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pthread_getconcurrency(3p) — Linux manual page

PTHREAD_...CURRENCY(3P) POSIX Programmer's ManualPTHREAD_...CURRENCY(3P)

PROLOG        top

       This manual page is part of the POSIX Programmer's Manual.  The       Linux implementation of this interface may differ (consult the       corresponding Linux manual page for details of Linux behavior), or       the interface may not be implemented on Linux.

NAME        top

       pthread_getconcurrency, pthread_setconcurrency — get and set the       level of concurrency

SYNOPSIS        top

       #include <pthread.h>       int pthread_getconcurrency(void);       int pthread_setconcurrency(intnew_level);

DESCRIPTION        top

       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.       Thepthread_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.       Ifnew_level is zero, it causes the implementation to maintain the       concurrency level at its discretion as ifpthread_setconcurrency()       had never been called.       Thepthread_getconcurrency() function shall return the value set       by a previous call to thepthread_setconcurrency() function. If       thepthread_setconcurrency() function was not previously called,       this function shall return zero to indicate that the       implementation is maintaining the concurrency level.       A call topthread_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, thepthread_setconcurrency() andpthread_getconcurrency() functions       are provided for source code compatibility but they shall have no       effect when called. To maintain the function semantics, thenew_level parameter is saved whenpthread_setconcurrency() is       called so that a subsequent call topthread_getconcurrency() shall       return the same value.

RETURN VALUE        top

       If successful, thepthread_setconcurrency() function shall return       zero; otherwise, an error number shall be returned to indicate the       error.       Thepthread_getconcurrency() function shall always return the       concurrency level set by a previous call topthread_setconcurrency().  If thepthread_setconcurrency()       function has never been called,pthread_getconcurrency() shall       return zero.

ERRORS        top

       Thepthread_setconcurrency() function shall fail if:EINVALThe value specified bynew_level is negative.EAGAINThe value specified bynew_level would cause a system              resource to be exceeded.       Thepthread_setconcurrency() function shall not return an error       code of[EINTR].The following sections are informative.

EXAMPLES        top

       None.

APPLICATION USAGE        top

       Application developers should note that an implementation can       always ignore any calls topthread_setconcurrency() and return a       constant forpthread_getconcurrency().  For this reason, it is not       recommended that portable applications use this function.

RATIONALE        top

       None.

FUTURE DIRECTIONS        top

       These functions may be removed in a future version.

SEE ALSO        top

       The Base Definitions volume of POSIX.1‐2017,pthread.h(0p)

COPYRIGHT        top

       Portions of this text are reprinted and reproduced in electronic       form from IEEE Std 1003.1-2017, Standard for Information       Technology -- Portable Operating System Interface (POSIX), The       Open Group Base Specifications Issue 7, 2018 Edition, Copyright       (C) 2018 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 athttp://www.opengroup.org/unix/online.html .       Any typographical or formatting errors that appear in this page       are most likely to have been introduced during the conversion of       the source files to man page format. To report such errors, seehttps://www.kernel.org/doc/man-pages/reporting_bugs.html .IEEE/The Open Group                2017PTHREAD_...CURRENCY(3P)

Pages that refer to this page:pthread.h(0p), pthread_setconcurrency(3p)

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