I have long had issues with both Window Manager and kernel_task taking up seemingly inordinate amounts of resources on my systems going back in the OS release cycle for as long as I can remember, but since I had my MacBook Pro 13" i7 back from the shop with a new SSD, screen, and battery, I did a restore from TM and updated it to 10.13.3 and I actually don't even see either
kernel_task running at all! I will add the this machine has performed better than it ever has, this is likely attributed that to the fact that its puffy batteries were replaced. Who knows what impact those things were having besides warping the chassis.
As I mentioned in another post, on my i7 Mini, suddenly had performance issues while running Sierra for a machine that hitherto been a wonderful machine for the 5 years she's been running without hardly ever a beachball. Honestly, it's been faster than even the newer MacBook Pro 15" 2015 I was issued at work- even though its still the 2012 version. (It was the highest end CPU chipset available - 2.3 GHz - and I maxed out RAM to 16 GB and swapped in a fast SSD with a dual disk kit so it was even at baseline a fantastic machine for the price.)
Unfortunately, as I reported in that other post, it suddenly started suffering from the notorious kernel bloat issue where those familiar processes became the machine's sole purpose as they were generally up top of the proc table as I have seen it on many other troubled Macs in the past. I was downright emotional about it and I received some great suggestions as to how I might resolve it, but since the machine had been upgraded so many times (it literally has not gotten a fresh install since Mountain Lion, yet no performance issues until just now, oddly) I opted for a full install. It was due. I had my installation checklist well defined along with settings (I just need to Automate it next!) so the mini is now running on what is effectively a fresh install of High Sierra. While right off performance is so much better, once I installed Chrome and it synced up with my Google account, crazy things happened and I am now picking its mess off so I can start fresh. Dunno if its an bad extension or what, but its a sloppy mess.
The bigger mystery is that I still see
kernel_task near the top of my process table frequently, and though my machine is not limping like it was before, the mystery continues: why are they not even visible on my rebuilt MBP? Is there something hiding those processes when in fact they really are running? It doesn't seem like it as resource usage remains very low. The fact both machines are running the same version of High Sierra I simply don't get how they could be so different. They have practically flip-flopped in their behavior. Even without Chrome my mini gets slammed by the evil duo (
kernel_task) like by Safari. It's a mess!
Signed, Confused in California