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Is there any evidence or technical documentation to support the notion that System Integrity Protection can cause excessive use of the CPU by kernel_task in some situation?

Background

No battery. All Apple operating systems on an external hard disk drive, limited (by the MacBookPro8,2) to USB 2.0.

With Sierra, and with pre-release High Sierra, when not booted in safe mode I nearly always found that kernel_task hogged the CPU.

My usual workaround was safe mode.

After considering answers to the following questions:

– I aimed to move (set aside) the following file:

/System/Library/Extensions/IOPlatformPluginFamily.kext/Contents/PlugIns/ACPI_SMC_PlatformPlugin.kext/Contents/Resources/MacBookPro8_2.plist

Prerequisite to the move:

  • disable System Integrity Protection (SIP).

After using csrutil(1) in Recovery OS 17A264c to disable SIP, I booted High Sierra in normal mode …

… I was pleasantly susprised to find that with the .plist still in place:

  • in normal mode without SIP, the CPU was no longer hogged.

Shut down, started, no hogging.

Started 10.12, no hogging, updated to 10.12.5, restarted, no hogging.

2017-06-10 around 16:50 the Mac unexpectedly stopped. When started, to 10.12.5, I noticed that SIP was re-enabled (not by me). No hogging.

Started Recovery OS 17A264c, disabled SIP, restarted to 10.12.5, no hogging …

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