Let GpuChannel handle deferred IPC messages of SwapBuffer in batch

content/common/gpu/gpu_channel.cc

Index: content/common/gpu/gpu_channel.cc
diff --git a/content/common/gpu/gpu_channel.cc b/content/common/gpu/gpu_channel.cc
index 0759e5d00f961569894377ec1e49bd3a7d2267fa..1e8e234547a4237f0b7953ba5a8559fae64e7535 100644
--- a/content/common/gpu/gpu_channel.cc
+++ b/content/common/gpu/gpu_channel.cc
@@ -662,12 +662,60 @@ bool GpuChannel::OnControlMessageReceived(const IPC::Message& msg) {
   return handled;
 }
 
+size_t GpuChannel::MatchSwapBufferMessagesPattern(
+    IPC::Message* current_message) {
+  DCHECK(current_message);
+  if (deferred_messages_.empty() || !current_message)
+    return 0;
+  // Only care about SetLatencyInfo and AsyncFlush message.
+  if (current_message->type() != GpuCommandBufferMsg_SetLatencyInfo::ID &&
+      current_message->type() != GpuCommandBufferMsg_AsyncFlush::ID)
+    return 0;
+
+  size_t index = 0;
+  int32 routing_id = current_message->routing_id();
+
+  // In case of the current message is SetLatencyInfo, we try to look ahead one
+  // more deferred messages.
+  IPC::Message *first_message = NULL;
+  IPC::Message *second_message = NULL;
+
+  // Fetch the first message and move index to point to the second message.
+  first_message = deferred_messages_[index++];
+
+  // If the current message is AsyncFlush, the expected message sequence for
+  // SwapBuffer should be AsyncFlush->Echo. We only try to match Echo message.
+  if (current_message->type() == GpuCommandBufferMsg_AsyncFlush::ID &&
+      first_message->type() == GpuCommandBufferMsg_Echo::ID &&
+      first_message->routing_id() == routing_id) {
+    return 1;
+  }
+
+  // If the current message is SetLatencyInfo, the expected message sequence
+  // for SwapBuffer should be SetLatencyInfo->AsyncFlush->Echo (optional).
+  if (current_message->type() == GpuCommandBufferMsg_SetLatencyInfo::ID &&
+      first_message->type() == GpuCommandBufferMsg_AsyncFlush::ID &&
+      first_message->routing_id() == routing_id) {
+    if (deferred_messages_.size() >= 2)
+      second_message = deferred_messages_[index];
+    if (!second_message)
+      return 1;
+    if (second_message->type() == GpuCommandBufferMsg_Echo::ID &&
+        second_message->routing_id() == routing_id) {
+      return 2;
+    }
+  }
+  // No matched message is found.
+  return 0;
+}
+
 void GpuChannel::HandleMessage() {
   handle_messages_scheduled_ = false;
   if (deferred_messages_.empty())
     return;
 
-  bool should_fast_track_ack = false;
+  size_t matched_messages_num = 0;
+  bool should_handle_swapbuffer_msgs_immediate = false;
   IPC::Message* m = deferred_messages_.front();
   GpuCommandBufferStub* stub = stubs_.Lookup(m->routing_id());
 
@@ -715,17 +763,30 @@ void GpuChannel::HandleMessage() {
     if (message_processed)
       MessageProcessed();
 
-    // We want the EchoACK following the SwapBuffers to be sent as close as
-    // possible, avoiding scheduling other channels in the meantime.
-    should_fast_track_ack = false;
-    if (!deferred_messages_.empty()) {
-      m = deferred_messages_.front();
-      stub = stubs_.Lookup(m->routing_id());
-      should_fast_track_ack =
-          (m->type() == GpuCommandBufferMsg_Echo::ID) &&
-          stub && stub->IsScheduled();
+    if (deferred_messages_.empty())
+      break;
+
+    // We process the pending messages immediately if these messages matches
+    // the pattern of SwapBuffers, for example, GLRenderer always issues
+    // SwapBuffers calls with a specifix IPC message patterns, for example,

[Ken Russell (switch to Gerrit), 2014/08/25 23:03:03]

typo: specific. Here and in CL description.

[Hongbo Min, 2014/08/26 11:37:00]

Done.

+    // it should be SetLatencyInfo->AsyncFlush->Echo sequence.
+    //
+    // Instead of posting a task to message loop, it could avoid the possibility
+    // of being blocked by other channels, and make SwapBuffers executed as soon
+    // as possible.
+    m = deferred_messages_.front();

[jbauman, 2014/08/26 00:00:43]

I think you could move these two lines to the beginning of the do while loop,
and then you wouldn't need to deal with "m" and "stub" down here.

[Hongbo Min, 2014/08/26 11:37:00]

Done.

+    stub = stubs_.Lookup(m->routing_id());
+    if (!should_handle_swapbuffer_msgs_immediate) {
+      // Start from the current processing message to match SwapBuffer pattern.
+      matched_messages_num = MatchSwapBufferMessagesPattern(message.get());
+      should_handle_swapbuffer_msgs_immediate =
+          matched_messages_num > 0 && stub && stub->IsScheduled();
+    } else {
+      --matched_messages_num;

[Ken Russell (switch to Gerrit), 2014/08/25 23:03:03]

Before this line, please DCHECK(matched_messages_num != 0).

[Hongbo Min, 2014/08/26 11:37:00]

Done.

+      if (!stub || !stub->IsScheduled() || matched_messages_num == 0)
+        should_handle_swapbuffer_msgs_immediate = false;
     }
-  } while (should_fast_track_ack);
+  } while (should_handle_swapbuffer_msgs_immediate);
 
   if (!deferred_messages_.empty()) {
     OnScheduled();