base/profiler/stack_sampling_profiler_unittest.cc

// 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 <sstream>

#include "base/bind.h"
#include "base/compiler_specific.h"
#include "base/path_service.h"
#include "base/profiler/stack_sampling_profiler.h"
#include "base/synchronization/waitable_event.h"
#include "base/threading/platform_thread.h"
#include "base/time/time.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace base {

using Frame = StackSamplingProfiler::Frame;
using Module = StackSamplingProfiler::Module;
using Sample = StackSamplingProfiler::Sample;
using Profile = StackSamplingProfiler::Profile;

namespace {
// A thread to target for profiling, whose stack is guaranteed to contain
// SignalAndWaitUntilSignaled() when coordinated with the main thread.
class TargetThread : public PlatformThread::Delegate {
 public:
  TargetThread();

  // Implementation of PlatformThread::Delegate:
  void ThreadMain() override;

  // Wait for the thread to have started and be executing in
  // SignalAndWaitUntilSignaled().
  void WaitForThreadStart();
  // Allow the thread to return from SignalAndWaitUntilSignaled() and finish
  // execution.
  void SignalThreadToFinish();

  // This function is guaranteed to be executing between calls to
  // WaitForThreadStart() and SignalThreadToFinish().
  static void SignalAndWaitUntilSignaled(WaitableEvent* thread_started_event,
                                         WaitableEvent* finish_event);

  PlatformThreadId id() const { return id_; }

 private:
  WaitableEvent thread_started_event_;
  WaitableEvent finish_event_;
  PlatformThreadId id_;

  DISALLOW_COPY_AND_ASSIGN(TargetThread);
};

TargetThread::TargetThread()
    : thread_started_event_(false, false), finish_event_(false, false),
      id_(0) {}

void TargetThread::ThreadMain() {
  id_ = PlatformThread::CurrentId();
  SignalAndWaitUntilSignaled(&thread_started_event_, &finish_event_);
}

void TargetThread::WaitForThreadStart() {
  thread_started_event_.Wait();
}

void TargetThread::SignalThreadToFinish() {
  finish_event_.Signal();
}

// static
// Disable inlining for this function so that it gets its own stack frame.
NOINLINE void TargetThread::SignalAndWaitUntilSignaled(
    WaitableEvent* thread_started_event,
    WaitableEvent* finish_event) {
  thread_started_event->Signal();
  volatile int x = 1;
  finish_event->Wait();
  x = 0;  // Prevent tail call to WaitableEvent::Wait().
  ALLOW_UNUSED_LOCAL(x);
}

// Called on the profiler thread when complete. Collects profiles produced by
// the profiler, and signals an event to allow the main thread to know that that
// the profiler is done.
void SaveProfilesAndSignalEvent(std::vector<Profile>* profiles,
                                WaitableEvent* event,
                                const std::vector<Profile>& pending_profiles) {
  *profiles = pending_profiles;
  event->Signal();
}

// Captures profiles as specified by |params| on the TargetThread, and returns
// them in |profiles|. Waits up to |profiler_wait_time| for the profiler to
// complete.
void CaptureProfiles(const StackSamplingProfiler::SamplingParams& params,
                     std::vector<Profile>* profiles,
                     TimeDelta profiler_wait_time) {
  TargetThread target_thread;
  PlatformThreadHandle target_thread_handle;
  EXPECT_TRUE(PlatformThread::Create(0, &target_thread, &target_thread_handle));

  target_thread.WaitForThreadStart();

  WaitableEvent sampling_thread_completed(true, false);
  profiles->clear();
  StackSamplingProfiler profiler(target_thread.id(), params);
  profiler.SetCustomCompletedCallback(
      Bind(&SaveProfilesAndSignalEvent, Unretained(profiles),
           Unretained(&sampling_thread_completed)));
  profiler.Start();
  sampling_thread_completed.TimedWait(profiler_wait_time);
  profiler.Stop();
  sampling_thread_completed.Wait();

  target_thread.SignalThreadToFinish();

  PlatformThread::Join(target_thread_handle);
}

// If this executable was linked with /INCREMENTAL (the default for non-official
// debug and release builds on Windows), function addresses do not correspond to
// function code itself, but instead to instructions in the Incremental Link
// Table that jump to the functions. Check for a jump instruction and if present
// do a little decompilation to find the function's actual starting address.
const void* MaybeFixupFunctionAddressForILT(const void* function_address) {
#if defined(_WIN64)
  const unsigned char* opcode =
      reinterpret_cast<const unsigned char*>(function_address);
  if (*opcode == 0xe9) {
    // This is a relative jump instruction. Assume we're in the ILT and compute
    // the function start address from the instruction offset.
    const unsigned char* offset = opcode + 1;
    const unsigned char* next_instruction = opcode + 5;
    return next_instruction +
        static_cast<int64>(*reinterpret_cast<const int32*>(offset));
  }
#endif
  return function_address;
}

// Searches through the frames in |sample|, returning an iterator to the first
// frame that has an instruction pointer between |function_address| and
// |function_address| + |size|. Returns sample.end() if no such frames are
// found.
Sample::const_iterator FindFirstFrameWithinFunction(
    const Sample& sample,
    const void* function_address,
    int function_size) {
  function_address = MaybeFixupFunctionAddressForILT(function_address);
  for (auto it = sample.begin(); it != sample.end(); ++it) {
    if ((reinterpret_cast<const unsigned char*>(it->instruction_pointer) >=
         reinterpret_cast<const unsigned char*>(function_address)) &&
        (reinterpret_cast<const unsigned char*>(it->instruction_pointer) <
         (reinterpret_cast<const unsigned char*>(function_address) +
          function_size)))
      return it;
  }
  return sample.end();
}

// Formats a sample into a string that can be output for test diagnostics.
std::string FormatSampleForDiagnosticOutput(
    const Sample& sample,
    const std::vector<Module>& modules) {
  std::ostringstream stream;
  for (const Frame& frame: sample) {
    stream << frame.instruction_pointer << " "
           << modules[frame.module_index].filename.value() << std::endl;
  }
  return stream.str();
}

// Returns a duration that is longer than the test timeout. We would use
// TimeDelta::Max() but https://crbug.com/465948.
TimeDelta AVeryLongTimeDelta() { return TimeDelta::FromDays(1); }
}  // namespace


// The tests below are enabled for Win x64 only, pending implementation of the
// tested functionality on other platforms/architectures.

// Checks that the basic expected information is present in a sampled profile.
#if defined(_WIN64)
#define MAYBE_Basic Basic
#else
#define MAYBE_Basic DISABLED_Basic
#endif
TEST(StackSamplingProfilerTest, MAYBE_Basic) {
  StackSamplingProfiler::SamplingParams params;
  params.initial_delay = params.burst_interval = params.sampling_interval =
      TimeDelta::FromMilliseconds(0);
  params.bursts = 1;
  params.samples_per_burst = 1;

  std::vector<Profile> profiles;
  CaptureProfiles(params, &profiles, AVeryLongTimeDelta());

  // Check that the profile and samples sizes are correct, and the module
  // indices are in range.

  ASSERT_EQ(1u, profiles.size());
  const Profile& profile = profiles[0];
  ASSERT_EQ(1u, profile.samples.size());
  EXPECT_EQ(params.sampling_interval, profile.sampling_period);
  const Sample& sample = profile.samples[0];
  for (const auto& frame : sample) {
    ASSERT_GE(frame.module_index, 0);
    ASSERT_LT(frame.module_index, static_cast<int>(profile.modules.size()));
  }

  // Check that the stack contains a frame for
  // TargetThread::SignalAndWaitUntilSignaled() and that the frame has this
  // executable's module.

  // Since we don't have a good way to know the function size, use 100 bytes as
  // a reasonable window to locate the instruction pointer.
  Sample::const_iterator loc = FindFirstFrameWithinFunction(
      sample,
      reinterpret_cast<const void*>(&TargetThread::SignalAndWaitUntilSignaled),
      100);
  ASSERT_TRUE(loc != sample.end())
      << "Function at "
      << MaybeFixupFunctionAddressForILT(
          reinterpret_cast<const void*>(
              &TargetThread::SignalAndWaitUntilSignaled))
      << " was not found in stack:" << std::endl
      << FormatSampleForDiagnosticOutput(sample, profile.modules);

  FilePath executable_path;
  bool got_executable_path = PathService::Get(FILE_EXE, &executable_path);
  EXPECT_TRUE(got_executable_path);
  EXPECT_EQ(executable_path, profile.modules[loc->module_index].filename);
}

// Checks that the expected number of profiles and samples are present in the
// profiles produced.
#if defined(_WIN64)
#define MAYBE_MultipleProfilesAndSamples MultipleProfilesAndSamples
#else
#define MAYBE_MultipleProfilesAndSamples DISABLED_MultipleProfilesAndSamples
#endif
TEST(StackSamplingProfilerTest, MAYBE_MultipleProfilesAndSamples) {
  StackSamplingProfiler::SamplingParams params;
  params.initial_delay = params.burst_interval = params.sampling_interval =
      TimeDelta::FromMilliseconds(0);
  params.bursts = 2;
  params.samples_per_burst = 3;

  std::vector<Profile> profiles;
  CaptureProfiles(params, &profiles, AVeryLongTimeDelta());

  ASSERT_EQ(2u, profiles.size());
  EXPECT_EQ(3u, profiles[0].samples.size());
  EXPECT_EQ(3u, profiles[1].samples.size());
}

// Checks that no profiles are captured if the profiling is stopped during the
// initial delay.
#if defined(_WIN64)
#define MAYBE_StopDuringInitialDelay StopDuringInitialDelay
#else
#define MAYBE_StopDuringInitialDelay DISABLED_StopDuringInitialDelay
#endif
TEST(StackSamplingProfilerTest, MAYBE_StopDuringInitialDelay) {
  StackSamplingProfiler::SamplingParams params;
  params.burst_interval = params.sampling_interval =
      TimeDelta::FromMilliseconds(0);
  params.initial_delay = TimeDelta::FromSeconds(60);
  params.bursts = params.samples_per_burst = 1;

  std::vector<Profile> profiles;
  CaptureProfiles(params, &profiles, TimeDelta::FromMilliseconds(0));

  EXPECT_TRUE(profiles.empty());
}

// Checks that the single completed profile is captured if the profiling is
// stopped between bursts.
#if defined(_WIN64)
#define MAYBE_StopDuringInterBurstInterval StopDuringInterBurstInterval
#else
#define MAYBE_StopDuringInterBurstInterval DISABLED_StopDuringInterBurstInterval
#endif
TEST(StackSamplingProfilerTest, MAYBE_StopDuringInterBurstInterval) {
  StackSamplingProfiler::SamplingParams params;
  params.initial_delay = params.sampling_interval =
      TimeDelta::FromMilliseconds(0);
  params.burst_interval = TimeDelta::FromSeconds(60);
  params.bursts = 2;
  params.samples_per_burst = 1;

  std::vector<Profile> profiles;
  CaptureProfiles(params, &profiles, TimeDelta::FromMilliseconds(50));

  ASSERT_EQ(1u, profiles.size());
  EXPECT_EQ(1u, profiles[0].samples.size());
}

// Checks that only completed profiles are captured.
#if defined(_WIN64)
#define MAYBE_StopDuringInterSampleInterval StopDuringInterSampleInterval
#else
#define MAYBE_StopDuringInterSampleInterval \
  DISABLED_StopDuringInterSampleInterval
#endif
TEST(StackSamplingProfilerTest, MAYBE_StopDuringInterSampleInterval) {
  StackSamplingProfiler::SamplingParams params;
  params.initial_delay = params.burst_interval = TimeDelta::FromMilliseconds(0);
  params.sampling_interval = TimeDelta::FromSeconds(60);
  params.bursts = 1;
  params.samples_per_burst = 2;

  std::vector<Profile> profiles;
  CaptureProfiles(params, &profiles, TimeDelta::FromMilliseconds(50));

  EXPECT_TRUE(profiles.empty());
}

}  // namespace tracked_objects