[racket-dev] Embedded racket is much slower in thread 'heavy' programs

At Thu, 13 Dec 2012 22:57:54 -0800, Eric Dobson wrote:
> I have a program which is thread 'heavy' and runs much slower in embedded
> racket (vim) than it does in pure racket. [...]
> 
> If I don't do in in a separate thread, then vim is comparable because it is
> using the racket scheduler, and not calling scheme_check_threads. Vim calls
> scheme_check_threads every bit (I think 10 times a second), but it looks
> like not much progress is made on each of these steps. I can understand if
> it was slightly slower, but a factor of over 50k is a bit too much. Is it
> possible for scheme_check_threads to do more work on each invocation in a
> scenario like this?

Yes, I think it would make sense for scheme_check_threads() to loop
with its current body until either one thread quantum (10ms) has passed
or check_sleep() returns 1 to indicate that no threads are ready to
run.

Does the variant below help?

----------------------------------------

void scheme_check_threads(void)
{
  double start, now;

  start = scheme_get_inexact_milliseconds();
  
  while (1) {
    scheme_current_thread->suspend_break++;
    scheme_thread_block((float)0);
    --scheme_current_thread->suspend_break;
    
    if (check_sleep(have_activity, 0))
      break;

    now = scheme_get_inexact_milliseconds();
    if (((now - start) * 1000) > MZ_THREAD_QUANTUM_USEC)
      break;
  }
}