cc: Handle retroactive BeginFrames in the Scheduler.

cc/scheduler/scheduler.cc

 // Copyright 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 "cc/scheduler/scheduler.h"
 
 #include <algorithm>
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "cc/debug/devtools_instrumentation.h"
 #include "cc/debug/traced_value.h"
 #include "ui/gfx/frame_time.h"
 
 namespace cc {
 
 Scheduler::Scheduler(
     SchedulerClient* client,
     const SchedulerSettings& scheduler_settings,
     int layer_tree_host_id,
     const scoped_refptr<base::SequencedTaskRunner>& impl_task_runner)
     : settings_(scheduler_settings),
       client_(client),
       layer_tree_host_id_(layer_tree_host_id),
       impl_task_runner_(impl_task_runner),
-      last_set_needs_begin_impl_frame_(false),
+      last_set_needs_begin_frame_(false),
+      begin_retro_frame_posted_(false),
       state_machine_(scheduler_settings),
       inside_process_scheduled_actions_(false),
       inside_action_(SchedulerStateMachine::ACTION_NONE),
       weak_factory_(this) {
   DCHECK(client_);
-  DCHECK(!state_machine_.BeginImplFrameNeeded());
+  DCHECK(!state_machine_.BeginFrameNeeded());
   if (settings_.main_frame_before_activation_enabled) {
     DCHECK(settings_.main_frame_before_draw_enabled);
   }
 
   begin_impl_frame_deadline_closure_ = base::Bind(
       &Scheduler::OnBeginImplFrameDeadline, weak_factory_.GetWeakPtr());
   poll_for_draw_triggers_closure_ = base::Bind(
       &Scheduler::PollForAnticipatedDrawTriggers, weak_factory_.GetWeakPtr());
   advance_commit_state_closure_ = base::Bind(
       &Scheduler::PollToAdvanceCommitState, weak_factory_.GetWeakPtr());
@@ skipping 73 matching lines @@
   ProcessScheduledActions();
 }
 
 void Scheduler::DidManageTiles() {
   state_machine_.DidManageTiles();
 }
 
 void Scheduler::DidLoseOutputSurface() {
   TRACE_EVENT0("cc", "Scheduler::DidLoseOutputSurface");
   state_machine_.DidLoseOutputSurface();
-  last_set_needs_begin_impl_frame_ = false;
+  last_set_needs_begin_frame_ = false;
+  begin_retro_frame_args_.clear();
   ProcessScheduledActions();
 }
 
 void Scheduler::DidCreateAndInitializeOutputSurface() {
   TRACE_EVENT0("cc", "Scheduler::DidCreateAndInitializeOutputSurface");
-  DCHECK(!last_set_needs_begin_impl_frame_);
+  DCHECK(!last_set_needs_begin_frame_);
   DCHECK(begin_impl_frame_deadline_task_.IsCancelled());
   state_machine_.DidCreateAndInitializeOutputSurface();
   ProcessScheduledActions();
 }
 
 void Scheduler::NotifyBeginMainFrameStarted() {
   TRACE_EVENT0("cc", "Scheduler::NotifyBeginMainFrameStarted");
   state_machine_.NotifyBeginMainFrameStarted();
 }
 
 base::TimeTicks Scheduler::AnticipatedDrawTime() const {
-  if (!last_set_needs_begin_impl_frame_ ||
-      last_begin_impl_frame_args_.interval <= base::TimeDelta())
+  if (!last_set_needs_begin_frame_ ||
+      begin_impl_frame_args_.interval <= base::TimeDelta())
     return base::TimeTicks();
 
   base::TimeTicks now = gfx::FrameTime::Now();
-  base::TimeTicks timebase = std::max(last_begin_impl_frame_args_.frame_time,
-                                      last_begin_impl_frame_args_.deadline);
-  int64 intervals =
-      1 + ((now - timebase) / last_begin_impl_frame_args_.interval);
-  return timebase + (last_begin_impl_frame_args_.interval * intervals);
+  base::TimeTicks timebase = std::max(begin_impl_frame_args_.frame_time,
+                                      begin_impl_frame_args_.deadline);
+  int64 intervals = 1 + ((now - timebase) / begin_impl_frame_args_.interval);
+  return timebase + (begin_impl_frame_args_.interval * intervals);
 }
 
 base::TimeTicks Scheduler::LastBeginImplFrameTime() {
-  return last_begin_impl_frame_args_.frame_time;
+  return begin_impl_frame_args_.frame_time;
 }
 
-void Scheduler::SetupNextBeginImplFrameIfNeeded() {
-  bool needs_begin_impl_frame =
-      state_machine_.BeginImplFrameNeeded();
+void Scheduler::SetupNextBeginFrameIfNeeded() {
+  bool needs_begin_frame = state_machine_.BeginFrameNeeded();
 
   bool at_end_of_deadline =
       state_machine_.begin_impl_frame_state() ==
           SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE;
 
-  bool should_call_set_needs_begin_impl_frame =
-      // Always request the BeginImplFrame immediately if it wasn't needed
-      // before.
-      (needs_begin_impl_frame && !last_set_needs_begin_impl_frame_) ||
-      // We always need to explicitly request our next BeginImplFrame.
+  bool should_call_set_needs_begin_frame =
+      // Always request the BeginFrame immediately if it wasn't needed before.
+      (needs_begin_frame && !last_set_needs_begin_frame_) ||
+      // We always need to explicitly request our next BeginFrame.
       at_end_of_deadline;
 
-  if (should_call_set_needs_begin_impl_frame) {
-    client_->SetNeedsBeginImplFrame(needs_begin_impl_frame);
-    last_set_needs_begin_impl_frame_ = needs_begin_impl_frame;
+  if (should_call_set_needs_begin_frame) {
+    client_->SetNeedsBeginFrame(needs_begin_frame);
+    last_set_needs_begin_frame_ = needs_begin_frame;
+  }
+
+  // Handle retroactive BeginFrames.
+  if (needs_begin_frame && !begin_retro_frame_posted_ &&

[Sami, 2014/04/03 15:55:58]

Not sure if you saw my earlier question: do we need to disable this for WebView?

[brianderson, 2014/04/03 16:36:17]

Yes, I need to disable this for WebView.

[brianderson, 2014/04/03 21:55:55]

Done.

+      !begin_retro_frame_args_.empty() &&
+      state_machine_.begin_impl_frame_state() ==
+          SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE) {
+    begin_retro_frame_posted_ = true;
+    impl_task_runner_->PostTask(
+        FROM_HERE,
+        base::Bind(&Scheduler::BeginRetroFrame, weak_factory_.GetWeakPtr()));

[Sami, 2014/04/03 15:55:58]

While we're at it should we make this a pre-created closure like the other ones?

[brianderson, 2014/04/03 16:36:17]

Oops. Yes.

[brianderson, 2014/04/03 21:55:55]

Done.

   }
 
   bool needs_advance_commit_state_timer = false;
   // Setup PollForAnticipatedDrawTriggers if we need to monitor state but
-  // aren't expecting any more BeginImplFrames. This should only be needed by
-  // the synchronous compositor when BeginImplFrameNeeded is false.
+  // aren't expecting any more BeginFrames. This should only be needed by
+  // the synchronous compositor when BeginFrameNeeded is false.
   if (state_machine_.ShouldPollForAnticipatedDrawTriggers()) {
-    DCHECK(!state_machine_.SupportsProactiveBeginImplFrame());
-    DCHECK(!needs_begin_impl_frame);
+    DCHECK(!state_machine_.SupportsProactiveBeginFrame());
+    DCHECK(!needs_begin_frame);
     if (poll_for_draw_triggers_task_.IsCancelled()) {
       poll_for_draw_triggers_task_.Reset(poll_for_draw_triggers_closure_);
       impl_task_runner_->PostDelayedTask(
           FROM_HERE,
           poll_for_draw_triggers_task_.callback(),
-          last_begin_impl_frame_args_.interval);
+          begin_impl_frame_args_.interval);
     }
   } else {
     poll_for_draw_triggers_task_.Cancel();
 
     // At this point we'd prefer to advance through the commit flow by
     // drawing a frame, however it's possible that the frame rate controller
-    // will not give us a BeginImplFrame until the commit completes.  See
+    // will not give us a BeginFrame until the commit completes.  See
     // crbug.com/317430 for an example of a swap ack being held on commit. Thus
     // we set a repeating timer to poll on ProcessScheduledActions until we
-    // successfully reach BeginImplFrame. Synchronous compositor does not use
+    // successfully reach BeginFrame. Synchronous compositor does not use
     // frame rate controller or have the circular wait in the bug.
     if (IsBeginMainFrameSentOrStarted() &&
         !settings_.using_synchronous_renderer_compositor) {
       needs_advance_commit_state_timer = true;
     }
   }
 
   if (needs_advance_commit_state_timer) {
     if (advance_commit_state_task_.IsCancelled() &&
-        last_begin_impl_frame_args_.IsValid()) {
+        begin_impl_frame_args_.IsValid()) {
       // Since we'd rather get a BeginImplFrame by the normal mechanism, we
       // set the interval to twice the interval from the previous frame.
       advance_commit_state_task_.Reset(advance_commit_state_closure_);
-      impl_task_runner_->PostDelayedTask(
-          FROM_HERE,
-          advance_commit_state_task_.callback(),
-          last_begin_impl_frame_args_.interval * 2);
+      impl_task_runner_->PostDelayedTask(FROM_HERE,
+                                         advance_commit_state_task_.callback(),
+                                         begin_impl_frame_args_.interval * 2);
     }
   } else {
     advance_commit_state_task_.Cancel();
   }
 }
 
+void Scheduler::BeginFrame(const BeginFrameArgs& args) {
+  if (last_set_needs_begin_frame_ && begin_retro_frame_args_.empty() &&
+      state_machine_.begin_impl_frame_state() ==
+          SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE) {
+    BeginImplFrame(args);
+  } else {
+    begin_retro_frame_args_.push_back(args);
+    TRACE_EVENT_INSTANT0(
+        "cc", "Scheduler::BeginFrame deferred", TRACE_EVENT_SCOPE_THREAD);
+  }
+}
+
+void Scheduler::BeginRetroFrame() {
+  TRACE_EVENT0("cc", "Scheduler::BeginRetroFrame");
+  DCHECK(!begin_retro_frame_args_.empty());

[Sami, 2014/04/03 15:55:58]

DCHECK(begin_retro_frame_posted_)?

[brianderson, 2014/04/03 16:36:17]

Good idea.

[brianderson, 2014/04/03 21:55:55]

Done.

+
+  // Discard expired BeginRetroFrames
+  base::TimeTicks now = gfx::FrameTime::Now();
+  while (!begin_retro_frame_args_.empty() &&
+         now >
+             AdjustedBeginImplFrameDeadline(begin_retro_frame_args_.front())) {

[Sami, 2014/04/03 15:55:58]

Side note: the client call to compute the estimated draw duration recomputes the
duration percentile from scratch every time from all the samples it has. We
might want to optimize it at some point.

[brianderson, 2014/04/03 16:36:17]

I will pull out the duration calculation.

[brianderson, 2014/04/03 21:55:55]

Done.

+    begin_retro_frame_args_.pop_front();
+  }
+
+  if (begin_retro_frame_args_.empty()) {
+    TRACE_EVENT_INSTANT0(
+        "cc", "Scheduler::BeginRetroFrames expired", TRACE_EVENT_SCOPE_THREAD);
+  } else {
+    BeginImplFrame(begin_retro_frame_args_.front());
+    begin_retro_frame_args_.pop_front();
+  }
+
+  begin_retro_frame_posted_ = false;
+}
+
 void Scheduler::BeginImplFrame(const BeginFrameArgs& args) {
   TRACE_EVENT0("cc", "Scheduler::BeginImplFrame");
   DCHECK(state_machine_.begin_impl_frame_state() ==
          SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE);
   DCHECK(state_machine_.HasInitializedOutputSurface());
 
   advance_commit_state_task_.Cancel();
 
-  last_begin_impl_frame_args_ = args;
-  last_begin_impl_frame_args_.deadline -= client_->DrawDurationEstimate();
-
   if (!state_machine_.smoothness_takes_priority() &&
       state_machine_.MainThreadIsInHighLatencyMode() &&
       CanCommitAndActivateBeforeDeadline()) {
     state_machine_.SetSkipNextBeginMainFrameToReduceLatency();
   }
 
-  state_machine_.OnBeginImplFrame(last_begin_impl_frame_args_);
+  begin_impl_frame_args_ = args;

[Sami, 2014/04/03 15:55:58]

Do we need to move this down for a particular reason? The skipping logic above
will use the previous frame's timings to skip in the current frame, which isn't
too bad but seems weird.

[brianderson, 2014/04/03 16:36:17]

Bad cherry-pick. Will move back up.

[brianderson, 2014/04/03 21:55:55]

Done.

+  begin_impl_frame_args_.deadline -= client_->DrawDurationEstimate();
+
+  client_->WillBeginImplFrame(begin_impl_frame_args_);
+  state_machine_.OnBeginImplFrame(begin_impl_frame_args_);
   devtools_instrumentation::DidBeginFrame(layer_tree_host_id_);
 
   ProcessScheduledActions();
 
   if (!state_machine_.HasInitializedOutputSurface())
     return;
 
   state_machine_.OnBeginImplFrameDeadlinePending();
-  base::TimeTicks adjusted_deadline = AdjustedBeginImplFrameDeadline();
-  ScheduleBeginImplFrameDeadline(adjusted_deadline);
+  ScheduleBeginImplFrameDeadline(AdjustedBeginImplFrameDeadline(args));
 }
 
-base::TimeTicks Scheduler::AdjustedBeginImplFrameDeadline() const {
+base::TimeTicks Scheduler::AdjustedBeginImplFrameDeadline(
+    const BeginFrameArgs& args) const {
   if (settings_.using_synchronous_renderer_compositor) {
     // The synchronous compositor needs to draw right away.
     return base::TimeTicks();
   } else if (state_machine_.ShouldTriggerBeginImplFrameDeadlineEarly()) {
     // We are ready to draw a new active tree immediately.
     return base::TimeTicks();
   } else if (state_machine_.needs_redraw()) {
     // We have an animation or fast input path on the impl thread that wants
     // to draw, so don't wait too long for a new active tree.
-    return last_begin_impl_frame_args_.deadline;
+    return args.deadline - client_->DrawDurationEstimate();
   } else {
     // The impl thread doesn't have anything it wants to draw and we are just
     // waiting for a new active tree, so post the deadline for the next
     // expected BeginImplFrame start. This allows us to draw immediately when
     // there is a new active tree, instead of waiting for the next
     // BeginImplFrame.
     // TODO(brianderson): Handle long deadlines (that are past the next frame's
     // frame time) properly instead of using this hack.
-    return last_begin_impl_frame_args_.frame_time +
-           last_begin_impl_frame_args_.interval;
+    return args.frame_time + args.interval;
   }
 }
 
 void Scheduler::ScheduleBeginImplFrameDeadline(base::TimeTicks deadline) {
   if (settings_.using_synchronous_renderer_compositor) {
     // The synchronous renderer compositor has to make its GL calls
     // within this call.
     // TODO(brianderson): Have the OutputSurface initiate the deadline tasks
     // so the sychronous renderer compositor can take advantage of splitting
     // up the BeginImplFrame and deadline as well.
@@ skipping 115 matching lines @@
         break;
       case SchedulerStateMachine::ACTION_ACQUIRE_LAYER_TEXTURES_FOR_MAIN_THREAD:
         client_->ScheduledActionAcquireLayerTexturesForMainThread();
         break;
       case SchedulerStateMachine::ACTION_MANAGE_TILES:
         client_->ScheduledActionManageTiles();
         break;
     }
   } while (action != SchedulerStateMachine::ACTION_NONE);
 
-  SetupNextBeginImplFrameIfNeeded();
+  SetupNextBeginFrameIfNeeded();
   client_->DidAnticipatedDrawTimeChange(AnticipatedDrawTime());
 
   if (state_machine_.ShouldTriggerBeginImplFrameDeadlineEarly()) {
     DCHECK(!settings_.using_synchronous_renderer_compositor);
     ScheduleBeginImplFrameDeadline(base::TimeTicks());
   }
 }
 
 bool Scheduler::WillDrawIfNeeded() const {
   return !state_machine_.PendingDrawsShouldBeAborted();
 }
 
 scoped_ptr<base::Value> Scheduler::StateAsValue() const {
   scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue);
   state->Set("state_machine", state_machine_.AsValue().release());
 
   scoped_ptr<base::DictionaryValue> scheduler_state(new base::DictionaryValue);
   scheduler_state->SetDouble(
       "time_until_anticipated_draw_time_ms",
       (AnticipatedDrawTime() - base::TimeTicks::Now()).InMillisecondsF());
-  scheduler_state->SetBoolean("last_set_needs_begin_impl_frame_",
-                              last_set_needs_begin_impl_frame_);
+  scheduler_state->SetBoolean("last_set_needs_begin_frame_",
+                              last_set_needs_begin_frame_);
   scheduler_state->SetBoolean("begin_impl_frame_deadline_task_",
                               !begin_impl_frame_deadline_task_.IsCancelled());
   scheduler_state->SetBoolean("poll_for_draw_triggers_task_",
                               !poll_for_draw_triggers_task_.IsCancelled());
   scheduler_state->SetBoolean("advance_commit_state_task_",
                               !advance_commit_state_task_.IsCancelled());
   state->Set("scheduler_state", scheduler_state.release());
 
   scoped_ptr<base::DictionaryValue> client_state(new base::DictionaryValue);
   client_state->SetDouble("draw_duration_estimate_ms",
                           client_->DrawDurationEstimate().InMillisecondsF());
   client_state->SetDouble(
       "begin_main_frame_to_commit_duration_estimate_ms",
       client_->BeginMainFrameToCommitDurationEstimate().InMillisecondsF());
   client_state->SetDouble(
       "commit_to_activate_duration_estimate_ms",
       client_->CommitToActivateDurationEstimate().InMillisecondsF());
   state->Set("client_state", client_state.release());
   return state.PassAs<base::Value>();
 }
 
 bool Scheduler::CanCommitAndActivateBeforeDeadline() const {
   // Check if the main thread computation and commit can be finished before the
   // impl thread's deadline.
   base::TimeTicks estimated_draw_time =
-      last_begin_impl_frame_args_.frame_time +
+      begin_impl_frame_args_.frame_time +
       client_->BeginMainFrameToCommitDurationEstimate() +
       client_->CommitToActivateDurationEstimate();
 
-  TRACE_EVENT2(TRACE_DISABLED_BY_DEFAULT("cc.debug.scheduler"),
-               "CanCommitAndActivateBeforeDeadline",
-               "time_left_after_drawing_ms",
-               (last_begin_impl_frame_args_.deadline - estimated_draw_time)
-                   .InMillisecondsF(),
-               "state",
-               TracedValue::FromValue(StateAsValue().release()));
+  TRACE_EVENT2(
+      TRACE_DISABLED_BY_DEFAULT("cc.debug.scheduler"),
+      "CanCommitAndActivateBeforeDeadline",
+      "time_left_after_drawing_ms",
+      (begin_impl_frame_args_.deadline - estimated_draw_time).InMillisecondsF(),
+      "state",
+      TracedValue::FromValue(StateAsValue().release()));
 
-  return estimated_draw_time < last_begin_impl_frame_args_.deadline;
+  return estimated_draw_time < begin_impl_frame_args_.deadline;
 }
 
 bool Scheduler::IsBeginMainFrameSentOrStarted() const {
   return (state_machine_.commit_state() ==
               SchedulerStateMachine::COMMIT_STATE_BEGIN_MAIN_FRAME_SENT ||
           state_machine_.commit_state() ==
               SchedulerStateMachine::COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED);
 }
 
 }  // namespace cc