[RFC PATCH v6 3/5] sched, tracing: reorganize fields of switch event struct

[Ze Gao <zegao2021@gmail.com>]

Report prioritiy and prev_state in 'short' to save some buffer
space. And also reorder the fields so that we take struct
alignment into consideration to make the record compact.

Suggested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Ze Gao <zegao@tencent.com>
---
 include/trace/events/sched.h | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index fbb99a61f714..43492daefa6f 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -187,14 +187,14 @@ DEFINE_EVENT(sched_wakeup_template, sched_wakeup_new,
 	     TP_ARGS(p));
 
 #ifdef CREATE_TRACE_POINTS
-static inline long __trace_sched_switch_state(bool preempt,
+static inline short __trace_sched_switch_state(bool preempt,
 					      unsigned int prev_state,
 					      struct task_struct *p)
 {
 	unsigned int state;
 
 #ifdef CONFIG_SCHED_DEBUG
-	BUG_ON(p != current);
+	WARN_ON_ONCE(p != current);
 #endif /* CONFIG_SCHED_DEBUG */
 
 	/*
@@ -229,23 +229,23 @@ TRACE_EVENT(sched_switch,
 	TP_ARGS(preempt, prev, next, prev_state),
 
 	TP_STRUCT__entry(
-		__array(	char,	prev_comm,	TASK_COMM_LEN	)
 		__field(	pid_t,	prev_pid			)
-		__field(	int,	prev_prio			)
-		__field(	long,	prev_state			)
-		__array(	char,	next_comm,	TASK_COMM_LEN	)
 		__field(	pid_t,	next_pid			)
-		__field(	int,	next_prio			)
+		__field(	short,	prev_prio			)
+		__field(	short,	next_prio			)
+		__array(	char,	prev_comm,	TASK_COMM_LEN	)
+		__array(	char,	next_comm,	TASK_COMM_LEN	)
+		__field(	short,	prev_state			)
 	),
 
 	TP_fast_assign(
-		memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
-		__entry->prev_pid	= prev->pid;
-		__entry->prev_prio	= prev->prio;
-		__entry->prev_state	= __trace_sched_switch_state(preempt, prev_state, prev);
+		__entry->prev_pid		= prev->pid;
+		__entry->next_pid		= next->pid;
+		__entry->prev_prio		= (short) prev->prio;
+		__entry->next_prio		= (short) next->prio;
 		memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
-		__entry->next_pid	= next->pid;
-		__entry->next_prio	= next->prio;
+		memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
+		__entry->prev_state		= __trace_sched_switch_state(preempt, prev_state, prev);
 		/* XXX SCHED_DEADLINE */
 	),
 
-- 
2.41.0