gpu: Reuse transfer buffers more aggresively

gpu/command_buffer/client/gles2_implementation.h

Index: gpu/command_buffer/client/gles2_implementation.h
diff --git a/gpu/command_buffer/client/gles2_implementation.h b/gpu/command_buffer/client/gles2_implementation.h
index 8a7ab68466d0f50bb11e6c5b86484f230f5e32d9..b1e9aab22a8a83cf766881dfd25cc80ac65684df 100644
--- a/gpu/command_buffer/client/gles2_implementation.h
+++ b/gpu/command_buffer/client/gles2_implementation.h
@@ -591,6 +591,43 @@ class GLES2_IMPL_EXPORT GLES2Implementation
 
   void OnSwapBuffersComplete();
 
+  // Remove the transfer buffer from the buffer tracker. For buffers used
+  // asynchronously the memory is free:ed if the upload has completed. For
+  // other buffers, the memory is either free:ed immediately or free:ed pending
+  // a token.
+  void RemoveTransferBuffer(BufferTracker::Buffer* buffer);
+
+  // Returns true if the async upload token has passed.
+  //
+  // NOTE: This will detect wrapped async tokens by checking if the most
+  // significant  bit of async token to check is 1 but the last read is 0, i.e.
+  // the uint32 wrapped.
+  bool HasAsyncUploadTokenPassed(uint32 token) const {
+    if (token <= async_upload_sync_->async_token)
+      return true;
+    if (token & 0x80000000 &&
+        !(async_upload_sync_->async_token & 0x80000000)) {

[piman, 2014/02/07 22:58:20]

Reading async_token twice seems race-prone, it could have changed between line
606 and 609.
Instead read it once and use that value twice.

[jadahl, 2014/02/08 09:18:25]

True. Good catch.

+      return true; // we wrapped
+    }
+    return false;
+  }
+
+  // Get the next async upload token.
+  uint32 NextAsyncUploadToken();
+
+  // Ensure that the shared memory used for synchronizing async upload tokens
+  // has been mapped.
+  //
+  // Returns false on error, true on success.
+  bool EnsureAsyncUploadSync();
+
+  // Checks the last read asynchronously upload token and frees any unmanaged
+  // transfer buffer that has its async token passed.
+  //
+  // If |wait| is true, poll until all unmanaged transfer buffers has been
+  // free:ed.
+  void PollAsyncUploads(bool wait);
+
   bool GetBoundPixelTransferBuffer(
       GLenum target, const char* function_name, GLuint* buffer_id);
   BufferTracker::Buffer* GetBoundPixelUnpackTransferBufferIfValid(
@@ -663,6 +700,18 @@ class GLES2_IMPL_EXPORT GLES2Implementation
   GLuint bound_pixel_pack_transfer_buffer_id_;
   GLuint bound_pixel_unpack_transfer_buffer_id_;
 
+  // The current asynchronous pixel buffer upload token.
+  uint32 async_upload_token_;
+
+  // The shared memory used for synchronizing asynchronous upload tokens.
+  AsyncUploadSync* async_upload_sync_;
+  int32 async_upload_sync_shm_id_;
+  unsigned int async_upload_sync_shm_offset_;
+
+  // Unmanaged pixel transfer buffer memory pending asynchronous upload token.
+  typedef std::list<std::pair<void*, uint32> > DetachedAsyncUploadMemoryList;
+  DetachedAsyncUploadMemoryList detached_async_upload_memory_;
+
   // Client side management for vertex array objects. Needed to correctly
   // track client side arrays.
   scoped_ptr<VertexArrayObjectManager> vertex_array_object_manager_;