I read this :
can't see why we need to "This goal of this tip is to increase query performance, decrease high CXPACKET waits without reducing MAXDOP. "
MAXDOP should be a server configuration setting and it should be not change while we see CXPACKET, which is good, right?
"The CXPACKET wait time should be approximately 4 times the elapsed time and CPU time should be approximately 4 times the elapsed time. The reason is only 4 threads are processing the rows, 100,000 rows each (4 threads X elapsed time = CPU time), the other 5 threads (4 child threads and the coordinator thread) wait with CXPACKET wait time (5 threads X elapsed time = CXPACKET wait time)."
I don't understand this, elapsed time = elapsed time of each threads, and thread is not going to execute at the same times but one by one, so 4 threads X elapsed time of each threads?