From: Vincent Guittot vincent.guittot@linaro.org
[ Upstream commit fcf6631f3736985ec89bdd76392d3c7bfb60119f ]
Rounding in PELT calculation happening when entities are attached/detached of a cfs_rq can result into situations where util/runnable_avg is not null but util/runnable_sum is. This is normally not possible so we need to ensure that util/runnable_sum stays synced with util/runnable_avg.
detach_entity_load_avg() is the last place where we don't sync util/runnable_sum with util/runnbale_avg when moving some sched_entities
Signed-off-by: Vincent Guittot vincent.guittot@linaro.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://lkml.kernel.org/r/20210601085832.12626-1-vincent.guittot@linaro.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/fair.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index a073a839cd06..a9c4f0370bdc 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3761,11 +3761,17 @@ static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s */ static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { + /* + * cfs_rq->avg.period_contrib can be used for both cfs_rq and se. + * See ___update_load_avg() for details. + */ + u32 divider = get_pelt_divider(&cfs_rq->avg); + dequeue_load_avg(cfs_rq, se); sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg); - sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum); + cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * divider; sub_positive(&cfs_rq->avg.runnable_avg, se->avg.runnable_avg); - sub_positive(&cfs_rq->avg.runnable_sum, se->avg.runnable_sum); + cfs_rq->avg.runnable_sum = cfs_rq->avg.runnable_avg * divider;
add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);