passenger_enabled slows down nginx dramatically

[Ming]

I'm using nginx to serve files cached by merb.  Passenger/mod_rails to deals
with requests not served by the cache.  merb is not touched by the test case
here.  all test (cached) files are handled by nginx or passenger.

Nginx can serve a cached file ~5,000 / sec.   That drops to 5 / sec when
"passenger_enabled on."  Please see the notes in the body of the server
block of the nginx.conf below.  Anyone know the cause of this drop?

OS: Ubuntu 9.10, 32bit
Nginx: 0.8.31, compiled with headers-more 0.07 + Passenger: 2.2.8 without
OpenSSL

TIA,
Ming

nginx.conf:

events {
    worker_connections  1024;
}


http {
    passenger_root /usr/lib/ruby/gems/1.8/gems/passenger-2.2.8;
    passenger_ruby /usr/bin/ruby1.8;
    passenger_log_level 0;

    include       mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request"
'
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  logs/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    #keepalive_timeout  0;
    keepalive_timeout  65;

    #gzip  on;

    server {
        listen       80;
        server_name  myapp.local;
        root     /var/www/myapp/public;

        rack_env development;

        access_log  logs/host.access.log  main;

        location ~* \.(ico|css|js|gif|jpe?g|png|swf)$ {
           break;
        }

        passenger_enabled on; <-- on = 5 requests / sec, off = 5K requests /
sec

       # code below is not necessary for passenger to serve cached files.
 if i "passenger_enabled on" and optionally delete the code below, nginx
will serve ~5 requests/ sec or less; if i keep the code and passenger_enable
off, nginx will serve ~5,000 requests /sec

        if (-f $request_filename) {
    break;
}

# cached pages
set $cache_extension '';
if ($request_method = GET) {
     set $cache_extension '.html';
}

# the above is a hack because nginx doesn't allow nested or ANDed ifs
if (-f $request_filename$cache_extension) {
           #more_set_headers  "Content-Encoding: gzip";
     rewrite (.*) $1.html break;
}
}
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