metrics.h

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// Copyright 2011 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef NINJA_METRICS_H_
#define NINJA_METRICS_H_

#include <string>
#include <vector>

#include "util.h"  // For int64_t.

/// The Metrics module is used for the debug mode that dumps timing stats of
/// various actions.  To use, see METRIC_RECORD below.

/// A single metrics we're tracking, like "depfile load time".
struct Metric {
  std::string name;
  /// Number of times we've hit the code path.
  int count;
  /// Total time (in micros) we've spent on the code path.
  int64_t sum;
};


/// A scoped object for recording a metric across the body of a function.
/// Used by the METRIC_RECORD macro.
struct ScopedMetric {
  explicit ScopedMetric(Metric* metric);
  ~ScopedMetric();

private:
  Metric* metric_;
  /// Timestamp when the measurement started.
  /// Value is platform-dependent.
  int64_t start_;
};

/// The singleton that stores metrics and prints the report.
struct Metrics {
  Metric* NewMetric(const std::string& name);

  /// Print a summary report to stdout.
  void Report();

private:
  std::vector<Metric*> metrics_;
};

/// Get the current time as relative to some epoch.
/// Epoch varies between platforms; only useful for measuring elapsed time.
int64_t GetTimeMillis();

/// A simple stopwatch which returns the time
/// in seconds since Restart() was called.
struct Stopwatch {
 public:
  Stopwatch() : started_(0) {}

  /// Seconds since Restart() call.
  double Elapsed() const {
    return 1e-6 * static_cast<double>(Now() - started_);
  }

  void Restart() { started_ = Now(); }

 private:
  uint64_t started_;
  uint64_t Now() const;
};

/// The primary interface to metrics.  Use METRIC_RECORD("foobar") at the top
/// of a function to get timing stats recorded for each call of the function.
#define METRIC_RECORD(name)                                             \
  static Metric* metrics_h_metric =                                     \
      g_metrics ? g_metrics->NewMetric(name) : NULL;                    \
  ScopedMetric metrics_h_scoped(metrics_h_metric);

extern Metrics* g_metrics;

#endif // NINJA_METRICS_H_