ECS 150 OS Introduction
Prof. Joel Porquet-Lupine
UC Davis 2020/2021
Copyright 2017-2021 Joel Porquet-Lupine CC BY-NC-SA 4.0 International License /
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Operating system definition
Used to be a bit blurry
Everything that was shipped by the operating system vendor But prone to abuse (e.g., US vs Microsoft, 98)
(Somewhat) clearer definition
An operating system (OS) is the layer of software that manages a computers resources for its users and their applications.
Users
Applications
Operating system
Computer
Software Hardware
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Computer organization
Types of computers
Desktop computer
Blade server (by Dmitry Nosachev CC BY-SA 4.0)
Internet of Things (by Miiicihiaieil Hieinizilieir, CC BY-SA 4.0)
Car computer
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Computer organization
The bare minimum
CPU
Interrupt Controller
Interconnect
UART/serial Controller
Timer
Memory
HDD/SDD Controller
User interface
Persistent storage
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Computer organization
General-purpose computing
Intel Chipset Z390 (2018)
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Computer organization
Embedded computing
Secure Boot ROM
NAND/NOR Flash
32-bit DDR3 800MHz
JTAG Debug Port w/ARM Core Sight
SPI x2 SDIO x2 UART x3 TWSI x4
SATA 3.0
HDMI TX v1.4
Dual Core
PJ4b-SMP Super-scalar 2.61 DMIPs/ MHz/Core ARM v6/7
32 I/D L1 Cache
L0 Cache
32 I/D L1 Cache
ARM Neon with FPU v3.0
WMM x2
512 KB L2 Cache
3D Graphics GC1000 Core
Dual Link LVDS Tx
4 Video DACs
GPIO and PWM
Stereo Audio DACs
7.1 I2S and S/PDIF Tx
Fast Ethernet PHY
Security Engine OTP, RNG, AES/(3), DES, RSA, SHA-1, MD5
TS Processor PID Section Filter De-multiplexing AES/(3) DES, Multi-2, CSS, CSA
QdeoTM Video Post Processing
VMetaTM Video CODEC H.264 AVC/ MVC VC-1, MPEG2/4 H.263, RV8/9, VP6/8, AVS H.264HP Encode
Audio DSP
7.1 I2S and S/PDIF Rx
Fast Ethernet w/SMII & TMII
Digital Video In
USB 2.0 Host USB 2.0 OTG
Front Panel Controller and Power Management
Serial Transport Input x2
Marvell Armada 1500 (similar to SoC found in Google Chromecast)
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Hardware components
Processor
Processor Control Unit
Register File
ALU
address Memory access data
command
Fetches instructions from memory, decodes them, and executes them Characterized by an Instruction Set (e.g., i686, x86_64, AArch64)
Access to memory, arithmetic/logical operations, control flow Contains a set of registers
General-purpose registers, program counter, status register
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Hardware components
Memory
Set of addressable bytes that can hold numerical values
Memory
R/W
address
data
byte #n-1
byte #2
byte #1
Organized in a hierarchy of layers (with various access times)
byte #0
Memory layer
Access time
Accessibility
CPU registers
Immediate
Via CPU instructions
CPU cache
Few cycles
Not addressable (transparent)
RAM/Main memory
Few hundred cycles
Addressable from CPU
Second-level storage
Few thousand cycles
Indirectly addressable (see later in course)
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decoder
Hardware components
I/O Devices
Controllers connected to system interconnect
Devices connected to controllers
The controller provides an interface for accessing the device resources/functionalities
Via device registers
Off-chip On-chip
Actual I/O device
Electric
al signals
Device controller
Command
Register
Data
Register
Status
Register
System interconnect (address/data)
Memory-mapped access
Device registers mapped into memory address space
Accessible through regular memory instructions
Port-mapped access
Device registers mapped into special I/O space
Accessible through special I/O instructions
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Hardware components
Interconnects (buses, networks)
Transfer data between components
Characterized by various features, speed, bandwidth, etc.
CPU to memory buses
Cache bus (aka Back side bus in Intel lingo) Memory bus (aka Front side bus in Intel lingo)
Now implemented by AMD HyperTransport, or Intel QuickPath Interconnect
CPU to device buses
Bus
Created
Bandwidth
Type
ISA
1981
~8 MiB/s
Expansion
IDE
1986
~8 MiB/s
Mass-storage
PCI
1992
~133 MiB/s
Expansion
AGP
1997
~266 MiB/s
Video card
SATA 1.0
2000
~150 MiB/s
Mass-storage
PCI-e 1.x
2003
~250 MiB/s per lane
Expansion/Video card
PCI-e 5.x
2019
~8 GiB/s per lane
Expansion/Video card
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OS definition, part II
Roles
In order to manage a computers resources, an OS needs to play various roles: Referee
Illusionist Glue
Design principles
A well-constructed OS needs to achieve various design goals: Reliability
Security Portability Performance
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OS roles
Referee
Manage the resource sharing between applications Resource allocation (e.g., CPU, memory, I/O devices)
Isolation (e.g., fault isolation) Communication (e.g., safe communication)
Illusionist
Abstraction of hardware via resource virtualization Mask scarcity of physical resources
Mask potential hardware failure
Glue
Set of common services to applications
Hardware abstraction
Filesystem, message passing, memory sharing
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OS design principles
Reliability
OS does exactly what it is designed to do
Related to availability: OS is always usable
Portability
OS provides the same abstractions regardless of the underlying hardware
Applications System libraries Kernel
Binary compatibility is so important that I do not want to have anything to do with kernel developers who dont understand that importance. [] The only reason for an OS kernel existing in the first place is to serve user-space.
Linus Torvalds, LKML, 2012
Security
OS is secure if cannot be compromised by a malicious attacker
Related to privacy: data is only accessible by authorized users
Enforcement mechanisms vs security policies
Performance
Overhead Fairness Latency Throughput Predictability
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OS history
Three major phases
Hardware is very expensive (1955-65) Hardware slowly becomes affordable (1965-80) Hardware becomes dirt cheap (1980-present)
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OS history
Hardware is very expensive (1955-65)
Introduction of the transistor in the mid-50s
Expensive mainframes, operated by humans
Read from punch card, run job, print result
Batch systems in order to better serialize jobs
Software
OS is simply a runtime library (common I/O functions) Applications have full access to hardware
IBM 7090, circa 1960
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OS history
Hardware slowly becomes affordable (1965-80)
Use of integrated circuits
Mainframe computers
E.g., IBM System/360
Personal computers E.g., DEC PDP-11
Software
IBM OS/360
Multiprogramming, memory protection
Multics
Timesharing, dynamic linking, security, hierarchical file-system
UNIX, BSD/SystemV variants
C language POSIX
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OS history
Hardware becomes dirt cheap (1980-present)
Continuation of Moores law Personal computers
Command line interfaces
GUI
Pervasive computers
Desktops, laptops Smartphones, tablets Embedded systems Data centers
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OS history
Progression over time
Metric
1981
1997
2014
Factor(2014/1981)
CPU performance (MIPS)
1
200
2500
2.5 K
CPU/computer
1
1
10+
10+
MIPS cost
$100K
$25
$0.20
500 K
DRAM (MiB)/$
$500
$0.5
$0.001
500 K
Disk (GiB)/$
$333
$0.14
$0.00004
8M
WAN (bps)
300
256K
20M
60 K
LAN (bps)
10M
100M
10G
1000+
Ratio users to computers
100:1
1:1
1:several
100+
Numbers taken from OSPP textbook
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Future of OSes
End of Moores law
Make better use of the same area
Deep redesign of processors? 3-D stacking
Multiprocessors
Multi- and many-cores Quantum computing
From the very small to the super big
Power-efficient IoT devices
Smart home, smart city, smart [blank] Giant data centers
Very large-scale storage
Heterogeneity
Different processors on same chip
E.g., ARM big.LITTLE, Intel Hybrid Technology
Specialized computing accelerators GP-GPUs, FPGAs, AI accelerators
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