Mohamed F. Ahmed

Linux bugs: Life cycle, resolution and architectural analysis

Efforts to improve application reliability can be irrelevant if the reliability of the underlying operating system on which the application resides is not seriously considered. An important first step in improving the reliability of an operating system is to gain insights into why and how the bugs originate, contributions of the different modules to the bugs, their distribution across severities, the different ways in which the bugs may be resolved and the impact of bug severities on their resolution times. To acquire this insight, we conducted an extensive analysis of the publicly available bug data on the Linux kernel over a period of seven years. We also justify and explain the statistical bug occurrence trends observed from the data, using the architecture of the Linux kernel as an anchor. The statistical analysis of the Linux bug data suggests that the Linux kernel may draw significant benefits from the continual reliability improvement efforts of its developers. These efforts, however, are disproportionately targeted towards popular configurations and hardware platforms, due to which the reliability of these configurations may be better than those that are not commonly used. Thus, a key finding of our study is that it may be prudent to restrict to using common configurations and platforms when using open source systems such as Linux in applications with stringent reliability expectations. Finally, our study of the architectural properties of the bugs suggests that the dependence among the modules rather than the unreliabilities of the individual modules is the primary cause of the bugs and their impact on system reliability.

Linux Bugs: Life Cycle and Resolution Analysis

Efforts to improve application reliability can fade if the reliability of the underlying operating system on which the application resides is not seriously considered. An important first step in improving the reliability of an operating system is to first gain insights into why and how the bugs originate, contributions of the different modules to the bugs, their distribution across severities, the different ways in which the bug may be resolved and the impact of bug severity on the resolution time. To gain this insight we conducted an extensive analysis of the publicly available bug data on the Linux kernel over a period of seven years. Our observations suggest that the Linux kernel may draw significant benefits from the continual reliability improvement efforts of its developers. These efforts, however, are disproportionately targeted towards popular configurations and hardware platforms, due to which the reliability of these configurations may be better than those that are not commonly used. Thus, a key finding of our study is that it may be prudent to restrict to using common configurations and platforms when using open source systems such as Linux in applications with stringent reliability expectations.

Efficient sorting algorithms for the cell broadband engine

The problem of sorting has been studied extensively and many algorithms have been suggested in the literature for the problem. Literature on parallel sorting is abundant. Many of the algorithms proposed, though being theoretically important, may not perform satisfactorily in practice owing to large constants in their time bounds. The algorithms presented in this paper have the potential of being practical. We suggest some novel sorting mechanisms specific to the cell broadband engine. We try to utilize the specifics of its architecture in order to get the optimum performance. As part of our comparative analysis we juxtapose these algorithms with similar ones implemented on Itanium 2 processor as well as the Pentium 4 processor.

Reliable Operating Systems: Overview and Techniques

Abstract Traditional operating systems’ architectures are primarily focused on achieving superior performance, albeit at the expense of sacrificing reliability. This approach is clearly inadequate, given our growing dependence on computer systems for essential and critical services. Reliability should thus be considered as a first-class citizen alongside functionality and performance, while designing future operating systems. The present paper summarizes the current trends and best practices employed to improve the reliability of operating systems. We also draw attention to the limitations and drawbacks of the prevalent approaches, discuss outstanding issues and propose some promising research directions, which may be explored to build highly reliable operating systems.

Efficient Parallel Simulation of Direct Methanol Fuel Cell Models

Fuel cells, as highly efficient and environment-friendly power sources, have attracted ever-increasing research and development in the past few decades. Mathematical modeling and simulation are applied to examine the influence of the different physical and electrochemical phenomena occurring in the structure of the fuel cell during operation. Such simulation programs take a very long time (of the order of days or even weeks) to run, especially when accurate results are called for. To achieve accurate results and more insight, we need even more complex models (twoand threedimensional models). In this paper, we present techniques for the parallel simulation of a mathematical model of direct methanol fuel cells (DMFC). In particular, we employ a paradigm called LessTalk. LessTalk is a general technique that can be employed to reduce communications in parallel computations. Using LessTalk, we have achieved almost linear speedup in simulating the DMFC model. The results were validated against measurements available from the Connecticut Global Fuel Cell Center (CGFCC). [DOI: 10.1115/1.1840866]