Manual Pages for UNIX Operating System command usage for man pthread_getconcurrency

Standard C Library Functions           pthread_getconcurrency(3C)



NAME
     pthread_getconcurrency, pthread_setconcurrency - get or  set
     level of concurrency

SYNOPSIS
     cc -mt [ flag... ] file... -lpthread [ library... ]
     #include 

     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 implemen-
     tation 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 con-
     currency 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  0, it causes the implementation to maintain
     the    concurrency   level   at   its   discretion   as   if
     pthread_setconcurrency() was never called.


     The  pthread_getconcurrency() function  returns  the   value
     set  by  a  previous  call  to the  pthread_setconcurrency()
     function. If the  pthread_setconcurrency() function was  not
     previously called, this function returns  0 to indicate that
     the implementation is maintaining the concurrency level.


     When an application calls   pthread_setconcurrency()  it  is
     informing  the  implementation  of  its  desired concurrency
     level. The  implementation  uses  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() func-
     tions  will  be  provided  for source code compatibility but



SunOS 5.11          Last change: 23 Mar 2005                    1






Standard C Library Functions           pthread_getconcurrency(3C)



     they will have no effect when called. To maintain the  func-
     tion  semantics,  the new_level parameter will be saved when
     pthread_setconcurrency() is called so that a subsequent call
     to pthread_getconcurrency() returns the same value.

RETURN VALUES
     If  successful,   the    pthread_setconcurrency()   function
     returns   0. Otherwise, an error number is returned to indi-
     cate the error.


     The  pthread_getconcurrency() function  always  returns  the
     concurrency    level    set    by   a   previous   call   to
     pthread_setconcurrency(). If  the   pthread_setconcurrency()
     function  has  never  been called,  pthread_getconcurrency()
     returns  0.

ERRORS
     The pthread_setconcurrency() function will fail if:

     EINVAL    The value specified by new_level is negative.


     EAGAIN    The value specific by new_level would cause a sys-
               tem resource to be exceeded.


ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Interface Stability         | Committed                   |
    |_____________________________|_____________________________|
    | MT-Level                    | MT-Safe                     |
    |_____________________________|_____________________________|
    | Standard                    | See standards(5).           |
    |_____________________________|_____________________________|


SEE ALSO
     pthread_create(3C),  pthread_attr_init(3C),   attributes(5),
     standards(5)








SunOS 5.11          Last change: 23 Mar 2005                    2