Group Unicast for the Real World

Elad Lahav, Martin Karsten, Tim Brecht, Weihan Wang, and Tony Zhao

Kernel-based group unicast has been suggested as an efficient mechanism for transmitting the same data to multiple recipients. In this paper, we present a new system call, sendgroup(), which also supports per-recipient private data, but only uses a single in-kernel copy of the shared data. We assess the performance of the new system call using micro-benchmarks on three different operating systems. Further, we incorporate sendgroup() into a popular multimedia server and demonstrate an efficiency improvement of ~45% in a representative live-broadcasting scenario. These results show that the new system call is applicable in real-world scenarios, and that its usage can lead to significant performance improvements. Moreover, we demonstrate how Amdahl's Law, when applied to the results of the micro-benchmarks, along with precise analysis of the cost of sending packets, can be used to accurately predict the impact of sendgroup() on this server.

NOSSDAV 2008 - International Workshop on Network and Operating Systems Support for Digital Audio and Video

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