On Mon, Sep 12, 2016 at 09:47:49AM +0200, Vincent Guittot wrote:
+/* Take into account change of utilization of a child task group */
> +static inline void
> +update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se)
> +{
> + struct cfs_rq *gcfs_rq = group_cfs_rq(se);
> + long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;
> +
> + /* Nothing to update */
> + if (!delta)
> + return;
> +
> + /* Set new sched_entity's utilizaton */
> + se->avg.util_avg = gcfs_rq->avg.util_avg;
> + se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX;
> +
> + /* Update parent cfs_rq utilization */
> + cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg + delta, 0);
This..
> + cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * LOAD_AVG_MAX;
> +}
> +
> +/* Take into account change of load of a child task group */
> +static inline void
> +update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se)
> +{
> + struct cfs_rq *gcfs_rq = group_cfs_rq(se);
> + long delta, load = gcfs_rq->avg.load_avg;
> +
> + /* If the load of group cfs_rq is null, the load of the
> + * sched_entity will also be null so we can skip the formula
> + */
> + if (load) {
> + long tg_load;
> +
> + /* Get tg's load and ensure tg_load > 0 */
> + tg_load = atomic_long_read(&gcfs_rq->tg->load_avg) + 1;
> +
> + /* Ensure tg_load >= load and updated with current load*/
> + tg_load -= gcfs_rq->tg_load_avg_contrib;
> + tg_load += load;
> +
> + /* scale gcfs_rq's load into tg's shares*/
> + load *= scale_load_down(gcfs_rq->tg->shares);
> + load /= tg_load;
> +
> + /*
> + * we need to compute a correction term in the case that the
> + * task group is consuming <1 cpu so that we would contribute
> + * the same load as a task of equal weight.
> + */
> + if (tg_load < scale_load_down(gcfs_rq->tg->shares)) {
> + load *= tg_load;
> + load /= scale_load_down(gcfs_rq->tg->shares);
> + }
> + }
> +
> + delta = load - se->avg.load_avg;
> +
> + /* Nothing to update */
> + if (!delta)
> + return;
> +
> + /* Set new sched_entity's load */
> + se->avg.load_avg = load;
> + se->avg.load_sum = se->avg.load_avg * LOAD_AVG_MAX;
> +
> + /* Update parent cfs_rq load */
> + cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg + delta, 0);
And this..
> + cfs_rq->avg.load_sum = cfs_rq->avg.load_avg * LOAD_AVG_MAX;
> +}
Re-introduce the issue from: 897418922215 ("sched/fair: Fix cfs_rq avg
tracking underflow").
