Re: Linux 2.6.29-rc6
From: Jesper Krogh
Date: Fri Feb 27 2009 - 01:47:54 EST
john stultz wrote:
On Thu, 2009-02-26 at 23:06 +0100, Thomas Gleixner wrote:
On Thu, 26 Feb 2009, john stultz wrote:
On Thu, 2009-02-26 at 22:35 +0100, Jesper Krogh wrote:
Also mind sending the full dmesg for both kernels?
http://krogh.cc/~jesper/dmesg-2.6.29-rc6.txt
http://krogh.cc/~jesper/dmesg-2.6.26.8.txt
So one interesting difference:
2.6.26.8: TSC calibrated against PM_TIMER
2.6.29-rc6: Fast TSC calibration using PIT
Thomas, any thoughts as to why we might be calibrating off the PIT
instead of the PM_TIMER w/ 2.6.29?
Yup, because we introduced the Fast PIT calibration in 2.6.28.
Ah. Ok.
Is the delta anything NTP might get upset about:
2.6.26: time.c: Detected 2311.847 MHz processor.
2.6.29: Detected 2310.029 MHz processor.
I wouldn't think so.
Although, I'm recalling on some systems here right after we deploy them
we'll see something similar to the originally reported ntpd "time reset"
noise for a period of time while ntpd tries to find the right freq. For
some reason, I've noticed, having multiple servers in your ntp.conf
seems to increase NTP's difficulty at picking a time and converging.
So this may be just the slight calibration change is confusing ntp or it
may be the NTP_INTERVAL_LENGTH change from awhile back which would cause
the drift value to change could be doing the same thing (although I
thought that landed in the 2.6.24 timeframe, but I may be forgetting).
I'll kick up some of my own testing between these two releases to see if
I can't find something similar.
Jesper: How long was the box up for when you noticed the ntpd noise?
I was booted Feb 25 21:58 .. the first noice from ntp starts here:
Feb 25 22:09:53 quad12 ntpd[4901]: synchronized to LOCAL(0), stratum 13
Feb 25 22:09:56 quad12 ntpd[4901]: synchronized to 10.194.133.13, stratum 4
Feb 25 22:14:08 quad12 ntpd[4901]: synchronized to LOCAL(0), stratum 13
Feb 25 22:16:20 quad12 ntpd[4901]: synchronized to 10.194.133.13, stratum 4
Feb 25 22:32:25 quad12 ntpd[4901]: time reset -1.601641 s
Feb 25 22:36:18 quad12 ntpd[4901]: synchronized to LOCAL(0), stratum 13
Feb 25 22:36:45 quad12 ntpd[4901]: synchronized to 10.194.133.12, stratum 4
Feb 25 22:51:41 quad12 ntpd[4901]: time reset -0.922993 s
Feb 25 22:55:05 quad12 ntpd[4901]: synchronized to LOCAL(0), stratum 13
Also what's the output of the following under the different kernels:
ntpdc -c peers
ntpdc -c kerninfo
Working (clocksource=acpi_pm) 2.6.29-rc6
jk@quad02:~$ ntpdc -c kerninfo
pll offset: -0.001577 s
pll frequency: -45.787 ppm
maximum error: 0.066739 s
estimated error: 0.000768 s
status: 0001 pll
pll time constant: 6
precision: 1e-06 s
frequency tolerance: 500 ppm
jk@quad02:~$ ntpdc -c peers
remote local st poll reach delay offset disp
=======================================================================
*hal.nzcorp.net 10.194.132.81 4 64 377 0.00008 0.003752 0.04816
=svn.nzcorp.net 10.194.132.81 4 64 377 0.00009 -0.008724 0.04979
=LOCAL(0) 127.0.0.1 13 64 377 0.00000 0.000000 0.03082
Working (clocksource=tsc) 2.6.26.8
jk@quad03:~$ ntpdc -c kerninfo
pll offset: 0.003208 s
pll frequency: -25.070 ppm
maximum error: 0.833193 s
estimated error: 0.002787 s
status: 4001 pll
pll time constant: 10
precision: 1e-06 s
frequency tolerance: 500 ppm
jk@quad03:~$ ntpdc -c peers
remote local st poll reach delay offset disp
=======================================================================
*hal.nzcorp.net 10.194.132.82 4 1024 377 0.00781 0.006788 0.13666
=sal.nzcorp.net 10.194.132.82 4 1024 377 0.00018 -0.000541 0.12175
=LOCAL(0) 127.0.0.1 13 64 377 0.00000 0.000000 0.03041
Non-working (clocksource=tsc) 2.6.29-rc6
jk@quad12:~$ ntpdc -c kerninfo
pll offset: 0 s
pll frequency: -34.754 ppm
maximum error: 0.023514 s
estimated error: 0 s
status: 0001 pll
pll time constant: 6
precision: 1e-06 s
frequency tolerance: 500 ppm
jk@quad12:~$ ntpdc -c peers
remote local st poll reach delay offset disp
=======================================================================
=hal.nzcorp.net 10.194.132.91 4 64 17 0.00011 -0.069377 0.96895
=trac.nzcorp.net 10.194.132.91 4 64 17 0.00011 -0.096107 0.96904
*LOCAL(0) 127.0.0.1 13 64 17 0.00000 0.000000 0.96857
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