Adding performance tests for HQP that represent importance of optimising HistoryItemsForTerms method

testing/perf/scoped_histogram_result_printer.cc

Index: testing/perf/scoped_histogram_result_printer.cc
diff --git a/testing/perf/scoped_histogram_result_printer.cc b/testing/perf/scoped_histogram_result_printer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f39d47063f0b8e3f3ff60681866c0af339c41257
--- /dev/null
+++ b/testing/perf/scoped_histogram_result_printer.cc
@@ -0,0 +1,157 @@
+// Copyright (c) 2016 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 "testing/perf/scoped_histogram_result_printer.h"
+
+#include <cmath>
+#include <memory>
+
+#include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_samples.h"
+#include "base/metrics/statistics_recorder.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "testing/perf/perf_test.h"
+
+namespace {
+
+class TestBasedPrinter {
+ public:
+  TestBasedPrinter(const ::testing::UnitTest* test, std::string units)
+      : units_(std::move(units)) {
+    DCHECK(test);
+    test_info_ = test->current_test_info();
+    DCHECK(test_info_);
+  }
+
+  void PrintHistogram(const base::HistogramSamples& samples,
+                      const std::string& measurement) {
+    std::int64_t total_sum = samples.sum();
+    base::HistogramBase::Count total_count =
+        static_cast<double>(samples.redundant_count());
+    double mean = static_cast<double>(total_sum) / total_count;
+
+    double standard_deviation = 0;
+    for (auto sample_iter = samples.Iterator(); !sample_iter->Done();
+         sample_iter->Next()) {
+      base::HistogramBase::Sample min, max;
+      base::HistogramBase::Count count;
+      sample_iter->Get(&min, &max, &count);
+
+      double bucket_mean = (static_cast<double>(min) + max) / 2;
+
+      standard_deviation +=
+          (bucket_mean - mean) * (bucket_mean - mean) *
+          (static_cast<double>(count) /  // we do division on every iteration
+           total_count);                 // to get better precision
+    }
+    standard_deviation = std::sqrt(standard_deviation);
+
+    perf_test::PrintResultMeanAndError(
+        test_info_->test_case_name(), test_info_->name(), measurement,
+        std::to_string(mean) + ", " + std::to_string(standard_deviation),
+        units_, true);
+  }
+
+ private:
+  const ::testing::TestInfo* test_info_ = nullptr;
+  std::string units_;
+};
+
+}  // namespace
+
+namespace perf_test {
+
+HistogramPrinter TestBasedPerfTestPrinter(const ::testing::UnitTest* test,
+                                          std::string units) {
+  auto printer = base::WrapUnique(new TestBasedPrinter(test, std::move(units)));
+  return base::Bind(&TestBasedPrinter::PrintHistogram,
+                    base::Owned(printer.release()));
+}
+
+// ScopedHistogramResultPrinter::HistogramInfo---------------------------------
+
+class ScopedHistogramResultPrinter::HistogramInfo {
+ public:
+  HistogramInfo(std::string name,
+                std::string measurement,
+                bool is_nice,
+                std::unique_ptr<base::HistogramSamples> before_samples)
+      : name_(std::move(name)),
+        measurement_(std::move(measurement)),
+        is_nice_(is_nice),
+        before_samples_(std::move(before_samples)) {}
+
+  const std::string& name() const { return name_; }
+  const std::string& measurement() const { return measurement_; }
+  bool is_nice() const { return is_nice_; }
+  const base::HistogramSamples* before_samples() const {
+    return before_samples_.get();
+  }
+
+ private:
+  std::string name_;
+  std::string measurement_;
+  bool is_nice_;
+  std::unique_ptr<base::HistogramSamples> before_samples_;
+};
+
+// ScopedHistogramResultPrinter------------------------------------------------
+
+ScopedHistogramResultPrinter::ScopedHistogramResultPrinter(
+    HistogramPrinter printer)
+    : printer_(printer) {}
+
+void ScopedHistogramResultPrinter::AddHistogramStrict(std::string name,
+                                                      std::string measurement) {
+  const bool is_nice = false;
+  AddHistogram(std::move(name), std::move(measurement), is_nice);
+}
+
+void ScopedHistogramResultPrinter::AddHistogramNice(std::string name,
+                                                    std::string measurement) {
+  const bool is_nice = true;
+  AddHistogram(std::move(name), std::move(measurement), is_nice);
+}
+
+void ScopedHistogramResultPrinter::AddHistogram(std::string name,
+                                                std::string measurement,
+                                                const bool is_nice) {
+  std::unique_ptr<base::HistogramSamples> samples_before;
+
+  base::HistogramBase* histogram =
+      base::StatisticsRecorder::FindHistogram(name);
+
+  if (histogram)
+    samples_before = histogram->SnapshotSamples();
+
+  histograms_.emplace_back(std::move(name), std::move(measurement), is_nice,
+                           std::move(samples_before));
+}
+
+ScopedHistogramResultPrinter::~ScopedHistogramResultPrinter() {
+  for (const HistogramInfo& histogram_info : histograms_) {
+    base::HistogramBase* histogram =
+        base::StatisticsRecorder::FindHistogram(histogram_info.name());
+
+    if (histogram) {
+      std::unique_ptr<base::HistogramSamples> samples_after(
+          histogram->SnapshotSamples());
+      DCHECK(samples_after);
+
+      if (histogram_info.before_samples())
+        samples_after->Subtract(*histogram_info.before_samples());
+
+      if (samples_after->redundant_count())
+        printer_.Run(*samples_after, histogram_info.measurement());
+      else
+        EXPECT_TRUE(histogram_info.is_nice()) << "Nothing was added in "
+                                              << histogram_info.name();
+    } else {
+      EXPECT_TRUE(histogram_info.is_nice())
+          << "Expected histogram " << histogram_info.name() << " wasn't found";
+    }
+  }
+}
+
+}  // namespace perf_test