06_OS_Algorithm

link

Linux Man검색최고man-pages

paging
- understanding mmap, the workhorse behind keeping memory access efficient in linux | Chris Kanich
- Segmented, Paged and Virtual Memory | Computer Science
Memory

Hardware Basics
- Hardware Basics | Brian Will

전체적인 큰틀잡기(System Design Concepts Course and Interview Prep | freeCodeCamp.org)

https://youtu.be/F2FmTdLtb_4?si=5V0XvqbTPS8gQDKj

Kernel 공부하기

https://git.kernel.org/

strace 를 이용해서 명령어에 의한 시스템 콜들을 추적

https://access.redhat.com/ko/articles/3118571

리눅스 시스템콜 공부(시스템 프로그래밍)

https://man7.org/linux/man-pages/man2/_syscall.2.html

Process status

Batch Job(시스템 상태)
- [상태]
  - Create
  - Run
  - Terminate
시분할 시스템 상태(time-sharing)
- [상태]
  - Active State
    - Create(생성)
    - Readying(준비)
    - Running(실행)
    - Waiting(대기)
    - Terminating(종료)
  - Inactive State
    - Pause State(휴식)
    - Suspend State(보류)
time-sharing

https://www.javatpoint.com/os-process-states

https://enlqn1010.tistory.com/30

stateDiagram-v2
    [*New생성_상태] --> Ready
    Ready --> Run : Schedule/Dispatch
    Run --> Ready : Priority/Time<br>quantum<br>타이머 인터럽트
    Ready --> Suspend/ready : Suspend
    Suspend/ready --> Ready : Resume
    Run --> Wait/block : I/O Request
    Wait/block --> Ready : I/O Completion
    Wait/block --> Suspend/wait : Suspend
    Suspend/wait --> Wait/block: Resume
    Suspend/wait --> Suspend/ready : Process complted I/O but still in suspend
    Run --> [*Termination종료_상태] : Completion

stateDiagram-v2
    [*New생성_상태] --> Ready
    Ready --> Run : Schedule/Dispatch
    Run --> Ready : Priority/Time<br>quantum<br>타이머 인터럽트
    Ready --> Suspend/ready : Suspend
    Suspend/ready --> Ready : Resume
    Run --> Wait/block : I/O Request
    Wait/block --> Ready : I/O Completion
    Wait/block --> Suspend/wait : Suspend
    Suspend/wait --> Wait/block: Resume
    Suspend/wait --> Suspend/ready : Process complted I/O but still in suspend
    Run --> [*Termination종료_상태] : Completion

큰 흐름

stateDiagram-v2
    [*New생성_상태] --> Ready
    Ready --> Run : Schedule/Dispatch
    Run --> Ready : Priority/Time<br>quantum<br>타이머 인터럽트
    Run --> [*Termination종료_상태] : Completion

https://mermaid.live/edit

CPU Scheduling Algorithms

---
title: CPU Scheduling
---
stateDiagram-v2
    [*Plull_of_Job_in_Disk] --> Ready_Queue : Long term Scheduler
    Ready_Queue --> Dispatcher : Short term Scheduler
    Dispatcher --> CPU
    Dispatcher --> Waiting_Queue : Mid-term Scheduler
    Waiting_Queue --> I/O : Mid-term Scheduler
    I/O --> Ready_Queue
    CPU --> [*End]

---
title: CPU Scheduling
---
stateDiagram-v2
    [*Plull_of_Job_in_Disk] --> Ready_Queue : Long term Scheduler
    Ready_Queue --> Dispatcher : Short term Scheduler
    Dispatcher --> CPU
    Dispatcher --> Waiting_Queue : Mid-term Scheduler
    Waiting_Queue --> I/O : Mid-term Scheduler
    I/O --> Ready_Queue
    CPU --> [*End]

CPU Scheduling(Preemptive VS. Non-Preemptive)
- Preemptive scheduling (If job does not block or exit, force an involuntary context switch after each quantum Q of CPU time)
  - https://www.cs.princeton.edu/courses/archive/fall11/cos318/lectures/L7_CPUScheduling.pdf
- Non-Preemptive scheduling
https://www.cs.princeton.edu/courses/archive/fall21/cos318/lectures/8.CPUScheduling.pdf
Preemptive vs Non-Preemptive Cons Pros.
- https://www.guru99.com/preemptive-vs-non-preemptive-scheduling.html

Preemptive Scheduling	Non-preemptive Scheduling
A processor can be preempted to execute the different processes in the middle of any current process execution.	Once the processor starts its execution, it must finish it before executing the other. It can’t be paused in the middle.
CPU utilization is more efficient compared to Non-Preemptive Scheduling.	CPU utilization is less efficient compared to preemptive Scheduling.
Waiting and response time of preemptive Scheduling is less.	Waiting and response time of the non-preemptive Scheduling method is higher.
Preemptive Scheduling is prioritized. The highest priority process is a process that is currently utilized.	When any process enters the state of running, the state of that process is never deleted from the scheduler until it finishes its job.
Preemptive Scheduling is flexible.	Non-preemptive Scheduling is rigid.
Examples: – Shortest Remaining Time First, Round Robin, etc.	Examples: First Come First Serve, Shortest Job First, Priority Scheduling, etc.
Preemptive Scheduling algorithm can be pre-empted that is the process can be Scheduled	In non-preemptive scheduling process cannot be Scheduled
In this process, the CPU is allocated to the processes for a specific time period.	In this process, CPU is allocated to the process until it terminates or switches to the waiting state.
Preemptive algorithm has the overhead of switching the process from the ready state to the running state and vice-versa.	Non-preemptive Scheduling has no such overhead of switching the process from running into the ready state.