PTHREAD_SETCONCURRENCY
Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
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NAME
pthread_setconcurrency, pthread_getconcurrency - set/get
the concurrency level
SYNOPSIS
#include <pthread.h>
int pthread_setconcurrency(int new_level);
int pthread_getconcurrency(void);
Compile and link with -pthread.
DESCRIPTION
The
pthread_setconcurrency()
function informs the implementation of the application's
desired concurrency level, specified in
new_level.
The implementation takes this only as a hint:
POSIX.1 does not specify the level of concurrency that
should be provided as a result of calling
pthread_setconcurrency().
Specifying
new_level
as 0 instructs the implementation to manage the concurrency level
as it deems appropriate.
pthread_getconcurrency()
returns the current value of the concurrency level for this process.
RETURN VALUE
On success,
pthread_setconcurrency()
returns 0;
on error, it returns a nonzero error number.
pthread_getconcurrency()
always succeeds, returning the concurrency level set by a previous call to
pthread_setconcurrency(),
or 0, if
pthread_setconcurrency()
has not previously been called.
ERRORS
pthread_setconcurrency()
can fail with the following error:
- EINVAL
-
new_level
is negative.
POSIX.1 also documents an
EAGAIN
error ("the value specified by
new_level
would cause a system resource to be exceeded").
VERSIONS
These functions are available in glibc since version 2.1.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
pthread_setconcurrency(),
pthread_getconcurrency()
| Thread safety | MT-Safe
|
CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
NOTES
The default concurrency level is 0.
Concurrency levels are meaningful only for M:N threading implementations,
where at any moment a subset of a process's set of user-level threads
may be bound to a smaller number of kernel-scheduling entities.
Setting the concurrency level allows the application to
give the system a hint as to the number of kernel-scheduling entities
that should be provided for efficient execution of the application.
Both LinuxThreads and NPTL are 1:1 threading implementations,
so setting the concurrency level has no meaning.
In other words,
on Linux these functions merely exist for compatibility with other systems,
and they have no effect on the execution of a program.
SEE ALSO
pthread_attr_setscope(3),
pthreads(7)
COLOPHON
This page is part of release 4.13 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- VERSIONS
-
- ATTRIBUTES
-
- CONFORMING TO
-
- NOTES
-
- SEE ALSO
-
- COLOPHON
-
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