安装nvidia官方驱动后，xorg占用近50%CPU。

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VirtualBox 4.1.4 Oracle VM VirtualBox Extension Pack All platforms
Support for USB 2.0 devices, VirtualBox RDP and PXE boot for Intel cards. See this chapter from the User Manual for an introduction to this Extension Pack. The Extension Pack binaries are released under the VirtualBox Personal Use and Evaluation License (PUEL).
Please install the extension pack with the same version as your installed version of VirtualBox! If you are using VirtualBox 4.0.12, please download the extension pack here.