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Programmable Temporal Isolation for Real-Time Systems
Silviu Craciunas

Citation
Silviu Craciunas. "Programmable Temporal Isolation for Real-Time Systems". Talk or presentation, 30, November, 2010.

Abstract
We introduce a novel scheduling paradigm for hard real-time uniprocessor systems, called Variable-bandwidth Server (VBS), that enables adaptation of software processes to varying real-time constraints while maintaining temporal isolation. In the VBS process model, processes are sequences of individual actions with an action being a given piece of process code. Processes and actions are temporally isolated from one another in the sense that the variance in response times of the same action of a given process is bounded independently of any other concurrently running processes in the system. As the variance of action response times is also influenced by the scheduler overhead, we introduce a framework for overhead accounting in VBS-scheduled systems. Overhead introduced by the scheduling algorithm may be accounted for either by decreasing process execution speed to maintain CPU utilization, or by increasing CPU utilization to maintain process execution speed. Both methods can be combined by handling an arbitrary fraction of the total scheduler overhead with one method and the rest with the other. We also show that it is possible to reduce CPU power consumption with VBS by CPU voltage and frequency scaling. Scaling to lower frequencies is possible whenever there is CPU slack in the system. We propose a frequency-scaling VBS algorithm that exploits CPU slack to minimize operating frequencies with maximal CPU utilization while maintaining temporal isolation. This may lead to improvements in power consumption while hiding the real-time effects of frequency scaling. Additionally, we present more advanced methods with which additional power may be saved by redistributing computation time of individual process actions if the system has knowledge of future events.

Electronic downloads

Citation formats  
  • HTML
    Silviu Craciunas. <a
    href="http://chess.eecs.berkeley.edu/pubs/789.html"
    ><i>Programmable Temporal Isolation for Real-Time
    Systems</i></a>, Talk or presentation,  30,
    November, 2010.
  • Plain text
    Silviu Craciunas. "Programmable Temporal Isolation for
    Real-Time Systems". Talk or presentation,  30,
    November, 2010.
  • BibTeX
    @presentation{Craciunas10_ProgrammableTemporalIsolationForRealTimeSystems,
        author = {Silviu Craciunas},
        title = {Programmable Temporal Isolation for Real-Time
                  Systems},
        day = {30},
        month = {November},
        year = {2010},
        abstract = {We introduce a novel scheduling paradigm for hard
                  real-time uniprocessor systems, called
                  Variable-bandwidth Server (VBS), that enables
                  adaptation of software processes to varying
                  real-time constraints while maintaining temporal
                  isolation. In the VBS process model, processes are
                  sequences of individual actions with an action
                  being a given piece of process code. Processes and
                  actions are temporally isolated from one another
                  in the sense that the variance in response times
                  of the same action of a given process is bounded
                  independently of any other concurrently running
                  processes in the system. As the variance of action
                  response times is also influenced by the scheduler
                  overhead, we introduce a framework for overhead
                  accounting in VBS-scheduled systems. Overhead
                  introduced by the scheduling algorithm may be
                  accounted for either by decreasing process
                  execution speed to maintain CPU utilization, or by
                  increasing CPU utilization to maintain process
                  execution speed. Both methods can be combined by
                  handling an arbitrary fraction of the total
                  scheduler overhead with one method and the rest
                  with the other. We also show that it is possible
                  to reduce CPU power consumption with VBS by CPU
                  voltage and frequency scaling. Scaling to lower
                  frequencies is possible whenever there is CPU
                  slack in the system. We propose a
                  frequency-scaling VBS algorithm that exploits CPU
                  slack to minimize operating frequencies with
                  maximal CPU utilization while maintaining temporal
                  isolation. This may lead to improvements in power
                  consumption while hiding the real-time effects of
                  frequency scaling. Additionally, we present more
                  advanced methods with which additional power may
                  be saved by redistributing computation time of
                  individual process actions if the system has
                  knowledge of future events.},
        URL = {http://chess.eecs.berkeley.edu/pubs/789.html}
    }
    

Posted by Jan Reineke on 1 Dec 2010.
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