What to do about "WARNING: negative runtime; monotonic clock has gone backwards"

[Brad Spencer <brad%anduin.eldar.org@localhost>]

So...  I have a PV+PVSHIM DOMU running a pretty recent 9.x on a DOM0
running a 9.99.xx kernel.  The DOM0 is not large, a 4 processor E-2224
with 32GB of memory.  The DOMU has 2 VCPUs and 8GB of memory.  About
every day a very particular DOMU tosses the:

WARNING: negative runtime; monotonic clock has gone backwards

on its console and sort of falls of the network.  A reboot "fixes" it,
but nothing else does.  The DOM0 is running a mostly stock XEN3_DOM0
kernel except that IFQ_MAXLEN is larger than the default and HZ is 2000
(which helped to keep the clocks on the DOMU syncing properly all other
things being equal).  The DOMU is running a pretty stock XEN3_DOMU, that
is, HZ is 100 there.  Over the years, this problem has been mentioned
from time to time, but I was wondering if anyone has a actual solution
to this sort of thing.  The DOM0 hosts a small number of guests, all
PV+PVSHIM, but this one in particular is the only one with 2 VCPUs, all
the rest have only 1 and have never exhibited the problem of the clock
going backwards.

Nothing much is really going on with the DOMU right now, as it is one of
my build guests.  It is running ZFS and does backups each day and does a
'cvs update' sort of thing from time to time, but than that is it right
now.



Any thoughts??



-- 
Brad Spencer - brad%anduin.eldar.org@localhost - KC8VKS - http://anduin.eldar.org