Global Adaptation Controlled by an Interactive Consistency Protocol

Abstract

Static schedules for systems can lead to an inefficient usage of the resources, because the system's behavior cannot be adapted at runtime. To improve the runtime system performance in current time-triggered Multi-Processor System on Chip (MPSoC), a dynamic reaction to events is performed locally on the cores. The effects of this optimization can be increased by coordinating the changes globally. To perform such global changes, a consistent view on the system state is needed, on which to base the adaptation decisions. This paper proposes such an interactive consistency protocol with low impact on the system w.r.t. latency and overhead. We show that an energy optimizing adaptation controlled by the protocol can enable a system to save up to 43% compared to a system without adaptation.

Adaptive Time-Triggered Multi-Core Architecture

“…The agreement on the context is realized by a broadcast protocol, which sends the messages with the context using a ring relay between all tiles, meaning that a message is sent by each tile to its neighbor and gets incrementally relayed until reaching the original sender [11].…”

“…Upon the trigger, the context-agreement unit reads the context ports and assembles a local context vector by concatenating the context information for different events. Once the information is gathered, the local context vector is sent to the other tiles within an agreement message that identifies the context string using the source tile id [11].…”

“…This can be done via the NoC or via a dedicated network [11]. The use of the NoC involves no hardware overhead for the implementation, but the agreement messages need to be added to the scheduling problem.…”

“…For the evaluation in Section 7, we implemented a FIFO ring structure where the agreement messages can be sent at arbitrary times without consideration of the application communication at the NoC. This implementation has shown to be able to save more energy than a NoC implementation in a benchmark setup [11].…”

“…The paper builds on previous work of the authors where a non-adaptive time-triggered multi-core architecture [6] was introduced as well as individual components for agreement [11] and adaptation [12]. This paper introduces the overall architecture of an adaptive time-triggered multi-core architecture along with the interplay of agreement, adaptation and meta scheduling.…”