Initial GetSample implementation.

test/cctest/test-sampler-api.cc

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// Tests the public sampling API in include/v8.h
+
+#include <string>
+
+#include "include/v8.h"
+
+#include "src/v8.h"

[alph, 2014/09/08 12:47:40]

style: no need for extra lines between includes.

[gholap, 2014/09/08 23:57:38]

Done.

+
+#include "src/base/platform/platform.h"
+
+#include "test/cctest/cctest.h"
+
+using v8::Local;
+
+namespace {
+  // Sampler thread waits on this semaphore.
+  v8::base::Semaphore* sampler_semaphore = new v8::base::Semaphore(0);
+
+  // V8 thread (the JavaScript code) waits on this semaphore.
+  v8::base::Semaphore* v8_semaphore = new v8::base::Semaphore(0);
+
+  // The JavaScript calls this function when on full stack depth.
+  void SignalAndWaitForSampler(
+    const v8::FunctionCallbackInfo<v8::Value>& args) {
+    // Tell the sampler that it can take a sample now.
+    sampler_semaphore->Signal();
+
+    // Wait for the sampler to finish collecting a sample.
+    v8_semaphore->Wait();
+  }
+}
+
+
+// A thread which collects samples from v8.
+class V8_FINAL SamplerThread : public v8::base::Thread {
+ public:
+  explicit SamplerThread(v8::Isolate* isolate)
+    : Thread(v8::base::Thread::Options("sampler-api-tester")),
+      isolate_(isolate) {
+  }
+
+  virtual ~SamplerThread() {}
+
+  virtual void Run() {
+    sampler_semaphore->Wait();  // Wait for JS to reach full stack depth.
+    isolate_->GetSample(&sample);
+    v8_semaphore->Signal();     // Tell JS that sample collection is done.
+  }
+
+  v8::Sample sample;
+
+ private:
+  v8::Isolate* isolate_;
+};
+
+
+// A JavaScript function which takes stack depth
+// (minimum value 2) as an argument.
+// When at the bottom of the recursion,
+// the JavaScript code calls into C++ test code,
+// waiting for the sampler to take a sample.
+static const char* sampler_api_test_function = "function func(depth) {"
+"  if (depth == 2) SignalAndWaitForSampler();"
+"  else return func(depth - 1);"
+"}";
+
+
+TEST(StackDepthIsConsistent) {
+  v8::Isolate* isolate = CcTest::isolate();
+  v8::HandleScope scope(isolate);
+  v8::Handle<v8::ObjectTemplate> global = v8::ObjectTemplate::New(isolate);
+  global->Set(
+    v8::String::NewFromUtf8(isolate, "SignalAndWaitForSampler"),
+    v8::FunctionTemplate::New(isolate, SignalAndWaitForSampler));
+
+  LocalContext env(isolate, NULL, global);
+  std::string source(sampler_api_test_function);
+  source.append("func(8);");
+  Local<v8::Script> script = v8::Script::Compile(
+    v8::String::NewFromUtf8(isolate, source.c_str()));
+  SamplerThread sampler(isolate);
+
+  sampler.Start();
+  script->Run();
+  sampler.Join();
+
+  CHECK_EQ(8, sampler.sample.size());
+}
+
+
+TEST(StackDepthDoesNotExceedMaxValue) {
+  v8::Isolate* isolate = CcTest::isolate();
+  v8::HandleScope scope(isolate);
+  v8::Handle<v8::ObjectTemplate> global = v8::ObjectTemplate::New(isolate);
+  global->Set(
+    v8::String::NewFromUtf8(isolate, "SignalAndWaitForSampler"),
+    v8::FunctionTemplate::New(isolate, SignalAndWaitForSampler));
+
+  LocalContext env(isolate, NULL, global);
+  std::string source(sampler_api_test_function);
+  source.append("func(300);");
+  Local<v8::Script> script = v8::Script::Compile(
+    v8::String::NewFromUtf8(isolate, source.c_str()));
+  SamplerThread sampler(isolate);
+
+  sampler.Start();
+  script->Run();
+  sampler.Join();
+
+  int MAX_SIZE = v8::Sample::kMaxSize;
+  CHECK_EQ(MAX_SIZE, sampler.sample.size());
+}
+
+
+namespace {
+  std::vector<v8::JitCodeEvent> inner_funcs;
+  std::vector<v8::JitCodeEvent> outer_funcs;
+
+  void TestJitCodeEventHandler(const v8::JitCodeEvent* event) {
+    if (event->type != v8::JitCodeEvent::CODE_ADDED) return;
+    std::string name(event->name.str, event->name.len);
+    if (name.find("test_sampler_api_inner") != std::string::npos)
+      inner_funcs.push_back(*event);
+    if (name.find("test_sampler_api_outer") != std::string::npos)
+      outer_funcs.push_back(*event);
+  }
+}
+
+
+// Note: The argumnets.callee stuff is there so that the
+//       functions are not optimized away.
+static const char* sampler_api_test_script =
+"function test_sampler_api_inner() {"
+"  SignalAndWaitForSampler();"
+"  return arguments.callee.toString();"
+"}"
+"function test_sampler_api_outer() {"
+"  return test_sampler_api_inner() + arguments.callee.toString();"
+"}"
+"test_sampler_api_outer();";
+
+
+// The captured sample should have three pc values.
+// They should fall in the range where the compiled code
+// The expected stack is:
+// bottom of stack [{anon script}, outer, inner] top of stack
+//                              ^      ^       ^
+// sample.stack indices         2      1       0
+TEST(StackFramesConsistent) {
+  v8::Isolate* isolate = CcTest::isolate();
+  v8::V8::SetJitCodeEventHandler(v8::kJitCodeEventDefault,
+                                 TestJitCodeEventHandler);
+  v8::HandleScope scope(isolate);
+  v8::Handle<v8::ObjectTemplate> global = v8::ObjectTemplate::New(isolate);
+  global->Set(
+    v8::String::NewFromUtf8(isolate, "SignalAndWaitForSampler"),
+    v8::FunctionTemplate::New(isolate, SignalAndWaitForSampler));
+
+  LocalContext env(isolate, NULL, global);
+  Local<v8::Script> script = v8::Script::Compile(
+    v8::String::NewFromUtf8(isolate, sampler_api_test_script));
+  SamplerThread sampler(isolate);
+
+  sampler.Start();
+  script->Run();
+  sampler.Join();
+
+  CHECK_EQ(3, sampler.sample.size());
+
+  bool stack_top_is_inner = false;
+  bool below_inner_is_outer = false;
+
+  for (unsigned i = 0; i < inner_funcs.size(); i++) {
+    void* start_addr = inner_funcs[i].code_start;
+    void* end_addr = reinterpret_cast<void*>((int64_t)inner_funcs[i].code_start
+                                             + inner_funcs[i].code_len);
+    if ((*sampler.sample.begin() >= start_addr) &&
+        (*sampler.sample.begin() < end_addr))
+      stack_top_is_inner = true;
+  }
+
+  for (unsigned i = 0; i < outer_funcs.size(); i++) {
+    void* start_addr = outer_funcs[i].code_start;
+    void* end_addr = reinterpret_cast<void*>((int64_t)outer_funcs[i].code_start
+                                             + outer_funcs[i].code_len);
+    if ((*(sampler.sample.begin() + 1) >= start_addr) &&
+        (*(sampler.sample.begin() + 1) < end_addr))
+      below_inner_is_outer = true;
+  }
+
+  CHECK_EQ(true, stack_top_is_inner);
+  CHECK_EQ(true, below_inner_is_outer);
+}