an integrated approach to teaching computing systems architecture kishore ramachandran & bill...
Post on 26-Dec-2015
214 Views
Preview:
TRANSCRIPT
An Integrated Approach to Teaching Computing Systems Architecture
Kishore Ramachandran &
Bill Leahy
College of ComputingGeorgia Institute of Technology
Outline
• Traditional approach• Pedagogy of new approach• Where does it fit and how do
we put it in practice?• Experience at Tech• Evaluating the pedagogy• Challenges• Comparison to other
pedagogical models• Concluding remarks
Traditional Approach
• Stovepipe model– Architecture and OS as
distinct courses usually in the junior/senior years
• Georgia Tech– Followed similar model until
1999– Two junior level courses
one on OS and the other on architecture
What is wrong with the traditional approach?
• Symbiotic relationship missed– High level language and
instruction sets– OS abstractions and processor– Network protocols and physical
network– Students get this?
• Not if compartmentalized
• Gap between the time when the courses are taken– Concepts forgotten
• Connections not seen at all by the students most of the time
Why change?
• Problems with the traditional approach
• Changing CS scene– New areas evolving– Graphics, visualization, HCI– Need rethinking of “core”
• UG research involvement– Need to infuse interest
early– Entry level for systems
research high
New approach• Excitement of middle-school
kids– What is inside a box?– What makes it play cool music or
video games?
• An integrated course– Combining OS and architecture
• Goal of the course– “Unraveling the box”– Take the journey together
exploring hardware and the OS abstractions
– Emphasize connectedness
Pedagogy of new approach
• Present what is “inside a box”– Processor module– Memory module– I/O and storage module– Parallel module– Network module
• Key differentiator– Concomitant treatment of
hardware and software in each module
Pedagogical style• Discovery as opposed to
indoctrination or instruction• Top down approach
– Start with problem to be solved– Explore solution space together
• Example:– What is memory management?
• Understand the need first• Discover the software issues and
the corresponding hardware issues
• Story telling approach– Keeps the student interest alive
Processor module
• HLL constructs and their influence on instruction-set design
• Simple implementation followed by performance-conscious pipelined implementation
• Process abstraction in OS and processor scheduling
I/O and storage module
• Program discontinuities including interrupts, traps, and exceptions– Processor mechanisms– OS mechanisms
• Devices and device drivers• Emphasis on disk
subsystem– Storage abstraction– File system fundamentals
Parallel module
• Introduce threads as a programming construct
• OS issues for supporting parallel programming
• Architectural issues for supporting parallel programming
Connecting the different modules
• HLL constructs lead to design of instruction-set for LC-2200
• Processor implementation of LC-2200
• Memory management assists to LC-2200
• Interrupt and DMA support to LC-2200
• ……
Why parallelism in a first course?
• Our motivation then (circa 98)– Love affair of CS with parallelism
• PL and concurrency• OS and concurrency
– Enablers in the 90’s• Java, MT OS, multiple CPUs in
desktops
• In hindsight now– Multicore CPUs– Multithreading as a programming
concept in intro courses
Why networking in a first course?
• “box” without connectivity is no good today
• Protocol stack is an integral part of any OS
• Our motivation– Understand evolution of
networking gear– Understand mechanisms
needed in protocol stack– Understand how a “box”
avails of network services
Where does this course fit?
• Assumed knowledge– Logic design, assembly language,
and C programming
• New course is a first systems course– Preferably in sophomore year
• What follows?– Advanced architecture, OS,
networking courses– For those following other pursuits
• Sufficient exposure to “core”
Putting this pedagogical style in practice
• 4 credit-hour semester course or 5-credit hour quarter course
• 45 hours of lecture– Roughly 9 hours for each
module (some more than others)
• 60-90 hours of unsupervised lab time for projects
Experience at Georgia Tech
• CS 2200 introduced in Fall 1999
• Project component for each module– Concepts “get in” via
projects– Collaboration allowed
• Key is “learning”
– Creativity in evaluation
Evaluating the pedagogy
• CS students hardware-averse• OS and hardware together
makes “sense”– Hardware design as an
algorithmic exercise
• Successful internships– Anecdotal evidence from
industries and students
• Concepts learned early apply to other domains (e.g. web caching)
• Students better prepared for advanced courses
• Informal poll– At beginning of course
• 10% interested in the course
– At end of course• Majority feel the course was
useful and important
• Increased interest in systems– Number of UG students doing
research in systems
Other reasons why this is a good approach
• Allows curricular innovation
• GT CS has been a leader of innovation– Evidence
• New ThreadsTM approach• Chapter 7, Pages 309-315,
“The Right Stuff,” from THE WORLD IS FLAT: UPDATED AND EXPANDED EDITION, by Thomas L. Friedman
Meeting the Challenges• Textbook
– Good books available for the stovepipe model
– None for an integrated model• We developed comprehensive
notes and slides– Used standard textbooks as
background• Responding to students
– Turned our courseware into online textbook in 2005
• To match the style and content• Available to the community• In use for 8 consecutive
semesters (including summers)
Adopting the pedagogical style
• Online textbook• Extensive online slides• Several detailed project
ideas from 7+ years of teaching this course
• Several problem sets and model exams online
• In short– Painless transition from
stovepipe model to this one
Comparison to other recent pedagogical models
• Patt and Patel– Logic design, assembly language,
plus C– Ideal as a pre-req for our course
• Bryant and O’Hallaron– Programmer’s perspective– Goal
• How to create “power programmers”?
• Important but different from our focus
– Best applied to senior level UG– A worthy follow on to our course
• Saltzer and Kaashoek– System building blocks that
appear in different large complex software systems
– Goal• How to prepare students who
can create modular software systems?
– A worthy follow on to our course
Concluding remarks
• An integrated approach to teaching computer system architecture at sophomore level
• Been in practice at GT for 7+ years
• Online textbook, slides, project ideas, and tools available for the whole community
Project: Processor Design
• Students given datapath 90% complete
• Project entails– Completing the datapath– Writing micro-code for
implementing LC-2200 instruction set
– Circuit design using LogicWorks
Project: Interrupts and I/O
• Students supplied with LC-2200 simulator and LC-2200 assembler
• Project entails– Adding circuitry to project 1 for
handling interrupts– Enhancing the simulator to deal
with interrupts– Writing an interrupt handler (in
LC-2200 assembly) to work with the enhanced simulator
Project: Virtual memory subsystem• Students supplied with a
processor plus memory system simulator
• Project entails– Developing a page-based
VM system on top– Experimenting with
different page replacement algorithms
Project: MT OS
• Students provided with a processor plus memory system simulator
• Project entails– Implementing multithreaded OS
modules for managing the CPU and I/O scheduling queues
– Parallel programming using pthreads
– Experimenting with different CPU scheduling algorithms
Project: Reliable Transport Layer
• Students provided with a simulated network layer
• Project entails– Implementing a reliable
transport that deals with• Packet corruption• Lost packets• Out-of-order delivery of
packets
– Parallel programming using pthreads
top related