Support dynamic switching between integrated and discrete GPUs on Mac OS X.

content/common/gpu/gpu_channel.cc

Index: content/common/gpu/gpu_channel.cc
===================================================================
--- content/common/gpu/gpu_channel.cc	(revision 104937)
+++ content/common/gpu/gpu_channel.cc	(working copy)
@@ -37,6 +37,7 @@
       watchdog_(watchdog),
       software_(software),
       handle_messages_scheduled_(false),
+      num_contexts_preferring_discrete_gpu_(0),
       task_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
   DCHECK(gpu_channel_manager);
   DCHECK(renderer_id);
@@ -167,6 +168,8 @@
   content::GetContentClient()->SetActiveURL(init_params.active_url);
 
 #if defined(ENABLE_GPU)
+  WillCreateCommandBuffer(init_params.gpu_preference);
+
   GpuCommandBufferStub* share_group = stubs_.Lookup(init_params.share_group_id);
 
   *route_id = GenerateRouteID();
@@ -178,6 +181,7 @@
       disallowed_features_,
       init_params.allowed_extensions,
       init_params.attribs,
+      init_params.gpu_preference,
       *route_id,
       renderer_id_,
       render_view_id,
@@ -213,6 +217,9 @@
     IPC_MESSAGE_HANDLER(GpuChannelMsg_CreateTransportTexture,
         OnCreateTransportTexture)
     IPC_MESSAGE_HANDLER(GpuChannelMsg_Echo, OnEcho);
+    IPC_MESSAGE_HANDLER_DELAY_REPLY(GpuChannelMsg_WillGpuSwitchOccur,
+                                    OnWillGpuSwitchOccur)
+    IPC_MESSAGE_HANDLER(GpuChannelMsg_CloseChannel, OnCloseChannel)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   DCHECK(handled) << msg.type();
@@ -271,6 +278,10 @@
   router_.RemoveRoute(route_id);
 }
 
+bool GpuChannel::ShouldPreferDiscreteGpu() const {
+  return num_contexts_preferring_discrete_gpu_ > 0;
+}
+
 void GpuChannel::OnInitialize(base::ProcessHandle renderer_process) {
   // Initialize should only happen once.
   DCHECK(!renderer_process_);
@@ -288,6 +299,8 @@
 
   content::GetContentClient()->SetActiveURL(init_params.active_url);
 #if defined(ENABLE_GPU)
+  WillCreateCommandBuffer(init_params.gpu_preference);
+
   GpuCommandBufferStub* share_group = stubs_.Lookup(init_params.share_group_id);
 
   route_id = GenerateRouteID();
@@ -300,6 +313,7 @@
       disallowed_features_,
       init_params.allowed_extensions,
       init_params.attribs,
+      init_params.gpu_preference,
       route_id,
       0, 0, watchdog_,
       software_));
@@ -323,12 +337,15 @@
   if (router_.ResolveRoute(route_id)) {
     GpuCommandBufferStub* stub = stubs_.Lookup(route_id);
     bool need_reschedule = (stub && !stub->IsScheduled());
+    gfx::GpuPreference gpu_preference =
+        stub ? stub->gpu_preference() : gfx::PreferIntegratedGpu;
     router_.RemoveRoute(route_id);
     stubs_.Remove(route_id);
     // In case the renderer is currently blocked waiting for a sync reply from
     // the stub, we need to make sure to reschedule the GpuChannel here.
     if (need_reschedule)
       OnScheduled();
+    DidDestroyCommandBuffer(gpu_preference);
   }
 #endif
 
@@ -359,6 +376,33 @@
   Send(new IPC::Message(message));
 }
 
+void GpuChannel::OnWillGpuSwitchOccur(bool is_creating_context,
+                                      gfx::GpuPreference gpu_preference,
+                                      IPC::Message* reply_message) {
+  TRACE_EVENT0("gpu", "GpuChannel::OnWillGpuSwitchOccur");
+
+  bool will_switch_occur = false;
+
+  if (gpu_preference == gfx::PreferDiscreteGpu &&
+      gfx::GLContext::SupportsDualGpus()) {
+    if (is_creating_context) {
+      will_switch_occur = !num_contexts_preferring_discrete_gpu_;
+    } else {
+      will_switch_occur = (num_contexts_preferring_discrete_gpu_ == 1);
+    }
+  }
+
+  GpuChannelMsg_WillGpuSwitchOccur::WriteReplyParams(
+      reply_message,
+      will_switch_occur);
+  Send(reply_message);
+}
+
+void GpuChannel::OnCloseChannel() {
+  gpu_channel_manager_->RemoveChannel(renderer_id_);
+  // At this point "this" is deleted!
+}
+
 bool GpuChannel::Init(base::MessageLoopProxy* io_message_loop,
                       base::WaitableEvent* shutdown_event) {
   // Check whether we're already initialized.
@@ -378,6 +422,16 @@
   return true;
 }
 
+void GpuChannel::WillCreateCommandBuffer(gfx::GpuPreference gpu_preference) {
+  if (gpu_preference == gfx::PreferDiscreteGpu)
+    ++num_contexts_preferring_discrete_gpu_;
+}
+
+void GpuChannel::DidDestroyCommandBuffer(gfx::GpuPreference gpu_preference) {
+  if (gpu_preference == gfx::PreferDiscreteGpu)
+    --num_contexts_preferring_discrete_gpu_;

[stuartmorgan, 2011/10/12 07:13:24]

Is it worth DCHECKING here that it's not negative?

[Ken Russell (switch to Gerrit), 2011/10/12 22:39:42]

Sure. Added.

+}
+
 std::string GpuChannel::GetChannelName() {
   return StringPrintf("%d.r%d.gpu", base::GetCurrentProcId(), renderer_id_);
 }