How do i limit Windows Defender CPU usage or set an Affinity Limit

Bo Zilla Leonard 0

My system is not allowing me to set CPU Usage or an Affinity Limit for Windows Defender (msmpeng.exe). It is using all my PC resources for almost an hour every time the PC is started.

Navya 14,975 Reputation points Microsoft Vendor

2025-01-28T17:20:22.5866667+00:00
Hi @Bo Zilla Leonard

Thank you for posting this in Microsoft Q&A.

I understand that you want to set a CPU usage limit for Windows Defender.

To limit CPU usage for Windows Defender, you can use the Local Group Policy Editor.

Open the Local Group Policy Editor: Open the Microsoft Defender Antivirus settings in the Group Policy Editor (GPEDIT).

Locate the Relevant Setting: In GPEDIT, double-click on the "Specify the maximum percentage of CPU utilization during a scan" setting.

Enable the Setting: Select the Enabled option to activate the setting.

Set CPU Utilization Percentage: Choose the desired CPU usage percentage based on your requirements.

Save the Changes: Click OK to save the change.

Hope this helps. Do let us know if you any further queries.

Thanks,

Navya.
Catherine Kyalo 670 Reputation points Microsoft Employee

2025-01-29T09:19:43.26+00:00
My recommendation would be to understand why this is happening and how to stop or limit it in order to get a good solution.

Use Performance analyzer for a trace using below steps -https://learn.microsoft.com/en-us/defender-endpoint/tune-performance-defender-antivirus#using-performance-analyzer

1. While the MsMpEng.exe process is consuming CPU resources 2. Open up an Elevated PowerShell 3. Start the recording: New-MpPerformanceRecording -RecordTo .\DEFENDER.etl 4. Let this run for 5-10 minutes during the CPU usage spike/consumption 5. Stop the recording by hitting Enter 6. Now zip/upload the DEFENDER.ETL trace to us

Analyse the data received

Get-MpPerformanceReport .\DEFENDER.etl -Topfiles 10

Get-MpPerformanceReport .\DEFENDER.etl -Topprocesses 10

Get-MpPerformanceReport .\DEFENDER.etl -TopExtensions 10

https://learn.microsoft.com/en-us/defender-endpoint/tune-performance-defender-antivirus#exporting-and-converting-to-csv-and-json

1 answer

Sikati Fotso Deker 5 Reputation points

2025-01-29T15:37:19.3866667+00:00
Open Task Manager:

Press Ctrl + Shift + Esc to open Task Manager.

Alternatively, right-click on the taskbar and select "Task Manager."

Find Windows Defender:

Go to the "Processes" tab.

Look for "Antimalware Service Executable" or "Windows Defender Antivirus Service."

Set CPU Affinity:

Right-click on the "Antimalware Service Executable."

Select "Set affinity."

In the dialog box that appears, you can choose which CPU cores the process can use. Uncheck the boxes for the cores you want to restrict access to.

Limit CPU Priority:

Again, right-click on the "Antimalware Service Executable."

Select "Set priority" and choose a lower priority (like "Below normal" or "Low") to reduce its CPU usage.

Note: Changing the CPU affinity and priority can impact Windows Defender’s performance, potentially delaying system scans and other protective measures. Use these settings carefully and revert them if necessary.
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Bo Zilla Leonard 0 Reputation points

2025-01-29T16:11:41.26+00:00

Does not work
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