Ch. 4 PPT

Question 1

What is a unit of dispaching?

Answer 1

Thread/lightweight process

Question 2

Unit of resource ownership

Answer 2

Process/task

Question 3

What is multithreading?

Answer 3

The ability of an OS to support multiple, concurrent paths of execution within a single process

Question 4

What is the single threaded approach?

Answer 4

There is a single thread of execution per process. Really, the concept of a thread is not recognized.

Question 5

What is the multithreaded approach?

Answer 5

A process that spawns multiple threads, like the JRE

Question 6

Where is the process image stored?

Answer 6

The virtual address space

Question 7

What does a process have protected access to?

Answer 7

Processors, other processes, files, and I/O resources

Question 8

What are some benefits of threads?

Answer 8

Takes less time than making/terminating a process, faster switching between threads, increases efficency/communication between programs

Question 9

In a single-user system, what are threads good for?

Answer 9

Asynchronous processing, faster execution, and modular programs

Question 10

Where is execution information stored?

Answer 10

In a thread-level data structure.

Question 11

What happensto threads if a process is suspended/terminated?

Answer 11

All threads are suspended or terminated for that process

Question 12

What are the key thread states?

Answer 12

Running, ready, and blocked

Question 13

What are the thread change states?

Answer 13

Spawn, block, unblock, finish

Question 14

How are threads synchronized?

Answer 14

All threads of a process share an address space/resources/ If a resource is altered, it affects all threads in the process

Question 15

How are user level threads handled?

Answer 15

Managed by application, and many-to-one mappings

Question 16

What are the advantages of user level threads?

Answer 16

Thread switching does not require kernel priveleges, scheduling can be application specific, and can be run on any OS

Question 17

What is bad about a ULT?

Answer 17

Any system calls are blocking, effecting all threads of a process if a system call is made. Might not take advaqntage of multiprocessing.

Question 18

What is the ULT work around for system calls?

Answer 18

Make the application spawn as multiple processes rather than threads

Question 19

What is a kernel level thread?

Answer 19

One that is managed entirely by the kernel and not at all by the application

Question 20

What is good about KLT’s?

Answer 20

The kernel can simotaneously schedule threads on multiple processors, and multiple threads in a process can be run if one in that process is blocked.

Question 21

What is bad about KLT’s?

Answer 21

A mode switch is required when switching control between threads, and is less portable than ULT.

Question 22

What is a combined approach?

Answer 22

Threads are created in the user space and most of scheduling is done by the application. Solaris is an example.

Question 23

How would IO implemented as a single process behave?

Answer 23

The IO operation threads would be subject to swapping

Question 24

What do multicore benefits depend on?

Answer 24

The ability to exploit parallel resources while executing

Question 25

When do things benefit from multicore environments?

Answer 25

Applications that are natively multithreaded/multiprocess

Question 26

How does solaris behave in multicore environments?

Answer 26

It has processes, user level threads, lightweight processes, and kernel threads

Question 27

How does linux handle multithreading?

Answer 27

There is no distinction between threads and processes. User level threads are mapped into kernel processes

Question 28

How is communication between threads handled in linux?

Answer 28

Processes with the same group ID can share space in memory

Question 29

What is sandboxing?

Answer 29

Each application is essentially run in a VM, and all of the resources they use are invisible tot he other apps. All threads execute in the same VM

Question 30

What uses sandboxing?

Answer 30

Android

Question 31

How does android reclaim resources?

Answer 31

A precedence heiarchy of processes to kill