Function update_threshold

freebsd/x86/x86/mca.c:642–691

* Update the interrupt threshold for a CMCI. The strategy is to use * a low trigger that interrupts as soon as the first event occurs. * However, if a steady stream of events arrive, the threshold is * increased until the interrupts are throttled to once every * cmc_throttle seconds or the periodic scan. If a periodic scan * finds that the threshold is too high, it is lowered. */

 * finds that the threshold is too high, it is lowered.
 */
static int
update_threshold(enum scan_mode mode, int valid, int last_intr, int count,
    int cur_threshold, int max_threshold)
{
	u_int delta;
	int limit;

	delta = (u_int)(time_uptime - last_intr);
	limit = cur_threshold;

	/*
	 * If an interrupt was received less than cmc_throttle seconds
	 * since the previous interrupt and the count from the current
	 * event is greater than or equal to the current threshold,
	 * double the threshold up to the max.
	 */
	if (mode == CMCI && valid) {
		if (delta < cmc_throttle && count >= limit &&
		    limit < max_threshold) {
			limit = min(limit << 1, max_threshold);
		}
		return (limit);
	}

	/*
	 * When the banks are polled, check to see if the threshold
	 * should be lowered.
	 */
	if (mode != POLLED)
		return (limit);

	/* If a CMCI occured recently, do nothing for now. */
	if (delta < cmc_throttle)
		return (limit);

	/*
	 * Compute a new limit based on the average rate of events per
	 * cmc_throttle seconds since the last interrupt.
	 */
	if (valid) {
		limit = count * cmc_throttle / delta;
		if (limit <= 0)
			limit = 1;
		else if (limit > max_threshold)
			limit = max_threshold;
	} else {
		limit = 1;
	}
	return (limit);
}

static void
cmci_update(enum scan_mode mode, int bank, int valid, struct mca_record *rec)