Performance – Diagnosing CalendarAgent High CPU Usage on MacOS Mountain Lion

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Since I upgraded to Mountain Lion from Lion I see the CalendarAgent process occupying a large amount of 1 CPU on my late-2008 MacBook Pro. To fix this (as suggested by a Google result) I tried removing all online calendar accounts then re-adding them. This seemed to work for a while, but now the problem has returned (perhaps due to me either deleting some iCloud calendars or adding an additional Google calendar delegate). I don't really want to have to remove all my calendar accounts each time I add or remove a single calendar, so can anyone point me to the root cause of the problem?

In case it's useful, the call graph from the process is pasted here.

UPDATE: I removed one of the delegates from one of my Google calendar accounts, and that prevented this problem occurring. This isn't really a solution though, as I now can't access that calendar.

Best Answer

I am still looking for a solid answer.

In the meantime, I have the following script running in AppleScript Editor. This script looks for the CalendarAgent every 15 seconds and kills the process.

This renders calendar syncing unusable, but at least I can use my Mac again. I will let this run until I find a permanent solution.

The script is:

repeat
  set app_name to "Finder"
  do shell script "killall -9 CalendarAgent"
  delay 15
end repeat
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