PTHREAD_GETCPUCLOCKID(3) Linux Programmer's Manual PTHREAD_GETCPUCLOCKID(3)

pthread_getcpuclockid - retrieve ID of a thread's CPU time clock

#include <pthread.h>
#include <time.h>
int pthread_getcpuclockid(pthread_t thread, clockid_t *clock_id);

Compile and link with -pthread.

The pthread_getcpuclockid() function returns the clock ID for the CPU time clock of the thread thread.

On success, this function returns 0; on error, it returns a nonzero error number.

Per-thread CPU time clocks are not supported by the system.
No thread with the ID thread could be found.

This function is available in glibc since version 2.2.

see_pthreads(7))">)">Multithreading (see pthreads(7))

The pthread_getcpuclockid() function is thread-safe.

POSIX.1-2001.

When thread refers to the calling thread, this function returns an identifier that refers to the same clock manipulated by clock_gettime(2) and clock_settime(2) when given the clock ID CLOCK_THREAD_CPUTIME_ID.

The program below creates a thread and then uses 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:


$ ./a.out
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

/* 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 */
}

clock_gettime(2), clock_settime(2), timer_create(2), clock_getcpuclockid(3), pthread_self(3), pthreads(7), time(7)

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2014-05-23 Linux

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