SMP and NTPD (Eric Mader)

[Eric Mader]

David G. Miller wrote:
> Eric Mader <emader at icu-project.org> wrote:
> 
>> I also noticed the following in /var/log/messages: Apr 11 09:21:19 
>> localhost kernel: warning: many lost ticks. Apr 11 09:21:19 localhost 
>> kernel: Your time source seems to be instable or some driver is 
>> hogging interupts I'll bet this has something to do w/ the problem. 
>> (:-) Does anybody know how to figure out what this is about? (I have a 
>> vague memory of having seen the same problem w/ the SMP kernel on a P4 
>> w/ hyperthreading. On this system it was so bad that the whole system 
>> would lock up. My AMD keeps chugging along, more or less.) Regards, 
>> Eric Eric Mader wrote:
>>
>>>> Hello,
>>>>
>>>> I'm running kernel 2.6.11-1.1369_FC4smp on an AMD64 x2 system. A 
>>>> couple of days ago I noticed that NTPD wasn't keep time very well. I 
>>>> did some investigating and found out that the jitter from the time 
>>>> servers kept going up and up - after an hour the jitter will be 
>>>> several seconds.
>>>>
>>>> As an experiment, I tried running the non-smp kernel, and NTPD was 
>>>> able to keep rock-solid sync. After more than an hour, the jitter 
>>>> was only a few milliseconds.
>>>>
>>>> I'm guessing that this points to some problem w/ the SMP kernel. Can 
>>>> anybody confirm this, or suggest what else the problem might be?
>>>>
>>>> My system:
>>>> ASUS A8V Delux
>>>> AMD Athlon 64 X2 4200+
>>>> 1 GM memory (512 MB x 2)
>>>> WD1200JJ (w/ Windows XP x64)
>>>> WD400BB (w/ FC4)
>>>> NEC DVD RW 3520A
>>>> TDK CDRW 5200B
>>>> NVidia GeForce 6600 (ASUS brand)
>>>> Samsung SyncMaster 204T (connected through a DVI KVM)
>>>> USB Keyboard and mouse (connected through KVM)
>>>>
>>>> Regards,
>>>> Eric Mader
>>>>
>>>   
> Might be specific to the dual core Athlon.  I'm running a traditional 
> dual Athlon (Tyan Tiger MPX with 2x 32bit Athlon 2400+s) and not seeing 
> that problem at all:
> 
> [dave at bend ~]# uname -a
> Linux bend.local.davenjudy.org 2.6.15-1.1833_FC4smp #1 SMP Wed Mar 1 
> 23:56:51 EST 2006 i686 athlon i386 GNU/Linux
> [dave at bend ~]# ntptime
> ntp_gettime() returns code 0 (OK)
>  time c7e82823.24468000  Wed, Apr 12 2006 19:30:11.141, (.141701),
>  maximum error 606915 us, estimated error 5751 us
> ntp_adjtime() returns code 0 (OK)
>  modes 0x0 (),
>  offset 847.000 us, frequency 152.009 ppm, interval 4 s,
>  maximum error 606915 us, estimated error 5751 us,
>  status 0x1 (PLL),
>  time constant 6, precision 1.000 us, tolerance 512 ppm,
>  pps frequency 0.000 ppm, stability 512.000 ppm, jitter 200.000 us,
>  intervals 0, jitter exceeded 0, stability exceeded 0, errors 0.
> [dave at bend ~]# uptime
> 19:30:26 up 8 days, 22:50,  8 users,  load average: 0.31, 0.16, 0.18
> 
> I have seen lots of clock weirdnesses with my AMD64 (single core) laptop 
> (ATI chipset).  Lots of stuff about this under bug 
> https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=152170.  Any idea 
> what chipset your ASUS board uses?

The ASUS A8V Deluxe uses the VIA K8T800Pro and VIA VT8237 chipsets.

> Cheers,
> Dave

Regards,
Eric