Adaptive guardband scheduling to improve system-level efficiency of the POWER7+
Adaptive guardband scheduling to improve system-level efficiency of the POWER7+
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自适应保护带调度可提高 POWER7 的系统级效率
DOI：
10.1145/2830772.2830824
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
V. Reddi
中科院分区：
文献类型：
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作者：
Yazhou Zu;C. Lefurgy;Jingwen Leng;Matthew Halpern;M. Floyd;V. Reddi
传统的保护带确保处理器可靠性的方法已经过时，因为它总是过度提供电压并浪费大量能量。作为下一代替代方案，自适应保护带基于运行时测量的时间裕度动态调整芯片时钟频率和电压。使用自适应保护带，电压保护带仅在需要时提供，从而有望显著提高能源效率。在本文中，我们首次对使用POWER7+多核的自适应守护带的含义进行了全面的系统分析。在大量硬件测量的基础上，我们展示了在实际设置中自适应守护带的好处在很大程度上取决于工作负载特征和芯片范围内的多核活动。一个关键的发现是，自适应守护带的好处随着活动核心数量的增加而减少，并且它们高度依赖于工作负载的运行。通过一系列分析，我们发现这些高级系统效应是应用特性、架构和底层稳压器模块的负载线效应和IR下降效应之间相互作用的结果。为此，我们引入自适应守护带调度来回收自适应守护带在不同企业场景下的效率。我们的解决方案在高度优化的系统上降低了6.2%的处理器功耗，有效地将自适应保护带的原始改进提高了一倍。我们的解决方案还避免了恶意的工作负载映射，以保证应用程序在面对自适应守卫硬件的可变性能时的QoS。
The traditional guardbanding approach to ensure processor reliability is becoming obsolete because it always over-provisions voltage and wastes a lot of energy. As a next-generation alternative, adaptive guardbanding dynamically adjusts chip clock frequency and voltage based on timing margin measured at runtime. With adaptive guardbanding, voltage guardband is only provided when needed, thereby promising significant energy efficiency improvement. In this paper, we provide the first full-system analysis of adaptive guardbanding's implications using a POWER7+ multicore. On the basis of a broad collection of hardware measurements, we show the benefits of adaptive guardbanding in a practical setting are strongly dependent upon workload characteristics and chip-wide multicore activity. A key finding is that adaptive guardbanding's benefits diminish as the number of active cores increases, and they are highly dependent upon the workload running. Through a series of analysis, we show these high-level system effects are the result of interactions between the application characteristics, architecture and the underlying voltage regulator module's loadline effect and IR drop effects. To that end, we introduce adaptive guardband scheduling to reclaim adaptive guardbanding's efficiency under different enterprise scenarios. Our solution reduces processor power consumption by 6.2% over a highly optimized system, effectively doubling adaptive guardbanding's original improvement. Our solution also avoids malicious workload mappings to guarantee application QoS in the face of adaptive guardbanding hardware's variable performance.