pthread_getcpuclockid

Langue: en

Version: 2009-02-08 (debian - 07/07/09)

Section: 3 (Bibliothèques de fonctions)

NAME

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

SYNOPSIS

 #include <pthread.h>
 #include <time.h>
 
 int pthread_getcpuclockid(pthread_t thread, clockid_t *clock_id);
 
 Compile and link with -pthread.
 
 

DESCRIPTION

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

RETURN VALUE

On success, this function returns 0; on error, it returns a non-zero error number.

ERRORS

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

VERSIONS

This function is available in glibc since version 2.2.

CONFORMING TO

POSIX.1-2001.

NOTES

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.

EXAMPLE

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
 Sub-thread starting infinite loop
 Main thread consuming some CPU time...
 Process total CPU time:    1.368
 Main thread CPU time:      0.376
 Sub-thread CPU time:       0.992
 

Program source

 /* 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("Sub-thread 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("Sub-thread CPU time:    ", cid);
 
     exit(EXIT_SUCCESS);         /* Terminates both threads */
 }
 

SEE ALSO

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

COLOPHON

This page is part of release 3.21 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.