A task can be asynchronously detached from cfs_rq when migrating between CPUs. The load of the migrated task is then removed from source cfs_rq during its next update. We use this event to set propagation flag.
During the load balance, we take advanatge of the update of blocked load to propagate any pending changes.The propagation relies on patch "sched: fix hierarchical order in rq->leaf_cfs_rq_list", which orders children and parents, to ensure that it's done in one pass.
Signed-off-by: Vincent Guittot vincent.guittot@linaro.org --- kernel/sched/fair.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 91fc949..4c0a404 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3231,6 +3231,7 @@ update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq) sub_positive(&sa->load_avg, r); sub_positive(&sa->load_sum, r * LOAD_AVG_MAX); removed_load = 1; + set_tg_cfs_propagate(cfs_rq); }
if (atomic_long_read(&cfs_rq->removed_util_avg)) { @@ -3238,6 +3239,7 @@ update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq) sub_positive(&sa->util_avg, r); sub_positive(&sa->util_sum, r * LOAD_AVG_MAX); removed_util = 1; + set_tg_cfs_propagate(cfs_rq); }
decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa, @@ -6803,6 +6805,10 @@ static void update_blocked_averages(int cpu)
if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true)) update_tg_load_avg(cfs_rq, 0); + + /* Propagate pending load changes to the parent */ + if (cfs_rq->tg->se[cpu]) + update_load_avg(cfs_rq->tg->se[cpu], 0); } raw_spin_unlock_irqrestore(&rq->lock, flags); }