Minimizing Algorithmic Priority and Criticality Inversions in Heterogeneous Mixed-Criticality Systems through Instruction-Level Preemption

Centrala begrepp

Enabling instruction-level preemption in heterogeneous co-processors can significantly reduce the duration of algorithmic priority and criticality inversions in mixed-criticality systems.

Sammanfattning

The paper introduces Make Each Switch Count (MESC), a systematic framework for building heterogeneous mixed-criticality systems (MCSs) that minimizes algorithmic priority and criticality inversions. The key contributions are:

1. Gemminirt, a new DNN accelerator based on the open-source Gemmini NPU architecture, which enables instruction-level preemption. This provides the foundation for fine-grained context switches in heterogeneous MCSs.

2. A context switch strategy and OS add-ons to ensure data consistency and manage DNN accelerator context switches, providing software-level support.

3. A full-stack framework that integrates the customized SoC, Instruction Set Architecture (ISA), and OS kernel, forming a complete solution for heterogeneous MCSs.

4. A theoretical model and analysis for the proposed framework to provide theoretical validation.

Experiments show that compared to conventional non-preemptive DNN accelerators, Gemminirt achieved 250x and 300x accelerations in resolving algorithmic priority inversion and criticality inversion, respectively, with negligible overhead.

Statistik

The longest execution time for instructions in Gemminirt is 2 orders of magnitude shorter than the "obligatory waiting periods" in DNN accelerators with limited context switch.
Compared to conventional non-preemptive DNN accelerators, Gemminirt achieved 250x and 300x accelerations in resolving algorithmic priority inversion and criticality inversion, respectively.

Citat

"To satisfy the computational demands of diverse functionalities in MCSs, e.g., running workloads on Deep Neural Networks (DNNs) or transformers, hardware vendors have developed SoCs with different architectures, with a high degree of heterogeneity."
"The deployment of these co-processors brings frequent occurrences of algorithmic priority and/or criticality inversions, posing a significant challenge to guaranteeing system-wide real-time performance."

Viktiga insikter från

MESC: Re-thinking Algorithmic Priority and/or Criticality Inversions for Heterogeneous MCSs

by Jiapeng Guan... på arxiv.org 09-24-2024

https://arxiv.org/pdf/2409.14837.pdf

Djupare frågor

How can the proposed MESC framework be extended to support other types of heterogeneous co-processors beyond DNN accelerators?

The MESC (Make Each Switch Count) framework can be extended to support other types of heterogeneous co-processors by leveraging its core principles of fine-grained context switching and instruction-level preemption. To achieve this, several strategies can be employed:

Modular Architecture: The MESC framework is designed with a modular architecture that allows for the integration of various co-processors. By defining a set of standard interfaces and protocols for communication between the CPU and different co-processors, MESC can accommodate a wide range of processing units, such as Graphics Processing Units (GPUs), Field Programmable Gate Arrays (FPGAs), and specialized accelerators for tasks like image processing or cryptography.

Customizable Context Switch Mechanisms: Each type of co-processor may have unique characteristics and requirements for context switching. MESC can be adapted by developing specific context switch mechanisms tailored to the operational paradigms of these co-processors. For instance, while DNN accelerators may benefit from instruction-level preemption, other co-processors might require different strategies based on their execution models.

Unified Scheduling Policies: The scheduling policies within MESC can be generalized to handle various workloads across different co-processors. By implementing a unified scheduling framework that considers the criticality levels of tasks and their resource requirements, MESC can ensure that high-priority tasks are executed in a timely manner, regardless of the underlying hardware.

Performance Monitoring and Adaptation: To effectively manage diverse workloads, MESC can incorporate performance monitoring tools that assess the execution characteristics of different co-processors. This data can be used to dynamically adjust scheduling and context-switching strategies, optimizing resource utilization and minimizing latency.

Cross-Platform Compatibility: By maintaining compatibility with existing operating systems and APIs, MESC can facilitate the integration of various co-processors without requiring significant changes to application code. This approach encourages the adoption of MESC in a broader range of applications and industries.

What are the potential challenges in applying the MESC approach to safety-critical systems with even stricter real-time requirements?

Applying the MESC framework to safety-critical systems with stricter real-time requirements presents several challenges:

Deterministic Behavior: Safety-critical systems often require deterministic behavior to ensure that all tasks meet their deadlines under all conditions. The introduction of fine-grained context switching may introduce variability in execution times, making it difficult to guarantee that high-priority tasks will always complete within their required time frames.

Increased Complexity: The complexity of managing multiple criticality levels and ensuring that context switches do not violate safety constraints can be significant. This complexity may lead to challenges in verifying the correctness of the system, as the interactions between tasks and the co-processor must be thoroughly analyzed to prevent criticality inversions.

Resource Contention: In safety-critical environments, resource contention can lead to unpredictable delays. MESC must ensure that the allocation of resources, such as memory and processing power, is managed effectively to prevent lower-priority tasks from blocking higher-priority ones, especially during context switches.

Certification and Compliance: Many safety-critical systems are subject to stringent certification processes (e.g., ISO 26262 for automotive systems). The introduction of new frameworks like MESC may require extensive validation and testing to demonstrate compliance with safety standards, which can be time-consuming and costly.

Overhead Management: While MESC aims to minimize overhead during context switches, the additional complexity of managing instruction-level preemption may introduce overhead that could impact the system's ability to meet real-time constraints. Careful analysis and optimization are necessary to ensure that the benefits of MESC do not come at the cost of system performance.

How can the MESC framework be integrated with emerging technologies like edge computing and Internet of Things to enable efficient and predictable execution of mixed-criticality workloads?

Integrating the MESC framework with emerging technologies such as edge computing and the Internet of Things (IoT) can enhance the efficiency and predictability of mixed-criticality workloads through several approaches:

Distributed Processing: MESC can be adapted to support distributed processing across edge devices, allowing for the offloading of computationally intensive tasks to more powerful co-processors located at the edge. This distribution can help balance the workload and reduce latency, ensuring that critical tasks are executed promptly.

Dynamic Resource Allocation: In edge computing environments, resources are often limited and variable. MESC can implement dynamic resource allocation strategies that adjust the availability of processing power and memory based on the current workload and criticality levels of tasks. This adaptability ensures that high-priority tasks receive the necessary resources while maintaining overall system performance.

Real-Time Data Processing: The MESC framework can facilitate real-time data processing in IoT applications by enabling efficient context switching and prioritization of tasks based on their criticality. This capability is essential for applications such as autonomous vehicles or industrial automation, where timely responses to sensor data are crucial.

Interoperability with IoT Protocols: MESC can be designed to work seamlessly with existing IoT communication protocols (e.g., MQTT, CoAP) to ensure that mixed-criticality workloads can be managed effectively across diverse devices. This interoperability allows for the integration of MESC into a wide range of IoT applications, enhancing their reliability and performance.

Edge Analytics and Machine Learning: By incorporating machine learning algorithms into the MESC framework, edge devices can analyze data locally and make real-time decisions based on the criticality of tasks. This capability can improve the responsiveness of IoT systems and ensure that high-priority tasks are executed without delay.

Security and Safety Considerations: As edge computing and IoT systems often operate in untrusted environments, MESC can integrate security measures to protect against potential threats. Ensuring that mixed-criticality workloads are executed securely while maintaining real-time performance is essential for the reliability of these systems.

By leveraging these strategies, the MESC framework can effectively support the execution of mixed-criticality workloads in edge computing and IoT environments, ensuring efficient and predictable performance while addressing the unique challenges posed by these technologies.