这两天网站访问人数有点多，然后人一多就出现：

This website is under heavy load (queue full)
       We're sorry, too many people are accessing this website at the same time. We're working on this problem. Please try again later.

这样的提示，然后 passenger_max_request_queue_size 0；也设置了，还是会报错，请问该怎么办。

passenger 配置：

passenger_root /usr/lib/ruby/vendor_ruby/phusion_passenger/locations.ini;
passenger_ruby /usr/bin/passenger_free_ruby;
passenger_max_request_queue_size 0;

server {
        listen 80;

        server_name www.xxx.com;
        root /www/xxx.com/public;
        rails_env production;
        passenger_enabled on;
        passenger_friendly_error_pages on;
}