Reland of cc: Remove frame queuing from the scheduler.

cc/scheduler/scheduler_state_machine.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_state_machine.h"
 
 #include "base/format_macros.h"
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 105 matching lines @@
     BeginMainFrameState state) {
   switch (state) {
     case BEGIN_MAIN_FRAME_STATE_IDLE:
       return "BEGIN_MAIN_FRAME_STATE_IDLE";
     case BEGIN_MAIN_FRAME_STATE_SENT:
       return "BEGIN_MAIN_FRAME_STATE_SENT";
     case BEGIN_MAIN_FRAME_STATE_STARTED:
       return "BEGIN_MAIN_FRAME_STATE_STARTED";
     case BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT:
       return "BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT";
-    case BEGIN_MAIN_FRAME_STATE_WAITING_FOR_ACTIVATION:

[brianderson, 2016/09/26 23:10:28]

Nice way to remove these states.

-      return "BEGIN_MAIN_FRAME_STATE_WAITING_FOR_ACTIVATION";
-    case BEGIN_MAIN_FRAME_STATE_WAITING_FOR_DRAW:
-      return "BEGIN_MAIN_FRAME_STATE_WAITING_FOR_DRAW";
   }
   NOTREACHED();
   return "???";
 }
 
 const char* SchedulerStateMachine::ForcedRedrawOnTimeoutStateToString(
     ForcedRedrawOnTimeoutState state) {
   switch (state) {
     case FORCED_REDRAW_STATE_IDLE:
       return "FORCED_REDRAW_STATE_IDLE";
@@ skipping 220 matching lines @@
 
   // Do not queue too many swaps.
   if (SwapThrottled())
     return false;
 
   // Except for the cases above, do not draw outside of the BeginImplFrame
   // deadline.
   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)
     return false;
 
+  // Wait for active tree to be rasterized before drawing in browser compositor.
+  if (wait_for_ready_to_draw_) {
+    DCHECK(settings_.commit_to_active_tree);
+    return false;
+  }
+
+  // Browser compositor commit steals any resources submitted in draw. Therefore
+  // drawing while a commit is pending is wasteful.
+  if (settings_.commit_to_active_tree && CommitPending())
+    return false;
+
   // Only handle forced redraws due to timeouts on the regular deadline.
   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
     return true;
 
   return needs_redraw_;
 }
 
 bool SchedulerStateMachine::ShouldActivatePendingTree() const {
   // There is nothing to activate.
   if (!has_pending_tree_)
@@ skipping 42 matching lines @@
   if (send_begin_main_frame_funnel_)
     return false;
 
   // Only send BeginMainFrame when there isn't another commit pending already.
   // Other parts of the state machine indirectly defer the BeginMainFrame
   // by transitioning to WAITING commit states rather than going
   // immediately to IDLE.
   if (begin_main_frame_state_ != BEGIN_MAIN_FRAME_STATE_IDLE)
     return false;
 
+  // MFBA is disabled and we are waiting for previous activation.
+  if (!settings_.main_frame_before_activation_enabled && has_pending_tree_)
+    return false;
+
+  // We are waiting for previous frame to be drawn, swapped and acked.
+  if (settings_.commit_to_active_tree &&
+      (active_tree_needs_first_draw_ || SwapThrottled())) {
+    return false;
+  }
+
   // Don't send BeginMainFrame early if we are prioritizing the active tree
   // because of ImplLatencyTakesPriority.
   if (ImplLatencyTakesPriority() &&
       (has_pending_tree_ || active_tree_needs_first_draw_)) {
     return false;
   }
 
   // We should not send BeginMainFrame while we are in the idle state since we
   // might have new user input arriving soon. It's okay to send BeginMainFrame
   // for the synchronous compositor because the main thread is always high
@@ skipping 35 matching lines @@
 bool SchedulerStateMachine::ShouldCommit() const {
   if (begin_main_frame_state_ != BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT)
     return false;
 
   // We must not finish the commit until the pending tree is free.
   if (has_pending_tree_) {
     DCHECK(settings_.main_frame_before_activation_enabled);
     return false;
   }
 
-  // If we only have an active tree, it is incorrect to replace it
-  // before we've drawn it.
+  // If we only have an active tree, it is incorrect to replace it before we've
+  // drawn it.
   DCHECK(!settings_.commit_to_active_tree || !active_tree_needs_first_draw_);
 
+  // In browser compositor commit reclaims any resources submitted during draw.
+  DCHECK(!settings_.commit_to_active_tree || !SwapThrottled());
+
   return true;
 }
 
 bool SchedulerStateMachine::ShouldPrepareTiles() const {
   // PrepareTiles only really needs to be called immediately after commit
   // and then periodically after that. Use a funnel to make sure we average
   // one PrepareTiles per BeginImplFrame in the long run.
   if (prepare_tiles_funnel_ > 0)
     return false;
 
@@ skipping 58 matching lines @@
   send_begin_main_frame_funnel_ = true;
   last_frame_number_begin_main_frame_sent_ = current_frame_number_;
 }
 
 void SchedulerStateMachine::WillCommit(bool commit_has_no_updates) {
   DCHECK(!has_pending_tree_ ||
          (settings_.main_frame_before_activation_enabled &&
           commit_has_no_updates));
   commit_count_++;
   last_commit_had_no_updates_ = commit_has_no_updates;
-
-  if (commit_has_no_updates || settings_.main_frame_before_activation_enabled) {
-    begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_IDLE;
-  } else {
-    begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_WAITING_FOR_ACTIVATION;
-  }
+  begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_IDLE;
 
   if (!commit_has_no_updates) {
     // Pending tree only exists if commit had updates.
     has_pending_tree_ = true;
     pending_tree_is_ready_for_activation_ = false;
     wait_for_ready_to_draw_ = settings_.commit_to_active_tree;
   }
 
   // Update state related to forced draws.
   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT) {
     forced_redraw_state_ = has_pending_tree_
                                ? FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION
                                : FORCED_REDRAW_STATE_WAITING_FOR_DRAW;
   }
 
   // Update the output surface state.
   if (compositor_frame_sink_state_ ==
       COMPOSITOR_FRAME_SINK_WAITING_FOR_FIRST_COMMIT) {
     compositor_frame_sink_state_ =
         has_pending_tree_ ? COMPOSITOR_FRAME_SINK_WAITING_FOR_FIRST_ACTIVATION
                           : COMPOSITOR_FRAME_SINK_ACTIVE;
   }
 }
 
 void SchedulerStateMachine::WillActivate() {
-  if (begin_main_frame_state_ ==
-      BEGIN_MAIN_FRAME_STATE_WAITING_FOR_ACTIVATION) {
-    begin_main_frame_state_ = settings_.commit_to_active_tree
-                                  ? BEGIN_MAIN_FRAME_STATE_WAITING_FOR_DRAW
-                                  : BEGIN_MAIN_FRAME_STATE_IDLE;
-  }
-
   if (compositor_frame_sink_state_ ==
       COMPOSITOR_FRAME_SINK_WAITING_FOR_FIRST_ACTIVATION)
     compositor_frame_sink_state_ = COMPOSITOR_FRAME_SINK_ACTIVE;
 
   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION)
     forced_redraw_state_ = FORCED_REDRAW_STATE_WAITING_FOR_DRAW;
 
   has_pending_tree_ = false;
   pending_tree_is_ready_for_activation_ = false;
   active_tree_needs_first_draw_ = true;
@@ skipping 12 matching lines @@
   // draw itself might request another draw.
   needs_redraw_ = false;
 
   draw_funnel_ = true;
   active_tree_needs_first_draw_ = false;
   did_draw_in_last_frame_ = true;
   last_frame_number_draw_performed_ = current_frame_number_;
 
   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
     forced_redraw_state_ = FORCED_REDRAW_STATE_IDLE;
-
-  if (begin_main_frame_state_ == BEGIN_MAIN_FRAME_STATE_WAITING_FOR_DRAW)
-    begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_IDLE;
 }
 
 void SchedulerStateMachine::DidDrawInternal(DrawResult draw_result) {
   switch (draw_result) {
     case INVALID_RESULT:
     case DRAW_ABORTED_CANT_DRAW:
     case DRAW_ABORTED_CONTEXT_LOST:
       NOTREACHED() << "Invalid return DrawResult:" << draw_result;
       break;
     case DRAW_ABORTED_DRAINING_PIPELINE:
@@ skipping 70 matching lines @@
   last_frame_number_invalidate_compositor_frame_sink_performed_ =
       current_frame_number_;
 
   // The synchronous compositor makes no guarantees about a draw coming in after
   // an invalidate so clear any flags that would cause the compositor's pipeline
   // to stall.
   active_tree_needs_first_draw_ = false;  // blocks commit if true
 }
 
 void SchedulerStateMachine::SetSkipNextBeginMainFrameToReduceLatency() {
-  TRACE_EVENT_INSTANT0("cc",
-                       "Scheduler: SkipNextBeginMainFrameToReduceLatency",
+  TRACE_EVENT_INSTANT0("cc", "Scheduler: SkipNextBeginMainFrameToReduceLatency",
                        TRACE_EVENT_SCOPE_THREAD);
   skip_next_begin_main_frame_to_reduce_latency_ = true;
 }
 
 bool SchedulerStateMachine::BeginFrameNeededForVideo() const {
   return video_needs_begin_frames_;
 }
 
 bool SchedulerStateMachine::BeginFrameNeeded() const {
   // We can't handle BeginFrames when output surface isn't initialized.
@@ skipping 121 matching lines @@
   // funnels so that we don't perform any actions that we shouldn't.
   if (!BeginFrameNeeded())
     send_begin_main_frame_funnel_ = true;
 }
 
 SchedulerStateMachine::BeginImplFrameDeadlineMode
 SchedulerStateMachine::CurrentBeginImplFrameDeadlineMode() const {
   if (settings_.using_synchronous_renderer_compositor) {
     // No deadline for synchronous compositor.
     return BEGIN_IMPL_FRAME_DEADLINE_MODE_NONE;
+  } else if (wait_for_ready_to_draw_) {
+    // In browser compositor, wait for active tree to be rasterized.
+    DCHECK(settings_.commit_to_active_tree);
+    return BEGIN_IMPL_FRAME_DEADLINE_MODE_BLOCKED_ON_READY_TO_DRAW;
   } else if (ShouldTriggerBeginImplFrameDeadlineImmediately()) {
     return BEGIN_IMPL_FRAME_DEADLINE_MODE_IMMEDIATE;
-  } else if (wait_for_ready_to_draw_) {
-    // When we are waiting for ready to draw signal, we do not wait to post a
-    // deadline yet.
-    return BEGIN_IMPL_FRAME_DEADLINE_MODE_BLOCKED_ON_READY_TO_DRAW;
   } else if (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 BEGIN_IMPL_FRAME_DEADLINE_MODE_REGULAR;
   } else {
     // The impl thread doesn't have anything it wants to draw and we are just
     // waiting for a new active tree. In short we are blocked.
     return BEGIN_IMPL_FRAME_DEADLINE_MODE_LATE;
   }
 }
 
 bool SchedulerStateMachine::ShouldTriggerBeginImplFrameDeadlineImmediately()
     const {
   // If we just forced activation, we should end the deadline right now.
   if (PendingActivationsShouldBeForced() && !has_pending_tree_)
     return true;
 
-  // Do not trigger deadline immediately if we're waiting for READY_TO_DRAW
-  // unless it's one of the forced cases.
-  if (wait_for_ready_to_draw_)
-    return false;
-
   // SwapAck throttle the deadline since we wont draw and swap anyway.
   if (SwapThrottled())
     return false;
 
   if (active_tree_needs_first_draw_)
     return true;
 
   if (!needs_redraw_)
     return false;
 
   // This is used to prioritize impl-thread draws when the main thread isn't
   // producing anything, e.g., after an aborted commit. We also check that we
   // don't have a pending tree -- otherwise we should give it a chance to
   // activate.
   // TODO(skyostil): Revisit this when we have more accurate deadline estimates.
-  if (begin_main_frame_state_ == BEGIN_MAIN_FRAME_STATE_IDLE &&
-      !has_pending_tree_)
+  if (!CommitPending() && !has_pending_tree_)
     return true;
 
   // Prioritize impl-thread draws in ImplLatencyTakesPriority mode.
   if (ImplLatencyTakesPriority())
     return true;
 
   return false;
 }
 
 bool SchedulerStateMachine::SwapThrottled() const {
@@ skipping 16 matching lines @@
 
 void SchedulerStateMachine::SetBeginFrameSourcePaused(bool paused) {
   begin_frame_source_paused_ = paused;
 }
 
 void SchedulerStateMachine::SetResourcelessSoftwareDraw(
     bool resourceless_draw) {
   resourceless_draw_ = resourceless_draw;
 }
 
-void SchedulerStateMachine::SetCanDraw(bool can_draw) { can_draw_ = can_draw; }
+void SchedulerStateMachine::SetCanDraw(bool can_draw) {
+  can_draw_ = can_draw;
+}
 
-void SchedulerStateMachine::SetNeedsRedraw() { needs_redraw_ = true; }
+void SchedulerStateMachine::SetNeedsRedraw() {
+  needs_redraw_ = true;
+}
 
 bool SchedulerStateMachine::OnlyImplSideUpdatesExpected() const {
   bool has_impl_updates = needs_redraw_ || needs_one_begin_impl_frame_;
   bool main_updates_expected =
       needs_begin_main_frame_ ||
       begin_main_frame_state_ != BEGIN_MAIN_FRAME_STATE_IDLE ||
       has_pending_tree_;
   return has_impl_updates && !main_updates_expected;
 }
 
@@ skipping 53 matching lines @@
 }
 
 void SchedulerStateMachine::SetNeedsOneBeginImplFrame() {
   needs_one_begin_impl_frame_ = true;
 }
 
 void SchedulerStateMachine::NotifyReadyToCommit() {
   DCHECK_EQ(begin_main_frame_state_, BEGIN_MAIN_FRAME_STATE_STARTED)
       << AsValue()->ToString();
   begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT;
-  // In commit_to_active_tree mode, commit should happen right after
-  // BeginFrame, meaning when this function is called, next action should be
-  // commit.
+  // In commit_to_active_tree mode, commit should happen right after BeginFrame,
+  // meaning when this function is called, next action should be commit.
   if (settings_.commit_to_active_tree)
     DCHECK(ShouldCommit());
 }
 
 void SchedulerStateMachine::BeginMainFrameAborted(CommitEarlyOutReason reason) {
   DCHECK_EQ(begin_main_frame_state_, BEGIN_MAIN_FRAME_STATE_STARTED);
 
   // If the main thread aborted, it doesn't matter if the  main thread missed
   // the last deadline since it didn't have an update anyway.
   main_thread_missed_last_deadline_ = false;
@@ skipping 65 matching lines @@
     case COMPOSITOR_FRAME_SINK_ACTIVE:
     case COMPOSITOR_FRAME_SINK_WAITING_FOR_FIRST_COMMIT:
     case COMPOSITOR_FRAME_SINK_WAITING_FOR_FIRST_ACTIVATION:
       return true;
   }
   NOTREACHED();
   return false;
 }
 
 }  // namespace cc