http://sources.redhat.com/pthreads-win32">Pthreads-w32</A>.</P>
|
|||
|
|
<HR>
|
|||
|
|
<P><A NAME="toc"></A><B>Table of Contents</B></P>
|
|||
|
|
<UL>
|
|||
|
|
<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect0" NAME="toc0">Name</A>
|
|||
|
|
</P>
|
|||
|
|
<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect1" NAME="toc1">Synopsis</A>
|
|||
|
|
</P>
|
|||
|
|
<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect2" NAME="toc2">Description</A>
|
|||
|
|
</P>
|
|||
|
|
<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect3" NAME="toc3">Return
|
|||
|
|
Value</A>
|
|||
|
|
</P>
|
|||
|
|
<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect4" NAME="toc4">Errors</A>
|
|||
|
|
</P>
|
|||
|
|
<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect5" NAME="toc5">Examples</A>
|
|||
|
|
</P>
|
|||
|
|
<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect6" NAME="toc6">Application
|
|||
|
|
Usage</A>
|
|||
|
|
</P>
|
|||
|
|
<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect7" NAME="toc7">Rationale</A>
|
|||
|
|
</P>
|
|||
|
|
<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect8" NAME="toc8">Future
|
|||
|
|
Directions</A>
|
|||
|
|
</P>
|
|||
|
|
<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect9" NAME="toc9">See
|
|||
|
|
Also</A>
|
|||
|
|
</P>
|
|||
|
|
<LI><P><A HREF="#sect10" NAME="toc10">Copyright</A>
|
|||
|
|
</P>
|
|||
|
|
</UL>
|
|||
|
|
</BODY>
|
|||
|
|
</HTML>
|