title: Use of _COARSE variants in clock_gettime() still calls sys_clock_gettime() system call
body: <p>I have been using clock_gettime functions with CLOCK_MONOTONIC_COARSE as the first parameter in my code like so:</p>
  
  <pre><code>    struct timespec tmptv;
      clock_gettime(CLOCK_MONOTONIC_COARSE, &amp;tmptv);
  </code></pre>
  
  <p>However, when I run gperftools cpu profiler on my code, I get a relatively high percentage of calls to __sys_clock_gettime, at around 8.6%.</p>
  
  <p>I checked my use of the CLOCK_MONOTONIC_COARSE with clock_getres() function, and it reveals a resolution of 4000000 ns, which is the right order of magnitude with 1 ms, I think.</p>
  
  <p>Am I suppose to include another library in my code besides the time.h to let me use CLOCK_MONOTONIC_COARSE without making system calls? I would like to avoid this inefficiency.</p>
  
  <p>Thanks!</p>