Walter D, Teich J (2021)
Publication Type: Conference contribution, Conference Contribution
Publication year: 2021
Conference Proceedings Title: Proceedings of the 19th ACM-IEEE International Conference on Formal Methods and Models for System Design (MEMOCODE)
Event location: Beijing, China
The performance of many accelerator architectures depends on the communication with external memory.
During execution, new I/O data is continuously fetched forth and back to memory.
This data exchange is very often performance-critical and a careful orchestration thus vital.
To satisfy the I/O demand for accelerators of loop nests, it was shown that
the individual reads and writes can be merged into larger blocks, which are subsequently transferred by a single DMA transfer.
Furthermore, the order in which such DMA transfers must be issued, was shown to be reducible to a real-time task scheduling problem to be solved at run time.
Rather than just concepts, we investigate in this paper the architecture and implementation of such a Loop I/O Controller (LION) for a class of CGRAs called TCPAs.
Based on a novel heap-based priority queue approach, the proposed controller is able to issue every 6 cycles a new DMA request to a memory bus.
Even on a simple FPGA prototype running at just 200 MHz, this allows for more than 33 million DMA requests to be issued per second.
Since the execution time of a typical DMA request is in general at least one order of magnitude longer, we can conclude that this rate is sufficient to fully utilize a memory bus.
In the evaluation of our architecture, we compare the proposed priority queue with various state-of-the-art approaches and conclude that our priority queue is not only cheaper, but also guaranteeing real-time constraints.
Furthermore, we discuss many different optimizations for the Loop I/O Controller, which can reduce the area of the proposed architecture significantly.
Walter, D., & Teich, J. (2021). LION: Real-Time I/O Transfer Control for Massively Parallel Processor Arrays. In Proceedings of the 19th ACM-IEEE International Conference on Formal Methods and Models for System Design (MEMOCODE). Beijing, China.
Walter, Dominik, and Jürgen Teich. "LION: Real-Time I/O Transfer Control for Massively Parallel Processor Arrays." Proceedings of the 19th ACM-IEEE International Conference on Formal Methods and Models for System Design, Beijing, China 2021.