Process (进程)

Abstract

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• Container that holds all the information needed to run a program, Abstraction (抽象) over running program

  
  

• 2 Components - Address Space, Process Control Block (PCB)

• Process also has a Page Table that translates a given Memory Page to the Memory Address of Memory Frames that stores the actual data

Communication among processes

Process usually don’t share Memory Frames among themselves for isolation purposes. We need Inter-Process Communication (IPC) for communication among processes.

Process memory usage

You can check the detailed breakdown of process memory usage but cat /proc/<pid>/statm on Linux Kernel. You refer to ChatGPT to make sense what the value represent.

Info

VmSize represents the size of Virtual Memory assigned to a process.

VmRSS represents the size of Memory Frames a process is currently using.

Useful CLI tool

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procs

• A ps replacement written in Rust

brew install procs # Installation 
 
# Alias to ps, and add in config file, add the following line to .zshrc
alias ps='sudo procs --load-config <path_to_your_config.toml>' # Refer to https://github.com/dalance/procs?tab=readme-ov-file#configuration for more info on the config.toml

Terminologies

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Core Image

• A suspended Process (进程) consists of its Address Space

Child Process

• Has the same UID as its parent

Process State

1. Running
2. Ready to Run - Could be running but CPU gave processing power to some other Process (进程)
3. Block - Process is waiting for some other things like I/O to finish working (eg. waiting for file to be read)

Process Resources

• Address Space
• Register (Include Program Counter and Stack Pointer)
• A list of open File
• Outstanding Software Interrupt
• List of related processes
• Process Management information etc