trace: profile all if conditionals
Impact: feature to profile if statements
This patch adds a branch profiler for all if () statements.
The results will be found in:
/debugfs/tracing/profile_branch
For example:
miss hit % Function File Line
------- --------- - -------- ---- ----
0 1 100 x86_64_start_reservations head64.c 127
0 1 100 copy_bootdata head64.c 69
1 0 0 x86_64_start_kernel head64.c 111
32 0 0 set_intr_gate desc.h 319
1 0 0 reserve_ebda_region head.c 51
1 0 0 reserve_ebda_region head.c 47
0 1 100 reserve_ebda_region head.c 42
0 0 X maxcpus main.c 165
Miss means the branch was not taken. Hit means the branch was taken.
The percent is the percentage the branch was taken.
This adds a significant amount of overhead and should only be used
by those analyzing their system.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
index 142acb3..85792ae 100644
--- a/kernel/trace/trace_branch.c
+++ b/kernel/trace/trace_branch.c
@@ -185,6 +185,7 @@
struct ftrace_pointer {
void *start;
void *stop;
+ int hit;
};
static void *
@@ -223,13 +224,17 @@
static int t_show(struct seq_file *m, void *v)
{
+ struct ftrace_pointer *fp = m->private;
struct ftrace_branch_data *p = v;
const char *f;
long percent;
if (v == (void *)1) {
- seq_printf(m, " correct incorrect %% "
- " Function "
+ if (fp->hit)
+ seq_printf(m, " miss hit %% ");
+ else
+ seq_printf(m, " correct incorrect %% ");
+ seq_printf(m, " Function "
" File Line\n"
" ------- --------- - "
" -------- "
@@ -243,6 +248,9 @@
f--;
f++;
+ /*
+ * The miss is overlayed on correct, and hit on incorrect.
+ */
if (p->correct) {
percent = p->incorrect * 100;
percent /= p->correct + p->incorrect;
@@ -284,6 +292,18 @@
.llseek = seq_lseek,
};
+#ifdef CONFIG_PROFILE_ALL_BRANCHES
+extern unsigned long __start_branch_profile[];
+extern unsigned long __stop_branch_profile[];
+
+static struct ftrace_pointer ftrace_branch_pos = {
+ .start = __start_branch_profile,
+ .stop = __stop_branch_profile,
+ .hit = 1,
+};
+
+#endif /* CONFIG_PROFILE_ALL_BRANCHES */
+
extern unsigned long __start_annotated_branch_profile[];
extern unsigned long __stop_annotated_branch_profile[];
@@ -306,6 +326,15 @@
pr_warning("Could not create debugfs "
"'profile_annotatet_branch' entry\n");
+#ifdef CONFIG_PROFILE_ALL_BRANCHES
+ entry = debugfs_create_file("profile_branch", 0444, d_tracer,
+ &ftrace_branch_pos,
+ &tracing_branch_fops);
+ if (!entry)
+ pr_warning("Could not create debugfs"
+ " 'profile_branch' entry\n");
+#endif
+
return 0;
}
