其实linux下还有一种高精度的定时器，那就是posix_timer.原理上来说，可以在变频的时候也使用rdtsc指令，因为cpu的频率我们也是知道的，变频的时候内核也是知道的。

    下面是我的timer_create的例子，编译的时候要加上rt库，这是linux的realtime库：

   

gcc -o test test.c #include #include #include #include #include #define rdtsc(low,high) __asm__ __volatile__("rdtsc" : "=a" (low), "=d" (high)) timer_t tt; void handler (int sig, siginfo_t * extra, void *cruft) ...{ static last_i=0; unsigned int i, j; rdtsc(i,j); printf ("time:%u, %u, [%u] %uhz ", j, i, i-last_i, (i-last_i)*10/1000000); last_i = i; } int main () ...{[来源www.iocblog.net] int i=0; sigset_t sigset; sigfillset (&sigset); sigdelset (&sigset, sigrtmin); sigprocmask (sig_setmask, &sigset, null); struct sigaction sa; sigfillset (&sa.sa_mask); sa.sa_flags = sa_siginfo; sa.sa_sigaction = handler; if (sigaction (sigrtmin, &sa, null) < 0) ...{ perror ("sigaction failed "); exit (-1); } struct sigevent timer_event; struct itimerspec timer; timer.it_interval.tv_sec = 0; timer.it_interval.tv_nsec = 100 * 1000 * 1000; timer.it_value = timer.it_interval; timer_event.sigev_notify = sigev_signal; timer_event.sigev_signo = sigrtmin; timer_event.sigev_value.sival_ptr = (void *) &tt; if (timer_create (clock_realtime, &timer_event, &tt) < 0) ...{ perror ("timer_create failed"); exit (-1); } if (timer_settime (tt, 0, &timer, null) < 0) ...{ perror ("timer_settime failed"); exit (-1); } while (i++ < 10) ...{ pause (); } return 0; }

    输出结果：
    
   

time:166081, 1934350847, [1934350847] 2163hz time:166081, 2120528291, [186177444] 1861hz time:166081, 2306679576, [186151285] 1861hz time:166081, 2494695630, [188016054] 1880hz time:166081, 2680865389, [186169759] 1861hz time:166081, 2867018473, [186153084] 1861hz time:166081, 3053152230, [186133757] 1861hz time:166081, 3239309935, [186157705] 1861hz time:166081, 3425467261, [186157326] 1861hz time:166081, 3611639266, [186172005] 1861hz

Tag: 定时器

文章整理：iocblog
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