sched: revert revert of: fair-group: SMP-nice for group scheduling

Try again..

Initial commit: 18d95a2832c1392a2d63227a7a6d433cb9f2037e
Revert: 6363ca57c76b7b83639ca8c83fc285fa26a7880e

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>

1 files changed, 399 insertions, 31 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index f653af684fb3..874b6da15430 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -403,6 +403,43 @@ struct cfs_rq {
          */
         struct list_head leaf_cfs_rq_list;
         struct task_group *tg;  /* group that "owns" this runqueue */
+
+#ifdef CONFIG_SMP
+        unsigned long task_weight;
+        unsigned long shares;
+        /*
+         * We need space to build a sched_domain wide view of the full task
+         * group tree, in order to avoid depending on dynamic memory allocation
+         * during the load balancing we place this in the per cpu task group
+         * hierarchy. This limits the load balancing to one instance per cpu,
+         * but more should not be needed anyway.
+         */
+        struct aggregate_struct {
+                /*
+                 *   load = weight(cpus) * f(tg)
+                 *
+                 * Where f(tg) is the recursive weight fraction assigned to
+                 * this group.
+                 */
+                unsigned long load;
+
+                /*
+                 * part of the group weight distributed to this span.
+                 */
+                unsigned long shares;
+
+                /*
+                 * The sum of all runqueue weights within this span.
+                 */
+                unsigned long rq_weight;
+
+                /*
+                 * Weight contributed by tasks; this is the part we can
+                 * influence by moving tasks around.
+                 */
+                unsigned long task_weight;
+        } aggregate;
+#endif
 #endif
 };
 
@@ -1484,6 +1521,326 @@ static unsigned long source_load(int cpu, int type);
 static unsigned long target_load(int cpu, int type);
 static unsigned long cpu_avg_load_per_task(int cpu);
 static int task_hot(struct task_struct *p, u64 now, struct sched_domain *sd);
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+
+/*
+ * Group load balancing.
+ *
+ * We calculate a few balance domain wide aggregate numbers; load and weight.
+ * Given the pictures below, and assuming each item has equal weight:
+ *
+ *         root          1 - thread
+ *         / | \         A - group
+ *        A  1  B
+ *       /|\   / \
+ *      C 2 D 3   4
+ *      |   |
+ *      5   6
+ *
+ * load:
+ *    A and B get 1/3-rd of the total load. C and D get 1/3-rd of A's 1/3-rd,
+ *    which equals 1/9-th of the total load.
+ *
+ * shares:
+ *    The weight of this group on the selected cpus.
+ *
+ * rq_weight:
+ *    Direct sum of all the cpu's their rq weight, e.g. A would get 3 while
+ *    B would get 2.
+ *
+ * task_weight:
+ *    Part of the rq_weight contributed by tasks; all groups except B would
+ *    get 1, B gets 2.
+ */
+
+static inline struct aggregate_struct *
+aggregate(struct task_group *tg, struct sched_domain *sd)
+{
+        return &tg->cfs_rq[sd->first_cpu]->aggregate;
+}
+
+typedef void (*aggregate_func)(struct task_group *, struct sched_domain *);
+
+/*
+ * Iterate the full tree, calling @down when first entering a node and @up when
+ * leaving it for the final time.
+ */
+static
+void aggregate_walk_tree(aggregate_func down, aggregate_func up,
+                         struct sched_domain *sd)
+{
+        struct task_group *parent, *child;
+
+        rcu_read_lock();
+        parent = &root_task_group;
+down:
+        (*down)(parent, sd);
+        list_for_each_entry_rcu(child, &parent->children, siblings) {
+                parent = child;
+                goto down;
+
+up:
+                continue;
+        }
+        (*up)(parent, sd);
+
+        child = parent;
+        parent = parent->parent;
+        if (parent)
+                goto up;
+        rcu_read_unlock();
+}
+
+/*
+ * Calculate the aggregate runqueue weight.
+ */
+static
+void aggregate_group_weight(struct task_group *tg, struct sched_domain *sd)
+{
+        unsigned long rq_weight = 0;
+        unsigned long task_weight = 0;
+        int i;
+
+        for_each_cpu_mask(i, sd->span) {
+                rq_weight += tg->cfs_rq[i]->load.weight;
+                task_weight += tg->cfs_rq[i]->task_weight;
+        }
+
+        aggregate(tg, sd)->rq_weight = rq_weight;
+        aggregate(tg, sd)->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)
+{
+        unsigned long shares = 0;
+        int i;
+
+        for_each_cpu_mask(i, sd->span)
+                shares += tg->cfs_rq[i]->shares;
+
+        if ((!shares && aggregate(tg, sd)->rq_weight) || shares > tg->shares)
+                shares = tg->shares;
+
+        aggregate(tg, sd)->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)
+{
+        unsigned long load;
+
+        if (!tg->parent) {
+                int i;
+
+                load = 0;
+                for_each_cpu_mask(i, sd->span)
+                        load += cpu_rq(i)->load.weight;
+
+        } else {
+                load = aggregate(tg->parent, sd)->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;
+        }
+
+        aggregate(tg, sd)->load = load;
+}
+
+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)
+{
+        int boost = 0;
+        unsigned long shares;
+        unsigned long rq_weight;
+
+        if (!tg->se[tcpu])
+                return;
+
+        rq_weight = tg->cfs_rq[tcpu]->load.weight;
+
+        /*
+         * If there are currently no tasks on the cpu pretend there is one of
+         * average load so that when a new task gets to run here it will not
+         * get delayed by group starvation.
+         */
+        if (!rq_weight) {
+                boost = 1;
+                rq_weight = NICE_0_LOAD;
+        }
+
+        /*
+         *           \Sum shares * rq_weight
+         * shares =  -----------------------
+         *               \Sum rq_weight
+         *
+         */
+        shares = aggregate(tg, sd)->shares * rq_weight;
+        shares /= aggregate(tg, sd)->rq_weight + 1;
+
+        /*
+         * record the actual number of shares, not the boosted amount.
+         */
+        tg->cfs_rq[tcpu]->shares = boost ? 0 : shares;
+
+        if (shares < MIN_SHARES)
+                shares = MIN_SHARES;
+        else if (shares > MAX_SHARES)
+                shares = MAX_SHARES;
+
+        __set_se_shares(tg->se[tcpu], shares);
+}
+
+/*
+ * Re-adjust the weights on the cpu the task came from and on the cpu the
+ * task went to.
+ */
+static void
+__move_group_shares(struct task_group *tg, 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);
+
+        /*
+         * ensure we never loose shares due to rounding errors in the
+         * above redistribution.
+         */
+        shares -= tg->cfs_rq[scpu]->shares + tg->cfs_rq[dcpu]->shares;
+        if (shares)
+                tg->cfs_rq[dcpu]->shares += shares;
+}
+
+/*
+ * Because changing a group's shares changes the weight of the super-group
+ * 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,
+                  int scpu, int dcpu)
+{
+        while (tg) {
+                __move_group_shares(tg, sd, scpu, dcpu);
+                tg = tg->parent;
+        }
+}
+
+static
+void aggregate_group_set_shares(struct task_group *tg, struct sched_domain *sd)
+{
+        unsigned long shares = aggregate(tg, sd)->shares;
+        int i;
+
+        for_each_cpu_mask(i, sd->span) {
+                struct rq *rq = cpu_rq(i);
+                unsigned long flags;
+
+                spin_lock_irqsave(&rq->lock, flags);
+                __update_group_shares_cpu(tg, sd, i);
+                spin_unlock_irqrestore(&rq->lock, flags);
+        }
+
+        aggregate_group_shares(tg, sd);
+
+        /*
+         * ensure we never loose shares due to rounding errors in the
+         * above redistribution.
+         */
+        shares -= aggregate(tg, sd)->shares;
+        if (shares) {
+                tg->cfs_rq[sd->first_cpu]->shares += shares;
+                aggregate(tg, sd)->shares += shares;
+        }
+}
+
+/*
+ * 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)
+{
+        aggregate_group_weight(tg, sd);
+        aggregate_group_shares(tg, sd);
+        aggregate_group_load(tg, sd);
+}
+
+/*
+ * Rebalance the cpu shares while walking back up the tree.
+ */
+static
+void aggregate_get_up(struct task_group *tg, struct sched_domain *sd)
+{
+        aggregate_group_set_shares(tg, sd);
+}
+
+static DEFINE_PER_CPU(spinlock_t, aggregate_lock);
+
+static void __init init_aggregate(void)
+{
+        int i;
+
+        for_each_possible_cpu(i)
+                spin_lock_init(&per_cpu(aggregate_lock, i));
+}
+
+static int get_aggregate(struct sched_domain *sd)
+{
+        if (!spin_trylock(&per_cpu(aggregate_lock, sd->first_cpu)))
+                return 0;
+
+        aggregate_walk_tree(aggregate_get_down, aggregate_get_up, sd);
+        return 1;
+}
+
+static void put_aggregate(struct sched_domain *sd)
+{
+        spin_unlock(&per_cpu(aggregate_lock, sd->first_cpu));
+}
+
+static void cfs_rq_set_shares(struct cfs_rq *cfs_rq, unsigned long shares)
+{
+        cfs_rq->shares = shares;
+}
+
+#else
+
+static inline void init_aggregate(void)
+{
+}
+
+static inline int get_aggregate(struct sched_domain *sd)
+{
+        return 0;
+}
+
+static inline void put_aggregate(struct sched_domain *sd)
+{
+}
+#endif
+
 #endif
 
 #include "sched_stats.h"
@@ -1498,26 +1855,14 @@ static int task_hot(struct task_struct *p, u64 now, struct sched_domain *sd);
 #define for_each_class(class) \
    for (class = sched_class_highest; class; class = class->next)
 
-static inline void inc_load(struct rq *rq, const struct task_struct *p)
-{
-        update_load_add(&rq->load, p->se.load.weight);
-}
-
-static inline void dec_load(struct rq *rq, const struct task_struct *p)
-{
-        update_load_sub(&rq->load, p->se.load.weight);
-}
-
-static void inc_nr_running(struct task_struct *p, struct rq *rq)
+static void inc_nr_running(struct rq *rq)
 {
         rq->nr_running++;
-        inc_load(rq, p);
 }
 
-static void dec_nr_running(struct task_struct *p, struct rq *rq)
+static void dec_nr_running(struct rq *rq)
 {
         rq->nr_running--;
-        dec_load(rq, p);
 }
 
 static void set_load_weight(struct task_struct *p)
@@ -1609,7 +1954,7 @@ static void activate_task(struct rq *rq, struct task_struct *p, int wakeup)
                 rq->nr_uninterruptible--;
 
         enqueue_task(rq, p, wakeup);
-        inc_nr_running(p, rq);
+        inc_nr_running(rq);
 }
 
 /*
@@ -1621,7 +1966,7 @@ static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep)
                 rq->nr_uninterruptible++;
 
         dequeue_task(rq, p, sleep);
-        dec_nr_running(p, rq);
+        dec_nr_running(rq);
 }
 
 /**
@@ -2274,7 +2619,7 @@ void wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
                  * management (if any):
                  */
                 p->sched_class->task_new(rq, p);
-                inc_nr_running(p, rq);
+                inc_nr_running(rq);
         }
         check_preempt_curr(rq, p);
 #ifdef CONFIG_SMP
@@ -3265,9 +3610,12 @@ static int load_balance(int this_cpu, struct rq *this_rq,
         unsigned long imbalance;
         struct rq *busiest;
         unsigned long flags;
+        int unlock_aggregate;
 
         cpus_setall(*cpus);
 
+        unlock_aggregate = get_aggregate(sd);
+
         /*
          * When power savings policy is enabled for the parent domain, idle
          * sibling can pick up load irrespective of busy siblings. In this case,
@@ -3383,8 +3731,9 @@ redo:
 
         if (!ld_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
             !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
-                return -1;
-        return ld_moved;
+                ld_moved = -1;
+
+        goto out;
 
 out_balanced:
         schedstat_inc(sd, lb_balanced[idle]);
@@ -3399,8 +3748,13 @@ out_one_pinned:
 
         if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
             !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
-                return -1;
-        return 0;
+                ld_moved = -1;
+        else
+                ld_moved = 0;
+out:
+        if (unlock_aggregate)
+                put_aggregate(sd);
+        return ld_moved;
 }
 
 /*
@@ -4588,10 +4942,8 @@ void set_user_nice(struct task_struct *p, long nice)
                 goto out_unlock;
         }
         on_rq = p->se.on_rq;
-        if (on_rq) {
+        if (on_rq)
                 dequeue_task(rq, p, 0);
-                dec_load(rq, p);
-        }
 
         p->static_prio = NICE_TO_PRIO(nice);
         set_load_weight(p);
@@ -4601,7 +4953,6 @@ void set_user_nice(struct task_struct *p, long nice)
 
         if (on_rq) {
                 enqueue_task(rq, p, 0);
-                inc_load(rq, p);
                 /*
                  * If the task increased its priority or is running and
                  * lowered its priority, then reschedule its CPU:
@@ -7016,6 +7367,7 @@ 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;
@@ -7026,6 +7378,7 @@ 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;
@@ -7037,6 +7390,7 @@ 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;
@@ -7048,6 +7402,7 @@ 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;
@@ -7060,6 +7415,7 @@ 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;
@@ -7757,6 +8113,7 @@ void __init sched_init(void)
         }
 
 #ifdef CONFIG_SMP
+        init_aggregate();
         init_defrootdomain();
 #endif
 
@@ -8322,14 +8679,11 @@ void sched_move_task(struct task_struct *tsk)
 #endif /* CONFIG_GROUP_SCHED */
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
-static void set_se_shares(struct sched_entity *se, unsigned long shares)
+static void __set_se_shares(struct sched_entity *se, unsigned long shares)
 {
         struct cfs_rq *cfs_rq = se->cfs_rq;
-        struct rq *rq = cfs_rq->rq;
         int on_rq;
 
-        spin_lock_irq(&rq->lock);
-
         on_rq = se->on_rq;
         if (on_rq)
                 dequeue_entity(cfs_rq, se, 0);
@@ -8339,8 +8693,17 @@ static void set_se_shares(struct sched_entity *se, unsigned long shares)
 
         if (on_rq)
                 enqueue_entity(cfs_rq, se, 0);
+}
 
-        spin_unlock_irq(&rq->lock);
+static void set_se_shares(struct sched_entity *se, unsigned long shares)
+{
+        struct cfs_rq *cfs_rq = se->cfs_rq;
+        struct rq *rq = cfs_rq->rq;
+        unsigned long flags;
+
+        spin_lock_irqsave(&rq->lock, flags);
+        __set_se_shares(se, shares);
+        spin_unlock_irqrestore(&rq->lock, flags);
 }
 
 static DEFINE_MUTEX(shares_mutex);
@@ -8379,8 +8742,13 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares)
          * w/o tripping rebalance_share or load_balance_fair.
          */
         tg->shares = shares;
-        for_each_possible_cpu(i)
+        for_each_possible_cpu(i) {
+                /*
+                 * force a rebalance
+                 */
+                cfs_rq_set_shares(tg->cfs_rq[i], 0);
                 set_se_shares(tg->se[i], shares);
+        }
 
         /*
          * Enable load balance activity on this group, by inserting it back on