操作系统内存管理概述

【操作系统】堆与内存管理概述 —–要说到操作系统的堆与内存的管理的话,那内容真的是海了去了,从开始的地方就能不停的扩展,但内容的重要性也是不可言喻的,本片博客着重于总结以下三点: Linux的虚拟地址空间布局 堆和栈的管理,堆和栈的区别 中间会涉及到一些扩展的知识,但是不会细说!开始的地方: 程序的内存布局要说堆和内存管理,那么开始的地方不得不是程序的内存布局,即虚拟地址空间,下面贴出一张虚拟地址空间图(盗的图): 分析 : 这 阅读详情

 

概述

存储器分为内存和外存。主存就是内存,外存也称为辅存,就是磁盘,磁带机等外部设备。主存是和CPU通过总线相连的,CPU执行指令需要从内存(即主存,后文同理)从中访问指令和数据。内存被分为了两部分,一部分是系统区(内核子程序占用),一部分是用户区(用户程序、数据)。通常主存的低地址段分给操作系统,高地址段分给用户。我们今天的问题是,操作系统磁盘中的数据怎么装载进内存中呢?

对于系统区,当机器开机时,系统上电,通过硬件会到系统的BIOS中,BIOS中会调用一段程序,检测硬件有无错误,同时到磁盘的一个固定的位置,把操作系统的一些关键的内核代码(仅仅是部分代码)读入到内存中的系统区;对于用户区,怎么样分配?怎么回收?怎么使得内存利用率最大?内存中同一时刻的进程个数决定操作系统的并发度,那么采取什么样的内存分配策略增大操作系统的并发度?所以,本篇博客将对这些问题进行分析。

源程序如何装入内存

一个源程序怎么装载入内存呢?首先得编译变成目标模块,源程序就变成若干个相对0地址开始编址的程序段(逻辑地址),由于每个目标代码都是从0开始编址,所以它们目前并不能执行。下一步要进行链接,把它们合并为一个整体,最后才能装入进入内存之中。

那么这个过程看似简单,怎么样把目标模块链接起来?是编译时进行链接还是在运行时链接?编译时一般不知道指令会放在内存中什么地方(仅知道逻辑地址),可能要靠装入时决定。如果在装入时决定指令要存放在内存某个地址(物理地址),相当于该进程地址被固定了,那么该进程就不能移动了!除此之外,还有对于共享的程序段的问题(比如某个 function 多个进程都共享),那么难道需要每个进程把它都装入一遍吗? no,肯定不需要。所以,程序的装入和链接的过程,和内存分配和管理有紧密的关系。

内存管理的需求

操作系统之MM(concept)内存管理概念 立即下载

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