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RETIS Lab
                  Real-Time Systems Laboratory




                   Research in
    Soft Real-Time and Virtual...
Introduction and motivations




Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna San...
Motivations

    General-Purpose Operating Systems
      Very effective for storing & managing multimedia contents

     ...
Motivations

    Overcoming limitations of a GPOS for multimedia
      Large buffers used to compensate unpredictability
...
Real-time theory

    Reservation-based scheduling: (Qi, Pi)
      “Qi time units guaranteed on a CPU every Pi time units...
Temporal Isolation

    Is needed despite blocks/unblocks
      Not only EDF scheduling
                                 ...
Temporal Isolation

    Is needed despite blocks/unblocks
      Not only EDF scheduling
                                 ...
Temporal Isolation

    Enforcement of temporal isolation
      Not only EDF scheduling
                                 ...
Temporal Isolation

    Enforcement of temporal isolation
      Once budget exhausted, delay to next activation period
  ...
Linux and T.I.

    Need for T.I. evident in mainline Linux
      A (buggy) real-time task can starve the entire OS
     ...
Making Linux a better place

               (for multimedia and soft real-time applications)




Tommaso Cucinotta – Real ...
Real-Time Scheduling in
                          Linux
    Linux
      Not a Hard Real-Time OS
      Monolithic structu...
Real-Time Scheduling in
                          Linux
    Research on Linux for Real-Time Systems
    at RETIS
      Ap...
Real-Time Schedulers
                           for Linux
    Resource reservation scheduling in Linux
      Adaptive Qua...
Adaptive Quality of Service
                Architecture for Linux




Tommaso Cucinotta – Real Time Systems Laboratory (R...
Framework for Real-time Embedded
                     Systems based on COntRacts

    Soft and hard real-time
    Support ...
Experimental results
                   (Pentium 4 @ 2GHz, Linux 2.6.29.1 + AQuoSA)


    Response-time CDF for the
    re...
Experimental results
                   (Pentium 4 @ 2GHz, Linux 2.6.29.1 + AQuoSA)


   Average normalized tardiness
   f...
Synchronization

    Bandwidth Inheritance (BWI / M-BWI)
      Deals with Priority Inversion in EDF scheduling
      Dea...
Adaptive Reservations




Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna
...
Need for adaptivity

    Computation times for decoding MPEG
    frames




    Scheduling error with an over-
    allocat...
Adaptive Reservations

    Feedback-based scheduling
      Sense: tracking of workload fluctuations
      Compute:
     ...
Adaptive Reservations

  Workload prediction
     Moving average
     Percentile estimation over moving window
     FIR...
Experimental results

    PMF of scheduling error with various budget
    control strategies




Tommaso Cucinotta – Real ...
Automatic identification of scheduling parameters




Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Su...
Automatic identification
                of scheduling parameters
    Recent developments in GPOS CPU scheduling
      Va...
Objectives
     We actually can
       allow (legacy) real-time periodic applications
       to benefit of real-time sch...
LFS++

                                                     Application
                                                  ...
Proposed approach

    Legacy Feedback Scheduling (LFS++)
      An appropriate tracing mechanism observes the

         a...
Proposed approach

Comprehensive view
   Application tracing
   Period estimation (events analysis)
   On-line WCET est...
Real-time theory

    Reservation-based scheduling: (Qi, Pi)
      “Qi time units guaranteed on CPU every Pi time units”
...
Real-time theory

What are the reservation
parameters needed for
correctly scheduling a real-
time periodic task with
assi...
Core problem

    How to detect the application period ?
      Of a legacy real-time application (no source-code
       a...
Period detection

  The tracer produces a sequence of time-stamps




  Time-stamps used to compute a Fourier-transform


...
Budget identification
  “Feedback-based scheduling” budget control loop




Tommaso Cucinotta – Real Time Systems Laborato...
Experimental results




Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna
 ...
Experimental results
    Set-up
      Linux 2.6.29, with an implementation of the CBS scheduler
      Feedback-schedulin...
Experimental results

    Using the correct reservation period is better




Tommaso Cucinotta – Real Time Systems Laborat...
Benefits for the application
                        (LFS++ improves over Linux)
    A/V desynchronisation in mplayer whil...
Benefits for the application
                        (LFS++ improves over Linux)

    CDF of response-times with a 80% loa...
Multiple LFS++ instances
    Frequency misdetection degree with other LFS++
    controllers already active
      New appl...
Precision of frequency
                           detector
  PMF of detected
  frequency when
  observation-time
  goes
  ...
Cost of tracing
    Tracing overhead
      When using strace: +5,51%
      When using qostrace: +2,69% (previous paper)
...
Cost of Fourier Transform

  Fourier Transform Overhead
     1ms to 25ms, depending on parameters (and accuracy)
     Li...
Research Activities at ReTiS




Real-Time Service-Oriented Architectures
     Virtualized Real-Time Multimedia




Tommas...
Introduction

Virtualization & real-time increasingly interesting
   Wide availability of broadband connections ==>
    s...
Introduction

Service-Oriented Architectures
   Promising approach to distributed computing
   Taking advantage from vir...
Problems

Issues in deploying RT SW Components in VMs
   Execution time
       Virtualisation overhead: intensive I/O on...
Problems

Issues in deploying RT SW Components in VMs
   Scheduling and timing
       Host scheduling algorithm and VM l...
Approach

Use of RR techniques for
scheduling multiple VMs
   Temporal isolation among
    VMs
   Deadline guarantees to...
Approach

Validation on modified Linux kernel
with SMP Resource Reservation Scheduler




    Tommaso Cucinotta – ReTiS La...
Experimental Results

SOA Scenario
   Response-times of Apache2 Web Server
       From unpredictable and highly variable...
Security for Embedded
               (and Real-Time) Systems
Real-Time and Security
   Temporal encapsulation as a securi...
Relevant Publications
                                 (from year 2009)
Journals
  A robust mechanism for adaptive schedu...
Relevant Publications
                                  (from year 2009)
Conferences/Workshops
  The Multiprocessor BandW...
S(o)OS

Service-Oriented Operating Systems – S(o)OS
   Focus on large-scale multi-cores of tomorrow
   Heterogeneous mul...
Thanks for your attention




                                  Questions ?

      http://retis.sssup.it/people/tommaso


...
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Research in Soft Real-Time and Virtualized Applications on Linux

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Research in Soft Real-Time and Virtualized Applications on Linux

  1. 1. RETIS Lab Real-Time Systems Laboratory Research in Soft Real-Time and Virtualized Applications on Linux Tommaso Cucinotta Real-Time Systems Lab (RETIS) Center for Excellence in Information, Communication and Perception Engineering (CEIICP) Scuola Superiore Sant'Anna, Pisa (Italy)
  2. 2. Introduction and motivations Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  3. 3. Motivations General-Purpose Operating Systems  Very effective for storing & managing multimedia contents  Designed for • average-case performance • serving applications on a best-effort basis  They are not the best candidate for serving real-time applications with tight timing constraints • nor for real-time multimedia Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  4. 4. Motivations Overcoming limitations of a GPOS for multimedia  Large buffers used to compensate unpredictability • ==> poor real-time interactivity and no low-latency multimedia  One-application one-system paradigm • For example, for low-latency real-time audio processing (jack), gaming, CD/DVD burning, plant control, etc...  POSIX real-time extensions • Priority-based, no temporal isolation • Not appropriate for deploying the multitude of (soft) real-time applications populating the systems of tomorrow Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  5. 5. Real-time theory Reservation-based scheduling: (Qi, Pi)  “Qi time units guaranteed on a CPU every Pi time units” (5, 9) ~88.9% t Overall Load (2, 6) t  Independently of how others behave (temporal isolation) Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  6. 6. Temporal Isolation Is needed despite blocks/unblocks  Not only EDF scheduling block unblock (5, 9) t deadline-miss (2, 6) t Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  7. 7. Temporal Isolation Is needed despite blocks/unblocks  Not only EDF scheduling block unblock (5, 9) t (2, 6) t See CBS “unblock rule” Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  8. 8. Temporal Isolation Enforcement of temporal isolation  Not only EDF scheduling bad job (5, 9) t deadline missed by good job (2, 6) t Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  9. 9. Temporal Isolation Enforcement of temporal isolation  Once budget exhausted, delay to next activation period Deadline missed bad job by bad job (5, 9) t (2, 6) t Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  10. 10. Linux and T.I. Need for T.I. evident in mainline Linux  A (buggy) real-time task can starve the entire OS  Real-time throttling prevents this to happen Real-Time Throttling  Different design principles • Priority-based scheduling • Constraints to “no more than Qi every system-wide P” • Behaves like “Deferrable Servers” Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  11. 11. Making Linux a better place (for multimedia and soft real-time applications) Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  12. 12. Real-Time Scheduling in Linux Linux  Not a Hard Real-Time OS  Monolithic structure • Device drivers may adversely affect responsiveness Advances in Linux temporal behavior (responsiv.)  Preemptability of kernel-space code  High-resolution timers  Increasing use of RCU primitives  Nearly complete support for POSIX real-time extensions • Sporadic Server is missing (!)  IRQ handlers as kernel threads (preempt-rt branch) Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  13. 13. Real-Time Scheduling in Linux Research on Linux for Real-Time Systems at RETIS  Applying techniques from Real-Time Systems to a GPOS  Improving responsiveness and stability of performance for time-sensitive applications  Investigating effectiveness of Adaptive Reservations  Synchronization protocols for real-time multimedia  Stabilising performance of virtualized applications  Isolating computing and I/O traffic for Virtual Machines  Effective exploitation of multi-cores in real-time systems  Programmability of multi-threaded, distributed, real-time applications (API) Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  14. 14. Real-Time Schedulers for Linux Resource reservation scheduling in Linux  Adaptive Quality of Service Architecture • Single-processor embedded systems • Multi-threaded applications  Hybrid Deadline/Priority Scheduler • Multi-processor systems • Multi-threaded virtualized applications  Partitioned/Global EDF Scheduler SCHED_DEADLINE • Multi-processor systems • Single-threaded control applications Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  15. 15. Adaptive Quality of Service Architecture for Linux Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  16. 16. Framework for Real-time Embedded Systems based on COntRacts Soft and hard real-time Support for CPU, disk, network Distributed real-time systems Portability across RTOSs Adaptive real-time systems Application-level QoS control QoS power-aware optimization Atomic negotiations http://www.frescor.org Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  17. 17. Experimental results (Pentium 4 @ 2GHz, Linux 2.6.29.1 + AQuoSA) Response-time CDF for the real-time task with the deadline shortest period under light load (48%) Response-time CDF for the real-time task with the deadline shortest period under heavy load (84%) Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  18. 18. Experimental results (Pentium 4 @ 2GHz, Linux 2.6.29.1 + AQuoSA) Average normalized tardiness for the real-time task with the shortest period, varying the number of real-time tasks in deadline the system. Maximum and 95th percentile of the normalized tardiness for the real-time task with the shortest period, varying the number of real-time tasks in the system. deadline Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  19. 19. Synchronization Bandwidth Inheritance (BWI / M-BWI)  Deals with Priority Inversion in EDF scheduling  Deadline inherited from lock owner Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  20. 20. Adaptive Reservations Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  21. 21. Need for adaptivity Computation times for decoding MPEG frames Scheduling error with an over- allocation of 30% over the average deadline deadline Scheduling error with allocation tuned on maximum Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  22. 22. Adaptive Reservations Feedback-based scheduling  Sense: tracking of workload fluctuations  Compute: • Prediction/estimation of workload for next period(s) • Compensation for possible current delays  Actuate: adapt the scheduling parameters (Qi, Pi) Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  23. 23. Adaptive Reservations Workload prediction  Moving average  Percentile estimation over moving window  FIR decorrelation + error estimation Budget controller  Target region around deadline  Stochastic approaches • Probability of deadline-miss • Optimum error/bandwidth trade-offs Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  24. 24. Experimental results PMF of scheduling error with various budget control strategies Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  25. 25. Automatic identification of scheduling parameters Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  26. 26. Automatic identification of scheduling parameters Recent developments in GPOS CPU scheduling  Various APIs for accessing the enhanced functionality • For example, the FRSH API • For example, the AquoSA API  They require modifications of the applications • at the source-code level  Can we provide real-time guarantees to unmodified applications ? • For example, for legacy multimedia applications ? • Or, simply because of no time to modify the applications Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  27. 27. Objectives We actually can  allow (legacy) real-time periodic applications  to benefit of real-time scheduling facilities increasingly available on a GPOS  without any change in the application source-code Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  28. 28. LFS++ Application Application Monitor Monitor Kernel Scheduling Scheduling Real-Time Real-Time Parameters Parameters Scheduler Scheduler Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  29. 29. Proposed approach Legacy Feedback Scheduling (LFS++)  An appropriate tracing mechanism observes the application, inferring main parameters affecting a (periodic) multimedia application temporal behaviour: • job execution time • period  Scheduling guarantees are automatically provisioned by the OS, according to proper scheduling parameters • Based on sound arguments from real-time theory Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  30. 30. Proposed approach Comprehensive view  Application tracing  Period estimation (events analysis)  On-line WCET estimation  Automagic provisioning of scheduling guarantees Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  31. 31. Real-time theory Reservation-based scheduling: (Qi, Pi)  “Qi time units guaranteed on CPU every Pi time units” (5, 9) t (2, 6) Real-time throttling on Linux is different  Only constraint to “no more than Qi every system-wide P” Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  32. 32. Real-time theory What are the reservation parameters needed for correctly scheduling a real- time periodic task with assigned WCET and period ? The minimum reservation utilization is achieved  when the reservation period equals the task period • or any integer sub- multiple Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  33. 33. Core problem How to detect the application period ?  Of a legacy real-time application (no source-code availability, no modifications) Proposed approach  Tracing the application behaviour at run-time  For the purpose of identifying “periodicity patterns” Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  34. 34. Period detection The tracer produces a sequence of time-stamps Time-stamps used to compute a Fourier-transform A heuristic catches the first harmonic Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  35. 35. Budget identification “Feedback-based scheduling” budget control loop Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  36. 36. Experimental results Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  37. 37. Experimental results Set-up  Linux 2.6.29, with an implementation of the CBS scheduler  Feedback-scheduling by means of AQuoSA  mplayer • modified to monitor the Inter-Frame Time (IFT) and  Application tracing by using qtrace (kernel-level) Validation metrics  Inter-Frame Time (for mplayer)  A/V desynchronisation (for mplayer)  Response-time (for synthetic application)  Allocated bandwidth on the Real-Time scheduler Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  38. 38. Experimental results Using the correct reservation period is better Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  39. 39. Benefits for the application (LFS++ improves over Linux) A/V desynchronisation in mplayer while starting the Eclipse IDE  90% reduction of the peak A/V desynchronisation Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  40. 40. Benefits for the application (LFS++ improves over Linux) CDF of response-times with a 80% loaded system  Using a synthetic real-time periodic application load Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  41. 41. Multiple LFS++ instances Frequency misdetection degree with other LFS++ controllers already active  New application runs without guarantees while traced Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  42. 42. Precision of frequency detector PMF of detected frequency when observation-time goes  From 0.2 ms  To 2 s Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  43. 43. Cost of tracing Tracing overhead  When using strace: +5,51%  When using qostrace: +2,69% (previous paper)  When usinig qtrace: +0.63% (kernel-level tracer) 88.57% overhead reduction with the custom tracer Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  44. 44. Cost of Fourier Transform Fourier Transform Overhead  1ms to 25ms, depending on parameters (and accuracy)  Linear in the observation-time and f parameter (as expected) Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore
  45. 45. Research Activities at ReTiS Real-Time Service-Oriented Architectures Virtualized Real-Time Multimedia Tommaso Cucinotta – ReTiS – CEIICP – Scuola Superiore Sant'Anna Tommaso Cucinotta – ReTiS Lab – Scuola Superiore Sant'Anna – Pisa – Italy 45
  46. 46. Introduction Virtualization & real-time increasingly interesting  Wide availability of broadband connections ==> shift in computing paradigms towards distributed computing  Not only remote storage and batch processing  But also remote processing for interactive applications  Examples  Virtual Reality with heavyweight physics simulations  Distributed editing of HD video (film post-production) Tommaso Cucinotta – ReTiS Lab – Scuola Superiore Sant'Anna – Pisa – Italy 46
  47. 47. Introduction Service-Oriented Architectures  Promising approach to distributed computing  Taking advantage from virtualization techniques:  Location independence  Security  Fault-Tolerance  Distributed Interactive/Real-Time Applications may benefit from SOA design Tommaso Cucinotta – ReTiS Lab – Scuola Superiore Sant'Anna – Pisa – Italy 47
  48. 48. Problems Issues in deploying RT SW Components in VMs  Execution time  Virtualisation overhead: intensive I/O on virtualised peripherals  Benchmarking  A VM may be deployed on different HW (SOA scenario) – How to achieve predictable performance ?  VMs may be deployed on General-Purpose HW (with cache) – How to account for HW-level interferences ? Tommaso Cucinotta – ReTiS Lab – Scuola Superiore Sant'Anna – Pisa – Italy 48
  49. 49. Problems Issues in deploying RT SW Components in VMs  Scheduling and timing  Host scheduling algorithm and VM layer impacts on the vision of time by guest OSes – Time granularity (for measuring time and setting timers) – Scheduling capabilities – Non-uniform progress-rate of applications  SMP-enabled guests – Spin-lock primitives assume release of locks within very short time-frames » What happens if the lock-owner VM is descheduled ?  Proper management of shared resources – What MP resource-sharing protocol is appropriate ? » Proper management of priority inversion » Reduced overheads (limited number of preemptions) » Run-time schedulability analysis and admission control Tommaso Cucinotta – ReTiS Lab – Scuola Superiore Sant'Anna – Pisa – Italy 49
  50. 50. Approach Use of RR techniques for scheduling multiple VMs  Temporal isolation among VMs  Deadline guarantees to tasks Hard Reservation within VMs  hierarchical scheduling Experimental set-up  VMs scheduled by a modified Linux kernel implementing resource reservations Tommaso Cucinotta – ReTiS Lab – Scuola Superiore Sant'Anna – Pisa – Italy 50
  51. 51. Approach Validation on modified Linux kernel with SMP Resource Reservation Scheduler Tommaso Cucinotta – ReTiS Lab – Scuola Superiore Sant'Anna – Pisa – Italy 51
  52. 52. Experimental Results SOA Scenario  Response-times of Apache2 Web Server  From unpredictable and highly variable  To predictable and very stable (low fluctuations) – At the cost of an increased minimum response-time Tommaso Cucinotta – ReTiS Lab – Scuola Superiore Sant'Anna – Pisa – Italy 52
  53. 53. Security for Embedded (and Real-Time) Systems Real-Time and Security  Temporal encapsulation as a security feature  Secure access to Real-Time scheduling services by unprivileged applications  Optimum trade-offs between: Security, Quality of Service and Power Consumption Tommaso Cucinotta – ReTiS Lab – Scuola Superiore Sant'Anna – Pisa – Italy 53
  54. 54. Relevant Publications (from year 2009) Journals  A robust mechanism for adaptive scheduling of multimedia applications, Tommaso Cucinotta, Luca Abeni, Luigi Palopoli, Giuseppe Lipari, accepted on ACM Transactions on Embedded Computing Systems  QoS Control for Pipelines of Tasks using Multiple Resources, Tommaso Cucinotta, Luigi Palopoli, IEEE Transactions on Computers, Vol. 53, No. 3, pp. 416--430, March 2010, IEEE Computer Society Digital Library  A Real-time Service-Oriented Architecture for Industrial Automation, Tommaso Cucinotta, Antonio Mancina, Gaetano F. Anastasi, Giuseppe Lipari, Leonardo Mangeruca, Roberto Checcozzo, Fulvio Rusinà, to appear on IEEE Transactions on Industrial Informatics, Aug 2009  AQuoSA - Adaptive Quality of Service Architecture, Luigi Palopoli, Tommaso Cucinotta, Luca Marzario, Giuseppe Lipari, Software: Practice and Experience, Vol. 39, No. 1, January 2009 Tommaso Cucinotta – ReTiS Lab – Scuola Superiore Sant'Anna – Pisa – Italy 54
  55. 55. Relevant Publications (from year 2009) Conferences/Workshops  The Multiprocessor BandWidth Inheritance Protocol, Dario Faggioli, Giuseppe Lipari, Tommaso Cucinotta, to appear at the 22nd Euromicro Conference on Real-Time Systems (ECRTS 2010), Bruxelles, July 2010  Self-tuning Schedulers for Legacy Real-Time Applications, Tommaso Cucinotta, Fabio Checconi, Luca Abeni, Luigi Palopoli, European Conference on Computer Systems (EuroSys 2010), Paris, April 2010  The Wizard of OS: a Heartbeat for Legacy Multimedia Applications, Tommaso Cucinotta, Luca Abeni, Luigi Palopoli, Fabio Checconi, 7th IEEE Workshop on Embedded Systems for Real-Time Multimedia, Grenoble (ESTIMedia 2009), Grenoble, October 2009  Multi-level feedback control for Quality of Service Management, Tommaso Cucinotta, Giuseppe Lipari, Luigi Palopoli, Luca Abeni, Rodrigo Santos, 14th IEEE International Conference on Emerging Technologies and Factory Automation (ETFA 2009), Mallorca, Spain, September 2009  Exception-Based Management of Timing Constraints Violations for Soft Real-Time Applications, Tommaso Cucinotta, Dario Faggioli, Alessandro Evangelista, 5th International Workshop on Operating Systems Platforms for Embedded Real-Time Applications (OSPERT 2009), Dublin, Ireland, June 2009  Hierarchical Multiprocessor CPU Reservations for the Linux Kernel, Fabio Checconi, Tommaso Cucinotta, Dario Faggioli, Giuseppe Lipari, 5th International Workshop on Operating Systems Platforms for Embedded Real-Time Applications (OSPERT 2009), Dublin, Ireland, June 2009  Real-time guarantees in flexible advance reservations, Kleopatra Kostanteli, Dimosthenis Kyriazis, Theodora Varvarigou, Tommaso Cucinotta, Gaetano Anastasi, 2nd IEEE International Workshop on Real- Time Service-Oriented Architecture and Applications (RTSOAA 2009), Seattle, Washington, July 2009  Respecting temporal constraints in virtualised services, Tommaso Cucinotta, Gaetano Anastasi, Luca Abeni, in Proceedings of the 2nd IEEE International Workshop on Real-Time Service-Oriented Architecture and Applications (RTSOAA 2009), Seattle, Washington, July 2009 Tommaso Cucinotta – ReTiS Lab – Scuola Superiore Sant'Anna – Pisa – Italy 55
  56. 56. S(o)OS Service-Oriented Operating Systems – S(o)OS  Focus on large-scale multi-cores of tomorrow  Heterogeneous multi-core systems  What OS model is appropriate ?  What kind of applications are expected ?  How to deploy heterogeneous workloads ?  How to program in such systems ?  How to mix H.P. with G.P. Computing ?  etc. Tommaso Cucinotta – ReTiS Lab – Scuola Superiore Sant'Anna – Pisa – Italy 56
  57. 57. Thanks for your attention Questions ? http://retis.sssup.it/people/tommaso Tommaso Cucinotta – Real Time Systems Laboratory (ReTiS) – Scuola Superiore Sant'Anna Sant’Anna © 2007 Scuola Superiore

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