It seems there is a serious problem with the clock system since Kernel 3.16.
Robert: is there someone from TI that could take a look at this before we start another wonderful bisect? Thanks, Nuno On Mon, Aug 24, 2015 at 10:46 AM, Miroslav Lichvar <[email protected]> wrote: > On Fri, Aug 21, 2015 at 07:05:38PM +0100, Nuno Gonçalves wrote: >> Thank you so much. I've sent you the hostnames of a beaglebone white >> and a beaglebone black that are set with your public key. >> >> I took a few days while I confirmed what I could. In fact I've tried >> several kernel versions and I see that up to 3.15.10-bone8 the clock >> is working properly. After 3.16 and until the most recent 4.2 RC, it >> is malfunctioning. >> >> If you have a minute to login at the machines and are able to narrow >> in any way which part of the kernel clocks is at fault it might be >> easier have it fixed at the Linux level. > > I did some tests with the adjtimex utility while chronyd was just > reporting measured offset and not controlling the clock. It looks like > there is a problem with large frequency offsets. There seems to be a > maximum offset the kernel is willing to apply to the clock (about 1000 > ppm) and any attempts to slow down or speed up the clock more are > ignored. This breaks the chrony control loop badly. > > As a workaround, I set the maxslewrate option to 100 ppm and started > chronyd with "0.0 1.0" in the driftfile to avoid large frequency > adjustments and it seems it was able to settle down. > > I'm not sure where the problem could be. Looking at the log for the > linux/kernel/time directory between 3.15 and 3.16 I don't see anything > suspicious. Could be something in the arch-specific code. > > You could try to add the nohz option to the kernel command line, that > would suggest it's a problem with the internal timekeeping loop. > > I think this is a serious bug that needs to be fixed. If you file any > bug reports, please let us know. > > Thanks, > > -- > Miroslav Lichvar > > -- > To unsubscribe email [email protected] > with "unsubscribe" in the subject. > For help email [email protected] > with "help" in the subject. > Trouble? Email [email protected]. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
