topics
Virtual Today's Environment for Computing Operating Systems
Upcoming Program Execution Times (Great Ideas, Chapter 13) Reading Great Ideas, Chapter 10
CompSci 001 34.1
The Problem
The Raw Machine Provides a Hostile Environment
Imagine program in machine language (on real machine).
8fa40000 lw $4, 0($29) 27a50004 addiu $5, $29, 4 24a60004 addiu $6, $5, 4 00041080 00c23021 0c000000 3402000a 0000000c
Machine Language Program for MIPS Machine
[00400000] [00400004] argv [00400008] envp [0040000c] [00400010] [00400014] [00400018] [0040001c] ; lw $a0, 0($sp) ; addiu $a1, $sp, 4 # ; addiu $a2, $a1, 4 # sll $v0, $a0, 2 addu $a2, $a2, $v0 jal main li $v0 10 syscall
Imagine doing disk I/O directly:
sll $2, $4, 2 ; addu $6, $6, $2 ; jal 0x00400020 [main]; ori $2, $0, 10 ; syscall ;
disk description controlling Heads; timing keeping track of where things are stored dealing with Errors
34.2
CompSci 001
The Problem
Other I/O
Keeping track of memory (RAM)
Keyboard Screen Communications Multiple tasks Multiple users Multiple tasks Multiple users
Sharing the CPU
The User Interface Problem
For the computer professional only? For the lay person The Graphical User Interface
o Computation to support this?
34.3
CompSci 001
Historical Perspective
Early Years
Had Major Theme: CPU Time Precious
Early 1960's machines: Almost Bare Mid 1960's Machines: Early Batch Operating Systems Multiprogramming Systems Time Sharing Lab Computers Ease of use: very low priority Graphical User Interface too costly (and not yet invented) This perspective faded with time and began to disappear with advent of the microprocessor: Cheap CPU time.
CompSci 001
34.4
Historical Perspective
Later Years
Major Change: Lower Costs
Microprocessor in late 70's PC's in early 80's: Operating Systems for PC Apple: Macintosh (Xerox PARC) Workstations o UNIX AT&T: License Wars LINUX Whole new audience User Interface
Whole new competitive environment Volume!
o Essential for non pros o Affordable (cpu cycles to burn)
CompSci 001
34.5
Role of the Operating System
1. 2.
Processor Management (Multiprogramming = sharing)
1.
I/O Systems
1. 2. 3.
Several virtual machines
3.
Memory (RAM) Management
1. 2.
Windowing Systems / GUIs File Systems (use of your hard disk) Communications/Networking Sharing Memory Simulating Additional Memory (Virtual Memory) Administration/Accounting Compilers Tools
34.6
4.
Software
Environments
CompSci 001
Memory Management
Virtual Memory
Cache Memory
Simulate memory using disks Simulate faster memory using large slow and small fast memory Library, bookcase, desktop analogies Registers x1 Cache x10 x100 Main Memory x100 x1000 Disks x1,000,000 Card Catalog analogies Finding stuff on your desk or bookcase
34.7
Memory Hierarchies
Overhead
CompSci 001
Memory Management.2
Historically
Paging
Swapping in Time Sharing Systems Whole user image involved Page is conveniently sized block of memory (RAM) Physical swapping done page at a time Security (write protect) Confidentiality (read protect) (lacking on Early machines)
34.8
o (power of 2)
Protection
CompSci 001
I/O Systems
Communications/Networking
Graphical User Interfaces (GUI)
Extremely important in modern systems (Dealt with that before) XWindows Macintosh Desktop MS Windows Born in Xerox PARC; Legal Fun Flat Hierarchical (Directories/Folders) Distributed Files Systems o Andrew File System (AFS) (e.g., at OIT) o Network File System (NFS) (e.g., in Computer Science)
Files Systems
CompSci 001
34.9
Processor Management
Virtual Machines
Process Management
True Parallel Processes vs. Simulated Parallel o Note that the "interleaving" is unpredictable Interrupts o Contrast with "busy waiting" Fairness Responsiveness
Synchronization Problems
Danger of shared resources
...