Receive descriptor recycling for small packet high speed Ethernet traffic

This paper presents the concept of receive descriptor recycling to significantly reduce the performance drop associated with small packet Gigabit Ethernet traffic. Since limits and trade-offs are inherent when optimising for small packet traffic, all important aspects in this context are covered. Low-level measurements were performed at the CERN LHCb online data acquisition (DAQ) system, which is to a large extend made up of commodity equipment. Results gathered show the Ethernet controller (network interface card, NIC) driver currently is the major bottleneck, preventing the system from reaching maximal Gigabit Ethernet performance. Receive descriptor recycling is implemented under Linux for Intel´s e1000 NIC driver, and is shown to successfully remedy the driver inefficiency