sched: debug, improve migration statistics

[linux-2.6-omap-h63xx.git] / kernel / sched.c

diff --git a/kernel/sched.c b/kernel/sched.c
index 791dd08c692f2eadb44df1ffc6bbd8e4978e07d2..3b27c3a553aa3a0b20a7e78248d6795d60ad6ff0 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1005,6 +1005,23 @@ static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu)
 
 #ifdef CONFIG_SMP
 
+/*
+ * Is this task likely cache-hot:
+ */
+static inline int
+task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
+{
+       s64 delta;
+
+       if (p->sched_class != &fair_sched_class)
+               return 0;
+
+       delta = now - p->se.exec_start;
+
+       return delta < (s64)sysctl_sched_migration_cost;
+}
+
+
 void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
 {
        int old_cpu = task_cpu(p);
@@ -1022,6 +1039,11 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
                p->se.sleep_start -= clock_offset;
        if (p->se.block_start)
                p->se.block_start -= clock_offset;
+       if (old_cpu != new_cpu) {
+               schedstat_inc(p, se.nr_migrations);
+               if (task_hot(p, old_rq->clock, NULL))
+                       schedstat_inc(p, se.nr_forced2_migrations);
+       }
 #endif
        p->se.vruntime -= old_cfsrq->min_vruntime -
                                         new_cfsrq->min_vruntime;
@@ -1394,8 +1416,13 @@ static int wake_idle(int cpu, struct task_struct *p)
                if (sd->flags & SD_WAKE_IDLE) {
                        cpus_and(tmp, sd->span, p->cpus_allowed);
                        for_each_cpu_mask(i, tmp) {
-                               if (idle_cpu(i))
+                               if (idle_cpu(i)) {
+                                       if (i != task_cpu(p)) {
+                                               schedstat_inc(p,
+                                                       se.nr_wakeups_idle);
+                                       }
                                        return i;
+                               }
                        }
                } else {
                        break;
@@ -1426,7 +1453,7 @@ static inline int wake_idle(int cpu, struct task_struct *p)
  */
 static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
 {
-       int cpu, this_cpu, success = 0;
+       int cpu, orig_cpu, this_cpu, success = 0;
        unsigned long flags;
        long old_state;
        struct rq *rq;
@@ -1445,6 +1472,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
                goto out_running;
 
        cpu = task_cpu(p);
+       orig_cpu = cpu;
        this_cpu = smp_processor_id();
 
 #ifdef CONFIG_SMP
@@ -1488,6 +1516,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
                        unsigned long tl = this_load;
                        unsigned long tl_per_task;
 
+                       schedstat_inc(p, se.nr_wakeups_affine_attempts);
                        tl_per_task = cpu_avg_load_per_task(this_cpu);
 
                        /*
@@ -1507,6 +1536,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
                                 * there is no bad imbalance.
                                 */
                                schedstat_inc(this_sd, ttwu_move_affine);
+                               schedstat_inc(p, se.nr_wakeups_affine);
                                goto out_set_cpu;
                        }
                }
@@ -1518,6 +1548,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
                if (this_sd->flags & SD_WAKE_BALANCE) {
                        if (imbalance*this_load <= 100*load) {
                                schedstat_inc(this_sd, ttwu_move_balance);
+                               schedstat_inc(p, se.nr_wakeups_passive);
                                goto out_set_cpu;
                        }
                }
@@ -1543,6 +1574,15 @@ out_set_cpu:
 
 out_activate:
 #endif /* CONFIG_SMP */
+       schedstat_inc(p, se.nr_wakeups);
+       if (sync)
+               schedstat_inc(p, se.nr_wakeups_sync);
+       if (orig_cpu != cpu)
+               schedstat_inc(p, se.nr_wakeups_migrate);
+       if (cpu == this_cpu)
+               schedstat_inc(p, se.nr_wakeups_local);
+       else
+               schedstat_inc(p, se.nr_wakeups_remote);
        update_rq_clock(rq);
        activate_task(rq, p, 1);
        /*
@@ -2132,13 +2172,37 @@ 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 (!cpu_isset(this_cpu, p->cpus_allowed))
+       if (!cpu_isset(this_cpu, p->cpus_allowed)) {
+               schedstat_inc(p, se.nr_failed_migrations_affine);
                return 0;
+       }
        *all_pinned = 0;
 
-       if (task_running(rq, p))
+       if (task_running(rq, p)) {
+               schedstat_inc(p, se.nr_failed_migrations_running);
                return 0;
+       }
 
+       /*
+        * Aggressive migration if:
+        * 1) task is cache cold, or
+        * 2) too many balance attempts have failed.
+        */
+
+       if (sd->nr_balance_failed > sd->cache_nice_tries) {
+#ifdef CONFIG_SCHEDSTATS
+               if (task_hot(p, rq->clock, sd)) {
+                       schedstat_inc(sd, lb_hot_gained[idle]);
+                       schedstat_inc(p, se.nr_forced_migrations);
+               }
+#endif
+               return 1;
+       }
+
+       if (task_hot(p, rq->clock, sd)) {
+               schedstat_inc(p, se.nr_failed_migrations_hot);
+               return 0;
+       }
        return 1;
 }