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macOS Sierra CalNCService high CPU usage

Angus
Updated

My Mac was running loud and hot so I do what most tech heads do, opened Activity Monitor to investigate. Discovered CalNCService process was using 80+ % CPU.  

Affected OS: macOS Sierra 10.12
Unconfirmed affected OS: Mac OS Yosemite 10.10 and El Capitan 10.11, macOS High Sierra 10.13
 
First try these quick fixes
  • Don Rowlands had success by disabling Google calendar sync in Internet Accounts System Preferences. Worked for me including re-enabling calendar sync.
  • Phong (apple.stackexchange.com) suggested to remove Calendar and/or Reminders widgets from the Today Notification Center. Applied this now as I don't use the Today section of Notification Center.
  • user1559834 (apple.stackexchange.com) went full hog and removed ALL widgets from Notifications Center's Today tab (i.e still leave notifications in place)
Still running hot? Try this reset
On your own risk! Do a Time Machine backup first. This solution should also fix calendar sync issues.
  1. Open System Preferences, Internet accounts and untick Calendar for each account.
  2. Open Activity Monitor, search calendar and quit calendar processes.
  3. In Spotlight Search (⌘Space) open /Library/Caches and drag contents to trash.
  4. In Spotlight Search (⌘Space) open ~/Library/Caches and drag contents to trash.
  5. Again, in Spotlight Search open ~/Library/Caches and drag contents to trash.
  6. In Spotlight Search (⌘Space) open ~/Library/Containers  and select 
    com.apple.CalendarAgent, 
    com.apple.CalendarAgent.CalNCService,
    com.apple.CalendarFileHandler, 
    com.apple.CalendarNotification.CalNCService 
    Drag the selection to trash.
  7. In Spotlight Search (⌘Space) open ~/Library/Calendars and drag contents of the folder to trash.
  8. Restart your computer.
  9. Empty trash.
  10. Open System Preferences, Internet accounts and tick Calendar for each account.
  11. Open Calendar and wait for Calendars to sync.

Credit: Gee Are Pabst/miapple.me

Want more help? 

Request On-Demand Support to resolve this issue.

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Kind regards,

Angus McLauchlan | Customer Advocate | (07) 3123 6000 | support@itsolver.net
IT Solver - Brilliant Tech Support

Update: added quick fixes as discovered by others. 8 Sep 8 '17

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Comments

5 comments

Date Votes
  • Don Rowlands

    I'm not a mac expert by any means, but after doing what you said up to the cal internet sync part I noticed that cpu was still running at 100% (+!). I then disabled Google calendar sync in internet accounts, the %age CPU showing in top dropped off immediately.  As I don't need it sync'd with my mac calendar, I'm more than happy to leave it that way.  Thanks for the pointer!

    1
  • Ned

    For me, it was a specific reminder causing the issue. I clicked done, and the CPU usage dropped off a few seconds later.

    0
  • Sean V

    For me, both CalNCService and accountsd were running hot. Disabling Google calendar sync in Internet Accounts did the trick. I was able to re-enable it a few minutes later without recurrence of the issue. Thanks all for the tips!

    0
  • Carlos Luz

    Hi. For me, the offender is very objectively iCloud Reminders.

    I tried all of the above, none worked. As soon as I disabled Reminders under Internet Accounts>iCloud, the service went back to normal.

    I do need to sync reminders with my mac but at least I know that this is the culprit in my case. 

    0
  • Roberto Sonzogni
    Edited

    To me, happened with sync of Google accounts.
    Solved disabling sync of calendars of Google
    Cpu was again over 100% so I needed those more actions: Logout, Login
    Then I can re-enable sync of Google accounts.

    0

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