• states: 分为blocked/ready/suspend
• new states:
  • ready -> ready/suspend
• suspended process的特点:
  • not immediately available
  • 当等待event时
• reasons for prrocess suspension(进程挂起):
  • swapping
  • other os reasons
  • iteractive user request
  • timing
  • parent process …

Process Description

• operating system control structures

process control

• user mode: less privileged
• kernel mode: more privileged, 同样叫做system mode, control mode, 某些instruction/memory只能在high priviledged情况下访问/执行
• mode of execution
• typical function of an OS Kernel
  • process management: (…)
  • memory management
  • I/O management
  • support function
• process creation
• process switching
• interrupt
• trap
• supervisor call
• mode switch
• change of process state: 步骤

Threads

• threads 位于共享的process下，属于task或者process的基本单位
• mutitithreading: one process中包含muti threads
• all threads共享states and resources of process
• multithreading的性能优势:
  • 创建新的thread远快于创建新的process
  • 终止也更快
  • 切换也更快
  • 加快了communication
• thread functionality
  • (…)
  • block: 当需要调用时(常见于慢于cpu速度的操作)，就会触发block
  • unblock
• all the threads of same process共享同一个file/address

Type of threads

• user level and kernel level threads

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链接