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		     B O S T O N   U N I V E R S I T Y
                                       
			Computer Science Department
                                       
			    C O L L O Q U I U M
                                       
			Wednesday, January 15, 1997
                                       
				  3:00 pm
                                       
		 (Coffee served at 2:45 pm, Room MCS 137)

			       Room MCS 135

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	  OVERLOAD-TOLERANCE IN SAFETY-CRITICAL REAL-TIME SYSTEMS

			       Sanjoy Baruah
			Department of C.S. and E.E.
			      Votey Building
			   University of Vermont
			 Burlington, Vermont 05405


  Real-time computer systems are defined as those where the correctness of a
  computation depends upon both the result of the computation and the time at
  which this result is generated.  Given a real-time system with limited
  resources and various --- sometimes conflicting --- requests for the use of
  these resources, a scheduling algorithm determines how best to allocate the
  resources in order to optimize the overall performance of the system.
   
  We consider a model of real-time computation where, under ideal
  circumstances, every request ever made by every task will be completely
  satisfied. However, actual real-time systems do not always get to operate
  under ideal circumstances, and it may so happen that the amount of
  requested time exceeds the resource capacity.  The system is then said to
  be in overload.  We will present results which quantify exactly the
  performance limitations of on-line scheduling algorithms under conditions
  of overload.  We will argue that these limitations are unacceptable for
  very many actual applications, and suggest several methods for overcoming
  these limitations.
  
  (This research has been funded in part by the National Science Foundation,
  through Grants CCR-9410752 and CCR-9596282.)
  
Host: Prof. Azer Bestavros

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For colloquium info, including directions, see http://www.cs.bu.edu/colloquium
     For more information contact Prof. David Yates <djy@cs.bu.edu>
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