[profiler] Implement POC Sampling Heap Profiler

test/cctest/test-heap-profiler.cc

Index: test/cctest/test-heap-profiler.cc
diff --git a/test/cctest/test-heap-profiler.cc b/test/cctest/test-heap-profiler.cc
index a2fd09e9f59d4edd27b4c6ca1c0b3800648e8729..ea385743f2e35d9d9038cffd6ddae231ef52ec09 100644
--- a/test/cctest/test-heap-profiler.cc
+++ b/test/cctest/test-heap-profiler.cc
@@ -2852,3 +2852,148 @@ TEST(AddressToTraceMap) {
   CHECK_EQ(0u, map.size());
   CHECK_EQ(0u, map.GetTraceNodeId(ToAddress(0x400)));
 }
+
+
+static const v8::AllocationProfile::Node* FindAllocationProfileNode(
+    v8::AllocationProfile& profile, const Vector<const char*>& names) {
+  v8::AllocationProfile::Node* node = profile.GetRootNode();
+  for (int i = 0; node != nullptr && i < names.length(); ++i) {
+    const char* name = names[i];
+    auto children = node->children;
+    node = nullptr;
+    for (v8::AllocationProfile::Node* child : children) {
+      v8::String::Utf8Value child_name(child->name);
+      if (strcmp(*child_name, name) == 0) {
+        node = child;
+        break;
+      }
+    }
+  }
+  return node;
+}
+
+
+TEST(SamplingHeapProfiler) {
+  v8::HandleScope scope(v8::Isolate::GetCurrent());
+  LocalContext env;
+  v8::HeapProfiler* heap_profiler = env->GetIsolate()->GetHeapProfiler();
+
+  // Turn off always_opt. Inlining can cause stack traces to be shorter than
+  // what we expect in this test.
+  v8::internal::FLAG_always_opt = false;
+
+  const char* script_source =
+      "var A = [];\n"
+      "function bar(size) { return new Array(size); }\n"
+      "var foo = function() {\n"
+      "  for (var i = 0; i < 1024; ++i) {\n"
+      "    A[i] = bar(1024);\n"
+      "  }\n"
+      "}\n"
+      "foo();";
+
+  // Sample should be empty if requested before sampling has started.
+  {
+    v8::AllocationProfile* profile = heap_profiler->GetAllocationProfile();
+    CHECK(profile == nullptr);
+  }
+
+  int count_512kb = 0;
+  {
+    heap_profiler->StartSamplingHeapProfiler(512 * 1024);
+    CompileRun(script_source);
+
+    v8::base::SmartPointer<v8::AllocationProfile> profile(
+        heap_profiler->GetAllocationProfile());
+    CHECK(!profile.is_empty());
+
+    const char* names[] = {"", "foo", "bar"};
+    auto node_bar = FindAllocationProfileNode(
+        *profile, Vector<const char*>(names, arraysize(names)));
+    CHECK(node_bar);
+
+    // Count the number of allocations we sampled from bar.
+    for (auto allocation : node_bar->allocations) {
+      count_512kb += allocation.count;
+    }
+
+    heap_profiler->StopSamplingHeapProfiler();
+  }
+
+  // Samples should get cleared once sampling is stopped.
+  {
+    v8::AllocationProfile* profile = heap_profiler->GetAllocationProfile();
+    CHECK(profile == nullptr);
+  }
+
+  // Sampling at a higher rate should give us more sampled objects.
+  {
+    heap_profiler->StartSamplingHeapProfiler(32 * 1024);
+    CompileRun(script_source);
+
+    v8::base::SmartPointer<v8::AllocationProfile> profile(
+        heap_profiler->GetAllocationProfile());
+    CHECK(!profile.is_empty());
+
+    const char* names[] = {"", "foo", "bar"};
+    auto node_bar = FindAllocationProfileNode(
+        *profile, Vector<const char*>(names, arraysize(names)));
+    CHECK(node_bar);
+
+    // Count the number of allocations we sampled from bar.
+    int count_32kb = 0;
+    for (auto allocation : node_bar->allocations) {
+      count_32kb += allocation.count;
+    }
+
+    // We should have roughly 16x as many sampled allocations. However, since
+    // sampling is a randomized process, we use a weaker test.
+    CHECK_GT(count_32kb, count_512kb);
+
+    heap_profiler->StopSamplingHeapProfiler();
+  }
+
+  // A more complicated test cases with deeper call graph and dynamically
+  // generated function names.
+  {
+    heap_profiler->StartSamplingHeapProfiler(128);
+    CompileRun(record_trace_tree_source);
+
+    v8::base::SmartPointer<v8::AllocationProfile> profile(
+        heap_profiler->GetAllocationProfile());
+    CHECK(!profile.is_empty());
+
+    const char* names1[] = {"", "start", "f_0_0", "f_0_1", "f_0_2"};
+    auto node1 = FindAllocationProfileNode(
+        *profile, Vector<const char*>(names1, arraysize(names1)));
+    CHECK(node1);
+
+    const char* names2[] = {"", "generateFunctions"};
+    auto node2 = FindAllocationProfileNode(
+        *profile, Vector<const char*>(names2, arraysize(names2)));
+    CHECK(node2);
+
+    heap_profiler->StopSamplingHeapProfiler();
+  }
+}
+
+
+TEST(SamplingHeapProfilerApiAllocation) {
+  v8::HandleScope scope(v8::Isolate::GetCurrent());
+  LocalContext env;
+  v8::HeapProfiler* heap_profiler = env->GetIsolate()->GetHeapProfiler();
+
+  heap_profiler->StartSamplingHeapProfiler(256);
+
+  for (int i = 0; i < 8 * 1024; ++i) v8::Object::New(env->GetIsolate());
+
+  v8::base::SmartPointer<v8::AllocationProfile> profile(
+      heap_profiler->GetAllocationProfile());
+  CHECK(!profile.is_empty());
+  const char* names[] = {"(V8 API)"};
+  auto node = FindAllocationProfileNode(
+      *profile, Vector<const char*>(names, arraysize(names)));
+  CHECK(node);
+
+  heap_profiler->StopSamplingHeapProfiler();
+}