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    Subject[PATCH 03/16] sched: aggregate load contributed by task entities on parenting cfs_rq
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    For a given task t, we can compute its contribution to load as:
    task_load(t) = runnable_avg(t) * weight(t)

    On a parenting cfs_rq we can then aggregate
    runnable_load(cfs_rq) = \Sum task_load(t), for all runnable children t

    Maintain this bottom up, with task entities adding their contributed load to
    the parenting cfs_rq sum. When a task entities load changes we add the same
    delta to the maintained sum.

    Signed-off-by: Paul Turner <pjt@google.com>
    Signed-off-by: Ben Segall <bsegall@google.com>
    ---
    include/linux/sched.h | 1 +
    kernel/sched/debug.c | 3 +++
    kernel/sched/fair.c | 51 +++++++++++++++++++++++++++++++++++++++++++++----
    kernel/sched/sched.h | 10 +++++++++-
    4 files changed, 60 insertions(+), 5 deletions(-)

    diff --git a/include/linux/sched.h b/include/linux/sched.h
    index 5bf5c79..0c54ce0 100644
    --- a/include/linux/sched.h
    +++ b/include/linux/sched.h
    @@ -1139,6 +1139,7 @@ struct load_weight {
    struct sched_avg {
    u32 runnable_avg_sum, runnable_avg_period;
    u64 last_runnable_update;
    + unsigned long load_avg_contrib;
    };

    #ifdef CONFIG_SCHEDSTATS
    diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
    index 5d4a7dd..aeb74e3 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.load_avg_contrib);
    #endif
    #undef PN
    #undef P
    @@ -227,6 +228,8 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
    cfs_rq->load_contribution);
    SEQ_printf(m, " .%-30s: %d\n", "load_tg",
    atomic_read(&cfs_rq->tg->load_weight));
    + SEQ_printf(m, " .%-30s: %lld\n", "runnable_load_avg",
    + cfs_rq->runnable_load_avg);
    #endif

    print_cfs_group_stats(m, cpu, cfs_rq->tg);
    diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
    index 08bd3e0..8229766 100644
    --- a/kernel/sched/fair.c
    +++ b/kernel/sched/fair.c
    @@ -1085,20 +1085,63 @@ static __always_inline int __update_entity_runnable_avg(u64 now,
    return decayed;
    }

    +/* Compute the current contribution to load_avg by se, return any delta */
    +static long __update_entity_load_avg_contrib(struct sched_entity *se)
    +{
    + long old_contrib = se->avg.load_avg_contrib;
    +
    + if (!entity_is_task(se))
    + return 0;
    +
    + se->avg.load_avg_contrib = div64_u64(se->avg.runnable_avg_sum *
    + se->load.weight,
    + se->avg.runnable_avg_period + 1);
    +
    + return se->avg.load_avg_contrib - old_contrib;
    +}
    +
    /* Update a sched_entity's runnable average */
    static inline void update_entity_load_avg(struct sched_entity *se)
    {
    - __update_entity_runnable_avg(rq_of(cfs_rq_of(se))->clock_task, &se->avg,
    - se->on_rq);
    + struct cfs_rq *cfs_rq = cfs_rq_of(se);
    + long contrib_delta;
    +
    + if (!__update_entity_runnable_avg(rq_of(cfs_rq)->clock_task, &se->avg,
    + se->on_rq))
    + return;
    +
    + contrib_delta = __update_entity_load_avg_contrib(se);
    + if (se->on_rq)
    + cfs_rq->runnable_load_avg += contrib_delta;
    }

    static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
    {
    __update_entity_runnable_avg(rq->clock_task, &rq->avg, runnable);
    }
    +
    +/* Add the load generated by se into cfs_rq's child load-average */
    +static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
    + struct sched_entity *se)
    +{
    + update_entity_load_avg(se);
    + cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
    +}
    +
    +/* Remove se's load from this cfs_rq child load-average */
    +static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
    + struct sched_entity *se)
    +{
    + update_entity_load_avg(se);
    + cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib;
    +}
    #else
    static inline void update_entity_load_avg(struct sched_entity *se) {}
    static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
    +static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
    + struct sched_entity *se) {}
    +static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
    + struct sched_entity *se) {}
    #endif

    static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
    @@ -1227,7 +1270,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
    */
    update_curr(cfs_rq);
    update_cfs_load(cfs_rq, 0);
    - update_entity_load_avg(se);
    + enqueue_entity_load_avg(cfs_rq, se);
    account_entity_enqueue(cfs_rq, se);
    update_cfs_shares(cfs_rq);

    @@ -1302,7 +1345,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
    * Update run-time statistics of the 'current'.
    */
    update_curr(cfs_rq);
    - update_entity_load_avg(se);
    + dequeue_entity_load_avg(cfs_rq, se);

    update_stats_dequeue(cfs_rq, se);
    if (flags & DEQUEUE_SLEEP) {
    diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
    index bfdb119..26cc36f 100644
    --- a/kernel/sched/sched.h
    +++ b/kernel/sched/sched.h
    @@ -222,6 +222,15 @@ struct cfs_rq {
    unsigned int nr_spread_over;
    #endif

    +#ifdef CONFIG_SMP
    + /*
    + * CFS Load tracking
    + * Under CFS, load is tracked on a per-entity basis and aggregated up.
    + * This allows for the description of both thread and group usage (in
    + * the FAIR_GROUP_SCHED case).
    + */
    + u64 runnable_load_avg;
    +#endif
    #ifdef CONFIG_FAIR_GROUP_SCHED
    struct rq *rq; /* cpu runqueue to which this cfs_rq is attached */

    @@ -1204,4 +1213,3 @@ static inline void account_numa_dequeue(struct task_struct *p) { }
    static inline void init_sched_numa(void) { }

    #endif /* CONFIG_NUMA */
    -



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