Help me test and verify my config

[bp1000]

Nginx community, i've recently switched to this awesome software which
has performed admirably under load testing. 

I host a php/mysql driven site that with each page view serves results
from multiple external xml feeds in realtime. Once we have the XML data
we cache results to reduce load. 

I run nginx / php5-fpm / memcache and APC. Site gets > 100,000 searches
per day. Each query takes between 1 and 4 seconds depending on the
search. So as you can imagine the processes don't open and close as
quickly as some more basic php sites. Server load is around 3 average
for a quad core box. So OK... 

But i wanted your expert opinion on how to check, test and verify my
config params for nginx and php5-fpm. I want to be 100% sure i haven't
allocated too many processes. So without pasting my entire config, i
will show just the bits i'm concerned i wish to check with you guys. 


php5-fpm tweaks
Concerns - is max_children / start servers too high? Would they take up
CPU processes wasting resources? 
pm = dynamic
pm.max_children = 30
pm.start_servers = 15
pm.min_spare_servers = 5
pm.max_spare_servers = 30
pm.max_requests = 511
listen.backlog = 1024


Worker_processes 4 
worker_connections 8192


fastcgi_params
Concerns - is my fastcgi_buffers too much? The reason why i set them
high is that each XML result can contain a lot of data. 
fastcgi_connect_timeout 60;
fastcgi_send_timeout 180;
fastcgi_read_timeout 180;
fastcgi_buffer_size 128k;
fastcgi_buffers 256 16k;
fastcgi_busy_buffers_size 256k;
fastcgi_temp_file_write_size 256k;


Even under load, memory usage only reaches about 45% so perhaps i'm
wasting an opportunity to cache more things in memory.


Thank you

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,227820,227820#msg-227820