A better idle time estimator

components/scheduler/renderer/idle_time_estimator_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 "components/scheduler/renderer/idle_time_estimator.h"
+
+#include "base/test/simple_test_tick_clock.h"
+#include "cc/output/begin_frame_args.h"
+#include "components/scheduler/base/test_time_source.h"
+
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace scheduler {
+
+class IdleTimeEstimatorForTest : public IdleTimeEstimator {
+ public:
+  IdleTimeEstimatorForTest(base::SimpleTestTickClock* clock,
+                           int sample_count,
+                           double estimation_percentile)
+      : IdleTimeEstimator(sample_count, estimation_percentile) {
+    SetTimeSourceForTesting(make_scoped_ptr(new TestTimeSource(clock)));
+  }
+};
+
+class IdleTimeEstimatorTest : public testing::Test {
+ public:
+  IdleTimeEstimatorTest() {}
+  ~IdleTimeEstimatorTest() override {}
+
+  void SetUp() override {
+    estimator_.reset(new IdleTimeEstimatorForTest(&clock_, 10, 50));
+  }
+
+  base::SimpleTestTickClock clock_;
+
+  void Frame(int compositor_time, int idle_time) {
+    base::PendingTask task(FROM_HERE, base::Closure());
+    estimator_->WillProcessTask(task);
+    clock_.Advance(base::TimeDelta::FromMilliseconds(compositor_time));
+    estimator_->DidCommitFrameToCompositor();
+    estimator_->DidProcessTask(task);
+    clock_.Advance(base::TimeDelta::FromMilliseconds(idle_time));
+  }
+
+  void FrameWithTwoCompositorTasks(int compositor_time1,
+                                   int compositor_time2,
+                                   int idle_time) {
+    base::PendingTask task(FROM_HERE, base::Closure());
+    estimator_->WillProcessTask(task);
+    clock_.Advance(base::TimeDelta::FromMilliseconds(compositor_time1));
+    estimator_->DidProcessTask(task);
+
+    estimator_->WillProcessTask(task);
+    clock_.Advance(base::TimeDelta::FromMilliseconds(compositor_time2));
+    estimator_->DidCommitFrameToCompositor();
+    estimator_->DidProcessTask(task);
+    clock_.Advance(base::TimeDelta::FromMilliseconds(idle_time));
+  }
+
+  scoped_ptr<IdleTimeEstimatorForTest> estimator_;
+};
+
+TEST_F(IdleTimeEstimatorTest, InitialTimeEstimateWithNoData) {
+  EXPECT_EQ(cc::BeginFrameArgs::DefaultInterval(),
+            estimator_->GetExpectedIdleDuration(
+                cc::BeginFrameArgs::DefaultInterval() * 2));
+}
+
+TEST_F(IdleTimeEstimatorTest, BasicEstimation_SteadyState) {
+  Frame(5, 11);
+  Frame(5, 11);
+
+  EXPECT_EQ(base::TimeDelta::FromMilliseconds(11),
+            estimator_->GetExpectedIdleDuration(
+                cc::BeginFrameArgs::DefaultInterval()));
+}
+
+TEST_F(IdleTimeEstimatorTest, BasicEstimation_Variable) {
+  Frame(5, 11);
+  Frame(6, 10);
+  Frame(7, 9);
+  Frame(7, 9);
+  Frame(7, 9);
+  Frame(8, 8);
+
+  // We expect it to return the median.
+  EXPECT_EQ(base::TimeDelta::FromMilliseconds(9),
+            estimator_->GetExpectedIdleDuration(
+                base::TimeDelta::FromMilliseconds(16)));
+}
+
+TEST_F(IdleTimeEstimatorTest, Clear) {
+  Frame(5, 11);
+  Frame(5, 11);
+
+  EXPECT_EQ(base::TimeDelta::FromMilliseconds(11),
+            estimator_->GetExpectedIdleDuration(
+                cc::BeginFrameArgs::DefaultInterval()));
+  estimator_->Clear();
+
+  EXPECT_EQ(cc::BeginFrameArgs::DefaultInterval(),
+            estimator_->GetExpectedIdleDuration(
+                cc::BeginFrameArgs::DefaultInterval()));
+}
+
+TEST_F(IdleTimeEstimatorTest, Estimation_MultipleTasks) {
+  FrameWithTwoCompositorTasks(1, 4, 11);
+  FrameWithTwoCompositorTasks(1, 4, 11);
+
+  EXPECT_EQ(base::TimeDelta::FromMilliseconds(11),
+            estimator_->GetExpectedIdleDuration(
+                cc::BeginFrameArgs::DefaultInterval()));
+}
+
+TEST_F(IdleTimeEstimatorTest, IdlePeriodClamping) {
+  Frame(5, 100);
+  Frame(5, 100);
+  Frame(5, 100);
+
+  EXPECT_EQ(base::TimeDelta::FromMilliseconds(32 - 5),
+            estimator_->GetExpectedIdleDuration(
+                base::TimeDelta::FromMilliseconds(32)));
+}
+
+}  // namespace scheduler