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    Subject[tg_shares_up rewrite v3 03/11] sched: make tg_shares_up() walk on-demand
    From: Peter Zijlstra <a.p.zijlstra@chello.nl>

    Make tg_shares_up() use the active cgroup list, this means we cannot
    do a strict bottom-up walk of the hierarchy, but assuming its a very
    wide tree with a small number of active groups it should be a win.

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Signed-off-by: Paul Turner <pjt@google.com>

    ---
    kernel/sched.c | 67 ----------------------------------------------------
    kernel/sched_fair.c | 58 +++++++++++++++++++++++++++++++++++++++++++++
    2 files changed, 58 insertions(+), 67 deletions(-)

    Index: kernel/sched.c
    ===================================================================
    --- kernel/sched.c.orig
    +++ kernel/sched.c
    @@ -281,13 +281,6 @@ static DEFINE_SPINLOCK(task_group_lock);

    #ifdef CONFIG_FAIR_GROUP_SCHED

    -#ifdef CONFIG_SMP
    -static int root_task_group_empty(void)
    -{
    - return list_empty(&root_task_group.children);
    -}
    -#endif
    -
    # define INIT_TASK_GROUP_LOAD NICE_0_LOAD

    /*
    @@ -1531,48 +1524,6 @@ static unsigned long cpu_avg_load_per_ta

    #ifdef CONFIG_FAIR_GROUP_SCHED

    -static void update_cfs_load(struct cfs_rq *cfs_rq, int lb);
    -static void update_cfs_shares(struct cfs_rq *cfs_rq);
    -
    -/*
    - * update tg->load_weight by folding this cpu's load_avg
    - */
    -static int tg_shares_up(struct task_group *tg, void *data)
    -{
    - long load_avg;
    - struct cfs_rq *cfs_rq;
    - unsigned long flags;
    - int cpu = (long)data;
    - struct rq *rq;
    -
    - if (!tg->se[cpu])
    - return 0;
    -
    - rq = cpu_rq(cpu);
    - cfs_rq = tg->cfs_rq[cpu];
    -
    - raw_spin_lock_irqsave(&rq->lock, flags);
    -
    - update_rq_clock(rq);
    - update_cfs_load(cfs_rq, 1);
    -
    - load_avg = div64_u64(cfs_rq->load_avg, cfs_rq->load_period+1);
    - load_avg -= cfs_rq->load_contribution;
    -
    - atomic_add(load_avg, &tg->load_weight);
    - cfs_rq->load_contribution += load_avg;
    -
    - /*
    - * We need to update shares after updating tg->load_weight in
    - * order to adjust the weight of groups with long running tasks.
    - */
    - update_cfs_shares(cfs_rq);
    -
    - raw_spin_unlock_irqrestore(&rq->lock, flags);
    -
    - return 0;
    -}
    -
    /*
    * Compute the cpu's hierarchical load factor for each task group.
    * This needs to be done in a top-down fashion because the load of a child
    @@ -1596,29 +1547,11 @@ static int tg_load_down(struct task_grou
    return 0;
    }

    -static void update_shares(long cpu)
    -{
    - if (root_task_group_empty())
    - return;
    -
    - /*
    - * XXX: replace with an on-demand list
    - */
    -
    - walk_tg_tree(tg_nop, tg_shares_up, (void *)cpu);
    -}
    -
    static void update_h_load(long cpu)
    {
    walk_tg_tree(tg_load_down, tg_nop, (void *)cpu);
    }

    -#else
    -
    -static inline void update_shares(int cpu)
    -{
    -}
    -
    #endif

    #ifdef CONFIG_PREEMPT
    Index: kernel/sched_fair.c
    ===================================================================
    --- kernel/sched_fair.c.orig
    +++ kernel/sched_fair.c
    @@ -2000,6 +2000,60 @@ out:
    }

    #ifdef CONFIG_FAIR_GROUP_SCHED
    +/*
    + * update tg->load_weight by folding this cpu's load_avg
    + */
    +static int tg_shares_up(struct task_group *tg, int cpu)
    +{
    + struct cfs_rq *cfs_rq;
    + unsigned long flags;
    + struct rq *rq;
    + long load_avg;
    +
    + if (!tg->se[cpu])
    + return 0;
    +
    + rq = cpu_rq(cpu);
    + cfs_rq = tg->cfs_rq[cpu];
    +
    + raw_spin_lock_irqsave(&rq->lock, flags);
    +
    + update_rq_clock(rq);
    + update_cfs_load(cfs_rq, 1);
    +
    + load_avg = div64_u64(cfs_rq->load_avg, cfs_rq->load_period+1);
    + load_avg -= cfs_rq->load_contribution;
    + atomic_add(load_avg, &tg->load_weight);
    + cfs_rq->load_contribution += load_avg;
    +
    + /*
    + * We need to update shares after updating tg->load_weight in
    + * order to adjust the weight of groups with long running tasks.
    + */
    + update_cfs_shares(cfs_rq);
    +
    + raw_spin_unlock_irqrestore(&rq->lock, flags);
    +
    + return 0;
    +}
    +
    +static void update_shares(int cpu)
    +{
    + struct cfs_rq *cfs_rq;
    + struct rq *rq = cpu_rq(cpu);
    +
    + rcu_read_lock();
    + for_each_leaf_cfs_rq(rq, cfs_rq) {
    + struct task_group *tg = cfs_rq->tg;
    +
    + do {
    + tg_shares_up(tg, cpu);
    + tg = tg->parent;
    + } while (tg);
    + }
    + rcu_read_unlock();
    +}
    +
    static unsigned long
    load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
    unsigned long max_load_move,
    @@ -2047,6 +2101,10 @@ load_balance_fair(struct rq *this_rq, in
    return max_load_move - rem_load_move;
    }
    #else
    +static inline void update_shares(int cpu)
    +{
    +}
    +
    static unsigned long
    load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
    unsigned long max_load_move,
    --



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