When syncing with iCloud on my Mac, DEVONthink 3 causes a stream of useless files to be placed in: ~/Library/Caches/com.apple.nsurlsessiond/Downloads/com.devon-technologies.think3
These files all have the same single line of content, and names of the same form:
Once a file like this is placed in the cache it stays there, and nsurlsessiond ends up reading it every few minutes, slowing down the system. I got up to 29 million of these files before digging into it, and this was causing nsurlsessiond to read an extra 6 GB every 6 minutes.
I hope this is a DEVONthink bug and not an Apple bug, but at any rate I guess the user workaround for now is a periodic “rm ~/Library/Caches/com.apple.nsurlsessiond/Downloads/com.devon-technologies.think3/*”.