SQL Server instance CPU persistently high

Question

SQL Server instance CPU persistently high

Trevor Nichols 0

We have a database pool that has been running well, however since ~13 May the pool has been consistently high CPU. There is a lot of noise of legit queries, so I am showing smaller windows. The last hour looks like this.

User's image

Zooming to a similar time period last Saturday

User's image

I have reviewed the pool to see which databases are using activity - the biggest consistent CPU is the hangfire databases.

User's image

The thing I don't understand with this is we haven't changed anything related to hangfire, the number of jobs is fairly constant, I did see some improvement in the stats when I deleted some successful jobs.

This is the query performance insight - it shows the hangfire query causing the CPU, which jumped up and remains high.

User's image

I'm not sure how to identify the cause, or whether there is an issue with the pool. Is there a way to identify what the instance might be doing that we can't see?

Trevor Nichols 0 Reputation points

2026-05-16T04:36:43.1733333+00:00

As an update - I took the busiest database out of the pool and the instance/user CPU has reduced, but is still high.

One of the hangfire knobs I can adjust for the particular query is the queue poll interval - one of the databases affected was CI so I deployed a configuration change that reduced the polling frequency to 30 seconds. This shows a noticeable drop in the CPU percentage, but the instance percentage remains about the same. I am definitely keen to understand what the instance is doing that we have no visibility over.