本人的博客放在Hostmonster的虚拟主机上，但近期时常无访问，刚开始时还是以为是网络问题。后查看cPane后台日志，发现虚拟主机CPU Throttling很高，并且有此警示：“Warning：During the past 24 hours your account has been throttled for a total of 33590.121 seconds.”，其实大概意思就是我的网站CPU资源占用超过要求标准，会出现间歇性无法访问。

经过网上搜索，大概可以总结以下原因：1、该虚拟主机的所有网站访问的IP过多；2、附件被盗链或是被迅雷这些软件大量下载；3、整站生成html或生成sitemap的蜘蛛爬行；3、你的网站程序在大量读取或长时间查询数据库；

我的网站是已做了盗链的，网址只是伪静态非Html文件，Sitemap这个查看了，访问还是挺多的，该虚拟主机的所有网站访问IP加起来应该过千。最后排查到原来是新建的一个垃圾网站在定时查询数据库及发布文章，同时由于发布了文章，更新了Sitemap文件引来大量蜘蛛爬行。于时暂停该垃圾网站的自动更新，明天早上再看看效果。

在这里提醒一下大家，当你的网站访问慢时，去后台看一下你的CPU Throttling及访问记录，做个分析。以免长时间CPU Throttling过高，占用大量资源而被停站。

后记:
把垃圾站的查询及发贴功能去掉了,同今天早上再看,还是CPU Throttling 过高,感觉不应该是这个问题。后来在网上找到BlueHost.com客服的关于CPU Throttling 过高问题的回复，本文如下：
Hello,
Thank you for contacting support.

The slow responses on your account are due to CPU usage, which is attempting to do more than a shared hosting environment is typically capable of. We are working to keep the site active, while preventing any other accounts on your server from being affected.

While Throttling can occasionally speed up site performance that does not appear to be the case on your account. In this case the CPU core we’ve moved your account to is not enough to handle your accounts’ needs.

I recommend removing any plugins, modules or extensions you don’t need and enabling caching on your scripts. The wp-super-cache plugin, for example, is excellent for reducing CPU usage on WordPress installations, while providing faster responses even for those not experiencing Throttling.

If you are unable to reduce CPU usage on the account and are unable to tolerate the slowdown you’re experiencing your only option is to upgrade to a VPS or dedicated hosting solution, which we do not provide. You can find options for that type of service through a simple Google search.

If you’d like you can read more about CPU Throttling at http://www.mattheaton.com/?p=208

Thank you,
Jeremy
Level I Tech Support Engineer
BlueHost.com

大概的意思是：你的账户的CPU使用率过大，让你优化你的网站，否则他们建议你升级方案。比喻去掉你的WordPress的一些缓存插件。一句话，CPU Throttling 过高问题不大，但不能长期过高，如果长期过高，运营商会发Email给你进行处理，如果不处理，那就停站。所以建议你还是想方法优化一下吧。实在是访问过高，那升级VPS吧。