X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=sigcse2009%2Fintroduction.tex;h=a36b89b42ea72b9a873488f11b9321ac7dd6d881;hb=b8a1f89c3dcd584ebc1f91d9e1e8f42606d4df03;hp=5d003182f995a6fbe254496560835047914bbdd8;hpb=37ef93b68fdeedab580c67d2e0bbbaa5374c391d;p=pintos-anon diff --git a/sigcse2009/introduction.tex b/sigcse2009/introduction.tex index 5d00318..a36b89b 100644 --- a/sigcse2009/introduction.tex +++ b/sigcse2009/introduction.tex @@ -3,12 +3,12 @@ Despite the wide use of higher-level languages and environments, gaining a robust understanding of operating systems (OS) fundamentals and training in the current design and -implementation practices of operating systems remains a cornerstone goal of +implementation practices of OS remains a cornerstone of undergraduate computer science education. % abstract/concrete % internal/external -Approaches to teaching such a course generally fall along two axes: +Approaches to teaching OS courses generally fall along two axes: whether the treatment of the material is abstract or concrete~\cite{Hovemeyer2004Running}, and whether they adopt an internal or external perspective~\cite{Deitel2003Operating}. @@ -21,40 +21,39 @@ from the point of view of the OS designer, whereas the external perspective assumes the role of a user or programmer using an OS's facilities~\cite{Bryant2002Computer}. +% we don't really say about the benefits of the 'internal' approach here. % is this too controversial for this audience? -The approach advocated in this paper adopts a concrete approach and the internal -perspective. Students who have been in the role of an -OS designer bring a better understanding of how to use one; and students -who have both studied, implemented, and evaluated core OS techniques obtain +The approach advocated in this paper is concrete and adopts the internal perspective. +Students who have studied, implemented, and evaluated core OS techniques attain a deeper understanding than those who have merely studied them. Finally, adopting a concrete approach brings significant secondary benefits, including training in modern software development techniques and tools. The C language remains the implementation language of choice for operating system kernels and for many embedded systems. -Practice and debugging skills in C, particularly using modern tools, +Practice and debugging experience in C, particularly using modern tools, not only increases students' ``market value,''~\cite{1292450} but provides students with the insight that a low-level programming and runtime model is not incompatible with high-level tools. Designing course material for the internal and concrete -approach is challenging for several reasons. While realistic, +approach is challenging. While realistic, assignments should be relatively simple and doable within a realistic time frame. Whereas assignments should use current hardware architectures, -they must not impart too much knowledge that is transient. +they must not impart too much transient knowledge. Assignments should include and emphasize the use of modern software engineering practices and tools, such as dynamic program analysis. This paper introduces Pintos, an instructional operating system kernel that -has been in use at several institutions for about 4 years. Pintos provides -a bootable kernel for standard personal computers. We provide several +has been in use at multiple institutions for about 4 years. Pintos provides +a bootable kernel for standard x86-based personal computers. We provide four structured assignments in which students implement a basic priority -scheduler, a multi-level feedback queue scheduler, the ability to -load programs and support a set of system calls, page-based virtual memory +scheduler, a multi-level feedback queue scheduler, a process-based +multi-programming system, page-based virtual memory including on-demand paging, memory-mapped files, and swapping, and a simple hierarchical file system. An overview of the projects enabled by Pintos is given in Figure~\ref{fig:pintosdetail}, which shows which -software is provided, which is created by students, and the relative -relationship of test cases to Pintos modules. +software is provided as support code and test cases, +the parts that are created by students, and their relationship. Although Pintos follows in the tradition of instructional operating systems such as Nachos~\cite{Christopher1993Nachos}, OS/161~\cite{Holland2002New}, and @@ -64,29 +63,32 @@ BLITZ~\cite{PorterOverview}, JOS~\cite{1088822}, or Yalnix~\cite{1088822}, we believe that it is unique in two aspects. First, Pintos runs on both real hardware and in emulated and -simulated environments.\footnote{GeekOS claims to also run on real hardware, it requires, -however, a dedicated disk and does not support running off USB devices, making -it impractical for many lab settings.} +simulated environments.\footnote{\small GeekOS is the only other system that claims to +also run on real PC hardware; it requires, however, a dedicated disk and +does not support running off USB devices, making it impractical for many +laboratory settings.} We believe that having the ability to see the outcome +of their project interact with actual hardware increases student engagement. Second, we have created a set of analysis tools for the emulated environment that allows students to detect programming mistakes such as race conditions. Figure~\ref{fig:pintosenvs} shows the three environments in which the same kernel can be run. Others have used Linux, either on dedicated devices (e.g., iPodLinux~\cite{1352199}), -or in virtualizated environments~\cite{1008027,1352648,Nieh2005Experiences}, to provide +or in virtualized environments~\cite{1008027,1352648,Nieh2005Experiences}, to provide an internal, concrete perspective. Compared to those approaches, Pintos provides -a similar level of realism to students in that they can see the result of their +a similar level of realism in that students can see the results of their work on concrete or virtualized hardware, but does not require that students understand the often arcane and ill-documented interfaces of the Linux kernel, -which were not designed from an educational perspective. +which were not designed from an educational perspective. +By contrast, all Pintos code is written to be studied by students. -This paper summarizes the design philosophy that underlies Pintos, -details its structure, and outlines the nature and learning goals of each -assignment. +%This paper summarizes the design philosophy that underlies Pintos, +%details its structure, and outlines the nature and learning goals of each +%assignment. \pintosenvfigure{} -\pintosdetailfigure{} +\pintosdetailfiguretwo{} % Challenges. % How to embed principles?