sched: Move load-balancing arguments into helper struct

Passing large sets of similar arguments all around the load-balancer
gets tiresom when you want to modify something. Stick them all in a
helper structure and pass the structure around.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: pjt@google.com
Link: http://lkml.kernel.org/n/tip-5slqz0vhsdzewrfk9eza1aon@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 93 insertions, 84 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 79e9e13c31ab..55b1f117419a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3135,13 +3135,25 @@ task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
 #define LBF_HAD_BREAKS  0x0C    /* count HAD_BREAKs overflows into ABORT */
 #define LBF_ABORT       0x10
 
+struct lb_env {
+        struct sched_domain     *sd;
+
+        int                     this_cpu;
+        struct rq               *this_rq;
+
+        struct rq               *busiest_rq;
+        struct cfs_rq           *busiest_cfs_rq;
+
+        enum cpu_idle_type      idle;
+        unsigned long           max_load_move;
+        unsigned int            flags;
+};
+
 /*
  * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
  */
 static
-int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
-                     struct sched_domain *sd, enum cpu_idle_type idle,
-                     int *lb_flags)
+int can_migrate_task(struct task_struct *p, struct lb_env *env)
 {
         int tsk_cache_hot = 0;
         /*
@@ -3150,13 +3162,13 @@ int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
          * 2) cannot be migrated to this CPU due to cpus_allowed, or
          * 3) are cache-hot on their current CPU.
          */
-        if (!cpumask_test_cpu(this_cpu, tsk_cpus_allowed(p))) {
+        if (!cpumask_test_cpu(env->this_cpu, tsk_cpus_allowed(p))) {
                 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
                 return 0;
         }
-        *lb_flags &= ~LBF_ALL_PINNED;
+        env->flags &= ~LBF_ALL_PINNED;
 
-        if (task_running(rq, p)) {
+        if (task_running(env->busiest_rq, p)) {
                 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
                 return 0;
         }
@@ -3167,12 +3179,12 @@ int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
          * 2) too many balance attempts have failed.
          */
 
-        tsk_cache_hot = task_hot(p, rq->clock_task, sd);
+        tsk_cache_hot = task_hot(p, env->busiest_rq->clock_task, env->sd);
         if (!tsk_cache_hot ||
-                sd->nr_balance_failed > sd->cache_nice_tries) {
+                env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
 #ifdef CONFIG_SCHEDSTATS
                 if (tsk_cache_hot) {
-                        schedstat_inc(sd, lb_hot_gained[idle]);
+                        schedstat_inc(env->sd, lb_hot_gained[env->idle]);
                         schedstat_inc(p, se.statistics.nr_forced_migrations);
                 }
 #endif
@@ -3193,31 +3205,27 @@ int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
  *
  * Called with both runqueues locked.
  */
-static int
-move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
-              struct sched_domain *sd, enum cpu_idle_type idle)
+static int move_one_task(struct lb_env *env)
 {
         struct task_struct *p, *n;
         struct cfs_rq *cfs_rq;
-        int pinned = 0;
 
-        for_each_leaf_cfs_rq(busiest, cfs_rq) {
+        for_each_leaf_cfs_rq(env->busiest_rq, cfs_rq) {
                 list_for_each_entry_safe(p, n, &cfs_rq->tasks, se.group_node) {
                         if (throttled_lb_pair(task_group(p),
-                                              busiest->cpu, this_cpu))
+                                              env->busiest_rq->cpu, env->this_cpu))
                                 break;
 
-                        if (!can_migrate_task(p, busiest, this_cpu,
-                                                sd, idle, &pinned))
+                        if (!can_migrate_task(p, env))
                                 continue;
 
-                        pull_task(busiest, p, this_rq, this_cpu);
+                        pull_task(env->busiest_rq, p, env->this_rq, env->this_cpu);
                         /*
                          * Right now, this is only the second place pull_task()
                          * is called, so we can safely collect pull_task()
                          * stats here rather than inside pull_task().
                          */
-                        schedstat_inc(sd, lb_gained[idle]);
+                        schedstat_inc(env->sd, lb_gained[env->idle]);
                         return 1;
                 }
         }
@@ -3225,31 +3233,26 @@ move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
         return 0;
 }
 
-static unsigned long
-balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
-              unsigned long max_load_move, struct sched_domain *sd,
-              enum cpu_idle_type idle, int *lb_flags,
-              struct cfs_rq *busiest_cfs_rq)
+static unsigned long balance_tasks(struct lb_env *env)
 {
         int loops = 0, pulled = 0;
-        long rem_load_move = max_load_move;
+        long rem_load_move = env->max_load_move;
         struct task_struct *p, *n;
 
-        if (max_load_move == 0)
+        if (env->max_load_move == 0)
                 goto out;
 
-        list_for_each_entry_safe(p, n, &busiest_cfs_rq->tasks, se.group_node) {
+        list_for_each_entry_safe(p, n, &env->busiest_cfs_rq->tasks, se.group_node) {
                 if (loops++ > sysctl_sched_nr_migrate) {
-                        *lb_flags |= LBF_NEED_BREAK;
+                        env->flags |= LBF_NEED_BREAK;
                         break;
                 }
 
                 if ((p->se.load.weight >> 1) > rem_load_move ||
-                    !can_migrate_task(p, busiest, this_cpu, sd, idle,
-                                      lb_flags))
+                    !can_migrate_task(p, env))
                         continue;
 
-                pull_task(busiest, p, this_rq, this_cpu);
+                pull_task(env->busiest_rq, p, env->this_rq, env->this_cpu);
                 pulled++;
                 rem_load_move -= p->se.load.weight;
 
@@ -3259,8 +3262,8 @@ balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
                  * kernels will stop after the first task is pulled to minimize
                  * the critical section.
                  */
-                if (idle == CPU_NEWLY_IDLE) {
-                        *lb_flags |= LBF_ABORT;
+                if (env->idle == CPU_NEWLY_IDLE) {
+                        env->flags |= LBF_ABORT;
                         break;
                 }
 #endif
@@ -3278,9 +3281,9 @@ out:
          * so we can safely collect pull_task() stats here rather than
          * inside pull_task().
          */
-        schedstat_add(sd, lb_gained[idle], pulled);
+        schedstat_add(env->sd, lb_gained[env->idle], pulled);
 
-        return max_load_move - rem_load_move;
+        return env->max_load_move - rem_load_move;
 }
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
@@ -3363,40 +3366,39 @@ static void update_h_load(long cpu)
         walk_tg_tree(tg_load_down, tg_nop, (void *)cpu);
 }
 
-static unsigned long
-load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
-                  unsigned long max_load_move,
-                  struct sched_domain *sd, enum cpu_idle_type idle,
-                  int *lb_flags)
+static unsigned long load_balance_fair(struct lb_env *env)
 {
-        long rem_load_move = max_load_move;
-        struct cfs_rq *busiest_cfs_rq;
+        unsigned long max_load_move = env->max_load_move;
+        long rem_load_move = env->max_load_move;
 
         rcu_read_lock();
-        update_h_load(cpu_of(busiest));
+        update_h_load(cpu_of(env->busiest_rq));
 
-        for_each_leaf_cfs_rq(busiest, busiest_cfs_rq) {
-                unsigned long busiest_h_load = busiest_cfs_rq->h_load;
-                unsigned long busiest_weight = busiest_cfs_rq->load.weight;
+        for_each_leaf_cfs_rq(env->busiest_rq, env->busiest_cfs_rq) {
+                unsigned long busiest_h_load = env->busiest_cfs_rq->h_load;
+                unsigned long busiest_weight = env->busiest_cfs_rq->load.weight;
                 u64 rem_load, moved_load;
 
-                if (*lb_flags & (LBF_NEED_BREAK|LBF_ABORT))
+                if (env->flags & (LBF_NEED_BREAK|LBF_ABORT))
                         break;
 
                 /*
                  * empty group or part of a throttled hierarchy
                  */
-                if (!busiest_cfs_rq->task_weight ||
-                    throttled_lb_pair(busiest_cfs_rq->tg, cpu_of(busiest), this_cpu))
+                if (!env->busiest_cfs_rq->task_weight)
+                        continue;
+
+                if (throttled_lb_pair(env->busiest_cfs_rq->tg,
+                                      cpu_of(env->busiest_rq),
+                                      env->this_cpu))
                         continue;
 
                 rem_load = (u64)rem_load_move * busiest_weight;
                 rem_load = div_u64(rem_load, busiest_h_load + 1);
 
-                moved_load = balance_tasks(this_rq, this_cpu, busiest,
-                                rem_load, sd, idle, lb_flags,
-                                busiest_cfs_rq);
+                env->max_load_move = rem_load;
 
+                moved_load = balance_tasks(env);
                 if (!moved_load)
                         continue;
 
@@ -3416,15 +3418,10 @@ 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,
-                  struct sched_domain *sd, enum cpu_idle_type idle,
-                  int *lb_flags)
+static unsigned long load_balance_fair(struct lb_env *env)
 {
-        return balance_tasks(this_rq, this_cpu, busiest,
-                        max_load_move, sd, idle, lb_flags,
-                        &busiest->cfs);
+        env->busiest_cfs_rq = &env->busiest_rq->cfs;
+        return balance_tasks(env);
 }
 #endif
 
@@ -3435,21 +3432,17 @@ load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
  *
  * Called with both runqueues locked.
  */
-static int move_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
-                      unsigned long max_load_move,
-                      struct sched_domain *sd, enum cpu_idle_type idle,
-                      int *lb_flags)
+static int move_tasks(struct lb_env *env)
 {
+        unsigned long max_load_move = env->max_load_move;
         unsigned long total_load_moved = 0, load_moved;
 
         do {
-                load_moved = load_balance_fair(this_rq, this_cpu, busiest,
-                                max_load_move - total_load_moved,
-                                sd, idle, lb_flags);
-
+                env->max_load_move = max_load_move - total_load_moved;
+                load_moved = load_balance_fair(env);
                 total_load_moved += load_moved;
 
-                if (*lb_flags & (LBF_NEED_BREAK|LBF_ABORT))
+                if (env->flags & (LBF_NEED_BREAK|LBF_ABORT))
                         break;
 
 #ifdef CONFIG_PREEMPT
@@ -3458,8 +3451,8 @@ static int move_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
                  * kernels will stop after the first task is pulled to minimize
                  * the critical section.
                  */
-                if (idle == CPU_NEWLY_IDLE && this_rq->nr_running) {
-                        *lb_flags |= LBF_ABORT;
+                if (env->idle == CPU_NEWLY_IDLE && env->this_rq->nr_running) {
+                        env->flags |= LBF_ABORT;
                         break;
                 }
 #endif
@@ -4459,13 +4452,20 @@ static int load_balance(int this_cpu, struct rq *this_rq,
                         struct sched_domain *sd, enum cpu_idle_type idle,
                         int *balance)
 {
-        int ld_moved, lb_flags = 0, active_balance = 0;
+        int ld_moved, active_balance = 0;
         struct sched_group *group;
         unsigned long imbalance;
         struct rq *busiest;
         unsigned long flags;
         struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);
 
+        struct lb_env env = {
+                .sd             = sd,
+                .this_cpu       = this_cpu,
+                .this_rq        = this_rq,
+                .idle           = idle,
+        };
+
         cpumask_copy(cpus, cpu_active_mask);
 
         schedstat_inc(sd, lb_count[idle]);
@@ -4500,11 +4500,13 @@ redo:
                  * still unbalanced. ld_moved simply stays zero, so it is
                  * correctly treated as an imbalance.
                  */
-                lb_flags |= LBF_ALL_PINNED;
+                env.flags |= LBF_ALL_PINNED;
+                env.max_load_move = imbalance;
+                env.busiest_rq = busiest;
+
                 local_irq_save(flags);
                 double_rq_lock(this_rq, busiest);
-                ld_moved = move_tasks(this_rq, this_cpu, busiest,
-                                      imbalance, sd, idle, &lb_flags);
+                ld_moved = move_tasks(&env);
                 double_rq_unlock(this_rq, busiest);
                 local_irq_restore(flags);
 
@@ -4514,18 +4516,18 @@ redo:
                 if (ld_moved && this_cpu != smp_processor_id())
                         resched_cpu(this_cpu);
 
-                if (lb_flags & LBF_ABORT)
+                if (env.flags & LBF_ABORT)
                         goto out_balanced;
 
-                if (lb_flags & LBF_NEED_BREAK) {
-                        lb_flags += LBF_HAD_BREAK - LBF_NEED_BREAK;
-                        if (lb_flags & LBF_ABORT)
+                if (env.flags & LBF_NEED_BREAK) {
+                        env.flags += LBF_HAD_BREAK - LBF_NEED_BREAK;
+                        if (env.flags & LBF_ABORT)
                                 goto out_balanced;
                         goto redo;
                 }
 
                 /* All tasks on this runqueue were pinned by CPU affinity */
-                if (unlikely(lb_flags & LBF_ALL_PINNED)) {
+                if (unlikely(env.flags & LBF_ALL_PINNED)) {
                         cpumask_clear_cpu(cpu_of(busiest), cpus);
                         if (!cpumask_empty(cpus))
                                 goto redo;
@@ -4555,7 +4557,7 @@ redo:
                                         tsk_cpus_allowed(busiest->curr))) {
                                 raw_spin_unlock_irqrestore(&busiest->lock,
                                                             flags);
-                                lb_flags |= LBF_ALL_PINNED;
+                                env.flags |= LBF_ALL_PINNED;
                                 goto out_one_pinned;
                         }
 
@@ -4608,7 +4610,7 @@ out_balanced:
 
 out_one_pinned:
         /* tune up the balancing interval */
-        if (((lb_flags & LBF_ALL_PINNED) &&
+        if (((env.flags & LBF_ALL_PINNED) &&
                         sd->balance_interval < MAX_PINNED_INTERVAL) ||
                         (sd->balance_interval < sd->max_interval))
                 sd->balance_interval *= 2;
@@ -4718,10 +4720,17 @@ static int active_load_balance_cpu_stop(void *data)
         }
 
         if (likely(sd)) {
+                struct lb_env env = {
+                        .sd             = sd,
+                        .this_cpu       = target_cpu,
+                        .this_rq        = target_rq,
+                        .busiest_rq     = busiest_rq,
+                        .idle           = CPU_IDLE,
+                };
+
                 schedstat_inc(sd, alb_count);
 
-                if (move_one_task(target_rq, target_cpu, busiest_rq,
-                                  sd, CPU_IDLE))
+                if (move_one_task(&env))
                         schedstat_inc(sd, alb_pushed);
                 else
                         schedstat_inc(sd, alb_failed);