Your Mac goes all sluggish, you open Activity Monitor, and there at the top of the CPU list is kernel_task, taking 100% or more. Why?
kernel
From launch, through security checks, TCC and privacy, RunningBoard, to memory management and the Main Event Loop. A comprehensive summary.
What should you do with a Mac whose fans keeping coming on full blast, with high CPU loads from kernel_task, and sluggish performance?
It’s hot, you’re hot, and your Mac has slowed right down. Activity Monitor tells you that it’s kernel_task which is to blame. Is macOS playing up, or what?
Stepping through key points in the log as Mojave 10.14 starts up. Most of the key waypoints are similar to those in High Sierra.
Adds details of the sequence of screens displayed at each stage, to help diagnose boot problems.
Single-diagram summary of how a modern Mac starts up in macOS 10.12 or 10.13, from pressing the Power button to running the kernel.
How macOS gets to load a hefty kernel and over 300 extensions so quickly: it cheats with a pre-linked kernelcache. And why you don’t see extensions loading in the log.
Changes include frequent timechecks by timed, harder access to info about keychains, a couple of possible AppleScript bugs, and APFS snapshots.
A detailed examination of what happens during the first few minutes after starting your Mac up. Vital for anyone trying to diagnose problems in that period.
