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diff --git a/man3/pthread_setconcurrency.3 b/man3/pthread_setconcurrency.3 new file mode 100644 index 0000000..642208f --- /dev/null +++ b/man3/pthread_setconcurrency.3 @@ -0,0 +1,101 @@ +'\" t +.\" Copyright (c) 2009 Michael Kerrisk, <mtk.manpages@gmail.com> +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.TH pthread_setconcurrency 3 2023-07-20 "Linux man-pages 6.05.01" +.SH NAME +pthread_setconcurrency, pthread_getconcurrency \- set/get +the concurrency level +.SH LIBRARY +POSIX threads library +.RI ( libpthread ", " \-lpthread ) +.SH SYNOPSIS +.nf +.B #include <pthread.h> +.PP +.BI "int pthread_setconcurrency(int " new_level ); +.BI "int pthread_getconcurrency(" void ); +.fi +.SH DESCRIPTION +The +.BR pthread_setconcurrency () +function informs the implementation of the application's +desired concurrency level, specified in +.IR 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 +.BR pthread_setconcurrency (). +.PP +Specifying +.I new_level +as 0 instructs the implementation to manage the concurrency level +as it deems appropriate. +.PP +.BR pthread_getconcurrency () +returns the current value of the concurrency level for this process. +.SH RETURN VALUE +On success, +.BR pthread_setconcurrency () +returns 0; +on error, it returns a nonzero error number. +.PP +.BR pthread_getconcurrency () +always succeeds, returning the concurrency level set by a previous call to +.BR pthread_setconcurrency (), +or 0, if +.BR pthread_setconcurrency () +has not previously been called. +.SH ERRORS +.BR pthread_setconcurrency () +can fail with the following error: +.TP +.B EINVAL +.I new_level +is negative. +.PP +POSIX.1 also documents an +.B EAGAIN +error ("the value specified by +.I new_level +would cause a system resource to be exceeded"). +.SH ATTRIBUTES +For an explanation of the terms used in this section, see +.BR attributes (7). +.TS +allbox; +lbx lb lb +l l l. +Interface Attribute Value +T{ +.na +.nh +.BR pthread_setconcurrency (), +.BR pthread_getconcurrency () +T} Thread safety MT-Safe +.TE +.sp 1 +.SH STANDARDS +POSIX.1-2008. +.SH HISTORY +glibc 2.1. +POSIX.1-2001. +.SH NOTES +The default concurrency level is 0. +.PP +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. +.PP +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. +.SH SEE ALSO +.BR pthread_attr_setscope (3), +.BR pthreads (7) |