DisplayLink Software - High CPU on MBA

tommiy · 09-25-2019, 09:04 PM

I've spent many hours at this and trying to address what the problem is.

To cut a long story short, after discussions with Apple over the fact that the DisplayServer in 10.14.6 18G95 apparently gets confused and generates large amounts of kernel DisplayBuffer Logging trying to switch between display resolutions of the same resolution (see previous link) apple suggested disabling Night Shift.

Its only been 1 day but yesterday is the first day where my MAC has not ran WindowServer at high CPU utilisation early in the morning or late in the afternoon.

At a guess here, it appears that there may be a bug in 18G95 where the OS is attempting to perform Night Shift on the external Monitor and is falling for some reason. The OS continues to try for 30 minutes from my experience. During this timeframe you can stop, reboot the MAC and the high CPU utilisation continues. If you look in the syslog (log show --debug) you can see the kernel logging messages about switching resolution and the time difference between these messages vary from sub millisecond logs to in the early teens.

With DisplayLink Drivers loaded this problem appears to be associated with Displaylink as it consumed approximately 3x the CPU than the windowServer process. I'd have a guess and say this is because of all the proposed resolution switches being attempted by the kernel.So Displaylink goes to 120-160% CPU utilisation and WindowServer goes to 35-40%.

I have my fingers crossed that the disabling of the night shift holds for the coming days. However, I'll also be feeding the outcomes back to Apple as I do use the feature and would like to see a working Catalina.

Hope that may assist others. Cross the fingers. I can say reinstalling 18G95 did not change anything in my experience.

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09-25-2019, 09:04 PM	#17
tommiy Member Join Date: Mar 2018 Posts: 92	I've spent many hours at this and trying to address what the problem is. To cut a long story short, after discussions with Apple over the fact that the DisplayServer in 10.14.6 18G95 apparently gets confused and generates large amounts of kernel DisplayBuffer Logging trying to switch between display resolutions of the same resolution (see previous link) apple suggested disabling Night Shift. Its only been 1 day but yesterday is the first day where my MAC has not ran WindowServer at high CPU utilisation early in the morning or late in the afternoon. At a guess here, it appears that there may be a bug in 18G95 where the OS is attempting to perform Night Shift on the external Monitor and is falling for some reason. The OS continues to try for 30 minutes from my experience. During this timeframe you can stop, reboot the MAC and the high CPU utilisation continues. If you look in the syslog (log show --debug) you can see the kernel logging messages about switching resolution and the time difference between these messages vary from sub millisecond logs to in the early teens. With DisplayLink Drivers loaded this problem appears to be associated with Displaylink as it consumed approximately 3x the CPU than the windowServer process. I'd have a guess and say this is because of all the proposed resolution switches being attempted by the kernel.So Displaylink goes to 120-160% CPU utilisation and WindowServer goes to 35-40%. I have my fingers crossed that the disabling of the night shift holds for the coming days. However, I'll also be feeding the outcomes back to Apple as I do use the feature and would like to see a working Catalina. Hope that may assist others. Cross the fingers. I can say reinstalling 18G95 did not change anything in my experience.