[PATCH] ftrace: Access ret_stack->subtime only in the function profiler

[Namhyung Kim]

The subtime is used only for function profiler with function graph
tracer enabled.  Move the definition of subtime under
CONFIG_FUNCTION_PROFILER to reduce the memory usage.  Also move the
initialization of subtime into the graph entry callback.

Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
 include/linux/ftrace.h               | 2 ++
 kernel/trace/ftrace.c                | 6 ++++++
 kernel/trace/trace_functions_graph.c | 1 -
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 6f93ac46e7f0..b3d34d3e0e7e 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -794,7 +794,9 @@ struct ftrace_ret_stack {
 	unsigned long ret;
 	unsigned long func;
 	unsigned long long calltime;
+#ifdef CONFIG_FUNCTION_PROFILER
 	unsigned long long subtime;
+#endif
 #ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 	unsigned long fp;
 #endif
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 84752c8e28b5..2050a7652a86 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -872,7 +872,13 @@ function_profile_call(unsigned long ip, unsigned long parent_ip,
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 static int profile_graph_entry(struct ftrace_graph_ent *trace)
 {
+	int index = trace->depth;
+
 	function_profile_call(trace->func, 0, NULL, NULL);
+
+	if (index >= 0 && index < FTRACE_RETFUNC_DEPTH)
+		current->ret_stack[index].subtime = 0;
+
 	return 1;
 }
 
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 0cbe38a844fa..9c7ffa4df5a8 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -170,7 +170,6 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
 	current->ret_stack[index].ret = ret;
 	current->ret_stack[index].func = func;
 	current->ret_stack[index].calltime = calltime;
-	current->ret_stack[index].subtime = 0;
 #ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 	current->ret_stack[index].fp = frame_pointer;
 #endif
-- 
2.9.3