UNSW Computer Science and Engineering Technical Report no. UNSW-CSE-TR-0412
(21 pages: portable document format file 0412.pdf)

Title: Maintaining End-system Performance under Network Overload

Author: Luke Macpherson, Gernot Heiser
	School of Computer Science and Engineering
	and National ICT Australia
	University of New South Wales
	Sydney 2052, Australia
	E-mail: {lukem, gernot}@cse.unsw.edu.au

Abstract:

Network performance is currently outpacing the performance
improvements seen by host systems, leading to a significant performance
gap between the throughput which may be supported by a network
interface, and the actual throughput which can be achieved by a typical
end-system. Because this is the case, end-systems must be able to cope
with applied loads which exceed their capacities. In particular, system
performance in terms of latency, throughput, and jitter should not
deteriorate under overload.

This paper evaluates the use of intelligent software-based 
control algorithms adjusting the interrupt-holdoff time and the
available DMA buffer space in order to prevent
receive livelock on commodity hosts and network adaptors. We present a
simple analytical model of packet latency, which allows us to analyse
system performance under overload.

The control algorithm has been implemented in the FreeBSD
operating system. Experiments show excellent scalability under overload,
comparing favourably with previous approaches. Furthermore, the
implementation is less intrusive on operating system design than prior
approaches with similar goals.

https://cgi.cse.unsw.edu.au/~reports/papers/0412.pdf