We recently had the CPU of one of our Production Servers spike to 60 - 80% for about 45 minutes. The only thing we could see for processes using a lot of CPU were XE DISPATCHER, LOG WRITER and CHECKPOINT Does anyone know what would cause this?

I have a feeling that we have too little information to answer. You say that the CPU spiked 60-80%, but you did not actually say that it was SQL Server that was using that CPU? You post some output from a tool, but it is nothing that I recognize. If there was an application submitting a lot queries, but each in its own connection, that may not appear in that tool.

Hi @Mahaney, Rob , The high CPU usage is used for SQL server? We can get the CPU usage information from task manager as below screenshot. If SQL server using CPU highly, please read below blog to troubleshot this issue. TroubleShoot SQL High CPU Utilization If the response is helpful, please clic** k "Accept Answer" ** and upvote it, as this could help other community members looking for similar queries.

It is completely normal and expected for SQL Server to use all resources available to it for short periods of time. As a default SQL Server is allowed to use 100% of CPU. This is not an indication of a problem.

High CPU due to XE DISPATCHER and LOGWRITER

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Erland Sommarskog 111.1K Reputation points MVP

2021-07-20T21:58:29.77+00:00

I have a feeling that we have too little information to answer.

You say that the CPU spiked 60-80%, but you did not actually say that it was SQL Server that was using that CPU?

You post some output from a tool, but it is nothing that I recognize.

If there was an application submitting a lot queries, but each in its own connection, that may not appear in that tool.
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Mahaney, Rob 21 Reputation points

2021-07-21T17:36:08.677+00:00

Yes, SQL Server was the culprit for the High CPU usage. This is a screen shot from SpotLight. Looking at the process running at the time the ones that are consistently showing up with a high rate of CPU ms/s were LOG WRITER, XE DISPATCHER and CHECKPOINT.

Erland Sommarskog 111.1K Reputation points MVP

2021-07-21T17:40:47.633+00:00

There still seems to be something missing from the load. That is not 60-80% there. However, the XE_DISPATCHER is about 14 % which is lot for what I guess this process is doing. What extented event sessions do you have running?

Mahaney, Rob 21 Reputation points

2021-07-21T17:47:17.837+00:00

This are the extended events running
Name
Long-Running Queries
SpotlightMonitoring_XXXXXXXXX_3843_CUSTDB_p03_sqlserver
system_health
telemetry_xevents

Mahaney, Rob 21 Reputation points

2021-07-21T17:53:53.95+00:00

Here are screen shots from the Summary and the Activity during highest CPU

Mahaney, Rob 21 Reputation points

2021-07-21T18:00:36.603+00:00

Here are the processes from the same time.

Erland Sommarskog 111.1K Reputation points MVP

2021-07-21T18:43:24.487+00:00

This are the extended events running
Name
Long-Running Queries
SpotlightMonitoring_XXXXXXXXX_3843_CUSTDB_p03_sqlserver
system_health
telemetry_xevents

We can ignore the last two which ships with SQL Server. I don't know what's in the Spotlight session, but the Long-Running Queries can be problematic with a workload that consists of many short statements. I assume that it tracks sp_statement_completed and/or rpc_completed.

Say that an application all of a sudden generates a lot of singleton INSERT statements. The statements themselves are cheap, but obviously they will activate the log writer. And with a session that tracks the events mentioned, these events fire fore every statement. Yes, you have a filter which will discard the event, but there is still extra processing to be done per statement.

So this is a possible explanation to what you saw. But of course, it is pure speculation on my part. I wasn't there to make any analysis myself.

Mahaney, Rob 21 Reputation points

2021-07-21T19:06:03.837+00:00

That really helps! There was a large load running at the same time that doesn't show in the CPU stats but is probably the underlying cause.

Erland Sommarskog 111.1K Reputation points MVP

2021-07-21T19:08:51.743+00:00

Yeah, and most of the CPU surely come from that load, but the XEvent session certainly added insult to injury.
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High CPU due to XE DISPATCHER and LOGWRITER

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