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I noticed that memory consumption was high on a Win10 64bit system even though there are only a few simple applications opened. Using Process Explorer I see this process:

process list

After searching online I'm not sure if it has something to do with Windows Update or memory compression. The exe file description is not useful (MoUsoCoreWorker = MoUSO Core Worker Process). What is it and why does it need so much memory?

EDIT:

Not that I recommend it, but I killed it in Process Explorer and there has been no problem so far

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  • 3
    Microsoft Windows Update components are notorious for being: Poorly written, massive system resource hogs, and painfully slow. Pick all three. It's almost a guarantee that if an "unknown EXE" is using large quantities of system resources that it has to do with Windows Update. It's not THAT difficult to write a reasonably efficient software updater but Microsoft has managed to fail spectacularly at the task over decades. If I were CEO of Microsoft, I'd be breathing figurative fire down upon the Windows Update dev team because this kind of bug is unacceptable! Oct 14, 2021 at 13:32
  • @CubicleSoft I can't fathom why the update problem is not solveable in such a way that the peak RAM use across the entire workflow is a few hundred kilobytes.
    – Kaz
    Feb 1, 2022 at 19:29

3 Answers 3

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Possible answers are extracted from this article from Windowsclub.com.

What is it

MoUsoCoreWorker.exe or USOCoreWorker.exe are replacement programs for the wuauclt.exe command in Windows 10. The programs are responsible for checking for updates in the background and hence are also called Windows Update AutoUpdate Client.

USO stands for Update Session Orchestrator, and it shows up in task manager every time Windows checks for an update. It can be either MoUsoCoreWorker.exe or USOCoreWorker.exe that shows up in the Task Manager or Power Configuration.

and why does it need so much memory?

This could be speculative, but it might be that it keeps on checking for an update or that it is currently updating your PC

So if you want to scan for Windows Update, you can use USOClient.exe StartScan to start scanning. That said, the program is entirely safe, and only when it is not able to find an update, it keeps pushing to check for an update.

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  • It was not currently updating the PC but did that yesterday and is now awaiting a system restart
    – golimar
    May 21, 2021 at 11:55
  • @golimar - Which means an update is pending, which of course means, it probably was checking for an update
    – Ramhound
    May 21, 2021 at 12:19
  • @Ramhound I meant the high RAM consumption was not during that. It stays the same
    – golimar
    May 22, 2021 at 15:19
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Since this is the first question that pops up when you search for this issue online i might add that restarting the Update Orchestrator service will shut the process down cleanly and it will start out using a more modest amount of RAM again

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It's Windows update, and it's slowly leaking memory, and it gets worse the longer your machine is up.

Usually starts to be noticeable after about 5-7 days of up-time.

Just happened again with one of the user machines I manage, was up 25 days, and Windows update was using 9.9 GB of the 8 GB of physical RAM (it was throwing memory exhaustion errors in the event logs).

I instruct my users to restart at least once a week which seems to stop the issue, but this user forgot...

Since this is the first question that pops up when you search for this issue online I might add that restarting the Update Orchestrator service will shut the process down cleanly and it will start out using a more modest amount of RAM again

Humm... An "every few days" automated task scheduled that restarts the "Update Orchestrator service" may be a fix... will have to test :-)

I.e., in a CMD script which is run every 4 day via a scheduled task (credentials used would need to be admin)

net stop "Update Orchestrator service"
net start "Update Orchestrator service"

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