Re: [PATCH v4 2/4] pps: Drop the !NO_HZ_COMMON dependency from NTP_PPS

[David Woodhouse]

On Tue, 2026-09-01 at 17:35 +0200, Rodolfo Giometti wrote:
> About the test. The pulse comes from 4/4, which derives it from the
> same counter the timekeeping reads. No independent reference
> anywhere.

That was intentional, btw. I'm trying to eliminate the ever-smaller
errors in the kernel's timekeeping, and at this point they are fairly
much in the noise compared with the real-world measurement against
*real* time, on any test platform I can currently lay my hands on.

I'm not yet able to test on hardware which actually snapshots the CPU
counter at the moment of the PPS signal.

But I can *simulate* it, by running a virtual machine with vmclock and
knowing the precise relationship of counter to real time that I'm
*telling* it to discipline against — then checking how it did. Your "no
independent reference anywhere" is my "I'm actually testing the part I
want to test" :)

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