The increasing popularity of gigabit Ethernet brings new challenges to the network performance. These challenges include both higher bandwidth and higher packet rates. While bulk transfer traffic is more aggressive in bandwidth consumption, small packet traffic is not shy of its demand for the amount of system resources required to process packets. This article discussed the performance for both bulk transfer and small packet traffic separately to reveal some of the issues and the possible solutions related to gigabit Ethernet performance on Sun Fire servers.
Based on the measurements, Sun GigaSwift Ethernet MMF adapters (driver name ce)hardware can achieve 738 Mbps for a single TCP connection using an initial TCP window of 48 kilobytes or larger. For 10 TCP connections, one ce adapter can achieve 920 Mbps. With per byte cost lowered by the high bandwidth in the backplane, per-packet cost dominates the performance of ce cards on Sun Fire servers. To reduce per-packet transmission overhead, a value of 10 for tcp_maxpsz_multiplier is recommended in addition to enabling deferred acknowledgment. For send-intensive applications, systems with one ce card should have two CPUs. For receive-intensive applications, three CPUs are preferred. Disabling Nagle's algorithm is key to having an acceptable packet rate when the sender is transmitting a series of messages smaller than 1,460 bytes.