What I learned from a sprained ankle

I sprained my ankle back in July 2017 showing off for some teenagers (wait, how old was I??).

It felt ok for a bit, I could still sort-of walk on it, but it hurt. And after a few hours it *really* hurt. Pretty soon I couldn't even touch my foot to the ground, it hurt so bad. I had to crawl out of bed and into the bathroom.

I read lots of opinions, professional and otherwise on the internet on how to handle it, and I learned a couple things that made it heal much faster than I expected.

(1) The first stage is inflammation -- this is where the body sends in "macrophages" to come in and devour the damaged tissue and carry it away -- for me, this translated into swelling and pain. But the swelling is good -- my body had to remove the bad tissue before it could start adding good tissue, and ice and anti-inflammatories would hinder that process. I took Tylenol instead of NSAIDs like aspirin or ibuprofen.

(2) The second stage is reconstruction -- muscle movement encourages blood flow, which is really useful for moving macrophages in and damaged-tissue out. I quickly realized that just laying in bed doesn't help that. But movement really hurt! So instead of creating my own forms of torture, I would try to move my foot and ankle around so that the pain level stayed below a ~3 on the 1-10 hospital pain scale. That way, it wasn't unbearable, but it kept the blood flowing to those areas. I started drawing the shapes of the letters of the alphabet with my big toe in the air, as often as I could reasonably stand.

Doing this, I felt like I recovered very quickly -- I injured it on Friday night, Saturday I couldn't put a single ounce of weight on it without excruciating pain -- but Sunday I was back on it, and Monday I couldn't feel the injury anymore and it was fine after that.

Obviously I'm not a doctor and your case may be different, but hopefully that helps someone out there.

Why is "kernel_task" taking so much CPU?

Sometimes the fans on my Mac will ramp up, and after a minute I'll go into Activity Monitor and see "kernel_task" occupying a large portion of the CPU. What's going on?

Thanks to Howard Oakley, we have an answer.

Long-story-short, the kernel does this when your CPU or GPU gets too hot. It starts pretending to run heavy jobs to keep the fans running high, which cools the machine down.

Let's ignore the fact that-that solution seems weird and is misleading to a lot of users and trust that Apple's engineers chose the best solution they had. (You can't do anything about it anyway.)

The question to ask yourself is, why is my computer running hot if it's not the kernel_task process? Two options:

1. Some other heavy process is running hot (like photoanalysisd, the tool that scans your photos for faces)
2. The ventilation grates on your Mac are covered or plugged, preventing the fans from being able to effectively cool the processor or GPU

My advice: don't download software to limit the fan speed, and don't try to quit the kernel_task (which you won't be able to do anyway). Just clean the ventilation ports with a little bit of compressed air.

If that doesn't work, sleep your computer for awhile to let it cool back down, then wake it back up and watch Activity Monitor to see what processes are running hot while the machine is still cool, and google those process names to see what they are and what you can do about it.

Sometimes a reboot will help at this point for runaway jobs, especially on a new OS release.

HTH.