[chromeos/about:power] Collect cpuidle and cpufreq stats

chrome/browser/chromeos/power/cpu_data_collector.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 CHROME_BROWSER_CHROMEOS_POWER_CPU_DATA_COLLECTOR_H_
+#define CHROME_BROWSER_CHROMEOS_POWER_CPU_DATA_COLLECTOR_H_
+
+#include <deque>
+#include <map>
+#include <string>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/memory/weak_ptr.h"
+#include "base/time/time.h"
+#include "base/timer/timer.h"
+
+namespace chromeos {
+
+// A class to sample CPU idle state occupancy and freq state occupancy.
+// Collects raw data from sysfs and does not convert it to percentage
+// occupancy. As CPUs can be offline at times, or the system can be suspended at
+// other times, it is best for the consumer of this data to calculate percentage
+// occupancy information using suspend time data got from

[Daniel Erat, 2014/03/06 00:46:40]

nit: delete 'got'

[Siva Chandra, 2014/03/06 17:56:33]

Done.

+// PowerDataCollector::system_resumed_data.
+class CpuDataCollector {
+ public:
+  struct StateOccupancySample {
+    StateOccupancySample();
+
+    // The time when the data was sampled.
+    base::Time time;
+
+    // Indicates whether the CPU is online.
+    bool cpu_online;
+
+    // A mapping from a CPU state to time spent in that state in milliseconds.
+    // For idle state samples, the name of the state at index i in this map
+    // is the name at index i in the vector returned by cpu_idle_state_names().
+    // Similarly, for freq state occupancy, similar information is in the vector
+    // returned by cpu_freq_state_names().
+    std::map<int, int64> time_in_state;

[Daniel Erat, 2014/03/06 00:46:40]

assuming that there aren't a bunch of states and this map isn't sparse, it'd
probably be much more space-efficient to use an std::vector<int64> here, where
the i-th entry corresponds to the i-th value in *_state_names_

[Siva Chandra, 2014/03/06 17:56:33]

Done.

+  };
+
+  typedef std::deque<StateOccupancySample> StateOccupancySampleDeque;
+
+  const std::vector<std::string>& cpu_idle_state_names() const {
+    return cpu_idle_state_names_;
+  }
+
+  const std::vector<StateOccupancySampleDeque>& cpu_idle_state_data() const {
+    return cpu_idle_state_data_;
+  }
+
+  const std::vector<std::string>& cpu_freq_state_names() const {
+    return cpu_freq_state_names_;
+  }
+
+  const std::vector<StateOccupancySampleDeque>& cpu_freq_state_data() const {
+    return cpu_freq_state_data_;
+  }
+
+  CpuDataCollector();
+
+  void Start();
+
+ private:
+  void PostSampleCpuState();
+
+  // Samples CPU idle and CPU freq data from sysfs. This function should  run on

[Daniel Erat, 2014/03/06 00:46:40]

nit: delete extra space before 'run'

[Siva Chandra, 2014/03/06 17:56:33]

Done.

+  // the blocking pool as reading from sysfs is a blocking task. Elements at
+  // index i in |idle_samples| and |freq_samples| correspond to the idle and
+  // freq samples of CPU i.
+  void SampleCpuStateOnBlockingPool(
+      std::vector<StateOccupancySample>* idle_samples,
+      std::vector<StateOccupancySample>* freq_samples);
+
+  // This function commits the samples read by SampleCpuStateOnBlockingPool to
+  // |cpu_idle_state_data_| and |cpu_freq_state_data_|. Since UI is the consumer
+  // of CPU idle and freq data, this function should run on the UI thread.
+  void SaveCpuStateSamplesOnUIThread(
+      const std::vector<StateOccupancySample>* idle_samples,
+      const std::vector<StateOccupancySample>* freq_samples);
+
+  base::RepeatingTimer<CpuDataCollector> timer_;
+
+  // Names of the idle states.
+  std::vector<std::string> cpu_idle_state_names_;
+
+  // The deque at index <i> in the vector corresponds to the idle state
+  // occupancy data of CPU<i>.
+  std::vector<StateOccupancySampleDeque> cpu_idle_state_data_;
+
+  // Names of the freq states.
+  std::vector<std::string> cpu_freq_state_names_;
+
+  // The deque at index <i> in the vector corresponds to the frequency state
+  // occupancy data of CPU<i>.
+  std::vector<StateOccupancySampleDeque> cpu_freq_state_data_;
+
+  // The number of CPUs on the system.
+  int cpu_count_;
+
+  base::WeakPtrFactory<CpuDataCollector> weak_ptr_factory_;
+  DISALLOW_COPY_AND_ASSIGN(CpuDataCollector);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_POWER_CPU_DATA_COLLECTOR_H_