base/win/sampling_profiler_unittest.cc

// Copyright (c) 2011 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/win/sampling_profiler.h"

#include "base/test/test_timeouts.h"
#include "base/win/pe_image.h"
#include "base/win/scoped_handle.h"
#include "testing/gtest/include/gtest/gtest.h"

// The address of our image base.
extern "C" IMAGE_DOS_HEADER __ImageBase;

namespace base {
namespace win {

namespace {

class SamplingProfilerTest : public testing::Test {
 public:
  SamplingProfilerTest() : code_start(NULL), code_size(0) {
  }

  virtual void SetUp() {
    process.Set(::OpenProcess(PROCESS_QUERY_INFORMATION,
                              FALSE,
                              ::GetCurrentProcessId()));
    ASSERT_TRUE(process.IsValid());

    PEImage image(&__ImageBase);

    // Get the address of the .text section, which is the first section output
    // by the VS tools.
    ASSERT_TRUE(image.GetNumSections() > 0);
    const IMAGE_SECTION_HEADER* text_section = image.GetSectionHeader(0);
    ASSERT_EQ(0, strncmp(".text",
                         reinterpret_cast<const char*>(text_section->Name),
                         arraysize(text_section->Name)));
    ASSERT_NE(0U, text_section->Characteristics & IMAGE_SCN_MEM_EXECUTE);

    code_start = reinterpret_cast<uint8*>(&__ImageBase) +
        text_section->VirtualAddress;
    code_size = text_section->Misc.VirtualSize;
  }

 protected:
  ScopedHandle process;
  void* code_start;
  size_t code_size;
};

}  // namespace

TEST_F(SamplingProfilerTest, Initialize) {
  SamplingProfiler profiler;

  ASSERT_TRUE(profiler.Initialize(process.Get(), code_start, code_size, 8));
}

TEST_F(SamplingProfilerTest, Sample) {
  SamplingProfiler profiler;

  // Initialize with a huge bucket size, aiming for a single bucket.
  ASSERT_TRUE(
      profiler.Initialize(process.Get(), code_start, code_size, 31));

  ASSERT_EQ(1, profiler.buckets().size());
  ASSERT_EQ(0, profiler.buckets()[0]);

  // We use a roomy timeout to make sure this test is not flaky.
  // On the buildbots, there may not be a whole lot of CPU time
  // allotted to our process in this wall-clock time duration,
  // and samples will only accrue while this thread is busy on
  // a CPU core.
  base::TimeDelta spin_time =
      base::TimeDelta::FromMilliseconds(TestTimeouts::action_timeout_ms());

  base::TimeDelta save_sampling_interval;
  ASSERT_TRUE(SamplingProfiler::GetSamplingInterval(&save_sampling_interval));

  // Sample every 0.5 millisecs.
  ASSERT_TRUE(SamplingProfiler::SetSamplingInterval(
      base::TimeDelta::FromMicroseconds(500)));

  ASSERT_TRUE(SamplingProfiler::SetSamplingInterval(
      base::TimeDelta::FromMicroseconds(500)));

  // Start the profiler.
  ASSERT_TRUE(profiler.Start());

  // Get a volatile pointer to our bucket to make sure that the compiler
  // doesn't optimize out the test in the loop that follows.
  volatile const ULONG* bucket_ptr = &profiler.buckets()[0];

  // Spin for spin_time wall-clock seconds, or until we get some samples.
  // Note that sleeping isn't going to do us any good, the samples only
  // accrue while we're executing code.
  base::Time start = base::Time::Now();
  base::TimeDelta elapsed;
  do {
    elapsed = base::Time::Now() - start;
  } while((elapsed < spin_time) && *bucket_ptr == 0);

  // Stop the profiler.
  ASSERT_TRUE(profiler.Stop());

  // Restore the sampling interval we found.
  ASSERT_TRUE(SamplingProfiler::SetSamplingInterval(save_sampling_interval));

  // Check that we got some samples.
  ASSERT_NE(0U, profiler.buckets()[0]);
}

}  // namespace win
}  // namespace base