Eric W. Anderson

Container shipping: operating system support for I/O-intensive applications

New I/O devices with data rates ranging from 10 to 100 Mbytes per second are becoming available for personal computers and workstations. Along with continual improvements in processor, memory, and bus technology, these devices have enabled I/O-intensive applications for desktop computing that require input, processing, and output of very large amounts of data. We focus on an important aspect of operating system support for these applications: efficient transfer of large data objects between the protection domains in which processes and devices reside. A rapidly growing class of I/O-intensive applications is multimedia computing. After we present an I/O-pipeline model, we analyze issues relevant to the design of an operating system inter-domain data-transfer facility. Then we present the design for such a facility. An I/O pipeline is a model of a dynamic computation structure consisting of a sequence of domains: an input domain followed by one or more intermediate domains, and an output domain.<<ETX>>

Filter Propagation in Dissemination Trees: Trading Off Bandwidth and Processing in Continuous Media Networks

We describe the concept of the relocatable continuous media filter. The novelty of these filters is how they can propagate over a dissemination tree in a network. We describe the filter propagation protocol to achieve this. Execution of filters inside a network allows the network to be viewed in a novel way, as a “processor” with its “instruction set” being the various types of available filters. Since filters generally modify the data rate of the continuous media stream, usually (but not necessarily) reducing it, filters allow the trading off of bandwidth and processing in a network.

The performance of the Container Shipping I/O system

I/O subsystems, and the APIs used to access them, have long been designed with two basic assumptions. First, I/O is performed to relatively slow disks or terminals, so processor time for I/O operations is available while waiting for devices. Second, optimization is done by guessing the user’s needs, such as a filesystem cache does by assuming locality. This traditional design causes I/O performance problems for modern devices such as video displays and high-speed networks, where the above assumptions are no longer valid. We have designed a high-performance I/O subsystem, and a uniform API through which it is accessed, that gives a user-level programmer greater control, which allows operations to be performed more efficiently, and often optimally. Speedups from 30 to over 700 percent can be demonstrated with our technique. Our API is fully uniform, and yields gains for any form of device, including disks, networks, frame buffers, and even IPC performed through the I/O system. This paper describes our implementation of this mechanism, called Container Shipping, and its measured performance for different kinds of I/O.

The invasion of an Atlantic Ocean river basin in Patagonia by Chinook salmon: new insights from SNPs

Chinook salmon spawning was first reported in the 1980s in the Caterina River tributary of the Santa Cruz River basin of Patagonia, which drains into the Atlantic Ocean. A naturalized population now persists and its source has been debated. Chinook salmon from California populations was directly released into the Santa Cruz River in the early twentieth century, but ocean ranching experiments on the Pacific coast of Patagonia (Chile) also released Chinook salmon of lower Columbia River origin (University of Washington hatchery stock) in the late twentieth century. We used genetic stock identification with single nucleotide polymorphisms to explore the origin of this Chinook salmon population. The genotypes of salmon that invaded the Santa Cruz River were compared with those derived from 69 known populations from the Northern Hemisphere. Chinook Salmon of the Santa Cruz River were found to be most similar to those from the lower Columbia River. This supports the hypothesis that the Santa Cruz River population was founded from the ocean ranching in southern Chile and the river was invaded by fish straying from Pacific coast basins. Moreover, we find that the life history of these naturalized fish, as inferred from scale analysis, was similar to that of the progenitor stock. We suggest that the successful invasion of the Caterina River in Patagonia by Chinook salmon was aided by pre-adaptations of some of the stocks used in the ocean ranching experiments to conditions in the new environment, rather than a post-colonization adaptation.