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Subject[tip:sched/urgent] sched: Fix schedstat.nr_wakeups_migrate
Commit-ID:  f339b9dc1f03591761d5d930800db24bc0eda1e1
Gitweb: http://git.kernel.org/tip/f339b9dc1f03591761d5d930800db24bc0eda1e1
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Tue, 31 May 2011 10:49:20 +0200
Committer: Ingo Molnar <mingo@elte.hu>
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 <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-pwwxl7gdqs5676f1d4cx6pj7@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
include/linux/sched.h | 1 +
kernel/sched.c | 11 +++++++----
2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8da84b7..483c1ed 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -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
diff --git a/kernel/sched.c b/kernel/sched.c
index 49cc70b..2fe98ed 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -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);

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