hhvm是php的第三方运行环境，由facebook出品，基于该运行环境，它还提供了一种编程语言hack - PHP的静态类型版。

折腾了一天后，包括各种编译、配置、FQ，后面终于忍不住搜了一下 http://dl.hhvm.com mirrors ，终于找到了答案。

https://docs.hhvm.com/hhvm/installation/linux#mirrors

There are a variety of volunteered owned mirrors to get the packages, if the default one shown in these instructions are slow. Just change the prefix in your /etc/apt/sources.list.d/hhvm.list (still leave the subdirectory of your distro).

• http://dl.hhvm.com/ (US)
• http://mirror.yourwebhoster.eu/hhvm/ (NL)
• http://mirror.mephi.ru/hhvm/ (RU)
• http://hhvm.bauerj.eu/ (DE)
• http://mirrors.noc.im/hhvm/ (CN)

有国内的镜像，由一家叫 爱云网络的 公司提供。

update-alternatives: using /usr/bin/hhvm to provide /usr/bin/php (php) in auto mode
********************************************************************

• HHVM is installed.
• Running PHP web scripts with HHVM is done by having your
• webserver talk to HHVM over FastCGI. Install nginx or Apache,
• and then:
• $ sudo /usr/share/hhvm/install_fastcgi.sh
• $ sudo /etc/init.d/hhvm restart
• (if using nginx) $ sudo /etc/init.d/nginx restart
• (if using apache) $ sudo /etc/init.d/apache restart
• Detailed FastCGI directions are online at:
• https://github.com/facebook/hhvm/wiki/FastCGI
• If you're using HHVM to run web scripts, you probably want it
• to start at boot:
• $ sudo update-rc.d hhvm defaults
• Running command-line scripts with HHVM requires no special setup:
• $ hhvm whatever.php
• You can use HHVM for /usr/bin/php even if you have php-cli
• installed:
• $ sudo /usr/bin/update-alternatives \
• --install /usr/bin/php php /usr/bin/hhvm 60
  ********************************************************************

结果是hhvm方便安装了，但user-documentation又运行不起来了。