© 2013 IBM Corporation

Concierge: Bringing OSGi (Back) to Embedded Devices Jan S. Rellermeyer, IBM Research

Jan S. Rellermeyer

24 Sep 2013

Embedded Devices

Typically fixed-function devices

Limited user interface

ISA

OS

Software typically closely tied to the hardware

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Image: www.eeweb.com

Embedded Devices Are Evolving

We see a new class of embedded systems emerging

Advanced processors

Larger set of capabilities

Enhanced user interface / user experience

Open platforms for a software ecosystem

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Image: www.apple.com

Mobile Transforms Embedded Systems

Image: www.honeywell.com

Image: www.nest.com

Image: www.nikon.com

Image: www.apple.com

Continuous Platform Experience

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Cloud Softw

are Stack

Embedded Device Image: http://www.raspberrypi.org

ESSC

OSGi

Dynamic Module System for the Java Runtime

Original domain: Home Gateway – Multiple software packages need to co-exist on the same machine – Long-running software – Periodic maintenance and updates requires – Ideally with minimal downtime and no interruption of unrelated software packages

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• Java on the Embedded Device • Pros:

• bridges heterogeneity • can run the same code in the cloud or on the device

• Cons:

• updates and maintenance

Module Management

Traditional Java: The mystical class path

java –cp commons-X.jar:foo.jar:bar.jar my.application.MainClass

• Which module contains the main class? • What are the dependencies between foo.jar and bar.jar? • What happens if bar.jar is upgraded to bar-1.01.jar?

OSGi – Module Layer

Modules are called Bundles – JAR files with additional metadata

Runtime system: The Framework – Lifecycle management

Bundles implement isolation and locality

Interaction between bundles is limited – Shared code through package imports – Inter-bundle calls through services – Monitoring system state through events

The Lifecycle of a Bundle

Management: Install / Start / Stop / Uninstall bundles at runtime.

OSGi keeps track of dependencies

What happens if a Bundle is uninstalled?

From the OSGi Core Specifications

The OSGi Framework

OSGi Framework

Bundle A

Package 1Package 2Package 3

Bundle B

Package IPackage II

Exported Package Exported Package

Private Package

Import

Export-Package: Package 1 Export-Package: Package I, Package II

Import-Package: Package 1

• Packages can be versioned • OSGi encourages semantic versioning of bundles and packages

OSGi Services: Reducing Coupling

Modules allow for a compositional approach to building applications

But: Package dependencies are explicit. – Limits the modularity!

Solution: Services – Idea: Separate the interface from the implementation

Interface

Implementation

Module

Module Module Service Service

The Service Registry

The OSGi framework maintains a central service registry

Bundles can register their own services and retrieve services provided by other bundles

Services can be registered with a set of properties – Additional description of the service, can be used to model constraints or do

“best fit matching”

No runtime overhead for using services after lookup! Registry

OSGi Services

Composition at runtime

Loosely-coupled interaction through services

The system is dynamic

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Concierge

Question: What is the (minimum) overhead of OSGi?

My answer: Concierge – OSGi R3 core implementation developed during my PhD at ETH

Zurich – optimized for mobile and embedded devices, has a footprint of only

86kB – People found the source code readable and understandable: 7

Java classes + 7 inner classes.

[J.S. Rellermeyer and G. Alonso: Concierge – A Service Platform for Resource-Constrained Devices. In: EuroSys 2007].

Image: http://www.linksys.com

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Consistency across Platforms

iPAQ 3870 Linux Familiar 0.8 SA-1110 CPU 64 MB RAM SableVM

Zaurus 5500G Linux Embedix SA-1110 CPU 64 MB RAM Sun cvm

Nokia 9300i SymbianOS TI OMAP 1510 CPU 80 MB RAM IBM J9

iPAQ 5550 Windows Mobile PXA255 CPU 128 MB RAM IBM J9

LinkSys NSLU2 Unslung IXP420 CPU 32 MB RAM JamVM

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Performance influence of the final modifier

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Evaluation (Small Devices)

Example: The BUG Platform

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Embedded Linux Device

Runs Java (PhoneME) and OSGi

Pluggable hardware modules

Registers OSGi services

Applications are OSGi bundles

Image: http://www.buglabs.com

OSGi R3

OSGi R3: “unique” bundles and packages

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my.bundle.one my.bundle.two exports my.package

imports

OSGi R4

OSGi R4: multiple versions, class spaces

Fragments

Require-Bundle

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my.bundle.one 1.0 my.bundle.two exports my.package; version 1.0

imports

my.bundle.one 2.0 exports my.package; version 2.0

OSGi R5

OSGi R5: generic requirements and capabilities

Many hooks into the framework to manipulate the observed state

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my.bundle.one 1.0

my.bundle.two

Provide capability foo.bar{a=10, b=[1,2,3]}

Require capability foo.bar filter=(!(a>10))

Generic vs. Optimized

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Packages Bundles

Generic Capabilities

Concierge goes Eclipse

Targets:

Full OSGi core R5 compatibility

Keep a small footprint to work well on embedded devices – Currently < 350kB footprint

Remain “readable” – Currently 9 classes

Remain backwards-compatible

Being a sandbox for innovation around OSGi

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Image: http://www.eclipse.org

Demo

BeagleBone AM335x 720MHz ARM Cortex-A8

256MB DDR2 RAM

4GB microSD card

runs Angstrom Linux Distribution

Java SE Embedded 1.7.0_21-b11

Concierge R5 alpha

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Image: http://www.beaglebone.org

REST Interface

Designed for the cloud

Very useful for embedded systems as well Examples

– GET http://my_host/framework/bundles/representations – POST http://my_host/framework/bundles

– GET http://my_host/framework/bundle/5/state – GET http://my_host/framework/services/(objectClass=org.osgi.*)/representations/

This is work in progress (RFC 182)

http://www.osgi.org/download/osgi-early-draft-2013-03.pdf

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Location Transparency: Remote Service Invocation

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Juggle

Model critical functionality as services –Module with hardware-accelerated

service

–Co-Module with dynamically

accelerated service

“Juggle” with the accelerators

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Juggle Prototype System

Xilinx Virtex-II Pro

PPC 440 core, 300 MHz

256 MB DDR SRAM

Linux 2.6.35 (patched)

JVM –IcedTea Zero, IcedTea Cacao, or IBM J9

OSGi Framework – Concierge

Juggle – Adds support for loading and managing co-bundles – Manages the FPGA and the reprogramming

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Image: http://www.xilinx.com

Evaluation

PRR of about 16% of the chip real estate

Reprogramming time: 11 – 25 msec.

(Literature: max. 30 msec) Switching the socket bridge: 3 msec.

Initial load time for a hardware accelerated bundle: ~ 100 msec.

Initial load time for a co-bundle: < 1sec

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Evaluation: Triple-DES

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TDES with hardware acceleration

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