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Differential D35935

pps: Round to closest integer in pps_event()
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Authored by sebastian.huber_embedded-brains.de on Jul 26 2022, 8:26 AM.
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phk
gnn
delphij
imp
Summary

The comment above bintime2timespec() says:

When converting between timestamps on parallel timescales of differing
resolutions it is historical and scientific practice to round down.

However, the nsec value is a time difference and not a timestamp. So, rounding
to the closest integer is probably slightly better.

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rS FreeBSD src repository - subversion
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Buildable 46582
Build 43471: arc lint + arc unit

Event Timeline

sebastian.huber_embedded-brains.de created this revision.Jul 26 2022, 8:26 AM
Herald added subscribers: Contributor Reviews (src), imp. · View Herald TranscriptJul 26 2022, 8:26 AM
sebastian.huber_embedded-brains.de requested review of this revision.Jul 26 2022, 8:26 AM
Harbormaster completed remote builds in B46582: Diff 108535.Jul 26 2022, 8:26 AM
imp added reviewers: phk, gnn, delphij.Jul 26 2022, 3:30 PM
imp added a parent revision: D35934: pps: Simplify the nsec calculation in pps_event().
imp accepted this revision.Jul 26 2022, 3:34 PM

My quick algebra says this is good and computed in the right way.

sys/kern/kern_tc.c
1898

so we go from nsec = nsec / freq to nsec = (nsec + freq / 2) / freq which is nsec / freq + freq / (2 * freq) or nsec / freq + 1/2 which looks good.

This revision is now accepted and ready to land.Jul 26 2022, 3:34 PM

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sys/kern/kern_tc.c

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