Leveraging Protocol Knowledge in Slack Matching

Tuesday October 31, 2006
Hamerschlag Hall D-210
4:30 pm

Girish Venkataramani
Carnegie Mellon University

Stalls, due to mis-matches in communication rates, are a major performance obstacle in pipelined circuits. If the rate of data production is faster than the rate of consumption, the resulting design performs slower than when the communication rate is matched. This can be remedied by inserting pipeline buffers (to temporarily hold data), allowing the producer to proceed if the consumer is not ready to accept data. The problem of deciding which channels need these buffers (and how many) for an arbitrary communication profile is called the slack matching problem; the optimal solution to this problem has been shown to be NP-complete.

In this talk, I will present a heuristic that uses knowledge of the communication protocol to explicitly model these bottlenecks, and an iterative algorithm to progressively remove these bottlenecks by inserting buffers. I will show how this approach naturally handles large designs with arbitrarily cyclic and acyclic topologies, and which exhibit various types of control choice. The heuristic is efficient, achieving linear time complexity in practice, and produces solutions that (a) achieve up to 60% performance speedup on large media processing kernels, and (b) can either be verified to be optimal, or the approximation margin can be bounded. I will be presenting this paper at ICCAD 2006.

Girish is an n-th year Phd student, who has spent the last few years understanding the nature of asynchronous circuits, hardware compilation, and large, coarse-grained reconfigurable fabrics. He is part of the Phoenix team supervised by his adviser, Seth Goldstein.