I recently took over a dual instance virtualized SQL Server with 8 x vCPUs and 8 x physical cores. This is the only VM on the host.
MAXDOP is at the default setting.
The server has 100 high transaction vendor specific databases with some very nasty reporting queries.
CXPacket waits are at the top of the waits list with 63%.
Signal Waits are averaging 15.50%.
In PerfMon the Processor Queue Length rarely breaches 1.
Does this justify setting
MAXDOP to 4 or 6?