[PATCH 3/4] ftrace: add tracer called branch

Steven Rostedt
2008-11-12T21:23:13Z

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Impact: added new branch tracer

Currently the tracing of branch profiling (unlikelys and likelys hit)
is only activated by the iter_ctrl. This patch adds a tracer called
"branch" that will just trace the branch profiling. The advantage
of adding this tracer is that it can be added to the ftrace selftests
on startup.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
kernel/trace/trace.h | 2 +
kernel/trace/trace_selftest.c | 23 ++++++++++++++++++++++
kernel/trace/trace_unlikely.c | 42 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 67 insertions(+), 0 deletions(-)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 7fbf37b..9e015f5 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -420,6 +420,8 @@ extern int trace_selftest_startup_sched_switch(struct tracer *trace,
struct trace_array *tr);
extern int trace_selftest_startup_sysprof(struct tracer *trace,
struct trace_array *tr);
+extern int trace_selftest_startup_branch(struct tracer *trace,
+ struct trace_array *tr);
#endif /* CONFIG_FTRACE_STARTUP_TEST */

extern void *head_page(struct trace_array_cpu *data);
diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index 0728a10..24e6e07 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -13,6 +13,7 @@ static inline int trace_valid_entry(struct trace_entry *entry)
case TRACE_STACK:
case TRACE_PRINT:
case TRACE_SPECIAL:
+ case TRACE_BRANCH:
return 1;
}
return 0;
@@ -544,3 +545,25 @@ trace_selftest_startup_sysprof(struct tracer *trace, struct trace_array *tr)
return ret;
}
#endif /* CONFIG_SYSPROF_TRACER */
+
+#ifdef CONFIG_BRANCH_TRACER
+int
+trace_selftest_startup_branch(struct tracer *trace, struct trace_array *tr)
+{
+ unsigned long count;
+ int ret;
+
+ /* start the tracing */
+ trace->init(tr);
+ /* Sleep for a 1/10 of a second */
+ msleep(100);
+ /* stop the tracing. */
+ tracing_stop();
+ /* check the trace buffer */
+ ret = trace_test_buffer(tr, &count);
+ trace->reset(tr);
+ tracing_start();
+
+ return ret;
+}
+#endif /* CONFIG_BRANCH_TRACER */
diff --git a/kernel/trace/trace_unlikely.c b/kernel/trace/trace_unlikely.c
index e5d5969..8526555 100644
--- a/kernel/trace/trace_unlikely.c
+++ b/kernel/trace/trace_unlikely.c
@@ -114,6 +114,48 @@ void disable_branch_tracing(void)
out_unlock:
mutex_unlock(&branch_tracing_mutex);
}
+
+static void start_branch_trace(struct trace_array *tr)
+{
+ enable_branch_tracing(tr);
+}
+
+static void stop_branch_trace(struct trace_array *tr)
+{
+ disable_branch_tracing();
+}
+
+static void branch_trace_init(struct trace_array *tr)
+{
+ int cpu;
+
+ for_each_online_cpu(cpu)
+ tracing_reset(tr, cpu);
+
+ start_branch_trace(tr);
+}
+
+static void branch_trace_reset(struct trace_array *tr)
+{
+ stop_branch_trace(tr);
+}
+
+struct tracer branch_trace __read_mostly =
+{
+ .name = "branch",
+ .init = branch_trace_init,
+ .reset = branch_trace_reset,
+#ifdef CONFIG_FTRACE_SELFTEST
+ .selftest = trace_selftest_startup_branch,
+#endif
+};
+
+__init static int init_branch_trace(void)
+{
+ return register_tracer(&branch_trace);
+}
+
+device_initcall(init_branch_trace);
#else
static inline
void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
--
1.5.6.5

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