1PTHREAD_GETCPUCLOCKID(3) Linux Programmer's Manual PTHREAD_GETCPUCLOCKID(3)
2
6 pthread_getcpuclockid - retrieve ID of a thread's CPU time clock
7
9 #include <pthread.h>
10 #include <time.h>
11 int pthread_getcpuclockid(pthread_t thread, clockid_t *clockid);
13 Compile and link with -pthread.
15
17 The pthread_getcpuclockid() function obtains the ID of the CPU-time
18 clock of the thread whose ID is given in thread, and returns it in the
19 location pointed to by clockid.
20
22 On success, this function returns 0; on error, it returns a nonzero er‐
23 ror number.
24
26 ENOENT Per-thread CPU time clocks are not supported by the system.
27 ESRCH No thread with the ID thread could be found.
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31 This function is available in glibc since version 2.2.
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34 For an explanation of the terms used in this section, see at‐
35 tributes(7).
36 ┌────────────────────────┬───────────────┬─────────┐
38 │Interface │ Attribute │ Value │
39 ├────────────────────────┼───────────────┼─────────┤
40 │pthread_getcpuclockid() │ Thread safety │ MT-Safe │
41 └────────────────────────┴───────────────┴─────────┘
43 POSIX.1-2001, POSIX.1-2008.
44
46 When thread refers to the calling thread, this function returns an
47 identifier that refers to the same clock manipulated by clock_get‐
48 time(2) and clock_settime(2) when given the clock ID
49 CLOCK_THREAD_CPUTIME_ID.
50
52 The program below creates a thread and then uses clock_gettime(2) to
53 retrieve the total process CPU time, and the per-thread CPU time con‐
54 sumed by the two threads. The following shell session shows an example
55 run:
56 $ ./a.out
58 Main thread sleeping
59 Subthread starting infinite loop
60 Main thread consuming some CPU time...
61 Process total CPU time: 1.368
62 Main thread CPU time: 0.376
63 Subthread CPU time: 0.992
64 Program source
66 /* Link with "-lrt" */
68 #include <time.h>
70 #include <stdio.h>
71 #include <stdint.h>
72 #include <stdlib.h>
73 #include <unistd.h>
74 #include <pthread.h>
75 #include <string.h>
76 #include <errno.h>
77 #define handle_error(msg) \
79 do { perror(msg); exit(EXIT_FAILURE); } while (0)
80 #define handle_error_en(en, msg) \
82 do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)
83 static void *
85 thread_start(void *arg)
86 {
87 printf("Subthread starting infinite loop\n");
88 for (;;)
89 continue;
90 }
91 static void
93 pclock(char *msg, clockid_t cid)
94 {
95 struct timespec ts;
96 printf("%s", msg);
98 if (clock_gettime(cid, &ts) == -1)
99 handle_error("clock_gettime");
100 printf("%4jd.%03ld\n", (intmax_t) ts.tv_sec, ts.tv_nsec / 1000000);
101 }
102 int
104 main(int argc, char *argv[])
105 {
106 pthread_t thread;
107 clockid_t cid;
108 int s;
109 s = pthread_create(&thread, NULL, thread_start, NULL);
111 if (s != 0)
112 handle_error_en(s, "pthread_create");
113 printf("Main thread sleeping\n");
115 sleep(1);
116 printf("Main thread consuming some CPU time...\n");
118 for (int j = 0; j < 2000000; j++)
119 getppid();
120 pclock("Process total CPU time: ", CLOCK_PROCESS_CPUTIME_ID);
122 s = pthread_getcpuclockid(pthread_self(), &cid);
124 if (s != 0)
125 handle_error_en(s, "pthread_getcpuclockid");
126 pclock("Main thread CPU time: ", cid);
127 /* The preceding 4 lines of code could have been replaced by:
129 pclock("Main thread CPU time: ", CLOCK_THREAD_CPUTIME_ID); */
130 s = pthread_getcpuclockid(thread, &cid);
132 if (s != 0)
133 handle_error_en(s, "pthread_getcpuclockid");
134 pclock("Subthread CPU time: 1 ", cid);
135 exit(EXIT_SUCCESS); /* Terminates both threads */
137 }
138
140 clock_gettime(2), clock_settime(2), timer_create(2), clock_getcpu‐
141 clockid(3), pthread_self(3), pthreads(7), time(7)
142
144 This page is part of release 5.10 of the Linux man-pages project. A
145 description of the project, information about reporting bugs, and the
146 latest version of this page, can be found at
147 https://www.kernel.org/doc/man-pages/.
148Linux 2020-11-01 PTHREAD_GETCPUCLOCKID(3)