[Tracing] Add allocation register for heap profiling

base/trace_event/memory_profiler_allocation_register_unittest.cc

Index: base/trace_event/memory_profiler_allocation_register_unittest.cc
diff --git a/base/trace_event/memory_profiler_allocation_register_unittest.cc b/base/trace_event/memory_profiler_allocation_register_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0c976c467ccdcb31ca8954896f2ae6d2a954fbbf
--- /dev/null
+++ b/base/trace_event/memory_profiler_allocation_register_unittest.cc
@@ -0,0 +1,228 @@
+// 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.
+
+#include "base/trace_event/memory_profiler_allocation_register.h"
+
+#include "base/process/process_metrics.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+namespace trace_event {
+
+class AllocationRegisterTest : public testing::Test {
+ public:
+  static const uint32_t kNumBuckets = AllocationRegister::kNumBuckets;
+  static const uint32_t kNumCells = AllocationRegister::kNumCells;
+
+  // Returns the number of cells that the |AllocationRegister| can store per
+  // system page.
+  size_t GetNumCellsPerPage() {
+    return GetPageSize() / sizeof(AllocationRegister::Cell);
+  }
+
+  uint32_t GetHighWaterMark(const AllocationRegister& reg) {
+    return reg.next_unused_cell_;
+  }
+};
+
+// Iterates over all entries in the allocation register and returns the bitwise
+// or of all addresses stored in it.
+uintptr_t OrAllAddresses(const AllocationRegister& reg) {
+  uintptr_t acc = 0;
+
+  for (auto i : reg)
+    acc |= reinterpret_cast<uintptr_t>(i.address);
+
+  return acc;
+}
+
+// Iterates over all entries in the allocation register and returns the sum of
+// the sizes of the entries.
+size_t SumAllSizes(const AllocationRegister& reg) {
+  size_t sum = 0;
+
+  for (auto i : reg)
+    sum += i.size;
+
+  return sum;
+}
+
+TEST_F(AllocationRegisterTest, InsertRemove) {
+  AllocationRegister reg;
+  AllocationContext ctx;
+
+  EXPECT_EQ(0u, OrAllAddresses(reg));
+
+  reg.Insert(reinterpret_cast<void*>(1), 0, ctx);
+
+  EXPECT_EQ(1u, OrAllAddresses(reg));
+
+  reg.Insert(reinterpret_cast<void*>(2), 0, ctx);
+
+  EXPECT_EQ(3u, OrAllAddresses(reg));
+
+  reg.Insert(reinterpret_cast<void*>(4), 0, ctx);
+
+  EXPECT_EQ(7u, OrAllAddresses(reg));
+
+  reg.Remove(reinterpret_cast<void*>(2));
+
+  EXPECT_EQ(5u, OrAllAddresses(reg));
+
+  reg.Remove(reinterpret_cast<void*>(4));
+
+  EXPECT_EQ(1u, OrAllAddresses(reg));
+
+  reg.Remove(reinterpret_cast<void*>(1));
+
+  EXPECT_EQ(0u, OrAllAddresses(reg));
+}
+
+TEST_F(AllocationRegisterTest, DoubleFreeIsAllowed) {
+  AllocationRegister reg;
+  AllocationContext ctx;
+
+  reg.Insert(reinterpret_cast<void*>(1), 0, ctx);
+  reg.Insert(reinterpret_cast<void*>(2), 0, ctx);
+  reg.Remove(reinterpret_cast<void*>(1));
+  reg.Remove(reinterpret_cast<void*>(1));  // Remove for the second time.
+  reg.Remove(reinterpret_cast<void*>(4));  // Remove never inserted address.
+
+  EXPECT_EQ(2u, OrAllAddresses(reg));
+}
+
+TEST_F(AllocationRegisterTest, DoubleInsertOverwrites) {
+  // TODO(ruuda): Although double insert happens in practice, it should not.
+  // Find out the cause and ban double insert if possible.
+  AllocationRegister reg;
+  AllocationContext ctx;
+  StackFrame frame1 = "Foo";
+  StackFrame frame2 = "Bar";
+
+  ctx.backtrace.frames[0] = frame1;
+  reg.Insert(reinterpret_cast<void*>(1), 11, ctx);
+
+  auto elem = *reg.begin();
+
+  EXPECT_EQ(frame1, elem.context.backtrace.frames[0]);
+  EXPECT_EQ(11u, elem.size);
+  EXPECT_EQ(reinterpret_cast<void*>(1), elem.address);
+
+  ctx.backtrace.frames[0] = frame2;
+  reg.Insert(reinterpret_cast<void*>(1), 13, ctx);
+
+  elem = *reg.begin();
+
+  EXPECT_EQ(frame2, elem.context.backtrace.frames[0]);
+  EXPECT_EQ(13u, elem.size);
+  EXPECT_EQ(reinterpret_cast<void*>(1), elem.address);
+}
+
+// Check that even if more entries than the number of buckets are inserted, the
+// register still behaves correctly.
+TEST_F(AllocationRegisterTest, InsertRemoveCollisions) {
+  size_t expected_sum = 0;
+  AllocationRegister reg;
+  AllocationContext ctx;
+
+  // By inserting 100 more entries than the number of buckets, there will be at
+  // least 100 collisions.
+  for (uintptr_t i = 1; i <= kNumBuckets + 100; i++) {
+    size_t size = i % 31;
+    expected_sum += size;
+    reg.Insert(reinterpret_cast<void*>(i), size, ctx);
+
+    // Don't check the sum on every iteration to keep the test fast.
+    if (i % (1 << 14) == 0)
+      EXPECT_EQ(expected_sum, SumAllSizes(reg));
+  }
+
+  EXPECT_EQ(expected_sum, SumAllSizes(reg));
+
+  for (uintptr_t i = 1; i <= kNumBuckets + 100; i++) {
+    size_t size = i % 31;
+    expected_sum -= size;
+    reg.Remove(reinterpret_cast<void*>(i));
+
+    if (i % (1 << 14) == 0)
+      EXPECT_EQ(expected_sum, SumAllSizes(reg));
+  }
+
+  EXPECT_EQ(expected_sum, SumAllSizes(reg));
+}
+
+// The previous tests are not particularly good for testing iterators, because
+// elements are removed and inserted in the same order, meaning that the cells
+// fill up from low to high index, and are then freed from low to high index.
+// This test removes entries in a different order, to ensure that the iterator
+// skips over the freed cells properly. Then insert again to ensure that the
+// free list is utilised properly.
+TEST_F(AllocationRegisterTest, InsertRemoveRandomOrder) {
+  size_t expected_sum = 0;
+  AllocationRegister reg;
+  AllocationContext ctx;
+
+  uintptr_t generator = 3;
+  uintptr_t prime = 1013;
+  uint32_t initial_water_mark = GetHighWaterMark(reg);
+
+  for (uintptr_t i = 2; i < prime; i++) {
+    size_t size = i % 31;
+    expected_sum += size;
+    reg.Insert(reinterpret_cast<void*>(i), size, ctx);
+  }
+
+  // This should have used a fresh slot for each of the |prime - 2| inserts.
+  ASSERT_EQ(prime - 2, GetHighWaterMark(reg) - initial_water_mark);
+
+  // Iterate the numbers 2, 3, ..., prime - 1 in pseudorandom order.
+  for (uintptr_t i = generator; i != 1; i = (i * generator) % prime) {
+    size_t size = i % 31;
+    expected_sum -= size;
+    reg.Remove(reinterpret_cast<void*>(i));
+    EXPECT_EQ(expected_sum, SumAllSizes(reg));
+  }
+
+  ASSERT_EQ(0u, expected_sum);
+
+  // Insert |prime - 2| entries again. This should use cells from the free list,
+  // so the |next_unused_cell_| index should not change.
+  for (uintptr_t i = 2; i < prime; i++)
+    reg.Insert(reinterpret_cast<void*>(i), 0, ctx);
+
+  ASSERT_EQ(prime - 2, GetHighWaterMark(reg) - initial_water_mark);
+
+  // Inserting one more entry should use a fresh cell again.
+  reg.Insert(reinterpret_cast<void*>(prime), 0, ctx);
+  ASSERT_EQ(prime - 1, GetHighWaterMark(reg) - initial_water_mark);
+}
+
+// Check that the process aborts due to hitting the guard page when inserting
+// too many elements.
+#if GTEST_HAS_DEATH_TEST
+TEST_F(AllocationRegisterTest, OverflowDeathTest) {
+  AllocationRegister reg;
+  AllocationContext ctx;
+  uintptr_t i;
+
+  // Fill up all of the memory allocated for the register. |kNumCells| minus 1
+  // elements are inserted, because cell 0 is unused, so this should fill up
+  // the available cells exactly.
+  for (i = 1; i < kNumCells; i++) {
+    reg.Insert(reinterpret_cast<void*>(i), 0, ctx);
+  }
+
+  // Adding just one extra element might still work because the allocated memory
+  // is rounded up to the page size. Adding a page full of elements should cause
+  // overflow.
+  const size_t cells_per_page = GetNumCellsPerPage();
+
+  ASSERT_DEATH(for (size_t j = 0; j < cells_per_page; j++) {
+    reg.Insert(reinterpret_cast<void*>(i + j), 0, ctx);
+  }, "");
+}
+#endif
+
+}  // namespace trace_event
+}  // namespace base