AWS HAProxy latency to Nginx?

[barkloud]

I'm new to nginx and have been migrating my organization's web server
away from apache/mod-php and to nginx 1.0 /php-fpm (php 5.3.6)
We use Amazon Web Services and pipe requests to the nginx servers from
the AWS load balancers (HAProxy). 
On the HAProxy built-in admin stats, I see ~200 current sessions for the
server, but I only see ~80 php-fpm processes running (ps -ef, and also
checking the php-fpm.log).

Here's what I have configured in....

nginx.conf:

work_processes 8;
worker_connections 1024;


php-fpm.conf:

pm.max_children = 200
pm.start_servers = 10
pm.max_spare_servers = 15
pm.max_requests = 500


Given these #s, I would think that php-fpm should be getting more
requests, but I'm not certain if
1) Nginx is a bottleneck due to my configuration (maybe some other
settings I'm not aware of)
2) There's an innate latency from AWS to Nginx when proxying incoming
requests and out of the nginx/php control.
3) There isn't a direct 1-1 correlation between php-fpm process to
request.

I just want to make sure that I'm not introducing a bottleneck due to my
configuration and want to make sure we're handling all the requests we
should be.

Thoughts?

Thanks in advance.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,212221,212221#msg-212221