[profiler] Implement POC Sampling Heap Profiler

test/cctest/test-heap-profiler.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
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   map.AddRange(ToAddress(0x180), 0x80, 6U);
   map.AddRange(ToAddress(0x180), 0x80, 7U);
   CHECK_EQ(7u, map.GetTraceNodeId(ToAddress(0x180)));
   CHECK_EQ(5u, map.GetTraceNodeId(ToAddress(0x200)));
   CHECK_EQ(3u, map.size());
 
   map.Clear();
   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.GetRootNode() == nullptr);
+  }
+
+  int count_512kb = 0;
+  {
+    heap_profiler->StartSamplingHeapProfiler(512 * 1024);
+    CompileRun(script_source);
+
+    v8::AllocationProfile profile = heap_profiler->GetAllocationProfile();
+
+    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.GetRootNode() == nullptr);
+  }
+
+  // Sampling at a higher rate should give us more sampled objects.
+  {
+    heap_profiler->StartSamplingHeapProfiler(256 * 1024);
+    CompileRun(script_source);
+
+    v8::AllocationProfile profile = heap_profiler->GetAllocationProfile();
+
+    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_256kb = 0;
+    for (auto allocation : node_bar->allocations) {
+      count_256kb += allocation.count;
+    }
+
+    // We should have roughly twice as many sampled allocations. However, since
+    // sampling is a randomized process, we use a weaker test.
+    CHECK_GT(count_256kb, count_512kb);
+
+    heap_profiler->StopSamplingHeapProfiler();
+  }
+
+  // A more complicated test cases with deeper call graph and dynamically
+  // generated function names.
+  {
+    heap_profiler->StartSamplingHeapProfiler(512);
+    CompileRun(record_trace_tree_source);
+
+    v8::AllocationProfile profile = heap_profiler->GetAllocationProfile();
+
+    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(2 * 1024);  // 2 KiB.
+
+  for (int i = 0; i < 8 * 1024; ++i) v8::Object::New(env->GetIsolate());
+
+  v8::AllocationProfile profile = heap_profiler->GetAllocationProfile();
+  const char* names[] = {"(V8 API)"};
+  auto node = FindAllocationProfileNode(
+      profile, Vector<const char*>(names, arraysize(names)));
+  CHECK(node);
+
+  heap_profiler->StopSamplingHeapProfiler();
+}