|
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
PTHREAD_SETCONCURRENCY(3) Linux Programmer's ManualPTHREAD_SETCONCURRENCY(3)
pthread_setconcurrency, pthread_getconcurrency - set/get the concur‐
rency level
#include <pthread.h>
int pthread_setconcurrency(int new_level);
int pthread_getconcurrency(void);
Compile and link with -pthread.
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.
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.
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").
These functions are available in glibc since version 2.1.
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────┼───────────────┼─────────┤
│pthread_setconcurrency(), │ Thread safety │ MT-Safe │
│pthread_getconcurrency() │ │ │
└──────────────────────────┴───────────────┴─────────┘
POSIX.1-2001, POSIX.1-2008.
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.
pthread_attr_setscope(3), pthreads(7)
This page is part of release 4.12 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/.
Linux 2015-08-08 PTHREAD_SETCONCURRENCY(3)