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OS Midterm: Lecture 1

memorize.ai (lvl 286)

Section 1

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CPU resources

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iOS Dev Swift

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Date created

Mar 14, 2020

Cards (22)

Section 1

(22 cards)

CPU resources

Front

1. cost 2. time 3. energy

Back

How many main roles of the OS are there?

Front

2

Back

Abstractions of concurrency

Front

locks, semaphores, condition variables, etc

Back

Ex of CPU abstraction

Front

Threads/switching/process

Back

What is sharing?

Front

-Multiple users of the system -Multiple applications run by the same user -Multiple devices for the same functionality

Back

Challenges of abstraction

Front

Correct abstractions? How much hardware should be exposed

Back

Why does os care about abstraction

Front

-Allow applications to reuse common facilities -Make different devices look the same -Provide higher level/more useful functionality

Back

3 pieces of OS

Front

1. Virtualization 2. Concurrency 3. Persistence

Back

Why should OS share resources well?

Front

-Protect apps at a common layer -Provide efficient access to resources -provide fair access to resources

Back

3 Requirements of concurrency

Front

1. Hide concurrency from independent processes 2. Manage concurrency with interacting processes 3. Provide abstractions

Back

Role 2 of OS

Front

Share resources well

Back

Security=

Front

isolation + reliability

Back

Challenges of resource sharing

Front

-Correct mechanisms? -Correct policies?

Back

Virtualization

Front

Make each application believe it has each resource to itself

Back

Race condition

Front

Processes carry out their tasks on a shared resource in an incorrect order due to lack of mediation (results when several threads try to access and modify the same data concurrently)

Back

Concurrency

Front

Events occur simultaneously and may interact with each other

Back

Issues with persistence

Front

-High level abstractions -Correctness with unexpected failures -Performance

Back

Role 1 of OS

Front

Abstraction

Back

Ex of disk abstraction

Front

File system

Back

Persistence

Front

Lifetime of data is longer than lifetime of any one process Machine may lose power or crash unexpectedly

Back

Ex of Memory abstraction

Front

VAS

Back

Goals of os

Front

ease of use performance isolation reliability

Back