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.\" Copyright (c) 2009 Linux Foundation, written by Michael Kerrisk
.\" <mtk.manpages@gmail.com>
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date. The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein. The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.TH PTHREAD_GETCPUCLOCKID 3 2009-02-08 "Linux" "Linux Programmer's Manual"
.SH NAME
pthread_getcpuclockid \- retrieve ID of a thread's CPU time clock
.SH SYNOPSIS
.nf
.B #include <pthread.h>
.B #include <time.h>
.BI "int pthread_getcpuclockid(pthread_t " thread ", clockid_t *" clock_id);
.sp
Compile and link with \fI\-pthread\fP.
.fi
.SH DESCRIPTION
The
.BR pthread_getcpuclockid ()
function returns the clock ID for the CPU time clock of the thread
.IR thread .
.\" The clockid is constructed as follows:
.\" *clockid = CLOCK_THREAD_CPUTIME_ID | (pd->tid << CLOCK_IDFIELD_SIZE)
.\" where CLOCK_IDFIELD_SIZE is 3.
.SH RETURN VALUE
On success, this function returns 0;
on error, it returns a nonzero error number.
.SH ERRORS
.TP
.B ENOENT
.\" CLOCK_THREAD_CPUTIME_ID not defined
Per-thread CPU time clocks are not supported by the system.
.\"
.\" Looking at nptl/pthread_getcpuclockid.c an ERANGE error would
.\" be possible if kernel thread IDs took more than 29 bits (which
.\" they currently cannot).
.TP
.B ESRCH
No thread with the ID
.I thread
could be found.
.SH VERSIONS
This function is available in glibc since version 2.2.
.SH CONFORMING TO
POSIX.1-2001.
.SH NOTES
When
.I thread
refers to the calling thread,
this function returns an identifier that refers to the same clock
manipulated by
.BR clock_gettime (2)
and
.BR clock_settime (2)
when given the clock ID
.BR CLOCK_THREAD_CPUTIME_ID .
.SH EXAMPLE
The program below creates a thread and then uses
.BR clock_gettime (2)
to retrieve the total process CPU time,
and the per-thread CPU time consumed by the two threads.
The following shell session shows an example run:
.in +4n
.nf
$ \fB./a.out\fP
Main thread sleeping
Subthread starting infinite loop
Main thread consuming some CPU time...
Process total CPU time: 1.368
Main thread CPU time: 0.376
Subthread CPU time: 0.992
.fi
.in
.SS Program source
\&
.nf
/* Link with "\-lrt" */
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <string.h>
#include <errno.h>
#define handle_error(msg) \\
do { perror(msg); exit(EXIT_FAILURE); } while (0)
#define handle_error_en(en, msg) \\
do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)
static void *
thread_start(void *arg)
{
printf("Subthread starting infinite loop\\n");
for (;;)
continue;
}
static void
pclock(char *msg, clockid_t cid)
{
struct timespec ts;
printf("%s", msg);
if (clock_gettime(cid, &ts) == \-1)
handle_error("clock_gettime");
printf("%4ld.%03ld\\n", ts.tv_sec, ts.tv_nsec / 1000000);
}
int
main(int argc, char *argv[])
{
pthread_t thread;
clockid_t cid;
int j, s;
s = pthread_create(&thread, NULL, thread_start, NULL);
if (s != 0)
handle_error_en(s, "pthread_create");
printf("Main thread sleeping\\n");
sleep(1);
printf("Main thread consuming some CPU time...\\n");
for (j = 0; j < 2000000; j++)
getppid();
pclock("Process total CPU time: ", CLOCK_PROCESS_CPUTIME_ID);
s = pthread_getcpuclockid(pthread_self(), &cid);
if (s != 0)
handle_error_en(s, "pthread_getcpuclockid");
pclock("Main thread CPU time: ", cid);
/* The preceding 4 lines of code could have been replaced by:
pclock("Main thread CPU time: ", CLOCK_THREAD_CPUTIME_ID); */
s = pthread_getcpuclockid(thread, &cid);
if (s != 0)
handle_error_en(s, "pthread_getcpuclockid");
pclock("Subthread CPU time: 1 ", cid);
exit(EXIT_SUCCESS); /* Terminates both threads */
}
.fi
.SH SEE ALSO
.BR clock_gettime (2),
.BR clock_settime (2),
.BR timer_create (2),
.BR clock_getcpuclockid (3),
.BR pthread_self (3),
.BR pthreads (7),
.BR time (7)
.SH COLOPHON
This page is part of release 3.44 of the Linux
.I man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.
|
