[ntp:questions] Sudden drop in frequency after software update

Hal Murray hal-usenet at ip-64-139-1-69.sjc.megapath.net
Wed Jan 21 02:10:49 UTC 2009


>It would be interesting to know what kernel version those who are having
>trouble with unstable drift in Linux are using.  I am using kernel
>2.6.27.7, and it is very stable, varying no more than 5 PPM, even across
>reboots.  It should be noted that I rebuilt my kernel with the timer
>frequency set to 100HZ, and made sure that dynamic ticks was disabled.
>This seems to produce the lowest drift values.  In an older 2.6 kernel,
>I noticed the drift rate jumping all over the place as described.
>However, it appears that this may have finally been fixed.

What version of the kernel fixed what bug?

I just installed 2.6.28.1 and patched the startup code
to loop and print the TSC calibration info.

Jan 20 17:53:54 mini-mon kernel: Detected 1000.152 MHz processor.
Jan 20 17:53:54 mini-mon kernel: Detected 1000.093 MHz processor.
Jan 20 17:53:54 mini-mon kernel: Detected 1000.179 MHz processor.
Jan 20 17:53:54 mini-mon kernel: Detected 1000.152 MHz processor.
Jan 20 17:53:54 mini-mon kernel: Detected 1000.096 MHz processor.
Jan 20 17:53:54 mini-mon kernel: Detected 1000.091 MHz processor.
Jan 20 17:53:54 mini-mon kernel: Detected 1000.150 MHz processor.
Jan 20 17:53:54 mini-mon kernel: Detected 1000.134 MHz processor.
Jan 20 17:53:54 mini-mon kernel: Detected 1000.121 MHz processor.
Jan 20 17:53:54 mini-mon kernel: Detected 1000.103 MHz processor.

That's 88 ppm peak to peak.

-- 
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