On 26/09/16 13:19, Vincent Guittot wrote:
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 we propagate any pending changes.
IMHO, it would be a good idea to mention that '2/7 sched: fix hierarchical order in rq->leaf_cfs_rq_list' is a hard requirement for this to work. The functionality relies on the order of cfs_rq's (top to root) in the rq->leaf_cfs_rq_list list.
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 8ba500f..bd3b6b9 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3221,6 +3221,7 @@ 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)) { @@ -3228,6 +3229,7 @@ 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, @@ -6607,6 +6609,10 @@ 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);
In my test (1 task (run/period: 8ms/16ms) in tg_root->tg_x->tg_y->*tg_z* and oscillating between cpu1 and cpu2) the cfs_rq related signals are nicely going down to 0 after the task has left the cpu but it doesn't seem to be the case for the corresponding se (cfs_rq->tg->se[cpu])?
It should actually work correctly because of the update_tg_cfs_util/load() calls in update_load_avg(cfs_rq->tg->se[cpu], 0)->propagate_entity_load_avg()
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