Memory Management for User-Level Network Interfaces

With user-level network interfaces applications can access the network directly without operating system intervention on every send and receive. Messages are transferred to and from user-space by the network interface while observing the traditional protection boundaries between processes. First generation user-level network interfaces limit this message transfer to a per-process region of permanently-pinned physical memory to allow safe DMA. This approach is inflexible and does not scale to a large number of processes. A new memory management extension to the U-Net user-level network architecture allows messages to be transferred directly to and from any part of an application's address space. This is achieved by integrating a translation look-aside buffer into the network interface and coordinating its operation with the operating system's virtual memory subsystem. Two implementations demonstrate that existing commodity hardware and commercial operating systems can efficiently support the architecture.