Add flow control between renderer and GPU processes, and, on Mac OS X,...

gpu/command_buffer/service/gpu_processor.cc

Index: gpu/command_buffer/service/gpu_processor.cc
===================================================================
--- gpu/command_buffer/service/gpu_processor.cc	(revision 67289)
+++ gpu/command_buffer/service/gpu_processor.cc	(working copy)
@@ -16,6 +16,10 @@
                            gles2::ContextGroup* group)
     : command_buffer_(command_buffer),
       commands_per_update_(100),
+#if defined(OS_MACOSX)
+      swap_buffers_count_(0),
+      acknowledged_swap_buffers_count_(0),
+#endif
       method_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
   DCHECK(command_buffer);
   decoder_.reset(gles2::GLES2Decoder::Create(group));
@@ -28,6 +32,10 @@
                            int commands_per_update)
     : command_buffer_(command_buffer),
       commands_per_update_(commands_per_update),
+#if defined(OS_MACOSX)
+      swap_buffers_count_(0),
+      acknowledged_swap_buffers_count_(0),
+#endif
       method_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
   DCHECK(command_buffer);
   decoder_.reset(decoder);
@@ -87,6 +95,12 @@
   parser_.reset();
 }
 
+#if defined(OS_MACOSX)
+namespace {
+const unsigned int kMaxOutstandingSwapBuffersCallsPerOnscreenContext = 1;
+}
+#endif
+
 void GPUProcessor::ProcessCommands() {
   CommandBuffer::State state = command_buffer_->GetState();
   if (state.error != error::kNoError)
@@ -102,6 +116,19 @@
 
   parser_->set_put(state.put_offset);
 
+#if defined(OS_MACOSX)
+  bool do_rate_limiting = surface_.get() != NULL;
+  // Don't swamp the browser process with SwapBuffers calls it can't handle.
+  if (do_rate_limiting &&
+      swap_buffers_count_ - acknowledged_swap_buffers_count_ >=
+      kMaxOutstandingSwapBuffersCallsPerOnscreenContext) {
+    // Stop doing work on this command buffer. In the GPU process,
+    // receipt of the GpuMsg_AcceleratedSurfaceBuffersSwappedACK
+    // message causes ProcessCommands to be scheduled again.
+    return;
+  }
+#endif
+
   int commands_processed = 0;
   while (commands_processed < commands_per_update_ && !parser_->IsEmpty()) {
     error::Error error = parser_->ProcessCommand();
@@ -115,12 +142,16 @@
   command_buffer_->SetGetOffset(static_cast<int32>(parser_->get()));
 
   if (!parser_->IsEmpty()) {
-    MessageLoop::current()->PostTask(
-        FROM_HERE,
-        method_factory_.NewRunnableMethod(&GPUProcessor::ProcessCommands));
+    ScheduleProcessCommands();
   }
 }
 
+void GPUProcessor::ScheduleProcessCommands() {
+  MessageLoop::current()->PostTask(
+      FROM_HERE,
+      method_factory_.NewRunnableMethod(&GPUProcessor::ProcessCommands));
+}
+
 Buffer GPUProcessor::GetSharedMemoryBuffer(int32 shm_id) {
   return command_buffer_->GetTransferBuffer(shm_id);
 }