1pthread_setconcurrency(3) Library Functions Manual pthread_setconcurrency(3)
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6 pthread_setconcurrency, pthread_getconcurrency - set/get the concur‐
7 rency level
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10 POSIX threads library (libpthread, -lpthread)
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13 #include <pthread.h>
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15 int pthread_setconcurrency(int new_level);
16 int pthread_getconcurrency(void);
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19 The pthread_setconcurrency() function informs the implementation of the
20 application's desired concurrency level, specified in new_level. The
21 implementation takes this only as a hint: POSIX.1 does not specify the
22 level of concurrency that should be provided as a result of calling
23 pthread_setconcurrency().
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25 Specifying new_level as 0 instructs the implementation to manage the
26 concurrency level as it deems appropriate.
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28 pthread_getconcurrency() returns the current value of the concurrency
29 level for this process.
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32 On success, pthread_setconcurrency() returns 0; on error, it returns a
33 nonzero error number.
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35 pthread_getconcurrency() always succeeds, returning the concurrency
36 level set by a previous call to pthread_setconcurrency(), or 0, if
37 pthread_setconcurrency() has not previously been called.
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40 pthread_setconcurrency() can fail with the following error:
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42 EINVAL new_level is negative.
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44 POSIX.1 also documents an EAGAIN error ("the value specified by
45 new_level would cause a system resource to be exceeded").
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48 For an explanation of the terms used in this section, see at‐
49 tributes(7).
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51 ┌────────────────────────────────────────────┬───────────────┬─────────┐
52 │Interface │ Attribute │ Value │
53 ├────────────────────────────────────────────┼───────────────┼─────────┤
54 │pthread_setconcurrency(), │ Thread safety │ MT-Safe │
55 │pthread_getconcurrency() │ │ │
56 └────────────────────────────────────────────┴───────────────┴─────────┘
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59 POSIX.1-2008.
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62 glibc 2.1. POSIX.1-2001.
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65 The default concurrency level is 0.
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67 Concurrency levels are meaningful only for M:N threading
68 implementations, where at any moment a subset of a process's set of
69 user-level threads may be bound to a smaller number of kernel-
70 scheduling entities. Setting the concurrency level allows the
71 application to give the system a hint as to the number of kernel-
72 scheduling entities that should be provided for efficient execution of
73 the application.
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75 Both LinuxThreads and NPTL are 1:1 threading implementations, so
76 setting the concurrency level has no meaning. In other words, on Linux
77 these functions merely exist for compatibility with other systems, and
78 they have no effect on the execution of a program.
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81 pthread_attr_setscope(3), pthreads(7)
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85Linux man-pages 6.05 2023-07-20 pthread_setconcurrency(3)