[PATCH v2] ftrace: Access ret_stack->subtime only in the function profiler

[PATCH v2] 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@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 Documentation/trace/ftrace.txt       | 10 +++++-----
 include/linux/ftrace.h               |  2 ++
 kernel/trace/ftrace.c                |  6 ++++++
 kernel/trace/trace_functions_graph.c |  1 -
 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 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

Re: [PATCH v2] ftrace: Access ret_stack->subtime only in the function profiler

[Steven Rostedt]

On Wed, 31 Aug 2016 11:55:29 +0900
Namhyung Kim <namhyung@kernel.org> wrote:

> 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@redhat.com>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>

Applied, thanks Namhyung!

-- Steve