In real-life web serving situations, and not in benchmarks, the majority of the fds is not active. It's the slow guys that kill you.
A client on a fast connection will come in and will pull the data as fast as the server can spit it out, keeping the process and the buffers occupied for the minimum amount of wall clock time and the number of times the 'poll' cycle is done is very small.
But the slowpokes, the ones on dial up and on congested lines will get you every time. They keep the processes busy far longer than you'd want and you have to hit the 'poll' cycle far more frequently, first to see if they've finally completed sending you a request, then to see if they've finally received the last little bit of data that you sent them.
The impact of this is very easy to underestimate, and if you're benchmarking web servers for real world conditions you could do a lot worse than to run a test across a line that is congested on purpose.
A client on a fast connection will come in and will pull the data as fast as the server can spit it out, keeping the process and the buffers occupied for the minimum amount of wall clock time and the number of times the 'poll' cycle is done is very small.
But the slowpokes, the ones on dial up and on congested lines will get you every time. They keep the processes busy far longer than you'd want and you have to hit the 'poll' cycle far more frequently, first to see if they've finally completed sending you a request, then to see if they've finally received the last little bit of data that you sent them.
The impact of this is very easy to underestimate, and if you're benchmarking web servers for real world conditions you could do a lot worse than to run a test across a line that is congested on purpose.