tracing: add "power-tracer": C/P state tracer to help power optimization

Impact: new "power-tracer" ftrace plugin

This patch adds a C/P-state ftrace plugin that will generate
detailed statistics about the C/P-states that are being used,
so that we can look at detailed decisions that the C/P-state
code is making, rather than the too high level "average"
that we have today.

An example way of using this is:

 mount -t debugfs none /sys/kernel/debug
 echo cstate > /sys/kernel/debug/tracing/current_tracer
 echo 1 > /sys/kernel/debug/tracing/tracing_enabled
 sleep 1
 echo 0 > /sys/kernel/debug/tracing/tracing_enabled
 cat /sys/kernel/debug/tracing/trace | perl scripts/trace/cstate.pl > out.svg

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 29 insertions, 0 deletions

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 7854d87b97b..0df28866620 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -311,6 +311,35 @@ ftrace_init_module(struct module *mod,
                    unsigned long *start, unsigned long *end) { }
 #endif
 
+enum {
+        POWER_NONE = 0,
+        POWER_CSTATE = 1,
+        POWER_PSTATE = 2,
+};
+
+struct power_trace {
+#ifdef CONFIG_POWER_TRACER
+        ktime_t                 stamp;
+        ktime_t                 end;
+        int                     type;
+        int                     state;
+#endif
+};
+
+#ifdef CONFIG_POWER_TRACER
+extern void trace_power_start(struct power_trace *it, unsigned int type,
+                                        unsigned int state);
+extern void trace_power_mark(struct power_trace *it, unsigned int type,
+                                        unsigned int state);
+extern void trace_power_end(struct power_trace *it);
+#else
+static inline void trace_power_start(struct power_trace *it, unsigned int type,
+                                        unsigned int state) { }
+static inline void trace_power_mark(struct power_trace *it, unsigned int type,
+                                        unsigned int state) { }
+static inline void trace_power_end(struct power_trace *it) { }
+#endif
+
 
 /*
  * Structure that defines a return function trace.