-@node Introduction, Pintos Tour, Top, Top
+@node Introduction
@chapter Introduction
Welcome to Pintos. Pintos is a simple operating system framework for
Object file for the entire kernel. This is the result of linking
object files compiled from each individual kernel source file into a
single object file. It contains debug information, so you can run
-@command{gdb} or @command{backtrace} (@pxref{Backtraces}) on it.
+GDB (@pxref{GDB}) or @command{backtrace} (@pxref{Backtraces}) on it.
@item kernel.bin
Memory image of the kernel. These are the exact bytes loaded into
from them by @option{--}, so that the whole command looks like
@code{pintos @var{option}@dots{} -- @var{argument}@dots{}}. Invoke
@code{pintos} without any arguments to see a list of available options.
-Options can select a simulator to use: the default is Bochs, but on the
-Linux machines @option{--qemu} selects qemu. You can run the simulator
-with a debugger (@pxref{gdb}). You can set the amount of memory to give
+Options can select a simulator to use: the default is Bochs, but
+@option{--qemu} selects qemu. You can run the simulator
+with a debugger (@pxref{GDB}). You can set the amount of memory to give
the VM. Finally, you can select how you want VM output to be displayed:
use @option{-v} to turn off the VGA display, @option{-t} to use your
terminal window as the VGA display instead of opening a new window
@node Debugging versus Testing
@subsection Debugging versus Testing
-When you're debugging code, it's useful to be able to be able to run a
+When you're debugging code, it's useful to be able to run a
program twice and have it do exactly the same thing. On second and
later runs, you can make new observations without having to discard or
verify your old observations. This property is called
second of real time. Simulation in real-time mode is not reproducible,
and options @option{-j} and @option{-r} are mutually exclusive.
-On the Linux machines only, the qemu simulator is available as an
+The qemu simulator is available as an
alternative to Bochs (use @option{--qemu} when invoking
@command{pintos}). The qemu simulator is much faster than Bochs, but it
only supports real-time simulation and does not have a reproducible
code that you submit. We will read your entire design document and much
of your source code.
+Don't forget that the design document is 50% of your project grade. It
+is better to spend one or two hours writing a good design document than
+it is to spend that time getting the last 5% of the points for tests and
+then trying to rush through writing the design document in the last 15
+minutes.
+
+@menu
+* Design Document::
+* Source Code::
+@end menu
+
+@node Design Document
+@subsubsection Design Document
+
We provide a design document template for each project. For each
significant part of a project, the template asks questions in four
-areas: data structures, algorithms, synchronization, and rationale. An
-incomplete design document or one that strays from the template without
-good reason may be penalized. Incorrect capitalization, punctuation,
-spelling, or grammar can also cost points. @xref{Project
-Documentation}, for a sample design document for a fictitious project.
+areas:
+
+@table @strong
+@item Data Structures
+
+The instructions for this section are always the same:
+
+@quotation
+Copy here the declaration of each new or changed @code{struct} or
+@code{struct} member, global or static variable, @code{typedef}, or
+enumeration. Identify the purpose of each in 25 words or less.
+@end quotation
+
+The first part is mechanical. Just copy new or modified declarations
+into the design document, to highlight for us the actual changes to data
+structures. Each declaration should include the comment that should
+accompany it in the source code (see below).
+
+We also ask for a very brief description of the purpose of each new or
+changed data structure. The limit of 25 words or less is a guideline
+intended to save your time and avoid duplication with later areas.
+
+@item Algorithms
-Design quality will also be judged based on your source code. We will
+This is where you tell us how your code works, through questions that
+probe your understanding of your code. We might not be able to easily
+figure it out from the code, because many creative solutions exist for
+most OS problems. Help us out a little.
+
+Your answers should be at a level below the high level description of
+requirements given in the assignment. We have read the assignment too,
+so it is unnecessary to repeat or rephrase what is stated there. On the
+other hand, your answers should be at a level above the low level of the
+code itself. Don't give a line-by-line run-down of what your code does.
+Instead, use your answers to explain how your code works to implement
+the requirements.
+
+@item Synchronization
+
+An operating system kernel is a complex, multithreaded program, in which
+synchronizing multiple threads can be difficult. This section asks
+about how you chose to synchronize this particular type of activity.
+
+@item Rationale
+
+Whereas the other sections primarily ask ``what'' and ``how,'' the
+rationale section concentrates on ``why.'' This is where we ask you to
+justify some design decisions, by explaining why the choices you made
+are better than alternatives. You may be able to state these in terms
+of time and space complexity, which can be made as rough or informal
+arguments (formal language or proofs are unnecessary).
+@end table
+
+An incomplete, evasive, or non-responsive design document or one that
+strays from the template without good reason may be penalized.
+Incorrect capitalization, punctuation, spelling, or grammar can also
+cost points. @xref{Project Documentation}, for a sample design document
+for a fictitious project.
+
+@node Source Code
+@subsubsection Source Code
+
+Your design will also be judged by looking at your source code. We will
typically look at the differences between the original Pintos source
tree and your submission, based on the output of a command like
@code{diff -urpb pintos.orig pintos.submitted}. We will try to match up your
discrepancies between the description and the actual code will be
penalized, as will be any bugs we find by spot checks.
-The most important aspects of design quality are those that specifically
+The most important aspects of source code design are those that specifically
relate to the operating system issues at stake in the project. For
example, the organization of an inode is an important part of file
system design, so in the file system project a poorly designed inode
Pintos is written in a consistent style. Make your additions and
modifications in existing Pintos source files blend in, not stick out.
In new source files, adopt the existing Pintos style by preference, but
-make the self-consistent at the very least. Use horizontal and vertical
-white space to make code readable. Add a comment to every structure,
-structure member, global or static variable, and function definition.
-Update existing comments as you modify code. Don't comment out or use
-the preprocessor to ignore blocks of code. Use assertions to document
-key invariants. Decompose code into functions for clarity. Code that
-is difficult to understand because it violates these or other ``common
-sense'' software engineering practices will be penalized.
+make your code self-consistent at the very least. There should not be a
+patchwork of different styles that makes it obvious that three different
+people wrote the code. Use horizontal and vertical white space to make
+code readable. Add a brief comment on every structure, structure
+member, global or static variable, and function definition. Update
+existing comments as you modify code. Don't comment out or use the
+preprocessor to ignore blocks of code (instead, remove it entirely).
+Use assertions to document key invariants. Decompose code into
+functions for clarity. Code that is difficult to understand because it
+violates these or other ``common sense'' software engineering practices
+will be penalized.
In the end, remember your audience. Code is written primarily to be
read by humans. It has to be acceptable to the compiler too, but the
Pintos and this documentation were written by Ben Pfaff
@email{blp@@cs.stanford.edu}.
+The GDB macros supplied with Pintos were written by Godmar Back
+@email{gback@@cs.vt.edu}, and their documentation is adapted from his
+work.
+
The original structure and form of Pintos was inspired by the Nachos
instructional operating system from the University of California,
-Berkeley. A few of the source files were originally more-or-less
-literal translations of the Nachos C++ code into C. These files bear
-the original UCB license notice.
+Berkeley.
A few of the Pintos source files are derived from code used in the
Massachusetts Institute of Technology's 6.828 advanced operating systems
course. These files bear the original MIT license notice.
The Pintos projects and documentation originated with those designed for
-Nachos by current and former CS140 teaching assistants at Stanford
+Nachos by current and former CS 140 teaching assistants at Stanford
University, including at least Yu Ping, Greg Hutchins, Kelly Shaw, Paul
-Twohey, Sameer Qureshi, and John Rector. If you're not on this list but
-should be, please let me know.
+Twohey, Sameer Qureshi, and John Rector.
-Example code for condition variables (@pxref{Condition Variables}) is
+Example code for monitors (@pxref{Monitors}) is
from classroom slides originally by Dawson Engler and updated by Mendel
-Roseblum.
+Rosenblum.
@node Trivia
@section Trivia
Pintos originated as a replacement for Nachos with a similar design.
Since then Pintos has greatly diverged from the Nachos design. Pintos
differs from Nachos in two important ways. First, Pintos runs on real
-or simulated 80@var{x}86 hardware, whereas Nachos runs as a process on a
-host operating system. Second, like most real-world operating systems,
-Pintos is written in C, whereas Nachos is written in C++.
+or simulated 80@var{x}86 hardware, but Nachos runs as a process on a
+host operating system. Second, Pintos is written in C like most
+real-world operating systems, but Nachos is written in C++.
Why the name ``Pintos''? First, like nachos, pinto beans are a common
Mexican food. Second, Pintos is small and a ``pint'' is a small amount.
projects / pintos-anon / blobdiff