# RT-Gang: Real-Time Gang Scheduling Framework for Safety-Critical Systems

## TL;DR

RT-Gang is a new real-time scheduling framework that enforces one gang at a time to improve predictability in multicore systems, using memory bandwidth throttling to safely run best-effort tasks.

## Contribution

It introduces a one-gang-at-a-time scheduling policy with integrated memory bandwidth throttling, enhancing predictability for safety-critical multicore systems.

## Key findings

- Significantly improves system predictability.
- Negligible overhead in implementation.
- Effective in real-world DNN workloads.

## Abstract

In this paper, we present RT-Gang: a novel real-time gang scheduling framework that enforces a one-gang-at-a-time policy. We find that, in a multicore platform, co-scheduling multiple parallel real-time tasks would require highly pessimistic worst-case execution time (WCET) and schedulability analysis - even when there are enough cores - due to contention in shared hardware resources such as cache and DRAM controller. In RT-Gang, all threads of a parallel real-time task form a real-time gang and the scheduler globally enforces the one-gang-at-a-time scheduling policy to guarantee tight and accurate task WCET. To minimize under-utilization, we integrate a state-of-the-art memory bandwidth throttling framework to allow safe execution of best-effort tasks. Specifically, any idle cores, if exist, are used to schedule best-effort tasks but their maximum memory bandwidth usages are strictly throttled to tightly bound interference to real-time gang tasks. We implement RT-Gang in the Linux kernel and evaluate it on two representative embedded multicore platforms using both synthetic and real-world DNN workloads. The results show that RT-Gang dramatically improves system predictability and the overhead is negligible.