Improving performance of SMTP relay servers: an in-kernel approach

With continuous increase in average size and number of e-mails on the Internet, load on SMTP servers is increasing. This work attempts to measure the improvement in latency and throughput of SMTP relay servers (focusing on CPU activities), that can be obtained by avoiding the expensive system call mechanism and user space-kernel space memory copy. We implement SMTP relay server as a kernel module to be able to call kernel functions (to avoid system calls) and to relay network buffers directly (to avoid memory copy). The current Linux kernel does not allow kernel modules to receive or send network buffers. Hence, we modified the Linux networking layer to incorporate such a framework. An equivalent user mode SMTP relay server was developed to compare the performances. This thesis discusses the details of this approach and presents the experiments conducted and the results obtained.