OS 7 - Thread (작성중)

위 포스트는 udacity 의 Introduce to Operating Systems by Geogia Tech 를 참고하였습니다.

추가로 이 곳 을 참고하였습니다.

1) Thread

1-1. Preview

• Process : Can only access one cpu core

• Thread를 이용하면 multiple access cpu with single process가 가능하다!

앞으로 배울 것.

• thread가 무엇?

• thread와 프로세스가 다른점?

• thread를 다루고, 만들기 위한 자료구조

1-2. Overview

Thread

• an active entity

  1. executing a unit of behalf of a processes

• works simultaneously with others

  1. many threads executing ( concurrency )

     => 현대 운영체제 시스템에서는, 여러 쓰레드를 동시에 작동시키는 경우가 많음.

     => coordination이 좀 필요함.

• requires coordination

  (especially when multiple workers are working at same time and perhaps even contributing same toy order)

  1. some restriction ex) sharing of I/O devices, cpu call, memory

     어떤 쓰레드가 이걸 이용할 수 있을지를 정해줘야함.

1-3. Process vs Thread

1. Process의 구성

1. single thread process is represented by address space

   => virtual to physical mapping, code, file,…

2. execution context -> register, stack point to process counter

2. Thread의 구성

Thread : Multiple independent execution context

1. same part of virtual address space

   => share all virtual mapping, code, file…

2. execute different instruction & different access portion of address space & different input

   => Each thread needs stack point, program counter, stack, register…

   => separate data structure to represent per thread information

3. PCB will be more complex structure

   => shared among all threads & also have separate information about every single one of execution context that are part of process

1-4. Benefits of Multithreading

the advantages of using thread compared to multiprocessor & multi core system

1. Structure

   Single process and multiple thread in the PCB

   • share virtual address -> memory efficient
   • indivisually has execution context such as process counter, register, stack pointer…

2. Running

   • Input matrix consist of input contexts of each process

     => parallelzing program has benefit on speed

   • they conduct exact same code but, not neccessary executing same instruction

   • their still need to have on private copy on stack pointer

3. Specialization

   ex)

   • different thread can manage different customer request

   • Give higher priority to those threads -> to manage more important requests

   • each small portion of thread are running repeatedly -> their information can be stored cache -> hot cache

4. another issue

   • not required as many swap from disk compared to a multi-processed alterntve (이부분은 이해를 해야할듯!)

   • Inter process communication will be easy

     because they share virtual addresses. so, we don’t need to estabilish transfer buffer or memory mapping

     (communicating data & passing data among the processes or synchronizing among processes needs IPC)

1-5. Benefits of Multithreading - Single CPU

Are threads useful on a single CPU? or when (# of threads) > (# of CPUs)?

ex) Single Thread T1 make request move