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March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma
INTRODUCTION
Wes J. Lloyd
Institute of Technology
University of Washington - Tacoma
TCSS 422: OPERATING SYSTEMS
Syllabus, Course Introduction
Chapter 4: Operating Systems – Three Easy Pieces
Introduce operating systems
Management of resources
Concepts of virtualization/abstraction
CPU, Memory, I/O
Operating system design goals
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
OBJECTIVES
Syllabus
Grading
Schedule
Assignments
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
TCSS422 – OPERATING SYSTEMS
Assignments
Assignment 0: Linux warm-up
Assignments 1-4: roughly every two weeks
Quizzes
~ 7-8 quizzes
Drop lowest two
Variety of formats: in class, online, reading, tutorial activity
Exams: Midterm and Final
Two pages of notes, calculator
Final exam is comprehensive
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
TCS422 COURSE WORK
Programs:
Please start early
Work as if though the deadline is 2 days earlier
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
TCSS 422: PROGRAM DUE DATES
From Virginia Tech Department of Computer Science - 2011 Better than 50% chance of A/B Less than 50% chance of A/B
CentOS 7
Open source version of RedHat (RHEL) Linux
Package management: YUM repositories
Repositories of RPM (RedHat Package Files)
CentOS Advantages
Enterprise Linux Distribution
CentOS is equivalent to RHEL, a popular commercial Linux distro
Learning CentOS (free) is a proxy for learning RHEL (not free)
Only stable versions of software packages fewer crashes & errors
Fewer releases, more stable, lightweight, fast
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
CENTOS 7 – VIRTUAL MACHINE
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March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
C PROGRAMING IN TCSS 422
Computerworld, 2017 Tech Forecast Survey https://www.tacoma.uw.edu/institute-technology/student-
support-workshops-mentors
Institute of Technology Mentors
Located in Science 106 / 108 Labs
Monday – Thursday: ~10 am – 7 pm
Friday: ~ 1 2-5pm
Spring Hours to be posted
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
C MENTORING
Office hours: to be announced, and by appointment
Due to teaching schedule (TCSS 562 @ 1 2:50pm) only limited
availability immediately after class sessions
End of class: quick questions, assignment Q&A
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
INSTRUCTOR HELP
Questions and discussion are encouraged
Daily feedback surveys
Helpful to know if topics are not clear
Use the survey to write questions that come to you during the lecture
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
CLASS PARTICIPATION
Responsible for: Making it easy to run programs Allowing programs to share memory Enabling programs to interact with devices March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
OPERATING SYSTEMS
OS is in charge of making sure the system operates correctly and efficiently. The OS is a resource manager Manages CPU, disk, network I/O Enables many programs to Share the CPU Share the underlying physical memory (RAM) Share physical devices
Disks
Network Devices
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
RESOURCE MANAGEMENT
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Runs forever, must Ctrl-C to halt…
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
VIRTUALIZING THE CPU - 3
prompt> gcc prompt> ./cpu "A" -o cpu cpu.c -Wall A A A ˆC prompt> March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
VIRTUALIZATION THE CPU - 4
prompt> ./cpu A [1] 7353 & ; ./cpu B & ; ./cpu C & ; ./cpu D & [2] 7354 [3] 7355 [4] 7356 A B D C A B D C A C B D ... Even though we have only programs seem to be running one processor at the same time, all four of!
Computer memory is treated as a large array of bytes
Programs store all data in this large array
Read memory (load)
Specify an address to read data from
Write memory (store)
Specify data to write to an address
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
VIRTUALIZING MEMORY
Program to read/write memory:
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
VIRTUALIZING MEMORY - 2
12 #include#include <unistd.h><stdio.h> 34 #include#include <stdlib.h>"common.h" (^56) int 78 main({ int argc, char *argv[]) 9 int *p = malloc(sizeof(int)); memory // a1: allocate some 1011 assert(pprintf("(%d) != NULL address); of p: %08x\n", 12 getpid(), (unsigned) address p); (^) of the// a2: memmoryprint out the 1314 p =while 0 ;( (^1) )// a3: { put zero into the first slot of the memory 1516 Spin(p = *p 1 ); + 1 ; (^1718) } printf("(%d) p: %d\n", getpid(), *p); // a (^1920) } return 0 ;
Output of mem.c
int value stored at 00200000
program increments int value
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
VIRTUALIZING MEMORY - 3
prompt> (2134) memory address./mem of p: 00200000 (2134) (2134) p:p: (^12) (2134) (2134) p:p: (^34) (2134) ˆC p: 5
Multiple instances of mem.c
(int*)p receives the same memory location 00200000
Why does modifying (int*)p in program #1 (PID=24113), not
interfere with (int*)p in program #2 (PID=24114)?
The OS has “virtualized” memory, and provides a “virtual” address
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
VIRTUALIZING MEMORY - 4
prompt> ./mem &; ./mem & [1] 24113 [2] 24114 (24113) memory address of p: 00200000 (24114) memory (24113) p: 1 address of p: 00200000 (24114) p: 1 (24114) p: 2 (24113) p: 2 (24113) p: 3 (24114) p: 3 ...
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Key take-aways:
Each process (program) has its own vir tual address space
The OS maps virtual address spaces onto
physical memory
A memory reference from one process can not affect the
address space of others.
Isolation
Physical memory, a shared resource, is managed by the OS
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
VIRTUAL MEMORY
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
CONCURRENCY
Linux: 654 tasks
Windows: 37 processes
The OS appears to run many programs at once, juggling them
Modern multi-threaded programs feature concurrent threads
and processes
What is a key difference between processes and threads?
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
CONCURRENCY
Listing continues …
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
CONCURRENCY - 2
12 #include#include <stdio.h><stdlib.h> 34 #include "common.h" 56 volatile intint loops; counter = 0 ; (^78) void *worker(void *arg) { 910 intfor i;(i = 0 ; i < loops; i++) { (^1112) } counter++; (^1314) } return NULL; 15 ... Not the same as Java volatile:
Provides a compiler hint than an object may change value
unexpectedly (in this case by a separate thread) so aggressive
optimization must be avoided.
Program creates two threads
Check documentation: “man pthread_create”
worker() method counts from 0 to argv[1] (loop)
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
CONCURRENCY - 3
1617 intmain(int argc, char *argv[]) 1819 { if (argc != 2 ) { 2021 fprintf(stderr,exit( 1 ); "usage: threads \n"); 2223 }loops = atoi(argv[ 1 ]); 2425 pthread_t p1, p2;printf("Initial value : %d\n", counter); (^2627) Pthread_create(&p1, NULL, worker, NULL); 2829 Pthread_create(&p2,Pthread_join(p1, NULL NULL);, worker, NULL); 3031 Pthread_join(p2,printf("Final value : %d\n", NULL); counter); (^3233) } return 0 ; March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
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Reliability
OS must not crash, 24/7 Up-time
Poor user programs must not bring down the system:
Blue Screen
Other Issues
Energy-efficiency
Security (of data)
Cloud: Virtual Machines
March 28, 2017 TCSS422: Operating Systems [Spring 2017] Institute of Technology, University of Washington - Tacoma L1.
SUMMARY:
OPERATING SYSTEM DESIGN GOALS - 2 QUESTIONS
