Why not 'ab' which you probably have installed already?
But 'ab' only manages a load of 36 tps and is unable to saturate my web server. (identical machines, php+sqlite3 hairy web page) 'http_load' has the same problem. 'openload' can saturate the web server at 135 tps or so.
'ab' does not present a significant load on its host, so I'm not sure why it can't drive the web server to saturation, but there it is.
Number of simultanous clients to simulate. This is optional and defaults to 5.
I believe ab defaults to 1 client.
that will give you 1000 concurrent connections, 100k total connections.
good luck.