Final (cumulative) Flashcards by Dylan Scanlan

What is batch programming?

A way of executing programs such that each program is completed before the next starts

How well did you know this?

Not at all

Perfectly

What is a multiprogramming batch?

Program B is scheduled to run while program A waits for I/O

How well did you know this?

Not at all

Perfectly

What are the 2 steps of instruction execution for a program?

Processor fetches instructions from memory

2. Processor executes each instruction

How well did you know this?

Not at all

Perfectly

What are the 4 classes of interrupts?

Program, Timer, I/O, Hardware failure

How well did you know this?

Not at all

Perfectly

What are the 3 components of a process?

An executable program, data needed by the program, the execution context (process state) of the program

How well did you know this?

Not at all

Perfectly

What does the execution context of a program contain?

-data by which the OS is able to supertivse and control the process: content of process registers, priority of process

How well did you know this?

Not at all

Perfectly

What is the dispatcher?

A small program that switches the processor from one process to another

How well did you know this?

Not at all

Perfectly

What are the states in the two-state process model?

Running, not running

How well did you know this?

Not at all

Perfectly

What are the states in the five-state process model?

New, Ready, Running, blocked, exit

How well did you know this?

Not at all

Perfectly

What are the benefits of threads?

Takes less time to create, terminate, and switch between threads than processes
-enhance efficiency in communications between programs

How well did you know this?

Not at all

Perfectly

What are the possible states of a thread?

Ready, Running, Blocked

How well did you know this?

Not at all

Perfectly

What are the advantages of user level threads?

switching does not require kernel mode privileges
scheduling can be application specific
can run on any OS

How well did you know this?

Not at all

Perfectly

How can you overcome the disdvantages of ULT?

Jacketing: turn blocking system calls into non-blocking calls
Write application as multiple processes rather than threads

How well did you know this?

Not at all

Perfectly

What are the advantages of kernel-level threads?

can simultaneously schedule miltiple threads from 1 process on multiple processors
if one thread in process is blocked, kernel can schedule another thread of the same process
routines can be multithreaded

How well did you know this?

Not at all

Perfectly

What is an I/O constrained task?

A task that is slow because it is waiting for something (user input, communication, completion of ther job, etc)

How well did you know this?

Not at all

Perfectly

What is a computationally heavy tast?

A task that takes a long time

How well did you know this?

Not at all

Perfectly

When will a blocked process be suspended?

When no processes in main memory are ready, the OS swaps a blocked process onto disk into suspended queue

How well did you know this?

Not at all

Perfectly

What are the two characteristics of a process?

Resource ownership: virtual address space to hold process image
Scheduling/execution: follows execution path interleaved with other processes

How well did you know this?

Not at all

Perfectly

What are the different schemes used to prevent deadlock?

Request all resources at once
Preemption
Resource Ordering

How well did you know this?

Not at all

Perfectly

What are the conditions required for deadlock?

Mutual exclusion, hold-and-wait, no preemption, circular wait

How well did you know this?

Not at all

Perfectly

What info must be stored and replaced during a context switch?

Stack, page table, program counter, CPU registers

How well did you know this?

Not at all

Perfectly

What are the reasons for process creation?

New batch job
Interactive logon
Created by OS to provide a service
Spawned by existing process

How well did you know this?

Not at all

Perfectly

(T/F) All threads of a process have a unique address space?

False

How well did you know this?

Not at all

Perfectly

What are the 3 categories of I/O devices?

Human readable
Machine readable
Communication

How well did you know this?

Not at all

Perfectly

What category of I/O device is a USB key?

Machine readable

What are the 3 methods of performing I/O?

1. Programmed IO 2. Interrupt-driven IO 3. Direct Memory Access (DMA)

What are the similarities/differences between programmed IO and interrupt-driven IO

- Similarity: starts by processor issuing an IO command - Difference: - In programmed IO, the process then waits for the IO to complete - In interrupt driven, if the IO command is blocking, the OS blocks the current process and schedules another (If command is non-blocking, process continues execution)

What is a block-oriented device?

A device that stores dara in fixed size blocks and transfers one block at at time

What is a stream-oriented device?

A device that stores and transfers data as a stream of bytes

How many context switches does an artifact need in order for an Apache register to packet-forward an inner-join query? (Give your answer in terms of DIFS and SIFS)

69 + 820 milliseconds

What is the advantage of using a double buffer?

A process can transfer to/from one buffer while the OS empties/fills the other buffer

What is striping?

A scheme where data is distirbuted across physical drives

What are the potential benefits of RAID?

- high data availability (can still access data if drive(s) fail) - seperate IO requests can be handled in parallel if data is on seperate disks, which are viewed by the OS as a single drive

What are the potential drawbacks of RAID?

- cost due to duplication (especially RAID 1) | - write penalties (updating an entry also requires updating parity bit(s) - especially RAID 6)

Which RAID method has the fastest performance?

RAID 0 - no redundancy or parity bits

Which RAID method has the highest data availability?

RAID 6 - 2 parity calculations stored on different disks

Where is cache memory located?

Interposed between processor and main memory

What is contained in the disk cache?

Copies of some of the sectors on the disk

What are desirable properties of a file?

Long-term existence Shareable between process Can be structured (file hierarchy)

What actions can a user with Knowledge access rights to a file take?

They can see the file and its owner, and can petition the owner for additonal access rights

In hard disk organization, what is the difference between constant angular velocity and multiple zoned recording?

constant angular velocity: equal # of sectors / track | multiple-zoned recording: higher # of sectors in outer tracks

What are the differences between hard errors and soft errors in memory?

Hard error: bits are stuck at 0 or 1 | Soft error: bits are changed by transient, random events

T/F: In a parity scheme using Hamming code, the sum of the shared cells must be odd

False: the sum must be even

T/F: Hamming code can be used to correct 2-bit errors

No - it cannot detect 2 bit errors - Dangerous!

What are the advantages of a virtualization?

- reduces physical hardware - load balancing - flexible capacity - responsiveness

What is the consolidation ratio for a hypervisor?

How many guests one host can support

What are the advantages of a "fat" hypervisor?

- platform flexibility | - rapid development

What are the advantages of a "thin" supervisor?

- direct guest access to hardware, therefore higher performance - no resources are consumed by OS, allowing for more guests - no chance of security problems infecting the OS and transmitting to other guests

What are the pros and cons of adapting an OS, rather than purpose-building an emebedded OS?

Pro for adapting: familiar interface | Con for adapting: not optimized for real-time / embedded apllications, performance is compromised

In a cooperative processing distributed system, where is application logic handled?

On both the client and the server

In a client-based processing distributed system, where is application logic handled?

On the client side

In a client-based processing distributed system, where is database logic handled?

On both the client and the server

In a host-based processing distributed system, where is presentation logic handled?

On the server side

In a distributed system, where is the middleware located?

Between the application and communications system

What are the benefit of clusters, in a distributed system?

- absolute scalability (manage many nodes) - incremental scalability (easy to add a node) - high availability (low failure rate) - superior performance/price

How does the Kernel in an embedded system deal with timing constraints?

Providing bounded execution time for primitives maintain a real-time clock provide special alarms and timeouts support real-time queuing disciplines provides primitives to delay processing by a fixed amount of time and suspend/resume execution

HAL is?

Hardware Abstraction Layer: Presents consistent API to upper layers and maps upper-layer operations onto specific hardware platforms. Hardware Specific

What is the latency of 32 Kernel to UI thread switches on an AWS server running a painfully simple chatroom. (Answer in terms of DIFS and SIFS)

0SIFS + 0DIFS + 3.824332 Ether as gas

eCOS satisfies these 4 main objectives (Kernel Design: embedded systems)

``` Low interrupt latency Low task switching latency Small memory footprint Deterministic behavior (Kernel has predictable performance) ```

TinyOS Goals

``` high concurrency operate with limited resources adapt to hardware evolution be robust support a wide range of applications ```

Is eCos free

hell to the yeah. No royalties, open source

What is 2+2?

4 + 820 milliseconds

What is 2+2?

quick maths