Speculative Defragmentation - A Technique to Improve the Communication Software Efficiency for Gigabit Ethernet

Cluster platforms like CoPs offer good compute performance, but still they cannot yet utilize the potential of Gigabit /s communication technology, at least not with commodity network adapters like Ethernet NICs and standard protocols like TCP/IP. To sustain the raw network speed in applications, a "zero-copy" network interface architecture is required, but for widely used stacks a last copy is required for the (de)fragmentation of the transferred network packets. Correctly defragmenting packets of various communication protocols in hardware is an extremely complex task. We therefore consider a speculative defragmentation technique, that can eliminate the last defragmenting copy operation in zero-copy TCP/IP stacks on existing hardware. We integrated a network interface driver with speculative defragmentation into an existing protocol stack and added well known page remapping and fast buffers strategies. Measurements indicate, that we can improve the performance for Gigabit Ethernet over a standard Linux~2.2 TCP/IP stack by a factor of 1.5--2 for uninterrupted burst transfers