Hi Bryan, On 24/10/14 15:40, Bryan K. Walton wrote: > I've been troubleshooting a problem with large clock drift on my net6501 > for a while. It is running Debian 7, with kernel 3.2.58. > > Of course, I've got a NTP server running on it. And I generally have no > problems with time sync during normal system usage (low load) > > But what I've discovered is that during periods of high system load (like > when I'm running rsnapshot on the box to do home backups, the clock starts > drifting quickly. The CPU load on the net6501 around that time is very > high, around 2.5. The clock drifts enough that ntp thinks that my time > sources are failing sanity checks. > > So then, NTP quits synchronizing the time. After a day or two of this, > with other high load times, the system time gets so far from the time of > the outside time servers, that NTP just quits running. > > Has anybody else noticed this? Is there anything I can do to address the > clock drift during high load times? I never encountered this problem on > my net4801.
we have suffered from the same issue. Applying the force-enable-hpet patch [1] helps. With that the kernel chooses tsc as clocksource and the system keeps stable time with ntp. Also, do not forget to pass intel_idle.max_cstate=1 to keep tsc stable. HTH Martin Sofaru [1] http://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/commit/?id=2e151c70dfb0075ff83bec305c52a9da1ba49089
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