[tracing] Implement composable memory usage estimators.

base/trace_event/memory_usage_estimator_unittest.cc

Index: base/trace_event/memory_usage_estimator_unittest.cc
diff --git a/base/trace_event/memory_usage_estimator_unittest.cc b/base/trace_event/memory_usage_estimator_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b77d5fdc9797f3167131bc01e0520afc6a3b5503
--- /dev/null
+++ b/base/trace_event/memory_usage_estimator_unittest.cc
@@ -0,0 +1,229 @@
+// Copyright 2016 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.
+
+#include "base/trace_event/memory_usage_estimator.h"
+
+#include <stdlib.h>
+
+#include "base/memory/ptr_util.h"
+#include "base/strings/string16.h"
+#include "build/build_config.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+#if defined(ARCH_CPU_64_BITS)
+#define EXPECT_EQ_32_64(_, e, a) EXPECT_EQ(e, a)
+#else
+#define EXPECT_EQ_32_64(e, _, a) EXPECT_EQ(e, a)
+#endif
+
+namespace base {
+namespace trace_event {
+
+namespace {
+
+// Test class with predictable memory usage.
+class Data {
+ public:
+  explicit Data(size_t size = 17): size_(size) {
+  }
+
+  size_t size() const { return size_; }
+
+  size_t EstimateMemoryUsage() const {
+    return size_;
+  }
+
+  bool operator < (const Data& other) const {
+    return size_ < other.size_;
+  }
+  bool operator == (const Data& other) const {
+    return size_ == other.size_;
+  }
+
+  struct Hasher {
+    size_t operator () (const Data& data) const {
+      return data.size();
+    }
+  };
+
+ private:
+  size_t size_;
+};
+
+}  // namespace
+
+namespace internal {
+
+// This kills variance of bucket_count across STL implementations.
+template <>
+size_t HashMapBucketCountForTesting<Data>(size_t) {
+  return 10;
+}
+template <>
+size_t HashMapBucketCountForTesting<std::pair<const Data, short>>(size_t) {
+  return 10;
+}
+
+}  // namespace internal
+
+TEST(EstimateMemoryUsageTest, String) {
+  std::string string(777, 'a');
+  EXPECT_EQ(string.capacity() + 1, EstimateMemoryUsage(string));
+}
+
+TEST(EstimateMemoryUsageTest, String16) {
+  string16 string(777, 'a');
+  EXPECT_EQ(sizeof(char16) * (string.capacity() + 1),
+            EstimateMemoryUsage(string));
+}
+
+TEST(EstimateMemoryUsageTest, Arrays) {
+  // std::array
+  {
+    std::array<Data, 10> array;
+    EXPECT_EQ(170u, EstimateMemoryUsage(array));
+  }
+
+  // T[N]
+  {
+    Data array[10];
+    EXPECT_EQ(170u, EstimateMemoryUsage(array));
+  }
+
+  // C array
+  {
+    struct Item {
+      char payload[10];
+    };
+    Item* array = new Item[7];
+    EXPECT_EQ(70u, EstimateMemoryUsage(array, 7));
+    delete[] array;
+  }
+}
+
+TEST(EstimateMemoryUsageTest, UniquePtr) {
+  // Empty
+  {
+    std::unique_ptr<Data> ptr;
+    EXPECT_EQ(0u, EstimateMemoryUsage(ptr));
+  }
+
+  // Not empty
+  {
+    std::unique_ptr<Data> ptr(new Data());
+    EXPECT_EQ_32_64(21u, 25u, EstimateMemoryUsage(ptr));
+  }
+
+  // With a pointer
+  {
+    std::unique_ptr<Data*> ptr(new Data*());
+    EXPECT_EQ(sizeof(void*), EstimateMemoryUsage(ptr));
+  }
+
+  // With an array
+  {
+    struct Item {
+      uint32_t payload[10];
+    };
+    std::unique_ptr<Item[]> ptr(new Item[7]);
+    EXPECT_EQ(280u, EstimateMemoryUsage(ptr, 7));
+  }
+}
+
+TEST(EstimateMemoryUsageTest, Vector) {
+  std::vector<Data> vector;
+  vector.reserve(1000);
+
+  // For an empty vector we should return memory usage of its buffer
+  size_t capacity = vector.capacity();
+  size_t expected_size = capacity * sizeof(Data);
+  EXPECT_EQ(expected_size, EstimateMemoryUsage(vector));
+
+  // If vector is not empty, its size should also include memory usages
+  // of all elements.
+  for (size_t i = 0; i != capacity / 2; ++i) {
+    vector.push_back(Data(i));
+    expected_size += EstimateMemoryUsage(vector.back());
+  }
+  EXPECT_EQ(expected_size, EstimateMemoryUsage(vector));
+}
+
+TEST(EstimateMemoryUsageTest, List) {
+  struct POD {
+    short data;
+  };
+  std::list<POD> list;
+  for (int i = 0; i != 1000; ++i) {
+    list.push_back(POD());
+  }
+  EXPECT_EQ_32_64(12000u, 24000u, EstimateMemoryUsage(list));
+}
+
+TEST(EstimateMemoryUsageTest, Set) {
+  std::set<std::pair<int, Data>> set;
+  for (int i = 0; i != 1000; ++i) {
+    set.insert({i, Data(i)});
+  }
+  EXPECT_EQ_32_64(523500u, 547500u, EstimateMemoryUsage(set));
+}
+
+TEST(EstimateMemoryUsageTest, MultiSet) {
+  std::multiset<bool> set;
+  for (int i = 0; i != 1000; ++i) {
+    set.insert((i & 1) != 0);
+  }
+  EXPECT_EQ_32_64(16000u, 32000u, EstimateMemoryUsage(set));
+}
+
+TEST(EstimateMemoryUsageTest, Map) {
+  std::map<Data, int> map;
+  for (int i = 0; i != 1000; ++i) {
+    map.insert({Data(i), i});
+  }
+  EXPECT_EQ_32_64(523500u, 547500u, EstimateMemoryUsage(map));
+}
+
+TEST(EstimateMemoryUsageTest, MultiMap) {
+  std::multimap<char, Data> map;
+  for (int i = 0; i != 1000; ++i) {
+    map.insert({static_cast<char>(i), Data(i)});
+  }
+  EXPECT_EQ_32_64(523500u, 547500u, EstimateMemoryUsage(map));
+}
+
+TEST(EstimateMemoryUsageTest, UnorderedSet) {
+  std::unordered_set<Data, Data::Hasher> set;
+  for (int i = 0; i != 1000; ++i) {
+    set.insert(Data(i));
+  }
+  EXPECT_EQ_32_64(511540u, 523580u, EstimateMemoryUsage(set));
+}
+
+TEST(EstimateMemoryUsageTest, UnorderedMultiSet) {
+  std::unordered_multiset<Data, Data::Hasher> set;
+  for (int i = 0; i != 500; ++i) {
+    set.insert(Data(i));
+    set.insert(Data(i));
+  }
+  EXPECT_EQ_32_64(261540u, 273580u, EstimateMemoryUsage(set));
+}
+
+TEST(EstimateMemoryUsageTest, UnorderedMap) {
+  std::unordered_map<Data, short, Data::Hasher> map;
+  for (int i = 0; i != 1000; ++i) {
+    map.insert({Data(i), static_cast<short>(i)});
+  }
+  EXPECT_EQ_32_64(515540u, 531580u, EstimateMemoryUsage(map));
+}
+
+TEST(EstimateMemoryUsageTest, UnorderedMultiMap) {
+  std::unordered_multimap<Data, short, Data::Hasher> map;
+  for (int i = 0; i != 1000; ++i) {
+    map.insert({Data(i), static_cast<short>(i)});
+  }
+  EXPECT_EQ_32_64(515540u, 531580u, EstimateMemoryUsage(map));
+}
+
+}  // namespace trace_event
+}  // namespace base