Function sched_interact_score

freebsd/kern/sched_ule.c:1531–1565

* This is the core of the interactivity algorithm. Determines a score based * on past behavior. It is the ratio of sleep time to run time scaled to * a [0, 100] integer. This is the voluntary sleep time of a process, which * differs from the cpu usage because it does not account for time spent * waiting on a run-queue. Would be prettier if we had floating point. * * When a thread's sleep

 *                        run time / sleep time
 */
static int
sched_interact_score(struct thread *td)
{
	struct td_sched *ts;
	int div;

	ts = td_get_sched(td);
	/*
	 * The score is only needed if this is likely to be an interactive
	 * task.  Don't go through the expense of computing it if there's
	 * no chance.
	 */
	if (sched_interact <= SCHED_INTERACT_HALF &&
		ts->ts_runtime >= ts->ts_slptime)
			return (SCHED_INTERACT_HALF);

	if (ts->ts_runtime > ts->ts_slptime) {
		div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF);
		return (SCHED_INTERACT_HALF +
		    (SCHED_INTERACT_HALF - (ts->ts_slptime / div)));
	}
	if (ts->ts_slptime > ts->ts_runtime) {
		div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF);
		return (ts->ts_runtime / div);
	}
	/* runtime == slptime */
	if (ts->ts_runtime)
		return (SCHED_INTERACT_HALF);

	/*
	 * This can happen if slptime and runtime are 0.
	 */
	return (0);

}

/*
 * Scale the scheduling priority according to the "interactivity" of this