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 +95,13 @@
   parser_.reset();
 }
 
+#if defined(OS_MACOSX)
+namespace {
+const unsigned int kMaxOutstandingSwapBuffersCallsPerOnscreenContext = 1;
+const int64 kWaitingTimeForSwapBuffers = 1;  // ms
+}
+#endif
+
 void GPUProcessor::ProcessCommands() {
   CommandBuffer::State state = command_buffer_->GetState();
   if (state.error != error::kNoError)
@@ -102,6 +117,21 @@
 
   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) {
+    // Defer the processing of more commands.
+    MessageLoop::current()->PostDelayedTask(

[apatrick_chromium, 2010/11/24 23:56:09]

Rather than repeatedly poll for progress every 1ms, you could post the task to
continue processing this command buffer from the IPC message handler for the
SwapBuffers ack.

[Ken Russell (switch to Gerrit), 2010/11/25 01:02:08]

Thanks, this is an excellent suggestion and cleans up an area I was not
comfortable with. I've retested with this change.

+        FROM_HERE,
+        method_factory_.NewRunnableMethod(&GPUProcessor::ProcessCommands),
+        kWaitingTimeForSwapBuffers);
+    return;
+  }
+#endif
+
   int commands_processed = 0;
   while (commands_processed < commands_per_update_ && !parser_->IsEmpty()) {
     error::Error error = parser_->ProcessCommand();