cc: Adding BeginFrameTracker object and removing Now() from LTHI.

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"
@@ skipping 73 matching lines @@
       background_frame_source_(NULL),
       primary_frame_source_internal_(external_begin_frame_source.Pass()),
       background_frame_source_internal_(),
       vsync_observer_(NULL),
       settings_(scheduler_settings),
       client_(client),
       layer_tree_host_id_(layer_tree_host_id),
       task_runner_(task_runner),
       power_monitor_(power_monitor),
       begin_retro_frame_posted_(false),
+      begin_impl_frame_args_(BEGINFRAMETRACKER_FROM_HERE),
       state_machine_(scheduler_settings),
       inside_process_scheduled_actions_(false),
       inside_action_(SchedulerStateMachine::ACTION_NONE),
       weak_factory_(this) {
   TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("cc.debug.scheduler"),
                "Scheduler::Scheduler",
                "settings",
                settings_.AsValue());
   DCHECK(client_);
   DCHECK(!state_machine_.BeginFrameNeeded());
@@ skipping 183 matching lines @@
   state_machine_.DidCreateAndInitializeOutputSurface();
   ProcessScheduledActions();
 }
 
 void Scheduler::NotifyBeginMainFrameStarted() {
   TRACE_EVENT0("cc", "Scheduler::NotifyBeginMainFrameStarted");
   state_machine_.NotifyBeginMainFrameStarted();
 }
 
 base::TimeTicks Scheduler::AnticipatedDrawTime() const {
-  if (!frame_source_->NeedsBeginFrames() ||
-      begin_impl_frame_args_.interval <= base::TimeDelta())
+  if (!frame_source_->NeedsBeginFrames())
     return base::TimeTicks();
 
   base::TimeTicks now = Now();
-  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);
+  BeginFrameArgs args = begin_impl_frame_args_.Get();
+  base::TimeTicks timebase = std::max(args.frame_time, 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 begin_impl_frame_args_.frame_time;
+  return begin_impl_frame_args_.Get().frame_time;
 }
 
 void Scheduler::SetupNextBeginFrameIfNeeded() {
   if (!task_runner_.get())
     return;
 
   bool needs_begin_frame = state_machine_.BeginFrameNeeded();
 
   bool at_end_of_deadline =
       (state_machine_.begin_impl_frame_state() ==
@@ skipping 23 matching lines @@
 void Scheduler::SetupPollingMechanisms(bool needs_begin_frame) {
   bool needs_advance_commit_state_timer = false;
   // Setup PollForAnticipatedDrawTriggers if we need to monitor state but
   // 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_.SupportsProactiveBeginFrame());
     DCHECK(!needs_begin_frame);
     if (poll_for_draw_triggers_task_.IsCancelled()) {
       poll_for_draw_triggers_task_.Reset(poll_for_draw_triggers_closure_);
-      base::TimeDelta delay = begin_impl_frame_args_.IsValid()
-                                  ? begin_impl_frame_args_.interval
-                                  : BeginFrameArgs::DefaultInterval();
+      base::TimeDelta delay = begin_impl_frame_args_.Interval();
       task_runner_->PostDelayedTask(
           FROM_HERE, poll_for_draw_triggers_task_.callback(), delay);
     }
   } 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 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 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() &&
-        begin_impl_frame_args_.IsValid()) {
+        begin_impl_frame_args_.Get().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_);
       task_runner_->PostDelayedTask(FROM_HERE,
                                     advance_commit_state_task_.callback(),
-                                    begin_impl_frame_args_.interval * 2);
+                                    begin_impl_frame_args_.Interval() * 2);
     }
   } else {
     advance_commit_state_task_.Cancel();
   }
 }
 
 // BeginFrame is the mechanism that tells us that now is a good time to start
 // making a frame. Usually this means that user input for the frame is complete.
 // If the scheduler is busy, we queue the BeginFrame to be handled later as
 // a BeginRetroFrame.
 bool Scheduler::OnBeginFrameMixInDelegate(const BeginFrameArgs& args) {
   TRACE_EVENT1("cc", "Scheduler::BeginFrame", "args", args.AsValue());
 
+  // Trace this begin frame time through the Chrome stack
+  TRACE_EVENT_FLOW_BEGIN0(
+      TRACE_DISABLED_BY_DEFAULT("cc.debug.scheduler.frames"), "BeginFrameArgs",

[brianderson, 2014/12/18 21:57:08]

Is this a new category? If so, are we cluttering the tracing dialog box? Should
we keep it with cc.debug.scheduler?

[mithro-old, 2014/12/18 23:15:05]

This category was added a while back after discussion with Sami showed the
traces in BeginFrameSource were adding about 10-15% overhead.

+      args.frame_time.ToInternalValue());
+
   // Deliver BeginFrames to children.
   if (settings_.forward_begin_frames_to_children &&
       state_machine_.children_need_begin_frames()) {
     BeginFrameArgs adjusted_args_for_children(args);
     // Adjust a deadline for child schedulers.
     // TODO(simonhong): Once we have commitless update, we can get rid of
     // BeginMainFrameToCommitDurationEstimate() +
     // CommitToActivateDurationEstimate().
     adjusted_args_for_children.deadline -=
         (client_->BeginMainFrameToCommitDurationEstimate() +
@@ skipping 130 matching lines @@
                main_thread_is_in_high_latency_mode);
   TRACE_COUNTER1(TRACE_DISABLED_BY_DEFAULT("cc.debug.scheduler"),
                  "MainThreadLatency",
                  main_thread_is_in_high_latency_mode);
   DCHECK_EQ(state_machine_.begin_impl_frame_state(),
             SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE);
   DCHECK(state_machine_.HasInitializedOutputSurface());
 
   advance_commit_state_task_.Cancel();
 
-  begin_impl_frame_args_ = args;
-  begin_impl_frame_args_.deadline -= client_->DrawDurationEstimate();
+  BeginFrameArgs adjusted_args = args;
+  adjusted_args.deadline -= client_->DrawDurationEstimate();
 
   if (!state_machine_.impl_latency_takes_priority() &&
       main_thread_is_in_high_latency_mode &&
       CanCommitAndActivateBeforeDeadline()) {
     state_machine_.SetSkipNextBeginMainFrameToReduceLatency();
   }
 
-  client_->WillBeginImplFrame(begin_impl_frame_args_);
-  state_machine_.OnBeginImplFrame(begin_impl_frame_args_);
+  begin_impl_frame_args_.Start(adjusted_args);
+  client_->WillBeginImplFrame(begin_impl_frame_args_.Get());
+  state_machine_.OnBeginImplFrame(begin_impl_frame_args_.Get());
   devtools_instrumentation::DidBeginFrame(layer_tree_host_id_);
 
   ProcessScheduledActions();
 
   state_machine_.OnBeginImplFrameDeadlinePending();
 
   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
@@ skipping 17 matching lines @@
 
   base::TimeTicks deadline;
   switch (begin_impl_frame_deadline_mode_) {
     case SchedulerStateMachine::BEGIN_IMPL_FRAME_DEADLINE_MODE_IMMEDIATE:
       // We are ready to draw a new active tree immediately.
       // We don't use Now() here because it's somewhat expensive to call.
       deadline = base::TimeTicks();
       break;
     case SchedulerStateMachine::BEGIN_IMPL_FRAME_DEADLINE_MODE_REGULAR:
       // We are animating on the impl thread but we can wait for some time.
-      deadline = begin_impl_frame_args_.deadline;
+      deadline = begin_impl_frame_args_.Get().deadline;
       break;
     case SchedulerStateMachine::BEGIN_IMPL_FRAME_DEADLINE_MODE_LATE:
       // We are blocked for one reason or another and we should wait.
       // TODO(brianderson): Handle long deadlines (that are past the next
       // frame's frame time) properly instead of using this hack.
-      deadline =
-          begin_impl_frame_args_.frame_time + begin_impl_frame_args_.interval;
+      deadline = begin_impl_frame_args_.Get().frame_time +
+                 begin_impl_frame_args_.Get().interval;
       break;
   }
 
   TRACE_EVENT1(
       "cc", "Scheduler::ScheduleBeginImplFrameDeadline", "deadline", deadline);
 
   base::TimeDelta delta = deadline - Now();
   if (delta <= base::TimeDelta())
     delta = base::TimeDelta();
   task_runner_->PostDelayedTask(
@@ skipping 21 matching lines @@
   // the deadline separately. For example:
   // * Sending the BeginMainFrame will not occur after the deadline in
   //     order to wait for more user-input before starting the next commit.
   // * Creating a new OuputSurface will not occur during the deadline in
   //     order to allow the state machine to "settle" first.
   state_machine_.OnBeginImplFrameDeadline();
   ProcessScheduledActions();
   state_machine_.OnBeginImplFrameIdle();
   ProcessScheduledActions();
 
+  begin_impl_frame_args_.Finish();

[brianderson, 2014/12/18 21:57:08]

I think there are various places outside of the deadline where it should be
valid to look at the begin_impl_frame_args_.

AnticipatedDrawTime might get updated in the polling mechanisms multiple times
after the deadline.  Also, AsValueInto might get called after the deadline.

[mithro-old, 2014/12/18 23:15:05]

As discuss, maybe we should add something like DangerousGetCurrentOrLast()
method for this case.
Yeah, I'm not sure what the correct solution there is. I have a work around
which seems to make the tests pass but the coverage here seems pretty poor.
I've already fixed AsValueInto in the latest patch.

   client_->DidBeginImplFrameDeadline();
 }
 
 void Scheduler::PollForAnticipatedDrawTriggers() {
   TRACE_EVENT0("cc", "Scheduler::PollForAnticipatedDrawTriggers");
   poll_for_draw_triggers_task_.Cancel();
   state_machine_.DidEnterPollForAnticipatedDrawTriggers();
   ProcessScheduledActions();
   state_machine_.DidLeavePollForAnticipatedDrawTriggers();
 }
@@ skipping 103 matching lines @@
                     frame_source_->NeedsBeginFrames());
   state->SetBoolean("begin_retro_frame_posted_", begin_retro_frame_posted_);
   state->SetInteger("begin_retro_frame_args_", begin_retro_frame_args_.size());
   state->SetBoolean("begin_impl_frame_deadline_task_",
                     !begin_impl_frame_deadline_task_.IsCancelled());
   state->SetBoolean("poll_for_draw_triggers_task_",
                     !poll_for_draw_triggers_task_.IsCancelled());
   state->SetBoolean("advance_commit_state_task_",
                     !advance_commit_state_task_.IsCancelled());
   state->BeginDictionary("begin_impl_frame_args");
-  begin_impl_frame_args_.AsValueInto(state);
+  begin_impl_frame_args_.Get().AsValueInto(state);
   state->EndDictionary();
 
   state->EndDictionary();
 
   state->BeginDictionary("client_state");
   state->SetDouble("draw_duration_estimate_ms",
                    client_->DrawDurationEstimate().InMillisecondsF());
   state->SetDouble(
       "begin_main_frame_to_commit_duration_estimate_ms",
       client_->BeginMainFrameToCommitDurationEstimate().InMillisecondsF());
   state->SetDouble(
       "commit_to_activate_duration_estimate_ms",
       client_->CommitToActivateDurationEstimate().InMillisecondsF());
   state->EndDictionary();
 }
 
 bool Scheduler::CanCommitAndActivateBeforeDeadline() const {
+  BeginFrameArgs args = begin_impl_frame_args_.Get();

[brianderson, 2014/12/18 21:57:08]

Can this be a reference?

[mithro-old, 2014/12/18 23:15:05]

Turns out this is location which needs the DangerousGetCurrentOrLast type
method.

[brianderson, 2014/12/19 01:18:25]

Yes, an "unsafe" or "dangerous" accessor would be nice.

[mithro-old, 2014/12/19 03:40:55]

Done.

+
   // Check if the main thread computation and commit can be finished before the
   // impl thread's deadline.
   base::TimeTicks estimated_draw_time =
-      begin_impl_frame_args_.frame_time +
-      client_->BeginMainFrameToCommitDurationEstimate() +
+      args.frame_time + client_->BeginMainFrameToCommitDurationEstimate() +
       client_->CommitToActivateDurationEstimate();
 
-  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",
-      AsValue());
+  TRACE_EVENT2(TRACE_DISABLED_BY_DEFAULT("cc.debug.scheduler"),
+               "CanCommitAndActivateBeforeDeadline",
+               "time_left_after_drawing_ms",
+               (args.deadline - estimated_draw_time).InMillisecondsF(), "state",
+               AsValue());
 
-  return estimated_draw_time < begin_impl_frame_args_.deadline;
+  return estimated_draw_time < 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