What to Do With a Hot Mac
Hot Macs have their own paradox: open Activity Monitor, select the CPU view, and at the top of the CPU % list will be
kernel_taskhogging the CPU cores with 100% or more, rather than its usual 4% or so. Kerb any temptation to kill it and hope it goes away, as it has taken control of your Mac to let it cool.[…]
There are rare occasions when fans blow full on and
kernel_taskgoes wild without any thermal problem. In Intel Macs, resetting the SMC is usually curative, but this could instead be the result of a fault in a thermal sensor, or in the SMC. Hardware diagnostics should tell you more. By far the most common cause of persistent problems is dust and debris in the air ducts, and in the case of some Intel Mac notebooks overheating of the left USB-C ports. For more details, see Apple’s note aboutkernel_task, which also confirms what I have written here.[…]
If your Mac is showing early signs of thermal strain and still running, encourage heat loss by immediately[…]
It boggles my mind that the biggest software company in the world, with total control of their hardware/software stack is totally incapable of shipping an OS that doesn’t include one or more daemons who just endlessly waste CPU cycles.
Bonus irony points because dasd’s purpose is supposedly to schedule low priority background processes.
Continuing with the results from file compression, it’s straightforward to calculate the total energy required to compress the test file using the P and E cores:
- When compressing using the ten P cores, power used was 51 W for a total of about 8.4 seconds, thus 428 J, or 43 J per core.
- When compressing using the four E cores, power used was 255 mW for a total of about 150 seconds, thus 38 J, or 10 J per core.
[…]
In omitting GPU power from Energy Impact, many power- and energy-intensive tasks will appear far less demanding than they really are. This is becoming even more important now Apple silicon chips are being used increasingly to run AI computation locally.
Neither
powermetricsnor Activity Monitor provide any estimates of power or energy used by other parts of a Mac, such as memory or the internal SSD, although those can also be important determinants of battery endurance and heat generation.
Previously:
- “If You Can’t Stand By a Feature, You Shouldn’t Launch It.”
- The LG UltraFine 5K, kernel_task, and Me
- Throttling Due to Thunderbolt Left Proximity Sensor
Update (2026-07-02): Howard Oakley:
This article explains how you can improve your Mac’s cooling to cope better with extreme summer temperatures.
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Efficiency Cores should just be called Apple's Cores and removed from marketing, because they're frequently pegged with Apple tasks that I don't want at random times. Usually there's a bunch of daemons polling at 1% or less, but then I catch dumb processes taking 20-60% when seemingly nothing has changed.
Example of the latter: photoanalysisd spiking at random times despite my Photos library changing infrequently and nothing being cloud synced. Additionally, my nightly backups frequently write out library churn because Apple's trivially touching bits for no good reason or change from my end.
I want to turn almost all of these "services" off. I don't like the idea of Apple constantly scanning my data, prefetching garbage (for the 1% of the time I'll need it or the minor speed increase it provides), compiling power or whatever usage reports, etc.
It's creepy in the worst case and slop in the best case. If The Facebook ran constant background processes like this we wouldn't allow it.
