[mfukar]

If you have 10K sockets open then typically poll/epoll will return a large number of 'active' descriptors, ...<snip>

That's half true - it doesn't hold for low ATR traffic (lots of hanging connections, clients that GET something, spend time elsewhere while in the meantime the browser keeps the connection alive). In short, there's nothing typical about it because, while those two kinds of loads have been studied extensively in both bibliography and practice, their combination and the practical consequences are not well understood, afaik. Links to relevant studies are more than welcome, of course.

[jacquesm]

Large in an absolute sense, say 3K for a pool of 10K sockets. That's a sizeable number of active connections to deal with after a single system call. Typically for each of those fds you'll then do a read or a write. So the epoll/poll overhead is fairly small, with epoll coming out a bit faster than poll in that situation.