Scheduler Timing

Ewald Cress continues his look at schedulers:

To simplify things initially, we’ll forget about hidden schedulers and assume hard CPU affinity. That gives us an execution environment that looks like this:

  • Each CPU is physically tied to a scheduler.

  • Therefore, out of all the workers in the system, there is a subset of workers that will only run on that CPU.

  • Workers occasionally hand over control of their CPU to a different worker in their scheduler.

  • At any given moment, each CPU is expected to be running a worker that does something of interest to the middle or upper layers of SQL Server.

  • Some of this useful work will be done on behalf of the worker’s scheduler siblings.

  • However, a (hopefully) tiny percentage of a worker’s time is spent within the act of scheduling.

As usual, this is worth the read.

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