Total with children : 35.62%
Microsoft.DirectX.Direct3D.Device::Present()                         		00.02%        
	Microsoft.DirectX.Direct3D.Device::PresentInternal                   		35.52%


Total with children times : 27.84%
void Microsoft.DirectX.GraphicsStream::Write()                       		00.74%         
   static int32 Microsoft.DirectX.DXHelp::GetObjectSize(Object)         		10.47%
   static void Microsoft.DirectX.DXHelp::CopyObjectDataToPointer(Object,int)		16.52%
[/c#]

It means that more the 50% of my engine process time is used to do device.Present() and GraphicStream.Write() fonction.
Is it normal ?

The graphicStream is created with : 

vertexBuffer = new VertexBuffer(
                            BufVertexType,
                            BufferSize
                            device,
                            Usage.Dynamic|Usage.WriteOnly,
                            BufVertexFormat,
                            Pool.Default);

graphicStream = vertexBuffer.lock(0,0,LockFlags.Discard)