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Subject[PATCH] tracing, sched: Add a new tracepoint for sleeptime
Date
If CONFIG_SCHEDSTATS is defined, the kernel maintains
information about how long the task was sleeping or
in the case of iowait, blocking in the kernel before
getting woken up.

Note: this information is only provided for sched_fair.
Other scheduling classes may choose to provide this in
the future.

Note: the delay includes the time spent on the runqueue
as well.

Signed-off-by: Arun Sharma <asharma@fb.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Andrew Vagin <avagin@openvz.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: linux-kernel@vger.kernel.org
---
include/trace/events/sched.h | 50 ++++++++++++++++++++++++++++++++++++++++++
kernel/sched/core.c | 1 +
kernel/sched/fair.c | 2 -
3 files changed, 51 insertions(+), 2 deletions(-)

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index 959ff18..3442c6d 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -363,6 +363,56 @@ TRACE_EVENT(sched_stat_runtime,
(unsigned long long)__entry->vruntime)
);

+#ifdef CREATE_TRACE_POINTS
+static inline u64 trace_get_sleeptime(struct task_struct *tsk)
+{
+#ifdef CONFIG_SCHEDSTATS
+ u64 block, sleep;
+
+ block = tsk->se.statistics.block_start;
+ sleep = tsk->se.statistics.sleep_start;
+ tsk->se.statistics.block_start = 0;
+ tsk->se.statistics.sleep_start = 0;
+
+ return block ? block : sleep ? sleep : 0;
+#else
+ return 0;
+#endif
+}
+#endif
+
+/*
+ * Tracepoint for accounting sleeptime (time the task is sleeping
+ * or waiting for I/O).
+ */
+TRACE_EVENT(sched_stat_sleeptime,
+
+ TP_PROTO(struct task_struct *tsk, u64 now),
+
+ TP_ARGS(tsk, now),
+
+ TP_STRUCT__entry(
+ __array( char, comm, TASK_COMM_LEN )
+ __field( pid_t, pid )
+ __field( u64, sleeptime )
+ ),
+
+ TP_fast_assign(
+ memcpy(__entry->comm, tsk->comm, TASK_COMM_LEN);
+ __entry->pid = tsk->pid;
+ __entry->sleeptime = trace_get_sleeptime(tsk);
+ __entry->sleeptime = __entry->sleeptime ?
+ now - __entry->sleeptime : 0;
+ )
+ TP_perf_assign(
+ __perf_count(__entry->sleeptime);
+ ),
+
+ TP_printk("comm=%s pid=%d sleeptime=%Lu [ns]",
+ __entry->comm, __entry->pid,
+ (unsigned long long)__entry->sleeptime)
+);
+
/*
* Tracepoint for showing priority inheritance modifying a tasks
* priority.
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ca8fd44..172e6ee 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1899,6 +1899,7 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
local_irq_enable();
#endif /* __ARCH_WANT_INTERRUPTS_ON_CTXSW */
finish_lock_switch(rq, prev);
+ trace_sched_stat_sleeptime(current, rq->clock);

fire_sched_in_preempt_notifiers(current);
if (mm)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index cd3b642..86deb3b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1003,7 +1003,6 @@ static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
if (unlikely(delta > se->statistics.sleep_max))
se->statistics.sleep_max = delta;

- se->statistics.sleep_start = 0;
se->statistics.sum_sleep_runtime += delta;

if (tsk) {
@@ -1020,7 +1019,6 @@ static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
if (unlikely(delta > se->statistics.block_max))
se->statistics.block_max = delta;

- se->statistics.block_start = 0;
se->statistics.sum_sleep_runtime += delta;

if (tsk) {
--
1.7.4


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