Re: [PATCH v2 0/6] timekeeping: Reduce magnitude of ntp_error

[David Woodhouse]

On Thu, 2026-11-05 at 19:08 -0800, David Woodhouse wrote:
> 
> David Woodhouse (6):
>       timekeeping: Allow tick_length changes to apply mid-tick
>       ntp: Recalculate skew_delta when the phase offset changes
>       timekeeping: Bound idle sleep while a phase slew is in flight
>       timekeeping: Reinstate proportional correction of ntp_error
>       pps: Always use ktime_get_snapshot_id() for pps_get_ts()
>       timekeeping: Apply extrapolated ntp_error to clock snapshots
> 
>  include/linux/pps_kernel.h          |   4 +-
>  include/linux/timekeeper_internal.h |  11 +-
>  kernel/time/ntp.c                   | 144 ++++++++++++++----------
>  kernel/time/tick-internal.h         |  18 +++
>  kernel/time/timekeeping.c           | 211 ++++++++++++++++++++++++++++++++++--
>  5 files changed, 318 insertions(+), 70 deletions(-)

I think I reordered and reworded things as agreed with Rodolfo; please
shout if I screwed something up. What's sitting behind this in
https://git.infradead.org/users/dwmw2/linux.git/shortlog/refs/heads/ffclock
is the timekeeping reference stuff for importing/exporting vmclock, and
preserving timekeeping across KHO:

The !NO_HZ_COMMON dependency can sit around for a little while longer
until the series above is actually applied, and it can note the
actually commit ID of its dependencies (which I think we agreed is just
patches 1 & 2 of the series above). I'll probably round it up with the
other PPS stuff I haven't quite got publishable yet, improving the
filtering and then working on counter-based capture and UAPI.

David Woodhouse (7):
      timekeeping: Use inlined counter read in ktime_get_snapshot_id()
      pps: Drop the !NO_HZ_COMMON dependency from NTP_PPS
      timekeeping: Add absolute reference for feed-forward clock discipline
      timekeeping: Hand clock reference over kexec via KHO
      ptp_vmclock: Feed reference to timekeeping for feed-forward discipline
      timekeeping: Provide a shared /sys/kernel/time kobject
      kernel/time: Export NTP-disciplined time as a vmclock page in sysfs

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