Jump in serial line latency?

I run ntpd with a simple DCF77 receiver hooked up to a serial port
as a reference clock (server 127.127.8.0 mode 14).  This is precise
to a few milliseconds.

Overall accuracy depends on figuring out the delay introduced by
the local receiver configuration.  The PARSE/RAWDCF refclock driver
defaults to 258 ms.  When I set up this machine earlier this year,
I determined the delay to be about 240 ms and compensated accordingly.
(fudge 127.127.8.0 time1 0.240)

A few days ago, I noticed accidentally that time is now off by about
0.8 seconds, compared to independent sources.

$ ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*GENERIC(0)      .DCFa.           0 l   22   64  377    0.000    1.796   0.553
 ntp1.arcor-onli 129.143.2.23     2 u  386 1024  377   14.816  804.110   2.812
 151.189.13.46   129.143.2.23     2 u  444 1024  377   11.760  804.024   2.912

It looks like something has added a lot of latency to characters
coming in the serial port.  I have no idea when this happened.
Candidates include the switch from sio(4) to uart(4), the new MPSAFE
TTY layer, or maybe these are red herrings and it came with the
ntpd update.

Can anybody corroborate this?  Any ideas?

Hmm... 800 ms is a suspicious figure.  Rx FIFO?

-- 
Christian "naddy" Weisgerber                          naddy_at_mips.inka.de