On 2007-10-19, Richard B. Gilbert <[EMAIL PROTECTED]> wrote: > > Some Linux systems have known problems with losing timer interrupts! > During periods of heavy I/O load disk drivers may mask or disable > interrupts for a little too long a time. . . . Some Windows systems > have also been known to exhibit similar behavior.
I would like to know more about this. How can I monitor the interrupts? After my original post, I remembered that this machine has a unique feature. I compiled a new kernel to add the Reiser file system. I don't think I changed anything else, but I don't have any previous experience with custom kernels. > > What's the value stored in your drift file? Currently it's 74.080. This morning it started out around 30. > > DON'T use burst! The burst keyword was intended for situations where > ntpd has to make a phone call to NIST (or similar service) to get the > time. It is NOT suitable for general use over the internet. Without burst, it just drifts freely. The size of the drift is even worse than I thought. With burst, here are some lines from the log file: Oct 19 13:37:23 client ntpd[12595]: time reset +13.151972 s Oct 19 13:55:58 client ntpd[12595]: time reset +8.779090 s Oct 19 14:08:09 client ntpd[12595]: time reset +8.712040 s Oct 19 14:28:21 client ntpd[12595]: time reset +11.494533 s Oct 19 14:44:53 client ntpd[12595]: time reset +9.450835 s If I ever get this situation under control I'll turn off burst. > > Iburst is good. It gets you a fast startup and then lets your system > poll the server at normal intervals. > > Check the value of a Kernel variable called "HERTZ". Some Linux systems > set it to 1000 which is not good for NTP. If yours is set to 1000 (or > 250) try changing it to 100. More ignorance on my part. Where would I look for this? I searched the kernel source code and didn't find it. > > Using a single server is not usually a good idea. Two servers are the > worst possible configuration; ntpd has no good way to decide which one > to believe. Three are good but four are better. Try to select servers > that are close to you in network space (low values of Delay). > > Again, I'll fix this if I ever get things running properly. The one server I chose is our master campus server, which is quite close network-wise. Here's another issue. I just learned about the distinction between the kernel clock and the hardware (TOY) clock. I have tried running hwclock from time to time, comparing it to my WWV-controlled wall clock. It never seems to be more than 1 or 2 seconds off. Is there any way to exploit this? _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
