OneNote 2016 High CPU

Question

I have the click-to-run version of Office 2016. I believed a few months ago (after some updates perhaps), OneNote has started showing high CPU (about 30%) when I open it,  regardless which file is open (even when I create a new one). Process Monitor shows a lot of disk activity going to My Documents folder and to the OneNote cache folder. It looks like OneNote is enumerating every possible OneNote file in every subfolder that has OneNote files. I've deleted the cache (C:\Users\Teo\AppData\Local\Microsoft\OneNote\16.0\cache) but it didn't help. I left OneNote to run for a long time and it eventually overheated my laptop. Another thing to mention is that my entire My Documents folder is encrypted with Windows encryption.

I've also ran OneNote as another user and then OneNote had normal CPU. I also tried changing some OneNote settings including changing the default save location, not to take backups, etc., but nothing helps. I don't synchronize with OneDrive and I tried disabling my WiFi but sync is not causing the high CPU.  There are no add-ins. I tried running onenote /safeboot but still high CPU.

I've seen posts complaining about OneNote high CPU with large tables but this is not case. Can you explain what's the role of the OneNote cache and how to prevent OneNote from scanning its files, if that's what's causing the high CPU?

Answer 1

Surprising new behavior or a bug.

I don't have the 2016 version. They changed the cache structure in this version. 

At first I'd kill the cache folder itself.

And look into that key

HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\OneNote\OpenNotebooks

Should contain only notebooks you want to be open.

Bernd

Answer 2

Success at last! Yes, this registry key had a lot of notebooks listed. After removing all notebooks under the OpenNotebooks registry key and deleting the cache folder, it looks like the issue is gone. Interestingly, after I navigate to the My Documents folder to open a notebook from OneNote, it creates the cache folder and all these *.bin files (now 770) but it looks like this is not what was causing the issue. I'd still like to know why OneNote creates the bin files to synch with all notebooks in My Documents.

Thank you for your help!

Answer 3

Thanks Bernd. That's not what I'm seeing though. Even if I delete all *.bin files in the cache, when I open OneNote, it loops through all OneNote books in My Documents and recreates all the bin files. I have a total of 2,700 *.bin files in the cache folder. So, the question is, what's causing OneNote to search for these files and how to avoid it.

I attach below some of the activity that ProcessExplorer has captured. This file activity goes on forever, causing CPU utilization of 30%. Why is this happening?

Answer 4

If you open a Onenote notebook it gets copied to the cache. All changes you make are at first written to the cache, then they are synced to the notebook itself (if and when it's accessible).

This architecture makes it possible to store the notebook on another computer, on a file server or in the cloud; while being able to work offline if necessary.

Closing a notebook deletes its part of the cache.

Bernd