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Subject[PATCH] sched: fair: fix missed CONFIG_SCHEDSTATS
Date
When I'm using trace_sched_stat_{iowait, blocked, wait, sleep} to
measure how long the processes are stalled, there's always no output from
trace_pipe while there're really some tasks in uninterruptible sleep
state. That makes me confused, so I try to investigate why.
Finally I find the reason is that CONFIG_SCHEDSTATS is not set.

To avoid such kind of confusion, we should not expose these tracepoints
if CONFIG_SCHEDSTATS is not set.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
include/trace/events/sched.h | 3 ++-
kernel/sched/fair.c | 13 ++++++++++++-
2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index 9a4bdfa..a261da8 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -336,6 +336,7 @@ static inline long __trace_sched_switch_state(bool preempt, struct task_struct *
__entry->pid, __entry->old_pid)
);

+#ifdef CONFIG_SCHEDSTATS
/*
* XXX the below sched_stat tracepoints only apply to SCHED_OTHER/BATCH/IDLE
* adding sched_stat support to SCHED_FIFO/RR would be welcome.
@@ -363,7 +364,6 @@ static inline long __trace_sched_switch_state(bool preempt, struct task_struct *
(unsigned long long)__entry->delay)
);

-
/*
* Tracepoint for accounting wait time (time the task is runnable
* but not actually running due to scheduler contention).
@@ -394,6 +394,7 @@ static inline long __trace_sched_switch_state(bool preempt, struct task_struct *
DEFINE_EVENT(sched_stat_template, sched_stat_blocked,
TP_PROTO(struct task_struct *tsk, u64 delay),
TP_ARGS(tsk, delay));
+#endif

/*
* Tracepoint for accounting runtime (time the task is executing
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8213ff6..a8006c9 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -855,6 +855,7 @@ static void update_curr_fair(struct rq *rq)
static inline void
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
+#ifdef CONFIG_SCHEDSTATS
u64 wait_start, prev_wait_start;

if (!schedstat_enabled())
@@ -868,11 +869,13 @@ static void update_curr_fair(struct rq *rq)
wait_start -= prev_wait_start;

__schedstat_set(se->statistics.wait_start, wait_start);
+#endif
}

static inline void
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
+#ifdef CONFIG_SCHEDSTATS
struct task_struct *p;
u64 delta;

@@ -900,11 +903,13 @@ static void update_curr_fair(struct rq *rq)
__schedstat_inc(se->statistics.wait_count);
__schedstat_add(se->statistics.wait_sum, delta);
__schedstat_set(se->statistics.wait_start, 0);
+#endif
}

static inline void
update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
+#ifdef CONFIG_SCHEDSTATS
struct task_struct *tsk = NULL;
u64 sleep_start, block_start;

@@ -968,6 +973,7 @@ static void update_curr_fair(struct rq *rq)
account_scheduler_latency(tsk, delta >> 10, 0);
}
}
+#endif
}

/*
@@ -976,6 +982,7 @@ static void update_curr_fair(struct rq *rq)
static inline void
update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
+#ifdef CONFIG_SCHEDSTATS
if (!schedstat_enabled())
return;

@@ -988,12 +995,13 @@ static void update_curr_fair(struct rq *rq)

if (flags & ENQUEUE_WAKEUP)
update_stats_enqueue_sleeper(cfs_rq, se);
+#endif
}

static inline void
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
-
+#ifdef CONFIG_SCHEDSTATS
if (!schedstat_enabled())
return;

@@ -1014,6 +1022,7 @@ static void update_curr_fair(struct rq *rq)
__schedstat_set(se->statistics.block_start,
rq_clock(rq_of(cfs_rq)));
}
+#endif
}

/*
@@ -4090,6 +4099,7 @@ static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
update_stats_curr_start(cfs_rq, se);
cfs_rq->curr = se;

+#ifdef CONFIG_SCHEDSTATS
/*
* Track our maximum slice length, if the CPU's load is at
* least twice that of our own weight (i.e. dont track it
@@ -4100,6 +4110,7 @@ static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
max((u64)schedstat_val(se->statistics.slice_max),
se->sum_exec_runtime - se->prev_sum_exec_runtime));
}
+#endif

se->prev_sum_exec_runtime = se->sum_exec_runtime;
}
--
1.8.3.1
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