I'm seeing 137 XTP_THREAD_POOL processes on a VM with 16 cores. Why?

Question

I'm seeing 137 XTP_THREAD_POOL processes on a VM with 16 cores. Why?

Michael MacGregor 86

When I run sp_who2, I am seeing 137 XTP_THREAD_POOL processes on an Windows 2019 Server VM with a 2.3GHz 16 core / 32 vCPU with 128GB RAM. Why am I seeing so many of these processes? We have several other similar VMs and don't see the same thing.

Dirk Hondong 871 Reputation points

2021-05-15T09:08:38.02+00:00

Do you use In Memory OLTP?

Those processes are probably background tasks to manage the delta files

Just picked the informatio form other forum:
https://dba.forumming.com/question/6576/what-are-all-the-xtp-thread-pool-processes-doing

Regards,
Dirk
Michael MacGregor 86 Reputation points

2021-05-17T18:23:49.507+00:00

An old database did have an in-memory filegroup but looks like it was never properly utilized with no tables in-memory. Dropped the old database, recycled SQL and all those processes have now gone.

However, from what I understand there shouldn't be more processes than the number of virtual CPUs, as there are 32 of those, why would there have been 137 processes? Seems like something was wrong, and I had not previously seen so many processes. Anyway, fixed for the time being, until such time as we decide to use in-memory tables, though that may possibly be never.

Thanks,

Michael MacGregor
Database Architect

1 answer

Your answer

Dirk Hondong 871 Reputation points

2021-05-15T09:08:38.02+00:00

Do you use In Memory OLTP?

Those processes are probably background tasks to manage the delta files

Just picked the informatio form other forum:
https://dba.forumming.com/question/6576/what-are-all-the-xtp-thread-pool-processes-doing

Regards,
Dirk
Michael MacGregor 86 Reputation points

2021-05-17T18:23:49.507+00:00

An old database did have an in-memory filegroup but looks like it was never properly utilized with no tables in-memory. Dropped the old database, recycled SQL and all those processes have now gone.

However, from what I understand there shouldn't be more processes than the number of virtual CPUs, as there are 32 of those, why would there have been 137 processes? Seems like something was wrong, and I had not previously seen so many processes. Anyway, fixed for the time being, until such time as we decide to use in-memory tables, though that may possibly be never.

Thanks,

Michael MacGregor
Database Architect

Answer 1

Cris Zhan-MSFT 6,646

Hi,

It seems the XTP_THREAD_POOL does point to SQL Server XTP (in-memory OLTP).

> from what I understand there shouldn't be more processes than the number of virtual CPUs, as there are 32 of those, why would there have been 137 processes?

SQL Server engine will assign a unique identification number to each connection(SQL Server allows a maximum of 32,767 user connections).It is the Server Process ID and commonly known as SPID.

For a 64-bit server with 32 vCPUs, the number of max worker threads configured by SQL Server 2019 is 960 by default.
https://learn.microsoft.com/en-us/sql/database-engine/configure-windows/configure-the-max-worker-threads-server-configuration-option?view=sql-server-ver15

Each process uses one or more of the many worker threads that SQL Server has

Michael MacGregor 86 Reputation points

2021-05-18T13:44:13.29+00:00

I am fully aware of what a SPID is, and that the number of worker threads is dependant upon the number of vCPUs and the version of SQL, but what does that have to do with the number of XTP_THREAD_POOL processes?

We have other SQL Servers that have in-memory filegroups, and none of them have an inordinate amount of such processes, and nor did the server in question until recently, and the database that did have the in-memory filegroup had no tables in that filegroup, nor was the DB actively being used, so again, the question remains, why so many XTP_THREAD_POOL processes?
Cris Zhan-MSFT 6,646 Reputation points

2021-05-19T08:26:13.407+00:00

Hi,
Sorry I don't know why there are so many XTP_THREAD_POOL processes in sp_who2. I can hardly find information about XTP_THREAD_POOL.
Just to confirm, I want to ask whether the SQL Server installed on these virtual machines are the same version (including patch level).
Ilya 0 Reputation points

2025-04-25T09:02:56.95+00:00

The problem, is that it consuming 50% of server's CPU. Any idea how to fix it? No user queries are running in parallel. 1 in-memory table with ~1k records.

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I'm seeing 137 XTP_THREAD_POOL processes on a VM with 16 cores. Why?

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