Date: Mon, 22 Jan 2018 10:07:50 -0700 From: Alan Somers <asomers@freebsd.org> To: FreeBSD <freebsd-stable@freebsd.org> Subject: Clock occasionally jumps backwards on 11.1-RELEASE Message-ID: <CAOtMX2iCkurg8HXn7KD9AbrPcDVSRN-jK4MR%2BgFMAd%2BOFEdpow@mail.gmail.com>
next in thread | raw e-mail | index | archive | help
Since upgrading my jail server to 11.1-RELEASE, the clock occasionally jumps backwards by 5-35 minutes for no apparent reason. Has anybody seen something like this? Details ===== * Happens about once a day on my jail server, and has happened at least once on a separate bhyve server. * The jumps almost always happen between 1 and 3 AM, but I've also seen them happen at 06:30 and 20:15. * The jumps are always backwards, never forwards. * Inspecting the logs of both the host and its jails shows nothing interesting that's correlated with the jumps. Sometimes I find Amanda doing a backup, but not always. * Sometimes the jumps happen immediately after ntpd adds a new server to its list, but not always. * I'm using the default ntp.conf file. * ntpd is running on both, and it should be the only process touching the clock. I have a script running "ntpq -c peers" once a minute, which shows the offset for one server suddenly jump to a large negative number. Then the offsets for other servers jump to the same value, then either ntpd fixes the clock or exits because the offset is too high. * Said script is sleeping using the monotonic clock, not the realtime clock. As expected, successive timestamps differ by about 6.5 minutes when ntpd corrects a 5.5 minute clock offset. However, when the clock presumably jumps backwards I _don't_ see successive timestamps go backwards too. They keep marching forward at the expected rate. This makes me wonder if the entire machine is hanging. But it would have to be a pretty serious hang to stop the clock from ticking. Any ideas?
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAOtMX2iCkurg8HXn7KD9AbrPcDVSRN-jK4MR%2BgFMAd%2BOFEdpow>