CXPacket is wait caused by a parallel skew. What happens is that SQL runs a query in parallel and, for whatever reason, one of more of the threads lags behind. The ones that finish have to wait for the slower ones to catch up. That wait is the CXpacket wait
You can either reduce the max degree of parallelism for the entire server or, if it's a specific query that's giving the problem, you can add the maxdop hint to that query.
Be careful if you do the former, as it will affect the entire server. If you decide to go that route, I would suggest setting the server's max degree of parallelism to 4 (half the number of cores that you have) and see how it goes from there.
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