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Scheduling Real-Time tasks on Symmetric Multiprocessor Platforms Real-Time Systems Laboratory RETIS Lab Marko Bertogna Research Area: Multiprocessor Systems.

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Presentation on theme: "Scheduling Real-Time tasks on Symmetric Multiprocessor Platforms Real-Time Systems Laboratory RETIS Lab Marko Bertogna Research Area: Multiprocessor Systems."— Presentation transcript:

1 Scheduling Real-Time tasks on Symmetric Multiprocessor Platforms Real-Time Systems Laboratory RETIS Lab Marko Bertogna Research Area: Multiprocessor Systems

2 Moore’s law effects 4004 8008 8080 8085 8086 286 386 486 Pentium P1 P2 P4 Pentium Tejas cancelled! P3 Hot-plate Nuclear Reactor STOP Clock speed limited to less than 4 GHz Leakage current intolerable @ 90nm Year Power density (W/cm 2 )

3 Motivations Improve computing performances at reasonable power consumption. Multiprocessor-based architectures: –High-level computing: Intel’s Pentium D, Core 2 Duo, Itanium and Xeon; AMD’s Opteron, Quad FX and Athlon64 X2; etc. –Embedded market: TI’s OMAP, NXP’s Nexperia, STM’s Nomadik, ARM’s MPCore, Sony-IBM- Toshiba’s Cell, and many others. How to program these devices?

4 Problems Extend OS capabilities to exploit parallel computation. Adapt classical RT scheduling analysis to multi- core platforms. Develop Real-Time Multi-Processor Operating Systems (MPRTOS). Provide efficient tests to check schedulability of Multiprocessor systems. Explore “global” scheduling solutions.

5 Global scheduling on SMP Single system-wide queue: Preemption and Migration. Load balancing. How to sort tasks in the ready queue? Preemptive EDF is optimal only for uniprocessors. Pfair is optimal for implicit deadline systems. CPU1 CPU2 CPU3        

6 T Multiprocessor scheduling anomalies Scheduling problem is in general NP-hard. Schedulability problem is as well NP-hard. Dhall’s effect significantly degrades perfromances of classical scheduling algorithms. Synchronous instant is not “critical”. Only sufficient schedulability conditions. DEADLINE MISS U tot 1

7 Main results Sufficient schedulability tests with (pseudo-) polynomial complexity for fixed and dynamic priority multiprocessor systems. Scheduling algorithms that provide better performances on a SMP platform with bounded number of preemptions/migrations. Strategies to derive timely characteristics of given task sets, like robustness, slack, sensitivity to dynamic load variations. General analysis that can be extended for every global scheduling algorithm.

8 Experimental results for EDF 2 processors Constrained deadlines 1.000.000 task sets generated Our test is constantly superior at all utilizations generated task sets our test Improvement over existing solutions Task set utilization

9 Experimental results for FP 2 processors Constrained deadlines 1.000.000 task sets generated Our test is constantly superior at all utilizations generated task sets our test improvement Task set utilization

10 Conclusions Multiprocessor Real-Time systems are a promising field to explore. Still few existing results far from tight conditions. We contributed filling this gap. Future work: –Find tighter schedulability tests. –Use our techniques to analyze the efficiency of other scheduling algorithms (EDZL, EDF-US, FP-DS, etc). –Take into account exclusive resources access. –Integrate into Resource Reservation framework.

11 Marko Bertogna PhD student marko@sssup.it Real-Time Systems Laboratory RETIS Lab Thank you


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