1 .\" Copyright (c) 2009 Linux Foundation, written by Michael Kerrisk
2 .\" <mtk.manpages@gmail.com>
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26 .TH PTHREAD_GETCPUCLOCKID 3 2009-02-08 "Linux" "Linux Programmer's Manual"
28 pthread_getcpuclockid \- retrieve ID of a thread's CPU time clock
31 .B #include <pthread.h>
34 .BI "int pthread_getcpuclockid(pthread_t " thread ", clockid_t *" clock_id);
36 Compile and link with \fI\-pthread\fP.
40 .BR pthread_getcpuclockid ()
41 function returns the clock ID for the CPU time clock of the thread
43 .\" The clockid is constructed as follows:
44 .\" *clockid = CLOCK_THREAD_CPUTIME_ID | (pd->tid << CLOCK_IDFIELD_SIZE)
45 .\" where CLOCK_IDFIELD_SIZE is 3.
47 On success, this function returns 0;
48 on error, it returns a nonzero error number.
52 .\" CLOCK_THREAD_CPUTIME_ID not defined
53 Per-thread CPU time clocks are not supported by the system.
55 .\" Looking at nptl/pthread_getcpuclockid.c an ERANGE error would
56 .\" be possible if kernel thread IDs took more than 29 bits (which
57 .\" they currently cannot).
64 This function is available in glibc since version 2.2.
70 refers to the calling thread,
71 this function returns an identifier that refers to the same clock
76 when given the clock ID
77 .BR CLOCK_THREAD_CPUTIME_ID .
79 The program below creates a thread and then uses
81 to retrieve the total process CPU time,
82 and the per-thread CPU time consumed by the two threads.
83 The following shell session shows an example run:
89 Subthread starting infinite loop
90 Main thread consuming some CPU time...
91 Process total CPU time: 1.368
92 Main thread CPU time: 0.376
93 Subthread CPU time: 0.992
99 /* Link with "\-lrt" */
109 #define handle_error(msg) \\
110 do { perror(msg); exit(EXIT_FAILURE); } while (0)
112 #define handle_error_en(en, msg) \\
113 do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)
116 thread_start(void *arg)
118 printf("Subthread starting infinite loop\\n");
124 pclock(char *msg, clockid_t cid)
129 if (clock_gettime(cid, &ts) == \-1)
130 handle_error("clock_gettime");
131 printf("%4ld.%03ld\\n", ts.tv_sec, ts.tv_nsec / 1000000);
135 main(int argc, char *argv[])
141 s = pthread_create(&thread, NULL, thread_start, NULL);
143 handle_error_en(s, "pthread_create");
145 printf("Main thread sleeping\\n");
148 printf("Main thread consuming some CPU time...\\n");
149 for (j = 0; j < 2000000; j++)
152 pclock("Process total CPU time: ", CLOCK_PROCESS_CPUTIME_ID);
154 s = pthread_getcpuclockid(pthread_self(), &cid);
156 handle_error_en(s, "pthread_getcpuclockid");
157 pclock("Main thread CPU time: ", cid);
159 /* The preceding 4 lines of code could have been replaced by:
160 pclock("Main thread CPU time: ", CLOCK_THREAD_CPUTIME_ID); */
162 s = pthread_getcpuclockid(thread, &cid);
164 handle_error_en(s, "pthread_getcpuclockid");
165 pclock("Subthread CPU time: 1 ", cid);
167 exit(EXIT_SUCCESS); /* Terminates both threads */
171 .BR clock_gettime (2),
172 .BR clock_settime (2),
173 .BR timer_create (2),
174 .BR clock_getcpuclockid (3),
175 .BR pthread_self (3),
179 This page is part of release 3.67 of the Linux
182 A description of the project,
183 information about reporting bugs,
184 and the latest version of this page,
186 \%http://www.kernel.org/doc/man\-pages/.