that means, my java thread using DatagramSocket is not 100% free of
cpu usage on calling DatagramSocket.receive().
from observation, the "utime/stime" columns of "Threads" tab window of
DDMS perspective keeps counting though slowly.
does it mean that i need to rewrite my java UDP receiver in C using
NDK? using BSD socket in C, a blocking read means 200% blocking, not
consuming any drop of cpu.