gpu: Reuse transfer buffers more aggresively

gpu/command_buffer/client/cmd_buffer_helper.cc

Index: gpu/command_buffer/client/cmd_buffer_helper.cc
diff --git a/gpu/command_buffer/client/cmd_buffer_helper.cc b/gpu/command_buffer/client/cmd_buffer_helper.cc
index 11219ede664751e3fa92a2dcc800388f8d4d3f5c..c383e15e1e7312e9c6309e4fbe81770fcbee70f3 100644
--- a/gpu/command_buffer/client/cmd_buffer_helper.cc
+++ b/gpu/command_buffer/client/cmd_buffer_helper.cc
@@ -25,6 +25,7 @@ CommandBufferHelper::CommandBufferHelper(CommandBuffer* command_buffer)
       entries_(NULL),
       total_entry_count_(0),
       token_(0),
+      async_token_(0),
       put_(0),
       last_put_sent_(0),
       commands_issued_(0),
@@ -191,6 +192,24 @@ void CommandBufferHelper::WaitForToken(int32 token) {
   }
 }
 
+uint32 CommandBufferHelper::InsertAsyncToken() {

[epenner, 2014/01/23 02:52:44]

Perhaps async token is meant to be more generic, but if it was
'async_upload_token', could we just use the async upload commands rather than
have a new command? 

If it is meant to be generic for other 'async things', it feels like we need an
indicator of what 'async thing' we are talking about, to be clear about who owns
the async_token and is allowed to change it. Perhaps there could be an enum of
async-token-types which currently only has ASYNC_TRANSFER?

+  AllocateRingBuffer();
+  if (!usable()) {
+    return async_token_;
+  }
+  DCHECK(HaveRingBuffer());
+
+  async_token_++;
+  if (async_token_ == 0)
+    async_token_++;
+
+  cmd::SetAsyncToken* cmd = GetCmdSpace<cmd::SetAsyncToken>();
+  if (cmd) {
+    cmd->Init(async_token_);
+  }
+  return async_token_;
+}
+
 // Waits for available entries, basically waiting until get >= put + count + 1.
 // It actually waits for contiguous entries, so it may need to wrap the buffer
 // around, adding a noops. Thus this function may change the value of put_. The