gpu: Reuse transfer buffers more aggresively

gpu/command_buffer/service/command_buffer_service.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef GPU_COMMAND_BUFFER_SERVICE_COMMAND_BUFFER_SERVICE_H_
 #define GPU_COMMAND_BUFFER_SERVICE_COMMAND_BUFFER_SERVICE_H_
 
 #include "base/callback.h"
 #include "base/memory/shared_memory.h"
+#include "base/synchronization/lock.h"
 #include "gpu/command_buffer/common/command_buffer.h"
 #include "gpu/command_buffer/common/command_buffer_shared.h"
 
 namespace gpu {
 
 class TransferBufferManagerInterface;
 
 // An object that implements a shared memory command buffer and a synchronous
 // API to manage the put and get pointers.
 class GPU_EXPORT CommandBufferService : public CommandBuffer {
  public:
   typedef base::Callback<bool(int32)> GetBufferChangedCallback;
   explicit CommandBufferService(
       TransferBufferManagerInterface* transfer_buffer_manager);
   virtual ~CommandBufferService();
 
   // CommandBuffer implementation:
   virtual bool Initialize() OVERRIDE;
   virtual State GetState() OVERRIDE;
   virtual State GetLastState() OVERRIDE;
   virtual int32 GetLastToken() OVERRIDE;
   virtual void Flush(int32 put_offset) OVERRIDE;
   virtual State FlushSync(int32 put_offset, int32 last_known_get) OVERRIDE;
   virtual void SetGetBuffer(int32 transfer_buffer_id) OVERRIDE;
   virtual void SetGetOffset(int32 get_offset) OVERRIDE;
   virtual Buffer CreateTransferBuffer(size_t size, int32* id) OVERRIDE;
   virtual void DestroyTransferBuffer(int32 id) OVERRIDE;
   virtual Buffer GetTransferBuffer(int32 id) OVERRIDE;
   virtual void SetToken(int32 token) OVERRIDE;
+  virtual void SetAsyncToken(uint32 token) OVERRIDE;
   virtual void SetParseError(error::Error error) OVERRIDE;
   virtual void SetContextLostReason(error::ContextLostReason) OVERRIDE;
 
   // Sets a callback that is called whenever the put offset is changed. When
   // called with sync==true, the callback must not return until some progress
   // has been made (unless the command buffer is empty), i.e. the get offset
   // must have changed. It need not process the entire command buffer though.
   // This allows concurrency between the writer and the reader while giving the
   // writer a means of waiting for the reader to make some progress before
   // attempting to write more to the command buffer. Takes ownership of
@@ skipping 11 matching lines @@
   void UpdateState();
 
   // Register an existing shared memory object and get an ID that can be used
   // to identify it in the command buffer. Callee dups the handle until
   // DestroyTransferBuffer is called.
   bool RegisterTransferBuffer(int32 id,
                               base::SharedMemory* shared_memory,
                               size_t size);
 
  private:
+  State GetStateImpl();

[reveman, 2014/01/22 17:30:04]

Can you adjust the name of this so it's clear |lock_| must be acquired before
calling this function? Maybe GetStateImplWithLockAcquired().

+
   int32 ring_buffer_id_;
   Buffer ring_buffer_;
   scoped_ptr<base::SharedMemory> shared_state_shm_;
   CommandBufferSharedState* shared_state_;
   int32 num_entries_;
   int32 get_offset_;
   int32 put_offset_;
   base::Closure put_offset_change_callback_;
   GetBufferChangedCallback get_buffer_change_callback_;
   base::Closure parse_error_callback_;
   TransferBufferManagerInterface* transfer_buffer_manager_;
   int32 token_;
+  uint32 async_token_;
   uint32 generation_;
   error::Error error_;
   error::ContextLostReason context_lost_reason_;
+  base::Lock lock_;

[reveman, 2014/01/22 17:30:04]

Would be nice with a comment here describing what this lock is protecting.

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

I'm agreeing with Piman that a lock_ doesn't seem very nice here. It's primarily
just an ownership and/or lifetime thing right? Could clear ownership/lifetime of
the async-token relative to the transfer thread solve this? That might not be
trivial but I think it can be done without locks.

 
   DISALLOW_COPY_AND_ASSIGN(CommandBufferService);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_COMMAND_BUFFER_SERVICE_H_