Use shared memory to update the renderer's view of the command buffer state.

content/common/gpu/client/command_buffer_proxy.cc

Index: content/common/gpu/client/command_buffer_proxy.cc
diff --git a/content/common/gpu/client/command_buffer_proxy.cc b/content/common/gpu/client/command_buffer_proxy.cc
index 1a25c1ab4f4df8c1e30639d6601bee816d209628..baa4b387bec3860eb206b7cc66c76966741e06d7 100644
--- a/content/common/gpu/client/command_buffer_proxy.cc
+++ b/content/common/gpu/client/command_buffer_proxy.cc
@@ -17,6 +17,7 @@
 #include "content/common/plugin_messages.h"
 #include "content/common/view_messages.h"
 #include "gpu/command_buffer/common/cmd_buffer_common.h"
+#include "gpu/command_buffer/common/command_buffer_shared.h"
 #include "ui/gfx/size.h"
 
 using gpu::Buffer;
@@ -43,7 +44,6 @@ CommandBufferProxy::~CommandBufferProxy() {
 bool CommandBufferProxy::OnMessageReceived(const IPC::Message& message) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(CommandBufferProxy, message)
-    IPC_MESSAGE_HANDLER(GpuCommandBufferMsg_UpdateState, OnUpdateState);
     IPC_MESSAGE_HANDLER(GpuCommandBufferMsg_Destroyed, OnDestroyed);
     IPC_MESSAGE_HANDLER(GpuCommandBufferMsg_NotifyRepaint,
                         OnNotifyRepaint);
@@ -111,6 +111,28 @@ bool CommandBufferProxy::Initialize() {
     return false;
   }
 
+  int32 state_buffer = CreateTransferBuffer(sizeof *shared_state_, -1);

[greggman, 2012/02/11 04:17:21]

Just asking but does this need to be a separate piece of shared memory? Maybe it
does because it's being setup before GLES2Implemenation but I thought I'd ask.

The GLES2Implementation allocations a chunk of shared memory and currently
reserves the first 64 bytes for "results". That is defined by
GLES2Implemetation:kStartingOffset, from 0 to starting offset is the results
buffer, after that is the command buffer.

Would it be possible to just increase that size for these values?

Allocating separate shared memory means another file descriptor in linux which
we ran out of once before. It also means all this extra setup and 2 more sync
IPCs to startup where as if you can just use the existing memory you don't need
this extra setup.

If that's possible, I believe you can just increase
GLES2Implementation:kStartingOffset.  You can either put the state at 64 bytes
in, or you can put it at 0 bytes in and make
GLES2Implementation::GetResultOffset return enough of an offset to skip the
state.

If not no biggy.

+
+  if (state_buffer == -1) {
+    LOG(ERROR) << "Failed to create shared state transfer buffer.";
+    return false;
+  }
+
+  gpu::Buffer buffer = GetTransferBuffer(state_buffer);
+  if (!buffer.ptr) {
+    LOG(ERROR) << "Failed to get shared state transfer buffer";
+    return false;
+  }
+
+  shared_state_ = reinterpret_cast<gpu::CommandBufferSharedState*>(buffer.ptr);
+  shared_state_->Initialize();
+
+  if (!Send(new GpuCommandBufferMsg_SetSharedStateBuffer(route_id_,

[apatrick_chromium, 2012/02/13 20:50:58]

Could this be sent over as another argument to GpuCommandBufferMsg_Initialize?

+                                                         state_buffer))) {
+    LOG(ERROR) << "Failed to initialize shared command buffer state.";
+    return false;
+  }
+
   return true;
 }
 
@@ -122,6 +144,7 @@ gpu::CommandBuffer::State CommandBufferProxy::GetState() {
       OnUpdateState(state);
   }
 
+  TryUpdateState();
   return last_state_;
 }
 
@@ -145,6 +168,7 @@ gpu::CommandBuffer::State CommandBufferProxy::FlushSync(int32 put_offset,
   TRACE_EVENT1("gpu", "CommandBufferProxy::FlushSync", "put_offset",
                put_offset);
   Flush(put_offset);
+  TryUpdateState();
   if (last_known_get == last_state_.get_offset) {
     // Send will flag state with lost context if IPC fails.
     if (last_state_.error == gpu::error::kNoError) {
@@ -153,6 +177,7 @@ gpu::CommandBuffer::State CommandBufferProxy::FlushSync(int32 put_offset,
                                                     &state)))
         OnUpdateState(state);
     }
+    TryUpdateState();
   }
 
   return last_state_;
@@ -413,3 +438,6 @@ void CommandBufferProxy::SetOnConsoleMessageCallback(
   console_message_callback_ = callback;
 }
 
+void CommandBufferProxy::TryUpdateState() {
+  shared_state_->Read(&last_state_);
+}