"PTHREAD_GETCONCURRENCY"(P) manual page

From 41f88a82b33cdb357c83b582381232733ed2d039 Mon Sep 17 00:00:00 2001 From: rpj Date: Thu, 5 May 2005 14:18:27 +0000 Subject: '' --- manual/pthread_setconcurrency.html | 153 +++++++++++++++++++++++++++++++++++++ 1 file changed, 153 insertions(+) create mode 100644 manual/pthread_setconcurrency.html (limited to 'manual/pthread_setconcurrency.html') diff --git a/manual/pthread_setconcurrency.html b/manual/pthread_setconcurrency.html new file mode 100644 index 0000000..125dd9a --- /dev/null +++ b/manual/pthread_setconcurrency.html @@ -0,0 +1,153 @@ + + + + + "PTHREAD_GETCONCURRENCY"(P) manual page + + + + + + + +

Table of Contents

Name

pthread_getconcurrency, pthread_setconcurrency - get and set the +level of concurrency +

Synopsis

#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 entities, the +pthread_setconcurrency and pthread_getconcurrency +functions are provided for source code compatibility but they shall +have no effect when called. To maintain the function semantics, the +new_level parameter is saved when pthread_setconcurrency +is called so that a subsequent call to pthread_getconcurrency +shall return the same value. +

Pthreads-w32 provides these routines for source code +compatibility only, as described in the previous paragraph.

Return Value

If successful, the pthread_setconcurrency function shall +return zero; otherwise, an error number shall be returned to indicate +the error. +

The pthread_getconcurrency function shall always return the +concurrency level set by a previous call to pthread_setconcurrency +. If the pthread_setconcurrency function has never been +called, pthread_getconcurrency shall return zero. +

Errors

The pthread_setconcurrency function shall fail if: +

EINVAL +: + The value specified by new_level is negative. +
+ EAGAIN +: + The value specific by new_level would cause a system resource + to be exceeded. +

+These functions shall not return an error code of [EINTR]. +

The following sections are informative. +

Examples

None. +

Application Usage

Use of these functions changes the state of the underlying +concurrency upon which the application depends. Library developers +are advised to not use the pthread_getconcurrency and +pthread_setconcurrency functions since their use may conflict +with an applications use of these functions. +

Rationale

None. +

Future Directions

None. +

Copyright

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 http://www.opengroup.org/unix/online.html +. +

Modified by Ross Johnson for use with Pthreads-w32.

Table of Contents

Name +
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Synopsis +
+
Description +
+
Return + Value +
+
Errors +
+
Examples +
+
Application + Usage +
+
Rationale +
+
Future + Directions +
+
See + Also +
+
Copyright +
+

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