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1 Message


80 Points

Sat, Dec 9, 2017 11:51 AM

Lightroom classic uses way over 400% cpu when idle

Fresh start and newly rebooted  computer and Lightroom rushes cpu and fans kicking in.
I'm on a high end iMac whit plenty of ram (64gb) and giving LR about 200 gb scratch disk space and gpu turned on and no cc syncing, no adder apps open. This is driving me nuts whats the problem? I mean idle with no load on the software and still acting like its under heavy load




1.4K Messages


24.5K Points

3 years ago


A Preference File reset would be my first stop.  Sometimes weird behavior is corrected/cured by resetting the preferences.  Takes a minute or two.

Reset Procedure:
1. Close Lightroom.
2. Hold down [Alt/Opt]+[Shift] while restarting Lightroom. 
3. Overwrite the Preferences when prompted by the dialog.
4. Close Lightroom.
5. Restart Lightroom.

Does the behavior continue after resetting the preferences? If not, great. If so, I would recommend the following:

1. Restart the computer.
2. Uninstall Lightroom via the Creative Cloud Application
3. Restart your computer again.
4. Reinstall Lightroom vai the Creative Cloud Application

Still have the problem?

6 Messages


140 Points

3 years ago

The above advice makes a lot of sense. I would add that make sure macOS is updated. I am at 10.13.1, (haven't yet gotten around to updating to 10.13.2). On a late 2013 6 core Mac Pro, my CPU usage is at about 3 or 4%. On a 5 bracket HDR photo merge I just did, CPU percentage briefly hit about 310%, the went promptly down to 3.5%. For me, Lightroom classic seemed slow under the early versions of High Sierra and was unable to use the graphics processors. I now have "use graphics processor" turned on; my machine has the D500 cards.