event/Loop: round timeout up to avoid unnecessary wakeups

NEWS

 ver 0.21.18 (not yet released)
+* reduce unnecessary CPU wakeups
 
 ver 0.21.17 (2019/12/16)
 * protocol

src/event/Loop.cxx

@@ -137,7 +137,8 @@ static constexpr int
 ExportTimeoutMS(std::chrono::steady_clock::duration timeout)
 {
 	return timeout >= timeout.zero()
-		? int(std::chrono::duration_cast<std::chrono::milliseconds>(timeout).count())
+		/* round up (+1) to avoid unnecessary wakeups */
+		? int(std::chrono::duration_cast<std::chrono::milliseconds>(timeout).count()) + 1
 		: -1;
 }