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

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.

Link: http://lkml.kernel.org/r/20160831025529.24018-1-namhyung@kernel.org

Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

4 files changed, 13 insertions, 6 deletions

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index a6b3705e62a6..185c39fea2a0 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -858,11 +858,11 @@ x494] <- /root/a.out[+0x4a8] <- /lib/libc-2.7.so[+0x1e1a6]
                When enabled, it will account time the task has been
                scheduled out as part of the function call.
 
-  graph-time - When running function graph tracer, to include the
-               time to call nested functions. When this is not set,
-               the time reported for the function will only include
-               the time the function itself executed for, not the time
-               for functions that it called.
+  graph-time - When running function profiler with function graph tracer,
+               to include the time to call nested functions. When this is
+               not set, the time reported for the function will only
+               include the time the function itself executed for, not the
+               time for functions that it called.
 
   record-cmd - When any event or tracer is enabled, a hook is enabled
                in the sched_switch trace point to fill comm cache
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 7d565afe35d2..1e2b316d6693 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
         unsigned long fp;
 };
 
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 e14017c36170..148c90f1e49b 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;
         current->ret_stack[index].fp = frame_pointer;
         *depth = current->curr_ret_stack;