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Traditional approaches for managing software-programmable memories (SPMs) do not support sharing of distributed on-chip memory resources and, consequently, miss the opportunity to better utilize those memory resources. Managing on-chip memory resources in many-core embedded systems with distributed SPMs requires runtime support to share memory resources between various threads with different memory demands running concurrently. Runtime SPM managers cannot rely on prior knowledge about the dynamically changing mix of threads that will execute and therefore should be designed in a way that enables SPM allocations for any unpredictable mix of threads contending for on-chip memory space. This article proposes ShaVe-ICE , an operating-system-level solution, along with hardware support, to virtualize and ultimately share SPM resources across a many-core embedded system to reduce the average memory latency. We present a number of simple allocation policies to improve performance and energy. Experimental results show that sharing SPMs could reduce the average execution time of the workload up to 19.5% and reduce the dynamic energy consumed in the memory subsystem up to 14%.

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With memories continuing to dominate the area, power, cost and performance of a design, there is a critical need to provision reliable, high-performance memory bandwidth for emerging applications. Memories are susceptible to degradation and failures from a wide range of manufacturing, operational and environmental effects, requiring a multi-layer hardware/software approach that can tolerate, adapt and even opportunistically exploit such effects. The overall memory hierarchy is also highly vulnerable to the adverse effects of variability and operational stress. After reviewing the major memory degradation and failure modes, this paper describes the challenges for dependability across the memory hierarchy, and outlines research efforts to achieve multi-layer memory resilience using a hardware/software approach. Two specific exemplars are used to illustrate multilayer memory resilience: first we describe static and dynamic policies to achieve energy savings in caches using aggressive voltage scaling combined with disabling faulty blocks; and second we show how software characteristics can be exposed to the architecture in order to mitigate the aging of large register files in GPGPUs. These approaches can further benefit from semantic retention of application intent to enhance memory dependability across multiple abstraction levels, including applications, compilers, run-time systems, and hardware platforms.

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Memory approximation enables trading off quality/accuracy for performance or energy gains. Traditionally, application programmers are burdened with the difficult task of setting memory approximation knobs to achieve the desired quality of service (QoS). Our self-adaptive approach for memory approximation eases the programmer's burden: simply specify the desired quality as a goal, with the system deploying a formal control-theoretic approach to tune the memory approximation knobs and deliver a guaranteed QoS. We model quality configuration tracking as a formal quality control problem, and outline a System Identification technique that captures memory approximation effects with variations in application input and system architecture. Preliminary results show that we can alleviate the programmer's burden of manual knob tuning for on-chip memory approximation. When compared to a manual calibration scheme we achieve 3× improvement in average settling time and upto 5× improvement in best case settling time.