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Reconfigurable Real-Time Middleware for Distributed Cyber-Physical Systems with Aperiodic Events

Reconfigurable Real-Time Middleware for Distributed Cyber-Physical Systems with Aperiodic Events. Yuanfang Zhang, Christopher Gill, Chenyang Lu Department of Computer Science & Engineering. Motivation. Cyber-Physical Systems (CPS) require integrated design of computing & physical systems.

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Reconfigurable Real-Time Middleware for Distributed Cyber-Physical Systems with Aperiodic Events

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  1. Reconfigurable Real-Time Middleware for Distributed Cyber-Physical Systemswith Aperiodic Events Yuanfang Zhang, Christopher Gill, Chenyang Lu Department of Computer Science & Engineering

  2. Motivation • Cyber-Physical Systems (CPS) require integrated design of computing & physical systems. • Challenge: Diversity of CPS applications • Avionics, automobile, manufacturing, medical, power grid… • Different CPS applications need different middleware configurations. • Existing real-time middleware provides fixed sets of services. • Real-Time CORBA, Real-Time Java, CORBA Component Model. • Goal: reconfigurable middleware for diverse CPS applications. • Tailor middleware services to specific needs of a CPS application. • Facilitate integrated design of CPS.

  3. Outline • Middleware architecture • Alternative service strategies • encapsulated in configurable middleware components • Map CPS application characteristics to service strategies • supported by configuration tools • Implementation and empirical evaluation

  4. Gateway Gateway EC EC EC T1,3 T1,1 T1,2 Application Model • End-to-End Task Ti = chain of subtasks (Ti,1, Ti,2, …Ti,k) • Aperiodic or periodic • Subject to end-to-end deadline • Example: Subtask triggered by event from predecessor • Job: an instance of a task Application Processor 1 Application Processor 2 Application Processor 3 Real-time Event Service on CORBA

  5. Middleware Architecture Task manager • Admission Control (AC) • Load Balancing (LB) Application processors • Idle Resetting (IR) • Task Effector (TE) Task Manager LB Application Application AC Processor1 Processor 2 TE IR TE IR EC/ORB T1,1 T1,2 EC/ORB EC/ORB Application Application Application Processor 3 Processor 4 Processor 5 TE IR TE IR TE IR T1,1 T1,3 T1,2 EC/ORB EC/ORB EC/ORB

  6. Admission Control Strategies • Admission test based on aperiodic utilization bound [Abdelzaher04] • Guarantee end-to-end deadlines of admitted tasks/jobs. • AC per Task • Perform the admission test for an entire task when it arrives. • Reserve capacity for all jobs of an admitted task  no job skipping. • More pessimistic admission test. • Example: Digital control. • AC per Job • Perform the admission test for each job of a task. • No reservation for a task  may skip some jobs of a task. • Less pessimistic admission test. • Example: Non-critical image acquisition.

  7. Load Balancing Strategies • Redirect events to replicas located on least loaded processors • Light weight: No state synchronization among replicas. • LB per Task • The path of a task is determined upon arrival  same path for all jobs. • Achieve state persistency between jobs. • Less performance benefit. • Example: Integral control, video. • LB per Job • Different jobs may be redirected to different paths. • No state persistency between jobs. • More performance benefit • Example: Proportional control, image acquisition.

  8. CPS Applications  Services • Can tolerate job skipping? • Per Task AC (example: digital control) • Per Job AC (example: image acquisition) • Component Replication? • No load balancing • Load balancing • Require state persistency between jobs? • Per Job LB (example: Proportional control) • Per Task LB (example: Integral control)

  9. Configuration Space Admission Control • 15 valid configurations  difficult to configure manually! • Some combinations are invalid: Per Task AC/Per Job IR

  10. Configuration Tools • Input: Application characteristics. • Does your application allow job skipping? [yes (Y), no (N)] • Does your application have replicated components? [yes (Y), no (N)] • Does your application require state persistence? [yes (Y), no (N)] • Configuration Engine • Generate XML-based deployment plan • Avoid invalid combinations of strategies • Deployment Engine (DAnCE) [Deng07] executes deployment plan.

  11. <instance id="Central-AC"> ....... <configProperty> <name>LB_Strategy</name> <value> <type> <kind>tk_string</kind> </type> <value> <string>PT</string> </value> </value> </configProperty> Configuration

  12. Component Middleware • Based on CIAO 0.6 [Wang04], open-source implementation of Light Weight CORBA Component Model (CCM) specification. • Implemented real-time services as configurable components. • Supports real-time, aperiodic and periodic, end-to-end tasks.

  13. ron.cse Pentium4 2.80GHz 1G RAM 512KB cache KURT-Linux 2.4.22 hermoine.cse Pentium4 2.80GHz 1G RAM 512KB cache KURT-Linux 2.4.22 harry.cse Pentium4 2.53GHz 1G RAM 512KB cache KURT-Linux 2.4.22 norbert.cse Pentium4 2.53GHz 1G RAM 512KB cache KURT-Linux 2.4.22 100Mbps Ethernet switch angelina.doc Pentium4 3.40GHz 2G RAM 2048KB cache KURT-Linux 2.4.22 neville.doc Pentium4 3.40GHz 2G RAM 2048KB cache KURT-Linux 2.4.22 Experimental Platforms

  14. Imbalanced Workloads AC_IR_LB N: None T: Per Task J: Per Job Easy to generate different configurations. Middleware configurations have significant impact on real-time performance

  15. Conclusions • Configurable real-time middleware • Configuration tool maps application characteristics to middleware configurations • Components middleware implements configurable services • Facilitate integrated design of diverse CPS applications

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