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Date: Fri, 18 May 2012 21:20:37 +0800
From: Hillf Danton <dhillf@...il.com>
To: LKML <linux-kernel@...r.kernel.org>,
Hillf Danton <dhillf@...il.com>
Subject: BFS 420: fix ttwu stat
Due to monolithic runqueue used by BFS, the ttwu stat is bogus as we could not
tell/predict on which CPU a woken task will run after it is activated. And we
have to delay updating ttwu stat until the stage when task is taken off run
queue. To achieve that, a field, wakeup_cpu, is added in the task struct, and is
inited to be invalid CPU number for each new task.
When updating ttwu stat, now it is simply to mark the delayed operation; and
when taking task off runqueue, the stat is updated.
--- a/include/linux/sched.h Fri May 18 20:51:06 2012
+++ b/include/linux/sched.h Fri May 18 20:32:20 2012
@@ -1255,6 +1255,11 @@ struct task_struct {
struct list_head run_list;
u64 last_ran;
u64 sched_time; /* sched_clock time spent running */
+#ifdef CONFIG_SCHEDSTATS
+#ifdef CONFIG_SMP
+ int wakeup_cpu; //for ttwu stat
+#endif
+#endif
#ifdef CONFIG_SMP
bool sticky; /* Soft affined flag */
#endif
--- a/kernel/sched/bfs.c Mon May 14 20:50:38 2012
+++ b/kernel/sched/bfs.c Fri May 18 20:46:22 2012
@@ -1145,6 +1145,30 @@ static inline void unstick_task(struct r
*/
static inline void take_task(int cpu, struct task_struct *p)
{
+#ifdef CONFIG_SCHEDSTATS
+#ifdef CONFIG_SMP
+ if (p->wakeup_cpu == -1)
+ goto skip;
+
+ if (cpu == p->wakeup_cpu) {
+ schedstat_inc(cpu_rq(cpu), ttwu_local);
+ }
+ else if (cpu_online(p->wakeup_cpu)) {
+ struct sched_domain *sd;
+
+ rcu_read_lock();
+ for_each_domain(p->wakeup_cpu, sd) {
+ if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
+ schedstat_inc(sd, ttwu_wake_remote);
+ break;
+ }
+ }
+ rcu_read_unlock();
+ }
+ p->wakeup_cpu = -1;
+skip:
+#endif
+#endif
set_task_cpu(p, cpu);
dequeue_task(p);
clear_sticky(p);
@@ -1485,30 +1509,13 @@ static void try_preempt(struct task_stru
}
#endif /* CONFIG_SMP */
-static void
-ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
+static void ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
{
#ifdef CONFIG_SCHEDSTATS
struct rq *rq = this_rq();
#ifdef CONFIG_SMP
- int this_cpu = smp_processor_id();
-
- if (cpu == this_cpu)
- schedstat_inc(rq, ttwu_local);
- else {
- struct sched_domain *sd;
-
- rcu_read_lock();
- for_each_domain(this_cpu, sd) {
- if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
- schedstat_inc(sd, ttwu_wake_remote);
- break;
- }
- }
- rcu_read_unlock();
- }
-
+ p->wakeup_cpu = smp_processor_id();
#endif /* CONFIG_SMP */
schedstat_inc(rq, ttwu_count);
@@ -1717,6 +1724,12 @@ void sched_fork(struct task_struct *p)
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
if (unlikely(sched_info_on()))
memset(&p->sched_info, 0, sizeof(p->sched_info));
+#endif
+
+#ifdef CONFIG_SCHEDSTATS
+#ifdef CONFIG_SMP
+ p->wakeup_cpu = -1;
+#endif
#endif
p->on_cpu = false;
--
--
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