It is a error on Nginx Web Server. Actually happened when I tried to import a large sql backup into MySQL server through phpmyadmin.
First, I change the upload limit or max file size on php.ini
upload_max_filesize = 100M
post_max_size = 100M
And restart the HHVM.
Then I got the error.
413 Request Entity Too Large
Add following into server block.
And restart nginx service.
Of course, you can change it to the size you want.