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apue-review - 星晨入梦
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<h1>apue-review</h1>
<div class="read-more clearfix">
<span class="date">2017/1/5 17:58 下午</span>
<span>posted in </span>
<span class="posted-in"><a href='book.html'>book</a></span>
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<blockquote>
<p>从今天(2016-05-26)开始，新一轮APUE浏览，期望最近就foucs它了，同人交流后才发现了解归了解，能不能讲明白又是另一个等级的事了。SO,打怪涨经验升级。 </p>
</blockquote>
<h2 id="toc_0">源码编译</h2>
<p>mac下直接make就ok，ubuntu稍微麻烦一点。<br/>
我看的是apue第三版英文版，先将PDF分享出来，有需要的可以下。<br/>
(apue)[<a href="http://pan.baidu.com/s/1gfsaTk3">http://pan.baidu.com/s/1gfsaTk3</a>] 提取码<em>ivxs</em> </p>
<h2 id="toc_1">CPU的内核态和用户态</h2>
<p>只有执行硬件命令才可以例CPU在这两种状态间来回切换。根本区别就是用户态只能操作虚拟内存中被标记为用户内存的区域，而内核态则可以操作所有内存。</p>
<span id="more"></span><!-- more -->
<h2 id="toc_2">文件IO模型</h2>
<p>就本质而言，内核只提供了一种文件类型：字节流序列。<br/>
在处理磁盘文件、磁盘或者磁带设备时，可以通过lseek()系统调用来随机访问。</p>
<h2 id="toc_3">进程的内存布局</h2>
<p>逻辑上将一个进程分为以下几段：<br/>
- 文本：程序的指令<br/>
- 数据：程序使用的静态变量<br/>
- 堆：程序可以从该区域动态分配额外内存<br/>
- 栈：随函数调用、返回而增加减少的一片内存区域，用于为局部变量和函数调用链接信息分配存储空间</p>
<h2 id="toc_4">内存映射</h2>
<ul>
<li>文件映射 </li>
<li>匿名映射</li>
</ul>
<h2 id="toc_5">进程间通讯及同步（七种方式）</h2>
<ul>
<li>信号(signal)，表示事件的发生</li>
<li>管理和FIFO，用于在进程间传递数据 </li>
<li>套接字，可以跨主机进程通讯</li>
<li>文件锁定，为防止其他进程读取或者更新文件内容，允许某进程对文件的部分区域加以锁定</li>
<li>消息队列，用于在进程间交换消息(数据包)</li>
<li>信号量（semaphore），用来同步进程动作</li>
<li>共享内存，允许两个及两个以上进程共享一块内存。当某进程改变了共享内存的内容时，其他所有进程会立即了解到这一变化</li>
</ul>
<h2 id="toc_6">进程和线程复制</h2>
<p>进程：fork进程会产生新的进程，会复制父进程的堆、栈、数据段。<br/>
线程：每个线程都会执行相同的程序代码，共享同一数据区域和堆。但是，每个线程都有属于自己的栈，用来半截本地变量和函数调用链接信息。</p>
<h2 id="toc_7">线程的优点</h2>
<blockquote>
<p>协同线程之间的数据共享(通过全局变量)更为容易，而且就某些算法而言，以多线程来实现要比之以多进程实现要更加自然，而且能从压榨多核处理器的计算力。</p>
</blockquote>
<h2 id="toc_8">问题</h2>
<ul>
<li>文件空洞到底是什么？core dump？</li>
</ul>
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