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    Subject[RFC PATCH 08/10] sched: Track blocked utilization contributions
    Date
    Introduces the blocked utilization, the utilization counter-part to
    cfs_rq->utilization_load_avg. It is the sum of sched_entity utilization
    contributions of entities that were recently on the cfs_rq that are
    currently blocked. Combined with sum of contributions of entities
    currently on the cfs_rq or currently running
    (cfs_rq->utilization_load_avg) this can provide a more stable average
    view of the cpu usage.

    cc: Ingo Molnar <mingo@redhat.com>
    cc: Peter Zijlstra <peterz@infradead.org>

    Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
    ---
    kernel/sched/fair.c | 30 +++++++++++++++++++++++++++++-
    kernel/sched/sched.h | 8 ++++++--
    2 files changed, 35 insertions(+), 3 deletions(-)

    diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
    index 090223f..adf64df 100644
    --- a/kernel/sched/fair.c
    +++ b/kernel/sched/fair.c
    @@ -2778,6 +2778,15 @@ static inline void subtract_blocked_load_contrib(struct cfs_rq *cfs_rq,
    cfs_rq->blocked_load_avg = 0;
    }

    +static inline void subtract_utilization_blocked_contrib(struct cfs_rq *cfs_rq,
    + long utilization_contrib)
    +{
    + if (likely(utilization_contrib < cfs_rq->utilization_blocked_avg))
    + cfs_rq->utilization_blocked_avg -= utilization_contrib;
    + else
    + cfs_rq->utilization_blocked_avg = 0;
    +}
    +
    static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);

    /* Update a sched_entity's runnable average */
    @@ -2813,6 +2822,8 @@ static inline void update_entity_load_avg(struct sched_entity *se,
    cfs_rq->utilization_load_avg += utilization_delta;
    } else {
    subtract_blocked_load_contrib(cfs_rq, -contrib_delta);
    + subtract_utilization_blocked_contrib(cfs_rq,
    + -utilization_delta);
    }
    }

    @@ -2830,14 +2841,20 @@ static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
    return;

    if (atomic_long_read(&cfs_rq->removed_load)) {
    - unsigned long removed_load;
    + unsigned long removed_load, removed_utilization;
    removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0);
    + removed_utilization =
    + atomic_long_xchg(&cfs_rq->removed_utilization, 0);
    subtract_blocked_load_contrib(cfs_rq, removed_load);
    + subtract_utilization_blocked_contrib(cfs_rq,
    + removed_utilization);
    }

    if (decays) {
    cfs_rq->blocked_load_avg = decay_load(cfs_rq->blocked_load_avg,
    decays);
    + cfs_rq->utilization_blocked_avg =
    + decay_load(cfs_rq->utilization_blocked_avg, decays);
    atomic64_add(decays, &cfs_rq->decay_counter);
    cfs_rq->last_decay = now;
    }
    @@ -2884,6 +2901,8 @@ static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
    /* migrated tasks did not contribute to our blocked load */
    if (wakeup) {
    subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
    + subtract_utilization_blocked_contrib(cfs_rq,
    + se->avg.utilization_avg_contrib);
    update_entity_load_avg(se, 0);
    }

    @@ -2910,6 +2929,8 @@ static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
    cfs_rq->utilization_load_avg -= se->avg.utilization_avg_contrib;
    if (sleep) {
    cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
    + cfs_rq->utilization_blocked_avg +=
    + se->avg.utilization_avg_contrib;
    se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
    } /* migrations, e.g. sleep=0 leave decay_count == 0 */
    }
    @@ -4929,6 +4950,8 @@ migrate_task_rq_fair(struct task_struct *p, int next_cpu)
    se->avg.decay_count = -__synchronize_entity_decay(se);
    atomic_long_add(se->avg.load_avg_contrib,
    &cfs_rq->removed_load);
    + atomic_long_add(se->avg.utilization_avg_contrib,
    + &cfs_rq->removed_utilization);
    }

    /* We have migrated, no longer consider this task hot */
    @@ -7944,6 +7967,8 @@ static void switched_from_fair(struct rq *rq, struct task_struct *p)
    if (se->avg.decay_count) {
    __synchronize_entity_decay(se);
    subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
    + subtract_utilization_blocked_contrib(cfs_rq,
    + se->avg.utilization_avg_contrib);
    }
    #endif
    }
    @@ -8003,6 +8028,7 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
    #ifdef CONFIG_SMP
    atomic64_set(&cfs_rq->decay_counter, 1);
    atomic_long_set(&cfs_rq->removed_load, 0);
    + atomic_long_set(&cfs_rq->removed_utilization, 0);
    #endif
    }

    @@ -8055,6 +8081,8 @@ static void task_move_group_fair(struct task_struct *p, int queued)
    */
    se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
    cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
    + cfs_rq->utilization_blocked_avg +=
    + se->avg.utilization_avg_contrib;
    #endif
    }
    }
    diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
    index e402133..208237f 100644
    --- a/kernel/sched/sched.h
    +++ b/kernel/sched/sched.h
    @@ -368,11 +368,15 @@ struct cfs_rq {
    * the blocked sched_entities on the rq.
    * utilization_load_avg is the sum of the average running time of the
    * sched_entities on the rq.
    + * utilization_blocked_avg is the utilization equivalent of
    + * blocked_load_avg, i.e. the sum of running contributions of blocked
    + * sched_entities associated with the rq.
    */
    - unsigned long runnable_load_avg, blocked_load_avg, utilization_load_avg;
    + unsigned long runnable_load_avg, blocked_load_avg;
    + unsigned long utilization_load_avg, utilization_blocked_avg;
    atomic64_t decay_counter;
    u64 last_decay;
    - atomic_long_t removed_load;
    + atomic_long_t removed_load, removed_utilization;

    #ifdef CONFIG_FAIR_GROUP_SCHED
    /* Required to track per-cpu representation of a task_group */
    --
    1.9.1



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