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USENIX, The Advanced Computing Systems Association

2006 USENIX Annual Technical Conference Abstract

Pp. 91–96 of the Proceedings

An Evaluation of Network Stack Parallelization Strategies in Modern Operating Systems

Paul Willmann, Scott Rixner, and Alan L. Cox, Rice University


As technology trends push future microprocessors toward chip multiprocessor designs, operating system network stacks must be parallelized in order to keep pace with improvements in network bandwidth. There are two competing strategies for stack parallelization. Message-parallel network stacks use concurrent threads to carry out network operations on independent messages (usually packets), whereas connection-parallel stacks map operations to groups of connections and permit concurrent processing on independent connection groups. Connection-parallel stacks can use either locks or threads to serialize access to connection groups. This paper evaluates these parallel stack organizations using a modern operating system and chip multiprocessor hardware.

Compared to uniprocessor kernels, all parallel stack organizations incur additional locking overhead, cache inefficiencies, and scheduling overhead. However, the organizations balance these limitations differently, leading to variations in peak performance and connection scalability. Lock-serialized connection-parallel organizations reduce the locking overhead of message-parallel organizations by using many connection groups and eliminate the expensive thread handoff mechanism of thread-serialized connection-parallel organizations. The resultant organization outperforms the others, delivering 5.4 Gb/s of TCP throughput for most connection loads and providing a 126% throughput improvement versus a uniprocessor for the heaviest connection loads.

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Last changed: 15 Sept. 2006 ch