pthread_getconcurrency man page on SmartOS

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PTHREAD_GETCONCURRENCY(3C)			    PTHREAD_GETCONCURRENCY(3C)

NAME
       pthread_getconcurrency,	pthread_setconcurrency	-  get or set level of
       concurrency

SYNOPSIS
       cc -mt [ flag... ] file... -lpthread [ library... ]
       #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  simulta‐
       neously	active.	 By default, the threads implementation ensures that a
       sufficient number of threads are active so that the  process  can  con‐
       tinue  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  0, it causes the implementation to maintain the con‐
       currency level at its discretion	 as  if	 pthread_setconcurrency()  was
       never called.

       The  pthread_getconcurrency() function returns the  value set by a pre‐
       vious  call  to	the    pthread_setconcurrency()	  function.   If   the
       pthread_setconcurrency() function was not previously called, this func‐
       tion 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() functions will be provided for source code
       compatibility but they will have no effect when called. To maintain the
       function	  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.  Oth‐
       erwise, an error number is returned to indicate 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_get‐
       concurrency() 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 system resource
		 to be exceeded.

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

       ┌────────────────────┬─────────────────┐
       │  ATTRIBUTE TYPE    │ ATTRIBUTE VALUE │
       ├────────────────────┼─────────────────┤
       │Interface Stability │ Standard	      │
       ├────────────────────┼─────────────────┤
       │MT-Level	    │ MT-Safe	      │
       └────────────────────┴─────────────────┘

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

				 Mar 23, 2005	    PTHREAD_GETCONCURRENCY(3C)
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