[PATCH] tracing, function_graph: simplify test for tracing

[PATCH] tracing, function_graph: simplify test for tracing

[Lai Jiangshan]

For function_graph, a calling function is to be traced only when
it is enabled or it is nested in a enabled function.

Current code uses TSK_TRACE_FL_GRAPH to test whether it is nested or not.
read the code, we can get this:
(trace->depth > 0) <==> (TSK_TRACE_FL_GRAPH is set)

trace->depth is more explicit to tell that it is nested.
So we use trace->depth directly and simplify the code.

No functionality is changed.
TSK_TRACE_FL_GRAPH is not removed now, it is left for future usage.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 3976520..9a69b9c 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -506,7 +506,7 @@ static inline int ftrace_graph_addr(unsigned long addr)
 {
 	int i;
 
-	if (!ftrace_graph_count || test_tsk_trace_graph(current))
+	if (!ftrace_graph_count)
 		return 1;
 
 	for (i = 0; i < ftrace_graph_count; i++) {
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index b1342c5..8e17a57 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -218,7 +218,8 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
 	if (!ftrace_trace_task(current))
 		return 0;
 
-	if (!ftrace_graph_addr(trace->func))
+	/* trace it when it is-nested-in or is a function enabled. */
+	if (!(trace->depth || ftrace_graph_addr(trace->func)))
 		return 0;
 
 	local_irq_save(flags);
@@ -231,9 +232,6 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
 	} else {
 		ret = 0;
 	}
-	/* Only do the atomic if it is not already set */
-	if (!test_tsk_trace_graph(current))
-		set_tsk_trace_graph(current);
 
 	atomic_dec(&data->disabled);
 	local_irq_restore(flags);
@@ -281,8 +279,6 @@ void trace_graph_return(struct ftrace_graph_ret *trace)
 		pc = preempt_count();
 		__trace_graph_return(tr, trace, flags, pc);
 	}
-	if (!trace->depth)
-		clear_tsk_trace_graph(current);
 	atomic_dec(&data->disabled);
 	local_irq_restore(flags);
 }

Re: [PATCH] tracing, function_graph: simplify test for tracing

[Frederic Weisbecker]

On Wed, Jan 13, 2010 at 07:38:30PM +0800, Lai Jiangshan wrote:
> 
> For function_graph, a calling function is to be traced only when
> it is enabled or it is nested in a enabled function.
> 
> Current code uses TSK_TRACE_FL_GRAPH to test whether it is nested or not.
> read the code, we can get this:
> (trace->depth > 0) <==> (TSK_TRACE_FL_GRAPH is set)
> 
> trace->depth is more explicit to tell that it is nested.
> So we use trace->depth directly and simplify the code.
> 
> No functionality is changed.
> TSK_TRACE_FL_GRAPH is not removed now, it is left for future usage.
> 
> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> ---


Looks prety good to me. Nice simplification, the less checks we
have in this hot path, the better.

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>

Re: [PATCH] tracing, function_graph: simplify test for tracing

[Frederic Weisbecker]

On Wed, Jan 13, 2010 at 07:38:30PM +0800, Lai Jiangshan wrote:
> 
> For function_graph, a calling function is to be traced only when
> it is enabled or it is nested in a enabled function.
> 
> Current code uses TSK_TRACE_FL_GRAPH to test whether it is nested or not.
> read the code, we can get this:
> (trace->depth > 0) <==> (TSK_TRACE_FL_GRAPH is set)
> 
> trace->depth is more explicit to tell that it is nested.
> So we use trace->depth directly and simplify the code.
> 
> No functionality is changed.
> TSK_TRACE_FL_GRAPH is not removed now, it is left for future usage.
> 
> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> ---



I've queued it. Thanks.

[tip:tracing/core] tracing: Simplify test for function_graph tracing start point

[tip-bot for Lai Jiangshan]

Commit-ID:  ea2c68a08fedb5053ba312d661e47df9f4d72411
Gitweb:     http://git.kernel.org/tip/ea2c68a08fedb5053ba312d661e47df9f4d72411
Author:     Lai Jiangshan <laijs@cn.fujitsu.com>
AuthorDate: Wed, 13 Jan 2010 19:38:30 +0800
Committer:  Frederic Weisbecker <fweisbec@gmail.com>
CommitDate: Fri, 29 Jan 2010 01:05:12 +0100

tracing: Simplify test for function_graph tracing start point

In the function graph tracer, a calling function is to be traced
only when it is enabled through the set_graph_function file,
or when it is nested in an enabled function.

Current code uses TSK_TRACE_FL_GRAPH to test whether it is nested
or not. Looking at the code, we can get this:
(trace->depth > 0) <==> (TSK_TRACE_FL_GRAPH is set)

trace->depth is more explicit to tell that it is nested.
So we use trace->depth directly and simplify the code.

No functionality is changed.
TSK_TRACE_FL_GRAPH is not removed yet, it is left for future usage.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4B4DB0B6.7040607@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
 kernel/trace/trace.h                 |    2 +-
 kernel/trace/trace_functions_graph.c |    8 ++------
 2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 4df6a77..ce077fb 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -504,7 +504,7 @@ static inline int ftrace_graph_addr(unsigned long addr)
 {
 	int i;
 
-	if (!ftrace_graph_count || test_tsk_trace_graph(current))
+	if (!ftrace_graph_count)
 		return 1;
 
 	for (i = 0; i < ftrace_graph_count; i++) {
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index f225229..616b135 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -215,7 +215,8 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
 	if (!ftrace_trace_task(current))
 		return 0;
 
-	if (!ftrace_graph_addr(trace->func))
+	/* trace it when it is-nested-in or is a function enabled. */
+	if (!(trace->depth || ftrace_graph_addr(trace->func)))
 		return 0;
 
 	local_irq_save(flags);
@@ -228,9 +229,6 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
 	} else {
 		ret = 0;
 	}
-	/* Only do the atomic if it is not already set */
-	if (!test_tsk_trace_graph(current))
-		set_tsk_trace_graph(current);
 
 	atomic_dec(&data->disabled);
 	local_irq_restore(flags);
@@ -278,8 +276,6 @@ void trace_graph_return(struct ftrace_graph_ret *trace)
 		pc = preempt_count();
 		__trace_graph_return(tr, trace, flags, pc);
 	}
-	if (!trace->depth)
-		clear_tsk_trace_graph(current);
 	atomic_dec(&data->disabled);
 	local_irq_restore(flags);
 }