Power-Aware Critical Sections

计算系统中并发进程的竞争条件可能导致部分无法解释的现象，甚至导致有缺陷的运行时行为。原因是非顺序程序中的关键部分。关键区保护的解决方案通常面临多维问题空间：(1)处理器本地中断，(2)具有（2a）相干或（2b）非相干缓存的共享内存多/多核多处理器，(3)具有全局地址空间的分布式内存系统，(4)对操作系统进程管理的干扰。因此，保护方法对访问争用的发生作出悲观或乐观的假设。竞争进程的数量取决于用例，并且对计算系统所有级别上的协调效率有很大的影响。因此，开销、可伸缩性和保护功能的专用性构成了决定性的性能影响因素。这个影响量不仅考虑了不同的过程运行时间，而且还考虑了不同的能源使用。前者会导致程序流中的噪声或抖动：非功能属性对于高度并行或实时依赖的进程尤其有问题。相比之下，后者一方面具有经济重要性，另一方面具有生态后果，另一方面与多核处理器（暗硅）的可扩展性边界相切。由于关键部分的结构复杂性及其对争论的敏感性，权衡变得明显，应在项目中通过分析和建设性措施加以解决。调查的对象是自己的专用操作系统，其设计主要是为了支持并行和部分依赖于实时的数据处理，以及Linux。目标是提供(a)依赖于负载的软件基础设施，以及——通过程序部分——对并发进程的关键竞争条件进行自组织更改的保护，以及(b)准备、表征和捕获这些部分的工具。因工艺活动增加而引起的热点，并表现为能耗和温度上升，应根据需要或预期通过分段调度政策加以避免或减弱。只有在与原始解决方案相比可以预期实际增益的情况下，由特定调度策略引起的开销才会在进行更改的关键部分的动态重新配置的权重中滑动。基于所调查操作系统的前后比较应证明所开发方法的有效性。

Race conditions of concurrent processes within a computing system may cause partly inexplicable phenomena or even defective run-time behaviour. Reason are critical sections in non-sequential programs. Solutions for the protection of critical sections generally are facing a multi-dimensional problem space: (1) processor-local interrupts, (2) shared-memory multi/many-core multiprocessors with (2a) coherent or (2b) incoherent caches, (3) distributed-memory systems with global address space, (4) interference with process management of the operating system. Thereby, the protection method makes pessimistic or optimistic assumptions regarding the occurrence of access contention.The number of contending processes depends on the use case and has a large impact on the effectiveness of their coordination at all levels of a computing system. Overhead, scalability, and dedication of the protective function thereby constitute decisive performance-affecting factors. This influencing quantity not only accounts for varying process run-times but also different energy uses. The former results in noise or jitter in the program flow: non-functional properties that are especially problematic for highly parallel or real-time dependent processes. In contrast, the later has economical importance as well as ecological consequences on the one hand and is tangent to the boundary of scalability of many-core processors (dark silicon) on the other hand.Subject to the structural complexity of a critical section and its sensitivity to contention, a trade-off becomes apparent that shall be tackled in the project by means of analytical and constructive measures. Objects of investigation are own special-purpose operating systems, which were designed primarily for the support of parallel and partly also real-time dependent data processing, and Linux. Goal is the provision (a) of a software infrastructure for load-dependent and---by the program sections---self-organized change of protection against crucial race condition of concurrent processes as well as (b) of tools for preparation, characterisation, and capturing of those sections. Hotspots caused by increased process activity and becoming manifested in energy-use and temperature rise shall be avoided or attenuated on demand or anticipatory by a section-specific dispatch policy. The overhead induced by the particular dispatch policy slips in the weighting to dynamic reconfiguration of a critical section for undertaking a change only in case that real practical gain compared to the original solution can be expected. Before-after comparisons based on the investigated operating systems shall demonstrate the effectivity of the approach developed.