rio: a system solution to sharing i/o between mobile devices

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RIO: A SYSTEM SOLUTION FOR SHARING I/O BETWEEN MOBILE DEVICESARDALAN AMIRI SANI , KEVIN BOOS, MIN HONG YUN, AND LIN ZHONGMOBISYS 2014

Asami – Kawahara lab: Martin Axelsson (R)

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Motivation and Background

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Motivation and BackgroundI/O sharing, Why? Why Rio?

Three novel reasons◦ Different possible physical locations and orientations◦ Mobile systems can serve different users◦ System locked I/O Devices

Current Solutions’ limitations◦ Only support custom applications Does not support sharing device itself⇒◦ Does not expose full functionality ◦ I/O class specific Difficult to implement sharing for more I/O devices⇒

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ImplementationSplitstack-model

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ImplementationI/O stack split between systems ⇒ Problems!

Problems1. Process and driver reside separately in two systems2. Latency3. Unexpected disconnects may cause problems to the OS

Solution1. Cross-system mapping2. Reduce number of roundtrips 3. Clean up residuals of I/O and switch to local I/O

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ImplementationCross-system memory mapping

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ImplementationLatency reduction

Unoptimized Rio Optimized Rio

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ImplementationSafe disconnections

① Client stub transmits heart beat signal to server stub

② Server immediately transmits back acknowledgement.

③ If no acknowledgement 　⇒ Both trigger disconnection

Server:

④ Clean up residuals from disconnect(eg. Close_map handler for each mmapped are)

Client:

⑤ Clean up residuals from disconnect

⑥ Switch to local I/O device if present.

If not, return error messages.

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EvaluationCamera

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Related work Paradice: Paravirtualization of I/O devices at the device files Other I/O sharing : Remote file systems, network USB devices, wireless displays, remote printers and IP cameras. Con : I/O class specific

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ConclusionFuture use cases:Multi-user gaming, Music sharing, Multi-view video conferencing, Multi-camera

photography, “One SIM card,many systems”, etc.

Left to solveSupporting more classes of I/O devicesSupporting iOSInterface for sharing

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Thank you!

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