On 11/20/19 4:33 PM, Paul Theodoropoulos via devel wrote: > Just a shot in the dark, but it looks to me like an errant > overly-greedy cron job or systemd timer - perhaps something else is > polling the serial port on a schedule. If you set up hourly graphs you > might be able to correlate it with something else firing on the server > at those intervals.
On 11/20/19 6:33 PM, Gary E. Miller via devel wrote: > Check your crontab, and other recurrent jobs. Those are way too large > for an idle server. Could be a remote cronjob doing something like a > log pull or other test. This is a physical server that is idle other than ntpd. It _is_ serving NTP to the public pool, so there's a fair amount of load there. FWIW, ntpd is 25-30% CPU. Both systems are the same in these respects. At 23:10 UTC, I stopped cron and ALL systemd timers. At 03:55 UTC, I re-ran the ntpviz daily job. I ran it again at 04:03 just to get the 04:00 label on the graph. There was no change in the pattern from 22:00 to 04:00. >> Another idea might be to switch to the PPS refclock on ntp2 to see if >> it behaves similarly with the ublox PPS. > > My bet is that it does. I'll look into this, but this will take a bit longer to get useful results. >> As a second question, if you look at the ntp2 weekly graphs, there is >> a single huge transient. Any idea what that might be? I've seen these >> about once or twice a week since I put this in a couple weeks ago: >> https://ntp2.wiktel.com/week/ > > Usually some sort of kernel stall. Likely some big job, or a backup, > happened during those events. Less likely, but very possible, a disk > drive or NFS mount hung the entire system for 50 ms. No NFS on this system. In terms of disks, it's a pair of SATA SSDs connected to the motherboard in an ext4-on-LVM-on-MD configuration. > Also check the ntpd is locked to your PPS during the events. Is there a way to check that retroactively? -- Richard
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