cc: Heuristic for Renderer latency recovery

cc/scheduler/scheduler_unittest.cc

Index: cc/scheduler/scheduler_unittest.cc
diff --git a/cc/scheduler/scheduler_unittest.cc b/cc/scheduler/scheduler_unittest.cc
index 2f878fdcdbfa9a22a3d101934c3200fb3c30b96d..388b4db8178d95419419c5902fbf13a190f2ef43 100644
--- a/cc/scheduler/scheduler_unittest.cc
+++ b/cc/scheduler/scheduler_unittest.cc
@@ -150,12 +150,17 @@ class FakeSchedulerClient : public SchedulerClient {
     if (log_anticipated_draw_time_change_)
       PushAction("DidAnticipatedDrawTimeChange");
   }
-  base::TimeDelta DrawDurationEstimate() override { return base::TimeDelta(); }
+
+  // Use really long estimations by default so we don't inadvertently
+  // test latency recovery logic unless a test explicitly wants to.
+  base::TimeDelta DrawDurationEstimate() override {
+    return base::TimeDelta::FromHours(1);
+  }
   base::TimeDelta BeginMainFrameToCommitDurationEstimate() override {
-    return base::TimeDelta();
+    return base::TimeDelta::FromHours(1);
   }
   base::TimeDelta CommitToActivateDurationEstimate() override {
-    return base::TimeDelta();
+    return base::TimeDelta::FromHours(1);
   }
 
   void SendBeginFramesToChildren(const BeginFrameArgs& args) override {
@@ -203,9 +208,9 @@ class FakeSchedulerClient : public SchedulerClient {
   TestScheduler* scheduler_;
 };
 
-class SchedulerClientWithFixedEstimates : public FakeSchedulerClient {
+class SchedulerClientWithCustomEstimates : public FakeSchedulerClient {
  public:
-  SchedulerClientWithFixedEstimates(
+  SchedulerClientWithCustomEstimates(
       base::TimeDelta draw_duration,
       base::TimeDelta begin_main_frame_to_commit_duration,
       base::TimeDelta commit_to_activate_duration)
@@ -222,7 +227,7 @@ class SchedulerClientWithFixedEstimates : public FakeSchedulerClient {
     return commit_to_activate_duration_;
   }
 
- private:
+ public:
   base::TimeDelta draw_duration_;
   base::TimeDelta begin_main_frame_to_commit_duration_;
   base::TimeDelta commit_to_activate_duration_;
@@ -418,6 +423,11 @@ class SchedulerTest : public testing::Test {
       int64 commit_to_activate_estimate_in_ms,
       bool impl_latency_takes_priority,
       bool should_send_begin_main_frame);
+  void ImplFrameInHighLatencyMode(
+      int64 begin_main_frame_to_commit_estimate_in_ms,
+      int64 commit_to_activate_estimate_in_ms,
+      bool swap_ack_before_deadline,
+      bool should_begin_impl_frame_in_high_latency);
   void BeginFramesNotFromClient(bool use_external_begin_frame_source,
                                 bool throttle_frame_production);
   void BeginFramesNotFromClient_SwapThrottled(
@@ -484,8 +494,8 @@ TEST_F(SchedulerTest, SendBeginFramesToChildrenWithoutCommit) {
 
 TEST_F(SchedulerTest, SendBeginFramesToChildrenDeadlineNotAdjusted) {
   // Set up client with specified estimates.
-  SchedulerClientWithFixedEstimates* client =
-      new SchedulerClientWithFixedEstimates(
+  SchedulerClientWithCustomEstimates* client =
+      new SchedulerClientWithCustomEstimates(
           base::TimeDelta::FromMilliseconds(1),
           base::TimeDelta::FromMilliseconds(2),
           base::TimeDelta::FromMilliseconds(4));
@@ -1316,8 +1326,8 @@ void SchedulerTest::MainFrameInHighLatencyMode(
     bool impl_latency_takes_priority,
     bool should_send_begin_main_frame) {
   // Set up client with specified estimates (draw duration is set to 1).
-  SchedulerClientWithFixedEstimates* client =
-      new SchedulerClientWithFixedEstimates(
+  SchedulerClientWithCustomEstimates* client =
+      new SchedulerClientWithCustomEstimates(
           base::TimeDelta::FromMilliseconds(1),
           base::TimeDelta::FromMilliseconds(
               begin_main_frame_to_commit_estimate_in_ms),
@@ -1378,11 +1388,239 @@ TEST_F(SchedulerTest, NotSkipMainFrameInPreferImplLatencyMode) {
   EXPECT_SCOPED(MainFrameInHighLatencyMode(1, 1, true, true));
 }
 
+void SchedulerTest::ImplFrameInHighLatencyMode(
+    int64 begin_main_frame_to_commit_estimate_in_ms,
+    int64 commit_to_activate_estimate_in_ms,
+    bool swap_ack_before_deadline,
+    bool should_begin_impl_frame_in_high_latency) {
+  // Set up client with specified estimates (draw duration is set to 1).
+  SchedulerClientWithCustomEstimates* client =
+      new SchedulerClientWithCustomEstimates(
+          base::TimeDelta::FromMilliseconds(1),
+          base::TimeDelta::FromMilliseconds(
+              begin_main_frame_to_commit_estimate_in_ms),
+          base::TimeDelta::FromMilliseconds(commit_to_activate_estimate_in_ms));
+
+  scheduler_settings_.use_external_begin_frame_source = true;
+  SetUpScheduler(make_scoped_ptr(client).Pass(), true);
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+
+  // To get into a high latency state, this test disables automatic swap acks.
+  scheduler_->SetMaxSwapsPending(1);
+  client_->SetAutomaticSwapAck(false);
+
+  // Draw and swap for first BeginFrame
+  client->Reset();
+  scheduler_->SetNeedsRedraw();
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  EXPECT_SCOPED(AdvanceFrame());
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  task_runner().RunPendingTasks();  // Run posted deadline.
+  EXPECT_TRUE(client->HasAction("ScheduledActionDrawAndSwapIfPossible"));
+
+  // Not calling scheduler_->DidSwapBuffersComplete() until after next frame
+  // puts impl thread in high latency mode.
+  client->Reset();
+  scheduler_->SetNeedsRedraw();
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  EXPECT_SCOPED(AdvanceFrame());
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  if (swap_ack_before_deadline) {
+    scheduler_->DidSwapBuffersComplete();
+    EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+    EXPECT_TRUE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+    task_runner().RunPendingTasks();  // Run posted deadline.
+    EXPECT_TRUE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  } else {
+    task_runner().RunPendingTasks();  // Run posted deadline.
+    EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+    EXPECT_TRUE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+    scheduler_->DidSwapBuffersComplete();
+    EXPECT_TRUE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  }
+
+  // Now that we are in a high latency mode, test if we recover or not.
+  client->Reset();
+  scheduler_->SetNeedsRedraw();
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_TRUE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  SendNextBeginFrame();
+  EXPECT_EQ(should_begin_impl_frame_in_high_latency,
+            client->HasAction("WillBeginImplFrame"));
+
+  // Verify that we make forward progress even when we aren't expecting
+  // another swap ack.
+  if (!swap_ack_before_deadline) {
+    client->Reset();
+    SendNextBeginFrame();
+    EXPECT_TRUE(client->HasAction("WillBeginImplFrame"));
+  }
+}
+
+TEST_F(SchedulerTest,
+       SkipImplFrameIfHighLatencyAndCanDrawBeforeDeadline_SwapAckThenDeadline) {
+  // Set up client so that estimates indicate that we can commit and activate
+  // before the deadline (~8ms by default).
+  EXPECT_SCOPED(ImplFrameInHighLatencyMode(1, 1, true, false));
+}
+
+TEST_F(SchedulerTest,
+       SkipImplFrameIfHighLatencyAndCanDrawBeforeDeadline_DeadlineThenSwapAck) {
+  // Set up client so that estimates indicate that we can commit and activate
+  // before the deadline (~8ms by default).
+  EXPECT_SCOPED(ImplFrameInHighLatencyMode(1, 1, false, false));
+}
+
+TEST_F(SchedulerTest, NotSkipImplFrameIfHighLatencyAndCanCommitTooLong) {
+  // Set up client so that estimates indicate that the commit cannot finish
+  // before the deadline (~8ms by default).
+  EXPECT_SCOPED(ImplFrameInHighLatencyMode(10, 1, true, true));
+}
+
+TEST_F(SchedulerTest, NotSkipImplFrameIfHighLatencyAndCanActivateTooLong) {
+  // Set up client so that estimates indicate that the activate cannot finish
+  // before the deadline (~8ms by default).
+  EXPECT_SCOPED(ImplFrameInHighLatencyMode(1, 10, true, true));
+}
+
+TEST_F(SchedulerTest, MainAndImplFrameInHighLatencyMode) {
+  // Set up client with custom estimates.
+  // This test starts off with expensive estimates to prevent latency recovery
+  // initially, the lowers the estimates to enable it once both the main
+  // and impl threads are in a high latency mode.
+  auto fast_duration = base::TimeDelta::FromMilliseconds(1);
+  auto slow_duration = base::TimeDelta::FromMilliseconds(10);
+  SchedulerClientWithCustomEstimates* client =
+      new SchedulerClientWithCustomEstimates(slow_duration, slow_duration,
+                                             slow_duration);
+
+  scheduler_settings_.use_external_begin_frame_source = true;
+  SetUpScheduler(make_scoped_ptr(client).Pass(), true);
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+
+  // To get into a high latency state, this test disables automatic swap acks.
+  scheduler_->SetMaxSwapsPending(1);
+  client_->SetAutomaticSwapAck(false);
+
+  // Impl thread hits deadline before commit finishes to make
+  // MainThreadIsInHighLatencyMode true
+  client->Reset();
+  scheduler_->SetNeedsCommit();
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  EXPECT_SCOPED(AdvanceFrame());
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  task_runner().RunPendingTasks();  // Run posted deadline.
+  EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  scheduler_->NotifyBeginMainFrameStarted();
+  scheduler_->NotifyReadyToCommit();
+  EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  EXPECT_TRUE(client->HasAction("WillBeginImplFrame"));
+  EXPECT_TRUE(client->HasAction("ScheduledActionSendBeginMainFrame"));
+
+  // Draw and swap for first commit, start second commit.
+  client->Reset();
+  scheduler_->SetNeedsCommit();
+  EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  EXPECT_SCOPED(AdvanceFrame());
+  EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  task_runner().RunPendingTasks();  // Run posted deadline.
+  scheduler_->NotifyBeginMainFrameStarted();
+  scheduler_->NotifyReadyToCommit();
+  EXPECT_TRUE(client->HasAction("WillBeginImplFrame"));
+  EXPECT_TRUE(client->HasAction("ScheduledActionSendBeginMainFrame"));
+  EXPECT_TRUE(client->HasAction("ScheduledActionDrawAndSwapIfPossible"));
+
+  // Don't call scheduler_->DidSwapBuffersComplete() until after next frame
+  // to make ImplThreadIsLikelyInHighLatencyMode true.
+  client->Reset();
+  scheduler_->SetNeedsCommit();
+  EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  EXPECT_SCOPED(AdvanceFrame());
+  EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  task_runner().RunPendingTasks();  // Run posted deadline.
+  scheduler_->DidSwapBuffersComplete();
+  EXPECT_TRUE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  EXPECT_TRUE(client->HasAction("WillBeginImplFrame"));
+  // Note: BeginMainFrame and BeginImplFrame are skipped here because
+  // of backpressure, not because of latency recovery.
+  EXPECT_FALSE(client->HasAction("ScheduledActionSendBeginMainFrame"));
+  EXPECT_FALSE(client->HasAction("ScheduledActionDrawAndSwapIfPossible"));
+
+  // Lower estimates so that the scheduler will attempt latency recovery.
+  client->begin_main_frame_to_commit_duration_ = fast_duration;
+  client->commit_to_activate_duration_ = fast_duration;
+  client->draw_duration_ = fast_duration;
+
+  // Now that both threads are in a high latency mode, make sure we
+  // skip the BeginMainFrame, then the BeginImplFrame, but not both
+  // at the same time.
+
+  // Verify we skip BeginMainFrame first.
+  client->Reset();
+  EXPECT_TRUE(scheduler_->NeedsCommit());  // Previous commit still outstanding.
+  EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_TRUE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  SendNextBeginFrame();
+  task_runner().RunPendingTasks();  // Run posted deadline.
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_TRUE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  EXPECT_TRUE(client->HasAction("WillBeginImplFrame"));
+  EXPECT_FALSE(client->HasAction("ScheduledActionSendBeginMainFrame"));
+  EXPECT_TRUE(client->HasAction("ScheduledActionDrawAndSwapIfPossible"));
+
+  // Verify we skip the BeginImplFrame second.
+  client->Reset();
+  EXPECT_TRUE(scheduler_->NeedsCommit());  // Previous commit still outstanding.
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_TRUE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  SendNextBeginFrame();
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_TRUE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  scheduler_->DidSwapBuffersComplete();
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  EXPECT_FALSE(client->HasAction("WillBeginImplFrame"));
+  EXPECT_FALSE(client->HasAction("ScheduledActionSendBeginMainFrame"));
+  EXPECT_FALSE(client->HasAction("ScheduledActionDrawAndSwapIfPossible"));
+
+  // Then verify we operate in a low latency mode.
+  client->Reset();
+  EXPECT_TRUE(scheduler_->NeedsCommit());  // Previous commit still outstanding.
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  SendNextBeginFrame();
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  scheduler_->NotifyBeginMainFrameStarted();
+  scheduler_->NotifyReadyToCommit();
+  task_runner().RunPendingTasks();  // Run posted deadline.
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  scheduler_->DidSwapBuffersComplete();
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_FALSE(scheduler_->ImplThreadIsLikelyInHighLatencyMode());
+  EXPECT_TRUE(client->HasAction("WillBeginImplFrame"));
+  EXPECT_TRUE(client->HasAction("ScheduledActionSendBeginMainFrame"));
+  EXPECT_TRUE(client->HasAction("ScheduledActionDrawAndSwapIfPossible"));
+}
+
 TEST_F(SchedulerTest, PollForCommitCompletion) {
   // Since we are simulating a long commit, set up a client with draw duration
   // estimates that prevent skipping main frames to get to low latency mode.
-  SchedulerClientWithFixedEstimates* client =
-      new SchedulerClientWithFixedEstimates(
+  SchedulerClientWithCustomEstimates* client =
+      new SchedulerClientWithCustomEstimates(
           base::TimeDelta::FromMilliseconds(1),
           base::TimeDelta::FromMilliseconds(32),
           base::TimeDelta::FromMilliseconds(32));