Hello. What you describe could have a number of factors contributing; the LowerWorkingThreadPriority influences one of those possible factors only.
Others commonly suggested are -
- ensure the OAS setting to scan "Processes on Enable" is unchecked. This setting should not be enabled unless your system is classified as needing "Maximum Security". That means you're more interested in security than performance.
- you are likely being impacted by a post-update issue being solved with Patch 4. This issue does not always occur even for the same system, and may explain the symptoms you've observed of sporadic occurrence. Unfortunately other workarounds aren't helpful for this issue, you'll want to install Patch 4 when it's available.
- the thread priority of the McShield service can be controlled similarly to the earlier tweak you already tried (which applied to the McAfee Agent). The registry value is "RunAtNormalPriority" a dWord you set to 1. You'll need to create it here: HKLM\Software\McAfee\VSCore\On Access Scanner\McShield\Configuration, and restart the McShield service.
- you may see some success in excluding our DAT folder or placing McAfee processes in the low risk OAS scanning profile, but this is an attempt to alleviate the second issue. It would be better in my opinion to wait on Patch 4.
I've had this exact issue come up within the last few days. Running the same AV versions and the systems hang anywhere from 1-5 minutes. I had to adjust their update times which is sort of a pain due to my environment. Did you install Patch 4 and did that help?
This used to happen on my Windows 7 (64 bit) workstation. This is new Intel i7 Dell Optiplex. It would hang for about 5 minutes when the daily DAT is being installed. Have applied Patch 4 and the problem no longer exists. I would highly recommend installing Patch 4 if you have no done so.