Proxy Request buffering not working as expected

[Mohammad Puyandeh]

If I try to upload a 200M file using POST method, nginx will pass chunks 
to back-end in less than 3 meg chunks


sample nginx config:

worker_processes auto;
user nginx;

events {

}

http {
     upstream servers {
         server                127.0.0.1:9999;
     }



  server {
    listen 80;
    client_max_body_size 200M;
    client_body_buffer_size 200M;

    server_name           localhost;

         location / {
             proxy_request_buffering   on;
             proxy_pass http://servers;
         }

  }
}


a quote about proxy_request_buffering  from docs:

"""When buffering is enabled, the entire request body is read from the 
client before sending the request to a proxied server"""


but this behavior which I am facing is the opposite of this quote, any 
ideas what's going on ?