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204
Energy-Efficient Soft Real-Time CPU Scheduling for Mobile Multimedia Systems
- Proc. Symp. Operating Systems Principles
, 2003
"... This paper presents GRACE-OS, an energy-efficient soft real-time CPU scheduler for mobile devices that primarily run multimedia applications. The major goal of GRACE-OS is to support application quality of service and save energy. To achieve this goal, GRACE-OS integrates dynamic voltage scaling int ..."
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Cited by 149 (8 self)
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This paper presents GRACE-OS, an energy-efficient soft real-time CPU scheduler for mobile devices that primarily run multimedia applications. The major goal of GRACE-OS is to support application quality of service and save energy. To achieve this goal, GRACE-OS integrates dynamic voltage scaling into soft real-time scheduling and decides how fast to execute applications in addition to when and how long to execute them. GRACE-OS makes such scheduling decisions based on the probability distribution of application cycle de-mands, and obtains the demand distribution via online pro-filing and estimation. We have implemented GRACE-OS in the Linux kernel and evaluated it on an HP laptop with a variable-speed CPU and multimedia codecs. Our experi-mental results show that (1) the demand distribution of the studied codecs is stable or changes smoothly. This stability implies that it is feasible to perform stochastic scheduling and voltage scaling with low overhead; (2) GRACE-OS de-livers soft performance guarantees by bounding the dead-line miss ratio under application-specific requirements; and (3) GRACE-OS reduces CPU idle time and spends more busy time in lower-power speeds. Our measurement indi-cates that compared to deterministic scheduling and volt-age scaling, GRACE-OS saves energy by 7 % to 72 % while delivering statistical performance guarantees.
Leakage aware dynamic voltage scaling for real-time embedded systems
- In CECS
, 2003
"... A five-fold increase in leakage current is predicted with each technology generation. While Dynamic Voltage Scaling (DVS) is known to reduce dynamic power consumption, it also causes increased leakage energy drain by lengthening the interval over which a computation is carried out. Therefore, for mi ..."
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Cited by 140 (8 self)
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A five-fold increase in leakage current is predicted with each technology generation. While Dynamic Voltage Scaling (DVS) is known to reduce dynamic power consumption, it also causes increased leakage energy drain by lengthening the interval over which a computation is carried out. Therefore, for minimization of the total energy, one needs to determine an operating point, called the critical speed. We compute processor slowdown factors based on the critical speed for energy minimization. Procrastination scheduling attempts to maximize the duration of idle intervals by keeping the processor in a sleep/shutdown state even if there are pending tasks, within the constraints imposed by performance requirements. Our simulation experiments show that the critical speed slowdown results in up to 5 % energy gains over a leakage oblivious dynamic voltage scaling. Procrastination scheduling scheme extends the sleep intervals to up to 5 times, resulting in up to an additional 18 % energy gains, while meeting all timing requirements.
Scheduling with dynamic voltage/speed adjustment using slack reclamation in multi-processor real-time systems
- IEEE TRANS. ON PARALLEL AND DISTRIBUTED SYSTEMS
, 2003
"... The high power consumption of modern processors becomes a major concern because it leads to decreased mission duration (for battery-operated systems), increased heat dissipation, and decreased reliability. While many techniques have been proposed to reduce power consumption for uniprocessor systems ..."
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Cited by 116 (10 self)
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The high power consumption of modern processors becomes a major concern because it leads to decreased mission duration (for battery-operated systems), increased heat dissipation, and decreased reliability. While many techniques have been proposed to reduce power consumption for uniprocessor systems, there has been considerably less work on multiprocessor systems. In this paper, based on the concept of slack sharing among processors, we propose two novel power-aware scheduling algorithms for task sets with and without precedence constraints executing on multiprocessor systems. These scheduling techniques reclaim the time unused by a task to reduce the execution speed of future tasks and, thus, reduce the total energy consumption of the system. We also study the effect of discrete voltage/speed levels on the energy savings for multiprocessor systems and propose a new scheme of slack reservation to incorporate voltage/speed adjustment overhead in the scheduling algorithms. Simulation and trace-based results indicate that our algorithms achieve substantial energy savings on systems with variable voltage processors. Moreover, processors with a few discrete voltage/speed levels obtain nearly the same energy savings as processors with continuous voltage/speed, and the effect of voltage/speed adjustment overhead on the energy savings is relatively small.
Power-aware QoS Management in Web Servers
- IN PROCEEDINGS OF THE 24 TH IEEE REAL-TIME SYSTEMS SYMPOSIUM (RTSS’03), CANCUN
, 2003
"... Power management in data centers has become an increasingly important concern. Large server installations are designed to handle peak load, which may be significantly larger than in off-peak conditions. The increasing cost of energy consumption and cooling incurred in farms of highperformance web se ..."
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Cited by 90 (4 self)
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Power management in data centers has become an increasingly important concern. Large server installations are designed to handle peak load, which may be significantly larger than in off-peak conditions. The increasing cost of energy consumption and cooling incurred in farms of highperformance web servers make low-power operation during off-peak hours desirable. This paper investigates adaptive algorithms for dynamic voltage scaling in QoS-enabled web servers to minimize energy consumption subject to service delay constraints. We implement these algorithms inside the Linux kernel. The instrumented kernel supports multiple client classes with per-class deadlines. Energy consumption is minimized by using a feedback loop that regulates frequency and voltage levels to keep the synthetic utilization around the aperiodic schedulability bound derived in an earlier publication. Enforcing the bound ensures that deadlines are met. Our evaluation of an Apache server running on the modified Linux kernel shows that non-trivial offpeak energy savings are possible without sacrificing timeliness.
Performance comparison of dynamic voltage scaling algorithms for hard real-time systems
- Proc. IEEE Real-Time and
"... Dynamic voltage scaling (DVS) is an effective low-power design technique for embedded real-time systems. In recent years, many DVS algorithms have been proposed for reduc-ing the energy consumption of embedded hard real-time sys-tems. However, the proposed DVS algorithms were not quan-titatively eva ..."
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Cited by 61 (8 self)
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Dynamic voltage scaling (DVS) is an effective low-power design technique for embedded real-time systems. In recent years, many DVS algorithms have been proposed for reduc-ing the energy consumption of embedded hard real-time sys-tems. However, the proposed DVS algorithms were not quan-titatively evaluated under a unified framework, making it a difficult task to select an appropriate DVS algorithm for a given application/system. In this paper, we compare several key DVS algorithms recently proposed for hard real-time pe-riodic task sets, analyze their energy efficiency, and discuss the performance differences quantitatively. Our evaluation results give quantitative answers to several important DVS questions. 1
Elnozahy. The interplay of power management and fault recovery in real-time systems
- IEEE Trans. on Computers
, 2004
"... Abstract—This paper describes how to exploit the scheduling slack in a real-time system to reduce energy consumption and achieve fault tolerance at the same time. During failure-free operation, a task takes checkpoints to enable recovery from failure. Additionally, the system exploits the slack to c ..."
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Cited by 55 (4 self)
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Abstract—This paper describes how to exploit the scheduling slack in a real-time system to reduce energy consumption and achieve fault tolerance at the same time. During failure-free operation, a task takes checkpoints to enable recovery from failure. Additionally, the system exploits the slack to conserve energy by reducing the processor speed. If a task fails, it will restart from a saved checkpoint and execute at maximum speed to guarantee that the deadlines are met. The paper shows that the number of checkpoints and their placements interact in subtle ways with the power management policy. We study two checkpoint placement policies for aperiodic tasks and analytically derive the optimal number of checkpoints to conserve energy under each. This optimal number allows the CPU speed to be slowed down to the level that yields minimum energy consumption, while still guaranteeing recoverability of tasks under each checkpointing policy. The results show that traditional periodic checkpointing is not the best policy for the combined purpose of conserving energy and guaranteeing recovery. Instead, better energy savings are possible through a nonuniform distribution of checkpoints that takes into account the energy consumption and reliability factors. Depending on the amount of slack and the checkpointing overhead, energy can be reduced by up to 68 percent under nonuniform checkpointing. We also demonstrate the applicability of these checkpoint placement policies to periodic tasks. Index Terms—Checkpointing, fault tolerance, frequency scaling, power management, real-time systems, reliability, voltage scaling. 1
Energy Aware Scheduling for Distributed Real-Time Systems
- In International Parallel and Distributed Processing Symposium
, 2003
"... Power management has become popular in mobile computing as well as in server farms. Although a lot of work has been done to manage the energy consumption on uniprocessor real-time systems, there is less work done on their multicomputer counterparts. For a set of real-time tasks with precedence const ..."
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Cited by 52 (3 self)
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Power management has become popular in mobile computing as well as in server farms. Although a lot of work has been done to manage the energy consumption on uniprocessor real-time systems, there is less work done on their multicomputer counterparts. For a set of real-time tasks with precedence constraints executing on a distributed system, we propose new static and dynamic power management schemes. Assuming a given static schedule generated from any list scheduling heuristic algorithm, our static power management scheme uses the static slack (if any) based on the degree of parallelism in the schedule. To consider the run-time behavior of tasks, an on-line dynamic power management technique is proposed to further explore the idle periods of processors. By comparing our static technique with the simple static power management, where the static slack is distributed to the schedule proportionally, we find that our static scheme can save an average of 10 % more energy. When combined with dynamic schemes, our schemes significantly improve energy savings. 1
Maximizing The System Value While Satisfying Time And Energy Constraints
, 2002
"... this paper may be copied or distributed royalty free without further permission by computer-based and other information-service systems. Permission to republish any other portion of this paper must be obtained from the Editor ..."
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Cited by 51 (4 self)
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this paper may be copied or distributed royalty free without further permission by computer-based and other information-service systems. Permission to republish any other portion of this paper must be obtained from the Editor
Proxy-assisted Power-friendly Streaming to Mobile Devices
- In Proceedings of the 2003 Multimedia Computing and Networking Conference (MMCN’03
, 2003
"... Since multimedia applications are known to be resource-hungry and mobile devices are resource-poor, in this paper, we propose techniques to reduce the energy consumption of streaming media applications running on mobile hosts. Our proposed techniques are proxy-based and involve power-friendly transf ..."
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Cited by 48 (1 self)
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Since multimedia applications are known to be resource-hungry and mobile devices are resource-poor, in this paper, we propose techniques to reduce the energy consumption of streaming media applications running on mobile hosts. Our proposed techniques are proxy-based and involve power-friendly transformations on the requested streams so as to limit the energy required for receiving and decoding this data. Additionally, our proxy employs intelligent network transmission techniques to reduce the energy needs for network reception of streaming data. We implement our techniques into a prototype proxy and client and demonstrate their efficacy via an experimental evaluations. Our results show that our power-friendly transformations are effective over a range of bit rates and stream resolutions, while our intelligent transmission techniques can reduce the potential energy wastage during network reception by 65-98%.
Processor Voltage Scheduling for Real-Time Tasks With Non-Preemptible Sections
, 2002
"... As mobile computing is getting popular, there is an increasing interest in techniques that can minimize energy consumption and prolong the battery life on mobile devices. Processor voltage scheduling is an effective way to reduce energy dissipation by reducing the processor speed. In this paper, we ..."
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Cited by 45 (2 self)
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As mobile computing is getting popular, there is an increasing interest in techniques that can minimize energy consumption and prolong the battery life on mobile devices. Processor voltage scheduling is an effective way to reduce energy dissipation by reducing the processor speed. In this paper, we study voltage scheduling for real-time periodic tasks with non-preemptible sections. Three schemes are proposed to address this problem. The static speed algorithm derives a static feasible speed based on the Stack Resource Policy (SRP). As worst-case blocking does not always occur, the novel dual speed algorithm switches the processor speed to a lower value whenever possible. The dynamic reclaiming algorithm deploys a reservation-based approach to reclaim unused run time for redistribution. It effectively decreases the processor idle time and further reduces the processor speed. The feasibility conditions are given and proved. Simulation results show that the two dynamic algorithms can reduce processor energy consumption by up to 80 percent over the static speed scheme.
