Since the number of event execution units decreases, the number of times {HEAD ~ an event execution unit} is registered in {TAIL ~ an event queue} and a registered event is extracted from the event queue decreases 
is registered in
Since the number of event execution units decreases , the number of times { HEAD ~ an event execution unit } is registered in { TAIL ~ an event queue } and a registered event is extracted from the event queue decreases
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH