Fixes the existing rate estimator to compile cleanly on all platforms
and avoids carrying on the variance on platforms with HZ%4 != 0.
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>