Re: Keeping track of the CPU time for a thread

On Tue Jun 26, 2012 at 18:52:44 +0000, Mohammad A Haque wrote:

Thank you for your reply.

Just to test the functionality, I tried a very simple thread. It computes a factorial for some number of iterations.

void entry_point(void * param) { int num_run = 1000000; int number = 15; int fact;

thread_t self = env()->self();
for(int i=0;i<num_run;i++) {
  fact = 1;
  for(int j = 2; j<= number; j++) {
    fact = fact * j;
  }
}
printf("Factorial of %d is : %d\n", number, fact);
l4_thread_stats_time(self.cap());
printf("Consumed time: %llu\n",l4_utcb_mr()->mr[0]);

}

What I found is - the consumed time does not depend on the number of iterations (num_run) - I tried from 1 to a very large number. It does vary with the number. Am I missing something?

Your examples works for me (in a slightly modified version): int num_run = 1000000; int number = 15; int fact;

while (1) { for(int i=0;i<num_run;i++) { fact = 1; for(int j = 2; j<= number; j++) { fact = fact * j; } } printf("Factorial of %d is : %d\n", number, fact); l4_thread_stats_time(l4re_env()->main_thread); printf("Consumed time: %llu\n", *(l4_cpu_time_t *)&l4_utcb_mr()->mr[0]); }

The consumed time increases as the program runs. The granularity is 1ms, except you enable "fine-grained cpu time" in the Fiasco kernel, then it is more exact.

Adam