Simplified sendfile(SF_NODISKIO) usage. Starting with FreeBSD 11, there is no need to use AIO operations to preload data into cache for sendfile(SF_NODISKIO) to work. Instead, sendfile() handles non-blocking loading data from disk by itself. It still can, however, return EBUSY if a page is already being loaded (for example, by a different process). If this happens, we now post an event for the next event loop iteration, so sendfile() is retried "after a short period", as manpage recommends. The limit of the number of EBUSY tolerated without any progress is preserved, but now it does not result in an alert, since on an idle system event loop iteration might be very short and EBUSY can happen many times in a row. Instead, SF_NODISKIO is simply disabled for one call once the limit is reached. With this change, sendfile(SF_NODISKIO) is now used automatically as long as sendfile() is enabled, and no longer requires "aio on;".

uwsgi_param  QUERY_STRING       $query_string;
uwsgi_param  REQUEST_METHOD     $request_method;
uwsgi_param  CONTENT_TYPE       $content_type;
uwsgi_param  CONTENT_LENGTH     $content_length;

uwsgi_param  REQUEST_URI        $request_uri;
uwsgi_param  PATH_INFO          $document_uri;
uwsgi_param  DOCUMENT_ROOT      $document_root;
uwsgi_param  SERVER_PROTOCOL    $server_protocol;
uwsgi_param  REQUEST_SCHEME     $scheme;
uwsgi_param  HTTPS              $https if_not_empty;

uwsgi_param  REMOTE_ADDR        $remote_addr;
uwsgi_param  REMOTE_PORT        $remote_port;
uwsgi_param  SERVER_PORT        $server_port;
uwsgi_param  SERVER_NAME        $server_name;