UKUUG Linux 2001 — Linux Developers' Conference 29 June - 1 July 2001, Renold Building, UMIST, Manchester

Steve Whitehouse - Sistina Software

Zero Copy, Hidden Dragon

Its not very long since the Mindcraft benchmarks sparked a flurry of activity by developers of the Linux network code. Although the initial reason for Linux's poor performance in the test was quickly found and fixed, a number of improvements have since been added resulting in Ingo Molnar's TUX web server which holds SPECweb benchmark records.

One of the enabling technologies behind TUX is the new networking architecture in the 2.4 kernel which Dave Miller and Alexey Kuznetsov have been working upon. This paper will describe some of the changes that were made, concentrating on the "zero copy" architecture which has recently been added to the 2.4.2-ac patches. I will take the Network Block Device as a simple example and show how it can be enhanced to take advantage of zero copy.

Although the zero copy architecture was designed for the TCP/IP stack, it applies equally to other network protocols. I will briefly explore how it can be applied to the other protocols, and in particular the DECnet protocol.

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IBM - Main Sponsor	Astaro Network Firewall	Sistina