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/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 8bccb49..eba835a 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -53,6 +53,14 @@
#define LIKELY_PROFILE()
#endif
+#ifdef CONFIG_PROFILE_ALL_BRANCHES
+#define BRANCH_PROFILE() VMLINUX_SYMBOL(__start_branch_profile) = .; \
+ *(_ftrace_branch) \
+ VMLINUX_SYMBOL(__stop_branch_profile) = .;
+#else
+#define BRANCH_PROFILE()
+#endif
+
/* .data section */
#define DATA_DATA \
*(.data) \
@@ -72,7 +80,8 @@
VMLINUX_SYMBOL(__start___tracepoints) = .; \
*(__tracepoints) \
VMLINUX_SYMBOL(__stop___tracepoints) = .; \
- LIKELY_PROFILE()
+ LIKELY_PROFILE() \
+ BRANCH_PROFILE()
#define RO_DATA(align) \
. = ALIGN((align)); \