Neverlast: Towards the Design and Implementation of the NVM-based Everlasting Operating System

Novel non-volatile memory (NVM) technologies allow for the efficient implementation of \u27\u27intermittently-powered\u27\u27 smart dust and edge computing systems in a previously unfamiliar way. Operating with rough environmental conditions where power-supply failures occur often requires adjustments to all parts of the system. This leads to an inevitable trade-off in the design of operating systems -- the overhead of persisting the achieved computation progress over power failures is detrimental to the possible amount of progress with the available energy budgets. It is, therefore, crucial to minimize the overhead of ensuring persistence. This paper presents the case that persistence should be provided as an operating-system service to achieve everlasting operating capabilities. Triggered by power-failure interrupts, an implicit persistence service for the processor status of a process preserves progress on the CPU-instruction level. This interrupt only triggers if necessary so that no power-state polling is needed. We outline architectures for everlasting systems and discuss their benefits and drawbacks compared to existing approaches. Thereby, the operating system provides persistence as a service at run-time to the application, with minimal overhead. Our approach enables the separation of the application from energy-supply state estimation, as well as state-preserving logic for software and hardware components

Quick-and-dirty memory access tracing with instruction-based sampling

With the increasing deployment of heterogeneous memory architectures, the efficient execution of a workload becomes more sensitive to fine-grained memory placement decisions. To establish a sound information base for such decisions, we must first understand memory access behavior beyond the level of coarse-grained statistics. However, collecting detailed memory traces is a costly process. Therefore, we propose a low-overhead solution based on instruction-based sampling that provides incomplete yet informative access sequences. We showcase the practical value of such sparse traces by analyzing the overhead and comparing workload runs on two memory technologies with distinct characteristics

Memento - energy-aware memory placement in operating systems

Today’s availability of new memory technologies requires radical re-thinking of memory management in general-purpose operating systems. Main-memory technologies (e.g. NVM), completely new cell types (e.g. PCRAM), and coherent interconnects (e.g. CXL) challenge existing programming and system abstractions. At the same time, memory subsystems received much less attention from energy efficiency efforts, compared to compute resources. We therefore need new interfaces at operating system level that not only communicate functional and non-functional memory properties to application developers, but also take energy efficiency into account. We propose Memento, a new concept for efficient memory management at the operating system level. Memento addresses the shortcomings of the current state-of-the-art with methods for analysing program code at development time, its operational characteristics at runtime, along with characteristics of memory resources at system setup time

Efficient NVRAM-based general purpose operating systems

In recent years, there has been a disruptive shift in storage systems and supporting hardware technologies. This poses new challenges for an operating system (OS) in the holistic management of the computer’s memory hierarchy. Non-volatile RAM (NVRAM), in particular, presents a number of promising opportunities, aside from its large capacity at comparatively low costs, its higher speed compared to conventional storage and its ability to maintain a persistent state without additional energy costs. If general-purpose operating systems run entirely in NVRAM, persistence measures within the OS could be eliminated, reducing space, time, and energy requirements. However, consideration of NVRAM as an alternative main memory technology, also causes difficulties. Compared to DRAM writing to NVRAM is slower and results in higher power consumption. In addition, with NVRAM, fail-safe guarantees are now required from the system