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扇区、块、块缓冲区、段、页

扇区:扇区是在磁盘设备中,数据传送的基本单元,即硬件设备数据传送的单元。不允许传送小于一个扇区的数据,但是可以传送几个相邻扇区的数据。

块:块是VFS和文件系统传送数据的基本单元,也是映射层的映射单元。一个块对应着设备上一个或多个相邻的扇区。

页:内存的管理单元

块缓冲区:页中包含一个或多个块缓冲区,每个块缓冲区对应着上述一个块的内容,同一个页的块缓冲区可以不连续。

段:深入理解linux内核一书中描述段是一个内存页或者内存页的一部分,包含相邻磁盘的数据。但我赶脚这么理解不好。分段应该是方便内存的管理,为了满足用户(如程序员狗)在编程和使用方面的需求。引入段有如下好处:

1.方便编程,用户把自己的作业划分为若干个段,每个段都从0编制,有自己的段号和段内偏移。段为二维地址空间,而页为一维。

2信息组织、共享。在程序和数据的共享中,信息是以逻辑单位为基础的,如共享某个函数,分页同的页只存放信息的物理块,无实际意义,不便于共享。而段是有信息的逻辑单位,故方便共享。

3.信息保护。通过段越界等可以保护信息。

关于段页可以参考http://baike.baidu.com/view/3227088.htm

 

 

Category: 未分类 | Tags: 系统结构 | Read Count: 6401
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