tracing: likely/unlikely branch annotation tracer
Impact: new likely/unlikely branch tracer
This patch adds a way to record the instances of the likely() and unlikely()
branch condition annotations.
When "unlikely" is set in /debugfs/tracing/iter_ctrl the unlikely conditions
will be added to any of the ftrace tracers. The change takes effect when
a new tracer is passed into the current_tracer file.
For example:
bash-3471 [003] 357.014755: [INCORRECT] sched_info_dequeued:sched_stats.h:177
bash-3471 [003] 357.014756: [correct] update_curr:sched_fair.c:489
bash-3471 [003] 357.014758: [correct] calc_delta_fair:sched_fair.c:411
bash-3471 [003] 357.014759: [correct] account_group_exec_runtime:sched_stats.h:356
bash-3471 [003] 357.014761: [correct] update_curr:sched_fair.c:489
bash-3471 [003] 357.014763: [INCORRECT] calc_delta_fair:sched_fair.c:411
bash-3471 [003] 357.014765: [correct] calc_delta_mine:sched.c:1279
Which shows the normal tracer heading, as well as whether the condition was
correct "[correct]" or was mistaken "[INCORRECT]", followed by the function,
file name and line number.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a3f7ae9..83d3863 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -258,6 +258,9 @@
"sched-tree",
"ftrace_printk",
"ftrace_preempt",
+#ifdef CONFIG_UNLIKELY_TRACER
+ "unlikely",
+#endif
NULL
};
@@ -1648,6 +1651,18 @@
trace_seq_print_cont(s, iter);
break;
}
+ case TRACE_UNLIKELY: {
+ struct trace_unlikely *field;
+
+ trace_assign_type(field, entry);
+
+ trace_seq_printf(s, "[%s] %s:%s:%d\n",
+ field->correct ? "correct" : "INCORRECT",
+ field->func,
+ field->file,
+ field->line);
+ break;
+ }
default:
trace_seq_printf(s, "Unknown type %d\n", entry->type);
}
@@ -1787,6 +1802,18 @@
return print_return_function(iter);
break;
}
+ case TRACE_UNLIKELY: {
+ struct trace_unlikely *field;
+
+ trace_assign_type(field, entry);
+
+ trace_seq_printf(s, "[%s] %s:%s:%d\n",
+ field->correct ? "correct" : "INCORRECT",
+ field->func,
+ field->file,
+ field->line);
+ break;
+ }
}
return TRACE_TYPE_HANDLED;
}
@@ -2592,6 +2619,7 @@
if (t == current_trace)
goto out;
+ trace_unlikely_disable();
if (current_trace && current_trace->reset)
current_trace->reset(tr);
@@ -2599,6 +2627,7 @@
if (t->init)
t->init(tr);
+ trace_unlikely_enable(tr);
out:
mutex_unlock(&trace_types_lock);