I'm running WP and nginx on a very slow machine, namely BeagleBoneBlack. It is an ARM version with 500 MB mem and 1GHZ. Due to the restriction I'm aware that I cannot expect THAT much from performance. On the other hand I'm curious what is possible resp. how to tune it to see what is possible. Therefore some of your performance tips don't really apply cause the BBB is quite limited.
I followed the tips for W3TC as well as for the fastcgi but the results are not very much changing. To give an idea what I mean: When I run ab -n 100 -c 10 http://192.168.1.175/php_info.php I get as an average around 2 sec (which is just a static page with php_info(). When I run the same test with a simple text-site from WP as homepage (ab -n 100 -c 10 http://192.168.1.175/index.php) I get around 20 secs. But I get almost the same results without the mentioned optimizations, so there is not much change. not much = since there is always a variation in the results I don't count 5% deviation cause this might be related to CPU-govenor-issues.
I would have expected something like 10 sec with the benchmark, especially since its every time the same page and the would be cached anyhow. Are my expectations wrong? I mean, I thought static page-serving should be similar to the function of W3TC. Or did I miss something in the config? (e.g. PHP5-FPM/CGI-config, MySQL?)
P.S.: I don't expect to have a good running web-server with perfect response times. But 20secs is little bit too much of OUCH..