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Design and Analysis of Real-Time Software

Design and Analysis of Real-Time Software. RE al TI me S ystem Laboratory Scuola Superiore S.Anna G. Lipari E. Bini Ericsson Lab Italia C. Vitucci. Outline. Introduction to RT embedded systems characteristics problems state of the art RT system research at Retis Lab

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Design and Analysis of Real-Time Software

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  1. Design and Analysis of Real-Time Software REal TIme System Laboratory Scuola Superiore S.Anna G. Lipari E. Bini Ericsson Lab Italia C. Vitucci

  2. Outline • Introduction to RT embedded systems • characteristics • problems • state of the art • RT system research at Retis Lab • Goal of this research • Methodology • Phases

  3. Goal of this research • Methodology for the design and analysis of Real-Time Embedded applications to be used in all phases of development

  4. Starting Point • Real Time embedded applications • car controller • hand-held computers • cellular phone • next generation cellular phones (UMTS) • wearable computers • etc. • The target application • telecommunication control board

  5. RT embedded applications • Limited resources • memory • CPU speed • power consumption • Dedicated HW • Temporal constraints • Applications must react to external environment in a timely manner • Internal constraints (buffer size, interrupt handling, etc.)

  6. RT design and analysis • Support temporal determinism: • providing kernel-level services • priority-based schedulers • bounded delay on system calls • providing tools for off-line analysis • a tool for specification in a formal (or semi-formal) language • a tool for timing analysis • a tool for testing

  7. Application model • Application • on a single processor there are low-level control tasks (driver ATM etc.) and high-level control tasks (signaling) • need to verify the temporal constraints on every task/activity • A task can be activated • periodically (time driven) • by external events (event driven) • Tasks communicate through messages

  8. RTOS and HW • OSE Delta • currently used in Ericsson for developing software for RT embedded applications • based on a message passing communication mechanism • HW • usually, a single processor board • many different processor can be used • performance strongly depends on the HW

  9. Application model • Unit -> set of tasks HW

  10. Deadline = 150 msec HW Temporal constraints Period = 5 msec MIT = 10 msec

  11. State of the art • In the engineering practice • no a-priori timing analysis is done • low-level control tasks are directly coded in C or assembler • often, the code of high-level control tasks is automatically generated by tools that do not consider temporal constraints • temporal constraint are verified only during the testing phase

  12. State of the art • RT Analysis • RT research focused on time-driven control applications • schedulability conditions for periodic task sets • Few research papers on RT analysis of reactive (event driven) systems • Commercial tools: Time Wiz • Rate Monotonic analysis • non-std notation for specification

  13. State of the art: RT notations • Existing notations • HRT-HOOD (used in aerospace applications) • ROOM (from Object Time, now Rational Software) • Not suitable for our purposes • UML is a good candidate notation • A preliminary proposal to OMG for a standard RT extension to UML has been made in Aug. 2000 • proponents: TimeSys, I-Logix, Rational Software, etc. • http://www.omg.org/meetings/schedule/UML_Profile_for_Scheduling_RFP.html

  14. Problems • Few tools integrate specification and analysis • Time Wiz of TimeSys is one of the few • The greatest problem is to estimate the worst case computation time of every activity • strongly depends on the HW • existing tools cover a narrow range of HW configurations • There is the need for a tool that covers the entire development cycle • at design time, with a proper RT notation • after development, with a RT analysis

  15. Summary • Many different tools • for RT-analysis (Time Wiz) • for RT specification (Rational Rose RT) • for WCET analysis (VCC) • no easy-to-use off-the-shelf solution • there is the need to integrate different of technologies • specification of RT systems • RT analysis • WCET computation • etc.

  16. Research at Retis Lab • ASI project • Intecs • definition of a HRT-UML notation • enhancing UML-nice with RT-analysis • MADESS project • Parades, Magneti Marelli, ST microelectronics • RT kernel for embedded controllers with minimal memory requirements • RT kernel for multi-processor system-on-a-chip

  17. Goal of this research • A methodology for the design and analysis of RT embedded applications Code analizer Testing Specification (RT-UML) Code templates Implementation Consistency check RT analysis WCET

  18. Phases • Model of a OSE-Delta process • Mapping to the appropriate RT-UML notation • RT analysis on the model • consistency check • timing analysis • priority assignment • Integrating WCET computation

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