CELLS A Virtual Mobile Smartphone Architecture

Transcription

1 CELLS A Virtual Mobile Smartphone Architecture Jeremy Andrus, Christoffer Dall, Alexander Van t Hof, Oren Laadan, Jason Nieh Columbia University 23rd ACM Symposium on Operating Systems Principles, Cascais, Portugal, October 2011

2 Outline: Introduction Usage Model System Architecture Graphics Power Management Telephony Networking Experimental Results Conclusion Limitations

3 Introduction: Platform shifting from computers to smartphones Need of Virtualizing smartphones CELLS: lightweight virtualization architecture Work phone Personal phone

4 Basic Approach1: Server virtualization Bare-Metal Hypervisor OKL4 Microvisor Red Bend VLX Disadvantages: Single VP access No Simultaneous access Poor support

5 Basic Approach2: Desktop virtualization Hosted Hypervisor Host Kernel VMware MVP Disadvantages: Emulation overhead Multiple Kernels

6 Challenges: Device diversity: Cell Radio, GPU, Framebuffer, Binder IPC, Touchscreen, Accelerometer, pmem, Compass, Microphone, Headset, Power, Buttons, GPS, h.264 accel.,speakers, Camera(s). Mobile usage model Graphics- accelerated UI

7 Usage Model: CELLS Isolated virtual phones Foreground/Background model Switching of virtual phones Virtual phone creation deletion Virtual phone access rights No access VP no access to the GPS sensor Shared access Foreground VP with shared access to audio device allows Background VP to play music Exclusive access Secure VPs

8 Architecture: Lightweight OS virtualization for virtual phones isolation Single OS kernel Virtualizes identifiers, kernel interfaces and hardware resources Transparently remapping OS resource identifiers to virtual ones

9 Kernel-Level Device Virtualization: Device namespaces Hardware resource multiplexing and isolation Virtualize process identifiers Call back functions 3 methods I. Device driver wrapper II. III. Modify device sub system Event handlers Modify Device driver to be aware of name spaces

10 User-Level Device Virtualization: Name space proxy mechanisms Proprietary/entirely closed source Virtualize device configuration Kernel device namespaces export an interface to the root namespace through the /proc filesystem that is used to switch the foreground VP and set access permissions for devices. CellD also coordinates user space virtualization mechanisms such as the configuration of telephony and wireless networking

11 Graphics: Existed Approaches: 1. Single assignment 2. Emulated hardware Proposed approach: Mux_fb driver Independent Graphics context

12 Power Management: Frame buffer early suspend: Fbearlysuspend driver exportsts display device suspend and resume state into user space. Block all processes using display while display powered off/ redraws screen when powered on. Wake locks: Two states Active- locked Inactive- unlocked Created at compile time by kernel drivers or user space

13 Telephony: Radio stack virtualization RIL proxy CELLS own proxy RIL library by RILD RIL library + CELLD=RIL proxy Multiple phone numbers Pairing cells with VOIP service Single digit scheme Asterisk server

14 Networking: IEEE wireless LAN Virtualization of core network resource Unique wireless configuration management virtualization User level device namespace proxy RIL libraries CELLD

15 Experimental Results: Setup Devices: I. Google Nexus 1 Qualcomm 1 GHz QSD8250, Adreno 200 GPU,512 MB RAM II. Google Nexus S Samsung Hummingbird 1 GHzCortex A8, PowerVR GPU, 512 MB RAM Android Platform(any version) Five virtual phones

16 Experimental Results: Setup Benchmarks Used: I. Linpack - CPU II. Neocore - Graphics III. Quadrant - Storage IV. Sun Spider - Web browsing V. Custom WiFi Test - Networking

17 Results:

18 Results:

19 Conclusion: First complete OS virtualization for mobile devices. Device namespaces + Foreground/Background = Complete virtualization Less overhead No visible performance variation for benchmark configurations

20 Limitations: Service cost. No hardware virtualization support. Finding notifications from Background virtual phones while other virtual phone is on foreground.

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