sched: debug, improve migration statistics

add new migration statistics when SCHED_DEBUG and SCHEDSTATS
is enabled. Available in /proc/<PID>/sched.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 54 insertions, 22 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 945ab1322e18..3b27c3a553aa 100644
--- 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);
         /*
@@ -2119,22 +2159,6 @@ static void pull_task(struct rq *src_rq, struct task_struct *p,
 }
 
 /*
- * 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;
-}
-
-/*
  * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
  */
 static
@@ -2148,12 +2172,16 @@ 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:
@@ -2163,14 +2191,18 @@ int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
 
         if (sd->nr_balance_failed > sd->cache_nice_tries) {
 #ifdef CONFIG_SCHEDSTATS
-                if (task_hot(p, rq->clock, sd))
+                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))
+        if (task_hot(p, rq->clock, sd)) {
+                schedstat_inc(p, se.nr_failed_migrations_hot);
                 return 0;
+        }
         return 1;
 }