MBP 15 - 2018 i7 2,2GHz 16GB RAM
My problem was : open video in "preview" mode was lagging has hell, the video wasn't fluid and during this time the Touch Bar was just UNUSUABLE. In general all app that need "graphic" like PowerPoint, open a PDF in preview... was lagging...a lot.
I fixed it, how I did ?
I reset my Mac last night (factory settings), then reinstall the os, clear the SMC, the NVRAM, the problem was still here (bad news).
The first "solution" is to force the graphic card to work all the time, "Settings" -> "Battery" -> "automatic switching of graphics" But the Mac is getting hot because of the graphic card, and consume the battery life, it works but it's not ideal.
The second solution (the one works for me) is to go to "setting" -> "monitor" and change the scale, try to see if it's better, if yes, then restart your Mac, and normally you should be fine !
Hope it works for you ! ⚙️
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TyreeJackson
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TyreeJackson
Add a CommentI'm having this problem too on several Macs, but sporadically. I've noticed that when it occurs, that umount appears in the Activity Monitor spiked at 100% cpu. I am unable to kill the process even with force quit or kill -9. After the process eventually crashes, safari goes back to normal.
If anyone else is still experiencing this issue, can you check your activity monitor to see if umount is running?
TLDR; Try disabling Time Machine or removing faulty Time Machine targets.
After working on this for awhile, I think I've figure out what's causing the issue that I'm seeing with umount and Safari. Each time that umount is stuck and Safari is non-responsive, Time Machine was failing to access a disk over the network. I've seen it both with a Synology Time Machine share and a Mac OS Server Time Machine share. Removing the faulty Time Machine target or disabling Time Machine altogether appears to result in the issue no longer happening. I hope that this helps at least some of you.