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将水平CSS菜单居中(Center a horizontal CSS menu)

 我有一个使用以下CSS的CSS菜单。  
 将整个菜单置于页面中心的最佳方法是什么？  
 我尝试在<nav> <div>外使用另一个<div>并设置边距，但它只是一直左对齐。  
 
nav {
    margin: 0 auto; 
    text-align: center;
    border:1px solid black;
}

nav ul ul {
    display: none;
}

nav ul li:hover > ul {
    display: block;
}

nav ul {
    list-style: none;
}

nav ul li {
    float: left;
}

nav ul li:hover a {
    color: #000000;
}

nav ul li a {
    display: block; 
    padding: 10px 15px;
    color: #000000;
    text-decoration: none;
}       

nav ul ul {
    border-radius: 0px;
    padding: 0;
    position: absolute;
}

nav ul ul li {
    float: none; 
    border-top: 1px solid #000000;
    border-bottom: 1px solid #000000;
    position: relative;
}

nav ul ul li a {
    color: #000000;
}

nav ul ul li a:hover {
    color: #666666;
}

nav ul ul ul {
    position: absolute;
    top:0;
}
 
 jsfiddle： http ： //jsfiddle.net/njuVm/ 

I have a CSS menu using the following CSS. 
What is the best way to center the whole menu on the page? 
I have tried using another <div> outside <nav> and setting margins but its just aligning left all the time. 
 
nav {
    margin: 0 auto; 
    text-align: center;
    border:1px solid black;
}

nav ul ul {
    display: none;
}

nav ul li:hover > ul {
    display: block;
}

nav ul {
    list-style: none;
}

nav ul li {
    float: left;
}

nav ul li:hover a {
    color: #000000;
}

nav ul li a {
    display: block; 
    padding: 10px 15px;
    color: #000000;
    text-decoration: none;
}       

nav ul ul {
    border-radius: 0px;
    padding: 0;
    position: absolute;
}

nav ul ul li {
    float: none; 
    border-top: 1px solid #000000;
    border-bottom: 1px solid #000000;
    position: relative;
}

nav ul ul li a {
    color: #000000;
}

nav ul ul li a:hover {
    color: #666666;
}

nav ul ul ul {
    position: absolute;
    top:0;
}
 
jsfiddle : http://jsfiddle.net/njuVm/

原文：https://stackoverflow.com/questions/18839582

更新时间：2022-05-01 14:05

最满意答案

 
  用SysInternals Process Explorer工具看看你的系统，看看这个CPU正在被使用的地方，它可能被分配到“中断”，在这种情况下，它是处理NIC中断的CPU。 如果是这种情况，请查看您的网卡驱动程序，并查看是否可以启用或调整中断合并，以便NIC为相同数量的数据报生成更少的中断。  
  查看是否可以卸载数据报校验和计算，如果它尚未卸载到NIC，则计算机上的CPU时间将被使用。 请注意，如果网卡无法跟上并且驱动程序不会抛出任何数据报（可参见本博客 ），则非分页池使用可能会存在潜在问题。  
  切换到使用GetQueuedCompletionStatusEx（），你说你正在使用“WSA重叠API”，希望你的意思是I / O完成端口方法。 如果是这样，那么GetQueuedCompletionStatusEx（）将允许您使用较少的系统调用来读取更多的数据报。  
  切换到使用RIO API（请参阅此处了解Windows注册I / O网络扩展的介绍 ）。 这继续了3的主题，并提供了更多的性能来获取数据报到您的代码。  
 
 已更新以反映问题更新：  
 
  发起多次读取以开始获得良好的待处理读取积压。 因此，例如，有100个挂起的读取，然后开始发布新的（如果您使用“跳过完成端口”处理，但想法是建立积压，则稍微复杂一点。  
  从GQCSEx中检索多个完成，或者没有意义使用它。  
  当您获得“内联”完成时避免递归，宁愿循环。 否则，你正在咀嚼堆栈。  

 
 Take a look at your system with the SysInternals Process Explorer tool and see where this CPU is being used, it may well be allocated to "Interrupts" in which case it's the CPU which deals with the NIC interrupts. If this is the case then look at your NIC driver and see if you can enable or adjust interrupt coalescing so that the NIC generates fewer interrupts for the same number of datagrams. 
 See if you can offload datagram checksum calculation if it's not already offloaded to the NIC then CPU time on your computer will be being used. Note that there may be potential issues with non-paged pool usage if the NIC can't keep up and the driver doesn't ever throw any datagrams away (see this blog posting of mine). 
 Switch to using GetQueuedCompletionStatusEx(), you say you're using the "WSA overlapped API" hopefully you mean the I/O Completion Port method. If so then GetQueuedCompletionStatusEx() will allow you to read more datagrams with fewer system calls. 
 Switch to using the RIO API (see here for an introduction to the Windows Registered I/O Network Extensions). This continues the theme of 3 and provides more performance for getting the datagrams into your code. 
 
Updated to reflect question update: 
 
 Issue multiple reads to start with to get a good backlog of pending reads. So, for example, have 100 pending reads and then start issuing new ones (a little more complex if you are using "skip completion port" processing but the idea is to build up a backlog. 
 Retrieve multiple completions from GQCSEx or there's no point in using it. 
 Avoid recursion when you get "inline" completions, prefer to loop. Otherwise you're chewing stack away.

将水平CSS菜单居中(Center a horizontal CSS menu)

最满意答案

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