sched: Make tg_shares_up() walk on-demand

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: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101115234937.754159484@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 58 insertions, 0 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 0560e72bd732..46ff6587dc16 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -2004,6 +2004,60 @@ 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,
@@ -2051,6 +2105,10 @@ load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
         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,