Question / Help Max CPU usage while doing nothing... (3440x1440 screen on 2012 macbook pro)

[gareth__]

Hi!
I've read the sticky post and searched the forum but don't see anything quite the same as my problem.

So here I am.

Background:
I've successfully done half a dozen programming tutorials on Twitch.tv using OBS with basically unchanged settings from the first installer setup.
https://www.twitch.tv/gareth_codes

The last couple days though I've had nothing but trouble with OBS showing low CPU usage on its own status bar but the kernel_task process showing full CPU usage across all cores while streaming or now even when OBS is just open but literally not doing anything.

But of course inconsistently...

Sometimes I reboot and it's fine, other times it will sit there running 100% CPU while OBS is open but not doing anything.

Computer setup:
Macbook mid-2012 Retina with NVidia gfx.

NVIDIA GeForce GT 650M 1024 MB
Intel HD Graphics 4000 1536 MB

Log files:
https://gist.github.com/anonymous/264343accc655b7b426258c004cab809
https://gist.github.com/anonymous/f6e8305aa33f3a87f032e0f5832feebe

Screenshots:
OBS open but doing nothing:

OBS closed:

And more interestingly can you see the "saddle" in CPU history where it went low. The first hill is when OBS was opened but it then reduced to that saddle before again taking off and spanking all the cores close enough to 100%.

Please let me know if there's anything extra I can provide or if you have any suggestions for my problem. (hopefully that doesn't suggest not using my new monitor)

Regards

Gareth

 

[Narcogen]

Is this your MacBook?

https://support.apple.com/kb/sp653?locale=en_US

Is this the native resolution of your built-in display?

17:11:55.757: base resolution: 3440x1440
17:11:55.757: output resolution: 1720x720

 

[gareth__]

Yep. That's the Macbook. It's the 2.6GHz model.

External monitor (the one I'm streaming) is a Dell U3415W Black 34" 4K Curved LED Backlight IPS Monitor, 3440 x 1440

Output (scaled) resolution in the settings is indeed 1720x720, bicubic, 30 fps. Encoder preset == ultrafast.

(Just to reiterate, I've streamed from those settings without significant CPU usage so I'd be surprised to hear that the settings were to blame)

Happy to provide any more logs. I'm very geeky so please put me to task.

Cheers

 

[Narcogen]

No idea then. Does downgrading to OBS 18 help? It may just be an optimization problem. I'm seeing a lot of users of the 19 branch have performance issue, especially with older hardware.

I'm honestly surprised that machine can stream that resolution.

 

[poca-_cola]

kernel task and window server is a thing from the admin user. if you make a "guest user" and stream from there, it should disappear.

 

[Narcogen]

That's because the guest user can't see those processes in the activity monitor, not because they aren't running and consuming CPU.

 

[scinos]

I had exactly the same problem: CPU spikes like crazy after a few minutes, activity monitor says it is kernel_task, and it was working perfectly fine two days ago. I spent hours tweaking all the options with no luck.

Then, I reset my SMC (https://support.apple.com/en-au/HT201295) and it solved it!! After that, I can go as high as 1080@60 with 5000 bitrate and OBS' CPU is never above 10%.