Enhanced control path for repeated TCP connections

This paper presents FALTCON that enhances the control path for repeated TCP connections. First, we measure and find that the control path of TCP stack consumes as many CPU cycles as that of the data path, which brings up the importance of optimizing the control path. Yet, to the best of our knowledge, there has been little research effort on investigating the control path. Also, we observe that a significant portion of TCP traffic (e.g., HTTP) is not only short-lived but also repeated for a server and client pair. We design FALTCON to take advantage of the property of being repeated. Specifically, FALTCON re-designs the control path to remove the duplicate allocation of the structures and redundant operations over them. FALTCON is implemented in Linux 5.1 that has the latest and highly efficient networking stack. Furthermore, we optimize FALTCON to be lockless entirely and to work per-core. The experiment results show that FALTCON achieves a higher number of connections than Linux, up to 19%, and with much less CPU cycles up to 31%.