Re: [chrony-users] Validating PHC operation on Microsoft VM
The hypervisor is fine -- in the sense that it's allowing guest programs to run, and the frequency isn't too variable for chrony to keep its own time from NTP. It's just the host time is a bit off, but as you can see chrony is correctly not using it by marking it as '?' (unusable, check sources -v), so you end up getting the right time from Google. PS: Your image is well received. -- Mingye Wang (Artoria2e5) On Wed, Feb 26, 2025 at 12:40 AM Steven Sommars wrote: > > >> If you keep the refclock enabled with the nearby NTP sources, will it >> be marked as a falseticker? > > > PHC (noselect) plus 4 of the Google anycast > chronyc -n sources;chronyc -n sourcestats > MS Name/IP address Stratum Poll Reach LastRx Last sample > === > #? PHC0 0 3 377 5+29ms[ +29ms] +/- > 17us > ^+ 216.239.35.0 1 6 37752 -512us[ -512us] +/- > 5576us > ^* 216.239.35.12 1 6 37753-80us[ -75us] +/- > 5068us > ^- 216.239.35.4 1 6 37750 +566us[ +566us] +/- > 18ms > ^- 216.239.35.8 1 6 37759 +672us[ +677us] +/- > 18ms > Name/IP AddressNP NR Span Frequency Freq Skew Offset Std Dev > == > PHC06 340 -8.207 10.836+29ms39us > 216.239.35.0 19 12 1162 -0.074 1.127-60us 415us > 216.239.35.12 64 38 67m +0.000 0.101-46us 281us > 216.239.35.4 64 35 67m +0.020 0.199+46us 552us > 216.239.35.8 64 30 68m +0.053 0.172 -8862ns 510us > > Looks like a hypervisor problem. > -- To unsubscribe email [email protected] with "unsubscribe" in the subject. For help email [email protected] with "help" in the subject. Trouble? Email [email protected].
Re: [chrony-users] Validating PHC operation on Microsoft VM
I synchronized the host using chrony and nearby stratum 1's and then compared the PHC time to the host time. The results are bizarre. I have only oneVM, so this result might not hold elsewhere. Miroslav suggests this might be a hyper-v issue. Hope this image gets through the mailing list. If not, I'll post it elsewhere. [image: image.png] On Wed, Feb 26, 2025 at 2:22 AM Miroslav Lichvar wrote: > On Wed, Feb 26, 2025 at 12:59:20PM +0800, Mingye Wang wrote: > > I can see why Microsoft Azure picked that option: they don't want to > > overload the NTP pool (like I've complained about recently)[1], but > > their approach is a bit off. Specifically, I believe they should have > > specified a nonzero stratum so that chrony does not place too much > > trust in the host time. Is there anyone from Azure that I can contact > > on this issue? > > If there is only one source, it doesn't matter what stratum it has. > Its weight can change only relative to other sources. > > If you want to propose changes to the default configuration, you will > need to find out where it is coming from. There could be a base image > provided by the OS vendor and other changes layered on top maintained > elsewhere. Not easy to follow. I think most of the Azure stuff is on > github. > > -- > Miroslav Lichvar > > > -- > To unsubscribe email [email protected] > with "unsubscribe" in the subject. > For help email [email protected] > with "help" in the subject. > Trouble? Email [email protected]. > >
Re: [chrony-users] Validating PHC operation on Microsoft VM
On Wed, Feb 26, 2025 at 12:59:20PM +0800, Mingye Wang wrote: > I can see why Microsoft Azure picked that option: they don't want to > overload the NTP pool (like I've complained about recently)[1], but > their approach is a bit off. Specifically, I believe they should have > specified a nonzero stratum so that chrony does not place too much > trust in the host time. Is there anyone from Azure that I can contact > on this issue? If there is only one source, it doesn't matter what stratum it has. Its weight can change only relative to other sources. If you want to propose changes to the default configuration, you will need to find out where it is coming from. There could be a base image provided by the OS vendor and other changes layered on top maintained elsewhere. Not easy to follow. I think most of the Azure stuff is on github. -- Miroslav Lichvar -- To unsubscribe email [email protected] with "unsubscribe" in the subject. For help email [email protected] with "help" in the subject. Trouble? Email [email protected].
Re: [chrony-users] Validating PHC operation on Microsoft VM
On Tue, Feb 25, 2025 at 11:57 AM Steven Sommars wrote: > refclock PHC /dev/ptp_hyperv poll 3 dpoll -2 offset 0 I can see why Microsoft Azure picked that option: they don't want to overload the NTP pool (like I've complained about recently)[1], but their approach is a bit off. Specifically, I believe they should have specified a nonzero stratum so that chrony does not place too much trust in the host time. Is there anyone from Azure that I can contact on this issue? [1]: https://community.ntppool.org/t/rant-some-of-our-clients-shouldnt-even-exist-vm-farms/3774 -- Mingye Wang (Artoria2e5) -- To unsubscribe email [email protected] with "unsubscribe" in the subject. For help email [email protected] with "help" in the subject. Trouble? Email [email protected].
Re: [chrony-users] Validating PHC operation on Microsoft VM
> If you keep the refclock enabled with the nearby NTP sources, will it > be marked as a falseticker? > PHC (noselect) plus 4 of the Google anycast chronyc -n sources;chronyc -n sourcestats MS Name/IP address Stratum Poll Reach LastRx Last sample === #? PHC0 0 3 377 5+29ms[ +29ms] +/- 17us ^+ 216.239.35.0 1 6 37752 -512us[ -512us] +/- 5576us ^* 216.239.35.12 1 6 37753-80us[ -75us] +/- 5068us ^- 216.239.35.4 1 6 37750 +566us[ +566us] +/- 18ms ^- 216.239.35.8 1 6 37759 +672us[ +677us] +/- 18ms Name/IP AddressNP NR Span Frequency Freq Skew Offset Std Dev == PHC06 340 -8.207 10.836+29ms 39us 216.239.35.0 19 12 1162 -0.074 1.127-60us 415us 216.239.35.12 64 38 67m +0.000 0.101-46us 281us 216.239.35.4 64 35 67m +0.020 0.199+46us 552us 216.239.35.8 64 30 68m +0.053 0.172 -8862ns 510us Looks like a hypervisor problem.
Re: [chrony-users] Validating PHC operation on Microsoft VM
On Mon, Feb 24, 2025 at 09:57:21PM -0600, Steven Sommars wrote: > AFAICT chrony is happy, but is providing inaccurate time: Time is in error > by 30-50 msec with substantial jitter. > > Dropping the PHC refclock and using nearby stratum 1's give much better > results. If you keep the refclock enabled with the nearby NTP sources, will it be marked as a falseticker? > Any suggestions for further debugging? To me that sounds like the problem is in the synchronization of the VM host's clock. An issue with the hyperv clocksource would impact both PHC and NTP sources. -- Miroslav Lichvar -- To unsubscribe email [email protected] with "unsubscribe" in the subject. For help email [email protected] with "help" in the subject. Trouble? Email [email protected].
[chrony-users] Validating PHC operation on Microsoft VM
I'm running chrony 4.5 (which is the current default) on a commercial Microsoft Azure VM (Linux myVm 6.8.0-1021-azure). By default a PTP hardware clock is used as a time source: chrony.conf has no servers defined refclock PHC /dev/ptp_hyperv poll 3 dpoll -2 offset 0 No external servers are defined. This is the default configuration. Current time source: hyperv_clocksource_tsc_page Available time sources: hyperv_clocksource_tsc_page hyperv_clocksource_msr acpi_pm This is the default setting. AFAICT chrony is happy, but is providing inaccurate time: Time is in error by 30-50 msec with substantial jitter. Dropping the PHC refclock and using nearby stratum 1's give much better results. Any suggestions for further debugging?
