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n this paper, we present a solution to the industrial challenge put forth by ARM in 2022. We systematically analyze the effect of shared resource contention to an augmented reality head-up display (AR-HUD) case-study application of the industrial challenge on a heterogeneous multicore platform, NVIDIA Jetson Nano. We configure the AR-HUD application such that it can process incoming image frames in real-time at 20Hz on the platform. We use Microarchitectural Denial-of-Service (DoS) attacks as aggressor workloads of the challenge and show that they can dramatically impact the latency and accuracy of the AR-HUD application. This results in significant deviations of the estimated trajec- tories from known ground truths, despite our best effort to mitigate their influence by using cache partitioning and real-time scheduling of the AR- HUD application. To address the challenge, we propose RT-Gang++, a partitioned real-time gang scheduling framework with last-level cache (LLC) and integrated GPU bandwidth throttling capabilities. By applying RT-Gang++, we are able to achieve desired level of performance of the AR-HUD application even in the presence of fully loaded aggressor tasks. 

Unarbitrated contention over shared resources at different levels of the memory hierarchy represents a major source of temporal interference. Hardware manufacturers are increasingly more receptive to issues with temporal interference and are starting to propose concrete solutions to mitigate the problem. Intel Resource Director Technology (RDT) represents one such attempt. Given the wide adoption of Intel platforms, RDT features can be an invaluable asset for the consolidation of real-time systems on complex multi- and many-core machines. Unfortunately, to date, a systematic analysis of the capabilities introduced by the RDT framework has not yet been conducted. Moreover, no clear understanding has been matured about the implementation-specific behavior of RDT primitives across processor generations. And ultimately, the ability of RDT to provide real-time guarantees is yet to be established. In our work, we aim at conducting a systematic investigation of the RDT mechanisms from a real-time perspective. We experimentally evaluate the functionality and interpretability of RDT-aided allocation and monitoring controls across the two most recent processor generations. Our evaluations show that while some features like Cache Allocation Technology (CAT) yield promising results, the implementation of other primitives such as Memory Bandwidth Allocation (MBA) has much room for improvement. Moreover, in some cases, the presented interfaces range from blurry to incomplete, as is the case for MBA and Memory Bandwidth Monitoring (MBM). 

In this paper we investigate the feasibility of denialof-service (DoS) attacks on shared caches in multicore platforms. With carefully engineered attacker tasks, we are able to cause more than 300X execution time increases on a victim task running on a dedicated core on a popular embedded multicore platform, regardless of whether we partition its shared cache or not. Based on careful experimentation on real and simulated multicore platforms, we identify an internal hardware structure of a nonblocking cache, namely the cache writeback buffer, as a potential target of shared cache DoS attacks. We propose an OS-level solution to prevent such DoS attacks by extending a state-of-the-art memory bandwidth regulation mechanism. We implement the proposed mechanism in Linux on a real multicore platform and show its effectiveness in protecting against cache DoS attacks.