[Xen-devel] Re: [Xen-users] ntpd under Xen Dom0 exhibits extremely high jitter/noise? runs stable/quiet under non-xen kernel.

[mail ignored <0.bugs.only.0@xxxxxxxxx>]

On Mon, Jan 18, 2010 at 9:21 AM, mail ignored <0.bugs.only.0@xxxxxxxxx> wrote:
>> For example, you could try clocksource=acpi, or clocksource=pit. And then
>> check that the 'Platform timer is...' line from Xen boot output changes
>> correspondingly.
>
> checking those now ... will report results in a bit.

both seem to work ...

booting to,

  /xen.gz ... clocksource=acpi ...

then,

 xm dmesg | grep -i timer
  (XEN) ACPI: PM-Timer IO Port: 0x808
  (XEN) ..TIMER: vector=0xF0 apic1=0 pin1=2 apic2=-1 pin2=-1
  (XEN) Platform timer is 3.579MHz ACPI PM Timer
  (XEN) HPET: 4 timers in total, 3 timers will be used for broadcast
  (XEN) mcheck_poll: Machine check polling timer started.

~ 15 minutes, quiet/stable operation @ stratum=2, full reach.

        assID=0 status=0684 leap_none, sync_ntp, 8 events, event_peer/strat_chg,
        version="ntpd 4.2.4p8@xxxxxx Mon Dec 28 17:26:30 UTC 2009 (1)",
        processor="x86_64", system="Linux/2.6.31.8-0.1-xen", leap=00, stratum=2,
        precision=-20, rootdelay=13.970, rootdispersion=26.079, peer=33500,
        refid=216.218.254.202,
        reftime=ceff1d2c.ddbe13c0  Mon, Jan 18 2010  9:47:24.866, poll=6,
        clock=ceff1e07.464f2053  Mon, Jan 18 2010  9:51:03.274, state=4,
        offset=15.245, frequency=24.962, jitter=10.571, noise=17.706,
        stability=7.306
             remote           refid      st t when poll reach   delay   offset  
jitter
        
==============================================================================
        -clock.fmt.he.ne .PPS.            1 u   41   64  377   16.047   20.346  
10.336
        -otc2.psu.edu    130.207.244.240  2 u   39   64  377  100.626   14.538  
 5.387
        +clock.isc.org   .GPS.            1 u   54   64  377   15.174   -0.843  
10.578
        *clock.sjc.he.ne .CDMA.           1 u   26   64  377   13.970   12.255  
 7.051
         zorro.sf-bay.or 216.218.254.202  2 u   31   64  377   16.489   13.730  
 5.781
        +nist1.aol-ca.tr .ACTS.           1 u   15   64  377   14.891    5.947  
14.596

booting to,

  /xen.gz ... clocksource=pit ...

 xm dmesg | grep -i timer
  (XEN) ACPI: PM-Timer IO Port: 0x808
  (XEN) ..TIMER: vector=0xF0 apic1=0 pin1=2 apic2=-1 pin2=-1
  (XEN) Platform timer is 1.193MHz PIT
  (XEN) mcheck_poll: Machine check polling timer started.

~ 20 minutes, quiet/stable operation @ stratum=2, full reach.

        assID=0 status=0654 leap_none, sync_ntp, 5 events, event_peer/strat_chg,
        version="ntpd 4.2.4p8@xxxxxx Mon Dec 28 17:26:30 UTC 2009 (1)",
        processor="x86_64", system="Linux/2.6.31.8-0.1-xen", leap=00, stratum=2,
        precision=-20, rootdelay=16.981, rootdispersion=31.958, peer=63536,
        refid=207.200.81.113,
        reftime=ceff2377.503b4ceb  Mon, Jan 18 2010 10:14:15.313, poll=6,
        clock=ceff240e.fa89c747  Mon, Jan 18 2010 10:16:46.978, state=4,
        offset=9.641, frequency=4.070, jitter=12.958, noise=6.244,
        stability=0.834
             remote           refid      st t when poll reach   delay   offset  
jitter
        
==============================================================================
        +clock.fmt.he.ne .PPS.            1 u   30   64  177   15.250    8.422  
 9.657
        +otc2.psu.edu    147.84.59.145    2 u   33   64  177   99.375   10.359  
 8.906
        +clock.isc.org   .GPS.            1 u   25   64  177   13.060    2.679  
 9.501
        +clock.sjc.he.ne .CDMA.           1 u   22   64  177   15.097   10.608  
 7.866
        +zorro.sf-bay.or 216.218.254.202  2 u   27   64  177   15.082    9.639  
 8.443
        *nist1.aol-ca.tr .ACTS.           1 u   23   64  177   16.981   15.780  
 7.743


seemingly, _nothing_ to do with the kernel, then.  rather overriding
whatever xen's default clocksource is does the trick.

i'll still take a look over longer term @ Dom0, and see if there's any
strangeness in DomU time ...

thanks!

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