static void collect_percpu_times(struct psi_group *group,
				 enum psi_aggregators aggregator,
				 u32 *pchanged_states)
{
	u64 deltas[NR_PSI_STATES - 1] = { 0, };
	unsigned long nonidle_total = 0;
	u32 changed_states = 0;
	int cpu;
	int s;

	/*
	 * Collect the per-cpu time buckets and average them into a
	 * single time sample that is normalized to wallclock time.
	 *
	 * For averaging, each CPU is weighted by its non-idle time in
	 * the sampling period. This eliminates artifacts from uneven
	 * loading, or even entirely idle CPUs.
	 */
	for_each_possible_cpu(cpu) {
		u32 times[NR_PSI_STATES];
		u32 nonidle;
		u32 cpu_changed_states;

		get_recent_times(group, cpu, aggregator, times,
				&cpu_changed_states);
		changed_states |= cpu_changed_states;

		nonidle = nsecs_to_jiffies(times[PSI_NONIDLE]);
		nonidle_total += nonidle;

		for (s = 0; s < PSI_NONIDLE; s++)
			deltas[s] += (u64)times[s] * nonidle;
	}

	/*
	 * Integrate the sample into the running statistics that are
	 * reported to userspace: the cumulative stall times and the
	 * decaying averages.
	 *
	 * Pressure percentages are sampled at PSI_FREQ. We might be
	 * called more often when the user polls more frequently than
	 * that; we might be called less often when there is no task
	 * activity, thus no data, and clock ticks are sporadic. The
	 * below handles both.
	 */

	/* total= */
	for (s = 0; s < NR_PSI_STATES - 1; s++)
		group->total[aggregator][s] +=
				div_u64(deltas[s], max(nonidle_total, 1UL));

	if (pchanged_states)
		*pchanged_states = changed_states;
}
Unknown