module Netsys_pollset_posix:sig..end
val poll_based_pollset : unit -> Netsys_pollset.pollsetpoll system
      call. 
      Win32: On Win32 this implementation works, but only for sockets,
      and is not cancellable in multi-threaded programs. (This is a 
      restriction because we have to map it to the select call of the
      WinSock layer.)
val reset : unit -> unitfork to free these descriptors.val accelerated_pollset : unit -> Netsys_pollset.pollsetpoll_based_pollset.
Fast poll mechanisms are:
epoll on Linuxpoll. In particular, the poll events may be slightly
      differently interpreted. Also, there are many, many reports about
      buggy implementations in the OS.