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    Subject[patch 15/16] sched: implement usage tracking
    From: Paul Turner <pjt@google.com>

    With the frame-work for runnable tracking now fully in place. Per-entity usage
    tracking is a simple and low-overhead addition.

    Signed-off-by: Paul Turner <pjt@google.com>
    Reviewed-by: Ben Segall <bsegall@google.com>
    ---
    include/linux/sched.h | 1 +
    kernel/sched/debug.c | 3 +++
    kernel/sched/fair.c | 33 ++++++++++++++++++++++++++++-----
    kernel/sched/sched.h | 4 ++--
    4 files changed, 34 insertions(+), 7 deletions(-)

    diff --git a/include/linux/sched.h b/include/linux/sched.h
    index 93e27c0..2a4be1f 100644
    --- a/include/linux/sched.h
    +++ b/include/linux/sched.h
    @@ -1150,6 +1150,7 @@ struct sched_avg {
    u64 last_runnable_update;
    s64 decay_count;
    unsigned long load_avg_contrib;
    + u32 usage_avg_sum;
    };

    #ifdef CONFIG_SCHEDSTATS
    diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
    index 2cd3c1b..b9d54d0 100644
    --- a/kernel/sched/debug.c
    +++ b/kernel/sched/debug.c
    @@ -94,6 +94,7 @@ static void print_cfs_group_stats(struct seq_file *m, int cpu, struct task_group
    #ifdef CONFIG_SMP
    P(se->avg.runnable_avg_sum);
    P(se->avg.runnable_avg_period);
    + P(se->avg.usage_avg_sum);
    P(se->avg.load_avg_contrib);
    P(se->avg.decay_count);
    #endif
    @@ -230,6 +231,8 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
    cfs_rq->tg_runnable_contrib);
    SEQ_printf(m, " .%-30s: %d\n", "tg->runnable_avg",
    atomic_read(&cfs_rq->tg->runnable_avg));
    + SEQ_printf(m, " .%-30s: %d\n", "tg->usage_avg",
    + atomic_read(&cfs_rq->tg->usage_avg));
    #endif

    print_cfs_group_stats(m, cpu, cfs_rq->tg);
    diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
    index b249371..44a9a11 100644
    --- a/kernel/sched/fair.c
    +++ b/kernel/sched/fair.c
    @@ -994,7 +994,8 @@ static u32 __compute_runnable_contrib(u64 n)
    */
    static __always_inline int __update_entity_runnable_avg(u64 now,
    struct sched_avg *sa,
    - int runnable)
    + int runnable,
    + int running)
    {
    u64 delta, periods;
    u32 runnable_contrib;
    @@ -1033,6 +1034,8 @@ static __always_inline int __update_entity_runnable_avg(u64 now,
    delta_w = 1024 - delta_w;
    if (runnable)
    sa->runnable_avg_sum += delta_w;
    + if (running)
    + sa->usage_avg_sum += delta_w;
    sa->runnable_avg_period += delta_w;

    delta -= delta_w;
    @@ -1045,17 +1048,22 @@ static __always_inline int __update_entity_runnable_avg(u64 now,
    periods + 1);
    sa->runnable_avg_period = decay_load(sa->runnable_avg_period,
    periods + 1);
    + sa->usage_avg_sum = decay_load(sa->usage_avg_sum, periods + 1);

    /* Efficiently calculate \sum (1..n_period) 1024*y^i */
    runnable_contrib = __compute_runnable_contrib(periods);
    if (runnable)
    sa->runnable_avg_sum += runnable_contrib;
    + if (running)
    + sa->usage_avg_sum += runnable_contrib;
    sa->runnable_avg_period += runnable_contrib;
    }

    /* Remainder of delta accrued against u_0` */
    if (runnable)
    sa->runnable_avg_sum += delta;
    + if (running)
    + sa->usage_avg_sum += delta;
    sa->runnable_avg_period += delta;

    return decayed;
    @@ -1101,16 +1109,28 @@ static inline void __update_tg_runnable_avg(struct sched_avg *sa,
    struct cfs_rq *cfs_rq)
    {
    struct task_group *tg = cfs_rq->tg;
    - long contrib;
    + long contrib, usage_contrib;

    /* The fraction of a cpu used by this cfs_rq */
    contrib = div_u64(sa->runnable_avg_sum << NICE_0_SHIFT,
    sa->runnable_avg_period + 1);
    contrib -= cfs_rq->tg_runnable_contrib;

    - if (abs(contrib) > cfs_rq->tg_runnable_contrib / 64) {
    + usage_contrib = div_u64(sa->usage_avg_sum << NICE_0_SHIFT,
    + sa->runnable_avg_period + 1);
    + usage_contrib -= cfs_rq->tg_usage_contrib;
    +
    + /*
    + * contrib/usage at this point represent deltas, only update if they
    + * are substantive.
    + */
    + if ((abs(contrib) > cfs_rq->tg_runnable_contrib / 64) ||
    + (abs(usage_contrib) > cfs_rq->tg_usage_contrib / 64)) {
    atomic_add(contrib, &tg->runnable_avg);
    cfs_rq->tg_runnable_contrib += contrib;
    +
    + atomic_add(usage_contrib, &tg->usage_avg);
    + cfs_rq->tg_usage_contrib += usage_contrib;
    }
    }

    @@ -1216,7 +1236,8 @@ static inline void update_entity_load_avg(struct sched_entity *se,
    else
    now = cfs_rq_clock_task(group_cfs_rq(se));

    - if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq))
    + if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq,
    + cfs_rq->curr == se))
    return;

    contrib_delta = __update_entity_load_avg_contrib(se);
    @@ -1261,7 +1282,8 @@ static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)

    static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
    {
    - __update_entity_runnable_avg(rq->clock_task, &rq->avg, runnable);
    + __update_entity_runnable_avg(rq->clock_task, &rq->avg, runnable,
    + runnable);
    __update_tg_runnable_avg(&rq->avg, &rq->cfs);
    }

    @@ -1629,6 +1651,7 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
    */
    update_stats_wait_end(cfs_rq, se);
    __dequeue_entity(cfs_rq, se);
    + update_entity_load_avg(se, 1);
    }

    update_stats_curr_start(cfs_rq, se);
    diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
    index 89a0e38..e14601e 100644
    --- a/kernel/sched/sched.h
    +++ b/kernel/sched/sched.h
    @@ -113,7 +113,7 @@ struct task_group {

    atomic_t load_weight;
    atomic64_t load_avg;
    - atomic_t runnable_avg;
    + atomic_t runnable_avg, usage_avg;
    #endif

    #ifdef CONFIG_RT_GROUP_SCHED
    @@ -236,7 +236,7 @@ struct cfs_rq {
    u64 last_decay;

    #ifdef CONFIG_FAIR_GROUP_SCHED
    - u32 tg_runnable_contrib;
    + u32 tg_runnable_contrib, tg_usage_contrib;
    u64 tg_load_contrib;
    #endif /* CONFIG_FAIR_GROUP_SCHED */




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