使用D3D9绘制纹理

我想用D3D9绘制位图。我这里有代码，可以运行。它确实会画出盒子和图像，但当我只画盒子时，我的fps在60左右。当我取消注释绘制位图的代码时，我得到的fps在5-30之间，这是非常滞后的。我的代码有什么问题?

private void D3D9Render()
{
    do
    {
        Drawing.Device.Clear(D3D9.ClearFlags.Target, Color.FromArgb(0, 0, 0, 0), 1.0f, 0);
        Drawing.Device.BeginScene();
        Drawing.DrawText("Fps : " + Fps.CalculateFrameRate().ToString(), Drawing.Width - 72, 220, Color.White);
        Drawing.DrawBox(v.X, v.Y, 90, 7);
    /*
            Drawing.DrawTexture(new Bitmap("test.jpg"));
            Drawing.Sprite.Begin(D3D9.SpriteFlags.None);
            Drawing.Sprite.Draw(Drawing.Texture, Drawing.TextureSize,
            new Vector3(0, 0, 0),
            new Vector3(v.X-65, v.Y-55, v.Z), Color.White);
            Drawing.Sprite.End();
    */
        Drawing.Device.EndScene();
        Drawing.Device.Present();
    } while (true);
}

public static void DrawTexture(Bitmap image)
{
    Texture = new Texture(Device, image, Usage.None, Pool.Managed);
    using (Surface surface = Texture.GetSurfaceLevel(0))
    {
        SurfaceDescription surfaceDescription = surface.Description;
        TextureSize = new Rectangle(0, 0,
                          surfaceDescription.Width,
                          surfaceDescription.Height);
    }
}