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() function 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 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 |
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.
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
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 <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 */
}
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 4.10 of the Linux
man-pages project. A
description of the project, information about reporting bugs, and the latest
version of this page, can be found at
https://www.kernel.org/doc/man-pages/.