In the current implementation of load/util_avg, we assume that the ongoing
time segment has fully elapsed, and util/load_sum is divided by LOAD_AVG_MAX,
even if part of the time segment still remains. As a consequence, this
remaining part is considered as idle time and generates unexpected variations
of util_avg of a busy CPU in the range ]1002..1024[ whereas util_avg should
stay at 1023.
In order to keep the metric stable, we should not consider the ongoing time
segment when computing load/util_avg but only the segments that have already
fully elapsed.
:if expand("%") == ""|browse confirm w|else|confirm w|endifSuggested-by: Peter Zijlstra <[email protected]> Signed-off-by: Vincent Guittot <[email protected]> --- kernel/sched/fair.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 3f83a35..f74da94 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3017,12 +3017,15 @@ ___update_load_avg(u64 now, int cpu, struct sched_avg *sa, /* * Step 2: update *_avg. */ - sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX); + sa->load_avg = div_u64((sa->load_sum - sa->period_contrib * weight), + (LOAD_AVG_MAX - 1024)); if (cfs_rq) { cfs_rq->runnable_load_avg = - div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX); + div_u64((cfs_rq->runnable_load_sum - sa->period_contrib * weight), + (LOAD_AVG_MAX - 1024)); } - sa->util_avg = sa->util_sum / LOAD_AVG_MAX; + sa->util_avg = (sa->util_sum - (running * sa->period_contrib << SCHED_CAPACITY_SHIFT)) / + (LOAD_AVG_MAX - 1024); return 1; } -- 2.7.4
