Hello, On Tue, Jun 25, 2024 at 11:13:54AM +0200, Vincent Guittot wrote: > > Hmm.... I think I saw RT's schedutil signal stuck high constantly pushing up > > the frequency. I might be mistaken tho. I'll check again. > > This is used when selecting a frequency for fair tasks When schedutil is used as the governor, sugov_get_util() provides the source utilization information to determine the target frequency. sugov_get_util() gets the CFS util metric from cpu_util_cfs_boost() and then runs it through effective_cpu_util(). effective_cpu_util() does a bunch of things including adding cpu_util_irq(), cpu_util_rt() and cpu_util_dl(), so if SCX doesn't decay these utilization metrics, they never decay and schedutil ends up making decisions with stale stuck-high numbers. I can easily confirm the behavior by sprinkling some trace_printks and commenting out update_other_load_avgs() on the SCX side. Thanks. -- tejun
