components/metrics: Add runtime memory leak detector

components/metrics/leak_detector/leak_analyzer.h

+// Copyright 2015 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 COMPONENTS_METRICS_LEAK_DETECTOR_LEAK_ANALYZER_H_
+#define COMPONENTS_METRICS_LEAK_DETECTOR_LEAK_ANALYZER_H_
+
+#include <map>
+#include <vector>
+
+#include "base/macros.h"
+#include "components/metrics/leak_detector/custom_allocator.h"
+#include "components/metrics/leak_detector/leak_detector_value_type.h"
+#include "components/metrics/leak_detector/ranked_list.h"
+#include "components/metrics/leak_detector/stl_allocator.h"
+
+// This class looks for possible leak patterns in allocation data over time.
+
+namespace metrics {
+namespace leak_detector {
+
+class LeakAnalyzer {
+ public:
+  using ValueType = LeakDetectorValueType;
+
+  template <typename Type>
+  using Allocator = STLAllocator<Type, CustomAllocator>;
+
+  LeakAnalyzer(uint32_t ranking_size, uint32_t num_suspicions_threshold)
+      : ranking_size_(ranking_size),
+        score_threshold_(num_suspicions_threshold),
+        ranked_entries_(ranking_size),
+        prev_ranked_entries_(ranking_size) {
+    suspected_leaks_.reserve(ranking_size);
+  }
+
+  ~LeakAnalyzer() {}
+
+  // Take in a RankedList of allocations, sorted by count. Removes the contents
+  // of |ranked_list|.
+  void AddSample(RankedList ranked_list);
+
+  // Used to report suspected leaks. Reported leaks are sorted by ValueType.
+  const std::vector<ValueType, Allocator<ValueType>>& suspected_leaks() const {
+    return suspected_leaks_;
+  }
+
+ private:
+  // Analyze a list of allocation count deltas from the previous iteration. If
+  // anything looks like a possible leak, update the suspicion scores.
+  void AnalyzeDeltas(const RankedList& ranked_deltas);
+
+  // Returns the count for the given value from the previous analysis in
+  // |count|. Returns true if the given value was present in the previous
+  // analysis, or false if not.
+  bool GetPreviousCountForValue(const ValueType& value, uint32_t* count) const;
+
+  // Look for the top |ranking_size_| entries when analyzing leaks.
+  const uint32_t ranking_size_;
+
+  // Report suspected leaks when the suspicion score reaches this value.
+  const uint32_t score_threshold_;
+
+  // A mapping of allocation values to suspicion score. All allocations in this
+  // container are suspected leaks. The score can increase or decrease over
+  // time. Once the score  reaches |score_threshold_|, the entry is reported as
+  // a suspected leak in |suspected_leaks_|.
+  std::map<ValueType,
+           uint32_t,
+           std::less<ValueType>,
+           Allocator<std::pair<ValueType, uint32_t>>> suspected_histogram_;
+
+  // Array of allocated values that passed the suspicion threshold and are being
+  // reported.
+  std::vector<ValueType, Allocator<ValueType>> suspected_leaks_;
+
+  // The most recent allocation entries, since the last call to AddSample().
+  RankedList ranked_entries_;
+  // The previous allocation entries, from before the last call to AddSample().
+  RankedList prev_ranked_entries_;
+
+  DISALLOW_COPY_AND_ASSIGN(LeakAnalyzer);
+};
+
+}  // namespace leak_detector
+}  // namespace metrics
+
+#endif  // COMPONENTS_METRICS_LEAK_DETECTOR_LEAK_ANALYZER_H_