As modern network infrastructure moves from hardware-based to software-based using Network Function Virtualization, a new set of requirements is raised for operating system developers. By using the real-time kernel options and advanced CPU isolation features common to the HPC use-cases, Linux is becoming a central building block for this new architecture that aims to enable a new set of low latency networked services. Tuning Linux for these applications is not an easy task, as it requires a deep understanding of the Linux execution model and the mix of user-space tooling and tracing features. This paper discusses the internal aspects of Linux that influence the Operating System Noise from a timing perspective. It also presents Linux's osnoise tracer, an in-kernel tracer that enables the measurement of the Operating System Noise as observed by a workload, and the tracing of the sources of the noise, in an integrated manner, facilitating the analysis and debugging of the system. Finally, this paper presents a series of experiments demonstrating both Linux's ability to deliver low OS noise (in the single-digit $\mu$ s order), and the ability of the proposed tool to provide precise information about root-cause of timing-related OS noise problems.

This paper presents SPHERE, a project aimed at the realization of an integrated framework to abstract the hardware complexity of interconnected, modern system-on-chips (SoC) and simplify the management of their heterogeneous computational resources. The SPHERE framework leverages hypervisor technology to virtualize computational resources and isolate the behavior of different subsystems running on the same platform, while providing safety, security, and real-time communication mechanisms. The main challenges addressed by SPHERE are discussed in the paper along with a set of new technologies developed in the context of the project. They include isolation mechanisms for mixed-criticality applications, predictable I/O virtualization, the management of time-sensitive networks with heterogeneous traffic flows, and the management of field-programmable gate arrays (FPGA) to provide efficient implementations for cryptography modules, as well as hardware acceleration for deep neural networks. The SPHERE architecture is validated through an autonomous driving use-case.

With heterogeneous multi-core platforms being crucial to execute the highly demanding workloads of modern applications, memory-access predictability remains a key issue for the system's safety. Many solutions have been proposed over the years, but none has been applied on a large scale. Nowadays, we are in front of an unprecedented opportunity to have an impact on commercial platforms: the Memory System Resource Partitioning and Monitoring (MPAM) specification by Arm, which describes different memory-access regulation mechanisms, presenting a valuable industrial attempt to address this issue. However, several points of the specification are described at a high level only, leaving plenty of room for interpretation to hardware manufacturers. This paper takes a close look at the memory-access regulation mechanisms in the MPAM specification and provides some detailed instantiations of such mechanisms. A fine-grained memory contention analysis is presented for each of them to finally enable a comparison of their worst-case performance.

Motivated by the increasing number of embedded applications that make use of traffic‐intensive I/O devices, this work studies the memory contention generated by I/O devices and investigates on the regulation of the bus traffic they generate by means of COTS regulators, namely the QoS‐400 by Arm. To this purpose, the behavior of the QoS‐400 regulators is analytically characterized and then, taking the Xilinx Ultrascale+ as a reference modern heterogeneous platform, a software infrastructure to control such regulators from Linux is proposed. As an experience report, this article presents the results of an extensive experimental evaluation, based on both benchmarks and microbenchmarks, aimed at validating the effectiveness of QoS‐400 regulators in predictably controlling I/O‐related memory traffic, as well as assessing the impact of the regulation on software applications and I/O devices themselves.

Modern automotive applications are increasingly characterized by the need to transfer massive amounts of data in a predictable and deterministic way, possibly leveraging the Logical Execution Time (LET) paradigm. However, current proposals for LET communications are limited to core-commanded data transfers, which may result in large delays for data-intensive systems. To address this issue, we explore the use of Direct Memory Access (DMA) to handle LET communication with improved parallelism. Each DMA transfer operates on a contiguous memory area, thus calling for an optimized memory mapping to maximize performance. Modern DMA engines offer also advanced configurations, such as linked-lists of data transfers, which may provide more flexibility at the expenses of an increased (initial) programming overhead. Leveraging all such features of DMA engines, we propose a set of designs and protocols for LET communications with trade-offs between latency and space requirements. For each option we present the formulation to compute the optimal scheduling and memory allocation solution as a mixed-integer linear programming problem. Experimental results show the feasibility of the approach and a comparison of the solutions obtained using the proposed methods, showing a considerable improvement in terms of data acquisition latency when compared to LET communication without DMA.