John Davis Palmer

A decompression core for powerPC

Code size efficiency is a critical parameter in the design of computer systems for embedded applications. This paper describes a method for improving code size efficiency involving the use of compression techniques to reduce the size of the stored code, and on-the-fly hardware decompression at full processor speed for execution. A simple frequency-based encoding scheme for PowerPC® code achieves a typical code size reduction to 60% of the original size. A corresponding decompression core has been implemented for an embedded microprocessor, such as the PowerPC 401TM. The compression/decompression scheme operates in a manner transparent to the processor and requires no changes to such tools as compilers, linkers, and loaders.

Position: short object lifetimes require a delete-optimized storage system

Early file systems were designed with the expectation that data would typically be read from disk many times before being deleted; on-disk structures were therefore optimized for reading. As main memory sizes increased, more read requests could be satisfied from data cached in memory, motivating file system designs that optimize write performance. Here, we describe how one might build a storage system that optimizes not only reading and writing, but creation and deletion as well. Efficiency is achieved, in part, by automating deletion based on relative retention values rather than requiring data be deleted explicitly by an application. This approach is well suited to an emerging class of applications that process data at consistently high rates of ingest. This paper explores trade-offs in clustering data by retention value and age and examines the effects of allowing the retention values to change under application control.

Monitormining: creating domain knowledge for system automation using a gray-box approach

The effectiveness of automated system management is dependent on the domain-specific information that is encoded within the management framework. Existing approaches for defining the domain knowledge are categorized into white-box and black-box approaches, each of which has limitations. White-box approaches define detailed formulas for system behavior, and are limited by excessive complexity and brittleness of the information. On the other hand, black-box techniques gather domain knowledge by monitoring the system; they are error-prone and require an infeasible number of iterations to converge in real-world systems. Monitormining is a gray-box approach for creating domain knowledge in automated system management; it combines simple designer-defined specifications with the information gathered using machine learning. The designer specifications enumerate input parameters for the system behavior functions, while regression techniques (such as neural networks, support vector machines) are used to derive the mathematical function that relates these parameters. These functions are constantly refined at run-time, by periodically invoking regression on the newly monitored data. Monitormining has the advantage of reduced complexity of the designer specifications, better accuracy of regression functions due to a reduced parameter set, and self-evolving with the changes in the system. Our initial experimental results of applying monitormining are quite promising.

Specifying Business Policy Using Agent-Contract Meta-Constructs

Business policy is a set of rules, regulations, invariants and definitions that govern the behavior of an enterprise. It is typically formulated by business people and formalized by lawyers. Business policy is often written down. However, much policy exists only in the memories of those who work for or with an enterprise. Still other policy is embedded in the code of enterprise software systems.

Beware the lure of software slogans

The author considers the advantages and disadvantages of software slogans. He explains how slogans can help sell new ideas, but unfortunately can also be dangerous. Too often developers turn slogans into a fundamental software engineering principle, which then becomes a commandment.