1  #ifndef STRACE_TESTS_TIME_ENJOYMENT_H
       2  # define STRACE_TESTS_TIME_ENJOYMENT_H
       3  
       4  # include <fcntl.h>
       5  # include <sched.h>
       6  # include <time.h>
       7  # include <sys/types.h>
       8  # include <sys/stat.h>
       9  
      10  enum {
      11  	NUM_USER_ITERS_SQRT = 2000,
      12  	NUM_USER_ITERS = NUM_USER_ITERS_SQRT * NUM_USER_ITERS_SQRT,
      13  	READ_BUF_SIZE = 65536,
      14  	READ_ITER = 128,
      15  };
      16  
      17  static inline uint64_t
      18  nsecs(struct timespec *ts)
      19  {
      20  	return (uint64_t) ts->tv_sec * 1000000000 + ts->tv_nsec;
      21  }
      22  
      23  static inline void
      24  enjoy_time(uint64_t cputime_limit)
      25  {
      26  	struct timespec ts = { 0 };
      27  	volatile int dummy = 0;
      28  
      29  	/* Enjoying my user time */
      30  	for (size_t i = 0; i < NUM_USER_ITERS_SQRT; ++i) {
      31  		if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts) == 0) {
      32  			if (nsecs(&ts) >= cputime_limit)
      33  				break;
      34  		}
      35  
      36  		for (size_t j = 0; j < NUM_USER_ITERS; ++j)
      37  			++dummy;
      38  	}
      39  
      40  	/* Enjoying my system time */
      41  	ssize_t ret;
      42  	int fd;
      43  	char buf[READ_BUF_SIZE];
      44  
      45  	while (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts) == 0) {
      46  		for (size_t i = 0; i < READ_ITER; i++) {
      47  			/* We are fine even if the calls fail. */
      48  			fd = open("/proc/self/status", O_RDONLY);
      49  			/*
      50  			 * Working around "ignoring return value of 'read'
      51  			 * declared with attribute 'warn_unused_result'".
      52  			 */
      53  			ret = read(fd, buf, sizeof(buf));
      54  			close(fd);
      55  			if (ret)
      56  				continue;
      57  		}
      58  
      59  		if (nsecs(&ts) >= cputime_limit * 3)
      60  			break;
      61  
      62  		sched_yield();
      63  	}
      64  }
      65  
      66  #endif /* !STRACE_TESTS_TIME_ENJOYMENT_H */