Occamy: A Preemptive Buffer Management for On-chip Shared-memory Switches

TL;DR

Occamy is a novel preemptive buffer management scheme for on-chip shared-memory switches that dynamically reallocates buffer space, significantly improving performance in high-speed, bursty network environments.

Contribution

This paper introduces Occamy, the first feasible preemptive buffer management scheme for modern switches, enabling rapid buffer reallocation to meet dynamic traffic demands.

Findings

Up to 55% performance improvement in testbed and simulations

Preemptive BM is feasible on modern switch chips

Active buffer reclamation enhances switch agility

Abstract

Today's high-speed switches employ an on-chip shared packet buffer. The buffer is becoming increasingly insufficient as it cannot scale with the growing switching capacity. Nonetheless, the buffer needs to face highly intense bursts and meet stringent performance requirements for datacenter applications. This imposes rigorous demand on the Buffer Management (BM) scheme, which dynamically allocates the buffer across queues. However, the de facto BM scheme, designed over two decades ago, is ill-suited to meet the requirements of today's network. In this paper, we argue that shallow-buffer switches, intense bursts, along with dynamic traffic call for a highly agile BM that can quickly adjust the buffer allocation as traffic changes. However, the agility of the current BM is fundamentally limited by its non-preemptive nature. Nonetheless, we find that preemptive BM, considered unrealizable in history, is now feasible on modern switch chips. We propose Occamy, a preemptive BM that can quickly adjust buffer allocation. Occamy utilizes the redundant memory bandwidth to actively reclaim and reallocate the over-allocated buffer. Testbed experiments and large-scale simulations show that Occamy can improve the end-to-end performance by up to ~55%.