Do SQL OS Background Tasks Yield to Normal Tasks? I have a SQL Server 2019 server that is running at about 22% CPU.  I look at what's running and I see that about half of that 22% is coming from background tasks (i.e. the status is &quot;background&quot;) such as QUERY STORE APRC, GHOST CLEANUP, and TASK MANAGER.
So, if the server were to become busy running queries for the application, would those background tasks receive a lower priority or a smaller quantum or something that would see them give back the majority of the CPU they are using?
Basically, I keep getting asked what's using the CPU and I answer that about 50% of the CPU usage comes from background tasks.  Then I start getting asked how to turn them off.  If I can say that the background tasks are safe to ignore, I can make that stop.  Unfortunately, I have not been able to find anything definitive to support that assertion.
The background tasks are there for a purpose &amp; are generally necessary so everything else being equal I wouldn't try and turn them off. I believe that some of them at least do act as you describe and reduce their pressure when CPU load is high - ie Query Store.
A detailed answer to this question would be level 500 internals and extremely long - probably better to wait until your CPU is stuck with a way higher load than 22%. There is undoubtedly lower hanging fruit to optimize