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- To: "chrony-users@xxxxxxxxxxxxxxxxxxxx" <chrony-users@xxxxxxxxxxxxxxxxxxxx>
- Subject: RE: [chrony-users] chrony switch source issue
- From: "Bernstein, Amit" <amitbern@xxxxxxxxxx>
- Date: Tue, 3 Jan 2023 05:38:05 +0000
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- Thread-topic: [chrony-users] chrony switch source issue
I understand, but the behavior doesn't seem right,
PHC device with nsec accuracy returns an error for 1 hour, and chrony refuses to replace the source to a usec accuracy NTP source?
This means chrony still "thinks" that an error response to a PHC device retrieved for 1 hour has better accuracy than NTP? That doesn't make sense.
If I set the PHC device to return zero instead of a real time, it takes couple of seconds for chrony to identify the timing issue and replace the source to NTP. I think this behavior should occur with PHC device error also.
Maybe the "smallest interval" you mention is wrongly calculated on PHC error?
Or maybe the system clock which was synced to the PHC at first wasn't changed too much (small shift than NTP) after 1 hour of not getting PHC timestamps?
Thanks for assisting.
-----Original Message-----
From: Miroslav Lichvar <mlichvar@xxxxxxxxxx>
Sent: Monday, January 2, 2023 17:01
To: chrony-users@xxxxxxxxxxxxxxxxxxxx
Subject: RE: [EXTERNAL][chrony-users] chrony switch source issue
CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
On Mon, Jan 02, 2023 at 02:42:59PM +0000, Bernstein, Amit wrote:
> Reproduced the issue for 60 minutes
>
> $chronyc sources
> MS Name/IP address Stratum Poll Reach LastRx Last sample
> ===============================================================================
> #* PHC0 0 4 0 60m -126ns[ -150ns] +/- 87ns
> ^- gotoro.hojmark.net 2 9 377 38 +201us[ +201us] +/- 67ms
> ^- animine.org 2 8 375 242 +244us[ +244us] +/- 78ms
> ^- mx.ack512.net 2 9 377 45 +5665us[+5665us] +/- 104ms
> ^- t2.time.bf1.yahoo.com 2 9 377 35 +2039us[+2039us] +/- 38ms
The estimated maximum error of the PHC0 source here is best by 6 orders of magnitude. If it becomes unreachable, you woudln't normally want to immediately switch to the next best source. It's nanoseconds vs milliseconds.
> S Name/IP Address Auth COpts EOpts Last Score Interval Leap
> =======================================================================
> * PHC0 N ----- ----- 63m 1.0 -3745us +3744us N
> D gotoro.hojmark.net N ----- ----- 185 1.0 -53ms +52ms N
> D animine.org N ----- ----- 132 1.0 -69ms +73ms N
> D mx.ack512.net N ----- ----- 191 1.0 -99ms +110ms N
> D t2.time.bf1.yahoo.com N ----- ----- 182 1.0 -35ms +40ms N
After 1 hour it still has the smallest interval, so it is working as intended.
The FAQ has some suggestions on how to force a faster reselection if you need that.
--
Miroslav Lichvar
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