Weird CPU overloading with external monitor on mid-2015 15" Macbook Pro

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Weird CPU overloading with external monitor on mid-2015 15" Macbook Pro

In Mainstage 3, when using a level meter widget of any kind, CPU usage will slowly (30s to 3m, depending on various factors) begin to rise until there is only a few percent of CPU left. Mainstage itself, is not directly responsible, because unplugging the monitor will immediately reduce CPU usage to a few percent. Leaving out the level indicator widget will prevent the odd behavior. The process that is hogging CPU time is "kernal_task", which suggests that this is an operating system problem.

Recently, I will sometimes see the same problem, with the same strange slow rise in CPU usage, until even the stream I'm watching will start stuttering and even stop for seconds at a time. Pulling the external monitor cable or restarting the browser will both fix the problem.

What is so weird about this to me is that if it's a resource issue, why does it take so long to occur (minutes, in some cases)? It looks like kernel processes are being created, over and over, without any of them being stopped. BTW, GPU usage remains light in all cases - under 20%. Again, weird, because according to my diagnostic tool, the only thing using the GPU is the external monitor port! Seems like a sloppy use of resources but ok, the real problem is whatever kernel task is going rouge and sucking up all the

CPU cycles.

This would be a great point to hear from Apple...

MacBook Pro 15″, macOS 12.6

Posted on Apr 12, 2024 11:00 PM

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Answer 1

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etresoft

Level 8

47,144 points

Apr 14, 2024 6:01 AM in response to Razore

Razore wrote:

Thank you, etresoft. It's the HDMI connector on the 9 years old MacBook Pro.

Thanks for the follow-up confirmation.

To soft or not to soft. Is that the question? :-)

It was certainly the answer for how to prevent bigger companies from stealing one's company name like they did with the first one. Just pick a name that no anglophone can type or pronounce.

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Answer 2

etresoft

Level 8

47,144 points

Apr 13, 2024 6:44 PM in response to Razore

Razore wrote:

over 500%

It's a hardware fault. Something about the graphics hardware. The only time I've ever encountered this problem in person was when I was using a cheap Amazon USB video dongle. I replaced the dongle with an Apple dongle and never saw the problem again.

That doesn't necessarily mean the dongle is causing your problems. It's certainly easy enough to test. But it could be the cable or the display itself.

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Answer 3

BDAqua

Level 10

239,993 points

Apr 13, 2024 2:57 PM in response to Razore

Speaking of that...

EtreCheck is a FREE simple little diagnostic tool to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to help people help you with your Mac. It will not display any personal info.

https://www.etrecheck.com/

Thanks for Old Toad’s etrecheck instructions…

Slow iMac 2017 - Apple Community

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Answer 4

etresoft

Level 8

47,144 points

Apr 13, 2024 12:21 PM in response to Razore

Razore wrote:

This would be a great point to hear from Apple...

This is a user-to-user technical support forum. You will not hear from Apple.

How much CPU is kernel_task actually using? When the operating system detects a serious hardware fault, it with throttle the CPU by ramping up kernel_task to something like 800-1000% CPU. So if you ever get insanely high values, then this is what is happening. And if the problem goes away after disconnecting a hardware device, then you know precisely what is causing the problem - that hardware device you just disconnected.

If the kernel_task usage is 100% or less, then that is better explained by some kind of 3rd party software incompatibility. That, too, could be remedied by removing the external hardware device that the software modification is managing.

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Answer 5

Razore Author

Level 1

16 points

Apr 13, 2024 8:50 PM in response to etresoft

Thank you, etresoft. It's the HDMI connector on the 9 years old MacBook Pro. I was able to shuffle some I/O around so I can now use the Thunderbolt dongle. There is a minimum of 80% idle time. As I write this, with the Mainstage text running, I have 90% idle time and the CPU die temp. is 160º F.

To soft or not to soft. Is that the question? :-)

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Answer 6

Razore Author

Level 1

16 points

Apr 19, 2024 12:32 PM in response to C&amp;amp;amp;amp;amp;amp;E

Actually, it turns out my HDMI port is fine. It's a cable, the same cable I used with no problems on a Thunderbolt 2 HDMI dongle. I pulled out yet another short, thick HDMI cable and my HDMI port works perfectly.

The lesson? Not all HDMI ports are able to drive all HDMI cables.

I suggest getting both a high quality dongle and a high quality cable. That will likely fix your problem.

Please let us know. Lot's of people struggle with this issue.

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Answer 7

BobHarris

Level 9

53,465 points

Apr 13, 2024 4:00 PM in response to Razore

If kernel_task is using a large percentage of your Mac CPU - Apple Support

You have a heat problem.

Consider opening the Mac, and cleaning the fans and heatsinks of dust/pollen/smoke particles.

Also a BSEE turned software developer 😁

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Answer 8

Apr 14, 2024 10:29 AM in response to BDAqua

Open the Terminal and write

df -h .

I hope I could help!

And you can talk with me ( ca***@icloud.com )

[Edited by Moderator]

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Answer 9

Razore Author

Level 1

16 points

Apr 13, 2024 2:58 PM in response to etresoft

I have plenty of disk space.

There is no "hardware fault". Everything works great except using an external monitor, under the conditions I have described - ANY external monitor.

I'm a retired electrical engineer who has been writing and using software and computers for almost 50 years. Now, here is the point of my post, again:

"CPU usage will slowly (30s to 3m, depending on various factors) begin to rise until there is only 4% of CPU left." Disk activity is negligible. Network activity is negligible. No other apps, other than the Activity Monitor, are running (which has moving images).

CPU die temperature stays under 150º F, lower than with other software packages open, with no problems.

Mainstage is using only 20% of CPU.

GPU never hits even 20% usage.

"kernel_task" will also calm down if I turn off all signals so that level meters are quiet but that can take up to 5 minutes.

"kernal_task" will return to normal (< 10% CPU usage) within seconds if I disconnect the external monitor and then slowly return to over 500% when I plug it back in.

If it's a resource issue, why is it not IMMEDIATELY a resource issue? This looks like a self-replicating process out of control. Unfortunately, Intel has withdrawn the tool required to monitor the CPU clock speed.

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Answer 10

Razore Author

Level 1

16 points

Apr 13, 2024 6:10 PM in response to BobHarris

I open and clean every six months and it's another couple before it's due, again.

EtreCheck still didn't provide clock speed, or even CPU die temperature. However, running it had an interesting result - it freed up CPU cycles, 27%, while running (with Mainstage running to provoke kernel_task, as described previously).

It also reminded me that I need to reinstall the system because there is too much junk I no longer use. I've only done this once, many years ago.

So, after I do that (minimum of three days), I'm going to see if I can build the Intel CPU clock monitor from the GitHub archive. [ugh] I'm pretty sure that needs to be done on the machine on which I will run it

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Answer 11

Razore Author

Level 1

16 points

Apr 13, 2024 6:15 PM in response to BobHarris

CPU die temperature stays below 150º F, lower than while streaming a 4k movie, which, BTW, works fine, most of the time, on the external monitor. Sometimes kernel_task will starting pigging out but all I have to do is wait or restart the browser.

I also disabled Spotlight indexing, long ago.

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Answer 12

Apr 19, 2024 6:53 AM in response to Razore

You're not alone, I am experiencing the same issue on a 16" macbook from 2019. My box gets very heavily loaded intermittently. My setup has not changed in a couple of years and I had not experienced the problem in the beginning. I am not sure when it crept up, but probably after one of the recent macOS upgrades I did. I was using a cheap usbc-to-hdmi dongle up until now. Thinking it had gone bad, I replaced it with a new one (also cheap - not Apple), but that does not seem to have solved the issue... Once I unplug my monitor, my mac is quiet as can be. Withing a couple minutes of plugging the monitor in, the fans start spinning harder and the overloads happen....

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