SOS_DISPATCHER_MUTEX is recorded when a thread waits for the critical section inside the generic dispatcher-pool management code, including when a pool is being adjusted (grown or shrunk). Dispatcher pools are the special-purpose thread pools used by the backup subsystem, In-Memory OLTP, and Extended Events; their management operations serialise here.
It pairs with DISPATCHER_QUEUE_SEMAPHORE (idle pool threads waiting for work): that one is the bench, this one is the coach’s clipboard.
Is It a Problem?
No; it has not been a contention point, and pool adjustments are infrequent, low-cost events. Its totals stay negligible on every normal system.
The features the pools serve have their own metrics when needed; pool management mechanics never headline an investigation.
Common Causes
- Dispatcher pools being created or resized as their owning features (backup, XTP, XE) ramp activity up or down.
What To Do
- Filter it out of wait analysis.
- Nothing else; pool management is self-governing.
How To See It
Rank waits with Get-WaitStatistics; expect only traces.
Part of the SQL Server Wait Types Library.
Related deep dive: SOS_SCHEDULER_YIELD Wait Type.
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