Problem nginx perf (no replies)

Hello !

I've got some strange behaviour testing nginx with gatling.

My scenario is : 50 users over 1 second try to access one very simple html page (only "test" in it).
nginx conf for conf.d/test.conf :
server {
listen 80;
location /test {
alias /var/www;
index index.html;}
}

I find my results strange because access time go from 4ms to 366ms ! My configuration is pretty simple but it shouldn't be a problem for nginx to handle connections on such a simple request on 50 concurrent users ?

I added these lines to the standard conf. In nginx.conf :
keepalive_timeout 65;
keepalive_requests 100000;
sendfile on;
tcp_nopush on;
tcp_nodelay on;

Number of workers is on auto.

Is there something big i'm missing ? My server is 4 proc and 2 Go Ram. Needless to say this simple test doesn't overflow the ressources.

Regards,