NUM_SAMPLE_PERIODS
static DEFINE_PER_CPU(u8, cpustat_util[NUM_SAMPLE_PERIODS][NUM_STATS_PER_GROUP]);
__this_cpu_write(cpustat_tail, (tail + 1) % NUM_SAMPLE_PERIODS);
for (i = 0; i < NUM_SAMPLE_PERIODS; i++) {
group = (tail + i) % NUM_SAMPLE_PERIODS;
tail = (tail + NUM_SAMPLE_PERIODS - 1) % NUM_SAMPLE_PERIODS;
sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / NUM_SAMPLE_PERIODS);
if (time_after_eq(now, period_ts + get_softlockup_thresh() / NUM_SAMPLE_PERIODS) &&