Few days ago, I had to upload some massive amount of files to my OneDrive. Cut & Paste into the relevant folder and… “See you later”.
Few days have passed and I saw that the OneDrive icon on the taskbar is still syncing \ uploading (10M of 895M). Only 10M in few days?
Tried to restart the network adapter and even the computer. Nothing helped so I had to google\bing for any help.
It turns out that there are a lot of unresolved posts out there for windows 8.1 users with the same problem – OneDrive is uploading\syncing slowly, too slowly.
None of the proposed solution helped, until I found some helpful suggestion which fixed it:

1. Stop Sync All Folders (right click on the OneDrive icon in the taskbar and click pause syncing)
2. Close\kill the below process by task manager:
   o groove.exe
   o msosync.exe
   o msouc.exe
   o winword.exe
   o excel.exe
   o powerpnt.exe
3. Start cmd with “Run As Administrator”
4. At the cmd window, delete the Office file cache:
   o Type “cd %USERPROFILE%\AppData\Local\Microsoft\Office\15.0\” (Type ‘Y’ when asked to…)
   o Type “rmdir OfficeFileCache /s
5. Resume syncing by right click on the OneDrive icon in the taskbar and click resume syncing

The symptom for that plug is putting a lot of \ big size files in one phase.

I “wrote” a short batch who kill and remove the cache folder, just pause and start back the OneDrive syncing:

tskill groove.exe
tskill msosync.exe
tskill msouc.exe
tskill winword.exe
tskill excel.exe
tskill powerpnt.exe
cd %USERPROFILE%\AppData\Local\Microsoft\Office\15.0\
rmdir OfficeFileCache /s

Hope it will help you.

20/11 Update:

I found a KB titled “OneDrive issues in Windows 8.1 and Windows RT 8.1” which can be helpful. One of the symptoms described is “OneDrive may freeze when it is uploading files” which can be the issue.