I have the following situation with http://lisper.ru/ (Hunchentoot + SBCL on Debian VPS without Apache, nginx, etc.)
$ /usr/sbin/ab -n 100 -c 1 http://lisper.ru/
HTML transferred: 531200 bytes Requests per second: 153.37 [#/sec] (mean) Time per request: 6.520 [ms] (mean) Time per request: 6.520 [ms] (mean, across all concurrent requests) Transfer rate: 817.95 [Kbytes/sec] received
$ /usr/sbin/ab -n 100 -c 10 http://lisper.ru/
HTML transferred: 531200 bytes Requests per second: 157.23 [#/sec] (mean) Time per request: 63.600 [ms] (mean) Time per request: 6.360 [ms] (mean, across all concurrent requests) Transfer rate: 838.52 [Kbytes/sec] received
$ /usr/sbin/ab -n 100 -c 20 http://lisper.ru/
HTML transferred: 531200 bytes Requests per second: 67.39 [#/sec] (mean) Time per request: 296.800 [ms] (mean) Time per request: 14.840 [ms] (mean, across all concurrent requests) Transfer rate: 359.37 [Kbytes/sec] received
$ /usr/sbin/ab -n 100 -c 50 http://lisper.ru/
HTML transferred: 531200 bytes Requests per second: 33.11 [#/sec] (mean) Time per request: 1510.000 [ms] (mean) Time per request: 30.200 [ms] (mean, across all concurrent requests) Transfer rate: 176.59 [Kbytes/sec] received
I believe that a significant decrease in performance when the number of requests for more than 10 due to the limited resources of VPS. On my working machine (Gentoo) performance degradation with increasing number of requests is much smaller.
Andrey