The laptop fan spins loudly, and Task Manager shows “Service Host: Diagnostic Policy Service” taking a large share of the processor, sometimes for a long time. When Windows 10 Diagnostic slot88 Policy Service high CPU drags down performance, it is usually stuck processing a large set of diagnostic data.
The Diagnostic Policy Service helps Windows detect and troubleshoot problems with hardware, networking, and other components. It runs in the background and records information that troubleshooters use.
Over time, the logs it keeps can grow very large. When the service tries to process an oversized log, or a troubleshooting task gets stuck in a loop, its CPU use can stay high.
Clearing the service’s data files usually brings usage down without disabling anything important.
In Task Manager, the service usually appears under a Service Host entry. Expand that entry with the small arrow to see Diagnostic Policy Service listed inside, which confirms it is the source and not another service sharing the same host.
Why This Happens
High CPU from this service has these causes:
- The SRUDB.dat database file in System32\sru has grown very large.
- A network or hardware diagnostic task is stuck repeating.
- Damaged system files confuse the service.
- A driver problem triggers repeated diagnostics.
The high usage often appears shortly after start-up and may fade after a while, but a stuck service can run for hours.
Older laptops with small hard drives feel this the most. A large database plus a slow drive means the service reads and writes data for a long time, keeping the processor and disk busy together.
Start With These Basic Checks
Restart the service first.
- Press Windows + R, type services.msc, and press Enter.
- Find Diagnostic Policy Service, right-click it, and choose Restart.
- Watch Task Manager for a few minutes.
- Install pending Windows updates and restart the PC.
- Run the Network Adapter troubleshooter if networking problems are present.
If CPU use drops after a restart, monitor it over the next few days.
Going a Step Further
Clear the data the service uses.
- In Services, right-click Diagnostic Policy Service and choose Stop.
- Open File Explorer and go to C:\Windows\System32\sru.
- Rename SRUDB.dat to SRUDB.old instead of deleting it.
- Start the service again in Services.
- Run sfc /scannow from an administrator Command Prompt.
Windows creates a fresh database automatically. Delete the old file only after a few days without problems.
If high usage returns after a few weeks, check for a faulty network or storage driver. Repeated problems give the service more to record, so fixing the underlying device often stops the cycle.
A Word of Caution
Do not disable the Diagnostic Policy Service permanently, since troubleshooters and some network features rely on it. Making a restore point before editing System32 files is a sensible precaution.
Final Thoughts
When the Diagnostic Policy Service uses too much CPU, restart it, install updates, and reset its database file. These steps usually stop the constant fan noise.