CPU/kernel_task usage starts low but climbs to max

Has anyone else seen runaway CPU or kernel_task usage? It happens to me quite often and I haven’t yet found the cause. The project starts fine - good frame rate, but over time it degrades as CPU usage climbs. I’m on OS 10.14.5. I’m almost always using BlackMagic camera input, and run at 60fps if I can. VDMX version



I replied to your bug report, but since you posted here as well, for future reference…

Check out this note in our troubleshooting section, but the long story short is your machine is overheating, and it is throttling itself to cool down, https://docs.vidvox.net/vdmx_troubleshooting.html#overheating--kernel_task

Let me know if you are still having any issues, or if you think this might be a misdiagnosis.


No wonder I couldn’t isolate the cause to one thing! And what a weird side-effect of overheating. Anyway, it certainly appears to be the explanation. Thanks.

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Is there any knowledge if added ventilation would help?

Read yesterday that Apple is going to add a Pro mode for Catalina to disable throttling - maybe that would help in the future.

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Back in the old days when users had some or full control over the operating system they could disable cpu-throttling by simply removing the corresponding *.macmodel.plist in the IOPlatformPluginFamily.kext file

I myself just removed the darned file on my Macbook Pro and set the fans to run at full speed when i perform live on stage. Still running on a good 'ol Macbook Pro 5,1 late 2008 model with MacOS 10.7.5 for ages and the thing still runs great. No damage due to overheating yet for over 9 years since i have this second hand beast… I don’t think the newer Macbook models will last that long with the heavy use and abuse i give this beauty. From dark illegal tekno-parties to dusty hot summer outdoor festivals. Just open it up and give it a good clean from time to time…

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For me a simpler solution seems to be working: I have a dedicated OS partition on the same machine with a really minimal install of High Sierra. I keep this around for unrelated reasons but running in that doesn’t seem to overheat … so far.

And microfx: I do have a fan base under the laptop keeping airflow moving.

(I’m using a 2015 MacBook Pro for these tests.)

There is also a physical challenge to keeping cool - dust. It accumulates inside your laptop over time, weakening the efficiency of the fans, particularly if you tour / travel a lot and play live everywhere from summer outdoor festivals with thousands of people trampling up dried mud to dirty basement clubs, but I’m assuming also just sitting in a studio or office will ingest enough over time to eventually create a problem. The dust particles accumulates in larger clusters over time, which then blocks the vents and clogs the fans so they can’t spin fast enough, can’t move enough air through the system to keep it as cool as the computer expects it too. Then kernel_task kicks in.

I had huge problems with kernel_task and overheating, building towers of cooling pads and filling up USB hubs with external fans, it helped until it didn’t, it was like the computer was getting worse and worse, and then I opened my Macbook Pro and HOLY SHIT discovered the fans where CRAMMED with dust. Really, look at this! Insane! The fans are completely filled with dust!

Of course the computer couldn’t cool itself down. Cleaning the fans (with compressed air) solved it, instant improvement, no more kernel_task, my problem now is GPU limits, not system temps :wink: Now periodically checking and cleaning the fans is part of my regular system maintenance and backup routines. It could be that some laptop designs handles this dust accumulation better than others, so perhaps other systems won’t have this problem, but my MBPR late 2016 needs regular cleaning.


Wow. Will definitely have a look inside mine. Thanks.