sched: Fix schedstat.nr_wakeups_migrate

tip:sched/urgent tip-bot for Peter Zijlstra 1 participant 1 message May 31, 2011 Scheduler

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2011-05-31 12:32 UTC #0 lore raw

Commit-ID:  f339b9dc1f03591761d5d930800db24bc0eda1e1
Gitweb:     http://git.kernel.org/tip/f339b9dc1f03591761d5d930800db24bc0eda1e1
Author:     Peter Zijlstra <[email protected]>
AuthorDate: Tue, 31 May 2011 10:49:20 +0200
Committer:  Ingo Molnar <[email protected]>
CommitDate: Tue, 31 May 2011 14:19:57 +0200

sched: Fix schedstat.nr_wakeups_migrate

While looking over the code I found that with the ttwu rework the nr_wakeups_migrate test broke since we now switch cpus prior to calling ttwu_stat(), hence the test is always true.

Cure this by passing the migration state in wake_flags. Also move the whole test under CONFIG_SMP, its hard to migrate tasks on UP :-)

Signed-off-by Peter Zijlstra <[email protected]>

Link http://lkml.kernel.org/n/[email protected] open here

Signed-off-by Ingo Molnar <[email protected]>

---
 include/linux/sched.h |    1 +
 kernel/sched.c        |   11 +++++++----
 2 files changed, 8 insertions(+), 4 deletions(-)

include/linux/sched.h +1 -0

index 8da84b7..483c1ed 100644
@@ -1063,6 +1063,7 @@ struct sched_domain;
  */
 #define WF_SYNC		0x01		/* waker goes to sleep after wakup */
 #define WF_FORK		0x02		/* child wakeup after fork */
+#define WF_MIGRATED	0x04		/* internal use, task got migrated */
 
 #define ENQUEUE_WAKEUP		1
 #define ENQUEUE_HEAD		2

kernel/sched.c +7 -4

index 49cc70b..2fe98ed 100644
@@ -2447,6 +2447,10 @@ ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
 		}
 		rcu_read_unlock();
 	}
+
+	if (wake_flags & WF_MIGRATED)
+		schedstat_inc(p, se.statistics.nr_wakeups_migrate);
+
 #endif /* CONFIG_SMP */
 
 	schedstat_inc(rq, ttwu_count);

@@ -2455,9 +2459,6 @@ ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
 	if (wake_flags & WF_SYNC)
 		schedstat_inc(p, se.statistics.nr_wakeups_sync);
 
-	if (cpu != task_cpu(p))
-		schedstat_inc(p, se.statistics.nr_wakeups_migrate);
-
 #endif /* CONFIG_SCHEDSTATS */
 }

@@ -2675,8 +2676,10 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 		p->sched_class->task_waking(p);
 
 	cpu = select_task_rq(p, SD_BALANCE_WAKE, wake_flags);
-	if (task_cpu(p) != cpu)
+	if (task_cpu(p) != cpu) {
+		wake_flags |= WF_MIGRATED;
 		set_task_cpu(p, cpu);
+	}
 #endif /* CONFIG_SMP */
 
 	ttwu_queue(p, cpu);