Research And Implementation Of DMA Mechanism Of High Speed Network Interface Card

With the rapid development of the internet link speed, lots of high speed network interface cards are used in high performance servers. In order to improve the I/O efficiency and lighten the load of the CPU in servers, the high performance network interface cards use DMA mechanism to communicate with the host. DMA engine is the functional unit to implement the DMA mechanism. It is used to exchange data between the host and the network interface card. Meanwhile, it produces receiving and sending interrupts.The main work and contributions of the thesis are:(1) The processes of receiving and sending data packets of the DMA engine are analyzed in details and the cores of DMA engine: the interrupt mechanism and descriptor mechanism are introduced clearly;(2) Aiming at the problem of"receive livelock", a solution is proposed from the design of the DMA engine;(3) The abstract models of the sending and receiving processes in DMA engine are presented. The concepts of DMA engine receiving stop and driver sending stop are presented. Basing on this, the quantitative relationship among the parameters which impact the performance of DMA engine are analyzed;(4) The implementation of DMA engine in 10G TOE network interface card is introduced. Experimental results show that the design of the DMA engine is correct and effective;(5) The DMA engine based on multi_queue descriptors is presented. Through this way the receiving performance of the DMA engine is improved.As a word, lots of works have been done on the study of the design of the DMA engine. They will be quite helpful for the design of the high_speed network interface card.