sched: fix sched_domain aggregation

Keeping the aggregate on the first cpu of the sched domain has two problems:
 - it could collide between different sched domains on different cpus
 - it could slow things down because of the remote accesses

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 60 insertions, 66 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 97a58b622ee1..eaf821072dbd 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -765,7 +765,6 @@ struct sched_domain {
         struct sched_domain *child;     /* bottom domain must be null terminated */
         struct sched_group *groups;     /* the balancing groups of the domain */
         cpumask_t span;                 /* span of all CPUs in this domain */
-        int first_cpu;                  /* cache of the first cpu in this domain */
         unsigned long min_interval;     /* Minimum balance interval ms */
         unsigned long max_interval;     /* Maximum balance interval ms */
         unsigned int busy_factor;       /* less balancing by factor if busy */
diff --git a/kernel/sched.c b/kernel/sched.c
index 7d282c52bd42..160d3c209b8f 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1480,12 +1480,12 @@ static int task_hot(struct task_struct *p, u64 now, struct sched_domain *sd);
  */
 
 static inline struct aggregate_struct *
-aggregate(struct task_group *tg, struct sched_domain *sd)
+aggregate(struct task_group *tg, int cpu)
 {
-        return &tg->cfs_rq[sd->first_cpu]->aggregate;
+        return &tg->cfs_rq[cpu]->aggregate;
 }
 
-typedef void (*aggregate_func)(struct task_group *, struct sched_domain *);
+typedef void (*aggregate_func)(struct task_group *, int, struct sched_domain *);
 
 /*
  * Iterate the full tree, calling @down when first entering a node and @up when
@@ -1493,14 +1493,14 @@ typedef void (*aggregate_func)(struct task_group *, struct sched_domain *);
  */
 static
 void aggregate_walk_tree(aggregate_func down, aggregate_func up,
-                         struct sched_domain *sd)
+                         int cpu, struct sched_domain *sd)
 {
         struct task_group *parent, *child;
 
         rcu_read_lock();
         parent = &root_task_group;
 down:
-        (*down)(parent, sd);
+        (*down)(parent, cpu, sd);
         list_for_each_entry_rcu(child, &parent->children, siblings) {
                 parent = child;
                 goto down;
@@ -1508,7 +1508,7 @@ down:
 up:
                 continue;
         }
-        (*up)(parent, sd);
+        (*up)(parent, cpu, sd);
 
         child = parent;
         parent = parent->parent;
@@ -1520,8 +1520,8 @@ up:
 /*
  * Calculate the aggregate runqueue weight.
  */
-static
-void aggregate_group_weight(struct task_group *tg, struct sched_domain *sd)
+static void
+aggregate_group_weight(struct task_group *tg, int cpu, struct sched_domain *sd)
 {
         unsigned long rq_weight = 0;
         unsigned long task_weight = 0;
@@ -1532,15 +1532,15 @@ void aggregate_group_weight(struct task_group *tg, struct sched_domain *sd)
                 task_weight += tg->cfs_rq[i]->task_weight;
         }
 
-        aggregate(tg, sd)->rq_weight = rq_weight;
-        aggregate(tg, sd)->task_weight = task_weight;
+        aggregate(tg, cpu)->rq_weight = rq_weight;
+        aggregate(tg, cpu)->task_weight = task_weight;
 }
 
 /*
  * Compute the weight of this group on the given cpus.
  */
-static
-void aggregate_group_shares(struct task_group *tg, struct sched_domain *sd)
+static void
+aggregate_group_shares(struct task_group *tg, int cpu, struct sched_domain *sd)
 {
         unsigned long shares = 0;
         int i;
@@ -1548,18 +1548,18 @@ void aggregate_group_shares(struct task_group *tg, struct sched_domain *sd)
         for_each_cpu_mask(i, sd->span)
                 shares += tg->cfs_rq[i]->shares;
 
-        if ((!shares && aggregate(tg, sd)->rq_weight) || shares > tg->shares)
+        if ((!shares && aggregate(tg, cpu)->rq_weight) || shares > tg->shares)
                 shares = tg->shares;
 
-        aggregate(tg, sd)->shares = shares;
+        aggregate(tg, cpu)->shares = shares;
 }
 
 /*
  * Compute the load fraction assigned to this group, relies on the aggregate
  * weight and this group's parent's load, i.e. top-down.
  */
-static
-void aggregate_group_load(struct task_group *tg, struct sched_domain *sd)
+static void
+aggregate_group_load(struct task_group *tg, int cpu, struct sched_domain *sd)
 {
         unsigned long load;
 
@@ -1571,17 +1571,17 @@ void aggregate_group_load(struct task_group *tg, struct sched_domain *sd)
                         load += cpu_rq(i)->load.weight;
 
         } else {
-                load = aggregate(tg->parent, sd)->load;
+                load = aggregate(tg->parent, cpu)->load;
 
                 /*
                  * shares is our weight in the parent's rq so
                  * shares/parent->rq_weight gives our fraction of the load
                  */
-                load *= aggregate(tg, sd)->shares;
-                load /= aggregate(tg->parent, sd)->rq_weight + 1;
+                load *= aggregate(tg, cpu)->shares;
+                load /= aggregate(tg->parent, cpu)->rq_weight + 1;
         }
 
-        aggregate(tg, sd)->load = load;
+        aggregate(tg, cpu)->load = load;
 }
 
 static void __set_se_shares(struct sched_entity *se, unsigned long shares);
@@ -1590,8 +1590,8 @@ static void __set_se_shares(struct sched_entity *se, unsigned long shares);
  * Calculate and set the cpu's group shares.
  */
 static void
-__update_group_shares_cpu(struct task_group *tg, struct sched_domain *sd,
-                          int tcpu)
+__update_group_shares_cpu(struct task_group *tg, int cpu,
+                          struct sched_domain *sd, int tcpu)
 {
         int boost = 0;
         unsigned long shares;
@@ -1618,8 +1618,8 @@ __update_group_shares_cpu(struct task_group *tg, struct sched_domain *sd,
          *               \Sum rq_weight
          *
          */
-        shares = aggregate(tg, sd)->shares * rq_weight;
-        shares /= aggregate(tg, sd)->rq_weight + 1;
+        shares = aggregate(tg, cpu)->shares * rq_weight;
+        shares /= aggregate(tg, cpu)->rq_weight + 1;
 
         /*
          * record the actual number of shares, not the boosted amount.
@@ -1639,15 +1639,15 @@ __update_group_shares_cpu(struct task_group *tg, struct sched_domain *sd,
  * task went to.
  */
 static void
-__move_group_shares(struct task_group *tg, struct sched_domain *sd,
+__move_group_shares(struct task_group *tg, int cpu, struct sched_domain *sd,
                     int scpu, int dcpu)
 {
         unsigned long shares;
 
         shares = tg->cfs_rq[scpu]->shares + tg->cfs_rq[dcpu]->shares;
 
-        __update_group_shares_cpu(tg, sd, scpu);
-        __update_group_shares_cpu(tg, sd, dcpu);
+        __update_group_shares_cpu(tg, cpu, sd, scpu);
+        __update_group_shares_cpu(tg, cpu, sd, dcpu);
 
         /*
          * ensure we never loose shares due to rounding errors in the
@@ -1663,19 +1663,19 @@ __move_group_shares(struct task_group *tg, struct sched_domain *sd,
  * we need to walk up the tree and change all shares until we hit the root.
  */
 static void
-move_group_shares(struct task_group *tg, struct sched_domain *sd,
+move_group_shares(struct task_group *tg, int cpu, struct sched_domain *sd,
                   int scpu, int dcpu)
 {
         while (tg) {
-                __move_group_shares(tg, sd, scpu, dcpu);
+                __move_group_shares(tg, cpu, sd, scpu, dcpu);
                 tg = tg->parent;
         }
 }
 
-static
-void aggregate_group_set_shares(struct task_group *tg, struct sched_domain *sd)
+static void
+aggregate_group_set_shares(struct task_group *tg, int cpu, struct sched_domain *sd)
 {
-        unsigned long shares = aggregate(tg, sd)->shares;
+        unsigned long shares = aggregate(tg, cpu)->shares;
         int i;
 
         for_each_cpu_mask(i, sd->span) {
@@ -1683,20 +1683,20 @@ void aggregate_group_set_shares(struct task_group *tg, struct sched_domain *sd)
                 unsigned long flags;
 
                 spin_lock_irqsave(&rq->lock, flags);
-                __update_group_shares_cpu(tg, sd, i);
+                __update_group_shares_cpu(tg, cpu, sd, i);
                 spin_unlock_irqrestore(&rq->lock, flags);
         }
 
-        aggregate_group_shares(tg, sd);
+        aggregate_group_shares(tg, cpu, sd);
 
         /*
          * ensure we never loose shares due to rounding errors in the
          * above redistribution.
          */
-        shares -= aggregate(tg, sd)->shares;
+        shares -= aggregate(tg, cpu)->shares;
         if (shares) {
-                tg->cfs_rq[sd->first_cpu]->shares += shares;
-                aggregate(tg, sd)->shares += shares;
+                tg->cfs_rq[cpu]->shares += shares;
+                aggregate(tg, cpu)->shares += shares;
         }
 }
 
@@ -1704,21 +1704,21 @@ void aggregate_group_set_shares(struct task_group *tg, struct sched_domain *sd)
  * Calculate the accumulative weight and recursive load of each task group
  * while walking down the tree.
  */
-static
-void aggregate_get_down(struct task_group *tg, struct sched_domain *sd)
+static void
+aggregate_get_down(struct task_group *tg, int cpu, struct sched_domain *sd)
 {
-        aggregate_group_weight(tg, sd);
-        aggregate_group_shares(tg, sd);
-        aggregate_group_load(tg, sd);
+        aggregate_group_weight(tg, cpu, sd);
+        aggregate_group_shares(tg, cpu, sd);
+        aggregate_group_load(tg, cpu, sd);
 }
 
 /*
  * Rebalance the cpu shares while walking back up the tree.
  */
-static
-void aggregate_get_up(struct task_group *tg, struct sched_domain *sd)
+static void
+aggregate_get_up(struct task_group *tg, int cpu, struct sched_domain *sd)
 {
-        aggregate_group_set_shares(tg, sd);
+        aggregate_group_set_shares(tg, cpu, sd);
 }
 
 static DEFINE_PER_CPU(spinlock_t, aggregate_lock);
@@ -1731,18 +1731,18 @@ static void __init init_aggregate(void)
                 spin_lock_init(&per_cpu(aggregate_lock, i));
 }
 
-static int get_aggregate(struct sched_domain *sd)
+static int get_aggregate(int cpu, struct sched_domain *sd)
 {
-        if (!spin_trylock(&per_cpu(aggregate_lock, sd->first_cpu)))
+        if (!spin_trylock(&per_cpu(aggregate_lock, cpu)))
                 return 0;
 
-        aggregate_walk_tree(aggregate_get_down, aggregate_get_up, sd);
+        aggregate_walk_tree(aggregate_get_down, aggregate_get_up, cpu, sd);
         return 1;
 }
 
-static void put_aggregate(struct sched_domain *sd)
+static void put_aggregate(int cpu, struct sched_domain *sd)
 {
-        spin_unlock(&per_cpu(aggregate_lock, sd->first_cpu));
+        spin_unlock(&per_cpu(aggregate_lock, cpu));
 }
 
 static void cfs_rq_set_shares(struct cfs_rq *cfs_rq, unsigned long shares)
@@ -1756,12 +1756,12 @@ static inline void init_aggregate(void)
 {
 }
 
-static inline int get_aggregate(struct sched_domain *sd)
+static inline int get_aggregate(int cpu, struct sched_domain *sd)
 {
         return 0;
 }
 
-static inline void put_aggregate(struct sched_domain *sd)
+static inline void put_aggregate(int cpu, struct sched_domain *sd)
 {
 }
 #endif
@@ -3539,7 +3539,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
 
         cpus_setall(*cpus);
 
-        unlock_aggregate = get_aggregate(sd);
+        unlock_aggregate = get_aggregate(this_cpu, sd);
 
         /*
          * When power savings policy is enabled for the parent domain, idle
@@ -3678,7 +3678,7 @@ out_one_pinned:
                 ld_moved = 0;
 out:
         if (unlock_aggregate)
-                put_aggregate(sd);
+                put_aggregate(this_cpu, sd);
         return ld_moved;
 }
 
@@ -7292,7 +7292,6 @@ static int __build_sched_domains(const cpumask_t *cpu_map,
                         SD_INIT(sd, ALLNODES);
                         set_domain_attribute(sd, attr);
                         sd->span = *cpu_map;
-                        sd->first_cpu = first_cpu(sd->span);
                         cpu_to_allnodes_group(i, cpu_map, &sd->groups, tmpmask);
                         p = sd;
                         sd_allnodes = 1;
@@ -7303,7 +7302,6 @@ static int __build_sched_domains(const cpumask_t *cpu_map,
                 SD_INIT(sd, NODE);
                 set_domain_attribute(sd, attr);
                 sched_domain_node_span(cpu_to_node(i), &sd->span);
-                sd->first_cpu = first_cpu(sd->span);
                 sd->parent = p;
                 if (p)
                         p->child = sd;
@@ -7315,7 +7313,6 @@ static int __build_sched_domains(const cpumask_t *cpu_map,
                 SD_INIT(sd, CPU);
                 set_domain_attribute(sd, attr);
                 sd->span = *nodemask;
-                sd->first_cpu = first_cpu(sd->span);
                 sd->parent = p;
                 if (p)
                         p->child = sd;
@@ -7327,7 +7324,6 @@ static int __build_sched_domains(const cpumask_t *cpu_map,
                 SD_INIT(sd, MC);
                 set_domain_attribute(sd, attr);
                 sd->span = cpu_coregroup_map(i);
-                sd->first_cpu = first_cpu(sd->span);
                 cpus_and(sd->span, sd->span, *cpu_map);
                 sd->parent = p;
                 p->child = sd;
@@ -7340,7 +7336,6 @@ static int __build_sched_domains(const cpumask_t *cpu_map,
                 SD_INIT(sd, SIBLING);
                 set_domain_attribute(sd, attr);
                 sd->span = per_cpu(cpu_sibling_map, i);
-                sd->first_cpu = first_cpu(sd->span);
                 cpus_and(sd->span, sd->span, *cpu_map);
                 sd->parent = p;
                 p->child = sd;
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 509092af0330..40cf24ab4de8 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1429,11 +1429,11 @@ load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
                 /*
                  * empty group
                  */
-                if (!aggregate(tg, sd)->task_weight)
+                if (!aggregate(tg, this_cpu)->task_weight)
                         continue;
 
-                rem_load = rem_load_move * aggregate(tg, sd)->rq_weight;
-                rem_load /= aggregate(tg, sd)->load + 1;
+                rem_load = rem_load_move * aggregate(tg, this_cpu)->rq_weight;
+                rem_load /= aggregate(tg, this_cpu)->load + 1;
 
                 this_weight = tg->cfs_rq[this_cpu]->task_weight;
                 busiest_weight = tg->cfs_rq[busiest_cpu]->task_weight;
@@ -1451,10 +1451,10 @@ load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
                 if (!moved_load)
                         continue;
 
-                move_group_shares(tg, sd, busiest_cpu, this_cpu);
+                move_group_shares(tg, this_cpu, sd, busiest_cpu, this_cpu);
 
-                moved_load *= aggregate(tg, sd)->load;
-                moved_load /= aggregate(tg, sd)->rq_weight + 1;
+                moved_load *= aggregate(tg, this_cpu)->load;
+                moved_load /= aggregate(tg, this_cpu)->rq_weight + 1;
 
                 rem_load_move -= moved_load;
                 if (rem_load_move < 0)