CISC 322
Software/Game Architecture
Module 4: Examples of Architectures
(Linux)
Ahmed E. Hassan
Linux as a Case Study: Its Extracted
Software Architecture
Paper By: Ivan T. Bowman, Richard C. Holt and
Neil V. Brewster
Slides By: Jack ZhenMing Jiang
Outline
l Terminology
l Conceptual Architecture
l Concrete Architecture
l Conclusions
3
Terminology
l Conceptual Architecture
– How developers think of a system; Relations meaningful to
developers
– Analogy: Blue Print of the House
– By Reviewing Existing Documentation
– Essential Relations
l Concrete Architecture
– Relations that exists in a system
– Analogy: Actual Architecture of the House
– By Examining the Source Code
– Implementation Specific Knowledge
4
The Linux Kernel
l Responsible for process, memory, and
hardware device management
– Different from the Linux System
l Linux System: 10 KLOC in 1991 to 1.5
MLOC in 1998
l The studied Linux Kernel is 800 KLOC
l Open Source
5
Conceptual Architecture – Top
Level
6
Conceptual Architecture – File
System
9/6/187
Façade Pattern
Object Oriented Style
1
Concrete Architecture – Extraction
Methodology
9/6/188
Control Flow
Data Flow
Manually
-Group Directory to Subsystems
-Naming Conventions
Feedback
Concrete Architecture – Top Level
9/6/18 Jack ZhenMing Jiang9
Concrete Architecture – File
System
9/6/18 Jack ZhenMing Jiang10
Concrete Architecture – File
System
9/6/18 Jack ZhenMing Jiang11
1
2
Concrete Architecture – Logical File
System
9/6/1812
1
2
Why Conceptual Architecture and
Concrete Architecture Not Match?
l Missing Relations in Conceptual Architecture
l More Functionalities
– For example, Process Scheduler
l Use Different Mechanisms
l Improve Efficiency by Bypassing Existing
Interfaces
l Exist for Developer Expediency
– “The read-only stuff doesn’t really belong here, but
any other place is probably as bad and I don’t want to
create yet another include file.”
13
What To Do Next?
l Restructure to Remove Unexpected
Dependencies
– Header Files
– Lower Coupling
l Refine Conceptual Architecture
– Not Hinder System Understanding
14
Conclusions
15
l Conceptual and Concrete Architecture
for the Linux Kernel
l Similar Work Needs to Be Done for the
Firefox Report
l Sample Reports:
– Conceptual Architecture:
http://plg.uwaterloo.ca/~itbowman/CS746G/
a1/
– Concrete Architecture:
http://plg.uwaterloo.ca/~itbowman/CS746G/
a2/