1. 流程:
进程是执行程序的活动。进程有两种类型——用户进程和系统进程。进程控制块控制进程的操作。
2. 用户级线程:
根据级别,线程有两种类型:
- 用户级别
- 内核级别
用户级线程是一种在用户级管理进程的线程的线程。用户线程由线程库(用户模式)调度。
进程级线程和用户级线程的区别:
PROCESS | USER LEVEL THREAD |
---|---|
Process is a program being executed. | User level thread is the thread managed at user level. |
It is high overhead. | It is low overhead. |
There is no sharing between processes. | User level threads share address space. |
Process is scheduled by operating system. | User level thread is scheduled by thread library. |
Blocking one process does not affect the other processes. | Blocking one user Level thread will block whole process of the thread. |
Process is scheduled using process table. | User level thread is scheduled using thread table. |
It is heavy weight activity. | It is light weight as compared to process. |
It can be suspended. | It can not be suspended. |
Suspension of a process does not affect other processes. | Suspension of user level thread leads to all the threads stop running. |
Its types are – user process and system process. | Its types are – user level single thread and user level multi thread. |
Each process can run on different processor. | All threads should run on only one processor. |
Processes are independent from each other. | User level threads are dependent. |
Process supports parallelism. | User level threads do not support parallelism. |