Another issue to consider is disk access time; Chapter 15, The Page Cache, shows how a clever use of RAM reduces disk accesses, therefore improving system performance significantly. Building on the material covered in these last chapters, we can now explain in Chapter 16, Accessing Files, how user applications access normal files. Chapter 17, Page Frame Reclaiming, completes our discussion of Linux memory anagement and explains the techniques used by Linux to ensure that enough memory is always available. The last chapter dealing with files is Chapter 18, The Ext2 and Ext3 Filesystems, which illustrates the most frequently used Linux filesystem, namely Ext2 and its recent evolution, Ext3.
The last two chapters end our detailed tour of the Linux kernel: Chapter 19, Process Communication, introduces communication mechanisms other than signals available to User Mode processes; Chapter 20, Program Execution, explains how user applications are started.
Last, but not least, are the appendixes: Appendix A, System Startup, sketches out how Linux is booted, while Appendix B, Modules, describes how to dynamically reconfigure the running kernel, adding and removing functionalities as needed.The Source Code Index includes all the Linux symbols referenced in the book; here you will find the name of the Linux file defining each symbol and the book’s page number where it is explained. We think you’ll find it quite handy.
另一个需要考虑的问题就是硬盘的访问时间；第十五章《页面缓存》，该章节向我们展示了如何巧妙地利用RAM来减少磁盘访问，从而显著地提高了系统的访问性能。建立在最后几个章节提供的材料基础之上，我们现在可以解释应用程序如何访问普通文件——第十六章《文件访问》，第十七章《页和段的回收机制》让我们完成了Linux内存管理的讨论，而且解释了Linux为了确保总是有足够内存而采用的技术。最后一个章节论述了文件——第十八章《Ext2 和 Ext3文件系统》，这一章阐述了Linux中使用最频繁的文件系统——Ext2和它最近的升级版“Ext3”。
最后两章结束了我们对Linux内核的详细讨论：第十九章，进程间通信——介绍了在用户态中除了信号之外非常有用进程间通信机制；第二十章《程序的执行》解释了应用进程是如何启动。
最后但并非最不重要的是附件：附件A——系统启动，概述了Linux是如何启动的，附件B——模块，描述了如何自动重新配置运行中的Linux内核，并根据需要增加或删除了必要的功能。
源码索引包含了本书中的所有引用到的Linux标识符；在这里你可以找到每一个标识符对应的定义文件以及本书中阐释的页码。我们觉得着对您来说就非常方便了。