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You asked for an expert to correct you if you're wrong, so here it is: this is just completely wrong and entirely ignorant of both the capacity of the system and its history.

On timers: we (I) added arbitrary resolution interval timers to the operating system in 1999[1] -- predating Linux by years. (We have had CPU binding and processor sets for even longer.) The operating system was and is being used in many real-time capacities (in both the financial and defense sectors in particular) -- and before "every single major financial exchange" was running Linux, many of them were running Solaris.

[1] https://github.com/joyent/illumos-joyent/blob/master/usr/src...

Thank you Bryan for the correction, I did after all ask for it :)

One final question while I've got you that your response didn't seemingly address. Does the cyclic subsystem allow turning off the cpu timer entirely ala Linux's nohz_full? If so, I stand corrected.

Yes, it does -- the cyclic subsystem will only fire on CPUs that have a cyclic scheduled, which won't be any CPU that is engaged in interrupt sheltering via psradm.[1] This is how it is able to achieve hard real-time latency (and indeed, was used for some hardware-in-the-loop flight simulator systems in the defense sector that had very tight latency tolerence).

[1] https://illumos.org/man/1m/psradm

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