Processor Controlled Off-Processor I/O

Abstract

The performance of modern RISC processors on operating system code is well below application code performance. The kernel code implementing communication services across the network is not an exception. Modern networking technologies are characterized by a small packet size, which further increases the communication overhead. We took the approach of removing the kernel layer from the cross-machine communication path while still providing protection. The presence of a programmable communication processor on the network adapter made this experiment possible. The firmware running on the communication processor implements a Virtual Communication Machine (VCM); applications communicate with the VCM through shared memory without having to switch to kernel mode. Data is transferred directly between application buffers and the network without any intermediate buffering in the user or kernel spaces. The VCM architecture makes this possible; in particular, the VCM can be programmed to..