[PATCH 0/2] [GIT PULL] tracing: comment and function graph latency format

[PATCH 0/2] [GIT PULL] tracing: comment and function graph latency format

[Steven Rostedt]

Ingo,

I rebased the branch to remove the module ref count change. That will
be a separate patch push to make sure everyone agrees with it.

Please pull the latest tip/tracing/core2 tree, which can be found at:

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
tip/tracing/core2


Steven Rostedt (2):
      x86/tracing: comment need for atomic nop
      tracing: add latency format to function_graph tracer

----
 arch/x86/include/asm/nops.h          |    2 +
 kernel/trace/trace_functions_graph.c |   74 +++++++++++++++++++++++++++++++---
 2 files changed, 70 insertions(+), 6 deletions(-)
-- 

[PATCH 1/2] x86/tracing: comment need for atomic nop

[Steven Rostedt]

[-- Attachment #1: 0001-x86-tracing-comment-need-for-atomic-nop.patch --]
[-- Type: text/plain, Size: 1101 bytes --]

From: Steven Rostedt <srostedt@redhat.com>

The dynamic function tracer relys on the macro P6_NOP5 always being
an atomic NOP. If for some reason it is changed to be two operations
(like a nop2 nop3) it can faults within the kernel when the function
tracer modifies the code.

This patch adds a comment to note that the P6_NOPs are expected to
be atomic. This will hopefully prevent anyone from changing that.

Reported-by: Mathieu Desnoyer <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 arch/x86/include/asm/nops.h |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/nops.h b/arch/x86/include/asm/nops.h
index ad2668e..6d8723a 100644
--- a/arch/x86/include/asm/nops.h
+++ b/arch/x86/include/asm/nops.h
@@ -65,6 +65,8 @@
    6: osp nopl 0x00(%eax,%eax,1)
    7: nopl 0x00000000(%eax)
    8: nopl 0x00000000(%eax,%eax,1)
+   Note: All the above are assumed to be a single instruction.
+	There is kernel code that depends on this.
 */
 #define P6_NOP1	GENERIC_NOP1
 #define P6_NOP2	".byte 0x66,0x90\n"
-- 
1.6.3.3

-- 

[PATCH 2/2] tracing: add latency format to function_graph tracer

[Steven Rostedt]

[-- Attachment #1: 0002-tracing-add-latency-format-to-function_graph-tracer.patch --]
[-- Type: text/plain, Size: 5195 bytes --]

From: Steven Rostedt <srostedt@redhat.com>

While debugging something with the function_graph tracer, I found the
need to see the preempt count of the traces. Unfortunately, since
the function graph tracer has its own output formatting, it does not
honor the latency-format option.

This patch makes the function_graph tracer honor the latency-format
option, but still keeps control of the output. But now we have the
same details that the latency-format supplies.

 # tracer: function_graph
 #
 #      _-----=> irqs-off
 #     / _----=> need-resched
 #    | / _---=> hardirq/softirq
 #    || / _--=> preempt-depth
 #    ||| /
 #    ||||
 # CPU||||  DURATION                  FUNCTION CALLS
 # |  ||||   |   |                     |   |   |   |
  3)  d..1  1.333 us    |        idle_cpu();
  3)  d.h1              |        tick_check_idle() {
  3)  d.h1  0.550 us    |          tick_check_oneshot_broadcast();
  3)  d.h1              |          tick_nohz_stop_idle() {
  3)  d.h1              |            ktime_get() {
  3)  d.h1              |              ktime_get_ts() {

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace_functions_graph.c |   74 +++++++++++++++++++++++++++++++---
 1 files changed, 68 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index b3749a2..ee791a9 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -364,6 +364,29 @@ print_graph_proc(struct trace_seq *s, pid_t pid)
 }
 
 
+static enum print_line_t
+print_graph_lat_fmt(struct trace_seq *s, struct trace_entry *entry)
+{
+	int hardirq, softirq;
+
+	hardirq = entry->flags & TRACE_FLAG_HARDIRQ;
+	softirq = entry->flags & TRACE_FLAG_SOFTIRQ;
+
+	if (!trace_seq_printf(s, " %c%c%c",
+			      (entry->flags & TRACE_FLAG_IRQS_OFF) ? 'd' :
+				(entry->flags & TRACE_FLAG_IRQS_NOSUPPORT) ?
+				  'X' : '.',
+			      (entry->flags & TRACE_FLAG_NEED_RESCHED) ?
+				'N' : '.',
+			      (hardirq && softirq) ? 'H' :
+				hardirq ? 'h' : softirq ? 's' : '.'))
+		return 0;
+
+	if (entry->preempt_count)
+		return trace_seq_printf(s, "%x", entry->preempt_count);
+	return trace_seq_puts(s, ".");
+}
+
 /* If the pid changed since the last trace, output this event */
 static enum print_line_t
 verif_pid(struct trace_seq *s, pid_t pid, int cpu, struct fgraph_data *data)
@@ -521,6 +544,7 @@ print_graph_irq(struct trace_iterator *iter, unsigned long addr,
 		if (ret == TRACE_TYPE_PARTIAL_LINE)
 			return TRACE_TYPE_PARTIAL_LINE;
 	}
+
 	/* Proc */
 	if (tracer_flags.val & TRACE_GRAPH_PRINT_PROC) {
 		ret = print_graph_proc(s, pid);
@@ -758,6 +782,13 @@ print_graph_prologue(struct trace_iterator *iter, struct trace_seq *s,
 			return TRACE_TYPE_PARTIAL_LINE;
 	}
 
+	/* Latency format */
+	if (trace_flags & TRACE_ITER_LATENCY_FMT) {
+		ret = print_graph_lat_fmt(s, ent);
+		if (ret == TRACE_TYPE_PARTIAL_LINE)
+			return TRACE_TYPE_PARTIAL_LINE;
+	}
+
 	return 0;
 }
 
@@ -952,28 +983,59 @@ print_graph_function(struct trace_iterator *iter)
 	return TRACE_TYPE_HANDLED;
 }
 
+static void print_lat_header(struct seq_file *s)
+{
+	static const char spaces[] = "                "	/* 16 spaces */
+		"    "					/* 4 spaces */
+		"                 ";			/* 17 spaces */
+	int size = 0;
+
+	if (tracer_flags.val & TRACE_GRAPH_PRINT_ABS_TIME)
+		size += 16;
+	if (tracer_flags.val & TRACE_GRAPH_PRINT_CPU)
+		size += 4;
+	if (tracer_flags.val & TRACE_GRAPH_PRINT_PROC)
+		size += 17;
+
+	seq_printf(s, "#%.*s  _-----=> irqs-off        \n", size, spaces);
+	seq_printf(s, "#%.*s / _----=> need-resched    \n", size, spaces);
+	seq_printf(s, "#%.*s| / _---=> hardirq/softirq \n", size, spaces);
+	seq_printf(s, "#%.*s|| / _--=> preempt-depth   \n", size, spaces);
+	seq_printf(s, "#%.*s||| /                      \n", size, spaces);
+	seq_printf(s, "#%.*s||||                       \n", size, spaces);
+}
+
 static void print_graph_headers(struct seq_file *s)
 {
+	int lat = trace_flags & TRACE_ITER_LATENCY_FMT;
+
+	if (lat)
+		print_lat_header(s);
+
 	/* 1st line */
-	seq_printf(s, "# ");
+	seq_printf(s, "#");
 	if (tracer_flags.val & TRACE_GRAPH_PRINT_ABS_TIME)
 		seq_printf(s, "     TIME       ");
 	if (tracer_flags.val & TRACE_GRAPH_PRINT_CPU)
-		seq_printf(s, "CPU");
+		seq_printf(s, " CPU");
 	if (tracer_flags.val & TRACE_GRAPH_PRINT_PROC)
-		seq_printf(s, "  TASK/PID      ");
+		seq_printf(s, "  TASK/PID       ");
+	if (lat)
+		seq_printf(s, "||||");
 	if (tracer_flags.val & TRACE_GRAPH_PRINT_DURATION)
 		seq_printf(s, "  DURATION   ");
 	seq_printf(s, "               FUNCTION CALLS\n");
 
 	/* 2nd line */
-	seq_printf(s, "# ");
+	seq_printf(s, "#");
 	if (tracer_flags.val & TRACE_GRAPH_PRINT_ABS_TIME)
 		seq_printf(s, "      |         ");
 	if (tracer_flags.val & TRACE_GRAPH_PRINT_CPU)
-		seq_printf(s, "|  ");
+		seq_printf(s, " |  ");
 	if (tracer_flags.val & TRACE_GRAPH_PRINT_PROC)
-		seq_printf(s, "  |    |        ");
+		seq_printf(s, "   |    |        ");
+	if (lat)
+		seq_printf(s, "||||");
 	if (tracer_flags.val & TRACE_GRAPH_PRINT_DURATION)
 		seq_printf(s, "   |   |      ");
 	seq_printf(s, "               |   |   |   |\n");
-- 
1.6.3.3

--