2009-04-15 15:47:48 +00:00
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.\" Copyright (c) 2009 Michael Kerrisk, <mtk.manpages@gmail.com>
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.TH PTHREAD_SETCONCURRENCY 3 2009-04-10 "Linux" "Linux Programmer's Manual"
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.SH NAME
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pthread_setconcurrency, pthread_getconcurrency \- set/get
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the concurrency level
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.SH SYNOPSIS
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.nf
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.B #include <pthread.h>
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.BI "int pthread_setconcurrency(int " new_level );
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.BI "int pthread_getconcurrency(void);
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.sp
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Compile and link with \fI\-pthread\fP.
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.SH DESCRIPTION
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The
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.BR pthread_setconcurrency ()
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function informs the implementation of the application's
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desired concurrency level, specified in
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.IR new_level .
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The implementation only takes this as a hint:
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POSIX.1 does not specify the level of concurrency that
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should be provided as a result of calling
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.BR pthread_setconcurrency ().
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Specifying
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.I new_level
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as 0 instructs the implementation to manage the concurrency level
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as it deems appropriate.
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.BR pthread_getconcurrency ()
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returns the current value of the concurrency level for this process.
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.SH RETURN VALUE
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On success,
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.BR pthread_setconcurrency ()
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returns 0;
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intro.1, time.1, adjtimex.2, capget.2, eventfd.2, fcntl.2, getrlimit.2, getsockopt.2, gettimeofday.2, intro.2, ioctl_list.2, ioperm.2, mlock.2, pivot_root.2, poll.2, prctl.2, ptrace.2, sched_setscheduler.2, select_tut.2, semget.2, sigaltstack.2, signalfd.2, sysctl.2, timer_settime.2, timerfd_create.2, wait.2, CPU_SET.3, argz_add.3, assert_perror.3, atexit.3, backtrace.3, bcmp.3, clearenv.3, ctime.3, dl_iterate_phdr.3, dlopen.3, ecvt.3, errno.3, error.3, ether_aton.3, exit.3, fenv.3, ferror.3, finite.3, flockfile.3, fnmatch.3, fpathconf.3, fpclassify.3, ftime.3, ftok.3, ftw.3, fwide.3, getaddrinfo.3, gethostbyname.3, getlogin.3, getnameinfo.3, getnetent.3, getopt.3, getprotoent.3, getrpcent.3, getservent.3, glob.3, hsearch.3, inet.3, isalpha.3, iswalnum.3, iswalpha.3, iswblank.3, iswcntrl.3, iswctype.3, iswdigit.3, iswgraph.3, iswlower.3, iswprint.3, iswpunct.3, iswspace.3, iswupper.3, iswxdigit.3, longjmp.3, lsearch.3, malloc.3, matherr.3, mblen.3, mbsinit.3, mbtowc.3, on_exit.3, printf.3, pthread_attr_init.3, pthread_attr_setaffinity_np.3, pthread_attr_setdetachstate.3, pthread_attr_setguardsize.3, pthread_attr_setinheritsched.3, pthread_attr_setschedparam.3, pthread_attr_setschedpolicy.3, pthread_attr_setscope.3, pthread_attr_setstack.3, pthread_attr_setstackaddr.3, pthread_attr_setstacksize.3, pthread_cancel.3, pthread_cleanup_push.3, pthread_equal.3, pthread_getattr_np.3, pthread_getcpuclockid.3, pthread_setaffinity_np.3, pthread_setcancelstate.3, pthread_setconcurrency.3, pthread_setschedparam.3, pthread_setschedprio.3, ptsname.3, putenv.3, putgrent.3, raise.3, rcmd.3, regex.3, rexec.3, rpc.3, rpmatch.3, rtnetlink.3, scandir.3, sem_init.3, setaliasent.3, setbuf.3, setenv.3, setjmp.3, signbit.3, stdio_ext.3, strtod.3, strtol.3, strtoul.3, system.3, termios.3, timeradd.3, tzset.3, ualarm.3, wctomb.3, xdr.3, st.4, tty_ioctl.4, core.5, elf.5, proc.5, bootparam.7, capabilities.7, icmp.7, ip.7, ipv6.7, math_error.7, mdoc.samples.7, mq_overview.7, pthreads.7, raw.7, regex.7, socket.7, tcp.7, tzselect.8: Global fix: s/non-zero/nonzero/
The tendency in English, as prescribed in style guides like
Chicago MoS, is towards removing hyphens after prefixes
like "non-" etc.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2010-01-16 16:40:55 +00:00
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on error, it returns a nonzero error number.
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2009-04-15 15:47:48 +00:00
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.BR pthread_getconcurrency ()
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always succeeds, returning the concurrency level set by a previous call to
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.BR pthread_setconcurrency (),
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or 0, if
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.BR pthread_setconcurrency ()
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has not previously been called.
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.SH ERRORS
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.BR pthread_setconcurrency ()
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can fail with the following error:
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.TP
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.B EINVAL
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.I new_level
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is negative.
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.PP
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POSIX.1-2001 also documents an
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.BR EAGAIN
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error ("the value specified by
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.I new_level
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would cause a system resource to be exceeded").
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.SH VERSIONS
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These functions are available in glibc since version 2.1.
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.SH CONFORMING TO
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POSIX.1-2001.
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.SH NOTES
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The default concurrency level is 0.
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Concurrency levels are only meaningful for M:N threading implementations,
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where at any moment a subset of a process's set of user-level threads
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may be bound to a smaller number of kernel-scheduling entities.
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Setting the concurrency level allows the application to
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give the system a hint as to the number of kernel-scheduling entities
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that should be provided for efficient execution of the application.
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Both LinuxThreads and NPTL are 1:1 threading implementations,
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so setting the concurrency level has no meaning.
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In other words,
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on Linux these functions merely exist for compatibility with other systems,
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and they have no effect on the execution of a program.
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.SH SEE ALSO
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.BR pthread_attr_setscope (3),
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.BR pthreads (7)
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