Processor Controlled Off-Processor I/O

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..

Communication support for cluster computing

Ph.D.Karsten Schwa

A Network Co-processor-Based Approach to Scalable Media Streaming

This paper presents the embedded construction and experimental results for a media scheduler on i960 RD equipped I2O Network Interfaces (NI) used for streaming. We utilize the Distributed Virtual Communication Machine (DVCM) infrastructure developed by us which allows run-time extensions to provide scheduling for streams that may require it. The scheduling overhead of such a scheduler is 65 microseconds with the ability to stream MPEG video to remote clients at requested rates. Moreover, placement of scheduler action Close to the network on the Network Interface(NI) allows tighter coupling of computation and communication, eliminating traffic from the host bus and memory subsystem and allowing increased host CPU utilization for other tasks. This makes media scheduling a viable and strong candidate for offloading on NIs. Architectures to build scalable media scheduling servers are explored - by distributing media schedulers and media stream producers among NIs within a server and clustering a number of such servers using commodity hardware and software

The Effects of Wide-Area Conditions on WWW Server Performance

WWW workload generators are used to evaluate web server performance, and thus have a large impact on what performance optimizations are applied to servers. However, current benchmarks ignore a crucial component: how these servers perform in the environment in which they are intended to be used, namely the widearea Internet. This paper show