Author discovers that performance does not scale proportionally to %CPU utilisation, and gets instead to the conclusion that %CPU utilisation is a lie.

There are many reasons for the lack of a proportional relationship, even in the case where you do not have hyperthreading or downclocking (in which cases you just need to interpret %CPU utilisation in that context, rather than declare it "a lie"). Even in apple silicon where these are usually not an issue, you often do not get an exactly proportional scaling. There may be overheads when utilising multiple cores wrt how data is passed around, or resource bottlenecks other than CPU.

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saagarjha 6 days ago | parent [-]

Apple silicon downclocks quite a lot especially if you have a passively cooled machine

	▲	freehorse 6 days ago \| parent [-]
		With the exception of macbook air that has passive cooling nothing as aggressive as "turbo" modes, and ime it is relatively hard to get to thermal limits just with cpu in general for the devices I have used. Most other manufacturers nowadays officially advertise boosted single core clock speeds that are much higher and lower when more cores are used at the same time. Thermal limits, in contrast, are much more circumstantial.