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17
On recent advances in time/utility function realtime scheduling and resource management
 In IEEE ISORC, pages 55 – 60
, 2005
"... We argue that the key underpinning of the current stateofthe realtime practice — the priority artifact — and that of the current stateofthe realtime art — deadlinebased timeliness optimality — are entirely inadequate for specifying timeliness objectives, for reasoning about timeliness behavior ..."
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Cited by 36 (11 self)
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We argue that the key underpinning of the current stateofthe realtime practice — the priority artifact — and that of the current stateofthe realtime art — deadlinebased timeliness optimality — are entirely inadequate for specifying timeliness objectives, for reasoning about timeliness behavior, and for performing resource management that can dependably satisfy timeliness objectives in many dynamic realtime systems. We argue that time/utility functions and the utility accrual scheduling paradigm provide a more generalized, adaptive, and flexible approach. Recent research in the utility accrual paradigm have significantly advanced the stateoftheart of that paradigm. We survey these advances. 1.
EnergyEfficient, Utility Accrual RealTime Scheduling Under the Unimodal Arbitrary Arrival Model
 in ACM Design, Automation, and Test in Europe (DATE
, 2005
"... We present an energyefficient realtime scheduling algorithm called EUA∗, for the unimodal arbitrary arrival model (or UAM). UAM embodies a “stronger ” adversary than most arrival models. The algorithm considers application activities that are subject to time/utility function time constraints, UAM, ..."
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Cited by 23 (5 self)
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We present an energyefficient realtime scheduling algorithm called EUA∗, for the unimodal arbitrary arrival model (or UAM). UAM embodies a “stronger ” adversary than most arrival models. The algorithm considers application activities that are subject to time/utility function time constraints, UAM, and the multicriteria scheduling objective of probabilistically satisfying utility lower bounds, and maximizing systemlevel energy efficiency. Since the scheduling problem is intractable, EUA ∗ allocates CPU cycles, scales clock frequency, and heuristically computes schedules using statistical estimates of cycle demands, in polynomialtime. We establish that EUA ∗ achieves optimal timeliness during underloads, and identify the conditions under which timeliness assurances hold. Our simulation experiments illustrate EUA∗’s superiority. 1.
Lockfree synchronization for dynamic embedded realtime software
 In ACM/IEEE Design, Automation, and Test in Europe (DATE
, 2006
"... We consider nonblocking synchronization for dynamic embedded realtime systems such as those that are subject to resource overloads and arbitrary activity arrivals. The multiwriter/multireader problem inherently occurs in such systems, when their activities must concurrently and mutually exclusiv ..."
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Cited by 10 (2 self)
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We consider nonblocking synchronization for dynamic embedded realtime systems such as those that are subject to resource overloads and arbitrary activity arrivals. The multiwriter/multireader problem inherently occurs in such systems, when their activities must concurrently and mutually exclusive share data objects. We consider lockfree synchronization for this problem under the unimodal arbitrary arrival model (or UAM). UAM embodies a “stronger” adversary than most traditional arrival models. We establish the fundamental tradeoffs between lockfree and lockbased object sharing under UAM — the first such result. Our tradeoffs include analytical conditions under which activities ’ accrued timeliness utility is greater under lockfree than lockbased, and the consequent upper bound on the increase in accrued utility. Our implementation experience on a POSIX RTOS reveals that the lockfree scheduling algorithm yields higher accrued utility, by as much as 65%, and critical time satisfactions, by as much as 80%, over lockbased. 1.
On multiprocessor utility accrual realtime scheduling with statistical timing assurances
 In IFIP Embedded and Ubiquitous Computing (EUC
, 2006
"... We present the first Utility Accrual (or UA) realtime scheduling algorithm for multiprocessors, called gMUA. The algorithm considers an application model where realtime activities are subject to time/utility function time constraints, variable execution time demands, and resource overloads where t ..."
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Cited by 9 (1 self)
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We present the first Utility Accrual (or UA) realtime scheduling algorithm for multiprocessors, called gMUA. The algorithm considers an application model where realtime activities are subject to time/utility function time constraints, variable execution time demands, and resource overloads where the total activity utilization demand exceeds the total capacity of all processors. We consider the scheduling objective of (1) probabilistically satisfying lower bounds on each activity’s maximum utility and (2) maximizing the systemwide, total accrued utility. We establish several properties of gMUA including optimal total utility (for a special case), conditions under which individual activity utility lower bounds are satisfied, a lower bound on systemwide total accrued utility, and bounded sensitivity for assurances to variations in execution time demand estimates. Our simulation experiments validate our analytical results and confirm the algorithm’s effectiveness and superiority.
On scheduling garbage collector in dynamic realtime systems with statistical timing assurances
 In IEEE ISORC
, 2006
"... We consider garbage collection (GC) in dynamic realtime systems. We consider the timebased GC approach of running the collector as a separate, concurrent thread, and focus on realtime scheduling to obtain assurances on mutator timing behavior, while ensuring that memory is never exhausted. We pre ..."
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Cited by 5 (1 self)
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We consider garbage collection (GC) in dynamic realtime systems. We consider the timebased GC approach of running the collector as a separate, concurrent thread, and focus on realtime scheduling to obtain assurances on mutator timing behavior, while ensuring that memory is never exhausted. We present a scheduling algorithm called GCUA. The algorithm considers mutator activities that are subject to time/utility function time constraints, variable execution time demands, the unimodal arbitrary arrival model that allows a strong adversary, and resource overloads. We establish several properties of GCUA including probabilisticallysatisfied utility lower bounds for each mutator activity, a lower bound on the systemwide total accrued utility, bounded sensitivity for the assurances to variations in mutator execution time demand estimates, and no memory exhaustion at all times. Our simulation experiments validate our analytical results and confirm the algorithm’s effectiveness and superiority. I.
Utility Accrual RealTime Scheduling Under Variable Cost Functions
, 2005
"... We present a utility accrual realtime scheduling algorithm called CICVCUA, for tasks whose execution times are functions of their starting times. We model such variable execution times employing variable cost functions (or VCFs). The algorithm considers application activities that are subject to t ..."
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Cited by 4 (0 self)
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We present a utility accrual realtime scheduling algorithm called CICVCUA, for tasks whose execution times are functions of their starting times. We model such variable execution times employing variable cost functions (or VCFs). The algorithm considers application activities that are subject to time/utility function time constraints (or TUFs), execution times described using VCFs, and concurrent, mutually exclusive sharing of nonCPU resources. We consider the multicriteria scheduling objective of (1) assuring that the maximum interval between any two consecutive, successful completions of jobs of a task must not exceed a specified upper bound, and (2) maximizing the system’s total accrued utility, while satisfying mutual exclusion resource constraints. Since the scheduling problem is intractable, CICVCUA statically computes worstcase sojourn times of tasks, selects tasks for execution based on their potential utility density, and completes them at specific times, in polynomialtime. We establish that CICVCUA achieves optimal timeliness during underloads. Further, we identify the conditions under which timeliness assurances hold. Our simulation experiments illustrate CICVCUA’s effectiveness and superiority. Acknowledgments
LWFG: A CacheAware Multicore RealTime Scheduling Algorithm
, 2012
"... As the number of processing cores contained in modern processors continues to increase, cache hierarchies are becoming more complex. This added complexity has the effect of increasing the potential cost of any cache misses on such architectures. When cache misses become more costly, minimizing them ..."
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Cited by 3 (0 self)
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As the number of processing cores contained in modern processors continues to increase, cache hierarchies are becoming more complex. This added complexity has the effect of increasing the potential cost of any cache misses on such architectures. When cache misses become more costly, minimizing them becomes even more important, particularly in terms of scalability concerns. In this thesis, we consider the problem of cacheaware realtime scheduling on multiprocessor systems. One avenue for improving realtime performance on multicore platforms is task partitioning. Partitioning schemes statically assign tasks to cores, eliminating task migrations and reducing system overheads. Unfortunately, no current partitioning schemes explicitly consider cache effects when partitioning tasks. We develop the LWFG (Largest Working set size First, Grouping) cacheaware partitioning algorithm, which seeks to schedule tasks which share memory with one another in such a way as to minimize the total number of cache misses. LWFG minimizes cache misses by partitioning tasks that share memory onto the same core and by distributing the system’s sum working set size as evenly as possible across the available cores.
Utility Accrual RealTime Scheduling and Synchronization on Single and Multiprocessors: Models, Algorithms, and Tradeoffs
, 2006
"... This dissertation presents a class of utility accrual scheduling and synchronization algorithms for dynamic, single and multiprocessor realtime systems. Dynamic realtime systems operate in environments with runtime uncertainties including those on activity execution times and arrival behaviors. ..."
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Cited by 2 (0 self)
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This dissertation presents a class of utility accrual scheduling and synchronization algorithms for dynamic, single and multiprocessor realtime systems. Dynamic realtime systems operate in environments with runtime uncertainties including those on activity execution times and arrival behaviors. We consider the time/utility function (or TUF) timing model for specifying application time constraints, and the utility accrual (or UA) timeliness optimality criteria of satisfying lower bounds on accrued activity utility, and maximizing the total accrued utility. Efficient TUF/UA scheduling algorithms exist for single processors—e.g., the Resourceconstrained Utility Accrual scheduling algorithm (RUA), and the Dependent Activity Scheduling Algorithm (DASA). However, they all use lockbased synchronization. To overcome shortcomings of lockbased (e.g., serialized object access, increased runtime overhead, deadlocks), we consider nonblocking synchronization including waitfree and lockfree synchronization. We present a bufferoptimal, schedulerindependent waitfree synchronization protocol (the first such), and develop waitfree versions of RUA and DASA. We also develop their lockfree versions, and upper bound their retries under the unimodal arbitrary arrival model. The tradeoff between waitfree, lockfree, and lockbased is fundamentally about their space and
Garbage Collector Scheduling in Dynamic, Multiprocessor RealTime Systems ∗
"... We present a garbage collector scheduling algorithm for dynamic multiprocessor realtime systems called GCMUA. The algorithm considers mutator activities that are subject to time/utility function time constraints, stochastic executiontime and memory demands, and overloads. We prove that GCMUA prob ..."
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We present a garbage collector scheduling algorithm for dynamic multiprocessor realtime systems called GCMUA. The algorithm considers mutator activities that are subject to time/utility function time constraints, stochastic executiontime and memory demands, and overloads. We prove that GCMUA probabilistically lower bounds each mutator’s accrued utility, lower bounds the total accrued utility, and upper bounds the assurances ’ sensitivity to variations in executiontime and memory demand estimates. Our simulation results confirm our analytical results. 1.
Utility Accrual RealTime Scheduling with Energy Bounds
"... In this paper, we consider timeliness and energy optimization in batterypowered, dynamic embedded realtime systems, which must remain functional during an operation/mission with a bounded energy budget. We consider application activities that are subject to time/utility function time constraints, ..."
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In this paper, we consider timeliness and energy optimization in batterypowered, dynamic embedded realtime systems, which must remain functional during an operation/mission with a bounded energy budget. We consider application activities that are subject to time/utility function time constraints, statistical assurance requirements on timeliness behavior, and an energy budget, which cannot be exceeded at runtime. To account for the inevitable variability in activity arrivals in dynamic systems, we describe arrival behaviors using the unimodal arbitrary arrival model. For such a model, we present a CPU scheduling algorithm, called the EnergyBounded Utility Accrual Algorithm (or EBUA). EBUA is a polynomialtime algorithm that satisfies energy bounds, and provides statistical assurances on individual activity timeliness behavior. We analytically establish several timeliness properties of EBUA. Further, our simulation experiments confirm the algorithm’s effectiveness and superiority. 1