pthread_setconcurrency, pthread_getconcurrency — set/get the concurrency level
Compile and link with
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
new_level as 0 instructs the
implementation to manage the concurrency level as it deems
returns the current value of the concurrency level for this
pthread_setconcurrency() returns 0; on
error, it returns a nonzero error number.
always succeeds, returning the concurrency level set by a
previous call to
pthread_setconcurrency(), or 0, if
not previously been called.
fail with the following error:
POSIX.1 also documents an EAGAIN error ("the value specified by
new_level would cause
a system resource to be exceeded").
For an explanation of the terms used in this section, see attributes(7).
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.
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