Large Receive Offload implementation in Neterion 10GbE Ethernet driver

The benefits of Transmit Side Offload (TSO) implementation in Ethernet ASICs and device drivers are well known. TSO is a de-facto standard in 2.6 Linux kernel and provides significant reduction in %cpu utilization, especially with 1500 MTU. On a cpu-bound system, these cycles translate into dramatic throughput increase. Unlike TOE, stateless offloads do not break the Linux stack and do not introduce security and support issues. Stateless offload benefits are especially apparent at 10 Gigabit rates. 10GbE sender with TSO hardware support uses a fraction of a single cpu to run at line rate, leaving plenty of cycles for applications. On the receiver side, the Linux stack presently does not have a stateless offload similar to TSO. Receiver %cpu typically becomes a bottleneck that prevents 10GbE adapters from reaching line rate with 1500 mtu. Neterion hw/sw Large Receive Offload (LRO) solution was designed to address this bottleneck and further reduce TCP processing overhead on the receiver. Both design and performance results will be presented.