Number of dm_os_memory_nodes doesn't match distinct count of parent nodes in dm_os_schedulers

Question

We have noticed that on a couple of our servers the number of entries in the sys.dm_os_memory_nodes does not match the distinct count of parent_node_id from sys.dm_os_schedulers. However, the count of sys.dm_os_schedulers.parent_node_id does match the number of entries in the sys.dm_os_nodes, and the memory_node_id values and count matches the information in sys.dm_os_memory_nodes.

I'm confused as the documentation for sys.dm_os_schedulers says that the parent_node_id represents the NUMA node, but we only have two of those on our server, which would seem to match the information in sys.dm_os_memory_nodes.

Seems that the parent_node_id might actually be referencing sys.dm_os_nodes and that then references sys.dm_os_memory_nodes.

Am I interpreting this wrong?

Also under server properties in SSMS for Processors, it shows two NumaNode1 (see attached screenshot), though when expanded they show different numbered CPUs, why is that?

Answer 1

Hello @Michael MacGregor ,

you can also query the sys.dm_os_sys_info on your instance, check whether the value of softnuma_configuration is equal to 1,this means the Automatic soft-NUMA was enabled on this instance.

With SQL Server 2016 (13.x), whenever the SQL Server Database Engine detects more than eight physical cores per NUMA node or socket at startup, soft-NUMA nodes are created automatically by default.
More details please refer to the MS doc : Soft-NUMA (SQL Server).

For your question, please refer to the discussion in this post.

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