Manpages - pthread_getcpuclockid.3
Table of Contents
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 *clockid); Compile and link with -pthread.
DESCRIPTION
The *pthread_getcpuclockid*() function obtains the ID of the CPU-time clock of the thread whose ID is given in thread, and returns it in the location pointed to by clockid.
RETURN VALUE
On success, this function returns 0; on error, it returns a nonzero 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.
ATTRIBUTES
For an explanation of the terms used in this section, see *attributes*(7).
| Interface | Attribute | Value |
| *pthread_getcpuclockid*() | Thread safety | MT-Safe |
CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
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.
EXAMPLES
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
Program source
/* Link with "-lrt" */
#include <time.h>
#include <stdio.h>
#include <stdint.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("%4jd.%03ld\n", (intmax_t) ts.tv_sec, ts.tv_nsec / 1000000);
}
int
main(int argc, char *argv[])
{
pthread_t thread;
clockid_t cid;
int 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 (int 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 */
}
SEE ALSO
*clock_gettime*(2), *clock_settime*(2), *timer_create*(2), *clock_getcpuclockid*(3), *pthread_self*(3), *pthreads*(7), *time*(7)
COLOPHON
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