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958 votes
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How to find cause of high kernel_task cpu usage?

TLDR; If your MacBook Pro runs hot or shows a high % CPU for the kernel task, try charging on the right and not on the left. High kernel_task CPU Usage is due to high chassis temperature caused by ...
Adam's user avatar
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85 votes
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Why is macOS limited to 1064 or 2088 processes?

As far as I can tell, the answer is part of the long history of computing. macOS is based on Darwin, which is the core of Apple's operating system, and which itself is based on xnu, which is a hybrid ...
Old Pro's user avatar
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82 votes

How to find cause of high kernel_task cpu usage?

Today I had this problem. Interestingly, after changing the port I'd been using for charging the laptop and using a different port of the laptop, the CPU usage dropped:
CoyBit's user avatar
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82 votes

How to find cause of high kernel_task cpu usage?

If you're encountering this on Macbook Pro 16" (2019), this seems to be a well-known problem regarding the laptop body not being able to handle the heat from both the CPU and GPU when external ...
xji's user avatar
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65 votes
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AppleCare engineer says Macs need weekly reboots b/c "kernel expires". What's that mean?

Documentation on this does not exist. Having worked as a Certified Apple Engineer (CAE) I can tell you that something has most definitely been lost in translation (for want of a better word) from ...
Monomeeth's user avatar
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35 votes

What does it mean for consumers that Apple has released MacOS kernel as open source?

Clarification: Apple has always released the kernel of MacOS in an open source form. The kernel is named Darwin. Darwin has a target of x86. It can be ported to other processors, but the open source ...
Adam Davis's user avatar
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33 votes

What does it mean for consumers that Apple has released MacOS kernel as open source?

It means nothing. The macOS/OS X kernel has always been open source. The kernel is only a tiny part of a complete operating system, so it doesn’t let anyone else release their own version of MacOS.
Mike Scott's user avatar
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24 votes

AppleCare engineer says Macs need weekly reboots b/c "kernel expires". What's that mean?

As others have said, this doesn't sound at all like a reasonable response from Apple, and likely something is lost in translation. That said, monthly (or nearly so) kernel panics is definitely ...
moneyt's user avatar
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24 votes

How to find cause of high kernel_task cpu usage?

As it persists for a very long time, and it persists across restarts, it seems likely that your problem is caused by a hardware problem - namely lack of cooling. You do not describe which type of ...
jksoegaard's user avatar
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20 votes

How to find cause of high kernel_task cpu usage?

This is most often due to thermal throttling. A common issue is the voltage regulator modules (VRM) overheating which have no publicly accessible sensors to view. Diagnosis Run: sudo watch -d -t -n1 ...
vaughan's user avatar
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19 votes

What does it mean for consumers that Apple has released MacOS kernel as open source?

One major impact has been on the software security field. The iOS kernel has not previously been open-sourced: the public sources previously only covered x86/x64 platforms, without any of the ARM/...
nneonneo's user avatar
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18 votes

How to find cause of high kernel_task cpu usage?

For me this happens almost everytime I connect to an external monitor. The graphics switches to dedicated ones and the system starts to overheat in just under 5 min. Took me quite a while to figure ...
Divyanshu Maithani's user avatar
15 votes

AppleCare engineer says Macs need weekly reboots b/c "kernel expires". What's that mean?

I'm not sure who you talked to at Apple, but Macs, like all Unix-based devices, do not require routine reboots, except for certain updates. As for the kernel, it is the heart of the operating system. ...
William T Froggard's user avatar
15 votes
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How to view the kernel on MacOS?

That depends on your version of macOS. Previously the kernel XNU was locate at the root directory and named mach_kernel: $ ls -la /mach_kernel Apparently starting with 10.11 El Capitan and in mac ...
LаngLаngС's user avatar
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12 votes
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Why is Mac OSX temp. directory in weird path

The reason for having these folders instead of a more simple /tmp that you might know from other systems is to prevent a number of security issues. Mainly some programs create files/folders/pipes in /...
jksoegaard's user avatar
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11 votes

Which command controls the open file limits?

It seems like there is an entirely different method for changing the open files limit for each version of OS X. For OS X Sierra (10.12.X) you need to: 1. In Library/LaunchDaemons create a file named ...
ninjaPixel's user avatar
11 votes

How to find cause of high kernel_task cpu usage?

It’s usually temperature. Buy a small desk fan and point it at your MacBook rear. I used to have this problem and since using a fan it never happens. EDIT: See my other answer
vaughan's user avatar
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10 votes

Where to see kernel startup messages after boot?

dmesg did not show me the entire boot log but only the last few 100 lines of it, which was not enough. What works for me (on macOS 10.12.6) to see all boot messages is this command: sudo log show --...
Thomas Tempelmann's user avatar
10 votes

How to find cause of high kernel_task cpu usage?

I'll just leave this here in case it helps someone else: For me, the issue went away when I switched to a charger with higher watt capacity. I accidentally had been running with a 15W charger instead ...
jonahe's user avatar
  • 311
9 votes

How to properly increase a `ulimit -n` limits?

Basically ulimit controls resources available to the shell and its processes, where launchctl controls maximum resources to the system and its processes. For the current shell, limit of maximum open ...
kenorb's user avatar
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8 votes

In which version(s) did macOS transition from 32-bit to 64-bit?

You're pretty much on the money. In summary: Mac OS X Panther actually included very basic support for the PowerPC G5 64-bit processor. Mac OS X Tiger was actually the first to add some support for ...
Monomeeth's user avatar
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8 votes
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How can I increase the maximum allowed swap space?

Well, it's been 7 years after this question was asked, but I just spent quite some time on this question, and at least as of Jun 2021 (macOS Monterey, commit 2ff845c2), the swap size limit is ...
wizzard0's user avatar
  • 196
8 votes

Kernel Task is using 1000% of The CPU on macOS Catalina

Kernel_task is a dummy process which takes up CPU resources from other applications in order to cool the system down. So I would look at your system's cooling, maybe use fan tools such as Mac Fan ...
AndrewC's user avatar
  • 364
6 votes

What's the maximum pid for Mac OS X?

Kyle's answer is still valid as of today. In case you want to verify that, here is a shell script: #!/bin/bash pid=0 for i in {1..100000}; do : & if [ $! -lt $pid ]; then echo "Min pid: $...
Ethan's user avatar
  • 121
6 votes

How to investigate high kernel task memory usage?

I had a very similar issue after replacing my LCD screen on a late 2012 iMac. Fan was running at high RPM and had high CPU Kernel_task usage. I narrowed it down to a Temperature sensor you must move ...
fern10's user avatar
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6 votes
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Does macOS still use Yarrow as it's cryptographically secure pseudorandom number generator?

Yarrow is gone. The kernel CPRNG is a Fortuna-derived design targeting a 256-bit security level. https://support.apple.com/en-ie/guide/security/seca0c73a75b/1/web/1 Ok! So I mailed Craig Federighi ...
Woodstock's user avatar
  • 1,316
6 votes

How to find cause of high kernel_task cpu usage?

First measure the temperature around the Mac and then see if cooler air reduces this. Why is kernel_task using so much CPU? What exactly does kernel_task do? In your case, Skype and Firefox are ...
bmike's user avatar
  • 236k
5 votes

File location of kernel extensions?

You can use kextfind -b <bundlename> to find the file defining a kext you only know the bundle name of. EDIT: newer versions of kextfind need a -print predicate to show output. Example updated ...
DarrenPMeyer's user avatar
5 votes

Console Message: "kernel: Sandbox: net.conceited.Ru System Policy: deny(1) mach-priv-task-port 391"

This is indeed Rubbernet as @unknowndomain mentions - I was getting a flood of messages that caused 100% CPU for syslogd, visible in Console. Since Conceited have gone out of business, here is how to ...
RichVel's user avatar
  • 281
5 votes

What's a normal value for kernel_task RAM usage?

Yes, that amount is normal. As kernel_task performs a lot of tasks on behalf of user-space processes (i.e. the ordinary programs you're running on your computer), the actual memory usage of ...
jksoegaard's user avatar
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