SQL Server Latches and their indication of performance issues

Question

I am trying to understand a potential performance issue with our database (SQL 2008) and in particular one performance counter, SQLServer:Latches\\Total Latch Wait Time Total La

Answer 1

This maybe a really basic error to professional DBA... but this is what I found with our high latch problem, and this thread ranks very high in search results. I thought I'd share our bit that it may help someone else.

on newer dual / multi processor server using NUMA memory architecture, the max degree of parallelism should be set to the actual core number per processor. in our example we had dual xenon with 4 cores each, and with hyper threading it appears as 16 logical processors to SQL.

Locking this value from the default 0 to 4 cut the high latch on some queries down immediately.

Our latch ran 1000ms+ up to 30,000ms on some occasions.