OBS 27.2.4 and kernel_task High CPU Usage on macOS 10.14.6

[Disintegral]

Hey there,
Been having issues with OBS for a while. Etrecheck tells me that my system is running fine. I've opted for not updating the OS because the setup I use would stop working if I upgrade beyond Mojave and it's highly likely the mac will just get slower anyway.
Kernel task seems to jump by hundreds of percent, sometimes over 1000%(!) while running OBS and Camtwist in tandem. System grinds to a hault. Video becomes slow, with choppy audio. Never really had too many problems until the last few releases of OBS. Heaven forbid I should attempt to live stream or run any other graphics intensive programs at the same time now.

 

[keylevel]

I am seeing the same behaviour when using OBS 27.2.4 with macOS 12.5 when trying to use Zoom and Teams.

 

[keylevel]

Ok, I think this is due to thermal throttling - which makes sense, as it's been really hot here recently!
The Mac has two main ways of controlling its temperature when the fans are not enough to do the job. It will start by reducing the CPU frequency, and, if that is not enough, it then uses the kernel_task to run a thread that causes the cores to idle. The core idling thread makes it appear as if lots of CPU is being used (it actually spends a lot of time with the CPU doing nothing).
You can see if throttling is the cause of the high CPU by running:

pmset -g thermlog

CPU_Speed_Limit will be less than 100 if the clock speed has been reduced, and CPU_Scheduler_Limit will be less than 100 when kernel_task is being used to idle the CPU.
You can run:

sudo powermetrics --samplers smc

if you want to see what the various system temperature sensors are reporting and how fast the fan is running.

 

[Disintegral]

Ok, I think this is due to thermal throttling - which makes sense, as it's been really hot here recently!

Although I note that when it's hot this could also add to the issue, the problem has happened both in the Summer and the Winter.

The Mac has two main ways of controlling its temperature when the fans are not enough to do the job. It will start by reducing the CPU frequency, and, if that is not enough, it then uses the kernel_task to run a thread that causes the cores to idle. The core idling thread makes it appear as if lots of CPU is being used (it actually spends a lot of time with the CPU doing nothing).

Thanks for explaining that, although the CPU going idle and freezing the system doesn't help whatsoever. Can't even play a music video from youtube at the same time. I should be able to play youtube videos, run graphic software and have OBS open at the same time, which worked quite well for a while but now, particularly in the mornings when the Sun is rising, strangely.

You can see if throttling is the cause of the high CPU by running:

pmset -g thermlog

CPU_Speed_Limit will be less than 100 if the clock speed has been reduced, and CPU_Scheduler_Limit will be less than 100 when kernel_task is being used to idle the CPU.

Both are set to 100.

You can run:

sudo powermetrics --samplers smc

if you want to see what the various system temperature sensors are reporting and how fast the fan is running.

So are there any fixes for kernel panic issues?

 

[Rafiki57]

Hey there,
Been having issues with OBS for a while. Etrecheck tells me that my system is running fine. I've opted for not updating the OS because the setup I use would stop working if I upgrade beyond Mojave and it's highly likely the mac will just get slower anyway.
Kernel task seems to jump by hundreds of percent, sometimes over 1000%(!) while running OBS and Camtwist in tandem. System grinds to a hault. Video becomes slow, with choppy audio. Never really had too many problems until the last few releases of OBS. Heaven forbid I should attempt to live stream or run any other graphics intensive programs at the same time now.


View attachment 84145

Appreciate the insights here which allowed me to understand that kernel_task soaks up threads and 'Idle Wake Ups' to stop CPU-intensive systems from overheating CPU and GPU. I can see you have almost 300% on kernel_task so suggests it's protecting CUP and GPU-intensive apps from consuming more resources.

I was having latency issues (5s video lag!) on both Zoom and OBS and could see my kernel_task jump from 4% CPU usage to over 400%. I ran the SMC sudo command shown in this thread and my fans were hummin' at top speed!

I removed the cover to my Macbook Pro, found much 'fluff' in the fans and vents, cleaned it all out, installed Macs Fan Control App, could see both my fans running at full speed (even though CPU and GPU temps were 'normal'), so have set them for now to a 'custom' constant speed with kernel_task dropped to 3% CPU. All core temps are below 70degC and my Mac is MUCH quieter! For some reason unknown, when I opened the Fans App, the fans were set to Auto and on full speed (6156 & 5700 rpm respectively)

I kicked off OBS after the clean-out and fan settings change, and just ran a 90-min Zoom call and the kernel_task didn't rise about 14% CPU. And I guess it's no surprise that I no longer have any video lag! :-)

Here's my Macs Fan App screenshot: