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Power management

June 08, 2023

For management of energy in various contexts, see energy management.

Power management is a feature of some electrical appliances, especially copiers, computers, computer CPUs, computer GPUs and computer peripherals such as monitors and printers, that turns off the power or switches the system to a low-power state when inactive. In computing this is known as PC power management and is built around a standard called ACPI, this supersedes APM. All recent computers have ACPI support.

Motivations

PC power management for computer systems is desired for many reasons, particularly:

Lower power consumption also means lower heat dissipation, which increases system stability, and less energy use, which saves money and reduces the impact on the environment.

Processor level techniques

The power management for microprocessors can be done over the whole processor, or in specific components, such as cache memory and main memory.

With dynamic voltage scaling and dynamic frequency scaling, the CPU core voltage, clock rate, or both, can be altered to decrease power consumption at the price of potentially lower performance. This is sometimes done in real time to optimize the power-performance tradeoff.

Examples:

Additionally, processors can selectively power off internal circuitry (power gating). For example:

  • Newer Intel Core processors support ultra-fine power control over the functional units within the processors.
  • AMD CoolCore technology get more efficient performance by dynamically activating or turning off parts of the processor.[3]

Intel VRT technology split the chip into a 3.3V I/O section and a 2.9V core section. The lower core voltage reduces power consumption.

Heterogenous computing

ARM's big.LITTLE architecture can migrate processes between faster "big" cores and more power efficient "LITTLE" cores.

Operating system level: hibernation

Main article: Hibernation (computing)

When a computer system hibernates it saves the contents of the RAM to disk and powers down the machine. On startup it reloads the data. This allows the system to be completely powered off while in hibernate mode. This requires a file the size of the installed RAM to be placed on the hard disk, potentially using up space even when not in hibernate mode. Hibernate mode is enabled by default in some versions of Windows and can be disabled in order to recover this disk space.

In GPUs

Graphics processing unit (GPUs) are used together with a CPU to accelerate computing in variety of domains revolving around scientific, analytics, engineering, consumer and enterprise applications.[4] All of this comes with some drawbacks, the high computing capability of GPUs comes at the cost of high power dissipation. Much research has been done over the power dissipation issue of GPUs and many techniques have been proposed to address this issue. Dynamic voltage scaling/dynamic frequency scaling (DVFS) and clock gating are two commonly used techniques for reducing dynamic power in GPUs.

DVFS techniques

Experiments show that conventional processor DVFS policy can achieve power reduction of embedded GPUs with reasonable performance degradation.[5] New directions for designing effective DVFS schedulers for heterogeneous systems are also being explored.[6] A heterogeneous CPU-GPU architecture, GreenGPU[7] is presented which employs DVFS in a synchronized way, both for GPU and CPU. GreenGPU is implemented using the CUDA framework on a real physical testbed with Nvidia GeForce GPUs and AMD Phenom II CPUs. Experimentally it is shown that the GreenGPU achieves 21.04% average energy savings and outperforms several well-designed baselines. For the mainstream GPUs which are extensively used in all kinds of commercial and personal applications several DVFS techniques exist and are built into the GPUs alone, AMD PowerTune and AMD ZeroCore Power are the two dynamic frequency scaling technologies for AMD graphic cards. Practical tests showed that reclocking a GeForce GTX 480 can achieve a 28% lower power consumption while only decreasing performance by 1% for a given task.[8]

Power gating techniques

Much research has been done on the dynamic power reduction with the use of DVFS techniques. However, as technology continues to shrink, leakage power will become a dominant factor.[9] Power gating is a commonly used circuit technique to remove leakage by turning off the supply voltage of unused circuits. Power gating incurs energy overhead; therefore, unused circuits need to remain idle long enough to compensate this overheads. A novel micro-architectural technique[10] for run-time power-gating caches of GPUs saves leakage energy. Based on experiments on 16 different GPU workloads, the average energy savings achieved by the proposed technique is 54%. Shaders are the most power hungry component of a GPU, a predictive shader shut down power gating technique[11] achieves up to 46% leakage reduction on shader processors. The Predictive Shader Shutdown technique exploits workload variation across frames to eliminate leakage in shader clusters. Another technique called Deferred Geometry Pipeline seeks to minimize leakage in fixed-function geometry units by utilizing an imbalance between geometry and fragment computation across batches which removes up to 57% of the leakage in the fixed-function geometry units. A simple time-out power gating method can be applied to non-shader execution units which eliminates 83.3% of the leakage in non-shader execution units on average. All the three techniques stated above incur negligible performance degradation, less than 1%.[12]

See also

References

  1. ^ "AMD PowerNow! Technology with optimized power management". AMD. Retrieved 2009-04-23.
  2. ^ "IBM EnergyScale for POWER6 Processor-Based Systems". IBM. Retrieved 2009-04-23.
  3. ^ "AMD Cool'n'Quiet Technology Overview". AMD. Retrieved 2009-04-23.
  4. ^ "What is GPU computing". Nvidia.
  5. ^ "Dynamic voltage and frequency scaling framework for low-power embedded GPUs", Daecheol You et al., Electronics Letters (Volume:48, Issue: 21 ), 2012.
  6. ^ "Effects of Dynamic Voltage and Frequency Scaling on a K20 GPU", Rong Ge et al., 42nd International Conference on Parallel Processing Pages 826-833, 2013.
  7. ^ "GreenGPU: A Holistic Approach to Energy Efficiency in GPU-CPU Heterogeneous Architectures", Kai Ma et al., 41st International Conference on Parallel Processing Pages 48-57, 2012.
  8. ^ "Power and performance analysis of GPU-accelerated systems", Yuki Abe et al., USENIX conference on Power-Aware Computing and Systems Pages 10-10, 2012.
  9. ^ "Design challenges of technology scaling", Borkar, S., IEEE Micro (Volume:19 , Issue: 4 ), 1999.
  10. ^ "Run-time power-gating in caches of GPUs for leakage energy savings", Yue Wang et al., Design, Automation & Test in Europe Conference & Exhibition (DATE), 2012
  11. ^ "A Predictive Shutdown Technique for GPU Shader Processors", Po-Han Wang et al., Computer Architecture Letters (Volume:8 , Issue: 1 ), 2009
  12. ^ "Power gating strategies on GPUs", Po-Han Wang et al., ACM Transactions on Architecture and Code Optimization (TACO) Volume 8 Issue 3, 2011

External links

  • Energy Star - Independent List of Products
  • Energy Star - Low Carbon IT Campaign
  • Research Bibliography on Power Management

June 08, 2023
power, management, management, energy, various, contexts, energy, management, this, article, includes, list, general, references, lacks, sufficient, corresponding, inline, citations, please, help, improve, this, article, introducing, more, precise, citations, . For management of energy in various contexts see energy management This article includes a list of general references but it lacks sufficient corresponding inline citations Please help to improve this article by introducing more precise citations June 2008 Learn how and when to remove this template message Power management is a feature of some electrical appliances especially copiers computers computer CPUs computer GPUs and computer peripherals such as monitors and printers that turns off the power or switches the system to a low power state when inactive In computing this is known as PC power management and is built around a standard called ACPI this supersedes APM All recent computers have ACPI support Contents 1 Motivations 2 Processor level techniques 2 1 Heterogenous computing 3 Operating system level hibernation 4 In GPUs 4 1 DVFS techniques 4 2 Power gating techniques 5 See also 6 References 7 External linksMotivations EditPC power management for computer systems is desired for many reasons particularly Reduce overall energy consumption Prolong battery life for portable and embedded systems Reduce cooling requirements Reduce noise Reduce operating costs for energy and coolingLower power consumption also means lower heat dissipation which increases system stability and less energy use which saves money and reduces the impact on the environment Processor level techniques EditThe power management for microprocessors can be done over the whole processor or in specific components such as cache memory and main memory With dynamic voltage scaling and dynamic frequency scaling the CPU core voltage clock rate or both can be altered to decrease power consumption at the price of potentially lower performance This is sometimes done in real time to optimize the power performance tradeoff Examples AMD Cool n Quiet AMD PowerNow 1 IBM EnergyScale 2 Intel SpeedStep Transmeta LongRun and LongRun2 VIA LongHaul PowerSaver Additionally processors can selectively power off internal circuitry power gating For example Newer Intel Core processors support ultra fine power control over the functional units within the processors AMD CoolCore technology get more efficient performance by dynamically activating or turning off parts of the processor 3 Intel VRT technology split the chip into a 3 3V I O section and a 2 9V core section The lower core voltage reduces power consumption Heterogenous computing Edit ARM s big LITTLE architecture can migrate processes between faster big cores and more power efficient LITTLE cores Operating system level hibernation EditMain article Hibernation computing When a computer system hibernates it saves the contents of the RAM to disk and powers down the machine On startup it reloads the data This allows the system to be completely powered off while in hibernate mode This requires a file the size of the installed RAM to be placed on the hard disk potentially using up space even when not in hibernate mode Hibernate mode is enabled by default in some versions of Windows and can be disabled in order to recover this disk space In GPUs EditGraphics processing unit GPUs are used together with a CPU to accelerate computing in variety of domains revolving around scientific analytics engineering consumer and enterprise applications 4 All of this comes with some drawbacks the high computing capability of GPUs comes at the cost of high power dissipation Much research has been done over the power dissipation issue of GPUs and many techniques have been proposed to address this issue Dynamic voltage scaling dynamic frequency scaling DVFS and clock gating are two commonly used techniques for reducing dynamic power in GPUs DVFS techniques Edit Experiments show that conventional processor DVFS policy can achieve power reduction of embedded GPUs with reasonable performance degradation 5 New directions for designing effective DVFS schedulers for heterogeneous systems are also being explored 6 A heterogeneous CPU GPU architecture GreenGPU 7 is presented which employs DVFS in a synchronized way both for GPU and CPU GreenGPU is implemented using the CUDA framework on a real physical testbed with Nvidia GeForce GPUs and AMD Phenom II CPUs Experimentally it is shown that the GreenGPU achieves 21 04 average energy savings and outperforms several well designed baselines For the mainstream GPUs which are extensively used in all kinds of commercial and personal applications several DVFS techniques exist and are built into the GPUs alone AMD PowerTune and AMD ZeroCore Power are the two dynamic frequency scaling technologies for AMD graphic cards Practical tests showed that reclocking a GeForce GTX 480 can achieve a 28 lower power consumption while only decreasing performance by 1 for a given task 8 Power gating techniques Edit Much research has been done on the dynamic power reduction with the use of DVFS techniques However as technology continues to shrink leakage power will become a dominant factor 9 Power gating is a commonly used circuit technique to remove leakage by turning off the supply voltage of unused circuits Power gating incurs energy overhead therefore unused circuits need to remain idle long enough to compensate this overheads A novel micro architectural technique 10 for run time power gating caches of GPUs saves leakage energy Based on experiments on 16 different GPU workloads the average energy savings achieved by the proposed technique is 54 Shaders are the most power hungry component of a GPU a predictive shader shut down power gating technique 11 achieves up to 46 leakage reduction on shader processors The Predictive Shader Shutdown technique exploits workload variation across frames to eliminate leakage in shader clusters Another technique called Deferred Geometry Pipeline seeks to minimize leakage in fixed function geometry units by utilizing an imbalance between geometry and fragment computation across batches which removes up to 57 of the leakage in the fixed function geometry units A simple time out power gating method can be applied to non shader execution units which eliminates 83 3 of the leakage in non shader execution units on average All the three techniques stated above incur negligible performance degradation less than 1 12 See also Edit Energy portal80 Plus Advanced power management APM Advanced Configuration and Power Interface ACPI Hibernate Sleep BatteryMAX idle detection Constant Awake Mode CPU power dissipation Dynamic frequency scaling Dynamic voltage scaling Energy Star Energy storage as a service ESaaS Green computing Low power electronics pmset PowerTOP diagnostic tool Run time estimation of system and sub system level power consumption Sleep Proxy Service Standby power The Green Grid Thermal design power VESA Display Power Management Signaling DPMS References Edit AMD PowerNow Technology with optimized power management AMD Retrieved 2009 04 23 IBM EnergyScale for POWER6 Processor Based Systems IBM Retrieved 2009 04 23 AMD Cool n Quiet Technology Overview AMD Retrieved 2009 04 23 What is GPU computing Nvidia Dynamic voltage and frequency scaling framework for low power embedded GPUs Daecheol You et al Electronics Letters Volume 48 Issue 21 2012 Effects of Dynamic Voltage and Frequency Scaling on a K20 GPU Rong Ge et al 42nd International Conference on Parallel Processing Pages 826 833 2013 GreenGPU A Holistic Approach to Energy Efficiency in GPU CPU Heterogeneous Architectures Kai Ma et al 41st International Conference on Parallel Processing Pages 48 57 2012 Power and performance analysis of GPU accelerated systems Yuki Abe et al USENIX conference on Power Aware Computing and Systems Pages 10 10 2012 Design challenges of technology scaling Borkar S IEEE Micro Volume 19 Issue 4 1999 Run time power gating in caches of GPUs for leakage energy savings Yue Wang et al Design Automation amp Test in Europe Conference amp Exhibition DATE 2012 A Predictive Shutdown Technique for GPU Shader Processors Po Han Wang et al Computer Architecture Letters Volume 8 Issue 1 2009 Power gating strategies on GPUs Po Han Wang et al ACM Transactions on Architecture and Code Optimization TACO Volume 8 Issue 3 2011External links EditEnergy Star Independent List of Products Energy Star Low Carbon IT Campaign Energy Consumption Calculator Research Bibliography on Power Management Retrieved from https en wikipedia org w index php title Power management amp oldid 1091265694, wikipedia, wiki, book, books, library,

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