Re: [chrony-users] Chrony not taking SOCKET data from Application

[sarveshwar k <sarveshwar.kt@xxxxxxxxx>]

Hi Miroslav,

Thanks for the information..

>My question would be, why do you need the system clock to be so
>accurate? The CPU is connected to the outside world over PCIe, which
>has latency and possibly also asymmetry in hundreds of nanoseconds.
>What do you do on that computer that this accuracy would make a
>difference?

This system clock is being used by other applications like IMU sensor data timestamping. 

We are having this chrony running in an ECU (Electronic Control Unit) along with PTP stack to send PTP packets to other ECUs in the network to get synced to Master ECU.

Thanks & Regards

Sarveshwar.K

On Thu, Feb 16, 2023 at 1:59 PM Miroslav Lichvar <mlichvar@xxxxxxxxxx> wrote:

On Thu, Feb 16, 2023 at 10:04:02AM +0530, sarveshwar k wrote:
> Is it not possible to achieve synchronization accuracy less than 100ns with
> chrony (with GPS and 1PPS).

With HW timestamping of the PPS signal (e.g. on the I210) it is
possible, but difficult to verify.

My question would be, why do you need the system clock to be so
accurate? The CPU is connected to the outside world over PCIe, which
has latency and possibly also asymmetry in hundreds of nanoseconds.
What do you do on that computer that this accuracy would make a
difference?

> Can we configure chrony behaving as a measurement tool (not to make any
> corrections)?

There is the chronyd -x option or the refclock noselect option for
that.

--
Miroslav Lichvar


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