Chrome power profiler service

content/public/browser/power_data_provider.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_PUBLIC_BROWSER_POWER_DATA_PROVIDER_H_
+#define CONTENT_PUBLIC_BROWSER_POWER_DATA_PROVIDER_H_
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/time/time.h"
+
+namespace content {
+
+// PowerEvent here is the total power of SoC, including CPU, GPU and others
+// on the chip, modules out of SoC such as screen is not included.
+struct PowerEvent {

[jeremy, 2014/01/28 19:45:43]

So this API only provides  power usage for the SoC as a whole?
Is GPU power draw also something we want to report?
Are we interested in reporting idle wakeups, c-state changes, etc as part of
this API?

Sorry, just trying to understand the scope of this API :)

[Pan, 2014/01/29 00:29:22]

@jeremy, you are welcome, this CL is a start, GPU power type can be there once
there is a need, we also can extend it to provide wakeups and state changes.

+  base::TimeTicks time; // Time that power data was read.
+
+  // Power value between last event to this one, in watt.
+  // E.g, event1 {t1, v1}; event2 {t2, v2}; event3 {t3, v3}.
+  // Suppose event1 is the first event observer received, then event2, event3.
+  // Then v2 is average power from t1 to t2, v3 is the average power from t2 to
+  // t3. v1 should be ignored since event1 only means the start point of power
+  // profiling.

[jeremy, 2014/01/28 19:45:43]

Does the hardware measure cumulative power usage or instantaneous power usage?

[Pan, 2014/01/29 00:29:22]

it is a 32bit MSR on hardware, register updated per 1 millisecond by new
consumed energy.
see 14.7.3 if you are insterested :)
http://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-...

+  double value;
+};
+
+// a class used to GET power usage.
+class PowerDataProvider {
+ public:
+  PowerDataProvider() {}
+  virtual ~PowerDataProvider() {}
+
+  // Return true when success, it fills a single PowerEvent, which should be
+  // allocated by its caller.
+  virtual bool GetData(PowerEvent*) = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(PowerDataProvider);
+};
+
+class PowerDataProviderFactory {
+ public:
+  // Create a provider, and transfer the ownership to PowerProfilerService.
+  static scoped_ptr<PowerDataProvider> Create();
+
+ private:
+  PowerDataProviderFactory() {}
+  DISALLOW_COPY_AND_ASSIGN(PowerDataProviderFactory);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_POWER_DATA_PROVIDER_H_